US-12628252-B2 - Switching power supply with constant current output and a method for controlling constant current of a switching power supply

US12628252B2US 12628252 B2US12628252 B2US 12628252B2US-12628252-B2

Abstract

The application discloses a switching power supply with constant current output and a method for controlling constant current of a switching power supply, wherein the switching power supply comprises a detection circuit and a logic control chip, and the detection circuit is configured to output a feedback voltage. The feedback voltage is a sum voltage of a first voltage and a second voltage, and the second voltage represents output current of the switching power supply. The logic control chip is configured to receive the feedback voltage and compare the feedback voltage with a reference voltage. When the output current changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant. The reference voltage set by a switching power supply with constant voltage output is very high, while operating current requirement of constant current drive is very small, and the reference voltage is too high relative to the second voltage, so the first voltage is introduced to bear part of the reference voltage, so that constant current reference is lowered, so as to take into account needs of constant current drive and power consumption.

Inventors

Xiaojia Wang
Jian Chen
Xiufeng Yu

Assignees

Shenzhen Kiwi Instruments Corporation

Dates

Publication Date: 20260512
Application Date: 20240227
Priority Date: 20230227

Claims (9)

1 . A switching power supply with constant current output, applied to light emitting diodes, the switching power supply comprising: a detection circuit, configured to generate a first voltage and a second voltage, wherein the first voltage is greater than the second voltage, and the second voltage represents output current of the switching power supply; and a logic control chip, configured to receive a feedback voltage and compare the feedback voltage with a reference voltage, when the output current of the switching power supply changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant; wherein the feedback voltage is a sum voltage of the first voltage and the second voltage; wherein the detection circuit further comprises an addition circuit, the addition circuit is configured to sum the first voltage and the second voltage to generate the feedback voltage.
2 . The switching power supply according to claim 1 , wherein the detection circuit comprises a voltage division circuit and a current sampling circuit, the voltage division circuit is configured to generate the first voltage, the current sampling circuit is configured to sample the output current of the switching power supply, and generates the second voltage based on the output current.
3 . The switching power supply according to claim 2 , wherein the current sampling circuit comprises a first resistance, one end of the first resistance is coupled to tail end of the light emitting diodes, and the other end of the first resistance is coupled to ground.
4 . The switching power supply according to claim 2 , wherein the voltage division circuit comprises a constant voltage source, the constant voltage source is configured to generate the first voltage.
5 . The switching power supply according to claim 3 , wherein the voltage division circuit comprises a second resistor and a third resistor, one end of the second resistor is coupled to head end of the light emitting diodes; one end of the third resistance is coupled to the first resistance, and the other end of the third resistance is coupled to the second resistance.
6 . A switching power supply with constant current output, the switching power supply comprising: a detection circuit, configured to generate a first voltage and a second voltage, wherein the second voltage represents output current of the switching power supply; and a logic control chip, configured to receive a feedback voltage and compare the feedback voltage with a reference voltage, when the output current of the switching power supply changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant; wherein the detection circuit further comprises an addition circuit, the addition circuit is configured to sum the first voltage and the second voltage to generate the feedback voltage.
7 . The switching power supply according to claim 6 , wherein the first voltage is greater than the second voltage.
8 . The switching power supply according to claim 6 , wherein the switching power supply is applied to light emitting diodes.
9 . A method for controlling constant current of a switching power supply, applied to light emitting diodes, the method comprising: generating a first voltage and a second voltage, wherein the first voltage is greater than the second voltage, and the second voltage represents output current of the switching power supply; summing the first voltage and the second voltage to generate a feedback voltage; and comparing the feedback voltage with a reference voltage, when the output current of the switching power supply changes, changing turn on time of the switching power supply based on comparison result to control the output current constant.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of Chinese Patent Applications No. 202310227843.4, filed on Feb. 27, 2023, which are incorporated herein by reference in its entirety. TECHNICAL FIELD This application relates to the power electronics technical field, in particular but not limited to a switching power supply with constant current output and a method for controlling constant current of a switching power supply. BACKGROUND Light emitting diodes, referred to as LEDs, emit light by combining electrons with holes to release energy, widely applied in field of lighting. When LEDs are applied as displays or lighting devices, in order to obtain expected brightness requirement, ensure consistency of each LED brightness and chroma, need to be driven by constant current. Displays or lighting devices are usually driven by a switching power supply, however, existing switching power supplies generally use constant voltage output, which does not match needs of LED constant current drive. In view of this, it is necessary to provide a new structure or control method for solving at least some of the above problems. SUMMARY In view of one or more problems in the prior art, a switching power supply with constant current output and a method for controlling constant current of a switching power supply is provided in the present application. An embodiment of the present application discloses a switching power supply with constant current output, applied to light emitting diodes, the switching power supply comprising: a detection circuit, configured to generate a first voltage and a second voltage, wherein the first voltage is greater than the second voltage, and the second voltage represents output current of the switching power supply; anda logic control chip, configured to receive a feedback voltage and compare the feedback voltage with a reference voltage, when the output current of the switching power supply changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant; wherein the feedback voltage is a sum voltage of the first voltage and the second voltage. Another embodiment of the present application discloses a switching power supply with constant current output, the switching power supply comprising: a detection circuit, configured to generate a first voltage and a second voltage, wherein the second voltage represents output current of the switching power supply; anda logic control chip, configured to receive a feedback voltage and compare the feedback voltage with a reference voltage, when the output current of the switching power supply changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant. Another embodiment of the present application discloses a method for controlling constant current of a switching power supply, applied to light emitting diodes, the method comprising: generating a first voltage and a second voltage, wherein the first voltage is greater than the second voltage, and the second voltage represents output current of the switching power supply;summing the first voltage and the second voltage to generate the feedback voltage; andcomparing the feedback voltage with a reference voltage, when the output current of the switching power supply changes, changing turn on time of the switching power supply based on comparison result to control the output current constant. BRIEF DESCRIPTION OF THE DRAWINGS The above aspects and implementation forms of the present application will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which FIG. 1 shows the structure diagram of a switching power supply with constant voltage output; FIG. 2 shows a schematic diagram of a switching power supply with constant current output according to an embodiment of the present application; FIG. 3 shows a schematic diagram of the detection circuit structure according to an embodiment of the present application; FIG. 4 shows a schematic diagram of the detection circuit structure according to another embodiment of the present application. DETAILED DESCRIPTION In order to further understand the present application, the following describes the preferred implementation scheme of the application in combination with embodiments, but it should be understood that these descriptions only for further illustrate the features and advantages of the present application, rather than limit the claims of the present application. The descriptions in this section is only for a few typical embodiments, and the present application is not limited to the scope of the description of the embodiments. Combinations of different embodiments, replacement of some technical features in different embodiments, and replacement of same or similar prior art means with some technical