Patent ID: 8344703

Claim:
For controlling a switching power converter having a primary switching element, an input voltage, an output voltage, and a load current, a variable on-time generator comprises: a primary feedback circuit comprising: a charge storage device connected in parallel with a bypass switch to a current source whereby the current source charges the charge storage device when the bypass switch is opened; and a comparison circuit connected to the charge storage device and to a reference voltage and having an output that changes state when the charge storage device reaches a voltage that is greater than the reference voltage; wherein the output of the comparison circuit is configured to control the primary switching element of the switching power converter; and at least one of a first variable control circuit and a second variable control circuit, wherein: the first variable control circuit comprises: a differential amplifier configured to compare the load current and the output voltage of the switching power converter; and a first transconductance amplifier connected to the current source of the primary feedback circuit and configured to shunt a portion of the current from the current source in response to an output of the differential amplifier of the first variable control circuit; and wherein the second variable control circuit comprises: a second transconductance amplifier connected to the current source of the primary feedback circuit and configured to shunt a portion of the current from the current source wherein the portion is dependent on the output voltage of the switching power converter.