Soft start system and method for switching regulator
First Claim
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1. A method for soft-starting a switching regulator that includes an error amplifier, a compensation capacitor, a flip-flop, a comparator, and a bias current regulating circuit;
- comprising;
monitoring a feedback voltage from the output terminal of said switching regulator;
providing a shutdown signal when said switching regulator is either disabled, under or over-temperature, under-voltage, or over-voltage to reset said flip-flop that has set, reset, and output terminals;
discharging said compensation capacitor responsive to said shutdown signal;
comparing said feedback voltage with a first reference voltage through said comparator and if said feedback voltage becomes larger than said first reference voltage, the output signal of said comparator sets said flip-flop; and
regulating the bias current of said error amplifier through said bias current regulating circuit responsive to said feedback voltage and the output signal of said flip-flop by;
(1) if said feedback voltage is less than said first reference voltage, the bias current of said error amplifier is regulated to a small value to ensure a soft start for said switching regulator;
(2) if said feedback voltage is larger than said first reference voltage, the bias current of said error amplifier has its normal value under normal operation;
wherein said error amplifier operates under close-loop condition when its bias current switches from said small value to its normal value.
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Abstract
The present invention introduces methods and circuits to provide a soft start for a switching regulator. A feedback voltage from output terminal is monitored and used to regulate the bias current of the regulator'"'"'s error amplifier. The present invention also enables a smooth transition from the soft start to normal operation.
49 Citations
6 Claims
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1. A method for soft-starting a switching regulator that includes an error amplifier, a compensation capacitor, a flip-flop, a comparator, and a bias current regulating circuit;
- comprising;
monitoring a feedback voltage from the output terminal of said switching regulator; providing a shutdown signal when said switching regulator is either disabled, under or over-temperature, under-voltage, or over-voltage to reset said flip-flop that has set, reset, and output terminals; discharging said compensation capacitor responsive to said shutdown signal; comparing said feedback voltage with a first reference voltage through said comparator and if said feedback voltage becomes larger than said first reference voltage, the output signal of said comparator sets said flip-flop; and regulating the bias current of said error amplifier through said bias current regulating circuit responsive to said feedback voltage and the output signal of said flip-flop by; (1) if said feedback voltage is less than said first reference voltage, the bias current of said error amplifier is regulated to a small value to ensure a soft start for said switching regulator; (2) if said feedback voltage is larger than said first reference voltage, the bias current of said error amplifier has its normal value under normal operation; wherein said error amplifier operates under close-loop condition when its bias current switches from said small value to its normal value. - View Dependent Claims (2, 3)
- comprising;
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4. A soft-start switching regulator, comprising:
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a shutdown circuit for providing a shutdown signal when said switching regulator is disabled, under- or over-temperature, under-voltage, or over-voltage; a feedback circuit being coupled to the output terminal of said switching regulator and providing a feedback voltage; a compensation capacitor; a comparator being coupled to said feedback voltage and a first reference voltage; an error amplifier being coupled to said feedback voltage and a second reference voltage, and providing a charging current to said compensation capacitor; a flip-flop having set, reset, and output terminals wherein said flip-flop is set by the output signal of said comparator, and reset by said shutdown signal; and a bias current regulating circuit responsive to said feedback voltage and the output signal of said flip-flop to regulate the bias current of said error amplifier; wherein if said feedback voltage is less than said first reference voltage, the bias current of said error amplifier is regulated to a small value to ensure a soft start for said switching regulator; wherein if said feedback voltage is larger than said first reference voltage, the bias current of said error amplifier has its normal value under normal operation; and wherein said error amplifier operates under close-loop condition when its bias current switches from said small value to its normal value. - View Dependent Claims (5, 6)
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Specification