Power Supply Apparatus
First Claim
1. A power supply apparatus, comprising:
- a control circuit which controls an output voltage of a booster circuit in a feedback manner so that a voltage at a feedback terminal provided on a path where a load circuit is driven by the booster circuit is brought close to a predetermined voltage value; and
a protection circuit provided on a feedback path from the feedback terminal to the control circuit;
wherein when a voltage at the feedback terminal has reached the predetermined voltage, said protection circuit has a voltage clamping function of preventing a voltage outputted to said control circuit from rising above a predetermined clamp voltage.
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Accused Products
Abstract
In a power supply apparatus in which a voltage at a terminal on a load circuit is fed back to a control circuit so as to control a step-up operation by use of a booster circuit, a protection function is provided for a voltage fed back to the control circuit. A power supply apparatus includes a booster circuit, a protection circuit, a PWM control circuit and a current control circuit, and the step-up operation is controlled by feeding back a cathode voltage of an LED. The protection circuit is provided between an LED terminal and the PWM control circuit, and the protection circuit includes a protection constant-current source, a clamping transistor and a protection resistor. Even in the case when the voltage at the LED terminal is high, a voltage at a source terminal of the clamping transistor inputted to the WM control circuit is clamped to a clamp voltage (Vbat-Vt) or below.
40 Citations
9 Claims
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1. A power supply apparatus, comprising:
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a control circuit which controls an output voltage of a booster circuit in a feedback manner so that a voltage at a feedback terminal provided on a path where a load circuit is driven by the booster circuit is brought close to a predetermined voltage value; and
a protection circuit provided on a feedback path from the feedback terminal to the control circuit;
wherein when a voltage at the feedback terminal has reached the predetermined voltage, said protection circuit has a voltage clamping function of preventing a voltage outputted to said control circuit from rising above a predetermined clamp voltage. - View Dependent Claims (2, 3, 4, 5, 9)
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6. A power supply apparatus, comprising a control circuit to which an output voltage, namely a first voltage, of a booster circuit and a second voltage resulting from driving a load with the first voltage are inputted respectively in a feedback manner, said control circuit comprising:
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a first comparator which compares the first voltage with a desired-value voltage thereof;
a second comparator which compares the second voltage with a desired-value voltage thereof; and
a detection circuit which detects that the first voltage is lower than the desired-value thereof as a result of comparison by the first comparator or detects that the second voltage is lower than the desired-value voltage thereof as a result of comparison by the second comparator, wherein said control circuit controls the booster circuit in response to a detection result of the detection circuit. - View Dependent Claims (7, 8)
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Specification