Light-emitting diode lighting circuit
AssigneeHonda Motor Co., Ltd.
InventorAtsuyuki Kobayashi
Life of this patent
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Abstract
A lighting circuit including a circuit for preventing erroneous illumination of LEDs wherein the lighting circuit, serving as a drive circuit for the LEDs, includes a transistor and a differential amplifier placed at a preceding stage of the transistor. A positive input side of the differential amplifier is connected to a battery through a switch and to a reference resistor Rref. A voltage of the battery is divided by resistors R1 and R2 and supplied to a negative input side of the differential amplifier. A resistance value (R1/R2)×Rref is set to be smaller than a leakage resistance value Rs of the switch. Thus, the differential amplifier is not turned on when the switch is opened even though there is a leakage at the switch. Therefore, the transistor is not turned on, and the LEDs are not illuminated.
Claims20
A light-emitting diode lighting circuit for activating a semiconductor switching device to illuminate at least one light-emitting diode, the light-emitting diode lighting circuit comprising:
- a differential amplifier provided at a preceding stage of the semiconductor switching device;
- a switch for inputting a supply voltage to a positive input side of the differential amplifier;
- a reference resistor having one end connected to the positive input side of the differential amplifier, and the other end grounded;
- and
- at least one voltage-dividing resistor connected to a negative input side of the differential amplifier for dividing the supply voltage,
- wherein a resistance value Rref of the reference resistor and a resistance value R1/R2 of the voltage-dividing resistors are decided such that a relationship between a leakage resistance value Rs of the switch and both resistance values Rref and R1/R2 becomes Rs>(R1/R2)×Rref.
A light-emitting diode lighting circuit comprising:
- at least one light-emitting diode;
- a semiconductor switching device for activating the at least one light-emitting diode to illuminate the light-emitting diode lighting circuit;
- a differential amplifier operative connected between the semiconductor switching device and the at least one light-emitting diode;
- a switch operatively connected to a positive input side of the differential amplifier;
- a reference resistor having a first end connected to the positive input side of the differential amplifier, and the a second end grounded;
- and
- at least one voltage-dividing resistor connected to a negative input side of the differential amplifier,
- wherein a leakage resistance value Rs of the switch is greater than the resistance value Rref of the reference resistor times a resistance value of the voltage-dividing resistor.
Dependencies are inferred from the claim text.