To suppress charging current when charged with a large current flow and secure proper charging current for a battery cell in the normal charging by installing a positive characteristic thermistor in a resistor circuit for controlling charging current connected in series with a diode for preventing the back flow of charging current in a lithium ion secondary battery.
A rectifier circuit 3 rectifies and smoothes the input to the voltage close to the DC voltage of the peak voltage. A DC-DC converter 4 is a switching regulator and steps down the DC supply voltage. A transistor Tr serves for a series regulator circuit. A charging control circuit 5 operates from the voltage outputted from the DC-DC converter 4 as the supply voltage, and controls the base current of the transistor Tr based on a voltage detection signal from a Vdtc terminal and a temperature detection signal from a Vth terminal of a battery pack to control charging current. A positive characteristic thermistor is used for a resistor of a circuit for controlling charging current. Due to this structure, when large charging current is caused flow at the time of charging, the excessive charging current can be suppressed.
YAMANOUCHI TOMOZO
TAKAOKA YUICHI
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