Balancing temperatures in a multi-phase DC/DC converter

1. A thermal compensation circuit for controlling duty cycles of a multi-phased DC/DC converter, the converter comprising a plurality of phased portions, each phased portion comprising a switch controlled to have a duty cycle, an on-time of the switch supplying a current through an inductor, the on-time being controlled by at least an output voltage feedback signal, the thermal compensation circuit comprising:

a duty-cycle adjustment circuit for each phased portion, the duty-cycle adjustment circuit sensing a temperature of each phased portion and adjusting the duty-cycle of each phased portion such that temperature differences between the plurality of phased portions are reduced,

wherein the duty-cycle adjustment circuit comprises:

a temperature sensor circuit for each phased portion, the temperature sensor circuit measuring a temperature proximate to its associated phased portion and generating a separate first signal for each phased portion corresponding to the temperature of that phased portion;

an averaging circuit for generating a second signal corresponding to an average of temperatures measured at the plurality of phased portions;

a temperature difference circuit for each phased portion generating a third signal for each phased portion corresponding to a difference between the first signal and the second signal; and

wherein the duty-cycle adjustment circuit for each phased portion adjusts the duty-cycle of each phased portion based on the third signal to reduce a magnitude of the third signal for each phased portion such that temperatures of the plurality of phased portions are substantially equal to the average of temperatures measured at the plurality of phased portions.

2. The thermal compensation circuit of claim 1 wherein the on-time of the switch in the converter for each phased portion is initiated by a clock signal having a different phase for each of the phased portions.

3. The thermal compensation circuit of claim 1 wherein the averaging circuit comprises:

a voltage to current conversion circuit for each first signal in each phased portion;

a current summing circuit for summing currents generated by the voltage to current conversion circuit for each first signal in each phased portion; and

a resistance for converting currents summed by the current summing circuit to the second signal corresponding to an average of temperatures measured at the plurality of phased portions.

4. The thermal compensation circuit of claim 1 wherein the temperature difference circuit for each phased portion comprises a transconductance amplifier detecting a difference between the first signal and the second signal for each of the phased portions to generate the third signal.

5. The thermal compensation circuit of claim 1 wherein the converter comprises a synchronous rectifier for each phased portion, and wherein the temperature sensor circuit for each phased portion measures a temperature proximate to the synchronous rectifier.

6. The thermal compensation circuit of claim 1 wherein the temperature sensor circuit for each phased portion measures a temperature proximate to the inductor.

7. The thermal compensation circuit of claim 1 wherein the converter is a peak current control converter.

8. A thermal compensation circuit for controlling duty cycles of a multi-phased DC/DC converter, the converter comprising a plurality of phased portions, each phased portion comprising a switch controlled to have a duty cycle, an on-time of the switch supplying a current through an inductor, the on-time being controlled by at least an output voltage feedback signal, the thermal compensation circuit comprising:

a duty-cycle adjustment circuit for each phased portion, the duty-cycle adjustment circuit sensing a temperature of each phased portion and adjusting the duty-cycle of each phased portion such that temperature differences between the plurality of phased portions are reduced,

wherein the converter generates a control voltage based on a level of an output voltage of the converter, the duty cycle adjustment circuit comprising:

a voltage to current conversion circuit for each of the phased portions converting the control voltage to a control current for each phased portion; and

a current offset circuit for offsetting the control current for each of the phased portions, to generate an offset control current,

wherein the offset current for each of the phased portions controls the duty cycle of each phased portion.

9. The thermal compensation circuit of claim 1 wherein portions of the converter are formed on a first integrated circuit chip and portions of the temperature compensation circuit are also formed on the first integrated circuit chip.

10. A method performed by a multi-phased DC/DC converter comprising:

supplying currents from a plurality of phased portions of the converter, each phased portion having a duty cycle to generate an output voltage at an output of the converter;

sensing a temperature for each phased portion to generate corresponding first signals for all the phases;

averaging the first signals to generate a second signal corresponding to an average temperature of the phased portions, wherein averaging the first signals to generate the second signal comprises:

converting the first signal in each phased portion to a current for each phased portion;

summing the current from each phased portion to generate a summed current; and

converting the summed current to a voltage, the voltage being the second signal corresponding to an average of temperatures measured at the plurality of phased portions;

generating a third signal for each phased portion corresponding to the difference between the first signal and the second signal; and

adjusting the duty cycle of each phased portion based on the third signal to control the temperature of each phased portion to be substantially equal to the average temperature of the phased portions sensed at the phased portions.

11. The method of claim 10 wherein sensing the temperature comprises sensing the temperature with a temperature sensor circuit for each phased portion, the temperature sensor circuit measuring a temperature proximate to its associated phased portion and generating the first signal for each phased portion corresponding to the temperature of that phased portion.

12. The method of claim 10 wherein supplying currents from a plurality of phased portions of the converter comprises:

controlling a switch in each phased portion to have a duty cycle, an on-time of the switch supplying a current through an inductor, the on-time being controlled by at least an output voltage feedback signal such that the output voltage of the converter is regulated to be substantially constant in a steady state.

13. The method of claim 12 wherein the on-time of the switch in the converter for each phased portion is initiated by a clock signal having a different phase for each of the phased portions.

14. The method of claim 10 wherein generating a third signal for each phased portion corresponding to the difference between the first signal and the second signal comprises detecting a difference between the first signal and the second signal by a transconductance amplifier for each of the phased portions to generate the third signal.

15. The method of claim 10 wherein the converter comprises a synchronous rectifier for each phased portion, and wherein sensing the temperature for each phased portion measures a temperature proximate to the synchronous rectifier.

16. The method of claim 10 wherein the converter comprises an inductor for each phased portion, and wherein sensing the temperature for each phased portion measures a temperature proximate to the inductor.

17. The method of claim 10 wherein the converter is a peak current control converter.

18. A method performed by a multi-phased DC/DC converter comprising:

supplying currents from a plurality of phased portions of the converter, each phased portion having a duty cycle to generate an output voltage at an output of the converter;

sensing a temperature for each phased portion to generate corresponding first signals for all the phases;

averaging the first signals to generate a second signal corresponding to an average temperature of the phased portions;

generating a third signal for each phased portion corresponding to the difference between the first signal and the second signal; and

adjusting the duty cycle of each phased portion based on the third signal to control the temperature of each phased portion to be substantially equal to the average temperature of the phased portions sensed at the phased portions,

wherein the converter generates a control voltage based on a level of the output voltage of the converter, wherein adjusting the duty cycle of each phased portion comprises:

converting the control voltage to a control current for each phased portion; and

offsetting the control current for each of the phased portions, to generate an offset control current,

wherein the offset current for each of the phased portions controls the duty cycle of each phased portion.