Over current protection method used in a switched-mode power supply and related controller
AssigneeLeadtrend Technology Corp.
InventorsKuo-Chien Huang, Ren-Yi Chen, Wen-Chung Yeh
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Abstract
Control methods and controller thereof for a power supply including a power switch and an inductor. The power switch is turned on to increase the inductor current through the inductor, which is sensed to generate a current-sense signal. The current-sense signal is added up with an adjusting signal to generate a summation signal. The power switch is turned off if the summation signal is higher than a peak limit. The turn-on time of the power switch is detected to update the adjusting signal.
Claims8
A control method applied in a power supply having a switch and an inductor coupled in series, comprising:
- turning on the switch for increasing an inductor current of the inductor;
- detecting the inductor current for generating a current-sense signal;
- generating a summation signal by adding the current-sense signal to an adjusting signal;
- comparing the summation signal with a peak limit and turning off the switch when the summation signal exceeds the peak limit;
- detecting a turn-on time or a duty cycle of the switch for updating the adjusting signal accordingly;
- providing a compensation signal associated with an output voltage of the power supply;
- and
- comparing the compensation signal with a predetermined value and ceasing to provide the adjusting signal when the compensation signal is lower than the predetermined value.
A controller for use in a power supply having a switch and an inductor coupled in series, comprising:
- a logic processing unit used to turn on the switch;
- a comparator used to turn off the switch when a voltage at a sensing node exceeds a peak limit;
- and
- a current generator used to generate and adjust an adjusting current which flows to an end of the switch via the detecting end according to a turn-on time or a duty cycle of the switch, the current generator comprising:
- a control unit configured to receive a compensation signal associated with an output voltage of the power supply, compare the compensation signal with a predetermined value, and terminate the adjusting current when the compensation signal is lower than a predetermined value;
- wherein the adjusting current is lowered when the turn-on time or the duty cycle increases and remains constant during the turn-on time or the duty cycle.
Dependencies are inferred from the claim text.