HA16114P Datasheet, PDF (34/38 Pages) Hitachi Semiconductor – Switching Regulator for Chopper Type DC/DC Converter

HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
Application Examples (3)
• External Synchronization with Primary-Control AC/DC Converter (cont.)
(2) Combination with a forward AC/DC converter (simplified schematic)
DFG1C8
D
Input
HRW26F
HA17431 and optocoupler
+
C
A
HA16107,
HA16666 etc.
B
SBD
module
Feedback
section
Main DC
output
−
2SC458
R₃
390Ω
FB
V_IN
Switching transformer
R₁
Coil A Primary, for main
Coil B Secondary, for output
Coil C Tertiary, for IC
R₂
Coil D For reset
6.2kΩ
Q
510Ω
2
10
SYNC
V_IN
HA16114,
HA16120
OUT
ZD
GND
1
9
Other parts as
on previous page
This circuit illustrates the combination of the HA16114/120 with a forward AC/DC converter. The
HA16114/120 synchronizes with the falling edge of the external sync signal, so with a forward
transformer, the sync pulses must be inverted. In the diagram, this is done by an external circuit
consisting of the following components:
• Q:
Transistor for inverting the pulses. Use a small-signal transistor.
• R₁ and R₂: These resistors form a voltage divider for driving the base of transistor Q. R₂ also provides
a path for base discharge, so that the transistor can turn off quickly.
• R₃:
• ZD:
Load resistor for transistor Q.
Zener diode for protecting the SYNC pin.
34