Control device for a rectifier of a switching converter

1. A control device, comprising:

a driver circuit configured to generate a first control signal configured to turn on and turn off a first transistor of a rectifier of a switching controller;

a measuring circuit configured to measure a conduction time of a body diode of the first transistor during each of plural converter switching cycles;

a comparison circuit configured to output a comparison signal indicative of whether a drain-source voltage of the first transistor is equal to or less than a voltage threshold, wherein the driver circuit is configured, in response to the comparison signal indicating that the drain-source voltage is greater than the voltage threshold, to turn off the first transistor and increase, in a next switching cycle, the voltage threshold by a quantity based on a measurement of the conduction time of the body diode;

wherein the measuring circuit is configured to determine whether the measured conduction time is greater or less than a threshold value;

wherein the driver circuit is configured to, in response to the measuring circuit determining that the measured conduction time is greater than the threshold value, delay an off time instant of the transistor by a fixed quantity in the next switching cycle, cycle by cycle until the measured conduction time is equal to or less than the threshold value; and

wherein the driver circuit is configured to, in response to the measuring circuit determining that the measured conduction time is equal to or less than the threshold value, maintain said voltage threshold.

2. The control device according to claim 1 , comprising a delay circuit configured to obtain a delayed drain-source voltage by delaying the drain-source voltage of the transistor, wherein the driver circuit is configured to turn off said transistor in response to determining that the drain-source voltage of the transistor is less than the voltage threshold and the delayed drain-source voltage reaches another voltage threshold.

3. The control device according to claim 1 , comprising a threshold setting circuit configured to vary said quantity as a function of the measured conduction time of the body diode of the at least one transistor.

4. The control device according to claim 3 , wherein said threshold setting circuit includes capacitor configured to be charged by a current for a time period depending on said measured conduction time of the body diode of the transistor, the threshold setting circuit being configured to set the quantity based on the time period.

5. The control device according to claim 3 , wherein the threshold setting circuit is configured to set progressively increasing threshold voltages by the quantity which progressively decreases depending on a progressive decrease of said measured conduction time.

6. A method, comprising:

controlling a rectifier of a switching converter, the controlling including:

determining whether a drain-source voltage of a transistor of the rectifier is equal to or less than a voltage threshold;

generating a turn off signal, configured to turn off the transistor, in response determining that the drain-source voltage is equal or less than the voltage threshold;

measuring a conduction time of a body diode of the transistor during each of a plurality of switching cycles; and

increasing, in a next switching cycle, the voltage threshold by a quantity based on the measured conduction time;

wherein, in response to determining that the drain-source voltage of the transistor is less than the voltage threshold, the method further comprises:

determining whether the measured conduction time is greater or less than a threshold value, and

if the measured conduction time is greater than the threshold value,

delaying an off time instant of the transistor by a fixed quantity in the next switching cycle, cycle by cycle until the measured conduction time is equal to or less than the threshold value.

7. The method according to claim 6 , wherein said quantity is variable and is a function of the measured conduction time of the body diode of the transistor.

8. The method according to claim 7 , comprising setting progressively increasing threshold voltages by the quantity which progressively decreases depending on a progressive decrease of said measured conduction time.

9. A switching converter, comprising:

a rectifier that includes a transistor; and

a control device configured to control the rectifier, the control device including:

a driver circuit configured to generate a first control signal configured to turn on and turn off a first transistor of a rectifier of a switching controller;

a measuring circuit configured to measure a conduction time of a body diode of the first transistor during each of plural converter switching cycles; and

a comparison circuit configured to output a comparison signal indicative of whether a drain-source voltage of the first transistor is equal to or less than a voltage threshold, wherein the driver circuit is configured, in response to the comparison signal indicating that the drain-source voltage is greater than the voltage threshold, to turn off the first transistor and increase, in a next switching cycle, the voltage threshold by a quantity based on a measurement of the conduction time of the body diode; and

wherein the measuring circuit is configured to determine whether the measured conduction time is greater or less than a threshold value;

wherein the driver circuit is configured to, in response to the measuring circuit determining that the measured conduction time is greater than the threshold value, delay an off time instant of the transistor by a fixed quantity in the next switching cycle, cycle by cycle until the measured conduction time is equal to or less than the threshold value; and

wherein the driver circuit is configured to, in response to the measuring circuit determining that the measured conduction time is equal to or less than the threshold value, maintain said voltage threshold.

10. The switching converter according to claim 9 , wherein the control device includes a delay circuit configured to obtain a delayed drain-source voltage by delaying the drain-source voltage of the transistor, wherein the driver circuit is configured to turn off said transistor in response to determining that the drain-source voltage of the transistor is less than the voltage threshold and the delayed drain-source voltage reaches another voltage threshold.

11. The switching converter according to claim 9 , wherein the control device includes a threshold setting circuit configured to vary said quantity as a function of the measured conduction time of the body diode of the at least one transistor.

12. The switching converter according to claim 11 , wherein said threshold setting circuit includes capacitor configured to be charged by a current for a time period depending on said measured conduction time of the body diode of the transistor, the threshold setting circuit being configured to set the quantity based on the time period.

13. The switching converter according to claim 11 , wherein the threshold setting circuit is configured to set progressively increasing threshold voltages by the quantity which progressively decreases depending on a progressive decrease of said measured conduction time.