1、June 2015 DocID026993 Rev 3 1/2626AN4599Application noteSTEVAL-ISA132V1 24 V 300 W peak power resonant converterby Riccardo TosoniIntroductionThis application note describes the features of the STEVAL-ISA132V1 evaluation board at 24 V, 300 W peak power conversion.The architecture is based on a singl
2、e-stage LLC resonant converter without PFC using the new L6699 resonant controller.The L6699 integrates some very innovative functions such as self-adjusting adaptive dead time, anti-capacitive mode protection and a proprietary “safe-start“ procedure which prevents hard switching at start-up.Thanks
3、to the chipset used, the main features of this power supply are: very high efficiency under high-load and low-load conditions safe start up procedure to avoid hard switching hard switching prevention under overload and low-load conditions burst mode under low-load conditions with smooth restart to p
4、revent audible noise the demo board can deliver more than 300 W peak power for a limited time thanks to the NTC thermal protection positioned near the output diodes. continuous power at 30C ambient temperature is 170 W. the MOSFET and diode power devices are in DPAK packagesFigure 1. STEVAL-ISA132V1
5、 300 W peak power SMP evaluation Contents AN45992/26 DocID026993 Rev 3Contents1 Main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.
6、1 Start-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2 Oscillator setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.3 Burst mode operation at no load or very light load . . . . . . . . . . . .
7、. . . . . . . 62.4 Brown out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.5 Overload and short circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.6 Thermal protection . . . . . . . . . . . . . . . . . . . . . . .
8、. . . . . . . . . . . . . . . . . . . . 93 Power components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Magnetic components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Functional and thermal test . . . . . . . . . . . . .
9、. . . . . . . . . . . . . . . . . . . . . 146 Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Bill of material . . . . . . . . . .
10、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Thermal measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2210 EMC precompliance test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2311 Conclusion and re
11、marks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2412 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25DocID026993 Rev 3 3/26AN4599 Main features261 Main featuresThe main features of the SMPS are: input mains range:
12、 from 190 to 264 VAC - frequency 50 Hz output voltage: 24 V 5% no-load consumption: 92% EMI: Within EN55022 Class-B limits conducted precompliance safety: Meets EN60950-1 dimensions: 90 x 90 mm, 50 mm component maximum height weight 220 grThe circuit consists of a single stage LLC resonant converter
13、.The MOSFET and diode power components are in DPAK packages.The L6699 integrates all the functions necessary to control the resonant converter with a 50 % fixed duty cycle and working with variable frequency.Circuit description AN45994/26 DocID026993 Rev 32 Circuit description2.1 Start-up sequenceD1
14、2, D4, R7, C13 in Figure 13 form the start-up circuit.When the VCC voltage reaches L6699 VCCon, the system begins the start-up sequence and changes the switching frequency from fstart to the operative frequency.2.2 Oscillator settingFigure 2. Oscillators internal block diagramThe oscillator is progr
15、ammed externally by means of a capacitor connected from pin 3 (CF) to ground that is alternately charged and discharged by the current defined with the network connected to pin 4 (RFmin).The pin provides an accurate 2 V reference with approximately 2 mA source capability; the higher the current sour
16、ced by the pin, the higher the oscillator frequency.The Figure 2 block diagram shows a simplified internal circuit explaining the operation.Table 1. Recommended values for CF as a function of the start-up frequency fstartfstart kHz CF pF fstart kHz CF pF150 680 230 - 240 180160 560 250 150170 470 26
17、0 120180 390 270 100190 - 200 330 280 82210 270 290 68210 220 300 56$0Y/95)PLQ the IC resumes normal operation when the voltage on pin exceeds 1.26 V + 30 mV.To implement burst mode operation, the voltage applied to the STBY pin needs to be associated with the feedback loop.The resonant converter sw
18、itching frequency and hence burst mode activation strongly depends on the variation of the input voltage.Use the circuit in Figure 3 when the input voltage range is quite large.Due to the high non-linear relationship between the switching frequency and input voltage, it is more practical to empirica
19、lly determine the correct magnitude for RA/(RA+RB) correction and RFmax to obtain an almost constant burst mode threshold in all input voltage ranges.In this application, we obtained a good compromise with RA = 56 k, RB = 150 k and RFmax = 3.3 k.Figure 3. Wide input voltage range schematic$0Y/67%5)P
20、LQ5)PLQ 5)PD/,1(5$%5%5/5+5$ 5%!5/DocID026993 Rev 3 7/26AN4599 Circuit description26With reference to the schematic in Figure 13: RA = R26 = 56 k RB = R6 = 150 k RH = R1 + R5 = 3 M RL = R8 = 27 k2.4 Brown outReferring to Figure 13, the Line pin is connected to the high voltage input bus with a resist
21、or divider: R1, R5 and R8.The partition is slightly influenced by resistors R6 and R26.A voltage below 1.25 V shuts down the IC and consequently lowers consumption and discharges the soft start capacitor.IC operation is enabled when the voltage exceeds 1.25 V the comparator is provided with current
22、hysteresis: an internal 13 A current generator remains on while the voltage applied at the Line pin is below 1.25 V.Test results:Decreasing VIN shut down is 100 VAC2.5 Overload and short circuit protectionReferenced to Figure 4.In the L6699, the current sense input ISEN (pin 6) monitors the current
23、flowing in the resonant tank to perform multiple tasks:1. primary overcurrent protection2. hard-switching cycle prevention at start up3. hard-switching cycle prevention during operationThe ISEN pin is able to withstand negative voltages in order to observe the voltage and current of the resonant tan
24、k.ISEN is internally connected to the input of a first comparator referenced to VISENX (0.8 V typ.) and a second comparator referenced to 1.5 V.If the voltage applied to ISEN exceeds 0.8 V, the first comparator is tripped which in turn activates an internal switch for 5 s, thus discharging the soft-
25、start capacitor CSS.This increases oscillator frequency, limiting the energy transfer.The circuit shown in Figure 4 operates as a capacitive current divider.Cs is typically selected with a value around Cr/100 and the sense resistor is selected as: RS=0.77/Icrpkx*(1+Cr/Cs).The OCP limits primary to s
26、econdary energy flow in case of overload or short circuit, but the output current in the secondary winding and in the rectifiers can still rise to dangerous levels.To prevent any damage and reduce power loss, the converter must be forced to operate intermittently.Circuit description AN45998/26 DocID
27、026993 Rev 3The DELAY pin manages the timing of the overcurrent protection.A resistor and a capacitor are connected from this pin and GND to set the maximum duration of an overcurrent condition before the IC stops switching and the delay after which the IC restarts switching.Every time the voltage o
28、n the ISEN pin exceeds 0.8 V, the capacitor on the DELAY pin is charged by 350 A and is slowly discharged by the external resistor. If the voltage on the DELAY pin riches 2 V, the soft start capacitor is completely discharged to push the switching frequency to its maximum value and a 350 A current s
29、ource is kept on. When the voltage on the DELAY pin exceeds 3.5 V, the IC stops switching and internal 350 A generator is turned off, causing the voltage on the pin to decay because of the external resistor.The IC enters soft-restart when the voltage drops below 0.3 V.In this way, the converter unde
30、r short-circuit or overload condition works intermittently with very low input average power.If the ISEN pin voltage exceeds 1.5 V, the L6699 is immediately stopped and the 350 A current source is kept ON until the DELAY pin voltage reaches 3.5 V, at which time the generator is turned OFF and the vo
31、ltage on the pin decays because of the external resistor; also in this case the IC enters soft-restart when the voltage drops below 0.3 VIs not easy to find a relationship that links charging time to the CDELAY value, so it is more practical to determine CDELAY experimentally.To give an approximate
32、indication: the time to reach 2 V on the DELAY pin is 100 ms every 1 F; the time from 2 V to 3.5 V is about 4.3*CDELAY; the time to discharge CDELAY pin from 3.5 V to 0.3 V is about 2.4*RDELAY*CDELAY.Referring to Figure 13, the resistor and capacitor on the DELAY pin are C21 = 470 nF and R29 = 330 k
33、.The protection times are: approx. 50 ms: slowly increase frequency approx. 1.8 s force frequency to fstart about 370 ns: switching is stoppedIf the overload is less than 50 ms, the system functions as a power limiter without shutdown.DocID026993 Rev 3 9/26AN4599 Circuit description26Figure 4. Curre
34、nt sensing lossless capacitive current divider2.6 Thermal protectionTo render the application unbreakable, it was necessary to apply thermal protection near the output diodes, the warmest area on the power (PWR) supply.A thermal resistor NTC2 in partition with the R2 resistance is processed by a TSM
35、103W, used as comparator with high hysteresis.When the output diodes reach 120 C, the output of TSM103W drives Q3 to drain the current from the optocoupler. The PWR supply shuts off and stays off as long as TSM103W is supplied./,6(1 they reduce losses from switching turn-off commutation and reduce t
36、he current consumption due to Qg.The D3 and D5 STPS20H100CG diodes are optimized to balance leakage current and voltage drop; they are avalanche rated with a high-junction temperature capacity of 175 C.DocID026993 Rev 3 11/26AN4599 Magnetic components264 Magnetic componentsFigure 5. Transformer (Cod
37、e 05801 Class Code 1860.0044 Magnetica)Table 2. Pin functionsPin n Function Pin n Function1 Not connected 8ASecondary A200 W MAX 24 V 8.3 A2 Primary Drain/source 9A3 Not present 10BGround secondary4 Primary with CR 11B5 Not present 12B6 Auxiliary (12 V 50 mA) 13CSecondary B7 Auxiliary ground (12 V 5
38、0 mA) 14CMagnetic components AN459912/26 DocID026993 Rev 3Figure 6. Transformer electrical diagram and featuresFigure 7. Common mode inductor (Code 07228 Class Code 2258.0001 Magnetica) inductance (1-2 = 4-3) 10.5 mH min (measured 1 kHz, TA 20 C) resistance (1-2 = 4-3) 240 m max (measured DC, TA 20
39、C) leakage inductance 0.53% nom (measured 1-2 and 4-3 in S.C, F 10 kHz, TA 20 C) operating current 1.8 A max (measured 1-2 and 4-3,TA 20 C) operating frequency 5060 Hz (current 1.8 A Max, TA 20 C) insulation (1-2 4-3) 1500 V max (F 50 HZ, duration test 2“, TA 20 C) ambient temperature range: 20 C to
40、 +85 CDocID026993 Rev 3 13/26AN4599 Magnetic components26 (IR 1.8 A max, with self trise 45 C) thermal CLASS B storage temperature range: 20 C to +85 C maximum dimensions: 25.4 x 19, H 28 mm, weight 18 g approx.Functional and thermal test AN459914/26 DocID026993 Rev 35 Functional and thermal testAll
41、 the measurements are typical and performed at 30 C ambient temperature.Thermal testing is performed starting with a power of 100 W applied for 30 min.Table 3. Functional and thermal testTest 190 Vac 230 Vac 265 VacFunctional Tstart (sec) 3.9 3 2.2Functional Pin no load (W) 1 0.6 0.5Functional load
42、6.5 A (%) 91 92 93Functional load 3.5 A (%) 91.5 92.5 93.5Functional Freq load6.5A (kHz 66 80 98Functional ILimit (A) 12 13.5 16Thermal Delay time thermal protection 200 W (sec) 45Thermal Delay time thermal protection 250 W (sec) 32DocID026993 Rev 3 15/26AN4599 Waveform266 WaveformFigure 8. IRES & V
43、HB load 6.5 A VIN min.Figure 9. IRES & VHB load 6.5 A VIN nom.Waveform AN459916/26 DocID026993 Rev 3Figure 10. IRES & VHB load 6.5 A VIN maxFigure 11. Startup 230 VACDocID026993 Rev 3 17/26AN4599 Waveform26Figure 12. Short circuit 230 VAC full loadElectrical diagram AN459918/26 DocID026993 Rev 37 El
44、ectrical diagramFigure 13. Electrical diagram*63*6*4514)$(4514)$(DocID026993 Rev 3 19/26AN4599 Bill of material268 Bill of materialTable 4. Bill of materialType/Value Modifier Part number Manuf. Description Qty Reference IDsNM 50V Generic Generic Generic capacitor - 0805 1 C20NM 50V Generic Generic
45、Generic capacitor - 1206 1 C29100pF 1KV Generic Generic Generic capacitor - 1206 2 C7, C17220pF 1KV Generic Generic Generic capacitor - 1206 1 C28220pF 50V Generic Generic Generic capacitor - 0805 1 C19560pF 50V Generic Generic Generic capacitor - 1206 1 C222.2nF 300Vac Y2 PHE850EA4220MA01R KEMET Ge
46、neric capacitor - P10.0 2 C1, C52.2nF 300Vac Y1 Generic KEMET Generic capacitor - P10.0 2 C152.2nF 50V Generic Generic Generic capacitor - 0805 1 C2315nF 1.5KV B32652A1153J EPCOS Generic capacitor - P15.0 2 C4, C2733nF 50V Generic Generic Generic capacitor - 0805 1 C25100nF 50V Generic Generic Gener
47、ic capacitor - 0805 2 C12, C14100nF 50V Generic Generic Generic capacitor - 1206 1 C16470nF 275Vac X2 Generic Generic Generic capacitor - P15.0 2 C2 C3470nF 50V Generic Generic Generic capacitor - 0805 1 C211F 50V Generic Generic Generic capacitor - 1206 1 C184.7F 16V Generic Generic Generic capacit
48、or - 0805 1 C2668F 35V Generic Generic Generic polarized capacitor -P3.5 1 C24100F 35V Generic Generic Generic polarized capacitor -P3.5 1 C13390F 400V Generic Generic Generic polarized capacitor -P10.0 1 C6470F 35V Generic Generic Generic polarized capacitor -P5.0 4 C8, C9, C10, C11KBU8M - Generic Generic Full-wave Bridge rectifier 1 D1LL4148 - Generic Generic Generic small signal diode - SOD80 5 D2, D4, D6, D8, D10NM - Generic Generic Zener diode - SOD123 1 D7NZH15B-115 15V NZH15B-115 NXP Zener diode - SOD123 1 D9STPS20H100CG 20A - 100V STPS20H100CG
