M51995AP/AFP

REJ03D0835-0300 Rev.3.00 Jun 06, 2008

Page 18 of 40

T-ON

From VF

signal

Vz = 4.2 V

T-OFF

CF

M51995A

Q3

Q4

1/16

Q2

SW2

SW1

Charging

Discharging

5.8 V

Switched by

charging and

discharging signal

Q1

2. Oscillator operation when intermittent action and OSC control circuit operates.

When over current signal is applied to CLM

+ or CLM− terminal, and the current limiting circuit, intermittent action

and OSC control circuit starts to operate. In this case T-OFF terminal voltage depends on VF terminal voltage, so

the oscillation frequency decreases and dead-time spreads.

The rise rate of oscillation waveform is given as

≈

(V/s)

………………………………………… (5)

The fall rate of oscillation waveform is given as

≈

+

(V/s)

………………… (6)

16

The maximum on-duration is just same as that in the no-operation state of intermittent and oscillation control circuit

and is given as follows;

≈

(s)

………………… (7)

The minimum off-duration is approximately given as;

+

≈

(s)

………………… (8)

16

The oscillation period is given by the summation of equation (7) and (8).