DRIVER CIRCUIT FOR A RESONANT CONVERTER, RELATED INTEGRATED CIRCUIT, ELECTRONIC CONVERTER AND METHOD

1 . A driver circuit for a resonant converter, comprising:

a first terminal configured to output a high-side gate drive signal to a high-side electronic switch of the resonant converter;

a second terminal configured to output a low-side gate drive signal to a low-side electronic switch of the resonant converter;

a third terminal configured to receive a signal proportional to a resonant current flowing in a primary side of the resonant converter;

a fourth terminal configured to receive a feedback signal based on an output voltage or an output current of the resonant converter;

an analog zero current comparator configured to generate a first control signal indicating when the resonant current changes sign as a function of the signal received at the third terminal,

a triangular wave generator circuit configured to provide a triangular signal; and

a comparison circuit configured to generate a second control signal indicating whether the triangular signal reaches a reference threshold;

wherein the driver circuit is configured to:

drive the high-side and the low-side electronic switch via the high-side and low-side gate drive signals during a first and a second consecutive switching semi-period, wherein each of the first and the second switching semi-period ends when the comparison circuit indicates that the triangular signal has reached the reference threshold,

once the first switching semi-period is started, open the low-side electronic switch, and close the high-side electronic switch after a first delay, and

once the second switching semi-period is started, open the high-side electronic switch, and close the low-side electronic switch after a second delay;

wherein the triangular wave generator circuit is configured to generate the triangular signal in each of the first and the second switching semi-period by:

in a first interval starting at the instant when the respective semi-period starts and ending at the instant when the first control signal indicates that the resonant current has changed sign, increasing the triangular signal with a first slope, and

in a second interval starting at the instant when the first control signal indicates that the resonant current has changed sign and ending at the instant when the second control signal indicates that the triangular signal has reached the reference threshold, decreasing the triangular signal with a second slope;

wherein the first slope has a positive value obtained by summing a negative first value to a positive second value, and the second slope has a negative value corresponding to the first negative value, wherein the absolute value of the first value is smaller than the absolute value of the second value and the first value is proportional to the feedback signal.

2 . The driver circuit according to claim 1 , wherein the triangular wave generator circuit comprises an integrator circuit configured to generate the triangular signal by integrating:

during the first interval, the sum of the positive second value and the negative first value, and

during the second interval, the negative first value.

3 . The driver circuit according to claim 2 , wherein the integrator circuit includes:

an integration capacitor connected to a node;

a first current source configured to sink a first current corresponding to the first value from the node; and

a second current source configured to source a second current corresponding to the second value to the node, wherein the second current source is enabled during the first interval.

4 . The driver circuit according to claim 3 , wherein the driver circuit includes a control circuit configured to:

assert a third control signal in response to determining that the second control signal indicates that the triangular signal reaches a reference threshold;

de-assert the third control signal in response to determining that the first control signal indicates that the resonant current changes sign;

wherein the second current source is enabled when the third control signal is asserted.

5 . The driver circuit according to claim 2 , wherein the triangular wave generator circuit comprises a bidirectional counter configured to:

during the first interval, increase a count value with a speed proportional to the sum of the positive second value and the negative first value, and

during the second interval, decrease the count value with a speed proportional to the negative first value.

6 . The driver circuit according to claim 1 , wherein the reference threshold is a ramp with a positive slope that starts at the beginning of the first and of the second switching semi-period, or that starts after a fixed delay from the beginning of the first and of the second switching semi-period, and wherein the ramp is reset at the end of the first and of the second switching semi-period.

7 . The driver circuit according to claim 6 , wherein:

the ramp reference threshold has a slope being greater than the first slope; or

the ramp reference threshold has a first slope during the first interval and a second slope during the second interval, wherein the second slope is greater than the first slope, and wherein an average value of the first slope and the second slope of the ramp reference threshold is greater than the first slope.

8 . The driver circuit according to claim 6 , wherein the ramp reference threshold is generated by a threshold generating circuit configured to receive the second control signal, and includes:

a control block configured to generate a control signal indicating a change in the reference signal;

a third switch coupled between an output node and a ground node;

a third current generator coupled between the output node and the ground node and configured to generate a third current; and

a second capacitor coupled between the output node and the ground node;

wherein the control block is configured to:

close the third switch when the control signal indicates a change in the reference signal; and

open the third switch when the control signal do not indicate a change in the reference signal.

9 . The driver circuit according to claim 8 , wherein the third current is larger than a threshold obtained as a function of the first value, the second value, the capacitance of the integration capacitor, and the capacitance of the second capacitor.

10 . The driver circuit according to claim 1 , wherein driver circuit is an integrated circuit, wherein the first, second, third and fourth terminal of the driver circuit are connected to respective pins of the integrated circuit.

11 . A device, comprising:

a driver circuit including:

a first terminal configured to output a high-side gate drive signal;

a second terminal configured to output a low-side gate drive signal;

a third terminal configured to receive a resonant current signal indicative of a resonant current external to the driver circuit;

a fourth terminal configured to receive a feedback signal based on an output signal external to the driver circuit;

an integrator circuit to generate a triangular integration signal based on the feedback signal; and

a control circuit configured to receive the integration signal and the resonant current signal and to generate the high-side gate drive signal and the low-side gate drive signal based on the integration signal and the resonant current signal.

12 . The device of claim 11 , comprising an electronic converter, the electronic converter including:

a positive input terminal and a negative input terminal;

two output terminals for providing the output signal, wherein the output signal is either an output voltage or output current;

at least one half-bridge including a high-side electronic switch and a low-side electronic switch connected in series between the positive input terminal and the negative input terminals, wherein an intermediate node between the high-side and the low-side electronic switch is a switching node, wherein the high-side electronic switch includes a gate terminal that receives the high-side gate drive signal, wherein the low-side electronic switch includes a gate terminal that receives the low-side gate drive signal.

13 . The device of claim 12 , wherein the electronic converter includes:

a resonant tank, rectifier and filter circuit connected between the switching node and the two output terminals, wherein the resonant current flows from the switching node to the resonant tank, rectifier and filter circuit;

a current sensor configured to generate the resonant current signal proportional to the resonant current;

a feedback circuit configured to generate the feedback signal as a function of the output signal.

14 . The device of claim 13 , wherein the resonant tank, rectifier and filter circuit comprises:

a transformer comprising a primary winding and a secondary winding;

a capacitor and a first inductance connected in series with the primary winding between the switching node and the positive or the negative input terminal;

a second inductance connected in parallel with the primary winding; and

a rectifier circuit D2connected between the secondary winding and the two output terminals.

15 . The device of claim 12 , wherein the control circuit includes:

an analog zero current comparator configured to generate a first control signal indicating when the resonant current changes sign as a function of the signal received at the third terminal; and

a comparison circuit configured to generate a second control signal indicating whether the triangular signal reaches a reference threshold, wherein the control circuit is configured to generate the high-side gate drive signal and the low-side gate drive signal based on the first control signal and the second control signal.

16 . The device of claim 14 , wherein the driver circuit is configured to:

drive the high-side and the low-side electronic switch via the high-side and low-side gate drive signals during a first and a second consecutive switching semi-period, wherein each of the first and the second switching semi-period ends when the comparison circuit indicates that the triangular signal has reached the reference threshold;

once the first switching semi-period is started, open the low-side electronic switch, and close the high-side electronic switch after a first delay; and

once the second switching semi-period is started, open the high-side electronic switch, and close the low-side electronic switch after a second delay.

17 . The device of claim 16 , wherein the integrator circuit is configured to generate the triangular integration signal in each of the first and the second switching semi-period by:

in a first interval starting at the instant when the respective semi-period starts and ending at the instant when the first control signal indicates that the resonant current has changed sign, increasing the triangular signal with a first slope; and

in a second interval starting at the instant when the first control signal indicates that the resonant current has changed sign and ending at the instant when the second control signal indicates that the triangular signal has reached the reference threshold, decreasing the triangular signal with a second slope;

wherein the first slope has a positive value obtained by summing a negative first value to a positive second value, and the second slope has a negative value corresponding to the first negative value, wherein the absolute value of the first value is smaller than the absolute value of the second value and the first value is proportional to the feedback signal.

18 . A method, comprising:

driving, with a driver circuit of a resonant converter, a high-side switch of the resonant converter with a high-side gate drive signal;

driving, with the driver circuit, a low-side switch of the resonant converter with a low-side gate drive signal;

receiving, with the driver circuit, a resonant current signal indicative of a resonant current in a primary side of the resonant converter;

receiving, with the driver circuit, a feedback signal based on an output signal of the resonant converter;

generating, with an integrator circuit of the driver circuit, a triangular integration signal based on the feedback signal; and

generating, with the driver circuit, the high-side gate drive signal and the low-side gate drive signal based on the integration signal and the resonant current signal.

19 . The method of claim 18 , comprising:

driving the high-side and the low-side electronic switch via the drive signals during a first and a second consecutive switching semi-period, wherein each of the first and the second switching semi-period ends when the triangular integration signal has reached a reference threshold;

once the first switching semi-period is started, opening the low-side electronic switch, and closing the high-side electronic switch after a first delay; and

once the second switching semi-period is started, opening the high-side electronic switch, and closing the low-side electronic switch after a second delay.

20 . The method of claim 19 , comprising:

generating the triangular integration signal in each of the first and the second switching semi-period by:

in a first interval starting at the instant when the respective semi-period starts and ending at the instant when the resonant current has changed sign, increasing the triangular integration signal with a first slope; and

in a second interval starting at the instant when the resonant current has changed sign and ending at the instant when the triangular integration signal has reached the reference threshold, decreasing the triangular signal with a second slope;

wherein the first slope has a positive value obtained by summing a negative first value to a positive second value, and the second slope has a negative value corresponding to the first negative value, wherein the absolute value of the first value is smaller than the absolute value of the second value and the first value is proportional to the feedback signal.