Switching regulator control circuit
The present invention discloses a switching regulator control circuit which distinguishes the output short-circuit condition, which imposes immediate danger, from other mild over current conditions. The switching regulator control circuit includes: an over current judgment circuit comparing a current sense signal with a current limit to generate an over current indication signal; a time comparison circuit comparing the over current indication signal with a clock signal to generate an output short-circuit indication signal; and a timer receiving the over current indication signal and the output short-circuit indication signal, wherein when the output short-circuit indication signal does not indicate output short-circuit, the timer counts a first time period, and when the output short-circuit indication signal indicates output short-circuit, the timer counts a second time period shorter than the first time period, for better safety protection.
1. A switching regulator control circuit comprising:
an over current judgment circuit comparing a current sense signal with a current limit to generate an over current indication signal;
a time comparison circuit comparing the over current indication signal with a clock signal to determine whether the current sense signal continuously reaches the current limit in a time period and generate an output short-circuit indication signal accordingly; and
a timer receiving the over current indication signal and the output short-circuit indication signal, wherein when the output short-circuit indication signal does not indicate an output short-circuit condition, the timer counts a first time period, and when the output short-circuit indication signal indicates an output short-circuit condition, the timer counts a second time period shorter than the first time period, and the timer outputs an output short-circuit protection signal at the end of the second time period.
2. The switching regulator control circuit of claim 1 , wherein the over current judgment circuit includes a comparator for comparing the current sense signal with the current limit.
3. The switching regulator control circuit of claim 1 , wherein the time comparison circuit includes a flip-flop which has a signal input terminal and a clock input terminal, wherein the signal input terminal is coupled to the clock signal and the clock input terminal is coupled to the over current indication signal.
4. The switching regulator control circuit of claim 1 , wherein the time comparison circuit includes:
a logic gate receiving the over current indication signal and the clock signal, and generating an output signal; and
a flip-flop having an signal input terminal and a clock input terminal, wherein the signal input terminal receives the output signal from the logic gate, and the clock input terminal receives the clock signal.
5. The switching regulator control circuit of claim 1 , wherein the switching regulator is an AC-DC switching power converter or a DC-DC switching power converter.