Full load test

AN1513

8/13

3

Full load test

The parameters checked at full load have been the efficiency and main working parameters

the minimum voltage ripple on the bulk capacitor when the power supply is connected to the

ac mains.

The drain voltage spike reaches its maximum value at full load and maximum input voltage.

This spike is caused at turn-off by the energy stored in the primary leakage inductance of

power transformer with a primary leakage inductance as low as possible. In addition a good

coupling between primary and secondaries improves total regulation, especially in SMPS

with more than one output.

Figure 2.

Adjustment for frequency reduction

The maximum peak voltage measured on the drain is 642 V, thanks to the clamp

1.5KE220A. This value guarantees a reliable operation of VIPer with a good margin with

able to withstand a momentary energy peak caused by voltage greater than 700 V.

R2

18R

R1

15K

C14

22nF

C13

2.2nF

C9

22nF

R8

68K

R9

15K

R10

18K

Q1

BC546

D7

BZX79-4V3

OSC

1

SOURCE

COMP

VDD

DRAIN

IC1

VIPer50A-E

Figure 3.

Drain current at full load

Figure 4.

Voltage current at full load