An input over / under voltage protection circuit
By simplifying the over- and under-voltage protection circuit and utilizing components such as Zener diodes and voltage divider resistors, the problem of reliance on MCU chips in existing automotive lighting designs is solved, achieving low-cost over- and under-voltage protection suitable for diverse automotive lighting power supplies.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHANGZHOU XINGYU AUTOMOTIVE LIGHTING SYST CO LTD
- Filing Date
- 2025-06-27
- Publication Date
- 2026-06-16
AI Technical Summary
In existing vehicle lighting designs, over- and under-voltage protection functions require MCU chips and complex hardware circuits, resulting in high design costs and limiting circuit design methods, failing to meet the needs of cost savings and functional diversification.
By utilizing the characteristic of the Zener diode operating in the reverse breakdown region, and combining it with voltage divider resistors and components such as transistors and MOSFETs, a simple over- and under-voltage protection circuit can be constructed to achieve over- and under-voltage protection functions without the need for an MCU chip.
Without increasing the number of components, over- and under-voltage protection functions for vehicle lights were achieved, reducing design costs and meeting the power supply needs of car manufacturers for diverse vehicle lights.
Smart Images
Figure CN224367524U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of automotive headlight input over / under voltage protection technology, and in particular to an input over / under voltage protection circuit. Background Technology
[0002] The development of automotive lighting is becoming increasingly technologically advanced, with a growing number of LEDs and more complex functions. This is particularly true in the new energy vehicle sector, where automakers are increasingly focusing on maximizing battery life and extending driving range. To address this, they are implementing over- and under-voltage protection management for various electrical components in the vehicle body. Furthermore, to save costs, fewer components are typically used to achieve different functions. For example, the normal input voltage for vehicle lighting is 9-16V, and automakers have corresponding over- and under-voltage management mechanisms for voltages below 9V and above 16V. Current market solutions typically require an MCU chip with external ADC detection hardware circuitry and software detection mechanisms to achieve these functions, significantly increasing design costs and limiting lighting circuit design methods, as well as increasing the overall cost of the lighting fixtures. Utility Model Content
[0003] The technical problem to be solved by this utility model is: In order to overcome the above-mentioned technical problems, this utility model provides an input over- and under-voltage protection circuit. By utilizing the characteristic of the Zener diode working in the reverse breakdown region, the over- and under-voltage protection function of the lamp can be realized without the MCU chip. Moreover, the functional requirements are achieved with a simple circuit and fewer components, which greatly saves costs.
[0004] The technical solution adopted by this utility model to solve its technical problem is: an input over / under voltage protection circuit, including a protection circuit and a switching circuit. The protection circuit includes an overvoltage protection circuit and an undervoltage protection circuit. The overvoltage protection circuit includes a Zener diode D3, a first voltage divider resistor R2, a second voltage divider resistor R3, and a transistor Q1. The undervoltage protection circuit includes a Zener diode D4, a third voltage divider resistor R5, and a fourth voltage divider resistor R4. The switching circuit includes a Zener diode D5, a filter capacitor C3, a fifth voltage divider resistor R6, a sixth voltage divider resistor R5, a transistor Q3, and a MOSFET Q2. The Zener diode D3, the first voltage divider resistor R2, and the second voltage divider resistor R3 are connected in series and then grounded. The positive terminal of the Zener diode D3 is connected to the first voltage divider resistor R2, and the negative terminal of the Zener diode D3 is connected to the negative terminal of the Zener diode D4 and the negative terminal of the Zener diode D5. The following components are connected in parallel: Zener diode D4, third voltage divider resistor R5, and fourth voltage divider resistor R4 are connected in series and then grounded. The positive terminal of Zener diode D4 is connected to the third voltage divider resistor R5. The base of transistor Q1 is connected in parallel to the connection terminal of first voltage divider resistor R2 and second voltage divider resistor R3. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected in parallel to the connection terminal of third voltage divider resistor R5 and fourth voltage divider resistor R4. The base of transistor Q3 is connected to the collector of transistor Q1. The emitter of transistor Q3 is grounded. Zener diode D5, filter capacitor C3, fifth voltage divider resistor R6, and MOSFET Q2 are connected in parallel and then connected to the collector of transistor Q3 through sixth voltage divider resistor R7. The gate of MOSFET Q2 is connected to sixth voltage divider resistor R7. The drain of MOSFET Q2 is connected to the power output terminal. The source of MOSFET Q2 is connected to the negative terminal of Zener diode D5.
[0005] Under normal operation, Zener diode D3 is off, Zener diode D4 is on, transistor Q3 is on, transistor Q2 is on, and the power supply outputs normally. When the input voltage at the power supply input terminal exceeds the predetermined overvoltage threshold, Zener diode D3 is on, transistor Q1 is on, transistor Q3 is off, MOSFET Q2 is off, and the power supply output does not output. When the input voltage at the power supply input terminal is below the predetermined undervoltage threshold, Zener diode D4 is off, transistor Q3 is off, MOSFET Q2 is off, and the power supply output does not output.
[0006] It also includes a power supply filter circuit and a reverse polarity protection diode D2. The power supply filter circuit includes a Zener diode D1, filter capacitors C1 and C2, and a resistor R1 connected in parallel between the power input terminal and the ground terminal. The reverse polarity protection diode D2 is connected in series between the power supply filter circuit and the protection circuit. When the voltage at the power input terminal is lower than the minimum normal voltage, the voltage output by the reverse polarity protection diode D2 is V1; when the voltage at the power input terminal is higher than the maximum normal voltage, the voltage output by the reverse polarity protection diode D2 is V2; and when the voltage at the power input terminal is at the maximum normal voltage, the voltage output by the reverse polarity protection diode D2 is V0. The reverse breakdown voltage of the Zener diode D4 is less than V1, and V0 is less than the reverse breakdown voltage of the Zener diode D3, which is less than V2. In specific design, further analysis is needed based on the specific input over / under voltage requirements to determine the final component selection.
[0007] Preferably, the Zener diode D1 is a bidirectional Zener diode.
[0008] As a preferred option, both transistors Q1 and Q3 are NPN transistors.
[0009] Preferably, MOSFET Q2 is a P-channel MOSFET.
[0010] The beneficial effects of this utility model are that the input over / under voltage protection circuit of this utility model utilizes the characteristic of the Zener diode working in the reverse breakdown region, thereby achieving the over / under voltage protection function of the lamp without the need for an MCU chip solution. Furthermore, it uses a simple circuit and fewer components to meet the voltage management function requirements, greatly reducing the overall lamp circuit design cost. At the same time, it can also meet the diverse automotive lamp requirements of car manufacturers for over / under voltage protection in lamp power supply. It is easy to implement and applicable to the vast majority of car models on the market. Attached Figure Description
[0011] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0012] Figure 1 This is a schematic diagram of the optimal embodiment of the input over / under voltage protection circuit of this utility model.
[0013] In the diagram: 1. Power supply filter circuit; 2. Overvoltage protection circuit; 3. Undervoltage protection circuit; 4. Switching circuit. Detailed Implementation
[0014] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.
[0015] like Figure 1As shown, this utility model discloses an input over / under voltage protection circuit, comprising a protection circuit and a switching circuit 4. The protection circuit includes an overvoltage protection circuit 2 and an undervoltage protection circuit 3. The overvoltage protection circuit 2 includes a Zener diode D3, a first voltage divider resistor R2, a second voltage divider resistor R3, and a transistor Q1. The undervoltage protection circuit 3 includes a Zener diode D4, a third voltage divider resistor R5, and a fourth voltage divider resistor R4. The switching circuit 4 includes a Zener diode D5, a filter capacitor C3, a fifth voltage divider resistor R6, a sixth voltage divider resistor R7, a transistor Q3, and a MOSFET Q2. Transistors Q3 and Q1 are both NPN transistors, and MOSFET Q2 is an N-channel MOSFET.
[0016] A Zener diode D3, the first voltage divider resistor R2, and the second voltage divider resistor R3 are connected in series and then grounded. The anode of Zener diode D3 is connected to the first voltage divider resistor R2. The cathodes of Zener diode D3, D4, and D5 are connected in parallel. A Zener diode D4, the third voltage divider resistor R5, and the fourth voltage divider resistor R4 are connected in series and then grounded. The anode of Zener diode D4 is connected to the third voltage divider resistor R5. The base of transistor Q1 is connected in parallel to the junction of the first and second voltage divider resistors R2 and R1. The emitter of transistor Q1 is connected to... The collector of transistor Q1 is connected in parallel to the junction of the third voltage divider resistor R5 and the fourth voltage divider resistor R4. The base of transistor Q3 is connected to the collector of transistor Q1, and the emitter of transistor Q3 is grounded. Zener diode D5, filter capacitor C3, fifth voltage divider resistor R6, and MOSFET Q2 are connected in parallel and then connected to the collector of transistor Q3 through the sixth voltage divider resistor R7. The gate of MOSFET Q2 is connected to the sixth voltage divider resistor R7. The drain of MOSFET Q2 is connected to the power output terminal PL+, and the source of MOSFET Q2 is connected to the cathode of Zener diode D5.
[0017] During normal operation, Zener diode D3 is not conducting, Zener diode D4 is conducting, transistor Q3 is conducting, MOSFET Q2 is conducting, and the power output terminal PL+ outputs normally.
[0018] When the input voltage at the power input terminal V_PL+ exceeds the predetermined overvoltage threshold, the Zener diode D3 is turned on, the transistor Q1 is turned on, the transistor Q3 is turned off, the MOSFET Q2 is not turned on, and the power output terminal PL+ does not output.
[0019] When the input voltage at the power input terminal V_PL+ is lower than the predetermined undervoltage threshold, the Zener diode D4 is not turned on, the transistor Q3 is cut off, the MOSFET Q2 is not turned on, and the power output terminal PL+ does not output.
[0020] The circuit also includes a power filter circuit 1 and a reverse polarity protection diode D2. The power filter circuit 1 includes a Zener diode D1, filter capacitors C1 and C2, and a resistor R1 connected in parallel between the power input terminal V_PL+ and the ground terminal. The Zener diode D1 is a bidirectional Zener diode. The reverse polarity protection diode D2 is connected in series between the power filter circuit 1 and the protection circuit. When the voltage at the power input terminal V_PL+ is lower than the minimum normal voltage, the output voltage of the reverse polarity protection diode D2 is V1; when the voltage at the power input terminal V_PL+ is higher than the maximum normal voltage, the output voltage of the reverse polarity protection diode D2 is V2; when the voltage at the power input terminal V_PL+ is at the maximum normal voltage, the output voltage of the reverse polarity protection diode D2 is V0. The reverse breakdown voltage of the Zener diode D4 is less than V1, and V0 is less than the reverse breakdown voltage of the Zener diode D3, which is less than V2. The Zener diodes D3 and D2 need to be selected based on the over / under voltage thresholds.
[0021] The power input terminal V_PL+ is the hard-wired power input for the vehicle position function, with a normal operating voltage of 9-16V. GND is the ground terminal.
[0022] The working principle of the input over / under voltage protection circuit of this utility model is as follows:
[0023] During normal operation, the voltage output from the power input terminal V_PL+ via the reverse polarity protection diode D2 is less than the reverse breakdown voltage of the Zener diode D3, so Zener diode D3 is not conducting. At this time, since the reverse breakdown voltage of Zener diode D4 is much lower than that of Zener diode D3, Zener diode D4 conducts. Then, through the third voltage divider resistor R5 and the fourth voltage divider resistor R41, the resistance value is adjusted so that the Vbe voltage of transistor Q3 reaches the turn-on threshold, transistor Q3 conducts, and then MOSFET Q2 conducts, and the power output terminal PL+ outputs normally.
[0024] Overvoltage protection mode: When the voltage output from the power input terminal V_PL+ via the reverse connection protection diode D2 is higher than the reverse breakdown voltage of the Zener diode D3, the Zener diode D3 conducts. The resistance values of the first voltage divider resistor R2 and the second voltage divider resistor R3 are configured so that the Vbe voltage of transistor Q1 reaches the turn-on threshold, and transistor Q1 conducts. The Vbe voltage of transistor Q3 becomes low level, and transistor Q3 is cut off. MOSFET Q2 does not conduct, and the power output terminal PL+ does not output.
[0025] Undervoltage protection mode: When the voltage output from the power input terminal V_PL+ via the reverse connection protection diode D2 is higher than the reverse breakdown voltage of the Zener diode D4, the Zener diode D4 will not conduct. The resistance values of the third and fourth voltage divider resistors R5 and R4 are configured so that the Vbe voltage of the transistor Q3 is lower than the turn-on threshold, the transistor Q3 is cut off, the MOSFET Q2 is not conducted, and the power output terminal PL+ does not output.
[0026] The Vbe voltages mentioned above refer to the voltage difference between the base and emitter of the transistor.
[0027] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. An input over / under voltage protection circuit, characterized in that: The circuit includes protection circuits and switching circuits. The protection circuits include overvoltage protection circuits and undervoltage protection circuits. The overvoltage protection circuit includes a Zener diode D3, a first voltage divider resistor R2, a second voltage divider resistor R3, and a transistor Q1. The undervoltage protection circuit includes a Zener diode D4, a third voltage divider resistor R5, and a fourth voltage divider resistor R6. The switching circuit includes a Zener diode D5, a filter capacitor C3, a fifth voltage divider resistor R6, a sixth voltage divider resistor R7, a transistor Q2, and a MOSFET Q3. The Zener diode D3, the first voltage divider resistor R2, and the second voltage divider resistor R3 are connected in series and then grounded. The positive terminal of the Zener diode D3 is connected to the first voltage divider resistor R2. The negative terminal of the Zener diode D3 is connected in parallel with the negative terminals of the Zener diodes D4 and D5. The Zener diode D4, the third voltage divider resistor R5, and the second voltage divider resistor R6 are connected in series and then grounded. The positive terminal of the Zener diode D3 is connected to the first voltage divider resistor R2. The negative terminals of the Zener diodes D3, D4, and D5 are connected in parallel. Resistor R5 and fourth voltage divider resistor R4 are connected in series and then grounded. The positive terminal of Zener diode D4 is connected to third voltage divider resistor R5. The base of transistor Q1 is connected in parallel to the connection terminal of first voltage divider resistor R2 and second voltage divider resistor R3. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected in parallel to the connection terminal of third voltage divider resistor R5 and fourth voltage divider resistor R4. The base of transistor Q3 is connected to the collector of transistor Q1. The emitter of transistor Q3 is grounded. Zener diode D5, filter capacitor C3, fifth voltage divider resistor R6 and MOSFET Q2 are connected in parallel and then connected to the collector of transistor Q3 through sixth voltage divider resistor R7. The gate of MOSFET Q2 is connected to sixth voltage divider resistor R7. The drain of MOSFET Q2 is connected to the power output terminal. The source of MOSFET Q2 is connected to the negative terminal of Zener diode D5.
2. The input over / under voltage protection circuit as described in claim 1, characterized in that: During normal operation, Zener diode D3 is not conducting, transistor Q1 is cut off, Zener diode D4 is conducting, transistor Q3 is conducting, MOSFET Q2 is conducting, and the power supply output is normal. When the input voltage at the power input terminal is greater than the predetermined overvoltage threshold, the Zener diode D3 is turned on, the transistor Q1 is turned on, the transistor Q3 is turned off, the MOSFET Q2 is not turned on, and the power output terminal does not output. When the input voltage at the power input terminal is lower than the predetermined undervoltage threshold, the Zener diode D4 is not turned on, the transistor Q3 is cut off, the MOSFET Q2 is not turned on, and the power output terminal does not output.
3. The input over / under voltage protection circuit as described in claim 1 or 2, characterized in that: It also includes a power filter circuit and a reverse connection protection diode D2. The power filter circuit includes a Zener diode D1, a filter capacitor C1, a filter capacitor C2, and a resistor R1 connected in parallel between the power input terminal and the ground terminal. The reverse connection protection diode D2 is connected in series between the power filter circuit and the protection circuit. When the voltage at the power input terminal is lower than the minimum normal voltage, the voltage output by the reverse connection protection diode D2 is V1. When the voltage at the power input terminal is higher than the maximum normal voltage, the voltage output by the reverse connection protection diode D2 is V2. When the voltage at the power input terminal is at the maximum normal voltage, the voltage output by the reverse connection protection diode D2 is V0. The reverse breakdown voltage of the Zener diode D4 is < V1, and V0 is < the reverse breakdown voltage of the Zener diode D3, which is < V2.
4. The input over / under voltage protection circuit as described in claim 3, characterized in that: Zener diode D1 is a bidirectional Zener diode.
5. The input over / under voltage protection circuit as described in claim 1 or 2, characterized in that: Both transistors Q3 and Q1 are NPN transistors.
6. The input over / under voltage protection circuit as described in claim 1 or 2, characterized in that: MOSFET Q2 is a P-channel MOSFET.