Architecture for AC/DC SMPS with PFC and multimode LLC DC/DC converter

A method of operating an AC input AC/DC Switching Mode Power Supply (SMPS)

• the AC/DC SMPS comprising:
• a first stage comprising a non-isolated AC/DC converter comprising a power factor correction (PFC) stage which receives an AC input voltage and provides a DC bus voltage;
• and a PFC controller;
• a second stage comprising an isolated DC/DC converter comprising an LLC resonant DC/DC converter which receives the DC bus voltage and provides an output voltage, and an LLC controller;
• the LLC resonant DC/DC converter comprising first and second half-bridge legs, which are operable in a half-bridge mode and in a full-bridge mode;
• and
• a control circuit;
• the method comprising, in the control circuit,
• sensing the AC input voltage,
• providing a first control signal, comprising a voltage feedback signal, to the PFC controller to regulate the output voltage of the PFC to provide a DC bus voltage, dependent on the AC input voltage;
• providing a second control signal, comprising one of a full-bride mode control signal and a half-bridge mode control signal, to the LLC controller to operate the LLC resonant DC/DC converter in the full-bridge mode or the half-bridge mode, dependent on the AC input voltage;
• and
• in a first operating mode, for a low line AC input at or below a threshold value, controlling the PFC stage to regulates the DC bus voltage to a first value and controlling the LLC resonant DC/DC converter to operate in full-bridge mode to provide a first output voltage;
• and
• in a second operating mode, for a high line AC input above the threshold value, controlling the PFC stage to regulate the DC bus voltage to a second value, which is twice the first value, and controlling the LLC resonant DC/DC converter to operate in the half-bridge mode to provide the first output voltage.

A control circuit for an AC input AC/DC Switching Mode Power Supply (SMPS),

• the AC/DC SMPS comprising:
• a first stage comprising a non-isolated AC/DC converter comprising a power factor correction (PFC) stage which receives an AC input voltage and provides a DC bus voltage, and a PFC controller;
• a second stage comprising an isolated DC/DC converter comprising an LLC resonant DC/DC converter which receives the DC bus voltage and provides an output voltage;
• and an LLC controller;
• the LLC resonant DC/DC converter comprising first and second half-bridge legs, which are operable in an half-bridge mode and in a full-bridge mode;
• the control circuit being configured for implementing a method comprising:
• sensing the AC input voltage,
• providing a first control signal, comprising a voltage feedback control signal, to the PFC controller to regulate the output voltage of the PFC to provide the DC bus voltage, dependent on the Ac input voltage;
• providing a second control signal, comprising one of a full bridge mode and a half-bridge mode control signal, to the LLC controller to operate the LLC resonant DC/DC converter in the full-bridge mode or the half-bridge mode, dependent on the AC input voltage;
• in a first operating mode, for a low line AC input at or below a threshold value, controlling the PFC to regulates the DC bus voltage to a first value and controlling the LLC resonant DC/DC converter to operate in a full-bridge mode to provide a first output voltage;
• and
• in a second operating mode, for a high line Ac input above the threshold value, controlling the PFC to regulates the DC bus voltage to a second value, which is twice the first value, and controlling the LLC resonant DC/DC converter to operate in the half-bridge mode to provide the first output voltage.