Patent ID: 7616454

Claim:
A control circuit having an adjustable waveform for limiting an output power of a power converter, comprising: a switch, coupled to a transformer for switching the transformer; an oscillation circuit, generating an oscillation signal; a first circuit, generating a temporally variable control signal to control the switch in response to the oscillation signal and a feedback signal for regulating the output of the power converter; said control signal having a temporal width responsive to a temporal width of a current signal; a second circuit, generating an adjustable waveform signal in accordance with the oscillation signal to control the control signal and limit the output power of the power converter; wherein the waveform signal is synchronized with the control signal, and the control signal is switched off when the voltage of the current signal exceeds the voltage of the waveform signal; a third circuit, generating a ramp signal in response to the oscillation signal; and a variable resistor, coupled to the second circuit to program the adjustable waveform of the waveform signal; said resistor externally interposed between ground and the control circuit; wherein the value of the resistor directly adjusts the voltage of the adjustable waveform signal; wherein the current signal is responsive to low and high input line voltages, such that the power converter produces equal output power for both the low and high input line voltages.