An isolated ac voltage detection circuit

Abstract

The utility model discloses an isolated alternating voltage detection circuit relates to electric signal detection field, and this isolated alternating voltage detection circuit includes diode D1, the positive pole of diode D1 is connected the negative pole of diode D2, the third end of flyback transformer T1, the first end of flyback transformer T1 is grounded, the negative pole of diode D1 is connected one end of capacitor E1, the input end of three -terminal voltage stabilizing chip IC1, the utility model has the beneficial effect is: the utility model utilizes the forward conduction voltage of flyback transformer to do feedback control, and the forward voltage is used to voltage stabilizing, also makes full use of the negative voltage of flyback transformer to monitor the size and power -down condition of flyback input alternating voltage, and voltage sampling is accurate, will not influence the grid voltage judgment, the component cost of whole circuit is low, and all adopt ordinary conventional device, and the economic benefit is very considerable, the selected device and material are all general spare, and the industrialization of circuit is very easy to realize.

Description

Technical Field

[0001] This utility model relates to the field of electrical signal detection, specifically an isolated AC voltage detection circuit. Background Technology

[0002] The voltage of the power grid in daily life fluctuates to some extent, and it is also easily affected by external weather factors (such as lightning and heavy loads). If the fluctuation of the power grid voltage cannot be monitored in time, both excessively high and low power supply will affect the product. At best, it will affect the normal operation of the product, and at worst, it will cause damage to the product.

[0003] Currently, the commonly used method is to sample the bus voltage using a non-isolated ADC dedicated chip, and then transmit the data to the microprocessor (MCU) on the non-isolated side via an optocoupler, or directly use a linear isolation optocoupler. However, the discreteness and temperature drift of the optocoupler can lead to inaccurate voltage sampling, affecting the judgment of the grid voltage, which needs to be improved. Utility Model Content

[0004] The purpose of this invention is to provide an isolated AC voltage detection circuit to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] An isolated AC voltage detection circuit includes a diode D1, the anode of diode D1 being connected to the cathode of diode D2 and the third terminal of flyback transformer T1, the first terminal of flyback transformer T1 being grounded, the cathode of diode D1 being connected to one end of capacitor E1 and the input terminal of three-terminal voltage regulator chip IC1, the other end of capacitor E1 being grounded, the ground terminal of three-terminal voltage regulator chip IC1 being grounded, the output terminal of three-terminal voltage regulator chip IC1 being connected to one end of resistor R1, the anode of diode D2 being connected to one end of resistor R2, the other end of resistor R2 being connected to one end of capacitor C1 and one end of resistor R3, the other end of capacitor C1 being grounded, the other end of resistor R3 being connected to the other end of resistor R1 and an MCU microprocessor.

[0007] As a further improvement of this utility model, the first and third ends of the flyback transformer T1 are secondary windings.

[0008] As a further improvement of this utility model, capacitor E1 is an electrolytic capacitor.

[0009] As a further improvement of this utility model, an electrolytic capacitor with a rated voltage of 400V is provided at the primary winding of the flyback transformer T1.

[0010] As a further improvement of this utility model, the output terminal of the three-terminal voltage regulator chip IC1 outputs a 5V voltage.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model uses the forward conduction voltage of the flyback transformer for feedback control, and the forward voltage is used for voltage stabilization. It also makes full use of the negative voltage of the flyback transformer to monitor the magnitude of the input AC voltage and the power failure status of the flyback transformer. The voltage sampling is accurate and will not affect the judgment of the grid voltage. The components selected in the entire circuit are low cost and all use ordinary conventional components, which is very economical. The selected components and materials are all general-purpose components, and the industrialization of the circuit can be easily realized. Attached Figure Description

[0012] Figure 1 This is a circuit diagram of an isolated AC voltage detection circuit. Detailed Implementation

[0013] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0014] Please see Figure 1 An isolated AC voltage detection circuit includes a diode D1, the anode of diode D1 being connected to the cathode of diode D2 and the third terminal of flyback transformer T1, the first terminal of flyback transformer T1 being grounded, the cathode of diode D1 being connected to one end of capacitor E1 and the input terminal of three-terminal voltage regulator chip IC1, the other end of capacitor E1 being grounded, the ground terminal of three-terminal voltage regulator chip IC1 being grounded, the output terminal of three-terminal voltage regulator chip IC1 being connected to one end of resistor R1, the anode of diode D2 being connected to one end of resistor R2, the other end of resistor R2 being connected to one end of capacitor C1 and one end of resistor R3, the other end of capacitor C1 being grounded, the other end of resistor R3 being connected to the other end of resistor R1 and an MCU microprocessor.

[0015] In this embodiment: Please refer to Figure 1 The first and third terminals of the flyback transformer T1 are the secondary windings.

[0016] The primary winding of flyback transformer T1 is connected to the mains voltage via a MOSFET. Flyback transformer T1 is a high-frequency transformer in a flyback switching power supply.

[0017] In this embodiment: Please refer to Figure 1 Capacitor E1 is an electrolytic capacitor.

[0018] The core competitiveness of electrolytic capacitors lies in their ability to provide a very large capacitance within a relatively small volume, thus maintaining the voltage supply to the circuit for a period of time after the mains voltage is disconnected.

[0019] In this embodiment: Please refer to Figure 1 An electrolytic capacitor with a rated voltage of 400V is installed at the primary winding of the flyback transformer T1.

[0020] The rated voltage of 400V was chosen because, in a 220V AC power system, considering voltage fluctuations in the power grid and transient high voltages such as lightning strikes, a 400V capacitor with sufficient margin can effectively ensure the reliability and safety of the circuit operation.

[0021] In this embodiment: Please refer to Figure 1 The output of the three-terminal voltage regulator IC1 is 5V.

[0022] The three-terminal voltage regulator IC1 can be of model such as LM78L05, LM78M05, AMS1117-5.0, etc. These are just three examples. In actual use, any three-terminal voltage regulator chip that can meet the requirements of 12V input and 5V output can be used.

[0023] The working principle of this utility model is as follows: Please refer to... Figure 1 The leftmost part of the diagram is the secondary winding of the high-frequency transformer T1 of the flyback switching power supply. When the MOSFET on the primary side of the switching power supply is turned off, the positive half-cycle waveform of the primary winding is rectified by diode D1 to output a 12V voltage, which is then output as a 5V voltage by the three-terminal voltage regulator IC1 as the working voltage of the MCU microprocessor.

[0024] When the MOSFET on the primary side of the switching power supply is turned on, the negative half-cycle waveform of the primary winding is rectified by diode D2 to produce a negative voltage. After being filtered by resistor R2 and capacitor C1, this negative voltage is divided by resistors R1 and R3 between the MOSFET and the 5V voltage. The resulting negative voltage is then processed and output as a positive AC-V signal to the MCU microprocessor for further processing. The higher the mains voltage input, the higher the negative voltage, resulting in a lower AC-V voltage after voltage division, and consequently, a lower voltage received by the MCU microprocessor.

[0025] When the mains voltage drops, the entire switching power supply maintains a positive voltage output thanks to the front-end capacitor (a 400V electrolytic capacitor is installed on the primary winding of the flyback transformer T1), allowing the 12V output to remain stable for a period of time. Since there is no negative voltage rectified through diode D2, the AC-V voltage will rise (due to the lack of negative voltage input maintaining the AC-V voltage). When the MCU microprocessor detects the continuously rising AC-V voltage, it can be considered an external power failure (plugged out). At this point, the 400V electrolytic capacitor can still maintain a 12V voltage at capacitor E1 through the flyback transformer T1 for a period of time, giving the MCU microprocessor sufficient time to complete a series of control operations. Increasing the capacitance of the front-end electrolytic capacitor will extend this time.

[0026] This circuit uses the forward conduction voltage of the flyback transformer for feedback control. The forward voltage is used for voltage stabilization, and the negative voltage of the flyback transformer is also fully utilized to monitor the magnitude of the input AC voltage of the flyback transformer and the power failure status.

[0027] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0028] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An isolated AC voltage detection circuit, characterized in that, The isolated AC voltage detection circuit includes diode D1. The positive terminal of diode D1 is connected to the negative terminal of diode D2 and the third terminal of flyback transformer T1. The first terminal of flyback transformer T1 is grounded. The negative terminal of diode D1 is connected to one end of capacitor E1 and the input terminal of three-terminal voltage regulator chip IC1. The other end of capacitor E1 is grounded. The ground terminal of three-terminal voltage regulator chip IC1 is grounded. The output terminal of three-terminal voltage regulator chip IC1 is connected to one end of resistor R1. The positive terminal of diode D2 is connected to one end of resistor R2. The other end of resistor R2 is connected to one end of capacitor C1 and one end of resistor R3. The other end of capacitor C1 is grounded. The other end of resistor R3 is connected to the other end of resistor R1 and the MCU microprocessor.

2. The isolated AC voltage detection circuit according to claim 1, characterized in that, The first and third terminals of the flyback transformer T1 are the secondary windings.

3. The isolated AC voltage detection circuit according to claim 1, characterized in that, Capacitor E1 is an electrolytic capacitor.

4. The isolated AC voltage detection circuit according to claim 3, characterized in that, An electrolytic capacitor with a rated voltage of 400V is installed at the primary winding of the flyback transformer T1.

5. The isolated AC voltage detection circuit according to claim 1, characterized in that, The three-terminal voltage regulator IC1 outputs a 5V voltage.

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