CN112188681B - LED driving system and discharge current control circuit and control method thereof - Google Patents
LED driving system and discharge current control circuit and control method thereof Download PDFInfo
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Abstract
The present disclosure provides an LED driving system and a leakage current control circuit and a control method thereof. The LED driving system utilizes a silicon controlled dimmer to dim the connected LED load. The LED driving system includes: a thyristor dimmer configured to receive and chop an alternating current signal; a rectification module configured to rectify the chopped AC signal to obtain an input voltage; a leakage current control module configured to derive a first signal indicative of whether the thyristor dimmer is on based on the input voltage; and a constant current control module configured to generate a second signal indicative of whether the LED load is conducting based on whether current is flowing through the LED load; wherein the bleed current control module is configured to control a bleed current of the LED drive system based on the first signal and the second signal.
Description
Technical Field
The present disclosure relates generally to the field of Light Emitting Diode (LED) lighting technologies, and more particularly, to an LED driving system for dimming using a silicon controlled dimmer, and a leakage current control circuit and a control method thereof.
Background
Silicon controlled dimming is a commonly used dimming method at present. A silicon controlled dimmer, such as a TRIAC dimmer, uses a phase control method to achieve dimming, i.e., the silicon controlled dimmer is controlled to be turned on every half cycle of a sine wave to obtain the same conduction phase angle. By adjusting the chopping phase of the silicon controlled dimmer, the size of the conduction phase angle can be changed, and dimming is realized.
Fig. 1 shows a typical LED driver system 100 that utilizes thyristor dimmer dimming. The system 100 has a wide application in the fields of LED lighting and the like due to its simple structure and low cost.
As shown in fig. 1, the system 100 includes a thyristor dimmer (U3) 101, a rectifier bridge (BD 1) 102, a diode (D1) 103, a capacitor (C1) 104, a constant current control unit (U1) 105, a bleed control unit (U2) 106, and an LED load 107.
The input (terminal A) of U3 101 is connected to an Alternating Current (AC) voltage (V) AC ) 110, the output end (terminal K) of U3 101 is connected to the first end of BD1102, the second end of BD1102 is connected to the anode of D1 103, and the third end of BD1102 is connected to V AC Negative pole of input, and fourth end of BD1102 is connected to reference ground: (GND). D1 The cathode of 103 is connected to a first terminal of C1 104, and a second leg terminal of C1 104 is connected to GND via U1 105. C1 104 provide an output voltage (V) out ) 108. The LED load 107 has its anode connected to the first terminal of C1 104 and its cathode connected to the second terminal of C1 104 and U1 105. The first terminal of U2 106 is connected to the second terminal of BD1102 and the anode of D1 103, and the second terminal of U2 106 is connected to GND.
BD1102 rectifies the incoming ac power to obtain a dc output as the input voltage (V) to U2 106 and the leg consisting of D1 103, LED load 107 and U1 105 in ) 109. D1 103 are used to isolate the reverse current.
FIG. 2 shows the input voltage (V) in the system 100 of FIG. 1 in ) 109 LED load current (I) LED ) 111, and a bleed current (I) bleeding ) 112. It can be seen that only V exists in one power frequency period (T) in 109 is higher than the turn-on voltage (V) of the output LED load 107 LED ) During a period (t 2-t 3, LED load 107 is on at time t2, and LED load 107 is off at time t 3) until I LED 111 are generated with no I during the remaining time periods (e.g., t 1-t 2, t 3-t 5) LED 111, to yield. In order to maintain the normal operation of U3 101, it is necessary to generate a constant I during the periods t1 to t2 and t3 to t5 bleeding 112, which causes some losses. In some existing bleeder current control techniques, I during the period (t 3-t 4) from when LED load 107 is turned off (t 3) to when U1 101 is turned off (t 4) may be set bleeding 112 are turned off to reduce the leakage current loss, but there is still a need to generate a sustained I during the period (t 1-t 2) from U1 on (t 1) to LED load 107 on (t 2) bleeding 112 to maintain normal operation after U1 is turned on.
Disclosure of Invention
In view of one or more of the above-described problems, the present disclosure provides a novel LED driving system dimming with a thyristor dimmer, and a leakage current control circuit and a control method thereof.
According to an aspect of an embodiment of the present disclosure, an LED driving system is disclosed. The LED driving system is configured to dim a connected LED load with a thyristor dimmer. The LED driving system includes: a thyristor dimmer configured to receive and chop an alternating current signal; a rectification module configured to rectify the chopped AC signal to obtain an input voltage; a leakage current control module configured to derive a first signal indicative of whether the thyristor dimmer is on based on the input voltage; and a constant current control module configured to generate a second signal indicative of whether the LED load is conducting based on whether current is flowing through the LED load; wherein the bleed current control module is configured to control a bleed current of the LED drive system based on the first signal and the second signal.
According to another aspect of the disclosed embodiments, a control method is disclosed for controlling a bleed current in an LED driving system including a thyristor dimmer, a rectification module, a bleed current control module, and a constant current control module. The method comprises the following steps: receiving an alternating current signal by the silicon controlled dimmer and chopping the alternating current signal; rectifying the chopped alternating current signal by a rectifying module to obtain an input voltage; obtaining a first signal representing whether the silicon controlled rectifier dimmer is conducted or not by the discharge current control module based on the input voltage; generating, by the constant current control module, a second signal indicative of whether the LED load is on based on whether current is flowing through the LED load connected to the LED driving system; and controlling, by the bleed current control module, a bleed current of the LED drive system based on the first signal and the second signal.
According to another aspect of the disclosed embodiments, a control circuit is disclosed. The control circuit is suitable for an LED driving system for dimming a connected LED load by using a silicon controlled dimmer, and the LED driving system comprises the silicon controlled dimmer and a rectifying module. The silicon controlled dimmer receives an alternating current signal and chops the alternating current signal. The rectification module rectifies the chopped AC signal to obtain an input voltage for the control circuit. The control circuit is configured to control a bleed current of the LED drive system based on a first signal indicative of whether the thyristor dimmer is conducting and a second signal indicative of whether the LED load is conducting.
Drawings
The present disclosure may be better understood from the following description of specific embodiments thereof taken in conjunction with the accompanying drawings. For simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements. In the drawings:
fig. 1 shows a typical LED driving system using thyristor dimmer dimming.
Fig. 2 shows a timing diagram of the partial signals involved in the LED driving system of fig. 1.
Fig. 3 shows a simplified schematic diagram of a thyristor dimmer according to an embodiment of the present disclosure.
Fig. 4 illustrates an LED driving system using thyristor dimmer dimming according to an embodiment of the present disclosure.
Fig. 5A shows an example of the internal structure of a constant current control unit used in the LED driving system of fig. 4.
Fig. 5B shows an example of an internal structure of the bleeding control unit used in the LED driving system of fig. 4.
Fig. 6 shows an example of the internal structure of the phase detection module of fig. 5.
Fig. 7 shows a timing diagram of part of the signals involved in the LED driving system of fig. 4.
Detailed Description
Features and exemplary embodiments of various aspects of the present disclosure will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, to one skilled in the art, that the present disclosure may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present disclosure by illustrating examples of the present disclosure. The present disclosure is in no way limited to any specific configuration and algorithm set forth below, but rather covers any modifications, substitutions, and alterations of elements, components, and algorithms without departing from the spirit of the present disclosure. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present disclosure.
It is to be noted that, in the following description, reference may be made to "an apparatus", "a module", "a unit", "a component", and the like, which refer to a circuit or a part of a circuit.
Embodiments of the present disclosure relate to controlling a constant current of an LED by applying a bleed current (I) in an LED constant current control system using a thyristor dimmer for dimming bleeding ) The self-adaptive control realizes the adjustment of the turn-off time of the silicon controlled rectifier dimmer, so that the maximum conduction angle of the silicon controlled rectifier dimmer during dimming is always close to the maximum conduction angle corresponding to the LED load. The technical scheme provided by the disclosure shortens the time length of the silicon controlled rectifier dimmer generating the discharge current under the condition of a large angle, thereby reducing the system loss and realizing the optimization of the system efficiency.
To clearly illustrate the various aspects of the present disclosure, a brief description of the operating principles of a thyristor dimmer (e.g., a TRIAC dimmer) is first presented. Fig. 3 shows a simplified schematic diagram of a thyristor dimmer 300 according to an embodiment of the present disclosure.
The triac dimmer 300 receives an ac voltage, e.g., a line voltage, at terminal a and connects to the LED lighting system at terminal K. Here, the symbol V is used A The voltage value at the A terminal of the SCR dimmer 300 is shown by the symbol V K Representing the voltage value at terminal K of the triac dimmer 300.
The triac dimmer 300 includes a first triac (M1) 301 and a second triac (M2) 302, where M2302 is the main switch that controls the switching of the line voltage. The anode of M2302 is connected to the A terminal, the cathode of M2302 is connected to the K terminal, and the control electrode of M2302 is connected to the cathode of M1301.
The thyristor dimmer 300 includes a first resistor (R1) 303 and a second resistor (R2) 304, where R2 is a variable resistor. The triac dimmer 300 also includes a first capacitor (C1) 305 and a second capacitor (C2) 306. One end of R1 303 is connected to the a terminal and the anode of M2302 and the other end thereof is connected to one end of R2 304. The other end of R2 304 is connected to one end of C2 306 and the anode of M1, and the other end of C2 306 is connected to the K terminal and the cathode of M2 302. C1 One end of 305 is connected to a terminal and one end of R1 303, and the other end of C1 305 is connected to K terminal and the other end of C2 306. C1 305 function to stabilize the pressure.
In this embodiment, V is when M2302 is on K ＝V A (ii) a When M2302 is turned off, V K And =0. After the A terminal is connected to the line voltage, before M2302 is turned on, capacitor C2 306 is charged through R1 303 and R2 304, when the voltage across C2 306 is "V" (at 0 "indicates") reaches the on voltage threshold of M1301, M1301 turns on and generates a current that turns on M2302, turning on M2302.
In one aspect, the voltage V across C2 306 can be varied by adjusting the resistance of variable resistor R2 304 0 The time to reach the conduction voltage threshold of M1301 changes the time for M2302 to turn on and on, i.e., changes the phase angle (defined as the "conduction angle") corresponding to the period between the conduction and the turn-off of the triac dimmer 300 (defined as the "conduction period").
On the other hand, by changing the voltages V at the A terminal and the K terminal of the triac dimmer 300 A And V K The voltage V across C2 306 may also be varied 0 The time of reaching the threshold of the conduction voltage of M1301, so as to change the time of turning on and conducting M2302, and also change the conduction angle corresponding to the conduction period of the triac dimmer 300.
As described above, before M2302 turns on, i.e., there is current to charge C2 306 during the off phase of triac dimmer 300, which results in leakage current from triac dimmer 300 during the off phase, and some leakage current is also generated across C1 due to the voltage difference. That is, there is a non-ideal leakage condition in the triac dimmer 300.
The present disclosure makes use of silicon controlled rectifier ingeniouslyThe dimmer 300 generates a leakage current to control the voltage V at the K terminal of the SCR dimmer 300 during the turn-off period K Thereby controlling the voltage V across C2 306 0 The time when the conduction voltage threshold of M1 is reached, that is, the time when the thyristor dimmer 300 starts to conduct, is controlled, so as to control the conduction angle of the thyristor dimmer 300, so that when the silicon dimmer 300 is used to dim an LED load, the maximum conduction angle of the thyristor dimmer 300 is always close to the maximum conduction angle corresponding to the LED load. Through the technical scheme, the working time of generating the discharge current after the silicon controlled dimmer 300 is switched on can be shortened to the greatest extent, so that the loss is reduced, and the efficiency optimization is realized.
Fig. 4 illustrates an LED driving system 400 utilizing thyristor dimmer dimming according to an embodiment of the present disclosure.
As shown in fig. 4, the system 400 includes a thyristor dimmer (U3) 401, a rectifier bridge (BD 1) 402, a diode (D1) 403, a capacitor (C1) 404, a constant current control unit (U1) 405, a bleed control unit (U2) 406, and an LED load 407.
The input terminal (terminal A) of U3 401 is connected to an Alternating Current (AC) voltage (V) AC ) The positive terminal of the 410 input, the output terminal (terminal K) of U3 401 is connected to the first terminal of BD1 402, the second terminal of BD1 402 is connected to the anode of D1 403, the third terminal of BD1 402 is connected to the negative terminal of the VAC input, and the fourth terminal of BD1 402 is connected to ground reference (GND). D1 403 has its cathode connected to the first terminal of C1404, and the second leg terminal of C1404 is connected to GND via to U1 405. C1404 provides an output voltage (V) out ) 408. The LED load 407 has its anode connected to a first terminal of C1404, and its cathode connected to a second terminal of C1404 and U1 405. A first terminal of U2 406 is connected to the second terminal of BD1 402 and the anode of D1 403, and a second terminal of U2 406 is connected to GND.
Unlike the conventional system shown in FIG. 1, in system 400, U1 405 generates an LED _ on signal that indicates whether LED load 407 is on, and U2 406 is based on V in 409 derives a signal Triac _ on signal that indicates whether U3 401 is on, so that U2 406 can adjust I based on the LED _ on signal and the Triac _ on signal bleeding 412, which in turn regulates the turn-on time of U3 401 to reduce the leakage loss, as will be described in detail below in conjunction with fig. 5A and 5B.
Fig. 5A shows an example of the internal structure of the constant current control unit (U1) 405 used in the LED driving system 400 of fig. 4. Fig. 5B shows an example of the internal structure of the bleeding control unit (U2) 406 used in the LED driving system 400 of fig. 4.
As shown in fig. 5A, U1 may include a first power regulating tube (M3) 501, a third resistor (R3) 502, a first amplifier (OP) 503, and a Current Sensing Module (CSM) 504. M3501 may be, for example, a metal oxide semiconductor field effect (MOS) transistor. The drain of M3501 is connected to the cathode of the LED load 407 shown in fig. 4, the source thereof is connected to the first end of R3 502, and the second end of R3 502 is connected to Ground (GND). R3 502 is used for sensing LED load current (I) LED )411。
The gate of M3501 is connected to the output of the first OP 503. The positive input terminal of the first OP 503 receives a first reference voltage (V) ref1 ) 505. The negative input of the first OP 503 is connected to the first end of R3 502 to sense the voltage drop across R3 502 by V R3 And 506, a step.
As shown in fig. 5B, U2 406 includes a second power adjusting transistor (M4) 508, a fourth resistor (R4) 509, a second amplifier (OP) 510, a third OP511, a Voltage Sensing Module (VSM) 512, a Phase Detection Module (PDM) 513, a counter 522, and a digital-to-analog converter (DAC) 523.
The gate of M4 508 is connected to the output of the second OP 510 and the output of the third OP 511. A positive input of the second OP 510 is connected to the output of the VSM 512 for receiving the sensing voltage (V) s ) 513. The input terminal of the VSM 512 is connected to the second terminal of the BD1 402 for comparing the input voltage (V) in ) 409 and passes V in 409 is subjected to partial pressure to obtain V s 513.VSM 512 is also configured to generate a signal Triac _ on 514 indicative of whether U3 (U3) 401 of fig. 4 is on when Triac dimmer (U3) 401 is on, and provide it to PDM 513. Meanwhile, PDM513 receives LED _ on507 from U1 405 of fig. 4.
The PDM513 detects the time phase difference between Triac _ on 514 and LED _ on507 and generates a pulse signal corresponding to the logical rising edge of Triac _ on 514 and LED _ on507 to characterize the time phase difference between the two signals, denoted by the symbol T phase 521 is shown. T is phase 521 may also be used for enabling of a third OP511, which will be described later. In the LED driving system 400 using triac dimming, U3 401 is always turned on before the LED load 407, i.e., at V, in the same voltage cycle in 409, triac on 514 always precedes LED on 507. If the time phase difference between Triac _ on 514 and LED _ on507 is greater than a predetermined threshold (by the symbol "T threshold "to) i.e. T phase >T threshold PDM513 generates signal F +515.F +515 will instruct counter 522 to count up. If the time phase difference between Triac _ on 514 and LED _ on507 is less than T threshold I.e. T phase <T threshold Then PDM513 generates signal F-516.F +516 will instruct counter 522 to count down.
The second OP 510 is configured to operate during the turn-off of U3 401, while the third OP511 is configured to operate during the turn-on of U3 401 and the LED load 407 is not yet on, i.e., when Triac _ on 514 transitions to a logic high level, the second OP 510 is turned off while the third OP511 is turned on, and the third OP511 is turned off after LED _ on507 transitions to a logic high level. As described above, the third OP511 may be turned on or off by the pulse signal T phase 521 to control. E.g. at T phase 521, opens a third OP511, and at T phase The logical falling edge of 521 turns off the third OP 511.
While Triac _ on 514 is at a logic low level, a second OP 510 is based on V s 513 and V c 518 generates a first control signal (not shown) to control I bleeding 412。
When Triac _ on 514 transitions to a logic high level, the second OP 510 is turned off and the third OP511 begins to operate. The positive input terminal of the third OP511 receives a second reference voltage (V) ref2 ) 519 having a negative input connected to the first terminal of R4509 to sense the voltage drop across R4509 at V R4 Indicated at 520. Third OP511 is based on V ref2 519 and V R4 520 generate a second control signal (not shown) to control I bleeding 412. When LED _ on507 transitions to a logic high level, M4 508 will I bleeding 412 close until V in 409 is too low to maintain the conduction point of U3 401 stable before turning on I again bleeding 412。
Fig. 6 shows an example of the internal structure of the Phase Detection Module (PDM) 513 of fig. 5. The PDM513 may include an RS flip-flop (Q1) 601, a threshold signal generator 602, and a comparison component 603.
The R terminal of Q1 601 receives Triac _ on 514 and the S terminal receives LED _ on507. As mentioned above, at V in 409, triac on 514 always precedes LED on 507. While Triac _ on 514 transitions to a logic high level, at which time LED _ on507 remains at a logic low level, Q1 601 begins outputting a logic high level and continues to output a logic high level until LED _ on507 also transitions to a logic high level. Thus, Q1 601 generates a pulse signal, T, corresponding to the logic rising edge of Triac _ on 514 and LED _ on507 phase 521, which characterizes the time phase difference between Triac on 514 and LED on 507. As described above, T phase 521 may be used for enabling the third OP511 of fig. 5.
The logic rising edge of the Triac _ on 514 also triggers the threshold signal generator 602 to generate a time threshold signal, also referred to above as T threshold And is denoted by reference numeral 604 in fig. 6.
The comparison component 603 compares T phase 521 and T threshold 604, at T phase >T threshold At time, a signal F +515 is generated which causes counter 522 of FIG. 5 to count up and at T phase <T threshold Signal F-516 is generated which causes counter 522 of fig. 5 to count down.
Fig. 7 shows a timing diagram of part of the signals involved in the LED driving system 400 of fig. 4. The operation principle of the respective elements in the bleed control unit (U2) 406 shown in fig. 5B will be further explained with reference to the timing chart of fig. 7.
In the timing diagram of fig. 7, the time instants are represented in tnm, where t is an abbreviation for time and n represents the position V in 409 cycle number, m denotes the time number in the same cycle, e.g. t11 denotes the 1 st V in At time 1 in 409 cycle, and t12 denotes the 1 st V in 409, at the 2 nd instant in the cycle, and so on.
At time t11, thyristor dimmer (U3) 401 is in an off state. Period t11 to t12, V in 409 of sensing voltage V s 513 is smaller than the voltage V received by the negative input terminal of the second OP 510 c 518. During this time, the second thyristor switch (M2) 302 of the thyristor dimmer 300 as shown in fig. 3 is turned off,the leakage current generated by the SCR dimmer 300 will be V in 409 is charged up to V AC 410 rectified by the rectifier bridge (BD 1) 402, so that the voltages at the A terminal and the K terminal of the SCR dimmer 300 are equal (V) A ＝V K ) As a result, the control capacitor (the second capacitor (C2) 306 in fig. 3) controlling the first thyristor switch (M1) 301 in the triac dimmer 300 cannot be charged, and the on-time of the triac dimmer 300 is not adjusted.
In the period from t12 to t13, V is adjusted by M4 508 and the second OP 510 s 513 to reach V c 518; during this time, the bleed current (I) flows through M4 508 bleeding ) 412 smaller, I bleeding 412 is comparable to the leakage current of the triac dimmer 300, such that V in 409 is maintained at a constant value (e.g., V1). During this period, the voltage at terminal a of the triac dimmer 300 is higher than the voltage at terminal K (V) A >V K ) So that the control capacitor (the second capacitor (C2) 306 in fig. 3) controlling the first thyristor switch (M1) 301 in the triac dimmer 300 starts to charge when the voltage of the control capacitor (V in fig. 3) 0 ) Upon reaching the turn-on voltage threshold of M1301, M1301 turns on and generates a current that turns on M2302, turning on M2302, which corresponds to time t13.
the t13 to t21 periods are on periods of the thyristor dimmer 300, that is, the thyristor dimmer 300 is turned on at time t13 and turned off at time t 21. When the Triac dimmer 300 is turned on, the Triac _ on 514 generated by the Voltage Sensing Module (VSM) 512 of fig. 5B transitions to a logic high level, such that the second OP 510 is turned off and the third OP511 starts to operate. In order to maintain the normal operation of the triac dimmer 300 during the conduction period, the bleeding control unit (U2) 406 generates a large bleeding current (I) under the control of the third OP511, the fourth resistor (R4) 509, and the second power adjusting tube (M4) 508 bleeding ) 412. With V in 409 is increased so that the output voltage (V) out ) The moment when 408 reaches the turn-on voltage of the LED load 407 is defined as t14. At time t14, LED load 407 is turned on and generates an LED load current (I) LED ) 411; meanwhile, the constant current control unit (U1) 405 of FIG. 5A outputs the characterization LED load 4 to U2 406 of FIG. 5B07 the signal LED _ on507 turned on or not, transitions to a logic high level, causing the third OP511 to be turned off, I bleeding 412 are also turned off.
Therefore, the length of the time period from T13 to T14 is the time phase difference T between the Triac _ on 514 and the LED _ on507 phase 521. As described above, if T phase Greater than a predetermined threshold value T threshold This indicates that the triac dimmer 300 is turned on too early, and therefore the control voltage V is adjusted and increased at time t14 c 518, the Phase Detection Module (PDM) 513 corresponding to fig. 5B generates the signal F +515 such that the turn-on time (e.g., T23) of the triac dimmer 300 is appropriately delayed for the next cycle, such that T phase 521 are reduced. In the same way, if T phase Less than T threshold Then, it indicates that the triac dimmer 300 is turned on too late, and therefore adjusts and decreases the control voltage V at time t14 c 518, the PDM513 corresponding to fig. 5B generates the signal F-516 such that the turn-on time (e.g., T23) of the triac dimmer 300 is properly advanced for the next cycle, such that T phase 521 are enlarged.
In the period from t14 to t15, V in 409 is always greater than the voltage threshold at which the LED load 407 is turned on, I bleeding 412 are turned off. In the period from t15 to t16, V in 409 is less than the voltage threshold that turns on the LED load 407, LED off, I bleeding 412 are still closed until time t16 due to V in 409 is too low and requires to turn I back on bleeding 412 to maintain the conduction point of the triac dimmer 300 stable.
In the following working cycle, the bleeding control unit (U2) 406 of FIG. 5B continuously detects the time phase difference between tn3 to tn4 and adjusts V c Of each V is actively controlled in The on time (namely tn 3) of the silicon controlled dimmer in the period finally makes the time phase difference between tn3 and tn4 be at the preset time threshold value T threshold And nearby, the working time of the discharge current after the silicon controlled dimmer is switched on is reduced to the greatest extent, so that the loss is reduced, and the efficiency optimization is realized.
The present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the disclosure being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (22)
1. An LED driving system configured to dim a connected LED load with a thyristor dimmer, the LED driving system comprising:
the thyristor dimmer configured to receive an alternating current signal and chop the alternating current signal;
a rectification module configured to rectify the chopped AC signal to obtain an input voltage;
a bleeder current control module configured to derive a first signal indicative of whether the thyristor dimmer is conducting based on the input voltage; and
a constant current control module configured to generate a second signal indicative of whether the LED load is conducting based on whether current is flowing through the LED load;
wherein the bleed current control module is configured to control a bleed current of the LED driving system based on the first signal and the second signal, and the bleed current control module comprises a phase detection unit configured to:
detecting a phase difference between the first signal and the second signal to generate a pulse signal characterizing a time phase difference between the first signal and the second signal; and is
Generating an addition count signal or a subtraction count signal based on a comparison of the pulse signal with a preset threshold.
2. The LED driving system of claim 1, wherein the leakage current control module further comprises a voltage sensing unit configured to derive a sensing voltage by dividing the input voltage and generate the first signal.
3. The LED driving system of claim 1, wherein the phase detection unit comprises an RS flip-flop, a threshold signal generator, and a comparison component:
the RS flip-flop receives the first signal and the second signal and generates the pulse signal corresponding to a logic rising edge of the first signal and a logic rising edge of the second signal;
the threshold signal generator generates the preset threshold;
the comparison component compares the pulse signal with the preset threshold value, and outputs the addition count signal when the pulse signal is greater than the preset threshold value, or outputs the subtraction count signal when the pulse signal is less than the preset threshold value.
4. The LED driving system of claim 2, wherein the bleed current control module comprises a counting unit configured to: performing addition counting or subtraction counting based on whether the addition count signal or the subtraction count signal is received from the phase detection unit, and outputting a count code signal.
5. The LED driving system according to claim 4, wherein the leakage current control module further comprises a digital-to-analog conversion unit configured to convert the count code signal into a corresponding analog voltage.
6. The LED driving system according to claim 5, wherein the leakage current control module further comprises a first amplifier configured to generate a first control signal based on the sensing voltage and the analog voltage.
7. The LED driving system according to claim 6, wherein the bleed current control module further comprises a second amplifier configured to generate a second control signal based on a preset reference voltage and a voltage signal related to the magnitude of the bleed current.
8. The LED driving system of claim 7, wherein the bleed current control module further comprises a power regulation tube configured to regulate the bleed current based on the first control signal or the second control signal.
9. The LED driving system according to claim 7, wherein the first amplifier is configured to operate when the first signal is at a logic low level and to be turned off after the first signal transitions to a logic high level; and is
The second amplifier is configured to be turned on when the first signal transitions to a logic high level and turned off when the second signal transitions to a logic high level.
10. The LED driving system of claim 9, wherein the second amplifier is configured to turn on or off based on the pulse signal generated by the phase detection unit:
is turned on at a logic rising edge of the pulse signal and is turned off at a logic falling edge of the pulse signal.
11. A control method for controlling a bleed current in an LED driving system, the LED driving system including a thyristor dimmer, a rectifying module, a bleed current control module, and a constant current control module, the method comprising:
receiving an alternating current signal and chopping the alternating current signal by the silicon controlled dimmer;
rectifying, by the rectification module, the chopped AC signal to obtain an input voltage;
obtaining, by the bleeder current control module, a first signal indicative of whether the thyristor dimmer is on based on the input voltage;
generating, by the constant current control module, a second signal indicative of whether an LED load connected to the LED drive system is conducting based on whether current is flowing through the LED load; and
controlling, by the bleed current control module, a bleed current of the LED drive system based on the first signal and the second signal,
wherein controlling, by the bleed current control module, the bleed current of the LED drive system based on the first signal and the second signal comprises:
generating, based on the first signal and the second signal, a pulse signal characterizing a time phase difference between the first signal and the second signal; and is
Generating an addition count signal or a subtraction count signal based on a comparison of the pulse signal with a preset threshold.
12. The control method of claim 11, wherein controlling, by the bleed current control module, the bleed current of the LED drive system based on the first and second signals further comprises:
performing addition counting or subtraction counting based on the addition count signal or the subtraction count signal to generate a count code signal; and
the count code signal is converted into a corresponding analog voltage.
13. The control method of claim 12, wherein controlling, by the bleed current control module, the bleed current of the LED drive system based on the first and second signals further comprises:
deriving a sensing voltage based on the input voltage; and
a first control signal is generated based on the sensing voltage and the analog voltage.
14. The control method of claim 13, wherein controlling, by the bleed current control module, the bleed current of the LED drive system based on the first and second signals further comprises:
generating a second control signal based on a preset reference voltage and a voltage signal related to the magnitude of the bleed current; and
adjusting the bleed current based on the first control signal or the second control signal.
15. The control method of claim 14, wherein controlling, by the bleed current control module, the bleed current of the LED drive system based on the first and second signals further comprises:
generating the first control signal and adjusting the bleed current based on the first control signal when the first signal is a logic low level;
stopping generating the first control signal and starting generating the second control signal after the first signal transitions to a logic high level, and adjusting the bleed current based on the second control signal; and
and after the first signal is changed into a logic high level, the second control signal is turned off.
16. The control method of claim 15, wherein the generating of the first control signal and the generating of the second control signal are stopped at a logical rising edge of the pulse signal, and the generating of the second control signal is stopped at a logical falling edge of the pulse signal.
17. A control circuit adapted for use in an LED drive system for dimming a connected LED load with a thyristor dimmer, the LED drive system comprising a thyristor dimmer that receives and chops an ac signal and a rectification module that rectifies the chopped ac signal to obtain an input voltage for the control circuit, the control circuit configured to: controlling a bleed current of the LED drive system based on a first signal indicative of whether the thyristor dimmer is conducting and a second signal indicative of whether the LED load is conducting, and the control circuit comprises:
a phase detection module configured to:
receiving the first signal and a second signal representing whether the LED load is conducted or not;
detecting a phase difference between the first signal and the second signal to generate a pulse signal characterizing a temporal phase difference between the first signal and the second signal; and is provided with
Generating an addition count signal or a subtraction count signal based on a comparison of the pulse signal with a preset threshold.
18. The control circuit of claim 17, further comprising:
a voltage sensing module configured to obtain a sensing voltage by dividing the input voltage and generate the first signal characterizing whether the thyristor dimmer is turned on;
a counter configured to perform addition counting or subtraction counting based on whether the addition count signal or the subtraction count signal is received from the phase detection module, and output a count code signal;
a digital-to-analog converter configured to convert the count code signal into a corresponding analog voltage;
a first amplifier configured to generate a first control signal based on the sensing voltage and the analog voltage; and
a power adjustment tube configured to adjust the bleed current based on the first control signal.
19. The control circuit of claim 18, further comprising: second amplifier and resistor:
the resistor is used for detecting a voltage signal related to the magnitude of the bleeder current;
the second amplifier is configured to generate a second control signal based on a preset reference voltage and the voltage signal related to the magnitude of the bleed current; and is
The power adjustment tube is configured to adjust the bleed current based on the second control signal.
20. The control circuit of claim 19, wherein the first amplifier is configured to operate when the first signal is at a logic low level and to be turned off after the first signal transitions to a logic high level; and is
The second amplifier is configured to be turned on when the first signal transitions to a logic high level and turned off when the second signal transitions to a logic high level.
21. The control circuit of claim 20, wherein the second amplifier is configured to turn on or off based on the pulse signal generated by the phase detection module:
is turned on at a logic rising edge of the pulse signal and is turned off at a logic falling edge of the pulse signal.
22. The control circuit of claim 17, wherein the phase detection module comprises an RS flip-flop, a threshold signal generator, and a comparison component:
the RS flip-flop receives the first signal and the second signal and generates the pulse signal corresponding to a logic rising edge of the first signal and a logic rising edge of the second signal;
the threshold signal generator generates the preset threshold;
the comparison component compares the pulse signal with the preset threshold value, and outputs the addition count signal when the pulse signal is greater than the preset threshold value, or outputs the subtraction count signal when the pulse signal is less than the preset threshold value.
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| CN202010944557.6A CN112188681B (en) | 2020-09-10 | 2020-09-10 | LED driving system and discharge current control circuit and control method thereof |
| TW109139041A TWI755928B (en) | 2020-09-10 | 2020-11-09 | LED drive system and discharge current control circuit and control method thereof |
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| CN110582136A (en) * | 2018-06-08 | 2019-12-17 | 美芯晟科技（北京）有限公司 | Dimmable LED drive circuit and control method |
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| TWI489911B (en) * | 2011-12-30 | 2015-06-21 | Richtek Technology Corp | Active bleeder circuit triggering triac in all phase and light emitting device power supply circuit and triac control method using the active bleeder circuit |
| CN107645804A (en) * | 2017-07-10 | 2018-01-30 | 昂宝电子（上海）有限公司 | System for LED switch control |
| US10531533B1 (en) * | 2018-09-16 | 2020-01-07 | Iml International | Light-emitting diode lighting system with automatic bleeder current control |
| CN110198580B (en) * | 2019-04-17 | 2021-04-27 | 美芯晟科技（北京）有限公司 | LED drive circuit, load control system, load system and control method |
| CN110582141B (en) * | 2019-07-04 | 2024-05-14 | 江苏帝奥微电子股份有限公司 | Linear constant current LED drive circuit compatible with silicon controlled rectifier dimming |
| CN110493913B (en) * | 2019-08-06 | 2022-02-01 | 昂宝电子（上海）有限公司 | Control system and method for silicon controlled dimming LED lighting system |
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| CN112188681A (en) | 2021-01-05 |
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