High-precision, flexible and adjustable overvoltage and undervoltage protection circuit

Abstract

The utility model discloses a high-precision flexible adjustable overvoltage and undervoltage protection circuit which is composed of three units, namely an overvoltage protection unit A, an undervoltage protection unit B and a post-stage load unit C. In the overvoltage protection unit A, a power supply positive electrode is connected with a resistor R2 and a capacitor C1 through a resistor R1, a power supply negative electrode is connected with a ground wire network, a first pin of a chip U1 is connected with the resistor R1 and the resistor R2, a third pin of the chip U1 is grounded, and a fourth pin of the chip U1 is grounded. A pin 2 of the chip U1 is connected with a pin 1 of the capacitor C2, a power supply positive electrode in the under-voltage protection unit B is connected with the resistor R4, the capacitor C2 and a pin 1 of the chip U2 through the resistor R3, a power supply negative electrode is connected with a ground wire network, a pin 3 of the chip U2 is connected with the resistor R3 and a pin 2 of the capacitor C3, a pin 2 of the chip U2 is connected with the pin 1 of the capacitor C3, a VDD in the rear-stage load C unit is connected with a pin 1 of the resistor R5, and a pin 2 of the resistor R5 is connected with the pin 2 of the chip U2 and the pin 1 of the capacitor C3. The overvoltage and undervoltage protection circuit is low in cost, high in circuit accuracy and flexible and adjustable in overvoltage and undervoltage protection range.

Description

Technical Field

[0001] The utility model relates to the field of electronic products, in particular to a high-precision, flexible and adjustable over-voltage and under-voltage protection circuit. Background Art

[0002] In many electronic products around us, the input power supply is a DC power supply, and the input power supply range is large (that is, the input end requires a wide power supply), for example: 5~12V; or 10~24V, etc. Customers require that the product can work normally within this voltage range. When this voltage range is exceeded, the product can enter the protection state. We usually need 1 to 2 integrated circuits to complete the circuit design. The traditional over-voltage and under-voltage protection circuit design has several major disadvantages: 1 to 2 ICs are required, and the circuit design cost is high; plus there are many devices around each chip, so when encountering a board with a small PCB size, when drawing the PCB board, the devices cannot be placed due to the small space. Utility Model Content

[0003] The purpose of the utility model is to provide a high-precision, flexible and adjustable over-voltage and under-voltage protection circuit to solve the above technical problems.

[0004] To achieve the above purpose, the utility model adopts the following technical solutions:

[0005] The invention discloses a high-precision, flexible and adjustable over- and under-voltage protection circuit. The circuit consists of three units, namely, an over-voltage protection unit A, an under-voltage protection unit B and a post-stage load C unit. In the over-voltage protection unit A, the positive pole of the power supply is connected to the resistor R2 and the capacitor C1 via the resistor R1, the negative pole of the power supply is connected to a grounding wire network, the 1st pin of the chip U1 is connected to the resistor R1 and the resistor R2, the 3rd pin of the chip U1 is connected to the ground, the 2nd pin of the chip U1 is connected to the 1st pin of the capacitor C2, in the under-voltage protection unit B, the positive pole of the power supply is connected to the resistor R4, the capacitor C2 and the 1st pin of the chip U2 via the resistor R3, the negative pole of the power supply is connected to the grounding wire network, the 3rd pin of the chip U2 is connected to the resistor R3 and the 2nd pin of the capacitor C3 respectively, the 2nd pin of the chip U2 is connected to the 1st pin of the capacitor C3, in the post-stage load C unit, VDD is connected to the 1st pin of the resistor R5, the 2nd pin of the resistor R5 is connected to the 2nd pin of the chip U2 and the 1st pin of the capacitor C3.

[0006] Chip U1 and chip U2 both use TL431.

[0007] Compared with the prior art, the utility model has the following advantages: the utility model has only a few simple discrete components and is low in cost; the number of components is extremely small, which greatly saves space when drawing the PCB board; the starting control voltage can accurately achieve a high progress of 1% error; the setting range of overvoltage and undervoltage can be flexibly adjusted according to circuit requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a circuit schematic diagram of the utility model. DETAILED DESCRIPTION

[0009] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0010] A high-precision, flexible and adjustable over- and under-voltage protection circuit, the circuit consists of three units, an over-voltage protection unit A, an under-voltage protection unit B, and a post-stage load C unit. In the over-voltage protection unit A, the positive pole of the power supply is connected to the resistor R2 and the capacitor C1 through the resistor R1, the negative pole of the power supply is grounded to a network, the 1st pin of the chip U1 is connected to the resistor R1 and the resistor R2, the 3rd pin of the chip U1 is grounded, and the 2nd pin of the chip U1 is connected to the 1st pin of the capacitor C2. In the under-voltage protection unit B, the positive pole of the power supply is connected to the resistor R4, the capacitor C2 and the 1st pin of the chip U2 through the resistor R3, the negative pole of the power supply is grounded to a network, the 3rd pin of the chip U2 is connected to the 2nd pin of the resistor R3 and the capacitor C3 respectively, the 2nd pin of the chip U2 is connected to the 1st pin of the capacitor C3, and in the post-stage load C unit, VDD is connected to the 1st pin of the resistor R5, and the 2nd pin of the resistor R5 is connected to the 2nd pin of the chip U2 and the 1st pin of the capacitor C3. The chip U1 and the chip U2 are both TL431.

[0011] Circuit control principle of the utility model:

[0012] 1) When the external power supply voltage is on ( Figure 1 ) in the output voltage range is ≤2.5V. When the network name "POWER" in the output voltage range does not exceed the set over / under voltage range (i.e., within the normal operating voltage range), the voltage of the voltage divider of R1, R2 (i.e., the first foot of U1) is ≥2.5V. When this voltage is compared with the internal reference voltage vref (2.5V) of U1, the output voltage of the second foot of U1 is ≥2.5V. When this voltage is compared with the internal reference voltage vref (2.5V) of U2, the second foot of U2 (i.e., the second foot of load R4) is pulled low, and current flows through load R4, i.e., load R4 is in normal operating state.

[0013] 2)) When the external power supply voltage is on ( Figure 1 ) begins to rise. When the voltage of the network name "POWER" in the circuit begins to rise and reaches the preset overvoltage, the voltage of the first pin of U1 will rise to ≥2.5V. This voltage is compared with the internal reference voltage vref (2.5V) of U1, and the output of the second pin of U1 is pulled down to ≤2.5V. This voltage is compared with the internal reference voltage vref (2.5V) of U2, and the output of the second pin of U2 immediately changes from the original low level to the high level, that is, the second pin of the load (R4) changes from the original low level during operation to the high level. The first pin of R4 is also at a high level. Since both ends of the load (R4) are at a high level, there is no current flowing through the load (R4), and the circuit enters the protection state.

[0014] 3) When the external power supply voltage is on ( Figure 1) begins to drop, and when it reaches the preset undervoltage voltage, the voltage of U2's first foot drops to ≤2.5V. This voltage is compared with U2's internal reference voltage vref (2.5V), and the output of U2's second foot immediately changes from the original low level to a high level. The first foot of R4 is also high level, that is, both ends of the load (R4) are high level, so no current flows through the load (R4), and the circuit enters the protection state.

[0015] The above is a preferred embodiment of the present invention. For ordinary technicians in this field, according to the teachings of the present invention, without departing from the principles and spirit of the present invention, changes, modifications, substitutions and variations made to the implementation methods are still within the scope of protection of the present invention.

Claims

1. A high-precision, flexible and adjustable over-voltage and under-voltage protection circuit, characterized in that: The circuit consists of three units: overvoltage protection unit A, undervoltage protection unit B, and post-load unit C. In the overvoltage protection unit A, the positive pole of the power supply is connected to the resistor R2 and the capacitor C1 via the resistor R1, the negative pole of the power supply is connected to the ground wire network, the pin 1 of the chip U1 is connected to the resistor R1 and the resistor R2, the pin 3 of the chip U1 is grounded, and the pin 2 of the chip U1 is connected to the pin 1 of the capacitor C2. In the undervoltage protection unit B, the positive pole of the power supply is connected to the resistor R4, the capacitor C2 and the pin 1 of the chip U2 via the resistor R3, the negative pole of the power supply is connected to the ground wire network, the pin 3 of the chip U2 is connected to the resistor R3 and the pin 2 of the capacitor C3 respectively, and the pin 2 of the chip U2 is connected to the pin 1 of the capacitor C3. In the post-stage load C unit, VDD is connected to the pin 1 of the resistor R5, and the pin 2 of the resistor R5 is connected to the pin 2 of the chip U2 and the pin 1 of the capacitor C3.

2. A high-precision, flexible and adjustable over-voltage and under-voltage protection circuit as claimed in claim 1, characterized in that: Chip U1 and chip U2 both use TL431.

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