CONTROL CIRCUIT AND CONTROL METHOD FOR SWITCHING REGULATOR AND SWITCHING REGULATOR WITH THE SAME

• US 20170338738A1
• Filed: 05/01/2017
• Published: 11/23/2017
• Est. Priority Date: 05/18/2016
• Status: Active Grant

• Current Assignee: Silergy Semiconductor Technology (Hangzhou) Ltd. (Silergy Corporation)
• Original Assignee: Silergy Semiconductor Technology (Hangzhou) Ltd. (Silergy Corporation)
• Inventors: Sun, Liangwei
• Granted Patent: US 10,110,124 B2
• Time in Patent Office: Days
• 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 1/15 using active elements
• 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

Abstract

A control circuit for a switching regulator can include: an ON signal generator that generates an ON signal; an OFF signal generator that generates a first control signal according to an input voltage and an output voltage of the switching regulator; an on time regulator that generates an adjustment signal according to a switching signal and the first control signal; and a logic circuit configured to generate an off signal according to the first control signal, and to generate the switching signal according to the ON signal and the OFF signal, where the on time of the first switch is regulated according to the off time of the first switch when the off time of the first switch is less than the reference time, in order to regulate a duty cycle of the switching signal.

Claims

1. A control circuit for a switching regulator having a first switch, the control circuit comprising:

a) an ON signal generator configured to generate an ON signal;

b) an OFF signal generator configured to generate a first control signal according to an input voltage and an output voltage of said switching regulator;

c) an on time regulator configured to generate an adjustment signal according to a switching signal and said first control signal, wherein an on time of said first switch is controlled to be a constant on time when an off time of said first switch is greater than or equal to a reference time; and

d) a logic circuit configured to generate an off signal according to said first control signal, and to generate said switching signal according to said ON signal and said OFF signal, wherein said on time of said first switch is regulated according to said off time of said first switch when said off time of said first switch is less than said reference time, in order to regulate a duty cycle of said switching signal.

2. The control circuit of claim 1, wherein said OFF signal generator is configured to regulate transition moments of said first control signal according to said adjustment signal, in order to change said on time of said first switch.

3. The control circuit of claim 1, wherein said on time regulator comprises:

a) a single-trigger circuit configured to generate a single-trigger signal according to said first control signal, wherein a time duration during which said single-trigger circuit is active equals to said reference time; and

b) a first charge and discharge circuit comprising a first capacitor that is charged when said single-trigger signal is active, and discharged when said switching signal is inactive, wherein a voltage across said first capacitor is configured as said adjustment signal.

4. The control circuit of claim 3, wherein said first charge and discharge circuit further comprises:

a) a first voltage controlled current source configured to charge said first capacitor when said single-trigger signal is active; and

b) a second voltage controlled current source configured to discharge said first capacitor when said switching signal is inactive.

5. The control circuit of claim 4, wherein currents of said first voltage controlled current source and said second voltage controlled current source are equal.

6. The control circuit of claim 4, wherein said on time regulator further comprises a clamp circuit configured to clamp said adjustment signal in a range between an upper voltage value and zero.

7. The control circuit of claim 6, wherein said on time regulator further comprises a delay circuit comprising a delay capacitor and a delay resistor coupled in series, and wherein said delay circuit is coupled with said capacitor in parallel.

8. The control circuit of claim 1, wherein said OFF signal generator comprises:

a) a second charge and discharge circuit comprising a second capacitor that is charged and discharged in order to generate a first voltage signal; and

b) a comparator configured to compare said first voltage signal against said reference voltage, in order to generate said first control signal, wherein said reference voltage is proportional to said output voltage.

9. The control circuit of claim 8, wherein said second charge and discharge circuit further comprises:

a) a third voltage controlled current source, a fourth current source, and a third switch coupled in parallel, wherein said third switch is turned on and off according to said first control signal;

b) wherein said third voltage controlled current source and said fourth current source are configured to charge said second capacitor when said third switch is off; and

c) said second capacitor being discharged through said third switch when said third switch is on.

10. The control circuit of claim 9, wherein:

a) said third voltage controlled current source is configured to generate a first current that is proportional to said adjustment voltage;

b) said fourth current source is configured to generate a second current that is proportional to said input voltage; and

c) said second current has an opposite direction to said first current.

11. The control circuit of claim 1, further comprising a minimum off time circuit configured to generate a second control signal according to said first control signal, wherein said second control signal is configured to maintain said first switch as off for a time that is at least as long as a predetermined minimum off time circuit, and wherein said reference time is greater than or equal to said minimum off time.

12. A switching regulator, comprising the control circuit of claim 1, and further comprising a power stage circuit having said first switch, wherein said control circuit generates said switching signal to control the turn on and off of said first switch.

13. The switching regulator of claim 12, wherein:

a) said power stage circuit further comprises a second switch coupled in series with said first switch in series; and

b) said switching signal is configured to control said second switch such that said first and second switches are alternately turned on and off.

14. A method of controlling a switching regulator having a first switch, the method comprising:

a) generating a switching signal;

b) controlling the turn on and off of said first switch by said switching signal;

c) comparing an off time of said first switch against a reference time, and generating an adjustment signal;

d) controlling an on time of said first switch according to said adjustment signal;

e) controlling, by said switching signal, said on time of said first switch to be a constant on time when said off time of said first switch is greater than or equal to a reference time; and

f) regulating said on time of said first switch according to said off time of said first switch in order to regulate a duty cycle of said switching signal when said off time of said first switch is less than said reference time.

15. The method of claim 14, wherein said generating said switching signal comprises:

a) generating an ON signal in a ripple control mode;

b) generating a first control signal according to an input voltage and an output voltage of said switching regulator;

c) generating an OFF signal according to said first control signal; and

d) generating said switching signal according to said ON signal and said OFF signal.

16. The method of claim 15, wherein said generating said adjustment signal comprises:

a) generating a single-trigger signal according to said first control signal, wherein a time duration during which said single-trigger signal is active equals said reference time;

b) generating said adjustment signal according to said single-trigger signal and said switching signal;

c) charging a first capacitor when said time duration during which said single-trigger signal is active is greater than or equal to said time duration during which said switching signal is active; and

d) discharging said first capacitor when said time duration during which said single-trigger signal is active is less than said time duration during which said switching signal is inactive.

17. The method of claim 15, wherein said controlling said on time of said first switch according to said adjustment signal comprises regulating the level transition moment of said first control signal according to said adjustment signal in order to change said on time of said first switch.

18. The method of claim 15, wherein said generating said first control signal comprises:

a) generating a first voltage signal by charging and discharging a second capacitor;

b) comparing said first voltage signal against reference voltage, and generating said first control signal; and

c) charging, by an adjustable first current and a constant second current, said second capacitor when said first control signal is inactive, and discharging said second capacitor when said first control signal is active, wherein said reference voltage is proportional to said output voltage, said first current is proportional to a high voltage, said second current is proportional to said input voltage, and said second current has an opposition direction to said first current.

19. The method of claim 15, further comprising controlling a second switch by said switching signal such that said first and second switches are alternately turned on and off.

20. The method of claim 15, further comprising generating a second control signal according to said first control signal, wherein said second control signal maintains said first switch as off for a time that is at least as long as a predetermined minimum off time, and wherein said reference time is greater than or equal to said minimum off time.