Si9113DB

Vishay Siliconix

www.Vishay Siliconix.com

S FaxBack 408-970-5600

2

Document Number: 71117

29-Feb-00

POWER UP CHECK LIST AND OPERATION

The Si9113D1 and Si9113D2 are designed to operate in

discontinuous mode at nominal line and load conditions. Both

demo boards use the same operational procedure, as follows:

1

Visually inspect the PCB to be sure that all the components

are intact and no foreign substance is lying on the board.

2

Solder the leads at C1 negative and MOSFET Q1 drain to

monitor the drain waveform on the oscilloscope.

3

Reduce the source voltage to zero and connect it through

application where input is of fixed polarity, the diode bridge

BR1 can be eliminated by shorting pin 1 to 4 and pin 2 to

3 to achieve even higher efficiency.

4

Connect the oscilloscope ground to C1 negative while the

probe to Q1 drain to observe the switching waveforms.

5

Slowly increase the input voltage while monitoring the input

current meter. Note the input current is less than 10

mA at

circuit turns on at approximately 24 V.

6

Set the input voltage to 48 V nominal and monitor the drain

waveform, switching frequency, input and output ripple and

noise.

7

The efficiency, line, load and cross regulation can be

measured by varing the line between 28 to 99 V, and the

load between 10% and 100%.

ACTUAL WAVEFORMS AND PERFORMANCE

Drain Voltage and Current

The circuit is designed to operate in discontinuous mode at

nominal line and full load. The transformer is cleverly designed

to reduce the leakage inductance. Refer to Figure 1 for the

drain voltage and current waveforms. The current starting from

zero indicates the discontinuous mode operation and absence

of any leakage spike at drain shows the tight coupling between

the windings.

Outputs – Full lLoad

Ch1 – Primary Current (0.1A/div)

Ch3 – Drain Voltage (20 V/div)

FIGURE 1. Drain Voltage and Current Waveform – Si9113D2

36.00

37.00

38.00

39.00

40.00

41.00

42.00

43.00

44.00

0

3.00

6.00

9.00

12.00

15.00

3.3 V @ 12 mA

3.3 V @ 120 mA