Silicon controlled rectifier dimming circuit and control method

Abstract

The invention provides a silicon controlled rectifier dimming circuit and a control method, and the circuit comprises a bleeder circuit which is connected between a high-potential end and a low-potential end of an input voltage and is used for generating a bleeder current to enable a silicon controlled rectifier dimmer to maintain conduction; the LED load and the first capacitor are connected in series and are connected between the high-potential end and the low-potential end of the input voltage, the input voltage can supply power to the LED load, or the input voltage can supply power to the LED load and the first capacitor at the same time, or the first capacitor can supply power to the LED load; the control method comprises the following steps: in a dimming state, in each period of the input voltage, reducing the total time length of the input voltage for supplying power to the LED load, and controlling the instantaneous value of the input current and the total time length of the input voltage for supplying power to the LED load to be in a negative correlation relationship. According to the invention, in the dimming state, in each period of the input voltage, the power supply duration of the input voltage is reduced, and the instantaneous value of the input current is increased, so that the magnitude of the discharge current and the output duration are reduced, and the discharge loss is reduced.

Description

Technical Field

[0001] The invention belongs to the field of lighting dimming, and in particular relates to a thyristor dimming circuit and a control method. Background Art

[0002] At present, there are patents in the prior art that propose Figure 1 In the thyristor dimming circuit shown, the LED load and the first capacitor C1 are connected in series. When the input voltage is greater than or equal to the sum of the conduction voltage drop VF of the LED load and the voltage VC1 of the first capacitor, the LED load and the first capacitor C1 are powered simultaneously. When the input voltage is lower than the conduction voltage drop of the LED load, the energy stored in the first capacitor C1 is used to power the LED load. Compared with the traditional thyristor dimming circuit without the first capacitor C1, the thyristor dimming circuit reduces the conduction voltage drop of the LED load by nearly half, and the LED load can work normally when the input voltage is low, thereby widening the effective range of the input current and reducing the discharge loss of the discharge circuit.

[0003] In practical applications, the output power of LED loads is generally reduced to achieve energy saving and environmental protection. Figure 1 When the thyristor dimming circuit shown is used in an environment where the LED load output power is low, the input current and the holding current of the thyristor dimmer differ greatly (the input current is less than the holding current), resulting in large discharge losses. Specifically, Figure 2 As shown, during T2, T3 and T4, since the input current is less than the holding current, the discharge circuit needs to generate a discharge current to compensate for the actual input current to maintain the conduction of the thyristor dimmer. The shaded portion is the discharge current that the discharge circuit needs to generate in each cycle of the input voltage.

[0004] In applications where LED loads have low power output, how to reduce discharge losses is an issue that needs to be addressed urgently. Summary of the invention

[0005] To reduce Figure 1 To solve the technical problem of the discharge loss of the thyristor dimming circuit, the present invention provides a thyristor dimming circuit and a control method.

[0006] Wherein, the thyristor dimming circuit comprises:

[0007] The discharge circuit is connected between the high and low potential ends of the input voltage and is used to generate a discharge current to keep the thyristor dimmer turned on;

[0008] The LED load and the first capacitor connected in series are connected between the high and low potential ends of the input voltage, the input voltage can power the LED load, or the input voltage can power the LED load and the first capacitor at the same time, or the first capacitor can power the LED load,

[0009] The control method comprises:

[0010] In the dimming state, in each cycle of the input voltage, the total time duration for which the input voltage supplies power to the LED load is reduced, and the instantaneous value of the input current is controlled to be negatively correlated with the total time duration for which the input voltage supplies power to the LED load.

[0011] Furthermore, the total duration of the input voltage supplying power to the LED load is controlled to be a preset duration, and the instantaneous value of the input current is adjusted.

[0012] Furthermore, the total duration of stopping power supply after the input voltage supplies power to the LED load is controlled to be a preset duration, and the instantaneous value of the input current is adjusted.

[0013] Furthermore, the instantaneous value of the input current is controlled to be a preset current, and the total time duration for which the input voltage supplies power to the LED load is adjusted.

[0014] Further, a one-to-one correspondence is established between the total duration of the input voltage supplying power to the LED load and the instantaneous value of the input current, and the total duration of the input voltage supplying power to the LED load in the current cycle is controlled to be the preset duration, and the instantaneous value of the input current is controlled to be the corresponding value of the preset duration;

[0015] Or, in the current cycle, the total duration of the input voltage supplying power to the LED load is controlled to be the preset duration, and the instantaneous value of the input current is adjusted according to the difference between the sampling signal and the reference signal, and the sampling signal represents the instantaneous value of the input current.

[0016] Further, a one-to-one correspondence is established between the total time that the input voltage stops supplying power to the LED load and the instantaneous value of the input current. In the current cycle, the total time that the input voltage stops supplying power to the LED load is controlled according to the total time that the input voltage stops supplying power to the LED load in the previous cycle and the preset time, and the instantaneous value of the input current is controlled to be a value corresponding to the preset time;

[0017] Or, in the current cycle, the total duration of the input voltage stopping powering the LED load is adjusted according to the total duration of the input voltage stopping powering the LED load in the previous cycle and the preset duration, and the instantaneous value of the input current is adjusted according to the difference between the sampling signal and the reference signal, and the sampling signal represents the instantaneous value of the input current.

[0018] Further, a one-to-one correspondence between the instantaneous value of the input current and the total duration of the input voltage supplying power to the LED load is established, the instantaneous value of the input current is controlled to be the preset current in the current cycle, and the total duration of the input voltage supplying power to the LED load is controlled to be the corresponding value of the preset current;

[0019] Or, in the current cycle, the instantaneous value of the input current is controlled to be the preset current, and the total time the input voltage supplies power to the LED load is adjusted according to the difference between the timing signal and the reference signal, and the timing signal represents the time the input voltage supplies power to the LED load.

[0020] Furthermore, in each cycle, when the input voltage rises to the on-state voltage drop of the LED load, the input voltage starts to power the LED load, and when the duration for which the input voltage simultaneously powers the LED load and the first capacitor reaches a first duration, the input voltage stops powering the LED load until the end of the cycle.

[0021] Furthermore, in each cycle, when the input voltage rises to the conduction voltage drop of the LED load, the input voltage starts to power the LED load, and when the duration for which the input voltage only powers the LED load reaches a first duration, the input voltage stops powering the LED load until the end of the cycle.

[0022] A silicon controlled dimming circuit, comprising:

[0023] A discharge circuit, when the input current is less than the holding current of the thyristor dimmer, generates a discharge current to keep the thyristor dimmer turned on;

[0024] The LED load and the first capacitor are connected in series and connected between the high and low potential ends of the input voltage;

[0025] A first switch tube, a first end of which is connected to the LED load, a second end of which is connected to a low potential, and an input voltage supplies power to the LED load through the first switch tube;

[0026] A second switch tube, a first end of which is connected to the first capacitor, a second end of which is connected to a low potential, and an input voltage is used to supply power to the LED load and the first capacitor through the second switch tube;

[0027] a discharge diode, wherein the positive electrode is connected to the positive electrode of the first capacitor, and the negative electrode is connected to the positive electrode of the LED load, and the first capacitor supplies power to the LED load through the discharge diode;

[0028] The control circuit, in dimming state, uses the control method described above.

[0029] Furthermore, the control circuit comprises:

[0030] A first operational amplifier, wherein an output end of the first operational amplifier is connected to a control end of a first switch tube;

[0031] A second operational amplifier, wherein the output end of the second operational amplifier is connected to the control end of the second switch tube;

[0032] The enabling circuit is connected to the enabling terminals of the first operational amplifier and the second operational amplifier, and the enabling circuit generates an invalid enabling signal to stop the first operational amplifier and the second operational amplifier from working, so as to reduce the total time length for the input voltage to supply power to the LED load.

[0033] Furthermore, it also includes a sampling resistor, the resistance of which is adjustable, and the instantaneous value of the input current can be adjusted by adjusting the value of the sampling resistor.

[0034] Furthermore, the method further includes a second capacitor, which is connected in parallel with the LED load. When the input voltage and the first capacitor stop supplying power to the LED load, the second capacitor discharges.

[0035] The present invention proposes that in a dimming state, within each cycle of the input voltage, the power supply time of the input voltage is reduced and the instantaneous value of the input current is increased, thereby reducing the size of the discharge current and the output time to reduce the discharge loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a silicon controlled rectifier dimming circuit in the prior art;

[0037] Figure 2 The waveform diagram of each signal change in the prior art

[0038] Figure 3 is a waveform diagram of each signal change in an embodiment;

[0039] Figure 4 is a waveform diagram of changes in each signal in another embodiment;

[0040] Figure 5 is a waveform diagram of changes in each signal in another embodiment;

[0041] Figure 6 The circuit structure of the thyristor dimming circuit proposed by the present invention;

[0042] Figure 7 is a circuit structure of an enabling circuit in an embodiment;

[0043] Figure 8 is a circuit structure of an enabling circuit in another embodiment;

[0044] Fig. 9 is a circuit diagram of a first timing unit;

[0045] Fig.10 FIG. 4 is a circuit diagram of an input terminal of a comparison unit. DETAILED DESCRIPTION

[0046] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0047] when Figure 1 When the thyristor dimming circuit shown in the figure works in a low output power scenario, such as Figure 2 As shown, there is a large difference between the holding current and the input current of the thyristor dimmer, so that in the dimming state, the discharge circuit needs to generate a large discharge current to maintain the conduction of the thyristor dimmer, resulting in a large discharge loss of the thyristor dimming circuit.

[0048] Based on this problem, the present invention proposes a control method based on the above-mentioned thyristor dimming circuit to reduce the discharge loss in the dimming state. The specific control method is:

[0049] In the dimming state, in each cycle of the input voltage, the total time that the input voltage supplies power to the LED load is reduced, and the instantaneous value of the input current is adjusted. Specifically, the instantaneous value of the controlled input current is negatively correlated with the total time that the input voltage supplies power to the LED load.

[0050] It can be seen from this that the present invention proposes that in the dimming state, in each cycle of the input voltage, the total time that the input voltage supplies power to the LED load is reduced, and the instantaneous value of the input current is controlled to be negatively correlated with the total time that the input voltage supplies power to the LED load. Therefore, in each cycle, the time that the input voltage supplies power to the LED load is shortened, and the time that the input voltage does not supply power to the LED load is correspondingly increased. When the input voltage does not supply power to the LED load, there is no need to control the thyristor dimmer to maintain conduction. Therefore, in the present invention, the working time of the discharge circuit is shortened and the discharge loss is reduced.

[0051] In one embodiment, by "controlling the total duration of the input voltage supplying power to the LED load to be a preset duration, and adjusting the instantaneous value of the input current", the total duration of the input voltage supplying power to the LED load is reduced, and the instantaneous value of the input current is controlled to be negatively correlated with the total duration of the input voltage supplying power to the LED load. Furthermore, the specific implementation of this implementation method includes a closed-loop control method and an open-loop control method. Specifically, under open-loop control, a one-to-one correspondence is established between the total duration of the input voltage supplying power to the LED load and the instantaneous value of the input current, and the timing is started when the input voltage starts to supply power to the LED load in the current cycle, and when the timing reaches the preset duration, the input voltage is controlled to stop supplying power to the LED load, so that the duration of the input voltage supplying power to the LED load in the current cycle is controlled to be the preset duration. At the same time, the instantaneous value of the input current corresponding to the preset duration is obtained according to the established corresponding relationship, and the instantaneous value of the input current in the current cycle is controlled to be the corresponding value. Under closed-loop control, the input voltage starts to supply power to the LED load during the current cycle, and the input voltage is controlled to stop supplying power to the LED load when the timing reaches the preset duration, so that the duration of the input voltage supplying power to the LED load during the current cycle is controlled to be the preset duration. At the same time, the instantaneous value of the input current is adjusted according to the difference between the sampling signal (characterizing the instantaneous value of the input current) and the reference signal (the expected instantaneous value of the input current) to achieve closed-loop regulation (feedback regulation) of the instantaneous value of the input current. It should be noted that there is a negative correlation between the expected instantaneous value of the input current and the total duration of the input voltage supplying power to the LED load.

[0052] In one embodiment, by "controlling the total time that the input voltage stops supplying power to the LED load to be a preset time, adjusting the instantaneous value of the input current", the total time that the input voltage supplies power to the LED load is reduced, and the instantaneous value of the input current is controlled to be negatively correlated with the total time that the input voltage supplies power to the LED load. Further, the specific implementation of this implementation includes a closed-loop control method and an open-loop control method. Specifically, under open-loop control, a one-to-one correspondence is established between the total time that the input voltage stops supplying power to the LED load and the instantaneous value of the input current, and the total time that the input voltage stops supplying power to the LED load in the current cycle is controlled according to the total time that the input voltage stops supplying power to the LED load in the previous cycle and the preset time. If the total time that the input voltage stops supplying power to the LED load in the previous cycle is less than the preset time, the moment when the input voltage stops supplying power to the LED load in the current cycle is controlled to be advanced; if the total time that the input voltage stops supplying power to the LED load in the previous cycle is greater than the preset time, the moment when the input voltage stops supplying power to the LED load in the current cycle is controlled to be delayed. At the same time, the instantaneous value of the input current corresponding to the preset duration is obtained according to the established corresponding relationship, and the instantaneous value of the input current is controlled to be the corresponding value in the current cycle. Under closed-loop control, the total duration of the input voltage stopping powering the LED load in the current cycle is controlled according to the total duration of the input voltage stopping powering the LED load in the previous cycle and the preset duration. If the total duration of the input voltage stopping powering the LED load in the previous cycle is less than the preset duration, the moment of controlling the input voltage to stop powering the LED load in the current cycle is advanced; if the total duration of the input voltage stopping powering the LED load in the previous cycle is greater than the preset duration, the moment of controlling the input voltage to stop powering the LED load in the current cycle is delayed. At the same time, according to the difference between the sampling signal (characterizing the instantaneous value of the input current) and the reference signal (the expected instantaneous value of the input current), the instantaneous value of the input current is adjusted to achieve closed-loop regulation (feedback regulation) of the input current. It should be noted that there is a positive correlation between the expected instantaneous value of the input current and the total duration of the input voltage stopping powering the LED load.

[0053] In one embodiment, by "controlling the instantaneous value of the input current to be a preset current and adjusting the total duration of the input voltage supplying power to the LED load", the total duration of the input voltage supplying power to the LED load is reduced, and the instantaneous value of the input current is controlled to be negatively correlated with the total duration of the input voltage supplying power to the LED load. Further, the specific implementation of this implementation method includes a closed-loop control method and an open-loop control method. Specifically, under open-loop control, a one-to-one correspondence is established between the total duration of the input voltage supplying power to the LED load and the instantaneous value of the input current, the instantaneous value of the input current is controlled to be a preset current in the current cycle, and the total duration corresponding to the preset current is obtained according to the established correspondence, so as to control the total duration of the input voltage supplying power to the LED load to be the corresponding value. Under closed-loop control, the instantaneous value of the input current is controlled to be a preset current in the current cycle, and the total duration of the input voltage supplying power to the LED load is adjusted according to the difference between the timing signal and the reference signal, the timing signal represents the duration of the input voltage supplying power to the LED load, and the reference signal represents the expected total duration of the input voltage supplying power to the LED load. It should be noted that the total time that the expected input voltage supplies power to the LED load is negatively correlated with the instantaneous value of the input current.

[0054] Specifically, Figure 3 and Figure 4 As shown, in one embodiment, the total duration of the input voltage supplying power to the LED load is controlled to be a preset duration Tth (or an expected total duration). Figure 3 As shown, during T1, when the input voltage Vin is greater than or equal to the conduction voltage drop of the LED load, the discharge circuit generates a discharge current to maintain the conduction state of the thyristor dimmer. During T2, the input current Iin is increased, so that the input current Iin increases from I1 to I3. During T3, the input current Iin is increased, so that the input current Iin increases from I2 to I4. During T4 and T5, the input voltage Vin does not supply power, and the input current Iin is zero. Therefore, by comparison Figure 2 and Figure 3 It can be seen that in the prior art, the discharge circuit needs to be controlled during T1, T2, T3, and T4 to enable the discharge current to be generated to maintain the conduction of the thyristor dimmer. The generated discharge current is as follows: Figure 2 As shown in the shaded portion in FIG. In the present invention, as Figure 3 As shown, it is only necessary to control the discharge circuit during T1, T2, and T3 to enable the discharge current to be generated. The generated discharge current is as follows: Figure 3 As shown in the shaded part in FIG, it is obvious that the working time of the discharge circuit in the present invention is reduced, and the discharge loss is reduced. At the same time, during T2 and T3, since the input current I3 is greater than the input current I1, and the input current I4 is greater than the input current I2, the discharge current generated by the discharge circuit in the present invention is also relatively small, and the discharge loss is further reduced. Figure 4As shown in the figure, during T1, when the input voltage Vin is greater than or equal to the conduction voltage drop of the LED load, the discharge circuit generates a discharge current to maintain the conduction state of the thyristor dimmer. During T2, the input current Iin is increased, so that the input current Iin increases from I1 to I5. During T3, T4, and T5, the input voltage Vin does not supply power, and the input current Iin is zero. Similarly, compared Figure 2 and Figure 4 It can be seen that the working time of the discharge circuit in the present invention is reduced, the discharge current is reduced, and the discharge loss is reduced. It should be noted that if Figure 2 , Figure 3 and Figure 4 In the control strategy shown, the average input currents are equal, that is, (I1*T2+I2*T3+I1*T4) / T=(I3*T2+I4*T3) / T=I5*T2 / T.

[0055] Specifically, Figure 5 As shown, in one embodiment, the total duration of stopping power supply after the input voltage is controlled to supply power to the LED load is a preset duration Tth. Figure 5 As shown, during T1, when the input voltage is greater than or equal to the conduction voltage drop of the LED load, the discharge circuit is enabled to generate a discharge current to maintain the conduction state of the thyristor dimmer. During T2, the input current Iin is increased, so that the input current Iin increases from I1 to I6. During T3, the input current Iin is increased, so that the input current Iin increases from I2 to I7. During T4 and T5, the input voltage Vin does not supply power, and the input current Iin is zero. Therefore, compared Figure 2 and Figure 5 It can be seen that the working time of the discharge circuit in the present invention is reduced, the discharge current is reduced, and the discharge loss is reduced.

[0056] Furthermore, when the condition of reducing the time duration for the input voltage to supply power to the LED load is met, the stage of the input voltage supplying power to the LED load alone and the input voltage supplying power to the LED load and the first capacitor simultaneously may be included. Figure 3 As shown, in each cycle, when the input voltage rises to the conduction voltage drop of the LED load, the input voltage starts to supply power to the LED load, and when the duration of the input voltage supplying power to the LED load and the first capacitor simultaneously reaches a first duration (the first duration is less than or equal to T3), the input voltage stops supplying power until the end of the cycle, thereby reducing the total duration of the input voltage supplying power to the LED load. Alternatively, when the conditions for reducing the duration of the input voltage supplying power to the LED load are met, only the stage of the input voltage supplying power to the LED load alone may be included. That is, as Figure 4As shown, in each cycle, the input voltage starts to power the LED load when the input voltage rises to the conduction voltage drop of the LED load, and when the time duration during which the input voltage only powers the LED load reaches a first time duration (the first time duration is less than or equal to T2), the input voltage stops powering the LED load until the end of the cycle, thereby reducing the total time duration during which the input voltage powers the LED load. Figure 4 compared to Figure 3 , a stage is added in which the input voltage supplies power to the LED load and the first capacitor at the same time, which is beneficial to reducing the ripple of the LED load current.

[0057] It should be noted that, when the input voltage Vin is not supplying power, the first capacitor supplies power to the LED load or the second capacitor connected in parallel at both ends of the LED load supplies power to the LED load. If the first switch tube is turned on when the input voltage stops supplying power, the first capacitor supplies power to the LED load; if the first switch tube is turned off when the input voltage stops supplying power, the second capacitor supplies power to the LED load.

[0058] It can be seen from the above embodiments that the control method of the thyristor dimming circuit proposed in the present invention can not only meet the requirement of low output power in the dimming state, but also further reduce the discharge loss and improve the system efficiency.

[0059] In addition, the present invention also provides a thyristor dimming circuit, which includes:

[0060] A bleeder circuit generates a bleeder current to keep the thyristor dimmer turned on when the input current is less than the holding current of the thyristor dimmer;

[0061] The LED load and the first capacitor C1 connected in series are connected between the high and low potential ends of the input voltage;

[0062] A first switch tube M1, a first end of which is connected to an LED load, and a second end of which is connected to a low potential, and an input voltage supplies power to the LED load through the first switch tube M1;

[0063] A second switch tube M2, a first end of which is connected to the first capacitor C1, and a second end of which is connected to a low potential, and the input voltage is used to supply power to the LED load and the first capacitor C1 simultaneously through the second switch tube M2;

[0064] A discharge diode D1, with an anode connected to the anode of the first capacitor C1 and a cathode connected to the anode of the LED load. The first capacitor C1 supplies power to the LED load through the discharge diode;

[0065] The control circuit controls the thyristor dimming circuit according to the control method proposed above in the dimming state.

[0066] Specifically, Figure 6 As shown, the control circuit includes:

[0067] A first operational amplifier OP1, when the first operational amplifier OP1 receives a valid enable signal and is in a normal working state, controls the on and off of the first switch tube M1 according to the sampling signal Vcs representing the LED load current and the first reference signal Vref1;

[0068] The second operational amplifier OP2 controls the on / off of the second switch tube M2 according to the sampling signal Vcs and the second reference signal Vref2 when the second operational amplifier OP2 receives a valid enable signal to be in a normal working state;

[0069] The enabling circuit is connected to the enabling terminals of the first operational amplifier OP1 and the second operational amplifier OP2, and the enabling circuit outputs an invalid enabling signal to control the first operational amplifier OP1 and the second operational amplifier OP2 to stop working, so as to reduce the total time length of the input voltage supplying power to the LED load in each cycle.

[0070] The first switch tube M1 and the second switch tube M2 are turned off during the period when the first operational amplifier OP1 and the second operational amplifier OP2 stop working.

[0071] Specifically, by “controlling the total time that the input voltage supplies power to the LED load to be a preset time, and adjusting the instantaneous value of the input current”, the total time that the input voltage supplies power to the LED load can be reduced. Figure 7 As shown, the enabling circuit includes: a first timing unit, timing the duration of the input voltage supplying power to the LED load in the current cycle to output a first timing signal; a comparison unit, comparing the first timing signal with a preset signal (indicating that the total duration of the input voltage supplying power to the LED load is the preset duration) to output a valid judgment signal; and a logic unit, outputting an invalid enabling signal according to the valid judgment signal. Specifically, as Fig. 9 As shown, the first timing unit can be composed of a comparator, a counter and a digital-to-analog converter. The counter starts timing when the input voltage rises to the conduction voltage drop of the LED load, and the digital-to-analog converter converts the output of the counter into a voltage analog quantity. The comparison unit can be implemented by a comparator, and the logic unit is composed of a combination of various logic gates, various triggers, etc. At the same time, a reference voltage less than the conduction voltage drop of the LED load is set, and when the input voltage changes to less than the reference voltage, the enabling circuit outputs a valid enabling signal to restore the first operational amplifier and the second operational amplifier to a working state.

[0072] Specifically, by “controlling the total duration of the input voltage stopping power supplying to the LED load to be a preset duration, and adjusting the instantaneous value of the input current”, the total duration of the input voltage powering the LED load can be reduced. Figure 8As shown, the enabling circuit includes: a first timing unit, timing the duration of the input voltage supplying power to the LED load in the current cycle to output a first timing signal; a second timing unit, timing the total duration of the input voltage supplying power to the LED load in the previous cycle to output a second timing signal; a difference calculation unit, calculating the total duration of the input voltage stopping supplying power to the LED load in the previous cycle according to the second timing signal and the cycle signal, to output a third timing signal, the cycle signal representing a complete cycle of the input voltage before rectification; an operational amplifier unit, outputting a compensation signal according to the difference between the third timing signal and the preset signal, the preset signal representing that the total duration of the input voltage stopping supplying power to the LED load is a preset duration; a comparison unit, outputting a valid judgment signal according to the difference signal of the first timing signal, the preset signal and the compensation signal; and a logic unit, outputting an invalid enabling signal according to the valid judgment signal. Similarly, both the first timing unit and the second timing unit can be as follows Fig. 9 The difference operation unit can be realized by a subtraction operation circuit, and the operational amplifier unit can be realized by an operational amplifier. This is a conventional technical means in the field and is not described here. The comparison unit can receive the difference signal of the preset signal and the compensation signal by controlling the current source to charge and discharge the capacitor, such as Fig.10 As shown, the on-time of K1 is controlled according to the preset signal, and the on-time of K2 or K3 is controlled according to the compensation signal (K2 or K3 is controlled to be on according to the positive and negative meanings of the compensation signal, and K2 and K3 are not turned on at the same time), so that the voltage V2 of the capacitor C1 is represented by the difference signal between the preset signal and the compensation signal. This method is also a conventional technical means in the field and will not be described in detail here.

[0073] In one embodiment, by "controlling the instantaneous value of the input current to be a preset current and adjusting the total time the input voltage supplies power to the LED load", the total time the input voltage supplies power to the LED load is reduced. In the open-loop control method, reference may be made to Figure 7 The enabling circuit is shown in the figure, and will not be described in detail here. In the closed-loop control mode, you can refer to Figure 8 An operational amplifier unit, a first timing unit, a comparison unit and a logic unit are set to form an enabling circuit. The operational amplifier unit receives a timing signal (indicating the duration of the input voltage supplying power to the LED load in the current cycle) and a reference signal (the total duration of the expected input voltage supplying power to the LED load) to obtain a compensation signal. The comparison unit compares the difference signal of the timing signal, the reference signal and the compensation signal to generate a judgment signal. The logic unit generates an invalid enabling signal according to the judgment signal. The principle is the same as Figure 8 , which will not be elaborated in detail here.

[0074] It should be noted that the above focuses on explaining how to set the enabling circuit to reduce the total duration of the input voltage to power the LED load, but during the control process, the control circuit will adjust the size of the sampling resistor Rcs so that the instantaneous value of the input current is negatively correlated with the power supply duration of the input voltage. When adjusting the instantaneous value of the input current, the size of the sampling resistor is adjusted according to the closed-loop control method and the open-loop control method to adjust the instantaneous value of the input current. For example, in open-loop control, it is only necessary to adjust the size of the sampling resistor according to the current value corresponding to the duration. In closed-loop control, the size of the sampling resistor is adjusted according to the difference between the expected current value and the real-time sampled value of the input current. The specific implementation circuits of the two methods are conventional technical means in this field and will not be elaborated here.

[0075] It should be noted that the specific implementation and corresponding illustrations given are merely a way of describing the implementation method of the present invention, and do not limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principle and essence of the present invention, but these changes and modifications fall within the scope of protection of the present invention.

[0076] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0077] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A control method for a thyristor dimming circuit, the thyristor dimming circuit comprising: The discharge circuit is connected between the high and low potential ends of the input voltage and is used to generate a discharge current to keep the thyristor dimmer turned on; The LED load and the first capacitor connected in series are connected between the high and low potential ends of the input voltage, the input voltage can power the LED load, or the input voltage can power the LED load and the first capacitor at the same time, or the first capacitor can power the LED load, Characterized in that the control method comprises: In the dimming state, in each cycle of the input voltage, the total time duration for which the input voltage supplies power to the LED load is reduced, and the instantaneous value of the input current is controlled to be negatively correlated with the total time duration for which the input voltage supplies power to the LED load.

2. The control method according to claim 1, characterized in that: The total duration of the input voltage supplying power to the LED load is controlled to be a preset duration, and the instantaneous value of the input current is adjusted.

3. The control method according to claim 1, characterized in that: The total duration of the input voltage stopping supplying power to the LED load after supplying power to the LED load is controlled to be a preset duration, and the instantaneous value of the input current is adjusted.

4. The control method according to claim 1, characterized in that: The instantaneous value of the input current is controlled to be a preset current, and the total time duration for which the input voltage supplies power to the LED load is adjusted.

5. The control method according to claim 2, characterized in that: Establishing a one-to-one correspondence between the total duration of the input voltage supplying power to the LED load and the instantaneous value of the input current, controlling the total duration of the input voltage supplying power to the LED load to the preset duration in the current cycle, and controlling the instantaneous value of the input current to be the corresponding value of the preset duration; Or, in the current cycle, the total duration of the input voltage supplying power to the LED load is controlled to be the preset duration, and the instantaneous value of the input current is adjusted according to the difference between the sampling signal and the reference signal, and the sampling signal represents the instantaneous value of the input current.

6. The control method according to claim 3, characterized in that: Establish a one-to-one correspondence between the total time that the input voltage stops supplying power to the LED load and the instantaneous value of the input current, and in the current cycle, control the total time that the input voltage stops supplying power to the LED load according to the total time that the input voltage stops supplying power to the LED load in the previous cycle and the preset time, and control the instantaneous value of the input current to be a value corresponding to the preset time; Or, in the current cycle, the total duration of the input voltage stopping powering the LED load is adjusted according to the total duration of the input voltage stopping powering the LED load in the previous cycle and the preset duration, and the instantaneous value of the input current is adjusted according to the difference between the sampling signal and the reference signal, and the sampling signal represents the instantaneous value of the input current.

7. The control method according to claim 4, characterized in that: Establishing a one-to-one correspondence between the instantaneous value of the input current and the total duration of the input voltage supplying power to the LED load, controlling the instantaneous value of the input current in the current cycle to be the preset current, and controlling the total duration of the input voltage supplying power to the LED load to be the corresponding value of the preset current; Or, in the current cycle, the instantaneous value of the input current is controlled to be the preset current, and the total time the input voltage powers the LED load is adjusted according to the difference between the timing signal and the reference signal, and the timing signal represents the time the input voltage powers the LED load.

8. The control method according to any one of claims 1 to 7, characterized in that: In each cycle, the input voltage starts to power the LED load when the input voltage rises to the conduction voltage drop of the LED load, and when the duration for which the input voltage simultaneously powers the LED load and the first capacitor reaches a first duration, the input voltage stops powering the LED load until the end of the cycle.

9. The control method according to any one of claims 1 to 7, characterized in that: In each cycle, the input voltage starts to power the LED load when the input voltage rises to the conduction voltage drop of the LED load, and when the duration for which the input voltage only powers the LED load reaches a first duration, the input voltage stops powering the LED load until the cycle ends.

10. A thyristor dimming circuit, characterized in that: include: A discharge circuit, when the input current is less than the holding current of the thyristor dimmer, generates a discharge current to keep the thyristor dimmer turned on; The LED load and the first capacitor are connected in series and connected between the high and low potential ends of the input voltage; A first switch tube, a first end of which is connected to the LED load, a second end of which is connected to a low potential, and an input voltage supplies power to the LED load through the first switch tube; A second switch tube, a first end of which is connected to the first capacitor, a second end of which is connected to a low potential, and an input voltage is used to supply power to the LED load and the first capacitor through the second switch tube; a discharge diode, wherein the positive electrode is connected to the positive electrode of the first capacitor, and the negative electrode is connected to the positive electrode of the LED load, and the first capacitor supplies power to the LED load through the discharge diode; The control circuit uses the control method described in any one of claims 1 to 9 in the dimming state.

11. The thyristor dimming circuit according to claim 10, characterized in that: The control circuit comprises: A first operational amplifier, wherein an output end of the first operational amplifier is connected to a control end of a first switch tube; A second operational amplifier, wherein the output end of the second operational amplifier is connected to the control end of the second switch tube; The enabling circuit is connected to the enabling terminals of the first operational amplifier and the second operational amplifier, and the enabling circuit generates an invalid enabling signal to stop the first operational amplifier and the second operational amplifier from working, so as to reduce the total time length for the input voltage to supply power to the LED load.

12. The thyristor dimming circuit according to claim 10, characterized in that: It also includes a sampling resistor, the resistance of which is adjustable, and the instantaneous value of the input current can be adjusted by adjusting the value of the sampling resistor.

13. The thyristor dimming circuit according to claim 10, characterized in that: The system further includes a second capacitor, which is connected in parallel with the LED load. When the input voltage and the first capacitor stop supplying power to the LED load, the second capacitor discharges.

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