ha16138 HITACHI, ha16138 Datasheet - Page 8

• Manufacturer Part Number: ha16138
• Description: Ac/dc Switching Converter Controller With High-voltage Power
• Manufacturer: HITACHI

HA16138PS
Oscillation Circuit
The oscillator generates a triangular voltage waveform through the discharge of the timing capacitance CT.
With a 220 pF CT connected, the oscillator operates at 100 kHz.
The triangular voltage waveform has a discharge time ratio of 3:1, with the charge side set to PWM on-
pulses, and the discharge side to dead-band pulses. The maximum PWM on duty can be controlled up to
70%.
OVP Latch Circuit
When the FB pin voltage reaches 5 V or above, the OVP latch circuit operates and forcibly stops PWM
output and the reference voltage generation circuit. While OVP latching is stopped, the starter circuit is
also stopped. Latch resetting can be performed by driving power supply voltage VDD to 4 V or below.
8
Figure 3 Oscillation Circuit Peripheral Waveform Timing
CT
DB pulse
(IC internal waveform)
1/3 COMP
(IC internal waveform)
CS
(IC internal waveform)
Power MOS FET
Gate voltage
(IC internal waveform)
Power MOS FET
Drain voltage
DRAIN
CT
FB
Vref
(IC internal
waveform)
Figure 4 OVP Latch Operation Timing
0
0
5V
0
0
5V