Method of detection for output short circuit of a flyback power supply
Disclosed are methods of detection for output short circuit of a flyback power supply, which detect the current sense signal provided by a current sense resistor serially connected to a power switch of the flyback power supply, and thus quickly identify whether or not the flyback power supply suffers output short circuit.
1. A method of detection for output short circuit of a flyback power supply including a power switch and a current sense resistor serially connected to the power switch to provide a current sense signal, the method comprising the steps of:
(A) detecting a peak value of the current sense signal during a first cycle;
(B) detecting an initial value of the current sense signal during a second cycle next to the first cycle; and
(C) identifying output short circuit by monitor a difference between the peak value and the initial value.
2. The method of claim 1 , wherein the step (A) comprises the step of sampling the current sense signal when the power switch is turned off during the first cycle.
3. The method of claim 1 , wherein the step (B) comprises the step of sampling the current sense signal when the power switch is turned on during the second cycle.
4. The method of claim 1 , wherein the step (C) comprises the steps of:
dividing the difference by an OFF-time of the power switch for recognizing a slope; and
if the slope is smaller than a threshold, concluding that the flyback power supply suffers output short circuit.
5. The method of claim 1 , wherein the step (C) comprises the step of concluding that the flyback power supply suffers output short circuit if the difference is smaller than a threshold.
6. A method of detection for output short circuit of a flyback power supply including a power switch and a current sense resistor serially connected to the power switch to provide a current sense signal, the method comprising the steps of
(A) detecting an initial value of the current sense signal during a cycle;
(B) detecting a peak value of the current sense signal during the cycle; and
(C) identifying output short circuit by monitor a difference between the peak value and the initial value.
7. The method of claim 6 , wherein the step (B) comprises the step of sampling the current sense signal when the power switch is turned off during the cycle.
8. The method of claim 6 , wherein the step (A) comprises the step of sampling the current sense signal when the power switch is turned on during the cycle.
9. The method of claim 6 , wherein the step (C) comprises the steps of:
dividing the difference by an OFF-time of the power switch for recognizing a slope; and
if the slope is smaller than a threshold, concluding that the flyback power supply suffers output short circuit.
10. The method of claim 6 , wherein the step (C) comprises the step of concluding that the flyback power supply suffers output short circuit if the difference is smaller than a threshold.
11. A method of detection for output short circuit of a flyback power supply including a power switch and a current sense resistor serially connected to the power switch to provide a current sense signal, the method comprising the steps of:
(A) detecting an initial value of the current sense signal during a cycle; and
(B) if the initial value is greater than a threshold, concluding that the flyback power supply suffers output short circuit.
12. The method of claim 11 , wherein the step (A) comprises the step of sampling the current sense signal when the power switch is turned on during the cycle.