Circuit for power supply frequency detection

Abstract

The utility model discloses a circuit for power supply frequency detection, which is characterized by comprising a first resistor, a second resistor, a capacitor, a first diode, a second diode, a voltage-regulator tube, a PMOS (P-channel Metal Oxide Semiconductor) tube and an optocoupler, the circuit can be directly connected to an alternating current power supply to detect a power supply waveform zero crossing point, and the optocoupler or an optical fiber is adopted to transmit signals. The problem that the alternating-current waveform is not stable enough due to the influence of a load when a signal is taken from the low-voltage side of the transformer is avoided; an energy storage element-capacitor C is used for providing large enough driving current for an optocoupler at a zero crossing point, so that the problem that the measurement precision is reduced due to zero crossing point jitter of an alternating current signal caused by instable alternating current waveform is further avoided; moreover, the circuit is simple in structure, employs passive devices, is low in power consumption, is stable and reliable in operation, and is higher in safety.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the electronic measurement technical field, concretely relates to a circuit for power frequency detection. BACKGROUND

[0002] The statements herein merely provide background information related to the utility model and do not necessarily constitute the prior art.

[0003] In order to evaluate the stability, efficiency and electromagnetic compatibility of the AC power supply, and provide the basis for the design, optimization and quality control of the power supply. Usually need to monitor the frequency of AC power supply, to ensure that the performance of the power supply under different working conditions meets the preset standards and user requirements.

[0004] The traditional method of detecting the frequency of AC power supply is to form a square wave from the AC waveform, and then measure the time difference of adjacent rising or falling edges to obtain the frequency data. However, the traditional circuit needs complex links and hardware such as voltage reduction, isolation, zero-crossing comparison, especially when taking signals from the low-voltage side of the transformer, the AC waveform is not stable due to the influence of the load, which will cause the zero-crossing point of the AC signal to jitter and reduce the measurement accuracy. UTILITY MODEL CONTENTS

[0005] The utility model aims at overcoming the insufficient of prior art, and provides a circuit for power frequency detection, which can be directly connected to the AC power supply to detect the zero-crossing point of the power waveform, and transmit signals through optical coupling or optical fiber, the circuit is simple, reliable, low in power consumption, and high in safety.

[0006] In order to achieve the above-mentioned purpose, the utility model is realized through the following technical scheme:

[0007] The technical scheme of the utility model provides a circuit for power frequency detection, a series branch of a first resistor, a first diode and a stabilizing tube is arranged between the live wire and the zero line of the AC power supply; a capacitor is connected in parallel across the two ends of the stabilizing tube; a series branch of a second resistor, an optical coupling and a PMOS tube source and drain is also connected in parallel across the two ends of the stabilizing tube; a second diode is connected in parallel across the two ends of the series branch of the first diode and the stabilizing tube; the gate of the PMOS tube is connected to the low-voltage end of the first resistor.

[0008] In at least one embodiment, the series branch of the first resistor, the first diode and the stabilizing tube is specifically: the high-voltage end of the first resistor is connected to the live wire of the AC power supply, the low-voltage end is connected to the anode of the first diode, the cathode of the first diode is connected to the negative electrode of the stabilizing tube, and the positive electrode of the stabilizing tube is connected to the zero line of the AC power supply.

[0009] In at least one embodiment, the second resistance, the light coupling and the series branch of the source and drain of the PMOS tube are specifically as follows: one end of the second resistance is connected to the negative electrode of the stabilizing tube, the other end is connected to the positive electrode of the light emitting tube of the light coupling, the negative electrode of the light emitting tube of the light coupling is connected to the source of the PMOS tube, and the drain of the PMOS tube is connected to the positive electrode of the stabilizing tube or the zero line of the alternating current power supply.

[0010] In at least one embodiment, the second diode and the stabilizing tube are connected in parallel at both ends of the series branch, and the second diode is specifically as follows: the negative electrode of the second diode is connected to the positive electrode of the first diode, and the positive electrode of the second diode is connected to the positive electrode of the stabilizing tube or the zero line of the alternating current power supply.

[0011] In at least one embodiment, the light coupling is a common light coupling.

[0012] In at least one embodiment, when long-distance transmission or high-voltage isolation is required, the light coupling is replaced by a fiber transceiver and an optical fiber.

[0013] In at least one embodiment, the voltage of the stabilizing tube is 5-20V.

[0014] In at least one embodiment, the PMOS tube is replaced by a PNP transistor; the emitter of the PNP transistor is connected to the negative electrode of the light emitting tube of the light coupling, the collector of the PNP transistor is connected to the positive electrode of the stabilizing tube or the zero line of the alternating current power supply, and the base of the PNP transistor is connected to the low-voltage end of the first resistance.

[0015] In at least one embodiment, the second diode is removed from the circuit.

[0016] In at least one embodiment, the voltage between the live wire and the zero line of the alternating current power supply is 100-400V.

[0017] The beneficial effects of the above technical scheme of the utility model are as follows:

[0018] The utility model discloses a kind of circuits for power frequency detection, including first resistance, second resistance, capacitor, first diode, second diode, stabilizing tube, PMOS tube and light coupling, can be directly connected to alternating current power supply to detect power waveform zero crossing point, and using light coupling or optical fiber transmission signal, avoid the problem that when signal is taken from transformer low-voltage side, load affects its alternating current waveform is not stable enough;By energy storage element-capacitor C, enough driving current is provided to light coupling at zero crossing point, further avoid the problem that because alternating current waveform is not stable enough, alternating current signal zero crossing point jitter reduces measurement accuracy;And, the circuit structure is simple, using passive device, power consumption is low and stable and reliable in work, higher safety. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide further understanding of the present application, the schematic embodiments of the present application and the explanations thereof are used to explain the present application, and do not constitute improper limitation on the present application.

[0020] Figure 1 is a circuit structure diagram of a circuit for power frequency detection of the present application;

[0021] Figure 2 is a waveform diagram of a circuit for power frequency detection of the present application;

[0022] Figure 3 is another circuit structure diagram of a circuit for power frequency detection of the present application. DETAILED DESCRIPTION

[0023] It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as that generally understood by the ordinary skilled in the art to which the present application belongs.

[0024] As introduced in the background, the purpose of the present application is to overcome the deficiencies in the prior art, and to provide a circuit for power frequency detection, which can be directly connected to an AC power supply to detect the zero-crossing point of the power waveform, and transmit signals through an optical coupling or an optical fiber, and the circuit structure is simple, reliable, low in power consumption, and high in safety.

[0025] Embodiment 1

[0026] As shown in Figure 1 , the present embodiment discloses a circuit for power frequency detection, which is provided with a branch circuit connected in series by a first resistor R1, a first diode D1 and a stabilizing tube Z between the live wire and the zero line of an AC power supply, and the two ends of the stabilizing tube Z are connected in parallel with a capacitor C, and the two ends of the stabilizing tube Z are also connected in parallel with a branch circuit connected in series by a second resistor R2, an optical coupling and a PMOS tube T source and drain, the two ends of the branch circuit connected in series by the first diode D1 and the stabilizing tube Z are connected in parallel with a second diode D2; the gate of the PMOS tube T is connected to the low-voltage end of the first resistor R1.

[0027] Among them, the series branch circuit of the first resistor R1, the first diode D1 and the stabilizing tube Z is specifically: the high-voltage end of the first resistor R1 is connected to the live wire of the AC power supply, the low-voltage end is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the negative electrode of the stabilizing tube Z, and the positive electrode of the stabilizing tube Z is connected to the zero line of the AC power supply.

[0028] The series connection branch of the second resistor R2, the photo-coupler and the PMOS tube T source and drain is as follows: one end of the second resistor R2 is connected to the negative electrode of the voltage stabilizing tube Z, the other end is connected to the positive electrode of the light emitting tube LED of the photo-coupler, the negative electrode of the light emitting tube LED of the photo-coupler is connected to the source of the PMOS tube T, and the drain of the PMOS tube T is connected to the positive electrode of the voltage stabilizing tube Z or the zero line of the alternating current power supply.

[0029] The second diode D2 is connected in parallel to the two ends of the series connection branch of the first diode D1 and the voltage stabilizing tube Z, and is as follows: the negative electrode of the second diode D2 is connected to the positive electrode of the first diode D1, and the positive electrode of the second diode D2 is connected to the positive electrode of the voltage stabilizing tube Z or the zero line of the alternating current power supply.

[0030] In combination Figure 2 In the positive half cycle of the alternating current power supply waveform u, the capacitor C is charged through the first resistor R1 and the first diode D1, and the voltage stabilizing tube Z limits the voltage across the capacitor C to be not too high, at this time, the gate voltage of the PMOS tube T is higher than the source voltage and the PMOS tube T is turned off. When the alternating current power supply waveform u approaches zero and is lower than the voltage uc across the voltage stabilizing tube Z, the PMOS tube T is turned on so that the uc passes through the second resistor and the PMOS tube T to generate a pulse current i for discharging the photo-coupler, the pulse current i drives the photo-coupler to generate a zero-crossing point signal. After the alternating current power supply waveform u continues to drop to the negative half cycle, the PMOS tube discharges, and the second diode D2 is turned on to prevent the gate of the PMOS tube from being broken down. The circuit can be directly connected to the alternating current power supply, and through the energy storage element-capacitor C, a large enough driving current is provided to the photo-coupler at the zero-crossing point, which can avoid the problem that when the signal is taken from the low voltage side of the transformer, the alternating current waveform is not stable enough due to the influence of the load, which can cause the zero-crossing point of the alternating current signal to jitter and reduce the measurement accuracy.

[0031] In the embodiment, the photo-coupler can transmit signals by using a common photo-coupler. The photo-coupler circuit is simple and small in size, and can isolate a voltage of about 1000V. Therefore, in the embodiment, the photo-coupler is used to isolate the 220V power supply and the frequency measurement circuit.

[0032] In the embodiment, when long-distance transmission or high-voltage isolation is required, a fiber transceiver and an optical fiber can be used to replace the photo-coupler to transmit signals. Because the fiber transceiver is equivalent to using an optical fiber to separate the distance between the transmitter and the receiver, and the optical fiber can isolate a voltage of more than 10000V, when long-distance transmission or high-voltage isolation is required, the fiber transceiver and the optical fiber are used to replace the photo-coupler to transmit signals.

[0033] In the embodiment, the voltage range of the voltage stabilizing tube Z can be 5-20V.

[0034] In the embodiment, the first resistor R1 is selected as a 510kΩ / 2512 resistor, the second resistor R2 is selected as a 200Ω resistor, the first diode D1 and the second diode D2 are both 1N4148 diodes, the voltage stabilizing tube Z is selected as a 10V voltage stabilizing tube, the capacitor C is selected as a 0.47μF chip capacitor, the PMOS tube T is an SI2301, an optical fiber transmitting module HFBR-1521Z is adopted, the zero-crossing LED pulse driving current is about 40mA, and the circuit can work in a 100V-400V AC power voltage range.

[0035] Embodiment 2

[0036] The embodiment discloses another circuit for power frequency detection, as shown in Figure 3 The embodiment discloses another circuit for power frequency detection, as shown in

[0037] In the embodiment, the first resistor R1 is selected as a 510kΩ / 2512 resistor, the second resistor R2 is selected as a 200Ω resistor, the first diode D1 and the second diode D2 are both 1N4148 diodes, the voltage stabilizing tube Z is selected as a 10V voltage stabilizing tube, the capacitor C is selected as a 0.47μF chip capacitor, the PMOS tube T is an SI2301, an optical fiber transmitting module HFBR-1521Z is adopted, the zero-crossing LED pulse driving current is about 40mA, and the circuit can work in a 100V-400V AC power voltage range.

[0038] The above only describes preferred embodiments of the utility model and is not used for limiting the utility model, for the person skilled in the art, the utility model can have various changes and changes. Any modification, equivalent replacement, improvement, etc. made in the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A circuit for mains frequency detection, characterized in that, A series branch of a first resistor, a first diode and a stabilizing tube is arranged between the live wire and the zero wire of an alternating current power supply; a capacitor is connected in parallel to the two ends of the stabilizing tube; a series branch of a second resistor, a photo-coupler and a PMOS tube source and drain is also connected in parallel to the two ends of the stabilizing tube; a second diode is connected in parallel to the two ends of the series branch of the first diode and the stabilizing tube; the gate of the PMOS tube is connected to the low-voltage end of the first resistor.

2. A circuit for power frequency detection as claimed in claim 1, characterized in that The series branch of the first resistor, the first diode and the stabilizing tube is specifically that the high-voltage end of the first resistor is connected to the live wire of the alternating current power supply, the low-voltage end is connected to the positive electrode of the first diode, the negative electrode of the first diode is connected to the negative electrode of the stabilizing tube, and the positive electrode of the stabilizing tube is connected to the zero wire of the alternating current power supply.

3. A circuit for power frequency detection as recited in claim 1, characterized by The series branch of the second resistor, the photo-coupler and the PMOS tube source and drain is specifically that one end of the second resistor is connected to the negative electrode of the stabilizing tube, the other end is connected to the positive electrode of the light-emitting tube of the photo-coupler, the negative electrode of the light-emitting tube of the photo-coupler is connected to the source of the PMOS tube, and the drain of the PMOS tube is connected to the positive electrode of the stabilizing tube or the zero wire of the alternating current power supply.

4. A circuit for power frequency detection as recited in claim 1, characterized by The second diode connected in parallel to the two ends of the series branch of the first diode and the stabilizing tube is specifically that the negative electrode of the second diode is connected to the positive electrode of the first diode, and the positive electrode of the second diode is connected to the positive electrode of the stabilizing tube or the zero wire of the alternating current power supply.

5. A circuit for power frequency detection as recited in claim 1, characterized by The photo-coupler is a common photo-coupler.

6. A circuit for power frequency detection as recited in claim 1, characterized by When long-distance transmission or high-voltage isolation is required, the photo-coupler is replaced by a fiber transceiver and an optical fiber.

7. A circuit for power frequency detection as recited in claim 1, characterized by The voltage of the stabilizing tube is 5-20V.

8. A circuit for mains frequency detection as claimed in any one of claims 1 to 7, characterized in that, The PMOS tube is replaced by a PNP triode; the emitter of the PNP triode is connected to the negative electrode of the light-emitting tube of the photo-coupler, the collector of the PNP triode is connected to the positive electrode of the stabilizing tube or the zero wire of the alternating current power supply, and the base of the PNP triode is connected to the low-voltage end of the first resistor.

9. A circuit for power frequency detection as claimed in claim 8, characterised in that, The second diode is removed from the circuit.

10. A circuit for power frequency detection as recited in claim 1, characterized by The voltage between the live wire and the zero wire of the alternating current power supply is 100-400V.

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