Control Circuit for Offline Power Converter without Input Capacitor

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.

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 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.