Control circuit and control method of LED driving circuit and LED driving circuit

Abstract

The present invention proposes a control circuit, a control method and an LED driving circuit for an LED driving circuit, wherein the control circuit includes a power supply circuit, a soft start circuit and a first regulating circuit. The control circuit is coupled to an input capacitor in the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit. The power supply circuit is used to receive a detection signal representing a bus voltage and output a preset signal according to the detection signal. The soft start circuit is used to perform soft start processing on a soft start receiving signal representing a preset signal and then output a first reference signal to control the soft start of the charging current of the input capacitor. The first regulating circuit is coupled to the soft start circuit, and the first regulating circuit is used to control the conduction state of the first transistor based on the first reference signal. The control circuit, the control method and the LED driving circuit for an LED driving circuit proposed in the present invention can meet the requirements of the new European standard for the input current waveform and effectively solve the EMI problem.

Description

Technical Field

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

[0002] LED lamps are widely used in the lighting field due to their high brightness, low power consumption, and long life. At present, the new European standard for LED lighting gives specific requirements for the input current corresponding to each range of conduction angles, that is, before the conduction angle is 60°, the input current of the LED driver circuit must reach at least 5% of the current peak; before the conduction angle is 65°, the input current needs to reach the maximum value, etc. The architecture of the LED driver circuit mostly uses linear control to meet the requirements of the new European standard for LED lighting for the input current waveform. The linear control specifically controls the current size of the input capacitor. However, this linear charging current is similar to a square wave signal, and there is an electromagnetic interference (EMI) effect on the input. Therefore, other capacitors besides the input capacitor need to be added after the rectifier circuit for filtering to meet the EMI requirements, but the cost of this technical solution is high, and the circuit structure is not easy to install.

[0003] In view of this, it is necessary to provide a new structure or control method to meet the requirements of the new European standard for LED lighting and solve its EMI problem. Summary of the invention

[0004] In order to solve at least part of the above problems, the present invention proposes a control circuit, a control method and an LED driving circuit of an LED driving circuit, which can meet the requirements of the new European standard for LED lighting on the input current waveform and effectively solve the EMI problem of the LED driving circuit.

[0005] The present invention discloses a control circuit for an LED driving circuit. The control circuit is coupled to an input capacitor in the LED driving circuit to control an input current of the LED driving circuit. The input capacitor is coupled to a first transistor in the LED driving circuit. The control circuit comprises:

[0006] A power supply circuit, used for receiving a detection signal representing a bus voltage, and outputting a preset signal according to the detection signal;

[0007] A soft start circuit, whose input end is coupled to the power supply circuit, is used to perform soft start processing on a soft start receiving signal representing a preset signal and then output a first reference signal to control the charging current of the input capacitor to soft start; and

[0008] The first regulating circuit has an input terminal coupled to the soft start circuit and an output terminal coupled to the first transistor, and is used for controlling the conduction state of the first transistor based on a first reference signal.

[0009] In one embodiment of the present invention, a first terminal of the input capacitor is coupled to the bus voltage terminal, and an input terminal of the power supply circuit is coupled to a second terminal of the input capacitor.

[0010] In one embodiment of the present invention, the input end of the power supply circuit is coupled to the bus voltage end, and the control circuit also includes: a reset circuit, whose input end is coupled to the second end of the input capacitor to obtain a terminal voltage signal, and whose output end is coupled to the soft start circuit, for resetting the soft start circuit based on the terminal voltage signal.

[0011] In one embodiment of the present invention, the control circuit further includes:

[0012] a compensation circuit, wherein an input terminal of the compensation circuit is coupled to the second terminal of the input capacitor and an output terminal of the compensation circuit outputs a compensation signal; and

[0013] The adder has a first input terminal coupled to the output terminal of the power supply circuit, a second input terminal coupled to the output terminal of the compensation circuit, and an output terminal coupled to the input terminal of the soft start circuit.

[0014] In one embodiment of the present invention, the soft start circuit comprises:

[0015] A current source, a power supply terminal of which is coupled to the output terminal of the power supply circuit;

[0016] A second capacitor, a first end of which is coupled to the output end of the current source, the first end of which is the output end of the soft start circuit, and a second end of which is coupled to the reference ground end; and

[0017] The second resistor has a first end coupled to the first end of the second capacitor and a second end coupled to the second end of the second capacitor.

[0018] In one embodiment of the present invention, the soft start circuit comprises:

[0019] A third resistor, a first end of which is coupled to the output end of the power supply circuit; and

[0020] The third capacitor has a first end coupled to the second end of the third resistor, a first end being the output end of the soft start circuit, and a second end coupled to the reference ground end.

[0021] In one embodiment of the present invention, the first regulating circuit is coupled to the first sampling resistor to obtain a first sampling signal, and the first regulating circuit controls a conduction state of the first transistor based on a first reference signal and the first sampling signal.

[0022] In one embodiment of the present invention, the control circuit further includes a first transistor, and the first regulating circuit is coupled to a control terminal of the first transistor.

[0023] In one embodiment of the present invention, the control circuit further includes:

[0024] A second transistor coupled to an LED load in the LED driving circuit; and

[0025] The second regulating circuit has an output terminal coupled to the control terminal of the second transistor and is used to control the conduction state of the second transistor based on a second reference signal.

[0026] The present invention also discloses an LED driving circuit, which includes a rectifier circuit, an input capacitor, an LED load and the control circuit as described above.

[0027] The present invention also discloses a control method for an LED driving circuit. The LED driving circuit includes a control circuit. The control circuit is coupled to an input capacitor in the LED driving circuit to control an input current of the LED driving circuit. The input capacitor is coupled to a first transistor in the LED driving circuit. The control method includes:

[0028] receiving a detection signal representing a bus voltage, and outputting a preset signal according to the detection signal;

[0029] After performing soft-start processing on a soft-start receiving signal representing a preset signal, a first reference signal is outputted to control the soft-start of a charging current of an input capacitor; and

[0030] A conduction state of the first transistor is controlled based on a first reference signal.

[0031] In one embodiment of the present invention, the detection signal is a bus voltage or a terminal voltage collected at the second end of the input capacitor.

[0032] In one embodiment of the present invention, the soft start receiving signal is a preset signal or is compensated based on the preset signal.

[0033] In one embodiment of the present invention, the waveform of the soft start receiving signal is saddle-shaped.

[0034] The present invention proposes a control circuit, a control method and an LED driving circuit of an LED driving circuit, wherein the control circuit includes a power supply circuit, a soft start circuit and a first regulating circuit. The control circuit is coupled to an input capacitor in the LED driving circuit to control the input current of the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit. The control circuit of the present invention receives a detection signal representing a bus voltage and outputs a preset signal according to the detection signal. The charging current of the input capacitor is soft-started by outputting a first reference signal after soft-start processing of a soft start receiving signal representing a preset signal, and the conduction state of the first transistor is controlled based on the first reference signal to slow down the rising edge of the input current of the LED driving circuit. The present invention can effectively solve the EMI problem of the LED driving circuit while meeting the requirements of the new European standard for LED lighting on the input current waveform. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 FIG. 4 is a circuit diagram of an LED driving circuit according to an embodiment of the present invention.

[0036] Figure 2 FIG. 4 is a circuit diagram of an LED driving circuit according to another embodiment of the present invention.

[0037] Figure 3 A schematic diagram of partial signal waveforms of an LED driving circuit according to another embodiment of the present invention is shown.

[0038] Figure 4 FIG. 4 is a circuit diagram of an LED driving circuit according to another embodiment of the present invention.

[0039] Figure 5 FIG. 4 is a circuit diagram of a soft start circuit according to an embodiment of the present invention.

[0040] Figure 6 FIG. 4 is a circuit diagram of a soft start circuit according to another embodiment of the present invention.

[0041] Figure 7 A schematic diagram of steps of a control method for an LED driving circuit according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0043] 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.

[0044] The description in 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.

[0045] The term "coupled" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrically conductive medium, which may have parasitic inductance or parasitic capacitance; indirect connection may also include connection through other active or passive devices on the basis of achieving the same or similar functional purpose, such as connection through circuits or components such as switches and follower circuits.

[0046] The embodiment of the present invention discloses a control circuit for an LED driving circuit, wherein the control circuit is coupled to an input capacitor in the LED driving circuit to control the input current of the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit. The control circuit includes a power supply circuit, a soft start circuit, and a first regulating circuit. The input end of the power supply circuit is coupled to a bus voltage end or a second end of the input capacitor, and the power supply circuit is used to receive a detection signal representing the bus voltage, and output a preset signal according to the detection signal. In one embodiment of the present invention, the power supply circuit outputs a preset signal according to the detection signal to power the soft start circuit. The input end of the soft start circuit is coupled to the power supply circuit, and the soft start circuit is used to perform soft start processing on a soft start receiving signal representing the preset signal and then output a first reference signal to control the soft start of the charging current of the input capacitor. The input end of the first regulating circuit is coupled to the soft start circuit, and the output end of the first regulating circuit is coupled to the first transistor, and the first regulating circuit is used to control the conduction state of the first transistor based on the first reference signal. In one embodiment of the present invention, the detection signal may be a bus voltage or a terminal voltage at the second end of the input capacitor. In one embodiment of the present invention, the preset signal may be a preset voltage or a preset current.

[0047] like Figure 1 As shown, one embodiment of the present invention discloses an LED driving circuit, wherein the LED driving circuit includes a rectifier circuit, an input capacitor C1, an LED load and a control circuit 10. The rectifier circuit is coupled to the first end of the input capacitor C1 and the LED load respectively, the control circuit 10 is coupled to the input capacitor C1 to control the input current of the LED driving circuit, and the input capacitor C1 is coupled to the first transistor Q1 in the LED driving circuit. The control circuit 10 includes a power supply circuit 100, a soft start circuit 200, a first adjustment circuit 300 and a first transistor Q1. In another embodiment of the present invention, the control circuit 10 does not include the first transistor Q1. The first transistor Q1 can be a field effect transistor (FET for short) or a bipolar transistor (BJT for short). As Figure 1As shown, in one embodiment of the present invention, the first transistor Q1 is a metal oxide semiconductor field effect transistor (MOSFET for short), the drain terminal of the first transistor Q1 is coupled to the second terminal of the input capacitor C1, the source terminal of the first transistor Q1 is coupled to the first terminal of the first sampling resistor Rcs1, the gate terminal of the first transistor Q1 is coupled to the output terminal of the first dimming circuit 300, the second terminal of the first sampling resistor Rcs1 is coupled to the reference ground terminal, and the first sampling signal can be obtained through the first sampling resistor Rcs1. In another embodiment of the present invention, the control circuit 10 also includes a first sampling resistor Rcs1. Figure 1 As shown, in one embodiment of the present invention, the LED driving circuit further includes a second transistor Q2, a second regulating circuit 400 and a second sampling resistor Rcs2, the second transistor Q2 is coupled to the LED load in the LED driving circuit, the input end of the second regulating circuit 400 is respectively coupled to the second reference signal end and the second sampling resistor Rcs2, the second reference signal end is used to provide a second reference signal Iref2, the output end of the second regulating circuit 400 is coupled to the control end of the second transistor Q2, and the second regulating circuit 400 is used to control the conduction state of the second transistor Q2 based on the second reference signal Iref2 and the second sampling signal to achieve dimming control of the LED driving circuit.

[0048] In one embodiment of the present invention, the LED driving circuit is a linear dimming driving circuit. The first regulating circuit 300 controls the conduction state of the first transistor Q1 according to the first reference signal and the first sampling signal, wherein the conduction state is specifically the conduction degree of the first transistor Q1, and the magnitude of the current flowing through the first transistor Q1 is controlled by controlling the conduction degree of the first transistor Q1, and the charging current flowing through the input capacitor is correspondingly controlled, thereby realizing the control of the input current of the LED driving circuit. In another embodiment of the present invention, the second regulating circuit 400 controls the conduction state of the second transistor Q2 according to the second reference signal and the second sampling signal, wherein the conduction state is specifically the conduction degree of the second transistor Q2, and the magnitude of the current flowing through the second transistor Q2 is controlled by controlling the conduction degree of the second transistor Q2, and the magnitude of the current flowing through the LED load is correspondingly controlled, thereby realizing the dimming control of the LED driving circuit.

[0049] In one embodiment of the present invention, the control circuit 10 receives a detection signal representing the bus voltage and outputs a preset signal according to the detection signal. The control circuit 10 performs soft start processing on the soft start receiving signal representing the preset signal and then outputs a first reference signal to control the soft start of the charging current of the input capacitor C1, and controls the conduction state of the first transistor Q1 based on the first reference signal and the first sampling signal to slow down the rising edge of the input current of the LED driving circuit, which can effectively solve the EMI problem of the LED driving circuit while meeting the requirements of the new European standard for LED lighting on the input current waveform.

[0050] In one embodiment of the present invention, the first reference signal may be a first reference voltage or a first reference current, and the first sampling signal may be a first sampling voltage or a first sampling current. In another embodiment of the present invention, the second reference signal may be a second reference voltage or a second reference current, and the second sampling signal may be a second sampling voltage or a second sampling current.

[0051] In one embodiment of the present invention, the first end of the input capacitor C1 is coupled to the bus voltage end, and the bus voltage end is used to provide the bus voltage. The input end of the power supply circuit 100 is coupled to the second end of the input capacitor C1 to obtain a voltage signal representing the bus voltage. Figure 1 As shown, the power supply circuit 100 receives the voltage signal Vdrain and outputs the preset current Iref according to the voltage signal Vdrain. In this embodiment, the soft start receiving signal representing the preset current is the preset current Iref. The soft start circuit 200 performs soft start processing on the preset current Iref and outputs the first reference current Iref1 to control the charging current soft start of the input capacitor C1. The first regulating circuit 300 controls the conduction state of the first transistor Q1 according to the first reference current Iref1 and the first sampling current so as to slow down the rising edge of the input current of the LED driving circuit.

[0052] In one embodiment of the present invention, the input end of the power supply circuit is coupled to the bus voltage end, the power supply circuit receives the bus voltage, and outputs a preset current Iref according to the bus voltage. The soft start circuit performs soft start processing on the preset current Iref and outputs a first reference current Iref to control the charging current soft start of the input capacitor C1. The control circuit also includes a reset circuit, the input end of the reset circuit is coupled to the second end of the input capacitor C1 to obtain a terminal voltage signal, the output end of the reset circuit is coupled to the soft start circuit, and the reset circuit is used to reset the soft start circuit based on the terminal voltage signal.

[0053] In one embodiment of the present invention, Figure 2As shown, the control circuit 10 includes a power supply circuit 100, a soft start circuit 200, a first regulating circuit 300, a compensation circuit 500 and a first transistor Q1. The drain of the first transistor Q1 is coupled to the second end of the input capacitor C1, and the first end of the input capacitor C1 is coupled to the rectifier circuit. The input end of the power supply circuit 100 is coupled to the second end of the input capacitor C1, and the output end of the power supply circuit 100 is coupled to the first input end of an adder. The power supply circuit 100 is used to output a preset current Iref according to the detection signal Vdrain. In one embodiment of the present invention, the preset current Iref is a square wave signal or a signal with a waveform similar to a square wave, so that the input current size that meets the requirements is achieved in the set conduction angle interval. The input end of the compensation circuit 500 is coupled to the second end of the input capacitor C1, and the output end of the compensation circuit 500 is coupled to the second input end of an adder. The compensation circuit 500 is used to generate a compensation signal to compensate for the preset current Iref output by the power supply circuit 100. The adder generates a compensation correction current Iref0 according to the preset current Iref and the compensation signal. In one embodiment of the present invention, the compensation correction current Iref0 is a saddle-shaped current waveform, and the power consumption of the LED driving circuit can be effectively reduced by the compensation circuit 500. The input end of the soft start circuit 200 is coupled to the output end of the adder, and the soft start circuit 200 is used to receive the compensation correction current Iref0, and output the first reference current Iref1 after performing soft start processing on the compensation correction current Iref0. The input end of the first adjustment circuit 300 is coupled to the output end of the soft start circuit 200, and the output end of the first adjustment circuit 300 is coupled to the first transistor Q1. The first adjustment circuit 300 is used to control the conduction state of the first transistor Q1 based on the first reference current Iref1.

[0054] In another embodiment of the present invention, Figure 2As shown, the control circuit 10 also includes a second transistor Q2 and a second regulating circuit 400, the second transistor Q2 is coupled to the LED load in the LED driving circuit, the output end of the second regulating circuit 400 is coupled to the control end of the second transistor Q2, and the second regulating circuit 400 is used to control the conduction state of the second transistor Q2 based on the second reference current Iref2. The first regulating circuit 300 and the second regulating circuit 400 can simultaneously have a comparison function and an error amplification function or a difference amplification function. In one embodiment of the present invention, the first regulating circuit 300 and the second regulating circuit 400 are operational amplifiers. The positive input end of the first regulating circuit 300 is coupled to the output end of the soft start circuit 200, the negative input end of the first regulating circuit 300 is coupled to the first end of the first sampling resistor Rcs1, and the second end of the first sampling resistor Rcs1 is coupled to the reference ground. The first regulating circuit 300 controls the conduction state of the first transistor Q1 according to the first reference current Iref1 and the first sampling current. The non-inverting input terminal of the second regulating circuit 400 receives the second reference current Iref2, the inverting input terminal of the second regulating circuit 400 is coupled to the first end of the second sampling resistor Rcs2, and the second end of the second sampling resistor Rcs2 is coupled to the reference ground. The second regulating circuit 400 controls the conduction state of the second transistor Q2 according to the second reference current Iref2 and the second sampling current.

[0055] like Figure 3 The figure shows a schematic diagram of some signal waveforms of the LED driving circuit of an embodiment of the present invention. The input voltage is rectified by the rectifier circuit to obtain the voltage Vac, and the waveform of the voltage Vac is a steamed bun wave. The voltage Vc is the voltage across the input capacitor C1, and the voltage Vdrain is the terminal voltage at the second end of the input capacitor or the drain voltage of the first transistor. When the voltage Vac is less than the voltage Vc, the voltage Vdrain is zero. When the voltage Vac is greater than the voltage Vc, the waveform of the voltage Vdrain is similar to a steamed bun wave. When the voltage Vac is greater than the voltage Vc, the power supply circuit outputs a preset signal, and the preset signal is a square wave signal. The current Iref0 is a soft start receiving signal obtained after the preset signal is compensated. The current Iref0 is a saddle-shaped waveform, which can effectively reduce the power consumption of the LED driving circuit. The soft start circuit receives the current Iref0 and performs soft start processing on the current Iref0 to obtain the first reference current Iref1, which is obtained by Figure 3 It can be seen that the rising edge of the first reference current slows down, and the rising edge of the input current of the LED driving circuit slows down by soft-starting the charging current of the input capacitor C1.

[0056] In one embodiment of the present invention, Figure 4As shown, the input end of the power supply circuit 100 in the control circuit 10 is coupled to the bus voltage end, and the control circuit 10 further includes a reset circuit 600, the input end of the reset circuit 600 is coupled to the second end of the input capacitor C1 to obtain the terminal voltage signal Vdrain, the output end of the reset circuit 600 is coupled to the soft start circuit 200, and the reset circuit 600 is used to reset the soft start circuit based on the terminal voltage signal. In a specific embodiment, when the terminal voltage signal Vdrain is zero, the reset circuit sends a reset signal to cause the soft start circuit 200 to reset. Therefore, when the voltage Vac is less than the voltage Vc, the first reference current Iref1 output by the soft start circuit 200 will be reset, that is, when the voltage Vac is less than the voltage Vc, the first reference current Iref1 is zero.

[0057] In one embodiment of the present invention, Figure 5 As shown, the soft start circuit includes a current source 210, a second capacitor C2 and a second resistor R2. The power supply end of the current source 210 is coupled to the output end of the power supply circuit. The first end of the second capacitor C2 is coupled to the output end of the current source 210, the first end of the second capacitor C2 is the output end of the soft start circuit, and the second end of the second capacitor C2 is coupled to the reference ground end. The first end of the second resistor R2 is coupled to the first end of the second capacitor C2, and the second end of the second resistor R2 is coupled to the second end of the second capacitor C2. In another embodiment of the present invention, the current source 210 is a voltage-controlled current source.

[0058] In one embodiment of the present invention, Figure 6 As shown, the soft start circuit includes a third resistor R3 and a third capacitor C3. The first end of the third resistor R3 is coupled to the output end of the power supply circuit. The first end of the third capacitor C3 is coupled to the second end of the third resistor R3, the first end of the third capacitor C3 is the output end of the soft start circuit, and the second end of the third capacitor C3 is coupled to the reference ground end.

[0059] An embodiment of the present invention discloses an LED driving circuit, which includes a rectifier circuit, an input capacitor, an LED load, and the control circuit as described above.

[0060] like Figure 7 As shown, an embodiment of the present invention further discloses a control method for an LED driving circuit, wherein the LED driving circuit includes a control circuit, the control circuit is coupled to an input capacitor in the LED driving circuit to control an input current of the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit. The control method includes:

[0061] S100, receiving a detection signal representing a bus voltage, and outputting a preset signal according to the detection signal;

[0062] S200, performing soft-start processing on a soft-start receiving signal representing a preset signal and then outputting a first reference signal to control the soft-start of a charging current of an input capacitor; and

[0063] S300 , controlling a conduction state of the first transistor based on a first reference signal.

[0064] In one embodiment of the present invention, the power supply circuit receives a detection signal representing the bus voltage, and the power supply circuit outputs a preset signal according to the detection signal. In another embodiment of the present invention, the detection signal may be the bus voltage or the terminal voltage collected at the second end of the input capacitor. The preset signal may be a preset voltage or a preset current.

[0065] In one embodiment of the present invention, the preset signal is a current signal with a square wave waveform. The soft start circuit performs soft start processing on the soft start receiving signal representing the preset signal and outputs a first reference signal. In one embodiment of the present invention, the soft start receiving signal can be a preset signal, or a signal obtained by compensating based on the preset signal. In another embodiment of the present invention, the waveform of the soft start receiving signal is saddle-shaped. Soft starting the soft start receiving signal by the soft start circuit can promote the soft start of the charging current of the input capacitor, thereby controlling the input current rising edge of the LED drive circuit to slow down. The first regulating circuit controls the conduction state of the first transistor based on the first reference signal and the first sampling signal to achieve the slow rising edge of the input current of the LED drive circuit.

[0066] In one embodiment of the invention, the grid voltage is converted into a voltage Vac after passing through a rectifier circuit, and the waveform of the voltage Vac is a steamed bun wave. In one embodiment of the invention, the detection signal received by the power supply circuit to represent the bus voltage is the terminal voltage collected at the second end of the input capacitor. When the voltage Vac is less than the voltage Vc across the input capacitor, the terminal voltage is zero, and correspondingly, the preset signal output by the power supply circuit according to the detection signal is zero. When the voltage Vac is greater than the voltage Vc across the input capacitor, the waveform of the terminal voltage is similar to a steamed bun wave, and correspondingly, the preset signal output by the power supply circuit according to the detection signal is a circuit signal with a square wave waveform. In another embodiment of the invention, the detection signal received by the power supply circuit to represent the bus voltage is the bus voltage. When the voltage Vac is less than the voltage Vc across the input capacitor, the soft start circuit needs to be reset by a reset circuit, so as to control the first reference signal output by the soft start circuit to be zero when the voltage Vac is less than the voltage Vc, thereby avoiding mis-conduction of the first transistor.

[0067] The present invention proposes a control circuit, a control method and an LED driving circuit of an LED driving circuit, wherein the control circuit includes a power supply circuit, a soft start circuit and a first regulating circuit. The control circuit is coupled to an input capacitor in the LED driving circuit to control the input current of the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit. A detection signal representing a bus voltage is received, and a preset signal is output according to the detection signal. A first reference signal is output after soft start processing of a soft start receiving signal representing the preset signal, thereby controlling the soft start of the charging current of the input capacitor, and the conduction state of the first transistor is controlled based on the first reference signal to slow down the rising edge of the input current of the LED driving circuit. While meeting the requirements of the new European standard for LED lighting on the input current waveform, the EMI problem of the LED driving circuit can be effectively solved.

[0068] The above description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above embodiments. The relevant descriptions of the effects or advantages involved in the embodiments may not be reflected in the experimental examples due to the uncertainty of the specific condition parameters, and are not used to limit the embodiments. The deformation and changes of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent components are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the present invention can be implemented 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 drive circuit, characterized in that: The control circuit is coupled to an input capacitor in the LED driving circuit to control an input current of the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit; The first end of the input capacitor is coupled to the bus voltage end; the control circuit comprises: A power supply circuit, whose input end is coupled to the second end of the input capacitor, is used to receive a detection signal representing the bus voltage and output a preset signal according to the detection signal; a soft start circuit, whose input end is coupled to the power supply circuit, for performing soft start processing on a soft start receiving signal representing the preset signal and then outputting a first reference signal to control the soft start of the charging current of the input capacitor; and The first regulating circuit has an input terminal coupled to the soft start circuit and an output terminal coupled to the first transistor, and is used for controlling the conduction state of the first transistor based on the first reference signal.

2. The control circuit according to claim 1, characterized in that: The input end of the power supply circuit is coupled to the bus voltage end, and the control circuit further includes: The reset circuit has an input terminal coupled to the second terminal of the input capacitor to obtain a terminal voltage signal, and an output terminal coupled to the soft start circuit for resetting the soft start circuit based on the terminal voltage signal.

3. The control circuit according to claim 1, characterized in that: The control circuit further comprises: a compensation circuit, whose input terminal is coupled to the second terminal of the input capacitor and whose output terminal outputs a compensation signal; and The adder has a first input terminal coupled to the output terminal of the power supply circuit, a second input terminal coupled to the output terminal of the compensation circuit, and an output terminal coupled to the input terminal of the soft start circuit.

4. The control circuit according to claim 1, characterized in that: The soft start circuit comprises: a current source, a power supply terminal of which is coupled to the output terminal of the power supply circuit; a second capacitor, a first end of which is coupled to the output end of the current source, the first end of which is the output end of the soft start circuit, and a second end of which is coupled to the reference ground end; and A second resistor has a first end coupled to the first end of the second capacitor, and a second end coupled to the second end of the second capacitor.

5. The control circuit according to claim 1, characterized in that: The soft start circuit comprises: A third resistor, a first end of which is coupled to the output end of the power supply circuit; and The third capacitor has a first end coupled to the second end of the third resistor, a first end being the output end of the soft start circuit, and a second end coupled to the reference ground.

6. The control circuit according to claim 1, characterized in that: The first regulating circuit is coupled to the first sampling resistor to obtain a first sampling signal. The first regulating circuit controls a conduction state of the first transistor based on the first reference signal and the first sampling signal.

7. The control circuit according to claim 1, characterized in that: The control circuit further includes a first transistor, and the first regulating circuit is coupled to a control terminal of the first transistor.

8. The control circuit according to claim 1, characterized in that: The control circuit further comprises: A second transistor coupled to an LED load in the LED driving circuit; and The second regulating circuit has an output terminal coupled to the control terminal of the second transistor and is used to control the conduction state of the second transistor based on a second reference signal.

9. An LED driving circuit, characterized in that: The LED driving circuit comprises a rectifier circuit, an input capacitor, an LED load and a control circuit as claimed in any one of claims 1 to 8.

10. A control method for an LED driving circuit, characterized in that: The LED driving circuit comprises a control circuit, wherein the control circuit is coupled to an input capacitor in the LED driving circuit to control an input current of the LED driving circuit, and the input capacitor is coupled to a first transistor in the LED driving circuit; The control method comprises: receiving a detection signal representing a bus voltage, and outputting a preset signal according to the detection signal; After performing soft-start processing on a soft-start receiving signal representing the preset signal, a first reference signal is outputted to control the soft-start of the charging current of the input capacitor; and A conduction state of the first transistor is controlled based on the first reference signal.

11. The control method according to claim 10, characterized in that: The detection signal is a bus voltage or a terminal voltage collected at the second end of the input capacitor.

12. The control method according to claim 10, characterized in that: The soft start receiving signal is the preset signal or is obtained by compensating based on the preset signal.

13. The control method according to claim 12, characterized in that: The waveform of the soft start receiving signal is saddle-shaped.

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