Adaptive switching frequency adjustment for a power supply

• US 10,404,165 B2
• Filed: 04/30/2013
• Issued: 09/03/2019
• Est. Priority Date: 01/29/2013
• Status: Active Grant

• Current Assignee: Semtech Corporation
• Original Assignee: Semtech Corporation
• Inventors: Mao, Min, Granger, Steven M., Xing, Kun
• Primary Examiner(s): Tran, Nguyen
• Assistant Examiner(s): Mata, Monica
• Application Number:
  US13/873,399
• Publication Number:
  US 20140210441A1
• Time in Patent Office: 2,317 Days
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

Described herein are systems and methods for providing a variable switching frequency for a power supply. The system includes a controller and a filter. The controller generates a switching frequency for a power supply. The switching frequency is modified as a function of an input voltage and an output voltage. The filter provides the output voltage to a load based at least in part on the switching frequency generated by the controller. In one example, the controller adaptively modifies the switching frequency as a function of the input voltage and the output voltage in order to maintain a peak to peak current for an inductor.

Claims

1. A system, comprising:

a controller that generates a switching frequency for a switch included in a power supply, wherein the controller varies the switching frequency as a function of an input voltage and an output voltage such that an inductor ripple current is kept substantially constant,

wherein the switching frequency has a first frequency value based on the input voltage having a first voltage value to achieve a defined duty cycle, wherein the switching frequency has a second frequency value based on the input voltage having a second voltage value,

wherein the first frequency value is less than the second frequency value and wherein the first voltage value is less than the second voltage, and wherein an output terminal of the switch is directly connected to a positive, non-inverting terminal of a comparator, and an output terminal of the comparator is electrically coupled to an input terminal of a pulse width modulator that generates a pulse width for a pulse width modulation signal,

wherein the comparator outputs an adaptive on-time signal that is received by the pulse width modulator, and wherein the output of the pulse width modulator is directly connected to the switch, wherein an input node of the controller is coupled to a resistor and a second resistor, wherein the resistor and the second resistor are coupled to one another at a second terminal, and

wherein the second terminal is directly coupled to a positive, non-inverting terminal of an amplifier, and wherein the negative terminal of the amplifier is directly connected to a first MOSFET and the first MOSFET is coupled between a second MOSFET and a third MOSFET, and wherein the third MOSFET is coupled to a first capacitor that is directly connected to the switch, the switch being distinct from a MOSFET and the switch being distinct from a flip flop; and

a filter that provides the output voltage to a load based at least in part on the pulse width modulation signal, wherein variation of the switching frequency facilitates minimization of active components and passive components in the filter.

2. The system of claim 1, wherein the controller is a direct current (DC)-direct current (DC) controller.

3. The system of claim 1, wherein the filter comprises an inductor.

4. The system of claim 3, wherein the controller adaptively modifies the switching frequency as a function of the input voltage and the output voltage to limit range of the inductor ripple current for the inductor in order to maintain a substantially constant inductor ripple current at different values of the input voltage and at different values of the output voltage.

5. The system of claim 1, wherein the controller generates the pulse width modulation signal based on the switching frequency for the switch.

6. The system of claim 1, wherein the switching frequency is further modified as a function of a fixed voltage provided by a fixed power source.

7. The system of claim 1, wherein the power supply is a switching mode power supply.

8. A system, comprising:

a signal generator that includes an input node, an output node electrically coupled to a fixed power source, and a switching frequency adjustment node electrically coupled to an output voltage, wherein the input node is coupled to a resistor and a second resistor, wherein the resistor and the second resistor are coupled to one another at a terminal, and wherein the terminal is directly coupled to a positive, non-inverting terminal of an amplifier, and wherein the negative terminal of the amplifier is directly connected to a first MOSFET and the first MOSFET is coupled between a second MOSFET and a third MOSFET, and wherein the third MOSFET is coupled to a first capacitor that is directly connected to a switch, the switch being distinct from a MOSFET and the switch being distinct from a flip flop,

wherein the signal generator controls a switching frequency for the switch included in a power supply such that the switching frequency varies as a function of a resistance value of a first resistor directly coupled to the output voltage on a first end and coupled at a second end to a terminal for an on-time signal,

wherein the first resistor is also coupled to a second resistor at the second end of the first resistor, the second resistor being coupled to ground at another end of the second resistor and wherein an output terminal of the switch is directly connected to a positive, non-inverting terminal of a comparator, and an output terminal of the comparator is electrically coupled to an input terminal of an on-time generator that generates a pulse width for a pulse width modulation signal via a pulse width modulation control, and

wherein an output of the pulse width modulation control is directly connected to the switch; and

a filter that comprises an inductor, wherein the filter generates the output voltage for a load based at least in part on the pulse width modulation signal.

9. The system of claim 8, wherein the signal generator controls the switching frequency as a function of the input voltage and the output voltage to limit range of the inductor ripple current for the inductor in order to maintain a substantially constant inductor ripple current at different values of the input voltage and at different values of the output voltage to facilitate over-current protection trip point accuracy employing a valley current sensing method.

10. The system of claim 8, wherein the fixed power source is electrically coupled to another input terminal of the on-time generator.

11. The system of claim 8, wherein the pulse width modulation signal is generated based at least in part on the switching frequency for the switch.

12. The system of claim 8, wherein the switching frequency adjustment node is electrically coupled to a first resistor and a second resistor.

13. The system of claim 12, wherein the second resistor is electrically coupled to the output voltage.

14. The system of claim 13, wherein the first resistor is electrically coupled to ground.

15. A method, comprising:

receiving an input voltage and an output voltage in a circuit;

generating a switching frequency for a switch included in a power supply, and wherein the circuit is configured to flexibly adjust the switching frequency by selecting among adjustment of;

a resistance value of a first resistor of the circuit;

a fixed voltage of the circuit;

an input voltage of the circuit; and

an output voltage of the circuit, wherein adjustment of the switching frequency can be performed such that inductor ripple current of the circuit is maintained at an approximately constant level and constant inductor ripple modulation is provided to a filter of the circuit;

generating a pulse width for a pulse width modulation signal via a pulse width modulator that comprises an input terminal electrically coupled to the switch, and wherein the switch is directly connected to a non-inverting input terminal of an amplifier, wherein an output of the pulse width modulator is directly connected to the switch, and wherein the negative terminal of the amplifier is directly connected to a first MOSFET; and

providing the output voltage to a load based on the pulse width modulation signal, wherein the switch is distinct from a MOSFET and distinct from a flip flop.

16. The method of claim 15, further comprising sending the pulse width modulation signal with the switching frequency to a filter.

17. The method of claim 16, further comprising maintaining a substantially constant inductor ripple current for an inductor of the filter.

18. The method of claim 15, wherein the generating switching frequency further includes generating the switching frequency as a function of a fixed voltage provided by a fixed power source.

19. The method of claim 18, wherein the receiving includes receiving the fixed voltage via an output voltage node and receiving the output voltage via a switching frequency adjustment node.