Sharp FO-CC500, Service Manual

Page: 74 / 162

FO-CC500A
FO-K01A
5 – 24
6. RUNTZ2099XHZZ LCD Terminal description (Cordless handset)
1 RS Register selection input
2 RW-WR This pin is connected to R/W pin of MPU
3 E-RD This pin is connected to E pin of MPU
4 CSB Chip selection input
5-8 DB7-DB4 Data bus
9 VDD Power supply for logic
10-14 V4-V0 Bias voltage level for LCD driving
15 VR Voltage adjust pin
16 VOUT DC/DC voltage converter output
17 CAP2- Capacitor connecting pin for the internal voltage converter
18 CAP2+ Capacitor connecting pin for the internal voltage converter
19 CAP1- Capacitor connecting pin for the internal voltage converter
20 CAP1+ Capacitor connecting pin for the internal voltage converter
21 VSS Ground
22 RESETB Hardware reset input
Pin No. Symbol Functions
[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
Fig. 20
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.
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.
Filter
Circuit
Rectifying/
Smoothing
Circuit
Switching
Circuit
+24V
AC IN
Photo Coupler
F1
T2.5A/250V
Control
Circuit
F2
T2.5A/250V
TRANSFORMER
+5V
Circuit
+5V
GND
F101
T4A/250V
+24V
Circuit