Constant current drive circuit
AssigneeNew Japan Radio Co., Ltd.
InventorsKazuyuki MIYAJIMA, Mitsuhiro ENOMOTO
Life of this patent
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Abstract
Provided is a constant current drive circuit that can improve accuracy of a stop timing of quick charge and prevent an overshoot, an insufficient quick charge, and the like from occurring. The constant current drive circuit includes a resistor R5 connected between the output side of the gm amplifier 6 and the input side of the transistor M1. The comparator 9 serving as a charge stopping circuit includes a voltage Vof, and stops charging by the quick charge circuit 8 based on a comparison result of the voltage Vof and the voltage Vs2 generated in the resistor R5.
Claims5
A constant current drive circuit comprising:
- an output transistor configured to drive a load to be ON/OFF;
- a transistor configured to drive the output transistor;
- a first resistor configured to detect a current flowing to the load and generate a first voltage;
- a first transconductance amplifier configured to receive the first voltage and a first reference voltage and control the output transistor so that the first voltage corresponds to the first reference voltage;
- a capacitor connected to an input side of the transistor configured to drive the output transistor;
- a PWM control transistor configured to turn ON/OFF the output transistor in accordance with a PWM signal;
- a quick charge circuit configured to charge the capacitor and accelerate a rise of operation of the output transistor when the load is switched from OFF to ON by the PWM control transistor;
- and
- a charge stopping circuit that is formed by a comparator which stops charging by the quick charge circuit,
- a second resistor connected between an output side of the first transconductance amplifier and the capacitor,
- wherein the charge stopping circuit includes a comparison voltage, and stops charging by the quick charge circuit based on a comparison result of the comparison voltage and a second voltage generated in the second resistor.
Dependencies are inferred from the claim text.