Sharp VL-E39S

10-1-3. Circuits
The circuits used for the adapterare explained according to
the circuit diagram in Figure 3.
1.lnput section
The input section consists of noise filter and condenser
input rectifying smoothing circuit. The noise filter, which
consists of L1, C1, C26, C38, C34 and C35, reduces
common mode noise.
R50 is a discharging resistor which is intended to elimi-
nate voltage from the input plug when the power is
turned off.
The rush current which is caused when the power is
turned on is greatly limited by R2, DCR of L1 and the
operating resistor of D1.
2.Switching section
The switchlnq circuit drives the transistor Q1 to act as a
switch by using the DC voltage rectified through C2
corresponding to the signals sent from the primary side
control section. It and the transformer T1 comprise a
high-frequency inverter.
C33 is a capacitor which absorbs the surge voltage
generated by switching.
3.Primary side control section
This section drives the switching section by converting
the pulse width of the signal sent from the secondary
side control circuit through the photocoupler.
The control IC (IC4) is used to drive Q1 (Mos FET).
This IC,as an overvoltage protector, contains a function
which stops oscillation when it detects the overvoltage
at D8.
4.0utput circuit section
For the secondary side output, a popular on-off system
is applied. Ripples and common mode noise are
re-
duced through the chokes of L2 and L4.
Q2 is a transistor for the charging switch. It is turned on
through Q3 by the output of pin 6 of IC3 during quick
charging and pre-/sub-charging.
D11 is used to prevent discharge troubles of the control
circuit section when the input is turned off with the
battery attached.
5.Battery detection circuit
When the battery is installed, SW2 is turned on by the
switch knob.
If the DC plug is not attached to CN2 at this time, the
GND level will be input to the pin 10 of IC3 by the
transistor Q7 in order to detect the installation of the
battery.
6.Secondary side control circuit
The function of the secondary side control section is to
control the switching section by error-amplifying the
detected outputvoltage andcurrent and transmitting the
signals to the primary side control circuit through the
photocoupler.
The constant voltage is set and detected in
IC2-1I,
whereas the adapter mode (4.5V)/charge mode (6.5V)
selection is made by changing the reference voltage
10-5
Vl-E39S
through the voltage switching operation of pin 5 of IC3.
The constant current and overcurrent protections are
set and detected in
IC2-1, while 1.5A/O.5A constant
current selection is made through the output of pin 7 of
IC3.
The overcurrent protection in the adapter mode is per-
'formed by the primary side control section.
IC1 has the constant voltage power function to provide
drive power for IC3 and the reference voltage for IC2, as
well as the reset function to prevent IC3 errors.
The constant voltage output of IC1 is used as a refer-
ence voltage when error amplifying of output voltage/
current.
7.Display
Only the D16 (red LED) lights up in the adapter mode.
In the charge mode, D17 (orange LED) lights up to-
gether with D16 during quick charging. When quick
charging is completed (in the trickle mode), only D17
goes out.
In the refresh mode, D16 lights, and D17 blinks. When
the discharging is completed, the quick charging starts
at once, and D17 begins to light stably.
D17 on-off is controlled through the pin 4 of IC3.
8.Discharge circuit
The discharging function in the refresh mode is enabled
by the discharging resistors R44, R46 and R47 and the
discharge circuit switch Q4.
The dischargecurrent value isdetermined bythe battery
voltage and the resistance of the discharging resistor.
Here, the constant current control is not performed.
The discharge end voltage is judged at the pin 22 of IC3
by converting the voltage of the discharging battery with
R38 and R41.