Power converter efficiency boost at low loads, keeping maximum constant switching frequency operation range

A power converter system configured to operate in a pulse-width modulation (PWM) continuous conduction mode (CCM), a PWM discontinuous conduction mode (DCM), and a deep-pulse frequency modulation (DPFM) mode, the power converter system comprising:

• an output terminal configured to deliver power to a load;
• an input terminal configured to receive an input voltage;
• and
• modulation circuitry connected to the input and output terminals and configured to:
• define a minimum on-time based on the input voltage,
• wherein an adjustment to the minimum on-time is proportional to an inverse magnitude of the input voltage, and
• wherein the minimum on-time is a minimum duration for an on-time of a duty cycle for an operating frequency of the power converter system
• wherein the power converter system is configured to:
• in response to a magnitude of the input voltage being less than or equal to a first threshold voltage, set the minimum on-time to a first fixed value;
• and
• in response to the magnitude of the input voltage exceeding a second threshold voltage, set the minimum on-time to a second fixed value, wherein the operating frequency of the power converter system has an associated operating period, and while operating in DPFM mode and in response to the associated operating period exceeding a threshold period duration, the power converter system is configured to increase the minimum on-time,
• wherein the power converter system is further configured to:
• update a value of a DPFM timer for the threshold period duration while operating in DPFM mode such that:
• the power converter system enters the DPFM mode with a first set of operating conditions of the input voltage and an output current, and
• the power converter system exits DPFM mode with a second set of operating conditions.

A method performed by a power converter that is configured to operate in a pulse-width modulation (PWM) continuous conduction mode (CCM), a PWM discontinuous conduction mode (DCM), and a deep-pulse frequency modulation (DPFM) mode, the method comprising:

• receiving, at an input terminal of the power converter, an input voltage;
• and
• receiving, by modulation circuitry of the power converter connected to the input terminal, the input voltage;
• and
• generating, by the modulation circuitry, an adjustment to a minimum on-time based on the input voltage,
• wherein the adjustment is proportional to an inverse magnitude of the input voltage, and
• wherein the minimum on-time is a minimum duration for an on-time of a duty cycle for an operating frequency of the power converter,
• the method further comprising:
• in response to a magnitude of the input voltage being less than or equal to a first threshold voltage, setting the minimum on-time to a first fixed value;
• and
• in response to the magnitude of the input voltage exceeding a second threshold voltage, setting the minimum on-time to a second fixed value, wherein the operating frequency of the power converter has an associated operating period, and while operating in DPFM mode and in response to the associated operating period exceeding a threshold period duration, the power converter is configured to increase the minimum on-time;
• and
• updating a value of a DPFM timer for the threshold period duration while operating in DPFM mode such that:
• the power converter enters the DPFM mode with a first set of operating conditions of the input voltage and an output current, and
• the power converter exits DPFM mode with a second set of operating conditions.