An LED linear driving circuit and LED lighting circuit

Abstract

The application relates to the technical field of LED driving, and discloses an LED linear driving circuit and an LED lighting circuit, wherein the LED linear driving circuit comprises a rectifying unit, a filter capacitor C1, a power MOS tube Q1, a sampling resistor RCS, a clamping unit, a first resistor R1, a second resistor R2 and a control unit; in use, firstly, the LED linear driving circuit is provided with the clamping unit, the first resistor R1 and the second resistor R2, so that the current flowing through the power MOS tube Q1 can be reduced when an alternating voltage is input at the beginning or a high voltage such as a surge occurs; secondly, the second clamping unit can clamp the gate voltage of the power MOS tube Q1, so that the current flowing through the power MOS tube Q1 can be reduced when the surge occurs; and finally, the third resistor R3 is arranged, so that the current flowing through the power MOS tube Q1 rises when the surge occurs, at this moment, the voltage on the third resistor R3 also rises, and the increase of the gate-source voltage of the power MOS tube Q1 is offset.

Description

Technical Field

[0001] This invention relates to the field of LED driving technology, specifically to an LED linear driving circuit and an LED lighting circuit. Background Technology

[0002] LED linear drive technology is a commonly used LED constant current drive technology. Unlike the switching drive architecture, this technology adopts the linear voltage regulation constant current working principle, connects the power regulation device in series with the LED load, and dynamically adjusts the equivalent on-resistance of the power device through a closed-loop current sampling feedback mechanism, thereby achieving constant control of the LED operating current and ensuring stable and consistent LED brightness.

[0003] The existing LED linear drive architecture eliminates the need for energy storage components such as inductors and transformers, resulting in a simple overall circuit structure, fewer external components, a small PCB footprint, and low production costs. Furthermore, this drive method eliminates high-frequency switching, preventing high-frequency electromagnetic interference during operation. It exhibits extremely low current output ripple, effectively avoiding high-frequency flicker issues. It also boasts excellent electromagnetic compatibility, high operational stability, and a long service life, making it widely applicable in low-power lighting, backlighting displays, indicator lights, and simple civilian lighting equipment.

[0004] In existing LED linear drive circuits, MOSFETs, as the main power devices, are subjected to the impact of large voltage and large current at the moment of input voltage startup or input voltage surge. The instantaneous increase in energy often burns out the MOSFETs and causes the drive power supply to fail. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides an LED linear driving circuit and an LED lighting circuit. The technical problem to be solved is that the existing LED linear driving circuit lacks overvoltage and surge protection for power MOSFETs.

[0006] To solve the above technical problems, in a first aspect, the present invention provides the following technical solution: an LED linear driving circuit, comprising a rectifier unit, a filter capacitor C1, a power MOSFET Q1, a sampling resistor RCS, a clamping unit, a first resistor R1, a second resistor R2, and a control unit; the control unit includes a power supply terminal, a ground terminal, a control terminal, and a sampling terminal; The rectifier unit is used to rectify the input AC power and output DC voltage; The DC voltage output terminal of the rectifier unit is electrically connected to the power supply terminal of the control unit and one end of the filter capacitor C1, respectively; the other end of the filter capacitor C1 is electrically connected to the input terminal of the clamping unit and the drain of the power MOSFET Q1, respectively; the output terminal of the clamping unit is electrically connected to the sampling terminal of the control unit through the first resistor R1. The source of the power MOSFET Q1 is electrically connected to one end of the sampling resistor RCS and one end of the second resistor R2, respectively. The other end of the sampling resistor RCS is grounded, and the other end of the second resistor R2 is electrically connected to the sampling terminal of the control unit. The control terminal of the control unit is electrically connected to the gate of the power MOSFET Q1, and inputs a control signal to the gate of the power MOSFET Q1; the control unit adjusts the magnitude of the control signal output by the control terminal based on the voltage on the sampling resistor RCS; The grounding terminal of the control unit is grounded.

[0007] In one embodiment of the first aspect, the clamping unit includes a Zener diode ZD1; the cathode of the Zener diode ZD1 is the input terminal of the clamping unit and is electrically connected to the drain of the power MOSFET Q1; the anode of the Zener diode ZD1 is the output terminal of the clamping unit and is electrically connected to the first resistor R1.

[0008] In one embodiment of the first aspect, the rectifier unit includes rectifier diodes D1, D2, D3, and D4; The anode of the rectifier diode D1 is electrically connected to the cathode of the rectifier diode D4. The cathode of the rectifier diode D1 is electrically connected to the cathode of the rectifier diode D2, and is used to output DC voltage; The anode of rectifier diode D2 is electrically connected to the cathode of rectifier diode D3; the anode of rectifier diode D3 is electrically connected to the anode of rectifier diode D4 for grounding. The anodes of rectifier diode D1 and rectifier diode D2 are AC input interfaces.

[0009] In one embodiment of the first aspect, the control unit includes a driver chip U1 of model PM2014, pin 1 of the driver chip U1 is the sampling terminal, pin 3 of the driver chip U1 is the control terminal, pin 4 of the driver chip U1 is the ground terminal, and pin 5 of the driver chip U1 is the power supply terminal.

[0010] In one embodiment of the first aspect, the clamping voltage of the clamping unit is 130V, the resistance of the first resistor R1 is 180KΩ, and the resistance of the second resistor R2 is 10KΩ.

[0011] In one embodiment of the first aspect, the invention further includes a second clamping unit, wherein the gate of the power MOSFET Q1 is grounded through the second clamping unit.

[0012] In one embodiment of the first aspect, the second clamping unit includes a Zener diode ZD2, the cathode of which is electrically connected to the gate of a power MOSFET Q1, and the anode of which is grounded.

[0013] In one embodiment of the first aspect, the clamping voltage of the Zener diode ZD2 is between 6.0V and 6.4V.

[0014] In one embodiment of the first aspect, the present invention further includes a third resistor R3, wherein the source of the power MOSFET Q1 is electrically connected to one end of the third resistor R3, and the other end of the third resistor R3 is electrically connected to one end of the sampling resistor RCS.

[0015] Secondly, the present invention also provides an LED lighting circuit, including the above-mentioned LED linear driving circuit, and further including an LED lamp LED1, wherein the anode of the LED lamp LED1 is electrically connected to one end of a filter capacitor C1, and the cathode of the LED lamp LED1 is electrically connected to the other end of the filter capacitor C1.

[0016] The beneficial effects of this invention compared to the prior art are: Firstly, in actual use, by adding a clamping unit, a first resistor R1, and a second resistor R2, the current flowing through the power MOSFET Q1 can be reduced when the AC voltage is first input or when high voltage surges occur. Secondly, by adding a second clamping unit, the gate voltage of the power MOSFET Q1 can be clamped, thereby reducing the current flowing through the power MOSFET Q1 when a surge occurs. Finally, by setting the third resistor R3, when a surge occurs, the current flowing through the power MOSFET Q1 increases, and the voltage across the third resistor R3 also increases, offsetting the increase in the gate-source voltage of the power MOSFET Q1. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of an existing LED lighting circuit. Figure 2 for Figure 1 The waveforms of the current flowing through the power MOSFET Q1 and the voltage across the power MOSFET Q1 when the AC voltage is first applied to the circuit. Figure 3 This is a circuit diagram showing the LED linear drive circuit and the connection of the LED lamp in Example 1; Figure 4 for Figure 3 The circuit shown contains the current flowing through the power MOSFET Q1 and the voltage waveforms across the source and drain of the power MOSFET Q1 when in use. Figure 5 for Figure 3The circuit shown is subjected to a surge 90° test, and the relevant signal waveforms are shown. Figure 6 This is a circuit diagram showing the LED linear drive circuit and the connection of the LED lamp in Example 2; Figure 7 for Figure 6 The circuit shown is subjected to a 90° surge test, and the relevant signal waveforms are shown. Figure 8 This is a circuit diagram showing the LED linear drive circuit and the connection of the LED lamp in Example 3; Figure 9 for Figure 8 The circuit shown is subjected to a surge 90° test, and the relevant signal waveforms are shown. Detailed Implementation

[0018] The illustrative embodiments of this application include, but are not limited to, an LED linear driving circuit and an LED lighting circuit.

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0020] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items. Words such as “comprising” or “including” mean that the element or object preceding “comprising” or “including” covers the element or object listed following “comprising” or “including” and its equivalents, and does not exclude other elements or objects. Words such as “connected” or “linked” are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect.

[0021] Example 1 Figure 1 This is an existing LED lighting circuit. Figure 1 When the circuit is powered on and connected to AC power, due to the presence of capacitor C1, capacitor C1 is essentially short-circuited at the moment of power-on. The rectified voltage is directly applied across MOSFET Q1. At this time, MOSFET Q1 simultaneously experiences a large voltage and a large current. The voltage waveform across MOSFET Q1 and the current waveform flowing through it are as follows: Figure 2 As shown.

[0022] exist Figure 2 In the first cycle, the voltage across MOSFET Q1 is equal to the rectified voltage after the rectifier bridge. As current flows through capacitor C1, the voltage across capacitor C1 begins to rise, so the voltage across MOSFET Q1 will decrease slightly in the second cycle. However, the voltage and current flowing through MOSFET Q1 in the previous few cycles are sufficient to cause MOSFET Q1 to fail due to overheating.

[0023] In addition, Figure 2 In the diagram, t0 is the point where the voltage is 0, the chip is not working, so there is no current in MOSFET Q1. t1 is the voltage when the voltage reaches the VI operating point, and current starts flowing through MOSFET Q1. The current of MOSFET Q1 is determined by VCS / RCS.

[0024] To provide surge high voltage protection for power MOSFET Q1, such as Figure 3 As shown, this embodiment provides an LED linear driving circuit, including a rectifier unit 1, a filter capacitor C1, a power MOSFET Q1, a sampling resistor RCS, a clamping unit 2, a first resistor R1, a second resistor R2, and a control unit 3; the control unit 3 includes a power supply terminal, a ground terminal, a control terminal, and a sampling terminal; The rectifier unit 1 is used to rectify the input AC power and output DC voltage; The DC voltage output terminal of rectifier unit 1 is electrically connected to the power supply terminal of control unit 3 and one end of filter capacitor C1, respectively; the other end of filter capacitor C1 is electrically connected to the input terminal of clamping unit 2 and the drain of power MOSFET Q1, respectively; the output terminal of clamping unit 2 is electrically connected to the sampling terminal of control unit 3 through first resistor R1. The source of power MOSFET Q1 is electrically connected to one end of sampling resistor RCS and one end of second resistor R2, respectively. The other end of sampling resistor RCS is grounded, and the other end of second resistor R2 is electrically connected to the sampling terminal of control unit 3. The control terminal of the control unit 3 is electrically connected to the gate of the power MOSFET Q1, and inputs a control signal to the gate of the power MOSFET Q1; the control unit 3 adjusts the magnitude of the control signal output from the control terminal based on the voltage on the sampling resistor RCS; The grounding terminal of control unit 3 is grounded.

[0025] Specifically, in this embodiment, in Figure 3 In the clamping unit 2, there is a Zener diode ZD1; the cathode of the Zener diode ZD1 is the input terminal of the clamping unit 2 and is electrically connected to the drain of the power MOSFET Q1; the anode of the Zener diode ZD1 is the output terminal of the clamping unit 2 and is electrically connected to the first resistor R1.

[0026] Specifically, in this embodiment, in Figure 3 In the circuit, rectifier unit 1 is a full-wave rectifier circuit, including rectifier diodes D1, D2, D3 and D4; The anode of rectifier diode D1 is electrically connected to the cathode of rectifier diode D4; The cathode of rectifier diode D1 is electrically connected to the cathode of rectifier diode D2 to output DC voltage; The anode of rectifier diode D2 is electrically connected to the cathode of rectifier diode D3; the anode of rectifier diode D3 is electrically connected to the anode of rectifier diode D4 for grounding. The anodes of rectifier diode D1 and rectifier diode D2 are AC input interfaces.

[0027] Specifically, in this embodiment, in Figure 3 In the control unit, there is a driver chip U1 with model number PM2014. The first pin of the driver chip U1 is the sampling terminal, the third pin of the driver chip U1 is the control terminal, the fourth pin of the driver chip U1 is the ground terminal, and the fifth pin of the driver chip U1 is the power supply terminal.

[0028] Additionally, it should be noted that the solution in this embodiment provides surge overvoltage protection and overcurrent protection for the power MOSFET Q1. In some implementations, other driver chips or other constant current drive circuits can be selected according to actual needs; this is not a limitation.

[0029] In this embodiment, the filter capacitor C1 can be an electrolytic capacitor, i.e., the filter capacitor C1 has positive and negative terminals. The positive terminal of the filter capacitor C1 is electrically connected to the DC voltage output terminal of the rectifier unit 1, and the negative terminal of the filter capacitor C1 is electrically connected to the drain of the power MOSFET Q1.

[0030] for Figure 3 In the circuit shown, the Zener diode ZD1 activates only when the drain voltage of the power MOSFET Q1 exceeds a certain value. Under normal application, there is already a certain voltage at the drain of the power MOSFET Q1, so the Zener diode ZD1 will not activate. The first resistor R1 and the second resistor R2 are voltage divider and current-limiting resistors, which allow for more precise control of the circuit's turn-off point.

[0031] In this embodiment, the clamping voltage of the Zener diode ZD1 is related to the maximum ground potential of the drain of the power MOSFET Q1. The greater the maximum ground potential of the drain of the power MOSFET Q1, the greater the clamping voltage of the Zener diode ZD1. For example, the clamping voltage of the Zener diode ZD1 can be 130V.

[0032] right Figure 3 The circuit shown was tested under the following conditions: The normal input voltage of rectifier unit 1 is 230V, and the maximum input voltage is 264V; the LED voltage of LED1 is 270V; the gate-source voltage (VCS) of power MOSFET Q1 is 0.5V; the clamping voltage of Zener diode ZD1 is 130V; the resistance of the first resistor R1 is 180KΩ; and the resistance of the second resistor R2 is 10KΩ.

[0033] The waveforms of the source-drain voltage and the current flowing through the power MOSFET Q1 are as follows: Figure 4 As shown, from Figure 4 As can be seen, when AC voltage is first applied, and the voltage across power MOSFET Q1 is greater than V1, the current flowing through power MOSFET Q1 is 0, thus preventing excessive current from flowing into power MOSFET Q1 and achieving protection. It remains unaffected during normal operation.

[0034] In summary, the LED linear drive circuit in this embodiment, by adding clamping unit 2, first resistor R1 and second resistor R2, can reduce the current flowing through power MOSFET Q1 when AC voltage is first input or when high voltage surges occur, thereby reducing losses and preventing damage to power MOSFET Q1.

[0035] Example 2 for Figure 3 The circuit shown can solve the problem of excessive power loss and damage to the power MOSFET Q1 caused by capacitor C1 when AC power is connected and the device is turned on. However, its surge performance in IEC61000-4-5 is very poor. This is because the surge pulse width is very narrow, and the sudden voltage change causes the drain voltage of the power MOSFET Q1 to rise to its maximum value within a few µs. Due to the presence of the MOSFET Miller capacitance, the gate of the power MOSFET Q1 is synchronously charged high, and the sudden increase in gate voltage causes the current flowing through the power MOSFET Q1 to increase sharply.

[0036] in Figure 5 This is a waveform diagram of the relevant signals during a 90-degree surge test. Figure 5 The purple color represents the drain-to-ground voltage of power MOSFET Q1; the blue color represents the gate voltage of power MOSFET Q1; the yellow color represents the RCS voltage of the sampling resistor; during a surge, the gate voltage of power MOSFET Q1 is charged from approximately 4.2V to 8.5V; the peak CS voltage is charged from 0.5V to 2.68V.

[0037] Since the current flowing through the power MOSFET Q1 is proportional to the square of its gate voltage, when the gate voltage of the power MOSFET Q1 increases, the current flowing through the power MOSFET Q1 will increase sharply. In order to avoid the abnormal increase in the current flowing through the power MOSFET Q1 due to abnormal reasons, it is necessary to clamp the maximum value of the gate voltage of the power MOSFET Q1.

[0038] Based on the above considerations, such as Figure 6 As shown, this embodiment provides another LED linear driving circuit, including a rectifier unit 1, a filter capacitor C1, a power MOSFET Q1, a sampling resistor RCS, a clamping unit 2, a first resistor R1, a second resistor R2, a control unit 3, and a second clamping unit 4; the control unit 3 includes a power supply terminal, a ground terminal, a control terminal, and a sampling terminal; The rectifier unit 1 is used to rectify the input AC power and output DC voltage; The DC voltage output terminal of rectifier unit 1 is electrically connected to the power supply terminal of control unit 3 and one end of filter capacitor C1, respectively; the other end of filter capacitor C1 is electrically connected to the input terminal of clamping unit 2 and the drain of power MOSFET Q1, respectively; the output terminal of clamping unit 2 is electrically connected to the sampling terminal of control unit 3 through first resistor R1. The source of power MOSFET Q1 is electrically connected to one end of sampling resistor RCS and one end of second resistor R2, respectively. The other end of sampling resistor RCS is grounded, and the other end of second resistor R2 is electrically connected to the sampling terminal of control unit 3. The control terminal of the control unit 3 is electrically connected to the gate of the power MOSFET Q1, and inputs a control signal to the gate of the power MOSFET Q1; the control unit 3 adjusts the magnitude of the control signal output from the control terminal based on the voltage on the sampling resistor RCS; The grounding terminal of control unit 3 is grounded; The gate of the power MOSFET Q1 is grounded through the second clamping unit 4.

[0039] Specifically, in this embodiment, in Figure 6 In the clamping unit 2, there is a Zener diode ZD1; the cathode of the Zener diode ZD1 is the input terminal of the clamping unit 2 and is electrically connected to the drain of the power MOSFET Q1; the anode of the Zener diode ZD1 is the output terminal of the clamping unit 2 and is electrically connected to the first resistor R1.

[0040] Specifically, in this embodiment, in Figure 6 In the circuit, rectifier unit 1 is a full-wave rectifier circuit, including rectifier diodes D1, D2, D3 and D4; The anode of rectifier diode D1 is electrically connected to the cathode of rectifier diode D4; The cathode of rectifier diode D1 is electrically connected to the cathode of rectifier diode D2 to output DC voltage; The anode of rectifier diode D2 is electrically connected to the cathode of rectifier diode D3; the anode of rectifier diode D3 is electrically connected to the anode of rectifier diode D4 for grounding. The anodes of rectifier diode D1 and rectifier diode D2 are AC input interfaces.

[0041] Specifically, in this embodiment, in Figure 6 In the control unit, there is a driver chip U1 with model number PM2014. The first pin of the driver chip U1 is the sampling terminal, the third pin of the driver chip U1 is the control terminal, the fourth pin of the driver chip U1 is the ground terminal, and the fifth pin of the driver chip U1 is the power supply terminal.

[0042] Additionally, it should be noted that the solution in this embodiment provides surge overvoltage protection and overcurrent protection for the power MOSFET Q1. In some implementations, other driver chips or other constant current drive circuits can be selected according to actual needs; this is not a limitation.

[0043] In this embodiment, the filter capacitor C1 can be an electrolytic capacitor, i.e., the filter capacitor C1 has positive and negative terminals. The positive terminal of the filter capacitor C1 is electrically connected to the DC voltage output terminal of the rectifier unit 1, and the negative terminal of the filter capacitor C1 is electrically connected to the drain of the power MOSFET Q1.

[0044] Specifically, in this embodiment, in Figure 6 In the second clamping unit 4, there is a Zener diode ZD2. The cathode of the Zener diode ZD2 is electrically connected to the gate of the power MOSFET Q1, and the anode of the Zener diode ZD2 is grounded.

[0045] Furthermore, in this embodiment, the clamping voltage of the Zener diode ZD2 is between 6.0V and 6.4V.

[0046] for Figure 6 In the circuit shown, the Zener diode ZD1 activates only when the drain voltage of the power MOSFET Q1 exceeds a certain value. Under normal operating conditions, the drain of the power MOSFET Q1 already has a certain voltage, so the Zener diode ZD1 will not activate. The first resistor R1 and the second resistor R2 are voltage divider and current-limiting resistors, allowing for more precise control of the circuit's turn-off point. The Zener diode ZD2 clamps the gate voltage of the power MOSFET Q1 to 6.3V during surges.

[0047] right Figure 6 The circuit shown underwent a 90° surge test. The test environment was as follows: the normal input voltage of rectifier unit 1 was 230V, and the maximum input voltage was 264V; the LED1's bead voltage was 270V; the gate-source voltage (VCS) of power MOSFET Q1 was 0.5V; the clamping voltage of Zener diode ZD1 was 130V; the resistance of the first resistor R1 was 180KΩ; the resistance of the second resistor R2 was 10KΩ; and the clamping voltage of Zener diode ZD2 was 6.2V.

[0048] The relevant test signal waveforms are shown below. Figure 7 As shown, from Figure 7It can be seen that the gate voltage of the power MOSFET Q1 is less than 5V during normal operation, so it does not affect normal operation; when a surge occurs, the gate voltage of MOSFET Q1 is clamped to 6.3V, and the peak CS voltage of the gate of MOSFET Q1 is reduced to 1.27V, proving that the Zener diode ZD2 is effective.

[0049] In summary, the LED linear drive circuit in this embodiment, when used in actual application, can reduce the current flowing through the power MOSFET Q1 by adding clamping unit 2, first resistor R1 and second resistor R2, when AC voltage is first input or when high voltage surges occur. Secondly, by adding a second clamping unit 4, the gate voltage of the power MOSFET Q1 can be clamped, thereby reducing the current flowing through the power MOSFET Q1 when a surge occurs.

[0050] Example 3 for Figure 6 The circuit shown can reduce the current flowing through the power MOSFET Q1 when a surge occurs by clamping the gate voltage of the power MOSFET Q1 through the second clamping unit 4, but the current flowing through the power MOSFET Q1 is still too large.

[0051] To further reduce the current flowing through the power MOSFET Q1 during a surge, such as Figure 8 As shown, this embodiment also provides another LED linear driving circuit, including a rectifier unit 1, a filter capacitor C1, a power MOSFET Q1, a sampling resistor RCS, a clamping unit 2, a first resistor R1, a second resistor R2, a third resistor R3, a control unit 3, and a second clamping unit 4; the control unit 3 includes a power supply terminal, a ground terminal, a control terminal, and a sampling terminal; The rectifier unit 1 is used to rectify the input AC power and output DC voltage; The DC voltage output terminal of rectifier unit 1 is electrically connected to the power supply terminal of control unit 3 and one end of filter capacitor C1, respectively; the other end of filter capacitor C1 is electrically connected to the input terminal of clamping unit 2 and the drain of power MOSFET Q1, respectively; the output terminal of clamping unit 2 is electrically connected to the sampling terminal of control unit 3 through first resistor R1. The source of power MOSFET Q1 is electrically connected to one end of the third resistor R3. The other end of the third resistor R3 is electrically connected to one end of the sampling resistor RCS and one end of the second resistor R2. The other end of the sampling resistor RCS is grounded, and the other end of the second resistor R2 is electrically connected to the sampling terminal of the control unit 3. The control terminal of the control unit 3 is electrically connected to the gate of the power MOSFET Q1, and inputs a control signal to the gate of the power MOSFET Q1; the control unit 3 adjusts the magnitude of the control signal output from the control terminal based on the voltage on the sampling resistor RCS; The grounding terminal of control unit 3 is grounded; The gate of the power MOSFET Q1 is grounded through the second clamping unit 4.

[0052] Specifically, in this embodiment, in Figure 8 In the clamping unit 2, there is a Zener diode ZD1; the cathode of the Zener diode ZD1 is the input terminal of the clamping unit 2 and is electrically connected to the drain of the power MOSFET Q1; the anode of the Zener diode ZD1 is the output terminal of the clamping unit 2 and is electrically connected to the first resistor R1.

[0053] Specifically, in this embodiment, in Figure 8 In the circuit, rectifier unit 1 is a full-wave rectifier circuit, including rectifier diodes D1, D2, D3 and D4; The anode of rectifier diode D1 is electrically connected to the cathode of rectifier diode D4; The cathode of rectifier diode D1 is electrically connected to the cathode of rectifier diode D2 to output DC voltage; The anode of rectifier diode D2 is electrically connected to the cathode of rectifier diode D3; the anode of rectifier diode D3 is electrically connected to the anode of rectifier diode D4 for grounding. The anodes of rectifier diode D1 and rectifier diode D2 are AC input interfaces.

[0054] Specifically, in this embodiment, in Figure 8 In the control unit, there is a driver chip U1 with model number PM2014. The first pin of the driver chip U1 is the sampling terminal, the third pin of the driver chip U1 is the control terminal, the fourth pin of the driver chip U1 is the ground terminal, and the fifth pin of the driver chip U1 is the power supply terminal.

[0055] Additionally, it should be noted that the solution in this embodiment provides surge overvoltage protection and overcurrent protection for the power MOSFET Q1. In some implementations, other driver chips or other constant current drive circuits can be selected according to actual needs; this is not a limitation.

[0056] In this embodiment, the filter capacitor C1 can be an electrolytic capacitor, i.e., the filter capacitor C1 has positive and negative terminals. The positive terminal of the filter capacitor C1 is electrically connected to the DC voltage output terminal of the rectifier unit 1, and the negative terminal of the filter capacitor C1 is electrically connected to the drain of the power MOSFET Q1.

[0057] Specifically, in this embodiment, in Figure 8 In the second clamping unit 4, there is a Zener diode ZD2. The cathode of the Zener diode ZD2 is electrically connected to the gate of the power MOSFET Q1, and the anode of the Zener diode ZD2 is grounded.

[0058] Furthermore, in this embodiment, the clamping voltage of the Zener diode ZD2 is between 6.0V and 6.4V.

[0059] for Figure 8 In the circuit shown, the Zener diode ZD1 activates only when the drain voltage of the power MOSFET Q1 exceeds a certain value. Under normal operating conditions, a certain drain voltage already exists at Q1, preventing ZD1 from activating. The first resistor R1 and the second resistor R2 are voltage divider and current-limiting resistors, allowing for more precise control of the circuit's turn-off point. Zener diode ZD2 clamps the gate voltage of the power MOSFET Q1 to 6.3V during surges. The third resistor R3 reduces the drain-source voltage of the power MOSFET Q1.

[0060] Figure 8 The process by which the circuit reduces the drain-source voltage of the power MOSFET Q1 is as follows: After the gate voltage of power MOSFET Q1 rises abnormally, the current flowing through power MOSFET Q1 increases. At the same time, the voltage flowing through the third resistor R3 also increases synchronously. According to the series voltage divider principle, the voltage across the third resistor R3 increases, and the drain-source voltage of power MOSFET Q1 decreases, which can offset part of the effect caused by the rise in the gate voltage of power MOSFET Q1.

[0061] right Figure 8 The circuit shown underwent a 90° surge test. The test environment was as follows: the normal input voltage of rectifier unit 1 was 230V, and the maximum input voltage was 264V; the LED1's bead voltage was 270V; the gate-source voltage (VCS) of power MOSFET Q1 was 0.5V; the clamping voltage of Zener diode ZD1 was 130V; the resistance of the first resistor R1 was 180KΩ; the resistance of the second resistor R2 was 10KΩ; and the clamping voltage of Zener diode ZD2 was 6.2V.

[0062] The relevant test signal waveforms are shown below. Figure 9 As shown, from Figure 9 As can be seen, when a surge occurs, the gate voltage of power MOSFET Q1 is clamped to 6.2V, and the current flowing through power MOSFET Q1 increases. This increase in current causes the voltage across the third resistor R3 to rise, offsetting the effect of the increased gate voltage of power MOSFET Q1. The third resistor R3 is not involved in the output current calculation during normal operation; the peak current flowing through power MOSFET Q1 is still determined by VCS / RCS.

[0063] In summary, in actual use, the LED linear drive circuit in this embodiment can reduce the current flowing through the power MOSFET Q1 when the AC voltage is first input or when high voltage surges occur by adding clamping unit 2, first resistor R1 and second resistor R2. Secondly, by adding a second clamping unit 2, the gate voltage of the power MOSFET Q1 can be clamped, thereby reducing the current flowing through the power MOSFET Q1 when a surge occurs. Finally, by setting the third resistor R3, when a surge occurs, the current flowing through the power MOSFET Q1 increases, and the voltage across the third resistor R3 also increases, offsetting the increase in the gate-source voltage of the power MOSFET Q1.

[0064] Example 4 This embodiment provides an LED lighting circuit, which can be... Figure 3 , Figure 6 or Figure 8 Any one of the circuits mentioned above. Additionally... Figure 3 , Figure 6 or Figure 8 After removing LED1, the circuit becomes an LED linear drive circuit. The anode of LED1 is electrically connected to one end of the filter capacitor C1, and the cathode of LED1 is electrically connected to the other end of the filter capacitor C1. Alternatively, the filter capacitor C1 can be an electrolytic capacitor, meaning it has positive and negative terminals. The positive terminal of the filter capacitor C1 is electrically connected to the DC voltage output terminal of rectifier unit 1, and the negative terminal of the filter capacitor C1 is electrically connected to the drain of power MOSFET Q1.

[0065] In the LED lighting circuit of this embodiment, by employing at least one of the following measures—clamping the drain of the power MOSFET Q1, clamping the gate voltage of the power MOSFET Q1, and clamping the source-drain voltage of the power MOSFET Q1—excessive current flowing through the power MOSFET Q1 can be avoided during surges, thereby reducing losses and protecting the power MOSFET Q1.

[0066] Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An LED linear driving circuit, characterized in that, It includes a rectifier unit, a filter capacitor C1, a power MOSFET Q1, a sampling resistor RCS, a clamping unit, a first resistor R1, a second resistor R2, and a control unit; the control unit includes a power supply terminal, a ground terminal, a control terminal, and a sampling terminal; The rectifier unit is used to rectify the input AC power and output DC voltage; The DC voltage output terminal of the rectifier unit is electrically connected to the power supply terminal of the control unit and one end of the filter capacitor C1, respectively; the other end of the filter capacitor C1 is electrically connected to the input terminal of the clamping unit and the drain of the power MOSFET Q1, respectively; the output terminal of the clamping unit is electrically connected to the sampling terminal of the control unit through the first resistor R1. The source of the power MOSFET Q1 is electrically connected to one end of the sampling resistor RCS and one end of the second resistor R2, respectively. The other end of the sampling resistor RCS is grounded, and the other end of the second resistor R2 is electrically connected to the sampling terminal of the control unit. The control terminal of the control unit is electrically connected to the gate of the power MOSFET Q1, and inputs a control signal to the gate of the power MOSFET Q1; the control unit adjusts the magnitude of the control signal output by the control terminal based on the voltage on the sampling resistor RCS; The grounding terminal of the control unit is grounded.

2. The LED linear driving circuit according to claim 1, characterized in that, The clamping unit includes a Zener diode ZD1; the cathode of the Zener diode ZD1 is the input terminal of the clamping unit and is electrically connected to the drain of the power MOSFET Q1; the anode of the Zener diode ZD1 is the output terminal of the clamping unit and is electrically connected to the first resistor R1.

3. The LED linear driving circuit according to claim 1, characterized in that, The rectifier unit includes rectifier diodes D1, D2, D3, and D4; The anode of the rectifier diode D1 is electrically connected to the cathode of the rectifier diode D4. The cathode of the rectifier diode D1 is electrically connected to the cathode of the rectifier diode D2, and is used to output DC voltage; The anode of rectifier diode D2 is electrically connected to the cathode of rectifier diode D3; the anode of rectifier diode D3 is electrically connected to the anode of rectifier diode D4 for grounding. The anodes of rectifier diode D1 and rectifier diode D2 are AC input interfaces.

4. The LED linear driving circuit according to claim 1, characterized in that, The control unit includes a driver chip U1 with model number PM2014. Pin 1 of the driver chip U1 is the sampling terminal, pin 3 of the driver chip U1 is the control terminal, pin 4 of the driver chip U1 is the ground terminal, and pin 5 of the driver chip U1 is the power supply terminal.

5. The LED linear driving circuit according to claim 1, characterized in that, The clamping voltage of the clamping unit is 130V, the resistance of the first resistor R1 is 180KΩ, and the resistance of the second resistor R2 is 10KΩ.

6. An LED linear driving circuit according to any one of claims 1-5, characterized in that, It also includes a second clamping unit, through which the gate of the power MOSFET Q1 is grounded.

7. The LED linear driving circuit according to claim 6, characterized in that, The second clamping unit includes a Zener diode ZD2, the cathode of which is electrically connected to the gate of the power MOSFET Q1, and the anode of which is grounded.

8. The LED linear driving circuit according to claim 7, characterized in that, The clamping voltage of the Zener diode ZD2 is between 6.0V and 6.4V.

9. The LED linear driving circuit according to claim 7, characterized in that, It also includes a third resistor R3, the source of the power MOSFET Q1 is electrically connected to one end of the third resistor R3, and the other end of the third resistor R3 is electrically connected to one end of the sampling resistor RCS.

10. An LED lighting circuit, characterized in that, The LED linear driving circuit according to any one of claims 1-9 further includes an LED lamp LED1, wherein the anode of the LED lamp LED1 is electrically connected to one end of the filter capacitor C1, and the cathode of the LED lamp LED1 is electrically connected to the other end of the filter capacitor C1.

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