AN1537 Datasheet, PDF (6/18 Pages) STMicroelectronics – A SIMPLE TRICK ENHANCES

AN1537 APPLICATION NOTE
Figure 5. 45W AC-DC adapter: f_sw vs. I_out (left); P_in (@ P_out = 0) and f_sw vs. ambient temperature (right)
fsw [kHz]
100
Tamb = 25 °C
50
Vin = 110 Vac, 230 Vac
30
20
10
5
3
0.001
0.01
0.1
1
Iout [A]
fsw [kHz]
7
6
fsw Pin
5
4
Pout = 0 W
Vin = 264 Vac
3
-20
0
20
40
Tamb[°C]
Pin [W]
0.58
0.57
0.56
0.55
0.54
60
80
Figure 6. 45W AC-DC adapter: waveforms @ P_out = 45W
RCT (pin 2 of L5991)
RCT (pin 2 of L5991)
Q1 Drain
Q1 Drain
Vin = 110 Vac, Pout = 45W
Vin = 220 Vac, Pout = 45W
Figure 7. 45W AC-DC adapter: waveforms @ P_out = 7W, just after the abrupt frequency shift
RCT (pin 2 of L5991)
RCT (pin 2 of L5991)
Q1 Drain
Q1 Drain
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Vin = 110 Vac, Pout = 7W
Vin = 220 Vac, Pout = 7W