Control circuit for offline power converter without input capacitor
View Patent ↗The present invention provides a control circuit for a power converter. The control circuit includes a switching circuit, an input-voltage detection circuit and a current-limit threshold. The switching circuit generates a switching signal coupled to switch a transformer of the power converter for regulating an output of the power converter in response to a feedback signal. The input-voltage detection circuit generates a control signal when an input voltage of the power converter is lower than a low-input threshold. The feedback signal is generated in response to the output of the power converter. A maximum duty of the switching signal is increased in response to the control signal. The current-limit threshold is for limiting a maximum value of a switching current flowing through the transformer. The current-limit threshold is increased in response to the control signal. An input of the power converter doesn't connect with electrolytic bulk capacitors.
1. A control circuit of a power converter comprising:
a switching circuit for generating a switching signal coupled to switch a transformer of said power converter for regulating an output of said power converter in response to a feedback signal; and
an input-voltage detection circuit for generating a control signal when an input voltage of said power converter is lower than a low-input threshold,
wherein said feedback signal is generated in response to said output of said power converter, and a maximum duty of said switching signal is increased in response to said control signal, and
wherein an input of said power converter doesn't connect with electrolytic bulk capacitors.
2. The control circuit as claimed in claim 1 , wherein a maximum value of a switching current flowing through said transformer is limited by a current-limit threshold, and said current-limit threshold is increased in response to said control signal.
3. The control circuit as claimed in claim 1 , wherein said input-voltage detection circuit detects a DC input voltage of said power converter via said transformer, and said input voltage of said power converter is correlated to said DC input voltage of said power converter.
4. A controller of a power converter, comprising:
a switching circuit for generating a switching signal coupled to switch a transformer of said power converter for regulating an output of said power converter in response to a feedback signal;
an input-voltage detection circuit for generating a control signal when an input voltage of said power converter is lower than a low-input threshold; and
a threshold-generation circuit for generating a current-limit threshold for limiting a maximum value of a switching current flowing through said transformer,
wherein said feedback signal is generated in response to said output of said power converter, and said current-limit threshold is increased in response to said control signal.
5. The controller as claimed in claim 4 further comprising:
a maximum-duty circuit for generating a maximum-duty signal for limiting a maximum duty of said switching signal,
wherein said maximum duty of said switching signal is increased in response to said control signal.
6. The controller as claimed in claim 4 , wherein an input of said power converter doesn't connect with electrolytic bulk capacitors.
7. The controller as claimed in claim 4 , wherein said input-voltage detection circuit detects a DC input voltage of said power converter via said transformer, and said input voltage of said power converter is correlated to said DC input voltage of said power converter.
8. A control circuit of an offline power converter comprising:
a switching circuit for generating a switching signal coupled to switch a transformer of said offline power converter for regulating an output of said offline power converter in response to a feedback signal;
an input-voltage detection circuit for generating a control signal when an input voltage of said offline power converter is lower than an input-voltage threshold;
a threshold-generation circuit for generating a current-limit threshold for limiting a maximum value of a switching current flowing through said transformer; and
a maximum-duty circuit for generating a maximum-duty signal for limiting a maximum duty of said switching signal,
wherein said feedback signal is generated in response to said output of said offline power converter, said current-limit threshold is increased in response to said control signal, and said maximum duty of said switching signal is increased in response to said control signal.
9. The control circuit as claimed in claim 8 , wherein said input of said power converter doesn't connect with electrolytic bulk capacitors.
10. The control circuit as claimed in claim 8 , wherein said input-voltage detection circuit detects said input voltage of said offline power converter via said transformer.