Control circuit for LED linear drive system, LED linear drive circuit and method

Abstract

The present invention discloses a control circuit, an LED linear drive circuit and a method for an LED linear drive system. The LED linear drive system includes a thyristor dimmer, a rectifier circuit, an LED load and a low voltage difference linear voltage regulator circuit LDO. The control circuit includes: a first input terminal, a second input terminal and an output terminal. The first input terminal is used to receive a first signal representing a current flowing through a transistor in the low voltage difference linear voltage regulator circuit. The second input terminal is used to receive a second signal representing a bus voltage after rectification. The output terminal is coupled to the control terminal of the transistor. The control circuit is used to control the current flowing through the transistor based on the first signal and the second signal. In a conduction cycle of the thyristor dimmer, the maximum current in the first half cycle is greater than the maximum current in the second half cycle. The present invention is used for a control circuit, an LED linear drive circuit and a method for an LED linear drive system, which can reduce circuit power consumption and improve circuit efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of LED driving, and in particular relates to a control circuit for an LED linear driving system. The present invention also relates to an LED linear driving circuit and method. Background Art

[0002] See also Figure 1 , Figure 1 FIG. 1 is a schematic diagram of a conventional linear LED driving circuit. Figure 1 As shown, an existing linear LED driving circuit includes a thyristor dimmer 1', a rectifier circuit 2', a discharge circuit 3', an LED load 4', a low voltage difference linear voltage regulator circuit LDO 5', and a resistor R; the output end of the thyristor dimmer 1' is coupled to the first input end of the rectifier circuit 2', the output end of the rectifier circuit 2' is respectively coupled to the positive electrode of the LED load 4' and the first end of the discharge circuit 3', the negative electrode of the LED load 4' is coupled to the first end of the low voltage difference linear voltage regulator circuit LDO 5', the second end of the discharge circuit 3' is respectively coupled to the second end of the low voltage difference linear voltage regulator circuit LDO 5' and the first end of the resistor R, and the second end of the resistor R is grounded.

[0003] For a thyristor dimmer, a thyristor requires a large current (holding current) when it is turned on, and only a small holding current is required to keep it turned on after it is turned on. In order to make the thyristor dimmer turn on normally, the prior art often uses a bleeder circuit to provide it with a higher holding current. However, a higher holding current will cause the bleeder circuit to consume more energy, resulting in reduced circuit efficiency.

[0004] In view of this, there is an urgent need to design a new linear LED driving circuit to overcome the above-mentioned defects of the existing linear LED driving circuit. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a control circuit, an LED linear drive circuit and a method for an LED linear drive system, which can reduce circuit power consumption and improve circuit efficiency.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A control circuit for an LED linear drive system, the LED linear drive system includes a thyristor dimmer, a rectifier circuit, an LED load and a low voltage drop linear regulator circuit LDO, the control circuit includes:

[0008] A first input terminal, used to receive a first signal representing a current flowing through a transistor of a low voltage difference linear voltage regulator circuit;

[0009] A second input terminal, used to receive a second signal representing the rectified bus voltage;

[0010] The output terminal is coupled to the control terminal of the transistor. The control circuit is used to control the system output current based on the first signal and the second signal. In a conduction cycle of the thyristor dimmer, the maximum current in the first half cycle is greater than the maximum current in the second half cycle.

[0011] As an implementation manner of the present invention, the maximum current in the middle one-third cycle is smaller than the maximum current in the last one-third cycle, and the maximum current in the last one-third cycle is smaller than the maximum current in the first one-third cycle.

[0012] As an implementation mode of the present invention, the control circuit includes:

[0013] A first waveform generating circuit generates a first waveform according to a second signal;

[0014] A second waveform generating circuit generates a second waveform according to a second signal, wherein in a conduction cycle of the thyristor dimmer, an early value of the second waveform is smaller than a later value;

[0015] a subtraction circuit, wherein a first terminal receives the first waveform, a second terminal receives the second waveform, and an output terminal generates a current reference signal; and

[0016] The driving circuit controls the current of the transistor based on the current reference signal.

[0017] As an implementation of the present invention, whether the dimmer is turned on or off is determined according to the second signal. When the dimmer is turned on, the first waveform is at a high level, and when the dimmer is turned off, the first waveform is at a zero level.

[0018] As an embodiment of the present invention, the second waveform generating circuit includes:

[0019] A fourth waveform generating circuit generates a steamed-bun wave when it is detected that the dimmer is turned on; and

[0020] Delay circuit delays the steamed bun wave.

[0021] As an embodiment of the present invention, the second waveform generating circuit includes:

[0022] The fourth waveform generating circuit generates a steamed-bun wave when it is detected that the dimmer is turned on;

[0023] a fifth waveform generating circuit, which generates a fifth waveform in one conduction cycle of the dimmer, wherein the value of the fifth waveform in an early stage is greater than the value in a later stage; and

[0024] The subtraction circuit subtracts the fifth signal from the steamed bun wave to obtain a second waveform.

[0025] As an embodiment of the present invention, the fifth waveform generating circuit receives the first signal for adjusting the fifth waveform.

[0026] As an implementation mode of the present invention, the current flowing through the transistor presents a concave curve waveform which is high at the beginning and low at the end during a conduction period of the thyristor dimmer.

[0027] As an embodiment of the present invention, the maximum current in the first one-third of the cycle is more than 20% greater than the maximum current in the last two-thirds of the cycle.

[0028] An LED linear driving circuit, comprising:

[0029] A thyristor dimmer coupled to a first end of an AC power source;

[0030] A rectifier circuit is coupled to the thyristor dimmer and the second end of the AC power source to provide a bus voltage at the DC bus;

[0031] A low voltage drop linear voltage regulator circuit is connected in series with the load between the DC bus and the ground; and

[0032] A control circuit as described in any of the above embodiments.

[0033] A control circuit for an LED linear drive system, the LED linear drive system includes a thyristor dimmer, a rectifier circuit, an LED load and a low voltage drop linear regulator circuit LDO, the control circuit includes:

[0034] A first waveform generating circuit generates a first waveform according to the conduction time information of the thyristor dimmer;

[0035] A second waveform generating circuit generates a second waveform according to the conduction time information of the thyristor dimmer, wherein in one conduction cycle of the thyristor dimmer, an early value of the second waveform is smaller than a later value; and

[0036] a subtraction circuit, configured to subtract the second waveform from the first waveform to generate a current reference signal;

[0037] The control circuit controls the current flowing through the transistor based on the current reference signal.

[0038] A LED linear drive control method, comprising:

[0039] receiving a first signal indicative of a current flowing through a transistor of a low voltage dropout linear regulator circuit;

[0040] receiving a second signal representing a bus voltage;

[0041] Controlling the output current of the system based on the first signal and the second signal In a conduction cycle of the thyristor dimmer, the maximum current in the first half cycle is greater than the maximum current in the second half cycle.

[0042] As an embodiment of the present invention, the method includes: controlling the system output current to present a concave curve shape that is high at the beginning and low at the end during a conduction cycle of the thyristor dimmer.

[0043] A control circuit for a linear LED driving circuit, the linear LED driving circuit comprising: a thyristor dimmer, a rectifier circuit, an LED load, and a low voltage dropout linear circuit LDO;

[0044] The control circuit receives a first signal representing a transistor current Io flowing through a low voltage difference linear circuit LDO and a second signal representing a bus voltage VBUS, and is used to control the current Io flowing through the low voltage difference linear circuit LDO, so that in a thyristor conduction period T0, the first maximum current I1 of the low voltage difference linear circuit LDO in the early stage of conduction is greater than the second maximum current I2 in the later stage of thyristor conduction, or the current average value in the early stage of conduction is greater than the current average value in the later stage of thyristor conduction.

[0045] The beneficial effects of the present invention are as follows: the control circuit, LED linear drive circuit and method for the LED linear drive system proposed in the present invention control the current flowing through the LDO to be larger in the early stage, which is beneficial to maintaining the holding current of the thyristor dimmer, and at the same time can reduce the demand for the discharge circuit and reduce the power consumption generated by it. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a circuit diagram of an existing linear LED driving circuit.

[0047] Figure 2 FIG. 4 is a schematic diagram of a LED linear driving system circuit according to an embodiment of the present invention.

[0048] Figure 3 FIG. 4 is a schematic diagram of waveforms of voltage VBUS and current Io in a control circuit according to an embodiment of the present invention.

[0049] Figure 4 Schematic diagram of a waveform of the current Io in an embodiment of the present invention, showing a concave curve shape that is high at the beginning and low at the end.

[0050] Figure 5 FIG. 4 is a circuit diagram of a control circuit in an embodiment of the present invention.

[0051] Figure 6 FIG. 4 is a circuit diagram of a second waveform generating circuit in an embodiment of the present invention.

[0052] Figure 7 For an embodiment of the present invention Figure 6 Schematic diagram of the waveforms of various signals in the circuit.

[0053] Figure 8 FIG. 4 is a circuit diagram of a second waveform generating circuit in an embodiment of the present invention.

[0054] Fig. 9 For an embodiment of the present invention Figure 8 Waveform diagram of each signal in the circuit. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0056] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0057] The description of this section is only for several typical embodiments, and the present invention is not limited to the scope of the embodiments. The same or similar prior art means and some technical features in the embodiments are mutually replaced within the scope of the present invention. The "coupling" or connection in the specification includes both direct connection and indirect connection, such as connection through some active devices, passive devices or electrically conductive media. "Multiple" refers to two or more.

[0058] See also Figure 2 , Figure 2 FIG. 1 is a circuit diagram of an LED linear drive system and its control circuit in one embodiment of the present invention. Figure 2 As shown, in one embodiment of the present invention, the LED linear driving system includes a thyristor dimmer 20, a rectifier circuit 30, an LED load 40, a low voltage dropout linear regulator circuit (LDO) 50 and a control circuit 10. The input end of the thyristor dimmer 20 is coupled to the first end of the AC power source AC, and the output end is coupled to the first input end of the rectifier circuit 30. The input end of the rectifier circuit 30 is coupled to the thyristor dimmer 20 and the second end of the AC power source AC, and the output end provides a bus voltage VBUS at the DC bus. In the illustrated embodiment, the output end of the rectifier circuit 30 is respectively coupled to the positive electrode of the LED load 40, and the negative electrode of the LED load 40 is coupled to the first end of the low voltage dropout linear regulator circuit (LDO) 50. The first input end of the control circuit 10 is coupled to the low voltage dropout linear regulator circuit (LDO) 50 for receiving the current sampling signal V1, and the second input end of the control circuit 10 is coupled to the DC bus for obtaining the second signal V2 of the bus voltage VBUS after sampling and rectification. The output terminal of the control circuit 10 is coupled to the control terminal of a transistor in a low dropout linear regulator circuit (LDO) 50 for controlling the system output current Io.

[0059] In the illustrated embodiment, the first end of the resistor R is coupled to the second end of the LDO 50 and the control circuit 10, the second end of the resistor R is grounded, and the first end of the resistor R is used to provide a sampling signal V1 proportional to the current. It should be noted that although the figure shows that the resistor R is used to provide sampling information representing the current flowing through the transistor (not shown) in the LDO, in other embodiments, the LED linear drive system may not include the resistor R and use other methods for current sampling. The configuration of the transistor in the LDO is common knowledge to those skilled in the art and will not be described in detail here.

[0060] In one embodiment, the positions of the LDO and the load can be interchanged. In one embodiment, a capacitor can be connected in parallel across the LED.

[0061] In one embodiment of the present invention, the control circuit 10 includes: a first input terminal, a second input terminal, and an output terminal. The first input terminal is used to receive a first signal V1 representing the current flowing through the transistor of the low voltage difference linear voltage regulator circuit 50; the second input terminal is used to receive a second signal V2 representing the bus voltage VBUS after rectification; the output terminal is coupled to the control terminal of the transistor, and the control circuit 10 is used to control the system output current based on the first signal V1 and the second signal. In a conduction cycle of the thyristor dimmer 20, the maximum current I1 in the first half cycle is greater than the maximum current I2 in the second half cycle. In a preferred embodiment, the control circuit controls the system output current so that the maximum current I1 in the first third of the cycle is greater than the maximum current I2 in the last two thirds of the cycle. See also Figure 3 , Figure 3 : is a waveform diagram of voltage VBUS and current Io in a control circuit in an embodiment of the present invention. In one embodiment, the system output current is the current flowing through the LED load. The system output current may also refer to the current at other locations in the system. In a preferred embodiment, Figure 2 As shown, the system output current is the current Io flowing through the transistor in the low voltage difference linear voltage regulator circuit LDO.

[0062] In a preferred embodiment of the present invention, the control circuit controls the system output current in a conduction cycle of the thyristor dimmer, the maximum current in the middle one-third cycle is smaller than the maximum current in the last one-third cycle, and the maximum current in the last one-third cycle is smaller than the maximum current in the first one-third cycle.

[0063] In one embodiment of the present invention, the maximum current in the middle half cycle of the system output current is smaller than the maximum current in the last quarter cycle, and the maximum current in the last quarter cycle is smaller than the maximum current in the first quarter cycle; wherein the cycle refers to a conduction cycle of the thyristor dimmer 20.

[0064] In one embodiment of the present invention, the control circuit receives a signal V1 representing the current Io flowing through the LDO transistor and a signal V2 representing the bus voltage VBUS, and is used to control the waveform of the current Io to be an asymmetric waveform with a high waveform at the front and a low waveform at the back.

[0065] In one embodiment of the present invention, the present invention controls the current Io flowing through the LDO to be a higher value in the early stage of conduction and drops to a lower value in the maintenance period, so that the LDO current is in a thyristor conduction period T0, and the maximum current I1 in the early stage is greater than the maximum current I2 in the later stage, which complies with the law of thyristor conduction. In one embodiment, in a conduction period T0, the maximum current I1 in the first third of the cycle is greater than the maximum current I2 in the last two thirds of the cycle. In one embodiment, the maximum current I1 in the first quarter of the cycle is greater than the maximum current I2 in the last quarter of the cycle. In one embodiment, the maximum current I1 in the first third of the cycle is more than 20% greater than the maximum current I2 in the last two thirds of the cycle. By increasing the current in the early stage, it is beneficial to maintain the holding current of the dimmer. In this way, the use of the discharge circuit can be omitted, or the current value in the discharge circuit can be reduced, thereby reducing the power loss of the discharge circuit. In one embodiment of the present invention, the VBUS and Io current waveforms can be as follows Figure 3 shown.

[0066] See also Figure 4 , Figure 4 Schematic diagram of current Io in one embodiment of the present invention; Figure 4 As shown, in one embodiment of the present invention, the current is in the shape of a concave curve that is high at the front and low at the back. When the VBUS voltage is high, that is, when the voltage across the LDO is high, reducing the current value is beneficial to reducing the loss on the LDO. In one embodiment, in a thyristor conduction cycle T0, the maximum current of the middle half cycle (1 / 4T0-3 / 4T0) is less than the maximum current I2 of the last quarter cycle (3 / 4T0-T0), and the maximum current I2 of the last quarter cycle (3 / 4T0-T0) is less than the maximum current I1 of the first quarter cycle.

[0067] For ease of description, Figure 3 Figure 4 The current Io flowing through the LDO is shown to rise to a high value I1 instantaneously at the beginning of T0, but in actual applications, the waveform of the current Io may include a process of rising from zero with a slope. The waveform of the current Io may include a process of falling to zero with a slope.

[0068] See also Figure 5 , Figure 5 FIG. 1 is a circuit diagram of a control circuit in an embodiment of the present invention; Figure 5As shown, in one embodiment of the present invention, the control circuit 10 internally includes: a first waveform generating circuit 11, a second waveform generating circuit 12, a subtraction circuit 13, and a driving circuit 14.

[0069] In one embodiment of the present invention, the first waveform generating circuit 11 generates the first waveform S1 according to the second signal V2; the second waveform generating circuit 12 generates the second waveform S2 according to the second signal V2, wherein in a conduction cycle of the thyristor dimmer, the value of the second waveform S2 in the early stage is less than the value in the later stage; the first end of the subtraction circuit 13 receives the first waveform S1, the second end receives the second waveform S2, and the output end generates a current reference signal S3; the driving circuit 14 controls the current Io based on the current reference signal S3. In one embodiment of the present invention, it is determined whether the dimmer is turned on or off according to the second signal V2. When the dimmer is turned on, the first waveform S1 is a high level, and when the dimmer is turned off, the first waveform S1 is a zero value. Of course, the first waveform may also have other shapes, and may have continuously changing values ​​such as a right-angle trapezoidal shape with a high front and a low back, and is not limited to a binary signal.

[0070] In one embodiment of the present invention, a first waveform generating circuit 11 generates a first waveform S1 according to the conduction time information of a thyristor dimmer; a second waveform generating circuit 12 generates a second waveform S2 according to the conduction time information of the thyristor dimmer, wherein the second waveform S2 has an early value that is smaller than a later value within a conduction period T0 of the thyristor dimmer; a subtraction circuit 13 is used to subtract the second waveform S2 from the first waveform S1 to generate a current reference signal S3; and a current following signal S3 flowing through the transistor is controlled based on the current reference signal S3.

[0071] like Figure 5 As shown, in one embodiment of the present invention, a comparator 15 can be arranged between the subtraction circuit 13 and the driving circuit 14, the positive input terminal of the comparator 15 is connected to the output terminal of the subtraction circuit 13, and the negative input terminal of the comparator 15 is connected to the first signal V1; the output terminal of the comparator 15 is connected to the driving circuit 14.

[0072] See also Figure 6 , Figure 6 FIG. 4 is a circuit diagram of a second waveform generating circuit according to an embodiment of the present invention; Figure 6 As shown, in one embodiment of the present invention, the second waveform generating circuit 12 includes a fourth waveform generating circuit 121 and a delay circuit 122. When the dimmer is detected to be turned on, the fourth waveform generating circuit 121 generates a steamed wave; the delay circuit 122 delays the steamed wave.

[0073] In addition, if Figure 6As shown, the second waveform generation circuit 12 may further include a comparator 120. The positive input terminal of the comparator 120 is connected to the second signal V2, the negative input terminal of the comparator 120 is connected to the reference voltage Vref, and the output terminal of the comparator 120 is connected to the fourth waveform generation circuit 121. The comparator 120 determines whether the second signal V2 is greater than the reference voltage Vref; when the second signal V2 is greater than the reference voltage Vref, that is, when it is determined that the dimmer is turned on, the fourth waveform generation circuit 121 generates a signal S4 such as a half-wave sine wave or a flat-top wave, and the delay circuit 122 delays S4 or performs a phase shift.

[0074] A typical waveform of the present invention is as Figure 7 shown Figure 7 which is the waveform diagram of each signal in the corresponding Figure 6 circuit of an embodiment of the present invention. Among them, S1 is high when VBUS > Vref and low or zero when VBUS < Vref; where Vref is a very small value such that the high-value interval of S1 is substantially equal to the period when the dimmer is turned on. S4 is a half-wave sine wave or a flat-top wave during the period when VBUS > Vref, that is, when S1 is high, or corresponds to the VBUS waveform. The waveform S4 can be provided by a waveform generation circuit or obtained by sampling the bus voltage VBUS. S2 is the signal obtained by delaying S4, or a phase-shifted signal with a phase shifted backward. S3 is the signal obtained by subtracting the S2 signal from the S1 signal. By comparing the S3 signal with the Io sampling signal V1, the state of the transistor in the LDO is controlled, so that Io follows the shape of S3, showing an asymmetric shape with a higher current in the early stage and a lower current in the later stage when the dimmer is just turned on.

[0075] Please refer to Figure 8 , Figure 8 which is the circuit schematic diagram of the second waveform generation circuit in another embodiment of the present invention; in an embodiment of the present invention, the second waveform generation circuit 12 includes a fourth waveform generation circuit 121, a fifth waveform generation circuit 124, and a subtraction circuit 125.

[0076] When it is detected that the dimmer is turned on, the fourth waveform generation circuit 121 generates a flat-top wave; during a conduction cycle of the dimmer, the fifth waveform generation circuit 124 generates a fifth waveform S5, where the value of the fifth waveform S5 in the early stage is greater than that in the later stage; the subtraction circuit 125 subtracts the fifth signal S2 from the flat-top wave S4 to obtain the second waveform S2. The fifth waveform generation circuit 124 may further receive the first signal V1 for adjusting the fifth waveform S5 according to the value of the current sampling signal V1.

[0077] In one embodiment of the present invention, the second waveform generating circuit 12 may further include a comparator 123, a positive input terminal of the comparator 123 is connected to the second signal V2, a negative input terminal of the comparator 123 is connected to the reference voltage Vref, and an output terminal of the comparator 123 is connected to the fourth waveform generating circuit 121.

[0078] In some embodiments of the present invention, the current flowing through the transistor presents a concave curve waveform with a high first and a low second in a conduction cycle of the thyristor dimmer. The maximum current in the first third of the cycle is more than 20% greater than the maximum current in the last two thirds of the cycle.

[0079] In one embodiment of the present invention, the subtraction circuit 125 subtracts the fifth waveform S5 from the steamed bun wave, wherein the fifth waveform S5 has a greater value in the early stage than in the late stage during a conduction period T0 of the thyristor dimmer; Fig. 9 shown.

[0080] In one embodiment, Figure 8 As shown, in order to achieve a constant current effect in each conduction period, the fifth waveform S5 can be further controlled by the current Io sampling signal V1 to adjust the value of the fifth waveform S5 in real time.

[0081] Of course, the control circuit may also include other components to perform other controls, such as controlling the voltage across the LDO to follow VBUS, etc., which are not shown here.

[0082] In some embodiments of the present invention, the LED linear drive system includes a thyristor dimmer, a rectifier circuit, an LED load and a low voltage drop linear regulator circuit LDO; the control circuit for the LED linear drive system includes: a first waveform generating circuit, a second waveform generating circuit, a subtraction circuit (refer to Figure 5 ). The first waveform generating circuit generates a first waveform according to the conduction time information of the thyristor dimmer; the second waveform generating circuit generates a second waveform according to the conduction time information of the thyristor dimmer, wherein in one conduction cycle of the thyristor dimmer, the value of the second waveform in the early stage is less than the value in the later stage; the subtraction circuit is used to subtract the second waveform from the first waveform to generate a current reference signal; the control circuit controls the current flowing through the transistor based on the current reference signal.

[0083] In some embodiments of the present invention, the linear LED driving circuit includes: a thyristor dimmer, a rectifier circuit, an LED load, and a low voltage difference linear voltage regulator circuit LDO; the control circuit for the linear LED driving circuit of the present invention receives a first signal representing a transistor current Io flowing through the low voltage difference linear voltage regulator circuit LDO and a second signal representing a bus voltage VBUS, and is used to control the current Io flowing through the low voltage difference linear voltage regulator circuit LDO, so that the current of the low voltage difference linear voltage regulator circuit LDO in a thyristor conduction cycle T0, the first maximum current in the early stage of conduction is greater than the second maximum current in the later stage of thyristor conduction, or the average current in the early stage of conduction is greater than the average current in the later stage of thyristor conduction. The specific control method can be referred to the above description, and of course other implementation methods can also be selected.

[0084] The present invention also discloses an LED linear drive circuit, comprising: a thyristor dimmer, a rectifier circuit, a low voltage drop linear voltage regulator circuit, and a control circuit. The thyristor dimmer is coupled to the first end of the AC power supply; the rectifier circuit is coupled to the thyristor dimmer and the second end of the AC power supply, and provides a bus voltage on the DC bus; the low voltage drop linear voltage regulator circuit and the load are connected in series between the DC bus and the ground; the control circuit can be any of the above control circuits.

[0085] The present invention also discloses a LED linear drive control method. In one embodiment of the present invention, the control method comprises the following steps:

[0086] receiving a first signal indicative of a current flowing through a transistor of a low voltage dropout linear regulator circuit;

[0087] receiving a second signal representing a bus voltage;

[0088] Controlling the current flowing through the transistor In one conduction cycle of the thyristor dimmer, the maximum current in the first third of the cycle is greater than the maximum current in the last two thirds of the cycle.

[0089] In one embodiment of the present invention, the method includes: controlling the current flowing through the transistor to present a concave curve shape with a high first and a low second during a conduction period of the thyristor dimmer.

[0090] The specific control process and implementation of the control method of the present invention can refer to the description of the control circuit part above, which will not be repeated here.

[0091] In one embodiment of the present invention, the control method includes:

[0092] Receiving a first signal representing a current Io flowing through a transistor of a low voltage difference linear voltage regulator circuit LDO;

[0093] Receiving a second signal representing a bus voltage VBUS;

[0094] The current Io flowing through the low voltage difference linear regulator circuit LDO is controlled so that, in a thyristor conduction period T0, the first maximum current of the low voltage difference linear regulator circuit LDO in the early stage of conduction is greater than the second maximum current in the later stage of thyristor conduction, or the average current in the early stage of conduction is greater than the average current in the later stage of thyristor conduction.

[0095] The specific control process and implementation of the control method of the present invention can refer to the description of the control circuit part above, which will not be repeated here.

[0096] In summary, the control circuit, LED linear drive circuit and method for the LED linear drive system proposed in the present invention control the current flowing through the LDO to be larger in the early stage, which is beneficial to maintaining the holding current of the thyristor dimmer, and at the same time can reduce the demand for the discharge circuit and reduce the power consumption generated by the discharge circuit.

[0097] The description and application of the present invention here are illustrative and are not intended to limit the scope of the present invention to the above-described embodiments. The deformation and changes of the embodiments disclosed here are possible, and the replacement of the embodiments and the various components equivalent to those of ordinary skill in the art are well known. It should be clear to those skilled in the art that the present invention can be realized in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential characteristics of the present invention. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the present invention.

Claims

1. A control circuit for an LED linear drive system, wherein the LED linear drive system includes a thyristor dimmer, a rectifier circuit, an LED load and a low voltage drop linear regulator circuit, and the control circuit includes: A first input terminal, used to receive a first signal representing a current flowing through a transistor of a low voltage difference linear voltage regulator circuit; A second input terminal, used to receive a second signal representing the rectified bus voltage; The output end is coupled to the control end of the transistor. The control circuit is used to control the system output current based on the first signal and the second signal in a conduction cycle of the thyristor dimmer, and the maximum current in the first half cycle is greater than the maximum current in the second half cycle; the control system output current presents a concave curve shape with high at the beginning and low at the end in a conduction cycle of the thyristor dimmer.

2. The control circuit according to claim 1, characterized in that: The maximum current in the middle one-third cycle is smaller than the maximum current in the last one-third cycle, and the maximum current in the last one-third cycle is smaller than the maximum current in the first one-third cycle.

3. The control circuit according to claim 1, characterized in that: The interior includes: A first waveform generating circuit generates a first waveform according to a second signal; A second waveform generating circuit generates a second waveform according to a second signal, wherein in a conduction cycle of the thyristor dimmer, an early value of the second waveform is smaller than a later value; a first subtraction circuit, wherein a first terminal receives the first waveform, a second terminal receives the second waveform, and an output terminal generates a current reference signal; as well as The driving circuit controls the current of the transistor based on the current reference signal.

4. The control circuit according to claim 3, characterized in that: Whether the dimmer is turned on or off is determined according to the second signal. When the dimmer is turned on, the first waveform is at a high level, and when the dimmer is turned off, the first waveform is at a zero level.

5. The control circuit according to claim 3, characterized in that: The second waveform generating circuit comprises: A fourth waveform generating circuit generates a steamed-bun wave when it is detected that the dimmer is turned on; and Delay circuit delays the steamed bun wave.

6. The control circuit according to claim 3, characterized in that: The second waveform generating circuit comprises: The fourth waveform generating circuit generates a steamed-bun wave when it is detected that the dimmer is turned on; a fifth waveform generating circuit, which generates a fifth waveform in one conduction cycle of the dimmer, wherein the value of the fifth waveform in an early stage is greater than the value in a later stage; and The second subtraction circuit subtracts the fifth signal from the steamed bun wave to obtain a second waveform.

7. The control circuit according to claim 6, characterized in that: The fifth waveform generating circuit receives the first signal and is used to adjust the fifth waveform.

8. The control circuit according to claim 1, characterized in that: During a conduction cycle of the thyristor dimmer, the current flowing through the transistor presents a concave curve waveform that is high at the beginning and low at the end.

9. The control circuit according to claim 1, characterized in that: The maximum current in the first one-third of the cycle is more than 20% greater than the maximum current in the last two-thirds of the cycle.

10. An LED linear drive circuit, characterized in that: include: A thyristor dimmer coupled to a first end of an AC power source; A rectifier circuit is coupled to the thyristor dimmer and the second end of the AC power source to provide a bus voltage at the DC bus; A low voltage drop linear voltage regulator circuit is connected in series with the load between the DC bus and the ground; and A control circuit as claimed in any one of claims 1 to 9.

11. A control circuit for an LED linear drive system, characterized in that: The LED linear drive system includes a thyristor dimmer, a rectifier circuit, an LED load and a low voltage drop linear regulator circuit. The control circuit includes: A first waveform generating circuit generates a first waveform according to the conduction time information of the thyristor dimmer; A second waveform generating circuit generates a second waveform according to the conduction time information of the thyristor dimmer, wherein in one conduction cycle of the thyristor dimmer, an early value of the second waveform is smaller than a later value; and a subtraction circuit, configured to subtract the second waveform from the first waveform to generate a current reference signal; The control circuit controls the current flowing through the transistor based on the current reference signal; the output current of the control system presents a concave curve shape that is high at the beginning and low at the end during a conduction cycle of the thyristor dimmer.

12. A LED linear drive control method, characterized in that: include: receiving a first signal indicative of a current flowing through a transistor of a low voltage dropout linear regulator circuit; receiving a second signal representing a bus voltage; Based on the first signal and the second signal, the control system output current in a conduction cycle of the thyristor dimmer, the maximum current in the first half cycle is greater than the maximum current in the second half cycle; the control system output current in a conduction cycle of the thyristor dimmer presents a concave curve shape with high at the beginning and low at the end.

13. A control circuit for a linear LED drive circuit, characterized in that: The linear LED driving circuit comprises: a thyristor dimmer, a rectifier circuit, an LED load, and a low voltage drop linear voltage regulator circuit; The control circuit receives a first signal representing the current flowing through the transistor of the low voltage difference linear circuit and a second signal representing the bus voltage, and is used to control the current flowing through the low voltage difference linear circuit, so that in a thyristor conduction cycle T0, the first maximum current I1 of the low voltage difference linear circuit LDO current in the early stage of conduction is greater than the second maximum current I2 in the later stage of thyristor conduction, or the average current in the early stage of conduction is greater than the average current in the later stage of thyristor conduction; the control system output current presents a concave curve shape with high at the beginning and low at the end in a conduction cycle of the thyristor dimmer.

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