CN109274910B

CN109274910B - Switching power supply and television

Info

Publication number: CN109274910B
Application number: CN201811317165.6A
Authority: CN
Inventors: 陈建忠; 杨寄桃; 沈思宽
Original assignee: Shenzhen Skyworth RGB Electronics Co Ltd
Current assignee: Shenzhen Skyworth RGB Electronics Co Ltd
Priority date: 2018-11-07
Filing date: 2018-11-07
Publication date: 2020-11-17
Anticipated expiration: 2038-11-07
Also published as: CN109274910A; WO2020094097A1

Abstract

The embodiment of the invention discloses a switching power supply and a television, wherein the switching power supply comprises: the PFC control management constant-voltage module, the PFC control management constant-current module and the linear constant-voltage module; the PFC control management constant voltage module is used for improving a power factor of constant voltage output and outputting constant voltage to supply power to the host chip; the PFC control management constant current module is used for improving the power factor of constant current output and outputting constant voltage to supply power to the constant current load; the linear constant voltage module is used for sequentially passing the voltage of the first input end and the voltage of the second input end to carry out relay power supply on the power supply end of the PFC control management constant current module in the process from standby to startup light load of the system, so that the constant current load is normally started. The situation that the LED backlight lamp cannot be normally started due to the fact that the power supply capacity of the power end of the PFC control and management constant current circuit is insufficient can be avoided through the switching power supply, and the stability of the system is improved.

Description

Switching power supply and television

Technical Field

The embodiment of the invention relates to the technical field of power supply control, in particular to a switching power supply and a television.

Background

With the rapid development of LED (Light Emitting Diode) lcd tvs, LED lcd tvs have become popular in every household.

The existing LED liquid crystal televisions all adopt a design mode of a power panel and a constant current panel, wherein the power panel is responsible for providing proper input voltage for the constant current panel and a television main board, the constant current panel is responsible for providing constant current for an LED backlight module, and the power panel and the constant current panel are collectively called as a switching power supply. When the whole television works, the switching power supply realizes constant voltage and constant current output, and the constant current requirement of the LED backlight lamp and the constant voltage requirement of a television mainboard (core) are met. However, the existing power supply design scheme has the defects of low power supply conversion efficiency, high cost, incapability of normally starting the LED backlight when the machine core is in light load and incapability of protecting the LED backlight after the LED backlight is abnormally overvoltage.

Disclosure of Invention

The embodiment of the invention provides a switching power supply and a television, when a system is in a process from standby to power-on and light-load, the LED backlight can be normally turned on through the switching power supply, the situation that the LED backlight cannot be normally turned on due to the insufficient power supply capacity of a power supply end of a PFC control and management constant current circuit is avoided, and the stability of the system is improved.

In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:

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

the PFC control management constant voltage module comprises a PFC control management constant voltage module, a linear constant voltage module and a host chip, wherein the input end of the PFC control management constant voltage module is connected with a power supply, the first output end of the PFC control management constant voltage module is connected with the host chip, the second output end of the PFC control management constant voltage module is connected with the linear constant voltage module, and the PFC control management constant voltage module is used for improving the power factor of constant voltage output, outputting constant voltage to supply;

the input end of the PFC control management constant current module is connected with the output end of the linear constant voltage module, the first output end of the PFC control management constant current module is connected with a constant current load, the second output end of the PFC control management constant current module is connected with the linear constant voltage module, and the PFC control management constant current module is used for improving the power factor of constant current output, outputting constant voltage to supply power to the constant current load and providing relay voltage for the linear constant voltage module;

the first input end of the linear constant voltage module is connected with the second output end of the PFC control management constant voltage module, the second input end of the linear constant voltage module is connected with the second output end of the PFC control management constant current module, the output end of the linear constant voltage module is connected with the input end of the PFC control management constant current module, and the linear constant voltage module is used for sequentially supplying power to the power supply end of the PFC control management constant current module through the voltage of the first input end and the voltage of the second input end in the process from shutdown to standby to startup light load so as to enable the constant current load to be started normally.

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

the PFC control management constant-voltage circuit is also used for controlling the on and off of the constant-voltage switching tube according to a signal at the output end of the constant-voltage control loop circuit so as to enable the constant-voltage transformer to output constant voltage;

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

the input end of the constant voltage control loop is connected with the output end of the constant voltage transformer main winding and used for sampling the constant voltage output by the constant voltage transformer main winding and sending the sampled voltage to the fourth end of the PFC control 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, and the constant voltage transformer outputs the constant voltage.

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

the PFC control management constant current circuit is also used for controlling the on and off of the constant current switch tube according to an output end signal of the overvoltage adjusting circuit so as to enable the constant current transformer to output constant voltage;

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

the input end of the overvoltage adjusting circuit is connected with the output end of the constant current load and used for sampling the voltage of the output end of the constant current load and sending the sampled voltage to the fourth end of the PFC control management constant current circuit, so that the PFC control management constant current circuit controls the on and off of the constant current switch tube according to the sampled voltage, and the constant current transformer outputs the constant voltage.

Further, the linear constant voltage module comprises a linear constant voltage circuit, a first input end of the linear constant voltage circuit is connected with an output end of the auxiliary winding of the constant voltage transformer, a second input end of the linear constant voltage circuit is connected with an output end of the auxiliary winding of the constant current transformer, a control end of the linear constant voltage circuit is connected with an enable signal, and an output end of the linear constant voltage circuit is connected with a power end of the PFC control management constant current circuit, so that the linear constant voltage circuit can be used for carrying out relay power supply on the power end of the PFC control management constant current circuit sequentially through the voltage of the first input end and the voltage of the second input end in the process from shutdown to standby to light startup load of the system, and the constant. Further, the switching power supply further includes: the high-voltage pre-starting circuit is connected with an alternating current power supply at the input end and connected with the first end of the PFC control and management constant-voltage circuit at the output end, and is used for providing power for the PFC control and management constant-voltage circuit in the process from shutdown to standby of a system so as to start the PFC control and management constant-voltage circuit and start working.

Furthermore, the power end of the PFC control management constant-voltage circuit is connected with the output end of the auxiliary winding of the constant-voltage transformer, and when the PFC control management constant-voltage circuit is started, the output end of the auxiliary winding of the constant-voltage transformer provides power for the PFC control management constant-voltage circuit, and the PFC control management constant-voltage circuit controls the high-voltage pre-starting circuit to be closed.

Further, the high voltage pre-start-up circuit comprises: the power supply 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 of the fourth diode is connected with a power supply, the cathode of the fourth diode is respectively connected with the first end of the ninth resistor and the first end of the tenth resistor, the second end of the ninth resistor is connected with the second end of the first control tube, the second end of the tenth resistor is connected with the first end of the first control tube and the tenth end of the PFC control management constant-voltage circuit, and the third end of the first control tube is connected with the first end of the PFC control management constant-voltage circuit.

Further, the switching power supply further includes: the input end of the electromagnetic filter circuit is connected with an alternating current power supply, the output end of the electromagnetic filter circuit is respectively connected with the input end of the high-voltage pre-starting circuit and the input end of the rectifying circuit, and the output end of the rectifying 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: and the input end of the overvoltage protection circuit is connected with the output end of the auxiliary winding of the constant current transformer, the output end of the overvoltage protection circuit is connected with the second end of the PFC control management constant current circuit, and the overvoltage protection circuit is used for enabling the PFC control management constant current circuit to reduce the voltage output by the constant current transformer to be within a set range by controlling the on and off of the constant current switching tube when the voltage output by the constant current transformer exceeds a set value.

Furthermore, a seventh end of the PFC control and management constant-current circuit is connected with the output end of the main winding of the constant-current transformer through a constant-current switching tube, and the seventh end of the PFC control and management constant-current circuit is grounded through a voltage sampling resistor.

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

Further, the linear constant voltage circuit includes: the circuit comprises 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 voltage stabilizing diode, a first triode, a second triode and a first optocoupler, wherein the anode of the first diode is connected with the output end of an auxiliary winding of a constant current transformer, the anode of the second diode is connected with the output end of an auxiliary winding of a constant voltage transformer, the cathode of the first diode, the cathode of the second diode, the fifth resistor, the first triode and the second capacitor are connected in series and then grounded, the base of the first triode is connected with the third end of the first optocoupler through the sixth resistor, the base of the first triode is grounded through the first voltage stabilizing triode, the cathode of the second diode is connected with the fourth end of the first optocoupler through the seventh resistor, the first end of the first optocoupler is connected with the output end of the constant-voltage transformer through the eighth resistor, the second end of the first optocoupler is grounded through the second triode, the base of the second triode is connected with an enabling signal provided by a host chip, the cathode of the third diode is connected with the base of the first triode, and the anode of the third diode is connected with the power end of the PFC control 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.

The switching power supply provided by the embodiment of the invention is characterized in that a first input end of a linear constant voltage circuit is connected with an output end of an auxiliary winding of a constant voltage transformer, a second input end of the linear constant voltage circuit is connected with an output end of the auxiliary winding of the constant current transformer, a control end of the linear constant voltage circuit is connected with an enable signal, and an output end of the linear constant voltage circuit is connected with a power end of a PFC control management constant current circuit, so that the power end of the PFC control management constant current circuit is subjected to relay power supply sequentially through the voltage of the first input end and the voltage of the second input end in the process from standby to light load starting of a system, the constant current load is normally started, the normal starting of an LED backlight lamp is realized, the condition that the LED backlight cannot be normally started due to the insufficient power supply capacity of the PFC control management constant current circuit cannot occur, the stability of the system is, the AC-DC conversion is directly carried out, the constant voltage source and the constant current source are respectively output, the power supply efficiency is improved, the system cost is reduced, and the constant current control and the constant voltage control are independent, so that the constant voltage source and the constant current source are not interfered with each other during dynamic loading, and the stability of the system is further improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the contents of the embodiments of the present invention and the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a switching power supply according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of another switching power supply according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a switching power supply according to a second embodiment of the present invention;

fig. 4 is a schematic circuit diagram of a switching power supply according to a second embodiment of the present invention;

fig. 5 is a schematic structural diagram of a linear constant voltage circuit according to a second embodiment of the present invention;

fig. 6 is a schematic circuit structure diagram of a constant current control loop according to a second embodiment of the present invention;

fig. 7 is a schematic structural diagram of an overvoltage protection circuit according to a second embodiment of the present invention;

fig. 8 is a schematic circuit diagram of a constant voltage control loop according to a second embodiment of the present invention.

Detailed Description

In order to make the technical problems solved, technical solutions adopted and technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

Fig. 1 is a schematic structural diagram of a switching power supply according to an embodiment 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 particularly suitable for the field of liquid crystal televisions, and is also suitable for related fields such as liquid crystal displays, projectors, medical instruments, military industrial equipment, and the like. The switching power supply provided by the embodiment can effectively improve the efficiency of a power supply system, realizes stable startup of a television, and has low cost and higher power factor. Referring specifically to fig. 1, the switching power supply includes: a PFC control and management constant voltage module 100, a PFC control and management constant current module 300 and a linear constant voltage module 500;

the PFC control and management constant voltage module 100 has an input terminal connected to a power supply, a first output terminal connected to a host chip, and a second output terminal connected to the linear constant voltage module 500, and is configured to increase a power factor of constant voltage output and output a constant voltage to supply power to the host chip, and simultaneously provide a pre-start voltage for the linear constant voltage module 500;

the input end of the PFC control 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, and is configured to improve a power factor of constant current output and output a constant voltage to supply power to the constant current load, and simultaneously provide a relay voltage for the linear constant voltage module 500;

the linear constant voltage module 500 has a first input end connected to the output end of the PFC control and management constant voltage module 100, a second input end connected to the output end of the PFC control and management constant current module 300, and an output end connected to the input end of the PFC control and management constant current module 300, and is configured to sequentially perform relay power supply on the power supply end of the PFC control and management constant current module 300 by the voltage at the first input end and the voltage at the second input end in the process from shutdown to standby to startup with light load, so as to normally start the constant current load.

For example, referring to the schematic structural diagram of another switching power supply shown in fig. 2, the PFC control management constant voltage module 100 includes: the PFC control management constant voltage circuit 110 comprises a PFC control management constant voltage circuit 110, a constant voltage switching tube Q17, a constant voltage transformer 120 and a constant voltage control loop 130, wherein the PFC control management constant voltage circuit 110 has a first end connected to a power supply, a fourth end connected to an output end of the constant voltage control loop 130, a sixth end connected to an output end of an auxiliary winding 121 of the constant voltage transformer 120, a seventh end connected to a control end of a main winding 122 of the constant voltage transformer 120 through a constant voltage switching tube Q17, for controlling the on and off of a constant voltage switching tube Q17 according to a zero-crossing detection signal provided by the output end of the auxiliary winding 121 of the constant voltage transformer 120 to improve a power factor of constant voltage output, the PFC control management constant voltage circuit 110 is further configured for controlling the on and off of a constant voltage switching tube Q17 according to a signal at the output end of the constant voltage control loop 130 to enable the constant; the input end of the main winding 122 of the constant voltage transformer 120 is connected with a power supply, and the output end is connected with the host machine core and used for providing a constant voltage VDD for the host machine chip under the control of the PFC control management constant voltage circuit 110; the input end of the constant voltage control loop 130 is connected to the output end of the primary winding of the constant voltage transformer 120, and is configured to sample the constant voltage VDD output by the primary winding of the constant voltage transformer 120, and send the sampled voltage to the fourth end 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 switching tube Q17 according to the sampled voltage, and the constant voltage transformer 120 outputs the constant voltage.

Illustratively, the PFC control manager constant current module 300 includes: the PFC control management constant current circuit 140, the constant current switching tube Q12, the constant current transformer 150 and the overvoltage adjusting circuit 160; the PFC control and management constant current circuit 140 has a power supply end connected to an output end of the linear constant voltage circuit 170, a fourth end connected to an output end of the overvoltage adjustment circuit 160, a sixth end connected to an output end of the auxiliary winding 151 of the constant current transformer, and a ninth end connected to a control end of the main winding 152 of the constant current transformer, and is configured to control on and off of the constant current switch Q12 according to a zero-crossing detection signal provided by the output end of the auxiliary winding 151 of the constant current transformer, so as to improve a power factor of constant current output, and the PFC control and management constant current circuit 140 is further configured to control on and off of the constant current switch Q12 according to an output end signal of the overvoltage adjustment circuit 160, so that the constant current transformer 150 outputs a constant voltage; the input end of the main winding 152 of the constant current transformer is connected with a power supply, and the output end is connected with a constant current load, and is used for providing 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 adjusting circuit 160 is connected to the output end of the constant current load, and is configured to sample the voltage at the output end of the constant current load and send the sampled voltage to the fourth end of the PFC control and management constant current circuit 140, so that the PFC control and management constant current circuit 140 controls the on and off of the constant current switching tube Q12 according to the sampled voltage, and the constant current transformer 150 outputs a constant voltage;

illustratively, the linear constant voltage module 500 includes a linear constant voltage circuit 170, a first input VCC1 of the linear constant voltage circuit 170 is connected to an output terminal of the auxiliary winding 121 of the constant voltage transformer, a second input VCC2 is connected to an output terminal of the auxiliary winding 151 of the constant current transformer, a control terminal is connected to the enable signal BL-EN, and an output terminal is connected to a power supply terminal of the PFC control management constant current circuit 140, and is configured to perform relay power supply for the power supply terminal of the PFC control management constant current circuit 140 through a voltage VCC1 at the first input terminal and a voltage VCC2 at the second input terminal in the process from shutdown to standby to startup light load, so that the constant current load is normally started.

In the switching power supply provided by this embodiment, 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, the second input end is connected to the output end of the auxiliary winding of the constant current transformer, 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, so that the power end of the PFC control and management constant current circuit is sequentially powered by the voltage of the first input end and the voltage of the second input end in the process from standby to light power on of the system, so as to normally start the constant current load, thereby realizing normal start of the LED backlight, avoiding the situation that the LED backlight cannot be normally started due to insufficient power supply capability of the power end of the PFC control and management constant current circuit in the process from standby to light power on of the system, and improving the stability of the system, the transformer is controlled through the single-stage PFC, AC-DC conversion is directly carried out, the constant voltage source and the constant current source are respectively output, power supply efficiency is improved, system cost is reduced, and constant current control and constant voltage control are independent of each other, so that the constant voltage source and the constant current source are not interfered with each other during dynamic loading, and system stability is further improved.

Example two

Fig. 3 is a schematic structural diagram of a switching power supply according to a second embodiment of the present invention. On the basis of the above embodiments, the present embodiment further optimizes the structure of the switching power supply, and by adding the high-voltage pre-start circuit, when the television is powered on for standby from power-off to power-on, the stable power supply voltage is provided for the PFC control management constant-voltage circuit, and the standby power consumption of the system can be effectively reduced; by adding the overvoltage protection circuit, the output voltage of the constant current transformer is ensured not to be too large, and the LED lamp strip is prevented from being damaged due to the fact that the output voltage of the constant current transformer is too large. Referring specifically to fig. 3, the switching power supply includes:

the power factor correction PFC control and management circuit comprises a constant voltage control and management circuit 110, a constant voltage transformer 120, a constant voltage control loop 130, a PFC control and management constant current circuit 140, a constant current transformer 150, an overvoltage adjusting circuit 160, a linear constant voltage circuit 170, a high-voltage pre-starting circuit 180, an electromagnetic filter circuit 190, a rectifying circuit 200 and an overvoltage protection circuit 210. For clarity of connection between circuits, see fig. 3 and 4 for the same time: the input end of the electromagnetic filter circuit 190 is connected with the alternating current power supply 1, the output end of the electromagnetic filter circuit is respectively connected with the input end of the high-voltage pre-starting circuit 180 and the input end of the rectifier circuit 200, and the output end of the rectifier circuit 200 is respectively connected with the input end of the constant-voltage transformer main winding 122 and the input end of the constant-current transformer main winding 152; the output end of the high-voltage pre-start circuit 180 is connected to the first end of the PFC control and management constant-voltage circuit 110, and is configured to provide power to the PFC control and management constant-voltage circuit 110 in a process from shutdown to standby, so that the PFC control and management constant-voltage circuit 110 starts and starts to operate, the power end of the PFC control and management constant-voltage circuit 110 is connected to the output end of the auxiliary winding 121 of the constant-voltage transformer, and when the PFC control and management constant-voltage circuit 110 is started, the output end of the auxiliary winding 121 of the constant-voltage transformer provides power to the PFC control and management constant-voltage circuit 110, and controls the high-voltage pre-start circuit 180 to. 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, so that when the voltage output by the constant current transformer 150 exceeds a set value, the PFC control and management constant current circuit 140 controls the on and off of the constant current switch Q12 to reduce the voltage output by the constant current transformer 150 to a set range. The seventh end of the PFC control and management constant current circuit 140 is connected to the output end of the constant current transformer main winding 152 through a constant current switching tube Q12, and the seventh end of the PFC control and management constant current circuit 140 is also grounded through a voltage sampling resistor R138. The fourth end of the PFC control management constant voltage circuit 110 is connected to the output end of the constant voltage control loop 130, the sixth end is connected to the output end of the auxiliary winding 121 of the constant voltage transformer 120 (in fig. 4, a line between the sixth end of the PFC control management constant voltage circuit 110 and the output end of the auxiliary winding 121 of the constant voltage transformer 120 is represented as ZCD1 in fig. 3), the seventh end is connected to the output end of the main winding 122 of the constant voltage transformer 120 through a constant voltage switching tube Q17, and is configured to control the constant voltage switching tube Q17Q17 to be turned on and off according to a zero-crossing detection signal provided by the output end of the auxiliary winding 121 of the constant voltage transformer 120, so as to improve the power factor of the constant voltage output, and the PFC control management constant voltage circuit 110 is further configured to control the constant voltage switching tube Q17Q17 to be turned on and off according to a signal at the output end of the; the output end of the constant voltage transformer 120 is connected with the host machine core and is used for providing constant voltage for the host machine chip under the control of the PFC control management constant voltage circuit 110; the input end of the constant voltage control loop 130 is connected to the output end of the constant voltage transformer 120, and is configured to sample the constant voltage VDD output by the constant voltage transformer 120, and send the sampled voltage to the fourth end 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 switching tube Q17Q17 according to the sampled voltage, so that the constant voltage transformer outputs the constant voltage; the PFC control and management constant current circuit 140 has a power supply terminal connected to the output terminal VCC-LED of the linear constant voltage circuit 170, a fourth terminal connected to the output terminal of the overvoltage adjustment circuit 160, a sixth terminal connected to the output terminal of the constant current transformer auxiliary winding 151 (in fig. 4, a 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), a ninth terminal connected to the output terminal of the constant current transformer main winding 152 through a constant current switching tube Q12, for controlling the on and off of the constant current switching tube Q12 according to the zero-crossing detection signal provided by the output terminal of the auxiliary winding 151 of the constant current transformer, the PFC control and management constant current circuit 140 is further configured to control the on/off of the constant current switching tube Q12 according to the output end signal of the overvoltage adjusting circuit 160, so that the constant current transformer 150 outputs a constant voltage; the output end of the constant current transformer is connected with the constant current load 2 and is used for providing 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 adjusting circuit 160 is connected to the output end of the constant current load 2, and is configured to sample the voltage at the output end of the constant current load 2, and send the sampled voltage to the fourth end of the PFC control and management constant current circuit 140, so that the PFC control and management constant current circuit 140 controls the on and off of the constant current switching tube Q12 according to the sampled voltage, and the constant current transformer 150 outputs a constant voltage; the first input end VCC1 of the linear constant voltage circuit 170 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 power supply end of the PFC control and management constant current circuit 140, so that the system performs relay power supply for the power supply end of the PFC control and management constant current circuit 140 sequentially through the voltage VCC1 of the first input end and the voltage VCC2 of the second input end in the process from standby to startup light load, so that the constant current load is normally started.

The operation principle of the switching power supply will be described with reference to fig. 3: the ac power supply 1 passes through the electromagnetic filter circuit 190 and the rectifier circuit 200 and then respectively delivers the constant voltage transformer 120 and the constant current transformer 150, and the constant voltage transformer 120 and the constant current transformer 150 further control the constant voltage switching tube and the constant current switching tube under the control and management of their respective single-stage PFCs (i.e., the PFC control and management constant voltage circuit 110 and the PFC control and management constant current circuit 140), so as to output stable constant voltage source and constant current source. The design framework does not need a high-voltage electrolytic capacitor, and the area and the cost of the PCB are saved. When the AC 1 is electrified, and the television system is in standby state from shutdown, the electromagnetic filter circuit 190 provides a starting voltage VCC1 for the PFC control management constant voltage circuit 110 through the high-voltage pre-starting circuit 180, after the PFC control 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 management constant voltage circuit 110, the high-voltage pre-starting circuit 180 is closed, the working frequency can be adjusted according to the load size condition, the standby power consumption is reduced, and the output of the constant voltage transformer 120 provides a stable working voltage for the movement after DC-DC voltage stabilization. Meanwhile, 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, so as to provide a pre-start voltage for the subsequent PFC control and management constant current circuit 140.

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

Further, when the television system is switched from standby to power-on under light load, the LED backlight turn-on signal BL-EN turns on the linear constant voltage circuit 170 through the first optocoupler, the output terminal of the linear constant voltage circuit 170 is connected to the power supply terminal of the PFC control management constant current circuit 140 to provide a pre-start working voltage for the PFC control management constant current circuit 140, and after the PFC control management constant current circuit 140 starts working, the constant current transformer 150 outputs a voltage VCC2, and at the same time, the constant current transformer 150 outputs a voltage VCC2 which is connected to the second input terminal of the linear constant voltage circuit 170, and the PFC control management constant current circuit 140 is supplied with power through the constant voltage VCC2, so that when the main board core starts working, because the voltage VCC1 is low, the voltage VCC2 generated by the constant current transformer 150 can be controlled by the PFC control management constant current circuit 140 to provide a sufficient and stable working voltage for the PFC control constant current circuit 140, and when the main board core starts working, the starting of the system is unstable due to insufficient starting voltage.

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

Further as described above, the output of the constant current transformer 150 is output to the LED1 and the LED2 through the rectifying filter 1, and outputs a constant current under the control of the constant current circuit 1 and the constant current circuit 2, respectively.

Further as described above, the output of the constant current transformer 150 is rectified and filtered 2 to output a constant voltage as a reference voltage, a constant current auxiliary IC voltage, and an opto-coupler supply voltage via the DC-DC linear constant voltage 2.

Further as described above, the LED1 and the LED2 are respectively connected to the second optocoupler through the overvoltage adjusting circuit 160, and then control and manage the constant current circuit 140.

Further, as the output constant voltage source and the output constant current source are respectively controlled, the constant voltage output and the constant current output are not interfered with each other when the movement is loaded dynamically, the constant voltage is not influenced by the cross of the deviation of the LED lamp, and the stability of the system is improved.

When the low level of the LED backlight turn-on signal BL-EN is turned off, the LED backlight turn-on signal BL-EN 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 management constant current circuit 140 stops working, no current passes through the LED, and the LED is turned off, so that the standby power consumption is low. When the LED backlight turn-on signal BL-EN is turned on, the LED backlight turn-on signal BL-EN is fed back to the linear constant voltage circuit 170 through the first optocoupler, so that the output voltage thereof is turned on, the PFC control and management constant current circuit 140 starts to operate, a current passes through the LED, and the constant current in the LED is controlled to be constant through the constant current circuit 1 and the constant current circuit 2. The brightness degree of the LED is adjusted through a PWM signal transmitted by the main board, when the PWM duty ratio is large, the LED lamp is bright, and when the PWM duty ratio is small, the LED lamp is dark.

As described above, when the voltage of the LED light bar is smaller than the output voltage of the constant current transformer 150, the overvoltage adjusting circuit 160-the second optocoupler controls the single-stage PFC to control and manage the constant current circuit 140, adjust the operating frequency or duty ratio of the PFC, and further control the constant current switching tube, so that the voltage output by the flyback transformer is reduced, the voltage output by the constant current transformer 150 is matched with the operating voltage of the LED light bar, and the temperature rise of the overvoltage adjusting circuit 160 can be reduced. The problem of output voltage difference that the voltage deviation of the same screen body LED lamp is great in volume production is solved.

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 a stable constant voltage source is output through DC-DC voltage stabilization after passing through the rectification filter 2. The constant voltage control loop 130 samples the voltage output by the constant voltage transformer 120 after passing through the rectification filter 2, controls the third optocoupler through the voltage stabilization sampling circuit, and further controls the PFC control management constant voltage circuit 110 to make the voltage output by the constant voltage transformer 120 constant. When the requirement on the ripple is low, a DC-DC voltage stabilizing module can be omitted from the output, so that the cost of the power supply is reduced.

Referring to the schematic circuit structure of the switching power supply shown in fig. 4, an AC power supply AC is subjected to EMI filtering and rectification filtering and then respectively transmitted to a constant current transformer T1 and a constant voltage transformer T2, without large electrolytic capacitor filtering, and a constant voltage switching tube Q17 and a constant current control switching tube Q12 further control the constant voltage transformer T2 and the constant current transformer T1 under the control of respective single-stage PFC control chips U14 and U13, so that the secondary output of the transformer supplies power to an LED backlight and a main board after rectification filtering. The switch module is controlled by adopting the single-stage PFC, and the switch transformer is further controlled, so that the design framework does not need a high-voltage electrolytic capacitor, higher power factor output is realized, and the area and the cost of the PCB are saved.

As further shown in 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 tube Q21, wherein the fourth diode D36 and the fifth diode D37 are connected in parallel, an anode is connected to the power supply, a cathode is connected to the first end of the ninth resistor R164 and the first end of the tenth resistor R165, the second end of the ninth resistor R164 is connected to the second end of the first control tube Q21, the second end of the tenth resistor R165 is connected to the first end of the first control tube Q21 and the tenth end of the PFC control management constant voltage circuit U14, and the third end of the first control tube Q21 is connected to the first end of the PFC control management constant voltage circuit U14. When the television system is powered on and standby from power off, after the AC is powered on, the AC passes through the EMI filter circuit, the fourth diode D36, the fifth diode D37, the ninth resistor R164, the first control tube Q21 and the pin 1 of the PFC control management constant voltage circuit IC U14 in the high voltage pre-start circuit, the tenth resistor R165 raises the G-pole level of the first control tube Q21, the first control tube Q21 is turned on, and further the pin 1 of the PFC control management constant voltage circuit IC U14 supplies voltage to the capacitor C88 connected to the pin 10 VCC thereof, when the voltage of the capacitor C88 reaches the start voltage of the PFC control management module U14, the PFC control management module U14 starts and starts working, at this time, the pin 9 of the PFC control management module U14 outputs the PWM signal control switch tube Q17 to control the oscillation of the transformer T38, the pin 5 output of the transformer T2 (i.e., the auxiliary winding output terminal 121) is rectified by the fifth diode VCC and the capacitor C86, the power is supplied to the pin 10 of the PFC control management module U14, then the pin 11 of the PFC control management module U14 outputs low level, the first control tube Q21 is closed, so that the PFC control management module IC U14 is supplied with power by the low-voltage VCC1 when the television system is in standby, the working frequency can be adjusted according to the load size, and the standby power consumption of the system is reduced.

As further described above, the voltage VCC1 output by the pin 5 of the constant voltage transformer T2 provides a stable operating 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, filtered by the fourth capacitor CE10, and then regulated by DC-DC to provide a stable operating voltage for the motherboard core. Referring also to the schematic circuit configuration 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, a sixth resistor R168, a seventh resistor R160, an eighth resistor R159, a second capacitor C1D62, a first zener diode ZD403, a first transistor QP9, a second transistor QP7 and a first optocoupler U15, wherein an anode of the first diode D407 is connected to an output terminal of the auxiliary winding 151 of the constant current transformer, an anode of the second diode D406 is connected to an output terminal of the auxiliary winding 121 of the constant current transformer, a cathode of the first diode D407, a cathode of the second diode D406, a fifth resistor R162, a first transistor QP9 and a second capacitor C1D62 are grounded after being connected in series, a base of the first transistor QP9 is connected to a third terminal of the first U15 through the sixth resistor R168, a base of the first transistor QP9 is further grounded through the first transistor ZD403, a cathode of the second diode D406D is further connected to a first four terminal 15 of the first optocoupler U15 through the seventh resistor R160, the first end of the first optocoupler U15 is connected with the output end of the constant voltage transformer 120 through an eighth resistor R159, the second end of the first optocoupler U15 is grounded through a second triode QP7, the base of the second triode QP7 is connected with an enable signal BL-EN provided by a host chip, the cathode of the third diode D405 is connected with the base of the first triode QP9, and the anode of the third diode D405 is connected with the power supply end of the PFC control management constant current circuit 140. The voltage VCC1 output by the pin 5 of the constant voltage transformer T2 is connected to the first input terminal of the constant voltage circuit 170, i.e., the output voltage VCC-LED is generated through the second diode D406, the fifth resistor R162, the first triode QP9 and the second capacitor C1D62, so as to provide a pre-start voltage for the PFC control management constant current circuit U13 after the subsequent LED backlight turn-on signal BL-EN is turned on. A voltage VCC2 output by a pin 5 of an auxiliary winding of the constant current transformer T1 is connected to a second input terminal of the linear constant voltage circuit 170, so as to provide a 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: when the television system is switched from standby to power-on and lightly loaded, the LED backlight turn-on signal BL-EN is at high level, the second triode QP7 is turned on, the 1-2 pin of the first optocoupler U15 is turned on, and then the 3-4 pin is turned on, the linear constant voltage circuit is turned on through the first triode QP9 and outputs the first voltage VCC _ LED (i.e. VCC1), the output of the linear constant voltage circuit is connected to the 10 pin of the PFC control management constant current circuit IC U13 to provide a pre-start working voltage for the same, after the PFC control management constant current circuit IC U13 starts working, the output of the auxiliary winding 5 pin of the constant current transformer T1 is filtered through the diode D1D3 and the first capacitor C3D 7 to generate the voltage VCC2, the voltage VCC2 is filtered through the first diode D407, the fifth resistor R162, the first triode QP9 and the second capacitor C1D 3 to generate the second output voltage VCC _ LED (i.e. VCC2), and the second output voltage VCC _ LED is used for providing power for the constant current control circuit IC 13, therefore, the problem that the LED backlight cannot be lightened due to the fact that the load is light, the voltage VCC1 is low in energy and the voltage is low when the mainboard core starts to work is solved. The constant-current switching tube Q12 is controlled by a PFC control and management constant-current circuit IC U13, so that the constant-current transformer T1 is controlled to generate a voltage VCC2, and the voltage VCC2 provides sufficient and stable working voltage for the continuous force of the PFC control and management constant-current circuit IC U13 through a linear constant-voltage circuit.

Further, the voltage output by the pin 5 of the constant voltage transformer T2 passes through the pins R148 and R147 of the ZCD1 circuit, is sampled and then connected to the pin 6 of the PFC control management constant voltage circuit IC 14, and provides a zero-crossing detection signal for the PFC control management constant voltage circuit U14, so as to improve the PFC power factor of the constant voltage output. The voltage output by the pin 5 of the constant current transformer T1 passes through the ZCD2 circuit, namely the resistor R149 and the resistor R150, is sampled and then is connected with the pin 6 of the PFC control management constant current circuit IC U13, and a zero-crossing detection signal is provided for the PFC control management constant current circuit, so that the power factor of the PFC output by constant current is improved.

Further, the output voltage of the constant current transformer T1 is rectified by a diode D20 and filtered by a capacitor CE1, and then is output to an LED1 … …, an LED1n and an LED2 … …, an LED2n, and constant currents are output under the control of the constant current circuit 1 and the constant current circuit 2, respectively. The specific circuit structures of the constant current circuit 1 and the constant current circuit 2 can be seen from the schematic circuit structure shown in fig. 6, meanwhile, the output voltage of pin 10 of the constant current transformer T1 is rectified by the fifth diode D408 in fig. 6, filtered by the fifth capacitor C4B9, and then passes through the DC-DC linear constant voltage circuit composed of the seventeenth resistor R428, the third triode Q0B20, and the sixth capacitor C414, and then outputs the constant voltage SVCC, which is used as the reference voltage of the constant current circuit, the voltage of the constant current auxiliary IC, and the power supply voltage of the second optocoupler U2.

Further, referring to a specific circuit structure schematic diagram of the overvoltage adjusting circuit 160 in fig. 6, the LED1 passes through a fourth diode D22, an eighteenth resistor R65, a third capacitor CE6 and a nineteenth resistor R64 in the overvoltage adjusting circuit, and the LED2 passes through a diode D35, a resistor R158, a capacitor CE11 and a resistor R157 and then is connected to a second optocoupler U2 through a second adjusting tube U16, and then the PFC is controlled to control and manage the constant current circuit IC U13, so that the output voltage of the constant current transformer T1 is finally matched with the voltage required by the LED light bar.

Furthermore, because the output constant voltage source and the output constant current source are respectively and independently controlled, the output of the constant voltage and the output of the constant current are not interfered with each other when the mainboard movement is in dynamic load, the constant voltage source is not influenced by the cross of the deviation of the LED lamp, and the stability of the system is improved.

Further, referring to the schematic circuit structure shown in fig. 4 and 5, when the television system is turned on from standby, and when the turn-on signal, i.e., the LED backlight turn-on signal BL-EN, becomes high level, the second transistor QP7 is turned on, the first transistor QP9 is turned on by the first optocoupler U15, and the voltage VCC1 firstly 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 management constant current circuit U13, so that the PFC control management constant current circuit U13 starts to operate, and then current passes through the LED, and the LED is in a bright state. In addition, the brightness control signal BL-ADJ that LED's bright and dark degree was transmitted through the mainboard controls the on-time of fourth triode Q8, and then adjusts the luminance of LED lamp, and when the PWM duty cycle is big, the LED lamp is brighter, and when the PWM duty cycle is little, the LED lamp is darker. When the LED backlight starting signal BL-EN is at a low level, the second triode QP7 is controlled to be cut off, the first optocoupler U15 is further controlled, the first triode QP9 is cut off through the first optocoupler U15, the output voltage VCC _ LED is cut off, the power supply voltage of the PFC control management constant current circuit U13 is cut off, the 10-pin VCC no-voltage of the PFC control management constant current circuit U13 is controlled, the PFC control management constant current circuit U13 stops working, the constant current flyback power supply stops working, and therefore standby power consumption is low.

Further, referring to the schematic circuit structure diagram of the constant current control loop shown in fig. 6, a constant current mode adopts a series constant current reference source for control, a constant current reference source is composed of a third adjusting tube U4, a fifth triode Q2 and a twentieth resistor R51, the third adjusting tube U4 is used as a reference voltage of a constant current to control the fifth triode Q2, so that voltages at two ends of the twentieth resistor R51 are constant, and further, a current flowing through the light bar is constant. When the output ripple voltage of the constant current transformer T1 is large, the fifth triode Q2 works in the amplification region, and the reference source controls the fifth triode Q2 to automatically adjust the C-E electrode voltage division, so that the current is more precise, and the current ripple is reduced. When the voltage of the light bar is small, because the output winding of the constant current transformer T1 is unchanged, the C-pole voltage of the fifth triode Q2 is increased, the second adjusting tube U16 is controlled to control the current flowing through the second optocoupler U2 through an overvoltage adjusting circuit composed of a nineteenth resistor R64, a third capacitor CE6, an eighteenth resistor R65 and a fourth diode D22, so that the PFC is controlled to control and manage the working frequency or duty ratio of the primary side of the constant current circuit ICU13, and further the voltage output by the output winding of the constant current transformer T1 is reduced, so that the voltage at two ends of the constant current source is reduced. The other constant current source composed of the sixth triode Q16, the seventh triode Q20 and the twenty-first resistor R154 is a current mirror body composed of the fifth triode Q2, the twentieth resistor R51 and the third adjusting tube U4, so that the constant current source composed of the sixth triode Q16, the seventh triode Q20 and the twenty-first resistor R154 is the same as the current of the current mirror body, and any same constant current source can be copied at the rear stage, so that the constant current output can be matched with the lamp strip of any channel. Furthermore, the constant current circuit can be expanded at will according to the number of channels of the light bars, so that the scheme can meet the requirement of matching the number of the channels of the backlight light bars at will, and the design of low cost and high power factor of a large-size television power supply is realized.

Further, referring to the schematic structure shown in fig. 4, after the AC power is turned on, the rectified and filtered voltage passes through the fourth diode D36, the fifth diode D37 and the ninth resistor R164, the first control tube Q21 pre-starts the pin 1 of the PFC control management constant voltage circuit IC U14, so that the VCC voltage of the pin U1410 of the PFC control management constant voltage circuit reaches the start voltage, the constant voltage transformer ICT2 starts oscillation operation, after stabilization, the pin 5 of the constant voltage transformer T2, i.e., the auxiliary winding output voltage, passes through the fifth diode D27, the capacitor C86 provides a stable working voltage for the PFC control management constant voltage circuit IC U14, then the pin 11 of the PFC control management constant voltage circuit IC U14 outputs a low level, and the first control tube Q21 is controlled to be turned off, so that the power supply of the PFC control management constant voltage circuit U14 is changed to the VCC1 output by the auxiliary winding of the transformer. Meanwhile, a pin 3 of the PFC control management constant-voltage circuit U14 samples an alternating-current voltage signal as a reference signal by detecting an alternating-current sampling circuit formed by a twenty-second resistor R166 and a twenty-third resistor R167, detects the current of a primary winding of the transformer by a current sampling resistor fifteenth resistor R148 and a sixteenth resistor R147, compares the current with the reference signal, and further controls the working frequency and the duty ratio of the constant-voltage switching tube Q17, and when the full-wave voltage is large, the working frequency is high, and the duty ratio is small; when the full-wave voltage is small, the working frequency is low, the duty ratio 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, the power factor is finally improved, and the AC-DC alternating current-DC conversion is realized.

Furthermore, the constant current source for supplying power to the LED backlight and the constant voltage source for supplying power to the main board of the movement are separately controlled, so that the working temperature rise of the constant current transformer T1 and the constant voltage transformer T2 and the working temperature rise of the constant current switch tube Q12 and the constant voltage switch tube Q17 are reduced, and the stability of independent control of the system is improved.

Further, when the voltage of the LED lamp strip is smaller than the voltage of the output winding of the constant current transformer T1, the second optocoupler U2 in the constant current control loop controls the single-stage PFC to manage the constant current circuit IC U13, the working frequency and the duty ratio of the PFC are adjusted to be reduced, the constant current switch tube Q12 is further controlled, the voltage output by the flyback constant current transformer T1 is reduced, the voltage output by the constant current transformer T1 is matched with the working voltage of the LED lamp strip, the temperature rise of the constant current control circuit can be further reduced, and the problem of large output voltage difference caused by large voltage deviation of the LED lamp with the same screen body in mass production is solved.

Further, referring to the schematic circuit structure of the overvoltage protection circuit 210 shown in fig. 7, the overvoltage protection circuit 210 includes: the current source circuit comprises a first capacitor C3D14, a first resistor R3B101, a second resistor R3B102, a third resistor R3B103 and a fourth resistor R3B104, wherein a first end of the first capacitor C3D14 is respectively connected with an output end (pin 5 of T1) of an auxiliary winding of the constant current transformer T1 and a first end of the first resistor C3D14, a second end of the first capacitor C3D14, a second end of the first resistor C3D14 and a second end of the third resistor R3B103 are all grounded, a first end of the first resistor C3D14 is further connected with a first end of the second resistor R3B102, a second end of the second resistor R3B102 is respectively connected with a first end of the third resistor R3B103 and a first end of the fourth resistor R3B104, and a second end of the fourth resistor R3B104 is connected with a second end of the PFC control management constant current circuit U13. The overvoltage protection circuit 210 is used for protecting the overcurrent and overvoltage output of the LED backlight, and the working principle specifically comprises: the current limiting resistor R28 is used as the current limiting resistor of the second optocoupler U2, the current sampling resistor thirteenth resistor R138 is connected to the 7 pins of the PFC control and management constant current circuit IC U13 after sampling, and when the output power is overlarge, the voltage sampled by the thirteenth resistor R138 is larger than the internal reference voltage of the 7 pins of the PFC control and management constant current circuit IC U13, so that the PFC control and management constant current circuit IC U13 is in overload protection and stops working. The sampling resistor 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 increased in the same way, and the pin 2 of the PFC control management constant current circuit IC U13 detects the voltage of the VCC2 through the sampling resistor second resistor R3B102 and the third resistor R3B103, so that the output voltage of the auxiliary winding of the constant voltage transformer T1 is limited in a safe range, and the LED light bar is prevented from being damaged due to the fact that the voltage output by the secondary winding of the constant voltage transformer T1 is too large.

Further, the constant voltage switching tube Q17 further controls the constant voltage transformer T2 under the control of the single-stage PFC control and management constant voltage circuit IC U14, and outputs a stable constant voltage source after being rectified by the sixth diode D30 and filtered by the fourth capacitor CE 10. Referring to the schematic circuit structure of the constant voltage control loop 130 shown in fig. 8, after passing through the twenty-fourth resistor R9D4 and the twenty-fifth resistor R9D3, the constant voltage control loop 130 controls the current of the 1-2 pin of the third optocoupler U1D1 through the first adjusting tube U3D1, and further controls the voltage of the 4 pin of the PFC control management constant voltage circuit U14, and then the PFC control management constant voltage circuit U14 controls the switching operating frequency or duty cycle of the constant voltage switching tube Q17, so that the output voltage is constant, when the requirement for ripple is high, a DC-DC voltage stabilizing module may be added at the output end of the constant voltage transformer T2, so that the output voltage ripple is small.

Furthermore, the single-stage PFC management constant current circuit IC U13 and the single-stage PFC management constant voltage circuit IC U14 can adopt a JP0010 digital chip of JPX, the functions of all pins are set through software, and the power supply switching frequency can be automatically controlled to be switched into a skip cycle working mode when the standby light load is carried out, so that the standby light load efficiency is improved, a standby transformer is not needed, the cost is saved, the constant current transformer T1 is turned off when the standby is carried out, and the standby power consumption is reduced.

In the switching power supply provided by this embodiment, on the basis of the first embodiment, by adding the high-voltage pre-start circuit, when the television is switched from power-off to power-on standby, the high-voltage pre-starting circuit is preferably used for supplying power to a VCC end of the PFC control management constant-voltage circuit, when the PFC control management constant voltage circuit starts to work, the high-voltage pre-starting circuit is closed, the voltage at the output end of the auxiliary winding of the constant-voltage transformer is used for supplying power to the VCC end of the PFC control management constant voltage circuit, so that stable power supply voltage is supplied to the PFC control management constant voltage circuit, the working frequency can be adjusted according to the load condition, the standby power consumption is reduced, meanwhile, the voltage of the output end of the auxiliary winding of the constant-voltage transformer passes through the first input end of the wired constant-voltage circuit, so that pre-starting voltage is provided for the PFC control management constant-current circuit when the system is started, and the stability of the system is improved; by adding the overvoltage protection circuit, the output voltage of the constant current transformer is ensured not to be too large, and the LED lamp strip is prevented from being damaged due to the fact that the output voltage of the constant current transformer is too large.

From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software and necessary general hardware, and certainly, can also be implemented by hardware, but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which may be stored in a computer-readable storage medium, such as a floppy disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a FLASH Memory (FLASH), a hard disk or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a storage medium, or a network device) to execute the embodiments of the present invention.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A switching power supply, characterized in that the power supply comprises: the PFC control management constant-voltage module, the PFC control management constant-current module and the linear constant-voltage module;

2. The switching power supply of claim 1, wherein the PFC control management constant voltage module comprises: the PFC control manages a constant voltage circuit, a constant voltage switching tube, a constant voltage transformer and a constant voltage control loop;

3. The switching power supply of claim 2, wherein the PFC control management constant current module comprises: the PFC control management constant current circuit, constant current switch tube, constant current transformer and overvoltage regulating circuit, the said linear constant voltage module includes the linear constant voltage circuit;

4. The switching power supply according to claim 3, wherein a first input terminal of the linear constant voltage circuit is connected to an output terminal of the auxiliary winding of the constant voltage transformer, a second input terminal of the linear constant voltage circuit is connected to an output terminal of the auxiliary winding of the constant current transformer, a control terminal of the linear constant voltage circuit is connected to an enable signal, and an output terminal of the linear constant voltage circuit is connected to a power supply terminal of the PFC control management constant current circuit, so that the linear constant voltage circuit can be used for performing relay power supply on the power supply terminal of the PFC control management constant current circuit sequentially through the voltage of the first input terminal and the voltage of the second input terminal in a process from shutdown to standby to a startup light load, so that the constant current load can be.

5. The switching power supply according to claim 3, further comprising: the high-voltage pre-starting circuit is connected with an alternating current power supply at the input end and connected with the first end of the PFC control and management constant-voltage circuit at the output end, and is used for providing power for the PFC control and management constant-voltage circuit in the process from shutdown to standby of a system so as to start the PFC control and management constant-voltage circuit and start working.

6. The switching power supply as claimed in claim 5, wherein the power terminal of the PFC control management constant voltage circuit is connected to the output terminal of the auxiliary winding of the constant voltage transformer, and the PFC control management constant voltage circuit is powered by the output terminal of the auxiliary winding of the constant voltage transformer after being started up, and controls the high voltage pre-start-up circuit to be turned off.

7. The switching power supply according to claim 5, wherein the high voltage pre-start-up circuit comprises: the power supply 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 of the fourth diode is connected with a power supply, the cathode of the fourth diode is respectively connected with the first end of the ninth resistor and the first end of the tenth resistor, the second end of the ninth resistor is connected with the second end of the first control tube, the second end of the tenth resistor is connected with the first end of the first control tube and the tenth end of the PFC control management constant-voltage circuit, and the third end of the first control tube is connected with the first end of the PFC control management constant-voltage circuit.

8. The switching power supply according to claim 5, further comprising: the input end of the electromagnetic filter circuit is connected with an alternating current power supply, the output end of the electromagnetic filter circuit is respectively connected with the input end of the high-voltage pre-starting circuit and the input end of the rectifying circuit, and the output end of the rectifying 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.

9. The switching power supply according to claim 3, further comprising: and the input end of the overvoltage protection circuit is connected with the output end of the auxiliary winding of the constant current transformer, the output end of the overvoltage protection circuit is connected with the second end of the PFC control management constant current circuit, and the overvoltage protection circuit is used for enabling the PFC control management constant current circuit to reduce the voltage output by the constant current transformer to be within a set range by controlling the on and off of the constant current switching tube when the voltage output by the constant current transformer exceeds a set value.

10. A television comprising a switching power supply according to any one of claims 1 to 9.