SWITCH-MODE POWER SUPPLY CONTROLLER

• US 20200136506A1
• Filed: 03/18/2019
• Published: 04/30/2020
• Est. Priority Date: 10/29/2018
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Yu, Yangwei
• Granted Patent: US 10,897,197 B2
• Time in Patent Office: Days
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H03K 2005/00078 Fixed delay
• CPC Class Codes: H03K 3/017 Adjustment of width or dutycycle of pulses pulse width modulation H03K7/08 ; to maintain energy constant H03K3/015
• CPC Class Codes: H03K 3/037 Bistable circuits
• CPC Class Codes: H03K 5/01 Shaping pulses discrimination against noise or interference H03K5/125
• CPC Class Codes: H03K 5/06 by the use of delay lines or other analogue delay elements
• 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 switch-mode power supply and control circuitry that reduces variation in the switching frequency of the power supply with changes in loading. In one example, a switch-mode power supply includes an inductor, a transistor, and control circuitry. The transistor is coupled to the inductor, and configured to charge the inductor. The control circuitry is coupled to the transistor. The control circuitry is configured to turn off the transistor for a first time period. The first time period is a function of voltage across the inductor during the first time period. The control circuitry is also configured to determine whether the switch-mode power supply is operating in continuous conduction mode or discontinuous conduction mode. The control circuitry is further configured to add a predetermined fixed interval to the first time based on the switch-mode power supply operating in discontinuous conduction mode.

Claims

1. A switch-mode power supply, comprising:

an inductor;

a transistor coupled to the inductor, and configured to charge the inductor;

a control circuit coupled to the transistor, the control circuit configured to;

turn off the transistor for a first time period that is a function of voltage across the inductor during the first time period;

determine whether the switch-mode power supply is operating in continuous conduction mode or discontinuous conduction mode; and

add a predetermined fixed interval to the first time period based on the switch-mode power supply operating in discontinuous conduction mode.

2. The switch-mode power supply of claim 1, wherein the transistor is a first transistor, and the switch-mode power supply further comprises a second transistor coupled to the inductor;

wherein the control circuit is coupled to the second transistor, and configured to turn on the second transistor after initiation of the first time period and turn off the second transistor at expiration of the first time period.

3. The switch-mode power supply of claim 1, wherein the control circuit is configured to not add the predetermined fixed interval to the first time period based on switch-mode power supply operating in continuous conduction mode.

4. The switch-mode power supply of claim 1, wherein the control circuit comprises a comparator configured to compare a current at a first terminal of the inductor to zero.

5. The switch-mode power supply of claim 4, wherein the control circuit comprises a delay circuit coupled to the comparator;

wherein the delay circuit comprises a delay element configured to delay a signal to turn on the transistor responsive to an output of the first comparator indicating that the current at the first terminal of the inductor is less than zero.

6. The switch-mode power supply of claim 5, wherein the delay element is configured to delay the signal by the predetermined fixed interval.

7. The switch-mode power supply of claim 5, wherein the delay circuit is configured to bypass the delay element responsive to the output of the first comparator indicating that the current at the first terminal of the inductor is greater than zero.

8. The switch-mode power supply of claim 1, further comprising a timer circuit configured to define the first time period.

9. A switch-mode power supply control circuit, comprising:

a transistor comprising a first terminal coupled to ground;

a flip-flop comprising an output terminal coupled to a second terminal of the transistor;

a comparator comprising;

a first input terminal coupled to a third terminal of the transistor; and

a second input terminal coupled to ground;

a delay circuit comprising;

a first input terminal coupled to an output terminal of the comparator;

a second input terminal coupled to a timer circuit; and

an output terminal coupled to an input terminal of the flip-flop.

10. The switch-mode power supply control circuit of claim 9, wherein the delay circuit comprises:

a delay element; and

a switch comprising;

an input terminal coupled to the second input terminal of the delay circuit and to an input terminal of the delay element;

a control terminal coupled to the first input terminal of the delay circuit;

an output terminal coupled to the output terminal of the delay circuit and to an output terminal of the delay element.

11. The switch-mode power supply control circuit of claim 9, wherein the transistor is a first transistor, the switch-mode power supply controller further comprises a second transistor comprising:

a first terminal coupled to the third terminal of the first transistor;

a second terminal coupled to the flip-flop.

12. The switch-mode power supply control circuit of claim 9, wherein the comparator is a first comparator, and the timer circuit comprises a second comparator, comprising an output terminal coupled to the second input terminal of the delay circuit.

13. The switch-mode power supply control circuit of claim 12, wherein the timer circuit comprises:

a capacitor comprising;

a first terminal coupled to a first input terminal of the second comparator; and

a second terminal coupled to ground;

a switch comprising;

a first terminal coupled to the first terminal of the capacitor;

a second terminal coupled to the second terminal of the capacitor; and

a third terminal coupled to the output terminal of the second comparator.

14. The switch-mode power supply control circuit of claim 9, wherein the comparator is a first comparator, and the switch-mode power supply control circuit comprises a second comparator, comprising:

an output terminal coupled to the flip-flop; and

an input terminal coupled to a source terminal of the transistor.

15. A switch-mode power supply control circuit, comprising:

an inductor terminal for connecting an inductor to the switch-mode power supply control circuit;

an input voltage terminal;

an output voltage terminal;

a first transistor configured to pull the inductor terminal to ground;

a second transistor configured to connect the inductor terminal to the output voltage terminal;

control circuitry coupled to the first transistor and the second transistor, the control circuitry configured to;

turn off the first transistor and turn on the second transistor for a first time period that is a function of voltage at the input voltage terminal and voltage at the output voltage terminal;

determine whether the switch-mode power supply is operating in continuous conduction mode or discontinuous conduction mode; and

add a predetermined fixed interval to the first time period based on the switch-mode power supply operating in discontinuous conduction mode.

16. The switch-mode power supply control circuit of claim 15, wherein the control circuitry is configured to turn on the second transistor after initiation of the first time period and turn off the second transistor at expiration of the first time period.

17. The switch-mode power supply control circuit of claim 15, wherein the control circuit is configured to not add the predetermined fixed interval to the first time period based on switch-mode power supply operating in continuous conduction mode.

18. The switch-mode power supply control circuit of claim 15, wherein the control circuit comprises a comparator configured to compare a current at the inductor terminal to zero.

19. The switch-mode power supply control circuit of claim 18, wherein the control circuit comprises a delay circuit coupled to the comparator;

wherein the delay circuit is configured to;

apply a delay element to delay a signal to turn on the first transistor responsive to an output of the first comparator indicating that the current at the inductor terminal is less than zero; and

bypass the delay element responsive to the output of the first comparator indicating that the current at the inductor terminal is greater than zero.

20. The switch-mode power supply control circuit of claim 19, wherein the delay element is configured to delay the signal by the predetermined fixed interval.