Alternating current-direct current conversion system for driving cold light plate

Abstract

The utility model relates to the technical field of cold light plate driving, and particularly discloses an AC / DC conversion system for driving a cold light plate, which comprises a power supply unit, a clock unit, a seven-frequency-division unit, a charging and discharging module, an H-bridge network and an output unit, the power supply unit is connected with the clock unit, the seven-frequency-division unit and the charging and discharging module. The clock unit, the seven-frequency-division unit and the charging and discharging module are connected in sequence; the input end of the H-bridge network is connected with the seven-frequency-division unit, and the output end of the H-bridge network is connected with the output unit; the output end of the charging and discharging module used for generating a charging magnetic field and releasing energy is connected with the output unit. The whole circuit is simple and low in cost, and the working frequency can be directly adjusted by the feedback resistor. Based on the coil inductance energy storage and release principle, the energy utilization redivision efficiency is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to cold light plate drive technical field, concretely relates to a kind of AC-DC conversion system for driving cold light plate. BACKGROUND

[0002] With the rapid development of lighting technology, cold light plate is widely used in various lighting scenes as an efficient and energy-saving lighting device. Electroluminescence EL lamp is basically a plastic strip coated with fluorescent material, which emits light when a high voltage >40V is first applied to it, and then removed or reversed. Long-term application of direct current to the material will cause damage and shorten its service life. Considering these factors, the ideal signal for driving EL lamp is a high-voltage sine wave. However, the existing cold light plate driving circuit has the problems of complex circuit, difficult to adjust working frequency, low efficiency, high cost, etc. At the same time, voltage fluctuation or current instability may cause poor lighting effect.

[0003] Therefore, the skilled person in the art proposes a series of improvement schemes, including: changing the output frequency by changing the capacitance, adjusting the working current by changing the inductance value, defects: changing the capacitance affects the oscillation frequency, causing the brightness to first increase and then decrease, changing the inductance affects the working current, and the relationship between the working current and the output performance needs to be balanced; using a constant current source, defect: the current output error of the constant current source affects the uniformity of the display; using a linear voltage regulator or a switching current regulator, defect: the output voltage of the linear voltage regulator is high, which affects the output noise performance and increases the design complexity; using PWM pulse width modulation dimming technology, defect: causing color spectrum shift, low contrast; using common cathode output and COT constant current control mode, defect: poor stability between components, high cost;

[0004] Therefore, the skilled person in the art needs to develop a new DC-AC converter for driving cold light plate to solve the problem of poor lighting effect caused by voltage fluctuation or current instability in the prior art. UTILITY MODEL CONTENT

[0005] Therefore, the utility model wants to solve the technical problem of overcoming the defects in the prior art, and to provide an AC-DC conversion system for driving cold light plate.

[0006] An AC-DC conversion system for driving cold light plate, comprising: a power supply unit, a clock unit, a seven-frequency unit, a charge-discharge module, an H-bridge network and an output unit.

[0007] The power supply unit for supplying power to the whole system is connected with the clock unit, the seven-frequency unit and the charge-discharge module respectively; and the clock unit, the seven-frequency unit and the charge-discharge module are connected in sequence, so that the clock unit uses a clock signal provided by an oscillator osc, the clock signal is divided into two control signals: f COIL signal and f LAMP signal, wherein f COIL is used for controlling the charge-discharge module, f LAMP is used for controlling the H-bridge network.

[0008] The input end of the H-bridge network for generating a high-voltage sine wave signal is connected with the seven-frequency unit, and the output end of the H-bridge network is connected with the output unit.

[0009] The output end of the charge-discharge module for generating a charging magnetic field and releasing energy is connected with the output unit.

[0010] Preferably, the clock unit is composed of the oscillator osc and an RC feedback network, in particular:

[0011] The RC feedback network is composed of a second capacitor C2 and a feedback resistor Rosc for adjusting the time frequency of the oscillator osc;

[0012] One end of the feedback resistor Rosc is connected with the second capacitor C2 and grounded; at the same time, one end of the feedback resistor Rosc is connected with the oscillator osc;

[0013] In addition, the other end of the feedback resistor Rosc is connected with a first voltage stabilizing unit in the power supply unit for stabilizing voltage and grounded, and the other end of the feedback resistor Rosc is connected with a power supply V BATT .

[0014] Preferably, the seven-frequency unit is an FFT7 frequency division circuit composed of seven flip-flops for dividing the clock signal;

[0015] The FFT7 frequency division circuit contains an input end, a first output end and a second output end;

[0016] The input end of the FFT7 frequency division circuit is connected with the output end of the oscillator osc;

[0017] The first output end and the second output end of the FFT7 frequency division circuit are both connected with the H-bridge network.

[0018] Preferably, it further includes a first AND gate circuit, a second AND gate circuit and a third AND gate circuit; the common input end of the first AND gate circuit, the second AND gate circuit and the third AND gate circuit is connected with a high-level control signal ELEN output by the power supply unit;

[0019] The output end of the oscillator osc is connected with a first switching element of the charge-discharge module through the first AND gate circuit.

[0020] The first output end of the FFT7 frequency division circuit is connected with the second switch element of the charge-discharge module through a second AND gate circuit, and the second output end of the FFT7 frequency division circuit is connected with the third switch element of the charge-discharge module through a third AND gate circuit;

[0021] The second switch element and the third switch element are connected with the H-bridge network, so that the H-bridge network as a high-voltage switch is triggered according to the energy released by the coil L1, thereby controlling the polarity of the charging of the output unit.

[0022] Preferably, the first switch element, the second switch element and the third switch element are all NPN type triodes, which are respectively the first transistor T1, the second transistor T2 and the third transistor T3;

[0023] The first AND gate circuit is connected with the base of the first transistor T1, and the emitter of the first transistor T1 is grounded;

[0024] The second AND gate circuit is connected with the base of the second transistor T2, and the emitter of the second transistor T2 is grounded;

[0025] The third AND gate circuit is connected with the base of the third transistor T3, and the emitter of the third transistor T3 is grounded.

[0026] Preferably, the H-bridge network is composed of a first silicon controlled rectifier SCR1 and a second silicon controlled rectifier SCR2;

[0027] The output end of the first silicon controlled rectifier SCR1 is connected with the output end of the second silicon controlled rectifier SCR2;

[0028] The input end of the first silicon controlled rectifier SCR1 is connected with the output end of the second transistor T2;

[0029] The input end of the second silicon controlled rectifier SCR2 is connected with the output end of the third transistor T3.

[0030] Preferably, the H-bridge network further includes a first protection unit, a second protection unit and a third protection unit;

[0031] The first protection unit adopts a second diode D2, the negative electrode of the second diode D2 is connected with the common output end of the first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2; the positive electrode of the second diode D2 is connected with the output end of the first transistor T1 and the output end of the coil L1;

[0032] The second protection unit adopts a third diode D3, the negative electrode of the third diode D3 is connected with the output end of the second switch element; the positive electrode of the third diode D3 is connected with the input end of the first silicon controlled rectifier SCR1 and the first interface EL1 of the output unit;

[0033] The third protection unit adopts a fourth diode D4, the negative electrode of the fourth diode D4 is connected with the output end of the third switch element; the positive electrode of the fourth diode D4 is connected with the input end of the second silicon controlled rectifier SCR2 and the second interface EL2 of the output unit.

[0034] Preferably, the power supply unit further comprises a second voltage stabilizing unit in addition to the first voltage stabilizing unit.

[0035] The second voltage stabilizing unit is composed of a first diode D1 and a capacitor C INT .

[0036] The positive electrode of the first diode D1 is connected with the output end of the coil L1; the negative electrode of the first diode D1 is connected with the common output end of the first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2.

[0037] The negative electrode of the first diode D1 is connected with the capacitor C INT , and the capacitor C INT is grounded.

[0038] The technical scheme of the utility model has the following advantages:

[0039] 1. The utility model provides a kind of AC-DC conversion system for driving cold light plate, and the utility model whole circuit is simple and low in cost, and working frequency can be directly regulated by feedback resistance.

[0040] 2. The utility model uses oscillator to generate clock signal, flip-flop stores state, transistor amplifier drives coil and electroluminescent lamp, silicon controlled rectifier controls current direction, finally realizes the brightness of electroluminescent lamp accurate and stable control;

[0041] 3. In the embodiment, control signal ELEN is also used to control the start-stop of control circuit, so as to ensure the safety of circuit while ensuring the accurate control of electroluminescent lamp. DRAWINGS

[0042] In order to more clearly illustrate the specific embodiments of the utility model or the technical scheme in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description, and obviously, the drawings in the following description are some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0043] Figure 1 It is the system principle diagram of the utility model;

[0044] Figure 2 It is the specific circuit principle diagram of the utility model;

[0045] Figure 3 The output voltage waveform schematic diagram of the circuit of the embodiment is shown in the figure;

[0046] Figure 4 The output voltage schematic diagram of the circuit of the embodiment 1 to electroluminescence is shown in the figure;

[0047] Figure 5 The output voltage schematic diagram of the circuit of the embodiment 2 to electroluminescence is shown in the figure. DETAILED DESCRIPTION

[0048] The technical scheme of the utility model will be described clearly and completely in combination with the drawings. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the ordinary skilled in the art without making creative labor belong to the protection scope of the utility model.

[0049] In the description of the utility model, it needs to be explained that the orientation or position relation indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like is the orientation or position relation shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and cannot be understood as indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the utility model. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0050] In the description of the utility model, it needs to be explained that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For the ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0051] In addition, the technical features involved in different embodiments of the utility model described below can be combined with each other as long as there is no conflict between them.

[0052] Embodiment 1

[0053] As Figure 1 An AC-DC conversion system for driving a cold light plate, comprising: a power supply unit, a clock unit, a seven division unit, a charge-discharge module, an H bridge network and an output unit; wherein the output unit is an electroluminescent lamp;

[0054] The power supply unit for supplying power to the whole system is connected with the clock unit, the seven-frequency unit and the impulse discharge module respectively; and the clock unit, the seven-frequency unit and the impulse discharge module are connected in sequence, so that the clock unit uses a clock signal provided by the oscillator osc, which is divided into two control signals: f COIL signal and f LAMP signal, wherein f COIL for controlling the impulse discharge module, f LAMP for controlling the H-bridge network to realize the optimization of the output of the electroluminescent lamp by changing the frequency of the oscillator osc, realizing the boost AC output;

[0055] The input end of the H-bridge network for generating a high-voltage sine wave signal is connected with the seven-frequency unit, and the output end of the H-bridge network is connected with the output unit;

[0056] The output end of the impulse discharge module for generating a charging magnetic field and releasing energy is connected with the output unit;

[0057] Wherein, the f COIL signal output by the oscillator osc is a signal with a duty cycle of 90%; according to the frequency of the oscillator osc, switching is performed, when f COIL signal is high, the coil L1 in the impulse discharge module is connected from the power supply V BATT of the power supply unit to the ground, so as to create a charged magnetic field in the coil L1; when f COIL signal is low, the ground connection of the coil L1 is switched to open circuit, the magnetic field disappears, and the energy in the coil L1 is forced to flow to the H-bridge network.

[0058] Specifically:

[0059] In this embodiment, the power supply unit uses the power supply provided by the battery, and the power supply voltage is 3.0v;

[0060] As Figure 2 In this embodiment, the clock unit is composed of the oscillator osc and the RC feedback network, specifically:

[0061] The RC feedback network is composed of the second capacitor C2 and the feedback resistor Rosc for adjusting the time frequency of the oscillator osc;

[0062] One end of the feedback resistor Rosc is connected with the second capacitor C2 and grounded; at the same time, one end of the feedback resistor Rosc is connected with the oscillator osc;

[0063] In addition, the other end of the feedback resistor Rosc is connected with the first voltage stabilizing unit in the power supply unit for stabilizing the voltage and grounded, and the other end of the feedback resistor Rosc is connected with the power supply V BATTThe end connection. It should be noted that the second capacitor C2 has a voltage stabilizing effect in this embodiment. In this embodiment, the feedback resistor R OSC The resistance of the feedback resistor is 450 kΩ; the inductance of the coil L1 is 470 µH; the first voltage stabilizing unit uses the first capacitor C1;

[0064] In this embodiment, the seven division unit is an FFT7 frequency division circuit composed of seven flip-flops for dividing the clock signal, which reduces the frequency input into the seven division unit to 1 / 128 of the original frequency;

[0065] The FFT7 frequency division circuit includes an input end, a first output end, and a second output end;

[0066] The input end of the FFT7 frequency division circuit is connected to the output end of the oscillator osc;

[0067] As shown in Figure 2 , in this embodiment, the first output end and the second output end of the FFT7 frequency division circuit are both connected to the H-bridge network. Specifically, as shown in Figure 2 , the first output end and the second output end of the FFT7 frequency division circuit are labeled and respectively, and the phases of the two output ends are opposite;

[0068] In this embodiment, a first AND gate circuit, a second AND gate circuit, and a third AND gate circuit are further included; the common input end of the first AND gate circuit, the second AND gate circuit, and the third AND gate circuit is connected to the high-level control signal ELEN output by the power supply unit;

[0069] The output end of the oscillator osc is connected to the first switching element of the charge-discharge module through the first AND gate circuit;

[0070] The first output end of the FFT7 frequency division circuit is connected to the second switching element of the charge-discharge module through the second AND gate circuit, and the second output end of the FFT7 frequency division circuit is connected to the third switching element of the charge-discharge module through the third AND gate circuit;

[0071] The second switching element and the third switching element are connected to the H-bridge network, so that the H-bridge network as a high-voltage switch is triggered according to the energy released by the coil L1, thereby controlling the polarity of the charging of the output unit. As shown in Figure 2 , the first AND gate circuit is controlled by the f COIL signal, the second AND gate circuit and the third AND gate circuit are controlled by the f LAMP signal, and the phases of the second AND gate circuit and the third AND gate circuit are opposite.

[0072] In the embodiment, the first, second and third switch elements are all NPN type triodes, which are respectively the first transistor T1, the second transistor T2 and the third transistor T3, and are used for controlling the coil L1 to discharge, and the models are all MMBT5551 transistors of Macro Orange type;

[0073] The first AND gate circuit is connected with the base of the first transistor T1, and the emitter of the first transistor T1 is grounded;

[0074] The second AND gate circuit is connected with the base of the second transistor T2, and the emitter of the second transistor T2 is grounded;

[0075] The third AND gate circuit is connected with the base of the third transistor T3, and the emitter of the third transistor T3 is grounded.

[0076] In the embodiment, the H-bridge network is composed of the first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2, and is used for changing the direction of the output voltage;

[0077] The output end of the first silicon controlled rectifier SCR1 is connected with the output end of the second silicon controlled rectifier SCR2;

[0078] The input end of the first silicon controlled rectifier SCR1 is connected with the output end of the second transistor T2;

[0079] The input end of the second silicon controlled rectifier SCR2 is connected with the output end of the third transistor T3.

[0080] In the embodiment, the H-bridge network further includes a first protection unit, a second protection unit and a third protection unit;

[0081] The first protection unit is a second diode D2, the negative electrode of the second diode D2 is connected with the common output end of the first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2, and the positive electrode of the second diode D2 is connected with the output end of the first transistor T1 and the output end of the coil L1;

[0082] The second protection unit is a third diode D3, the negative electrode of the third diode D3 is connected with the output end of the second switch element, and the positive electrode of the third diode D3 is connected with the input end of the first silicon controlled rectifier SCR1 and the first interface EL1 of the output unit;

[0083] The third protection unit is a fourth diode D4, the negative electrode of the fourth diode D4 is connected with the output end of the third switch element, and the positive electrode of the fourth diode D4 is connected with the input end of the second silicon controlled rectifier SCR2 and the second interface EL2 of the output unit. The first interface EL1 and the second interface EL2 are both outputs, and are used for driving the electroluminescent lamp ELLamp;

[0084] In this embodiment, the power supply unit further includes, in addition to the first voltage stabilizing unit: a second voltage stabilizing unit;

[0085] The second voltage stabilizing unit is composed of a first diode D1 and a capacitor C INT constitute;

[0086] The anode of the first diode D1 is connected to the output end of the coil L1; the cathode of the first diode D1 is connected to the common output end of the first silicon-controlled rectifier SCR1 and the second silicon-controlled rectifier SCR2;

[0087] The cathode of the first diode D1 and the capacitor C INT In this embodiment, the first capacitor C1, the second capacitor C2 and the capacitor C INT The capacitance values ​​are 100 nF, 10 nF, and 1800 nF respectively.

[0088] In this embodiment, the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are all 1N4148. The voltage output from the system to the electroluminescent lamp is shown in FIG. Figure 4 shown.

[0089] Based on the circuit connection structure of the AC-DC conversion system for driving the cold light panel in the above embodiment, the working principle and working process of this embodiment are further explained:

[0090] Figure 2 The first internal control signal generated by the oscillator osc is f COIL The frequency of the signal is controlled by the feedback resistor Rosc. f COIL The frequency of the signal is 51200 Hz, which illustrates the working process of the drive system. The oscillator osc output frequency is divided by 7 internal flip-flops to generate a second internal control signal of 400 Hz. f LAMP Signal. f COIL Signal and f LAMP The ratio of the signal is equal to 128. Coil L1 is connected to the power supply V BATT Connect the terminal to the power supply unit. According to the formula EL=1 / 2LI P ², energy is stored in coil L1, where I P In a first approximation, it is equal to (t ON )(V BATT - VCE ) / L, t ON is the time required for the coil L1 to reach peak current, V CE is the voltage drop across the internal NPN switching transistor: first transistor T1, L is the inductance of the coil, EL represents the recovered energy. When the internal NPN switching transistor: first transistor T1 switch is off, the energy is forced to pass through an internal diode: first diode D1 or second diode D2, which drives the H-bridge network. Energy recovery is directly related to the brightness of the electroluminescent lamp output. f COIL The signal controls a first transistor T1 that acts as a coil switch, which connects the end of the coil L1 to ground or open circuit. f COIL The signal is a 90% duty cycle signal that switches at a frequency of 51200 Hz generated internally by the oscillator oscC. In f COIL When the signal is high, the coil L1 is connected to the power supply V BATT The end is connected to ground and creates a charged magnetic field in the coil L1. When f COIL The signal is low, the ground connection is switched to open circuit, the magnetic field disappears and the energy in the coil L1 is forced to flow to the H-bridge network that acts as a high voltage switch. f COIL The signal sends a series of charging pulses to the electroluminescent lamp. Each pulse increases the voltage drop across the electroluminescent lamp in discrete steps. When the electroluminescent lamp voltage potential approaches the maximum, the discrete steps become smaller.

[0091] The H-bridge network consists of two silicon controlled rectifier structures, first silicon controlled rectifier SCR1 and second silicon controlled rectifier SCR2, which act as high voltage switches that control the polarity of the charging of the electroluminescent lamp. The two high voltage switches are f LAMP Controlled by the signal, the 7 flip-flops will drive f LAMP = 400 Hz. When the energy in the coil L1 is released, a high voltage spike is generated that will trigger a high voltage switch. The direction of the current is determined by which high voltage switch is enabled. A complete cycle of the H-bridge network will create 128 voltage steps on the first interface EL1 and the second interface EL2 of the electroluminescent lamp from ground to 80V, with adjacent voltage steps 180 degrees out of phase, the output differential representation is as shown in Figure 3 The circuit of this embodiment is simple and low cost, the operating frequency can be directly adjusted by the feedback resistor. Using the principle of inductive energy storage and release, it can be used to redivide with high efficiency.

[0092] Example 2:

[0093] The resistance value of the feedback resistor Rosc is changed to 500kΩ based on Example 1;

[0094] The inductance of the coil L1 is 470 µH, the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are all selected as 1N4148, the capacitance values of the first capacitor C1, the second capacitor C2 and the capacitor C INT are respectively selected as 100 nF, 10nF and 1800 nF. The first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2 are selected as MCR100-8 silicon controlled rectifiers of Huaxianyang Electronics. The first transistor T1, the second transistor T2 and the third transistor T3 are selected as MMBT5551 transistors of Hongga Orange. The circuit output is shown in Figure 5 .

[0095] Obviously, the above examples are only examples for clearly illustrating, but not limit the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. An AC-DC conversion system for driving a cold light panel, characterized in that: The power supply unit, the clock unit, the seven frequency division unit, the impulse discharge module, the H bridge network and the output unit are connected in series. The input end of the H bridge network for generating high-voltage sine wave signal is connected with the seven frequency division unit, and the output end of the H bridge network is connected with the output unit. The power supply unit for supplying power to the whole system is connected with the clock unit, the seven frequency division unit and the charge-discharge module respectively; and the clock unit, the seven frequency division unit and the charge-discharge module are connected in sequence, so that the clock unit uses a clock signal provided by an oscillator osc, and the clock signal is divided into two control signals: f COIL signal and f LAMP signal, wherein f COIL is used for controlling the charge-discharge module, f LAMP is used for controlling the H bridge network; The output end of the impulse discharge module for generating charging magnetic field and releasing energy is connected with the output unit. The clock unit is composed of an oscillator osc and an RC feedback network, specifically:

2. The AC-DC conversion system for driving a cold light panel according to claim 1, wherein The RC feedback network is composed of a second capacitor C2 and a feedback resistor Rosc for adjusting the time frequency of the oscillator osc. One end of the feedback resistor Rosc is connected with the second capacitor C2 and grounded. The seven frequency division unit is a FFT7 frequency division circuit composed of seven flip-flops for frequency division of the clock signal. In addition, the other end of the feedback resistor Rosc is connected to a first voltage stabilizing unit for stabilizing voltage in the power supply unit and then grounded, and the other end of the feedback resistor Rosc is connected to the power supply V BATT end.

3. The AC-DC conversion system for driving a cold light panel according to claim 2, wherein The FFT7 frequency division circuit includes an input end, a first output end and a second output end. The input end of the FFT7 frequency division circuit is connected with the output end of the oscillator osc. The first output end and the second output end of the FFT7 frequency division circuit are both connected with the H bridge network. The first AND gate circuit, the second AND gate circuit and the third AND gate circuit are also included, and the common input end of the first AND gate circuit, the second AND gate circuit and the third AND gate circuit is connected with the high-level control signal ELEN output by the power supply unit.

4. The AC-DC conversion system for driving a cold light panel according to claim 3, wherein The output end of the oscillator osc is connected with the first switching element of the impulse discharge module through the first AND gate circuit. The first output end of the FFT7 frequency division circuit is connected with the second switching element of the impulse discharge module through the second AND gate circuit, and the second output end of the FFT7 frequency division circuit is connected with the third switching element of the impulse discharge module through the third AND gate circuit. The second switching element and the third switching element are connected with the H bridge network, so that the H bridge network as a high-voltage switch is triggered according to the energy released by the coil L1, thereby controlling the polarity of the charging of the output unit. The first switching element, the second switching element and the third switching element are all NPN type transistors, which are respectively the first transistor T1, the second transistor T2 and the third transistor T3.

5. The AC-DC conversion system for driving a cold light panel according to claim 4, wherein The first AND gate circuit is connected with the base of the first transistor T1, and the emitter of the first transistor T1 is grounded. The second AND gate circuit is connected with the base of the second transistor T2, and the emitter of the second transistor T2 is grounded. The third AND gate circuit is connected with the base of the first transistor T3, and the emitter of the first transistor T3 is grounded. The H bridge network is composed of a first silicon controlled rectifier SCR1 and a second silicon controlled rectifier SCR2.

6. The AC-DC conversion system for driving a cold light panel according to claim 5, wherein The output end of the first silicon controlled rectifier SCR1 and the output end of the second silicon controlled rectifier SCR2 are connected. The input end of the first silicon controlled rectifier SCR1 is connected with the output end of the second transistor T2. The input end of the second silicon controlled rectifier SCR2 is connected with the output end of the third transistor T3. The H bridge network also includes a first protection unit, a second protection unit and a third protection unit.

7. The AC-DC conversion system for driving a cold light panel according to claim 6, wherein The first protection unit adopts a second diode D2, the negative electrode of the second diode D2 is connected with the common output end of the first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2, and the positive electrode of the second diode D2 is connected with the output end of the first transistor T1 and the output end of the coil L1. ​ The second protection unit adopts a third diode D3, a negative electrode of the third diode D3 is connected with an output end of the second switch element; a positive electrode of the third diode D3 is connected with an input end of the first silicon controlled rectifier SCR1 and a first interface EL1 of the output unit; The third protection unit adopts a fourth diode D4, a negative electrode of the fourth diode D4 is connected with an output end of the third switch element; a positive electrode of the fourth diode D4 is connected with an input end of the second silicon controlled rectifier SCR2 and a second interface EL2 of the output unit.

8. The AC-DC conversion system for driving a cold light panel according to claim 7, wherein The power supply unit further comprises a second voltage stabilizing unit in addition to the first voltage stabilizing unit; The second voltage stabilizing unit is composed of a first diode D1 and a capacitor C INT constituted; A positive electrode of the first diode D1 is connected with an output end of the coil L1; a negative electrode of the first diode D1 is connected with common output ends of the first silicon controlled rectifier SCR1 and the second silicon controlled rectifier SCR2; The negative pole of the first diode D1 and the capacitor C INT Connect the ground after.

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