Alternating current on-off circuit based on MOS tube control

Abstract

The invention provides an alternating current on-off circuit based on MOS (Metal Oxide Semiconductor) tube control, which is characterized by comprising a zero-cross detection circuit, an MOS tube power switch circuit, a driving circuit and a bidirectional current detection and limit value overcurrent alarm circuit, the zero-cross detection circuit is provided with a voltage-regulator tube diode Z1 for stabilizing the voltage reduced by a divider resistor, and the MOS tube power switch circuit and the driving circuit are connected with the bidirectional current detection and limit value overcurrent alarm circuit; a Schottky diode D2 is adopted to clamp the negative phase voltage of the alternating current; the MOS tube power switch circuit and the driving circuit adopt a back-to-back MOS tube Q2 and a back-to-back MOS tube Q3, and a sampling resistor R4 is connected in series between the MOS tube Q2 and the MOS tube The bidirectional current detection and limit value overcurrent alarm circuit adopts two independent current detection amplifier chips, signal input ends of the two independent current detection amplifier chips are subjected to mutual reverse connection processing, and forward current and reverse current are subjected to differential detection respectively. According to the invention, the switch response speed is improved, and the electrical loss is greatly reduced; bidirectional current collection is realized under a single power supply system, and a hardware overcurrent alarm function is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high and low frequency alternating current on-off control, and particularly relates to an alternating current on-off circuit based on MOS tube control. BACKGROUND

[0002] In actual application, the mainstream alternating current on-off circuit is mostly realized based on an optical coupling module circuit. When the phase of alternating current changes, the optical coupling module circuit outputs a high or low pulse signal, and a driving circuit controls the switching action of a power device in the next stage when detecting the pulse signal. The conventional power circuit device is mainly composed of a mechanical switch, a relay (including a solid-state relay), and a bidirectional thyristor. Meanwhile, in actual application, if there is a current collection requirement, the mainstream is to realize the coupling of alternating current on the loop through a current transformer. The above application has a wide range of use cases in low-frequency alternating current and scenarios without special requirements for volume, but cannot meet the design requirements in high-frequency alternating current applications and small-volume application scenarios. For example, the optical coupling response is slow, the phase error is large, and it cannot be applied to high-frequency alternating current scenarios (such as 400 HZ or above). The traditional power device and current transformer are large in volume, the power device is slow in response speed, large in power consumption, and short in service life.

[0003] Through patent retrieval, it is found that 2 patent application contents are related to the present application, wherein:

[0004] The document with the patent application number CN202420644261.6 provides a zero-crossing on-off circuit based on MOS tube control. The zero-crossing detection circuit is realized by an optical coupling, which is used to detect the position and time of the zero-crossing point of the positive half-wave and negative half-wave of alternating current. The driving output circuit is used to drive the MOS switch in the driving output circuit in response to the detection of the zero-crossing point by the zero-crossing detection circuit.

[0005] The document with the patent application number CN202322019739.4 provides an alternating current zero-crossing detection circuit. The fire terminal is connected to the gate of the MOS tube through a protection module to provide the corresponding alternating input voltage for the protection module through the fire terminal. The drain of the MOS tube is connected to the negative primary side of the optical coupling isolation module, and the source of the MOS tube is grounded. When the supply voltage flowing through the MOS tube is greater than the threshold voltage, the MOS tube is turned on, and the primary side of the optical coupling isolation module is turned on, and the secondary side collector of the optical coupling isolation module outputs the corresponding flip signal.

[0006] The difference from the present application is that the zero-crossing detection circuit in the above patent document is a common optical coupler, which has slow response speed, optical coupler switch delay (about 10 microseconds), and is not suitable for high-frequency alternating current zero-crossing detection. The signal linearity is poor, the built-in LED of the optical coupler has a large conduction threshold (about 1V), which may cause a small phase error (±1°~±5°) in the zero-crossing detection. The alternating voltage amplitude dependence is high, and it may not be able to reliably trigger at low voltage (such as <50VAC). The present patent uses a comparator with built-in hysteresis function or a common comparator with resistance feedback to the in-phase input end to form a double-threshold hysteresis voltage, which is converted into a hysteresis comparator for zero-crossing detection circuit design. The peripheral circuit is simple, and the comparator bandwidth can be selected from KHZ to GHZ range, which makes the circuit of the present application not only meet the zero-crossing point detection of low frequency, but also meet the zero-crossing detection of high frequency or even super high frequency. The response speed is fast (ns level), and the zero-crossing detection phase error can be controlled within ±0.1°. The divided resistance is suitable for any alternating voltage application (such as 220Vac or as low as 1Vac). At the same time, the present application increases the bidirectional current collection and limit current overcurrent alarm function circuit of the power loop. The circuit of the present application has higher practicality in the actual development and design of products. SUMMARY

[0007] The main purpose of the present application is to adopt a new zero-crossing detection method, combine the low loss and fast response characteristics of power MOS tube, and increase the design idea of bidirectional current detection and limit overcurrent alarm function, which makes up for the shortcomings of the design of optical coupler module and mechanical power switch in traditional alternating current control, such as not meeting the high frequency application occasion and fast response, and provides a complete and practical circuit design scheme.

[0008] To achieve the above purpose, the present application provides an alternating current on-off circuit based on MOS tube control, which is characterized in that it comprises a zero-crossing detection circuit, a MOS tube power switch circuit and a driving circuit, a bidirectional current detection and limit overcurrent alarm circuit, the zero-crossing detection circuit attenuates and steps down the positive and negative phase voltage between the live wire L and the neutral wire N of the alternating current through resistance division, sets the voltage stabilizing diode Z1 to stabilize the voltage after resistance division, and uses the low forward conduction voltage drop Schottky diode D2 to clamp the negative phase voltage of the alternating current; the MOS tube power switch circuit and the driving circuit use back-to-back MOS tube Q2 and MOS tube Q3 with a sampling resistor R4 in series in the middle, and use chip U1 to drive the two MOS tubes simultaneously; the bidirectional current detection and limit overcurrent alarm circuit uses two independent current detection amplifier chips U3 and U4, the signal input ends of which are connected in a reciprocal manner, and differentially detect the forward current and the reverse current.

[0009] Further, it further comprises an isolated power supply circuit, and the ground GND potential of the system is floating, thereby obtaining a relative ground GND potential.

[0010] Further, it further comprises a bootstrap circuit, and low voltage output by the isolation transformer is bootstrapped to higher voltage, so as to meet the requirement of the MOS tube driving voltage.

[0011] Further, in the zero-crossing detection circuit, the ±200V AC voltage at the input end is divided by resistors R7, R10 and R11, and then is attenuated to -0.1-1V by a Zener diode Z1 and a Schottky diode D2, and is input to the positive input end of a hysteresis comparator U2, and the negative input end of the hysteresis comparator U2 is grounded, and a square wave output with a magnitude of 3.3V is synchronously generated at the output end of the hysteresis comparator U2 at the zero-crossing point.

[0012] Further, in the MOS tube power switch circuit and the driving circuit, the gate of the MOS tube Q2 and the gate of the MOS tube Q3 are pulled low by the resistor R3 by default, and the MOS tubes are turned off, and after the driving chip U1 receives an enable signal, the high and low levels of the gates of the MOS tube Q2 and the MOS tube Q3 are set, and the on-off action of the MOS tubes is driven.

[0013] Further, in the bidirectional current detection and limit overcurrent alarm circuit, after the output across the resistor R4 is input to a filter circuit composed of resistors R5, R6 and a capacitor C3, the filter circuit is input to the positive and negative input ends of current detection amplifiers U3 and U4, respectively, and then is filtered by resistors R9, a capacitor C6, a resistor R16 and a capacitor C9 and is output.

[0014] Further, the output voltage of the current detection amplifiers U3 and U4 is divided by resistors R12, R14 and resistors R17, R20, respectively, and is input to the CMPIN end of the current detection amplifiers U3 and U4 as an input voltage signal of the alarm threshold, and then is output after the alarm signals are processed in parallel by diodes D3 and D4.

[0015] Further, the alarm signals are input to the base electrode end of a triode Q1, and the MOS tube driving circuit is forcibly disabled by hardware.

[0016] The application has the advantages that the application adopts a novel zero-crossing detection technology and a bidirectional current detection technology, and a resistor and an isolated power supply are used in series in the back-to-back MOS tube switch circuit to generate a relative floating ground potential, so that a novel AC on-off circuit can be realized, the traditional AC on-off control can be met, the switching response speed is improved, and the electrical loss is greatly reduced; and through the bidirectional current acquisition and overcurrent alarm circuit, bidirectional current acquisition and the hardware overcurrent alarm function can be realized under a single power supply system, so that the application is more practical and operable. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The schematic diagram of the system circuit composition is shown in Figure 1.

[0018] Figure 2 The schematic diagram of the zero-crossing detection circuit is shown in Figure 2.

[0019] Figure 3 The schematic diagram of the MOS tube switching circuit and the driving circuit is shown in Figure 3.

[0020] Figure 4 The schematic diagram of the bidirectional current detection and overcurrent alarm circuit is shown in Figure 4.

[0021] Figure 5 The schematic diagram of the isolation power supply circuit and the bootstrap circuit is shown in Figure 5.

[0022] Figure 6 The schematic diagram of the zero-crossing detection waveform is shown in Figure 6. DETAILED DESCRIPTION

[0023] The specific embodiments of the present application are described in further detail below in combination with the accompanying drawings.

[0024] Figure 1 The schematic diagram of the system circuit composition is shown in Figure 1. Figure 1 As shown in Figure 1, the present application provides an alternating current on-off circuit based on MOS tube control, which is composed of zero-crossing detection, MOS tube switching driving, bidirectional current detection and overcurrent alarm, and power supply design. The input alternating current (±200V) is divided by resistors R7, R10, and R11, and then the amplitude is attenuated to -0.1~1V by a zener diode Z1 and a Schottky diode D2, and then input to the positive input end of a hysteresis comparator U2, and the negative input end of the hysteresis comparator U2 is grounded. A square wave output with an amplitude of 3.3V is synchronously generated at the output end of the hysteresis comparator U2 at the zero-crossing position. The MOS tubes Q2 and Q3 are pulled low at the gate by the resistor R3 by default, and the MOS tubes are turned off. After the driving chip U1 receives the enable signal, the gate of the MOS tubes Q2 and Q3 is set to high and low levels, and the on-off action of the MOS tubes is driven. After the output between the resistors R4 is input to the filter circuit composed of resistors R5, R6, and capacitor C3, the positive and negative input ends of current detection amplifiers U3 and U4 are input, and then the output is filtered by resistors R9, capacitor C6, and resistors R16, capacitor C9. At the same time, the output voltage of the current detection amplifiers U3 and U4 is divided by resistors R12, R14 and resistors R17, R20, and then input to the CMPIN end of the current detection amplifiers U3 and U4 as the input voltage signal of the alarm threshold. After the alarm signals are processed in parallel by diodes D3 and D4, the alarm signals are output. At the same time, the alarm signals are input to the base electrode end of the triode Q1, and the MOS tube driving circuit is forcibly disabled by hardware.

[0025] Specifically, the design mainly consists of four circuit units, which are zero-crossing detection circuit, MOS power switch circuit and drive circuit, bidirectional current detection and limit overcurrent alarm circuit, and isolation power supply circuit. The main function of the zero-crossing detection circuit is to accurately detect the time point when the AC voltage changes from the positive half cycle to the negative half cycle, or from the negative half cycle to the positive half cycle, at which time the voltage instantaneous value is zero, at which time the load is turned on, and the current starts to rise smoothly from zero, which can minimize the inrush current and switching noise, and provide the best load connection time point for the MOS power switch circuit and drive circuit. The MOS power switch circuit and drive circuit are a voltage-controlled high-speed electronic switch, which uses a weak gate voltage signal to control the on-off of the large current between the drain and the source, and the drive circuit is specially designed to provide a fast and reliable gate drive signal for the MOS power switch circuit to turn on and off the MOS tube, provide appropriate gate drive voltage and sufficient drive current, improve switching speed and reduce MOS switch loss. The main function of the bidirectional current detection and limit overcurrent alarm circuit is to detect the current value between the two ends of the current sampling resistor in the system loop. The circuit can realize bidirectional current collection and set the overcurrent alarm threshold. When the current in the circuit loop reaches the maximum alarm current value, an alarm signal is output and the MOS tube gate drive signal is turned off. The isolation power supply circuit provides reliable and stable power supply for the whole system, and the input side and the output side are separated by physical means, so that there is no direct electrical connection between them, achieving the effect of electrical safety isolation. At the same time, in order to meet the voltage requirement of the MOS tube drive circuit, the design increases the voltage bootstrap circuit to boost the low voltage output by the isolation transformer to the gate drive voltage value.

[0026] Figure 2 The zero-crossing detection circuit is shown in Figure 1. Figure 2 As shown in Figure 1, the zero-crossing detection circuit is set as follows: the zero-crossing detection circuit attenuates and reduces the positive and negative phase voltage between the live wire L and the neutral wire N through resistance division, and the voltage after resistance reduction is stabilized by the additional zener diode Z1 for reliability. At the same time, due to the limitation of the reverse common-mode voltage of the hysteresis comparator, a Schottky diode D2 with low forward conduction voltage drop is needed to clamp the AC negative phase voltage. The above design ensures that the voltage input to the hysteresis comparator meets the voltage limit requirement, so that the comparator circuit can normally perform zero-crossing detection.

[0027] Figure 3 The MOS switch circuit and drive circuit are shown in Figure 2. Figure 3As shown in the figure, the application further sets MOS power switch circuit and driving circuit as follows: the design of back-to-back MOS Q2 and MOS Q3 with sampling resistor R4 in series in the middle realizes bidirectional current control with low conduction loss and high switching speed, and the current sampling resistor is cleverly connected in series, and the chip U1 drives two MOS tubes at the same time, ensuring the synchronization and consistency of switching response.

[0028] Figure 4 The figure is a schematic diagram of bidirectional current detection and overcurrent alarm circuit. Figure 4 As shown in the figure, the application further sets bidirectional current detection and limit overcurrent alarm circuit as follows: two independent current detection amplifier chips (U3 and U4) are used, the signal input ends are connected in reverse, and the forward current and reverse current are detected differentially.

[0029] Figure 5 The figure is a schematic diagram of isolation power supply circuit and bootstrap circuit. Figure 5 As shown in the figure, the application further sets isolation power supply circuit when the system is applied as follows: the design scheme of using isolation power supply for system power supply processes the floating of the system ground (GND) potential, thereby obtaining a relatively floating ground (GND) potential (the upper part of Figure 5 The bootstrap circuit is additionally set, which boosts the low voltage output by the isolation transformer to a higher voltage to meet the driving voltage requirement of the MOS tube (the lower part of Figure 5 ).

[0030] Figure 6 The figure is a schematic diagram of zero-crossing detection waveform. As shown in the figure, the green line is the input AC voltage waveform, and the red line is the output square wave signal of the zero-crossing detection circuit. Figure 6 When the input AC crosses zero, the rising and falling square wave signals are generated, and the system drives the MOS tube on-off operation through the zero point.

[0031] The application is suitable for high and low frequency aviation power supply, power control, industrial automation, consumer electronics and other application occasions.

[0032] It should be noted that the above is only a schematic description and elaboration of the application, and those skilled in the art should understand that any modification and replacement of the application belongs to the protection scope of the application.

Claims

1. An AC power on-off circuit based on MOS control, characterized by, It includes zero-crossing detection circuit, MOS power switch circuit and drive circuit, two-way current detection and limit over-current alarm circuit, the zero-crossing detection circuit attenuates and reduces the positive and negative phase voltage between the live wire L and the neutral wire N of the alternating current by resistance voltage division, sets the voltage stabilizing diode Z1 to stabilize the voltage after the voltage reduction of the resistance, and uses the low forward voltage drop Schottky diode D2 to clamp the negative phase voltage of the alternating current; the MOS power switch circuit and drive circuit use the back-to-back MOS Q2 and MOS Q3 with a sampling resistor R4 in series in the middle, and use the chip U1 to drive the two MOS simultaneously; the two-way current detection and limit over-current alarm circuit uses two independent current detection amplifier chips U3 and U4, the signal input ends of which are connected in a reciprocal manner, and the forward current and the reverse current are detected differentially.

2. An AC power on-off circuit based on MOS control according to claim 1, characterized in that, It further includes an isolation power supply circuit, which floats the ground GND potential of the system, thereby obtaining a relative ground GND potential.

3. An AC power on-off circuit based on MOS control according to claim 1, characterized in that, It further includes a bootstrap circuit, which boosts the low voltage output by the isolation transformer to a higher voltage to meet the driving voltage requirement of the MOS.

4. An AC power on-off circuit based on MOS control according to claim 1, characterized in that, In the zero-crossing detection circuit, the ±200V input alternating current is attenuated to-0.1~1V after being divided by resistors R7, R10 and R11, and then input to the positive input end of the hysteresis comparator U2, and the negative input end of the hysteresis comparator U2 is grounded, and the hysteresis comparator U2 outputs a square wave with an amplitude of 3.3V at the zero-crossing point.

5. An AC power on-off circuit based on MOS control according to claim 4, characterized in that, In the MOS power switch circuit and drive circuit, the resistor R3 pulls down the gate of the MOS Q2 and Q3 by default, turns off the MOS, and the drive chip U1 sets the high and low levels of the gate of the MOS Q2 and Q3 after receiving the enable signal, and drives the on-off action.

6. An AC power on-off circuit based on MOS control according to claim 5, characterized in that, In the two-way current detection and limit over-current alarm circuit, the output across the resistor R4 is input to the positive and negative input ends of the current detection amplifiers U3 and U4 after being filtered by the filter circuit composed of resistors R5, R6 and capacitor C3, and then output after being filtered by resistors R9, capacitor C6 and resistors R16, capacitor C9.

7. An AC power on-off circuit based on MOS control according to claim 6, characterized in that, The output voltage of the current detection amplifiers U3 and U4 is divided by resistors R12, R14 and resistors R17, R20, and then input to the CMPIN end of the current detection amplifiers U3 and U4 as the input voltage signal of the alarm threshold, and then output after being processed in parallel by diodes D3 and D4.

8. An AC power on-off circuit based on MOS control according to claim 7, characterized in that, The alarm signal is input to the base electrode end of the triode Q1, which forcibly disables the MOS drive circuit.

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