LED drive circuit based on constant voltage source

Abstract

The utility model provides an LED driving circuit based on a constant voltage source, the driving circuit comprises the constant voltage source, an energy storage circuit, at least two paths of constant current driving circuits and a controller, the output end of the constant voltage source is electrically connected with the first end of the energy storage circuit so as to store the output electric energy into the energy storage circuit; each constant-current driving circuit is connected in parallel between the second end of the energy storage circuit and the output end of the controller; the controller is used for outputting a pulse width modulation signal to each constant-current driving circuit, and each constant-current driving circuit controls the conduction of the constant-current driving circuit based on the pulse width modulation signal after receiving the pulse width modulation signal and provides a constant current for an LED lamp bead in the constant-current driving circuit. The energy storage circuit provides driving voltage for the LED lamp beads under the condition that all the constant-current driving circuits are switched on, and therefore the LED lamp beads are driven to work normally. By replacing a constant current source with a constant voltage source and an energy storage circuit, the purchase cost of a power supply module can be greatly reduced, and the driving cost of a plurality of strings of LED lamps working in a pulse constant current mode is further reduced.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of LED driving, and in particular to an LED driving circuit based on a constant voltage source. BACKGROUND

[0002] In a conventional infrared backlight touch system, a constant current source is used to supply power to a plurality of LED lamp strings working in a pulse constant current mode. Assuming that there are 4 LED lamp strings in the system, and the pulse constant current of each LED lamp string is 2A, the constant current source needs to output a current of 8A. The voltage output by the constant current source varies with the number of lamp beads, and the number of lamp beads varies with the size of the screen. Taking an 86-inch screen as an example, the 86-inch screen needs 220 lamp beads, and all the lamp beads are divided into 4 strings, each string having 55 lamp beads. The voltage required by 55 lamp beads is calculated to be about 130V, so the constant current source needs to output a voltage of 130V. In this case, the pulse instantaneous power provided by the constant current source is P=UxI=130x8=1040W, and the cost of the constant current source capable of providing such a large instantaneous power is very high. Therefore, how to reduce the driving cost of the plurality of LED lamp strings working in the pulse constant current mode is a technical problem to be solved by those skilled in the art. SUMMARY

[0003] Therefore, the present disclosure provides an LED driving circuit based on a constant voltage source, which can reduce the driving cost of the plurality of LED lamp strings working in the pulse constant current mode.

[0004] According to a first aspect of the present disclosure, an A driving circuit is provided, comprising a constant voltage source, an energy storage circuit, at least two constant current driving circuits, and a controller, wherein each constant current driving circuit comprises a plurality of LED lamp beads connected in series.

[0005] An output end of the constant voltage source is electrically connected to a first end of the energy storage circuit, so as to store the output electrical energy in the energy storage circuit.

[0006] Each constant current driving circuit is connected in parallel between a second end of the energy storage circuit and an output end of the controller.

[0007] The controller is configured to output a pulse width modulation signal to each constant current driving circuit. After receiving the pulse width modulation signal, each constant current driving circuit controls the conduction of the constant current driving circuit based on the pulse width modulation signal and provides a constant current to the LED lamp beads inside the constant current driving circuit. The energy storage circuit provides a driving voltage to the LED lamp beads when each constant current driving circuit is conducting, so as to drive the LED lamp beads to work normally.

[0008] In a possible implementation, the constant voltage source comprises a rectifier filter circuit and a switching power supply circuit.

[0009] The rectification filter circuit is electrically connected between the external power supply and the voltage input end of the switching power supply circuit, for rectifying and filtering the alternating current output by the external power supply to obtain a pulse direct current signal, and inputting the pulse direct current signal to the switching power supply circuit, and the switching power supply circuit converts the pulse direct current signal into a constant voltage after receiving the pulse direct current signal.

[0010] The voltage output end of the switching power supply circuit is electrically connected to the output end of the constant voltage source and the first end of the energy storage circuit as the constant voltage source, so as to store the constant voltage in the form of electric energy into the energy storage circuit.

[0011] In a possible implementation, the switching power supply circuit is realized based on a UC3844 controller.

[0012] In a possible implementation, the constant voltage source further comprises a working enable circuit.

[0013] The first end of the working enable circuit is electrically connected to the screen power supply to read the screen power supply voltage, the second end of the working enable circuit is connected to the VREF pin of the UC3844 controller to read the reference voltage of the VREF pin, and the third end of the working enable circuit is electrically connected to the COMP pin of the UC3844 controller, so that when the screen power supply is turned off, a low voltage is output to the COMP pin of the UC3844 controller through the third end of the working enable circuit, so that the UC3844 controller controls the constant voltage source to be turned off, thereby reducing the power consumption of the constant voltage source.

[0014] In a possible implementation, the switching power supply circuit comprises a jumper cap voltage adjustment module.

[0015] The jumper cap voltage adjustment module is electrically connected between the voltage output end and the ground end of the switching power supply circuit after being connected in series with a plurality of resistors, so as to adjust the size of the constant voltage through the jumper cap voltage adjustment module.

[0016] In a possible implementation, the energy storage circuit comprises two groups of parallel magnetic beads and at least two energy storage units, wherein each energy storage unit is composed of a general capacitor and a polar capacitor in parallel.

[0017] The first end of the first group of parallel magnetic beads is electrically connected to the output end of the constant voltage source as the first end of the energy storage circuit, and the second end of the first group of parallel magnetic beads is electrically connected to the voltage input end of each constant current driving circuit as the second end of the energy storage circuit.

[0018] The energy storage units are connected in parallel between the second end of the energy storage circuit and a power supply ground, and the ground end of one energy storage unit is also connected to the second group of parallel magnetic beads.

[0019] In a possible implementation, each constant current drive circuit is implemented based on an LED constant current controller.

[0020] In a possible implementation, a pulse width limiting circuit is further included.

[0021] The pulse width limiting circuit is electrically connected between the output end of the controller and the enable end of each constant current drive circuit, configured to limit the pulse width of the pulse width modulation signal output by the controller, and output the pulse width limited pulse width modulation signal to the enable end of each constant current drive circuit.

[0022] In a possible implementation, the pulse width limiting circuit includes a twenty-ninth resistor to a thirty-third resistor, a thirty-fourth resistor to a fortieth resistor, a sixth transistor, a seventh transistor, an eighth transistor, a twenty-third capacitor, a ninth diode, and a sixth zener diode.

[0023] The base of the eighth transistor is connected to the power supply ground through a thirty-eighth resistor and a thirty-ninth resistor in series, and the connection point of the thirty-eighth resistor and the thirty-ninth resistor is electrically connected to the output end of the controller as the input end of the pulse width limiting circuit, to receive the pulse width modulation signal output by the controller; the collector of the eighth transistor is connected to the working power supply through a thirty-second resistor, and the collector of the eighth transistor is also electrically connected to the base of the seventh transistor through a resistor R36; and the emitter of the eighth transistor is connected to the power supply ground.

[0024] The collector of the seventh transistor is connected to the working power supply through a twenty-ninth resistor, and the collector of the seventh transistor is also electrically connected to the base of the sixth transistor through a thirty-third resistor; and the emitter of the seventh transistor is connected to the power supply ground.

[0025] The collector of the sixth transistor is connected to the working power supply, and the emitter of the sixth transistor is connected to the power supply ground through a thirty-seventh resistor and a fortieth resistor in series; and the connection point of the thirty-seventh resistor and the fortieth resistor is electrically connected to the enable end of each constant current drive circuit as the output end of the pulse width limiting circuit.

[0026] One end of the thirty-third resistor electrically connected to the seventh transistor is also connected to the power supply ground through a thirtieth resistor, and one end of the thirty-third resistor electrically connected to the seventh transistor is also connected to the power supply ground through a thirty-fifth resistor and the twenty-third capacitor in series.

[0027] The one end of the thirty-third resistor electrically connected with the sixth triode is also connected with the working power supply through the thirty-first resistor, and the one end of the thirty-third resistor electrically connected with the sixth triode is also electrically connected with the anode of the ninth diode, the cathode of the ninth diode is electrically connected with the second pin of the sixth voltage stabilizing diode, the third pin of the sixth voltage stabilizing diode is connected with the ground, and the first pin of the sixth voltage stabilizing diode is connected with the one end of the point connection of the twenty-third capacitor and the thirty-fifth resistor.

[0028] In a possible implementation, the driving circuit further comprises a high-voltage power-off delay circuit.

[0029] The high-voltage power-off delay circuit is electrically connected between the second end of the energy storage circuit and the second pin of the sixth voltage stabilizing diode, and is used for detecting whether the energy storage circuit is fully charged, and outputting a pulse width limited pulse width modulation signal to the enable end of each constant current driving circuit in the case that the energy storage circuit is fully charged.

[0030] The present disclosure provides a constant voltage source based LED driving circuit, which comprises a constant voltage source, an energy storage circuit, at least two constant current driving circuits and a controller, wherein each constant current driving circuit comprises a plurality of serially connected LED lamp beads; the output end of the constant voltage source is electrically connected with the first end of the energy storage circuit, so as to store the output electric energy in the energy storage circuit; each constant current driving circuit is connected in parallel between the second end of the energy storage circuit and the output end of the controller; the controller is used for outputting a pulse width modulation signal to each constant current driving circuit, each constant current driving circuit controls the conduction of the constant current driving circuit based on the pulse width modulation signal and provides a constant current to the LED lamp beads in the constant current driving circuit after receiving the pulse width modulation signal, and the energy storage circuit provides a driving voltage for the LED lamp beads in the case that each constant current driving circuit is turned on, so as to drive the LED lamp beads to work normally. In the present disclosure, the constant current source is replaced by the mode of constant voltage source plus energy storage circuit, which can greatly reduce the procurement cost of the power supply module, and further reduce the driving cost of the multi-string LED lamp working in the pulse constant current mode.

[0031] Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the present disclosure and serve to explain the principles of the present disclosure.

[0033] Figure 1 FIG. 1 shows a circuit diagram of a constant voltage source based LED driving circuit according to an embodiment of the present disclosure;

[0034] Figure 2FIG. 1 shows a circuit diagram of a rectifier filter circuit according to an embodiment of the present disclosure;

[0035] Figure 3 FIG. 2 shows a circuit diagram of a switching power supply circuit according to an embodiment of the present disclosure;

[0036] Figure 4 FIG. 3 shows a circuit diagram of an operation enable circuit according to an embodiment of the present disclosure;

[0037] Figure 5 FIG. 4 shows a circuit diagram of an energy storage circuit according to an embodiment of the present disclosure;

[0038] Figure 6 FIG. 5 shows a circuit diagram of a constant current drive circuit according to an embodiment of the present disclosure;

[0039] Figure 7 FIG. 6 shows a circuit diagram of a pulse width limiting circuit according to an embodiment of the present disclosure;

[0040] Figure 8 FIG. 7 shows a circuit diagram of a high voltage brown-out delay circuit according to an embodiment of the present disclosure;

[0041] Figure 9 FIG. 8 shows a circuit diagram of an operating power conversion circuit according to an embodiment of the present disclosure;

[0042] Figure 10 FIG. 9 shows a filter circuit diagram of an output terminal of an operating power conversion circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0043] Various exemplary embodiments, features, and aspects of the present disclosure will be described herein below with reference to the accompanying drawings. Identical reference numerals in the drawings denote elements having the same or similar functions or meanings. Although various aspects of embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless specifically stated.

[0044] The term "exemplary" is used herein in the sense of being an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0045] In addition, for the purpose of convenience and brevity, detailed descriptions of well-known functions and structures incorporated herein can be omitted so as to avoid unnecessarily obscuring the underlying principles of the present disclosure. In some instances, driving circuits, means, elements and circuits well known to those of ordinary skill in the art are not described in detail in order to avoid unnecessarily obscuring the present disclosure.

[0046] <Driving Circuit Embodiments>

[0047] Figure 1A circuit block diagram of an LED driving circuit based on a constant voltage source is shown according to an embodiment of the present disclosure. As shown in Figure 1 The driving circuit 100 includes a constant voltage source 110, an energy storage circuit 120, at least two constant current driving circuits 130, and a controller 140, wherein each constant current driving circuit 130 includes a plurality of LED lamp beads connected in series.

[0048] The output end of the constant voltage source 110 is electrically connected to the first end of the energy storage circuit 120 to store the output power in the energy storage circuit 120; each constant current driving circuit 130 is connected in parallel between the second end of the energy storage circuit 120 and the output end of the controller 140; the controller 140 is configured to output a pulse width modulation signal to each constant current driving circuit 130, and each constant current driving circuit 130 controls the conduction of the constant current driving circuit 130 based on the pulse width modulation signal and provides a constant current to the LED lamp beads inside the constant current driving circuit after receiving the pulse width modulation signal, and the energy storage circuit 120 provides a driving voltage for the LED lamp beads in the constant current driving circuit 130 when the constant current driving circuit 130 is turned on, thereby driving the normal operation of each LED lamp bead.

[0049] It should be noted that the size of the screen determines the number of LED lamp bead strings required by the screen and the number of LED lamp beads connected in series in each string, and the number of constant current driving circuits 130 is equal to the number of LED lamp bead strings required by the screen, and the output power of the constant voltage source is only required to be greater than or equal to the average power of each LED lamp bead string, and the average power P of each LED lamp bead string is U*I*D. Wherein, U is the working voltage required by each LED lamp bead when working, I is the constant current provided by the constant current driving circuit, and D is the duty cycle of the pulse width modulation signal output by the controller. For example, each LED lamp bead string includes 55 LED lamp beads, and the working voltage U required by each LED lamp bead when working is 130V, and when the constant current provided by the constant current driving circuit I is 2A and the duty cycle D of the pulse width modulation signal output by the controller is 1 / 10, the average power P of each LED lamp bead is 130*2*1 / 10=104W, that is, as long as the output power of the constant voltage source 110 is greater than or equal to 104W, the normal work of the LED lamp beads in each constant current driving circuit can be realized. However, if a constant current source is selected, the output power of the selected constant current source is 1040W (see the reasoning process in the background section), so it can be seen that the mode of replacing the constant current source with the constant voltage source and the energy storage circuit in the present disclosure can greatly reduce the procurement cost of the power module, thereby reducing the driving cost of the multi-string LED lamp working in the pulse constant current mode.

[0050] Further, since the controller 140 is in PMW modulation constant current energy guiding mode, as long as the voltage of the energy storage circuit is higher than the required minimum voltage value, the voltage output by the constant voltage source 110 is not required to be high in precision, thereby further reducing the difficulty of the power module design.

[0051] In a possible implementation, the constant voltage source 110 includes a rectification filter circuit and a switching power supply circuit. The rectification filter circuit is electrically connected between an external power source and a voltage input end of the switching power supply circuit, and is configured to rectify and filter alternating current output by the external power source to obtain a pulse direct current signal, and input the obtained pulse direct current signal to the switching power supply circuit. After receiving the pulse direct current signal, the switching power supply circuit can convert the pulse direct current signal into a constant voltage. A voltage output end of the switching power supply circuit is electrically connected to the first end of the energy storage circuit 120 as an output end of the constant voltage source 110, so as to store the converted constant voltage in the energy storage circuit 120 in the form of electrical energy.

[0052] In a possible implementation, a circuit diagram of the rectification filter circuit can be as shown in Figure 2 The rectification filter circuit includes a terminal J6, a fuse F2, an adjustable resistor RV1, a thermistor ntc, a common mode filter FL1, a capacitor C54, a resistor R77, a resistor R76, a resistor R26, a resistor R23, a common mode filter FL2, a rectifier bridge D12, and a polarity capacitor C6. The terminal J6 is electrically connected to an external alternating current power source as an input end of the rectification filter circuit. A first pin of the terminal J6 is electrically connected to a second pin of the common mode filter FL1 through the fuse F2. A third pin of the terminal J6 is electrically connected to a fourth pin of the common mode filter FL1 through the thermistor ntc. A second pin of the terminal J6 is provided in a suspended manner. The adjustable resistor RV1 is further electrically connected between the second pin and the fourth pin of the common mode filter FL1. A first pin of the common mode filter FL1 is electrically connected to a first pin of the common mode filter FL2. A third pin of the common mode filter FL1 is electrically connected to a third pin of the common mode filter FL2. The capacitor C54 is electrically connected between the first pin and the third pin of the common mode filter FL1. The resistor R77 and the resistor R76 are connected in series and then electrically connected between the first pin and the third pin of the common mode filter FL1. The resistor R26 and the resistor R23 are connected in series and then electrically connected between the first pin and the third pin of the common mode filter FL1. A second pin of the common mode filter FL2 is electrically connected to a third pin of the rectifier bridge D12. A fourth pin of the common mode filter FL2 is electrically connected to a second pin of the rectifier bridge D12. A fourth pin of the rectifier bridge D12 is connected to a current source ground. A first pin of the rectifier bridge D12 is electrically connected to a voltage input end VIN H of the switching power supply circuit as an output end of the rectification filter circuit. The first pin of the rectifier bridge D12 is further connected to the power source ground through the polarity capacitor C6.

[0053] In one possible implementation, the switching power supply circuit is based on a UC3844 controller. Specifically, a switching power supply circuit based on a UC3844 controller is as follows: Figure 3 As shown.

[0054] In one possible implementation, the constant voltage source 110 also includes an enable circuit. The first terminal of the enable circuit is electrically connected to the screen power supply to read the screen power supply voltage. The second terminal of the enable circuit is connected to the VREF pin of the UC3844 controller to read the reference voltage of the VREF pin. The third terminal of the enable circuit is electrically connected to the COMP pin of the UC3844 controller. When the screen power supply is off, the first terminal of the enable circuit loses voltage, causing the third terminal of the enable circuit to output a low voltage to the COMP pin of the UC3844 controller. When the voltage at the COMP pin of the UC3844 controller is pulled low, the voltage output at the OUT pin is zero. At this time, the switching transistor Q11, which is electrically connected to the OUT pin and used to control the operation of the transformer in the switching power supply circuit, is turned off, thereby stopping the transformer in the switching power supply circuit. At this time, the voltage HVIN at the output terminal of the constant voltage source 110 is zero, and the constant voltage source 110 operates in low-power mode, thereby reducing the power consumption of the constant voltage source 110.

[0055] In one possible implementation, the circuit diagram of the enable circuit is as follows: Figure 4 As shown, it includes: resistor R46, resistor R61, resistor R64, resistor R65, resistor R72, transistor Q12, optocoupler U8, capacitor C60, and terminal J8. Terminal J8 serves as the first terminal of the enable circuit and is electrically connected to the screen power supply. The first pin of terminal J8 is electrically connected to the first pin of optocoupler U8 through resistor R64. The first pin of terminal J8 is also connected to power ground through resistor R72. The second pin of terminal J8 is connected to power ground. The first pin of optocoupler U8 is also connected to power ground through capacitor C60. The second pin of optocoupler U8 is connected to protective ground. The third pin of optocoupler U8 is connected to power ground. The fourth pin of optocoupler U8 is electrically connected to the first terminal of resistor R46. The second terminal of resistor R46 serves as the second terminal of the enable circuit and is connected to the VREF pin of the UC3844 controller. The fourth pin of optocoupler U8 is also electrically connected to the base of transistor Q12 through resistor R65. The end of resistor R65 connected to the base of transistor Q12 is also connected to power ground through resistor R61. The emitter of transistor Q12 is connected to power ground. The collector of transistor Q12 serves as the third terminal of the enable circuit and is electrically connected to the COMP pin of the UC3844 controller.

[0056] In different size screens, the number of LED lamp beads in each string is different, and the more the number of LED lamp beads in series in each string, the higher the constant voltage source output voltage value needs to be. To adapt to different size screens, in one possible implementation, the switching power supply circuit further includes a jumper cap voltage adjustment module as shown in Figure 3 The jumper cap voltage adjustment module is connected in series with a plurality of resistors (resistor R100, resistor R101, and resistor R99) and electrically connected between the voltage output end (i.e., the HVIN end in Figure 3 ) of the switching power supply circuit and the ground end (protect ground) to adjust the constant voltage source 110 output voltage value through the jumper cap voltage adjustment module to adapt to the needs of different size screens.

[0057] In one specific implementation, the jumper cap voltage adjustment module includes a terminal J4 including 10 pins, as shown in Figure 3 The first pin is electrically connected to the resistor R100 through a 22k resistor R108, the second pin is electrically connected to the voltage output end of the switching power supply circuit to output 80V voltage externally, forming a first voltage output circuit; the third pin is electrically connected to the resistor R100 through a 43k resistor R110, the fourth pin is electrically connected to the voltage output end of the switching power supply circuit to output 100V voltage externally, forming a second voltage output circuit; the fifth pin is electrically connected to the resistor R100 through a 88.7k resistor R104, the sixth pin is electrically connected to the voltage output end of the switching power supply circuit to output 120V voltage externally, forming a third voltage output circuit; the seventh pin is electrically connected to the resistor R100 through a 160k resistor R103, the eighth pin is electrically connected to the voltage output end of the switching power supply circuit to output 140V voltage externally, forming a fourth voltage output circuit; the ninth pin is electrically connected to the resistor R100 through a 430k resistor R102, and the tenth pin is electrically connected to the voltage output end of the switching power supply circuit to output 160V voltage externally, forming a fifth voltage output circuit; and further includes a 75K resistor R98 electrically connected between the resistor R100 and the voltage output end of the switching power supply circuit to output 180V voltage externally, forming a sixth voltage output circuit.

[0058] In one possible implementation, the energy storage circuit 120 is as shown in Figure 5As shown, the energy storage circuit 120 comprises two groups of parallel magnetic beads and at least two energy storage units, wherein each energy storage unit is composed of a common capacitor and a polar capacitor in parallel; the first end of the first group of parallel magnetic beads (i.e. magnetic beads L14 and L13) is electrically connected to the output end of the constant voltage source 110 as the first end (i.e. the end marked with HVIN) of the energy storage circuit 120, and the second end of the first group of parallel magnetic beads (i.e. the end marked with HVCC) is electrically connected to the voltage input end of each constant current driving circuit 130 as the second end of the energy storage circuit 120; each energy storage unit is connected in parallel between the second end of the energy storage circuit 120 and the power supply ground, wherein the ground end of the energy storage unit close to the second end of the energy storage circuit 120 is also protected by the second group of parallel magnetic beads (i.e. magnetic beads L15 and L16). The number of energy storage units is determined according to the number of constant current driving circuits. For example, in the case of 4-way constant current driving circuit, 4 groups of energy storage units are set, so as to obtain the energy storage circuit as shown in Figure 2

[0059] In a possible implementation, each constant current driving circuit 130 is implemented based on an LED constant current controller. In a specific embodiment, each constant current driving circuit is constructed by using an LED constant current controller of model TX6121. Since the circuit structures of the constant current driving circuits are the same, one constant current driving circuit is taken as an example for description of the circuit structure of each constant current driving circuit. Specifically, the circuit diagram of the constant current driving circuit is as shown in Figure 6 ​As shown, it comprises: LED constant current controller TX6121, resistor R9, resistor R4, resistor R105, resistor R13, resistor R17, resistor R47, resistor R21, capacitor C17, capacitor C45, capacitor C13, capacitor C37, capacitor C12, capacitor C5, capacitor C6, switch tube Q1, diode D5, diode SS220, magnetic bead L1 and the first LED lamp string. The DIM pin of TX6121 is electrically connected to the output end of the controller 104 as the enable end of the constant current driving circuit, for receiving the pulse width modulation signal EN1 output by the controller 104, the VDD pin of TX6121 is connected to the 5.5V working power supply through resistor R9, the VDD pin of TX6121 is also connected to the power supply ground through capacitor C45 and capacitor C13 respectively, the TOFF pin of TX6121 is connected to the power supply ground through capacitor C17, the GND pin of TX6121 is connected to the power supply ground, the DVR pin of TX6121 is electrically connected to the gate of switch tube Q1 through resistor R13, resistor R17 and diode D5 are connected in series and then connected in parallel to the two ends of resistor R13, the gate of switch tube Q1 is also connected to the power supply ground through resistor R105, the source of switch tube Q1 is connected to the power supply ground through resistor R21, the CS pin of TX6121 is electrically connected to the source of switch tube Q1 through resistor R47, the CS pin of TX6121 is also connected to the power supply ground through capacitor C37, the drain of switch tube Q1 is electrically connected to the negative end of the first LED lamp string through magnetic bead L1, the positive end of the first LED lamp string is electrically connected to the second end of the energy storage circuit as the voltage input end of the constant current driving circuit, capacitor C5 and capacitor C6 are connected in parallel and then electrically connected between the positive and negative ends of the first LED lamp string, diode SS220 is connected in parallel between the positive end of the first LED lamp string and the drain of switch tube Q1, and resistor R4 and capacitor C12 are connected in series and then connected in parallel between the positive end of the first LED lamp string and the drain of switch tube Q1. In the working state, after the DIM pin of TX6121 receives the pulse width modulation signal EN1 output by the controller 104, the conduction of switch tube Q1 is controlled based on the pulse width modulation signal EN1, so as to realize the conduction control of the constant current driving circuit and provide 2A constant current for the LED lamp beads inside the constant current driving circuit. At the same time, in the conduction state of the constant current driving circuit, the energy storage circuit is guided to release a transient high voltage, which provides working voltage for the LED lamp beads inside the constant current driving circuit, so that the LED lamp beads work normally.

[0060] The circuit diagrams of other constant current driving circuits are described in detail in the following. Figure 6 Here, no longer tedious.

[0061] In a possible implementation, the driving circuit further comprises a pulse width limiting circuit; the pulse width limiting circuit is electrically connected between the output end of the controller 140 and the enable end of each constant current driving circuit 130, used for limiting the pulse width of the pulse width modulation signal output by the controller 140, and outputting the pulse width modulation signal after pulse width limiting to the enable end of each constant current driving circuit 130. Wherein, the pulse width is limited, that is, the time width of the pulse width is limited and adjusted.

[0062] In a possible implementation, the pulse width limiting circuit comprises, as shown in the figure, resistors R29 (i.e., resistor R29) to R33 (i.e., resistor R33), resistors R34 (i.e., resistor R34) to R40 (i.e., resistor R40), a transistor Q6 (i.e., transistor Q6), a transistor Q7 (i.e., transistor Q7), a transistor Q8 (i.e., transistor Q8), a capacitor C23 (i.e., capacitor C23), a diode D9 (i.e., diode D9), and a voltage stabilizing diode U6 (i.e., voltage stabilizing diode U6). Figure 7

[0063] The base of the transistor Q8 is connected to the power supply ground through resistors R38 and R39 in series, the connection point of the resistors R38 and R39 is electrically connected to the output end of the controller 140 as the input end of the pulse width limiting circuit, so as to receive the pulse width modulation signal (i.e., LED_CTL in the figure) output by the controller 140, the collector of the transistor Q8 is connected to the 5.5V working power supply through the resistor R32, and the collector of the transistor Q8 is also electrically connected to the base of the transistor Q7 through the resistor R36, and the emitter of the transistor Q8 is connected to the power supply ground.

[0064] The collector of the transistor Q7 is connected to the 5.5V working power supply through the resistor R29, and the collector of the transistor Q7 is also electrically connected to the base of the transistor Q6 through the resistor R33, and the emitter of the transistor Q7 is connected to the power supply ground.

[0065] The collector of the transistor Q6 is connected to the 5.5V working power supply, and the emitter of the transistor Q6 is connected to the power supply ground through resistors R37 and R40 in series, and the connection point of the resistors R37 and R40 is electrically connected to the enable end of each constant current driving circuit 130 as the output end of the pulse width limiting circuit, so as to transmit the pulse width modulation signal after pulse width adjustment to each constant current driving circuit.

[0066] One end of the resistor R33 electrically connected to the transistor Q7 is also connected to the power supply ground through the resistor R30, and one end of the resistor R33 electrically connected to the transistor Q7 is also connected to the power supply ground through resistors R35 and capacitor C23 in series.

[0067] ​The one end of the resistor R33 electrically connected with the triode Q6 is also connected to the positive pole of the diode D9 through the resistor R31, the negative pole of the diode D9 is electrically connected to the second pin of the voltage stabilizing diode U6, the third pin of the voltage stabilizing diode U6 is connected to the power supply ground, and the first pin of the voltage stabilizing diode U6 is connected to the one end of the capacitor C23 and the resistor R35.

[0068] In a possible implementation, the driving circuit further comprises a high-voltage power-off delay circuit.

[0069] The high-voltage power-off delay circuit is electrically connected between the second end of the energy storage circuit 120 and the second pin of the voltage stabilizing diode U6.

[0070] In a possible implementation, the high-voltage power-off delay circuit can comprise, as shown in Figure 8 Fig. 6, a capacitor C32, a capacitor C33, a resistor R42, a resistor R43, a resistor R45, a resistor R44, a resistor R41, a triode Q9 and a triode Q10. The first end of the capacitor C32 is electrically connected to the second end of the energy storage circuit 120 as an input end of the high-voltage power-off delay circuit, the first end of the capacitor C32 is electrically connected to the base of the triode Q9 through the resistor R42 and the resistor R43, the base of the triode Q9 is further connected to the ground through the resistor R45, the collector of the triode Q9 is electrically connected to the 5.5V power supply, the emitter of the triode Q9 is connected to the power supply ground through the capacitor C33, the emitter of the triode Q9 is further electrically connected to the base of the triode Q10 through the resistor R44, the emitter of the triode Q10 is connected to the power supply ground, and the collector of the triode Q10 is electrically connected to the second pin of the voltage stabilizing diode U6 of the pulse width limiting circuit as an output end of the high-voltage power-off delay circuit. The high-voltage power-off delay circuit can detect whether the voltage of the second end of the energy storage circuit, i.e., the end marked with HVCC, is stable: if the voltage is stable, it indicates that the constant voltage source has completed the charging of the energy storage circuit, at this time, the pulse width modulated signal after the pulse width limiting is output to the enable end of each constant current driving circuit to control the LED lamp string in each constant current driving circuit to work normally. If the voltage is not stable, it indicates that the constant voltage source is still charging the energy storage circuit, at this time, the pulse width modulated signal output by the pulse width limiting circuit is limited, so that the LED lamp string can work in a stable voltage state.

[0071] In addition, the driving circuit further comprises a conversion circuit of the internal 5.5V power supply, which is used to generate the 5.5V power supply for each device in the driving circuit, as shown in Figure 9 Fig. 7. In the embodiment, the output end of the 5.5V power supply is also connected to the power supply ground through the parallel connection of the capacitor C34 and the capacitor C35, as shown in Figure 10 Fig. 8.

[0072] Having described above several embodiments of the disclosure, any modifications and variations that fall within the scope of the described embodiments are also contemplated. It is also contemplated that the application covered by the claims extends to any alternative combination of claim elements not specifically disclosed. It is intended that the appended claims cover all such modifications and variations as falling within the scope of the described embodiments.

Claims

1. A constant-voltage source based LED driving circuit, characterized in that, The constant voltage source comprises a rectifier filter circuit and a switching power supply circuit. The rectifier filter circuit is electrically connected between an external power supply and a voltage input end of the switching power supply circuit, and is used for rectifying and filtering alternating current output by the external power supply to obtain a pulse direct current signal, and inputting the pulse direct current signal to the switching power supply circuit. The switching power supply circuit converts the pulse direct current signal into a constant voltage after receiving the pulse direct current signal. The voltage output end of the switching power supply circuit is electrically connected to the first end of the energy storage circuit as the output end of the constant voltage source, so as to store the constant voltage in the form of electric energy into the energy storage circuit. The switching power supply circuit is realized based on a UC3844 controller.

2. The drive circuit according to claim 1, characterized in that, The constant voltage source further comprises a working enable circuit. A first end of the working enable circuit is electrically connected to a screen power supply to read the screen power supply voltage. A second end of the working enable circuit is connected to a VREF pin of the UC3844 controller to read the reference voltage of the VREF pin.

3. The drive circuit according to claim 2, characterized in that, A third end of the working enable circuit is electrically connected to a COMP pin of the UC3844 controller.

4. The drive circuit according to claim 3, characterized in that, When the screen power supply is turned off, a low voltage is output to the COMP pin of the UC3844 controller through the third end of the working enable circuit, so that the UC3844 controller controls the constant voltage source to be turned off, thereby reducing the power consumption of the constant voltage source. The switching power supply circuit comprises a jumper cap voltage adjustment module.

5. The drive circuit according to claim 2, characterized by The jumper cap voltage adjustment module is connected in series with a plurality of resistors and is electrically connected between the voltage output end of the switching power supply circuit and a ground end, so as to adjust the size of the constant voltage through the jumper cap voltage adjustment module. The energy storage circuit comprises two groups of parallel magnetic beads and at least two energy storage units.

6. The drive circuit of claim 1, wherein A first end of a first group of parallel magnetic beads is electrically connected to the output end of the constant voltage source as the first end of the energy storage circuit. A second end of the first group of parallel magnetic beads is electrically connected to the voltage input end of each constant current driving circuit as the second end of the energy storage circuit. Each of the energy storage units is connected in parallel between the second end of the energy storage circuit and a power supply ground, and a grounding end of one of the energy storage units is further connected to the power supply ground through a second set of parallel magnetic beads.

7. The drive circuit of claim 1, wherein Each of the constant current drive circuits is implemented based on an LED constant current controller.

8. The drive circuit of claim 1, wherein, A pulse width limiting circuit is further included. The pulse width limiting circuit is electrically connected between an output end of the controller and an enable end of each of the constant current drive circuits, and is configured to limit a pulse width of a pulse width modulation signal output by the controller and output the pulse width limited pulse width modulation signal to the enable end of each of the constant current drive circuits.

9. The drive circuit of claim 8, wherein, The pulse width limiting circuit includes a twenty-ninth resistor to a thirty-third resistor, a thirty-fourth resistor to a fortieth resistor, a sixth transistor, a seventh transistor, an eighth transistor, a twenty-third capacitor, a ninth diode, and a sixth voltage stabilizing diode. A base of the eighth transistor is connected to the power supply ground through a thirty-eighth resistor and a thirty-ninth resistor connected in series, a connection point of the thirty-eighth resistor and the thirty-ninth resistor is electrically connected to the output end of the controller as an input end of the pulse width limiting circuit to receive the pulse width modulation signal output by the controller, a collector of the eighth transistor is connected to a working power supply through a thirty-second resistor, and the collector of the eighth transistor is further electrically connected to a base of the seventh transistor through a resistor R36, and an emitter of the eighth transistor is connected to the power supply ground. A collector of the seventh transistor is connected to the working power supply through the twenty-ninth resistor, and the collector of the seventh transistor is further electrically connected to a base of the sixth transistor through the thirty-third resistor, and an emitter of the seventh transistor is connected to the power supply ground. A collector of the sixth transistor is connected to the working power supply, and an emitter of the sixth transistor is connected to the power supply ground through a thirty-seventh resistor and a fortieth resistor connected in series, and a connection point of the thirty-seventh resistor and the fortieth resistor is electrically connected to the enable end of each of the constant current drive circuits as an output end of the pulse width limiting circuit. One end of the thirty-third resistor electrically connected to the seventh transistor is further connected to the power supply ground through a thirtieth resistor, and one end of the thirty-third resistor electrically connected to the seventh transistor is further connected to the power supply ground through a thirty-fifth resistor and the twenty-third capacitor connected in series. One end of the thirty-third resistor electrically connected to the sixth transistor is further connected to the working power supply through a thirty-first resistor, and one end of the thirty-third resistor electrically connected to the sixth transistor is further electrically connected to a positive electrode of the ninth diode, a negative electrode of the ninth diode is electrically connected to a second pin of the sixth voltage stabilizing diode, a third pin of the sixth voltage stabilizing diode is connected to the power supply ground, and a first pin of the sixth voltage stabilizing diode is connected to one end of the twenty-third capacitor and the thirty-fifth resistor.

10. The drive circuit according to claim 9, characterized in that, A high-voltage power-off delay circuit is further included. The high-voltage power-off delay circuit is electrically connected between the second end of the energy storage circuit and the second pin of the sixth voltage stabilizing diode, and is configured to detect whether the energy storage circuit is fully charged, and output the pulse width limited pulse width modulation signal to the enable end of each of the constant current drive circuits in the case that the energy storage circuit is fully charged.

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