CN113840424A - Silicon controlled rectifier dimming LED driving system and method thereof - Google Patents

Silicon controlled rectifier dimming LED driving system and method thereof Download PDF

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Publication number
CN113840424A
CN113840424A CN202010582303.4A CN202010582303A CN113840424A CN 113840424 A CN113840424 A CN 113840424A CN 202010582303 A CN202010582303 A CN 202010582303A CN 113840424 A CN113840424 A CN 113840424A
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voltage
current
silicon controlled
control module
led load
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CN113840424B (en
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刘军
李国成
张识博
吴泉清
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CRM ICBG Wuxi Co Ltd
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CRM ICBG Wuxi Co Ltd
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/345—Current stabilisation; Maintaining constant current
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits

Abstract

The invention provides a silicon controlled rectifier dimming LED driving system and a method thereof, wherein the system comprises: an LED load; the constant current control module is connected with the cathode end of the LED load and is used for performing constant current control on the LED load; the energy storage capacitor is connected with the positive end of the LED load and discharges to the LED load when the input voltage is less than the voltage on the energy storage capacitor; the charging current control module is connected with the LED load negative electrode end and the lower pole plate of the energy storage capacitor and used for adjusting the charging current of the energy storage capacitor based on the detected input voltage and the discharging voltage of the energy storage capacitor; the leakage and discharge current control module is connected with the constant current control module and the charging current control module, is started when the input end of the system is connected with the controlled silicon, maintains the conduction of the controlled silicon by regulating and controlling the leakage current, and regulates and controls the reference voltage according to the conduction angle of the controlled silicon to control the output current of the LED load. The invention solves the problems of low efficiency and stroboscopic output of the LED driving system in the prior art.

Description

Silicon controlled rectifier dimming LED driving system and method thereof
Technical Field
The invention relates to the field of integrated circuit design, in particular to a silicon controlled dimming LED driving system and a method thereof.
Background
Generally, the overall efficiency in the single-stage linear LED driving is determined by the LED on-voltage and the input voltage, and satisfies:
Figure BDA0002552798160000011
wherein, VLEDIs the LED on-voltage, VINIs the input voltage.
FIG. 1 shows a conventional single-stage linear LED driving structure 1', IN which an AC input voltage AC _ IN is converted into an input voltage V by a rectifier module 10INThe anode of the series LED is connected to the output end of the rectifier module 10 ', the cathode of the series LED is connected to the constant current control chip 20', the sampling end of the constant current control chip 20 'is grounded via the sampling resistor 30', and the adjustable module 40 'is connected in parallel to the two ends of the rectifier module 10'. Since the number of series-connected LEDs is fixed, at the input voltage VINOver LED forward voltage drop VLEDIn the meantime, the excess voltage is borne by a constant current control tube (not shown) under the LED, VIN-VLEDNamely the voltage on the constant current control tube; input voltage VINThe higher the efficiency Eff of the system; and when the silicon controlled rectifier is dimmed, the LED load output has stroboscopic.
Therefore, how to improve the overall efficiency of the system and avoid the output stroboflash has become one of the problems to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a driving system and a method thereof for a silicon controlled dimming LED, which are used to solve the problems of low efficiency and stroboscopic output of the driving system in the prior art.
To achieve the above and other related objects, the present invention provides a silicon controlled dimming LED driving system, including:
the positive terminal of the LED load is connected with input voltage;
the constant current control module is connected to the negative end of the LED load and is used for performing constant current control on the LED load;
the upper pole plate of the energy storage capacitor is connected to the positive end of the LED load and used for discharging to the LED load when the input voltage is smaller than the voltage on the energy storage capacitor;
the charging current control module is connected to the negative end of the LED load and the lower pole plate of the energy storage capacitor and used for adjusting the charging current of the energy storage capacitor according to the detected input voltage and the detected discharging voltage of the energy storage capacitor;
the discharge current control module is connected with the constant current control module and the charging current control module, and is used for being switched on when the input end of the silicon controlled rectifier dimming LED driving system is connected with a silicon controlled rectifier and being switched off when the input end of the silicon controlled rectifier dimming LED driving system is not connected with the silicon controlled rectifier; when the LED constant current control module is started, the sum of the leakage current, the output current of the LED load and the charging current of the energy storage capacitor is not less than the set current by regulating and controlling the leakage current so as to maintain the conduction of the controllable silicon, and meanwhile, the reference voltage of the constant current control module is regulated and controlled according to the conduction angle of the controllable silicon so as to control the output current of the LED load.
Optionally, the constant current control module includes: the LED load circuit comprises a first power switch tube, a first sampling resistor, a first operational amplifier and a reference voltage generating unit, wherein the drain electrode end of the first power switch tube is connected to the negative electrode end of the LED load, the source electrode end of the first power switch tube is connected to one end of the first sampling resistor, the other end of the first sampling resistor is grounded, the grid electrode end of the first power switch tube is connected to the output end of the first operational amplifier, the non-inverting input end of the first operational amplifier is connected to the reference voltage generating unit to be connected to the reference voltage, and the inverting input end of the first operational amplifier is connected to the source electrode end of the first power switch tube; wherein the reference voltage generating unit is controlled by the bleeder current control module.
Optionally, the charging current control module comprises:
the discharge voltage detection unit is connected to the negative end of the LED load and used for judging the discharge voltage of the energy storage capacitor according to the negative end voltage of the LED load and generating a corresponding control signal;
an input voltage detection unit for performing voltage detection on the input voltage;
and the charging current control unit is connected with the output end of the discharging voltage detection unit, the output end of the input voltage detection unit and the lower polar plate of the energy storage capacitor and is used for adjusting the charging current of the energy storage capacitor according to the control signal and the input voltage detection value.
Optionally, the discharge voltage detection unit includes:
the detection part is connected to the negative terminal of the LED load and is used for detecting the voltage of the negative terminal of the LED load;
and the comparison part is connected with the output end of the detection part and used for generating a first control signal when the voltage detection value of the negative end is greater than a first preset voltage and generating a second control signal when the voltage detection value of the negative end is less than a second preset voltage, wherein the first preset voltage is greater than the second preset voltage.
Optionally, the detection part comprises: one end of the first voltage-dividing resistor is connected to the negative electrode end of the LED load, the other end of the first voltage-dividing resistor is connected to one end of the second voltage-dividing resistor and serves as the output end of the detection part, and the other end of the second voltage-dividing resistor is grounded; the comparison section includes: the output end of the first comparator is used as the first output end of the comparison part, the in-phase input end of the second comparator is connected with the second preset voltage, the reverse-phase input end of the second comparator is connected with the output end of the detection part, and the output end of the second comparator is used as the second output end of the comparison part.
Optionally, the charging current control unit includes:
the compensation part is connected with the output end of the discharge voltage detection unit and used for generating corresponding compensation voltage according to the corresponding control signal generated by the discharge voltage detection unit;
and the current adjusting part is connected with the output end of the input voltage detecting unit and the output end of the compensating part and is used for adjusting the charging current of the energy storage capacitor according to the difference value of the compensating voltage and the input voltage detection value.
Optionally, the compensation part comprises: the control end of the first current source is connected to the first output end of the discharge voltage detection unit, the first connection end of the first current source is grounded, the second connection end of the first current source is connected to the first connection end of the second current source and the upper polar plate of the compensation capacitor, the lower polar plate of the compensation capacitor is grounded, the control end of the second current source is connected to the second output end of the discharge voltage detection unit, the second connection end of the second current source is connected to the working voltage, the input end of the compensation voltage generation circuit is connected to the upper polar plate of the compensation capacitor, and the output end of the compensation voltage generation circuit serves as the output end of the compensation part; the current adjusting section includes: the first input end of the subtracter is connected to the output end of the compensation part, the second input end of the subtracter is connected to the output end of the input voltage detection unit, the output end of the subtracter is connected to the non-inverting input end of the second operational amplifier, the inverting input end of the second operational amplifier is connected to the source end of the second power switch tube, the output end of the second operational amplifier is connected to the grid end of the second power switch tube, the drain end of the second power switch tube is connected to the lower pole plate of the energy storage capacitor, the source end of the second power switch tube is connected to one end of the second sampling resistor, and the other end of the second sampling resistor is grounded.
Optionally, the compensation part further comprises: the non-inverting input end of the third comparator is connected to the gate end of a first power switch tube in the constant current control module, the inverting input end of the third comparator is connected to a third preset voltage, the output end of the third comparator is connected to the control end of the third current source, the first connection end of the third current source is connected to the upper polar plate of the compensation capacitor, and the second connection end of the third current source is connected to a working voltage.
Optionally, the leakage current control module includes:
the phase detection unit is used for carrying out phase detection on the input voltage so as to judge whether the input end of the silicon controlled light dimming LED driving system is connected with the silicon controlled, and generating a starting signal when the input end of the silicon controlled light dimming LED driving system is connected with the silicon controlled, and meanwhile, judging the size of a conduction angle of the silicon controlled according to a phase detection value so as to regulate and control the reference voltage of the constant current control module, and generating a turn-off signal when the input end of the silicon controlled light dimming LED driving system is not connected with the silicon controlled;
the setting current generating unit is connected to the output end of the phase detection unit and is used for generating the setting current under the control of the starting signal;
and the leakage current control unit is connected with the output end of the set current generation unit, one end of a first sampling resistor in the constant current control module and one end of a second sampling resistor in the charging current control module, and is used for detecting the leakage current, the output current of the LED load and the charging current of the energy storage capacitor and controlling the leakage current to enable the sum of the leakage current, the output current of the LED load and the charging current of the energy storage capacitor to be not less than the set current so as to maintain the conduction of the silicon controlled rectifier.
Optionally, the leakage current control unit includes: a third power switch tube, a third sampling resistor, a third operational amplifier, a first detection resistor, a second detection resistor and a third detection resistor, wherein the drain terminal of the third power switch tube is connected to the input voltage, the source terminal of the third power switch tube is connected to one end of the third sampling resistor, the other end of the third sampling resistor is grounded, the gate terminal of the third power switch tube is connected to the output terminal of the third operational amplifier, the non-inverting input terminal of the third operational amplifier is connected to the output terminal of the set current generating unit, the inverting input terminal of the third operational amplifier is respectively connected to one end of the first detection resistor, one end of the second detection resistor and one end of the third detection resistor, the other end of the first detection resistor is connected to one end of the third sampling resistor, and the other end of the second detection resistor is connected to one end of the first sampling resistor in the constant current control module, the other end of the third detection resistor is connected to one end of a second sampling resistor in the charging current control module.
Optionally, the thyristor-controlled dimming LED driving system further includes: and the direct current blocking diode is connected between the input voltage and the LED load and used for converting the input voltage into bus voltage.
The invention also provides a silicon controlled rectifier dimming LED driving method, which comprises the following steps: when the LED load in the silicon controlled dimming LED driving system is subjected to silicon controlled dimming,
if the input end of the silicon controlled rectifier dimming LED driving system is connected with a silicon controlled rectifier, a leakage current control module is started, leakage current is regulated and controlled based on the leakage current control module, the sum of the leakage current, the output current of the LED load and the charging current of an energy storage capacitor is not less than a set current so as to maintain the conduction of the silicon controlled rectifier, and meanwhile, the reference voltage of a constant current control module is regulated and controlled according to the conduction angle of the silicon controlled rectifier so as to control the output current of the LED load;
and if the input end of the LED driving system is not connected with the controlled silicon, the leakage current control module is switched off.
Optionally, phase detection is performed on the input voltage based on a phase detection unit to determine whether the input end of the silicon controlled rectifier dimming LED driving system is connected to the silicon controlled rectifier, and meanwhile, the conduction angle of the silicon controlled rectifier is determined according to the phase detection value.
As described above, the silicon controlled dimming LED driving system and method thereof of the present invention have the following beneficial effects:
1. the silicon controlled dimming LED driving system and the method thereof detect the voltage of the negative terminal of the LED load to control the charging current of the energy storage capacitor, and control the loss of the constant current power switch tube to be minimum under the condition of ensuring that the output LED has no stroboflash.
2. The silicon controlled dimming LED driving system and the method thereof detect the grid voltage of the constant-current power switch tube to accelerate the loop response speed and ensure quick start.
3. According to the silicon controlled dimming LED driving system and the method thereof, the LED load is supplied with power through the energy storage capacitor at the input voltage valley bottom, and meanwhile, the charging current of the energy storage capacitor is reduced when the input voltage is high, so that the system has high power factor and high efficiency.
4. According to the silicon controlled rectifier dimming LED driving system and the method thereof, the external control of the bleeder current is performed through the phase detection, when the output current of the LED load and the charging current of the energy storage capacitor are reduced to cause insufficient input current, the conduction of the silicon controlled rectifier can be maintained by regulating the bleeder current, the problem of flicker of the silicon controlled rectifier due to turn-off is prevented, the dimming performance is optimized while the dimming requirement of the silicon controlled rectifier is met, and the dimming is free from stroboflash in the whole dimming process.
5. The peripheral circuit of the silicon controlled dimming LED driving system is simplified to the greatest extent, and the system cost is low.
Drawings
Fig. 1 is a schematic diagram of a single-segment linear LED driving structure in the prior art.
Fig. 2 is a schematic structural diagram of the thyristor dimming LED driving system according to the present invention.
Fig. 3 is a block diagram of an actual application of the scr dimming LED driving system shown in fig. 2.
Fig. 4 is a simplified block diagram of the practical application of fig. 3.
Fig. 5 is a waveform diagram illustrating a driving method of the thyristor-controlled dimming LED according to the present invention.
Description of the element reference numerals
1' LED driving structure
10' rectifier module
20' constant current control chip
20' sampling resistor
40' adjustable module
1 silicon controlled rectifier dimming LED driving system
10 constant current control module
11 reference voltage generating unit
111 reference voltage setting part
20 charging current control module
21 discharge voltage detection unit
211 detecting section
212 comparison section
22 input voltage detection unit
23 charging current control unit
231 compensation section
2311 compensating voltage generating circuit
232 current regulating part
30 bleeder current control module
31 phase detection unit
32 set current generating unit
321 set current generating part
33 bleeder current control unit
40 rectifier module
50 working voltage generation module
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 2 to 5. It should be noted that the drawings provided in the present embodiment are only schematic and illustrate the basic idea of the present invention, and although the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity and proportion of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
Example one
As shown in fig. 2, the present embodiment provides a thyristor dimming LED driving system, where the thyristor dimming LED driving system 1 includes:
the LED load has a positive terminal connected with an input voltage Vin;
the constant current control module 10 is connected to the negative end of the LED load and is configured to perform constant current control on the LED load;
an upper electrode plate of the energy storage capacitor Co is connected to the positive end of the LED load and is used for discharging to the LED load when the input voltage Vin is smaller than the voltage on the energy storage capacitor Co;
the charging current control module 20 is connected to the negative end of the LED load and the lower plate of the energy storage capacitor Co, and configured to adjust the charging current of the energy storage capacitor Co according to the detected input voltage Vin and the detected discharging voltage of the energy storage capacitor Co;
the discharging current control module 30 is connected to the constant current control module 10 and the charging current control module 20, and is configured to turn on when the thyristor is connected to the input end of the thyristor dimming LED driving system 1, and turn off when the thyristor is not connected to the input end of the thyristor dimming LED driving system 1; when the constant current control module is started, the sum of the leakage current, the output current of the LED load and the charging current of the energy storage capacitor Co is not less than the set current by regulating and controlling the leakage current so as to maintain the conduction of the controllable silicon, and meanwhile, the reference voltage of the constant current control module 10 is regulated and controlled according to the conduction angle of the controllable silicon so as to control the output current of the LED load.
As an example, as shown in fig. 2, the scr dimming LED driving system 1 further includes: the rectifying module 40 is configured to rectify an alternating current power supply AC _ IN to obtain the input voltage Vin, where the input voltage Vin is a rectified voltage obtained by rectifying a sinusoidal voltage.
Specifically, as shown IN fig. 2, the rectifier module 40 includes a rectifier bridge structure BD1 and a fuse F1, the rectifier bridge structure BD1 includes two diode groups connected IN parallel, each diode group includes two diodes connected IN series, and the AC power source AC _ IN is connected between the two diodes of each diode group through the fuse F1.
As an example, as shown in fig. 2, the scr dimming LED driving system 1 further includes: a blocking diode D1, connected between the input voltage Vin and the LED load (the anode end of which is connected to the input voltage Vin, and the cathode end of which is connected to the anode end of the LED load), for blocking the input voltage Vin and converting the input voltage Vin into a bus voltage Vbus; wherein the blocking diode D1 blocks the input voltage Vin from the bus voltage Vbus.
As an example, as shown in fig. 2, the scr dimming LED driving system 1 further includes: and the working voltage generating module 50 is connected to the cathode end of the blocking diode D1, and is configured to provide a working voltage for the silicon controlled dimming LED driving system 1 according to the bus voltage Vbus. In this example, the bus voltage Vbus generates the working voltage VDD through the working voltage generation module 50 to supply power to the silicon controlled dimming LED driving system 1.
As an example, as shown in fig. 2, a positive terminal of the LED load is connected to a negative terminal of the dc blocking diode D1 to connect the bus voltage Vbus, and the LED load includes a plurality of LEDs connected in series; of course, the LED load may also be a series-parallel structure of a plurality of LEDs, which is not limited in this example. In this example, when the voltage across the LED load reaches its turn-on voltage, the LEDs in the LED load are lit to provide illumination.
As an example, as shown in fig. 2, the constant current control module 10 includes: a first power switch Q1, a first sampling resistor Rs1, a first operational amplifier OP1 and a reference voltage generating unit 11, wherein a drain terminal of the first power switch Q1 is connected to a negative terminal of the LED load, a source terminal of the first power switch Q1 is connected to one terminal of the first sampling resistor Rs1, another terminal of the first sampling resistor Rs1 is grounded, a gate terminal of the first power switch Q1 is connected to an output terminal of the first operational amplifier OP1, a non-inverting input terminal of the first operational amplifier OP1 is connected to an output terminal of the reference voltage generating unit 11 to access the reference voltage Vref, and an inverting input terminal of the first operational amplifier OP1 is connected to the source terminal of the first power switch Q1; wherein, the reference voltage generating unit 11 is controlled by the bleeder current control module 30. In this example, the first sampling resistor Rs1 samples the current flowing through the LED load to obtain a sampling voltage, and the first operational amplifier OP1 compares the sampling voltage with the reference voltage Vref to control the current flowing through the LED load, so as to implement constant current control; during the period of constant current control, if the input end of the silicon controlled rectifier dimming LED driving system 1 is connected to the silicon controlled rectifier, at this time, the reference voltage generating unit 11 is controlled by the leakage current control module 30 to adjust the output reference voltage Vref according to the conduction angle of the silicon controlled rectifier, so as to control the output current of the LED load, so that the output current of the LED load changes along with the change of the conduction angle of the silicon controlled rectifier, and the silicon controlled rectifier dimming LED driving system realizes no stroboscopic output at the same time.
Specifically, as shown in fig. 2, the reference voltage generating unit 11 includes: and a reference voltage setting part 111 for generating a corresponding reference voltage Vref according to the magnitude of the thyristor conduction angle detected by the bleeder current control module 30 to output. In a specific application, the reference voltage generating unit 11 in this example may further include: and an adjusting resistor Rcs having one end connected to the reference voltage setting part 111 and the other end grounded, for adjusting the reference voltage Vref generated by the reference voltage setting part 111 by changing a resistance value of the adjusting resistor Rcs.
As an example, as shown in fig. 2, an upper plate of the energy storage capacitor Co is connected to the positive terminal of the LED load, and a lower plate of the energy storage capacitor Co is connected to the charging current control module 20. In this example, when the input voltage Vin is greater than the voltage across the energy storage capacitor Co, the input voltage Vin charges the energy storage capacitor Co, and the input voltage Vin supplies power to the LED load; and when the input voltage Vin is less than the voltage on the energy storage capacitor Co, the energy storage capacitor Co supplies power to the LED load.
As an example, as shown in fig. 2, the charging current control module 20 includes:
the discharge voltage detection unit 21 is connected to the negative terminal of the LED load, and is configured to determine the discharge voltage of the energy storage capacitor Co according to the negative terminal voltage of the LED load and generate a corresponding control signal;
an input voltage detection unit 22 for performing voltage detection on the input voltage Vin;
and the charging current control unit 23 is connected to the output end of the discharge voltage detection unit 21, the output end of the input voltage detection unit 22 and the lower plate of the energy storage capacitor Co, and is configured to adjust the charging current of the energy storage capacitor Co according to the control signal and the input voltage detection value. In this example, when the scr dimming LED driving system 1 includes the blocking diode D1, the input voltage detection unit 22 detects the bus voltage Vbus, and the charging current control unit 23 adjusts the charging current of the energy storage capacitor Co according to the control signal and the detected bus voltage value.
Specifically, as shown in fig. 2, the discharge voltage detection unit 21 includes:
a detection portion 211 connected to a negative terminal of the LED load for detecting a voltage of the negative terminal of the LED load;
and a comparing part 212 connected to an output terminal of the detecting part 211, for generating a first control signal when the voltage detection value of the negative terminal is greater than a first preset voltage Vref1, and generating a second control signal when the voltage detection value of the negative terminal is less than a second preset voltage Vref2, wherein the first preset voltage Vref1 is greater than the second preset voltage Vref 2.
Wherein, as shown in fig. 2, the detecting section 211 includes: a first divider resistor R1 and a second divider resistor R2, wherein one end of the first divider resistor R1 is connected to the negative terminal of the LED load, the other end of the first divider resistor R1 is connected to one end of the second divider resistor R2, and the other end of the second divider resistor R2 is grounded as the output terminal of the detection portion 211. In this example, the first voltage dividing resistor R1 and the second voltage dividing resistor R2 are connected in series between the negative terminal of the LED load and ground, and the negative terminal voltage detection value is obtained by voltage division.
As shown in fig. 2, the comparing part 212 includes: a first comparator CMP1 and a second comparator CMP2, wherein a non-inverting input terminal of the first comparator CMP1 is connected to an output terminal of the detecting portion 211, an inverting input terminal of the first comparator CMP1 is connected to the first preset voltage Vref1, an output terminal of the first comparator CMP1 is used as a first output terminal of the comparing portion 212 to generate the first control signal, a non-inverting input terminal of the second comparator CMP2 is connected to the second preset voltage Vref2, an inverting input terminal of the second comparator CMP2 is connected to an output terminal of the detecting portion 211, and an output terminal of the second comparator CMP2 is used as a second output terminal of the comparing portion 212 to generate the second control signal. In this example, when the negative terminal voltage detection value is greater than the first preset voltage Vref1, the first comparator CMP1 outputs a high level when the first control signal is active; on the contrary, when the negative terminal voltage detection value is less than the first preset voltage Vref1, the first comparator CMP1 outputs a low level, and the first control signal is invalid; when the negative terminal voltage detection value is greater than the second preset voltage Vref2, the second comparator CMP2 outputs a low level, at which time the second control signal is invalid; on the contrary, when the negative terminal voltage detection value is less than the second preset voltage Vref2, the second comparator CMP2 outputs a high level, and the second control signal is active at this time.
Specifically, as shown in fig. 2, the input voltage detection unit 22 includes: a third voltage dividing resistor R3 and a fourth voltage dividing resistor R4, wherein one end of the third voltage dividing resistor R3 is connected to the bus voltage Vbus, the other end of the third voltage dividing resistor R3 is connected to one end of the fourth voltage dividing resistor R4, and is also used as the output end of the input voltage detecting unit 22, and the other end of the fourth voltage dividing resistor R4 is grounded. In this example, the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4 are connected in series between the output end of the rectifier module 40 and the ground, and the bus voltage detection value is obtained by voltage division.
Specifically, as shown in fig. 2, the charging current control unit 23 includes:
a compensation part 231 connected to an output terminal of the discharge voltage detection unit 21, for generating a corresponding compensation voltage according to a corresponding control signal generated by the discharge voltage detection unit 21;
the current adjusting part 232 is connected to the output end of the input voltage detecting unit 22 and the output end of the compensating part 231, and is configured to adjust the charging current of the energy storage capacitor Co according to a difference between the compensation voltage and the input voltage detection value.
In this example, when the scr dimming LED driving system 1 includes the dc blocking diode D1, the current adjusting part 232 adjusts the charging current of the energy storage capacitor Co according to the difference between the compensation voltage and the detected value of the bus voltage. Wherein, as shown in fig. 2, the compensation part 231 includes: a first current source I1, a second current source I2, a compensation capacitor Ccomp and a compensation voltage generating circuit 2311, wherein a control terminal of the first current source I1 is connected to a first output terminal of the discharge voltage detecting unit 21, a first connection terminal of the first current source I1 is grounded, a second connection terminal of the first current source I1 is connected to a first connection terminal of the second current source I2 and an upper plate of the compensation capacitor Ccomp, a lower plate of the compensation capacitor Ccomp is grounded, a control terminal of the second current source I2 is connected to a second output terminal of the discharge voltage detecting unit 21, a second connection terminal of the second current source I2 is connected to an operating voltage, an input terminal of the compensation voltage generating circuit 2311 is connected to the upper plate of the compensation capacitor Ccomp, and an output terminal of the compensation voltage generating circuit 2311 serves as an output terminal of the compensation part 231. In this example, when the first control signal output by the discharge voltage detection unit 21 is active, the first current source I1 is turned on and discharges the compensation capacitor Ccomp; when the second control signal output by the discharge voltage detection unit 21 is active, the second current source I2 is turned on and charges the compensation capacitor Ccomp; the compensation voltage generated by the compensation voltage generation circuit 2311 is adjusted by charging and discharging the compensation capacitor Ccomp through the first current source I1 and the second current source I2. It should be noted that the compensation capacitor Ccomp can be disposed outside the chip, or can be integrated inside the chip by using digital filtering technology to reduce peripheral components and simplify the system.
As shown in fig. 2, the compensation part 231 further includes: a third comparator CPM3 and a third current source I3, a non-inverting input terminal of the third comparator CPM3 is connected to a gate terminal of a first power switch Q1 in the constant current control module 10, an inverting input terminal of the third comparator CPM3 is connected to a third preset voltage Vref3, an output terminal of the third comparator CPM3 is connected to a control terminal of the third current source I3, a first connection terminal of the third current source I3 is connected to the upper plate of the compensation capacitor Ccomp, and a second connection terminal of the third current source I3 is connected to a working voltage. In this example, when the gate terminal voltage of the first power switch Q1 is greater than the third preset voltage Vref3, the third comparator CMP3 outputs a high level, and the third control signal is asserted and controls the third current source I3 to be turned on.
Wherein, as shown in fig. 2, the current adjusting part 232 includes: a subtracter, a second operational amplifier OP2, a second power switch Q2, and a second sampling resistor Rs2, a first input terminal of the subtractor is connected to the output terminal of the compensation part 231, a second input terminal of the subtractor is connected to the output terminal of the input voltage detection unit 22, the output end of the subtractor is connected to the non-inverting input end of the second operational amplifier OP2, the inverting input terminal of the second operational amplifier OP2 is connected to the source terminal of the second power switch Q2, the output end of the second operational amplifier OP2 is connected to the gate end of the second power switch Q2, the drain end of the second power switch Q2 is connected to the lower plate of the energy storage capacitor Co, the source terminal of the second power switch Q2 is connected to one end of the second sampling resistor Rs2, and the other end of the second sampling resistor Rs2 is grounded. In this example, the subtractor subtracts the compensation voltage and the detected bus voltage value to obtain a difference therebetween, the second sampling resistor Rs2 samples the current flowing through the energy storage capacitor Co to obtain a sampling voltage, and the second operational amplifier OP2 compares the sampling voltage and the difference between the compensation voltage output by the subtractor and the detected bus voltage value to adjust the charging current of the energy storage capacitor Co.
As an example, as shown in fig. 2, the leakage current control module 30 includes:
the phase detection unit 31 is configured to perform phase detection on the input voltage Vin to determine whether the input end of the silicon controlled dimming LED driving system 1 is connected to the silicon controlled rectifier, generate a turn-on signal when the input end of the silicon controlled dimming LED driving system 1 is connected to the silicon controlled rectifier, determine a conduction angle of the silicon controlled rectifier according to a phase detection value to regulate and control the reference voltage of the constant current control module 10, and generate a turn-off signal when the input end of the silicon controlled dimming LED driving system 1 is not connected to the silicon controlled rectifier;
a set current generating unit 32 connected to the output terminal of the phase detecting unit 31, for generating the set current I _ ref under the control of the turn-on signal;
and a leakage current control unit 33, connected to the output end of the set current generation unit 32, one end of the first sampling resistor Rs1 in the constant current control module 10, and one end of the second sampling resistor Rs2 in the charging current control module 20, for detecting the leakage current, the output current of the LED load, and the charging current of the energy storage capacitor Co, and controlling the leakage current to make the sum of the leakage current, the output current of the LED load, and the charging current of the energy storage capacitor Co not less than the set current I _ ref so as to maintain the conduction of the thyristor.
Specifically, the phase detection unit 31 performs phase detection on the input voltage Vin to determine whether the input voltage Vin has phase cut according to a detected phase detection value; when the input voltage Vin is subjected to phase switching, the input end of the silicon controlled light dimming LED driving system 1 is judged to be connected with the silicon controlled, and a starting signal is generated at the moment to be output; and when the input voltage Vin is not subjected to phase switching, judging that the input end of the silicon controlled light dimming LED driving system 1 is not connected with the silicon controlled, and generating a turn-off signal to output. When the input end of the silicon controlled rectifier dimming LED driving system 1 is connected to the silicon controlled rectifier, the phase detection unit 31 further determines the conduction angle of the silicon controlled rectifier according to the detected phase detection value, so as to regulate the reference voltage Vref of the constant current control module 10.
Specifically, as shown in fig. 2, the setting current generating unit 32 includes: a set current generating part 321, configured to generate the set current I _ ref according to the turn-on signal generated by the phase detecting unit 31 to output the set current I _ ref when the thyristor is connected to the input terminal of the thyristor-controlled dimming LED driving system 1. In a specific application, the setting current generating unit 32 may further include: an adjusting resistor Rdn, one end of which is connected to the setting current generating part 321 and the other end of which is grounded, is used for adjusting the magnitude of the setting current I _ ref generated by the setting current generating part 321 by changing the resistance value of the adjusting resistor Rdn.
Specifically, as shown in fig. 2, the leakage current control unit 33 includes: a third power switch Q3, a third sampling resistor Rs3, a third operational amplifier OP3, a first detecting resistor Rc1, a second detecting resistor Rc2 and a third detecting resistor Rc3, wherein a drain terminal of the third power switch Q3 is connected to the input voltage Vin, a source terminal of the third power switch Q3 is connected to one end of the third sampling resistor Rs3, the other end of the third sampling resistor Rs3 is grounded, a gate terminal of the third power switch Q3 is connected to an output terminal of the third operational amplifier OP3, a non-inverting input terminal of the third operational amplifier OP3 is connected to an output terminal of the set current generating unit 32, inverting input terminals of the third operational amplifier OP3 are connected to one end of the first detecting resistor Rc1, one end of the second detecting resistor Rc2 and one end of the third detecting resistor Rc3, the other end of the first detecting resistor Rc1 is connected to one end of the third sampling resistor Rs3, the other end of the second sensing resistor Rc2 is connected to one end of the first sampling resistor Rs1 in the constant current control module 10, and the other end of the third sensing resistor Rc3 is connected to one end of the second sampling resistor Rs2 in the charging current control module 20. In this example, the third power switch Q3 and the third sampling resistor Rs3 constitute a bleeding branch of the thyristor, the bleeding and discharging current control unit 33 detects a bleeding current flowing through the bleeding branch through the first detection resistor Rc1, detects an output current flowing through the LED load through the second detection resistor Rc2, detects a charging current of a branch in which the energy storage capacitor Co is located through the third detection resistor Rc3, and compares the sum of the three (i.e., the sum of the bleeding current, the output current of the LED load, and the charging current of the energy storage capacitor Co) with the set current I _ ref through the third operational amplifier OP3 to control the bleeding current of the bleeding branch, so that the sum of the three is not less than the set current I _ ref, thereby maintaining the conduction of the thyristor and avoiding flicker caused by turn-off.
In this embodiment, since the discharge current of the energy storage capacitor Co is equal to the output current of the LED load, the resistance of the first sampling resistor is set to be equal to the resistance of the second sampling resistor (i.e., Rs1 is Rs2), and the resistance of the first detection resistor is set to be equal to the resistance of the second detection resistor is set to be equal to the resistance of the third detection resistor (i.e., Rc1 is Rc2 is Rc3), so that the control of the bleeder current is not affected when the energy storage capacitor Co discharges (signals generated when the energy storage capacitor Co discharges Rs1 and Rs2 cancel each other, and only Rs3 functions).
Fig. 3 is a block diagram of an actual application of the scr dimming LED driving system 1 shown in fig. 2, wherein the compensation capacitor Ccomp is disposed outside the chip, but it can also be integrated inside the chip by using a digital filtering technology to reduce peripheral components, so as to simplify the system. In a specific application, as shown in fig. 4, the diode D1 and the rectifying module can be further integrated inside the chip, and the adjusting resistors Rcs and Rdn are also integrated inside the chip to be a fixed current output, so that the periphery of the whole application system can be very simple.
Example two
As shown in fig. 2 and 5, the present embodiment provides a driving method of a thyristor-controlled dimming LED, where the driving method of the LED includes:
when the thyristor dimming is performed on the LED load in the thyristor dimming LED driving system 1,
if the input end of the silicon controlled rectifier dimming LED driving system 1 is connected to a silicon controlled rectifier, the leakage current control module 30 is turned on and the leakage current is controlled based on the leakage current control module 30, so that the sum of the leakage current and the output current of the LED load and the charging current of the energy storage capacitor Co is not less than the set current I _ ref to maintain the conduction of the silicon controlled rectifier, thereby avoiding flicker caused by turn-off, and meanwhile, the reference voltage of the constant current control module 10 is controlled according to the conduction angle of the silicon controlled rectifier to control the output current of the LED load, so that the output current of the LED load changes along with the change of the conduction angle of the silicon controlled rectifier, and the silicon controlled rectifier dimming is realized while no stroboscopic output is realized;
if the input end of the LED driving system is not connected to the thyristor, the leakage current control module 30 is turned off to reduce leakage current loss and improve system efficiency.
As an example, the phase detection unit 31 performs phase detection on the input voltage Vin to determine whether the input end of the silicon controlled dimming LED driving system 1 is connected to the silicon controlled rectifier, and meanwhile, the conduction angle of the silicon controlled rectifier is determined according to the phase detection value.
Specifically, the phase detection unit 31 performs phase detection on the input voltage Vin to determine whether the input voltage Vin has phase cut according to a phase detection value; if the input voltage Vin is subjected to phase cut, judging that the input end of the silicon controlled dimming LED driving system 1 is connected with the silicon controlled rectifier; and if the input voltage Vin does not generate phase cut, judging that the input end of the silicon controlled rectifier dimming LED driving system 1 is not connected with the silicon controlled rectifier. When the input end of the silicon controlled rectifier dimming LED driving system 1 is connected to the silicon controlled rectifier, the phase detection unit 31 further determines the conduction angle of the silicon controlled rectifier according to the phase detection value, so as to regulate the reference voltage Vref of the constant current control module 10.
Specifically, when the input end of the silicon controlled rectifier dimming LED driving system 1 is connected with the silicon controlled rectifier, the setting current generating unit 32 generates the setting current I _ ref under the control of the on signal generated by the phase detecting unit 31, the bleeder current control unit 33 detects the bleeder current flowing through the bleeder branch through the first detection resistor Rc1, the output current flowing through the LED load is detected through the second detection resistor Rc2, the charging current of the branch of the energy storage capacitor Co is detected through the third detection resistor Rc3, and comparing the sum of the three (i.e. the sum of the leakage current, the output current of the LED load and the charging current of the energy storage capacitor Co) with the set current I _ ref to regulate the leakage current of the leakage branch, so that the sum of the three is not less than the set current I _ ref, thereby maintaining the conduction of the thyristor.
As an example, when performing thyristor dimming on an LED load in the thyristor-dimmed LED driving system 1, the LED driving method further includes:
when the input voltage Vin is smaller than the on-state voltage of the LED load, the energy storage capacitor Co discharges the LED load, and the LED load is subjected to constant current control based on the constant current control module 10;
when the input voltage Vin is greater than the on-state voltage of the LED load, the input voltage Vin supplies power to the LED load, and the constant current control module 10 performs constant current control on the LED load, and simultaneously charges the energy storage capacitor Co;
when the input voltage Vin is smaller than the voltage of the energy storage capacitor Co, the energy storage capacitor Co discharges the LED load, and the LED load is subjected to constant current control based on the constant current control module 10.
Specifically, when the input voltage Vin is smaller than the turn-on voltage of the LED load, the input voltage Vin is not enough to turn on the LED load, and at this time, the energy storage capacitor Co discharges the LED load to turn on the LED load, and the current flowing through the LED load is subjected to constant current control by the constant current control module 10. The constant current control module 10 samples the current flowing through the LED load through the first sampling resistor Rs1 to obtain a sampling voltage, and the first operational amplifier OP1 compares the sampling voltage with the reference voltage Vref to control the current flowing through the LED load, so as to realize constant current control, and ensure that the current flowing through the LED load is constant to eliminate stroboflash. In this example, during normal operation, the voltage across the energy storage capacitor Co does not drop very low, so that power can be supplied to the chip during the valley period of the input voltage Vin to ensure that current still flows through the LED load during the valley period of the input voltage Vin.
Specifically, as the input voltage Vin gradually increases, when the input voltage Vin is greater than the on-state voltage of the LED load, the input voltage Vin supplies power to the LED load and charges the energy storage capacitor Co. In this example, the charging current of the energy storage capacitor Co is controlled by the second power switch Q2, the second operational amplifier OP2 and the second sampling resistor Rs2, so as to extend the conduction angle of the input current to improve the power factor.
When the input voltage Vin charges the energy storage capacitor Co, the input voltage detection unit 22 detects the bus voltage VbusHV, and when the bus voltage Vbus is too high, the charging current of the energy storage capacitor Co is reduced until zero, so that the loss of the second power switch tube Q2 is reduced, and the overall efficiency of the system is improved. In order to ensure the highest system efficiency, the discharge voltage of the energy storage capacitor Co cannot be too high, and in order to keep the output LED current constant, and therefore, the discharge voltage of the energy storage capacitor Co cannot be too low, the discharge voltage of the energy storage capacitor Co is determined by the voltage at the LED negative terminal (VOUT — VLED). More specifically, the voltage of the negative terminal of the LED load is detected by the detecting portion 211, when the detected voltage of the negative terminal is higher than the first preset voltage Vref1, which indicates that the discharging voltage of the energy storage capacitor Co is higher, the first comparator CMP1 controls the first current source I1 to be turned on, so as to discharge the compensation capacitor Ccomp, and reduce the compensation voltage output by the compensation voltage generating circuit 2311, so as to reduce the charging current of the energy storage capacitor Co, and thus reduce the discharging voltage of the energy storage capacitor Co; when the detected voltage of the negative electrode terminal is lower than a second preset voltage Vref2, it is indicated that the discharging voltage of the energy storage capacitor Co is relatively low, the second comparator CMP2 controls the second current source I2 to be turned on, the compensation capacitor Ccomp is charged, the compensation voltage output by the compensation voltage generation circuit 2311 is increased, so as to increase the charging current of the energy storage capacitor Co, and thus, the discharging voltage of the energy storage capacitor Co is increased. In order to filter power frequency ripples, the compensation capacitor Ccomp is large, and the loop response is slow; when the output voltage is lower than a large amount, the LED current decreases, and at this time, the gate voltage of the first power switch Q1 increases to be higher (especially, the compensation voltage is lower when just starting up), when the third comparator CMP3 detects that the gate voltage of the first power switch Q1 exceeds a third preset voltage Vref3, the third current source I3 is controlled to be turned on (in this example, the current flowing through the third current source is larger than the current flowing through the second current source, i.e., I3> I2), the compensation voltage output by the compensation voltage generation circuit 2311 is rapidly increased, and the charging current of the energy storage capacitor Co is increased, so as to rapidly increase the discharging voltage of the energy storage capacitor Co.
Specifically, the input voltage Vin gradually decreases after reaching a peak value, and when the input voltage Vin is smaller than the voltage of the energy storage capacitor Co, the energy storage capacitor Co discharges to the LED load until the input voltage Vin is again larger than the on-state voltage of the LED load or the voltage on the energy storage capacitor Co is smaller than the on-state voltage of the LED load.
Fig. 5 is a working waveform diagram of the LED driving method according to the present embodiment:
as shown in fig. 5, when the thyristor is not connected to the input end of the thyristor dimming LED driving system 1, the reference voltage Vref is the maximum voltage value, and Vref is Ref clamp; at this time, the operating waveform of the LED driving method is shown at times t0-t 3.
As shown in fig. 5, when the input end of the scr dimming LED driving system 1 is connected to a scr and the conduction angle of the scr gradually increases, the value of the reference voltage Vref gradually decreases from Ref clamp to 0 as the conduction angle increases; at this time, the operating waveform of the LED driving method is shown at times t4-t 26.
In summary, the silicon controlled dimming LED driving system and the method thereof of the present invention have the following beneficial effects: 1. the silicon controlled dimming LED driving system and the method thereof detect the voltage of the negative terminal of the LED load to control the charging current of the energy storage capacitor, and control the loss of the constant current power switch tube to be minimum under the condition of ensuring that the output LED has no stroboflash. 2. The silicon controlled dimming LED driving system and the method thereof detect the grid voltage of the constant-current power switch tube to accelerate the loop response speed and ensure quick start. 3. According to the silicon controlled dimming LED driving system and the method thereof, the LED load is supplied with power through the energy storage capacitor at the input voltage valley bottom, and meanwhile, the charging current of the energy storage capacitor is reduced when the input voltage is high, so that the system has high power factor and high efficiency. 4. According to the silicon controlled rectifier dimming LED driving system and the method thereof, the external control of the bleeder current is performed through the phase detection, when the output current of the LED load and the charging current of the energy storage capacitor are reduced to cause insufficient input current, the conduction of the silicon controlled rectifier can be maintained by regulating the bleeder current, the problem of flicker of the silicon controlled rectifier due to turn-off is prevented, the dimming performance is optimized while the dimming requirement of the silicon controlled rectifier is met, and the dimming is free from stroboflash in the whole dimming process. 5. The peripheral circuit of the silicon controlled dimming LED driving system is simplified to the greatest extent, and the system cost is low. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (13)

1. The utility model provides a silicon controlled rectifier LED actuating system that adjusts luminance which characterized in that, silicon controlled rectifier LED actuating system that adjusts luminance includes:
the positive terminal of the LED load is connected with input voltage;
the constant current control module is connected to the negative end of the LED load and is used for performing constant current control on the LED load;
the upper pole plate of the energy storage capacitor is connected to the positive end of the LED load and used for discharging to the LED load when the input voltage is smaller than the voltage on the energy storage capacitor;
the charging current control module is connected to the negative end of the LED load and the lower pole plate of the energy storage capacitor and used for adjusting the charging current of the energy storage capacitor according to the detected input voltage and the detected discharging voltage of the energy storage capacitor;
the discharge current control module is connected with the constant current control module and the charging current control module, and is used for being switched on when the input end of the silicon controlled rectifier dimming LED driving system is connected with a silicon controlled rectifier and being switched off when the input end of the silicon controlled rectifier dimming LED driving system is not connected with the silicon controlled rectifier; when the LED constant current control module is started, the sum of the leakage current, the output current of the LED load and the charging current of the energy storage capacitor is not less than the set current by regulating and controlling the leakage current so as to maintain the conduction of the controllable silicon, and meanwhile, the reference voltage of the constant current control module is regulated and controlled according to the conduction angle of the controllable silicon so as to control the output current of the LED load.
2. The silicon controlled dimming LED driving system according to claim 1, wherein the constant current control module comprises: the LED load circuit comprises a first power switch tube, a first sampling resistor, a first operational amplifier and a reference voltage generating unit, wherein the drain electrode end of the first power switch tube is connected to the negative electrode end of the LED load, the source electrode end of the first power switch tube is connected to one end of the first sampling resistor, the other end of the first sampling resistor is grounded, the grid electrode end of the first power switch tube is connected to the output end of the first operational amplifier, the non-inverting input end of the first operational amplifier is connected to the reference voltage generating unit to be connected to the reference voltage, and the inverting input end of the first operational amplifier is connected to the source electrode end of the first power switch tube; wherein the reference voltage generating unit is controlled by the bleeder current control module.
3. The silicon controlled dimming LED driving system according to claim 1, wherein the charging current control module comprises:
the discharge voltage detection unit is connected to the negative end of the LED load and used for judging the discharge voltage of the energy storage capacitor according to the negative end voltage of the LED load and generating a corresponding control signal;
an input voltage detection unit for performing voltage detection on the input voltage;
and the charging current control unit is connected with the output end of the discharging voltage detection unit, the output end of the input voltage detection unit and the lower polar plate of the energy storage capacitor and is used for adjusting the charging current of the energy storage capacitor according to the control signal and the input voltage detection value.
4. The SCR-dimmed LED driving system according to claim 3, wherein the discharge voltage detection unit comprises:
the detection part is connected to the negative terminal of the LED load and is used for detecting the voltage of the negative terminal of the LED load;
and the comparison part is connected with the output end of the detection part and used for generating a first control signal when the voltage detection value of the negative end is greater than a first preset voltage and generating a second control signal when the voltage detection value of the negative end is less than a second preset voltage, wherein the first preset voltage is greater than the second preset voltage.
5. The thyristor dimmed LED drive system according to claim 4, wherein the detection portion comprises: one end of the first voltage-dividing resistor is connected to the negative electrode end of the LED load, the other end of the first voltage-dividing resistor is connected to one end of the second voltage-dividing resistor and serves as the output end of the detection part, and the other end of the second voltage-dividing resistor is grounded; the comparison section includes: the output end of the first comparator is used as the first output end of the comparison part, the in-phase input end of the second comparator is connected with the second preset voltage, the reverse-phase input end of the second comparator is connected with the output end of the detection part, and the output end of the second comparator is used as the second output end of the comparison part.
6. The silicon controlled dimming LED driving system according to claim 3, wherein the charging current control unit comprises:
the compensation part is connected with the output end of the discharge voltage detection unit and used for generating corresponding compensation voltage according to the corresponding control signal generated by the discharge voltage detection unit;
and the current adjusting part is connected with the output end of the input voltage detecting unit and the output end of the compensating part and is used for adjusting the charging current of the energy storage capacitor according to the difference value of the compensating voltage and the input voltage detection value.
7. The triac-dimmed LED driving system according to claim 6, wherein the compensation portion comprises: the control end of the first current source is connected to the first output end of the discharge voltage detection unit, the first connection end of the first current source is grounded, the second connection end of the first current source is connected to the first connection end of the second current source and the upper polar plate of the compensation capacitor, the lower polar plate of the compensation capacitor is grounded, the control end of the second current source is connected to the second output end of the discharge voltage detection unit, the second connection end of the second current source is connected to the working voltage, the input end of the compensation voltage generation circuit is connected to the upper polar plate of the compensation capacitor, and the output end of the compensation voltage generation circuit serves as the output end of the compensation part; the current adjusting section includes: the first input end of the subtracter is connected to the output end of the compensation part, the second input end of the subtracter is connected to the output end of the input voltage detection unit, the output end of the subtracter is connected to the non-inverting input end of the second operational amplifier, the inverting input end of the second operational amplifier is connected to the source end of the second power switch tube, the output end of the second operational amplifier is connected to the grid end of the second power switch tube, the drain end of the second power switch tube is connected to the lower pole plate of the energy storage capacitor, the source end of the second power switch tube is connected to one end of the second sampling resistor, and the other end of the second sampling resistor is grounded.
8. The triac-dimmed LED driving system according to claim 7, wherein the compensation portion further comprises: the non-inverting input end of the third comparator is connected to the gate end of a first power switch tube in the constant current control module, the inverting input end of the third comparator is connected to a third preset voltage, the output end of the third comparator is connected to the control end of the third current source, the first connection end of the third current source is connected to the upper polar plate of the compensation capacitor, and the second connection end of the third current source is connected to a working voltage.
9. The triac-dimmed LED driving system according to any of claims 1 to 8, wherein the leakage current control module comprises:
the phase detection unit is used for carrying out phase detection on the input voltage so as to judge whether the input end of the silicon controlled light dimming LED driving system is connected with the silicon controlled, and generating a starting signal when the input end of the silicon controlled light dimming LED driving system is connected with the silicon controlled, and meanwhile, judging the size of a conduction angle of the silicon controlled according to a phase detection value so as to regulate and control the reference voltage of the constant current control module, and generating a turn-off signal when the input end of the silicon controlled light dimming LED driving system is not connected with the silicon controlled;
the setting current generating unit is connected to the output end of the phase detection unit and is used for generating the setting current under the control of the starting signal;
and the leakage current control unit is connected with the output end of the set current generation unit, one end of a first sampling resistor in the constant current control module and one end of a second sampling resistor in the charging current control module, and is used for detecting the leakage current, the output current of the LED load and the charging current of the energy storage capacitor and controlling the leakage current to enable the sum of the leakage current, the output current of the LED load and the charging current of the energy storage capacitor to be not less than the set current so as to maintain the conduction of the silicon controlled rectifier.
10. The triac-dimmed LED driving system according to claim 9, wherein the leakage current control unit comprises: a third power switch tube, a third sampling resistor, a third operational amplifier, a first detection resistor, a second detection resistor and a third detection resistor, wherein the drain terminal of the third power switch tube is connected to the input voltage, the source terminal of the third power switch tube is connected to one end of the third sampling resistor, the other end of the third sampling resistor is grounded, the gate terminal of the third power switch tube is connected to the output terminal of the third operational amplifier, the non-inverting input terminal of the third operational amplifier is connected to the output terminal of the set current generating unit, the inverting input terminal of the third operational amplifier is respectively connected to one end of the first detection resistor, one end of the second detection resistor and one end of the third detection resistor, the other end of the first detection resistor is connected to one end of the third sampling resistor, and the other end of the second detection resistor is connected to one end of the first sampling resistor in the constant current control module, the other end of the third detection resistor is connected to one end of a second sampling resistor in the charging current control module.
11. The triac dimmed LED drive system according to claim 1, wherein the triac dimmed LED drive system further comprises: and the direct current blocking diode is connected between the input voltage and the LED load and used for converting the input voltage into bus voltage.
12. A silicon controlled rectifier dimming LED driving method is characterized by comprising the following steps: when the LED load in the silicon controlled dimming LED driving system is subjected to silicon controlled dimming,
if the input end of the silicon controlled rectifier dimming LED driving system is connected with a silicon controlled rectifier, a leakage current control module is started, leakage current is regulated and controlled based on the leakage current control module, the sum of the leakage current, the output current of the LED load and the charging current of an energy storage capacitor is not less than a set current so as to maintain the conduction of the silicon controlled rectifier, and meanwhile, the reference voltage of a constant current control module is regulated and controlled according to the conduction angle of the silicon controlled rectifier so as to control the output current of the LED load;
and if the input end of the LED driving system is not connected with the controlled silicon, the leakage current control module is switched off.
13. The method as claimed in claim 12, wherein the phase detection unit is used to perform phase detection on the input voltage to determine whether the input terminal of the driving system is connected to the thyristor, and the conduction angle of the thyristor is determined according to the phase detection value.
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