HA16158P/FP

Rev.2.00 Jan 30, 2007 page 11 of 23

Functional Description

1. UVL Circuit

The UVL circuit monitors the Vcc voltage and halts operation of the IC in the event of a low voltage.

The voltage for detecting Vcc has a hysteresis characteristic, with 16.0 V as the start threshold and 10.0 V as the

shutdown threshold.

When the IC has been halted by the UVL circuit, control is performed to fix driver circuit output low and halt VREF

output and the oscillator.

Vcc

VREF

V_CT

(internal signal)

PWM-RESET

(internal signal)

PWM-OUT

PFC-OUT

PFC-DT

(internal signal)

PFC-RAMP

(internal signal)

16.0V

10.0V

4.5V

4.5V

Figure 1