A driver circuit for a resonant converter configured to generate an output voltage or output current at two output terminals from an input voltage applied to a positive and a negative input terminal, said resonant converter comprising:
- at least one half-bridge including a high side electronic switch and a low side electronic switch connected in series between said positive and said negative input terminals, wherein an intermediate node between said high side electronic switch and said low side electronic switch represents a switching node;
- and
- a resonant tank, rectifier and filter circuit connected between said switching node and said two output terminals;
- wherein said driver circuit comprises:
- a first and a second terminal configured to be connected to control terminals of said high-side electronic switch and said low-side electronic switch in order to drive said half-bridge via respective drive signals;
- a third terminal configured to be connected to a current sensor in order to receive a signal proportional to a resonant current flowing from the switching node to said resonant tank, rectifier and filter circuit;
- a fourth terminal configured to be connected to a feedback circuit in order to receive a feedback signal determined as a function of said output voltage or said output current;
- a comparator configured to generate a first control signal indicating when the resonant current changes sign as a function of the signal received at said third terminal;
- a first ramp generator circuit configured to output a first ramp signal;
- and
- a comparison circuit configured to determine whether said first ramp signal reaches at least one reference threshold;
- wherein the driver circuit is configured to:
- drive said high-side electronic switch and said low-side electronic switch via said drive signals during consecutive first and second switching semi-periods, wherein each of said first and said second switching semi-period ends when said comparison circuit indicates that said first ramp signal has reached a respective reference threshold;
- once said first switching semi-period is started, open said low-side electronic switch and close said high-side electronic switch after a delay;
- and
- once said second switching semi-period is started, open said high-side electronic switch and close said low-side electronic switch after said delay;
- wherein said driver circuit further comprises:
- a control circuit configured to generate in each of said first and said second switching semi-periods one or more control signals indicating:
- a first interval starting at an instant when a respective semi-period is started and ending at an instant when said first control signal indicates that the resonant current has changed sign;
- and
- a second interval starting at an instant when said first control signal indicates that the resonant current has changed sign and an instant when said comparison circuit indicates that said first ramp signal has reached a respective reference threshold;
- and
- a correction circuit configured to:
- modify said first ramp signal provided at input to said comparison circuit, whereby said first ramp signal has a first gradient value during said first interval and a second gradient value during said second interval, said first gradient value being a non-zero value and an absolute value of said second gradient value being greater than an absolute value of said first gradient value;
- or
- modify one or more of the reference thresholds of said comparison circuit by adding a second ramp signal to a respective initial threshold value.