Constant current circuit with overvoltage protection
By introducing a reference circuit and a voltage detection and protection circuit into the constant current circuit, the problem of damage when the load is short-circuited or high voltage is applied is solved, the overvoltage protection of the circuit is realized, the stability and reliability are improved, and the parameters are adjustable.
Patent Information
- Application Number
- CN202423310194.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2034-12-31
AI Technical Summary
Existing constant current circuits lack overvoltage protection when the load is short-circuited or when a high voltage is mistakenly connected, which leads to increased power consumption, overheating and damage to the transistors, resulting in poor circuit instability and reliability.
The circuit employs a reference circuit, a constant current control circuit, and a voltage detection and protection circuit. Overvoltage protection is achieved through a circuit structure consisting of a voltage divider, an operational amplifier, an NPN transistor, and resistors. The overvoltage protection threshold is adjusted by the voltage division ratio of R6 and R7. The NPN transistor Q2 conducts to protect transistor Q1 from high voltage damage.
The circuit is protected from damage in case of load short circuit or wiring error, improving the stability and reliability of the circuit. Furthermore, the circuit parameters are adjustable to adapt to different usage requirements.
Smart Images
Figure CN223501345U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of constant current circuit technology, specifically relating to a constant current circuit with overvoltage protection. Background Technology
[0002] In current technology, many circuit applications or device uses require a constant supply current, such as LED power supply scenarios.
[0003] The existing constant current circuit is shown in the appendix. Figure 1 As shown, during operation, current flows through the load RL, and R4 is a current sampling resistor. When the current in the load RL increases / decreases, the voltage across R4 increases / decreases accordingly. This voltage is fed back to the inverting input of the operational amplifier U1 through R5. After adjustment by U1, it is sent to the base of the transistor Q1 through R3 to control the operating state of the transistor Q1 and adjust the voltage across R4 to the set value. At this time, the current flowing through the load RL is also adjusted to the design value. However, when the load is short-circuited or connected to high voltage by mistake, the collector and emitter of the transistor are subjected to high voltage, and the power consumption of the transistor increases, leading to heat generation and damage.
[0004] Therefore, the circuit in the existing technology does not have overvoltage protection against high voltage. Utility Model Content
[0005] To address the aforementioned problems in the existing technology, this utility model provides a constant current circuit with overvoltage protection, which prevents damage to components when the load is short-circuited or mistakenly connected to high voltage, thereby improving the reliability and stability of the circuit.
[0006] To achieve the above objectives, this utility model provides the following technical solution: a constant current circuit with overvoltage protection, comprising a reference circuit, a constant current control circuit, and a voltage detection and protection circuit; the reference circuit includes a voltage divider composed of resistors R1 and R2 connected in series; the constant current control circuit includes an operational amplifier U1, an NPN transistor Q1, a resistor R3, a sampling resistor R4, and a feedback resistor R5, wherein the output of the voltage divider is connected to the positive input terminal of the operational amplifier U1, the output terminal of the operational amplifier U1 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the base of the NPN transistor Q1, and the collector of the NPN transistor Q1 is connected to a load RL. One end of the sampling resistor R4 is connected to the emitter of the NPN transistor Q1, and the other end of the sampling resistor R4 is grounded. One end of the feedback resistor R5 is connected to the emitter of the NPN transistor Q1, and the other end is connected to the inverting input terminal of the operational amplifier U1. The voltage detection and protection circuit includes an NPN transistor Q2, a resistor R6, and a resistor R7. One end of the resistor R6 is connected to the collector of the NPN transistor Q1, and the other end is connected to the base of the NPN transistor Q2. One end of the resistor R7 is connected to the base of the NPN transistor Q2, and the other end is grounded. The collector of the NPN transistor Q2 is connected to the base of the NPN transistor Q1, and the emitter of the NPN transistor Q2 is grounded.
[0007] As a preferred technical solution of the constant current circuit with overvoltage protection according to this utility model, the end of resistor R1 that is different from resistor R2 is connected to the system power supply.
[0008] As a preferred technical solution of the constant current circuit with overvoltage protection according to this utility model, the voltage division ratio of the resistor R1 and the resistor R2 can be changed, and the current limiting value of the circuit can be set by changing the resistance value of the sampling resistor R4.
[0009] As a preferred technical solution of the constant current circuit with overvoltage protection according to this utility model, the voltage division ratio of resistor R6 and resistor R7 is adjustable, thereby setting the overvoltage protection threshold.
[0010] Compared with the prior art, the beneficial effects of this utility model are: when the circuit of this utility model is used, the current limiting value of the circuit can be set by changing the voltage division ratio of R1 and R2 and changing the resistance value of sampling resistor R4. It has the feature of overvoltage protection. When high voltage is connected due to load short circuit or wiring error, the internal circuit will not be damaged. Compared with the existing technical solution, the overvoltage protection function is added, the protection is more comprehensive, and the stability and reliability of the circuit are improved.
[0011] Furthermore, the circuit parameters are flexible and can be adjusted according to different current limiting values and overvoltage protection thresholds, making it highly practical. Attached Figure Description
[0012] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:
[0013] Figure 1 This is a schematic diagram of a current constant current circuit in the prior art;
[0014] Figure 2 This is a schematic diagram of the constant current circuit in this utility model. Detailed Implementation
[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example
[0016] Please see Figure 2 As shown, this utility model provides the following technical solution: a constant current circuit with overvoltage protection, including a reference circuit, a constant current control circuit, and a voltage detection and protection circuit, with the specific connection form as follows:
[0017] The reference circuit includes a voltage divider consisting of resistors R1 (also known as R1) and R2 (also known as R2) connected in series.
[0018] The constant current control circuit includes an operational amplifier U1, an NPN transistor Q1 (also called Q1), a resistor R3 (also called R3), a sampling resistor R4 (also called R4), and a feedback resistor R5 (also called R5).
[0019] The voltage divider output is connected to the positive input of operational amplifier U1. The output of operational amplifier U1 is connected to one end of resistor R3. The other end of resistor R3 is connected to the base of NPN transistor Q1. The collector of NPN transistor Q1 is connected to the load RL (i.e., the collector of NPN transistor Q1 is connected to one end of the load RL). The other end of the load RL is connected to the B+ power supply. One end of sampling resistor R4 is connected to the emitter of NPN transistor Q1. The other end of sampling resistor R4 is grounded. One end of feedback resistor R5 is connected to the emitter of NPN transistor Q1. The other end is connected to the inverting input of operational amplifier U1.
[0020] The voltage detection and protection circuit includes an NPN transistor Q2 (also called Q2), a resistor R6 (also called R6), and a resistor R7 (also called R7). One end of resistor R6 is connected to the collector of NPN transistor Q1, and the other end is connected to the base of NPN transistor Q2. One end of resistor R7 is connected to the base of NPN transistor Q2, and the other end is grounded. The collector of NPN transistor Q2 is connected to the base of NPN transistor Q1, and the emitter of NPN transistor Q2 is grounded.
[0021] The end of resistor R1 that is different from resistor R2 is connected to the system power supply, as shown in the attached diagram. Figure 2 As shown, 5V is used as the system power supply. The current limit value of the circuit can be set by changing the voltage division ratio of R1 and R2 and changing the resistance value of the sampling resistor R4 (that is, the voltage division ratio of resistors R1 and R2 can be changed, and the current limit value of the circuit can be set by changing the resistance value of the sampling resistor R4). The overvoltage protection threshold can be set by adjusting the voltage division ratio of R6 and R7 (that is, the voltage division ratio of resistors R6 and R7 can be adjusted, thereby setting the overvoltage protection threshold).
[0022] The specific working process is as follows: When the B+ power supply voltage or load changes, the current flowing through the load RL changes, so the voltage across the sampling resistor R4 changes accordingly. This voltage is fed back to the inverting input of the operational amplifier U1 through R5. After adjustment, the operational amplifier U1 sends the voltage to the base of the NPN transistor Q1 through R3. The change in the base current of the NPN transistor Q1 causes a change in the collector current. Adjusting the voltage across R4 to be the same as the voltage division value of R1 and R2, the current flowing through the load RL also returns to the level before adjustment.
[0023] When a short circuit or wiring error causes high voltage to be applied to the collector of NPN transistor Q1, the voltage divided by R6 and R7 exceeds the cutoff voltage of NPN transistor Q2. At this time, Q2 conducts, pulling the base input of Q1 low, causing Q1 to turn off and no current to flow. Q1 will not be damaged due to excessive power consumption caused by the high voltage input, ensuring the reliable operation of the entire circuit. This new circuit, compared to the original constant current circuit (see appendix), offers advantages over conventional constant current circuits. Figure 1 For example, it has the feature of overvoltage protection, which protects the internal circuit from damage when high voltage is connected due to load short circuit or wiring error, thus improving the stability and reliability of the circuit. The circuit of this solution has the feature of flexible parameter adjustment.
[0024] Meanwhile, this utility model provides a constant current circuit with overvoltage protection, and is not limited to the description in the specification and implementation method;
[0025] Therefore, all equivalent changes or modifications made to the structure, features and principles of this utility model patent application should be included within the scope of this utility model patent application. For example, Q1 can use other types of switching transistors, provide current-limiting reference voltage through MCU or DAC functions, or replace the constant current circuit with a constant current circuit of other structures. All of these should be included within the protection scope of this utility model circuit.
[0026] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.
Claims
1. A constant current circuit with overvoltage protection, characterized in that, Includes a reference circuit, a constant current control circuit, and a voltage detection and protection circuit; The reference circuit includes a voltage divider consisting of resistors R1 and R2 connected in series. The constant current control circuit includes an operational amplifier U1, an NPN transistor Q1, a resistor R3, a sampling resistor R4, and a feedback resistor R5. The output of the voltage divider is connected to the positive input terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the base of the NPN transistor Q1. The collector of the NPN transistor Q1 is connected to a load RL. One end of the sampling resistor R4 is connected to the emitter of the NPN transistor Q1, and the other end of the sampling resistor R4 is grounded. One end of the feedback resistor R5 is connected to the emitter of the NPN transistor Q1, and the other end is connected to the inverting input terminal of the operational amplifier U1. The voltage detection and protection circuit includes an NPN transistor Q2, a resistor R6, and a resistor R7. One end of the resistor R6 is connected to the collector of the NPN transistor Q1, and the other end is connected to the base of the NPN transistor Q2. One end of the resistor R7 is connected to the base of the NPN transistor Q2, and the other end is grounded. The collector of the NPN transistor Q2 is connected to the base of the NPN transistor Q1, and the emitter of the NPN transistor Q2 is grounded.
2. The constant current circuit with overvoltage protection according to claim 1, characterized in that: The end of resistor R1 that is different from resistor R2 is connected to the system power supply.
3. The constant current circuit with overvoltage protection according to claim 1, characterized in that: The voltage division ratio of resistors R1 and R2 can be changed, and the current limiting value of the circuit can be set by changing the resistance value of the sampling resistor R4.
4. A constant current circuit with overvoltage protection according to claim 1, characterized in that: The voltage division ratio of resistor R6 and resistor R7 is adjustable, thereby setting the overvoltage protection threshold.