Circuit Description Of Power Supply Pwb - Sharp FO-CC500 Service Manual

FO-CC500A
FO-K01A
6. RUNTZ2099XHZZ LCD Terminal description (Cordless handset)
Pin No. Symbol
1 RS
2 RW-WR
3 E-RD
4 CSB
5-8 DB7-DB4
9 VDD
10-14 V4-V0
15 VR
16 VOUT
17 CAP2-
18 CAP2+
19 CAP1-
20 CAP1+
21 VSS
22 RESETB

[6] Circuit description of power supply PWB

This power supply unit has the function to convert the AC 220 - 240 V
50/60 Hz to DC +24 V, and provide these outputs to the equipment. The
following explains the function of each block. (See Fig. 20)
1. Block diagram
F1
T2.5A/250V
AC IN
F2
T2.5A/250V
2-1. Filter circuit
This circuit reduces the outgoing noise through the input lines which is
generated in the power supply unit, and prevents the invasion of the
noise from the lines.(the excessive surge such as the thunder is pre-
vented by the varistor(Z1).)
2-2. Rectifying/smoothing circuit
This circuit rectifies and smoothes the AC input, and provides the DC
voltage to the switching circuit block.
2-3. Switching circuit
This circuit converts the DC voltage(provided from the Rectification and
smoothing circuit block) to the high frequency pulse voltage by FET(Q1)'s
switching(on/off repeat), and provides the energy to the transformer(T1).
It discharges the energy(charged during the FET ON time) to the sec-
ondary side during the FET OFF time through the secondary windings.
The output voltage on the secondary side provided by the energy de-
pend on the ratio of the winding turns(primary : secondary) etc.
Register selection input
This pin is connected to R/W pin of MPU
This pin is connected to E pin of MPU
Chip selection input
Data bus
Power supply for logic
Bias voltage level for LCD driving
Voltage adjust pin
DC/DC voltage converter output
Capacitor connecting pin for the internal voltage converter
Capacitor connecting pin for the internal voltage converter
Capacitor connecting pin for the internal voltage converter
Capacitor connecting pin for the internal voltage converter
Ground
Hardware reset input
Rectifying/
Filter
Smoothing
Circuit
Circuit
Functions
Switching
TRANSFORMER
Circuit
Control
Circuit
Photo Coupler
Fig. 20
2-4. Control circuit
This circuit block controls the output voltage by transmitting the detected
+24 V voltage to the primary control circuit through the photo-
coupler(PC1). In case of the over-current, this circuit reduces providing
the energy to the transformer. In case of the over-voltage, this circuit
reduces providing the energy to the transformer by letting the Power-
Zener(D104; connected between the +24 V output voltage and GND)
into the short mode and letting the over-current protection circuit work.
2-5. +24V circuit
This circuit block rectifies and smoothes the high-frequency pulse volt-
age provided by the transformer, and provides the DC +24 V output to
the equipment. The output voltage is adjusted by the variable
resistor(VR101).
2-6. +5V circuit
This circuit block rectifies and smoothes the high-frequency pulse volt-
age provided by the transformer, and provides about DC +6 V output to
the regulator IC, and provides the DC +5 V output to the equipment.
5 – 24
F101
T4A/250V
+24V
+24V
Circuit
+5V
+5V
Circuit
GND