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version 1. 4 application note shindengen electric manufacturing co., ltd. provision for standby mode operation partial resonance power supply ic module mr4000 series
shindengen electric m fg.co.,ltd - 2 - thank you for purchasing this product. when using this ic, please follow the warnings and cautions given below to ensure safety. warning ! improper handling may result in death, serious injury, or major property damage. caution ! improper handling may result in minor injury or property damage. warning ! ! we strive at all times to improve the quality and reliability of our products. however, a certain risk of malfunctions is inevitable with semiconductor products. you are responsible for producing a design that meets safety requirements (wheth er a redundant design, a design that prevents the spread of fire, or designs that minimize the possibility of malfunctions) necessary to avoid injury, fire, or damage to social credibility that may result should any of our products malfunction. the semico nductor product described in this document is not designed or manufactured for use in a device or a system required to demonstrate mission - critical reliability or safety, or whose malfunction may directly cause injuries or endanger human life. contact us b efore using the product for any of the following special or specific applications: special applications transport equipment (e.g., automobiles and ships), communications equipment for a backbone network, traffic signal equipment, disaster or crime prevent ion equipment, medical devices, various types of safety equipment, and other applications specific applications nuclear power control systems, aircraft equipment, aerospace equipment, submarine repeaters, medical equipment used in life - support, and other a pplications even if the equipment is not designed for a special or specific application, please consult with us before using any of our ic products in equipment required to run continuously for extended periods. caution ! ! ! ! ! never attempt to repair or modify the product. doing so may lead to serious accidents. <> in the event of a problem, an excessive voltage may arise at an output terminal, or the voltage may drop. anticipate these fluctuations and any consequential malfunctions or destruction and provide adequate protection for equi pment, such as overvoltage or overcurrent protection. check the polarity of the input and output terminals. make sure they are properly connected before turning on power. <> use only the specified input voltage. deploy a protective element on the input line. <> in the event of a malfunction or other anomaly, shut power off and contact us immediately. ? the contents of this d ocument are subject to change without notice. ? use of this product constitutes acceptance of the formal specifications. ? we have taken every possible measure to ensure the accuracy of the information in this document. however, we will not be held liable for any losses or damages incurred or infringements of patents or other rights resulting from use of this information. ? this document does not guarantee or license the execution of patent rights, intellectual property rights or any other rights of shinden gen or third parties. ? no part of this document may be reproduced in any form without prior consent from shindengen. precautions mr 4000 series application note
shindengen electric mfg.co.,ltd - 3 - 1. overview ? 4 1.1 introduction ? 4 1.2 characteristics ? 4 1.3 applicati ons ? 4 1. 1 4 absolute maximum ratings and reference output capacities ? 4 1.5 dimensions and equivalent circuit ? 5 1.6 basic circuit ? 5 2. block diagram ? 6 2.1 block diagram ? 6 2.2 pin function description ? 6 3. operating principles ? 7 3.1 startup circuit ? 7 6. supplementary design information ? 49 3.2 on - trigger circuit ? 8 6.1 supplementary notes on design ? 51 3.3 partial resonance ? 8 6.2 noise reduction ? 58 3.4 standby mode con trol (patent pending) ? 9 6.3 supplemental information on surface mounting ? 60 3.5 output voltage control (normal operation) ? 10 6.4 precautions for waveform measurements ? 61 3.6 soft drive circuit (patent pending) ? 10 6.5 notes on pattern des ign ? 62 3.7 circuit for load shorts ? 11 6.6 application circuit examples ? 64 3.8 collector pin (mr40xx series) ? 11 6.7 troubleshooting list ? 67 3.9 thermal shutdown circuit (tsd) ? 11 6.8 glossary ? 69 3.10 overvoltage protection circui t (ovp) ? 11 3.11 leading edge blank (leb) ? 11 3.12 malfunction prevention circuit (patent pending) ? 12 3.13 overcurrent protection circuit ? 12 4. design procedure ? 13 4.1 design flow chart ? 13 4.2 reference c onditions for main transformer design ? 13 4.3 reference formulas for main transformer design ? 14 4.4 selecting constants for peripheral components ? 16 4.5 selecting constants for droop circuit ? 17 4.6 cooling design ? 18 contents mr 4000 series application note
shindengen electric mfg.co.,ltd - 4 - 1.1 introduction the mr4000 series ic modules incorporate a burst - mode switching function at micro - loads. these are partial resonance modules consisting of a switching device optimized for 100 v, 200 v, an d auto - sensing power supply input and a control ic. the ic modules are designed to provide the following power supply characteristics: 1.2 characteristics 1. high efficiency and low noise through partial resonance 2. second - generation high - speed igbt with 900 - v resistance simplifies design for auto - sensing power supply input. (mr40xx series) 3. burst mode helps reduce power consumption at micro - loads. 4. onboard startup circuit eliminates the need for startup resistors. 5. soft - drive circuit achieves l ow noise levels. 6. overcurrent protection function (ton limit and primary current limit), overvoltage protection, and thermal shutdown function 7. allow configuration of a power supply circuit with fewer external components. 8. full - mold package facilitat es insulation design. 1.3 applications televisions, displays, printers, video recorders, dvd, stb, refrigerators, and other appliances; various automated business machines 1.4 absolute maximum ratings and reference output capacities main switching device maximum output capacity po[w] input voltage range vds/vce [v] ac90 - 132v ac180 - 276v ac90 - 276v mr4500 12 ( 20 ) D D mr4510 25 ( 40 ) D D mr4520 50 ( 80 ) D D mr4530 500 80 ( 100 ) D D mr4710 D 25 ( 40 ) 1 2 ( 20 ) mr4720 mosfet 700 D 50 ( 80 ) 25 ( 40 ) mr4010 D 65 45 mr4020 D 105 70 mr4030 D 135 90 MR4040 second ? generation high - speed igbt 900 D 180 120 maximum output capacity and input voltage range vary with design parameters. output capacities in parenthese s are peak values. 1. overview mr 4000 series application note
shindengen electric mfg.co.,ltd - 5 - 1.5 dimensions and equivalent circuit 1.6 basic circuit equivalent circuit 1. overview 10 . 0 0 . 2 0 . 97 0 . 25 0 . 50 + 0 . 20 - 0 . 10 3 . 2 + 0 . 2 - 0 . 1 terminal number 0 . 50 + 0 . 20 - 0 . 10 7 . 05 0 . 50 2 . 70 0 . 20 2 . 70 0 . 20 4 . 50 0 . 20 marking area 3 . 88 0 . 30 1 . 94 0 . 30 1 . 94 0 . 30 ( 4 . 1 )
shindengen electric mfg.co.,ltd - 6 - 2.1 block diagram 2.2 pin function description pin numb er abbreviation description 1 z/c zero current detection pin 2 f/b feedback signal input pin 3 gnd gnd pin 4 v cc v cc (ic power supply) pin mr45xx series source/ocl mr47xx series main switching device source and ocl (current detection) pin 5 emit ter/ocl mr40xx series main switching device emitter and ocl (current detection) pin 6 D 7 v in vin (startup) pin 8 D mr45xx series drain mr47xx series main switching device drain pin 9 collector mr40xx series main switching device collector pin 2. block diagram mr 4000 series application note
shindengen electric mfg.co.,ltd - 7 - 3.1 startup circuit in a conventional startup circuit employing a startup resistor, an electric current continues to flow after the power supply starts, wasting power and reducing ef ficiency, especially during standby. see [conventional startup circuit] in fig. 3.1 comparison of startup circuits. in the mr4000 series startup circuit, the startup current is supplied from the input voltage and shut off when the power supply starts up. the startup circuit supplies the i startup current from the constant current source in the ic until the voltage at the v cc pin reaches v cc(start) = v cc(startup off) . this current is consumed internally in the ic and also used as the charging current for th e capacitor connected externally between the v cc pin and gnd. this design allows stable startup with minimal dependence on the input voltage. when the voltage at the v cc pin reaches v cc(startup off) = v cc(start) , the startup circuit disconnects, and the st artup current is halted. as soon as it stops, oscillation begins. the current to be consumed in the ic is then supplied from the control coil. see [mr4000 startup circuit] in fig. 3.1 comparison of startup circuits. in the case of an instantaneous power f ailure or a load short, oscillation stops when the voltage at the v cc pin reaches v cc(stop) . when this voltage drops still further to v cc(startup on) , the startup circuit begins to operate once again, and the voltage at the v cc pin begins to rise. see fig. 3.2. incorporating the functions above improves efficiency, particularly during standby, and eliminates the need for a startup resistor, thereby reducing the overall number of components. [ conventional startup circuit ] ic startup current the startup current flows even during steady - state operation , resulting in losses . v cc pin vin pin v cc ( startup off ) / v cc ( startup on ) [ mr 4000 startup circuit ] control coil 7 4 the startup current switches off after startup , eliminating the need for a startup resistor . fig. 3.1 comparison of startup circuits [ vin ] v cc ( stop ) v cc ( startup on ) v cc ( startup off ) = v cc ( start ) load short instantaneous power failure [ v cc ] [ v ds ( v ce )] [ v out ] fig. 3.2 startup circuit operation sequence 3. operating principles mr 4000 series applicati on note
shindengen electric mfg.co.,ltd - 8 - 3.2 on - trigger circuit the mr4000 series employs a current - critical operation system. when an energy burst to the secondary side of the main transformer is detected, the main switching device is tu rned on. energy discharge timing is detected at a negative edge of the control coil voltage waveform. the main switching device is turned on upon detection of the discharge to perform current - critical operations. see the point with approx. 0.3 v in fig. 3 .3 on - trigger operation sequence. the on - trigger detection voltage (approx. 0.3 v) features 50 mv hysteresis for improved noise resistance. 3.3 partial resonance in a current - critical switching power supply (rcc), w hen the secondary current in the circuit with a resonating capacitor connected between the drain (collector) and gnd of the main switching device as shown on the right reaches 0 a, damping begins at the resonance frequency determined by the primary inducta nce l p of the main transformer and the resonating capacitor c q . the discharge current of the resonating capacitor c q flows through the primary coil and returns energy to the input. adjusting the cr time constant applied to the z/c pin (see the diagram on the right) allows the main switching device to be turned on at the trough of the damping voltage waveform, reducing turn - on losses. in a partial resonance circuit, the energy stored in the resonating capacitor c q during the off period of the main switchin g device is returned to the input, reducing turn - on losses. this allows the connection of a high - capacity capacitor between the drain (collector) and gnd of the main switching device, thereby reducing noise. the use of partial resonance improves efficienc y and reduces noise with simple circuit configurations. [ v z / c ] approx . 0 . 3 v [ i d ( i c )] [ secondary rectification diode current ] [ v ds ( v ce )] [ control coil voltage ] fig. 3.3 on - trigger operation sequence [ i d ( i c )] [ secondary rectification diode current ] turn - on delay damping begins at the resonance frequency determined by l p and c q . [ v ds ( v ce )] 9 1 3 z / c pin drain ( collector ) pin gnd pin c r resonating capacitor on - timing is delayed with cr time constant . 5 source / ocl ( emitter / ocl ) pin c q l p fig. 3.4 partial resonance 3. operating principles
shindengen electric mfg.co.,ltd - 9 - 3.4 standby mode control (patent pending) the mr4000 series is capable of switching between two methods of output voltage control, no rmal operation mode and standby mode, in a single power supply. this ic uses the burst method for standby mode. intermittent operation is performed under light loads to reduce the oscillation frequency and reduce switching losses. the burst method effectiv ely reduces the standby input voltage under micro - loads. this ic uses a burst mode that performs intermittent operation without stopping ic control, thereby minimizing the output ripple. the z/c pin is clamped to a voltage of v z/c(burst) or less by an external signal to switch to standby mode control. to exit standby mode i.e., to return to normal mode the clamp of the z/c pin voltage is released, and the v z/c(burst) or higher voltage is applied to the pin. in no rmal operation, the on range of the main switching device is linearly controlled by voltage variations at the f/b pin. in standby mode, the current detection threshold of the source/ocl (emitter/ocl) pin switches from v th(ocl) for normal mode to v th(burst ocl) for standby mode, and the drain (collector) current is limited. the peak value of the drain (collector) current is set by the current detection threshold, and the burst mode is selected. in standby mode, oscillation occurs when the voltage at the f/b pin is v f/b(burst start) or higher. oscillation stops when this voltage is v f/b(burst stop) or lower. since the output voltage control in standby mode sets the peak value of the drain (collector) current for each oscillation cycle, the duty ratio of the o scillating and non - oscillating intervals varies to ensure a constant voltage. fig. 3.5 standby mode control fig. 3.6 standby mode control sequence fig. 3.7 standby signal receiving sequence 3. operating principles
shindengen electric mfg.co.,ltd - 10 - 3.5 output voltage control (normal operation) the mr4000 series controls output voltage w ith an on range proportional to voltage at the f/b pin. controlled linearly, the on range is t on(min) when the voltage at the f/b pin is 1.5 v and becomes t on(max) when the voltage is 4.5 v. a current of if/b flows at the f/b pin. the impedance of the pho tocoupler transistor connected externally between the f/b pin and gnd varies depending on the control signal from the secondary output detection circuits, which controls the on range of the main switching device to produce a constant voltage. the maximum on range is limited by setting the maximum value for the voltage at the f/b pin using a resistor connected externally between the f/b pin and gnd. thus, the droop point is determined. 3.6 soft drive circuit (patent pending) the mr4000 series supplies the main switching device gate drive voltage from two separate drive circuits. a voltage exceeding the threshold for the main switching device is supplied from the first drive circuit at the leading edge of t he drive voltage waveform to turn the main switching device on at the optimal timing. the drive voltage is then gradually supplied from the second drive circuit (see fig. 3.9). the gradual supply of the drive voltage reduces drive losses and reduces nois e due to the gate charge current and the current discharged when the resonating capacitor switches on. f / b pin 2 the output voltage is controlled by varying the impedance of the photocoupler . i f / b 5 vref droop resistor output voltage error detection feedback signal t on ( max ) 1 . 5 4 . 5 feedback voltage v f / b [ v ] t on ( min ) fig. 3.8 output voltage control fig. 3.9 comparison of drive circuits
shindengen electric mfg.co.,ltd - 11 - 3.7 circuit for load shorts the mr4000 series is designed so that voltage droop occurs under excessive load, ca using the output voltage to drop, and so that the control coil voltage drops proportionally. when the control coil voltage falls below v z/c(burst) , the control switches to standby mode, and the source/ocl (emitter/ocl) pin threshold changes from v th(ocl) t o v th(burst ocl) , thereby limiting the drain (collector) current to approximately 1/10 of its previous value. this design reduces the stress on the mr4000 series ic in the case of a load short and controls the short - circuit current to the secondary diode a nd the load circuit. 3.8 collector pin (mr40xx series) the collector pin on the main switching device (pin 7) the transformer must be designed and the resonating capacitor must be set to ensure that v ce(max) is less than 900 v. depending on input conditions, the collector pin may be subject to reverse bias for a certain period during partial resonance. this ic uses the second - generation high - speed igbt as the main switching device. unlike mosfets, this device has no body diode structure and thus requires the connection of an external high - speed diode between the collector and emitter/ocl pins (see fig. 3.12). 3.9 thermal shutdown circuit (tsd) the mr4000 series incorporates a thermal shutdown circuit. the onboard i c is latched at 150c (typical), after which oscillation is halted. unlatching is achieved by momentarily dropping the voltage at the vcc pin to vul (unlatch voltage) or lower. 3.10 overvoltage protection circuit (ovp) the mr4000 series incorporates an overvoltage protection circuit (ovp). latching occurs when the control coil voltage exceeds v ovp , providing indirect overvoltage protection for the secondary output. unlatching is achieved in the same manner as for the overheat protection circuit. 3.11 le ading edge blank (leb) the mr4000 series has the leading edge blank function. this function improves the margin of noise by rejecting trigger signals from the drain current detection circuit for a certain time after the main switching device is turned on . this function prevents false detections due to the gate drive current produced the moment the main switching device is turned on or due to the discharge current of a resonating capacitor. fig. 3.10 circuit for load shorts 3. operating principles
shindengen electric mfg.co.,ltd - 12 - 3.12 malfunction prevention circuit (patent pending) the current - critical operation of the mr4000 series ensures that the main transformer does not become saturated as long as the droop setting is optimized. at startup and in the event of a lo ad short, the output voltage is significantly lower than the set voltage. since the control coil voltage is proportional to the output voltage, it also drops significantly, and the on - trigger timing may be incorrectly detected due to the ringing voltage ge nerated while the main switching device is off. the device may then be turned on before the current - critical point. to counter this problem, the mr4000 series incorporates a circuit to prevent on - trigger error at startup or in the event of a load short. t his function disables the on - trigger for a period, t ondead , after the main switching device in the ic is turned off (on - dead time). this prevents false detection due to the ringing voltage while the device is off. this design permits detection of the tran sformer secondary current of 0 a to turn on the main switching device even at startup or in the event of a load short. this prevents the magnetic saturation of the transformer. 3.13 overcurrent protection circuit a current detection resistor is connected between the source/ocl (emitter/ocl) pin and gnd to detect currents between the source (emitter) of the main switching device and the source (emitter) current detection pin. during stable operation, the main s witching device current is limited by pulse - by - pulse operation with the v th(ocl) threshold. during standby, the threshold changes to v th(burst ocl) , and the oscillation noise from the transformer due to burst oscillation is reduced. [ secondary rectification diode ] [ v ds ( v ce )] [ v out ] [ v z / c ] enlarged view [ i c ( i d )] [ v z / c ] on - trigger is disabled during this period . t ondead [ secondary rectification diode ] approx . 0 . 3 v [ i d ( i c )] fig. 3.11 malfunction prevention circuit fig. 3.12 current detection resis tor 3. operating principles
shindengen electric mfg.co.,ltd - 13 - this design procedure provides an example of an electrical design procedure. confirm that insulation materials, insulation configurations, and structures meet the safety standards specified by the relevant authorities. 4.1 design flow chart selecting primary circuit components main transformer design specifications determined cooling design trial manufacture operational checks completion no problems problem found r e e x a m i n a t i o n refer to : [ 4 . 2 reference conditions for main transformer design ] refer to : [ 4 . 3 reference formulas for main transformer design ] p . 13 p . 14 refer to : [ 4 . 6 cooling design ] p . 18 refer to : [ 4 . 4 selecting constants for peripheral components ] refer to : [ 4 . 5 selecting constants for droop circuit ] p . 16 p . 17 4.2 reference conditions for main transformer design the values given below are provided for reference only. they should be adjusted to suit specific load conditions. reference value symbol unit mr45xx series mr47xx series mr40xx series minimu m input voltage v ac(min) v D rated output voltage v o v D rated output current i o a D maximum output current i o(max) a D efficiency 0.80 - 0.85 minimum oscillation frequency f (min) khz 30k - 50khz 25k - 40khz 25k - 50khz on duty ratio d 0.40 0.55 0.28 0.55 0.50 0.70 control coil voltage v nc v 15 - 17v effective cross - sectional area of transformer core a e mm 2 D magnetic flux density variation b mt 250 - 320mt coil current density a/mm 2 4 - 6a/mm 2 4. design procedure mr 4000 series application note
shindengen electric mfg.co.,ltd - 14 - 4.3 reference formulas for main transformer design 1 minimum dc input voltage ac(min) dc(min) v 1.2 v ? ? [v] 2 maximum dc input voltage ac(max) dc(max) v 2 v ? ? [v] 3 oscillation cycle (min) (max) f 1 t ? [s] 4 maximum on period (min) on(max)1 f d t ? [s] 5 ma ximum off period q f1 o1 p on(max)1 dc(min) s1 off(max) t ) v (v n t v n t ? ? ? ? ? ? [s] 6 resonance period 2 c l 2 t q p q ? ? ( 2 1 ? ) [s] 7 maximum load power o(max) o o(max) i v p ? ? [w] 8 maximum output power (reference value) o(max) l p 1.3 p ? ? [w] 9 peak drain (co llector) current d v p 2 ) (i i dc(min) l cp dp ? ? ? ? [a] 10 primary coil inductance ) (i i t v l cp dp on(max)1 dc(min) p ? ? [h] 11 number of turns in primary coil e 9 on(max)1 dc(min) p a b 10 t v n ? ? ? ? [turn] 12 core gap p 2 p e 10 g l n a 10 4 l ? ? ? ? ? [mm] the gap ig is the center gap value. review t he transformer core size and oscillation frequency and redesign if ig is 1 mm or greater. 4. design procedure resonance cycle
shindengen electric mfg.co.,ltd - 15 - 13 number of turns in control output coil [turn] 14 number of turns in non - control output coil f1 o1 f2 o2 s1 s2 v v v v n n ? ? ? ? [turn ] 15 number of turns in control coil f1 o1 fnc nc s1 c v v v v n n ? ? ? ? [turn] consider the secondary diode forward voltage v f for each output when determining the number of turns in an output coil. v fnc is the control coil voltage rectification diode forward volt age. the reference value for determining the control coil voltage v nc(min) is 15 v to 17 v. if the v nc(min) is too small, startup characteristics may degrade, making startup difficult. if the v nc(min) is too large, the overvoltage latch stop voltage v op m ay be reached relatively easily. check the v nc(min) voltage within an actual circuit at the design stage to determine the optimal value. 16 primary coil size (min) on(max)1 dc(min) o np f t v 3 p d 2 a ? ? ? ? ? ? ? ? [mm 2 ] 17 secondary coil size (min) q off(max) o (min) q ns f ) t (t 3 i ) f (t d 1 2 a ? ? ? ? ? ? ? ? ? ? [mm 2 ] a nc = 0.2 m m dia. is recommended for the n c coil to simplify calculations. 4. design procedure on(max)1 dc(min) q on(max)1 (min) p f1 o1 s1 t v ) t - t - f 1 ( n ) v (v n ? ? ? ? ?
shindengen electric mfg.co.,ltd - 16 - 4.4 selecting constants for peripheral components the table below gives constants for mr4000 peripheral components. reference v alue component mr45xx series mr47xx series mr40xx series c112 this capacitor determines the resonance frequency. select the value based on noise, efficiency, and other factors. 1200p - 3300pf - 330pf 820pf - 2200pf c113 this is the power supply voltage rectif ication capacitor. if the value is small, operation at startup easily becomes intermittent. if this is too large, startup time will lengthen. 47 - 100 f c114 this is the partial resonance adjustment capacitor. adjust this capacitor with r115 so that turn - on occurs at the resonance trough. 10p - 330pf c115 this capacitor is used to reduce noise at pin 2. it is also beneficial for gain phase adjustme nts. if the value is too large, the frequency response may degrade. 4700pf 100p - 2200pf r113 this is the current limiting damper resistor for c108. select the value after considering noise, efficiency, and other factors. 0 to several ohms r114 this is t he overcurrent detection resistor. it determines the droop point. see [4.5 selecting constants for droop circuit]. r115 this resistor limits the z/c pin current. a p p r o x i m a t e l y 2 0 k ? r116 this resistor limits the z/c pin current. a p p r o x i m a t e l y 1 0 k ? r117 adjust the value according to the droop characteristics. set to a value slightly higher than the droop point set with r114. tens of k ? r151 this resistor compens ates for droop based on the input voltage. adjust the value based on droop characteristics. not required a p p r o x i m a t e l y 5 0 k ? d111 select a high - speed diode in the 900 v and 1a class. not required high - speed diode, 900 v and 1 a class dz151 this zener dio de compensates for droop based on the input voltage. not required see section 4.5. r151, d151 and dz151 are additional components for auto - sensing input specifications. t101 c104 c103 d101 c105 l101 c101 f101 c106 r101 vin d112 r114 ph111 2 1 4 3 7 r151 r115 d141 dz151 c114 ph141 c115 c113 r117 9 5 ic111 d151 c201 l201 c204 r266 c262 d201 v o r261 r263 r262 r201 r202 c261 ic261 r265 ph141 q241 r241 sw241 r248 r247 c112 r113 d111 ph111 r116 fig. 4.1 mr4000 series reference power supply circuit 4. design procedure
shindengen electric mfg.co.,ltd - 17 - 4.5 selecting constants for droop circuit the following are methods of determining the constant of a droop circuit. they are recommended for the mr4000 series standard power supplies. 4.5.1 mr45xx series the following is the method recommended for the mr45xx series standard circuit. (1) apply the following formula to calculate the overcurrent detection resistance r114: ) (i i v r114 cp dp th(ocl) ? [ ] (2) adjust r117 on an actual board. set a droop point slightly higher than that set with r114. t h i s v a l u e w i l l b e o n t h e o r d e r o f s e v e r a l t e n s o f k ? . 4.5.2 mr40xx series the following method is reco mmended for the mr40xx series standard circuit. (1) apply the following formula to calculate the overcurrent detection resistance r114: ) (i i v r114 cp dp th(ocl) ? [ ] (2) adjust r117 on an actual board. set a droop point slightly higher than that set with r114. t h i s v a l u e w i l l b e o n t h e o r d e r o f s e v e r a l t e n s o f k ? . (3) select the voltage for dz151, a zene r diode that compensates for droop based on the input voltage. apply the following formula to calculate the zener voltage: the compensation beginning voltage is assumed to be 150 v. p c n n 150 1.3 ? ?R ? ? ? [ v ] (4) adjust r151, a resistor that compensates for droop based on the input voltage, on an actual board. t h e v a l u e o f r 1 5 1 i s a p p r o x i m a t e l y 5 0 ? . (5) set c115 at about 2200 pf. mr4000 d112 ph111 c115 r117 2 4 3 5 r114 fig. 4.2 mr45xx series droop circuit v th(ocl) overcurrent limit threshold voltage i dp (i cp ) drain (collector) peak current at maximum output power mr4000 5 r114 d112 ph111 c115 r117 2 4 3 d151 r151 dz151 fig. 4.3 mr40xx series droop circuit v th(ocl) overcurrent limit threshold voltage i dp ( i cp ) drain (collector) peak current at maximum output power 4. design procedure zener voltage
shindengen electric mfg.co.,ltd - 18 - 4.6 cooling design tj(max) for the mr4000 series is 150c. since the operation of the mr4000 series is accompanied by an increase in temperature asso ciated with power losses, you must carefully consider the type of heat sink needed. additionally, if the design must ensure that tj(max) is not exceeded, you must also consider the thermal shutdown function (tsd = 150c (typical)). the extent to which tj i s derated in a design is critical for improving reliability. most power losses that occur while the devices in the mr series operate are associated with the internal mosfet. if most power losses are considered on losses, they may be expressed as follows: p d = v ds i d t h e t e m p e r a t u r e i n c r e a s e t j a t t r i b u t a b l e t o p o w e r l o s s e s p d i s e x p r e s s e d a s f o l l o w s : t j + t a Q t j(max) if t sd(min) is assumed to be 120c, considering tsd = 150c (typical), pd is constrained to satisfy the following equation: t j +t a Q t sd(min) t j may be calculated as follows using thermal resistance ja . t j = ( p d ja ) + t a ja , the junction - to - ambient thermal resistance, is expressed as follows: ja = jc + cf + fa the thermal shutdown (t sd ) protective function stops and latches operation at 150c in the event of abnormal heat buildup in the mr series. this means circuit design must incorporate a cooling de sign whereby the temperature is sufficiently derated. shindengen recommends setting a cooling design target so that the case temperature will not exceed 100c. 4.6.1 junction temperature and power losses 4.6.2 junction temperature and thermal resistance symbol unit junction - to - ambient thermal resistance ja c /w junction - to - case thermal re sistance jc c /w case - to - fin thermal resistance (contact thermal resistance) cf c /w fin - to - ambient thermal resistance (fin thermal resistance) fa c /w 4.6.3 cautions for cooling design 4. design procedure
shindengen electric mfg.co.,ltd - 49 - this chapter provides supplementary information for mr4000 series power supply circuits. use this information when designing or evaluating mr4000 series power supply circuits. supplementary design information: contents 6. s upplementary design information 51 6.1.1 v cc control 51 (1) increasing the damper resistance (2) nc coil winding method (3) adding a dummy resistor 51 6.1.2 ringing voltage at turn - off of main switching device 52 (1) transformer leaka ge inductance (2) clamp circuit 52 6.1.3 resonating capacitor 54 selecting the resonating capacitor (2) capacity of resonating capacitor 54 6.1.4 constants of components around z/c pin in the circuit 55 (1) partial resonance capac itor c114 (2) partial resonance resistor r115 (3) z/c pin current limiting resistor r116 55 6.1.5 enhancing the peak surge current of v cc pin 56 6.1.6 phase correction 57 (1) insert c and r between the cathode and ref of the shunt re gulator. (2) insert c and r between the front of the secondary lc filter and ref of the shunt regulator. (3) insert c and r between the rear of the secondary lc filter and ref of the shunt regulator. (4) place the power supply side of the pho tocoupler in front of the lc filter. 57 6.2 noise reduction 58 6.2.1 redesigning the transformer 58 6.2.2 changing y capacitor 58 6.2.3 using a snubber circuit 58 6.2.4 connecting a capacitor to a secondary diode in parallel 59 6.2.5 capacitive coupling 59 6.2.6 other measures 59 6.3 supplemental information on surface mounting 60 6.3.1 greasing 60 6.3.2 screws 60 6.3.3 radiation fin 60 6. supplementary design information mr 4000 series application note
shindengen electric mfg.co.,ltd - 50 - 6.4 precautions for waveform me asurements 61 6.4.1 isolating the ac line 61 61 6.4.2 simultaneous measurement of primary and secondary sides 61 6.5 notes on pattern design 62 6.5.1 pattern design for primary side 62 6.5.2 pattern design around nc coil 62 6.5.3 pattern design for secondary side 62 6.5.4 pattern design around gnd pin 62 6.5.5 connecting a capacitor 62 6.5.6 pattern of c114 62 6.5.7 pattern of r116 63 6.5.8 location of ocl resistor 63 6.6 application circuit exampl es 64 6.6.1 indirect control 64 6.6.2 oscillation stop circuit in case of low voltage input 65 6.6.3 remote on/off circuit for mr4000 series 65 6.6.4 ovp latch circuit by secondary side detection using auxiliary coil 66 6.7 trou bleshooting list 67 6.8 glossary 6 9 6.8.1 power supply operation 69 6.8.2 transformer design 70 6.8.3 ic functions 70 6.8.4 other 72 6. supplementary design information
shindengen electric mfg.co.,ltd - 51 - 6.1 supplementary notes on design 6.1.1 v cc control since the ic control current is very low, v cc can be significantly affected by the ringing voltage caused by transformer leakage inductance. this will increase the v cc voltage of the mr4000 series beyond the design value. under certain load conditions, th e ic may be latched and stopped or the v cc may become too low. the ringing voltage caused by the transformer leakage inductance is reduced with a dcr snubber circuit. several other solutions are also available, as shown below. (1) increasing the damper r esistance increasing this resistance reduces voltage variations. increasing the resistance will affect v cc . make sure the design accounts for possible stoppage of mr4000 series products due to a fall in v cc . set the resistance on an actual board between several ohms and tens of ohms. note that a light load may decrease efficiency under certain circumstances. (2) n c coil winding method bring the n c coil into closer contact with a secondary coil that has limited contact with the primary coil. doing so will reduce the ringing generated in the n c coil. this is our recommended winding method. (3) adding a dummy resistor if using a dummy resistor increases power consumption and decreases efficiency, this circuit will improve these performance somewhat. if the v cc voltage exceeds the level determined by the zener diode, the dummy resistor will control th e voltage increase. we recommend a zener diode for 16 v or higher. mr 4000 3 4 increase this resistance . fig. 6.1 damper resistance fig. 6.2 transformer winding to improve contact fig. 6.3 adding a dummy resistor 6. supplementary design information
shindengen electric mfg.co.,ltd - 52 - 6.1.2 ringing voltage at turn - off of main switching device a significant voltage surge component is generated in the main switch if the transformer leak age inductance is too large or if a relatively high current is output. the most effective way to reduce the voltage surge component is to reduce the leakage inductance. the voltage surge component can be also reduced by a clamp circuit. reducing the voltag e surge component protects the main switch. in the case of a multi - output power supply, it also improves cross regulation in the outputs. (1) transformer leakage inductance when the main switching device is turned off, a ringing voltage is added to the voltage, as shown in fig. 6.4, due to the leakage inductance of the transformer primary coil. the voltage applied to the main switching device must be designed to accommodate the ringing voltage. the leakage inducta nce of the primary coil is measured as shown in fig. 6.4. (2) clamp circuit a clamp circuit may be required if the withstand voltage limit of the main switching device is exceeded due to load or other c onditions or if the design margin is insufficient due to a ringing voltage caused by the leakage inductance. we recommend a dcr snubber circuit as a clamp circuit. see the next page for dcr snubber circuit design procedures. fig. 6.4 leakage inductance mr4000 3 5 9 fig. 6.5 dcr snubber circuit 6. supplementary design information
shindengen electric mfg.co.,ltd - 53 - design of dcr snubber circuit use the following formulas to estimate the constants for a dcr snubber circuit: if all the energy of the leakage inductance l i is assumed to be consumed in the snubber circuit, the following formula holds true: ? ? 2 np np s 2 cp dp l v 1.2v c 2 1 ) (i i l 2 1 ? ? ? ? ? ? ? ( 1 ) energy of leakage inductance l i = energy of snubber capacitor c s np s s v 1.2 i r ? ? ? ? ( 2 ) voltage of snubber resistor r s = charging voltage of snubber capacitor c s f ) (i i l 2 1 i r 2 cp dp 2 l 2 s s ? ? ? ? ? ? ( 3 ) power consumption of snubber resi stor r s = power of leakage inductance l i if we assume that l i is 2.5% of the primary inductance l p and that the charging voltage of snubber capacitor c s is 1.2 times v np , c s is given as follows: from formula (1), 2 np 2 cp dp p s v ) (i i l 0.625 c ? ? ? [f] from formulas ( 1) and (3), we obtain formula (4). ? ? f v 1.2v c 2 1 i r 2 np np 2 s 2 s s ? ? ? ? ? ? ? ( 4 ) formula (2) is equivalent to formula (5). s np s r v 1.2 i ? ? ? ( 5 ) when we substitute formula (5) into formula (4), we obtain formula (6). f c 72 1 r 1 s s ? ? ? ? ( 6 ) we substitute c s int o formula (6) to obtain r s . 2 cp dp p 2 np s ) (i i l f v 115.2 r ? ? ? ? [ ] p rs , power consumption in r s is: 2 s s rs i r p ? ? [w] these values assume that l i is 2.5% of the primary inductance l p and that the charging voltage of snubber capacitor c s is 1.2 times the value of v n p . adjustments must be made on an actual board. * calculation example when oscillation frequency f = 25 khz, l p = 0.5 mh, i dp = 5 a and v np = 200v; c s = 0.2 uf, r s = 1 4 . 7 k ? a n d p rs = 3.9 w. fig. 6.6 design of dcr snubber circuit l l leakage inductance i dp (i cp ) peak current of main switching device c s snubber capacitor l p primary inductance of transformer v np flyback voltage generated with primary inductance l p r s snubber resisto r i s current flowing to snubber resistor f oscillation frequency of power supply 6. supplementary design information
shindengen electric mfg.co.,ltd - 54 - 6.1.3 resonating capacitor (1) selecting the resonating capacitor the resonating capacitor must have the following characteristics: 1) the withstand voltage is significantly greater th an that of the main switching device. 2) tangent of loss angle tan is small. 3) the upper temperature limit is high. ideally, use a mica or polypropylene capacitor. a low - loss ceramic capacitor should also be adequate. consult with the manufacturer befor e using this capacitor type. (2) capacity of resonating capacitor noise is reduced by the resonance determined by the resonating capacitor and the primary coil inductance. this has both favorable and adverse effects, as shown in the table below. consider these effects when setting the capacity of the capacitor. item small capacitor capacity large efficiency during standby increases decreases heat buildup in the transformer decreases increases ringing voltage at turn - off of main switching device increases decreases noise increases decreases operating frequency incre ases decreases 6. supplementary design informatio n
shindengen electric mfg.co.,ltd - 55 - 6.1.4 constants of components around z/c pin in the circuit at the design stage, keep in mind the following aspects of the constants for the components around the z/c pin (pin 1) in the cir cuit. mr4000 d112 ph141 c114 r115 1 4 3 fig. 6.7 circuit around z/c pin (1) partial resonance capacitor c114 the capacity of c114 capacitor should be around 100 pf. since the z/c pin (pin 1) is susceptible to noise, the capacity should not be lower. (2) partial resonance r esistor r115 keep in mind the following when determining the value for r115: 1) 5ma r v 115 cc ? and 5ma n r n v p 115 c in ? ? ? the absolute maximum rating for the z/c pin (pin 1) is 5 ma. current flowing to the pin cannot exceed this level. (vin represents the input capacitor voltage when the maximum input voltage is applied.) 2) determine r115 so that the main switching device is turned on at the trough of its partial resonance. (3) z/c pin cu rrent limiting resistor r116 if requirements 1) and 2) of section (2) above cannot be met simultaneously, add r116 as shown in fig. 6.9. r116 should be a r o u n d 1 0 k ? . r115 is used to set the partial resonance trough o f the main switching device. set in the same way as described in section (2) above. large small r 115 trough fig. 6.8 adjusting the resonance trough mr4000 d112 ph141 c114 r115 1 4 3 r116 fig. 6.9 addition of r116 6. supplementary design information
shindengen electric mfg.co.,ltd - 56 - 6.1.5 enhancing the peak surge current of v cc pin this measure helps enhance resistance against surge currents applied from exter nal sources. add a capacitor between the v cc pin (pin 4) and gnd pin (pin 3). use a capacitor with good frequency characteristics. place the capacitor as close as possible to the v cc and gnd pins (pins 4 and 3). fig. 6.10 capacitor between v cc pin and gnd pin 6. supplementary design information
shindengen electric mfg.co.,ltd - 57 - 6.1.6 phase correction in an rcc circuit, delays in the phase of the photocoupler, capacitor, or coil may result in hunting. if so, oscillations may become audible or output voltage ripp les may become very large. the following countermeasures are available: (1) insert c and r between the cathode and ref of the shunt regulator. (2) insert c and r between the front of the secondary lc filter and ref of the shunt regulator. output output (3 ) insert c and r between the rear of the secondary lc filter and ref of the shunt regulator. (4) place the power supply side of the photocoupler in front of the lc filter. output output if the oscillation tends to be intermi ttent under light load, one solution is to lower the feedback gain. insert a resistor as shown in fig. 6.11. set the resistor to 2.2 k ? o r l e s s . mr4000 d112 ph111 c115 r117 2 4 3 fig. 6.11 lowering feedback gain 6. supplementary design information
shindengen electric mfg.co.,ltd - 58 - 6.2 noise reduction this section describes noise reduction methods for the mr4000. check these methods on an actual board to determine the best combination of methods. 6.2.1 redesigning the transfo rmer redesign the transformer to reduce noise, considering the following factors. proceed carefully with respect to the withstand voltage, operating frequency, and other relevant parameters of the main switching device. (1) improve coil contact. that wi ll reduce ringing at turn - off and reduce noise. (2) increase the on duty ratio. taking full advantage of the partial resonance function will reduce surge currents at turn - on and reduce noise. (3) decrease the operating frequency. that will reduce noise att ributable to fundamental waves or harmonics thereof. we can reduce noise not only by changing the location of a y capacitor or adding a y capacitor, but by also changing the capacit y. the effect varies with pcb patterns. check carefully with an actual board. (1) try changing the location of the y capacitor at the filter. (2) connect to ground from the negative side of the input capacitor. (3) connect to ground from the positive side of the input capacitor. 6.2.3 using a snubber circuit (1) add a dcr snubber. that will lower the peak of a ringing voltage at turn - off and reduce noise. (2) add a damping resistor. connect to the resonating capacitor i n series. this will advance the damping of a ringing voltage at turn - off and reduce noise. (3) connect a capacitor in parallel to the dcr snubber diode. this will reduce noise from the diode handling switching. ideally, use a mica or polypropylene capacit or as the capacitors in (2) and (3). a low - loss ceramic capacitor should also prove adequate. consult with the manufacturer before using this type of capacitor. 6.2.2 changing y capacitor ac in fig. 6.12 considerations for y capacitor mr4000 9 3 5 fig. 6.13 snubber circuit 6. supplementary design information
shindengen electric mfg.co.,ltd - 59 - 6.2.4 connecting a capacitor to a secondary diode in parallel the secondary diode handles switching. add a capacitor to reduce noise. try the diodes on an actual board to determine which is most effective. it may help to connect a damping resistor to this cap acitor in series. ideally, use a mica or polypropylene capacitor. a low - loss ceramic capacitor should also prove adequate. consult with the manufacturer before using this type of capacitor. 6.2.5 capacitive coupling you can also couple the primary gnd and the secondary gnd with a capacitor. take great care to consider the leakage current between the primary and secondary and the safety standards. 6.2.6 other measures (1) place bead cores around the dr ain (collector) pin (pin 9). (2) place bead cores around the secondary diode. n s 1 n s 2 fig. 6.14 adding a capacitor to the secondary side n s 1 n s 2 n c n p n s 1 fig. 6.15 capacitive coupli ng 6. supplementary design information
shindengen electric mfg.co.,ltd - 60 - 6.3 supplemental information on surface mounting 6.3.1 greasing when using a radiation fin (heat sink), apply a thin uniform film of si licon grease between the mr4000 series and the fin. this will reduce contact thermal resistance and enhance the heat radiation effect. 6.3.2 screws use m3 round head, pan head, binding head, or fillister head screws. avoid countersunk head screws. use p lain washers and spring washers to keep the screws tight. use small, plain 3 - mm washers. do not use washers that are 3.5 mm or larger or washers with one polished side. 6.3.3 radiation fin the mounting surface of the radiation fin for the mr4000 series must be flat and free of any unevenness, torsion, or warping to protect the device from excessive stress and to avoid impairing radiation effects. make sure the edge of the mounting hole is free of burrs. use a long fin positioned laterally. this shape res ults in more effective radiation than other shapes. fig. 6.16 mounting the radiation fin 6. supplementary design information
shindengen electric mfg.co.,ltd - 61 - 6.4 precautions for waveform measurements 6.4.1 isolating the ac line when measuring the mr4000 series or a peripheral circuit using an oscilloscope or other such instrument, isolate the ac line between the circuit to be measured and the measuring instrument to prevent electric shock and leakage. 6.4.2 si multaneous measurement of primary and secondary sides in the case of a power supply using the mr4000 series, the ac input (primary) side and the dc output (secondary) side are isolated from each other by a transformer. do not use a measuring instrument o n the primary and secondary sides simultaneously. otherwise, gnds of different potentials may be connected; this can affect the operation of the power supply or measurement results. (example of method to avoid: measure the primary and secondary waveforms s imultaneously using the voltage probe of an oscilloscope.) to check both the primary and secondary waveforms simultaneously, use a differential probe for one of the two. fig. 6.17 isolating the ac line mr do not measure simultaneously . measurement gnd fig. 6.18 simultaneous measurement of primary and secondary sides 6. supplementary design information
shindengen electric mfg.co.,ltd - 62 - 6.5 notes on pattern design patterns must be as short as possible to make the loops as small as possible. keep the following in mind at the design stage: 6.5.1 pattern design for primary side 6.5.2 pattern design ar ound nc coil c106 c112 mr4000 3 5 9 r114 4 3 c113 d112 mr4000 a high - speed switching current flows through the loop. reducing the loop area will reduce noise. make the loop connecting the transformer, d112, and c113 thick and short. 6.5.3 pattern design for secondary side 6.5.4 pattern desi gn around gnd pin d 201 short short l 201 c 202 c 201 place as close to the output pin as possible . make the loop connecting the transformer, rectification diode, and output capacitor thick and short. place the capacitor at the rear of the output choke coil as close to the output pin as possible. connect the gnd pin (pin 3) dire ctly to the negative side of c106. do not connect any other component. do not place the end of the control circuit inside r114 (closer to gnd pin). 6.5.5 connecting a capacitor 6.5.6 pattern of c114 make sure the pattern passes through the cap acitor pads. the z/c pin (pin 1) is susceptible to noise. connect the pattern near the z/c pin (pin 1) and gnd pin (pin 3). 6. supplementary design information
shindengen electric mfg.co.,ltd - 63 - 6.5.7 pattern of r116 6.5.8 location of ocl resistor c 112 r 114 mr 4000 5 9 3 place close to pins 3 and 5 . for patterns incorporating r116, m ake the pattern short as shown in the diagram above. place the current detection resistor as close as possible to the ocl pin (pin 5) and gnd pin (pin 3). the ocl detection level is low and readily affected by the inductance or resistance component of the current detection loop wire. placing r114 close to pins 3 and 5 will help prevent errors due to noise and increase detection accuracy. 6. supplementary design information
shindengen electric mfg.co.,ltd - 64 - 6.6 application circuit examples 6.6.1 indirect control if output voltage precision is not an issue, a constant voltage control can be provided at the primary side without using a photocoupler. figure 6.19 shows an example of 12 v output design. (1) circuit configuration the circuit consists of a transistor a nd a current control resistor that control the f/b pin (pin 2) and a zener diode that detects voltage. in cases where an increase in voltage under light load is an issue, add a dummy resistor on the secondary side. (2) circuit operation the zener diode in the additional component for indirect control surrounded in a frame in the diagram detects the output voltage of the control coil. the detection signal controls the f/b pin (pin 2) directly via the transistor. (3) problem a ringing voltage attributable to transformer leakage inductance can result in significant variations in voltage precision. this can also increase the output voltage under a light load. fig. 6.19 indirect control 6. supplementary design information
shindengen electric mfg.co.,ltd - 65 - 6.6.2 oscillation stop circuit in case of low voltage input this protection circuit prevents input from a 100 v group power source to a 200 v group power supply. the circuit monitors input voltages. on detecting an inpu t of 100 v, the circuit stops the oscillation of the mr4000 series. on detecting an input of 200 v, the circuit allows regular oscillation. (1) circuit configuration the circuit consists of a transistor q1 that short - circuits the input voltage detection r esistor and the f/b pin (pin 2), a transistor q2 that turns q1 off, and a zener diode that corrects for variations in vbe of q2 and temperature characteristics. (2) circuit operation the transistor q1 short - circuits the f/b pin (pin 2) of the mr4000 series until the input voltage vin exceeds 138 v (a maximum voltage in the 100 v group), thereby keeping the mr from oscillating. when vin reaches 170 v (a minimum voltage in the 200 v group), q2 is turned on, turning q1 off. the mr4000 series begins oscillating . (3) problem efficiency is reduced during standby. standby characteristics are decreased due to the current required for the i n p u t v o l t a g e d e t e c t i o n c i r c u i t a n d t h e c u r r e n t f l o w i n g t o q 1 a n d q 2 . i f t h e r e s i s t o r r 1 i s s e t t o 5 6 k ? o r l e s s , t h e ic can not s tart up. (4) precautions i f r e s i s t o r r 1 i s s e t t o 5 6 k ? o r l e s s , t h e i c m a y n o t s t a r t u p . carefully consider the startup characteristics if a resistor or any other component is connected to the v cc pin (pin 4) of the mr4000 series for other purposes. 6.6. 3 remote on/off circuit for mr4000 series the oscillation of mr4000 series devices can be turned on and off with an external on/off signal. (1) circuit configuration the circuit consists of a transistor that sh ort - circuits the f/b pin (pin 2) and an external on/off signal on the primary side. the external signal can be input from the secondary side using a photocoupler instead of the transistor. (2) circuit operation upon receipt of the external signal, the tran sistor is turned on, short - circuiting the f/b pin (pin 2) and halting the power supply. when a low external signal is input, the transistor is turned off, and oscillation resumes. (3) problem if the power supply has been turned off by the external signal, the built - in startup circuit will continue charging and discharging the v cc , resulting in losses. 10 k 0 . 033 f c 106 d 112 ic 111 2 4 3 9 c 113 2 sc 945 r 1 62 k 2 sc 945 8 . 2 v 39 k 360 k 360 k n p n c q 1 q 2 fig. 6.20 oscillation stop circuit in case of low voltage input fig. 6.21 mr4000 series on/off circuit 6. supplementary design information
shindengen electric mfg.co.,ltd - 66 - 6.6.4 ovp latch circuit by secondary side detection using auxiliary coil c201 l201 c202 c205 d201 +12v gnd d112 4 3 pc1 ps2501 c113 35v 100 f d1nl20u d1 d1nl20u c1 0.047 f nc2 nc1 zd2 15v,b2 pc1 ps2501 470 ns1 r1 100 fig. 6.22 ovp circuit using auxiliary coil (1) circuit configuration this circuit consists of n c 2, an auxiliary coil; pc1, a photocoupler for ovp; r1; c1; d1; and zd2, a zener diode for secondary output detection. (2) circuit operation set the n c 2 coil voltage to 22 v (v cc(ovp) x 1.1) or greater. if t he output voltage exceeds the zener voltage, as the f/b pin is opened, the photocoupler will activate. as a result, the n c 2 coil voltage is applied to the v cc pin (pin 4) of the mr4000 series, the v cc voltage exceeds 20 v, and the ic is latched and stopped for ovp. (3) precautions take steps to ensure the circuit does not exceed 21 v, the absolute maximum rating for the withstand voltage of the ic. proceed carefully while referring to the constants of the components in the diagram above. 6. supplementary design information
shindengen electric mfg.co.,ltd - 67 - 6.7 troubleshooting list the table below shows common problems with power supply designs using the mr4000 series, possible causes, and solutions. problem possible cause solution the polarity o f the transformer is incorrect. check winding directions for n p , n s , and n c . adjust the droop compensation circuit. the droop compensation circuit is inadequate. the on range setting (resistance between the f/b pin and gnd pin) is small. a consta nt current load or constant power load is used. change to a constant resistance load. adjust the number of turns in the n c coil. review the transformer coil structure. combine a zener diode and a resistor to clamp v c c . the overvoltage latch is on. insert a resistor between the n c coil and rectification diode. the input to the z/c pin is incorrect. review the circuit around the z/c pin. the ic is activated under a heavy load. startup under a light load is recommended for the mr4000 serie s. t on(max) has reached the limit value. review the transformer design. 1 does not start up. there are too few turns in the n c coil. adjust the number of turns in the n c coil. review the core b. the transformer is causing magnetic saturation. adjust the resistance between the f/b pin and gnd pin. adjust the droop compensation circuit. the droop compensation circuit is inadequate. adjust the resistance between the f/b pin and gnd pin. provide a snubber circuit. review the transformer design. 2 mr4000 series is defective. the voltage exceeded the withstand level of the main switching device. review the transformer coil structure. 3 a control output voltage rises. adjust the current limiting resistance of the photodiode. adjust the current limiting re sistance of the photodiode. add a dummy resistor or damper resistor at the output end. 4 a non - control output voltage rises. peak charging to the output capacitor due to a surge voltage review the transformer design. the constants for the output voltage detection circuit are inappropriate. reexamine the output voltage detection resistance. adjust the resistance between the f/b pin and gnd pin. the droop compensation circuit is inadequate. adjust the ocl resistance. increase the oscillation frequency. 5 the output voltage or current d oes not reach the desired level. t on(max) has reached the limit value. set the on duty ratio lower. the heat sink is too small or missing. provide a heat sink or repla ce with a larger one. reduce the oscillation frequency. the switching loss is large. use a smaller resonating capacitor. the tightening torque is insufficient. tighten at the torque recommended by shindengen. apply silicone grease. contact with the heat sink is poor . insert a radiation sheet. timing for partial resonance is incorrect. adjust the delay setting for partial resonance. 6 mr4000 series generate excessive heat. the partial resonance trough is high. increase the on duty ratio. the oscillation frequency is high. reduce the oscillation frequency. the phase compensation circuit is inadequate. adjust the circuit around the shunt regulator. increase the current limiting resistance on the diode side of the photocoupler. 7 intermittent oscillation occurs und er a light load. the feedback gain is high. connect a resistor in series with the transistor side of the photocoupler. 6. supplementary design information
shindengen electric mfg.co.,ltd - 68 - problem possible cause solution place the secondary f/b pin in front of l. adjust the circuit around the shunt regulator. 8 abnormal oscillation during steady - state operation this results in hunting . the phase has shifted. adjust the circuit around the photocoupler. adjust the ocl re sistance. 9 the droop operation is ineffective. the droop circuit is inadequate. adjust the resistance between the f/b pin and gnd pin. the on duty ratio is large. redesign on duty ratio. the transformer coupling is poor. review the transformer coil structure. the ratio of numbers of turns in coils is inappropriate. review the transformer design. adjust the resonating capacitor. provide a snubber circuit. add a power clamper. 10 v ds or v ce exceeds the withstand level. the surge is large. connect a resistor in series with the resonating capacitor. the current to the photodiode is too low. adjust the current - limiting resistance of the photodiode. increase the capacity of the capacitor between the z/c pin and gnd pin. 11 the ic cannot enter standby mode. noise is superimposed on the z/c pin. impro ve the pcb pattern. adjust the number of turns in the n c coil. review the transformer coil structure. combine a zener diode and a resistor to clamp v cc . 12 the oscillation halts when the output load is increased. the overvoltage latch is on. a dd a damper resistor for v cc . reinforce impregnation (e.g., double impregnation, use of adhesive) 13 the transformer generates an oscillating tone in standby mode. transformer vibrations optimize the load. noise is superimposed on the z/c pin. increase the capacity of the capacitor between the z/c pin and gnd pin. increase the current rating of the diode. the vf of the secondary diode is large. use a schottky diode. 14 the input power is large in the case of a load short. the transformer cou pling is poor. review the transformer coil structure. 15 the droop point varies. the resistor between the f/b pin and gnd pin is operating. make sure the voltage droops only with the ocl pin resistance. the tan of the resonating capacitor is large. use a capacitor with a smaller tan . 16 the standby power is large. the capacity of the resonating capacitor is large. adjust the resonating capacitor (carefully monitor vds or vce to ensure that the withstand level is not exceeded.) 6. supplementary design information
shindengen electric mfg.co.,ltd - 69 - 6.8 glossary this section provides a glossary of terms used in the mr series application note, power supply reference data, and other technical materials. it provides various definitions for technical use, such as power supply des ign and ic functions. 6.8.1 power supply operation [resonating capacitor] a capacitor for a damper snubber circuit in a power supply circuit using partial resonance damper snubber [clamper snubber] a snubber circuit consisting of diode, capacitor, and resistor at the primary coil end (dcr snubber) or a snubber circuit using a power zener diode snubber circuit [gain and phase] important parameters for a feedback control circuit. [conducted emissions] conducted noise fed back to the input side; also called input feedback noise [output ripple voltage] output voltage is not completely dc and has various superimposed frequency components. general ripple voltage comp onents result from commercial and switching frequencies. [droop characteristics] output characteristics when an overcurrent protection function activates [droop compensation circuit] a compensation circuit used to minimize the dependence of the droop fun ction on input voltage [snubber circuit] a circuit used to reduce stress on a switching device. snubber circuits are divided into clamper snubber and damper snubber. [damper snubber] a cr snubber circuit consisting of a resistor and a capacitor between t he drain and the source or between the collector and the emitter of a main switching device. in a partial resonance power supply circuit, c represents a resonating capacitor and r a damper resistor. snubber circuit [current - critical system] a power supply control system for an isolated flyback transformer in which the main switching device activates when the secondary diode is turned off [input feedback noise] conducted noise fed back to the input side; also called conducted emissions [burst mode] control mode for a switching power supply using intermittent oscillation with the mr series, the drain current peak value during intermittent oscillation is limited to i dp(burst limit) . 6. supplementary design information
shindengen electric mfg.co.,ltd - 70 - [hunting] a situation in which the gain or phase in a feedback control system is not adequate, resulting in abnormal oscillations [feedback] signal fed back to the primary control circuit upon detection of the output voltage feedback is use d for constant voltage control. [radiated emissions] disturbance field strengths released into the air; also called radiated noise [partial resonance] a soft - switching method or technology used in a circuit that reduces switching losses at startup of the main switching device in a switching power supply [radiated noise] disturbance field strengths broadcast into the air; also called radiated emissions [ringing voltage] in th is application note , it refers in particular to the oscillation voltage immediat ely after the main switching device is turned off. 6.8.2 transformer design [duty ratio] a ratio of the on range to the oscillation period; sometimes referred to as d. [ton - t ratio] the same as duty ratio [on duty ratio] the same as duty ratio [core gap] a gap in a transformer core in a flyback power supply, this gap is used to adjust inductance. [control coil] a coil used to supply the source voltage to the internal ic of the mr series and to output the z/c signal. [magnetic saturation] state in w hich the maximum magnetic flux density of a transformer is exceeded if magnetic saturation occurs, the inductor will not function; a sudden excessive current may flow and damage the power supply. [magnetic flux density] the magnetic flux per unit area gen erated at the core by an excitation current 6.8.3 ic functions leb see leading edge blank. 6. supplementary design information
shindengen electric mfg.co.,ltd - 71 - [ocp] see overcurrent protection. [ovp] see overvoltage protection. [tsd] see thermal shutdown. [under voltage lock out] a function that incorporates several volts of hysteresis into startup ch aracteristics. this function stabilizes startup characteristics; sometimes referred to as uvlo. [uvlo] see under voltage lock out. [on - dead timer] a function that disables the main switching device for a certain period to prevent unintended operation due to the ringing voltage when turned off [on - trigger] with the mr series, the z/c pin (pin 2) detects a falling edge of the control coil signal and uses it as a trigger signal to turn on the main switching device. [on - trigger disabled period] in switching operations, this refers to a period during which the turn - on signal is not accepted to prevent unintended operations due to ringing voltage when turned off. [overvoltage protection] a function that limits the output voltage to prevent damage to the power supply sometimes referred to as ovp [overcurrent protection] a function that limits the output current to prevent damage to the power supply; sometimes referred to as ocp [thermal shutdown] a function that limits the ic junction temperature to prevent damage to the ic. if the temperature exceeds a certain level, the ic is latched and stopped; sometimes referred to as tsd; also referred to as overheat protection. latch stop [soft drive] a drive system of the main switching device of a switc hing power supply that reduces noise and enhances efficiency under a light load. shindengen has applied for a patent on this technology. [negative edge] a falling edge of a rectangular wave [latch stop] one of ic s stop modes following activation of a pr otection function; in this mode, the ic will not restart unless power is applied again. 6. supplementary design information
shindengen electric mfg.co.,ltd - 72 - [leading edge blank] a function that prevents the main switching device from being turned off for a certain period to prevent unintended o perations due to a surge voltage at turn - on; sometimes referred to as leb [restart timer] the mr series re - oscillates in standby mode or at startup if it does not receive a trigger signal for a certain period of time. the restart timer determines this dur ation. 6.8.4 other [ultra fast igbt] a switching device developed by shindengen that offers sufficient speed characteristics for switching power supplies; employed as the main switching device in the mr2900 series, mr40xx series, and mr5000 series. 6. supplementary design information
shindengen electric mfg.co.,ltd - 73 - we offer various applications that make it easier to design power supply circuits using the mr series. we will continue to update and add new data and know - how. please contact our sales department to order reference materials o r to inquire about the latest editions. selection guide lists the line - up of mr series and provides product overviews. (we are currently working to include the mr4000 series.) application note mr1000 series presents mr1000 series operating princi ples, design procedures for power supply circuits, and supplemental design information. mr2000 series presents mr2000 series operating principles, design procedures for power supply circuits, and supplemental design information. mr4000 series presents mr4000 series operating principles, design procedures for power supply circuits, and supplemental design information. mr5000 series presents mr5000 series operating principles, design procedures for power supply circuits, and supplemental design informat ion. power supply reference data mr1000 series provides power supply reference data for mr1000 series and abnormal test tables. mr2000 series provides power supply reference data for mr2000 series and abnormal test tables. mr4000 series in prepar ation mr5000 series in preparation guides for mr series applications mr 4000 series application note

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