Control circuit and switching power supply

• US 9,960,673 B2
• Filed: 02/12/2016
• Issued: 05/01/2018
• Est. Priority Date: 02/16/2015
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Matsuura, Ken, Lin, Min
• Primary Examiner(s): Dole, Timothy J
• Assistant Examiner(s): JAMALI, ISHRAT F
• Application Number:
  US15/042,965
• Publication Number:
  US 20160241145A1
• Time in Patent Office: 809 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 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• 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 1/14 Arrangements for reducing ripples from dc input or output
• 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: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02M 3/335 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 control circuit according to an embodiment of the present invention is configured to control a switching element of a switching power supply. The control circuit includes a comparator having a first input terminal configured to receive an output voltage of the switching power supply. The comparator has a second input terminal that is connectable to a positive terminal of a reference voltage source. The comparator has an output. The output brings the reference voltage to a first voltage while the output signal takes a first voltage level. The output brings the reference voltage to a second voltage while the output signal takes a second voltage level. The constant voltage source has a positive terminal connected to a negative terminal of the reference voltage source and a ground of the comparator.

Claims

1. A control circuit configured to be connected to a switching element connected to a first output terminal and a second output terminal, the first output terminal being higher in voltage level than a second output terminal the control circuit comprising:

a reference voltage source;

a constant voltage source having a positive terminal and a negative terminal, the positive terminal being configured to be connected to the first output terminal,

and a voltage between the positive terminal and the negative terminal being constant;

a comparator having a first input terminal, a second input terminal, and a third output terminal, the first input terminal being connected to the negative terminal of the constant voltage source, and the second input terminal being connected to the reference voltage source; and

a controller configured to be connected between the third output terminal of the comparator and the switching element, the controller being configured to control the switching element based on the output an output of the comparator,

wherein a voltage of the reference voltage source becomes a first voltage in a case that the output of the comparator is at a first voltage level,

the voltage of the reference voltage source becomes a second voltage in a case that the output of the comparator is at a second voltage level different from the first voltage level, and

the second voltage is different from the first voltage.

2. The control circuit of claim 1, wherein the constant voltage source comprises

a Zener diode having a cathode and an anode, the cathode being configured to be connected between the switching power supply element and the first output terminal;

and

a resistor having a first end and a second end, the first end being connected between the first input terminal of the comparator and the anode of the Zener diode, and the second end being grounded.

3. The control circuit of claim 1, wherein the constant voltage source comprises a shunt regulator configured to adjust a setting voltage.

4. The control circuit of claim 1, wherein the controller is configured to control the switching element to:

perform switching a plurality of times in a case that the output of the comparator is at a first level; and

stop switching in a case that the output of the comparator is a second level different from the first level.

5. The control circuit of claim 1, wherein the controller is configured to turn off the switching element in a case that a current input to the first output terminal becomes a predetermined value or more.

6. A switching power supply device comprising:

a switching element connected to a first output terminal and a second output terminal of the switching power supply device, the first output terminal being higher in voltage level than the second output terminal; and

a control circuit connected to the switching element and configured to control switching element,

the control circuit comprising;

a reference voltage source;

a constant voltage source having a positive terminal and a negative terminal, the positive terminal being connected to the first output terminal, and a voltage between the positive terminal and the negative terminal being constant;

a comparator having at least a first input terminal, a second input terminal, and a third output terminal, the first input terminal being connected to the negative terminal of the constant voltage source, and the second input terminal being connected to the reference voltage source; and

a controller connected between the third output terminal of the comparator and the switching element, the controller being configured to control the switching element based on an output of the comparator,

wherein a voltage of the reference voltage source becomes a first voltage in a case that the output of the comparator is at a first voltage level,

the voltage of the reference voltage source becomes a second voltage in a case that the output of the comparator is at a second voltage level different from the first voltage level, and

the second voltage is different from the first voltage.

7. The switching power supply device of claim 6, wherein the constant voltage source comprises:

a Zener diode having a cathode and an anode, the cathode being configured to be connected between the switching element and the first output terminal; and

a resistor having a first end and a second end, the first end being connected between the first input terminal of the comparator and the anode of the Zener diode, and the second end being grounded.

8. The switching power supply device of claim 6, wherein the constant voltage source comprises a shunt regulator configured to adjust a setting voltage.

9. The switching power supply device of claim 6, wherein the controller is configured to control the switching element to:

perform switching a plurality of times in a case that the output of the comparator is at a first voltage level; and

stop switching in a case that the output of the comparator is at a second voltage level different from the first voltage level.

10. The switching power supply device according to claim 6, wherein the controller is configured to turn off the switching element in a case that a current input to the first output terminal becomes a predetermined value or more.

11. The switching power supply device according to claim 6, wherein the switching element comprises a resonant converter.