CN105634382A - A single-phase AC motor protection circuit, fan and air conditioner - Google Patents

Abstract

The invention relates to a single-phase alternating current motor protection circuit, a fan and an air conditioner. The circuit comprises an alternating current motor or a main winding and an auxiliary winding thereof, a main switch loop, a discharge loop and a pulse signal generating circuit; the alternating current motor or the main and auxiliary windings thereof and the main switch loop are connected in series between a zero line and a live line of alternating current, and the discharge loop is connected in parallel with the alternating current motor or the main and auxiliary windings thereof; the main switch loop or the bleeder loop comprises a first rectifying circuit, a first direct current electronic switch and a reference voltage circuit. The invention can solve the problems that when the dead time of the direct current electronic switch in the discharge loop and the direct current electronic switch in the main switch loop in the alternating current speed regulating circuit is short, and when the circuit is interfered or the circuit is abnormal, the direct current electronic switch in the discharge loop and the direct current electronic switch in the main switch loop are short-circuited for a short time to cause larger impact current, so that the direct current electronic switch is seriously overheated, enters an unstable state and even is burnt.

Description

A single-phase AC motor protection circuit, fan and air conditioner

technical field

The invention relates to the field of motors, in particular to a single-phase AC motor protection circuit, a fan and an air conditioner.

Background technique

At present, there is a form of motor speed regulation circuit as shown in Figure 1. The basic principle is: through PWM modulation of "single-phase AC switching circuit", the voltage at both ends of the motor is switched at high speed, so as to adjust the average voltage at both ends of the motor to achieve regulation. purpose of speed. When the "motor inductive current discharge circuit" is a switch circuit, it can be simplified as the schematic diagram shown in Figure 2, where K1 represents the "motor inductive current discharge circuit" in Figure 1, and K2 represents the "single circuit" in Figure 1 phase alternating current switch circuit", the time control schematic diagram in Figure 2 is shown in Figure 3, at this time, this speed regulating circuit has the following defects:

1) When the switch dead time between K1 and K2 (ie: the time from K1 off to K2 on and the time from K2 off to K1 on) is to control the switch of K1 according to the feedback voltage after K2 is disconnected, the advantage is The reverse voltage at both ends of the motor is very low, the disadvantage is that the dead time is too short, and it is not easy to control, if the time characteristic difference caused by the characteristic difference of the device, K1 and K2 may have a temporary short circuit, causing the temperature rise of K1 and K2 High, even burned.

2) If the symmetrical PWM self-locking mode is used to drive K1 and K2, the dead time usually needs to be 1-2uS, so the back pressure of the AC motor will be very high, and it is usually necessary to connect a large-capacity capacitor C and resistor in parallel at both ends of the motor R to absorb, called the RC absorption loop, in the RC absorption loop, the capacitance C is too large will lead to high heat generation of the resistor R, increased loss, which is not conducive to the stable and reliable operation of the circuit, and the required volume is also large, which is not conducive to Circuit miniaturization. If the dead time is reduced to 0.1-1uS, when interference occurs, there may be a temporary short circuit between K1 and K2, which will burn K1 and K2.

Contents of the invention

The technical problem to be solved by the present invention is to provide a single-phase AC motor protection circuit, a fan and an air conditioner in view of the deficiencies of the prior art.

The first technical solution of the present invention to solve the above-mentioned technical problems is as follows: a single-phase AC motor protection circuit, which is characterized in that it includes an AC motor or its primary and secondary windings, a main switch circuit, a discharge circuit and a pulse signal generating circuit;

The AC motor or its primary and secondary windings and the main switch circuit are connected in series between the neutral wire and the live wire of the AC power, and the discharge circuit is connected in parallel with the AC motor or its primary and secondary windings;

The main switch circuit or the discharge circuit includes a first rectifier circuit, a first DC electronic switch and a reference voltage circuit, the first terminal and the second terminal of the first DC electronic switch are respectively connected to the first The negative output terminal of the rectifier circuit is connected to the positive output terminal, the drive terminal of the first DC electronic switch is connected to the pulse signal output terminal of the pulse signal generating circuit, and the input terminal of the reference voltage circuit is respectively connected to the first The second terminal of a DC electronic switch is connected to the DC power supply, the output terminal of the reference voltage circuit is connected to the drive terminal of the first DC electronic switch or connected to the discharge circuit, or the reference voltage circuit The output end of the circuit is connected with the drive end of the first DC electronic switch or with the main switch circuit.

The beneficial effects of the present invention are: the present invention can solve the problem that when the dead time of the DC electronic switch in the discharge circuit and the DC electronic switch of the main switch circuit is very short (0.1-1.5uS) in the AC speed regulating circuit, when the When there is interference or circuit abnormality, the short-circuit of the DC electronic switch in the discharge circuit and the DC electronic switch of the main switch circuit will cause a large inrush current, which will seriously overheat the DC electronic switch, enter an unstable state or even burn out.

On the basis of the above technical solutions, the present invention can also be improved as follows.

Further, the main switch circuit includes a first rectifier circuit, a first DC electronic switch and a reference voltage circuit, and when the output terminal of the reference voltage circuit is connected to the discharge circuit, the reference voltage circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a filter capacitor and a comparator, the first resistor is connected in series with the second end of the first DC electronic switch, and the two ends of the first resistor are connected by The filter circuit composed of the second resistor and the filter capacitor is connected to the negative end of the comparator, one end of the third resistor is connected to a DC power supply, and the other end of the third resistor is respectively connected to the comparator The positive end of the comparator is connected in series with the fourth resistor, the other end of the fourth resistor is grounded, and the output end of the comparator is connected to the discharge circuit.

Further, the discharge circuit includes a second rectifier circuit, a second DC electronic switch and an optocoupler, and the first terminal and the second terminal of the second DC electronic switch are connected to the negative output terminal and the negative output terminal of the second rectifier circuit respectively. connected to the positive output terminal, the emitter and collector of the triode in the optocoupler are respectively connected to the drive terminal of the second DC electronic switch and the DC power supply, and the positive pole and negative pole of the light emitting diode in the optocoupler are respectively connected to the pulse The pulse signal output terminal of the signal generation circuit is connected with the output terminal of the comparator.

Further, when the main switch circuit includes a first rectifier circuit, a first DC electronic switch and a reference voltage circuit, and when the output terminal of the reference voltage circuit is connected to the drive terminal of the first DC electronic switch, the The reference voltage circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a filter capacitor and a comparator, the first resistor is connected in series with the second end of the first DC electronic switch, the first The two ends of the resistor are connected to the filter circuit composed of the second resistor and the filter capacitor and then connected to the positive terminal of the comparator, one end of the third resistor is connected to a DC power supply, and the other end of the third resistor Connect the negative end of the comparator and the fourth resistor in series, the other end of the fourth resistor is grounded, and the output end of the comparator is connected to the drive end of the first DC electronic switch.

Further, the discharge circuit includes a second rectifier circuit, a second DC electronic switch and an optocoupler, and the first terminal and the second terminal of the second DC electronic switch are connected to the negative output terminal and the negative output terminal of the second rectifier circuit respectively. The positive output terminal is connected, the emitter and the collector of the triode in the optocoupler are respectively connected to the drive terminal of the second DC electronic switch and the DC power supply, and the positive pole of the light emitting diode in the optocoupler is connected to the pulse signal generating circuit The pulse signal output terminal of the optocoupler is connected, and the cathode of the light-emitting diode in the optocoupler is grounded.

Further, the discharge circuit includes a first unidirectional electronic switch circuit and a second unidirectional electronic switch circuit symmetrically connected to both ends of the AC motor or its primary and secondary windings.

Further, the first unidirectional electronic switch circuit includes a first body circuit composed of a first triode and a first diode, and a first Zener diode, a first capacitor and a first current limiting resistor The first bias circuit; the cathode of the first diode is connected to the collector of the first triode and connected in parallel to both ends of the AC motor or its primary and secondary windings, wherein the first triode The emitter of the tube is connected to the first end of the AC motor or its primary and secondary windings, one end of the first current limiting resistor is connected to the base of the first triode, and the other end is connected to the parallel connection of the first capacitor and The first Zener diode, wherein the anode of the first Zener diode is connected to the first end of the AC motor or its primary and secondary windings;

Further, the second unidirectional electronic switch circuit includes a second main body circuit composed of a second triode and a second diode, and a second Zener diode, a second capacitor and a second current limiting resistor The second bias circuit; the cathode of the second diode is connected to the collector of the second triode and connected in parallel to both ends of the AC motor or its primary and secondary windings, wherein the second triode The emitter of the tube is connected to the second end of the AC motor or its primary and secondary windings, one end of the second current limiting resistor is connected to the base of the second triode, and the other end is connected to the parallel connection of the second capacitor and The second Zener diode, wherein the anode of the second Zener diode is connected to the second terminal of the AC motor or its primary and secondary windings.

Further, the discharge circuit includes a first rectifier circuit, a first DC electronic switch and a reference voltage circuit, and when the output terminal of the reference voltage circuit is connected to the main switch circuit, the reference voltage circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a filter capacitor and a comparator, the first resistor is connected in series with the second end of the first DC electronic switch, and the two ends of the first resistor are connected by The filter circuit composed of the second resistor and the filter capacitor is connected to the negative end of the comparator, one end of the third resistor is connected to a DC power supply, and the other end of the third resistor is respectively connected to the comparator The positive end of the comparator is connected in series with the fourth resistor, the other end of the fourth resistor is grounded, and the output end of the comparator is connected to the main switch circuit.

Further, the main switch circuit includes a second rectifier circuit, a second DC electronic switch and an optocoupler, the first terminal and the second terminal of the second DC electronic switch are connected to the negative output terminal and the negative output terminal of the second rectifier circuit respectively. connected to the positive output terminal, the emitter and collector of the triode in the optocoupler are respectively connected to the drive terminal of the second DC electronic switch and the DC power supply, and the positive pole and negative pole of the light emitting diode in the optocoupler are respectively connected to the pulse The pulse signal output terminal of the signal generation circuit is connected with the output terminal of the comparator.

Further, the discharge circuit includes a first rectifier circuit, a first DC electronic switch and a reference voltage circuit, and when the output terminal of the reference voltage circuit is connected to the drive terminal of the first DC electronic switch, the The reference voltage circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a filter capacitor and a comparator, the first resistor is connected in series with the second end of the first DC electronic switch, the first The two ends of the resistor are connected to the filter circuit composed of the second resistor and the filter capacitor and then connected to the positive terminal of the comparator, one end of the third resistor is connected to a DC power supply, and the other end of the third resistor Connect the negative end of the comparator and the fourth resistor in series, the other end of the fourth resistor is grounded, and the output end of the comparator is connected to the drive end of the first DC electronic switch.

Further, the main switch circuit includes a second rectifier circuit, a second DC electronic switch and an optocoupler, the first terminal and the second terminal of the second DC electronic switch are connected to the negative output terminal and the negative output terminal of the second rectifier circuit respectively. The positive output terminal is connected, the emitter and the collector of the triode in the optocoupler are respectively connected to the drive terminal of the second DC electronic switch and the DC power supply, and the positive pole of the light emitting diode in the optocoupler is connected to the pulse signal generating circuit The pulse signal output terminal of the optocoupler is connected, and the cathode of the light-emitting diode in the optocoupler is grounded.

Further, the DC electronic switch used in the single-phase AC motor protection circuit is a triode or MOS tube. When the DC electronic switch is a triode, its first terminal is a collector, and its second terminal is an emitter. The terminal is the base; when the DC electronic switch is a MOS tube, the first terminal is the drain, the second terminal is the source, and the driving terminal is the gate.

Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

The second technical solution of the present invention to solve the above-mentioned technical problems is as follows: a fan includes the above-mentioned single-phase AC motor protection circuit.

The third technical solution of the present invention to solve the above-mentioned technical problems is as follows: an air conditioner comprising the above-mentioned fan.

Description of drawings

Fig. 1 is a single-phase AC motor speed regulating circuit diagram in the prior art;

Fig. 2 is a simplified schematic diagram of the circuit diagram shown in Fig. 1;

Fig. 3 is the time control schematic diagram of schematic diagram shown in Fig. 2;

4a-4b are the protection circuit diagrams of the single-phase AC motor described in Embodiments 1 and 2 of the present invention;

5a-5b are the protection circuit diagrams of the single-phase AC motor described in Embodiments 3 and 4 of the present invention;

Fig. 6 is a circuit diagram of a single-phase AC motor protection circuit according to Embodiment 5 of the present invention.

detailed description

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

Fig. 4a is a circuit diagram of a single-phase AC motor protection circuit according to Embodiment 1 of the present invention.

As shown in Figure 4a, the single-phase AC motor protection circuit in Embodiment 1 of the present invention includes an AC motor, a main switch circuit, a discharge circuit and a pulse signal generating circuit, and the AC motor and the main switch circuit are connected in series to the zero line and live line of the AC power Between them, the discharge circuit is connected in parallel with the AC motor, and the two ends of the AC motor are connected in parallel with an RC absorption circuit composed of a resistor RM1 and a capacitor CM2; the main switch circuit includes a rectifier circuit (composed of diodes D6-D9), a DC electronic switch K2 and In the reference voltage circuit, the first terminal and the second terminal of the DC electronic switch K2 are respectively connected to the negative output terminal and the positive output terminal of the rectification circuit, wherein the positive output terminal of the rectification circuit is connected to the DC electronic circuit through the current sampling resistor in the reference voltage circuit. The second end of the switch K2 is connected, and the driving end of the DC electronic switch K2 is connected to the pulse signal output end of the pulse signal generating circuit. The pulse signal output terminal of the signal generating circuit is connected; the reference voltage circuit is respectively connected with the DC power supply, the second terminal of the DC electronic switch K2 and the discharge circuit, specifically, the second terminal of the DC electronic switch K2 is connected in series with a current sampling resistor RK1, the resistor Both ends of RK1 are connected to the filter circuit composed of resistor RK2 and capacitor CK1, and then connected to the negative terminal of comparator UK1, one end of resistor RK4 is connected to DC power supply VCC2, and the other end of resistor RK4 is respectively connected to the positive terminal of comparator UK1 and resistor RK3 connected in series, the other end of the resistor RK3 is grounded, and the output end of the comparator UK1 is connected to the discharge circuit.

The discharge circuit includes a rectifier circuit (composed of diodes D1-D4), a DC electronic switch K1 and an optocoupler P1. The first terminal and the second terminal of the DC electronic switch K1 are respectively connected to the negative output terminal and the positive output terminal of the rectifier circuit. The emitter and the collector of the triode in the coupler P1 are respectively connected to the driving terminal of the DC electronic switch K1 and the DC power supply VCC1. In Embodiment 1 of the present invention, the collector of the triode in the optocoupler P1 is connected to the DC power supply VCC1 through a resistor R7 The anode and the cathode of the light-emitting diode in the optocoupler P1 are respectively connected with the pulse signal output end of the pulse signal generating circuit and the output end of the comparator UK1. In Embodiment 1 of the present invention, the anode of the light-emitting diode in the optocoupler P1 passes through the resistor R6 is connected with the pulse signal output end of the pulse signal generating circuit.

In the present invention, when the DC electronic switches K1 and K2 are triode tubes, the first terminal thereof is a collector, the second terminal is an emitter, and the driving terminal is a base; when the DC electronic switches K1 and K2 are MOS tubes, The first end is the drain, the second end is the source, and the driving end is the gate. The DC electronic switches K1 and K2 used in the single-phase AC motor protection circuit diagram shown in Figure 4a are MOS tubes, specifically depletion type MOS tube.

In Embodiment 1 of the present invention, if the normal current flowing through RK1 is 200mA, and the DC voltage of VCC2 is equal to 5V, according to V=R*I=0.2*1=0.2V, it can be concluded that during normal operation, the resistor RK1 The voltage at both ends is equal to 0.2V. After being filtered by the resistor RK2 and the capacitor CK1, it is input to the negative terminal of the comparator UK1, and the calculation process of the reference voltage input to the positive terminal of the comparator UK1 is: VCC2*(RK3/(RK4+RK3)=5 *2.5/(20+2.5)=0.56V, that is, the voltage input to the positive terminal of the comparator UK1 is 0.56V. The comparator UK1 in the embodiment 1 is preferably an open-drain comparator, such as LM358. During normal operation, the comparator outputs Low level, the pulse signal generation circuit can choose a single-chip microcomputer (MCU). In Figure 4a, U2 is used to represent the single-chip microcomputer. The PWM1 pulse output by the single-chip microcomputer (MCU) U2 forms a loop through the resistor R6, the optocoupler P1 and the comparator UK1. The DC electronic switch K1 works normally.

When the DC electronic switch K1 and DC electronic switch K2 are abnormal, if the current flowing through the DC electronic switch K2 reaches 570mA, the voltage across the resistor RK1 is V=R*I=0.57*1=0.57V, and the comparator UK1 The reference voltage of the positive terminal is 0.56V, the comparator UK1 outputs high resistance, the PWM1 pulse sent by the microcontroller (MCU) U2 cannot form a loop through the resistor R6, the optocoupler P1 and the comparator UK1, and the DC electronic switch K1 stops working. Part of the back pressure of the AC motor is absorbed by the RC absorbing circuit composed of resistor RM1 and capacitor CM2 connected in parallel at both ends of the AC motor. The back pressure at both ends of the AC motor increases and the efficiency decreases, but it will not cause the AC motor to stop running or the DC electronic switch Faults such as burning. When the interference or abnormality recovers, the current flowing through the resistor RK1 returns to 200mA, the voltage across the resistor RK1 returns to 0.2V, the comparator UK1 returns to output low level, and the pulse sent by the microcontroller (MCU) U2 passes through the resistor R6, the optocoupler P1 and comparator UK1 form a loop again, and the DC electronic switch K1 resumes normal operation.

Fig. 4b is a circuit diagram for protecting a single-phase AC motor according to Embodiment 2 of the present invention.

As shown in Figure 4b, the difference between the single-phase AC motor protection circuit in Embodiment 2 of the present invention and the single-phase AC motor protection circuit in Embodiment 1 is that the circuit structure and connection mode of the discharge circuit in Embodiment 2 are the same as those in Embodiment 2. The circuit structure and connection mode of the main switch circuit in Example 1 are the same, the circuit structure and connection mode of the main switch circuit in Embodiment 2 are the same as the circuit structure and connection mode of the discharge circuit in Embodiment 1, and the specific working principle can refer to the implementation example 1.

Fig. 5a is a circuit diagram for protecting a single-phase AC motor according to Embodiment 3 of the present invention.

As shown in Figure 5a, the difference between the single-phase AC motor protection circuit in Embodiment 3 of the present invention and the single-phase AC motor protection circuit in Embodiment 1 is that both ends of the resistor RK1 are connected to a filter circuit composed of a resistor RK2 and a capacitor CK1 Connect to the positive end of comparator UK1, one end of resistor RK4 is connected to DC power supply VCC2, the other end of resistor RK4 is respectively connected to the negative end of comparator UK1 and connected in series with resistor RK3, the other end of resistor RK3 is grounded, and the output end of comparator UK1 Connect the driving end of the DC electronic switch K2; the cathode of the light-emitting diode in the optocoupler P1 in the discharge circuit is grounded.

In Embodiment 3 of the present invention, if the normal current flowing through the resistor RK1 is 200mA, and the DC voltage of the DC voltage VCC2 is equal to 5V, according to V=R*I=0.2*1=0.2V, it can be obtained that during normal operation, The voltage at both ends of the resistor RK1 is equal to 0.2V, and after being filtered by the resistor RK2 and the capacitor CK1, it is input to the positive terminal of the comparator UK1. The calculation process of the reference voltage input to the negative terminal of the comparator UK1 is: VCC2*(RK3/(RK4+RK3)=5*2.5/(20+2.5)=0.56V, that is, the voltage input to the negative terminal of the comparator UK1 is 0.56V, which is normal When working, the output terminal of the comparator UK1 is high impedance, and the PWM2 pulse sent by the microcontroller (MCU) U2 drives the DC electronic switch K2 to work normally through the resistor R8, and the output of the comparator UK1 is low, which does not affect the normal operation of the DC electronic switch K2.

When the DC electronic switch K1 and DC electronic switch K2 are abnormal, if the current flowing through the DC electronic switch K2 reaches 570mA, the voltage across the resistor RK1 is V=R*I=0.57*1=0.57V, and the comparator UK1 The reference voltage of the negative terminal is 0.56V, the output terminal of the comparator UK1 immediately becomes low level, and the PWM1 pulse sent by the microcontroller (MCU) U2 drives the comparator UK1 to output a low level through the resistor R6, forcing the gate of the DC electronic switch K2 When the voltage is zero, the DC electronic switch K2 stops working, and the AC motor stops running, which can prevent the DC electronic switch from burning out and other failures. When the interference or abnormality recovers, the current flowing through the resistor RK1 returns to 200mA, the voltage across the resistor RK1 returns to 0.2V, the comparator UK1 returns to output high impedance, and the pulse sent by the microcontroller (MCU) U2 passes through the resistor R6 without affecting the DC Electronic switch K2 works.

Fig. 5b is a circuit diagram for protecting a single-phase AC motor according to Embodiment 4 of the present invention.

As shown in Figure 5b, the difference between the single-phase AC motor protection circuit of Embodiment 4 of the present invention and the single-phase AC motor protection circuit of Embodiment 3 lies in that the circuit structure and connection mode of the discharge circuit in Embodiment 4 are the same as those of the implementation The circuit structure and connection mode of the main switch circuit in Example 3 are the same, the circuit structure and connection mode of the main switch circuit in Embodiment 4 are the same as the circuit structure and connection mode of the discharge circuit in Embodiment 3, and the specific working principle can refer to the implementation Example 3.

Fig. 6 is a circuit diagram of a single-phase AC motor protection circuit according to Embodiment 5 of the present invention.

As shown in Figure 6, the discharge circuit in Embodiment 5 of the present invention includes a first unidirectional electronic switch circuit and a second unidirectional electronic switch circuit that are symmetrically connected to both ends of the AC motor, and the first unidirectional electronic switch circuit includes a triode The main circuit composed of Q1 and diode D1, and the bias circuit composed of Zener diode Z1, capacitor C1 and current limiting resistor R1; the second unidirectional electronic switch circuit includes the main circuit composed of triode Q2 and diode D2, and A bias circuit composed of Zener diode Z2, capacitor C2 and current limiting resistor R2; the cathode of diode D1 is connected to the collector of triode Q1 and then connected in parallel to both ends of the AC motor, where the emitter of transistor Q1 is connected to the first end of the AC motor , one end of the current limiting resistor R1 is connected to the base of the transistor Q1, and the other end is connected to a parallel capacitor C1 and Zener diode Z1, wherein the anode of the Zener diode Z1 is connected to the first end of the AC motor; the cathode of the diode D2 is connected to the collector of the transistor Q2 The electrodes are connected in parallel to both ends of the AC motor, wherein the emitter of the triode Q2 is connected to the second end of the AC motor, one end of the current limiting resistor R2 is connected to the base of the triode Q2, and the other end is connected to the parallel capacitor C2 and Zener diode Z2, wherein The anode of the Zener diode Z2 is connected to the second terminal of the AC motor.

In the positive half cycle of the single-phase AC, that is, during the positive voltage at the A terminal and the negative voltage at the B terminal, when the pulse signal generated by the pulse signal generating circuit is at a high level, the single-phase AC switch circuit is turned on, and the current flows through the Zener The diode Z1, the AC motor, and the Zener diode Z2 flow through to drive the AC motor to run; at the same time, the Zener diode Z1 conducts in reverse, and a voltage is generated at its two ends, and the capacitor C1 is charged, and the current generated by the voltage generated at both ends passes through the resistor R1 , The base and emitter of the transistor Q1 flow through, the transistor Q1 is turned on, the diode D1 blocks the power supply current and bypasses the motor through the resistor R1, and the collector of the transistor Q1 flows; at the same time, the Zener diode Z2 is forward-conducting, and a voltage is generated at both ends , the capacitor C2 is charged, the base of the transistor Q2 is reverse biased, the transistor Q2 is cut off, and the power supply current cannot bypass the AC motor and flow through the diode D2 and the transistor Q2. When the pulse signal is at low level, the single-phase AC switching circuit is turned off. At this time, due to the discharge of the capacitor C1, the transistor Q1 continues to conduct, and due to the discharge of the capacitor C2, the transistor Q2 continues to be cut off; at this time, the inductive current of the motor passes through the diode D1, the transistor Q1 forms a bleeder loop. Similarly, in the negative half cycle of the single-phase alternating current, that is, when the A terminal is a negative voltage and the B terminal is a positive voltage, the inductive current of the motor forms a discharge circuit through the diode D2 and the transistor Q2.

The main switching circuit in Embodiment 5 includes a rectification circuit (made up of diodes D3-D6), a DC electronic switch Q3 and a reference voltage circuit, and the first end and the second end of the DC electronic switch Q3 are respectively connected to the negative output terminal and the negative pole output terminal of the rectification circuit. The positive output terminal is connected, the driving terminal of the DC electronic switch Q3 is connected to the pulse signal output terminal of the pulse signal generating circuit, and the reference voltage circuit is respectively connected to the DC power supply, the second terminal of the DC electronic switch Q3 and the driving terminal of the DC electronic switch Q3, Specifically, the second end of the DC electronic switch Q3 is connected in series with a current sampling resistor RK1, the two ends of the resistor RK1 are connected to a filter circuit composed of a resistor RK2 and a capacitor CK1, and then connected to the positive end of the comparator UK1, and one end of the resistor RK4 is connected to the DC power supply VCC , the other end of the resistor RK4 is respectively connected to the negative end of the comparator UK1 and connected in series with the resistor RK3, and the output end of the comparator UK1 is connected to the driving end of the DC electronic switch Q3. In the present invention, when the DC electronic switch is a three-stage tube, its first end is a collector, the second end is an emitter, and the driving end is a base; when the DC electronic switch is a MOS tube, its first end is a drain pole, the second end is the source, and the driving end is the gate. The DC electronic switches Q1, Q2 and Q3 used in the single-phase AC motor protection circuit diagram shown in Figure 6 are triodes.

In Embodiment 5 of the present invention, if the normal current flowing through the resistor RK1 is 200mA, and the DC voltage of VCC is equal to 5V, according to V=R*I=0.2*1=0.2V, it can be concluded that the resistor The voltage at both ends of RK1 is equal to 0.2V, and after being filtered by resistor RK2 and capacitor CK1, it is input to the positive terminal of comparator UK1. The calculation method of the reference voltage of the negative terminal of the comparator UK1 is VCC2*(RK3/(RK4+RK3)=5*2.5/(20+2.5)=0.56V, that is, the voltage input to the negative terminal of the comparator UK1 is 0.56V, and the comparator UK1 An open-drain comparator is preferred, such as LM358. The output terminal of the comparator UK1 is high impedance during normal operation, and the pulse generated by the pulse signal generating circuit drives the DC electronic switch Q3 to work normally.

When the DC electronic switches Q1, Q2, and Q3 are abnormal, if the current flowing through the DC electronic switch Q3 reaches 570mA, the voltage across the resistor RK1 is V=R*I=0.57*1=0.57V, and the comparator UK1 negative terminal reference voltage is 0.56V, the output terminal of the comparator UK1 becomes low level immediately, the pulse signal generated by the pulse signal generating circuit is short-circuited, the base voltage of the DC electronic switch Q3 is forced to be zero, and the DC electronic switch Q3 stops working. The AC motor stops running to prevent failures such as burning of the DC electronic switch. When the interference or abnormality recovers, the current flowing through the resistor RK1 returns to 200mA, the voltage across the resistor RK1 returns to 0.2V, the comparator UK1 returns to the high-impedance state, and the pulse signal sent by the pulse signal generating circuit normally drives the DC electronic switch Q3 to work .

The AC motors in all the above-mentioned embodiments of the present invention can also be replaced with primary and secondary windings of the AC motor.

The invention can solve the problem of leakage in the AC speed regulating circuit when the dead time of the DC electronic switch in the discharge circuit and the DC electronic switch of the main switch circuit is very short (0.1-1.5uS). The DC electronic switch in the discharge circuit and the DC electronic switch in the main switch circuit have a short-circuit short circuit that causes a large inrush current, causing the DC electronic switch to overheat severely, enter an unstable state or even burn out.

The invention converts the AC current of the AC motor into a DC current through rectification, which facilitates detection by a comparator or a pulse signal generating circuit. When the DC electronic switch is working, detect the change of the DC current when the DC electronic switch is working, and preset different current thresholds according to the magnitude of the current. When the current reaches different thresholds, stop outputting PWM1 or PWM1 and PWM2 pulse signals respectively. , to avoid damage and interference to the DC electronic switch, and after the abnormal recovery, the circuit automatically returns to the normal working state to avoid device burnout.

The present invention also provides a fan, including the single-phase AC motor protection circuit described in Embodiments 1-5 above.

The present invention also provides an air conditioner, including the above-mentioned fan.

In the description of this specification, descriptions referring to the terms "embodiment one", "embodiment two", "example", "specific examples", or "some examples" mean specific methods described in conjunction with this embodiment or example , device or feature is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, methods, devices or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (15)

1. a load motor protection circuit, it is characterised in that, comprise alternating current machine or its main auxiliary winding, main switch loop, bleed-off circuit and pulse signal generating circuit;

Described alternating current machine or its main auxiliary winding and described main switch loop are series between the zero line of alternating-current and live wire, and described bleed-off circuit and described alternating current machine or its main auxiliary winding are in parallel;

Described main switch loop or described bleed-off circuit comprise the first rectifying circuit, first DC electronic switch and reference voltage circuit, the first end of described first DC electronic switch and the 2nd end respectively cathode output end and cathode output end with described first rectifying circuit be connected, the described drive end of the first DC electronic switch is connected with the pulse signal output end of described pulse signal generating circuit, the input terminus of described reference voltage circuit respectively the 2nd end and direct supply with described first DC electronic switch be connected, the output terminal of described reference voltage circuit is connected with the drive end of described first DC electronic switch or is connected with described bleed-off circuit, or, the output terminal of described reference voltage circuit is connected with the drive end of described first DC electronic switch or is connected with described main switch loop.

2. load motor according to claim 1 protection circuit, it is characterized in that, when described main switch loop comprises the first rectifying circuit, when the output terminal of the first DC electronic switch and reference voltage circuit and described reference voltage circuit is connected with described bleed-off circuit, described reference voltage circuit comprises the first resistance, 2nd resistance, 3rd resistance, 4th resistance, filter capacitor and comparer, described first resistance is connected with the 2nd end of described first DC electronic switch, the negative terminal of described comparer is accessed at the two ends of described first resistance after connecting the filtering circuit being made up of described 2nd resistance and described filter capacitor, one termination direct supply of described 3rd resistance, the other end of described 3rd resistance connects the just end of described comparer respectively and connects with described 4th resistance, the other end ground connection of described 4th resistance, the output terminal of described comparer is connected with described bleed-off circuit.

3. load motor according to claim 2 protection circuit, it is characterized in that, described bleed-off circuit comprises the 2nd rectifying circuit, 2nd DC electronic switch and optocoupler, the first end of described 2nd DC electronic switch and the 2nd end respectively cathode output end and cathode output end with described 2nd rectifying circuit be connected, in described optocoupler the emitter and collector of triode respectively drive end and direct supply with described 2nd DC electronic switch be connected, in described optocoupler, the positive pole of photodiode and negative pole are connected with the pulse signal output end of described pulse signal generating circuit and the output terminal of described comparer respectively.

4. load motor according to claim 1 protection circuit, it is characterized in that, described main switch loop comprises the first rectifying circuit, when the output terminal of the first DC electronic switch and reference voltage circuit and described reference voltage circuit is connected with the drive end of described first DC electronic switch, described reference voltage circuit comprises the first resistance, 2nd resistance, 3rd resistance, 4th resistance, filter capacitor and comparer, described first resistance is connected with the 2nd end of described first DC electronic switch, the just end of described comparer is accessed at the two ends of described first resistance after connecting the filtering circuit being made up of described 2nd resistance and described filter capacitor, one termination direct supply of described 3rd resistance, the other end of described 3rd resistance connects the negative terminal of described comparer respectively and connects with described 4th resistance, the other end ground connection of described 4th resistance, the output terminal of described comparer is connected with the drive end of described first DC electronic switch.

5. load motor according to claim 4 protection circuit, it is characterized in that, described bleed-off circuit comprises the 2nd rectifying circuit, 2nd DC electronic switch and optocoupler, the first end of described 2nd DC electronic switch and the 2nd end respectively cathode output end and cathode output end with described 2nd rectifying circuit be connected, in described optocoupler the emitter and collector of triode respectively drive end and direct supply with described 2nd DC electronic switch be connected, in described optocoupler, the positive pole of photodiode is connected with the pulse signal output end of described pulse signal generating circuit, the negative pole ground connection of photodiode in described optocoupler.

6. load motor according to claim 4 protection circuit, it is characterised in that, described bleed-off circuit comprises the first unidirectional electronic switching circuit and the 2nd unidirectional electronic switching circuit that symmetry is connected to described alternating current machine or its main auxiliary winding two ends.

7. load motor according to claim 6 protection circuit, it is characterized in that, described first unidirectional electronic switching circuit comprises the first main body circuit being made up of the first triode and the first diode, also has the first biasing circuit that the first Zener diode, the first electric capacity and the first current limliting resistance are formed; It is connected in parallel on described alternating current machine or the two ends of its main auxiliary winding after the collector electrode of negative pole described first triode of connection of described first diode, the emtting electrode of wherein said first triode connects described alternating current machine or the first end of its main auxiliary winding, described first current limliting resistance one end connects the base stage of described first triode, the other end connects described first electric capacity in parallel and described first Zener diode, and the positive pole of wherein said first Zener diode auxiliary winding first end main with described alternating current machine or its is connected.

8. load motor according to claim 6 protection circuit, it is characterized in that, described 2nd unidirectional electronic switching circuit comprises the 2nd main body circuit being made up of the 2nd triode and the 2nd diode, also has the 2nd biasing circuit that the 2nd Zener diode, the 2nd electric capacity and the 2nd current limliting resistance are formed; It is connected in parallel on described alternating current machine or the two ends of its main auxiliary winding after the collector electrode of negative pole described 2nd triode of connection of described 2nd diode, the emtting electrode of wherein said 2nd triode connects the 2nd end of described alternating current machine or its main auxiliary winding, described 2nd current limliting resistance one end connects the base stage of described 2nd triode, the other end connects described 2nd electric capacity in parallel and described 2nd Zener diode, and the positive pole of wherein said 2nd Zener diode is connected with the main auxiliary winding of described alternating current machine or its 2nd end.

9. load motor according to claim 1 protection circuit, it is characterized in that, described bleed-off circuit comprises the first rectifying circuit, when the output terminal of the first DC electronic switch and reference voltage circuit and described reference voltage circuit is connected with described main switch loop, described reference voltage circuit comprises the first resistance, 2nd resistance, 3rd resistance, 4th resistance, filter capacitor and comparer, described first resistance is connected with the 2nd end of described first DC electronic switch, the negative terminal of described comparer is accessed at the two ends of described first resistance after connecting the filtering circuit being made up of described 2nd resistance and described filter capacitor, one termination direct supply of described 3rd resistance, the other end of described 3rd resistance connects the just end of described comparer respectively and connects with described 4th resistance, the other end ground connection of described 4th resistance, the output terminal of described comparer is connected with described main switch loop.

10. load motor according to claim 9 protection circuit, it is characterized in that, described main switch loop comprises the 2nd rectifying circuit, 2nd DC electronic switch and optocoupler, the first end of described 2nd DC electronic switch and the 2nd end respectively cathode output end and cathode output end with described 2nd rectifying circuit be connected, in described optocoupler the emitter and collector of triode respectively drive end and direct supply with described 2nd DC electronic switch be connected, in described optocoupler, the positive pole of photodiode and negative pole are connected with the pulse signal output end of described pulse signal generating circuit and the output terminal of described comparer respectively.

11. load motor according to claim 1 protection circuit, it is characterized in that, described bleed-off circuit comprises the first rectifying circuit, when the output terminal of the first DC electronic switch and reference voltage circuit and described reference voltage circuit is connected with the drive end of described first DC electronic switch, described reference voltage circuit comprises the first resistance, 2nd resistance, 3rd resistance, 4th resistance, filter capacitor and comparer, described first resistance is connected with the 2nd end of described first DC electronic switch, the just end of described comparer is accessed at the two ends of described first resistance after connecting the filtering circuit being made up of described 2nd resistance and described filter capacitor, one termination direct supply of described 3rd resistance, the other end of described 3rd resistance connects the negative terminal of described comparer respectively and connects with described 4th resistance, the other end ground connection of described 4th resistance, the output terminal of described comparer is connected with the drive end of described first DC electronic switch.

12. load motor according to claim 11 protection circuit, it is characterized in that, described main switch loop comprises the 2nd rectifying circuit, 2nd DC electronic switch and optocoupler, the first end of described 2nd DC electronic switch and the 2nd end respectively cathode output end and cathode output end with described 2nd rectifying circuit be connected, in described optocoupler the emitter and collector of triode respectively drive end and direct supply with described 2nd DC electronic switch be connected, in described optocoupler, the positive pole of photodiode is connected with the pulse signal output end of described pulse signal generating circuit, the negative pole ground connection of photodiode in described optocoupler.

The 13. load motor protection circuit according to any one of claim 1-12, it is characterized in that, the DC electronic switch used in described load motor protection circuit is triode or MOS pipe, when DC electronic switch is three grades of pipes, its first end is collector electrode, 2nd end is emtting electrode, and drive end is base stage; When DC electronic switch is MOS pipe, its first end is drain electrode, and the 2nd end is source electrode, and drive end is grid.

14. 1 kinds of fans, it is characterised in that, comprise the protection circuit of the load motor described in the arbitrary item of claim 1-13.

15. 1 kinds of air-conditionings, it is characterised in that, comprise fan according to claim 14.