GW Instek PPH-1503 - Manual (Page 15)

OVERVIEW
15
Operating Principals
Overview The PPH-1503 mainly consists of the follow
components:
 AC to DC Switching power supply
 DC to DC Buck converter circuit
 Precision output control circuit
The block diagram below shows a function
description of each of the circuits. The following
page will show detailed decriptions of each
component.
Block Diagram
AC INPUT
AC TO DC
SWITCH POWER
DC TO DC
BUCK CIRCUIT
U201,Q201,Q202
L202
LINEAR
CONTROL
Q306~Q308,U303
ON/OFF SWITCH
Q309,Q310,
Q315,Q316
AUXILIARY
POWER SUPPLY
U101,T101,
Q102~Q105
V-SET
I-SET
AND
VOLTAGE
COMPARATOR
U301A
VOLTAGE
SAMPLING
CIRCUIT
U401,U402
CURRENT
COMPARATOR
U301B
CURRENT
SAMPLING
CIRCUIT
U430
SAMPLE
RESISTANCE
R366,R366A
R367,R367A
OUTPUT
Swtiching Power
Supply AC power is converted to 24VDC by the switch
mode power supply module.
DC Down
Conversion To reduce the input voltage to 24VDC (slightly
higher than the settable voltage) the U201 Buck IC
is used in conjunction with two power MOSFETS
(Q201/Q202) and an inductor (L202).