MR4530 datasheet(9/43 Pages) SHINDENGEN

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Shindengen Electric MFG.CO.,LTD

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3.4 Standby mode control (patent pending)

The MR4000 Series is capable of switching between

two methods of output voltage control, normal

operation mode and standby mode, in a single power

supply. This IC uses the burst method for standby

mode. Intermittent operation is performed under light

loads to reduce the oscillation frequency and reduce

switching losses. The burst method effectively

reduces the standby input voltage under micro-loads.

This IC uses a burst mode that performs intermittent

operation without stopping IC control, thereby

minimizing the output ripple. The Z/C pin is clamped

to a voltage of VZ/C(burst) or less by an external signal

to switch to standby mode control. To exit standby

mode— i.e., to return to normal mode— the clamp of the

Z/C pin voltage is released, and the VZ/C(burst) or

higher voltage is applied to the pin.

In normal operation, the ON range of the main switching

device is linearly controlled by voltage variations at the

F/B pin. In standby mode, the current detection

threshold of the Source/OCL (Emitter/OCL) pin switches

from Vth(OCL) for normal mode to Vth(burst OCL) for standby

mode, and the drain (collector) current is limited.

The peak value of the drain (collector) current is set

by the current detection threshold, and the burst

mode is selected.

In standby mode, oscillation occurs when the voltage

at the F/B pin is VF/B(burst start) or higher. Oscillation

stops when this voltage is VF/B(burst stop) or lower.

Since the output voltage control in standby mode sets the peak value of the drain (collector) current for each oscillation

cycle, the duty ratio of the oscillating and non-oscillating intervals varies to ensure a constant voltage.

Fig. 3.5 Standby mode control

Fig. 3.6 Standby mode control sequence

Fig. 3.7 Standby signal receiving sequence

3. Operating principles

MR4530 Datasheet(PDF) 9 Page - Shindengen Electric Mfg.Co.Ltd