A controller for use in a power converter, the controller comprising: an input configured to receive a request signal (136, 236, 336, 436) that includes request events (137, 337) responsive to an output of the power converter, wherein the request events have periods T REQ between successive request events and a frequency f REQ of the request events is equal to one over the period T REQ, wherein each request event indicates that the controller should turn on a power switch coupled to an input of the power converter in response to the request event; and a frequency to on-time converter (138, 238) coupled to the input and configured to receive the request signal to generate a primary drive signal (128, 228, 328, 428) in response to the request signal to control switching of the power switch to control a transfer of energy from an input of the power converter to an output of the power converter, wherein the on-time (356, 456) of the primary drive signal (128, 228, 328, 428) has a one-to-one relationship with the frequency fREQ of request events (137, 337) in the request signal (136, 236, 336, 436), and the on-time (356, 456) is increased linearly responsive to an increase in the frequency f REQ of the request events in the request signal, the frequency to on-time converter is configured to determine the on-time of the power switch for a current switching cycle of the primary drive signal in response to the frequency fREQ of the request events in the request signal in a previous switching cycle, characterized in that the frequency to on-time converter comprises a first integrator configured to generate a respective first voltage in response to each of the request events (137, 337), a sample and hold circuit coupled to the first integrator and configured to receive each of the request events to generate a respective second voltage in response to each of the first voltages, a voltage-controlled current source coupled to the sample and hold circuit and configured to generate a voltage-controlled current in response to each of the second voltages, a second integrator coupled to the voltage-controlled current source and configured to receive each of the request events to generate a respective third voltage in response to the voltage-controlled current, and a comparator coupled to the second integrator and configured to compare each of the third voltages and a reference voltage to generate the drive signal. an input configured to receive a request signal (136, 236, 336, 436) that includes request events (137, 337) responsive to an output of the power converter, wherein the request events have periods T REQ between successive request events and a frequency f REQ of the request events is equal to one over the period T REQ, wherein each request event indicates that the controller should turn on a power switch coupled to an input of the power converter in response to the request event; and a frequency to on-time converter (138, 238) coupled to the input and configured to receive the request signal to generate a primary drive signal (128, 228, 328, 428) in response to the request signal to control switching of the power switch to control a transfer of energy from an input of the power converter to an output of the power converter, wherein the on-time (356, 456) of the primary drive signal (128, 228, 328, 428) has a one-to-one relationship with the frequency fREQ of request events (137, 337) in the request signal (136, 236, 336, 436), and the on-time (356, 456) is increased linearly responsive to an increase in the frequency f REQ of the request events in the request signal, the frequency to on-time converter is configured to determine the on-time of the power switch for a current switching cycle of the primary drive signal in response to the frequency fREQ of the request events in the request signal in a previous switching cycle, characterized in that the frequency to on-time converter comprises a first integrator configured to generate a respective first voltage in response to each of the request events (137, 337), a sample and hold circuit coupled to the first integrator and configured to receive each of the request events to generate a respective second voltage in response to each of the first voltages, a voltage-controlled current source coupled to the sample and hold circuit and configured to generate a voltage-controlled current in response to each of the second voltages, a second integrator coupled to the voltage-controlled current source and configured to receive each of the request events to generate a respective third voltage in response to the voltage-controlled current, and a comparator coupled to the second integrator and configured to compare each of the third voltages and a reference voltage to generate the drive signal. a first integrator configured to generate a respective first voltage in response to each of the request events (137, 337), a sample and hold circuit coupled to the first integrator and configured to receive each of the request events to generate a respective second voltage in response to each of the first voltages, a voltage-controlled current source coupled to the sample and hold circuit and configured to generate a voltage-controlled current in response to each of the second voltages, a second integrator coupled to the voltage-controlled current source and configured to receive each of the request events to generate a respective third voltage in response to the voltage-controlled current, and a comparator coupled to the second integrator and configured to compare each of the third voltages and a reference voltage to generate the drive signal.