AM-300DE
[3] Circuit description of power supply PWB
This power supply unit has the function to convert the AC230 V (50/605. +24 V SUB output circuit block
Hz) to DC+24V, and provide these output to the equipment. The fol-
This circuit block rectifies and smoothes the high-frequency pulse volt-
lowing explains the function of each block. (See Fig. 17)
age provided by the transformer, and provides the DC+24V output to
the equipment. The output voltage is adjusted by the variable resistor
1. Filter circuit block(VR101).
This circuit reduces the outgoing noise through the input lines which is
generated in the power supply unit, and prevents the invasion of the6. +24 V MAIN output circuit block
noise from the lines. (The excessive surge such as thunder is pre-
vented by the varistor (Z1).)This circuit block supplies DC+24V output to equipment through a con-
nector (CN2) from +24V provided by the transformer.
2. Rectification and smoothing circuit block
7. +5 V output circuit block
This circuit rectifies and smoothes AC input, and provides the DC volt-
age to the switching circuit block.This circuit block rectifies and smoothes the high-frequency pulse volt-
age provided by the transformer and provides about DC+7V output to
the regulator IC, and provides the DC+5V output to the equipment.
3. Switching circuit block
This circuit converts the DC voltage (provided from the rectification8. +3.3 V output circuit block
and smoothing circuit block) to the high-frequency pulse voltage by
This circuit block supplies +3.3V output that is stable by the chopper
FET (Q1)?s switching (on/off repeat), and provides the energy to the
circuit which considered the above-mentioned +24V as the input. This
transformer (T1). It discharges the energy (charged during the FET
ON time) to the secondary side during the FET OFF time through thesystem supplies energy to load through L271 during the ON of MOS
secondary windings. The output voltages on the secondary side pro-FET Q271, and is making the energy accumulated L271 return to load
by D271 during the OFF. Control of constant voltage is performing +5V
vided by the energy depend on the ratio of the winding turns (primary :
output by applying detection and feedback by Integrated circuit regula-
secondary) etc..
tor IC201. It maintains an output OFF state until Q274 turns off a short
circuit protection circuit and it re-switches on a power supply, when
4. Control circuit block
output voltage becomes lower than the Zener potential of D274.
This circuit block controls the output voltage by transmitting the
detected +24V voltage to the primary control circuit through the photo-9. AC output circuit block
coupler (PC1). In case of the over-current, this circuit reduces provid-
This circuit block supplies AC output from AC input to equipment
ing the energy to the transformer. In case of the over-voltage, this cir-
through the optical-isolator (PC2) and the power-relay (RL1) by sig-
cuit reduces providing the energy to the transformer by letting the
nals (+24VS, /HEATER_ON, /PWRLY).
power-zener (D104 : connected between the +24V output voltage and
GND) into the short mode and letting the over-current protection circuit
work.10. Zero cross circuit block
This circuit block rectifies the AC input, and provides the ZC signal to
equipment through the photo-coupler (PC3).
Power relay
AC OUT+24VS
(9)/HEATER_ON
AC output
circuit block/PWRLY
Optical isolator(6)
+24V Main circuit
block
+24V MAIN
CN2
Transformer
(1)(2)(3)(5)
+24V circuit+24V SUB
FilterRectificationSwitching
Inputcircuitand smoothingcircuitblock
blockcircuit blockblock(7)
+5V circuit+5V
(4)block
Control
circuit block
(8)
+3.3V circuit+3.3V
block
Photo-coupler
(10)GND
Zero-cross
circuit block/ZC
Fig. 17
5 - 17 |
ACEC
SHARP
