CN111970793A

CN111970793A - LED drive circuit, control method thereof and LED drive device

Info

Publication number: CN111970793A
Application number: CN202010737875.5A
Authority: CN
Inventors: 叶美盼; 林星宇
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2020-07-28
Filing date: 2020-07-28
Publication date: 2020-11-20
Anticipated expiration: 2040-07-28
Also published as: CN111970793B

Abstract

Disclosed is an LED drive circuit including: the leakage protection circuit detects whether a leakage phenomenon exists or not and generates a leakage control signal; and the dimming circuit is connected with the electric leakage protection circuit and receives the electric leakage control signal, and when the electric leakage phenomenon does not exist, the dimming circuit performs dimming according to the electric leakage control signal, and when the electric leakage phenomenon exists, the dimming circuit stops dimming according to the electric leakage control signal. According to the LED driving circuit provided by the embodiment of the invention, when the leakage detection is carried out and the leakage phenomenon exists, the leakage protection circuit controls the bypass module to be switched on intermittently for leakage detection and protection, and when the leakage phenomenon does not exist, the dimming module controls the bypass module to be switched on or switched off for dimming data and power transmission, so that dimming is realized.

Description

LED drive circuit, control method thereof and LED drive device

Technical Field

The present application relates to the field of power electronics, and in particular, to an LED driving circuit, a control method thereof, and an LED driving apparatus.

Background

The LED lamp is more and more applied in the field of illumination, such as being applied to classrooms, shopping malls, office buildings and the like, wherein the LED lamp comprises a fluorescent lamp, and two ends of the fluorescent lamp are respectively connected with commercial power through a zero line and a live wire. When the leakage protection circuit is installed, one end is usually installed firstly, then the other end is installed, if an operator carelessly touches hands or other parts of a body to the electrode at the other end when the one end is installed, a human body and the power grid form a loop to cause electric shock, and the leakage protection circuit is added to solve the problem at present.

A conventional LED driving circuit 100 with leakage protection function includes a leakage protection circuit 101 and a power conversion circuit 102, as shown in fig. 1. The LED driving circuit 100 obtains an ac input voltage from an external power source 110, obtains a dc bus voltage VH after being rectified by a rectifier bridge 120, and converts the dc bus voltage VH to generate a dc output voltage, thereby driving an external load 130, such as an LED lamp. When the leakage protection circuit 101 detects that an electric shock condition is input, it controls the LED driving circuit 100 to be in a turn-off state; when the earth leakage protection circuit 101 detects that there is no electric shock in the input, the LED driving circuit 100 operates normally to turn on the LED lamp.

However, as the requirement for energy saving is higher and higher, the LED driving circuit of the fluorescent lamp with the leakage protection function also needs to be dimmed to adapt to different environments and requirements. Because the LED driving circuit of the fluorescent lamp with the leakage protection function only has two ends for input, namely the input ends of the zero line and the live line, and no other ports are used for dimming.

In addition, although the existing dimming technology can solve the dimming input at two ends of the fluorescent lamp, the existing dimming technology does not have the leakage protection function.

A conventional LED driving circuit 200 with a dimming function includes an LED dimming circuit and a power conversion circuit 202. As shown in fig. 2, the LED dimming circuit includes a bypass circuit 203, a zero-crossing detection circuit 204, a data sampling circuit 205, and an MCU module 206. The rectifier bridge 120 rectifies an output signal of the dimmer 140 to generate a dc bus voltage VH, and the zero-crossing detection circuit 204 performs zero-crossing detection on the dc bus voltage VH to generate a zero-crossing detection signal; the data sampling circuit 205 samples the bus dc voltage VH to generate a data sampling signal, the MCU module 206 generates a bypass control signal according to the zero-cross detection signal and the data sampling signal, the bypass control signal is used to control the on/off of the bypass circuit 203, when the bypass switch is on, the external power source 110, the dimmer 140 and the bypass circuit 203 form a conductive loop, and when the bypass switch is off, the conductive loop is turned off. The MCU module 206 further analyzes the dimming data transmitted by the dimmer according to the data sampling signal, so as to generate different PWM signals to adjust the output current of the LED.

Therefore, it is desired to further improve the LED driving circuit of the fluorescent lamp while solving the leakage problem and the dimming problem.

Disclosure of Invention

In view of the above, an object of the present invention is to provide an LED driving circuit, a control method thereof, and an LED driving apparatus, which can realize both leakage protection and dimming.

According to an aspect of the present invention, there is provided an LED driving circuit including: the leakage protection circuit detects whether a leakage phenomenon exists and generates a leakage control signal; and the dimming circuit is connected with the electric leakage protection circuit and receives the electric leakage control signal, and when the electric leakage phenomenon does not exist, the dimming circuit performs dimming according to the electric leakage control signal, and when the electric leakage phenomenon exists, the dimming circuit stops dimming according to the electric leakage control signal.

Preferably, the leakage protection circuit generates a leakage detection signal, and determines whether a leakage phenomenon exists according to a dc bus voltage with the dimming data.

Preferably, the dimming circuit generates a leakage current according to the leakage detection signal when performing the leakage detection and the leakage phenomenon exists, and analyzes the dimming data from the dc bus voltage when the leakage phenomenon does not exist, and generates the pulse width modulation signal according to the dimming data.

Preferably, the dimming circuit includes: the bypass module is connected with the electric leakage protection circuit and receives an electric leakage detection signal; the dimming module is connected with the bypass module and generates a pulse width modulation signal and a bypass control signal according to the voltage of the direct-current bus; the bypass module generates a leakage current according to the leakage detection signal when the leakage detection is performed and the leakage phenomenon exists, and generates a bypass current according to the bypass control signal when the leakage phenomenon does not exist.

Preferably, the leakage protection circuit multiplexes the bypass module to perform leakage detection, and when the leakage detection is performed and a leakage phenomenon exists, the leakage detection signal controls the bypass module to be intermittently conducted; and when the electric leakage phenomenon does not exist, the bypass control signal controls the bypass module to be switched on or switched off.

Preferably, the dimming module is further connected to the leakage protection circuit, receives the leakage control signal, and performs dimming when there is no leakage and stops dimming when there is leakage according to the leakage control signal.

Preferably, the bypass module comprises a second transistor, a first diode, a second resistor and a third resistor, wherein the second transistor and the third resistor are connected in series between a first output end and a second output end of the direct current bus voltage; the grid electrode of the second transistor is connected with the second output end of the direct current bus voltage through a second resistor; the anode of the first diode is connected with the leakage protection circuit, and the cathode of the first diode is connected with the grid of the second transistor; the anode of the second diode is connected with the dimming module, and the cathode of the second diode is connected with the grid of the second transistor; a first node between the second transistor and the third resistor outputs a sampling signal of the leakage current or a sampling signal of the bypass current.

Preferably, when the leakage phenomenon exists, the leakage detection signal controls the second transistor to be switched on intermittently, and the power supply source, the second transistor and the third resistor form a leakage current loop.

Preferably, when the leakage phenomenon does not exist, the bypass control signal controls the second transistor to be turned on and off, and the power supply, the second transistor and the third resistor form a bypass loop.

Preferably, the dimming circuit further comprises: the high-voltage starting module is connected with the leakage protection circuit and the bypass module and generates power supply voltage according to the voltage of the direct-current bus; and when the electric leakage phenomenon does not exist, the high-voltage starting module supplies power to the dimming module according to the electric leakage control signal.

Preferably, the high-voltage starting module comprises a first transistor, a voltage regulator tube, a first resistor, a third diode, a fourth diode, a first capacitor and a first switch, wherein the first resistor and the voltage regulator tube are connected in series between a first output end and a second output end of the direct-current bus voltage; the grid electrode of the first transistor is connected with a second node between the first resistor and the voltage regulator tube; the anode of the third diode is connected with the second output end of the direct current bus voltage through the first capacitor, and the cathode of the third diode is connected with the grid of the first transistor; the anode of the fourth diode is connected with a node between the first transistor and the second transistor, and the cathode of the fourth diode is connected with the anode of the third diode; a third node between the third diode and the fourth diode outputs a power supply voltage, and the third node is connected with the dimming module through a first switch; and the control end of the first switch receives the electric leakage control signal and is switched on and off according to the electric leakage control signal.

Preferably, when the leakage detection is performed and the leakage phenomenon exists, the leakage detection signal controls the second transistor to be turned on intermittently, and the power supply forms a leakage current loop with the first transistor, the second transistor and the third resistor.

Preferably, when the leakage phenomenon does not exist, the bypass control signal controls the second transistor to be turned on and off, and the power supply forms a bypass loop with the first transistor, the second transistor and the third resistor.

Preferably, the power supply forms a power supply loop with the first transistor, the fourth diode and the first capacitor.

Preferably, the dimming module includes: the voltage detection unit is used for generating a bypass control signal according to the voltage of the direct-current bus, and the bypass control signal controls the on and off of the bypass module; the data acquisition unit is used for generating a data signal according to the DC bus voltage; and the control unit is connected with the data acquisition unit and used for generating a pulse width modulation signal according to the data signal.

Preferably, the voltage detection module includes a first comparator, a second comparator, a third operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a second switch, and a third switch; the fifth resistor and the sixth resistor are connected in series between a first output end and a second output end of the direct-current bus voltage; a first input end of the first comparator is connected with a node between the fifth resistor and the sixth resistor, a second input end of the first comparator receives the first reference voltage, and an output end of the first comparator outputs a second control signal; a first input end of the second comparator is connected with a node between the fifth resistor and the sixth resistor, a second input end of the second comparator receives a second reference voltage, and an output end of the second comparator outputs a third control signal; a first input end of the third operational amplifier receives a bypass current sampling signal output by the bypass module, a second input end of the third operational amplifier receives a third reference voltage through a seventh resistor and a second switch, the second input end of the third operational amplifier is connected with a second output end of the direct-current bus voltage through a fourth resistor, the fourth reference voltage is received through a third switch, and the output end of the third operational amplifier outputs a bypass control signal; the second control signal controls the second switch to be switched on and switched off, and the third control signal controls the third switch to be switched on and switched off.

Preferably, the leakage protection circuit includes: the voltage sampling module is used for acquiring direct-current bus voltage and sampling the direct-current bus voltage to obtain sampling voltage; the leakage current control module is connected with the voltage sampling module and used for generating a sampling control signal and a leakage detection signal according to the sampling voltage and the reference voltage; and the electric leakage judging module is connected with the voltage sampling module and the electric leakage current control module and used for acquiring a first sampling voltage at a first sampling moment and a second sampling voltage at a second sampling moment according to the sampling control signal, judging whether an electric leakage phenomenon exists or not and generating an electric leakage control signal according to the first sampling voltage and the second sampling voltage, wherein the first sampling moment is earlier than the second sampling moment.

Preferably, the leakage current control module generates a leakage detection signal when or after the dc bus voltage is greater than a reference voltage.

Preferably, the leakage current linearly increases to a predetermined current value or linearly decreases after increasing for a predetermined time.

Preferably, the leakage current curve rises to a preset current value or the curve falls after the curve rises and is maintained for a preset time.

Preferably, the first sampling time is before the generation of the leakage current or when the generation of the leakage current starts, and the second sampling time is before the linear decrease of the leakage current.

Preferably, the first sampling time and the second sampling time are during a linear rise of the leakage current.

Preferably, when the second sampling voltage is less than or equal to the first sampling voltage, a leakage phenomenon exists; when the second sampling voltage is greater than the first sampling voltage, no leakage phenomenon exists.

Preferably, when the second sampling voltage is less than or equal to the sum of the first sampling voltage and a preset bias voltage, a leakage phenomenon exists; when the second sampling voltage is larger than the sum of the first sampling voltage and a preset bias voltage, no electric leakage phenomenon exists.

Preferably, when the power supply is just powered on, the leakage protection circuit detects whether a leakage phenomenon exists, and when the leakage phenomenon does not exist, the dimming circuit works normally; when the leakage phenomenon exists, the dimming circuit does not work, and the leakage detection is repeated until the leakage phenomenon does not exist.

According to a second aspect of the present invention, there is provided a control method of an LED driving circuit, comprising: detecting whether the electric leakage phenomenon exists or not and generating an electric leakage control signal; and when the electric leakage phenomenon does not exist, dimming is started according to the electric leakage control signal, and when the electric leakage phenomenon exists, dimming is stopped according to the electric leakage control signal.

Preferably, the control method further includes: and generating a leakage detection signal, and judging whether a leakage phenomenon exists according to the voltage of the direct current bus with the dimming data.

Preferably, the control method further includes: generating leakage current according to the leakage detection signal when leakage detection is carried out or leakage phenomenon exists, analyzing dimming data from the direct current bus voltage when the leakage phenomenon does not exist, and generating a pulse width modulation signal according to the dimming data to carry out dimming.

Preferably, the control method further includes: when the leakage phenomenon does not exist, generating a bypass control signal according to the voltage of the direct-current bus; and generating a bypass current according to the bypass control signal; the current path of the leakage current is the same as the current path of the bypass current.

Preferably, the control method further includes: generating a supply voltage according to the DC bus voltage; and controlling power supply according to the leakage control signal so as to control whether dimming is performed or not, performing power supply according to the leakage control signal so as to start dimming when the leakage phenomenon does not exist, and stopping power supply according to the leakage control signal so as to stop dimming when leakage detection is performed and the leakage phenomenon exists.

Preferably, the step of dimming comprises: generating a data signal according to the DC bus voltage; and generating a pulse width modulation signal according to the data signal.

Preferably, the step of detecting whether there is a leakage phenomenon includes: acquiring direct current bus voltage, and sampling the direct current bus voltage to obtain sampling voltage; generating a sampling control signal and a leakage detection signal according to the sampling voltage and the reference voltage; and acquiring a first sampling voltage at a first sampling moment and a second sampling voltage at a second sampling moment according to the sampling control signal, and judging whether a leakage phenomenon exists and generating a leakage control signal according to the first sampling voltage and the second sampling voltage, wherein the first sampling moment is earlier than the second sampling moment.

Preferably, the leakage detection signal is generated when or after the dc bus voltage is greater than a reference voltage.

Preferably, when the power supply is started, whether the electric leakage phenomenon exists is detected, and when the electric leakage phenomenon does not exist, dimming is carried out; when the electric leakage phenomenon exists, dimming is stopped, and electric leakage detection is repeated until the electric leakage phenomenon does not exist.

According to a third aspect of the present invention, there is provided an LED driving device comprising: a dimmer having a first input terminal connected to the ac input first terminal and generating an ac input voltage with dimming data based on a dimming operation; the first input end of the rectifier bridge is connected with the first output end of the dimmer, the second input end of the rectifier bridge is connected with the alternating current input second end, and the rectifier bridge is used for rectifying the alternating current input voltage with dimming data to output a direct current bus voltage with dimming data; the LED driving circuit and the power conversion circuit are connected with the dimming circuit and used for converting the direct current bus voltage into direct current output voltage according to the pulse width modulation signal output by the LED driving circuit and supplying power to a load.

Preferably, the power conversion circuit comprises a diode and a power conversion module, wherein the anode of the diode is connected with the first output end of the direct current bus voltage, and the cathode of the diode is connected with the power conversion module; the power conversion module is used for converting the direct current bus voltage into direct current output voltage according to the pulse width modulation signal and supplying power to a load.

Preferably, the dimmer further comprises a second input end, the second input end of the dimmer is connected to the second end of the alternating current input, and the second output end of the dimmer is connected to the second input end of the rectifier bridge.

According to the LED driving circuit provided by the embodiment of the invention, when the leakage phenomenon exists, the bypass module is intermittently conducted to perform leakage protection, and when the leakage phenomenon does not exist, the bypass module is conducted and disconnected to perform transmission of dimming data and power so as to realize dimming.

Furthermore, the leakage protection circuit performs leakage detection by detecting leakage current generated by the bypass module, and the leakage protection circuit multiplexes the bypass module in a time-sharing manner to realize leakage protection.

The LED driving circuit provided by the embodiment of the invention can realize leakage detection, high-voltage starting and power supply and bypass control by controlling the transistor in the bypass module through time-sharing multiplexing, thereby realizing LED dimming, and having simple circuit and reduced cost.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

Fig. 1 shows a schematic circuit diagram of a prior art LED driving apparatus with a leakage protection circuit.

Fig. 2 shows a schematic circuit diagram of a prior art LED driving apparatus with a dimming function.

Fig. 3 shows a schematic circuit diagram of an LED driving apparatus provided in a first embodiment of the present invention.

FIG. 4 shows a schematic circuit diagram of the bypass module of FIG. 3;

FIG. 5 is a schematic circuit diagram of an LED driving apparatus according to a second embodiment of the present invention

Fig. 6 shows a schematic circuit diagram of the dimming circuit of fig. 5;

fig. 7 shows a schematic circuit diagram of the leakage protection circuit and a schematic structure diagram of the dimming circuit in fig. 5.

Fig. 8 is a signal waveform diagram of the LED driving circuit provided by the embodiment of the invention when no leakage phenomenon exists.

FIG. 9 is a signal waveform diagram illustrating the leakage phenomenon of the LED driving circuit for leakage protection connected in parallel across the normal LED driving circuit;

fig. 10 is a signal waveform diagram illustrating a leakage phenomenon when the LED driving circuit and the dimmer are connected in series according to an embodiment of the present invention.

Fig. 11 shows a schematic circuit diagram of an LED driving device of a third embodiment of the present invention.

Fig. 12 shows a schematic circuit diagram of an LED driving device of a fourth embodiment of the present invention.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

Fig. 3 shows a schematic circuit diagram of an LED driving device of a first embodiment of the present invention. The LED driving apparatus includes a dimmer 140, a rectifier bridge 120, an LED driving circuit 300, and a power conversion circuit 150. The dimmer 140 obtains an ac input voltage from the external ac power supply 110 (i.e., a power supply source), and outputs the ac input voltage with dimming data based on a dimming operation. The rectifier bridge 120 rectifies the ac input voltage with the dimming data to output a dc bus voltage VH with the dimming data. The LED driving circuit 300 performs dimming according to the dc bus voltage VH with dimming data, and the power conversion circuit 150 steps down the dc bus voltage VH to obtain a dc output voltage, thereby driving the external load 130, such as an LED lamp.

In the present embodiment, the dimmer 140 includes a first input terminal and a first output terminal, wherein the first input terminal is connected to a first terminal or a power supply terminal (i.e., a first terminal of the external ac power source 110) of the ac input, and generates an ac input voltage with dimming data based on the dimming operation. The rectifier bridge 120 is, for example, a full-wave rectifier circuit, and rectifies an ac input voltage into a dc bus voltage VH. The rectifier bridge 120 has a first input terminal connected to the first output terminal of the dimmer 140, and a second input terminal connected to the second terminal of the ac input (i.e., the second terminal of the external ac power source 110). The first output terminal of the rectifier bridge 120 is a high potential terminal, and the second output terminal is a low potential terminal. The second output is for example connected to ground.

As shown in fig. 3, the LED driving circuit 300 includes a leakage protection circuit 301 and a dimming circuit 302. The leakage protection circuit 301 detects whether a leakage phenomenon exists and generates a leakage control signal; the dimming circuit 302 is connected to the leakage protection circuit 301, receives the leakage control signal, and when there is no leakage, the leakage control signal controls the dimming circuit 302 to start dimming, and when there is leakage, the leakage control signal controls the dimming circuit 302 to stop dimming.

Specifically, the leakage protection circuit 301 is connected between the first output terminal and the second output terminal of the rectifier bridge 120. The leakage protection circuit 301 generates a leakage detection signal according to the dc bus voltage VH with the dimming data and determines whether there is a leakage phenomenon according to the dc bus voltage VH. The power conversion circuit 150 is configured to step down a dc bus voltage VH to obtain a dc output voltage. A first input terminal of the power conversion circuit 150 is connected to a first output terminal of the rectifier bridge 120, a second input terminal of the power conversion circuit 150 is connected to a second output terminal of the rectifier bridge 120, and the power conversion circuit 150 is configured to supply power to an external load 130 (e.g., an LED lamp). The power conversion circuit 150 may be implemented by a switching power supply or a linear constant current control circuit. For example, the power conversion circuit 150 may be implemented by using a switching power supply with various topologies, such as a Buck (Buck) topology, a Buck-BOOST (Buck-BOOST) topology, and a FLYBACK (FLYBACK) topology.

The dimming circuit 302 is connected between the first output terminal and the second output terminal of the rectifier bridge 120, and is connected to the leakage protection circuit 301, and generates a leakage current according to a leakage detection signal when leakage detection is performed or a leakage phenomenon exists, and parses dimming data from the dc bus voltage VH when no leakage phenomenon exists, and generates a pulse width modulation signal PWM according to the dimming data, and generates a bypass control signal according to the dc bus voltage VH. In this embodiment, the leakage current linearly increases to a predetermined current value or linearly decreases after the leakage current increases for a predetermined time.

In a preferred embodiment, the leakage current curve rises to a preset current value or falls after the curve rises for a preset time.

In this embodiment, the dimming circuit 302 includes a bypass module 303 and a dimming module 304. The bypass module 303 is connected to the leakage protection circuit 301, and configured to generate a leakage current according to the leakage detection signal when leakage detection is performed and a leakage phenomenon exists; the dimming module 304 is connected to the bypass module, and generates a pulse width modulation signal PWM and a bypass control signal according to the dc bus voltage VH, and the bypass module 303 is further configured to generate a bypass current according to the bypass control signal when there is no leakage.

In this embodiment, the dimming module 304 parses the dimming data signal from the dc bus voltage VH and generates a pulse width modulation signal PWM according to the dimming data signal, and the third input terminal of the power conversion circuit 150 receives the pulse width modulation signal PWM and supplies power to the external load 130 according to the pulse width modulation signal PWM.

The leakage protection circuit 301 multiplexes the bypass module 303 to perform leakage detection, when leakage detection is performed and a leakage phenomenon exists, a leakage detection signal output by the leakage protection circuit 301 controls the bypass module 303 to be intermittently conducted, and the dimming module 304 stops dimming according to the leakage detection signal; when the leakage phenomenon does not exist, the dimming module 304 starts dimming according to the leakage control signal, and the bypass control signal output by the dimming module 304 controls the bypass module 303 to be turned on or off to transmit dimming data or power.

Specifically, the leakage protection circuit 301 determines whether there is a leakage phenomenon according to the dc bus voltage VH, and when there is a leakage phenomenon, repeats leakage detection until it is determined that there is no leakage phenomenon; when the leakage phenomenon does not exist, the dimming module 303 provides the pulse width modulation signal PWM for the power conversion circuit 150, where the pulse width modulation signal PWM is used to control the on/off of a main switching tube in the power conversion circuit 150, and the duty ratio of the pulse width modulation signal PWM is changed to control the magnitude of the output current, so as to adjust the brightness of the LED lamp 130.

The power conversion circuit 150 includes a diode D0 and a power conversion module 151, wherein an anode of the diode D0 is connected to the first output terminal of the dc bus voltage VH (i.e., the first output terminal of the rectifier bridge 120), and a cathode thereof is connected to the power conversion module 151, so as to prevent the sine wave voltage from being capacitively filtered, mainly for dc blocking. In this embodiment, the leakage protection circuit 301 and the dimming circuit 302 are connected between the rectifier bridge 120 and the power conversion circuit 150 in sequence.

Fig. 4 shows a circuit schematic of the bypass module of fig. 3. As shown in fig. 4, referring to fig. 4, the bypass module 303 includes a second transistor Q2, a first diode D1, a second diode D2, a second resistor R2, and a third resistor R3. The second transistor Q2 and the third resistor R3 are connected in series between the first output terminal and the second output terminal of the dc bus voltage VH. The gate of the second transistor Q2 is connected to the second output terminal of the dc bus voltage VH via a second resistor R2. The first diode D1 has an anode connected to the leakage protection circuit 301 and a cathode connected to the gate of the second transistor Q2. The anode of the second diode D2 is connected to the dimming module 304, and the cathode is connected to the gate of the second transistor Q2. The second output end of the dc bus voltage VH is grounded GND. The second transistor Q2 is turned on or off according to the leakage detection signal or the bypass control signal. When leakage detection is carried out (for example, when the circuit is just powered on) and a leakage phenomenon exists, the leakage detection signal controls the second transistor Q2 to be switched on intermittently, and the power supply, the second transistor Q2 and the third resistor R3 form a leakage current loop; when the leakage phenomenon does not exist, the bypass control signal controls the second transistor Q2 to be conducted, and the power supply, the second transistor Q2 and the third resistor R3 form a bypass loop.

According to the LED driving circuit provided by the embodiment of the invention, when the leakage detection is carried out and the leakage phenomenon exists, the bypass module is intermittently conducted to carry out leakage protection, and when the leakage phenomenon does not exist, the bypass module is conducted or turned off to carry out the transmission of dimming data and power so as to realize dimming.

Fig. 5 shows a schematic circuit diagram of an LED driving device of a second embodiment of the present invention. Compared with the first embodiment of the present invention, the dimming module 302 further includes a high voltage starting module 308, and the high voltage starting module 308 is connected to the leakage protection circuit 301 and the bypass module 303, and is configured to generate a power supply voltage Vcc according to the dc bus voltage VH and control whether to supply power to the dimming module 304 according to the leakage control signal.

The leakage protection circuit 301 multiplexes the bypass module 303 to perform leakage detection, when leakage detection is performed and a leakage phenomenon exists, a leakage detection signal output by the leakage protection circuit 301 controls the bypass module 303 to be intermittently switched on, a leakage control signal controls a power supply path between the high-voltage starting module 308 and the dimming module 304 to be switched off, and the dimming module 304 and the power conversion circuit 150 do not work; when it is determined that there is no leakage, the bypass control signal output by the dimming module 304 controls the bypass module 303 to be turned on or off to transmit dimming data or power, the leakage control signal controls the power supply path between the high voltage start module 308 and the dimming module 304 to be turned on, and the dimming module 304 and the power conversion circuit 150 operate normally.

The bypass module 303 and the high-voltage start module 308 are connected between a first output end and a second output end of the dc bus voltage VH (i.e., between the first output end and the second output end of the rectifier bridge 120), the bypass module 303 is connected to the leakage protection circuit 301 and the dimming module 304, receives a leakage detection signal generated by the leakage protection circuit 301 and a bypass control signal generated by the dimming module 304, and controls the bypass module 303 to be turned on or off according to the leakage detection signal or the bypass control signal.

Specifically, when leakage detection is performed (immediately after power-on) and a leakage phenomenon exists, the leakage detection signal output by the leakage protection circuit 301 controls the bypass module 303 to be intermittently turned on; when the leakage phenomenon does not exist, the bypass control signal output by the dimming module 304 controls the bypass module 303 to be turned on or off.

The high voltage starting module 308 is connected between the first output terminal and the second output terminal of the dc bus voltage VH (i.e., between the first output terminal and the second output terminal of the rectifier bridge 120), and is configured to generate a power supply voltage according to the dc bus voltage VH, and is connected to the leakage protection circuit 301, and is configured to control whether to supply power to the dimming module 304 according to a leakage control signal generated by the leakage protection circuit 301.

Fig. 6 shows a schematic circuit diagram of the dimming module of fig. 5. As shown in fig. 6, the dimming module 304 includes a voltage detection unit 305, a data acquisition unit 306, and a control unit 307. The voltage detection unit 305, the data acquisition unit 306 and the control unit 307 are all powered by a high voltage starting module 308.

The voltage detection unit 305 receives the dc bus voltage VH, and generates a bypass control signal for controlling the on/off of the bypass module 303 according to the dc bus voltage VH.

The data acquisition unit 306 acquires the dc bus voltage VH, and samples the dc bus voltage VH to obtain a data signal. The data signal is transmitted to the control unit 307 for processing, so as to implement functions of dimming, color temperature adjustment, grouping management, and the like of the lamp.

The control unit 307 is connected to the data acquisition unit 305, and receives a data signal. The control unit 307 obtains the dimming data generated by the dimmer 140 according to the data signal, so as to generate different pulse width modulation signals PWM, control the magnitude of the output current or voltage generated by the power conversion circuit 150, and implement the dimming function of the LED lamp 130.

The control unit 307 may provide multiple PWM signals to control dimming of multiple LED lamps according to the dimming requirement.

Fig. 7 shows a schematic circuit diagram of the leakage protection circuit in fig. 5 and a schematic structure diagram of the dimming circuit. As shown in fig. 7, the leakage protection circuit 301 includes a voltage sampling module 309, a leakage current control module 310, and a leakage determining module 311.

The voltage sampling module 309 is configured to sample the dc bus voltage VH to obtain a sampling voltage Vs.

In this embodiment, the voltage sampling module 309 includes a first end to a third end, where the first end and the second end of the voltage sampling module 309 are respectively connected to a first output end and a second output end of the dc bus voltage VH; the third terminal of the voltage sampling module 309 is connected to the leakage current control module 310 and the leakage judging module 311, respectively, and is configured to provide the sampling voltage Vs representing the dc bus voltage VH to the leakage current control module 310 and the leakage judging module 311.

The leakage current control module 310 is connected to the voltage sampling module 309, and configured to generate a sampling control signal and a leakage detection signal according to the sampling voltage Vs and the reference voltage, so as to control generation of leakage current. Specifically, the leakage current control module 122 is electrically connected to the third terminal of the voltage sampling module 121, and receives the sampled voltage Vs.

In this embodiment, the leakage current control module 310 generates a leakage detection signal when or after the dc bus voltage VH is greater than the reference voltage.

The bypass module 303 generates a leakage current according to the leakage detection signal. The change rate of the leakage current is controllable, and the expected value is achieved by controlling the slope of the leakage current. The bypass module 303 may generate any leakage current according to the leakage detection signal, that is, may control a slope of the leakage current. The leakage current may vary linearly or may be a gentle parabola. When the leakage current linearly changes, the leakage current linearly rises to a preset current value or linearly falls after rising and maintaining for a preset time; when the leakage current is a gentle parabola, the leakage current curve rises to a preset current value or the curve rises and maintains the curve to fall after a preset time.

The rate of change (i.e., slope) of the sampled voltage Vs in the event of leakage may be greater than, less than, or equal to the rate of change (i.e., slope) in the event of no leakage.

The leakage determining module 311 is configured to obtain a first sampling voltage Vs1 at a first sampling time and obtain a second sampling voltage Vs2 at a second sampling time according to the sampling control signal; and judging whether the leakage phenomenon exists according to the first sampling voltage Vs1 and the second sampling voltage Vs2, wherein the first sampling time is earlier than the second sampling time, and the first sampling time and the second sampling time are before the end of the leakage current Ileak.

In this embodiment, the first sampling time is before the generation of the leakage current Ileak or when the generation of the leakage current Ileak is started, and the second sampling time is before the linear decrease of the leakage current Ileak.

In a preferred embodiment, the first sampling time and the second sampling time are during the linear rising of the leakage current Ileak, and the first sampling time is earlier than the second sampling time.

Specifically, when the leakage phenomenon does not exist, the leakage human body resistance is 0 ohm, and Vs2 is more than Vs 1; when the leakage phenomenon exists, the leakage human body resistance is larger than 500 ohms, and Vs2 is smaller than or equal to Vs 1. Therefore, whether the leakage phenomenon exists can be judged by comparing the magnitudes of the first sampling voltage Vs1 and the second sampling voltage Vs2, namely when Vs2 > Vs1, the leakage phenomenon does not exist; when Vs2 is less than or equal to Vs1, a leakage phenomenon exists.

The electric leakage determining module 311 is further configured to generate an electric leakage control signal Ctrl1 according to the sampling control signal and the sampling voltage Vs; the leakage control signal Ctrl1 is used to control the power supply path between the high-voltage start module 308 and the dimming module 304 to be turned on and off. When the leakage detection is performed and the leakage phenomenon is judged to exist, the leakage control signal Ctrl1 controls the power supply path between the high-voltage starting module 308 and the dimming module 304 to be turned off; and when the leakage phenomenon does not exist, controlling the power supply path between the high-voltage starting module 308 and the dimming module 304 to be conducted.

Referring to fig. 7, the bypass module 303 includes a second transistor Q2, a first diode D1, a second diode D2, a second resistor R2, and a third resistor R3. The first transistor Q1, the second transistor Q2 and the third resistor R3 are connected in series between the first output terminal and the second output terminal of the dc bus voltage VH. A first node between the second transistor Q2 and the third resistor R3 outputs a leakage current sampling signal or a sampling signal of a bypass current, and a gate of the second transistor Q2 is connected to a second output terminal of the dc bus voltage VH through the second resistor R2. The anode of the first diode D1 is connected to the leakage current control module 310, and the cathode is connected to the gate of the second transistor Q2. The anode of the second diode D2 is connected to the voltage detection unit 305, and the cathode is connected to the gate of the second transistor Q2. The second output end of the dc bus voltage VH is grounded. The second transistor Q2 is turned on or off according to the leakage detection signal or the bypass control signal. When the circuit is just powered on and has a leakage phenomenon, the leakage detection signal controls the second transistor Q2 to be switched on intermittently, and the power supply, the first transistor Q1, the second transistor Q2 and the third resistor R3 form a leakage current loop; when the leakage phenomenon does not exist, the bypass control signal controls the second transistor Q2 to be turned on, the power supply, the first transistor Q1, the second transistor Q2 and the third resistor R3 form a bypass loop, and at this time, the bypass module 303 multiplexes the first transistor in the high-voltage starting module 308 to realize the bypass function.

The high voltage start-up module 308 includes a first transistor Q1, a voltage regulator tube Z1, a first resistor R1, a third diode D3, a fourth diode D4, a first capacitor C1, and a first switch K1. A first resistor R1 and a zener Z1 are connected in series between the first output terminal and the second output terminal of the dc bus voltage VH. The gate of the first transistor Q1 is connected to a second node between the first resistor R1 and the regulator tube Z1. The anode of the third diode D3 is connected to ground through the first capacitor C1, and the cathode is connected to the gate of the first transistor Q1. An anode of the fourth diode D4 is connected to a node between the first transistor Q1 and the second transistor Q2, and a cathode is connected to an anode of the third diode D3. The power supply source, the first transistor Q1, the fourth diode D4, and the first capacitor C1 form a power supply loop, a third node between an anode of the third diode D3 and a cathode of the fourth diode D4 outputs a power supply voltage Vcc for supplying power to the dimming module 304, and the third node is connected to the dimming module 304 through the first switch K1. The control terminal of the first switch K1 is connected to the leakage determining module 311, receives the leakage control signal Ctrl1 output by the leakage determining module 311, and controls the power supply path between the high-voltage starting module 308 and the dimming module 304 to be turned on or off according to the leakage control signal Ctrl 1.

The grid voltage of the first transistor Q1 is stabilized at Vz1 through the first resistor R1 and the voltage regulator tube Z1, the first transistor Q1 works in a linear region, the fourth diode D4 is conducted, and the cathode of the fourth diode D4 outputs the power supply voltage Vcc, so that the starting voltage can be quickly established when the circuit is started, and at the moment, Vcc is Vz1-V_Q1gs-Vd4, wherein,vz1 is the voltage across the stabilivolt Z1, V_Q1gsVd4 is the voltage across the fourth diode D4, which is the gate-source voltage of the first transistor Q1. When the dc bus voltage VH reaches the valley, that is, when the voltage value of the dc bus voltage VH is low, the power supply voltage Vcc is maintained by the first capacitor C1, and the power supply voltage Vcc is fed back to the gate of the first transistor Q1 through the third diode D3, so that the first transistor Q1 is ensured to have a sufficient gate voltage to operate in a linear region to maintain the normal operation of the transistor Q1.

The leakage current control module 310 is connected to the gate of the second transistor Q2 through the first diode D1, and generates a leakage detection signal to control the on state of the second transistor Q2. The dimming module 304 is connected to the gate of the second transistor Q2 through the second diode D2, and generates a bypass control signal to control the on state of the second transistor Q2. When both the leakage detection signal and the bypass control signal are low, the second transistor Q2 is turned off. When the anode voltage of the first diode D1 is higher than the anode voltage of the second diode D2, the leakage detection signal controls the on state of the second transistor Q2 to perform leakage detection; when the anode voltage of the second diode D2 is higher than the anode voltage of the first diode D1, the bypass control signal controls the on state of the second transistor Q2. When the second transistor Q2 is turned on, the bypass module 303 is turned on, and the ac input power, the dimmer 140 and the bypass module 303 form a conductive loop. When the second transistor Q2 is turned off, the bypass module 303 is turned off, and the conductive loop is opened, so that the transmission of dimming data and power is performed, and dimming is realized.

The voltage detection module 305 includes a first comparator U1, a second comparator U2, a third operational amplifier U3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a second switch K2, and a third switch K3. The fifth resistor R5 and the sixth resistor R6 are connected in series between the first output terminal and the second output terminal of the dc bus voltage VH, and a fourth node between the fifth resistor R5 and the sixth resistor R6 outputs a voltage-divided signal corresponding to the dc bus voltage VH. The first input terminal of the first comparator U1 receives the divided voltage signal, the second input terminal receives the first reference voltage Vref1, and the output terminal outputs a second control signal Ctrl2, wherein the second control signal Ctrl2 controls the second switch K2 to be turned on or turned off. A first input terminal of the second comparator U2 is connected to a fourth node between the fifth resistor R5 and the sixth resistor R6, a second input terminal receives the second reference voltage Vref2, and an output terminal outputs a third control signal Ctrl3, wherein the third control signal Ctrl3 controls the third switch K3 to be turned on or off. A first input terminal of the third operational amplifier U3 is connected to a first node between the second transistor Q2 and the third resistor R3, receives a sampling signal of a leakage current or a bypass current, the second input terminal receives the third reference voltage Vref3 through the seventh resistor R7 and the second switch K2, the second input terminal is connected to ground (a second terminal of the dc bus voltage VH) through the fourth resistor R4, the second input terminal receives the fourth reference voltage Vref4 through the third switch K3, and the output terminal outputs a bypass control signal, which controls the operating state of the second transistor Q2 through the second diode D2, and is connected to the anode of the second diode D2. The first input terminal of the first comparator U1 is an inverting input terminal, and the second input terminal is a non-inverting input terminal, but the present invention is not limited thereto. The first input terminal of the second comparator U2 is an inverting input terminal, and the second input terminal is a non-inverting input terminal, but the present invention is not limited thereto. The first input terminal of the third operational amplifier U3 is an inverting input terminal, and the second input terminal is a non-inverting input terminal, but the present invention is not limited thereto.

As shown in fig. 7, when power-up starts, the leakage protection circuit 301 controls the second transistor Q2 to be turned on intermittently through the first diode D1, at this time, the first switch K1 is turned off, the dimming module 304 and the power conversion circuit 150 do not operate, the anode of the second diode D2 is at a low level, and the leakage control module 310 controls the second transistor Q2 to be turned on according to the leakage detection signal, so as to generate the leakage current Ileak. Before the leakage current control module 310 generates the leakage current Ileak or when the leakage current Ileak starts to be generated, the leakage determination module 311 controls the leakage determination module 311 to obtain a first sampling voltage Vs1 from the voltage sampling module 309; before the leakage current Ileak linearly decreases, the sampling control signal controls the leakage judging module 311 to obtain a second sampling voltage Vs2 from the voltage sampling module 309. When Vs2 is greater than Vs1, there is no leakage, and then the leakage detection signal is at a low level, that is, the anode of the first diode D1 is always at a low level, and the leakage control signal Ctrl1 generated by the leakage determining module 311 controls the first switch K1 to be closed, so as to supply power to the dimming module 304. When the voltage Vs2 is less than or equal to the voltage Vs1, a leakage phenomenon exists, the leakage control signal Ctrl1 controls the first switch K1 to be switched off, the leakage detection signal is a pulse square wave, and the second transistor Q2 is controlled to be switched on intermittently until the leakage phenomenon is detected to be absent.

In normal operation, that is, when there is no leakage, the leakage control signal Ctrl1 controls K1 to be closed, the anode voltage of the first diode D1 is at a low level, the second transistor Q2 is controlled by the bypass control signal output by the third operational amplifier U3, the high level maintaining time of the bypass control signal is the same as the high level maintaining time of the second control signal Ctrl2, the bypass control signal controls the current of the second transistor Q2 and the on and off of the second transistor Q2, the transmission of dimming data, the power transmission and the power supply path of the dimmer are performed, and the dimming module 304 operates normally. .

Referring to fig. 8, when the second control signal Ctrl2 generated at the output terminal of the first comparator U1 is at a high level, the second switch K2 is closed, the voltage at the positive input terminal of the third operational amplifier U3 is Vref3 × R4/(R4+ R7), the first transistor Q1 and the second transistor Q2 are controlled to operate in a linear region, and the current flowing through the first transistor Q1 and the second transistor Q2 is Vref3 × R4/((R4+ R7) × R3). At this time, the dimmer 140 generates dimming data, and the bypass module 303 is turned on for transmission of the dimming data.

Similarly, when the third control signal Ctrl3 output by the second comparator U2 controls the bypass module 303 to be turned on during the chopping of the dimmer 140 (i.e., when the dimmer 140 is off), so as to supply power to the dimmer 140, the ac input power source, the dimmer and the bypass module form a power supply loop. That is, when the third control signal Ctrl3 is at a high level, the third switch K3 is closed, so that the first transistor Q1 and the second transistor Q2 are controlled to operate in a linear region, and the current flowing through the first transistor Q1 and the second transistor Q2 is Vref 4/R3.

The current flowing through the first transistor Q1 and the second transistor Q2 are set to different values at different stages to achieve different impedances of the bypass module 303, which can be used for supplying power to the dimmer and transmitting dimming data, respectively.

When the second control signal Ctrl2 and the third control signal Ctrl3 are both low, the second transistor Q2 is turned off, and the first transistor Q1 operates in a linear region to continue outputting the power supply voltage Vcc. At this time, the bypass module 303 is turned off to perform power transmission.

According to the LED driving circuit provided by the embodiment of the invention, when electric leakage detection is carried out and electric leakage phenomenon exists, the bypass module is intermittently conducted to carry out electric leakage judgment, and meanwhile, a power supply path between the high-voltage starting module and the dimming module is turned off to carry out electric leakage protection; when no electric leakage exists, the bypass module is turned off to realize power transmission, so that the dimming of the LED lamp is realized.

Furthermore, the leakage protection circuit performs leakage detection by detecting leakage current generated by the bypass module, and the leakage protection circuit multiplexes the bypass module to realize leakage protection.

When the LED driving circuit with leakage protection is connected in parallel to two ends of a normal LED driving circuit (an LED driving circuit without leakage protection), the dimmer 140 can operate normally, the waveform of the dc bus voltage VH carries dimming information, as shown in fig. 9, the second sampling voltage Vs2 obtained at time t2 is smaller than the first sampling voltage Vs1 obtained at time t1, and the LED driving circuit with leakage protection performs leakage protection until Vs2 is greater than Vs 1.

When a single LED driving circuit is connected in series with the dimmer 140, only the leakage protection circuit 301 works, and the dimming module 304 and the power conversion circuit 150 do not work when performing leakage protection, as shown in fig. 10, the waveform of the dc bus voltage VH does not have dimming information, and only a leakage loop can be generated through the internal capacitor of the dimmer 140. When leakage protection is performed, if the second sampling voltage Vs2 obtained at the time t2 is smaller than the first sampling voltage Vs1 obtained at the time t1, leakage protection is performed until Vs2 > Vs 1.

Fig. 11 shows a schematic circuit diagram of an LED driving apparatus provided by a third embodiment of the present invention. Compared to the first embodiment of the present invention, the dimmer 140 further comprises a second input end, the second input end of the dimmer 140 is connected to the second end of the ac input, and the second output end of the dimmer is connected to the second input end of the rectifier bridge.

According to the LED driving circuit provided by the embodiment of the invention, when electric leakage detection is carried out and electric leakage phenomenon exists, the bypass module is conducted intermittently to carry out electric leakage protection, and when the electric leakage phenomenon does not exist, the bypass module is conducted, the alternating current input power supply, the light modulator and the bypass module form a conductive loop, so that power supply of the light modulator and transmission of light modulation data are realized; when no electric leakage exists, the bypass module is turned off to realize power transmission, so that the dimming of the LED lamp is realized.

Fig. 12 shows a schematic circuit diagram of an LED driving apparatus provided by a fourth embodiment of the present invention. Compared with the second embodiment of the present invention, the dimmer 140 further comprises a second input end, the second input end of the dimmer 140 is connected to the second end of the ac input, and the second output end of the dimmer is connected to the second input end of the rectifier bridge.

According to the LED driving circuit provided by the embodiment of the invention, when the leakage phenomenon exists, the bypass module is intermittently conducted to judge the leakage, and simultaneously, the power supply path between the high-voltage starting module and the dimming module is turned off to perform leakage protection; when no electric leakage exists, the bypass module is turned off to realize power transmission, so that the dimming of the LED lamp is realized.

Embodiments of the invention are described above, and these embodiments do not set forth any exhaustive details or limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The scope of the invention should be determined from the following claims.

Claims

1. An LED driving circuit, comprising:

the leakage protection circuit detects whether a leakage phenomenon exists and generates a leakage control signal;

and the dimming circuit is connected with the electric leakage protection circuit and receives the electric leakage control signal, and when the electric leakage phenomenon does not exist, the dimming circuit performs dimming according to the electric leakage control signal, and when the electric leakage phenomenon exists, the dimming circuit stops dimming according to the electric leakage control signal.

2. The LED driving circuit of claim 1, wherein the leakage protection circuit generates a leakage detection signal and determines whether a leakage phenomenon exists according to a dc bus voltage with the dimming data.

3. The LED driving circuit of claim 2, wherein the dimming circuit generates a leakage current according to the leakage detection signal when the leakage detection is performed and the leakage phenomenon exists, and resolves the dimming data from the dc bus voltage when the leakage phenomenon does not exist, and generates the pulse width modulation signal according to the dimming data.

4. The LED driving circuit according to claim 1, wherein the dimming circuit comprises:

the bypass module is connected with the electric leakage protection circuit and receives an electric leakage detection signal;

the dimming module is connected with the bypass module and generates a pulse width modulation signal and a bypass control signal according to the voltage of the direct-current bus;

the bypass module generates a leakage current according to the leakage detection signal when the leakage detection is performed and the leakage phenomenon exists, and generates a bypass current according to the bypass control signal when the leakage phenomenon does not exist.

5. The LED driving circuit according to claim 4, wherein the leakage protection circuit multiplexes the bypass module for leakage detection, and when leakage detection is performed and a leakage phenomenon exists, the leakage detection signal controls the bypass module to be turned on intermittently; and when the electric leakage phenomenon does not exist, the bypass control signal controls the bypass module to be switched on or switched off.

6. The LED driving circuit according to claim 4, wherein the dimming module is further connected to the leakage protection circuit, receives a leakage control signal, and performs dimming when there is no leakage and stops dimming when there is leakage according to the leakage control signal.

7. The LED driving circuit according to claim 6, wherein the bypass module comprises a second transistor, a first diode, a second resistor, and a third resistor,

the second transistor and the third resistor are connected in series between a first output end and a second output end of the direct-current bus voltage;

the grid electrode of the second transistor is connected with the second output end of the direct current bus voltage through a second resistor;

the anode of the first diode is connected with the leakage protection circuit, and the cathode of the first diode is connected with the grid of the second transistor;

the anode of the second diode is connected with the dimming module, and the cathode of the second diode is connected with the grid of the second transistor;

a first node between the second transistor and the third resistor outputs a sampling signal of the leakage current or a sampling signal of the bypass current.

8. The LED driving circuit according to claim 7, wherein when there is a leakage phenomenon, the leakage detection signal controls the second transistor to be turned on intermittently, and the power supply forms a leakage current loop with the second transistor and the third resistor.

9. The LED driving circuit according to claim 7, wherein the bypass control signal controls the second transistor to turn on and off when there is no leakage, and the power supply, the second transistor and the third resistor form a bypass loop.

10. The LED driving circuit according to claim 4, wherein the dimming circuit further comprises:

the high-voltage starting module is connected with the leakage protection circuit and the bypass module and generates power supply voltage according to the voltage of the direct-current bus;

and when the electric leakage phenomenon does not exist, the high-voltage starting module supplies power to the dimming module according to the electric leakage control signal.

11. The LED driving circuit according to claim 10, wherein the high voltage start-up module comprises a first transistor, a voltage regulator tube, a first resistor, a third diode, a fourth diode, a first capacitor and a first switch,

the first resistor and the voltage-regulator tube are connected in series between a first output end and a second output end of the direct-current bus voltage;

the grid electrode of the first transistor is connected with a second node between the first resistor and the voltage regulator tube;

the anode of the third diode is connected with the second output end of the direct current bus voltage through the first capacitor, and the cathode of the third diode is connected with the grid of the first transistor;

the anode of the fourth diode is connected with a node between the first transistor and the second transistor, and the cathode of the fourth diode is connected with the anode of the third diode;

a third node between the third diode and the fourth diode outputs a power supply voltage, and the third node is connected with the dimming module through a first switch;

and the control end of the first switch receives the electric leakage control signal and is switched on and off according to the electric leakage control signal.

12. The LED driving circuit of claim 11, wherein the leakage detection signal controls the second transistor to turn on intermittently when leakage detection is performed and leakage occurs, and the power supply forms a leakage current loop with the first transistor, the second transistor and the third resistor.

13. The LED driving circuit of claim 11, wherein the bypass control signal controls the second transistor to turn on and off when there is no leakage, and the power supply forms a bypass loop with the first transistor, the second transistor, and the third resistor.

14. The LED driving circuit of claim 11, wherein the power supply forms a power supply loop with the first transistor, the fourth diode, and the first capacitor.

15. The LED driving circuit according to claim 4 or 10, wherein the dimming module comprises:

the voltage detection unit is used for generating a bypass control signal according to the voltage of the direct-current bus, and the bypass control signal controls the on and off of the bypass module;

the data acquisition unit is used for generating a data signal according to the DC bus voltage;

and the control unit is connected with the data acquisition unit and used for generating a pulse width modulation signal according to the data signal.

16. The LED driving circuit according to claim 15, wherein the voltage detection module comprises a first comparator, a second comparator, a third operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a second switch, and a third switch;

the fifth resistor and the sixth resistor are connected in series between a first output end and a second output end of the direct-current bus voltage;

a first input end of the first comparator is connected with a node between the fifth resistor and the sixth resistor, a second input end of the first comparator receives the first reference voltage, and an output end of the first comparator outputs a second control signal;

a first input end of the second comparator is connected with a node between the fifth resistor and the sixth resistor, a second input end of the second comparator receives a second reference voltage, and an output end of the second comparator outputs a third control signal;

a first input end of the third operational amplifier receives a bypass current sampling signal output by the bypass module, a second input end of the third operational amplifier receives a third reference voltage through a seventh resistor and a second switch, the second input end of the third operational amplifier is connected with a second output end of the direct-current bus voltage through a fourth resistor, the fourth reference voltage is received through a third switch, and the output end of the third operational amplifier outputs a bypass control signal;

the second control signal controls the second switch to be switched on and switched off, and the third control signal controls the third switch to be switched on and switched off.

17. The LED driving circuit according to claim 3, wherein the leakage protection circuit comprises:

the voltage sampling module is used for acquiring direct-current bus voltage and sampling the direct-current bus voltage to obtain sampling voltage;

the leakage current control module is connected with the voltage sampling module and used for generating a sampling control signal and a leakage detection signal according to the sampling voltage and the reference voltage;

and the electric leakage judging module is connected with the voltage sampling module and the electric leakage current control module and used for acquiring a first sampling voltage at a first sampling moment and a second sampling voltage at a second sampling moment according to the sampling control signal, judging whether an electric leakage phenomenon exists or not and generating an electric leakage control signal according to the first sampling voltage and the second sampling voltage, wherein the first sampling moment is earlier than the second sampling moment.

18. The LED driving circuit of claim 17, wherein the leakage current control module generates a leakage detection signal when or after the dc bus voltage is greater than a reference voltage.

19. The LED driving circuit according to claim 17, wherein the leakage current linearly increases to a predetermined current value or decreases after the leakage current increases for a predetermined time.

20. The LED driving circuit according to claim 17, wherein the leakage current curve rises to a predetermined current value or falls after the curve rises for a predetermined time.

21. The LED driving circuit according to claim 17, wherein the first sampling time is before the leakage current is generated or when the leakage current starts to be generated, and the second sampling time is before the leakage current linearly decreases.

22. The LED driving circuit according to claim 17, wherein the first sampling timing and the second sampling timing are during a linear rise of the leakage current.

23. The LED driving circuit according to claim 17, wherein when the second sampling voltage is less than or equal to the first sampling voltage, a leakage phenomenon exists;

when the second sampling voltage is greater than the first sampling voltage, no leakage phenomenon exists.

24. The LED driving circuit according to claim 17, wherein when the second sampling voltage is less than or equal to a sum of the first sampling voltage and a preset bias voltage, a leakage phenomenon exists;

when the second sampling voltage is larger than the sum of the first sampling voltage and a preset bias voltage, no electric leakage phenomenon exists.

25. The LED driving circuit according to claim 1, wherein the leakage protection circuit detects whether there is leakage when power is turned on, and the dimming circuit operates normally when there is no leakage; when the leakage phenomenon exists, the dimming circuit does not work, and the leakage detection is repeated until the leakage phenomenon does not exist.

26. A control method of an LED drive circuit is characterized by comprising the following steps:

detecting whether the electric leakage phenomenon exists or not and generating an electric leakage control signal;

and when the electric leakage phenomenon does not exist, dimming is started according to the electric leakage control signal, and when the electric leakage phenomenon exists, dimming is stopped according to the electric leakage control signal.

27. The control method according to claim 26, characterized by further comprising:

and generating a leakage detection signal, and judging whether a leakage phenomenon exists according to the voltage of the direct current bus with the dimming data.

28. The control method according to claim 27, further comprising:

generating leakage current according to the leakage detection signal when leakage detection is carried out or leakage phenomenon exists, analyzing dimming data from the direct current bus voltage when the leakage phenomenon does not exist, and generating a pulse width modulation signal according to the dimming data to carry out dimming.

29. The control method according to claim 26, characterized by further comprising:

when the leakage phenomenon does not exist, generating a bypass control signal according to the voltage of the direct-current bus; and

generating a bypass current according to the bypass control signal;

the current path of the leakage current is the same as the current path of the bypass current.

30. The control method according to claim 26, characterized by further comprising:

generating a supply voltage according to the DC bus voltage; and

controlling power supply according to the leakage control signal to control whether to adjust light,

and when the leakage detection is carried out and the leakage phenomenon exists, the power supply is stopped according to the leakage control signal to stop dimming.

31. The control method of claim 26, wherein the step of dimming comprises:

generating a data signal according to the DC bus voltage; and

and generating a pulse width modulation signal according to the data signal.

32. The control method of claim 26, wherein the step of detecting whether the leakage phenomenon exists comprises:

acquiring direct current bus voltage, and sampling the direct current bus voltage to obtain sampling voltage;

generating a sampling control signal and a leakage detection signal according to the sampling voltage and the reference voltage;

and acquiring a first sampling voltage at a first sampling moment and a second sampling voltage at a second sampling moment according to the sampling control signal, and judging whether a leakage phenomenon exists and generating a leakage control signal according to the first sampling voltage and the second sampling voltage, wherein the first sampling moment is earlier than the second sampling moment.

33. The control method of claim 32, wherein a leakage detection signal is generated when or after the dc bus voltage is greater than a reference voltage.

34. The control method of claim 32, wherein the leakage current linearly increases to a predetermined current value or linearly decreases after the leakage current increases for a predetermined time.

35. The control method of claim 32, wherein the leakage current curve rises to a predetermined current value or falls after the curve rises for a predetermined time.

36. The control method of claim 32, wherein the first sampling time is before the generation of the leakage current or when the generation of the leakage current starts, and the second sampling time is before the leakage current linearly decreases.

37. The control method of claim 32, wherein the first sampling time and the second sampling time are during a linear rise of the leakage current.

38. The control method according to claim 32, wherein when the second sampling voltage is less than or equal to the first sampling voltage, a leakage phenomenon exists;

39. The control method of claim 32, wherein when the second sampling voltage is less than or equal to the sum of the first sampling voltage and a preset bias voltage, a leakage phenomenon exists;

40. The control method according to claim 26, wherein upon power-up, it is detected whether there is a leakage phenomenon, and when there is no leakage phenomenon, dimming is performed; when the electric leakage phenomenon exists, dimming is stopped, and electric leakage detection is repeated until the electric leakage phenomenon does not exist.

41. An LED driving apparatus, comprising: a dimmer having a first input terminal connected to the ac input first terminal and generating an ac input voltage with dimming data based on a dimming operation;

the first input end of the rectifier bridge is connected with the first output end of the dimmer, the second input end of the rectifier bridge is connected with the alternating current input second end, and the rectifier bridge is used for rectifying the alternating current input voltage with dimming data to output a direct current bus voltage with dimming data;

the LED driver circuit as claimed in any of claims 1-25, and

and the power conversion circuit is connected with the dimming circuit and used for converting the direct current bus voltage into direct current output voltage according to the pulse width modulation signal output by the LED driving circuit and supplying power to a load.

42. The LED driver circuit of claim 41, wherein the power conversion circuit comprises a diode and a power conversion module,

the anode of the diode is connected with a first output end of the direct-current bus voltage, and the cathode of the diode is connected with the power conversion module;

the power conversion module is used for converting the direct current bus voltage into direct current output voltage according to the pulse width modulation signal and supplying power to a load.

43. The LED driving apparatus according to claim 41, wherein the dimmer further comprises a second input terminal, the second input terminal of the dimmer is connected to the second terminal of the AC input, and the second output terminal of the dimmer is connected to the second input terminal of the rectifier bridge.