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march 2009 rev 1 1/37 AN2844 application note 15 w wide range smps for metering based on esbt? stc03de220hv and l6565 pwm controller 1 introduction this document describes a 15-w flyback switched mode power supply (smps) application that uses an emitter-switched bipolar transistor (esbt?) switch (stc03de220hv) and l6565 quasi-resonant pulse-width modulation (pwm) controller. the application is a universal, cost-effective flyback converter used in metering applications, with an excellent wide-voltage input range from 125 to 1250 vdc, achieved using the esbt as the main switch and a quasi-resonant pwm driver. this document is associated with the release of the demonstration board steval-isa057v1 ( figure 1 ). figure 1. steval- isa057v1 www.st.com
contents AN2844 2/37 contents 1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 adapter features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 main characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 waveforms and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4 electrical performances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5 functional check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.1 startup behavior at full loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.2 power-down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.3 short-circuit tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 6 thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7 bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8 pcb layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 9 transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9.1 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9.2 mechanical aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 10 ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 11 conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 12 references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 13 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
AN2844 list of tables 3/37 list of tables table 1. line and load regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 table 2. efficiency at 125 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 table 3. efficiency at 500 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 table 4. efficiency at 1000 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 table 5. power consumption in no-load conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 table 6. temperature of key components at 125 vdc - full load (3 a output current) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 table 7. temperature of key components at 1250 vdc - low load (3 a output current). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 table 8. bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 table 9. winding characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 table 10. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
list of figures AN2844 4/37 list of figures figure 1. steval- isa057v1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 figure 2. electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 3. esbt - internal schematic and symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 figure 4. v in = 125 vdc and maximum output power in steady-state conditions . . . . . . . . . . . . . . . 10 figure 5. v in = 125 vdc and no output power (no load) in steady-state conditions . . . . . . . . . . . . . 11 figure 6. v in = 125 vdc and maximum output power in steady-state conditions - switch-on highlighted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 7. v in = 125 vdc and maximum output power in steady-state conditions - switch-off highlighted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 figure 8. 620 vdc and maximum output power in steady-state conditions . . . . . . . . . . . . . . . . . . . 12 figure 9. 620 vdc and no output power (no load) in steady-state conditions. . . . . . . . . . . . . . . . . . 13 figure 10. 620 vdc and maximum output power in steady-state conditions - switch-on highlighted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 11. 620 vdc and maximum output power in steady-state conditions - switch-off highlighted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 figure 12. 1250 vdc and maximum output power in steady-state conditions . . . . . . . . . . . . . . . . . . 14 figure 13. 1250 vdc and no output power (no load) in steady-state conditions. . . . . . . . . . . . . . . . . 15 figure 14. 1250 vdc and maximum output power in steady-state conditions - switch-on highlighted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 15. 1250 vdc and maximum output power in steady-state conditions - switch-off highlighted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 figure 16. efficiency versus output power at v in = 125 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 17. efficiency versus output power at v in = 500 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 18. efficiency versus output power at v in = 1000 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 19. connector description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 20. startup at 125 vdc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 21. power-down at 125 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 22. short-circuit test at v in = 125 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 23. short-circuit test at v in = 620 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 24. short-circuit test at v in = 1250 vdc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 25. silk screen - top side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 26. silk screen - bottom side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 27. copper tracks - top side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 28. copper tracks - bottom side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 29. electrical diagram of the transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 figure 30. winding position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 figure 31. hole arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
AN2844 adapter features 5/37 2 adapter features 2.1 main characteristics the following is a list of the specifications and main parameters of the demonstration board. minimum input voltage: 125 vdc maximum input voltage: 1250 vdc output voltage: 5 v - 3.0 a maximum output power: 15 w short-circuit protection based on auto-restart feature minimum switching frequency limited to 30 khz overall converter efficiency > 60% non-galvanic isolated solution used in most metering applications pcb type and size: ? material used for pcb: fr-4 ? double-sided layout ? thickness of copper: 35 m ? total diameter of demonstration board: 58 x 120 mm. 2.2 circuit description this device is a flyback converter, a very popular and well-known topology in switch-mode power supply applications where the required output power is in the range of 5 to 200 w. the popularity of this type of converter comes from the simplicity of its design, the small number of components and its resulting low cost compared to other topologies in the same output power range. the converter is based on the l6565 pwm driver that operates in quasi-resonant mode, meaning zero voltage or valley switching during the turn-off phase. current mode control is the primary control method. an esbt switch must be used for this application. the esbt is a cascade configuration of a high-voltage bipolar junction transistor (bjt) and a low- voltage power mosfet. stmicroelectronics? optimizes the performance of both devices and offers this kind of switch in one single package so as to simplify the application?s design, reduce electromagnetic interference and price, and increase reliability and performance (see figure 3 ). the esbt switch, compared to a high-voltage switch, offers a low on-state voltage drop like a bjt. the switch is very robust, easy to drive and has a relatively fast switching speed similar to that of a mosfet. for more detailed information on the design of the discontinuous conduction-mode flyback converter, refer to the application note an1889 " esbt stc03de170hv in 3-phase aux iliary power supply ".
adapter features AN2844 6/37 figure 2. electrical diagram d8 bav103 d10 18 v f1 fuse 1 a 100 pf c14 100 nf c5 10 nf c10 470 pf c17 33 f c8 450 v cs 4 gnd 6 comp 2 inv 1 v ff 3 out 7 v cc 8 zcd 5 u1 l6565 r1 10 ? 200 k ? r8 10 k ? r42 200 k ? r13 470 ? r39 3.9 ? r33 910 ? / 0.6 w r22 270 k ? r40 22 ? r26 3.9 ? r34 1.5 ? r20 22 k ? r41 1 k ? r32 10 k ? r35 10 k ? r38 n.c. r5 d4 stps1150 1 2 j2 connector out 5 v / 3 a gnd + primary lp = 5.8 mh 15 w smps 5 v / 3 a secondary 680 k ? r10 68 f / 25 v c15 10 nf c16 np / ns = 70.2 primary 1 2 3 j1 connector in 33 f c11 450 v 200 k ? r17 200 k ? r23 33 f c13 450 v 200 k ? r28 200 k ? r30 1.8 m ? r9 1.8 m ? r14 1.8 m ? r18 1.8 m ? r24 1.8 m ? r29 1.8 m ? r31 56 k ? r4 56 k ? r6 56 k ? r15 56 k ? r19 56 k ? r25 1000 f c3 1000 f c4 56 k ? r11 56 k ? r12 aux. 1 2 12 10 3 4 6 7 t1 transf_etd_29 1 2 4 3 q2 stc03de220hv q4 stp03d200 q5 bc847 d3 stps10l60 d1 bav103 100 nf c2 2.2 f c9 q6 bc847 q7 bc847 d6 bav103 33 k ? r37 12 k ? r16 12 k ? r21 33 pf c18 120 k ? / 0.6 w r2 120 k ? / 0.6 w r3 2.2 nf / 2000 v c1 d2 stth112 d5 stth112 2.2 k ? r7 d7 15 v 68 nf c6 47 f / 50 v c7 q3 bc847 82 k ? r27 910 ? r36 12 nf c12 d9 bav103 q1 2stf1360 47 nf c19 am003536
AN2844 adapter features 7/37 the operational voltage of the converter ranges from 125 to 1250 vdc, which enables the demonstration board to be used in various technologies, particularly in metering applications. the output voltage is 5 v and the maximum output power is 15 w. the board is protected with a 1-a fuse in the primary area. a negative temperature coefficient (ntc) resistor is inserted in series with the input line to protect the demonstration board from inrush current. for voltage purposes on the input dc line, the main 450 v filtering capacitors are connected in series. figure 3. esbt - internal schematic and symbol a non-dissipative active startup circuit has been implemented to optimize the converter?s efficiency. the alternative option of using a pure resistive startup circuit was rejected due to unacceptable power losses. the active startup circuit has been designed with q4, q5 and related passive parts. the r4, r6, r11, r15, r19 and r25 resistors provide the supply current to the pwm driver during the start-up phases and have been calculated from the minimal input supply voltage of the converter and required supply current of the pwm controller l6565, plus the related supply current required to charge the c15 filtering capacitor within a reasonable time to maintain an acceptable startup time. the balance resistors r8, r13, r17 and r23 are used to ensure the same voltage drop across each input capacitor. r28 and r30 supply the current into the base of the q4 high-voltage darlington transistor. when the rising voltage on the c15 capacitor reaches the start-up threshold of the l6565 pwm controller, the voltage on the transformer's auxiliary winding turns on the q5 transistor, which in turn shorts the base of the q4 transistor. this means that the active startup is blocked. the main power dissipation under normal working conditions of the startup circuit is due to the balance resistors. refer to an2454 " universal input voltage power supply for esbt-based breaker and metering applications " for more information on active startup issues. the self-supply circuit that provides the supply energy to the controller has been built around q1, which acts as a linear voltage regulator. this voltage regulator offers a stable output supply voltage, which guarantees the performance of the converter?s overall input voltage range at very low or no loads. the voltage regulator is mandatory in such applications with a wide input voltage range. the value of the auxiliary voltage is set with the zener diode d7 and is approximately 14.5 v. the primary side of the converter incorporates the l6565 pwm controller that includes all the features required for building a complete system working in qr mode with a minimal number of external components. information relating to the zero voltage switching comes from the transformer?s auxiliary winding. the auxiliary winding is also used for the controller?s self-supply. to keep a relatively constant output power across the entire input voltage range, the line voltage is fed through resistors r9, r14, r18, r24, r29 and r31 into the line voltage feed-forward pin (v ff ) of the l6565. c c b b g g s s am003535
adapter features AN2844 8/37 this information is used to change the set point of the pulse-by-pulse current limitation. in the standard application circuit with l6565 as u1, an off-time limitation circuit with a q3 transistor has been added. this transistor limits the maximum switching frequency of the converter to approximately 70 khz. the input information coming from the out pin is fed into q3 with a delay. this feature provides some anticipated time during the off time by blocking the zcd pin of the converter, and enables the reflected voltage on the auxiliary winding to be sensed after that time. this means that the controller has skipped one or several valleys of the flyback voltage during the turn-off phases and has limited the maximum switching frequency. the circuit?s time constant is set with capacitor c12 and resistor r36. the limitations of the application?s frequency keep power losses on the primary esbt switch within reasonable values and contribute to the converter?s overall stability. refer to the l6565 datasheet for detailed information on the l6565 and function of the circuit. all features, including the calculation of all setting components, are described in stmicroelectronics? application note an1326 " l6565 quasi-resonant controller ". this application note also describes the zvs concept. the output voltage is controlled by a non-galvanic isolated primary feedback loop with resistor dividers r38 and r42, and frequency response compensation components r39, r40 and c14. all formulas related to the calculation of the frequency response compensation during first trials and testing in this type of application are described in stmicroelectronics? application note an2495 " 80 w very wide input voltage range 3-phase smps design based on l6565 and esbt stc04ie170hv ". in smps applications, where the load can vary, the current of the primary switch also fluctuates. to minimize power losses on the esbt switch, the base current should be proportional to the collector current or at least constant with the initial current overpeak of the switching pulse - this is called the modifying envelope. it is important to avoid radical over-saturation of the device at low loads and aim to optimize performance at full loads. to achieve these driving requirements with a cost-effective solution, a simple driving circuit providing a constant current into the base of the esbt has been designed. this type of solution is simple, cost-effective and minimizes power losses. the bias current for the base of the esbt is provi ded directly by the auxilia ry power supply through the r22 resistor. for a related base bias current, the value of this resistor is calculated according to the collector current. according to the stc03de220hv datasheet, for a maximum peak collector current of 0.6 a, the gain and related base current should be 16 ma. during the storage time, when the collector current for a certain period flows trough the b-c junction before this junction recovers from conduction, the current flows into the c10 capacitor which stores some energy and provides it again for the next swit ching cycle to create an initial base current spike. current that is not stored can also flow through d8 to the auxiliary supply area. note that during the storage time the collector current flows through the base and is stored in the base capacitor c10, so that the quasi totality of energy is recovered. the r20 resistor limits the inrush current floating from the c10 capacitor to the base of the q2 transistor. in this topology, the base current always has the same value and does not follow the variation of the collector current, which appears while unloading the output. the constant base bias current can cause over-saturation of the bjt structure in the esbt in low- or no-l oad conditions. however, in a case like this, the driver guarantees the appropriate switching of the esbt thr ough the zvs pin when the device is fully switched off and the carriers in the bjt are fully recombined. this solution ? which is very simple and cost-effective ? implies that the esbt be driven with a constant current.
AN2844 adapter features 9/37 esbts with this type of configuration offer very good performance in terms of power losses, and have a low cost compared to other available switches such as very high voltage power mosfets. for further information on driving networks, refer to stmicroelectronics? application note an2454 " universal input voltage power supply for esbt-based breaker and metering applications ". the main t1 transformer used is a layered-type transformer, which uses a standard etd29 core with a bobbin. the etd29 bobbin has been chosen because of its strong voltage isolation capacities at such high input voltages. in terms of just power requirements, an even smaller core area than the etd29 could be used. a sandwich topology has been used for the design of the winding, offering better coupling of windings compared to standard topologies with only one primary winding. this transformer has been designed according to stmicroelectronics? released application notes, with a flyback voltage of 250 v. the turn ratio between the primary and secondary side has been calculated and is approximately 70. refer to an1326 " quasi-resonant controller " and an2495 "8 0 w very wide input voltage range 3-phase smps design based on l6565 and esbt stc04ie170hv" for all necessary calculations. as is common in flyback applications, the total voltage across the switch can reach very high voltages. the calculation is done with the formula: v off = v inmax + v fl + v spike where v fl is the flyback voltage = (v out + vf diode) x np/ns. np is the number of turns on the primary side while ns is the number of turns on the secondary side. v spike is the maximum overvoltage allowed by the clamping network and has been fixed to 200 v. allowing for some margin, a related switch stc03de220hv with a breakdown voltage of 2200 v fills the requir ements for these types of application. a clamp network is used for leakage inductance demagnetization. in this particular case, a c1 capacitor with related passive resistors r2, r3 and blocking diodes d2 and d5 used in series because of voltage stresses, has been selected for this purpose. the secondary side comprises a schottky barrier diode d3 as rectifier, and filtering capacitors c3 and c4 featuring low serial resistance. the short-circuit protection features for the converter have been designed with transistors q7 and q6 and related passive parts. the q7 transistor senses the output voltage through the resistor dividers r38 and r42. in normal conditions, the q7 transistor keeps the q6 transistor turned off. during a short-circuit condition where the output voltage is very low or equal to zero, the q7 transistor is closed. energy stored in the tank capacitor c9 can start to provide the supply current for q6, which starts to block the function of the converter through the l6565?s zcd pin. this condition continues until all the energy from the c9 c apacitor has been discharged. the time cycle is set with the r37 resistor and capacity of c9. once all the energy in c9 has been discharged, the converter starts to work again. if the short connection on the output is still present, the short-circuit protection repeats until the short circuit is removed.
waveforms and results AN2844 10/37 3 waveforms and results figure 4 to figure 15 show the main waveforms in steady-state conditions, and depict the function of the converter with full loads or no loads and with various input voltages. the figures also show the turn-on and turn-off behavior in various conditions. of particular interest is the behavior of the base current, where an initial high-peak pulse is needed to minimize the effect of the dynamic saturation voltage. figure 4. v in = 125 vdc and maximum output power in steady-state conditions
AN2844 waveforms and results 11/37 figure 5. v in = 125 vdc and no output power (no load) in steady-state conditions figure 6. v in = 125 vdc and maximum output power in steady-state conditions - switch-on highlighted
waveforms and results AN2844 12/37 figure 7. v in = 125 vdc and maximum output power in steady-state conditions - switch-off highlighted figure 8. 620 vdc and maximum output power in steady-state conditions
AN2844 waveforms and results 13/37 figure 9. 620 vdc and no output power (no load) in steady-state conditions figure 10. 620 vdc and maximum output power in steady-state conditions - switch-on highlighted
waveforms and results AN2844 14/37 figure 11. 620 vdc and maximum output power in steady-state conditions - switch-off highlighted figure 12. 1250 vdc and maximum output power in steady-state conditions
AN2844 waveforms and results 15/37 figure 13. 1250 vdc and no output power (no load) in steady-state conditions figure 14. 1250 vdc and maximum output power in steady-state conditions - switch-on highlighted
waveforms and results AN2844 16/37 figure 15. 1250 vdc and maximum output power in steady-state conditions - switch-off highlighted
AN2844 electrical performances 17/37 4 electrical performances ta b l e 1 shows the output loads for different input voltages. the maximum difference on the output voltage is only about 50 mv. figure 16 , figure 17 and figure 18 show the converter's efficiency depending on the output load with various input voltage values. figure 16. efficiency versus output power at v in = 125 vdc table 1. line and load regulation output load [a] input voltage 125 vdc input voltage 620 vdc input voltage 1250 vdc 0 5.00 5.01 5.01 0.5 4.99 5.00 5.00 1 4.98 4.99 5.00 1.5 4.97 4.98 4.98 2 4.95 4.97 4.98 3 4.95 4.96 4.97 efficiency / output power 0 10 20 30 40 50 60 70 80 0.00 5.00 10.00 15.00 p out (w) n (%) am003544
electrical performances AN2844 18/37 figure 17. efficiency versus output power at v in = 500 vdc figure 18. efficiency versus output power at v in = 1000 vdc efficiency / output power 0 10 20 30 40 50 60 70 80 0 5 10 15 p out (w) n (%) am003545 efficiency / output power 0 10 20 30 40 50 60 70 80 0 5 10 15 p out (w) n (%) am003546
AN2844 electrical performances 19/37 : table 2. efficiency at 125 vdc load [a] pin [w] p out [w] eff [%] 0 0.27 0.00 0.00 0.2 1.85 0.97 52.43 0.5 3.70 2.45 66.22 0.8 5.62 3.91 69.57 1 6.94 4.88 70.32 1.2 8.27 5.84 70.62 1.5 10.31 7.27 70.51 2 13.94 9.64 69.15 2.5 17.80 11.96 67.19 3 21.93 14.28 65.12 table 3. efficiency at 500 vdc load [a] pin [w] p out [w] eff [%] 00.4700.00 0.2 2.07 0.97 46.86 0.5 4.2 2.46 58.57 0.8 6.19 3.94 63.65 1 7.44 4.9 65.86 1.2 8.7 5.87 67.47 1.5 10.62 7.31 68.83 2 13.89 9.68 69.69 2.5 17.2 11.99 69.71 3 20.57 14.3 69.52 table 4. efficiency at 1000 vdc load [a] pin [w] p out [w] eff [%] 01.500.00 0.2 3.31 0.97 29.31 0.5 5.68 2.46 43.31 0.8 7.99 3.94 49.31 1 9.4 4.91 52.23 1.2 10.49 5.88 56.05 1.5 12.45 7.33 58.88 2 16.37 9.69 59.19 2.5 19.66 12.03 61.19 3 22.94 14.33 62.47
electrical performances AN2844 20/37 ta b l e 5 shows the device?s power consumption in no-load conditions. this board has been designed to work in continuous cycles even with no loads. the reason for this is an improved transfer response of the circuit, a lower output ripple and enhanced stability of the converter. the switching frequency of the zvs control method used with the l6565 varies according to the load and input voltage. this behavior has a positive impact on the switching losses mainly in low-load conditions where the switching frequency rises dramatically to 60 khz, the maximum frequency that the application can tolerate. table 5. power consumption in no-load conditions v in = 125 vdc v in = 500 vdc v in = 1000 vdc pin [w] 0.27 0.47 1.50
AN2844 functional check 21/37 5 functional check figure 19 shows the placement of the input and output connectors on the pcb. figure 19. connector description the following sections describe the main functional parameters of the board. 5.1 startup behavior at full loads figure 20 shows the board?s startup behavior at full loads. figure 20. startup at 125 vdc
functional check AN2844 22/37 5.2 power-down figure 21 shows the reaction of the board when it is unplugged from the mains. the output voltage as well as the auxiliary self-supply voltage have clear transitions with no glitches or restart trials. figure 21. power-down at 125 vdc 5.3 short-circuit tests the following figures depict the board?s behavior when a short circuit occurs on the output connector. throughout the duration of a short-circuit condition, the output voltage is sensed through logic circuits which contain q6 and q7 and the l6565 driver is shut down through pin 5. once all the energy from the c9 capacitor has been discharged, a logical stop reacts on the output voltage and the board starts to operate normally. if the short-circuit condition persists, the whole cycle repeats until the short-circuit condition stops. when a short-circuit connection is removed, the converter starts to operate normally again.
AN2844 functional check 23/37 figure 22. short-circuit test at v in = 125 vdc figure 23. short-circuit test at v in = 620 vdc
functional check AN2844 24/37 figure 24. short-circuit test at v in = 1250 vdc
AN2844 thermal measurements 25/37 6 thermal measurements a thermal analysis of the major components of the board is shown in ta b l e 6 and ta ble 7 . all measurements were performed after one hour of operation. t a : the ambient temperature for all measurements is 25 c. table 6. temperature of key components at 125 vdc - full load (3 a output current) ref. component description temperature [c] r2 ntc 35 d2 clamp resistors (r2; r3) 35 q1 esbt switch stc03de220hv 37 u1 l6565 35 t1 transformer - ferrite 44 t1 transformer - windings 65 q2 output diode 80 c12/c13 bulk capacitors 35 table 7. temperature of key components at 1250 vdc - low load (3 a output current) ref. component description temperature [c] r2 ntc 35 d2 clamp resistors (r2; r3) 45 q1 esbt switch stc03de220hv 75 u1 l6565 35 t1 transformer - ferrite 48 t1 transformer - windings 55 q2 output diode 73 c12/c13 bulk capacitors 35
bill of materials AN2844 26/37 7 bill of materials ta b l e 8 presents the list of components used to build the demonstration board. the majority of components used are available from stmicroelectronics. the main transformer is supplied by egston gmbh. table 8. bill of materials index quantity reference value/generic part number package/class manufacturer 1 1 c1 2.2 nf / 700 vac axialcap-rm 15 mm epcos 2 1 c2 100 nf capacitor, smd 0805 avx 3 2 c3, c4 1000 f / 10 v elyt. capacitor, radial, rm 5 mm rubycon 4 1 c5 100 nf capacitor, smd 0805 avx 5 1 c6 68 nf capacitor, smd 0805 avx 6 1 c7 47 f / 50 v capacitor, smd 0805 rubycon 7 3 c8, c11, c13 33 f / 450 v elyt capacitor, radial, rm 7.5 mm rubycon 8 1 c9 2.2 f / 10 v elyt capacitor, radial, rm 2.5 mm rubycon 9 1 c10 10 nf capacitor, smd 0805 avx 10 1 c12 12 nf capacitor, smd 0805 avx 11 1 c14 100 pf capacitor, smd 0805 avx 12 1 c15 68 f / 25 v elyt capacitor, radial, rm 2.5 mm rubycon 13 1 c16 10 nf capacitor, smd 0805 avx 14 1 c17 470 pf capacitor, smd 0805 avx 15 1 c18 33 pf capacitor, smd 0805 avx 16 1 c19 47 nf capacitor, smd 0805 avx 17 1 r1 10 ? ntc resistor; rm 7.5 mm epcos 18 2 r2, r3 120 k ? resistor 0207; 0.6 w vishay? 19 6 r4, r6, r11, r15, r19, r25, 56 k ? resistor, smd 1206 vishay 20 1 r5 not connected resistor 0207; 0.6 w vishay 21 6 r8, r13, r17, r23, r28, r30 200 k ? resistor, smd 1206 vishay 22 6 r9, r14, r18, r24, r29, r31 1.8 m ? resistor, smd 1206 vishay 23 1 r10 680 k ? resistor, smd 0805 vishay 24 1 r7 2.2 k ? resistor, smd 0805 vishay 25 1 r12 56 k ? resistor, smd 0805 vishay 26 2 r16, r21 12 k ? resistor, smd 0805 vishay 27 1 r22 910 ? resistor 0207; 0.6 w vishay
AN2844 bill of materials 27/37 28 1 r26 22 ? resistor, smd 0805 vishay 29 1 r20 1.5 ? resistor, smd 1206 vishay 30 1 r27 82 k ? resistor, smd 0805 vishay 31 1 r41 22 k ? resistor, smd 0805 vishay 32 1 r32 1 k ? resistor, smd 0805 vishay 33 2 r33, r34 3.9 ? resistor 0207; 0.6 w vishay 34 1 r35 10 k ? resistor, smd 0805 vishay 35 1 r36 910 ? resistor, smd 0805 vishay 36 1 r37 33 k ? resistor, smd 0805 vishay 37 1 r39 470 ? resistor, smd 0805 vishay 38 1 r40 270 k ? resistor, smd 0805 vishay 39 2 r38, r42 10 k ? resistor, smd 0805, 1% vishay 40 4 d1, d6, d8, d9 bav103 diode, minimelf vishay 41 1 d4 stps1150a diode, do-214ac stmicroelectronics 42 2 d2, d5 stth112a hv diode, sma stmicroelectronics 43 1 d3 stps10l60d power schottky rectifier, to-220ac stmicroelectronics 44 1 d7 bzv55c15smd zener diode, sod80, 15 v vishay 45 1 d10 bzv55c18smd zener diode, sod80, 18 v vishay 46 1 q1 2stf1360 npn transistor, sot-89 stmicroelectronics 47 1 q2 stc03de220hv esbt, to247-4l hv stmicroelectronics 48 4 q3, q5, q6, q7 bc847 npn transistor, sot-23 fairchild 49 1 q4 stp03d200 npn darlington, to-220 stmicroelectronics 50 1 u1 l6565d pwm smart driver, so-8 stmicroelectronics 51 1 f1 fuse 1 a fuse with holder, 1 a, slow 52 1 j1 connector ark ark 53 1 j2 ark210/5 mm connector ark ark 54 2 t1 egston 39663 transformer egston etd29 core egston 55 2 het1, het2 v7142a heatsink v7142a pada engineering table 8. bill of materials (continued) index quantity reference value/generic part number package/class manufacturer
pcb layout AN2844 28/37 8 pcb layout the application uses a standard double-layer coppered pcb with a copper thickness of 35 m. the pcb is made of fr-4. the board?s diameters are: length: 124.2 mm width: 65.9 mm thickness of pcb: 1.55 mm figure 25. silk screen - top side figure 26. silk screen - bottom side
AN2844 pcb layout 29/37 figure 27. copper tracks - top side figure 28. copper tracks - bottom side
transformer specification AN2844 30/37 9 transformer specification application type: customer, home appliances winding type: layer coil former: vertical type - 14 pins material of coil former: gfr thermostatic plastic ul 94 v-0 maximum temperature increase: 45 c maximum operating ambient temperature: 60 c mains insulation: according to en60950 9.1 electrical characteristics converter topology: flyback working in boundary mode minimum switching frequency: > 32 khz lp = 5.8 mh np/ns = 70.2 reflected flyback voltage: 400 vdc core type: etd29 - epcos core material: n87 from epcos or similar air gap: 0.60 mm the design of the related power transformer has been further optimized by egston system electronics eggenburg gmbh, manufacturer of the transformer. the ordering type is 39663. figure 29. electrical diagram of the transformer am003547 90 t 90 t 12 t 1 2 3 4 6 7 12 10 1/2 a primary 1/2 b primary auxiliary secondary 3t
AN2844 transformer specification 31/37 for enhanced magnetic coupling, a sandwich topology has been used for the windings. the secondary winding is placed beside the split of the primary winding. the primary winding parts have half the total number of turns and are connected in series. the order of the windings, starting from the winding nearest the core, is: primary - a, secondary, primary - b, and then the top auxiliary winding for the smps? self-supply. figure 30. winding position 9.2 mechanical aspects maximum height from pcb: 40 mm occupied area on pcb: 35 mm x 25 mm coil former: 14 pins diameter of pins: 1.3 mm + 0.1 mm raster of pins: 5 mm figure 31 shows the mechanical arrangement of the transformer. the figure should be viewed from a mounting angle. table 9. winding characteristics pins winding number of turns wire type 1-2 primary - a 90 1 x avg34 10-12 secondary 3 3 x avg24 3-4 primary - b 90 1 x avg34 6-7 auxiliary 12 1 x avg32 3 mm 3 mm auxiliary primary - b secondary primary - a coil former insulation tape am003548
transformer specification AN2844 32/37 figure 31. hole arrangement am003549 mounting holes: 1,5 20 6 x 5.08 top view 1 14 78
AN2844 ordering information 33/37 10 ordering information the application board is orderable online at http://www.st.com/stonline/domains/buy/buy_dev.htm with the order code steval-isa057v1 . the deliverable contains the assembled application board, related documentation, pcb manufacturing data such as gerber and assembly files (pick and place) as well as component documentation.
conclusion AN2844 34/37 11 conclusion this document describes the flyback converter based on the quasi-resonant principle with an esbt switch driven by a constant current. smps is specifically designed for metering applications where wide input voltage ranges are required. the use of an esbt switch as the main switch has the advantage of simplifying the circuit?s design and providing a cost- effective solution.
AN2844 references 35/37 12 references 1. stmicroelectronics l6565 device datasheet. 2. stmicroelectronics stc03de220hv device datasheet. 3. stmicroelectronics application note an1326: l6565 quasi-resonant controller. 4. stmicroelectronics application note an1889: stc03de170hv in 3-phase auxiliary power supply . 5. stmicroelectronics application note an2495: 80 w very wide input voltage range 3-phase smps designed based on l6565 and esbt stc04ie170hv . 6. stmicroelectronics application note an2454: universal input voltage power supply for esbt-based breaker and metering applications .
revision history AN2844 36/37 13 revision history table 10. document revision history date revision changes 13-mar-2009 1 initial release.
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