ST AN828 Application note
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AN828 |
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APPLICATION NOTE |
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1500W - 440V POWER FACTOR CORRECTOR |
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PREREGULATOR |
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The application here described has been tailored to supply a three phase inverter for motion control (see fig.1). To reduce the current in the switches of the inverter, the output voltage of the power factor has been held quite high.
The target specification of the PFC application is:
Mains supply Vin(rms) |
= 220Vac ±20% |
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(f = 50/60Hz) |
Output Voltage Vout |
= 440Vdc |
Output Power Pout |
= 1500W |
A switching frequency of 60kHz has been chosen as a good compromise between requirements of small size magnetics and low switching losses.
For this application a full isolated ISOTOP(TM) STE30NA50-DK has been used.
This module is especially intended for boost applications and consists off the integration of a low RDS/500V Mosfet with a TURBOSWITCH(TM) diode.
The use of the module allows a compact and ef-
Figure 1: Schematic Diagram
fective solution in terms of layout and power dissipation. The output stage of the L4981A/B is capable of driving directly the module without the aid of a buffer stage. The L4981A controller is supplied by the auxiliary of the boost inductor, a Graetz bridge and a simple resistor for the startup phase. The Output capacitor filter has been realized connecting in parallel four tap in "series" configuration. This solution allows the use standard parts, in terms of the rated voltage, resulting easier to be implemented in comparison with a "single" configuration. To be noted that the high frequency filter (C1 + C2) has been split in two parts. In this way it is possible to held a low value capacitor (C2) connected to the output of the rectifier bridge, minimising the harmonic distortion (introduced by the rectified DC contents). On the other hand, the capacitor (C1) connected to the AC side of the bridge, performs most of the high frequency filter function without introducing DC content.
The schematic circuit is shown in fig.1
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T |
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C2 |
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220nF |
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- |
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R4 |
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R3 |
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FUSE |
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75K |
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1M |
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10A/250V |
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1W |
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R5 |
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BRIDGE |
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47 |
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KBPC25-04 |
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500mW |
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C1 |
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Vi |
2.2μF |
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250V |
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- |
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4 |
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19 |
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176VAC/265VAC |
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1 |
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7 |
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6 |
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11 |
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R1 |
2 |
8 |
5 |
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5.1K |
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1% |
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R6 100K |
C3 |
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5% |
330nF |
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R2 |
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R8 |
R9 |
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220 |
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3.9K |
3.9K |
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1% |
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5% |
5% |
RS 10mΩ
Transformer
Core: THOMSON - CSF GER55x28x25
Gap: 3.1mm for a total primary inductance of 440μH
Primary: 42 turns of 8x0.5mm (#24 AWG)
Secondary: 4 turns of #27 AWG (0.15mm)
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STE30NA50-DK |
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D2 |
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R14 |
R16 |
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4 x |
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820K |
909K |
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1N4150 |
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1% |
1% |
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Dz 18V 500mW |
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C6 330nF |
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C4 220μF 25V |
R10 120K 5% |
R11 3.9K 5% |
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Rx |
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13 |
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14 |
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150K |
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3 |
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L4981A |
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Rx |
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R12 15 5% |
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150K |
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20 |
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R13 |
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1 5% |
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9 |
18 |
17 |
12 |
10 |
D3 |
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1N4150 |
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R15 |
R17 |
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10K |
10K |
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1% |
1% |
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C5 |
R7 |
C7 |
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105nF |
27K |
10μF |
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1% |
16V |
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D95IN249C |
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Po=1500W
Vo=440V
4 x
470μF
315V Co
1μF
4 x 630V
470μF
315V
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October 2002 |
1/3 |
AN828 APPLICATION NOTE
L4981A PARTS LIST
Boost inductor (T) L = 0.44mH |
Rs = 10mΩ /1W |
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Core :Thomson - E 55x28x25 |
R1 |
= 5.1kΩ /1% |
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Gap = 3mm |
R2 |
= 220Ω /1% |
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Primary Turns = 42 (8 x 0.5mm) |
R3 |
= 75kΩ/1Ω |
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Secondary Turns = 4 (0.15mm) |
R4 |
= 1M |
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R5 |
= 47 /1/2Ω |
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Co= 940μF = [(4 + 4) x 470μF/315V + 1μF/630V] |
R6 |
= 100kΩ |
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R7 |
= 27k /1% |
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C1 |
= 2.2μF/250Vac |
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C2 |
= 220nF/630V |
R8 |
+ R9 = 3.9kΩ |
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R10 |
= 120kΩ |
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C3 |
= 330nF |
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R11 |
= 3.9kΩ |
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C4 |
= 220μF/25V |
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R12 |
+ R13 = 15Ω |
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C5 |
= 1.5nF |
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R14 |
= 820kΩ /1% |
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C6 |
= 330nF |
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R15 |
= 10kΩ /1% |
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C7 |
= 10μF |
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R16 |
= 909kΩ |
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Power Switch = STE30NA50-DK |
R17 |
= 10kΩ |
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Input Bridge = KPBC25-04 |
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D2 |
= 1N4150 (X 4) |
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D3 |
= 1N4150 |
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Table 1: Test Result.
Mains rms |
Vout |
Pout |
Power |
Harmonic Distortion (%) |
Efficiency |
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(V) |
(V) |
(W) |
Factor |
THD |
AH3 |
(%) |
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176 |
451 |
509 |
0.998 |
2.0 |
1.9 |
94.2 |
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176 |
444 |
937 |
0.999 |
1.4 |
1.3 |
94.0 |
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176 |
438 |
1396 |
0.999 |
1.0 |
0.9 |
94.0 |
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220 |
451 |
509 |
0.996 |
2.1 |
1.9 |
95.6 |
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220 |
445 |
941 |
0.998 |
1.5 |
1.4 |
95.2 |
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220 |
438 |
1396 |
0.999 |
1.0 |
0.9 |
95.3 |
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260 |
452 |
511 |
0.993 |
2.5 |
1.9 |
95.1 |
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260 |
446 |
945 |
0.997 |
1.4 |
1.3 |
96.4 |
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260 |
439 |
1402 |
0.999 |
1.1 |
0.8 |
96.1 |
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CONCLUSIONS
The evaluation has been done using the "A" version of the L4981 controller, without using additional features obtaining high performance results, in terms of efficiency and harmonic content.
Further improvements are possible using the additional features of the I.C. such as the LFF (pin 16) for the best control of the output voltage or by the use of the B version to minimise the EMI filter.
2/3
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