Sharp VL-SW50U Service Manual page 134

VL-SWSOU
13-l. OPERATION MANUAL
13-l -1. Outline
This adapter is designed as the power supply for camcoder as well as the quick charger of the battery used in it.
As shown in Fig. 13-I -1 block diagram, the adapter consists of the separately excited switching reguiator which employs control
IC, and a multi-functional circuit on the secondary side.
The primary control circuitry and the secondary multi-functional circuitry, composed mainly of the components mounted
on the surface, are housed in the small, portable case. They are applicable for a variety of operational conditions of the
user.
The multi-input type adapter of 1 IOV to 240 V 50/60 Hz is employed to satisfy the conditions for various input voltages in
order to allow the adapter to be worldwide carried around and used.
The basic operation is controlled by two sections. In the power switching section, constant-voltage and constant-current
controls are performed by comparing with the reference voltage at the secondary side. The battery charging section, on the
other hand, is provided with timers, various detection circuits and sequence controller. As an AC adapter, the adapter feeds
the constant-voltage DC power through the special 3-pin DC jack, and as a battery charger, the adapter starts the rapid
charging operation when the exclusive battery is place din position with the DC plug unconnected.
Input
AC 110-240V
ADP output (4.5 V 2 A)
50/60Hz
0
Filter -
Rectifier/
Insulating
Rectifier/
smoother
- lnverter -
transformer
smoother
Battery terminal
1
Primary
side
control
section
I
1 Voltage switch
I I
I -
control
13-l -2. Operation
Fig. 13-1-1 Block diagram (Camcorder adapter)
1 .Adapter mode
When the DC plug is attached to the adapter, the constant DC voltage (4.5 V, 2 A) can be continuously obtained via
the DC jack to operate the camcorder.
The power consumption can be kept constant over the entire control input rage, regardless of input fluctuation
The output is so available up to 1.3 or more times of the rated current as to resist the starting current, rush current and
other transient current which flow in the main body of camcorder.
Also, the adapter output overcurrent protector with fold back current, which controls the power when the short
circuit
from the outside occurs, is used to prevent the adapter from being destroyed or broken down. It also prevents the
temperature inside the adapter from rising too excessively.
.
2.Ni-Cd charge mode
This adapter, when Ni-Cd battery is attached, can be used as a quick charger. This charging operation is divided into
the operating modes of three stages. The adapter goes through these modes sequentially.
The first stage is called initial charging. A constant current of 1.5 A is charged in the range which is limited by the voltage
of 5.7 V and the timer of 5 minutes.
The voltage is thus limited in order to protect the battery against overvoltage, and overcharge which would otherwise occur
in the fully charged state.
The time limit serves to prevent the charging error which would occur on the dead battery due to the initial voltage drop.
The second stage is a quick charging mode. Like in the initial charging, a rapid charge of 1.5 A is made in the range
which is limited by the voltage of 5.7 V, and the timer of 180 minutes which are different from those of the initial charging.
Toward the end of this mode, a battery voltage drop (-AV phenomenon)
is detected to tell the end of the quick charging, to
stop the charging and to go to the next stage. At this charging current of 1.5 A, the 1500 mAh battery, and the 2500 mAh
nickel-hydrogen later mentioned are fully charged for about 60 minutes, and about 140 minutes, respectively. The timer is
set at 180 minutes to avoid an danger of overcharge which is possible due to -AV detection error.
Here, the -AV detection level is 40 to 80 mV.
In the third stage called auxiliary charging, the fully charged state is kept even after the quick charging is completed.
The auxiliary charging is generally set at l/30 to 1/4OC depending on the characteristics of a battery. This adapter adopts
a charging system which is controlled by the operation output controlled at the constant voltage and the fixed resistance.
These charging states are shown by the characteristics in Fig. 13-l -2.
13-2