AN8032 データシートの表示（PDF） - Panasonic Corporation

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AN8032

Active filter control IC

Panasonic Corporation 

Voltage Regulators

AN8032

s Application Notes (continued)

[2] Operation descriptions (continued)

1. Normal control (continued)

3) Description of each function (continued)

(1) VB (continued)

<Setting the VB terminal constant> (continued)

• Zero-cross switching

Zero-cross switching can be realized by using

the local resonance when turning on the power

MOSFET in order to suppress the loss.

By connecting the resonance capacitor CP be-

tween the drain and source of the power MOSFET,

and using the inductance of the transformer's pri-

mary side LP, the resonance is produced after dis-

charging the accumulated energy of the transformer.

The capacitor for delay should be connected to the

VB terminal so that the next turn-on could occur at

the time when the resonance occurred and the drain

voltage of the power MOSFET has reached around

0 V.

However, it is necessary to take care that the

zero-cross conditions could deviate since the delay

amount varies depending on the conditions such as

the input voltage.

(2) CS

AN8032

VB

VOUT

Delay capacitor

A

B

CB

LP

RB

CP

A-point voltage

0V

Resonance capacitor

Resonance by LP − CP

Zero-cross

switching

B-point voltage VBTH

0V

Delay

Power MOSFET

On

Power MOSFET

Off

The terminal for detecting the current when the power MOSFET is turned on.

The current flow when the power MOSFET is turned on is equivalent to the current flow in the

inductor. Therefore, the necessary power value can be controlled by controlling the peak value of the

above current.

The input D-range of this terminal is from 0 V to 5 V. However, since dissipation becomes larger if

the power MOSFET current detecting resistance is set at larger value. A value from 0.22 Ω to 0.47 Ω is

the standard considering the relationship with the S/N.

The charge and discharge current to and from the parasitic capacitance of the power MOSFET,

transformer or printed circuit wiring flow in the power MOSFET detection resistor at turning-on and off.

Since such current generates noise and causes malfunction, it is necessary to incorporate a filter to re-

move such irregular element.

Parasitic

capacitance

Spike

VB

Filter

ICS

0A

Spike

(3) MPI

Figure 6. CS terminal explanation

The MPI is the terminal for monitoring the AC input voltage. The voltage which is resistance-divided

from the input voltage after full-wave rectification is input. The input D-range of the multiplier is from

0 V to 4.5 V typical and output D-range is from 0 V to 5.4 V typical.

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