High beam and low beam switching circuit based on NMOS tube

Abstract

The utility model relates to a high beam and low beam switching circuit based on an NMOS (N-channel Metal Oxide Semiconductor) tube. The circuit comprises an interface unit, a constant current driving unit and a lamp panel unit which are connected in sequence, and further comprises a switching unit connected with the lamp panel unit, the switching unit comprises a magnetic bead B1, a first capacitor C1, a second capacitor C2, a third capacitor C3, a triode Q1, an NMOS tube Q2, a Zener tube Z1, a voltage-regulator tube Z2, a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7.

Description

Technical Field

[0001] This utility model relates to a vehicle lighting circuit, and in particular discloses a high / low beam switching circuit based on an NMOS transistor. Background Technology

[0002] With the development of the automotive industry, the requirements for the intelligence and reliability of vehicle lighting systems are increasing. Rapid and stable switching between high and low beams is crucial for nighttime driving safety. Currently, automotive high and low beam switching circuits mainly rely on traditional relay or transistor drive solutions, but these technologies have the following problems in practical applications:

[0003] Limitations of relay solutions:

[0004] Relays rely on mechanical contacts to switch on and off, which has problems such as slow response speed (usually millisecond-level delay), short lifespan due to mechanical wear, and easy failure with frequent switching.

[0005] Its large size makes it difficult to meet the integration requirements of compact in-vehicle electronic devices;

[0006] Contact sparks can cause electromagnetic interference (EMI), affecting the stability of vehicle electronic systems.

[0007] The shortcomings of conventional transistor solutions:

[0008] Bipolar junction transistors (BJTs) have a high on-state voltage drop, resulting in high energy consumption and significant heat generation, requiring additional heat dissipation design.

[0009] The switching speed is limited, making it difficult to achieve high-frequency switching, which may cause brief flickering when the lights switch.

[0010] Lacking comprehensive protection functions, such as overcurrent, overvoltage, and temperature protection, the circuit is easily damaged by sudden load changes or short circuit faults.

[0011] Based on the above problems, there is an urgent need for an efficient, reliable and integrated solution for switching between high and low beam headlights. Summary of the Invention

[0012] The purpose of this invention is to overcome the defects in the existing technology and provide an NMOS-based high / low beam switching circuit that improves the response speed, energy efficiency and reliability of high / low beam switching.

[0013] This utility model is implemented as follows: A high / low beam switching circuit based on an NMOS transistor includes an interface unit, a constant current driving unit, and a lamp board unit connected in sequence, and also includes a switching unit connected to the lamp board unit. The switching unit includes a magnetic bead B1, a first capacitor C1, a second capacitor C2, a third capacitor C3, a transistor Q1, an NMOS transistor Q2, a Zener transistor Z1, a Zener diode Z2, a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.

[0014] One end of the magnetic bead B1 is connected to the lamp board unit, and the other end of the magnetic bead B1 is connected to one end of the third capacitor C3 and the drain of the NMOS transistor Q2. The other end of the third capacitor C3 is grounded. The source of the NMOS transistor Q2 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7. The other end of the sixth resistor R6 is connected to the other end of the seventh resistor R7 and then grounded.

[0015] The gate of the NMOS transistor Q2 is connected to one end of the second capacitor C2, one end of the fifth resistor R5, the negative terminal of the Zener diode Z2, one end of the fourth resistor R4, and the collector of the transistor Q1. The other end of the second capacitor C2 is connected to the other end of the fifth resistor R5 and the positive terminal of the Zener diode Z2 and then grounded. The other end of the fourth resistor R4 is connected to the voltage terminal.

[0016] The emitter of transistor Q1 is grounded. The base of transistor Q1 is connected to one end of the third resistor R3, one end of the first capacitor C1, and one end of the first resistor R1. The other end of the third resistor R3 is connected to the other end of the first capacitor C1 and then grounded. The other end of the first resistor R1 is connected to one end of the second resistor R2 and the positive terminal of Zener diode Z1. The other end of the second resistor R2 is grounded. The negative terminal of Zener diode Z1 is connected to the negative terminal of diode D1. The positive terminal of diode D1 is connected to the positive terminal of HB of the interface unit.

[0017] The lamp panel unit includes a first lamp group and a second lamp group connected in series, and one end of the magnetic bead B1 is connected between the first lamp group and the second lamp group.

[0018] When the first light group is lit alone, it forms the low beam working state; when the first light group and the second light group are lit at the same time, it forms the high beam working state.

[0019] When the HB positive signal of the interface unit is low, the transistor Q1 is turned off, and the gate of the NMOS transistor Q2 forms a high level through the voltage division of the fourth resistor R4 and the fifth resistor R5, so the NMOS transistor Q2 is turned on, and the low beam headlights are in the working state. When the HB positive signal of the interface unit is high, the transistor Q1 is turned on, and the gate of the NMOS transistor Q2 is grounded through the transistor Q1, so the NMOS transistor Q2 is turned off, and the high beam headlights are in the working state.

[0020] The beneficial effects of this invention are as follows: By using the NMOS transistor Q2 and the transistor Q1, the response speed, energy efficiency, and reliability of high / low beam switching are improved. It solves the problems of slow switching speed, high energy consumption, and poor reliability in existing technologies. This invention can limit the rate of current surges and reduce spikes. It achieves efficient and stable high / low beam switching, and the series connection structure of the first and second lamp groups can save the cost of one set of drivers. The components used in this invention are all common discrete components, with small size and high integration. High integration of electronic components can improve performance and reduce power consumption, which is in line with the development trend of high integration in the automotive market. The ferrite bead B1 can suppress high-frequency noise and electromagnetic interference (EMI), ensuring the stable operation of the switching circuit. The first capacitor C1, the second capacitor C2, and the third capacitor C3 can provide electrostatic protection, protecting the transistor Q1 and the NMOS transistor Q2, and protecting the switching circuit from electrostatic damage. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the circuit structure of this utility model. Detailed Implementation

[0022] according to Figure 1 This utility model is a high / low beam switching circuit based on an NMOS transistor, comprising an interface unit, a constant current driving unit, and a lamp board unit connected in sequence, and a switching unit connected to the lamp board unit. The switching unit includes a magnetic bead B1, a first capacitor C1, a second capacitor C2, a third capacitor C3, a transistor Q1, an NMOS transistor Q2, a Zener diode Z1, a Zener diode Z2, a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.

[0023] One end of the magnetic bead B1 is connected to the lamp board unit, and the other end of the magnetic bead B1 is connected to one end of the third capacitor C3 and the drain of the NMOS transistor Q2. The other end of the third capacitor C3 is grounded. The source of the NMOS transistor Q2 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7. The other end of the sixth resistor R6 is connected to the other end of the seventh resistor R7 and then grounded.

[0024] The gate of the NMOS transistor Q2 is connected to one end of the second capacitor C2, one end of the fifth resistor R5, the negative terminal of the Zener diode Z2, one end of the fourth resistor R4, and the collector of the transistor Q1. The other end of the second capacitor C2 is connected to the other end of the fifth resistor R5 and the positive terminal of the Zener diode Z2 and then grounded. The other end of the fourth resistor R4 is connected to the voltage terminal.

[0025] The emitter of transistor Q1 is grounded. The base of transistor Q1 is connected to one end of the third resistor R3, one end of the first capacitor C1, and one end of the first resistor R1. The other end of the third resistor R3 is connected to the other end of the first capacitor C1 and then grounded. The other end of the first resistor R1 is connected to one end of the second resistor R2 and the positive terminal of Zener diode Z1. The other end of the second resistor R2 is grounded. The negative terminal of Zener diode Z1 is connected to the negative terminal of diode D1. The positive terminal of diode D1 is connected to the positive terminal of HB of the interface unit.

[0026] The lamp panel unit includes a first lamp group and a second lamp group connected in series, and one end of the magnetic bead B1 is connected between the first lamp group and the second lamp group.

[0027] Preferably, the first lamp unit is a first light-emitting diode LD1 and the second lamp unit is a second light-emitting diode LD2. The positive terminal of the first light-emitting diode LD1 is connected to the constant current driving unit, and the negative terminal of the second light-emitting diode LD2 is grounded. One end of the magnetic bead B1 is connected to the negative terminal of the first light-emitting diode LD1 and the positive terminal of the second light-emitting diode LD2, respectively. When the first lamp unit is lit alone, it forms the low beam lighting state; when the first lamp unit and the second lamp unit are lit simultaneously, it forms the high beam lighting state.

[0028] When this utility model is in use, when the first light-emitting diode LD1 is lit, it realizes the low beam function; when the first light-emitting diode LD1 and the second light-emitting diode LD2 are lit at the same time, it realizes the high beam function.

[0029] When LB is powered on and HB is not powered on, HB is at a low level, and the base of the transistor Q1 connected to it is at a low level, so transistor Q1 is turned off. VS is at a high level, and VS, through the fourth resistor R4 and the fifth resistor R5, divides the voltage, making the gate (G) of NMOS transistor Q2 high. At this time, the voltage of NMOS transistor Q2 is... GS >V th When NMOS transistor Q2 is turned on, the current from the constant current drive unit flows through the first LED LD1, the magnetic bead B1, and the NMOS transistor Q2 to GND, and the first LED LD1 lights up, realizing the low beam function.

[0030] When HB is powered on and LB is not powered on, HB is at a high level, and the base of transistor Q1 connected to it becomes high, turning on transistor Q1. After transistor Q1 turns on, the gate of NNMOS transistor Q2 is connected to GND through transistor Q1. At this time, the V0 of NNMOS transistor Q2... GS <V th When the NNMOS transistor Q2 is turned off, the current from the constant current drive unit flows directly to GND through the first LED LD1 and the second LED LD2. The first LED LD1 and the second LED LD2 are lit simultaneously, thus realizing the high beam function.

[0031] By powering on and off LB and HB respectively, the function of switching between high and low beam headlights can be achieved.

[0032] The first light-emitting diode LD1 and the second light-emitting diode LD2 are connected in series, which can save the cost of one set of drivers.

[0033] Among them, the Zener diode Z2 can protect the gate of the NMOS transistor Q2 from damage due to overvoltage; the Zener diode Z1 can set a threshold voltage for switching between high and low beams to ensure the stability of switching; the ferrite bead B1 can suppress high-frequency noise and electromagnetic interference (EMI) to ensure the stable operation of the circuit; and the first capacitor C1 can play an anti-static role to protect the NMOS transistor Q2.

[0034] The sixth resistor R6 and the seventh resistor R7 are connected in series at the source of the NMOS transistor Q2 to form a voltage drop of L*di / dt+i*(R6 / / R7), where L is the parasitic inductance, which limits the rate of current change and reduces spikes.

[0035] This design leverages the low on-resistance (Rds(on)) and fast switching speed of NMOS transistors, combining them with other discrete components to create a high-efficiency, fast-switching, low-power, high-reliability, thermally stable, small-size, highly interference-resistant, easy-to-integrate, low-cost, comprehensive protection, and highly compatible high- and low-beam switching circuit. This addresses the shortcomings of traditional relay or transistor driving solutions.

Claims

1. A high / low beam switching circuit based on an NMOS transistor, comprising an interface unit, a constant current drive unit, and a lamp board unit connected in sequence, characterized in that: It also includes a switching unit connected to the lamp board unit, the switching unit including a magnetic bead B1, a first capacitor C1, a second capacitor C2, a third capacitor C3, a transistor Q1, an NMOS transistor Q2, a Zener transistor Z1, a Zener diode Z2, a diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; One end of the magnetic bead B1 is connected to the lamp board unit, and the other end of the magnetic bead B1 is connected to one end of the third capacitor C3 and the drain of the NMOS transistor Q2. The other end of the third capacitor C3 is grounded. The source of the NMOS transistor Q2 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7. The other end of the sixth resistor R6 is connected to the other end of the seventh resistor R7 and then grounded. The gate of the NMOS transistor Q2 is connected to one end of the second capacitor C2, one end of the fifth resistor R5, the negative terminal of the Zener diode Z2, one end of the fourth resistor R4, and the collector of the transistor Q1. The other end of the second capacitor C2 is connected to the other end of the fifth resistor R5 and the positive terminal of the Zener diode Z2 and then grounded. The other end of the fourth resistor R4 is connected to the voltage terminal. The emitter of transistor Q1 is grounded. The base of transistor Q1 is connected to one end of the third resistor R3, one end of the first capacitor C1, and one end of the first resistor R1. The other end of the third resistor R3 is connected to the other end of the first capacitor C1 and then grounded. The other end of the first resistor R1 is connected to one end of the second resistor R2 and the positive terminal of Zener diode Z1. The other end of the second resistor R2 is grounded. The negative terminal of Zener diode Z1 is connected to the negative terminal of diode D1. The positive terminal of diode D1 is connected to the positive terminal of HB of the interface unit.

2. The high / low beam switching circuit based on an NMOS transistor according to claim 1, characterized in that: The lamp panel unit includes a first lamp group and a second lamp group connected in series, and one end of the magnetic bead B1 is connected between the first lamp group and the second lamp group.

3. The high / low beam switching circuit based on an NMOS transistor according to claim 2, characterized in that: When the first light group is lit alone, it forms the low beam working state; when the first light group and the second light group are lit at the same time, it forms the high beam working state.

4. The high / low beam switching circuit based on an NMOS transistor according to claim 1, characterized in that: When the HB positive signal of the interface unit is low, the transistor Q1 is turned off, and the gate of the NMOS transistor Q2 forms a high level through the voltage division of the fourth resistor R4 and the fifth resistor R5, so the NMOS transistor Q2 is turned on, and the low beam headlights are in the working state. When the HB positive signal of the interface unit is high, the transistor Q1 is turned on, and the gate of the NMOS transistor Q2 is grounded through the transistor Q1, so the NMOS transistor Q2 is turned off, and the high beam headlights are in the working state.

Images