CN109274910B - Switching power supply and television - Google Patents

Abstract

The embodiment of the invention discloses a switching power supply and a TV. The switching power supply includes: a PFC control and management constant voltage module, a PFC control and management constant current module and a linear constant voltage module; wherein the PFC control and management constant voltage module is used to improve the constant voltage voltage output power factor and output constant voltage to supply power to the host chip; PFC control and management constant current module is used to improve the power factor of constant current output and output constant voltage to supply power to the constant current load; the linear constant voltage module uses During the process of the system from standby to light load at startup, the voltage of the first input terminal and the voltage of the second input terminal are successively used to relay power supply for the power supply terminal of the PFC control and management constant current module, so that the constant current load is normal. start up. Through the switching power supply, the situation that the LED backlight cannot be normally turned on due to the insufficient power supply capability of the power supply end of the PFC control and management constant current circuit will not occur, and the stability of the system is improved.

Description

A switching power supply and TV

technical field

Embodiments of the present invention relate to the technical field of power supply control, and in particular, to a switching power supply and a television.

Background technique

With the rapid development of LED (Light Emitting Diode, light-emitting diode) LCD TVs, at present, LED LCD TVs have been popularized in thousands of households.

Existing LED LCD TVs all adopt the design method of power board + constant current board, in which the power board is responsible for providing appropriate input voltage for the constant current board and TV main board, and the constant current board is responsible for providing constant current for the LED backlight module. The power board + constant current board are collectively referred to as switching power supply. When the TV is working, the switching power supply realizes constant voltage and constant current output, which not only meets the constant current demand of the LED backlight, but also meets the constant voltage demand of the TV motherboard (movement). However, the existing power supply design scheme has the defects of low power conversion efficiency and high cost, the LED backlight cannot be turned on normally when the movement is lightly loaded, and protection cannot be performed when the LED backlight is abnormally overvoltage.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a switching power supply and a TV. When the system is switched from standby to light-loaded, the LED backlight can be normally turned on through the switching power supply, and the power supply of the constant current circuit due to PFC control and management will not occur. The power supply capacity of the terminal is insufficient, which leads to the situation that the LED backlight cannot be turned on normally, which improves the stability of the system.

To achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:

In a first aspect, an embodiment of the present invention provides a switching power supply, which includes: a PFC (Power Factor Correction, power factor correction) control and management constant voltage module, a PFC control and management constant current module, and a linear constant voltage module;

Among them, the input end of the PFC control and management constant voltage module is connected to the power supply, the first output end is connected to the host chip, and the second output end is connected to the linear constant voltage module, which is used to improve the power factor of the constant voltage output and output a constant voltage to the supplying power to the host chip, while providing a pre-start voltage for the linear constant voltage module;

The input end of the PFC control and management constant current module is connected to the output end of the linear constant voltage module, the first output end is connected to the constant current load, and the second output end is connected to the linear constant voltage module for improving the constant current output power factor and output a constant voltage to supply power to the constant current load, and at the same time provide a relay voltage for the linear constant voltage module;

The first input end of the linear constant voltage module is connected to the second output end of the PFC control and management constant voltage module, the second input end is connected to the second output end of the PFC control and management constant current module, and the output end is connected to the second output end of the PFC control and management constant current module. The input terminals of the PFC control and management constant current module are connected to each other, and are used for the PFC control management constant current through the voltage of the first input terminal and the voltage of the second input terminal in turn when the system is turned off to standby and then turned on with a light load. The power supply terminal of the current module performs relay power supply, so that the constant current load can be started normally.

Further, the PFC control and management constant voltage module includes: a PFC control and management constant voltage circuit, a constant voltage switch tube, a constant voltage transformer and a constant voltage control loop;

Among them, the first end of the PFC control and management constant voltage circuit is connected to the power supply, the sixth end is connected to the output end of the auxiliary winding of the constant voltage transformer, and the seventh end is connected to the control end of the main winding of the constant voltage transformer through the constant voltage switch tube, It is used to control the turn-on and turn-off of the constant voltage switch tube according to the zero-crossing detection signal provided by the output end of the auxiliary winding of the constant voltage transformer, so as to improve the power factor of the constant voltage output, the PFC controls and manages the fourth end of the constant voltage circuit Connected to the output end of the constant voltage control loop, the PFC control and management constant voltage circuit is also used to control the turn-on and turn-off of the constant voltage switch tube according to the signal at the output end of the constant voltage control loop, so as to make the constant voltage switch on and off. Transformer output constant voltage;

The input end of the main winding of the constant voltage transformer is connected to the power supply, and the output end is connected to the core of the host, for providing constant voltage to the host chip under the control of the PFC control and management constant voltage circuit;

The input end of the constant voltage control loop is connected to the output end of the main winding of the constant voltage transformer, for sampling the constant voltage output by the main winding of the constant voltage transformer, and sending the sampled voltage to the PFC control The fourth end of the management constant voltage circuit, so that the PFC control management constant voltage circuit controls the on and off of the constant voltage switch tube according to the sampled voltage, so that the constant voltage transformer outputs a constant voltage.

Further, the PFC control and management constant current module includes: a PFC control and management constant current circuit, a constant current switch tube, a constant current transformer and an overvoltage adjustment circuit,

The power supply terminal of the PFC control and management constant current circuit is connected to the output terminal of the linear constant voltage circuit, the sixth terminal is connected to the output terminal of the auxiliary winding of the constant current transformer, and the ninth terminal is connected to the constant current through the constant current switch tube. The control terminal of the main winding of the transformer is connected to control the on and off of the constant current switch tube according to the zero-crossing detection signal provided by the output terminal of the auxiliary winding of the constant current transformer, so as to improve the power factor of the constant current output. The PFC control The fourth terminal of the management constant current circuit is connected to the output terminal of the overvoltage adjustment circuit, and the PFC control management constant current circuit is also used to control the conduction of the constant current switch tube according to the output terminal signal of the overvoltage adjustment circuit and off, so that the constant current transformer outputs a constant voltage;

The input end of the main winding of the constant current transformer is connected to the power supply, and the output end is connected to the constant current load, for providing a constant voltage to the constant current load under the control of the PFC control and management constant current circuit;

The input terminal of the overvoltage adjustment circuit is connected to the output terminal of the constant current load, and is used for sampling the output terminal voltage of the constant current load, and sending the sampled voltage to the first part of the PFC control and management constant current circuit. Four terminals, so that the PFC control and management constant current circuit controls the on and off of the constant current switch tube according to the sampled voltage, so that the constant current transformer outputs a constant voltage.

Further, the linear constant voltage module includes a linear constant voltage circuit, the first input end of the linear constant voltage circuit is connected with the output end of the auxiliary winding of the constant voltage transformer, and the second input end is connected with the auxiliary winding of the constant current transformer. The output end of the winding is connected, the control end is connected to the enable signal, and the output end is connected to the power end of the PFC control and management constant current circuit. The voltage of an input terminal and the voltage of the second input terminal provide relay power supply for the power terminal of the PFC control and management constant current circuit, so that the constant current load can be started normally. Further, the switching power supply further includes: a high-voltage pre-start circuit, the input end of the high-voltage pre-start circuit is connected to the AC power supply, and the output end is connected to the first end of the PFC control and management constant voltage circuit, used for During the process from shutdown to standby, the system provides power for the PFC control and management constant voltage circuit, so that the PFC control and management constant voltage circuit starts and starts to work.

Further, the power supply terminal of the PFC control and management constant voltage circuit is connected to the output terminal of the auxiliary winding of the constant voltage transformer. When the PFC control and management constant voltage circuit is started, the output terminal of the auxiliary winding of the constant voltage transformer is: It provides power and controls the high voltage pre-start circuit to shut down.

Further, the high-voltage pre-start circuit includes: a fourth diode, a fifth diode, a ninth resistor, a tenth resistor, and a first control tube, wherein the fourth diode and the fifth diode The tubes are connected in parallel, the anode is connected to the power supply, the cathode is respectively connected to the first end of the ninth resistor and the first end of the tenth resistor, and the second end of the ninth resistor is connected to the first end of the first control tube. The two ends are connected, the second end of the tenth resistor is connected to the first end of the first control tube and the eleventh end of the PFC control and management constant voltage circuit, and the third end of the first control tube is connected It is connected with the first end of the PFC control and management constant voltage circuit.

Further, the switching power supply further includes: an electromagnetic filter circuit and a rectifier circuit, wherein an input end of the electromagnetic filter circuit is connected to an AC power supply, and an output end is respectively connected to the input end of the high-voltage pre-start circuit and the rectifier circuit. The input end of the circuit is connected, and the output end of the rectifier circuit is respectively connected with the input end of the main winding of the constant voltage transformer and the input end of the main winding of the constant current transformer.

Further, the switching power supply further includes: an overvoltage protection circuit, the input end of the overvoltage protection circuit is connected to the output end of the auxiliary winding of the constant current transformer, and the output end is connected to the first end of the PFC control and management constant current circuit. The two ends are connected, and when the voltage output by the constant current transformer exceeds the set value, the PFC control and management constant current circuit controls the on and off of the constant current switch to make the constant current The voltage at the output of the transformer falls within the set range.

Further, the seventh end of the PFC control and management constant current circuit is connected to the output end of the main winding of the constant current transformer through a constant current switch tube, and the seventh end of the PFC control and management constant current circuit is also connected through a voltage sampling resistor. ground.

Further, the overvoltage protection circuit includes: a first capacitor, a first resistor, a second resistor, a third resistor and a fourth resistor, wherein the first end of the first capacitor is respectively connected with the auxiliary winding of the constant current transformer. The output end is connected to the first end of the first resistor, the second end of the first capacitor, the second end of the first resistor and the second end of the third resistor are all grounded, and the first resistor The first end of the second resistor is also connected to the first end of the second resistor, and the second end of the second resistor is connected to the first ends of the third resistor and the fourth resistor, respectively, and the fourth resistor The second end of the PFC is connected to the second end of the PFC control and management constant current circuit.

Further, the linear constant voltage circuit includes: a first diode, a second diode, a third diode, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second capacitor, a first A Zener diode, a first triode, a second triode and a first optocoupler, wherein the anode of the first diode is connected to the output end of the auxiliary winding of the constant current transformer, and the second diode The anode of the constant voltage transformer is connected to the output end of the auxiliary winding of the constant voltage transformer, the cathode of the first diode, the cathode of the second diode, the fifth resistor, the first transistor and the first diode Two capacitors are connected in series and then grounded, the base of the first triode is connected to the third end of the first optocoupler through the sixth resistor, and the base of the first triode is also connected to the third end of the first optocoupler through the sixth resistor. A zener transistor is grounded, the cathode of the second diode is also connected to the fourth end of the first optocoupler through the seventh resistor, and the first end of the first optocoupler is connected to the eighth The resistor is connected to the output end of the constant voltage transformer, the second end of the first optocoupler is grounded through the second triode, and the base of the second triode is connected to the enable signal provided by the host chip The cathode of the third diode is connected to the base of the first triode, and the anode is connected to the power supply terminal of the PFC control and management constant current circuit.

In a second aspect, an embodiment of the present invention further provides a television, where the television includes the switching power supply described in the first aspect.

In a switching power supply provided by an embodiment of the present invention, the first input end of a linear constant voltage circuit is connected to the output end of the auxiliary winding of the constant voltage transformer, and the second input end is connected to the output end of the auxiliary winding of the constant current transformer. The control terminal is connected to the enable signal, and the output terminal is connected to the power supply terminal of the PFC control and management constant current circuit, which is used to sequentially pass the voltage of the first input terminal and the second power supply terminal during the process of the system from standby to start-up with light load. The voltage of the input terminal is used to relay power supply for the power terminal of the PFC control and management constant current circuit, so that the constant current load can be started normally, and the normal opening of the LED backlight is realized, and there will be no power supply of the constant current circuit due to the PFC control and management. The power supply capacity of the terminal is insufficient, which leads to the situation that the LED backlight cannot be turned on normally, which improves the stability of the system. Through the single-stage PFC control transformer, the AC-DC conversion is directly performed, and the constant voltage and constant current sources are output respectively, which improves the power supply. Efficiency reduces the system cost, and the constant current control and the constant voltage control are independent of each other, so that the constant voltage source and the constant current source do not interfere with each other during dynamic load, which further improves the stability of the system.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. , for those of ordinary skill in the art, other drawings can also be obtained according to the contents of the embodiments of the present invention and these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a switching power supply according to Embodiment 1 of the present invention;

FIG. 2 is a schematic structural diagram of another switching power supply provided in Embodiment 1 of the present invention;

3 is a schematic structural diagram of a switching power supply according to Embodiment 2 of the present invention;

4 is a schematic diagram of a circuit structure of a switching power supply according to Embodiment 2 of the present invention;

5 is a schematic structural diagram of a linear constant voltage circuit according to Embodiment 2 of the present invention;

6 is a schematic diagram of a circuit structure of a constant current control loop according to Embodiment 2 of the present invention;

7 is a schematic structural diagram of an overvoltage protection circuit according to Embodiment 2 of the present invention;

FIG. 8 is a schematic diagram of a circuit structure of a constant voltage control loop according to Embodiment 2 of the present invention.

Detailed ways

In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved more clearly, the technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only the present invention. Some examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

FIG. 1 is a schematic structural diagram of a switching power supply according to Embodiment 1 of the present invention. The switching power supply disclosed in this embodiment can provide a constant voltage source and a constant current source at the same time, and is especially suitable for the field of liquid crystal televisions, and is also suitable for related fields such as liquid crystal displays, projectors, medical equipment, and military industrial equipment. The application scenario of the switching power supply is an LCD TV as an example for illustration, and the constant current load is an LED light bar. The switching power supply provided by this embodiment can effectively improve the efficiency of the power supply system, realize stable startup of the TV, low cost and high power factor. 1, the switching power supply includes: a power factor correction PFC control and management constant voltage module 100, a PFC control and management constant current module 300 and a linear constant voltage module 500;

Among them, the input end of the PFC control and management constant voltage module 100 is connected to the power supply, the first output end is connected to the host chip, and the second output end is connected to the linear constant voltage module 500, which is used to improve the power factor of the constant voltage output and output a constant The voltage supplies power to the host chip, and provides a pre-start voltage for the linear constant voltage module 500 at the same time;

The input end of the PFC control and management constant current module 300 is connected to the output end of the linear constant voltage module 500, the first output end is connected to the constant current load, and the second output end is connected to the linear constant voltage module 500, for improving the constant current output power factor and output a constant voltage to supply power to the constant current load, and at the same time provide a relay voltage for the linear constant voltage module 500;

The first input terminal of the linear constant voltage module 500 is connected to the output terminal of the PFC control management constant voltage module 100 , the second input terminal is connected to the output terminal of the PFC control management constant current module 300 , and the output terminal is connected to the PFC control management constant current module 300 The input terminal of the PFC is connected to the power supply terminal of the PFC control and management constant current module 300 for relaying power supply through the voltage of the first input terminal and the voltage of the second input terminal in turn when the system is switched from shutdown to standby to start-up with a light load. so that the constant current load starts normally.

Exemplarily, referring to the schematic structural diagram of another switching power supply shown in FIG. 2 , the PFC control and management constant voltage module 100 includes: a power factor correction PFC control and management constant voltage circuit 110 , a constant voltage switch tube Q17 , a constant voltage transformer 120 and The constant voltage control loop 130, wherein the first end of the PFC control and management constant voltage circuit 110 is connected to the power supply, the fourth end is connected to the output end of the constant voltage control loop 130, and the sixth end is connected to the auxiliary winding of the constant voltage transformer 120 The output end of 121 is connected, and the seventh end is connected to the control end of the main winding 122 of the constant voltage transformer 120 through the constant voltage switch Q17, and is used to control the constant voltage according to the zero-crossing detection signal provided by the output end of the auxiliary winding 121 of the constant voltage transformer 120 The switch Q17 is turned on and off to improve the power factor of the constant voltage output. The PFC control and management constant voltage circuit 110 is also used to control the conduction of the constant voltage switch Q17 according to the signal at the output end of the constant voltage control loop 130 and off, so that the constant voltage transformer 120 outputs a constant voltage VDD; the input end of the main winding 122 of the constant voltage transformer 120 is connected to the power supply, and the output end is connected to the host machine core for controlling the control of the constant voltage circuit 110 in the PFC control management Provide a constant voltage VDD for the host chip; the input end of the constant voltage control loop 130 is connected to the output end of the main winding of the constant voltage transformer 120 for sampling the constant voltage VDD output by the main winding of the constant voltage transformer 120, and the sampling The voltage is sent to the fourth terminal of the PFC control and management constant voltage circuit 110, so that the PFC control and management constant voltage circuit 110 controls the on and off of the constant voltage switch tube Q17 according to the sampled voltage, so that the constant voltage transformer 120 outputs a constant voltage .

Exemplarily, the PFC control and management constant current module 300 includes: a PFC control and management constant current circuit 140 , a constant current switch tube Q12 , a constant current transformer 150 , and an overvoltage adjustment circuit 160 ; wherein the PFC control and management constant current circuit 140 power supply The terminal is connected to the output terminal of the linear constant voltage circuit 170, the fourth terminal is connected to the output terminal of the overvoltage adjustment circuit 160, the sixth terminal is connected to the output terminal of the auxiliary winding 151 of the constant current transformer, and the ninth terminal constant current switch tube Q12 is connected to the output terminal of the constant current transformer auxiliary winding 151. The control terminal of the main winding 152 of the constant current transformer is connected to control the on and off of the constant current switch tube Q12 according to the zero-crossing detection signal provided by the output terminal of the auxiliary winding 151 of the constant current transformer, so as to improve the power factor of the constant current output , the PFC control and management constant current circuit 140 is also used to control the on and off of the constant current switch tube Q12 according to the output signal of the overvoltage adjustment circuit 160, so that the constant current transformer 150 outputs a constant voltage; the constant current transformer main winding 152 The input end is connected to the power supply, and the output end is connected to the constant current load, which is used to provide a constant voltage for the constant current load under the control of the PFC control and management constant current circuit 140; the input end of the overvoltage adjustment circuit 160 is connected to the constant current load. The output terminal of the current load is connected to the output terminal for sampling the output terminal voltage of the constant current load, and the sampled voltage is sent to the fourth terminal of the PFC control and management constant current circuit 140, so that the PFC control and management constant current circuit 140 according to the The sampling voltage controls the on and off of the constant current switch tube Q12, so that the constant current transformer 150 outputs a constant voltage;

Exemplarily, the linear constant voltage module 500 includes a linear constant voltage circuit 170. The first input terminal VCC1 of the linear constant voltage circuit 170 is connected to the output terminal of the constant voltage transformer auxiliary winding 121, and the second input terminal VCC2 is connected to the constant current transformer auxiliary winding. The output terminal of 151 is connected to the output terminal of 151, the control terminal is connected to the enable signal BL-EN, and the output terminal is connected to the power supply terminal of the PFC control and management constant current circuit 140, which is used in the process of turning off the system from shutdown to standby and then to start-up with light load. The power supply terminal of the PFC control and management constant current circuit 140 is powered by the voltage VCC1 of the first input terminal and the voltage VCC2 of the second input terminal, so that the constant current load can be started normally.

This embodiment provides a switching power supply, wherein the first input end of a linear constant voltage circuit is connected to the output end of the auxiliary winding of the constant voltage transformer, and the second input end is connected to the output end of the auxiliary winding of the constant current transformer , the control terminal is connected to the enable signal, and the output terminal is connected to the power supply terminal of the PFC control and management constant current circuit, which is used to sequentially pass the voltage of the first input terminal and the second input terminal during the process of the system from standby to start-up with light load. The voltage of the terminal is used to relay power supply to the power terminal of the PFC control and management constant current circuit, so that the constant current load can be started normally, and the normal opening of the LED backlight can be realized, and there will be no process when the system goes from standby to starting with a light load. Due to the insufficient power supply capacity of the power supply end of the constant current circuit of the PFC control and management, the LED backlight cannot be turned on normally, which improves the stability of the system. The single-stage PFC control transformer directly performs AC-DC conversion and outputs separately. The constant voltage source and the constant current source improve the power efficiency and reduce the system cost, and the constant current control and the constant voltage control are independent of each other, so that the constant voltage source and the constant current source do not interfere with each other during dynamic load, which further improves the system stability.

Embodiment 2

FIG. 3 is a schematic structural diagram of a switching power supply according to Embodiment 2 of the present invention. On the basis of the above embodiment, this embodiment further optimizes the structure of the switching power supply. By adding a high-voltage pre-start circuit, when the TV is turned off from power-off to power-on standby, the constant voltage circuit for PFC control and management is realized. Providing a stable power supply voltage can also effectively reduce the standby power consumption of the system; by adding an overvoltage protection circuit, it can ensure that the output voltage of the constant current transformer will not be too large, and avoid damage to the LED due to the excessive output voltage of the constant current transformer. Light. Specifically, as shown in FIG. 3, the switching power supply includes:

Power factor correction PFC control and management constant voltage circuit 110, constant voltage transformer 120, constant voltage control loop 130, PFC control and management constant current circuit 140, constant current transformer 150, overvoltage adjustment circuit 160, linear constant voltage circuit 170, high voltage pre- The startup circuit 180 , the electromagnetic filter circuit 190 , the rectifier circuit 200 and the overvoltage protection circuit 210 . In order to clearly illustrate the connection relationship between the circuits, please refer to FIG. 3 and FIG. 4 at the same time: wherein, the input end of the electromagnetic filter circuit 190 is connected to the AC power supply 1, and the output end is respectively connected to the input end of the high voltage pre-start circuit 180 and The input end of the rectifier circuit 200 is connected, and the output end of the rectifier circuit 200 is respectively connected with the input end of the main winding 122 of the constant voltage transformer and the input end of the main winding 152 of the constant current transformer; the output end of the high voltage pre-start circuit 180 is connected with the PFC control management constant The first end of the voltage circuit 110 is connected to provide power for the PFC control and management constant voltage circuit 110 during the process from shutdown to standby, so that the PFC control and management constant voltage circuit 110 starts and starts to work, and the PFC control and management constant voltage circuit 110 The power supply terminal of the voltage circuit 110 is connected to the output terminal of the auxiliary winding 121 of the constant voltage transformer. When the PFC control and management constant voltage circuit 110 is started, the output terminal of the auxiliary winding 121 of the constant voltage transformer provides power for it, and controls the high voltage pre-start circuit 180 closure. The input end of the overvoltage protection circuit 210 is connected to the output end of the auxiliary winding 151 of the constant current transformer, and the output end is connected to the second end of the PFC control and management constant current circuit 140, for when the voltage output by the constant current transformer 150 exceeds the set value At the time, the PFC control and management constant current circuit 140 controls the on and off of the constant current switch tube Q12 to make the voltage output by the constant current transformer 150 drop to the set range. The seventh terminal of the PFC control and management constant current circuit 140 is connected to the output terminal of the constant current transformer main winding 152 through the constant current switch Q12, and the seventh terminal of the PFC control and management constant current circuit 140 is also grounded through the voltage sampling resistor R138. The fourth end of the PFC control and management constant voltage circuit 110 is connected to the output end of the constant voltage control loop 130, and the sixth end is connected to the output end of the auxiliary winding 121 of the constant voltage transformer 120 (in FIG. 4, the PFC control and management constant voltage circuit 110 The line between the sixth end of the constant voltage transformer 120 and the output end of the auxiliary winding 121 of the constant voltage transformer 120 is represented as ZCD1 in FIG. It is used to control the turn-on and turn-off of the constant voltage switch Q17 and Q17 according to the zero-crossing detection signal provided by the output end of the auxiliary winding 121 of the constant voltage transformer 120 to improve the power factor of the constant voltage output. The PFC control and management constant voltage circuit 110 also uses In accordance with the signal at the output end of the constant voltage control loop 130, the on and off of the constant voltage switch tubes Q17 and Q17 are controlled, so that the constant voltage transformer 120 outputs a constant voltage; Under the control of the PFC control and management constant voltage circuit 110, a constant voltage is provided for the host chip; the input end of the constant voltage control loop 130 is connected to the output end of the constant voltage transformer 120, and is used for the constant voltage VDD output by the constant voltage transformer 120. Sampling is performed, and the sampled voltage is sent to the fourth terminal of the PFC control and management constant voltage circuit 110, so that the PFC control and management constant voltage circuit 110 controls the on and off of the constant voltage switches Q17 and Q17 according to the sampled voltage, so that the The constant voltage transformer outputs a constant voltage; the power supply terminal of the PFC control and management constant current circuit 140 is connected to the output terminal VCC-LED of the linear constant voltage circuit 170, the fourth terminal is connected to the output terminal of the overvoltage adjustment circuit 160, and the sixth terminal is connected to the constant voltage circuit 160. The output terminal of the auxiliary winding 151 of the current transformer is connected (in FIG. 4, the line between the sixth terminal of the PFC control and management constant current circuit 140 and the output terminal of the auxiliary winding 121 of the constant current transformer 150 is represented as ZCD2 in FIG. 3), The ninth terminal is connected to the output end of the main winding 152 of the constant current transformer through the constant current switching tube Q12, and is used to control the conduction and closing of the constant current switching tube Q12 according to the zero-crossing detection signal provided by the output end of the auxiliary winding 151 of the constant current transformer. In order to improve the power factor of the constant current output, the PFC control and management constant current circuit 140 is also used to control the on and off of the constant current switch tube Q12 according to the output terminal signal of the overvoltage adjustment circuit 160, so as to make the constant current transformer 150 Output constant voltage; the output end of the constant current transformer is connected to the constant current load 2, and is used to provide a constant voltage for the constant current load 2 under the control of the PFC control management constant current circuit 140; the input end of the overvoltage adjustment circuit 160 is connected to the constant current load 2. The output terminals of the constant current load 2 are connected to each other for sampling the output terminal voltage of the constant current load 2, and the sampled voltage is sent to the fourth terminal of the PFC control management constant current circuit 140, so that the PFC control management constant current The current circuit 140 controls the on and off of the constant current switch Q12 according to the sampled voltage, so that the constant current transformer 150 outputs a constant voltage; the first input terminal VCC1 of the linear constant voltage circuit 170 It is connected to the output end of the auxiliary winding 121 of the constant voltage transformer, the second input end VCC2 is connected to the output end of the auxiliary winding 151 of the constant current transformer, the control end is connected to the enable signal BL-EN, and the output end is connected to the PFC control and management constant current circuit 140 connected to the power supply terminal of the PFC control and management constant current circuit 140 for relaying power supply to the power supply terminal of the PFC control and management constant current circuit 140 through the voltage VCC1 of the first input terminal and the voltage VCC2 of the second input terminal in turn when the system is in the process from standby to start-up with light load. Make the constant current load start normally.

3, the working principle of the switching power supply is described: the AC power supply 1 transmits the constant voltage transformer 120 and the constant current transformer 150, the constant voltage transformer 120 and the constant current respectively after passing through the electromagnetic filter circuit 190 and the rectification circuit 200. The transformer 150 further controls the constant voltage switch tube and the constant current switch tube under the respective single-stage PFC control management (ie the PFC control management constant voltage circuit 110 and the PFC control management constant current circuit 140), so as to output a stable constant voltage source and A constant current source. This design architecture eliminates the need for high-voltage electrolytic capacitors, saving PCB area and cost. When the AC 1 is powered on and the TV system is turned off to standby, the electromagnetic filter circuit 190 provides the PFC control and management constant voltage circuit 110 with the starting voltage VCC1 through the high-voltage pre-start circuit 180. When the PFC control and management constant voltage circuit 110 starts to work, The auxiliary winding output voltage VCC1 of the constant voltage transformer 120 provides a stable working voltage for the PFC control and management constant voltage circuit 110, the high voltage pre-start circuit 180 is turned off, and the working frequency can be adjusted according to the load size to reduce the standby power consumption, so that the constant voltage transformer The output of 120 is regulated by DC-DC to provide a stable working voltage for the movement. At the same time, the auxiliary winding output voltage VCC1 of the constant voltage transformer 120 is connected to the first input terminal of the linear constant voltage circuit 170 to provide a pre-start voltage for the subsequent PFC control and management constant current circuit 140 .

As further described above, the output of the auxiliary winding of the constant voltage transformer 120 provides a zero-crossing detection signal for the PFC control and management constant voltage circuit 110 through the ZCD1 circuit, so as to improve the power factor of the PFC.

Further, when the TV system is turned on from standby to light-loaded, the LED backlight turn-on signal BL-EN turns on the linear constant voltage circuit 170 through the first optocoupler, and the output terminal of the linear constant voltage circuit 170 is connected to the PFC control and management constant current circuit 140 . The power supply terminal of the constant current transformer 150 provides the pre-start working voltage for it. After the PFC control and management constant current circuit 140 starts to work, the constant current transformer 150 outputs the voltage VCC2, and the output voltage VCC2 of the constant current transformer 150 is connected to the second input of the linear constant voltage circuit 170. At the terminal, the VCC2 after the constant voltage relays power supply for the PFC control and management constant current circuit 140, which realizes that when the main board movement is just started, because the voltage of VCC1 is low, the constant current transformer can be controlled by the PFC control and management constant current circuit 140. The voltage VCC2 generated by 150 provides a sufficient and stable working voltage for the PFC control and management constant current circuit 140 after linear constant voltage, which avoids the problem of unstable startup of the system due to insufficient starting voltage when the main board core starts to work.

As further described above, the output of the constant current transformer 150 provides a zero-crossing detection signal for the PFC control and management constant current circuit 140 through the ZCD2 circuit, so as to improve the power factor of the PFC.

As further described above, the output of the constant current transformer 150 is output to the LED1 and LED2 through the rectification filter 1, and the constant current is output under the control of the constant current circuit 1 and the constant current circuit 2, respectively.

As further described above, the output of the constant current transformer 150 is rectified and filtered through the DC-DC linear constant voltage 2 to output a constant voltage as the reference voltage, the constant current auxiliary IC voltage, and the optocoupler power supply voltage.

As further described above, LED1 and LED2 are respectively connected to the second optocoupler through the overvoltage adjustment circuit 160 , and then control the PFC to control and manage the constant current circuit 140 .

Further as mentioned above, because the output constant voltage source and constant current source are controlled separately, the constant voltage and constant current output do not interfere with each other when the movement is dynamically loaded, and the constant voltage is not affected by the crossover of the LED lamp deviation, which improves the system. stability.

When the LED backlight turn-on signal BL-EN is turned off at low level, it is fed back to the linear constant voltage circuit 170 through the first optocoupler, so that the output voltage is cut off, the PFC control and management constant current circuit 140 stops working, and no current flows through the LED. , the LED is off, making the standby power consumption low. When the LED backlight turn-on signal BL-EN is turned on, it is fed back to the linear constant voltage circuit 170 through the first optocoupler to turn on the output voltage, the PFC control and management constant current circuit 140 starts to work, the current flows through the LED, and the The constant current circuit 1 and the constant current circuit 2 control the current in the LED to be constant. The brightness of the LED is adjusted by the PWM signal sent from the main board. When the PWM duty cycle is large, the LED light is brighter, and when the PWM duty cycle is small, the LED light is darker.

Further as described above, when the voltage of the LED light bar is smaller than the output voltage of the constant current transformer 150, the single-stage PFC control and management constant current circuit 140 is controlled through the overvoltage adjustment circuit 160-the second optocoupler to adjust the operating frequency or occupation of the PFC. The duty ratio is further controlled to reduce the output voltage of the flyback transformer, so that the output voltage of the constant current transformer 150 matches the working voltage of the LED light bar, thereby reducing the temperature rise of the overvoltage adjustment circuit 160 . It solves the problem of large output voltage difference caused by the large voltage deviation of LED lamps on the same screen in mass production.

As further described above, under the control of the PFC control and management constant voltage circuit 110, the constant voltage transformer 120 is further controlled, and after rectification and filtering 2, a stable constant voltage source is output through DC-DC voltage regulation. The constant voltage control loop 130 samples the output voltage of the constant voltage transformer 120 after rectification and filtering 2, controls the third optocoupler through the voltage stabilization sampling circuit, and then controls the PFC control and management constant voltage circuit 110 to make the constant voltage transformer 120 output. voltage is constant. When the ripple requirement is low, the DC-DC voltage regulator module can be omitted at the output to reduce the power supply cost.

Referring to the schematic diagram of the circuit structure of the switching power supply shown in Figure 4, the AC power supply AC is sent to the constant current transformer T1 and the constant voltage transformer T2 after EMI filtering and rectification filtering, respectively, without the need for large electrolytic capacitor filtering, the constant voltage switching tube Q17 and constant current The control switch tube Q12 further controls the constant voltage transformer T2 and the constant current transformer T1 under the control of the respective single-stage PFC control chips U14 and U13, so that the secondary output of the transformer is rectified and filtered to supply power to the LED backlight and the motherboard. The single-stage PFC control switch module is used above, and the switching transformer is further controlled. This design structure does not require high-voltage electrolytic capacitors, has high power factor output, and saves PCB area and cost.

Further referring to FIG. 4 , the high-voltage pre-start circuit 180 includes: a fourth diode D36, a fifth diode D37, a ninth resistor R164, a tenth resistor R165, and a first control transistor Q21, wherein the fourth diode The tube D36 and the fifth diode D37 are connected in parallel, the anode is connected to the power supply, the cathode is respectively connected to the first end of the ninth resistor R164 and the first end of the tenth resistor R165, and the second end of the ninth resistor R164 is connected to the first end of the ninth resistor R164. The second end of a control tube Q21 is connected, the second end of the tenth resistor R165 is connected to the first end of the first control tube Q21 and the eleventh end of the PFC control and management constant voltage circuit U14, the first control tube Q21 The third end of the PFC is connected to the first end of the PFC control and management constant voltage circuit U14. When the TV system is switched from power-off to power-on standby, the AC alternating current will pass through the EMI filter circuit after power-on, and then pass through the fourth diode D36, the fifth diode D37, the ninth resistor R164, the third diode D36 in the high-voltage pre-start circuit, and the A control tube Q21, PFC controls and manages pin 1 of the constant voltage circuit IC U14, the tenth resistor R165 sets the G pole level of the first control tube Q21 high, the first control tube Q21 is turned on, and then the constant voltage is controlled and managed by the PFC The 1 pin of the circuit ICU14 provides voltage to the capacitor C88 connected to its 10 pin VCC. When the voltage of the capacitor C88 reaches the starting voltage of the PFC control and management module U14, the PFC control and management module U14 starts and starts to work. At this time, the PFC control and management module Pin 9 of U14 outputs the PWM signal to control the switch tube Q17, which in turn controls the oscillation of the constant voltage transformer T2. The output of pin 5 of the constant voltage transformer T2 (ie auxiliary winding output end 121) is rectified by the fifth diode D27 and filtered by the capacitor C86 and then output The voltage VCC1 supplies power to pin 10 of the PFC control and management module U14, and then the 11-pin of the PFC control and management module U14 outputs a low level to turn off the first control tube Q21, so that when the TV system is in standby, the low-voltage voltage VCC1 controls the PFC. The management module IC U14 supplies power, and can adjust the operating frequency according to the size of the load, which reduces the standby power consumption of the system.

Further as described above, the voltage VCC1 output from pin 5 of the constant voltage transformer T2 provides a stable working voltage for the PFC management constant voltage circuit IC U14, so that the output of the constant voltage transformer T2 is rectified by the sixth diode D30 and the fourth capacitor CE10 After filtering, it can provide a stable working voltage for the main board movement after being stabilized by DC-DC. Also referring to the schematic circuit structure diagram of the linear constant voltage circuit 170 shown in FIG. 5 , the linear constant voltage circuit 170 includes: a first diode D407 , a second diode D406 , a third diode D405 , a fifth resistor R162 , The sixth resistor R168, the seventh resistor R160, the eighth resistor R159, the second capacitor C1D62, the first Zener diode ZD403, the first transistor QP9, the second transistor QP7 and the first optocoupler U15, wherein the third The anode of a diode D407 is connected to the output end of the auxiliary winding 151 of the constant current transformer, the anode of the second diode D406 is connected to the output end of the auxiliary winding 121 of the constant voltage transformer, the cathode of the first diode D407, the second diode D407 The cathode of the diode D406, the fifth resistor R162, the first transistor QP9 and the second capacitor C1D62 are connected in series and then grounded. The base of the first transistor QP9 is connected to the third end of the first optocoupler U15 through the sixth resistor R168 connected, the base of the first transistor QP9 is also grounded through the first voltage regulator transistor ZD403, the cathode of the second diode D406 is also connected to the fourth end of the first optocoupler U15 through the seventh resistor R160, the first light The first end of the coupler U15 is connected to the output end of the constant voltage transformer 120 through the eighth resistor R159, the second end of the first optocoupler U15 is grounded through the second transistor QP7, and the base of the second transistor QP7 is connected to the host The enable signal BL-EN provided by the chip is connected, the cathode of the third diode D405 is connected to the base of the first triode QP9, and the anode is connected to the power terminal of the PFC control and management constant current circuit 140. The voltage VCC1 output by pin 5 of the constant voltage transformer T2 is the first input end of the wiring constant voltage circuit 170, that is, through the second diode D406, the fifth resistor R162, the first transistor QP9, and the second capacitor C1D62 to generate The output voltage VCC-LED provides a pre-start voltage for the PFC control and management constant current circuit U13 after the subsequent LED backlight turn-on signal BL-EN is turned on. The voltage VCC2 output from the auxiliary winding pin 5 of the constant current transformer T1 is the second input terminal of the linear constant voltage circuit 170, so as to provide the relay voltage for the PFC control and management constant current circuit U13 through the second input terminal of the linear constant voltage circuit 170. Specifically, It is: when the TV system is turned on from standby to light-loaded, the LED backlight turn-on signal BL-EN is high, the second transistor QP7 is turned on, the 1-2 pins of the first optocoupler U15 are turned on, and then 3- Pin 4 is turned on, the linear constant voltage circuit is turned on through the first transistor QP9 and outputs the first voltage VCC_LED (ie VCC1). The output of the linear constant voltage circuit is connected to the 10 pin of the PFC control and management constant current circuit IC U13, for Provide the pre-start working voltage. After the PFC control and management constant current circuit IC U13 starts to work, the output of pin 5 of the auxiliary winding of the constant current transformer T1 is filtered by the diode D1D3 and the first capacitor C3D14 to generate the voltage VCC2, and the voltage VCC2 passes through the first diode. The tube D407, the fifth resistor R162, the first transistor QP9, and the second capacitor C1D62 generate the second output voltage VCC_LED (ie VCC2), and the second output voltage VCC_LED is the PFC control and management constant current circuit IC U13 for relay power supply, thereby Solved the problem that the LED backlight could not be lit due to light load, low voltage VCC1 energy and low voltage when the main board movement was first started. The constant current switch tube Q12 is controlled by the PFC control and management constant current circuit IC U13, and then the constant current transformer T1 is controlled to generate the voltage VCC2. After the voltage VCC2 passes through the linear constant voltage circuit, the PFC control and management constant current circuit IC U13 provides sufficient and stable continuous force energy operating voltage.

Further, the voltage output from pin 5 of the constant voltage transformer T2 passes through R148 and R147 of the ZCD1 circuit, and is sampled and then connected to pin 6 of the PFC control and management constant voltage circuit IC U14 to provide a zero-crossing detection signal for the PFC control and management constant voltage circuit U14. , in order to improve the PFC power factor of the constant voltage output. The voltage output by pin 5 of constant current transformer T1 passes through ZCD2 circuit, namely resistor R149 and resistor R150. After sampling, it is connected to pin 6 of PFC control and management constant current circuit IC U13 to provide zero-crossing detection signal for PFC control and management constant current circuit. In order to improve the power factor of the PFC that improves the constant current output.

Further, the output voltage of the constant current transformer T1 is rectified by the diode D20 and filtered by the capacitor CE1, and then connected to LED1...LED1n and LED2...LED2n, and output constant current under the control of constant current circuit 1 and constant current circuit 2 respectively. The specific circuit structure of the constant current circuit 1 and the constant current circuit 2 can refer to the schematic diagram of the circuit structure shown in Figure 6. At the same time, the output voltage of pin 10 of the constant current transformer T1 is rectified by the fifth diode D408 in After filtering by C4B9, the DC-DC linear constant voltage circuit composed of the seventeenth resistor R428, the third transistor Q0B20 and the sixth capacitor C414 outputs a constant voltage SVCC, which is used as the reference voltage of the constant current circuit, and the constant current Auxiliary IC voltage, and the power supply voltage of the second optocoupler U2.

Further, referring to the specific circuit structure diagram of the overvoltage adjustment circuit 160 in FIG. 6 , the LED1 passes through the fourth diode D22, the eighteenth resistor R65, the third capacitor CE6 and the nineteenth resistor R64 in the overvoltage adjustment circuit, LED2 passes through diode D35, resistor R158, capacitor CE11 and resistor R157, and then connects to second optocoupler U2 through second adjustment tube U16, and then controls PFC to control and manage constant current circuit IC U13, and finally realizes the output voltage of constant current transformer T1 and LED light strips to match the desired voltage.

Further, because the output constant voltage source and constant current source are independently controlled, the output of constant voltage and constant current does not interfere with each other when the mainboard movement is dynamically loaded, and the constant voltage source is not affected by the crossover of LED lamp deviation, Improved system stability.

Further, referring to the schematic diagram of the circuit structure shown in FIG. 4 and FIG. 5, when the TV system is turned on from standby, when the power-on signal, that is, the LED backlight turn-on signal BL-EN, changes to a high level, the second transistor QP7 is turned on. , the first transistor QP9 is turned on through the first optocoupler U15, first, the voltage VCC1 passes through the second diode D406, the fifth resistor R162, the first transistor QP9, and the second capacitor C1D62 to generate the output voltage VCC_LED , to supply power to the PFC control and management constant current circuit U13, so that the PFC control and management constant current circuit U13 starts to work, then there is current flowing through the LED, and the LED is in a bright state. In addition, the brightness of the LED is controlled by the brightness control signal BL-ADJ sent from the main board to control the conduction time of the fourth transistor Q8, thereby adjusting the brightness of the LED light. When the PWM duty cycle is large, the LED light is brighter. When the PWM duty cycle is small, the LED light is dim. When the LED backlight turn-on signal BL-EN is at a low level, the second transistor QP7 is controlled to be turned off, and then the first optocoupler U15 is controlled to turn off the first transistor QP9 through the first optocoupler U15, and the output voltage VCC_LED is cut off , the power supply voltage of the PFC control and management constant current circuit U13 is cut off, the 10-pin VCC of the PFC control and management constant current circuit U13 has no voltage, the PFC control and management constant current circuit U13 stops working, and the constant current flyback power supply stops working, making the standby power consumption less Low.

Further, referring to the schematic diagram of the circuit structure of the constant current control loop shown in FIG. 6 , the constant current mode is controlled by a series constant current reference source, which is composed of a third adjusting tube U4, a fifth transistor Q2, and a twentieth resistor R51. The constant current reference source, the third adjusting tube U4 is used as the constant current reference voltage to control the fifth tertiary transistor Q2, so that the voltage across the twentieth resistor R51 is constant, thereby making the current flowing through the light bar constant. When the output ripple voltage of the constant current transformer T1 is large, because the fifth transistor Q2 works in the amplification area, the reference source controls the fifth transistor Q2 to automatically adjust the C-E pole voltage division, making the current more precise and reducing the current ripple. When the voltage of the light bar is small, because the output winding of the constant current transformer T1 remains unchanged, the C-pole voltage of the fifth tertiary tube Q2 increases. The overvoltage adjustment circuit composed of the fourth diode D22 controls the second adjustment tube U16 to control the current flowing through the second optocoupler U2, and then controls the PFC to control the operating frequency or duty cycle of the primary side of the constant current circuit ICU13, Further, the voltage output by the output winding of the constant current transformer T1 is reduced, so that the voltage at both ends of the constant current source is reduced. Another constant current source composed of the sixth transistor Q16, the seventh transistor Q20, and the twenty-first resistor R154 uses the fifth transistor Q2, the twentieth resistor R51, and the third adjusting tube U4 as a current mirror body, so that the constant current source composed of the sixth transistor Q16, the seventh transistor Q20, and the twenty-first resistor R154 has the same current as the current mirror body. Stream output can match any channel's light bar. Further, the constant current circuit can be arbitrarily expanded according to the number of channels of the light bar, so that the solution can meet the requirement of matching any number of channels of the backlight light bar, and realize the low cost and high power factor design of the large-size TV power supply.

Further, referring to the schematic structural diagram shown in FIG. 4 , when the alternating current AC is powered on, the rectified and filtered voltage passes through the fourth diode D36, the fifth diode D37 and the ninth resistor R164, and the first control transistor Q21 Pre-start pin 1 of the PFC control and management constant voltage circuit IC U14, so that the VCC voltage of the 10th pin of the PFC control and management constant voltage circuit U14 reaches the turn-on voltage, and the constant voltage transformer ICT2 starts to oscillate. After stabilization, the 5th pin of the constant voltage transformer T2 That is, the output voltage of the auxiliary winding passes through the fifth diode D27, and the capacitor C86 provides a stable working voltage for the PFC control and management constant voltage circuit IC U14, and then the PFC control and management constant voltage circuit IC U14 pin 11 outputs a low level to control the first The control tube Q21 is turned off, so that the power supply of the PFC control and management constant voltage circuit U14 becomes the VCC1 output by the auxiliary winding of the transformer. At the same time, pin 3 of the PFC control and management constant voltage circuit U14 detects the AC sampling circuit formed by the twenty-second resistor R166 and the twenty-third resistor R167, and samples the AC voltage signal as a reference signal. The current sampling resistor, the fifteenth resistor R148 and the The sixteenth resistor R147 detects the current of the primary winding of the transformer, compares it with the reference signal, and then controls the operating frequency and duty cycle of the constant voltage switch Q17. When the full-wave voltage is large, the operating frequency is high and the duty cycle is small; when When the full-wave voltage is small, the operating frequency is low, and the duty cycle is large, so that the full-wave voltage signal and the current flowing through the primary winding of the constant voltage transformer T2 are in the same phase, which ultimately improves the power factor, and also realizes AC-DC AC-DC. transform.

Further, through the separate control of the constant current source that will power the LED backlight and the constant voltage source that will power the core board, both the working temperature rise of the constant current transformer T1 and the constant voltage transformer T2, as well as the constant current switch tube Q12 are reduced. The working temperature rise of the constant voltage switch tube Q17 also improves the stability of the independent control of the system.

Further, when the voltage of the LED light bar is smaller than the voltage of the output winding of the constant current transformer T1, the single-stage PFC management constant current circuit IC U13 is controlled by the second optocoupler U2 in the constant current control loop to adjust the working frequency and occupation of the PFC. The air ratio becomes smaller, and the constant current switch tube Q12 is further controlled, so that the output voltage of the flyback constant current transformer T1 becomes smaller, so that the output voltage of the constant current transformer T1 matches the working voltage of the LED light bar, thereby reducing the constant current control. The temperature rise of the circuit solves the problem of large output voltage difference caused by the large voltage deviation of the same screen LED lamp in mass production.

Further, referring to the schematic circuit structure diagram of the overvoltage protection circuit 210 shown in FIG. 7 , the overvoltage protection circuit 210 includes: a first capacitor C3D14 , a first resistor R3B101 , a second resistor R3B102 , a third resistor R3B103 and a fourth resistor R3B104, wherein the first end of the first capacitor C3D14 is respectively connected to the output end of the auxiliary winding of the constant current transformer T1 (pin 5 of T1) and the first end of the first resistor C3D14, the second end of the first capacitor C3D14, all The second end of the first resistor C3D14 and the second end of the third resistor R3B103 are both grounded, the first end of the first resistor C3D14 is also connected to the first end of the second resistor R3B102, and the second end of the second resistor R3B102 is connected to the ground. The terminals are respectively connected to the first terminals of the third resistor R3B103 and the fourth resistor R3B104, and the second terminal of the fourth resistor R3B104 is connected to the second terminal of the PFC control and management constant current circuit U13. The overvoltage protection circuit 210 is used to protect the overcurrent and overvoltage output of the LED backlight. The working principle is as follows: the current limiting resistor R28 is used as the current limiting resistor of the second optocoupler U2, and the current sampling resistor 13 resistor R138 after sampling Connect to pin 7 of PFC control and management constant current circuit IC U13. When the output power is too large, the voltage sampled by the thirteenth resistor R138 will be greater than the internal reference voltage of pin 7 of PFC control and management constant current circuit IC U13, so that PFC control The management constant current circuit IC U13 stops working due to overload protection. Sampling resistors The second resistor R3B102 and the third resistor R3B103 sample the voltage VCC2 output by the auxiliary winding of the constant current transformer T1. When the voltage output by the constant voltage transformer T1 is too high, the output voltage of the auxiliary winding on the primary side of the constant voltage transformer T1 is the same. The voltage of VCC2 is detected by the second resistor R3B102 and the third resistor R3B103 of the PFC control and management constant current circuit IC U13, so that the output voltage of the auxiliary winding of the constant voltage transformer T1 is limited to a safe range. Therefore, it is avoided that the voltage output by the secondary winding of the constant voltage transformer T1 is too large to damage the LED light bar.

Further, under the control of the single-stage PFC control PFC control and management constant voltage circuit IC U14, the constant voltage switch tube Q17 further controls the constant voltage transformer T2, rectified by the sixth diode D30, and filtered by the fourth capacitor CE10 to output a stable voltage. constant voltage source. Referring to the schematic diagram of the circuit structure of the constant voltage control loop 130 shown in FIG. 8 , the constant voltage control loop 130 controls the third light through the first adjustment tube U3D1 through the sampling resistors twenty-fourth resistor R9D4 and twenty-fifth resistor R9D3 Coupling the current of pins 1-2 of U1D1, and then control the voltage of pin 4 of the PFC control and management constant voltage circuit U14, and then make the PFC control and manage the constant voltage circuit U14 to control the switching frequency or duty cycle of the constant voltage switch Q17, so that the output The voltage is constant. When the requirement for ripple is high, a DC-DC voltage regulator module can be added to the output end of the constant voltage transformer T2 to make the output voltage ripple smaller.

Further, the single-stage PFC management constant current circuit IC U13 and the single-stage PFC management constant voltage circuit IC U14 can use the JP0010 digital chip of JPX, and set the function of each pin through software, and can automatically control the power switch during standby light load. The frequency is switched to the working mode of skip cycle, which improves the standby light-load efficiency, saves the cost without the need for a standby transformer, and turns off the constant current transformer T1 during standby, reducing the standby power consumption.

This embodiment provides a switching power supply, on the basis of the above-mentioned first embodiment, by adding a high-voltage pre-start circuit, when the TV is turned off from power-off to power-on standby, it is preferable to use the high-voltage pre-start circuit to control and manage the constant voltage circuit for the PFC. When the PFC control and management constant voltage circuit starts to work, the high-voltage pre-start circuit is turned off, and the voltage at the output terminal of the auxiliary winding of the constant voltage transformer is changed to supply power to the VCC terminal of the PFC control and management constant voltage circuit. The PFC control and management constant voltage circuit provides a stable power supply voltage, and the operating frequency can be adjusted according to the size of the load to reduce standby power consumption. In order to provide a pre-start voltage for the constant current circuit of the PFC control and management when the power is turned on, the stability of the system is improved; by adding an overvoltage protection circuit, it is realized to ensure that the output voltage of the constant current transformer will not be too large, and avoid the constant current transformer. The output voltage is too large to damage the LED strip.

From the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be realized by software and necessary general-purpose hardware, and of course can also be realized by hardware, but in many cases the former is a better embodiment . Based on such understanding, the technical solutions of the present invention can be embodied in the form of software products in essence or the parts that make contributions to the prior art, and the computer software products can be stored in a computer-readable storage medium, such as a floppy disk of a computer , read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), flash memory (FLASH), hard disk or CD, etc., including several instructions to make a computer device (which can be a personal computer, storage medium, or network device, etc.) to execute the embodiments of the present invention.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (10)

1. A switching power supply, characterized in that the power supply comprises: a PFC control and management constant voltage module, a PFC control and management constant current module and a linear constant voltage module; Among them, the input end of the PFC control and management constant voltage module is connected to the power supply, the first output end is connected to the host chip, and the second output end is connected to the linear constant voltage module, which is used to improve the power factor of the constant voltage output and output a constant voltage to the supplying power to the host chip, while providing a pre-start voltage for the linear constant voltage module; The input end of the PFC control and management constant current module is connected to the output end of the linear constant voltage module, the first output end is connected to the constant current load, and the second output end is connected to the linear constant voltage module for improving the constant current output power factor and output a constant voltage to supply power to the constant current load, and at the same time provide a relay voltage for the linear constant voltage module; The first input end of the linear constant voltage module is connected to the second output end of the PFC control and management constant voltage module, the second input end is connected to the second output end of the PFC control and management constant current module, and the output end is connected to the second output end of the PFC control and management constant current module. The input terminals of the PFC control and management constant current module are connected to each other, and are used for the PFC control management constant current through the voltage of the first input terminal and the voltage of the second input terminal in turn when the system is turned off to standby and then turned on with a light load. The power supply terminal of the current module performs relay power supply, so that the constant current load can be started normally. 2. The switching power supply according to claim 1, wherein the PFC control and management constant voltage module comprises: a PFC control and management constant voltage circuit, a constant voltage switch tube, a constant voltage transformer and a constant voltage control loop; Among them, the first end of the PFC control and management constant voltage circuit is connected to the power supply, the sixth end is connected to the output end of the auxiliary winding of the constant voltage transformer, and the seventh end is connected to the control end of the main winding of the constant voltage transformer through the constant voltage switch tube, It is used to control the turn-on and turn-off of the constant voltage switch tube according to the zero-crossing detection signal provided by the output end of the auxiliary winding of the constant voltage transformer, so as to improve the power factor of the constant voltage output, the PFC controls and manages the fourth end of the constant voltage circuit Connected to the output end of the constant voltage control loop, the PFC control and management constant voltage circuit is also used to control the turn-on and turn-off of the constant voltage switch tube according to the signal at the output end of the constant voltage control loop, so as to make the constant voltage switch on and off. Transformer output constant voltage; The input end of the main winding of the constant voltage transformer is connected to the power supply, and the output end is connected to the core of the host, for providing constant voltage to the host chip under the control of the PFC control and management constant voltage circuit; The input end of the constant voltage control loop is connected to the output end of the main winding of the constant voltage transformer, for sampling the constant voltage output by the main winding of the constant voltage transformer, and sending the sampled voltage to the PFC control The fourth end of the management constant voltage circuit, so that the PFC control management constant voltage circuit controls the on and off of the constant voltage switch tube according to the sampled voltage, so that the constant voltage transformer outputs a constant voltage. 3. The switching power supply according to claim 2, wherein the PFC control and management constant current module comprises: a PFC control and management constant current circuit, a constant current switch tube, a constant current transformer and an overvoltage adjustment circuit, the linear The constant voltage module includes a linear constant voltage circuit; The power supply terminal of the PFC control and management constant current circuit is connected to the output terminal of the linear constant voltage circuit, the sixth terminal is connected to the output terminal of the auxiliary winding of the constant current transformer, and the ninth terminal is connected to the constant current through the constant current switch tube. The control terminal of the main winding of the transformer is connected to control the on and off of the constant current switch tube according to the zero-crossing detection signal provided by the output terminal of the auxiliary winding of the constant current transformer, so as to improve the power factor of the constant current output. The PFC control The fourth terminal of the management constant current circuit is connected to the output terminal of the overvoltage adjustment circuit, and the PFC control management constant current circuit is also used to control the conduction of the constant current switch tube according to the output terminal signal of the overvoltage adjustment circuit and off, so that the constant current transformer outputs a constant voltage; The input end of the main winding of the constant current transformer is connected to the power supply, and the output end is connected to the constant current load, for providing a constant voltage to the constant current load under the control of the PFC control and management constant current circuit; The input terminal of the overvoltage adjustment circuit is connected to the output terminal of the constant current load, and is used for sampling the output terminal voltage of the constant current load, and sending the sampled voltage to the first part of the PFC control and management constant current circuit. Four terminals, so that the PFC control and management constant current circuit controls the on and off of the constant current switch tube according to the sampled voltage, so that the constant current transformer outputs a constant voltage. 4 . The switching power supply according to claim 3 , wherein the first input end of the linear constant voltage circuit is connected to the output end of the auxiliary winding of the constant voltage transformer, and the second input end is connected to the constant current transformer. 5 . The output end of the auxiliary winding is connected to the output end, the control end is connected to the enable signal, and the output end is connected to the power end of the PFC control and management constant current circuit. The voltage of the first input terminal and the voltage of the second input terminal provide relay power supply for the power supply terminal of the PFC control and management constant current circuit, so that the constant current load can be started normally. 5 . The switching power supply according to claim 3 , further comprising: a high-voltage pre-start circuit, an input end of the high-voltage pre-start circuit is connected to an AC power supply, and an output end is connected to the PFC control and management constant voltage circuit. 6 . The first end of the PFC control and management constant voltage circuit is connected to provide power for the PFC control and management constant voltage circuit in the process from shutdown to standby of the system, so that the PFC control and management constant voltage circuit starts and starts to work. 6 . The switching power supply according to claim 5 , wherein the power supply end of the PFC control and management constant voltage circuit is connected to the output end of the auxiliary winding of the constant voltage transformer, and when the PFC control and management constant voltage circuit starts. 7 . Then, the output end of the auxiliary winding of the constant voltage transformer provides power for it, and controls the high-voltage pre-start circuit to close. 7. The switching power supply according to claim 5, wherein the high-voltage pre-start circuit comprises: a fourth diode, a fifth diode, a ninth resistor, a tenth resistor, and a first control tube, wherein , the fourth diode and the fifth diode are connected in parallel, the anode is connected to the power supply, the cathode is connected to the first end of the ninth resistor and the first end of the tenth resistor respectively, the ninth resistor is connected The second end of the first control tube is connected to the second end of the first control tube, the second end of the tenth resistor is connected to the first end of the first control tube and the eleventh end of the PFC control and management constant voltage circuit The third end of the first control tube is connected to the first end of the PFC control and management constant voltage circuit. 8 . The switching power supply according to claim 5 , further comprising: an electromagnetic filter circuit and a rectifier circuit, wherein an input end of the electromagnetic filter circuit is connected to an AC power supply, and an output end is respectively connected to the high-voltage preheater. The input end of the starting circuit is connected to the input end of the rectifier circuit, and the output end of the rectifier circuit is respectively connected to the input end of the main winding of the constant voltage transformer and the input end of the main winding of the constant current transformer. 9 . The switching power supply according to claim 3 , further comprising: an overvoltage protection circuit, the input end of the overvoltage protection circuit is connected to the output end of the auxiliary winding of the constant current transformer, and the output end is connected to the The second end of the PFC control and management constant current circuit is connected to the second end, and is used to make the PFC control and management constant current circuit control the conduction of the constant current switch tube when the voltage output by the constant current transformer exceeds the set value. And turn off, so that the voltage output by the constant current transformer drops to the set range. 10. A television, characterized by comprising the switching power supply according to any one of claims 1-9.

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