AC voltage detection method

Abstract

The invention provides an AC voltage detection method. A detection circuit comprises an isolation sampling circuit, a proportion and offset circuit, a comparator circuit and a load driving circuit. The isolation sampling circuit samples the AC voltage; the proportion and offset circuit offsets the sampling voltage to a measurable range, reduces the sampling voltage according to the proportion and outputs the sampling voltage to the comparator circuit; the comparator circuit compares the input voltage with the reference voltage and outputs a comparison result to the load driving circuit, when the input voltage is smaller than the overvoltage reference voltage and larger than the undervoltage reference voltage, the comparator circuit outputs a normal signal, and when the input voltage is larger than the overvoltage reference voltage or smaller than the undervoltage reference voltage, the comparator circuit outputs a normal signal. The comparator circuit outputs a fault signal; the load driving circuit drives the AC circuit to be closed when inputting a normal signal, and drives the AC circuit to be disconnected when inputting a fault signal. The AC voltage detection method provided by the invention is short in response time, low in power consumption and high in reliability.

Description

Technical Field

[0001] The invention belongs to the field of AC circuit applications, and in particular, relates to an AC voltage detection method. Background Art

[0002] For devices using AC power, they have their own rated working voltages. In actual use, due to the instability of the power grid, the output voltage signal may be too high, causing damage to the electronic devices and electrical equipment in the subsequent circuits. At the same time, the line voltage may drop significantly or even disappear in a short period of time, which may also cause damage to electronic devices and electrical equipment. In order to ensure the normal operation of the equipment, it should be ensured that when an abnormal situation occurs and causes the voltage fluctuation of the power grid, the equipment can automatically protect itself, stop working, and other operations. To achieve this function, an AC voltage detection and protection solution is required. Today's solutions generally use MCUs with programming capabilities to perform real-time detection of power grid signals. When abnormal voltage is detected, corresponding protection is performed through certain logical operations. However, this detection and protection method has problems such as high failure rate, high power consumption, and insufficient response in actual applications. Other methods that use hardware for detection also have limitations such as only being able to detect overcurrent in AC circuits.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide an AC voltage detection method which has a quick response time, low power consumption, high reliability and can simultaneously detect whether the AC circuit voltage is too high or too low.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] An AC voltage detection method, the detection circuit includes: an isolation sampling circuit, a ratio and offset circuit, a comparator circuit, and a load driving circuit.

[0007] The isolated sampling circuit samples the AC voltage; the proportional and offset circuit offsets the sampled voltage to a measurable range, and reduces the offset sampled voltage proportionally and outputs it to the comparator circuit; the comparator circuit compares the input voltage with the reference voltage and outputs the comparison result to the load driving circuit; when the input voltage is less than the overvoltage reference voltage and greater than the undervoltage reference voltage, the comparator circuit outputs a normal signal; when the input voltage is greater than the overvoltage reference voltage or less than the undervoltage reference voltage, the comparator circuit outputs a fault signal; when the load driving circuit inputs a normal signal, the AC circuit is driven to close, and when a fault signal is input, the AC circuit is driven to open.

[0008] Preferably, it is characterized in that the isolation sampling circuit includes an isolation transformer, a first resistor, a second resistor, and a third resistor.

[0009] The isolation transformer electrically isolates the AC circuit from the detection circuit; the first resistor and the second resistor are arranged on the primary side of the isolation transformer to divide the AC voltage; the third resistor is arranged on the secondary side of the isolation transformer to sample the AC voltage.

[0010] Preferably, the proportion and offset circuit includes a fourth resistor, a fifth resistor, a sixth resistor, an eleventh resistor, a second capacitor, and an operational amplifier.

[0011] The fourth resistor and the fifth resistor shift the sampled voltage to a measurable range; the sixth resistor, the eleventh resistor, the second capacitor, and the operational amplifier scale down the shifted sampled voltage in proportion.

[0012] Preferably, the comparator circuit includes a first comparator, a second comparator, a first diode, a second diode, a ninth resistor, and a voltage-stabilizing diode.

[0013] The first comparator compares the input voltage with the overvoltage reference voltage, and the second comparator compares the input voltage with the undervoltage reference voltage; when the input voltage is less than the overvoltage reference voltage and greater than the undervoltage reference voltage, the first comparator and the second comparator both output a low-level signal or a high-level signal at the same time, so that the first diode and the second diode are both cut off, the voltage regulator diode is cut off, and the comparator circuit outputs a low-level signal.

[0014] Preferably, when the input voltage is less than the undervoltage reference voltage, the first comparator outputs a low-level signal and the second comparator outputs a high-level signal, so that the first diode is cut off and the second diode is turned on; or the first comparator outputs a high-level signal and the second comparator outputs a low-level signal, so that the first diode is turned on and the second diode is cut off; the Zener diode operates in a regulated state, and the comparator circuit outputs a high-level signal.

[0015] Preferably, when the input voltage is greater than the overvoltage reference voltage, the first comparator outputs a high-level signal and the second comparator outputs a low-level signal, so that the first diode is turned on and the second diode is cut off; or the first comparator outputs a low-level signal and the second comparator outputs a high-level signal, so that the first diode is cut off and the second diode is turned on; the Zener diode operates in a regulated state, and the comparator circuit outputs a high-level signal.

[0016] Preferably, the detection circuit further includes a state latch, which receives the level signal output by the comparator circuit and outputs the level signal to the load driving circuit.

[0017] When the state latch receives a low level signal, it outputs a high level signal; after receiving a high level signal, it continues to output a low level signal; when and only when the reset signal outputs a low level, the state latch switches to outputting a high level signal.

[0018] Preferably, the load driving circuit includes a driving chip and a relay.

[0019] When the load driving circuit inputs a high level signal, the driving chip drives the relay to close and the AC circuit to close; when the load driving circuit inputs a low level signal, the driving chip drives the relay to open and the AC circuit to open.

[0020] Preferably, the detection circuit further includes a follower, which receives the current output by the proportional and offset circuit and outputs it to the comparator circuit to isolate the previous and next stage circuits.

[0021] Preferably, the detection circuit further includes a first capacitor, and the first capacitor is used to filter out low-frequency interference of the sampling current of the isolation and sampling circuit.

[0022] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0023] 1. The AC voltage detection method provided by the present invention is based on a hardware detection method with fast response time, high reliability and low power consumption; and can promptly drive the AC circuit to disconnect when it is detected that the AC circuit voltage is too high or too low, thereby having a better protection effect on the equipment connected in the AC circuit.

[0024] 2. The AC voltage detection method provided by the present invention electrically isolates the detected circuit from the detection circuit, thereby avoiding electrical interference between the strong current line and the weak current line and improving the reliability of detection.

[0025] 3. The AC voltage detection method provided by the present invention can realize the fault latching function, thereby avoiding the situation where the circuit is opened and then closed before the voltage is too high or too low, thereby causing damage to the equipment on the circuit.

[0026] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0028] Figure 1 It is a circuit principle diagram of the AC voltage detection method of the present invention.

[0029] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0031] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] like Figure 1 As shown, the present invention provides an AC voltage detection method for detecting whether the voltage value of an AC circuit remains within a normal range, and can disconnect the AC circuit in time when the voltage value exceeds the normal range, so as to prevent the equipment in the AC circuit from being unable to be used normally or being damaged when the voltage is too high or too low.

[0034] The detection circuit includes: an isolated sampling circuit 1, a proportional and offset circuit 2, a comparator circuit 4, and a load driving circuit 6; the AC circuit to be tested is connected to the input end of the isolated sampling circuit 1, the output end of the isolated sampling circuit 1 is connected to the input end of the proportional and offset circuit 2, the output end of the proportional and offset circuit 2 is connected to the input end of the comparator circuit 4, the output end of the comparator circuit 4 is connected to the input end of the load driving circuit 6, and the control end of the load driving circuit 6 is connected to the AC circuit.

[0035] The isolated sampling circuit 1 samples the AC voltage; the proportional and offset circuit 2 offsets the sampled voltage to a measurable range, and reduces the offset sampled voltage proportionally and outputs it to the comparator circuit 4; the comparator circuit 4 compares the input voltage with the reference voltage and outputs the comparison result to the load driving circuit 6. When the input voltage is less than the overvoltage reference voltage and greater than the undervoltage reference voltage, the comparator circuit 4 outputs a normal signal; when the input voltage is greater than the overvoltage reference voltage or less than the undervoltage reference voltage, the comparator circuit 4 outputs a fault signal; when the load driving circuit 6 inputs a normal signal, it drives the AC circuit to close; when a fault signal is input, it drives the AC circuit to open.

[0036] The isolation sampling circuit 1 includes an isolation transformer CT1 , a first resistor R1 , a second resistor R2 , and a third resistor R3 .

[0037] The primary side of the isolation transformer CT1 is connected to the AC circuit to be tested, one end of the primary winding is connected to the live wire of the AC circuit, and the other end of the primary winding is connected to the neutral wire of the AC circuit. The secondary side is connected to the input end of the proportional and offset circuit 2 as the output end of the isolation sampling circuit 1, so as to electrically isolate the AC circuit to be tested from the detection circuit; the first resistor R1 and the second resistor R2 are voltage-dividing resistors, which are arranged on the primary side of the isolation transformer CT1 and are arranged in series with the primary winding to divide the AC voltage; the third resistor R3 is a sampling resistor, which is arranged on the secondary side of the isolation transformer CT1 and is arranged in parallel with the secondary winding to sample the voltage of the AC circuit to be tested and obtain a sampled voltage.

[0038] The ratio and offset circuit 2 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, an eleventh resistor R11, a second capacitor C2, and an operational amplifier U1.

[0039] The fifth resistor R5 is arranged in parallel with the secondary winding of the isolation transformer CT1; one end of the fourth resistor R4 is connected to the fifth resistor R5, and the other end is connected to the power supply end; the output end of the operational amplifier U1 is connected to the input end of the comparator circuit 4 as the output end of the proportional and offset circuit 2, and the in-phase input end is connected to one end of the fifth resistor R5; one end of the eleventh resistor R11 is connected to the inverting input end of the operational amplifier U1, and the other end is connected to one end of the second capacitor C2; the other end of the second capacitor C2 is divided into two paths, one path is connected to the other end of the fifth resistor R5, and the other path is grounded; one end of the sixth resistor R6 is connected to the inverting input end of the operational amplifier U1, and the other end is connected to the output end of the operational amplifier U1.

[0040] The fourth resistor R4 and the fifth resistor R5 are voltage shift resistors, which shift the sampling voltage to a measurable range between 0-VDD; the sixth resistor R6, the eleventh resistor R11, the second capacitor C2 and the operational amplifier U1 form a proportional operation circuit, which scales down the offset sampling voltage in proportion, and outputs the scaled-down sampling voltage to the comparator circuit 4.

[0041] The comparator circuit 4 includes a first comparator U3 and a second comparator U4.

[0042] The non-inverting input terminal of the first comparator U3 and the inverting input terminal of the second comparator U4 are connected to the output terminal of the proportional and offset circuit 2 as the input terminal of the comparator circuit 4, the overvoltage reference voltage is input to the inverting input terminal of the first comparator U3, and the undervoltage reference voltage is input to the non-inverting input terminal of the second comparator U4; or, the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4 are connected to the output terminal of the proportional and offset circuit 2 as the input terminal of the comparator circuit 4, the overvoltage reference voltage is input to the non-inverting input terminal of the first comparator U3, and the undervoltage reference voltage is input to the inverting input terminal of the second comparator U4.

[0043] The comparator circuit 4 further includes a first diode D1 , a second diode D2 , an eighth resistor R8 , a ninth resistor R9 , and a voltage stabilizing diode ZD1 .

[0044] The anode of the first diode D1 is connected to the output end of the first comparator U3, the anode of the second diode D2 is connected to the output end of the second comparator U4, and the cathodes of the first diode D1 and the second diode D2 are connected to one end of the eighth resistor R8; the other end of the eighth resistor R8 is divided into three paths, the first path is connected to the input end of the load driving circuit 6, the second path is connected to the cathode of the voltage regulator diode ZD1, and the third path is connected to one end of the ninth resistor R9; the other end of the ninth resistor R9 is divided into two paths, one path is connected to the anode of the voltage regulator diode ZD1, and the other path is grounded.

[0045] The eighth resistor R8 is a current limiting resistor, and the ninth resistor R9 is a pull-down resistor.

[0046] The first comparator U3 compares the input voltage with an overvoltage reference voltage, and the second comparator U4 compares the input voltage with an undervoltage reference voltage.

[0047] When the input voltage is less than the overvoltage reference voltage and greater than the undervoltage reference voltage: the first comparator U3 and the second comparator U4 both output a low level signal or a high level signal at the same time, so that the first diode D1 and the second diode D2 are both cut off, the Zener diode ZD1 is cut off, and the comparator circuit 4 outputs a low level signal.

[0048] When the input voltage is less than the undervoltage reference voltage: the first comparator U3 outputs a low level signal and the second comparator U4 outputs a high level signal, so that the first diode D1 is cut off and the second diode D2 is turned on; or the first comparator U3 outputs a high level signal and the second comparator U4 outputs a low level signal, so that the first diode D1 is turned on and the second diode D2 is cut off; the Zener diode ZD1 works in the voltage stabilization state, and the comparator circuit 4 outputs a high level signal.

[0049] When the input voltage is greater than the overvoltage reference voltage: the first comparator U3 outputs a high-level signal, and the second comparator U4 outputs a low-level signal, so that the first diode D1 is turned on and the second diode D2 is turned off; or the first comparator U3 outputs a low-level signal, and the second comparator U4 outputs a high-level signal, so that the first diode D1 is turned off and the second diode D2 is turned on; the Zener diode ZD1 works in a regulated state, and the comparator circuit 4 outputs a high-level signal.

[0050] The detection circuit may further include a state latch U5 , an input end of the state latch U5 is connected to an output end of the comparator circuit 4 , and an output end of the state latch U5 is connected to an input end of the load driving circuit 6 .

[0051] The state latch U5 receives the level signal output by the comparator circuit 4, and outputs the level signal to the load driving circuit 6; when the state latch U5 receives a low level signal, it outputs a high level signal; after receiving a high level signal, it outputs a low level signal, and no matter how the input level signal changes subsequently, the state latch U5 always continues to output a low level signal; when and only when the reset signal outputs a low level, the output state of the state latch U5 will change and turn to output a high level signal.

[0052] The load driving circuit 6 includes a tenth resistor R10, a driving chip U6, a third capacitor C3, and a relay RL1.

[0053] One end of the tenth resistor R10 is connected to the output end of the state latch U5 as the input end of the load driving circuit 6, and the other end is connected to the signal end of the driving chip U6; the input end of the relay RL1 is connected to the driving end of the driving chip U6, and the two contacts of the relay RL1 are respectively connected to the incoming and outgoing lines of the live wire of the AC circuit; the working power supply is connected to the driving chip U6 and is grounded after passing through the driving chip U6, and one end of the third capacitor C3 is connected to the working power supply, and the other end is grounded.

[0054] The tenth resistor R10 is a current limiting resistor, and the third capacitor C3 is a filter capacitor.

[0055] When the load driving circuit 6 inputs a high level signal, the driving chip U6 drives the relay RL1 to close, and the AC circuit is closed; when the load driving circuit 6 inputs a low level signal, the driving chip U6 drives the relay RL1 to open, and the AC circuit is opened.

[0056] The detection circuit may further include a follower circuit 3 , wherein the follower circuit 3 includes a follower U2 and a seventh resistor R7 .

[0057] One input end of the follower U2 is connected to the output end of the ratio and offset circuit 2, and the output end of the follower U2 is connected to the input end of the comparator circuit 4; one end of the seventh resistor R7 is connected to the output end of the follower U2, and the other end is connected to the other input end of the follower U2. Preferably, the other end of the seventh resistor R7 is connected to the inverting input end of the follower U2, and the non-inverting input end of the follower U2 is connected to the output end of the ratio and offset circuit 2.

[0058] The follower U2 receives the current output by the proportional and offset circuit 2 and outputs it to the comparator circuit 4 to isolate the previous and next stage circuits.

[0059] The detection circuit may further include a first capacitor C1, which is an AC coupling capacitor connected in series between the isolation sampling circuit 1 and the ratio and offset circuit 2 to couple the AC signal of the front stage to the back stage circuit to filter out low-frequency interference.

[0060] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0061] 1. The AC voltage detection method provided by the present invention is based on a hardware detection method with fast response time, high reliability and low power consumption; and can promptly drive the AC circuit to disconnect when it is detected that the AC circuit voltage is too high or too low, thereby having a better protection effect on the equipment connected in the AC circuit.

[0062] 2. The AC voltage detection method provided by the present invention electrically isolates the detected circuit from the detection circuit, thereby avoiding electrical interference between the strong current line and the weak current line and improving the reliability of detection.

[0063] 3. The AC voltage detection method provided by the present invention can realize the fault latching function, thereby avoiding the situation where the circuit is opened and then closed before the voltage is too high or too low, thereby causing damage to the equipment on the circuit.

[0064] The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content suggested above without departing from the scope of the technical solution of the present invention. The implementation scheme in the above embodiment can also be further combined or replaced. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the solution of the present invention.

Claims

1. An AC voltage detection method, characterized in that: The detection circuit includes: an isolation sampling circuit, a ratio and offset circuit, a comparator circuit, and a load driving circuit; The isolated sampling circuit samples the AC voltage; the proportional and offset circuit offsets the sampled voltage to a measurable range, and reduces the offset sampled voltage proportionally and outputs it to the comparator circuit; the comparator circuit compares the input voltage with the reference voltage and outputs the comparison result to the load driving circuit; when the input voltage is less than the overvoltage reference voltage and greater than the undervoltage reference voltage, the comparator circuit outputs a normal signal; when the input voltage is greater than the overvoltage reference voltage or less than the undervoltage reference voltage, the comparator circuit outputs a fault signal; when the load driving circuit inputs a normal signal, the AC circuit is driven to close; when a fault signal is input, the AC circuit is driven to open.

2. The AC voltage detection method according to claim 1, characterized in that: The isolation sampling circuit includes an isolation transformer, a first resistor, a second resistor, and a third resistor; The isolation transformer electrically isolates the AC circuit from the detection circuit; the first resistor and the second resistor are arranged on the primary side of the isolation transformer to divide the AC voltage; the third resistor is arranged on the secondary side of the isolation transformer to sample the AC voltage.

3. The AC voltage detection method according to claim 1, characterized in that: The ratio and offset circuit includes a fourth resistor, a fifth resistor, a sixth resistor, an eleventh resistor, a second capacitor, and an operational amplifier; The fourth resistor and the fifth resistor shift the sampled voltage to a measurable range; the sixth resistor, the eleventh resistor, the second capacitor, and the operational amplifier scale down the shifted sampled voltage in proportion.

4. The AC voltage detection method according to claim 1, characterized in that: The comparator circuit includes a first comparator, a second comparator, a first diode, a second diode, a ninth resistor, and a voltage stabilizing diode; The first comparator compares the input voltage with the overvoltage reference voltage, and the second comparator compares the input voltage with the undervoltage reference voltage; when the input voltage is less than the overvoltage reference voltage and greater than the undervoltage reference voltage, the first comparator and the second comparator both output a low-level signal or a high-level signal at the same time, so that the first diode and the second diode are both cut off, the voltage regulator diode is cut off, and the comparator circuit outputs a low-level signal.

5. The AC voltage detection method according to claim 4, characterized in that: When the input voltage is less than the undervoltage reference voltage, The first comparator outputs a low level signal and the second comparator outputs a high level signal, so that the first diode is turned off and the second diode is turned on; or the first comparator outputs a high level signal and the second comparator outputs a low level signal, so that the first diode is turned on and the second diode is turned off; The voltage stabilizing diode operates in a voltage stabilizing state, and the comparator circuit outputs a high level signal.

6. The AC voltage detection method according to claim 4, characterized in that: When the input voltage is greater than the overvoltage reference voltage, The first comparator outputs a high level signal and the second comparator outputs a low level signal, so that the first diode is turned on and the second diode is turned off; or the first comparator outputs a low level signal and the second comparator outputs a high level signal, so that the first diode is turned off and the second diode is turned on; The voltage stabilizing diode operates in a voltage stabilizing state, and the comparator circuit outputs a high level signal.

7. The AC voltage detection method according to any one of claims 4 to 6, characterized in that: The detection circuit also includes a state latch, which receives the level signal output by the comparator circuit and outputs the level signal to the load driving circuit; When the state latch receives a low level signal, it outputs a high level signal; after receiving a high level signal, it continues to output a low level signal; when and only when the reset signal outputs a low level, the state latch switches to outputting a high level signal.

8. The AC voltage detection method according to claim 7, characterized in that: The load driving circuit includes a driving chip and a relay; When the load driving circuit inputs a high level signal, the driving chip drives the relay to close and the AC circuit to close; when the load driving circuit inputs a low level signal, the driving chip drives the relay to open and the AC circuit to open.

9. The AC voltage detection method according to claim 1, characterized in that: The detection circuit also includes a follower, which receives the current output by the ratio and offset circuit and outputs it to the comparator circuit to isolate the previous and next stage circuits.

10. The AC voltage detection method according to claim 1, characterized in that: The detection circuit also includes a first capacitor, which is used to filter out low-frequency interference of the sampling current of the isolation and sampling circuit.

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