Icom IC-2GA Service Manual

10-4 CIRCUIT DESCRIPTION
This charger is designed for the following battery packs:
ВР-2, BP-3, BP-4, BP-5, ВР-БА, ВР-7 and BP-70. The char-
ger's selector board, which selects the correct charging
current for the battery pack, as well as the battery pack
sensors, prevent overcharging. The phase angle control
circuit, a feedback loop, ensures charging at a stable
current.
(1) PHASE ANGLE CONTROL CIRCUIT
An SCR (D6) controls the current using the phase angle. In
order to synchronize the gate pulse with the supplied
voltage, the charger generates a saw-tooth wave synchro-
nized with the rectified AC input. A gate pulse of the
desired phase angle (approx. 40°~160°) is generated by
changing the fall time of the saw-tooth wave.
Diagram 1
Threshold
Diagram 3
E
Threshold
[e]
Diagram 4
E
Threshold |— — — — ==
0
о 180
Explanation of diagrams:
1) Rectified АС Sine Wave (3607)
2) Voltage Waveform When the Current is Increased.
3) Voltage Waveform When the Current is Increased.
4) Voltage Waveform When the Current is Stable.
When the rectified voltage is less than +9 V, the saw-tooth
wave generator circuit (02, ОБ) charges C9 to 47.8 V. 0215
turned on. When the voltage exceeds +9 V, C9 discharges
through Q5 (Diagrams 2—4), creating a saw-tooth wave
voltage.
This voltage is applied to IC2 (pin 12). When the voltage is
less than +9 V, ІС2 (pin 11) is "HIGH." ОЗ and 04 are
turned on. A pulse, applied to the gate of the SCR (D6),
turns on D6. D6 remains on if the current exceeds +9 V.
The entire rectified wave (360°) is applied to the anode of
D6. When the voltage becomes less than +9 V, reverse
bias turns off D6. |
53~55 аге used to select the correct impedance of the
series R37—R42, and thus the charging current. R37—R42
are connected in series between the battery and ground.
C16 and R14 differentiate the voltage across these resistors.
The resulting voltage is applied to the differential amplifier
(Q5, Q6). The Vcc voltage (+9 V), divided by R11 and R12,
is applied to the base of Q5. Q5 collector current, control-
led by the base voltage of Q6, controls the discharge time.
constant of C9.
When the charging current exceeds a specified level, Q6
collector current increases. O5 collector current decreases,
increasing the discharge time constant of C9. Hence, the
gate of D6 receives a pulse with a delayed phase angle,
decreasing the current. When the charging current is less
than the specified level, the circuit functions in reverse,
keeping the charging current constant.
(2) OVERCHARGE PROTECTOR
Using microswitches (S3—S5) and a charging detector
(010), the overcharge protector circuit prevents overcharg-
ing. When charging BP-2, BP-5, BP-7 or BP-8, the micro-
Switches on the base of the battery pack closes $5.
Thermo-sensors are included in all quick-charge battery
packs. After the pack is fully charged, the temperature
inside the pack rises. The charger shuts off current flow to
the pack and stops charging. D10 and Q10 are used to
detect charging current.
During normal speed charging, 25 mA, 45 mA and 70 mA
are consecutively applied to the battery cells. During quick
charging, 600 mA is reapplied to the cells until the thermo-
sensor begins to function. The negative charging terminal
inside the battery pack is unconnected. Q10 is turned off,
and 1С2 (pin 5) becomes "LOW." The RS flip-flop works in
reverse.
IC2 (pin 10) becomes "HIGH." Q4 remains off. Even if the
temperature cools, D6 shuts off the current, preventing
further charging. The CHG INDICATOR goes out, indicating
that the pack is fully charged. Removing the battery pack at
this time opens 55. ІСІ (pin 5) becomes “LOW,” resetting
the RS flip-flop. |
D1 and Q1 supply +9 V of stable voltage to the overcharge
protector circuit.

Icom IC-2GA Specifications

General

Brand	Icom
Model	IC-2GA
Category	Transceiver
Language	English