MR4530 datasheet(8/43 Pages) SHINDENGEN

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Shindengen Electric MFG.CO.,LTD

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3.2 On-trigger circuit

The MR4000 Series employs a current-critical

operation system. When an energy burst to the

secondary side of the main transformer is detected,

the main switching device is turned on.

Energy discharge timing is detected at a negative

edge of the control coil voltage waveform. The main

switching device is turned on upon detection of the

discharge to perform current-critical operations.

See the point with approx. 0.3 V in Fig. 3.3 On-trigger

operation sequence.

The on-trigger detection voltage (approx. 0.3 V)

features 50 mV hysteresis for improved noise

resistance.

3.3 Partial resonance

In a current-critical switching power supply (RCC),

when the secondary current in the circuit with a

resonating capacitor connected between the drain

(collector) and GND of the main switching device as

shown on the right reaches 0 A, damping begins at

the resonance frequency determined by the primary

inductance LP of the main transformer and the

resonating capacitor Cq.

The discharge current of the resonating capacitor Cq

flows through the primary coil and returns energy to

the input. Adjusting the CR time constant applied to

the Z/C pin (see the diagram on the right) allows the

main switching device to be turned on at the trough of

the damping voltage waveform, reducing turn-on

losses.

In a partial resonance circuit, the energy stored in the

resonating capacitor Cq during the OFF period of the

main switching device is returned to the input,

reducing turn-on losses. This allows the connection of

a high-capacity capacitor between the drain

(collector) and GND of the main switching device,

thereby reducing noise.

The use of partial resonance improves efficiency and

reduces noise with simple circuit configurations.

[VZ/C]

Approx.

0.3 V

[ID(IC)]

[Secondary rectification diode current]

[VDS(VCE)]

[Control coil voltage]

Fig. 3.3 On-trigger operation sequence

[ID (IC)]

[Secondary rectification diode current]

Turn-on delay

Damping begins at the

resonance frequency

determined by LP and Cq.

[VDS (VCE)]

Z/C pin

Drain (collector) pin

GND pin

Resonating

capacitor

On-timing is delayed with

CR time constant.

Source/OCL

(emitter/OCL)

Fig. 3.4 Partial resonance

3. Operating principles

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