Silicon controlled rectifier dimming circuit and lighting system

Abstract

The invention discloses a silicon controlled rectifier dimming circuit, alternating current input obtains input voltage through a silicon controlled rectifier dimmer and a rectifying circuit, and the silicon controlled rectifier dimming circuit comprises a bleeder circuit, a first current control circuit, an energy storage capacitor, a second current control circuit and a discharge diode; two ends of the bleeder circuit are respectively connected with high and low potential ends of an input voltage, and the first current control circuit is connected with the high and low potential ends of the input voltage after being connected in series with the LED load to form a first series circuit; the energy storage capacitor is connected in series with the LED load; the second current control circuit is connected with the LED load and the energy storage capacitor in series to form a second series circuit and then is connected with the high-low potential end of the input voltage. The positive electrode of the discharge diode is connected with the positive electrode of the energy storage capacitor, and the negative electrode is connected with the positive electrode of the LED load. According to the invention, the bleeder time of the bleeder circuit is reduced, the loss of the bleeder circuit is reduced, the effective range of the input current is widened, and a larger bleeder current can be set on the basis of reducing the bleeder time so as to improve the compatibility of a lighting system.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a thyristor dimming circuit and a lighting system. Background Art

[0002] Existing linear thyristor (TRIAC) dimming circuits such as Figure 1 As shown, the thyristor dimmer includes a bleeder circuit, a bleeder control circuit, a load switch, and a load current control circuit for driving the load switch. The thyristor dimmer is connected to the AC input. The AC input is rectified by a bridge rectifier to produce a rectified input voltage. The bleeder circuit is connected between the high and low potentials of the input voltage. Load current is only reflected from the input when the input voltage exceeds the load's forward voltage drop. Therefore, when the dimming angle is large, the bleeder circuit needs to operate for a longer time, approximately 1.5 milliseconds, and the bleeder loss is still significant.

[0003] For example, when the AC input is 230V and the input voltage is 260V, the thyristor dimmer's power loss exceeds 1W when the holding current is maintained at 30mA and the dimming angle is set to a maximum of 150°. Furthermore, for some thyristor dimmers with higher holding currents, the bleeder loss can be even greater, exceeding 1.5W. High bleeder losses place higher demands on the heat dissipation of the chip or system, leading to poor compatibility of the thyristor dimmer. Summary of the Invention

[0004] In order to address the deficiencies of the prior art, the purpose of this application is to provide a thyristor dimming circuit and lighting system that can reduce the loss of the discharge circuit, so as to solve the problem of poor compatibility of thyristor dimmers caused by the large loss of the discharge circuit in the prior art, so as to improve compatibility.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a thyristor dimming circuit, which includes: a thyristor dimmer and a rectifier circuit, wherein an AC input is passed through the thyristor dimmer and the rectifier circuit to obtain an input voltage, and the thyristor dimming circuit further includes:

[0007] A discharge circuit, wherein both ends of the discharge circuit are connected to the high potential end and the low potential end of the input voltage respectively;

[0008] A first current control circuit is connected in series with the LED load to form a first series circuit, which is then connected to the high and low potential ends of the input voltage, and the input voltage supplies power to the LED load through the first series circuit;

[0009] Energy storage capacitor, connected in series with the LED load;

[0010] A second current control circuit is connected in series with the LED load and the energy storage capacitor to form a second series circuit, which is then connected to the high and low potential ends of the input voltage. The input voltage is used to simultaneously power the LED load and the energy storage capacitor through the second series circuit.

[0011] Discharge diode: the positive electrode of the discharge diode is connected to the positive electrode of the energy storage capacitor, and the negative electrode is connected to the positive electrode of the LED load. The energy storage capacitor supplies power to the LED load through the discharge diode.

[0012] Furthermore, the conduction voltage drop of the LED load is close to half of the peak value of the input voltage, which reduces the operating time of the discharge circuit.

[0013] Furthermore, the first current control circuit includes a first switching tube and a first control unit. The first end of the first switching tube is connected to the LED load, the second end is connected to the low potential, and the control end is connected to the first control unit. When the input voltage is less than the sum of the conduction voltage drop of the LED load and the voltage of the energy storage capacitor, the first control unit controls the first switching tube to turn on.

[0014] Furthermore, the second current control circuit includes a second switching tube and a second control unit, the first end of the second switching tube is connected to the energy storage capacitor, the second end is connected to the low potential, and the control end is connected to the second control unit. When the input voltage is greater than or equal to the sum of the conduction voltage drop of the LED load and the voltage of the energy storage capacitor, the second control unit controls the second switching tube to turn on.

[0015] Furthermore, the first control unit includes a first operational amplifier, the output end of the first operational amplifier is connected to the control end of the first switching tube, the reverse input end of the first operational amplifier receives a voltage sampling signal, and the positive input end of the first operational amplifier receives a first voltage reference signal, wherein the voltage sampling signal represents the load current, and the first voltage reference signal represents the load current when the input voltage is simultaneously powered by the LED load and the energy storage capacitor.

[0016] Furthermore, the second control circuit includes a second operational amplifier, the output end of the second operational amplifier is connected to the control end of the second switching tube, the reverse input end of the second operational amplifier receives a voltage sampling signal, the positive input end of the second operational amplifier receives a second voltage reference signal, the voltage sampling signal represents the load current, the second voltage reference signal is greater than the first voltage reference signal, and the first voltage reference signal represents the load current when the input voltage is simultaneously powered by the LED load and the energy storage capacitor.

[0017] Furthermore, the thyristor dimming circuit also includes a sampling resistor, one end of the sampling resistor is connected to the common end of the first current control circuit and the second current control circuit, and the other end is connected to the reference ground, and the voltage of the sampling resistor is the voltage sampling signal.

[0018] Furthermore, the first current control circuit and the second current control circuit are integrated on a chip, and the thyristor dimming circuit also includes a second diode and a third diode. The second diode is connected in series between the energy storage capacitor and the second switching tube, and the positive pole of the second diode is connected to the negative pole of the energy storage capacitor. The positive pole of the third diode is grounded and the negative pole is connected to the negative pole of the energy storage capacitor.

[0019] Furthermore, the thyristor dimming circuit further includes a fourth diode, which is connected in series between the LED load and the energy storage capacitor, and the cathode of the fourth diode is connected to the anode of the energy storage capacitor.

[0020] In a second aspect, the present application further provides a lighting system, which includes any one of the thyristor dimming circuits in the first aspect.

[0021] Compared with the prior art, the technical solution of the present invention has the following advantages: Based on the existing thyristor dimming circuit, the present invention adds an energy storage capacitor in series with the load, and designs corresponding paths to realize the input voltage to power the load alone, the input voltage to power the load and the energy storage capacitor simultaneously, or the energy storage capacitor to power the load. As a result, the on-state voltage drop of the load in the circuit is reduced by nearly half, thereby increasing the effective range of the input current, shortening the operating time of the bleeder circuit, and thus reducing the power consumption of the bleeder circuit. In addition, it allows the configuration of a bleeder circuit with a higher bleeder current, thereby improving the compatibility of the thyristor dimming circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a circuit block diagram of a thyristor dimming circuit in the prior art;

[0023] Figure 2 This is a structural block diagram of the thyristor dimming circuit proposed in this application;

[0024] Figure 3 This is a further refined structural block diagram of the thyristor dimming circuit proposed in this application;

[0025] Figure 4 This is a timing diagram of input voltage and input current in an embodiment of the present application;

[0026] Figure 5 A timing diagram of enabling the discharge circuit in the prior art;

[0027] Figure 6 This is a timing diagram of enabling the discharge circuit in an embodiment of the present application;

[0028] Figure 7 This is a specific circuit diagram of the thyristor dimming circuit in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the specific implementation of the present application will be clearly and completely described below in conjunction with the drawings in the implementation of the present application.

[0030] The following paragraphs describe the present application in more detail by way of example with reference to the accompanying drawings. It should be noted that the drawings are simplified and not to exact proportions, and are only used for the purpose of conveniently and clearly explaining the embodiments of the present application.

[0031] like Figure 2 As shown, the present application provides a thyristor dimming circuit for use in lighting systems. The thyristor dimming circuit includes a thyristor dimmer (TRIAC) and a rectifier circuit. The thyristor dimmer (TRIAC) is connected in series between an AC input (AC) and the rectifier circuit. The AC input (AC) is fed through the thyristor dimmer (TRIAC) and the rectifier circuit to generate an input voltage (Vin) for driving an LED load.

[0032] As an implementation method, the thyristor dimming circuit includes:

[0033] The discharge circuit has two ends connected to the high and low potential ends of the input voltage Vin, respectively. The discharge circuit is used to generate a discharge current to keep the thyristor dimmer TRIAC in the on state.

[0034] Exemplarily, when the input current Iin is lower than the holding current of the TRIAC, the bleeder circuit generates a bleeder current to maintain the TRIAC in the on state.

[0035] It should be noted that the thyristor dimmer TRIAC is equivalent to a switch, and when the input current Iin is greater than or equal to the holding current of the thyristor dimmer TRIAC, the thyristor dimmer TRIAC remains in the on state, and when the input current Iin is less than the holding current of the thyristor dimmer TRIAC, the thyristor dimmer TRIAC is turned off.

[0036] The first current control circuit is connected in series with the LED load to form a first series circuit. The first series circuit connects the high and low potential ends of the input voltage Vin. The input voltage Vin supplies power to the LED load through the first series circuit.

[0037] Energy storage capacitor, energy storage capacitor is connected in series with LED load;

[0038] The second current control circuit is connected in series with the LED load and the energy storage capacitor to form a second series circuit. The second series circuit is connected to the high and low potential ends of the input voltage Vin. The input voltage Vin supplies power to the load and charges the energy storage capacitor through the second series circuit.

[0039] The discharge diode D1 has its anode connected to the anode of the energy storage capacitor and its cathode connected to the anode of the LED load. The energy storage capacitor supplies power to the LED load through the discharge diode D1.

[0040] Specifically, such as Figure 3 As shown, the first current control circuit includes a first switching transistor and a first control unit. The first switching transistor has a first terminal connected to an LED load, a second terminal connected to a low potential, and a control terminal connected to the first control unit. When the input voltage is lower than the sum of the forward voltage drop of the LED load and the voltage of the energy storage capacitor, the first control unit controls the first switching transistor to conduct. The second current control circuit includes a second switching transistor and a second control unit. The second switching transistor has a first terminal connected to the energy storage capacitor, a second terminal connected to a low potential, and a control terminal connected to the second control unit. When the input voltage is greater than or equal to the sum of the forward voltage drop of the LED and the voltage of the energy storage capacitor, the second control unit controls the second switching transistor to conduct. A fourth diode D4 is also connected in series between the LED load and the energy storage capacitor, with the cathode of the fourth diode D4 connected to the anode of the energy storage capacitor to prevent the energy storage capacitor from discharging when the input voltage is supplied to the load through the first switching transistor. The forward voltage drop of the LED load is close to half of the peak input voltage, and the sum of the forward voltage drop of the LED load and the rated voltage of the energy storage capacitor is close to the peak input voltage. To ensure that the energy storage capacitor can supply power to the LED load, the rated voltage of the energy storage capacitor is greater than the forward voltage drop of the LED load.

[0041] In order to clearly illustrate the technical solution of the embodiment of the present application, the following is also provided: Figure 4 The timing diagram of the input voltage Vin / input current Iin changes is shown in FIG. Figure 4 The horizontal axis represents time T. In one cycle, the time is divided into t1, t2, t3, t4, and t5 according to the change of the input voltage Vin. The vertical axis represents the input voltage Vin / input current Iin.

[0042] In the dimming state, during time period t1, the TRIAC dimmer is off (V1 represents the trigger voltage that turns on the TRIAC dimmer). The voltage across the energy storage capacitor (VC) is greater than the forward voltage drop (VF) of the LED load. At this point, the discharge diode D1 is on, and the first switch is on. The energy storage capacitor provides power to the LED load, and the input current Iin is zero. During time period t2, the TRIAC dimmer is on, and the input voltage Vin is greater than or equal to the forward voltage drop (VF) of the LED load. At this point, the first switch is on, and the input voltage Vin supplies power to the LED load, with the input current Iin reaching I1. During time period t3, the input voltage Vin continues to rise, and becomes greater than or equal to the sum of the forward voltage drop (VF) of the LED load and the voltage across the energy storage capacitor (VC). At this point, the first switch is off, and the second switch is on. The input voltage Vin supplies power to both the LED load and the energy storage capacitor, and the input current Iin reaches I2. During time period t4, the input voltage Vin decreases and becomes less than the sum of the conduction voltage drop VF of the LED load and the voltage VC of the energy storage capacitor. At this point, the first switch is turned on and the second switch is turned off. The input voltage Vin supplies power to the LED load, and the input current Iin is I1. During time period t5, the input voltage Vin decreases below the load voltage VF. At this point, the discharge diode D1 and the first switch are turned on, the energy storage capacitor provides power to the LED load, and the input current Iin is zero.

[0043] In existing thyristor dimming circuits, LED loads with large on-state voltage drops are generally selected, and the selected LED load's on-state voltage drop is close to the peak value of the input voltage Vin. For example, when the input voltage Vin is 170V, the LED load's on-state voltage drop is 130V to 140V, thereby ensuring load efficiency. However, when the LED load's on-state voltage drop is large, the effective range of the input current Iin is narrowed, the bleeder circuit's operating time is prolonged, and the discharge loss is high. Compared to existing thyristor dimming circuits, the present application designs a series connection between an energy storage capacitor and the LED load. Based on changes in the input voltage, the input voltage is controlled to power the LED load alone, the input voltage to power both the LED load and the energy storage capacitor simultaneously, or the energy storage capacitor to power the LED load alone. This reduces the on-state voltage drop of the LED load in the present application by half. For example, when the input voltage Vin is 170V, the load voltage is 70V. This widens the effective range of the input current Iin, reduces the operating time of the bleeder circuit, and reduces discharge loss.

[0044] Specifically, assuming that the conduction angle and holding current of the thyristor dimmer are the same, and the input voltage Vin is the same, take any one cycle as an example, such as Figure 5As shown in the figure, in the prior art, the TRIAC dimmer is turned on at time T0, but the input voltage Vin is less than the conduction voltage drop VF of the LED load. Then the bleeder circuit needs to work from time T0 to time T1, when the LED load is turned on and the input current Iin is generated. Figure 6 As shown, in this application, the TRIAC dimmer is turned on at the same time T0, but the input voltage Vin is less than the forward voltage drop VF' of the LED load at this time. Therefore, the bleeder circuit needs to start operating at time T0. However, compared with the prior art, the forward voltage drop VF' of the LED load in this application is reduced by half. Therefore, the turn-on time T1 of the LED load in this application is significantly advanced. As a result, the operating time of the bleeder circuit in this application is significantly reduced, the bleeder loss is effectively reduced, and the effective range of the input current is widened.

[0045] It should be noted that Figure 6 This is only to show that compared with the prior art, this application can reduce the working time of the discharge circuit, reduce the discharge loss, and widen the effective range of the input current. It does not mean that in the dimming state, the working time of the discharge circuit must be greater than zero in the present application. For example, taking the AC input AC of 230V, the DC input voltage Vin of 140V, and the dimming angle of 150° as an example, the working time of the discharge circuit in the present application is 0ms (see Figure 4 Specifically, the operating time T0 of the discharge current satisfies the following relationship:

[0046] T0=(150 / 180*10mS-(10mS-arcsin(140 / 230 / sqrt(2)) / 180*10mS)=-0.3ms);

[0047] As can be seen, in the solution of this application, in the dimming state, the operating time of the bleeder circuit is greatly reduced and can be reduced to zero, greatly reducing useless bleeder losses and improving system efficiency. In special circumstances, a larger bleeder current can be set to improve system compatibility. In addition, due to the presence of the energy storage capacitor, when the input voltage Vin is lower than the voltage of the energy storage capacitor, the energy storage capacitor can continue to provide current, ensuring that the load current ILED flowing through the load has a small current ripple throughout the entire power frequency cycle.

[0048] like Figure 7As shown, as an implementation, the first control unit includes a first operational amplifier U1, the non-inverting input terminal of the first operational amplifier U1 receiving a first voltage reference signal Vref1, the inverting input terminal of the first operational amplifier U1 receiving a voltage sampling signal, and the output terminal of the first operational amplifier U1 being connected to the control terminal of the first switching transistor M1. The first voltage reference signal Vref1 represents the LED load current when the input voltage is simultaneously powered by the LED load and the energy storage capacitor, and the voltage sampling signal represents the LED load current. The second control unit includes a second operational amplifier U2, the non-inverting input terminal of the second operational amplifier U2 receiving a second voltage reference signal, the inverting input terminal of the second operational amplifier U2 receiving the voltage sampling signal, and the output terminal of the second operational amplifier U2 being connected to the control terminal of the second switching transistor M2. The second voltage reference signal is slightly greater than the first voltage reference signal, for example, the difference between the two is between 15mV and 50mV.

[0049] When the voltage sampling signal is less than the first voltage reference signal Vref1, the output of the first operational amplifier U1 outputs a positive voltage, and a certain voltage drop exists between the drain and source of the first switch M1, turning on the first switch M1. When the voltage sampling signal is greater than the first voltage reference signal Vref1, the output of the first operational amplifier U1 outputs a negative voltage, and the first switch M1 turns off. This controls the operating state of the first switch M1 based on changes in the input voltage Vin. When the voltage sampling signal is less than the second voltage reference signal Vref2, the output of the second operational amplifier U2 outputs a positive voltage, and a certain voltage drop exists between the drain and source of the second switch M2 (a voltage drop exists between the drain and source of the second switch M2 when the voltage sampling signal is greater than the first voltage reference signal), the second switch M2 turns on. When the voltage sampling signal is greater than the second voltage reference signal Vref2, the output of the second operational amplifier U2 outputs a negative voltage, and the second switch M2 turns off.

[0050] In the above embodiment, the first switch tube and the second switch tube are MOS tubes as an example, but are not limited to MOS tubes. Other types of switch tubes such as BJT may also be used.

[0051] As an implementation method, the thyristor dimming circuit also includes a sampling resistor Rcs, one end of the sampling resistor Rcs is connected to the second end of the first switch tube M1 and the second switch tube M2, and the other end is connected to the reference ground, and the inverting input ends of the first operational amplifier U1 and the second operational amplifier U2 are connected to the sampling resistor Rcs to obtain a voltage sampling signal.

[0052] Furthermore, the first current control circuit and the second current control circuit are integrated on a chip. In order to avoid the generation of negative current in the chip when the energy storage capacitor supplies power to the LED load (the current in the loop returns from the body diode of the second switch tube M2 to the energy storage capacitor), the thyristor dimming circuit also includes a second diode D2 and a third diode D3. The positive pole of the second diode D2 is connected to the negative pole of the energy storage capacitor, and the negative pole is connected to the second switch tube M2. The positive pole of the third diode D3 is connected to the reference ground, and the negative pole is connected to the negative pole of the energy storage capacitor.

[0053] As an implementation, the thyristor dimming circuit includes a dimming state and a non-dimming state. In the dimming state, when the input current is lower than the holding current of the thyristor dimmer TRIAC, the bleeder circuit is enabled to generate a bleeder current, so that the input current Iin is higher than the holding current of the thyristor dimmer TRIAC. In the non-dimming state, the bleeder circuit is disabled.

[0054] Specifically, the thyristor dimming circuit also includes a discharge control circuit, which is connected to the discharge circuit. The discharge control circuit compares the input current Iin with the holding current of the thyristor dimmer TRIAC. When the input current Iin is lower than the holding current of the thyristor dimmer TRIAC, the discharge control circuit controls the discharge circuit to generate a discharge current.

[0055] It should be noted that the input voltage Vin may vary across regions, or the device standards used may differ. Consequently, the holding current of a TRIAC dimmer may vary. A higher holding current in a TRIAC dimmer facilitates compatibility with dimming circuits in different regions. In the examples of this application, a TRIAC dimmer circuit with a shorter discharge time is configured to allow the configuration of a bleeder circuit with a higher discharge current, thereby improving the compatibility of the TRIAC dimmer circuit.

[0056] It's important to note that the forward voltage drop across the LED load in a thyristor dimming circuit is close to half the peak input voltage. Specifically, this voltage drop can be quantified as fluctuating around a certain percentage of half the peak input voltage. For example, with a 230V AC input, the forward voltage drop range is: half the peak input voltage * 80% to half the peak input voltage * 85%. For other inputs, the percentage setting may vary and is not a specific limitation.

[0057] In summary, the thyristor dimming circuit of the present invention, by providing an energy storage capacitor, a second current control circuit for controlling the charging and discharging of the energy storage capacitor, and a discharge diode D1, is compatible with loads having a smaller conduction voltage drop, thereby increasing the effective range of input current, shortening the operating time of the bleeder circuit, and thus reducing the power consumption of the bleeder circuit. Furthermore, it allows the provision of a bleeder circuit with a higher bleeder current, thereby improving the compatibility of the thyristor dimming circuit.

[0058] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the claims appended to this application.

Claims

1. A thyristor dimming circuit, comprising: The thyristor dimmer and the rectifier circuit, the AC input is passed through the thyristor dimmer and the rectifier circuit to obtain the input voltage, characterized in that the thyristor dimming circuit also includes: A discharge circuit, wherein two ends of the discharge circuit are respectively connected to the high potential end and the low potential end of the input voltage; A first current control circuit is connected in series with the LED load to form a first series circuit, and then connected to the high and low potential ends of the input voltage, and the input voltage supplies power to the LED load through the first series circuit; An energy storage capacitor is connected in series with the LED load; A second current control circuit is connected in series with the LED load and the energy storage capacitor to form a second series circuit, and then connected to the high and low potential ends of the input voltage, and the input voltage supplies power to the LED load and the energy storage capacitor simultaneously through the second series circuit; A discharge diode, wherein the positive electrode of the discharge diode is connected to the positive electrode of the energy storage capacitor and the negative electrode is connected to the positive electrode of the LED load, and the energy storage capacitor supplies power to the LED load through the discharge diode.

2. The thyristor dimming circuit according to claim 1, characterized in that: The conduction voltage drop of the LED load is close to half of the peak value of the input voltage, so that the working time of the discharge circuit is reduced.

3. The thyristor dimming circuit according to claim 1, characterized in that: The first current control circuit includes a first switch tube and a first control unit, wherein the first end of the first switch tube is connected to the LED load, the second end is connected to a low potential, and the control end is connected to the first control unit. When the input voltage is less than the sum of the conduction voltage drop of the LED load and the voltage of the energy storage capacitor, the first control unit controls the first switch tube to turn on.

4. The thyristor dimming circuit according to claim 1, characterized in that: The second current control circuit includes a second switch tube and a second control unit, wherein the first end of the second switch tube is connected to the energy storage capacitor, the second end is connected to the low potential, and the control end is connected to the second control unit, and when the input voltage is greater than or equal to the sum of the conduction voltage drop of the LED load and the voltage of the energy storage capacitor, the second control unit controls the second switch tube to turn on.

5. The thyristor dimming circuit according to claim 3, characterized in that: The first control unit includes a first operational amplifier, the output end of the first operational amplifier is connected to the control end of the first switch tube, the reverse input end of the first operational amplifier receives a voltage sampling signal, and the forward input end of the first operational amplifier receives a first voltage reference signal, wherein the voltage sampling signal represents the load current, and the first voltage reference signal represents the load current when the input voltage is used to power the LED load and the energy storage capacitor at the same time.

6. The thyristor dimming circuit according to claim 4, characterized in that: The second control circuit includes a second operational amplifier, the output end of the second operational amplifier is connected to the control end of the second switch tube, the reverse input end of the second operational amplifier receives a voltage sampling signal, the forward input end of the second operational amplifier receives a second voltage reference signal, the voltage sampling signal represents the load current, the second voltage reference signal is greater than the first voltage reference signal, and the first voltage reference signal represents the load current when the input voltage is used to power the LED load and the energy storage capacitor at the same time.

7. The thyristor dimming circuit according to claim 5 or 6, characterized in that: The thyristor dimming circuit also includes a sampling resistor, one end of which is connected to a common end of the first current control circuit and the second current control circuit, and the other end is connected to a reference ground, and the voltage of the sampling resistor is the voltage sampling signal.

8. The thyristor dimming circuit according to claim 4, characterized in that: The first current control circuit and the second current control circuit are integrated on a chip, and the thyristor dimming circuit also includes a second diode and a third diode. The second diode is connected in series between the energy storage capacitor and the second switch tube, and the positive electrode of the second diode is connected to the negative electrode of the energy storage capacitor. The positive electrode of the third diode is grounded and the negative electrode is connected to the negative electrode of the energy storage capacitor.

9. The thyristor dimming circuit according to claim 1, characterized in that: The thyristor dimming circuit further includes a fourth diode, which is connected in series between the LED load and the energy storage capacitor, and a cathode of the fourth diode is connected to a cathode of the energy storage capacitor.

10. A lighting system, characterized in that: The invention comprises the thyristor dimming circuit according to any one of claims 1 to 9.

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