MR4530 datasheet(10/43 Pages) SHINDENGEN

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Shindengen Electric MFG.CO.,LTD

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3.5 Output voltage control (normal operation)

The MR4000 Series controls output voltage with an

ON range proportional to voltage at the F/B pin.

Controlled linearly, the ON range is ton(min) when the

voltage at the F/B pin is 1.5 V and becomes ton(max)

when the voltage is 4.5 V. A current of IF/B flows at

the F/B pin. The impedance of the photocoupler

transistor connected externally between the F/B pin

and GND varies depending on the control signal from

the secondary output detection circuits, which

controls the ON range of the main switching device to

produce a constant voltage.

The maximum ON range is limited by setting the

maximum value for the voltage at the F/B pin using a

resistor connected externally between the F/B pin

and GND. Thus, the droop point is determined.

3.6 Soft drive circuit (patent pending)

The MR4000 Series supplies the main switching

device gate drive voltage from two separate drive

circuits.

A voltage exceeding the threshold for the main

switching device is supplied from the first drive circuit

at the leading edge of the drive voltage waveform to

turn the main switching device on at the optimal

timing.

The drive voltage is then gradually supplied from the

second drive circuit (see Fig. 3.9).

The gradual supply of the drive voltage reduces drive

losses and reduces noise due to the gate charge

current and the current discharged when the

resonating capacitor switches on.

F/B pin

The output voltage is controlled

by varying the impedance of the

photocoupler.

IF/B

5Vref

Droop

resistor

Output voltage

error detection

feedback

signal

ton

(max)

1.5

4.5

Feedback voltage

VF/B [V]

ton

(min)

Fig. 3.8 Output voltage control

Fig. 3.9 Comparison of drive circuits

MR4530 Datasheet(PDF) 10 Page - Shindengen Electric Mfg.Co.Ltd

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