Thermally compensated current sensing of intrinsic power converter elements

Abstract

A DC-to-DC converter includes one or more power switches, a pulse width modulation circuit for generating control pulses for the power switches, and an output inductor connected to the power switches. A thermally compensated current sensor is connected to an intrinsic current sensing element exhibiting a temperature-based parameter non-linearity. The thermally compensated current sensor has a temperature coefficient that substantially matches a temperature coefficient of an intrinsic power converter element used to measure current flow, thus linearizing the current measurement. Also, a current feedback loop circuit cooperates with the pulse width modulation circuit to control the power switches responsive to the thermally compensated current sensor.

1. A DC-to-DC converter comprising:
 at least one power switch; 
 a control circuit for generating control pulses for the at least one power switch; 
 an output inductor connected to the at least one power switch; and 
 a thermally compensated current sensor operatively connected in parallel to the output inductor for sensing current in the output inductor, the thermally compensated current sensor having a temperature coefficient that substantially matches a temperature coefficient of the output inductor wherein the at least one power switch is responsive to the thermally compensated current sensor. 
 
     
     
       2. A DC-to-DC converter according to  claim 1 , wherein the at least one power switch comprises at least one field effect transistor. 
     
     
       3. A DC-to-DC converter according to  claim 1 , wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together. 
     
     
       4. A DC-to-DC converter according to  claim 1 , wherein the at least one power switch comprises a low side power switch and a high side power switch connected together. 
     
     
       5. A DC-to-DC converter according to  claim 1 , wherein the thermally compensated current sensor comprises a resistor and capacitor connected in series. 
     
     
       6. A DC-to-DC converter according to  claim 5 , wherein the resistor of the thermally compensated current sensor comprises a positive temperature coefficient resistor. 
     
     
       7. A DC-to-DC converter comprising:
 at least one power switch; 
 a control circuit for generating control pulses for the at least one power switch; 
 an output inductor connected to the at least one power switch; and 
 a thermally compensated current sensor connected to the at least one power switch for providing a sensed current related to a current being conducted through the output inductor, and having a temperature coefficient that substantially matches a temperature coefficient of an on-state resistance of the at least one power switch wherein the at least one power switch is responsive to the thermally compensated current sensor. 
 
     
     
       8. A DC-to-DC converter according to  claim 7 , wherein the at least one power switch comprises at least one field effect transistor. 
     
     
       9. A DC-to-DC converter according to  claim 7 , wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together. 
     
     
       10. A DC-to-DC converter according to  claim 7 , wherein the at least one power switch comprises a low side power switch and a high side power switch connected together. 
     
     
       11. A DC-to-DC converter according to  claim 7 , wherein the thermally compensated current sensor is connected between the at least one power switch and a current feedback loop circuit. 
     
     
       12. A DC-to-DC converter according to  claim 11 , wherein the thermally compensated current sensor comprises a resistor. 
     
     
       13. A multiphase DC-to-DC converter comprising:
 at least first and second channels each comprising 
 a power device including a low side power switch and a high side power switch connected together; 
 a control circuit for generating control pulses for the power device; 
 an output inductor connected to the power device; and 
 a thermally compensated current sensor connected to the power device for providing a sensed current related to a current being conducted through the output inductor, the thermally compensated current sensor having a temperature coefficient that substantially matches a temperature coefficient of an on-state resistance of the low side power switch, wherein the power device is responsive to the thermally compensated current sensor. 
 
     
     
       14. A multiphase DC-to-DC converter according to  claim 13 , wherein each of the power switches comprises a field effect transistor. 
     
     
       15. A multiphase DC-to-DC converter according to  claim 13 , wherein the thermally compensated current sensor is connected between the power device and a current feedback loop circuit. 
     
     
       16. A multiphase DC-to-DC converter according to  claim 15 , wherein the thermally compensated current sensor comprises a resistor. 
     
     
       17. A multiphase DC-to-DC converter comprising:
 at least first and second channels each comprising 
 a power device including a low side power switch and a high side power switch connected together; 
 a control circuit for generating control pulses for the power device; 
 an output inductor connected to the power device; 
 a current sensor connected to the power device for providing a sensed current proportional to a current being conducted through the output inductor; 
 a current feedback loop circuit cooperating with the control circuit for controlling the power device responsive to the current sensor; and 
 a feedback resistive network connected between an input of the control circuit of each of the at least first and second channels and the output terminal, and comprising a resistor having a temperature coefficient that substantially matches a temperature coefficient of an on-state resistance of the low side power switch of the power device of the at least first and second channels. 
 
     
     
       18. A multiphase DC-to-DC converter according to  claim 17 , wherein each of the power switches comprises a field effect transistor. 
     
     
       19. A method of regulating a DC-to-DC converter comprising at least one power switch, a control circuit for generating control pulses for the at least one power switch, and an output inductor connected to the at least one power switch, the method comprising:
 sensing current passing through the inductor using a thermally compensated current sensor connected in parallel to the output inductor and having a temperature coefficient that substantially matches a temperature coefficient of the output inductor; and 
 controlling the at least one power switch in response to the thermally compensated current sensor. 
 
     
     
       20. A method according to  claim 19 , wherein the at least one power switch comprises at least one field effect transistor. 
     
     
       21. A method according to  claim 19 , wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together. 
     
     
       22. A method according to  claim 19 , wherein the thermally compensated current sensor comprises a resistor and capacitor connected in series. 
     
     
       23. A method according to  claim 22 , wherein the resistor comprises a positive temperature coefficient resistor. 
     
     
       24. A method of regulating a DC-to-DC converter comprising at least one power switch, a control circuit for generating control pulses for the at least one power switch, and an output inductor connected to the at least one power switch, the method comprising:
 providing a sensed current related to a current being conducted through the output inductor using a thermally compensated current sensor connected to the at least one power switch and having a temperature coefficient that substantially matches a temperature coefficient of an on-state resistance of the at least one power switch; and 
 controlling the at least one power switch in response to the thermally compensated current sensor. 
 
     
     
       25. A method according to  claim 24 , wherein the at least one power switch comprises at least one field effect transistor. 
     
     
       26. A method according to  claim 24 , wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together. 
     
     
       27. A method according to  claim 24 , wherein the thermally compensated current sensor is connected between the at least one power switch and a current feedback loop circuit. 
     
     
       28. A method according to  claims 24 , wherein the thermally compensated current sensor comprises a resistor. 
     
     
       29. A DC-to-DC power converter adapted for use in electronic devices comprising:
 a board adapted for mounting within the electronic device; and 
 at least one power switch, a control circuit for generating control pulses for the at least one power switch, an output inductor connected to the at least one power switch, and a thermally compensated current sensor operatively connected to the output conductor, said power switch, control circuit, output inductor and current sensor being mounted on the board and wherein the thermally compensated current sensor has a temperature coefficient matching a temperature coefficient of the output inductor and is responsive to the thermally compensated current sensor operative for sensing current in the output inductor. 
 
     
     
       30. A DC-to-DC converter according to  claim 29 , wherein the at least one power switch comprises at least one field effect transistor. 
     
     
       31. A DC-to-DC converter according to  claim 29 , wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor connected together. 
     
     
       32. A DC-to-DC converter according to  claim 29 , wherein the at least one power switch comprises a low side power switch and a high side power switch connected together. 
     
     
       33. A DC-to-DC converter according to  claim 29 , wherein the thermally compensated current sensor comprises a resistor. 
     
     
       34. A DC-to-DC converter comprising:
 at least one power switch;   a control circuit for generating control pulses for the at least one power switch;   an output inductor connected to the at least one power switch;   a current sensor connected for sensing current in the output inductor; and   a thermal compensation circuit having a temperature coefficient that substantially compensates for the effect of a temperature coefficient of the output inductor, wherein the at least one power switch is responsive to the thermal compensation circuit and the current sensor.   
     
     
       35. The DC-to-DC converter of claim 34, wherein the thermal compensation circuit comprises a portion of the current sensor. 
     
     
       36. The DC-to-DC converter of claim 34, wherein the thermal compensation circuit comprises a thermal compensation resistor. 
     
     
       37. The DC-to-DC converter of claim 34, wherein the thermal compensation circuit comprises a positive temperature coefficient resistor. 
     
     
       38. The DC-to-DC converter of claim 34, wherein the thermal compensation circuit comprises a negative temperature coefficient resistor. 
     
     
       39. The DC-to-DC converter of claim 34, wherein the at least one power switch comprises a low side field effect transistor and a high side field effect transistor coupled together. 
     
     
       40. The DC-to-DC converter of claim 34, wherein the current sensor comprises a resistor and capacitor coupled in series. 
     
     
       41. The DC-to-DC converter of claim 40, wherein the resistor of the current sensor comprises a positive temperature coefficient resistor. 
     
     
       42. A DC-to-DC converter comprising:
 at least one power switch;   a control circuit for generating control pulses for the at least one power switch;   an output inductor connected to the at least one power switch;   a current sensor connected to the at least one power switch for providing a sensed current related to a current being conducted through the output inductor, wherein the current sensor is coupled across the output inductor; and   a thermal compensation circuit having a temperature coefficient that substantially matches a temperature coefficient of the output inductor to cancel the effect of the temperature coefficient of the output inductor wherein the at least one power switch is responsive to the thermal compensation circuit and the current sensor.   
     
     
       43. The DC-to-DC converter of claim 42, wherein the current sensor is connected between the at least one power switch and a current feedback loop circuit. 
     
     
       44. The DC-to-DC converter of claim 42, wherein the thermal compensation circuit comprises a portion of the current sensor. 
     
     
       45. The DC-to-DC converter of claim 42, wherein the thermal compensation circuit comprises a thermal compensation resistor. 
     
     
       46. The DC-to-DC converter of claim 42, wherein the thermal compensation circuit comprises a positive temperature coefficient resistor. 
     
     
       47. The DC-to-DC converter of claim 42, wherein the thermal compensation circuit comprises a negative temperature coefficient resistor. 
     
     
       48. A multiphase DC-to-DC converter comprising:
 at least first and second channels each comprising a power device including a low side power switch and a high side power switch coupled together;   a control circuit for generating control pulses for the power devices;   an output inductor connected to the power devices;   a current sensor connected to the power devices for providing a sensed current related to a current being conducted through the output inductor, wherein the current sensor is coupled across the output inductor; and   a thermal compensation circuit having a temperature coefficient that substantially cancels the effect of temperature on the output inductor caused by the temperature coefficient of the output inductor, wherein the power device is responsive to the thermal compensation circuit and to the current sensor.   
     
     
       49. The multiphase DC-to-DC converter of claim 48, wherein the thermal compensation circuit comprises a portion of the current sensor. 
     
     
       50. The multiphase DC-to-DC converter of claim 48, wherein the thermal compensation circuit comprises a thermal compensation resistor. 
     
     
       51. The multiphase DC-to-DC converter of claim 48, wherein the thermal compensation circuit comprises a positive temperature coefficient resistor. 
     
     
       52. The multiphase DC-to-DC converter of claim 48, wherein the thermal compensation circuit comprises a negative temperature coefficient resistor. 
     
     
       53. A multiphase DC-to-DC converter comprising:
 at least first and second channels each comprising a power device including a low side power switch and a high side power switch connected together;   a control circuit for generating control pulses for the power devices;   an output inductor connected to the power devices;   a current sensor connected to the power devices for providing a sensed current proportional to a current being conducted through the output inductor, wherein the current sensor is coupled across the output inductor;   a current feedback loop circuit cooperating with the control circuit for controlling the power devices responsive to the current sensor; and   a resistive circuit element coupled to the control circuit, the resistive circuit element having a temperature coefficient that substantially matches a temperature coefficient of the output inductor such that the effect of fluctuations in temperature in the output inductor are compensated for by the resistive circuit element.   
     
     
       54. A method of regulating a DC-to-DC converter comprising at least one power switch, a control circuit for generating control pulses for the at least one power switch, and an output inductor connected to the at least one power switch, the method comprising:
 sensing current passing through the inductor using a current sensor connected in parallel to the output inductor;   compensating the sensed current with a circuit element having a temperature coefficient that is selected to substantially match a temperature coefficient of the output inductor such that the effect of temperature on the output inductor is substantially cancelled by the circuit element; and   controlling the at least one power switch in response to the thermally compensated sensed current.   
     
     
       55. A DC-to-DC power converter adapted for use in electronic devices comprising:
 a board adapted for mounting within the electronic device; and   at least one power switch,   a control circuit for generating control pulses for the at least one power switch,   an output inductor connected to the at least one power switch,   a current sensor operatively connected to the output inductor, and   a thermal compensation circuit coupled to the control circuit,   said power switch, control circuit, output inductor, current sensor and thermal compensation circuit being mounted on the board, and   wherein the thermal compensation circuit has a temperature coefficient that corrects the measure of the current sensed by the current sensor to account substantially for the effect of temperature on the current in the output inductor caused by a temperature coefficient of the output inductor.