Silicon controlled rectifier dimming circuit

Abstract

The invention provides a silicon controlled rectifier dimming circuit which comprises the components of a bleeder circuit which is connected between high and low potential ends 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; in the non-dimming state, in each period of the input voltage, the silicon controlled rectifier dimming circuit comprises a first stage and a second stage, in the first stage, the control circuit controls the input voltage to supply power to the LED load and the first capacitor, and in the second stage, the control circuit controls the first capacitor to supply power to the LED load. According to the silicon controlled rectifier dimming circuit provided by the invention, in a non-dimming state, the input voltage is controlled to only supply power to the LED load and the first capacitor at the same time in each period, so that the power supply duration of the input voltage is reduced, the loss is reduced, and the dimming efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the field of lighting, and in particular relates to a silicon controlled rectifier dimming circuit. 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. In the dimming state, the thyristor dimming circuit widens the effective range of the input current and reduces the discharge loss of the discharge circuit.

[0003] However, in the thyristor dimming circuit, we need to pay attention not only to the discharge loss in the dimming state, but also to the system efficiency in the non-dimming state. Figure 2 As shown, in the non-dimming state, in each cycle of the input voltage, the first capacitor C1 supplies power to the LED load during T1, the input voltage supplies power to the LED load during T2, the input voltage supplies power to the LED load and the first capacitor during T3, the input voltage supplies power to the LED load during T4, and the first capacitor supplies power to the LED load during T5.

[0004] It can be seen that in the non-dimming state, the time for drawing power from the input voltage is longer in each cycle of the input voltage (which also corresponds to a larger effective range of the input current). When the input voltage is used to power the LED load, the voltage difference between the input voltage and the LED load is large, resulting in large power consumption on the first switch tube, reducing system efficiency. Similarly, when the input voltage is used to power the LED load and the first capacitor, the power consumption on the second switch tube is large, reducing system efficiency.

[0005] In summary, the efficiency of the above-mentioned thyristor dimming circuit in the non-dimming state needs to be optimized. Summary of the invention

[0006] To improve Figure 1 The efficiency of the thyristor dimming circuit in the non-dimming state is improved. The present invention provides a thyristor dimming circuit, comprising:

[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 in the dimming state;

[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] In the non-dimming state, the thyristor dimming circuit includes a first stage and a second stage in each cycle of the input voltage.

[0010] Wherein, in the first stage, the control circuit controls the input voltage to supply power to the LED load and the first capacitor, and in the second stage, the control circuit controls the first capacitor to supply power to the LED load.

[0011] Furthermore, in the first stage, the input voltage is greater than or equal to the sum of the on-state voltage drop of the LED load and the first capacitor voltage; and in the second stage, the input voltage is less than the on-state voltage drop of the LED load.

[0012] Furthermore, the thyristor dimming circuit further includes a first switch tube, a first end of the first switch tube is connected to the LED load, and a second end of the first switch tube is connected to a low potential, wherein:

[0013] When the input voltage is greater than or equal to the preset voltage, the control circuit controls the first switch tube to be turned off; when the input voltage is less than the preset voltage, the control circuit controls the first switch tube to be turned on.

[0014] Wherein, the preset voltage is less than or equal to the conduction voltage drop of the LED load.

[0015] Furthermore, the control circuit includes a first operational amplifier and an enabling circuit, wherein the output end of the first operational amplifier is connected to the control end of the first switch tube, and the enabling circuit is connected to the enabling end of the first operational amplifier.

[0016] The enabling circuit outputs an invalid enabling signal according to the detection signal, the sampling signal and the reference signal to control the first operational amplifier to stop working, and the first switch tube is turned off when the first operational amplifier stops working.

[0017] The detection signal indicates that the thyristor dimming circuit is in a non-dimming state, the sampling signal indicates an input voltage, and the reference signal indicates the preset voltage.

[0018] Further, the enabling circuit includes:

[0019] A detection unit, detecting a transition edge width of the input voltage to output the detection signal;

[0020] A comparison unit, for comparing the sampling signal with the reference signal, so as to output a valid judgment signal when the sampling signal is greater than the reference signal;

[0021] A logic unit is configured to output the invalid enable signal after performing logic processing on the detection signal and the valid judgment signal.

[0022] Furthermore, when the sampling signal is smaller than the reference signal, the comparison unit outputs an invalid judgment signal, and the logic unit outputs a valid enable signal after logical processing based on the detection signal and the invalid judgment signal to control the first operational amplifier to resume operation.

[0023] Furthermore, the detection unit includes: a rising edge detection circuit, a falling edge detection circuit, and a logic circuit.

[0024] The rising edge detection circuit detects the rising edge width of the input voltage to output a first detection signal.

[0025] The falling edge detection circuit detects the falling edge width of the input voltage to output a second detection signal.

[0026] The logic circuit performs logic processing on the first detection signal and the second detection signal and outputs the detection signal.

[0027] Furthermore, the thyristor dimming circuit also includes:

[0028] 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;

[0029] A discharge diode has a positive electrode connected to the positive electrode of the first capacitor and a negative electrode connected to the positive electrode of the LED load, and the first capacitor supplies power to the LED load through the discharge diode.

[0030] Furthermore, the control circuit further includes a second operational amplifier, the output end of the second operational amplifier is connected to the control end of the second switch tube,

[0031] The second operational amplifier controls the on-off of the second switch tube according to a sampling voltage and a second reference voltage, and the sampling voltage represents the current of the LED load.

[0032] Furthermore, the LED load is connected in parallel with a second capacitor, and when the input voltage and the first capacitor stop supplying power to the LED load, the second capacitor discharges.

[0033] In the non-dimming state, the thyristor dimming circuit proposed in the present invention controls the input voltage to only supply power to the LED load and the first capacitor at the same time in each cycle, thereby reducing the time the input voltage supplies power to the LED load, reducing losses, and improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a silicon controlled rectifier dimming circuit in the prior art;

[0035] Figure 2 It is a signal waveform diagram of a thyristor dimming circuit in the prior art in a non-dimming state;

[0036] Figure 3 It is a signal waveform diagram of the thyristor dimming circuit of the present invention in a non-dimming state;

[0037] Figure 4 A circuit diagram of a thyristor dimming circuit of the present invention;

[0038] Figure 5 FIG. 1 is a circuit diagram of the enabling circuit. DETAILED DESCRIPTION

[0039] 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.

[0040] In the prior art, in the non-dimming state, Figure 1 The thyristor dimming circuit shown, in the non-dimming state, when the input voltage is supplied, the voltage difference between the input voltage and the LED load is large, which will cause the power consumption of the first switch tube or the second switch tube to be large, thereby reducing the efficiency of the thyristor dimming circuit.

[0041] Therefore, in order to solve the above problem and improve the efficiency of the above thyristor dimming circuit in a non-dimming state, the present invention proposes a thyristor dimming circuit.

[0042] Specifically, the thyristor dimming circuit proposed in the present invention includes:

[0043] The discharge circuit is connected between the high and low potential ends of the input voltage and is used to generate a discharge current in the dimming state to keep the thyristor dimmer turned on;

[0044] The LED load and the first capacitor are connected in series, and connected between the high and low potential ends of the input voltage;

[0045] A first switch tube, 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;

[0046] A second switch tube, a first end of which is connected to the first capacitor, and a second end of which is connected to a low potential, and the input voltage supplies power to the LED load and the first capacitor through the second switch tube;

[0047] 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;

[0048] The control circuit includes a first stage and a second stage in each cycle of the input voltage in a non-dimming state, wherein:

[0049] In the first stage, the control circuit controls the input voltage to supply power to the LED load and the first capacitor simultaneously, and the input voltage in the first stage is greater than or equal to the sum of the conduction voltage drop of the LED load and the voltage of the first capacitor;

[0050] In the second stage, the control circuit controls the first capacitor to supply power to the LED load, and in the second stage, the input voltage is less than the conduction voltage drop of the LED load.

[0051] From this we can see that Figure 2 and Figure 3 As shown, in the non-dimming state, compared with the prior art shown, the thyristor dimming circuit of the present invention only draws power from the input voltage during T3, and the input voltage does not supply power during T2 and T4. Therefore, during T2 and T4, no large power consumption will be generated on the first switch tube due to the large voltage difference. Therefore, after comparison, it can be seen that the thyristor dimming circuit proposed in the present invention is in the non-dimming state. In each cycle, the input voltage is controlled to supply power to only the LED load and the first capacitor at the same time, thereby reducing the time that the input voltage supplies power to the LED load, reducing losses, and improving efficiency.

[0052] It should be noted that during the period T2 and T4, the LED load is powered by the second capacitor connected in parallel at both ends thereof.

[0053] Specifically, Figure 4 As shown, the control circuit includes:

[0054] A first operational amplifier OP1, wherein the output end of the first operational amplifier OP1 is connected to the control end of the first switch tube M1, and the first operational amplifier OP1 controls the on / off of the first switch tube according to the sampling voltage Vcs and the first reference voltage Vref1 during operation (when receiving a valid enable signal);

[0055] A second operational amplifier OP2, wherein the output end of the second operational amplifier OP2 is connected to the control end of the second switch tube M2, and the second operational amplifier OP2 controls the on-off of the second switch tube according to the sampling voltage Vcs and the second reference voltage Vref2;

[0056] The enabling circuit is connected to the enabling terminal of the first operational amplifier. The enabling circuit outputs an invalid enabling signal according to the detection signal, the sampling signal and the reference signal to control the first operational amplifier to stop working. When the first operational amplifier stops working, the first switch tube is turned off.

[0057] Among them, the sampling signal represents the input voltage, the detection signal represents the non-dimming state, the reference signal represents the preset voltage, and the preset voltage is less than or equal to the on-state voltage drop of the LED load, the sampling voltage represents the LED load current, the first reference voltage represents the current when the input voltage is the LED load and the first capacitor are powered at the same time, and the second reference voltage is slightly greater than the first reference voltage.

[0058] Further, such as Figure 5 As shown, the enabling circuit includes:

[0059] A detection unit, detecting a change edge width of an input voltage to output a detection signal T1;

[0060] A comparison unit, comparing the sampling signal Vcs' and the reference signal Vth, so as to output a valid determination signal T2 when the sampling signal Vcs' is greater than the reference signal Vth;

[0061] The logic unit outputs an invalid enable signal EN after logic processing of the detection signal T1 and the valid judgment signal T2.

[0062] At the same time, when the sampling signal is smaller than the reference signal, the comparison unit outputs an invalid judgment signal, and the logic unit outputs a valid enable signal after logic processing of the detection signal and the invalid judgment signal, so as to resume the operation of the first operational amplifier.

[0063] In summary, in the non-dimming state, when the input voltage is greater than or equal to the preset voltage, the enable circuit outputs an enable signal of an invalid state to control the first op amp OP1 to be disabled, and at this time the first switch tube M1 is turned off, wherein the preset voltage is less than or equal to the conduction voltage drop of the LED. Therefore, when the input voltage rises to the conduction voltage drop of the LED load, the first switch tube M1 is turned off, resulting in the input voltage being unable to supply power to the LED load. When the input voltage continues to rise to the sum of the conduction voltage drop of the LED load and the voltage of the first capacitor, the second op amp OP2 controls the second switch tube M2 to be turned on, so the input voltage supplies power to the LED load and the first capacitor at the same time. When the input voltage is less than the preset voltage, the enable circuit outputs an enable signal of a valid state to control the first op amp OP1 to be enabled, and at this time the first op amp OP1 controls the first switch tube M1 to be turned on, and the first capacitor supplies power to the LED load. Therefore, the control circuit realizes the control of the thyristor dimming circuit in each cycle in the non-dimming state, including the first stage and the second stage.

[0064] It should be noted that if the on-state voltage drop of the LED load has been obtained through detection before designing the circuit, the preset voltage can be set equal to the on-state voltage drop of the LED load. If the on-state voltage drop of the LED load is not specifically known through detection, the technicians in this field will determine the on-state voltage drop of the LED load based on the design experience and the LED usage market, and set a voltage value less than the experience value as the preset voltage.

[0065] Further, such as Figure 5 As shown, the detection unit includes a rising edge detection circuit, a falling edge detection circuit and a logic circuit. The rising edge detection circuit detects the rising edge width of the input voltage to output a first detection signal T11 representing the rising edge width. The falling edge detection circuit detects the falling edge width of the input voltage to output a second detection signal T12 representing the falling edge width. The logic circuit performs logic processing on the first detection signal T11 and the second detection signal T12 and then outputs a detection signal T1. Specifically, when the rising edge width is greater than the first preset width and the falling edge width is greater than the second preset width, the detection signal indicates that the thyristor dimmer is not connected to the thyristor dimming circuit at this time, that is, it is in a non-dimming state at this time. It should be noted that how to design the specific rising edge detection circuit and the falling edge detection circuit belongs to conventional technical means in this field and will not be elaborated here.

[0066] 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.

[0067] 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.

[0068] 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 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 in the dimming state; 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, It is characterized in that, in the non-dimming state, the thyristor dimming circuit includes a first stage and a second stage in each cycle of the input voltage, Wherein, in the first stage, the control circuit controls the input voltage to supply power to the LED load and the first capacitor, and in the second stage, the control circuit controls the first capacitor to supply power to the LED load.

2. The thyristor dimming circuit according to claim 1, characterized in that: In the first stage, the input voltage is greater than or equal to the sum of the conduction voltage drop of the LED load and the first capacitor voltage; in the second stage, the input voltage is less than the conduction voltage drop of the LED load.

3. The thyristor dimming circuit according to claim 1 or 2, characterized in that: The thyristor dimming circuit further includes a first switch tube, a first end of which is connected to the LED load, and a second end of which is connected to a low potential, wherein: When the input voltage is greater than or equal to the preset voltage, the control circuit controls the first switch tube to be turned off; when the input voltage is less than the preset voltage, the control circuit controls the first switch tube to be turned on. Wherein, the preset voltage is less than or equal to the conduction voltage drop of the LED load.

4. The thyristor dimming circuit according to claim 3, characterized in that: The control circuit includes a first operational amplifier and an enabling circuit, wherein the output end of the first operational amplifier is connected to the control end of the first switch tube, and the enabling circuit is connected to the enabling end of the first operational amplifier. The enabling circuit outputs an invalid enabling signal according to the detection signal, the sampling signal and the reference signal to control the first operational amplifier to stop working, and the first switch tube is turned off when the first operational amplifier stops working. The detection signal indicates that the thyristor dimming circuit is in a non-dimming state, the sampling signal indicates an input voltage, and the reference signal indicates the preset voltage.

5. The thyristor dimming circuit according to claim 4, characterized in that: The enabling circuit comprises: A detection unit, detecting a transition edge width of the input voltage to output the detection signal; A comparison unit, for comparing the sampling signal with the reference signal, so as to output a valid judgment signal when the sampling signal is greater than the reference signal; A logic unit is configured to output the invalid enable signal after performing logic processing on the detection signal and the valid judgment signal.

6. The thyristor dimming circuit according to claim 5, characterized in that: The comparison unit outputs an invalid judgment signal when the sampling signal is smaller than the reference signal, and the logic unit outputs a valid enable signal after logic processing based on the detection signal and the invalid judgment signal to control the first operational amplifier to resume operation.

7. The thyristor dimming circuit according to claim 5, characterized in that: The detection unit includes: a rising edge detection circuit, a falling edge detection circuit, and a logic circuit. The rising edge detection circuit detects the rising edge width of the input voltage to output a first detection signal. The falling edge detection circuit detects the falling edge width of the input voltage to output a second detection signal. The logic circuit performs logic processing on the first detection signal and the second detection signal and outputs the detection signal.

8. The thyristor dimming circuit according to claim 3, characterized in that: The silicon controlled rectifier dimming circuit also includes: 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 has a positive electrode connected to the positive electrode of the first capacitor and a negative electrode connected to the positive electrode of the LED load, and the first capacitor supplies power to the LED load through the discharge diode.

9. The thyristor dimming circuit according to claim 8, characterized in that: The control circuit further 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 second operational amplifier controls the on-off of the second switch tube according to a sampling voltage and a second reference voltage, and the sampling voltage represents the current of the LED load.

10. The thyristor dimming circuit according to claim 1, characterized in that: The LED load is connected in parallel with a second capacitor, and when the input voltage and the first capacitor stop supplying power to the LED load, the second capacitor discharges.

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