Power supply control method for constant current constant power control

• US 9,118,239 B2
• Filed: 03/15/2013
• Issued: 08/25/2015
• Est. Priority Date: 03/29/2012
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Xu, Shanguang, Ye, Zhong
• Primary Examiner(s): Han, Jessica
• Assistant Examiner(s): Dang, Trinh
• Application Number:
  US13/835,427
• Publication Number:
  US 20130258731A1
• Time in Patent Office: 893 Days
• Field of Search: 323/282, 323/283, 323/284, 323/285, 323/318
• US Class Current: 1/1
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A digital power supply and power supply controller are presented, including a voltage control loop and a current control loop, with a controller for pulse width modulating a switching power supply according to a voltage control loop duty cycle output or a current control loop duty cycle output, in which the controller selectively presets the voltage control loop duty cycle output to a predetermined value before switching from current loop control to voltage loop control and/or inhibits increase in a voltage loop integrator value during current loop control to mitigate voltage overshoot.

Claims

1. A power supply controller for controlling a switching power supply, comprising:

a voltage control circuit, including;

a voltage error circuit providing a voltage error signal or value based at least partially on a reference voltage signal or value and an output voltage of the switching power supply, and

a voltage compensator circuit providing a voltage control duty cycle signal or value based at least partially on the voltage error signal or value;

a current control circuit, including;

a current error circuit providing a current error signal or value based at least partially on a reference current signal or value and an output current of the switching power supply, and

a current compensator circuit providing a current control duty cycle signal or value based at least partially on the current error signal or value;

a pulse width modulation circuit operative to pulse width modulate at least one switch of the switching power supply at least partially according to a duty cycle input signal or value; and

a control circuit selectively operative in a first mode to provide the voltage control duty cycle signal or value as the duty cycle input signal or value, and in a second mode to provide the current control duty cycle signal or value as the duty cycle input signal or value, the control circuit comprising a logic circuit operative to;

switch the control circuit from the first mode to the second mode if a sum of the voltage control duty cycle signal or value plus a predetermined non-zero hysteresis value is greater than the current control duty cycle signal or value, and

selectively preset the voltage control duty cycle signal or value to a predetermined duty cycle signal or value and then switch the control circuit from the second mode to the first mode if the voltage control duty cycle signal or value is less than the current control duty cycle signal or value.

2. The power supply controller of claim 1, wherein the logic circuit is operative to prevent increase of an integrator signal or value of the voltage compensator circuit while the control circuit is in the second mode.

3. The power supply controller of claim 1, wherein the voltage compensator circuit comprises:

a proportional integral derivative (PID) circuit operative to;

generate a proportional compensation signal or value based on the voltage error signal or value and a proportional constant,

generate an integral compensation signal or value based on an integral of the voltage error signal or value and an integral constant,

generate a derivative compensation signal or value based on a rate of change of the voltage error signal or value and a derivative constant, and

to generate a PID output signal or value as a sum of the proportional compensation signal or value, the integral compensation signal or value, and the derivative compensation signal or value; and

a presetting circuit operative to provide the voltage control duty cycle signal or value as either the PID output signal or value or as the predetermined duty cycle signal or value based on a preset control signal;

wherein the logic circuit is operative to selectively preset the voltage control duty cycle signal or value to the predetermined duty cycle value by providing the preset control signal to the presetting circuit if the current control duty cycle signal or value is less than the voltage control duty cycle signal or value.

4. The power supply controller of claim 1, wherein the logic circuit is operative to selectively refrain from presetting the voltage control duty cycle signal or value to the predetermined duty cycle signal or value if the voltage control duty cycle signal or value is less than the predetermined duty cycle value prior to switching the control circuit from the second mode to the first mode.

5. The power supply controller of claim 1:

wherein the voltage error circuit is operative to provide a digital voltage error value representing a difference between the reference voltage signal or value and the output voltage of the switching power supply;

wherein the voltage compensator circuit comprises an adder circuit to provide an integrator value based at least partially on prior samples of the digital voltage error value,

wherein the voltage compensator circuit computes an integral compensation value based at least partially on the integrator value and wherein the voltage compensator circuit provides the voltage control duty cycle signal or value based at least partially on the integral compensation value; and

wherein the logic circuit provides a control signal to the voltage compensator circuit to selectively prevent increase of the integrator value while the control circuit is in the second mode, and selectively provides a preset control signal to cause the voltage compensator circuit to provide the voltage control duty cycle signal or value as the predetermined duty cycle signal or value prior to switching the control circuit from the second mode to the first mode.

6. The power supply controller of claim 1, comprising:

a comparator circuit including;

a digital to analog converter operative to convert the duty cycle input signal or value to an analog duty cycle input signal, and

a comparator generating a comparator output signal based on a comparison of the analog duty cycle input signal with a feedback current signal representing a switching current of the switching power supply;

wherein the logic circuit is operative to selectively provide an input select control signal to the pulse width modulation circuit to cause the pulse width modulation circuit to pulse width modulate the at least one switch according to the duty cycle input signal or value when the control circuit is in the first mode, and to pulse width modulate the at least one switch according to the comparator output signal when the control circuit is in the second mode.

7. The power supply controller of claim 1, wherein the predetermined duty cycle value is close to a current command value for peak current mode control at light load or to a duty cycle command value for voltage mode control at light load.

8. The power supply controller of claim 2:

wherein the voltage error circuit is operative to provide a digital voltage error value representing a difference between the reference voltage signal or value and the output voltage of the switching power supply;

wherein the voltage compensator circuit comprises a digital adder circuit to provide the integrator signal or value based at least partially on a current integral value and previous error samples; and

wherein the logic circuit provides a control signal to the voltage compensator circuit to selectively prevent increase of the integrator value of the adder circuit while the control circuit is in the second mode.

9. The power supply controller of claim 8, wherein the voltage compensator circuit comprises:

a digital proportional integral derivative (PID) circuit operative to;

compute a proportional compensation value based on the digital voltage error value and a proportional constant,

compute an integral compensation value based on a current sample of the digital voltage error value, the integrator value, and an integral constant,

compute a derivative compensation value based on a difference between a current sample of the digital voltage error value and a preceding sample of the digital voltage error value, and a derivative constant, and

to compute a digital voltage control duty cycle value as a sum of the proportional compensation value, the integral compensation value, and the derivative compensation value; and

a presetting circuit operative to provide the voltage control duty cycle signal or value as either the digital voltage control duty cycle value or as the predetermined duty cycle signal or value based on a preset control signal;

wherein the logic circuit is operative to selectively preset the voltage control duty cycle signal or value to the predetermined duty cycle signal or value by providing the preset control signal to the presetting circuit if the current control duty cycle signal or value is less than the voltage control duty cycle signal or value.

10. The power supply controller of claim 9, wherein the logic circuit is operative to selectively refrain from presetting the voltage control duty cycle signal or value to the predetermined duty cycle signal or value if the voltage control duty cycle signal or value is less than the predetermined duty cycle signal or value prior to switching the control circuit from the second mode to the first mode.

11. A switching power supply, comprising:

an input configured to receive input power from a connected source;

an output operative to provide output power to a connected load;

at least one switch operative according to a switching control signal to selectively convert the input power from the input to provide the output power to the output; and

a power supply controller operative to provide the switching control signal to the at least one switch, the power supply controller comprising;

a voltage control circuit, including;

a voltage error circuit providing a voltage error signal or value representing a difference between a reference voltage signal or value and an output voltage of the switching power supply, and

a voltage compensator circuit with a digital adder circuit providing an integrator signal or value based at least partially on a current error value and previous error samples, the voltage compensator circuit providing a voltage control duty cycle signal or value based at least partially on the voltage error signal or value and on the integrator signal or value, the voltage compensator circuit comprising a digital proportional integral derivative (PID) circuit operative to compute a proportional compensation value based on the digital voltage error value and a proportional constant, to compute an integral compensation value based on a current sample of the digital voltage error value, the integrator value, and an integral constant, to compute a derivative compensation value based on a difference between a current sample of the digital voltage error value and a preceding sample of the digital voltage error value, and a derivative constant, and to compute a digital voltage control duty cycle value as a sum of the proportional compensation value, the integral compensation value, and the derivative compensation value, and

a presetting circuit operative to provide the voltage control duty cycle signal or value as either the digital voltage control duty cycle value or as the predetermined duty cycle signal or value based on a preset control signal,

a current control circuit, including;

a current error circuit providing a current error signal or value based at least partially on a reference current signal or value and an output current of the switching power supply, and

a current compensator circuit providing a current control duty cycle signal or value based at least partially on the current error signal or value,

a pulse width modulation circuit operative to pulse width modulate at least one switch of the switching power supply at least partially according to a duty cycle input signal or value, and

a control circuit selectively operative in a first mode to provide the voltage control duty cycle signal or value as the duty cycle input signal or value, and in a second mode to provide the current control duty cycle signal or value as the duty cycle input signal or value, the control circuit comprising a logic circuit operative to switch the control circuit from the first mode to the second mode if a sum of the voltage control duty cycle signal or value plus a predetermined non-zero hysteresis value is greater than the current control duty cycle signal or value, to selectively preset the voltage control duty cycle signal or value to a predetermined duty cycle signal or value by providing the preset control signal to the presetting circuit if the current control duty cycle signal or value is less than the voltage control duty cycle signal or value and then switch the control circuit from the second mode to the first mode if the voltage control duty cycle signal or value is less than the current control duty cycle signal or value, and to selectively prevent increase of the integrator signal or value of the voltage compensator circuit while the control circuit is in the second mode.

12. A power supply controller for controlling a switching power supply, comprising:

a voltage control circuit operative to determine a voltage error signal or value based on a difference between a reference voltage signal or value and an output voltage of the switching power supply, and to determine an integrator value based at least partially on prior samples of the voltage error signal or value, the voltage control circuit providing a voltage control duty cycle signal or value based at least partially on the voltage error signal or value and the integrator value;

a current control circuit providing a current control duty cycle signal or value based at least partially on a reference current signal or value and an output current of the switching power supply;

a pulse width modulation circuit operative to pulse width modulate at least one switch of the switching power supply at least partially according to a duty cycle input signal or value; and

a control circuit selectively operative in a first mode to provide the voltage control duty cycle signal or value as the duty cycle input signal or value, and in a second mode to provide the current control duty cycle signal or value as the duty cycle input signal or value, the control circuit comprising a logic circuit operative to;

switch the control circuit from the first mode to the second mode for constant current control of the switching power supply if a sum of the voltage control duty cycle signal or value plus a predetermined non-zero hysteresis value is greater than the current control duty cycle signal or value,

selectively prevent increase of the integrator value while the control circuit is in the second mode, and

switch the control circuit from the second mode to the first mode for constant power or constant voltage control of the switching power supply if the voltage control duty cycle signal or value is less than the current control duty cycle signal or value.

13. The power supply controller of claim 12, wherein the control circuit is operative, if the voltage control duty cycle signal or value is greater than a predetermined duty cycle value, to selectively preset the voltage control duty cycle signal or value to the predetermined duty cycle signal or value before switching the control circuit from the second mode to the first mode.

14. The power supply controller of claim 12, comprising:

a comparator circuit including;

a digital to analog converter operative to convert the duty cycle input signal or value to an analog duty cycle input signal, and

a comparator generating a comparator output signal based on a comparison of the analog duty cycle input signal with a feedback current signal representing a switching current of the switching power supply;

wherein the logic circuit is operative to selectively provide an input select control signal to the pulse width modulation circuit to cause the pulse width modulation circuit to pulse width modulate the at least one switch according to the duty cycle input signal or value when the control circuit is in the first mode, and to pulse width modulate the at least one switch according to the comparator output signal when the control circuit is in the second mode.

15. The power supply controller of claim 13, wherein the predetermined duty cycle value is close to a current command value for peak current mode control at light load or to a duty cycle command value for voltage mode control at light load.

16. The power supply controller of claim 13:

wherein the voltage control circuit comprises;

a voltage error circuit operative to provide a digital voltage error value representing a difference between the reference voltage signal or value and the output voltage of the switching power supply;

a voltage compensator circuit with an adder circuit operative to provide the integrator value based at least partially on prior samples of the digital voltage error value; and

wherein the logic circuit provides a control signal to the voltage compensator circuit to selectively prevent increase of the integrator value while the control circuit is in the second mode, and selectively provides a preset control signal to cause the voltage compensator circuit to provide the voltage control duty cycle signal or value as the predetermined duty cycle signal or value prior to switching the control circuit from the second mode to the first mode.

17. A method of providing pulse width modulation signals for pulse width modulation of at least one switch of a switching power supply, the method comprising:

comparing a voltage loop duty cycle to a current loop duty cycle;

pulse width modulating the at least one switch according to the current loop duty cycle if a sum of the voltage loop duty cycle plus a predetermined non-zero hysteresis value is greater than the current loop duty cycle; and

if the voltage loop duty cycle is less than the current loop duty cycle, selectively presetting the voltage loop duty cycle to a predetermined duty cycle, and then pulse width modulating the at least one switch according to the voltage loop duty cycle.

18. The method of claim 17, comprising preventing increase of an integrator value used in computing the voltage loop duty cycle while pulse width modulating the at least one switch according to the current loop duty cycle.

19. The method of claim 17, comprising selectively refraining from presetting the voltage loop duty cycle to the predetermined duty cycle if the voltage control duty cycle is less than the predetermined duty cycle.

20. The method of claim 18, comprising selectively refraining from presetting the voltage loop duty cycle to the predetermined duty cycle if the voltage control duty cycle is less than the predetermined duty cycle.