Leakage protection circuit

Abstract

Disclosed in the present invention is a leakage protection circuit, relating to the technical field of LEDs. The leakage protection circuit comprises: a power supply circuit, a step-down circuit, an LED circuit, and a detection circuit; an input end of the power supply circuit is connected to output pins of a power supply end, and an output end of the power supply circuit is separately connected to an input end of the step-down circuit and an input end of the LED circuit, and the power supply circuit is used for performing rectification processing on an output power supply of the power supply end so as to output a power supply to the step-down circuit and the LED circuit; an output end of the step-down circuit is connected to the detection circuit, and the step-down circuit is used for performing step-down processing on the power supply outputted by the power supply circuit so as to output a reference voltage to the detection circuit; the detection circuit is separately connected to the output pins of the power supply end and to the LED circuit, and is used for controlling the operating state of the LED circuit on the basis of a real-time voltage difference between the output pins of the power supply end and on the basis of the reference voltage outputted by the step-down circuit. By means of the present invention, the operating state of an LED circuit can be controlled on the basis of a real-time voltage difference and a reference voltage, and leakage protection is thereby implemented.

Description

Leakage protection circuit Technical Field

[0001] This invention relates to the field of LED technology, and in particular to a leakage current protection circuit. Background Technology

[0002] Currently, lamps can be powered either directly by AC mains power or by connecting to a ballast. When AC mains power is selected, it is typically 220V / 50Hz or other voltages; while when a ballast is connected, high voltage is present at the connectors at both ends of the lamp.

[0003] In the lighting field, lamps are divided into two types: single-ended input and double-ended input. Single-ended input means that all the AC input terminals are located at the same end, while double-ended input means that they are located at both ends of the lamp. Since many lamp holders still retain double-ended input interfaces, double-ended input lamps are generally used when replacing or installing existing lamps.

[0004] During the installation of lamp tubes, operators typically insert one end of the lamp tube into the lamp holder first, and then insert the other end. This may result in partial connection. Since the operator's hand needs to hold the end of the lamp tube, if the human body accidentally touches the conductive metal end, electric shock may easily occur, affecting operational safety. Therefore, it is particularly important to implement leakage protection for lamp tubes.

[0005] Current technology primarily uses a switching transistor connected to the power input terminal to detect the current flowing through it, thereby determining whether leakage current exists and achieving leakage protection. However, this technology is not effective in all situations; when there is poor contact at the input terminal, the leakage protection circuit will fail, and the operator will still be at risk of electric shock. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a leakage protection circuit that can achieve leakage protection.

[0007] To address the aforementioned technical problems, this invention provides a leakage current protection circuit, comprising: a power supply circuit, a step-down circuit, an LED circuit, and a detection circuit; the input terminal of the power supply circuit is connected to the output pin of the power supply terminal, and the output terminal of the power supply circuit is respectively connected to the input terminal of the step-down circuit and the input terminal of the LED circuit, for rectifying the output power of the power supply terminal to output power to the step-down circuit and the LED circuit; the output terminal of the step-down circuit is connected to the detection circuit, for stepping down the power supply output by the power supply circuit to output a reference voltage to the detection circuit; the detection circuit is respectively connected to the output pin of the power supply terminal and the LED circuit, for controlling the operating state of the LED circuit based on the real-time voltage difference between the output pins of the power supply terminal and the reference voltage output by the step-down circuit.

[0008] As an improvement to the above solution, the detection circuit includes two differential pressure detection modules, a control module, and a switching module. The control module has two real-time sampling terminals and one reference sampling terminal. The two sets of output pins of the differential pressure detection modules, the real-time sampling terminals, and the power supply terminal correspond one-to-one. The differential pressure detection module is connected to the corresponding set of output pins to detect the real-time differential pressure between the corresponding set of output pins, and controls the detection signal output by the differential pressure detection module according to the real-time differential pressure. The real-time sampling terminal is connected to the corresponding differential pressure detection module to obtain the detection signal. The reference sampling terminal is connected to the output terminal of the step-down circuit to obtain the reference voltage. The output terminal of the control module is connected to the switching module to control the on / off state of the switching module according to the detection signal and the reference voltage.

[0009] As an improvement to the above solution, the differential pressure detection module includes a rectifier bridge and an optocoupler; the rectifier bridge is connected to a corresponding set of output pins to rectify the output power between the output pins; the input terminal of the optocoupler is connected to the rectifier bridge, and the output terminal of the optocoupler is connected to the control module, which controls the on / off state of the output terminal of the optocoupler according to the real-time differential pressure of the output power after rectification by the rectifier bridge.

[0010] As an improvement to the above solution, the switch module includes a first switch, the control terminal of the first switch is connected to the output terminal of the control module, one terminal of the first switch is connected to the LED circuit, and the other terminal of the first switch is connected to the power supply circuit.

[0011] As an improvement to the above solution, the control module includes a second switch and a third switch; the second switch is connected to a real-time sampling terminal and a reference sampling terminal of the control module, respectively, and is used to adjust its on / off state according to the detection signal obtained by the real-time sampling terminal and the reference voltage obtained by the reference sampling terminal; the third switch is connected to another real-time sampling terminal of the control module and the output terminal of the second switch, and is used to adjust its on / off state according to the detection signal obtained by the other real-time sampling terminal and the output signal of the second switch; the output terminal of the third switch is connected to the switch module, and the on / off state of the third switch controls the on / off state of the switch module, which in turn controls the operating state of the LED circuit.

[0012] As an improvement to the above solution, when the second switch and the third switch are turned on, the switch module is turned on so that the power supply circuit, the LED circuit and the detection circuit form an LED loop and the LED circuit works; when the second switch and / or the third switch are turned off, the switch module is turned off so that the LED circuit is disconnected from the detection circuit.

[0013] As an improvement to the above scheme, the control electrode of the second switch is connected to the output terminal of a differential pressure detection module through a real-time sampling terminal, the first electrode of the second switch is connected to the output terminal of the step-down circuit through a reference sampling terminal, and the second electrode of the second switch is connected to the first electrode of the third switch; the control electrode of the third switch is connected to the output terminal of another differential pressure detection module through another real-time sampling terminal, and the second electrode of the third switch is connected to the switch module.

[0014] As an improvement to the above solution, the detection circuit further includes an anti-interference module, and the control module and the switch module are connected through the anti-interference module.

[0015] As an improvement to the above solution, the LED circuit includes a driver module and an LED module. The input terminal of the driver module is connected to the output terminal of the LED module, and is used to control the working state of the LED module according to the power supply. When the power supply circuit is connected to a ballast, the driver circuit does not work. When the power supply circuit is connected to AC power, the driver circuit controls the on / off state between the driver module and the LED module according to the power supply to control the working state of the LED circuit.

[0016] As an improvement to the above solution, the driving module includes a driving chip, which has a detection pin and an open-drain pin. The open-drain pin has a built-in switch. The detection pin is connected to the power supply circuit and is used to detect the power supply output by the power supply circuit. The open-drain pin is connected to the LED module, and the built-in switch switches between on and off states according to the power supply to control the on / off state between the driving module and the LED module.

[0017] The beneficial effects of implementing this invention are as follows:

[0018] The leakage protection circuit of this invention uses the electrical signal between the output pins before rectification as the detection target, and combines the real-time voltage difference between the output pins of the power supply end with the reference voltage. Using the voltage difference factor as the judgment basis, it realizes accurate detection of leakage from the perspective of voltage difference, which greatly improves the accuracy of detection. This effectively controls the on / off state of the LED circuit, plays a role in preventing leakage, and ensures human safety.

[0019] Furthermore, the leakage protection circuit of this invention incorporates control components such as switching transistors and optocouplers, enabling flexible switching of the circuit and thus more precisely controlling the on / off state of the LED circuit with high accuracy. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the leakage protection circuit of the present invention;

[0021] Figure 2 is a circuit diagram of an embodiment of the leakage current protection circuit of the present invention;

[0022] Figure 3 is a circuit diagram of an embodiment of the step-down circuit in the leakage protection circuit of the present invention;

[0023] Figure 4 is a circuit diagram of another embodiment of the step-down circuit in the leakage protection circuit of the present invention;

[0024] Figure 5 is a circuit diagram of an embodiment of the drive module in the leakage protection circuit of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It is hereby declared that the directional terms such as up, down, left, right, front, back, inside, and outside used in this text are based solely on the accompanying drawings and are not intended to specifically limit the invention.

[0026] Referring to Figure 1, which shows the specific structure of the leakage current protection circuit of the present invention, it includes a power supply circuit 1, a step-down circuit 2, an LED circuit 3, and a detection circuit 4. Specifically:

[0027] The input terminal of power supply circuit 1 is connected to the output pin of the power supply terminal. The output terminal of the power supply circuit is connected to the input terminal of step-down circuit 2 and the input terminal of LED circuit 3 respectively. It is used to rectify the output power of the power supply terminal to output power to step-down circuit 2 and LED circuit 3.

[0028] The output of step-down circuit 2 is connected to detection circuit 4 and is used to step down the power supply output from power supply circuit 1 to output a reference voltage to detection circuit 4.

[0029] The detection circuit 4 is connected to the output pin of the power supply terminal and the LED circuit 3 respectively. It is used to control the working state of the LED circuit 3 according to the real-time voltage difference between the output pins of the power supply terminal and the reference voltage output by the step-down circuit 2, thereby realizing leakage current control.

[0030] It should be noted that the leakage protection circuit of the present invention can be applied to mains power only, or it can be applied to both mains power and ballast. Therefore, the power supply terminal can be the mains power supply terminal or the ballast power supply terminal. At the same time, the leakage protection circuit of the present invention can realize leakage protection of the ballast alone, or it can realize leakage protection of both the ballast and the mains power at the same time.

[0031] In existing technologies, leakage current protection circuits typically detect a single electrical signal after rectification to achieve leakage current protection. Unlike existing technologies, the leakage current protection circuit of this invention uses the electrical signal before rectification (i.e., the electrical signal between the output pins) as the detection target and uses the voltage difference factor as the judgment criterion, achieving accurate leakage current detection from the perspective of voltage difference, thus greatly improving the accuracy of detection.

[0032] The power supply circuit 1, the step-down circuit 2, the LED circuit 3, and the detection circuit 4 are described in detail below with reference to specific embodiments:

[0033] I. Power Supply Circuit 1

[0034] As shown in Figure 2, in this embodiment, the power supply circuit 1 includes a first rectifier bridge BD1, a second rectifier bridge BD2, a second diode D2, a third diode D3, a seventh diode D7, an eighth diode D8, a second capacitor C2, an eighth capacitor C8, and input ports F1, F2, F3, and F4.

[0035] One AC input terminal of the first rectifier bridge BD1 is connected to input port F1, and the other AC input terminal is connected to input port F2. The negative terminal of the DC output is connected to the step-down circuit 2 and the LED circuit 3, and the positive terminal of the DC output is grounded. The positive terminal of the second diode D2 is connected to input port F1, and the negative terminal is connected to the LED circuit 3. The positive terminal of the third diode D3 is connected to input port F2, and the negative terminal is connected to the LED circuit 3. One end of the second capacitor C2 is connected to input port F1, and the other end is connected to input port F2.

[0036] Similarly, one AC input terminal of the second rectifier bridge BD2 is connected to input port F3, and the other AC input terminal is connected to input port F4. The negative terminal of the DC output is connected to the step-down circuit 2 and the LED circuit 3, and the positive terminal of the DC output is grounded. The positive terminal of the seventh diode D7 is connected to input port F3, and the negative terminal is connected to the LED circuit 3. The positive terminal of the eighth diode D8 is connected to input port F4, and the negative terminal is connected to the LED circuit 3. One end of the eighth capacitor C8 is connected to input port F3, and the other end is connected to input port F4.

[0037] When this invention is applied to a ballast, the input ports F1, F2, F3 and F4 can be connected to the four pins of the ballast.

[0038] When this invention is applied to mains power, any two input ports can be selected to connect to two pins of the mains power, for example, input ports F1 and F2, or input ports F3 and F4, or input ports F1 and F3, or input ports F1 and F4, or input ports F2 and F3, or input ports F2 and F4.

[0039] Therefore, the power supply circuit 1 can rectify the output power of the power supply terminal to output a stable power supply to the step-down circuit 2 and the LED circuit 3.

[0040] II. Step-down circuit 2

[0041] As shown in Figure 2, in this embodiment, the step-down circuit 2 includes a voltage divider resistor group (first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, and fifth resistor R5), a first capacitor C1, and a first Zener diode D1. One end of the first resistor R1 is connected to the power supply circuit 1, and the other end is grounded through the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 in sequence. The fifth resistor R5 is connected in parallel with the first capacitor C1 and the first Zener diode D1, respectively. The positive terminal of the first Zener diode D1 is grounded, and the negative terminal is connected to the detection circuit 4.

[0042] Therefore, the step-down circuit 2 can step down the power supply output from the power supply circuit 1 and convert it into a 12V reference voltage for use by the detection circuit 4.

[0043] In other embodiments, different numbers and resistance values ​​of resistors can be selected for voltage reduction according to actual needs.

[0044] As shown in Figure 3, in this embodiment, the voltage divider resistor group includes four resistors connected in series (second resistor R2, third resistor R3, fourth resistor R4 and fifth resistor R5).

[0045] In other embodiments, voltage reduction can be achieved using a step-down chip.

[0046] As shown in Figure 4, in this embodiment, the step-down circuit 2 includes a step-down chip U2, an eleventh diode D11, a twelfth diode D12, a third inductor L3, a fourth inductor L4, a sixteenth capacitor C16, a seventeenth capacitor C17, a second polarity capacitor CE2, a third polarity capacitor CE3, a fourth polarity capacitor CE4, a fortieth resistor R40, a forty-first resistor R41, and a current-limiting resistor RS1. Specifically, the ground pin GND of the step-down chip U2 is connected to the negative terminal of the twelfth diode D12; the clock pin SCL and the power supply pin VCC are respectively connected to the negative terminal of the eleventh diode D11; the open-drain pin DRAIN is connected to the power supply circuit 1 through the third inductor L3; and the chip select pin CS is open. The current-limiting resistor RS1 is connected to the negative terminal of the twelfth diode D12; the positive terminal of the twelfth diode D12 is grounded, and the negative terminal is connected to the detection circuit 4 through the fourth inductor L4 and to the negative terminal of the eleventh diode D11 through the seventeenth capacitor C17. The positive terminal of the eleventh diode D11 is connected to the detection circuit 4; one end of the fortieth resistor R40 is connected to the detection circuit 4, and the other end is grounded. The fortieth resistor R40, the sixteenth capacitor C16, and the second polarity capacitor CE2 are connected in parallel; the forty-first resistor R41 is connected in parallel with the third inductor L3; the positive terminal of the fourth polarity capacitor CE4 is connected to the open-drain pin DRAIN, and the negative terminal is grounded; the positive terminal of the third polarity capacitor CE3 is connected to the power supply circuit 1, and the negative terminal is grounded.

[0047] It should be noted that when connected to mains power, whether it is a single-ended input to input ports F1 and F2, a single-ended input to input ports F3 and F4, or a dual-ended input, the voltage after rectification by the first rectifier bridge DB1 and the second rectifier bridge DB2 is 310VDC, which is consistent with the working state of the step-down chip U2. Therefore, the step-down chip U2 can work normally, playing the role of step-down constant current, and supplying a constant reference voltage to the detection circuit 4.

[0048] Therefore, in applications, different step-down circuits 2 can be used to step down the power output of power supply circuit 1 according to actual needs, and no restrictions are imposed here.

[0049] III. LED Circuit 3

[0050] (1) When the leakage protection circuit of the present invention is only applied to the ballast, the LED circuit 3 may not be equipped with a driving module.

[0051] (2) When the leakage protection circuit of the present invention is applied to both mains power and ballast, the LED circuit 3 includes a driving module 32 and an LED module 31, and the input terminal of the driving module 32 is connected to the output terminal of the LED module 31.

[0052] in:

[0053] (2.1) When the power supply circuit 1 is connected to the ballast, the drive module 32 does not work;

[0054] (2.2) When the power supply circuit 1 is connected to the mains power and the drive module 32 has leakage protection function, the drive module 32 controls the on / off state between the drive module 32 and the LED module 31 according to the power supply output of the power supply circuit 1, so as to control the working state of the LED circuit 31.

[0055] For example, when the driver module 32 does not detect leakage, the driver module 32 is connected to the LED module 31, and the driver module 32 drives the LED module 31, thereby ensuring the constant current power supply to the LED module 31;

[0056] For example, when the drive module 32 detects leakage, the drive module 32 disconnects from the LED module 31, and the LED module 31 is open-circuited.

[0057] In some embodiments, the LED module 31 includes a plurality of light-emitting diodes connected in series. The driving module 32 includes a driving chip U1, which has a detection pin REC and an open-drain pin DRAIN. The open-drain pin DRAIN has a built-in switch. The detection pin REC is connected to the power supply circuit 1 and is used to detect the power supply output by the power supply circuit 1. The open-drain pin DRAIN is connected to the LED module 31, and the built-in switch switches between on and off states according to the power supply to control the on / off state between the driving module 32 and the LED module 31.

[0058] As shown in Figure 2, in this embodiment, the driving module 32 includes a driving chip U1, a first transformer coil T1, a sixth diode D6, a Zener diode TVS1, a first polarized capacitor CE1, a seventh capacitor C7, a ninth capacitor C9, a tenth capacitor C10, an eighth resistor R8, a ninth resistor R9, an eleventh resistor R11, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a seventeenth resistor R17, and an eighteenth resistor R18. The open-drain pin DRAIN of the driving chip U1 is connected to the negative terminal of the LED module 31 through the first transformer coil T1; the compiler pin ISP is grounded through the seventeenth resistor R17 and the eighteenth resistor R18; the ground pin GND is grounded and connected to the sixth diode D6 through the ninth capacitor C9. The positive terminal of the sixth diode D6 is connected to the positive terminal of the LED module 31; the detection pin REC is connected to the power supply circuit 1 through the fourteenth resistor R14 and the thirteenth resistor R13, and grounded through the Zener diode TVS1 and the fifteenth resistor R15 respectively; the power supply pin VIN is connected to the positive terminal of the LED module through the eighth resistor R8; one end of the tenth capacitor C10 is grounded, and the other end is connected to the detection circuit 4 and the negative terminal of the LED module 31 respectively; one end of the ninth resistor R9 is connected to the positive terminal of the LED module 31, and the other end is connected to the open-drain pin DRAIN through the seventh capacitor C7; one end of the first polarized capacitor CE1 is connected to the positive terminal of the LED module 31, and the other end is connected to the negative terminal of the LED module 31; the eleventh resistor R11 is connected in parallel with the first polarized capacitor CE1.

[0059] It should be noted that the detection pin REC of the driver chip U1 has an input current detection function; when the power supply is greater than 72mA, the driver chip U1 turns on the built-in switch of the open-drain pin DRAIN; when the power supply is less than 72mA, the driver chip U1 turns off the built-in switch of the open-drain pin DRAIN. Preferably, the driver chip U1 can be JW1830, JW1831, JW1832 or other similar solutions, but this is not a limitation.

[0060] Furthermore, in this embodiment, the LED circuit 3 also includes a filter circuit 33. The input terminal of the filter circuit 33 is connected to the output terminal of the power supply circuit 1, and the output terminal of the filter circuit 33 is connected to the driving module 32 and the LED module 31 respectively.

[0061] As shown in Figure 2, in this embodiment, the filter circuit 33 includes a first inductor L1, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a seventh resistor R7, and a thermistor RV1. The power supply pin VCC of the driver chip U1 is grounded through the fifth capacitor C5. One end of the thermistor RV1 is connected to the positive terminal of the LED module 31, and the other end is grounded. One end of the third capacitor C3 is connected to the power supply circuit 1, and the other end is grounded. One end of the fourth capacitor C4 is connected to the positive terminal of the LED module, and the other end is grounded. One end of the first inductor L1 is connected to the power supply circuit 1, and the other end is connected to the positive terminal of the LED module. The seventh resistor R7 is connected in parallel with the first inductor L1.

[0062] Therefore, the power supply voltage output by the power supply circuit 1 can be filtered by the filter circuit 33 to supply power to the drive module 32 and the LED module 31.

[0063] (2.3) When the power supply circuit 1 is connected to the mains power and the drive module 32 does not have leakage protection function, the drive module 32 works to drive the LED module 31, thereby ensuring the constant current power supply of the LED circuit 3.

[0064] As shown in Figure 5, in this embodiment, the driving module 32 includes a driving chip U1, a second inductor L2, a thirteenth diode D13, a tenth capacitor C10, an eighteenth polarity capacitor C18, a nineteenth capacitor C19, a twentieth capacitor C20, an eighth resistor R8, a seventeenth resistor R17, an eighteenth resistor R18, and a forty-first resistor R41. Specifically: the overvoltage protection pin OVP of the driver chip U1 is grounded through the forty-first resistor R41; the power input pin VIN is connected to the positive terminal of the LED module 31 through the eighth resistor R8; the open-drain pin DRAIN is connected to the positive terminal of the LED module 31 through the thirteenth diode D13 and to the negative terminal of the LED module 31 through the second inductor L2; the compiler pin ISP is grounded through the seventeenth resistor R17 and the eighteenth resistor R18 respectively; one end of the twentieth capacitor C20 is connected to the positive terminal of the LED module 31, and the other end is grounded; the positive terminal of the eighteenth polarity capacitor C18 is connected to the positive terminal of the LED module 31, the negative terminal of the eighteenth polarity capacitor C18 is connected to the detection circuit 4 and the negative terminal of the LED module 31, and is grounded through the tenth capacitor C10; the eighteenth polarity capacitor C18 and the nineteenth capacitor C19 are connected in parallel.

[0065] Therefore, when connected to mains power, the LED module 31 can be driven by constant current through the driver chip U1 to ensure that the LED module 31 can be used normally.

[0066] IV. Detection Circuit 4

[0067] As shown in Figure 2, the detection circuit 4 includes two differential pressure detection modules 41, a control module 42 and a switch module 43. The control module 42 is provided with two real-time sampling terminals and one reference sampling terminal. The two sets of output pins of the differential pressure detection module 41, the real-time sampling terminal and the power supply terminal correspond one-to-one.

[0068] The differential pressure detection module 41 is connected to a corresponding set of output pins to detect the real-time differential pressure between the corresponding set of output pins, and controls the detection signal output by the differential pressure detection module 41 according to the real-time differential pressure.

[0069] The real-time sampling end is connected to the corresponding differential pressure detection module 41 to obtain the detection signal;

[0070] The reference sampling terminal is connected to the output terminal of step-down circuit 2 to obtain the reference voltage;

[0071] The output terminal of the control module 42 is connected to the switch module 43 and is used to control the on / off state of the switch module 43 according to the detection signal and the reference voltage.

[0072] Therefore, through the cooperation between the differential pressure detection module 41, the control module 42 and the switching module 43, the switching module 43 can accurately switch on and off based on the real-time differential pressure between the output pins and the reference voltage of the step-down circuit 2, with high precision.

[0073] The differential pressure detection module 41, the control module 42, and the switch module 43 are described in detail below:

[0074] (1) Differential Pressure Detection Module

[0075] The differential pressure detection module 41 includes a rectifier bridge and an optocoupler. The rectifier bridge is connected to a corresponding set of output pins to rectify the output power between the output pins. The input of the optocoupler is connected to the rectifier bridge, and the output of the optocoupler is connected to the control module 42, which controls the on / off state of the output of the optocoupler according to the real-time differential pressure of the output power after rectification by the rectifier bridge.

[0076] As shown in Figure 2, in this embodiment, the differential pressure detection module 41 includes a third rectifier bridge BD3, a fourth rectifier bridge BD4, a tenth resistor R10, a twelfth resistor R12, a twenty-first resistor R21, a twenty-second resistor R22, a sixth capacitor C6, a twelfth capacitor C12, a first optocoupler U3, and a second optocoupler U4. Wherein:

[0077] One AC input terminal of the third rectifier bridge BD3 is connected to input port F1, and the other AC input terminal is connected to input port F2; one end of the sixth capacitor C6 is connected to the negative DC output terminal of the third rectifier bridge BD3, and the other end is connected to the positive DC output terminal of the third rectifier bridge BD3; the twelfth resistor R12 is connected in parallel with the sixth capacitor C6; the positive terminal of the emitter of the first optocoupler U3 is connected to the negative DC output terminal of the third rectifier bridge BD3 through the tenth resistor R10, the negative terminal of the emitter is connected to the positive DC output terminal of the third rectifier bridge BD3, the collector is connected to a real-time sampling terminal of the control module 42, and the emitter is grounded;

[0078] Similarly, one AC input terminal of the fourth rectifier bridge BD4 is connected to input port F3, and the other AC input terminal is connected to input port F4; one end of the twelfth capacitor C12 is connected to the negative DC output terminal of the fourth rectifier bridge BD4, and the other end is connected to the positive DC output terminal of the fourth rectifier bridge BD4; the twenty-second resistor R22 is connected in parallel with the twelfth capacitor C12; the positive terminal of the emitter of the second optocoupler U4 is connected to the negative DC output terminal of the fourth rectifier bridge BD4 through the twenty-first resistor R21, the negative terminal of the emitter is connected to the positive DC output terminal of the fourth rectifier bridge BD4, the collector is connected to another real-time sampling terminal of the real-time sampling terminal, and the emitter is grounded.

[0079] Therefore, through the cooperation between its components, the differential pressure detection module 41 can effectively detect the real-time differential pressure between its output pins, so as to flexibly control the on / off state of the optocoupler and thus output different detection signals to the control module 42.

[0080] (2) Control Module

[0081] In some embodiments, the control module 42 includes a second switch Q2 and a third switch Q3. The second switch Q2 is connected to a real-time sampling terminal and a reference sampling terminal of the control module 42, respectively. The second switch Q2 is used to adjust its on / off state according to the detection signal obtained by the real-time sampling terminal and the reference voltage obtained by the reference sampling terminal. The third switch Q3 is connected to another real-time sampling terminal of the control module 41 and the output terminal of the second switch Q2. It is used to adjust its on / off state according to the detection signal obtained by the other real-time sampling terminal and the output signal of the second switch Q2. The output terminal of the third switch Q3 is connected to the switch module 43. The on / off state of the third switch Q3 controls the on / off state of the switch module 43. The on / off state of the switch module 43 controls the working state of the LED circuit 3.

[0082] Furthermore, the control electrode of the second switch Q2 is connected to the output terminal of a differential pressure detection module 41 through a real-time sampling terminal, the first electrode of the second switch Q2 is connected to the output terminal of the step-down circuit 2 through a reference sampling terminal, and the second electrode of the second switch Q2 is connected to the first electrode of the third switch Q3; the control electrode of the third switch Q3 is connected to the output terminal of another differential pressure detection module 41 through another real-time sampling terminal, and the second electrode of the third switch Q3 is connected to the switch module 43.

[0083] As shown in Figure 2, in this embodiment, the control module 42 includes a second switch Q2, a third switch Q3, a forty-fourth resistor R44, and a forty-fifth resistor R45. The source of the second switch Q2 is connected to the step-down circuit 2, the gate of the second switch Q2 is connected to a differential voltage detection module 41, the drain of the second switch Q2 is connected to the source of the third switch Q3, the gate of the third switch Q3 is connected to another differential voltage detection module 41, and the drain of the third switch Q3 is connected to the switch module 43. One end of the forty-fourth resistor R44 is connected to the step-down circuit 2, and the other end is connected to the gate of the third switch Q3. One end of the forty-fifth resistor R45 is connected to the step-down circuit 2, and the other end is connected to the gate of the second switch Q2.

[0084] Therefore, when the second switch Q2 and the third switch Q3 are turned on, the switch module 43 is turned on, so that the power supply circuit 1, the LED circuit 3 and the detection circuit 4 form an LED circuit and the LED circuit 3 works; when the second switch Q2 and / or the third switch Q3 are turned off, the switch module 43 is turned off, so that the LED circuit 1 is disconnected from the detection circuit 4.

[0085] (3) Switching module

[0086] As shown in Figure 2, in this embodiment, the switch module 43 includes a first switch Q1. The control terminal of the first switch Q1 is connected to the output terminal of the control module 4. One terminal of the first switch Q1 is connected to the LED circuit 3, and the other terminal of the first switch Q1 is connected to the power supply circuit 1.

[0087] Therefore, when the first switch Q1 is turned on, the power supply circuit 1, the LED circuit 3 and the detection circuit 4 form an LED circuit and the LED circuit 3 works; when the first switch Q1 is turned off, the LED circuit 3 is disconnected from the detection circuit 4.

[0088] Furthermore, the detection circuit 4 also includes an anti-interference module 44, and the control module 42 and the switch module 43 are connected through the anti-interference module 44.

[0089] As shown in Figure 2, in this embodiment, the anti-interference module 44 includes a 30th resistor R30, a 32nd resistor R32, and an RC circuit (with a 33rd resistor R33 and a 13th capacitor C13 connected in parallel); the 30th resistor R30 is connected in series between the control module 42 and the switch module 43; one end of the 32nd resistor R32 is connected to the switch module 43, and the other end is connected to the power supply circuit (i.e., ground); one end of the RC circuit is connected to the control module 42, and the other end is connected to the power supply circuit (i.e., ground).

[0090] Therefore, the anti-interference module 44 can isolate the control module 42 from the switch module 43, avoid interference to the switch module 43, and improve the accuracy of the switch module 43.

[0091] The leakage current detection principle of the embodiment shown in Figure 2 is further described below:

[0092] 1. Connecting the ballast

[0093] When the ballast is connected, there is a real-time voltage difference between input ports F1 and F2. After the real-time voltage difference is rectified by the third rectifier bridge BD3, the current passes through the tenth resistor R10 to turn on the first optocoupler U3. At this time, the voltage of the collector C of the first optocoupler U3 is pulled to ground by the transistor, and the second switch Q2 is turned on.

[0094] Similarly, there is a real-time voltage difference between input ports F3 and F4. After the real-time voltage difference is rectified by the fourth rectifier bridge BD4, the current passes through the twenty-first resistor R21 to turn on the second optocoupler U4. At this time, the voltage of the collector E of the second optocoupler U4 is pulled to ground by the transistor, and the third switch Q3 is turned on.

[0095] Voltage enters the control terminal of the first switch Q1 through the second switch Q2 and the third switch Q3. At this time, the first switch Q1 is turned on, causing the output power of the power supply circuit 1 to flow sequentially from the negative DC output terminals of the first rectifier bridge BD1 and the second rectifier bridge BD2 through the first inductor L1, the LED module 31, and the first switch Q1, finally returning to the positive DC output terminals of the first rectifier bridge BD1 and the second rectifier bridge BD2, thus forming an LED circuit and lighting the LED module 31. At this time, the negative terminal of the LED module 31 is pulled to ground by the first switch Q1. The open-drain pin DRAIN of the driver chip U1 is essentially grounded, and the driver chip U1 does not meet the operating conditions and does not participate in operation.

[0096] When one end of the lamp tube detaches, there is no voltage difference between input ports F1 and F2, or F3 and F4. At this time, the second switch Q2 or the third switch Q3 will not conduct. Since one of them is not conducting, there is no voltage or current at the control terminal of the first switch Q1. The first switch Q1 is in the off state, thus cutting off the LED circuit. This makes it safe for installers to touch the other end, thus preventing leakage current.

[0097] II. Connecting to mains power

[0098] When connected to AC mains power, power supply circuit 1 can operate normally with either single-ended or double-ended inputs. When AC mains power is input to input ports F1 and F2, or F3 and F4, the input voltage depends on the actual design and can be wide voltage, narrow voltage, or single voltage, etc. The following explanation uses 220V / 50HZ to illustrate the working principle:

[0099] When connected to AC power, the voltage input path is through input ports F1 and F2, or input ports F3 and F4, or combinations of input ports F1, F2, F3, and F4 (e.g., input from F1 and F3, or F1 and F4, or F2 and F3, or F2 and F4). Regardless of the method, it is input through two pins. In this case, the second switch Q2 or the third switch Q3 is not conducting. Since one is not conducting, there is no voltage or current at the control electrode of the first switch Q1, and the first switch Q1 is in the off state. Thus, the first switch Q1 does not work, which does not affect the operation of the driver chip U1. The output power of the power supply circuit 1 flows from the negative DC output terminals of the first rectifier bridge BD1 and the second rectifier bridge BD2 through the first inductor L1, the LED module 31, the open-drain pin DRAIN, the driver chip U1, and the compiler pin ISP, and finally returns to the positive DC output terminals of the first rectifier bridge BD1 and the second rectifier bridge BD2 to form an LED circuit, so that the LED module 31 lights up normally.

[0100] At this time, when one of the input pins disconnects and comes into contact with a person, since the person's internal resistance is greater than 500Ω, it is equivalent to connecting a resistor to the detection pin REC of the driver chip U1. The current of the detection pin REC will decrease, changing the previous state of greater than 72mA to less than 72mA. At this time, the built-in switch of the open-drain pin DRAIN is turned off, which cuts off the LED circuit and plays the role of leakage protection.

[0101] In summary, the leakage current protection circuit of this invention uses the electrical signal between the output pins before rectification as the detection target, combines the real-time voltage difference between the output pins of the power supply end with the reference voltage, and uses the voltage difference factor as the judgment basis to achieve accurate leakage current detection from the perspective of voltage difference, which greatly improves the accuracy of detection. This effectively controls the on / off state of the LED circuit, plays a role in preventing leakage current, and ensures human safety. Furthermore, the leakage current protection circuit of this invention introduces control components such as switching transistors and optocouplers, realizing flexible switching of the circuit, thereby more accurately controlling the on / off state of the LED circuit with high accuracy.

[0102] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A leakage current protection circuit, characterized in that, Includes power supply circuit, step-down circuit, LED circuit and detection circuit; The input terminal of the power supply circuit is connected to the output pin of the power supply terminal, and the output terminal of the power supply circuit is connected to the input terminal of the step-down circuit and the input terminal of the LED circuit respectively, for rectifying the output power of the power supply terminal to output power to the step-down circuit and the LED circuit. The output terminal of the step-down circuit is connected to the detection circuit, and is used to step down the power supply output by the power supply circuit to output a reference voltage to the detection circuit. The detection circuit is connected to the output pin of the power supply terminal and the LED circuit respectively, and is used to control the working state of the LED circuit according to the real-time voltage difference between the output pins of the power supply terminal and the reference voltage output by the step-down circuit.

2. The leakage protection circuit as described in claim 1, characterized in that, The detection circuit includes two differential pressure detection modules, a control module, and a switch module. The control module has two real-time sampling terminals and one reference sampling terminal. The two sets of output pins of the differential pressure detection module, the real-time sampling terminal, and the power supply terminal correspond one-to-one. The differential pressure detection module is connected to a corresponding set of output pins to detect the real-time differential pressure between the corresponding set of output pins, and controls the detection signal output by the differential pressure detection module according to the real-time differential pressure. The real-time sampling terminal is connected to the corresponding differential pressure detection module to obtain the detection signal; The reference sampling terminal is connected to the output terminal of the step-down circuit to obtain the reference voltage; The output terminal of the control module is connected to the switch module and is used to control the on / off state of the switch module according to the detection signal and the reference voltage.

3. The leakage protection circuit as described in claim 2, characterized in that, The differential pressure detection module includes a rectifier bridge and an optocoupler; The rectifier bridge is connected to a corresponding set of output pins to rectify the output power between the output pins; The input terminal of the optocoupler is connected to the rectifier bridge, and the output terminal of the optocoupler is connected to the control module, which controls the on / off state of the output terminal of the optocoupler according to the real-time voltage difference of the output power supply after rectification by the rectifier bridge.

4. The leakage protection circuit as described in claim 2, characterized in that, The switching module includes a first switch, the control terminal of the first switch is connected to the output terminal of the control module, one terminal of the first switch is connected to the LED circuit, and the other terminal of the first switch is connected to the power supply circuit.

5. The leakage current protection circuit as described in claim 2, characterized in that, The control module includes a second switch and a third switch; The second switch is connected to a real-time sampling terminal and a reference sampling terminal of the control module, respectively. The second switch is used to adjust its on / off state according to the detection signal obtained by the real-time sampling terminal and the reference voltage obtained by the reference sampling terminal. The third switch is connected to another real-time sampling terminal of the control module and the output terminal of the second switch, and is used to adjust its on / off state according to the detection signal obtained by the other real-time sampling terminal and the output signal of the second switch. The output terminal of the third switch is connected to the switch module. The on / off state of the third switch controls the on / off state of the switch module, and the on / off state of the switch module controls the working state of the LED circuit.

6. The leakage current protection circuit as described in claim 5, characterized in that, When the second and third switches are turned on, the switch module is turned on, so that the power supply circuit, LED circuit and detection circuit form an LED circuit and the LED circuit works; When the second switch and / or the third switch are turned off, the switch module is disconnected, thereby disconnecting the LED circuit from the detection circuit.

7. The ballast leakage protection circuit compatible with mains power as described in claim 5, characterized in that, The control electrode of the second switch is connected to the output of a differential pressure detection module through a real-time sampling terminal; the first electrode of the second switch is connected to the output of a step-down circuit through a reference sampling terminal; and the second electrode of the second switch is connected to the first electrode of a third switch. The control electrode of the third switch is connected to the output terminal of another differential pressure detection module through another real-time sampling terminal, and the second electrode of the third switch is connected to the switch module.

8. The ballast-based leakage protection circuit as described in claim 2, characterized in that, The detection circuit further includes an anti-interference module, and the control module and the switch module are connected through the anti-interference module.

9. The leakage protection circuit as described in claim 1, characterized in that, The LED circuit includes a driver module and an LED module. The input terminal of the driver module is connected to the output terminal of the LED module, and is used to control the working state of the LED module according to the power supply. When the power supply circuit is connected to the ballast, the drive circuit does not work; When the power supply circuit is connected to the mains power, the drive circuit controls the on / off state between the drive module and the LED module according to the power supply, so as to control the working state of the LED circuit.

10. The leakage current protection circuit as described in claim 9, characterized in that, The driving module includes a driving chip, which has a detection pin and an open-drain pin, and the open-drain pin has a built-in switch. The detection pin is connected to the power supply circuit and is used to detect the power supply output by the power supply circuit. The open-drain pin is connected to the LED module, and the built-in switch switches the on / off state according to the power supply to control the on / off state between the driver module and the LED module.

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