MR4530 datasheet(28/43 Pages) SHINDENGEN

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Shindengen Electric MFG.CO.,LTD

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6.2 Noise reduction

This section describes noise reduction methods for the MR4000. Check these methods on an actual board to

determine the best combination of methods.

6.2.1 Redesigning the transformer

Redesign the transformer to reduce noise, considering the following factors. Proceed carefully with respect to the

withstand voltage, operating frequency, and other relevant parameters of the main switching device.

(1)

Improve coil contact.

That will reduce ringing at turn-off and reduce noise.

(2)

Increase the ON duty ratio.

Taking full advantage of the partial resonance function will reduce surge currents at turn-on and reduce noise.

(3)

Decrease the operating frequency.

That will reduce noise attributable to fundamental waves or harmonics thereof.

We can reduce noise not only by changing the

location of a Y capacitor or adding a Y capacitor, but

by also changing the capacity. The effect varies with

PCB patterns. Check carefully with an actual board.

(1)

Try changing the location of the Y capacitor at

the filter.

(2)

Connect to ground from the negative side of the

input capacitor.

(3)

Connect to ground from the positive side of the

input capacitor.

6.2.3 Using a snubber circuit

(1)

Add a DCR snubber.

That will lower the peak of a ringing voltage at turn-off and reduce noise.

(2)

Add a damping resistor.

Connect to the resonating capacitor in series. This will advance the damping of

a ringing voltage at turn-off and reduce noise.

(3)

Connect a capacitor in parallel to the DCR snubber diode.

This will reduce noise from the diode handling switching.

Ideally, use a mica or polypropylene capacitor as the capacitors in (2) and (3). A low-

loss ceramic capacitor should also prove adequate. Consult with the manufacturer

before using this type of capacitor.

6.2.2 Changing Y capacitor

AC in

①

②

③

Fig. 6.12 Considerations for Y capacitor

MR4000

①

②

③

Fig. 6.13 Snubber circuit

6. Supplementary design information

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