Cancellation of slope compensation effect on current limit
AssigneeLinear Technology Corporation
InventorKarl Edwards
Life of this patent
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Abstract
A current-mode switching regulator that maintains a substantially constant maximum current limit over a virtually full range of duty cycles is provided. The regulator has a control circuit that includes a buffer circuit, an adjustable voltage clamp circuit, and a slope compensation circuit. The buffer circuit isolates a control signal from capacitive loading associated with control circuit. The threshold level of the adjustable voltage clamp circuit varies with respect to the amount of slope compensation provided to the voltage regulator. This allows a control voltage to increase as slope compensation increases so that a substantially constant maximum current limit is maintained.
Claims35
A method for maintaining a maximum output current limit of a current-mode switching regulator;
- the method comprising:
- generating a slope compensation signal when a duty cycle of the regulator is above a preset value;
- and
- adjusting a current limit point of the regulator as a function of the slope compensation signal to maintain the maximum output current limit of the regulator substantially constant.
A method for maintaining a maximum output current limit of a current-mode switching regulator;
- the method comprising:
- generating a first slope compensation signal when a duty cycle of the regulator is above a preset value;
- generating a second slope compensation signal when the duty cycle of the regulator is above the preset value;
- and
- adjusting a current limit point of the regulator as a function of said second slope compensation signal to maintain the current limit substantially constant.
A switching regulator circuit that maintains a substantially constant maximum output current limit and provides a regulated voltage to a load, the switching regulator having an output circuit that includes a switch circuit coupled to a power source and an output terminal, the output circuit providing a feedback signal that is indicative of the regulated voltage, the switching regulator comprising:
- a control circuit coupled to said output circuit that receives said feedback signal, said control circuit providing a first control signal to said output circuit in response to said feedback signal that controls a turn-off threshold of said switch circuit, said control circuit comprising:
- (a) a switch timing circuit that generates a ramp signal;
- (b) a slope compensation circuit coupled to said switch timing circuit that generates a first slope compensation signal in response to said ramp signal;
- and
- (c) a voltage clamp circuit that receives said first slope compensation signal, said voltage clamp circuit having a clamp threshold that varies with respect to said first slope compensation signal.
Dependencies are inferred from the claim text.