Power supply circuit of display system

Abstract

The utility model provides a power supply circuit of a display system, in a flyback topology circuit of the power supply circuit, an input end of an output unit is connected with a rectification circuit through a transformer and an input unit in sequence, and two output ends of the output unit are respectively used as two output ends of the flyback topology circuit; the input unit and the output unit are both provided with a controller; the two controllers are connected through an isolation optocoupler; the output unit is provided with at least two switch tubes, the switch tubes are controlled by the controller, and the conduction states of the two switch tubes influence the output states of the first output end and the second output end of the output unit; namely, in the output unit, energy transmitted by the flyback topology circuit is balanced by controlling two switching tubes, one-path constant-voltage output and one-path constant-current output are realized, the constant-voltage and constant-current requirements of the LED matrix and the mainboard are met on the basis of not increasing a Buck / Boost circuit, and a power supply circuit is simple and low in cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of power electronics, and more specifically, particularly relates to a power supply circuit for a display system. Background Technique

[0002] In modern electronic product design, for products with a power demand less than 75W, the design of the power supply system is crucial. To meet the voltage and current requirements of different components, a variety of circuit topologies are adopted; among them, the flyback circuit is widely used due to its simple structure and low cost.

[0003] Currently, a flyback circuit is used to output two voltages, which are respectively supplied to the main board and the LED matrix. To achieve constant current drive of the LED matrix, a Buck / Boost circuit is usually added between the flyback circuit and the LED matrix.

[0004] However, although this solution can meet the current requirements of the LED matrix, it also brings the problem of reduced circuit efficiency. In addition, the added Buck / Boost circuit not only increases the complexity of the circuit but also raises the overall manufacturing cost. Content of the Utility Model

[0005] In view of this, the purpose of the utility model is to provide a power supply circuit for a display system, which can meet the constant voltage and constant current requirements of the LED matrix and the main board without adding a Buck / Boost circuit, and the power supply circuit is simple and has low cost.

[0006] The present application discloses a power supply circuit for a display system, including: a rectifier circuit and a flyback topology circuit;

[0007] The input end of the rectifier circuit serves as the input end of the power supply circuit to receive alternating current;

[0008] The output end of the rectifier circuit is connected to the input end of the flyback topology circuit;

[0009] The first output end of the flyback topology circuit is connected to the LED matrix of the display system;

[0010] The second output end of the flyback topology circuit is connected to the main board of the display system;

[0011] The flyback topology circuit includes an input unit, an output unit, an isolation optocoupler, and a transformer;

[0012] The input end of the input unit serves as the input end of the flyback topology circuit;

[0013] The output end of the input unit is connected to the input end of the output unit through the transformer;

[0014] The first output terminal of the output unit serves as the first output terminal of the flyback topology circuit;

[0015] The second output terminal of the output unit serves as the second output terminal of the flyback topology circuit;

[0016] Both the input unit and the output unit are provided with controllers; and the two controllers are connected through an isolation optocoupler; the output unit is provided with at least two switching tubes, the switching tubes are all controlled by the controller, and the conduction states of the two switching tubes affect the output states of the first output terminal and the second output terminal of the output unit.

[0017] Optionally, the input unit includes: a first switching unit and a first controller;

[0018] The first input terminal of the first switching unit serves as the input terminal of the input unit;

[0019] The second input terminal of the first switching unit is connected to the GATE pin of the first controller;

[0020] The detection terminal of the first switching unit is connected to the IS pin of the first controller;

[0021] The first output terminal of the first switching unit is connected to one end of the primary winding of the transformer;

[0022] The second output terminal of the first switching unit is connected to the other end of the primary winding of the transformer.

[0023] Optionally, the first switching unit includes: a first resistor, a first capacitor, a first diode, a first switching tube, and a second resistor;

[0024] One end of the first resistor and one end of the first capacitor are connected, and the connection point is respectively connected to the first input terminal and the first output terminal of the first switching unit;

[0025] The other end of the first resistor is respectively connected to the other end of the first capacitor and the cathode of the first diode;

[0026] The anode of the first diode is respectively connected to the other end of the primary winding of the transformer and one end of the first switching tube;

[0027] The control terminal of the first switching tube serves as the second input terminal of the first switching unit;

[0028] The other end of the first switching tube is connected to one end of the second resistor, and the connection point serves as the detection terminal of the first switching unit;

[0029] The other end of the second resistor is connected to the power ground.

[0030] Optionally, the FB pin of the first controller is connected to the power ground through the receiving side of the isolation optocoupler.

[0031] Optionally, the output unit includes: a first output subunit, a second output subunit, a second controller, and a detection unit;

[0032] The input end of the first output subunit is connected to the first end of the secondary winding of the transformer;

[0033] The first control end of the first output subunit is connected to the LED pin of the second controller;

[0034] The second control end of the first output subunit is connected to the GATE3 pin of the second controller;

[0035] The detection end of the first output subunit is connected to the IS pin of the second controller;

[0036] The output end of the first output subunit serves as the first output end of the output unit;

[0037] The input end of the second output subunit is connected to the second end of the secondary winding of the transformer;

[0038] The control end of the second output subunit is connected to the GATE1 pin of the second controller;

[0039] The detection end of the second output subunit is connected to the CV pin of the second controller;

[0040] The output end of the second output subunit serves as the second output end of the output unit;

[0041] The input end of the detection unit is connected to the third end of the secondary winding of the transformer;

[0042] The output end of the detection unit is connected to the SW pin of the second controller.

[0043] Optionally, the first output subunit includes: a third diode, a third capacitor, a third switching transistor, a fifth resistor, a sixth resistor, and an eighth resistor;

[0044] The anode of the third diode serves as the input end of the first output subunit;

[0045] The cathode of the third diode is connected to one end of the third capacitor and one end of the fifth resistor, and the connection point serves as the positive pole of the output end of the first output subunit;

[0046] The other end of the fifth resistor is connected to one end of the sixth resistor, and the connection point serves as the first control terminal of the first output subunit;

[0047] One end of the third switching transistor serves as the negative pole of the output terminal of the first output subunit;

[0048] The other end of the third switching transistor is connected to one end of the eighth resistor, and the connection point serves as the detection terminal of the first output subunit;

[0049] The control terminal of the third switching transistor serves as the second control terminal of the first output subunit;

[0050] The other ends of the third capacitor, the sixth resistor, and the eighth resistor are all grounded.

[0051] Optionally, the second output subunit includes: a second switching transistor, a second capacitor, a third resistor, and a fourth resistor;

[0052] One end of the second switching transistor serves as the input terminal of the second output subunit;

[0053] The other end of the second switching transistor is respectively connected to one end of the second capacitor and one end of the third resistor, and the connection point serves as the output terminal of the second output subunit;

[0054] The control terminal of the second switching transistor serves as the control terminal of the second output subunit;

[0055] The other end of the third resistor is connected to one end of the fourth resistor, and the connection point serves as the detection terminal of the second output subunit;

[0056] The other ends of the second capacitor and the fourth resistor are both grounded.

[0057] Optionally, the detection unit includes: a zener diode, a seventh resistor, a ninth resistor, and a second switching unit;

[0058] The cathode of the zener diode is connected to the first end of the second switching unit, and the connection point serves as the input terminal of the detection unit;

[0059] The anode of the zener diode is connected to one end of the seventh resistor;

[0060] The other end of the seventh resistor is connected to one end of the ninth resistor, and the connection point serves as the output terminal of the detection unit;

[0061] The second end of the second switching unit and the other end of the ninth resistor are both grounded.

[0062] Optionally, the second switching unit includes a second diode or a fourth switching transistor;

[0063] When the second switching unit includes a second diode, the anode of the second diode serves as the second terminal of the second switching unit; the cathode of the second diode serves as the first terminal of the second switching unit;

[0064] When the second switching unit includes a fourth switching transistor, one end of the fourth switching transistor serves as the second terminal of the second switching unit; the other end of the fourth switching transistor serves as the first terminal of the second switching unit; the control terminal of the fourth switching transistor is connected to the GATE2 pin of the second controller.

[0065] Optionally, the FB pin of the second controller is grounded through the light-emitting side of the isolation optocoupler.

[0066] As can be seen from the above technical solutions, a power supply circuit for a display circuit provided by the present invention has an input end of a flyback topology circuit connected to an alternating current through a rectifying circuit; and two output ends of the flyback topology circuit are respectively connected to an LED matrix and a main board of the display system; in this flyback topology circuit, an input end of an output unit is sequentially connected to the rectifying circuit through a transformer and an input unit, and two output ends of the output unit respectively serve as two output ends of the flyback topology circuit; controllers are provided in both the input unit and the output unit; and the two controllers are connected through an isolation optocoupler; at least two switching transistors are provided in the output unit, and the switching transistors are all controlled by the controller, and the on states of the two switching transistors affect the output states of the first output end and the second output end of the output unit; that is, in the output unit, by controlling the two switching transistors, the energy transmitted by the flyback topology circuit is balanced, realizing a constant voltage output and a constant current output, meeting the constant voltage and constant current requirements of the LED matrix and the main board without adding a Buck / Boost circuit, the power supply circuit is simple and the cost is low; in addition, the PCB board occupation area is reduced, and at the same time, the energy loss of circuit conversion is reduced, so that the circuit efficiency is increased to a high level of more than 90%, realizing a compact and efficient power supply circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0068] Figure 1 is a schematic diagram of a power supply circuit for a display circuit provided by an embodiment of the present invention;

[0069] Figure 2It is a schematic diagram of a flyback topology circuit involved in a power supply circuit of a display circuit provided by an embodiment of the present utility model;

[0070] Figure 3 It is another schematic diagram of a flyback topology circuit involved in a power supply circuit of a display circuit provided by an embodiment of the present utility model. Detailed implementation manners

[0071] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0072] In this application, the terms "include", "comprise", or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device including a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the phrase "including a..." does not exclude the presence of additional identical elements in the process, method, article, or device including the element. In addition, the terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of this application described herein can be implemented in an order other than those illustrated or described herein.

[0073] The embodiment of this application provides a power supply circuit for a display system, which is used to solve the problems in the prior art that an additional Buck / Boost circuit needs to be provided, resulting in a reduction in circuit efficiency, an increase in circuit complexity, and an increase in the overall manufacturing cost.

[0074] Refer to Figure 1 , the power supply circuit of the display system includes: a rectifier circuit 10 and a flyback topology circuit 20.

[0075] The input end of the rectifier circuit 10 serves as the input end of the power supply circuit to receive alternating current.

[0076] The output end of the rectifier circuit 10 is connected to the input end of the flyback topology circuit 20.

[0077] The rectifier circuit 10 is responsible for converting alternating current (AC) into direct current (DC). Specifically, the input end of the rectifier circuit 10 serves as the front end of the power supply circuit and receives the alternating current signal provided externally. That is, it introduces the alternating current from the external power grid as the first step in the entire power conversion process. The rectifier circuit 10 converts the input alternating current waveform into a pulsating direct current through the rectifier elements inside, such as diodes or thyristors.

[0078] The output end of the rectifier circuit 10 directly transmits the direct current to the input end of the flyback topology circuit 20.

[0079] The flyback topology circuit 20 is a switching power supply topology structure that can further convert the input pulsating direct current into the required stable direct current output.

[0080] The first output end of the flyback topology circuit 20 is connected to the LED matrix of the display system.

[0081] The second output end of the flyback topology circuit 20 is connected to the main board of the display system.

[0082] It should be noted that the LED matrix requires constant current power supply, and the main board requires constant voltage power supply. Therefore, the first output end of the flyback topology circuit 20 realizes constant current output to provide constant current power supply for the LED matrix; the second output end of the flyback topology circuit 20 realizes constant voltage output to provide constant voltage power supply for the main board.

[0083] See Figure 2 , the flyback topology circuit 20 includes an input unit 21, an output unit 22, an isolation optocoupler 23, and a transformer T.

[0084] The input end of the input unit 21 serves as the input end of the flyback topology circuit 20 and is connected to the output of the rectifier circuit 10. That is to say, the input unit 21 receives the electrical signal after the rectifier circuit 10 rectifies the alternating current.

[0085] The output end of the input unit 21 is connected to the input end of the output unit 22 through the transformer T.

[0086] Specifically, the output end of the input unit 21 is connected to the primary winding of the transformer T, and the secondary winding of the transformer T is connected to the input end of the output unit 22.

[0087] The turns ratio of the transformer T can be set, and thus the working input voltage range of the output unit 22 can be set.

[0088] The first output end of the output unit 22 serves as the first output end of the flyback topology circuit 20.

[0089] The second output end of the output unit 22 serves as the second output end of the flyback topology circuit 20.

[0090] That is to say, the output unit 22 has two output terminals. One output terminal is connected to the LED matrix, and the other output terminal is connected to the main board. Specifically, the first output terminal of the output unit 22 is connected to the LED matrix, and the second output terminal of the output unit 22 is connected to the main board.

[0091] The input unit 21 and the output unit 22 are both provided with controllers, and the two controllers are connected through an isolation optocoupler 23. The output unit 22 is provided with at least two switching tubes, and the switching tubes are all controlled by the controller. The on-state of the two switching tubes affects the output states of the first output terminal and the second output terminal of the output unit 22.

[0092] Specifically, the input unit 21 and the output unit 22 are both provided with controllers, that is, the input unit 21 and the output unit 22 can be controlled separately to ensure the efficient operation of the system.

[0093] The two controllers are connected through an isolation optocoupler 23, which not only ensures the accurate transmission of signals, but also provides electrical isolation, enhancing the safety and reliability of the system. The isolation optocoupler 23 can be an optoelectronic coupler.

[0094] Two switching tubes are provided in the output unit 22, and each switching tube is directly and precisely controlled by the controller. Its on and off states determine the electrical characteristics of the first output terminal and the second output terminal of the output unit 22. That is to say, one switching tube is used to achieve constant current output at the first output terminal, and the other switching tube is used to achieve constant voltage output at the second output terminal. The cooperative working mode of the switching tubes has a decisive influence on the output state of the output unit 22. By precisely controlling the on-state of the switching tubes, precise regulation of the output voltage and current can be achieved to meet the requirements of different loads.

[0095] In this embodiment, the input end of the flyback topology circuit 20 is connected to the alternating current through the rectification circuit 10; and the two output ends of the flyback topology circuit 20 are respectively connected to the LED matrix and the main board of the display system; in the flyback topology circuit 20, the input end of the output unit 22 is connected to the rectification circuit 10 through the transformer T and the input unit 21 in sequence, and the two output ends of the output unit 22 are respectively used as the two output ends of the flyback topology circuit 20; controllers are arranged in both the input unit 21 and the output unit 22; and the two controllers are connected through an isolation optocoupler 23; the output unit 22 is provided with at least two switching tubes, the switching tubes are all controlled by the controller, and the conduction states of the two switching tubes affect the output states of the first output end and the second output end of the output unit 22; that is, in the output unit 22, the energy transmitted by the flyback topology circuit 20 is balanced by controlling the two switching tubes, realizing a constant voltage output for one path and a constant current output for one path. Without adding a Buck / Boost circuit, the constant voltage and constant current requirements of the LED matrix and the main board are met, the power supply circuit is simple, and the cost is low; in addition, the PCB board occupation area is reduced, and at the same time, the energy loss of circuit conversion is reduced, so that the circuit efficiency is increased to a high level above 90%, realizing a compact and efficient power supply circuit.

[0096] Optionally, referring to Figure 2 , the input unit 21 includes: a first switching unit 211 and a first controller U1.

[0097] The first input end of the first switching unit 211 serves as the input end of the input unit 21 and is connected to the output of the rectification circuit 10 to receive the electrical signal after rectifying the rectified current.

[0098] The second input end of the first switching unit 211 is connected to the GATE pin of the first controller U1 to receive the first signal output from the GATE pin of the first controller U1.

[0099] The detection end of the first switching unit 211 is connected to the IS pin of the first controller U1 to receive the second signal output from the IS pin of the first controller U1.

[0100] That is to say, the first controller U1 can control the on and off states of the first switching unit 211. Specifically, it can be jointly controlled by the first signal and the second signal. For example, when the first signal is a first value and the second signal is a second value, the first switching unit 211 is controlled to conduct, and in other cases, the first switching unit 211 is controlled to cut off. Of course, other control logics are also possible, which will not be elaborated here one by one and are all within the protection scope of this application.

[0101] The first output end of the first switching unit 211 is connected to one end of the primary winding of the transformer T.

[0102] The second output terminal of the first switching unit 211 is connected to the other end of the primary winding of the transformer T.

[0103] Specifically, the first output terminal of the first switching unit 211 is connected to the highest tap of the primary winding of the transformer T; the second output terminal of the first switching unit 211 is connected to the lowest tap of the primary winding of the transformer T; Low Tap: The tap that provides the lowest output voltage. High Tap: The tap that provides the highest output voltage, and each tap serves as one end of the transformer T.

[0104] That is to say, the two output terminals of the first switching unit 211 are respectively connected to both ends of the primary winding of the transformer T.

[0105] Optionally, refer to Figure 2 , the first switching unit 211 includes: a first resistor R1, a first capacitor C1, a first diode D1, a first switching transistor Q1, and a second resistor R2.

[0106] One end of the first resistor R1 and one end of the first capacitor C1 are connected, and the connection point is respectively connected to the first input terminal and the first output terminal of the first switching unit 211.

[0107] Specifically, the connection point between the first resistor R1 and the first capacitor C1 is respectively connected to the output terminal of the rectifier circuit 10 and one end of the primary winding of the transformer T.

[0108] The other end of the first resistor R1 is respectively connected to the other end of the first capacitor C1 and the cathode of the first diode D1.

[0109] The anode of the first diode D1 is respectively connected to the other end of the primary winding of the transformer T and one end of the first switching transistor Q1.

[0110] The control terminal of the first switching transistor Q1 serves as the second input terminal of the first switching unit 211 and is connected to the GATE pin of the first controller U1 to receive the signal of the GATE pin of the first controller U1.

[0111] The other end of the first switching transistor Q1 is connected to one end of the second resistor R2, and the connection point serves as the detection terminal of the first switching unit 211; it is connected to the IS pin of the first controller U1 to receive the signal of the IS pin of the first controller U1.

[0112] The other end of the second resistor R2 is connected to the power ground PGND.

[0113] That is to say, when the first controller U1 issues a driving signal to control the first switching transistor Q1 to conduct, the energy output by the rectifier circuit 10 is stored in the primary winding of the transformer T; when the same-name terminal of the transformer T flips, that is, when the first controller U1 issues a driving signal to control the first switching transistor Q1 to turn off, the energy is transferred from the primary winding to the secondary winding.

[0114] The second resistor R2 is a current-limiting resistor, which acts on the detection circuit of the U1 controller.

[0115] The second resistor R2 can play a role in limiting the current flowing through the first switching transistor Q1, preventing the current from being too large and damaging the first switching transistor Q1; at the same time, the connection point between the second resistor R2 and the first switching transistor Q1 can be used as a detection point and connected to the IS pin of the first controller U1 to realize the detection of the electrical signal at this detection point by the first controller U1, so that the first controller U1 can control the working state of the first switching transistor Q1 according to the detected electrical signal.

[0116] The first resistor R1, the first capacitor C1 and the first diode D1 form an RCD circuit, which is usually used to suppress the voltage spikes caused by the leakage inductance of the transformer T and the parasitic parameters of the switching device; that is, it can consume the leakage inductance energy of the flyback topology circuit 20.

[0117] Specifically, in the switching power supply, when the switching transistor changes from conduction to cutoff, due to the resonance between the leakage inductance of the transformer T and the switching transistor, a high-voltage spike will be generated at the drain of the switching transistor. The RCD circuit can absorb this spike energy to prevent damage to the switching transistor.

[0118] When the switching transistor turns off, if the drain voltage rises above the set value, the first diode D1 will conduct, and the energy in the leakage inductance will flow to the first capacitor C1 through the first diode D1, and the first capacitor C1 stores this part of the energy, thereby reducing the impact on the switching transistor. The size of the first capacitor C1 determines the absorption effect, and the role of the first resistor R1 is to consume the energy stored in the first capacitor C1 and release it in the form of heat.

[0119] Optionally, the FB pin of the first controller U1 is connected to the power ground PGND through the receiving side of the isolation optocoupler 23.

[0120] Specifically, the FB pin of the first controller U1 is connected to one end of the photosensitive triode U3A, and the other end of the photosensitive triode U3A is connected to the power ground PGND.

[0121] Optionally, see Figure 2 , the output unit 22 includes: a first output subunit 221, a second output subunit 222, a second controller U2, and a detection unit 223.

[0122] The input end of the first output sub-unit 221 is connected to the first end of the secondary winding of the transformer T.

[0123] It should be noted that the secondary winding of the transformer T has three taps, and each tap serves as one end of the secondary winding; these three taps can be the highest tap, the lowest tap, and the middle tap respectively; Low Tap: The tap that provides the lowest output voltage. Mid Tap: The tap that provides an output voltage between the lowest and the highest. High Tap: The tap that provides the highest output voltage. The first end of the secondary winding is the highest tap, the second end of the secondary winding is the middle tap, and the third end of the secondary winding is the lowest tap.

[0124] The first control end of the first output sub-unit 221 is connected to the LED pin of the second controller U2.

[0125] The second control end of the first output sub-unit 221 is connected to the GATE3 pin of the second controller U2.

[0126] That is to say, the first output sub-unit 221 is controlled by the second controller U2. The second controller U2 can control the state of the first output sub-unit 221 through its own GATE3 pin, thereby controlling the state of the first output end of the flyback topology circuit 20, that is, realizing constant current output.

[0127] The detection end of the first output sub-unit 221 is connected to the IS pin of the second controller U2.

[0128] Specifically, the second controller U2 can detect the signal at the detection end of the first output sub-unit 221, and then adjust the output signal of its own GATE3 pin according to this signal.

[0129] The output end of the first output sub-unit 221 serves as the first output end of the output unit 22 and is connected to the LED matrix.

[0130] The input end of the second output sub-unit 222 is connected to the second end of the secondary winding of the transformer T.

[0131] The control end of the second output sub-unit 222 is connected to the GATE1 pin of the second controller U2.

[0132] That is to say, the second output sub-unit 222 is controlled by the second controller U2. The second controller U2 can control the state of the second output sub-unit 222 through its own GATE1 pin, thereby controlling the state of the second output end of the flyback topology circuit 20, that is, realizing constant voltage output.

[0133] The detection end of the second output sub-unit 222 is connected to the CV pin of the second controller U2.

[0134] Specifically, the second controller U2 can detect the signal at the detection end of the second output subunit 222, and then adjust the output signal of its own GATE1 pin according to this signal.

[0135] The output end of the second output subunit 222 serves as the second output end of the output unit 22 and is connected to the main board of the display system.

[0136] The input end of the detection unit 223 is connected to the third end of the secondary winding of the transformer T.

[0137] The output end of the detection unit 223 is connected to the SW pin of the second controller U2.

[0138] That is to say, the detection unit 223 is controlled by the second controller U2, and the second controller U2 can control the state of the detection unit 223 through its own SW pin.

[0139] Optionally, the FB pin of the second controller U2 is grounded through the light-emitting side of the isolation optocoupler 23.

[0140] Specifically, the FB pin of the second controller U2 is connected to the anode of the light-emitting diode U3B in the isolation optocoupler 23, and the cathode of the light-emitting diode U3B in the isolation optocoupler 23 is grounded.

[0141] The FB pin of the second controller U2 is used to drive the isolation optocoupler 23, cooperate with the first controller U1 to work, and form a feedback loop. This feedback loop enables the duty cycle of the drive signal issued by the first controller U1 to be accurately adjusted, improving the stability of the electrical signal output by the flyback topology circuit 20. For example, realizing the constant current output and constant voltage output of the flyback topology circuit 20.

[0142] Optionally, referring to Figure 2 , the first output subunit 221 includes: a third diode D3, a third capacitor C3, a third switching transistor Q3, a fifth resistor R5, a sixth resistor R6, and an eighth resistor R8.

[0143] The anode of the third diode D3 serves as the input end of the first output subunit 221 and is connected to the first end of the secondary winding of the transformer T.

[0144] The cathode of the third diode D3 is connected to one end of the third capacitor C3 and one end of the fifth resistor R5, and the connection point serves as the positive pole of the output end of the first output subunit 221 and is connected to the positive pole of the LED matrix.

[0145] The other end of the fifth resistor R5 is connected to one end of the sixth resistor R6, and the connection point serves as the first control end of the first output subunit 221.

[0146] One end of the third switching transistor Q3 serves as the negative electrode of the output terminal of the first output sub-unit 221 and is connected to the negative electrode of the LED matrix.

[0147] It should be noted that the LED matrix may include a plurality of light-emitting diodes, and the light-emitting diodes are connected in series. The anodes after series connection serve as the positive electrode of the LED matrix, and the cathodes after series connection serve as the negative electrode of the LED matrix. For example Figure 2 As shown, the LED matrix includes: light-emitting diodes LED1B, LED2B, LED3B, LED4B, and LED5B; the anode of LED1B serves as the positive electrode of the LED matrix, and the cathode of LED1B is connected to the anode of LED2B; the cathode of LED2B is connected to the anode of LED3B; the cathode of LED3B is connected to the anode of LED4B; the cathode of LED4B is connected to the anode of LED5B; the cathode of LED5B serves as the negative electrode of the LED matrix.

[0148] The other end of the third switching transistor Q3 is connected to one end of the eighth resistor R8, and the connection point serves as the detection terminal of the first output sub-unit 221 and is connected to the IS pin of the second controller U2.

[0149] The control terminal of the third switching transistor Q3 serves as the second control terminal of the first output sub-unit 221 and is connected to the GATE3 pin of the second controller U2.

[0150] That is to say, the second controller U2 can output a signal through its own GATE3 pin to control the on-off of the third switching transistor Q3, and further control the first output terminal of the flyback topology circuit 20 to achieve constant current control.

[0151] The other end of the third capacitor C3, the other end of the sixth resistor R6, and the other end of the eighth resistor R8 are all grounded.

[0152] The eighth resistor R8 is a current-limiting resistor and acts on the detection circuit of the second controller U2.

[0153] The eighth resistor R8 can play a role in limiting the current flowing through the third switching transistor Q3 to prevent damage to the third switching transistor Q3 due to excessive current; at the same time, the connection point between the eighth resistor R8 and the third switching transistor Q3 can be used as a detection point and connected to the IS pin of the second controller U2 to realize the detection of the electrical signal at this detection point by the second controller U2, so that the second controller U2 can control the working state of the third switching transistor Q3 according to the detected electrical signal.

[0154] Optionally, refer to Figure 2 , the second output sub-unit 222 includes: a second switching transistor Q2, a second capacitor C2, a third resistor R3, and a fourth resistor R4.

[0155] One end of the second switching transistor Q2 serves as the input end of the second output sub-unit 222 and is connected to the second end of the transformer T.

[0156] The other end of the second switching transistor Q2 is respectively connected to one end of the second capacitor C2 and one end of the third resistor R3. The connection point serves as the output end of the second output sub-unit 222 and is connected to the main board.

[0157] The control end of the second switching transistor Q2 serves as the control end of the second output sub-unit 222 and is connected to the GATE1 pin of the second controller U2.

[0158] That is to say, the second controller U2 can output a signal through its own GATE1 pin to control the on-off of the second switching transistor Q2, and further control the second output end of the flyback topology circuit 20 to achieve constant voltage control.

[0159] The other end of the third resistor R3 is connected to one end of the fourth resistor R4. The connection point serves as the detection end of the second output sub-unit 222 and is connected to the CV pin of the second controller U2.

[0160] The other ends of the second capacitor C2 and the fourth resistor R4 are both grounded.

[0161] Optionally, referring to Figure 2 , the detection unit 223 includes: a zener diode ZD1, a seventh resistor R7, a ninth resistor R9, and a second switching unit (including D2 as shown in Figure 2 or Q4 as shown in Figure 3 ).

[0162] The cathode of the zener diode ZD1 is connected to the first end of the second switching unit. The connection point serves as the input end of the detection unit 223 and is connected to the third end of the transformer T.

[0163] The anode of the zener diode ZD1 is connected to one end of the seventh resistor R7.

[0164] The other end of the seventh resistor R7 is connected to one end of the ninth resistor R9. The connection point serves as the output end of the detection unit 223 and is connected to the SW pin of the second controller U2.

[0165] The second end of the second switching unit and the other end of the ninth resistor R9 are both grounded.

[0166] Optionally, the second switching unit includes a second diode D2 or a fourth switching transistor Q4.

[0167] As shown in Figure 2As shown, when the second switching unit includes the second diode D2, the anode of the second diode D2 serves as the second terminal of the second switching unit, that is, the anode of the second diode D2 is grounded; the cathode of the second diode D2 serves as the first terminal of the second switching unit and is connected to the cathode of the first voltage regulator diode.

[0168] As Figure 3 shown, when the second switching unit includes the fourth switching transistor Q4, one end of the fourth switching transistor Q4 serves as the second terminal of the second switching unit, that is, one end of the fourth switching transistor Q4 is grounded; the other end of the fourth switching transistor Q4 serves as the first terminal of the second switching unit and is connected to the cathode of the first voltage regulator diode; the control terminal of the fourth switching transistor Q4 is connected to the GATE2 pin of the second controller U2.

[0169] Next, taking Figure 2 the structure shown as an example, the working process of the flyback topology circuit 20 will be described:

[0170] When the first switching transistor Q1 is turned on, energy is stored in the secondary winding of the transformer T. At this time, the third diode D3 and the second diode D2 connected to the secondary winding of the transformer T are both reverse-biased and cut off, and the second switching transistor Q2 is in the off state.

[0171] When the first switching transistor Q1 is turned off, the transformer T transfers energy from the primary winding to the secondary winding; the second diode D2 conducts forward, and the second controller U2 issues a driving signal to turn on the second switching transistor Q2, storing the energy in the second capacitor C2 and outputting the Vout voltage (the output voltage of the second output terminal). When the Vout voltage meets the requirements, for example, is greater than the threshold, the second controller U2 issues a driving signal to turn off the second switching transistor Q2; the third diode D3 conducts forward, the energy transferred by the transformer T is stored in the third capacitor C3, and the second controller U2 issues a driving signal to turn on the third switching transistor Q3, turning on and lighting the LED array of LED1B to LED5B.

[0172] The working process of the second controller U2 is as follows:

[0173] When the transformer T transfers energy from the primary winding to the secondary winding, the Pin9 pin (SW pin) of the second controller U2 detects a low level, and the second controller U2 issues a driving signal to turn on the second switching transistor Q2, and the output voltage is detected through the third resistor R3 and the fourth resistor R4 and fed back to the Pin5 pin (CV pin) of the second controller U2.

[0174] When the output voltage between the third resistor R3 and the fourth resistor R4 meets the requirements, the second controller U2 issues a driving signal to turn off the second switching transistor Q2.

[0175] After the second switching transistor Q2 is turned off, the energy of the transformer T is transferred through the third diode D3. The output voltage is detected through the fifth resistor R5 and the sixth resistor R6 and fed back to the Pin6 (LED pin) of the second controller U2. The second controller U2 issues a driving signal to turn on the third switching transistor Q3. The output voltage is detected through the eighth resistor R8 and fed back to the Pin8 (IS pin) of the second controller U2.

[0176] Since the resistance value of the eighth resistor R8 is determined, the current flowing through the eighth resistor R8 can be determined by the voltage across the eighth resistor R8. At the same time, the eighth resistor R8 is in series with the LED matrix, so the current of the LED matrix can be obtained. Furthermore, when the output current of the eighth resistor R8 meets the requirements, the second controller U2 issues a driving signal to turn off the third switching transistor Q3.

[0177] When the second diode D2 is reversely cut off, the voltage regulator diode ZD1 conducts. The output voltage is detected through the seventh resistor R7 and the ninth resistor R9 and fed back to the Pin9 (SW pin) of the second controller U2. At this time, the second controller U2 can judge the working state of the transformer T to process the driving signal of the second switching transistor Q2.

[0178] The voltage of the Pin9 (SW pin) of the second controller U2 can be calculated according to the following formula:

[0179] Vsw = (Vout + Vin × Ns1 / Np1) - VZD1) × R9 / (R7 + R9);

[0180] For example: Vout = 12V, Vin = 90V, Ns1 / Np1 = 1 / 8, VZD1 = 5.1V, R7 = 200K, R9 = 39K, calculate Vsw = 2.96V; with other parameters unchanged, when Vin = 264V, then calculate Vsw = 6.51V.

[0181] Among them, Vsw is the voltage of the SW pin; Vout is the output voltage of the first output terminal of the flyback topology circuit 20; Vin is the input voltage of the flyback topology circuit 20; Np1 is the number of turns of the primary winding of the transformer T; Ns1 is the number of turns between the second end and the third end of the secondary winding of the transformer T; VZD1 is the regulated voltage value of the voltage regulator diode ZD1; R9 is the resistance value of the ninth resistor R9; R7 is the resistance value of the seventh resistor R7.

[0182] Therefore, the voltage of the Pin9 of the second controller U2 can be set at 2.8V < Vpin9 < 6.7V. Furthermore, when the voltage of the Pin9 of the second controller U2 exceeds this range, the second controller U2 enters the protection state. Correspondingly, the range of the input voltage can be set, without the need to additionally increase the detection circuit, reducing the complexity of the circuit and improving the reliability of the product at the same time.

[0183] The function of introducing the voltage stabilizing diode ZD1 is to ensure that the input voltage is always greater than the threshold. During the switching process of the same-name terminals of the transformer T, voltage oscillations may occur. At this time, the voltage stabilizing diode ZD1 can stabilize the voltage and reduce the errors caused by circuit differences. By selecting diodes with different voltage stabilizing values, the circuit performance can be adjusted and optimized, further improving the reliability and stability of the product, enhancing the robustness of the circuit, and simplifying the overall circuit solution.

[0184] Take Figure 3 shown as an example, Figure 3 it is based on Figure 2 and replaces the second diode D2 with the fourth switching tube Q4. When the Vout outputs a large current, the loss of the second diode D2 will increase, resulting in an increase in temperature rise and a decrease in the efficiency of the system. Optimizing the second diode D2 into the fourth switching tube Q4 and adding a path of drive to the second controller U2 to achieve the synchronous rectification effect can improve the system efficiency, reduce the heat sink area of the PCB board, and make the circuit more concise. The fourth switching tube Q4 can be a MOS tube.

[0185] During the control process, it can be ensured that the reflected voltage of the constant voltage loop is lower than that of the constant current loop, that is, the working voltage of the main board needs to be lower than the working voltage of the LED matrix.

[0186] In this embodiment, after the alternating current passes through the rectifying circuit 10, a flyback topology circuit 20 is used to achieve dual outputs; one output is specifically supplied to the LED matrix, and the other provides the required power for the main board. A flyback topology circuit 20 integrates two output modes of constant voltage and constant current, corresponding to different load requirements. Through this integrated design, an additional boost or buck circuit is avoided, thereby reducing the PCB board area occupied by the circuit. At the same time, due to the simplified circuit structure, the loss during the energy conversion process of the circuit is also reduced, significantly improving the overall efficiency of the system. The design of this power supply system not only achieves a high level of efficiency above 90%, but also realizes the compactness and high efficiency of the power supply solution.

[0187] The features described in each of the embodiments in this specification can be replaced or combined with each other. For the same or similar parts among the embodiments, reference can be made to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for a system or a system embodiment, since it is basically similar to a method embodiment, the description is relatively simple, and reference can be made to the corresponding part of the method embodiment for the relevant content. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative work.

[0188] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Skilled professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0189] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power supply circuit for a display system, characterized in that, It includes: A rectifier circuit and a flyback topology circuit; The input end of the rectifier circuit serves as the input end of the power supply circuit to receive alternating current; The output end of the rectifier circuit is connected to the input end of the flyback topology circuit; The first output end of the flyback topology circuit is connected to the LED matrix of the display system; The second output end of the flyback topology circuit is connected to the main board of the display system; The flyback topology circuit includes an input unit, an output unit, an isolation optocoupler, and a transformer; The input end of the input unit serves as the input end of the flyback topology circuit; The output end of the input unit is connected to the input end of the output unit through the transformer; The first output end of the output unit serves as the first output end of the flyback topology circuit; The second output end of the output unit serves as the second output end of the flyback topology circuit; Both the input unit and the output unit are provided with controllers; and the two controllers are connected through an isolation optocoupler; the output unit is provided with at least two switching tubes, and the switching tubes are all controlled by the controller, and the conduction states of the two switching tubes affect the output states of the first output end and the second output end of the output unit.

2. The power supply circuit of the display system according to claim 1, wherein The input unit includes: a first switching unit and a first controller; The first input end of the first switching unit serves as the input end of the input unit; The second input end of the first switching unit is connected to the GATE pin of the first controller; The detection end of the first switching unit is connected to the IS pin of the first controller; The first output end of the first switching unit is connected to one end of the primary winding of the transformer; The second output end of the first switching unit is connected to the other end of the primary winding of the transformer.

3. The power supply circuit of the display system according to claim 2, wherein, The first switching unit includes: a first resistor, a first capacitor, a first diode, a first switching tube, and a second resistor; One end of the first resistor and one end of the first capacitor are connected, and the connection point is respectively connected to the first input end and the first output end of the first switching unit; The other end of the first resistor is respectively connected to the other end of the first capacitor and the cathode of the first diode; The anode of the first diode is respectively connected to the other end of the primary winding of the transformer and one end of the first switching tube; The control end of the first switching tube serves as the second input end of the first switching unit; The other end of the first switching tube is connected to one end of the second resistor, and the connection point serves as the detection end of the first switching unit; The other end of the second resistor is connected to the power ground.

4. The power supply circuit of the display system according to claim 2, characterized in that, The FB pin of the first controller is connected to the power ground through the receiving side of the isolation optocoupler.

5. The power supply circuit of the display system according to claim 1, characterized in that, The output unit includes: a first output sub-unit, a second output sub-unit, a second controller, and a detection unit; The input end of the first output sub-unit is connected to the first end of the secondary winding of the transformer; The first control end of the first output sub-unit is connected to the LED pin of the second controller; The second control end of the first output sub-unit is connected to the GATE3 pin of the second controller; The detection end of the first output sub-unit is connected to the IS pin of the second controller; The output terminal of the first output subunit serves as the first output terminal of the output unit; The input terminal of the second output subunit is connected to the second end of the secondary winding of the transformer; The control terminal of the second output subunit is connected to the GATE1 pin of the second controller; The detection terminal of the second output subunit is connected to the CV pin of the second controller; The output terminal of the second output subunit serves as the second output terminal of the output unit; The input terminal of the detection unit is connected to the third end of the secondary winding of the transformer; The output terminal of the detection unit is connected to the SW pin of the second controller.

6. The power supply circuit of the display system according to claim 5, characterized in that, The first output subunit includes: a third diode, a third capacitor, a third switching transistor, a fifth resistor, a sixth resistor, and an eighth resistor; The anode of the third diode serves as the input terminal of the first output subunit; The cathode of the third diode is connected to one end of the third capacitor and one end of the fifth resistor, and the connection point serves as the positive pole of the output terminal of the first output subunit; The other end of the fifth resistor is connected to one end of the sixth resistor, and the connection point serves as the first control terminal of the first output subunit; One end of the third switching transistor serves as the negative pole of the output terminal of the first output subunit; The other end of the third switching transistor is connected to one end of the eighth resistor, and the connection point serves as the detection terminal of the first output subunit; The control terminal of the third switching transistor serves as the second control terminal of the first output subunit; The other ends of the third capacitor, the sixth resistor, and the eighth resistor are all grounded.

7. The power supply circuit of the display system according to claim 5, characterized in that The second output subunit includes: a second switching transistor, a second capacitor, a third resistor, and a fourth resistor; One end of the second switching transistor serves as the input terminal of the second output subunit; The other end of the second switching transistor is respectively connected to one end of the second capacitor and one end of the third resistor, and the connection point serves as the output terminal of the second output subunit; The control terminal of the second switching transistor serves as the control terminal of the second output subunit; The other end of the third resistor is connected to one end of the fourth resistor, and the connection point serves as the detection terminal of the second output subunit; The other ends of the second capacitor and the fourth resistor are all grounded.

8. The power supply circuit of the display system according to claim 5, characterized in that, The detection unit includes: a zener diode, a seventh resistor, a ninth resistor, and a second switching unit; The cathode of the zener diode is connected to the first end of the second switching unit, and the connection point serves as the input terminal of the detection unit; The anode of the zener diode is connected to one end of the seventh resistor; The other end of the seventh resistor is connected to one end of the ninth resistor, and the connection point serves as the output terminal of the detection unit; The second end of the second switching unit and the other end of the ninth resistor are all grounded.

9. The power supply circuit of the display system according to claim 8, characterized in that, The second switching unit includes a second diode or a fourth switching transistor; When the second switching unit includes a second diode, the anode of the second diode serves as the second end of the second switching unit; the cathode of the second diode serves as the first end of the second switching unit; When the second switching unit includes a fourth switching transistor, one end of the fourth switching transistor serves as the second end of the second switching unit; the other end of the fourth switching transistor serves as the first end of the second switching unit; and the control end of the fourth switching transistor is connected to the GATE2 pin of the second controller.

10. The power supply circuit of the display system according to claim 5, characterized in that The FB pin of the second controller is grounded through the light-emitting side of the isolation optocoupler.

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