Power converter with adaptive voltage positioning controller

• US 8,674,674 B1
• Filed: 02/07/2012
• Issued: 03/18/2014
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Alabama (University of Alabama System)
• Original Assignee: Board of Trustees of The University of Alabama (University of Alabama System)
• Inventors: Abu Qahouq, Jaber A.
• Primary Examiner(s): Laxton, Gary L
• Assistant Examiner(s): Torres-Rivera, Alex
• Application Number:
  US13/368,142
• Time in Patent Office: 770 Days
• Field of Search: 323/282, 323/283, 323/284, 323/271, 323/351
• US Class Current: 323/283
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A power converter has a controller that uses as input a voltage output of the converter and provides a signal for controlling the duty cycle without the need for current sensing. In one embodiment, the output characteristic of the converter is similar to the output characteristic provided by conventional adaptive voltage positioning (AVP) controllers, but by eliminating the need to sense current, the converter'"'"'s cost, complexity, and power consumption can be reduced.

Claims

1. A converter having an input voltage and providing an output voltage, the converter comprising:

conversion elements including switching devices, an inductor and a capacitor, wherein the output voltage is available across terminals of the capacitor;

a compensator configured to provide an error voltage in response to the output voltage and a reference voltage;

a pulse width modulator configured to transmit a pulse width modulator signal in response to the error voltage, wherein the pulse width modulator signal has a duty cycle; and

a controller configured to determine a duty cycle value based on the error voltage and to combine the duty cycle value with a predefined constant, thereby providing a combined value, the controller further configured to provide the reference voltage to the compensator, wherein the duty cycle value is indicative of the duty cycle, and wherein the reference voltage is based on the combined value.

2. The converter of claim 1, wherein the predefined constant is based on a minimum duty cycle value and a maximum duty cycle value.

3. The converter of claim 1, wherein the reference voltage is bound between an upper limit and a lower limit.

4. The converter of claim 3, wherein the upper limit is a value of the output voltage when a load current has a minimum allowed value and the lower limit is a value of the output voltage when the current has a maximum allowed value.

5. The converter of claim 1, wherein the reference voltage of the controller responds to changes in a nominal value for the output voltage.

6. The converter of claim 1, wherein an increase in output current results in a decrease in output voltage.

7. The converter of claim 1, wherein the proportion of the predefined constant is dependent on a maximum output voltage and a minimum output voltage.

8. A method for controlling an output voltage of a converter, comprising:

applying the output voltage to a compensator;

combining a predefined constant and a duty cycle value associated with a pulse width modulator;

providing a reference voltage based on the combining;

applying the reference voltage to the compensator;

generating an error voltage via the compensator in response to the output voltage and the reference voltage; and

transmitting a pulse width modulator signal from the pulse width modulator to switching elements of the converter in response to the error voltage.

9. The method of claim 8, further comprising keeping the reference voltage greater than a lower threshold value.

10. The method of claim 9, further comprising keeping the reference voltage less than an upper threshold value.

11. The method of claim 8, further comprising adjusting the duty cycle of the pulse width modulator signal in response to the error voltage.

12. The method of claim 8, further comprising changing the predefined constant if a nominal value for the output voltage is changed.

13. The method of claim 8, further comprising changing the predefined constant if a nominal value for the input voltage is changed.

14. A power converter, comprising:

power conversion elements including a switching device, an inductor and a capacitor, the conversion elements for providing an output voltage in response to an input voltage and a pulse width modulator signal having a duty cycle;

a pulse width modulator configured to transmit the pulse width modulator signal in response to an error voltage;

a compensator configured to receive the output voltage and a reference voltage and to provide the error voltage; and

a controller configured to determine, based on the error voltage, a duty cycle value indicative of the duty cycle and to combine the duty cycle value and a predefined constant, thereby providing a combined value the controller further configured to generate the reference voltage based on the combined value.

15. The power converter of claim 14, wherein the combined value is based on a lower value of the duty cycle value and an upper value of the duty cycle.

16. The power converter of claim 14, wherein the output voltage of the converter decreases as the load current increases.

17. The power converter of claim 14, wherein the controller is configured to respond to an input voltage of the converter.

18. The power converter of claim 14, wherein the response of the converter to the controller provides an adaptive voltage positioning output voltage characteristic.

19. The power converter of claim 14, wherein the controller configured to respond to variations in the input voltage and the output voltage.

20. A method for converting an input voltage to an output voltage comprising:

providing a pulse modulator cycle to power conversion elements that receive the input voltage and provide the output voltage, wherein the pulse width modulator signal is based on an error voltage;

sensing the output voltage;

determining duty cycle value indicative of the duty cycle;

combining the duty cycle value and a first predefined constant hereby providing a combined value;

providing a reference voltage based on the combining; and

generating the error voltage based on the reference voltage and the sensed output voltage.

21. The method of claim 20, wherein the combining comprises multiplying the duty cycle value and the first predefined constant, and wherein the method further comprises summing the combined value and a second predefined constant.