Switch control circuit and buck converter comprising the same

• US 10,277,128 B2
• Filed: 06/29/2016
• Issued: 04/30/2019
• Est. Priority Date: 06/29/2015
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Moon, SangCheol, Koo, Gwanbon, Jin, Chenghao, Chung, Bonggeun
• Primary Examiner(s): Finch, III, Fred E
• Assistant Examiner(s): Gibson, Demetries A
• Application Number:
  US15/196,409
• Publication Number:
  US 20160380540A1
• Time in Patent Office: 1,035 Days
• CPC Class Codes: G01R 19/04 Measuring peak values or amplitude or envelope of ac or of pulses
• CPC Class Codes: H02M 1/0003 Details of control, feedback or regulation circuits
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• 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 1/0048 Circuits or arrangements for reducing losses using snubbers H02M1/34
• CPC Class Codes: H02M 1/0054 Transistor switching losses periodically suspending operation of switching converter in low power mode H02M1/0035
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• 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 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• 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 buck converter includes a power switch having a first end to receive an input voltage, a synchronous switch connected between a second end of the power switch and the ground, an inductor having a first end connected to the other end of the power switch, and a switch control circuit configured to turn off the synchronous switch when a zero voltage delay time passes after an inductor current flowing through the inductor reaches a predetermined reference value, calculate a dead time based on the input voltage and the zero voltage delay time, and turn on the power switch when the dead time passes following the turn-off time of the synchronous switch.

Claims

1. A switch control circuit for a power switch and a synchronous switch that are connected to an inductor, the switch control circuit comprising:

a comparator configured to compare a detection voltage indicating a present magnitude of an inductor current flowing through the inductor with a predetermined reference voltage;

a delay unit configured to delay an output of the comparator by a zero voltage delay time; and

a dead time calculation unit configured to;

produce, by measuring an OFF time of the power switch using an OFF counter, a TOFF signal having a value corresponding to the OFF time, and

calculate a dead time based on the zero voltage delay time, the TOFF signal, and an input voltage that is input to the power switch,

wherein the switch control circuit is configured to control a turn-off time of the synchronous switch according to an output of the delay unit, and turn on the power switch when the dead time passes following the turn-off time of the synchronous switch.

2. The switch control circuit of claim 1, wherein,

the zero voltage delay time is constant;

and

the dead time calculation unit is configured to;

produce, by measuring an ON time of the power switch using an ON counter, a TON signal having a value corresponding to the ON time,

and calculate the dead time based on the zero voltage delay time, the value of the TOFF signal, and the value of the TON signal.

3. The switch control circuit of claim 2, wherein the dead time calculation unit is configured to calculate the dead time by dividing the value of the TON signal by the value of the TOFF signal and multiplying the quotient by the zero voltage delay time.

4. The switch control circuit of claim 1, further comprising a pin for setting the zero voltage delay time, wherein

the delay unit is configured to set the zero voltage delay time according to a voltage that is input through the pin.

5. The switch control circuit of claim 1, wherein,

the switch control circuit is configured to:

produce, by measuring an ON time of the power switch using an ON counter, a TON signal having a value corresponding to the ON time, and

calculate the zero voltage delay time based on a delay time, the value of the TON signal, and the value of the TOFF signal; and

the delay time is determined based on the inductor and parasitic capacitors of the power switch and the synchronous switch.

6. The switch control circuit of claim 5, wherein the dead time calculation unit is configured to calculate the dead time based on a switching cycle of the power switch, the value of the TOFF signal, and the delay time.

7. The switch control circuit of claim 6, further comprising a pin for setting the delay time, wherein

the dead time calculation unit is configured to set the delay time according to a voltage that is input through the pin.

8. The switch control circuit of claim 6, wherein the dead time calculation unit is configured to calculate the dead time by dividing the switching cycle by the value of the TOFF signal and multiplying the quotient by the delay time.

9. The switch control circuit of claim 5, further comprising a pin for setting the delay time, wherein

the delay unit is configured to set the delay time according to a voltage that is input through the pin.

10. The switch control circuit of claim 9, wherein the dead time calculation unit is configured to receive the delay time from the delay unit.

11. The switch control circuit of claim 5, wherein the switch control circuit is configured to calculate the zero voltage delay time based on a result of adding the value of the TON signal and the value of the TOFF signal to produce a sum, dividing the sum by the value of the TON signal to produce a quotient, and multiplying the quotient by the delay time.

12. A buck converter comprising:

a power switch having a first end to receive an input voltage;

a synchronous switch connected between a second end of the power switch and ground;

an inductor having a first end connected to the second end of the power switch; and

a switch control circuit configured to;

receive an indication of a present magnitude of an inductor current flowing through the inductor,

turn off the synchronous switch when a zero voltage delay time passes after the inductor current flowing through the inductor reaches a predetermined reference value,

measure an OFF time of the power switch using an off counter,

calculate a dead time based on the input voltage, the OFF time, and the zero voltage delay time, and

turn on the power switch when the dead time passes following the turn-off time of the synchronous switch.

13. The buck converter of claim 12, wherein,

the zero voltage delay time is constant;

and

the switch control circuit is configured to;

measure an ON time of the power switch using an on counter, and

calculate the dead time based on the zero voltage delay time, the ON time, and the OFF time.

14. The buck converter of claim 13, wherein the switch control circuit is configured to calculate the dead time by dividing the ON time by the OFF time and multiplying the quotient by the zero voltage delay time.

15. The buck converter of claim 12, wherein the switch control circuit includes a pin to which a voltage for setting the zero voltage delay time is input.

16. The buck converter of claim 12, wherein,

the switch control circuit is configured to:

measure an ON time of the power switch using an on counter, and

calculate the zero voltage delay time based on a delay time, the ON time, and the OFF time; and

the delay time is determined based on the inductor and parasitic capacitors of the power switch and the synchronous switch.

17. The buck converter of claim 16, wherein the switch control circuit is configured to calculate the dead time based on a switching cycle of the power switch, the OFF time, and the delay time.

18. The buck converter of claim 17, wherein the switch control circuit includes a pin for setting the delay time.

19. The buck converter of claim 17, wherein the switch control circuit is configured to calculate the dead time by dividing the switching cycle by the OFF time and multiplying the quotient by the delay time.

20. The buck converter of claim 16, wherein the switch control circuit is configured to calculate the zero voltage delay time based on a result of adding the ON time and the OFF time, dividing the sum by the ON time, and multiplying the quotient by the delay time.