Discharge current control module and LED driving system with thyristor dimming

Abstract

The application provides a kind of discharge current control module and thyristor dimming LED drive system, including: power switch tube, respectively via first, second resistance connection input voltage positive, negative electrode;Third resistance, between LED constant current control module and input voltage negative electrode;Voltage conversion unit, negative voltage on third resistance is converted into positive voltage;First comparator, compare voltage conversion unit output voltage with first reference voltage;Discharge current control unit, feedback voltage of power switch tube second end, and when voltage conversion unit output voltage is greater than first reference voltage, output discharge current off control signal;First constant current source, between voltage conversion unit and discharge current control unit;Fourth resistance, between first constant current source and power switch tube;First operational amplifier, based on the output voltage of discharge current control unit and second reference voltage generates drive signal.The application can ensure that each part works normally, with small loss and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit design, and in particular to a discharge current control module and a silicon controlled rectifier (SCR) dimming LED driving system. Background Technology

[0002] In LED driver applications using SCR dimming, there is a holding current requirement for the SCR to conduct. Once the input current is less than the holding current, the SCR will turn off and then restart, which will cause the LED to flicker. Therefore, an external Bleed circuit is generally required to meet the holding current requirement of the SCR, so that the SCR can conduct continuously within the operating range and avoid LED flickering.

[0003] In existing SCR-based LED driver circuits, problems commonly exist, such as the discharge current affecting the constant current accuracy of the LED and the inability to achieve constant current control under certain circumstances. Therefore, how to maintain constant current and normal operation of the SCR, and improve circuit performance, has become one of the urgent problems to be solved by those skilled in the art. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a discharge current control module and a silicon controlled rectifier (SCR) dimming LED driving system to solve the problems in the prior art where the discharge current affects the constant current accuracy of the LED and the constant current control function cannot be realized normally.

[0005] To achieve the above and other related objectives, the present invention provides a discharge current control module for maintaining the conduction of a silicon controlled rectifier (SCR), wherein the discharge current control module comprises at least:

[0006] The system includes a power switching transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a voltage conversion unit, a first comparator, a bleed current control unit, a first constant current source, and a first operational amplifier.

[0007] The first terminal of the power switch is connected to the positive terminal of the input voltage via the first resistor, and the second terminal is connected to the negative terminal of the input voltage via the second resistor.

[0008] The first end of the third resistor is connected to the ground terminal of the LED constant current control module, and the second end is connected to the negative terminal of the input voltage.

[0009] The input terminal of the voltage conversion unit is connected to the second terminal of the third resistor, converting the negative voltage at the second terminal of the third resistor into a positive voltage;

[0010] The first input terminal of the first comparator is connected to the output terminal of the voltage conversion unit, and the second input terminal receives the first reference voltage and outputs the comparison result.

[0011] The discharge current control unit is connected to the second terminal of the power switch tube, receives the comparison result, outputs a feedback signal of the voltage at the second terminal of the power switch tube, and outputs a discharge current turn-off control signal when the output voltage of the voltage conversion unit is greater than the first reference voltage.

[0012] The input terminal of the first constant current source is connected to the output terminal of the voltage conversion unit, and the output terminal is connected to the output terminal of the discharge current control unit;

[0013] One end of the fourth resistor is connected to the output terminal of the first constant current source, and the other end is connected to the second terminal of the power switch transistor;

[0014] The first input terminal of the first operational amplifier is connected to the output terminal of the discharge current control unit, and the second input terminal receives a second reference voltage. The drive signal of the power switch control terminal is generated based on the difference between the output voltage of the discharge current control unit and the second reference voltage.

[0015] Optionally, the voltage conversion unit includes a fifth resistor, a sixth resistor, a first diode, and a second operational amplifier;

[0016] The fifth resistor and the sixth resistor are connected in series between the input and output terminals of the voltage conversion unit;

[0017] The cathode of the first diode is connected to the input terminal of the voltage conversion unit, and the anode is connected to the ground terminal of the LED constant current control module;

[0018] The first input terminal of the second operational amplifier is connected between the fifth resistor and the sixth resistor, the second input terminal is connected to the anode of the first diode, and the output terminal is connected to the output terminal of the voltage conversion unit.

[0019] Alternatively, the fifth resistor has the same resistance value as the sixth resistor.

[0020] Alternatively, the operating voltage across the third resistor is less than the forward conduction voltage of the first diode.

[0021] Alternatively, the first diode may be implemented using a parasitic diode of a chip interface ESD protection device.

[0022] Alternatively, the discharge current control module further includes a discharge time detection unit, which is connected to the first terminal of the power switch to detect the discharge time during the input voltage rise time period; the discharge current control unit is connected to the output terminal of the discharge time detection unit, and outputs a discharge current turn-off control signal when the discharge time during the input voltage rise time period is greater than a set value.

[0023] Alternatively, the discharge current control module further includes an input voltage detection unit connected to the first terminal of the power switch to detect the input voltage; the discharge current control unit is connected to the output terminal of the input voltage detection unit, and maintains the output discharge current turn-off control signal when the input voltage value during the falling phase is less than the LED's turn-on voltage.

[0024] Alternatively, the discharge current control module further includes a discharge voltage clamping unit; the discharge voltage clamping unit is connected between the first terminal of the power switch and the negative terminal of the input voltage, and its output terminal is connected to the output terminal of the discharge current control unit; when the voltage at the first terminal of the power switch is less than a preset voltage, a compensation signal is generated based on the voltage value at the first terminal of the power switch, wherein the smaller the voltage at the first terminal of the power switch, the larger the compensation signal.

[0025] Alternatively, the discharge voltage clamping unit includes a seventh resistor, an eighth resistor, a transconductance operational amplifier, and a second constant current source;

[0026] The seventh resistor and the eighth resistor are connected in series between the first terminal of the power switch and the negative terminal of the input voltage;

[0027] The first input terminal of the transconductance operational amplifier is connected between the seventh resistor and the eighth resistor, the second input terminal is connected to the third reference voltage, and the output terminal is connected to the input terminal of the second constant current source.

[0028] The output terminal of the second constant current source is connected to the output terminal of the discharge current control unit.

[0029] To achieve the above and other related objectives, the present invention provides a silicon controlled rectifier (SCR) dimming LED driving system, wherein the SCR dimming LED driving system comprises at least:

[0030] Voltage input module, LED constant current control module and the aforementioned discharge current control module;

[0031] The voltage input module receives AC voltage and converts it into DC input voltage;

[0032] The LED constant current control module is connected to the output terminal of the voltage input module, and realizes constant current output of the LED based on the input voltage;

[0033] The discharge current control module is connected to the output terminal of the voltage input module and provides discharge current according to the current flowing through the LED constant current control module to maintain the conduction of the voltage input module.

[0034] Optionally, the voltage input module includes a rectifier unit and a thyristor; the AC terminal of the rectifier unit is connected to the AC voltage, and the DC terminal outputs the input voltage; the thyristor is connected in series to the AC terminal of the rectifier unit.

[0035] Alternatively, the LED constant current control module includes a second diode, a first LED load, a first capacitor, and a constant current control unit;

[0036] The anode of the second diode is connected to the input voltage, and the cathode is connected to the positive terminal of the first LED load; the first capacitor is connected in parallel across the first LED load.

[0037] The constant current control unit is connected to the negative terminal of the first LED load and performs constant current control on the current flowing through the first LED load.

[0038] Alternatively, the LED constant current control module includes a third diode, a second LED load, a second capacitor, and a current control unit;

[0039] The anode of the third diode is connected to the input voltage, and the cathode is connected to the upper plate of the second capacitor and the positive terminal of the second LED load.

[0040] The current control unit is connected to the lower plate of the second capacitor and the negative terminal of the second LED load, respectively controlling the charging current of the second capacitor and the current flowing through the second LED load, thereby achieving constant current and flicker-free control of the second LED load.

[0041] As described above, the discharge current control module and the SCR-modulated LED driving system of the present invention have the following beneficial effects:

[0042] 1. In the LED driving system of the present invention, the negative voltage signal generated by the current flowing through the LED constant current control module is processed by the operational amplifier to obtain a positive voltage signal to participate in the circuit feedback control, and a diode is used as a protection device to avoid the problem of the system failing to work.

[0043] 2. The discharge current control module and the LED driver system with thyristor dimming of the present invention detect the LED output current and the current of the anti-flicker section in real time through the negative voltage signal of the Vs port, so as to perform corresponding subsequent control actions without affecting the normal constant current operation.

[0044] 3. The discharge current control module and the LED driver system with thyristor dimming of the present invention determine whether the system is connected to the thyristor by the conduction time of the discharge current, which is simple and effective.

[0045] 4. The discharge current control module and the thyristor-controlled LED driver system of the present invention will turn off the discharge current when the thyristor is not connected to the system, thereby reducing system losses, improving system efficiency, and reducing chip heat generation.

[0046] 5. The discharge current control module and the LED driver system with thyristor dimming of the present invention turn off the discharge current during the falling edge of the input voltage when the system is connected to the thyristor; or delay the thyristor conduction time through the discharge voltage clamping unit to reduce the conduction time of the discharge current; thereby reducing discharge current loss, improving system efficiency and reducing chip heat generation. Attached Figure Description

[0047] Figure 1 The diagram shows a structural schematic of a linear LED driving system with silicon controlled rectifier (SCR) dimming.

[0048] Figure 2 This is another schematic diagram of a linear LED driving system with silicon controlled rectifier dimming.

[0049] Figure 3 This is another schematic diagram of a linear LED driving system with silicon controlled rectifier dimming.

[0050] Figure 4 The diagram shown is a structural schematic of the discharge current control module of the present invention.

[0051] Figure 5 This is a schematic diagram of another structure of the discharge current control module of the present invention.

[0052] Figure 6 The diagram shown illustrates the working principle of the discharge current control module of this invention.

[0053] Figure 7 This is a schematic diagram of another structure of the discharge current control module of the present invention.

[0054] Figure 8 The diagram shown is another structural schematic of the discharge current control module of the present invention.

[0055] Figure 9 The diagram shown is a structural schematic of the voltage discharge clamping unit of the present invention.

[0056] Figure 10 The diagram shows the working process of the discharge current control module of the present invention.

[0057] Figure 11 The diagram shown is a structural schematic of a silicon controlled rectifier (SCR) dimming LED driving system according to the present invention.

[0058] Figure 12The diagram shown is another structural schematic of the thyristor-controlled dimming LED driving system of the present invention.

[0059] Component designation explanation

[0060] 11. Thyristor

[0061] 12 Rectifier Bridge

[0062] 13a-13c discharge current control circuit

[0063] 14a-14b Linear LED Constant Current Control Circuit

[0064] 14c ERP Linear LED Constant Current Control Circuit

[0065] 2. Discharge current control module

[0066] 21 Voltage conversion unit

[0067] 22 First comparator

[0068] 23. Discharge current control unit

[0069] 24 Discharge Time Detection Unit

[0070] 25 Input Voltage Detection Unit

[0071] 26 Discharge voltage clamping unit

[0072] 3 Voltage Input Module

[0073] 31 Rectifier Unit

[0074] 32 thyristors

[0075] 4 LED constant current control module

[0076] 41 Constant Current Control Unit

[0077] 42 Operating Voltage Generation Module

[0078] 43 Current Control Unit Detailed Implementation

[0079] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0080] Please see Figures 1-12It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0081] like Figure 1 The diagram shows a linear LED driving system with SCR dimming. The SCR 11 is connected in series at the AC terminal of the rectifier bridge 12. A discharge current control circuit 13a is connected to the output terminal of the rectifier bridge 12. The anode of diode Da is connected to the output terminal of the rectifier bridge 12. The positive terminal of the LED is connected to the cathode of diode Da. A capacitor Ca is connected in parallel across the LED. A linear LED constant current control circuit 14a is connected to the negative terminal of the LED. The current setting pin of the discharge current control circuit 13a is connected to the current setting pin of the linear LED constant current control circuit 14a through a resistor Ra, and then connected to GND through a resistor Rb. When the LED is not conducting, the discharge current is... , where V Bleed The reference voltage for the bleeder circuit is V; when current flows through the LED, and the voltage drop across resistor Rb is greater than or equal to the reference voltage V of the bleeder circuit. Bleed When this happens, the discharge current is turned off. In this scheme, the discharge current affects the feedback of the LED output current, which degrades the constant current accuracy of the LED.

[0082] like Figure 2 As shown, an improved SCR-based linear LED driving system with dimming is proposed. The ground of the linear LED constant current control circuit 14b (one end of resistor Rd is connected to the current setting pin of the linear LED constant current control circuit 14b, and the other end is grounded) is superimposed on the current setting pin of the bleeder current control circuit 13b, and then connected to the GND of the bridge rectifier through resistor Rc. When the voltage drop generated by the LED current across resistor Rc is greater than or equal to the reference voltage V of the bleeder circuit... Bleed When the current is turned off, the bleed current is cut off. The diode Db is used to clamp and protect the bleed current setting pin to prevent the high voltage generated by the spike current from damaging the chip.

[0083] Neither of the above two solutions can meet the ERP's requirements for output flicker; therefore, a different approach is proposed. Figure 3The illustrated SCR-modulated linear LED driver system separates the LED constant current control circuit 14c from the capacitor charging and discharging circuit, achieving constant current and flicker reduction functions through two current control circuits. One end of resistor Re is connected to the charging current setting pin of the ERP linear LED constant current control circuit 14c, and the other end is grounded. One end of resistor Rf is connected to the LED current setting pin of the ERP linear LED constant current control circuit 14c, and the other end is grounded. The current from the ERP linear LED constant current control circuit 14c generates a negative voltage across resistor Rc. If the discharge current control module 13c is integrated with the ERP linear LED constant current control circuit 14c on a single chip, it cannot directly process the negative voltage signal and needs to be converted before control, because excessively high chip negative voltage will prevent the chip from functioning properly. Figure 2 The proposed solution has the same problems, which will not be elaborated here.

[0084] Based on the above reasons, this invention proposes a discharge current control module and a silicon controlled rectifier (SCR) dimming LED driving system to reduce losses and improve efficiency. The specific solution is as follows. Example 1

[0085] like Figure 4 As shown, this embodiment provides a discharge current control module 2, which is used to maintain the conduction of the thyristor. The discharge current control module 2 includes:

[0086] The system includes a power switch Q1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a voltage conversion unit 11, a first comparator 22, a bleed current control unit 23, a first constant current source I1, and a first operational amplifier OP1.

[0087] like Figure 4 As shown, the first terminal of the power switch Q1 is connected to the positive terminal of the input voltage Vin via the first resistor R1, and the second terminal is connected to the negative terminal of the input voltage Vin via the second resistor R2.

[0088] Specifically, by controlling the on and off states of the power switch Q1, the current flowing through the power switch Q1 is adjusted, thereby controlling the discharge current. The discharge current is used to maintain the thyristor's conduction when the input current is less than the thyristor's on-state current, thus preventing LED flickering. In this embodiment, the power switch Q1 is a MOSFET, with its first terminal being the drain, its second terminal the source, and its control terminal the gate. In actual use, the type of power switch Q1 can be set as needed, and the ports can be adjusted adaptively; these details are not elaborated here.

[0089] like Figure 4As shown, the first end of the third resistor R3 is connected to the ground terminal of the LED constant current control module (not shown in the figure), and the second end is connected to the negative terminal of the input voltage Vin.

[0090] Specifically, the third resistor R3 obtains the current flowing through the LED constant current control module from the ground terminal of the LED constant current control module. This current includes, but is not limited to, the output current of the LED and the charging and discharging current of the capacitor. Any current flowing out of the positive terminal of the input voltage Vin and into the ground terminal of the LED constant current control module is also included, and will not be elaborated here. A negative voltage, denoted as -Vs, is obtained across the third resistor R3.

[0091] like Figure 4 As shown, the input terminal of the voltage conversion unit 21 is connected to the second terminal of the third resistor R3, converting the negative voltage at the second terminal of the third resistor R3 into a positive voltage.

[0092] Specifically, in this embodiment, the voltage conversion unit 21 includes a fifth resistor R5, a sixth resistor R6, a first diode D1, and a second operational amplifier OP2. The fifth resistor R5 and the sixth resistor R6 are connected in series between the input and output terminals of the voltage conversion unit 21. The cathode of the first diode D1 is connected to the input terminal of the voltage conversion unit 21, and the anode is connected to the ground terminal of the LED constant current control module (i.e., the first end of the third resistor). The first input terminal of the second operational amplifier OP2 is connected between the fifth resistor R5 and the sixth resistor R6, the second input terminal is connected to the anode of the first diode D1, and the output terminal is connected to the output terminal of the voltage conversion unit 21. As an example, the inverting input terminal of the second operational amplifier OP2 is connected between the fifth resistor R5 and the sixth resistor R6, and the non-inverting input terminal is connected to the anode of the first diode D1. In actual use, the relationship between the input signal and the polarity of the corresponding input terminal can be adjusted by an inverter, and this embodiment is not the only limitation.

[0093] More specifically, in this embodiment, the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 are equal, so the output voltage VA of the voltage conversion unit 21 is equal to Vs. In actual use, the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 may not be equal. In this case, the output voltage VA of the voltage conversion unit 21 has a certain proportional relationship with the absolute value Vs of the voltage across the third resistor R3, which will not be elaborated here.

[0094] More specifically, since excessively high negative voltage can affect the operation of the discharge current control module 2, the internal circuit is clamped and protected by the first diode D1, and the operating voltage across the third resistor R3 is set to be less than the forward conduction voltage of the first diode D1. As an example, when the discharge current control module 2 is integrated into a chip, the first diode D1 can be implemented using the parasitic diode of the chip interface ESD protection device; the first diode D1 can also be an independently configured device, not limited to this embodiment.

[0095] like Figure 4 As shown, the first input terminal of the first comparator 22 is connected to the output terminal of the voltage conversion unit 21, and the second input terminal receives the first reference voltage Ref1 and outputs the comparison result.

[0096] Specifically, in this embodiment, the non-inverting input of the first comparator 22 is connected to the output of the voltage conversion unit 21, and the inverting input is connected to the first reference voltage Ref1. In actual use, the relationship between the polarity of the input signal and the corresponding input terminal can be adjusted by an inverter, and this embodiment is not the limitation. The first comparator 22 compares the output voltage VA of the voltage conversion unit 21 with the first reference voltage Ref1 to determine whether the current flowing through the LED constant current control module reaches a preset value (in this embodiment, the preset value is VRef1 / Rs, where Vref1 is the voltage value of the first reference voltage). If the preset value is reached, the input current is greater than the conduction current of the thyristor. At this time, there is no need to discharge current. Therefore, the power switch Q1 can be turned off based on the comparison result, thereby turning off the discharge current and reducing power consumption.

[0097] It should be noted that when the discharge current control module 2 is integrated into the chip, the third resistor R3 can be set outside the chip to facilitate the adjustment of the resistance value and thus set a suitable preset value.

[0098] like Figure 4 As shown, the discharge current control unit 23 is connected to the second terminal of the power switch Q1 and receives the comparison result. It is used to output a feedback signal of the voltage at the second terminal of the power switch Q1 and outputs a discharge current turn-off control signal when the output voltage of the voltage conversion unit 21 is greater than the first reference voltage Ref1.

[0099] Specifically, when the output voltage of the voltage conversion unit 21 is less than or equal to the first reference voltage Ref1, a discharge current needs to be provided. At this time, the discharge current control unit 23 feeds back the voltage at the second terminal of the power switch Q1 to the input terminal of the first operational amplifier OP1. When the output voltage of the voltage conversion unit 21 is greater than the first reference voltage Ref1, no discharge current needs to be provided. At this time, the discharge current control unit 23 outputs a discharge current turn-off control signal to turn off the power switch Q1; as an example, the discharge current turn-off control signal is high level.

[0100] like Figure 4 As shown, the input terminal of the first constant current source I1 is connected to the output terminal of the voltage conversion unit 21, and the output terminal is connected to the output terminal of the discharge current control unit 23. One end of the fourth resistor R4 is connected to the output terminal of the first constant current source I1, and the other end is connected to the second terminal of the power switch Q1.

[0101] like Figure 4 As shown, the first input terminal of the first operational amplifier OP1 is connected to the output terminal of the discharge current control unit 23, and the second input terminal receives the second reference voltage Ref2. The drive signal of the control terminal of the power switch Q1 is generated based on the difference between the output voltage of the discharge current control unit 23 and the second reference voltage Ref2.

[0102] Specifically, in this embodiment, the inverting input of the first operational amplifier OP1 is connected to the output of the discharge current control unit 23, the non-inverting input is connected to the second reference voltage Ref2, and the output is connected to the gate of the power switch Q1. In practical use, the relationship between the input signal and the polarity of the corresponding input terminal can be adjusted by an inverter, and this embodiment is not the only limitation.

[0103] Specifically, the output voltage VA of the voltage conversion unit 21 controls the first constant current source I1 to generate a voltage with an amplitude of Vs across the fourth resistor R4, thereby offsetting the effect of the negative voltage across the third resistor R3 on the second terminal of the power switch Q1. Let I1 = K1 * Vs, I1 * R4 = Vs, thus obtaining K1 * R4 = 1, where K1 is a control coefficient determined by setting the resistance value of the fourth resistor R4. At this time, the discharge current I... Bleed The following relationship must be satisfied:

[0104] Where Vref2 is the voltage value of the second reference voltage.

[0105] It should be noted that the second resistor R2 is used to adjust the discharge current I. BleedRegarding the size of the discharge current control module 2, when the discharge current control module 2 is integrated into the chip, the second resistor R2 can be set outside the chip to facilitate the discharge current I. Bleed The second resistor R2 can also be placed inside the chip to create a fixed discharge current application scheme, thereby reducing the number of chip pins. Example 2

[0106] like Figure 5 As shown, this embodiment provides a discharge current control module 2, which differs from the first embodiment in that the discharge current control module 2 further includes a discharge time detection unit 24.

[0107] like Figure 5 As shown, the input terminal of the discharge time detection unit 24 is connected to the first terminal of the power switch Q1 to detect the discharge time during the rise time of the input voltage Vin, and the output terminal is connected to the input terminal of the discharge current control unit 23. It should be noted that any circuit structure capable of detecting the discharge time during the rise time of the input voltage Vin is applicable to this invention, and will not be elaborated upon here.

[0108] like Figure 5 As shown, the discharge current control unit 23 is connected to the output terminal of the discharge time detection unit 24. When the discharge time during the rise period of the input voltage Vin is greater than the set value, the discharge current turn-off control signal is output.

[0109] Specifically, the discharge time detection unit 23 compares the time detected by the discharge time detection unit 24 with a set value. When the discharge time during the rise of the input voltage Vin is less than or equal to the set value, it is determined that a thyristor is connected in the system, and discharge current control is required. When the discharge time during the rise of the input voltage Vin is greater than the set value, it is determined that no thyristor is connected in the system, and discharge current is not required. Therefore, a discharge current turn-off control signal is output to turn off the power switch Q1, and the discharge current control module 2 is no longer turned on, reducing power consumption, preventing chip overheating, and improving system efficiency.

[0110] Specifically, such as Figure 6As shown, when the input voltage Vin rises from zero to the LED's turn-on voltage Vled, the discharge current conduction time is the t0-t1 time period since no thyristor is connected. After connecting the thyristor, the maximum conduction time will be shortened to the t5-t6 time period (less than the t0-t1 time period) because the thyristor requires a start-up time (t4-t5 time period). Since the mains input voltage and frequency are basically stable, and the LED's turn-on voltage Vled is also relatively stable, the t0-t1 time period can be considered constant. When the discharge time during the rise of the input voltage Vin (e.g., the t5-t6 time period) is less than or equal to the set value (e.g., the t0-t1 time period), the system can be considered to have a thyristor connected.

[0111] Specifically, if the current system is not connected to a thyristor, the discharge current will always exist when the input voltage Vin is less than the LED's turn-on voltage Vled. This discharge current will cause significant losses and can easily lead to chip overheating. Therefore, this embodiment uses the discharge time detection unit 24 and the discharge current control unit 23 to determine whether the system is connected to a thyristor. If the system is not connected to a thyristor, the discharge current will be turned off, and no further discharge current will flow in each subsequent power frequency cycle. Example 3

[0112] like Figure 7 As shown, this embodiment provides a discharge current control module 2, which differs from embodiments one and two in that the discharge current control module 2 further includes an input voltage detection unit 25.

[0113] like Figure 7 As shown, the input voltage detection unit 25 is connected to the first terminal of the power switch Q1 to detect the input voltage Vin.

[0114] Specifically, the input voltage detection unit 25 detects the amplitude of the input voltage Vin, and outputs a valid detection signal when the input voltage Vin is at its falling edge and the voltage value of the input voltage Vin is less than the conduction voltage Vled of the LED.

[0115] like Figure 7 As shown, the discharge current control unit 23 is connected to the output terminal of the input voltage detection unit 25. When the input voltage Vin is less than the LED's turn-on voltage Vled during the falling phase, the current flowing through the third resistor R3 is less than the set current, maintaining the output discharge current turn-off control signal to turn off the power switch Q1, reduce power consumption, avoid chip overheating, and improve system efficiency.

[0116] Specifically, during the decreasing phase of the input voltage Vin, when the input voltage Vin is lower than the LED's turn-on voltage Vled ( Figure 6 During the t13-t14 time period, even if the thyristor is turned off, it will not affect the output current of the LED. Therefore, the discharge current can be turned off at this time to reduce system losses and chip heat generation. Example 4

[0117] like Figure 8 As shown, this embodiment provides a discharge current control module 2, which differs from embodiments one, two and three in that the discharge current control module 2 further includes a discharge voltage clamping unit 26.

[0118] like Figure 8 As shown, the discharge voltage clamping unit 26 is connected between the first terminal of the power switch Q1 and the negative terminal of the input voltage Vin, and its output terminal is connected to the output terminal of the discharge current control unit 23. When the voltage at the first terminal of the power switch Q1 is less than a preset voltage, a compensation signal is generated based on the voltage value at the first terminal of the power switch Q1, wherein the smaller the voltage at the first terminal of the power switch Q1, the larger the compensation signal.

[0119] Specifically, such as Figure 9 As shown, in this embodiment, the discharge voltage clamping unit 26 includes a seventh resistor R7, an eighth resistor R8, a transconductance operational amplifier GM, and a second constant current source I2. The seventh resistor R7 and the eighth resistor R8 are connected in series between the first terminal of the power switch Q1 and the negative terminal of the input voltage Vin. The first input terminal of the transconductance operational amplifier GM is connected between the seventh resistor R7 and the eighth resistor R8, the second input terminal is connected to the third reference voltage Ref3, and the output terminal is connected to the input terminal of the second constant current source I2. As an example, the inverting input terminal of the transconductance operational amplifier GM is connected between the seventh resistor R7 and the eighth resistor R8, and the non-inverting input terminal is connected to the third reference voltage Ref3. In actual use, the relationship between the input signal and the polarity of the corresponding input terminal can be adjusted by an inverter, and this embodiment is not the only limitation. The output terminal of the second constant current source I2 is connected to the output terminal of the discharge current control unit 23.

[0120] More specifically, the seventh resistor R7 and the eighth resistor R8 divide the voltage at the first terminal of the power switch Q1, and then compare it with the third reference voltage Ref3. The transconductance operational amplifier GM controls the output of a compensation current I2, which generates a voltage drop across the fourth resistor R4 to compensate for the discharge current. The lower the voltage at the first terminal of the power switch Q1, the larger the compensation current I2, and the larger the voltage drop across the fourth resistor R4, thus reducing the discharge current flowing through the power switch Q1, satisfying the following condition: When the voltage at the first terminal of the power switch Q1 exceeds the preset voltage, the transconductance operational amplifier GM no longer controls the output current of the second constant current source I2, and the voltage drop across the fourth resistor R4 caused by the compensation current I2 is zero. As a result, the magnitude of the discharge current flowing through the power switch Q1 is only controlled by the second reference voltage Ref2 and the second resistor R2.

[0121] More specifically, due to the presence of the second constant current source I2, Figure 6 During the input voltage rise period t9-t10, the discharge current is very small, and the thyristor startup circuit is in the off state, which is equivalent to being delayed in turning on. The thyristor does not enter the startup stage until t10-t11. After t11, the thyristor turns on, and the discharge current flows during the t11-t12 period. The discharge current conduction time is shortened by further reducing the t9-t10 period compared to the t5-t6 period. By setting appropriate parameters for the third reference voltage Ref3, the seventh resistor, and the eighth resistor, the discharge current conduction time t11-t12 can be shortened as much as possible, thereby reducing the discharge current loss. Example 5

[0122] This embodiment provides a discharge current control module, including all the devices and units of embodiments one, two, three, and four; their specific structures are not described in detail here. Figure 10 As shown, the workflow of the discharge current control module in this embodiment is as follows:

[0123] 1) When the system is powered on, the power switch is turned on, the current is discharged and output, and the system reaches a stable state after working for a number of power frequency cycles.

[0124] 2) Detect the discharge time during the input voltage rise period. If the discharge time during the input voltage rise period is greater than the set value, it is determined that the system is not connected to the thyristor and the discharge current is turned off. If the discharge time during the input voltage rise period is less than or equal to the set value, it is determined that the system is connected to the thyristor, the discharge current during the input voltage fall phase is turned off, and the discharge voltage clamping unit is activated.

[0125] 3) The system is working normally. Example 6

[0126] like Figure 11 and Figure 12 As shown, this embodiment provides a silicon controlled rectifier (SCR) dimming LED driving system, which includes:

[0127] The module consists of a discharge current control module 2, a voltage input module 3, and an LED constant current control module 4.

[0128] like Figure 11 and Figure 12As shown, the voltage input module 2 receives AC voltage and converts AC voltage into DC input voltage Vin.

[0129] Specifically, in this embodiment, the voltage input module 2 includes a rectifier unit 31 and a silicon controlled rectifier (SCR) 32. The AC terminal of the rectifier unit 31 is connected to the AC voltage AC, and the DC terminal outputs the input voltage Vin. The SCR 32 is connected in series to the AC terminal of the rectifier unit 31. As another implementation of the present invention, the voltage input module 2 further includes a fuse F1, which is connected in series to the AC terminal of the rectifier unit 31.

[0130] like Figure 11 and Figure 12 As shown, the LED constant current control module 4 is connected to the output terminal of the voltage input module 3, and realizes the constant current output of the LED based on the input voltage Vin.

[0131] Specifically, such as Figure 11 As shown, as an example, the LED constant current control module 4 includes a second diode D2, a first LED load LED1, a first capacitor C1, and a constant current control unit 41. The anode of the second diode D2 is connected to the input voltage Vin, and the cathode is connected to the positive terminal of the first LED load LED1. The first capacitor C1 is connected in parallel across the first LED load LED1. The constant current control unit 41 is connected to the negative terminal of the first LED load LED1 to perform constant current control on the current flowing through the first LED load LED1. Figure 12 As shown, the LED constant current control module 4 includes a third diode D3, a second LED load LED2, a second capacitor C2, and a current control unit 43. The anode of the third diode D3 is connected to the input voltage Vin, and the cathode is connected to the upper plate of the second capacitor C2 and the positive terminal of the second LED load LED2. The current control unit 43 is connected to the lower plate of the second capacitor C2 and the negative terminal of the second LED load LED2, and controls the charging current of the second capacitor C2 and the current flowing through the second LED load LED2, respectively, to achieve constant current and flicker-free control of the second LED load LED2.

[0132] It should be noted that the discharge current control module 2 and the LED constant current control module 4 (excluding the capacitor and LED load) can be integrated into a chip, and the resistors for adjusting the current can be located outside the chip, not limited to the illustration in this embodiment. Figure 11 and Figure 12As shown, the LED constant current control module 4 also includes a working voltage generation module 42, which is connected to the upper plate of the capacitor (first capacitor C1 or second capacitor C2) to provide working voltage for the chip.

[0133] like Figure 11 and Figure 12 As shown, the discharge current control module 2 is connected to the output terminal of the voltage input module 3, and provides discharge current according to the current flowing through the LED constant current control module 4, so as to maintain the conduction of the voltage input module 3 (i.e., the thyristor).

[0134] Specifically, the discharge current control module 2 is the discharge current control module of Embodiment 1, 2, 3, 4, or 5. In this embodiment, the discharge current control module of Embodiment 1 is used as an example. The circuit structure and working principle of the discharge current control module 2 will not be described in detail here.

[0135] In summary, this invention provides a discharge current control module and a silicon controlled rectifier (SCR) dimming LED driving system, comprising: a power switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a voltage conversion unit, a first comparator, a discharge current control unit, a first constant current source, and a first operational amplifier; the first terminal of the power switch is connected to the positive terminal of the input voltage via the first resistor, and the second terminal is connected to the negative terminal of the input voltage via the second resistor; the first terminal of the third resistor is connected to the ground terminal of the LED constant current control module, and the second terminal is connected to the negative terminal of the input voltage; the input terminal of the voltage conversion unit is connected to the second terminal of the third resistor, converting the negative voltage at the second terminal of the third resistor into a positive voltage; the first input terminal of the first comparator is connected to the output terminal of the voltage conversion unit, and the second input terminal receives a first reference voltage. The comparison result is output; the discharge current control unit is connected to the second terminal of the power switch and receives the comparison result, outputs a feedback signal of the voltage at the second terminal of the power switch, and outputs a discharge current turn-off control signal when the output voltage of the voltage conversion unit is greater than the first reference voltage; the input terminal of the first constant current source is connected to the output terminal of the voltage conversion unit, and the output terminal is connected to the output terminal of the discharge current control unit; one end of the fourth resistor is connected to the output terminal of the first constant current source, and the other end is connected to the second terminal of the power switch; the first input terminal of the first operational amplifier is connected to the output terminal of the discharge current control unit, the second input terminal receives the second reference voltage, and generates a drive signal for the control terminal of the power switch based on the difference between the output voltage of the discharge current control unit and the second reference voltage. In the LED driving system with SCR dimming and a discharge current control module of this invention, the negative voltage signal generated by the current flowing through the LED constant current control module is processed by an operational amplifier to obtain a positive voltage signal for circuit feedback control. A diode is used as a protection device to prevent system malfunction. The negative voltage signal at the Vs port is used to detect the LED output current and the current of the flicker-reducing section in real time, thereby performing corresponding subsequent control actions without affecting normal constant current operation. The conduction time of the discharge current determines whether the system is connected to the SCR, which is simple and effective. When the system is not connected to the SCR, the discharge current is turned off, thereby reducing system losses, improving system efficiency, and reducing chip heat generation. When the system is connected to the SCR, the discharge current is turned off during the falling edge of the input voltage; or the discharge voltage clamping unit delays the SCR conduction time, reducing the conduction time of the discharge current. This reduces discharge current losses, improves system efficiency, and reduces chip heat generation. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0136] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A discharge current control module for maintaining the conduction of a silicon controlled rectifier (SCR), characterized in that, The discharge current control module includes at least: The system includes a power switching transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a voltage conversion unit, a first comparator, a bleed current control unit, a first constant current source, and a first operational amplifier. The first terminal of the power switch is connected to the positive terminal of the input voltage via the first resistor, and the second terminal is connected to the negative terminal of the input voltage via the second resistor. The first end of the third resistor is connected to the ground terminal of the LED constant current control module, and the second end is connected to the negative terminal of the input voltage. The input terminal of the voltage conversion unit is connected to the second terminal of the third resistor, converting the negative voltage at the second terminal of the third resistor into a positive voltage; The first input terminal of the first comparator is connected to the output terminal of the voltage conversion unit, and the second input terminal receives the first reference voltage and outputs the comparison result. The discharge current control unit is connected to the second terminal of the power switch tube, receives the comparison result, outputs a feedback signal of the voltage at the second terminal of the power switch tube, and outputs a discharge current turn-off control signal when the output voltage of the voltage conversion unit is greater than the first reference voltage. The input terminal of the first constant current source is connected to the output terminal of the voltage conversion unit, and the output terminal is connected to the output terminal of the discharge current control unit; One end of the fourth resistor is connected to the output terminal of the first constant current source, and the other end is connected to the second terminal of the power switch transistor; The first input terminal of the first operational amplifier is connected to the output terminal of the discharge current control unit, and the second input terminal receives a second reference voltage. The drive signal of the power switch control terminal is generated based on the difference between the output voltage of the discharge current control unit and the second reference voltage.

2. The discharge current control module according to claim 1, characterized in that: The voltage conversion unit includes a fifth resistor, a sixth resistor, a first diode, and a second operational amplifier; The fifth resistor and the sixth resistor are connected in series between the input and output terminals of the voltage conversion unit; The cathode of the first diode is connected to the input terminal of the voltage conversion unit, and the anode is connected to the ground terminal of the LED constant current control module; The first input terminal of the second operational amplifier is connected between the fifth resistor and the sixth resistor, the second input terminal is connected to the anode of the first diode, and the output terminal is connected to the output terminal of the voltage conversion unit.

3. The discharge current control module according to claim 2, characterized in that: The fifth resistor has the same resistance value as the sixth resistor.

4. The discharge current control module according to claim 2, characterized in that: The operating voltage across the third resistor is less than the forward voltage of the first diode.

5. The discharge current control module according to claim 2, characterized in that: The first diode is implemented using a parasitic diode of the chip interface ESD protection device.

6. The discharge current control module according to any one of claims 1-5, characterized in that: The discharge current control module further includes a discharge time detection unit, which is connected to the first terminal of the power switch to detect the discharge time during the input voltage rise time period. The discharge current control unit is connected to the output terminal of the discharge time detection unit, and outputs a discharge current turn-off control signal when the discharge time during the input voltage rise time period is greater than a set value.

7. The discharge current control module according to any one of claims 1-5, characterized in that: The discharge current control module further includes an input voltage detection unit, which is connected to the first terminal of the power switch to detect the input voltage. The discharge current control unit is connected to the output terminal of the input voltage detection unit. When the input voltage is less than the LED's turn-on voltage during the falling phase, the control unit maintains the output discharge current turn-off control signal.

8. The discharge current control module according to any one of claims 1-5, characterized in that: The discharge current control module further includes a discharge voltage clamping unit; the discharge voltage clamping unit is connected between the first terminal of the power switch and the negative terminal of the input voltage, and its output terminal is connected to the output terminal of the discharge current control unit; when the voltage at the first terminal of the power switch is less than a preset voltage, a compensation signal is generated based on the voltage value at the first terminal of the power switch, wherein the smaller the voltage at the first terminal of the power switch, the larger the compensation signal.

9. The discharge current control module according to claim 8, characterized in that: The discharge voltage clamping unit includes a seventh resistor, an eighth resistor, a transconductance operational amplifier, and a second constant current source; The seventh resistor and the eighth resistor are connected in series between the first terminal of the power switch and the negative terminal of the input voltage; The first input terminal of the transconductance operational amplifier is connected between the seventh resistor and the eighth resistor, the second input terminal is connected to the third reference voltage, and the output terminal is connected to the input terminal of the second constant current source. The output terminal of the second constant current source is connected to the output terminal of the discharge current control unit.

10. A silicon controlled rectifier (SCR) dimming LED driving system, characterized in that, The thyristor-controlled dimming LED driving system includes at least: Voltage input module, LED constant current control module and discharge current control module as described in any one of claims 1-9; The voltage input module receives AC voltage and converts it into DC input voltage; The LED constant current control module is connected to the output terminal of the voltage input module, and realizes constant current output of the LED based on the input voltage; The discharge current control module is connected to the output terminal of the voltage input module and provides discharge current according to the current flowing through the LED constant current control module to maintain the conduction of the voltage input module.

11. The thyristor-controlled dimming LED driving system according to claim 10, characterized in that: The voltage input module includes a rectifier unit and a thyristor; the AC terminal of the rectifier unit is connected to the AC voltage, and the DC terminal outputs the input voltage; the thyristor is connected in series with the AC terminal of the rectifier unit.

12. The thyristor-controlled dimming LED driving system according to claim 10 or 11, characterized in that: The LED constant current control module includes a second diode, a first LED load, a first capacitor, and a constant current control unit; The anode of the second diode is connected to the input voltage, and the cathode is connected to the positive terminal of the first LED load; the first capacitor is connected in parallel across the first LED load. The constant current control unit is connected to the negative terminal of the first LED load and performs constant current control on the current flowing through the first LED load.

13. The thyristor-controlled dimming LED driving system according to claim 10 or 11, characterized in that: The LED constant current control module includes a third diode, a second LED load, a second capacitor, and a current control unit; The anode of the third diode is connected to the input voltage, and the cathode is connected to the upper plate of the second capacitor and the positive terminal of the second LED load. The current control unit is connected to the lower plate of the second capacitor and the negative terminal of the second LED load, respectively controlling the charging current of the second capacitor and the current flowing through the second LED load, thereby achieving constant current and flicker-free control of the second LED load.

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