Method and apparatus for control of semi-resonant and resonant converters

A method of digitally controlling cycle-by-cycle switching of a multi-phase voltage converter, each phase including a high-side switch connected between an input voltage terminal and a switching node, a low-side switch connected between the switching node and ground, a passive circuit connecting the switching node to a common output node of the multi-phase voltage converter, and a synchronous rectification (SR) switch connected between the passive circuit and ground and through which a half cycle sinusodial-like current is conducted when turned on, the method comprising for each phase:

• at the beginning of each switching cycle, entering a first state of a digital PWM (pulse width modulation) state machine in which a control signal for the high-side switch is activate and control signals for the low-side and SR switches are deactivate;
• exiting the first state and entering a second state of the digital PWM state machine in which the control signals for all switches are deactivate;
• exiting the second state and entering a third state of the digital PWM state machine in which the control signal for the high-side switch is deactivate and the control signals for the low-side and SR switches are activate;
• exiting the third state and entering a fourth state of the digital PWM state machine in which the control signals for the high-side and low-side switches are deactivate and the control signal for the SR switch is activate and then exiting the fourth state and entering a fifth state of the digital PWM state machine in which the control signals for all switches are deactivate, or exiting the third state and entering the fifth state without entering the fourth state;
• and
• exiting the fifth state and entering the first state at the beginning of the next switching cycle.