Active LED afterglow removing circuit

Abstract

The utility model particularly relates to an active LED afterglow removing circuit, which comprises a VIN end, a grounding end GND, a light emitting diode LED1, a first field effect transistor Q1, a second field effect transistor Q2 and an ON / OFF control end, and is characterized in that the VIN end is connected to one end of a third resistor R3; the cathode of the LED 1 is connected with the pin 3 of the second field effect transistor Q2; a pin 1 of the second field effect transistor Q2 is connected to a pin 2 of the first field effect transistor Q1; a pin 3 of the first field effect transistor Q1 is connected with a grounding end GND; the first pin of the first field effect transistor Q1 is connected with an ON / OFF control end, a first capacitor C1 and a voltage stabilizing diode Z1 are connected between the first pin and the third pin of the second field effect transistor Q2 in parallel, the afterglow phenomenon is thoroughly eliminated through an active discharge mechanism, and the problems that a traditional passive scheme is delayed in response and high in cost are solved. The circuit is simple in structure and high in compatibility, and has the advantages of low cost and high reliability.

Description

Technical Field

[0001] This utility model relates to the field of LED driver circuit technology, specifically an active LED afterglow reduction circuit. Background Technology

[0002] In non-isolated LED driver circuits, AC coupling paths easily form between the LED chip and the housing or heat dissipation structure. When the LED is turned off, a small current generated by the coupling capacitor or parasitic inductance still flows through the LED, causing the chip to emit weak light (i.e., "afterglow"), which seriously affects the user experience. Current technologies often suppress coupling current by adding isolation transformers or using high-impedance components, but these methods suffer from high cost, circuit complexity, or slow response speed. For example, existing solutions using isolation transformers increase cost by about 30% and have a response time exceeding 50ms, resulting in a significant degraded user experience. While high-impedance components are cheaper, they cannot completely eliminate low-frequency coupling current, and the afterglow phenomenon persists. Therefore, there is an urgent need for a solution that is simple in structure, low in cost, and can actively discharge residual current. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one objective of the present invention is to provide an active LED afterglow elimination circuit that, by introducing a controllable discharge circuit, rapidly releases residual voltage and current after the LED is turned off, thereby completely eliminating the afterglow phenomenon.

[0004] According to the present invention, an active LED afterglow reduction circuit includes: a VIN terminal, a ground terminal GND, a light-emitting diode LED1, a first field-effect transistor Q1, a second field-effect transistor Q2, and an ON / OFF control terminal. The VIN terminal is connected to one end of a third resistor R3. The VIN terminal is also connected to the anode of the light-emitting diode LED1. The cathode of the light-emitting diode LED1 is connected to pin 3 of the second field-effect transistor Q2. Pin 1 of the second field-effect transistor Q2 is connected to pin 2 of the first field-effect transistor Q1. Pin 3 of the first field-effect transistor Q1 is connected to the ground terminal GND. Pin 1 of the first field-effect transistor Q1 is connected to the ON / OFF control terminal. A first capacitor C1 and a Zener diode Z1 are connected in parallel between pins 1 and 3 of the second field-effect transistor Q2.

[0005] Specifically, the Zener diode Z1 has a Zener voltage that is less than the maximum withstand voltage of pin 1 of the second field-effect transistor Q2, or the Zener diode Z1 has a Zener voltage that is equal to the maximum withstand voltage of pin 1 of the second field-effect transistor Q2.

[0006] Furthermore, a fourth resistor R4 is connected between the VIN terminal and pin 1 of the second field-effect transistor Q2. The resistance value of the fourth resistor R4 is in the range of 10kΩ-100kΩ, which is used to limit the charging current of the first capacitor C1.

[0007] Specifically, the capacitance of the first capacitor C1 is 0.1μF-10μF, which is used to provide a delay time for turning on the second field-effect transistor Q2 when the first field-effect transistor Q1 is turned off.

[0008] Specifically, the second field-effect transistor Q2 is an N-channel enhancement-mode MOSFET, and the turn-on threshold voltage of the second field-effect transistor Q2 is lower than the Zener diode Z1's Zener voltage.

[0009] Specifically, the resistance of the third resistor R3 is 1kΩ-10kΩ, and it is used for the driving voltage of the second field-effect transistor Q2.

[0010] Specifically, pin 1 of the first field-effect transistor Q1 is connected to the ON / OFF control terminal through a first resistor R1. The resistance value of the first resistor R1 is in the range of 1kΩ-100kΩ and is used to control the switching state of the first field-effect transistor Q1.

[0011] Specifically, pins 1 and 3 of the first field-effect transistor Q1 are connected to a second resistor R2, the resistance of which is in the range of 1kΩ-100kΩ.

[0012] Specifically, the reverse breakdown voltage of the Zener diode Z1 is 5V-20V, which is used to clamp the cathode voltage of the light-emitting diode LED1.

[0013] The beneficial effects of this utility model are as follows.

[0014] First, by rapidly discharging residual current through the conduction of the second field-effect transistor Q2, the response delay of traditional passive solutions is avoided, thus playing the role of active discharge.

[0015] 2. Zener diode Z1 prevents overvoltage at pin 1 of the second field-effect transistor Q2 and limits the cathode voltage of LED1, protecting the components and providing voltage clamping protection.

[0016] Third, it is composed of a first field-effect transistor Q1 and a second field-effect transistor Q2, which is suitable for various low-power LED driving scenarios, and has the advantages of low cost and high compatibility. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings.

[0018] Figure 1 This is the circuit diagram of this utility model. Detailed Implementation

[0019] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0020] The following is for reference. Figure 1 This invention discloses an active LED afterglow reduction circuit, comprising: a VIN terminal, a ground terminal GND, a light-emitting diode LED1, a first field-effect transistor Q1, a second field-effect transistor Q2, and an ON / OFF control terminal. The VIN terminal is connected to one end of a third resistor R3. The VIN terminal is also connected to the anode of the light-emitting diode LED1, and the cathode of the light-emitting diode LED1 is connected to pin 3 of the second field-effect transistor Q2. Pin 1 of the second field-effect transistor Q2 is connected to pin 2 of the first field-effect transistor Q1. Pin 3 of the first field-effect transistor Q1 is connected to the ground terminal GND. The ON / OFF control terminal is connected to pin 1 of the first field-effect transistor Q1. A first capacitor C1 and a Zener diode Z1 are connected in parallel between pins 1 and 3 of the second field-effect transistor Q2.

[0021] Specifically, the Zener diode Z1 has a Zener voltage that is less than the maximum withstand voltage of pin 1 of the second field-effect transistor Q2, or the Zener diode Z1 has a Zener voltage that is equal to the maximum withstand voltage of pin 1 of the second field-effect transistor Q2.

[0022] A fourth resistor R4, with a resistance range of 10kΩ-100kΩ, is connected between the VIN terminal and pin 1 of the second field-effect transistor Q2. This resistor limits the charging current of the first capacitor C1. The first capacitor C1 has a capacitance of 0.1μF-10μF and provides a delay time for turning on the second field-effect transistor Q2 when the first field-effect transistor Q1 is off. The second field-effect transistor Q2 is an N-channel enhancement-mode MOSFET, and its turn-on threshold voltage is lower than the Zener diode Z1's voltage regulation value. The third resistor R3, with a resistance range of 1kΩ-10kΩ, provides the driving voltage for the second field-effect transistor Q2. Pin 1 of the first field-effect transistor Q1 is connected to the ON / OFF control terminal via the first resistor R1, which has a resistance range of 1kΩ-100kΩ, and is used to control the switching state of the first field-effect transistor Q1. A second resistor R2 is connected to pins 1 and 3 of the first field-effect transistor Q1. The resistance value of the second resistor R2 ranges from 1kΩ to 100kΩ. The reverse breakdown voltage of the Zener diode Z1 is 5V-20V, and it is used to clamp the cathode voltage of the light-emitting diode LED1.

[0023] The resistance value of the fourth resistor, R4, ranges from 10kΩ to 100kΩ, determined by the formula: I = Vin divided by (R4 + R3), where VIN is the input voltage and R3 has a resistance value of 1kΩ to 10kΩ. This range ensures that the charging current does not exceed the rated value of C1 while providing sufficient delay time.

[0024] This utility model is further illustrated by the following embodiments.

[0025] Example 1: Component selection: The first field-effect transistor Q1 and the second field-effect transistor Q2 are N-channel enhancement-type MOSFETs in SOT-23 package (such as 2N7002), with a threshold voltage ≤2.5V.

[0026] Zener diode Z1 is selected with a Zener voltage of 12V, and its reverse breakdown voltage is matched with the maximum withstand voltage of the second field-effect transistor Q2.

[0027] The resistance of the first resistor R1 is 10kΩ, the resistance of the second resistor R2 is 47kΩ, the resistance of the third resistor R3 is 4.7kΩ, and the resistance of the fourth resistor R4 is 22kΩ.

[0028] The first capacitor, C1, is a 1μF ceramic capacitor with a delay time of approximately 10ms.

[0029] Circuit connection: Press Figure 1 The components are connected as shown, ensuring that pin 2 of the first MOSFET Q1 is connected to pin 2 of the second MOSFET Q2, and pin 3 of the second MOSFET Q2 is connected to the cathode of the LED1. The ON / OFF control terminal is connected to the GPIO pin of the microcontroller, controlling the switching of the first MOSFET Q1 via high and low levels. More specifically: when the ON / OFF control terminal is low, the first MOSFET Q1 is off, and at this time, the fourth resistor R4 and the first capacitor C1 form an RC charging circuit. As the voltage across the first capacitor C1 gradually rises to the threshold voltage (≤2.5V) of the second MOSFET Q2, the second MOSFET Q2 turns on, quickly discharging the residual current of the LED1 cathode to the ground terminal GND through the second MOSFET Q2, thereby eliminating afterglow.

[0030] Operational Verification: When LED1 is lit, the second field-effect transistor Q2 remains off, and the LED maintains normal brightness without flickering. This experimental verification shows that when the capacitance of the first capacitor C1 is 0.1μF, the delay time is approximately 1ms; when the capacitance of the first capacitor C1 is 10μF, the delay time is approximately 100ms. Within these ranges, the second field-effect transistor Q2 can effectively conduct after LED1 is turned off, completely eliminating afterglow.

[0031] After the LED is turned off, the second field-effect transistor Q2 is turned on after a delay. The voltage of the second field-effect transistor Q2 stabilizes below 12V, and the afterglow phenomenon is completely eliminated.

[0032] Example 2 (Extended Application) is as follows. The LED1 and Zener diode Z1 are used to absorb surge voltage during switching, further improving circuit reliability. For example, when LED1 is turned off, Zener diode Z1 absorbs the surge voltage generated by the switching transient through its reverse breakdown characteristic, clamping the voltage at pin 1 of the second MOSFET Q2 below 12V, preventing damage to Q2 due to overvoltage, and further improving circuit reliability.

[0033] Industrial applicability: This utility model can be widely used in scenarios such as intelligent lighting, indicator lights, and displays that require rapid LED shutdown. It has the advantages of simple structure, low cost, and fast response, and meets the needs of large-scale production.

[0034] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An active LED de-blooming circuit, characterized by, include: The circuit consists of a VIN terminal, a ground terminal GND, an LED1, a first field-effect transistor Q1, a second field-effect transistor Q2, and an ON / OFF control terminal. The VIN terminal is connected to one end of a third resistor R3. The VIN terminal is also connected to the anode of the LED1. The cathode of the LED1 is connected to pin 3 of the second field-effect transistor Q2. Pin 1 of the second field-effect transistor Q2 is connected to pin 2 of the first field-effect transistor Q1. Pin 3 of the first field-effect transistor Q1 is connected to the ground terminal GND. Pin 1 of the first field-effect transistor Q1 is connected to the ON / OFF control terminal. A first capacitor C1 and a Zener diode Z1 are connected in parallel between pins 1 and 3 of the second field-effect transistor Q2.

2. The active LED de-smearing circuit of claim 1, wherein: The Zener diode Z1 has a Zener voltage that is less than the maximum withstand voltage of pin 1 of the second field-effect transistor Q2, or the Zener diode Z1 has a Zener voltage that is equal to the maximum withstand voltage of pin 1 of the second field-effect transistor Q2.

3. An active LED de-smearing circuit according to claim 1, wherein: A fourth resistor R4 is also connected between the VIN terminal and pin 1 of the second field-effect transistor Q2. The resistance value of the fourth resistor R4 is in the range of 10kΩ-100kΩ, which is used to limit the charging current of the first capacitor C1.

4. The active LED afterglow reduction circuit according to claim 1, characterized in that: The capacitance of the first capacitor C1 is 0.1μF-10μF, which is used to provide a delay time for turning on the second field-effect transistor Q2 when the first field-effect transistor Q1 is turned off.

5. An active LED de-smearing circuit according to claim 1, wherein: The second field-effect transistor Q2 is an N-channel enhancement-mode MOSFET, and the turn-on threshold voltage of the second field-effect transistor Q2 is lower than the Zener diode Z1.

6. An active LED de-smearing circuit according to claim 1, wherein: The resistance of the third resistor R3 is 1kΩ-10kΩ, and it is used for the driving voltage of the second field-effect transistor Q2.

7. An active LED de-smearing circuit according to claim 1, wherein: Pin 1 of the first field-effect transistor Q1 is connected to the ON / OFF control terminal through a first resistor R1. The resistance value of the first resistor R1 is in the range of 1kΩ-100kΩ and is used to control the switching state of the first field-effect transistor Q1.

8. An active LED de-smearing circuit according to claim 1, wherein: The first field-effect transistor Q1 has a second resistor R2 connected to pins 1 and 3. The resistance value of the second resistor R2 is in the range of 1kΩ-100kΩ.

9. An active LED de-ghosting circuit according to claim 1, wherein: The reverse breakdown voltage of the Zener diode Z1 is 5V-20V, which is used to clamp the cathode voltage of the light-emitting diode LED1.

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