M51995AP/AFP

REJ03D0835-0300 Rev.3.00 Jun 06, 2008

Page 17 of 40

Oscillator Section

The oscillation waveform is the triangle one. The ON-duration of output pulse depends on the rising duration of the

triangle waveform and dead-time is decided by the falling duration.

Waveform of

CF terminal

terminal in Max

ON dutycondition

≈ 4.4 V

≈ 2.0 V

Figure 2 OSC Waveform at Normal Condition

(no-operation of intermittent action and OSC control circuit)

1. Oscillator operation when intermittent action and OSC control circuit does not operate

Figure 3 shows the equivalent charging and discharging circuit diagram of oscillator when the current limiting

circuit does not operate. It means that intermittent action and OSC control circuit does not operate.

≈

(V/s)

………………………………………… (1)

The maximum on duration is approximately given as

≈

(s)

………………… (2)

Q3 and Q4 when SW1, SW2 are switched to “discharge side”.

So fall rate of CF terminal is given as

≈

+

(V/s)

………………… (3)

16

The minimum off duration approximately is given as

≈

(s)

…………………… (4)

+

16

The cycle time of oscillation is given by the summation of equations 2 and 4.

The frequency including the dead-time is not influenced by the temperature because of the built-in temperature

compensating circuit.