Protection circuit for power converter
View Patent ↗A protection circuit of a power converter without an input capacitor is disclosed. The protection circuit comprises a high voltage switch, a detection circuit and a control circuit. The switch senses an input voltage of the power converter via a resistor for generating a first signal. The detection circuit coupled to a transformer senses the input voltage of the power converter for generating a second signal. The control circuit controls a switching signal in response to the first signal and the second signal. The switching signal is utilized to switching the transformer for regulating the power converter; and the level of the first signal and the second signal is correlated a level of the input voltage of the power converter.
1. A protection circuit of a power converter, comprising:
a switch configured to sense an input voltage of the power converter via a resistor for generating a first signal;
a detection circuit coupled to a transformer to sense the input voltage of the power converter for generating a second signal;
a control circuit configured to control a switching signal in response to the first signal and the second signal;
wherein the switching signal is utilized to switching the transformer for regulating the power converter; a level of the first signal and the second signal is correlated to a level of the input voltage of the power converter,
wherein the detection circuit receives the switching signal, and the second signal is generated in response to the enable of the switching signal,
wherein when a power voltage is applied to the protection circuit, the protection circuit generates a pulse signal for over voltage protection; an over-voltage signal is generated when the pulse signal is at an enable state and the first signal is higher than a first threshold, wherein the over-voltage signal is coupled to disable the switching signal,
wherein the switch is controlled by the pulse signal and is turned on in response to enablement of the pulse signal so as to generate the first signal accordingly.
2. The protection circuit as claimed in claim 1 , further comprising a low-pass filter for the generation of the second signal.
3. The protection circuit as claimed in claim 1 , in which the switching signal is generated by a primary-side controlled controller.
4. The protection circuit as claimed in claim 1 , in which the over-voltage signal is further generated once the second signal is higher than a second threshold; an under-voltage signal is generated once the second signal is lower than a third threshold, wherein the under-voltage signal is coupled to limit the switching signal.
5. The protection circuit as claimed in claim 1 , in which the first signal is generated in response to turn on of the protection circuit.
6. The protection circuit as claimed in claim 1 , in which the control circuit further comprising a de-bounce circuit providing a delay time for generating an under-voltage signal once the second signal is lower than a third threshold.
7. The protection circuit as claimed in claim 1 , in which a switching frequency of the switching signal is decreased in response to an enable of an under-voltage signal.
8. The protection circuit as claimed in claim 1 , in which the second signal is generated during the switching of the transformer.