ZXGD3104EV2

Issue 1 – October, 2011

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2

Evaluation guide

There are two possible test setups for the evaluation board. The preferred setup is low side

synchronous rectification (see Figure 2b), due to the ease of acquiring the supply voltage to the board

directly from the output of the power supply. The other option is shown in Figure 3a. Figure 3a shows

the board driving a MOSFET for high side rectification.

Low side synchronous rectification

1.

Remove the original Schottky from the power supply

2.

Apply a short across the Schottky’s K and A terminals

3.

Cut the track that connects the negative terminal of the output filter capacitor to the output of

the transformer winding.

4.

Insert a low on-resistance MOSFET between the cut tracks. The Drain terminal of the

MOSFET should be connected to the output of the transformer winding, whilst the Source

terminal is connected to the output capacitor.

Caution: The MOSFET breakdown must be higher than the maximum Drain-Source voltage

spike, plus a 10% to 30% margin.

5.

Connect the power supply’s output voltage, 19V, to the terminal block P1 (see Figure 2b).

6.

Connect an AC voltage source to the power supply’s input.

7.

Turn on the AC voltage source and measure the efficiency.

High side synchronous rectification

8.

Remove the original Schottky from the power supply

9.

Insert a low on-resistance MOSFET to replace the Schottky. The Source terminal of the

MOSFET should be connected to the output of the transformer winding, whilst the Drain

terminal should be connected to the output capacitor

10. Connect a 10V auxiliary supply to terminal block P1 (see Figure 2a).

11. Connect an AC voltage source voltage to the power supply’s input.

12. Turn on the power supply and measure the efficiency.

(a)

(b)

Figure 2: Test options for evaluation board a) high side rectification and b) low side

rectification