Switching DC-to-Dc converter having on-time signal generation circuit and method for generating signal indicative of converter on-time

A DC-to-DC converter, comprising:

• a switching controller configured to generate control signals and having switching period Tosc;
• and
• power circuitry, coupled to the controller and configured to define at least one power channel including an inductor and at least one power switch, wherein the power circuitry asserts an output potential during steady state operation, in response to the control signals and an input potential Vin, wherein the switching controller includes an on-time signal generation circuit, said on-time generation signal circuit comprising:
• a comparator having a first input and a second input and a comparator output;
• a ramp generator having an output coupled to the first input of the comparator and an input coupled to receive the input potential Vin, wherein the ramp generator is configured to assert at said output a periodic ramped potential, having peak level kVin+Voffset and period Tosc, in response to said input potential Vin, wherein Voffset can but need not have a nonzero value;
• and
• an amplifier having an amplifier output coupled to the second input of the comparator and an amplifier input coupled to receive an amplifier input potential Vout, wherein the amplifier input potential is one of the output potential and a DC potential proportional to a desired level of the output potential, the amplifier is configured to assert at the amplifier output an amplified potential kVout in response to the amplifier input potential Vout, the comparator asserts an on-time signal at the comparator output in response to the periodic ramped potential and the amplified potential, and the switching controller includes circuitry coupled to the comparator output and configured to generate the control signals in response to signals including said on-time signal.

A method for generating an on-time signal which is a pulse train comprising pulses TON, such that each of the pulses TON has a width equal to TOSC (Vout/Vin), where TOSC, Vout, and Vin are, respectively, a switching period of a DC-to-DC converter, a control potential, and an input potential of the DC-to-DC converter, wherein the control potential Vout is one of an output potential of the DC-to-DC converter and a DC potential proportional to a desired level of said output potential, said method including the steps of:

• (a) in response to the input potential Vin of the DC-to-DC converter, generating a periodic ramped potential having peak level kVin+Voffset and the period Tosc, where Voffset can but need not have a nonzero value;
• (b) in response to the control potential Vout, generating an amplified potential kVout;
• and
• (c ) generating the binary pulse train by comparing the periodic ramped potential with the amplified potential.