Hysteretic power-supply controller with adjustable switching frequency, and related power supply, system, and method

• US 20080129264A1
• Filed: 08/31/2007
• Published: 06/05/2008
• Est. Priority Date: 10/06/2006
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Moussaoui, Zaki, Agarwal, Sandeep, Vivrekar, Javant
• Granted Patent: US 7,944,192 B2
• Time in Patent Office: Days
• US Class Current: 323/283
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

An embodiment of a hysteretic power-supply controller includes a signal generator, frequency adjuster, and signal combiner. The signal generator is operable to generate a switching signal having a first level in response to a control signal being greater than a first reference value and having a second level in response to the control signal being less than a second reference value, the switching signal having an actual frequency and being operable to drive a switching stage that generates a regulated output signal. The frequency adjuster is operable to generate a frequency-adjust signal that is related to a difference between the actual frequency and a desired frequency. And the signal combiner is operable to generate the control signal from the frequency-adjust signal and the regulated output signal. Such a hysteretic power-supply controller may allow one to set the switching frequency to a desired value independently of the parameters of the power supply.

Claims

1. A power-supply controller, comprising:

a signal generator operable to generate a switching signal having a first level in response to a control signal being greater than a first reference value and having a second level in response to the control signal being less than a second reference value, the switching signal having an actual frequency and being operable to drive a switching stage that generates a regulated output signal;

a frequency adjuster coupled to the signal generator and operable to generate a frequency-adjust signal that is related to a first difference between the actual frequency and a desired frequency; and

a signal combiner coupled to the frequency adjuster and operable to generate the control signal from the frequency-adjust signal and the regulated output signal.

2. The power-supply controller of claim 1 wherein:

the first level comprises a switching-stage-off level; and

the second level comprises a switching-stage-on level.

3. The power-supply controller of claim 1 wherein the signal generator comprises:

a window comparator operable to generate a first signal in response to the control signal being greater than the first reference value and to generate a second signal in response to the control signal being less than the second reference value; and

a flip-flop operable to generate the switching signal having the first level in response to the first signal and to generate the switching signal having the second level in response to the second signal.

4. The power-supply controller of claim 3 wherein the frequency adjuster comprises:

an integrator operable to generate a ramp signal from the switching signal;

a variable-gain amplifier coupled to the integrator, operable to amplify the ramp signal with a gain that is related to a gain-control signal, and operable to generate the frequency-adjust signal from the amplified ramp signal;

a frequency determiner operable to generate a frequency value that represents the frequency of the switching signal;

a comparator operable to compare the frequency value to the desired frequency and to generate a comparison signal;

an accumulator operable to generate the gain-control signal from the comparison signal.

5. The power-supply controller of claim 1 wherein the signal combiner comprises an adder operable to generate the control signal from a sum of the frequency-adjust signal and a ripple component of the regulated output signal.

6. The power-supply controller of claim 1 wherein the control signal is operable to cause the actual frequency of the switching signal to substantially equal the desired frequency.

7. The power-supply controller of claim 1, further comprising a low-pass filter disposed between the signal generator and the signal combiner.

8. The power-supply controller of claim 1, further comprising:

an amplifier operable to generate a second difference between the regulated output signal and a reference signal; and

wherein the signal combiner comprises an adder operable to generate the control signal from a sum of the frequency-adjust signal and the second difference.

9. A power supply, comprising:

a first switching stage operable to generate a regulated output voltage in response to a first switching signal having an actual frequency; and

a power-supply controller including

a signal generator operable to generate the first switching signal having a first level in response to a control signal being greater than a first reference value and having a second level in response to the control signal being less than a second reference value;

a first feedback loop including a frequency adjuster coupled to the signal generator and operable to generate a frequency-adjust signal that is related to a first difference between the actual frequency and a desired frequency; and

a signal combiner coupled to the frequency adjuster and operable to generate the control signal from the frequency-adjust signal and the regulated output voltage.

10. The power supply of claim 9 wherein the first switching stage comprises:

first and second supply nodes;

a stage input node operable to receive the control signal;

a stage output node operable to provide the regulated output voltage;

a first switch having a control node coupled to the input node, a first conduction node coupled to the first supply node, and a second conduction node;

a second switch having a control node coupled to the input node, a first conduction node coupled to the second conduction node of the first switch, and a second conduction node coupled to the second supply node; and

a filter having a filter input node coupled to the second conduction node of the first switch and having a filter output node coupled to the stage output node.

11. The power supply of claim 10 wherein the filter comprises:

an inductor coupled between the filter input and output nodes; and

a capacitor coupled between the filter output node and the second supply node.

12. The power supply of claim 9 wherein the control signal is operable to cause the actual frequency of the switching signal to substantially equal the desired frequency.

13. The power supply of claim 9, further comprising:

a second feedback loop including an amplifier operable to generate a second difference between the regulated output voltage and a reference voltage; and

wherein the signal combiner comprises an adder operable to generate the control signal from a sum of the frequency-adjust signal and the second difference.

14. The power supply of claim 9, further comprising:

wherein the first switching signal has a duty cycle and a first phase;

a second switching stage operable to generate the regulated output voltage in response to a second switching signal having the actual frequency, the duty cycle, and a second phase that is shifted by a predetermined amount relative to the first phase; and

wherein the signal generator is operable to generate the second switching signal.

15. The power supply of claim 9, further comprising:

wherein the first switching signal has a duty cycle and a first phase;

wherein the first switching stage is operable to generate a first current signal related to an amount of output current that the first switching stage provides;

a second switching stage operable to generate the regulated output voltage in response to a second switching signal having the actual frequency, the duty cycle, and a second phase that is shifted by a predetermined amount relative to the first phase, the second switching stage further operable to generate a second current signal related to an amount of output current that the second switching stage provides;

wherein the signal generator is operable to generate the second switching signal;

a current balancer operable to generate a balance signal from the first and second current signals; and

wherein the signal combiner is operable to generate the control signal from the frequency-adjust signal, the regulated output voltage, and the balance signal.

16. An electronic system, comprising:

a power supply including

a switching stage operable to generate a regulated output voltage in response to a switching signal having an actual frequency; and

a power-supply controller including

a signal generator operable to generate the switching signal having a first level in response to a control signal being greater than a first reference value and having a second level in response to the control signal being less than a second reference value;

a feedback loop including a frequency adjuster coupled to the signal generator and operable to generate a frequency-adjust signal that is related to a first difference between the actual frequency and a desired frequency; and

a signal combiner coupled to the frequency adjuster and operable to generate the control signal from the frequency-adjust signal and the regulated output voltage.

17. A method, comprising:

generating a regulated output signal in response to a switching signal having an actual frequency;

generating the switching signal having a first level in response to a control signal being greater than a first reference value and having a second level in response to the control signal being less than a second reference value; and

adjusting the control signal to cause the actual frequency to substantially equal a predetermined frequency.

18. The method of claim 17 wherein adjusting the control signal comprises adjusting the control signal to cause a difference between the actual and predetermined frequencies to substantially equal a predetermined value.

19. The method of claim 17, further comprising:

generating the control signal having an amplitude and a ramped portion; and

wherein adjusting the control signal comprises adjusting the amplitude of the control signal.

20. The method of claim 17, further comprising:

integrating the switching signal to generate a ramp signal having an amplitude;

adjusting the amplitude of the ramp signal based on a difference between the actual and predetermined frequencies; and

generating the control signal from the amplitude-adjusted ramp signal and a ripple component of the regulated output signal.