A direct current power supply power failure detection circuit and power failure detection module

Abstract

The application discloses a DC power supply power-off detection circuit and a power-off detection module. The DC power supply power-off detection circuit comprises an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a first diode. The non-inverting input end of the operational amplifier is grounded, the inverting input end thereof is connected to a DC negative power supply through the first resistor, the inverting input end thereof is also connected to the first end of the second resistor, and the output end thereof is connected to the negative electrode of the first diode. The positive electrode of the first diode is connected to the first end of the third resistor. The first end of the fourth resistor is connected to a DC positive power supply. The first end of the fifth resistor is grounded. The second end of the second resistor, the second end of the third resistor, the second end of the fourth resistor and the second end of the fifth resistor are all connected to the detection end of a control chip. The power-off detection module comprises the power-off detection circuit and the control chip. The application can simultaneously monitor the voltage changes of the positive power supply and the negative power supply, and has high detection precision.

Description

Technical Field

[0001] This invention relates to the field of circuit technology, specifically to a DC power failure detection circuit and a power failure detection module. Background Technology

[0002] Many electronic products require monitoring of DC power supply voltage. Currently, most power-down protection circuits output a voltage level to the microcontroller chip when the voltage drops below a certain reference value, causing the microcontroller chip to enter power-down mode; when the voltage rises above the reference value, they output another voltage level to the microcontroller chip, causing the microcontroller chip to enter normal operating mode. However, existing DC protection circuits cannot simultaneously detect voltage changes of both positive and negative power supplies, and their accuracy is not high. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects or problems in the prior art and to provide a DC power supply power failure detection circuit and power failure detection module that can simultaneously monitor the voltage changes of the positive and negative power supplies with high detection accuracy.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] Technical Solution 1: A DC power failure detection circuit for connection to the detection terminal of a control chip; the control chip is adapted to output a first signal when the voltage at the detection terminal is higher than a set threshold, and to output a second signal when it does not exceed the set threshold; the DC power failure detection circuit includes an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a first diode; the non-inverting input terminal of the operational amplifier is grounded, its inverting input terminal is connected to a negative DC power supply through the first resistor, its inverting input terminal is also connected to the first terminal of the second resistor, and its output terminal is connected to the negative terminal of the first diode; the positive terminal of the first diode is connected to the first terminal of the third resistor; the first terminal of the fourth resistor is connected to a positive DC power supply; the first terminal of the fifth resistor is grounded; the second terminals of the second, third, fourth, and fifth resistors are all connected to the detection terminal.

[0006] Based on technical solution one, there is also technical solution two, in which a sixth resistor is connected in series between the second end of the second resistor and the detection end.

[0007] Based on technical solution one, there is also technical solution three, in which the operational amplifier is model OPA2171.

[0008] Technical Solution 4: A power failure detection module, comprising a control chip and a DC power failure detection circuit as described in any one of Technical Solutions 1 to 3. The control chip has a first pin, a second pin, and a third pin. The first pin is grounded, and the third pin forms the detection terminal. The control chip is adapted to output a first signal at the second pin when the voltage at the detection terminal is higher than a set threshold, and is adapted to output a second signal at the second pin when the voltage at the detection terminal does not exceed the set threshold.

[0009] Based on technical solution four, there is also technical solution five, in which the control chip model is TLV809K33.

[0010] Based on technical solution four, there is also technical solution six, in which the first signal is a high-level signal and the second signal is a low-level signal.

[0011] Based on technical solution four, there is also technical solution seven, which includes a seventh resistor, and the second pin of the control chip is connected to the first end of the seventh resistor.

[0012] Based on technical solution seven, there is also technical solution eight, which further includes a second diode, an eighth resistor, and a positive power supply. The negative terminal of the second diode is connected to the second end of the seventh resistor, and the positive terminal of the second diode is connected to the positive power supply through the eighth resistor.

[0013] Based on technical solution eight, there is also technical solution nine, which includes a third diode, the negative terminal of which is connected to the second terminal of the seventh resistor, and the positive terminal of the third diode is grounded.

[0014] Based on technical solution nine, there is also technical solution ten. Technical solution ten further includes a first capacitor and a second capacitor. The first end of the first capacitor is connected to the detection terminal, and the second end is grounded. The first end of the second capacitor is connected to the second end of the seventh resistor and the first end of the seventh resistor, and the second end is grounded.

[0015] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. In technical solution one, changes in both the positive and negative DC power supply voltages affect the voltage change at the inverting input of the operational amplifier. Assuming the positive DC power supply voltage is Vp and the negative DC power supply voltage is Vn, when a positive voltage is input to the inverting input of the operational amplifier, the output of the operational amplifier is low, the first diode conducts, and the inverting input, output, first diode, third resistor, and second resistor form a closed-loop circuit. The voltage at the inverting input will continuously adjust until it becomes 0V, and the voltage at the detection terminal is (0...). -Vn) / R1*R2, therefore, the voltage at the detection terminal has a linear relationship with the DC negative power supply voltage. When the DC negative power supply voltage drops to a set threshold, the voltage at the detection terminal also drops to a set threshold, so the control chip can output a first signal or a second signal accordingly; therefore, the circuit of this application can perform power-down detection of the DC negative power supply voltage; when a negative voltage is input to the inverting input terminal of the operational amplifier, the output terminal of the operational amplifier outputs a high level, the first diode is cut off, and at this time, the voltage at the detection terminal is ((Vp / R4+Vn / (R1+R2)) /

[0017] ((1 / (R1+R2)+1 / R4+1 / R5), therefore, when the DC positive power supply voltage drops to a set threshold, the voltage at the detection terminal also drops to a set threshold. Thus, the circuit of this application can perform power-down detection of the DC positive power supply voltage. Therefore, the detection circuit of this solution, whether the DC positive power supply voltage drops or the DC negative power supply voltage drops, the detection terminal can output a certain value according to the change of the DC positive power supply voltage and the DC negative power supply voltage, so that the control chip can output different signals according to the voltage value at the detection terminal, realizing high-precision detection when the DC power supply drops. In practical applications, the resistance values ​​of the first resistor, the second resistor, the third resistor, the fourth resistor, and the fifth resistor can be set accordingly to ensure that the detection terminal reaches the same threshold when the DC positive power supply voltage and the DC negative power supply voltage drop to the same range.

[0018] 2. In technical solution two, a sixth resistor is connected in series between the second end of the second resistor and the detection end to facilitate adjustment of the voltage at the detection end.

[0019] 3. In technical solution three, the operational amplifier model is OPA2171, which is inexpensive and provides precise control.

[0020] 4. In technical solution four, the control chip outputs a first signal at the second pin when the input voltage at the detection end is greater than the set threshold, and outputs a second signal at the second pin when the input voltage at the detection end is less than or equal to the set threshold. This can convert the changes in the DC positive and negative power supply voltages into control signal outputs, resulting in precise control. Specifically, if the DC negative power supply becomes 0V, the first diode conducts, and the terminal voltage VD of the first diode is 0.6-0.7V. At this time, the voltage at the detection end is ((Vp / R4+Vn / (R1+R2)+VD / R3) / ((1 / (R1+R2)+1 / R4+1 / R5). By setting the resistance values ​​of resistors R1-R6, it can be ensured that the voltage at the second pin of the control chip is always greater than the supply voltage.

[0021] 5. In technical solution five, the control chip is model TV809K33, which is inexpensive and provides precise control.

[0022] 6. In technical solution six, the first signal is a high-level signal and the second signal is a low-level signal, which is easy to implement.

[0023] 7. In technical solution seven, the seventh resistor can divide the voltage of the second pin of the control chip.

[0024] 8. In technical solution eight, the configuration of the second diode, the eighth resistor, and the positive power supply ensures that when the second pin of the control chip outputs a high level, the second diode is cut off, and the positive power supply maintains the output potential through the eighth resistor.

[0025] 9. In technical solution nine, when the third pin of the control chip outputs a low level, the third diode can maintain the third pin at a relatively low potential.

[0026] 10. In technical solution ten, the setting of the first capacitor and the second capacitor can achieve the filtering effect. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments are briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the power failure detection module of the present invention;

[0029] Explanation of key figure labels:

[0030] Operational amplifier IC1A; first resistor R1; second resistor R2; third resistor R3; fourth resistor R4; fifth resistor R5; sixth resistor R6; seventh resistor R7; eighth resistor R8; first capacitor C1; second capacitor C2; control chip IC2; first diode D1; second diode D2; third diode D3. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and accompanying drawings of this invention is for distinguishing different objects and not for describing a specific order.

[0033] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0034] See Figure 1 , Figure 1 A power failure detection module is shown, including a DC power failure detection circuit and a control chip IC2.

[0035] The DC power failure detection circuit is used to connect to the detection terminal of the control chip IC2. Figure 1 Point A in the diagram is connected; the control chip IC2 is adapted to output a first signal when the voltage at the detection end is higher than a set threshold, and is adapted to output a second signal when the voltage at the detection end does not exceed the set threshold. Specifically, the control chip IC2 has a first pin 1, a second pin 2, and a third pin 3. The first pin 1 is grounded, and the third pin 3 is connected to the detection end. The control chip IC2 is adapted to output a first signal at the second pin 2 when the voltage at the detection end is higher than the set threshold, and is adapted to output a second signal at the second pin 2 when the voltage at the detection end does not exceed the set threshold. In this embodiment, the control chip IC2 is a TLV809K33, the first signal is a high-level signal, and the second signal is a low-level signal. It is inexpensive and provides precise control.

[0036] The DC power failure detection circuit includes an operational amplifier ICIA, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first diode D1; the non-inverting input of the operational amplifier ICIA is grounded, and its inverting input is connected to the DC negative power supply through the first resistor R1. Figure 1 The inverter (R1) is connected to the first terminal of the second resistor R2, and its output terminal is connected to the cathode of the first diode D1; the anode of the first diode D1 is connected to the first terminal of the third resistor R3; the first terminal of the fourth resistor R4 is connected to the DC positive power supply. Figure 1 The middle value is +15VD); the first terminal of the fifth resistor R5 is grounded; the second terminals of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are all connected to the detection terminal. Figure 1 (Point A in the diagram) A sixth resistor R6 is connected in series between the second end of the second resistor R2 and the detection end. The resistance value of the sixth resistor R6 can be set accordingly to adjust the voltage at the inverting input of the operational amplifier. In this embodiment, R1 is 100KΩ, R2 is 24KΩ, R3 is 1KΩ, R4 is 12KΩ, R5 is 4.7KΩ, and R6 is 0KΩ.

[0037] In specific implementation, the power failure detection module also includes a seventh resistor R7, a second diode D2, an eighth resistor R8, a +5V power supply, a third diode D3, a first capacitor C1, and a second capacitor C2. The second pin 2 of the control chip IC2 is connected to the first end of the seventh resistor R7. The cathode of the second diode D2 is connected to the second end of the seventh resistor R7, and the anode of the second diode D2 is connected to the +5V power supply through the eighth resistor R8. The cathode of the third diode D3 is connected to the second end of the seventh resistor R7, and the anode of the third diode D3 is grounded. The first end of the first capacitor C1 is connected to the detection terminal, and the second end is grounded. The first end of the second capacitor C2 is connected to the second end of the seventh resistor R7, and the second end is grounded.

[0038] The working principle of the power failure detection module in this application is as follows:

[0039] Changes in the voltage of both the positive and negative DC power supply will affect the voltage change at the inverting input terminal of the operational amplifier ICIA. For ease of description, the positive DC power supply voltage is Vp = 15V, the negative DC power supply voltage is Vn = -15V, the voltage at the detection terminal is Vin, and the voltage at the inverting input terminal of the operational amplifier ICIA is Vo.

[0040] When a positive voltage Vo is input to the inverting input terminal of operational amplifier ICIA, the output terminal of operational amplifier ICIA outputs a low level, and the first diode D1 conducts. The input and output terminals of operational amplifier ICIA, the first diode D1, the third resistor R3, and the second resistor R2 form a closed loop. The voltage Vo at the inverting input terminal will continuously adjust until it becomes 0V. The voltage Vin at the detection terminal is (0-Vn) / R1*(R2+R6) = 3.6V. Therefore, the voltage Vin at the detection terminal has a linear relationship with the DC negative power supply voltage. When the DC negative power supply voltage decreases... When the voltage Vin at the detection terminal drops to a set threshold, the voltage Vin at the detection terminal also drops to a set threshold. Therefore, the circuit of this application can perform power-down detection of the DC negative power supply voltage. In this embodiment, the set threshold of the control chip IC2 is 2.93V. Therefore, when the DC negative power supply voltage Vn drops to -12.2V, the second pin 2 of the control chip IC2 outputs a low-level signal. At this time, the third diode D3 can maintain the second pin 2 at a relatively low potential. The seventh resistor R7 can divide the voltage output from the second pin. The setting of the first capacitor C1 and the second capacitor C2 can achieve a filtering effect.

[0041] When a negative voltage Vo is input to the inverting input terminal of the operational amplifier ICIA, the output terminal of the operational amplifier ICIA outputs a high level, and the first diode D1 is cut off. At this time, the voltage Vin at the detection terminal is ((Vp / R4+Vn / (R1+R2+R6)) / ((1 / (R1+R2+R6)+1 / R4+1 / R5)=3.712V(R6=0);

[0042] At this time, the voltage Vo at the inverting input terminal of the op-amp is Vo = (Vin - Vn) / R1 * (R2 + R6) = 0.09V. If the calculated Vo potential is positive, then the voltage Vin at the holding detection terminal is calculated as described above as Vin = (0 - Vn) / R1 * (R2 + R6) = 3.6V. If the calculated Vo potential is negative, then the voltage Vin at the detection terminal is still ((Vp / R4 + Vn / (R1 + R2 + R6)) / ((1 / (R1 + R2 + R6) + 1 / R4 + 1 / R5).

[0043] Therefore, when the DC positive power supply voltage drops to a set threshold, the voltage Vin at the detection terminal also drops to a set threshold. Thus, the circuit of this application can perform power-down detection of the DC positive power supply voltage. When the inverting input Vo of the operational amplifier ICIA is input with a negative potential, changes in either the DC positive or negative power supply voltage will cause changes in the voltage at the detection terminal. However, in this case, the primary detection is still the change in the DC positive power supply voltage. For a set threshold of 2.93V, the second trigger of the control chip IC2 can be achieved when Vn = -15V and Vp = 12.15V. When pin 2 outputs a low-level signal, if Vn = -14V, then Vp = 12.05V will trigger the second pin 2 of control chip IC2 to output a low-level signal; if Vn = -16V, then Vp = 12.25V will trigger the second pin 2 of control chip IC2 to output a low-level signal. It can be seen that in this embodiment, both the DC positive power supply and the DC negative power supply trigger the second pin 2 of control chip IC2 to output a low-level signal when the voltage drops to about 12V. That is, when the voltage of the DC positive power supply and the DC negative power supply drops to the same range, the detection end reaches the same threshold.

[0044] When Vn fluctuates significantly, such as when the DC negative power supply Vn becomes 0V, the input voltage Vo at the inverting input terminal of the operational amplifier is also 0V. At this time, the first diode D1 conducts, and the terminal voltage VD of the first diode D1 is 0.6-0.7V. At this time, the voltage Vin at the detection terminal is ((Vp / R4+Vn / (R1+R2)+VD / R3) / ((1 / (R1+R2+R6)+1 / R4+1 / R5)=1.326V (VD=0.6V, R6=0), thus ensuring that the voltage of the third pin of the control chip IC2 is always greater than the supply voltage of the control chip 1V, ensuring the normal operation of the control chip IC2.

[0045] It should be understood that when the input voltage Vo at the inverting input terminal of the operational amplifier is 0V, the voltage Vn at the detection terminal can be calculated in the two ways mentioned above. In practical applications, the larger calculated value is used as the input voltage at the detection terminal.

[0046] When the DC power supply is working normally, the second pin 2 of the control chip IC2 outputs a high-level signal. The settings of the second diode D2, the eighth resistor R8, and the positive power supply +5VD ensure that when the second pin 2 of the control chip IC2 outputs a high level, the second diode D2 is cut off, so that the positive power supply +5VD maintains the output potential through the eighth resistor R8, which is beneficial for connecting to external circuits.

[0047] Therefore, the detection circuit of this solution can output a specific value based on the changes in the DC positive and negative power supply voltages, regardless of whether the DC positive or negative power supply voltage is lost. In practical applications, this allows connection to the detection terminal of an external control chip, enabling the control chip to output different signals based on the voltage values ​​at the detection terminal, achieving high-precision detection when the DC power supply is lost. In practical applications, the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 can be set accordingly to ensure that the detection terminal reaches the same set threshold when the DC positive and negative power supply voltages drop to the same range. The above description of the specification and embodiments is used to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or some of its technical features that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the above embodiments, should all be included within the scope of protection of this invention.

Claims

1. A DC power failure detection circuit, for connection to the detection terminal of a control chip; the control chip is adapted to output a first signal when the voltage at the detection terminal is higher than a set threshold, and to output a second signal when the voltage does not exceed the set threshold; characterized in that... The DC power failure detection circuit includes an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a first diode; The non-inverting input of the operational amplifier is grounded, its inverting input is connected to a DC negative power supply through a first resistor, its inverting input is also connected to the first end of a second resistor, and its output is connected to the negative terminal of a first diode. The positive terminal of the first diode is connected to the first end of the third resistor; The first terminal of the fourth resistor is connected to a positive DC power supply. The first terminal of the fifth resistor is grounded; The second terminals of the second resistor, the third resistor, the fourth resistor, and the fifth resistor are all connected to the detection terminal.

2. The DC power failure detection circuit as described in claim 1, characterized in that, A sixth resistor is connected in series between the second end of the second resistor and the detection end.

3. The DC power supply failure detection circuit as described in claim 1, characterized in that, The operational amplifier is model OPA2171.

4. A power failure detection module, characterized in that, It includes a control chip and a DC power failure detection circuit as described in any one of claims 1-3, wherein the control chip has a first pin, a second pin and a third pin, the first pin is grounded and the third pin forms the detection terminal; The control chip is adapted to output a first signal at the second pin when the voltage at the detection end is higher than a set threshold, and is adapted to output a second signal at the second pin when the voltage at the detection end does not exceed the set threshold.

5. A power failure detection module as described in claim 4, characterized in that, The control chip is model TLV809K33.

6. A power failure detection module as described in claim 4, characterized in that, The first signal is a high-level signal, and the second signal is a low-level signal.

7. A power failure detection module as described in claim 5, characterized in that, It also includes a seventh resistor, with the second pin of the control chip connected to the first end of the seventh resistor.

8. A power failure detection module as described in claim 7, characterized in that, It also includes a second diode, an eighth resistor, and a positive power supply. The negative terminal of the second diode is connected to the second end of the seventh resistor, and the positive terminal of the second diode is connected to the positive power supply through the eighth resistor.

9. A power failure detection module as described in claim 8, characterized in that, It also includes a third diode, the negative terminal of which is connected to the second terminal of the seventh resistor, and the positive terminal of the third diode is grounded.

10. A power failure detection module as described in claim 9, characterized in that, It also includes a first capacitor and a second capacitor. The first end of the first capacitor is connected to the detection terminal, and the second end is grounded. The first end of the second capacitor is connected to the second end of the seventh resistor and the first end of the seventh resistor, and the second end is grounded.

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