Digital power supply controller with voltage positioning

• US 7,319,312 B2
• Filed: 03/31/2005
• Issued: 01/15/2008
• Est. Priority Date: 07/27/2004
• Status: Expired due to Fees

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Xiao, Jenwin, Leung, Ka Y.
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US11/096,853
• Publication Number:
  US 20060025892A1
• Time in Patent Office: 1,020 Days
• Field of Search: 323/285, 323/283, 363/16
• US Class Current: 323/285
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/33515 with digital control
• CPC Class Codes: H02M 3/33569 having several active switching elements H02M3/3353 takes precedence
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A method for controlling the output of a switching power converter to account for high and low current loads is disclosed. A reference voltage is generated with a voltage reference generator representing a desired DC output voltage for the power converter. Then the DC voltage output of the power converter is sensed with a digital control system and generating switching control signals to control the operation thereof to minimize the difference between sensed DC voltage and the reference voltage. The current through the power converter is then determined and the operation of the voltage reference generator controlled to set the value of the reference voltage to a level that is a function of the sensed current so as to anticipate future current loading.

Claims

1. A system for controlling the output of a switching power converter to account for high and low current loads, comprising:

a voltage reference generator for generating a reference voltage that represents a desired DC output voltage for the power converter;

the power converter having a desired operating voltage that operates within predetermined limits;

a digital control system for sensing the DC voltage output of the power converter and generating switching control signals to control the operation thereof to minimize the difference between the sensed DC voltage and the reference voltage;

a current sense circuit for determining the current through the power converter; and

a control system for controlling the operation of said voltage reference generator to set the value of said reference voltage to a present control value that has a level that is a function of the determined current so as to anticipate future current loading, wherein the present control value can have a level different than the median value between the predetermined limits, which is dependant upon future loading on the output of the power converter.

2. The system of claim 1, wherein said voltage reference generator is a digitally controlled voltage reference generator for receiving a digital reference voltage value and said control system is a digital control system for varying the digital value.

3. The system of claim 2, wherein said digital control system includes an analog-to-digital converter (ADC) for converting the DC voltage output of the power converter to a digital voltage for comparison with said reference voltage to determine the difference therebetween as a digital error voltage and said digital control system operable to reduce said error voltage.

4. The system of claim 3, wherein said digitally controlled voltage reference generator includes a digital-to-analog converter (DAC) for converting said digital reference voltage value to an analog voltage reference and said ADC comprises a difference ADC for receiving the DC voltage output of the power converter and the analog voltage reference and determining the difference therebetween as said digital error voltage.

5. The system of claim 4, wherein said digital control system is operable to vary said analog voltage reference by varying the input to said DAC during operation of the power converter.

6. The system of claim 2, wherein said current sense circuit comprises a analog-to-digital converter for receiving a voltage representing the current through the power converter and converting it to a digital value for use by said digital control system.

7. The system of claim 2, wherein the power converter has a series inductive element and an output capacitor connected between the output and ground, and said current sense circuit is operable to sense the current through both the inductive element and the output capacitor separately, and said current sense circuit comprises a first analog-to-digital converter (ADC) for receiving a voltage representing the current through the inductive element and converting it to a digital value for use by said digital control system, and a second ADC for receiving a voltage representing the current through the output capacitance and converting it to a digital value for use by said digital control system.

8. The system of claim 7, wherein said voltage representing the current through the inductive element is referenced to the equivalent series resistance (ESR) associated with the inductive element and said voltage representing the current through the output capacitance is referenced to its associated ESR and said digital control system has stored therein information relating to the value of said associated ESRs and is operable to determine from the measured voltages and the known values of the ESRs the current through the respective inductive element and output capacitor, the sum of which equals the total current through the power converter.

9. The system of claim 8, wherein said voltage representing the current through the inductive element is determined from an inductor shunt circuit comprised of a series connected capacitor and resistor connected across the inductive element and its associated ESR, where said voltage representing the current through the inductive element is tapped off of the junction between said series connected resistor and capacitor.

10. The system of claim 9, wherein said voltage representing the current through the output capacitance is determined from a capacitor shunt circuit connected between ground and the output of the power converter and comprised of a series connected resistor and capacitor, wherein said capacitor in said capacitor shunt circuit is substantially smaller than the output capacitor, wherein said voltage representing the current through the output capacitor is tapped off the junction between the series connected capacitor and resistor.

11. A method for controlling the output of a switching power converter to account for high and low current loads, comprising the steps of:

generating a reference voltage with a voltage reference generator that represents a desired DC output voltage for the power converter;

the power converter having a desired operating voltage that operates within predetermined limits;

sensing the DC voltage output of the power converter with a digital control system and generating switching control signals to control the operation thereof to minimize the difference between the sensed DC voltage and the reference voltage;

determining with a current sense circuit the current through the power converter; and

controlling the operation of the voltage reference generator to set the value of the reference voltage to present control value that has a level that is a function of the determined current so as to anticipate future current loading, wherein the present control value can have a level different than the median value between the predetermined limits, which is dependant upon future loading on the output of the power converter.

12. The method of claim 11, wherein the voltage reference generator is a digitally controlled voltage reference generator for receiving a digital reference voltage value and the step of controlling is operable to utilize a digital control system for the step of varying the digital value.

13. The method of claim 12, wherein the step of controlling is operable to convert the DC voltage output of the power converter with an analog-to-digital converter (ADC) as a part of the digital control system to a digital voltage for comparison with the reference voltage to determine the difference therebetween as a digital error voltage and the step of controlling operable to reduce the error voltage.

14. The method of claim 13, wherein the step of generating the digital reference voltage with the digitally controlled voltage reference generator includes the step of converting the digital reference voltage value to an analog voltage reference with a digital-to-analog converter (DAC) and the ADC comprises a difference ADC for receiving the DC voltage output of the power converter and the analog voltage reference and determining the difference therebetween as the digital error voltage.

15. The method of claim 14, wherein the digital control system is operable to vary the analog voltage reference by varying the input to the DAC during operation of the power converter.

16. The method of claim 12, wherein the step of sensing current comprises the step of converting a voltage representing the current through the power converter to a digital value for use by the digital control system with an analog-to-digital converter (ADC).

17. The method of claim 12, wherein the power converter has a series inductive element and an output capacitor connected between the output and ground, and the step of determining with a current sense circuit is operable to sense the current through both the inductive element and the output capacitor separately, and the step of determining with a current sense circuit comprises receiving a voltage representing the current through the inductive element and converting it with a first analog-to-digital converter (ADC) to a digital value for use by the digital control system, and receiving a voltage representing the current through the output capacitance and converting it with a second ADC to a digital value for use by the digital control system.

18. The method of claim 17, wherein the voltage representing the current through the inductive element is referenced to the equivalent series resistance (ESR) associated with the inductive element and the voltage representing the current through the output capacitance is referenced to its associated ESR and the digital control system has stored therein information relating to the value of the associated ESRs and is operable to determine from the measured voltages and the known values of the ESRs the current through the respective inductive element and output capacitor, the sum of which equals the total current through the power converter.

19. The method of claim 18, wherein the voltage representing the current through the inductive element is determined by the steps of disposing an inductor shunt circuit comprised of a series connected capacitor and resistor connected across the inductive element and its associated ESR, and sensing the voltage representing the current through the inductive element from the junction between the series connected resistor and capacitor.

20. The method of claim 19, wherein the voltage representing the current through the output capacitance is determined by the steps of disposing a capacitor shunt circuit between ground and the output of the power converter and comprised of a series connected resistor and capacitor, wherein the capacitor in the capacitor shunt circuit is substantially smaller than the output capacitor, and sensing the voltage representing the current through the output capacitor from the junction between the series connected capacitor and resistor.