Rectification switching circuit

Abstract

A rectification switching circuit comprises a full-wave rectification circuit and a switching circuit. The full-wave rectifier circuit comprises two three-phase rectifier bridges; the switching circuit comprises three equivalent resistors which are in star connection with three phase lines of the motor, and a frequency sensitive circuit which is used for comparing a neutral point voltage formed at a connection point of the three equivalent resistors with any phase voltage of the high-speed winding and outputting a frequency sensitive signal. The frequency change circuit is used for converting the frequency sensitive signal into a frequency signal; and the switching execution circuit is used for switching the working winding according to the frequency signal. The switching execution circuit comprises an N-channel field effect transistor Q13; positive electrodes of the two three-phase rectifier bridges are directly communicated to serve as a motor output positive electrode, negative electrodes of the two three-phase rectifier bridges are connected through the Q13, a drain end of the Q13 serves as a motor output negative electrode, and a common-positive-electrode output mode is formed; the switching of the working rectifier bridge is realized through the on-off of the Q13. According to the utility model, the output capability of the motor at high and low rotating speeds can be considered, and the circuit is concise in design and easy to maintain.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of switching circuit for motor high-low speed switching. BACKGROUND

[0002] This part provides merely background information related to the present disclosure, which is not necessarily prior art.

[0003] With the increasingly mature unmanned aerial vehicle technology, unmanned aerial vehicles are increasingly widely used in military and civilian fields. In addition to small battery-driven unmanned aerial vehicles, fuel-powered unmanned aerial vehicles need to be equipped with dedicated generators. Due to task requirements, the generators used by fuel-powered unmanned aerial vehicles need to be small in size, light in weight, wide in speed range, and large in output capacity. To meet the above requirements, two sets of windings need to be designed to switch to meet the high and low speed requirements of unmanned aerial vehicles for motors.

[0004] There are many existing switching technologies, most of which focus on how to implement winding switching, which requires the use of external complex switching circuits or MCU logic control or control lines to describe the principle, but the specific implementation method is not specific and cannot be implemented. Although the first two methods can be implemented, the circuit is complex and prone to damage, affecting the service life of the product. The scheme provided by the present patent can realize winding switching through a simple and easy-to-maintain hardware circuit. SUMMARY

[0005] The present application aims to solve the above problems of the prior art and provide a rectifier switching circuit.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the utility model lies in: a rectifier switching circuit, comprising a full-wave rectifier circuit and a switching circuit; the full-wave rectifier circuit comprises two three-phase rectifier bridges connected to the high-speed winding and the low-speed winding of the motor respectively; the two neutral points of the two sets of three-phase windings of the motor are not connected to each other; the switching circuit comprises three equivalent resistors connected in star to the three-phase lines of the motor, a frequency-sensitive circuit for comparing the neutral point voltage formed by the connection points of the three equivalent resistors with the voltage of any one phase of the high-speed winding and outputting a frequency-sensitive signal, a frequency change circuit for converting the frequency-sensitive signal into a frequency signal, and a switching execution circuit for switching the working winding according to the frequency signal; the switching execution circuit comprises an N-channel field effect transistor Q13; the positive poles of the two three-phase rectifier bridges are directly connected to each other as the output positive pole of the motor, the negative poles of the two three-phase rectifier bridges are connected to each other through the N-channel field effect transistor Q13, the drain terminal of the N-channel field effect transistor Q13 serves as the output negative pole of the motor, forming a common positive pole output mode; the switching of the working rectifier bridge, i.e. the high-speed winding and the low-speed winding, is realized by the on-off of the N-channel field effect transistor Q13.

[0007] The frequency sensitive circuit comprises a charge-discharge circuit and a differential amplification circuit. The charge-discharge circuit is composed of a photo-coupler U4 and resistors R32 and capacitor C18, and the voltage between the neutral point of the motor and the phase voltage is obtained through the charge-discharge circuit to obtain a sawtooth wave with a period varying with the rotating speed. The differential amplification circuit is composed of resistors R33-R35, R38-R40 and an operational amplifier U5A. The differential amplification circuit intercepts the peak part of the sawtooth wave to improve the sensitivity of the frequency sensitive circuit, thereby ensuring the stability of the system.

[0008] The frequency variation circuit receives the frequency sensitive signal output by the frequency sensitive circuit. The frequency sensitive signal is obtained through a filter circuit in the frequency variation circuit to obtain a direct current voltage varying with the rotating speed of the motor. When the rotating speed of the motor is low, the direct current voltage is high, and the operational amplifier U5B in the frequency variation circuit outputs a low level. When the rotating speed of the motor is high, the direct current voltage is low, and the U5B in the frequency variation circuit outputs a high level. After a delay, the switching execution circuit outputs a frequency signal.

[0009] The switching execution circuit comprises a photo-coupler U3. The N-channel field effect transistor Q13 is controlled to be turned on through the photo-coupler U3 to realize level isolation and to serve as a switch for switching two rectifier bridges in the circuit. When the operational amplifier U5B outputs a high level, the photo-coupler U3 is turned on, the field effect transistor Q13 is cut off, the high-speed winding works, and the motor works in a high rotating speed mode. When the operational amplifier U5B outputs a low level, the photo-coupler U3 is cut off, the field effect transistor Q13 is turned on, the low-speed winding works, and the motor works in a low rotating speed mode.

[0010] When the rotating speed of the motor is higher than a set threshold value, the photo-coupler U4 is turned on for a long time, the voltage of the capacitor C18 is lower than the threshold value, the output voltage of the operational amplifier U5A is lower than the threshold value, the operational amplifier U5B outputs a high level, the photo-coupler U3 is turned on, the gate voltage of the field effect transistor Q13 is lower than the source voltage, the field effect transistor Q13 is cut off, the high-speed winding works, and the motor works in a high rotating speed mode. When the rotating speed of the motor is lower than the set threshold value, the photo-coupler U4 is turned on for a short time, the voltage of the capacitor C18 is higher than the threshold value, the output voltage of the operational amplifier U5A is higher than the threshold value, the operational amplifier U5B outputs a low level, the photo-coupler U3 is cut off, the gate voltage of the field effect transistor Q13 is higher than the source voltage, the field effect transistor Q13 is turned on, the low-speed winding works, and the motor works in a low rotating speed mode.

[0011] The full-wave rectification switching output circuit further comprises a filter circuit and a sampling voltage regulation circuit. The filter circuit is used to filter out the ripple in the rectified output voltage to improve the quality of the direct current voltage. The sampling voltage regulation circuit is used to sample and regulate the direct current voltage to control the output voltage of the motor.

[0012] The three equivalent resistors are connected to the three-phase lines of the high-speed winding.

[0013] The three-phase rectifier bridge comprises six field effect transistors.

[0014] The high-speed winding A phase output line is connected with the gate electrode of the field effect transistor Q1, the source electrode of the field effect transistor Q1 and the drain electrode of the field effect transistor Q4 respectively; the B phase output line is connected with the gate electrode of the field effect transistor Q2, the source electrode of the field effect transistor Q2 and the drain electrode of the field effect transistor Q5 respectively; the C phase output line is connected with the gate electrode of the field effect transistor Q3, the source electrode of the field effect transistor Q3 and the drain electrode of the field effect transistor Q6 respectively; the low-speed winding U phase output line is connected with the gate electrode of the field effect transistor Q7, the source electrode of the field effect transistor Q7 and the drain electrode of the field effect transistor Q10 respectively; the V phase output line is connected with the gate electrode of the field effect transistor Q8, the source electrode of the field effect transistor Q8 and the drain electrode of the field effect transistor Q11 respectively; the W phase output line is connected with the gate electrode of the field effect transistor Q9, the source electrode of the field effect transistor Q9 and the drain electrode of the field effect transistor Q12 respectively; the drain electrodes of the field effect transistors Q1-Q6 are connected; the gate electrodes and the source electrodes of the field effect transistors Q4, Q5, Q6, Q10, Q11 and Q12 are connected to the ground simultaneously.

[0015] The utility model discloses a three -phase rectifier bridge is adopted six N channel field effect transistor, and its source and gate direct connection, utilizes the inside body diode and realizes rectification purpose, adopts this structure design compact, the degree of integration is high, can effectively save the space, the positive pole of two three -phase rectifier bridges direct communication is as the output positive pole of motor, and the negative pole of two rectifier bridges is connected through N channel field effect transistor Q13, and the drain end of field effect transistor Q13 is as the output negative pole of motor, forms the output mode of common positive pole, and the two neutral points of motor two sets of windings are not connected, and three equivalent resistances are connected in star type on the three -phase line of motor, and the connecting point of the three resistances is formed neutral point, and the voltage of certain phase voltage of winding and this neutral point is compared, and the unidirectional conductivity of the light emitting diode in photo -coupler is obtained square wave signal, and the square wave signal can obtain the direct current voltage that the amplitude and the rotational speed are proportional through RC charge -discharge loop, differential amplification loop and filter loop, and the switching signal of certain rotational speed corresponding to the reference voltage can be obtained by comparing the direct current voltage and the reference voltage, and the signal controls N channel field effect transistor Q13 on -off work, realizes the free switching of motor high, low rotational speed.

[0016] The rectification switching circuit provided by the utility model is used for switching of motor winding, realizes the consideration of output capacity when the motor is high or low speed, and the circuit design is simple and easy to maintain. According to different working speed requirements, the motor winding is automatically switched through the rectification switching circuit to realize real-time switching of the motor high or low speed, and meet the power generation demand of the high or low speed range of the motor of the unmanned aerial vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is the circuit diagram of the utility model.

[0018] Figure 2 It is the circuit diagram of the full -wave rectification circuit.

[0019] Figure 3 is a circuit diagram of a low-speed winding and a second rectifier bridge.

[0020] Figure 4 is a circuit diagram of a low-speed winding and a second rectifier bridge.

[0021] Figure 5 is a circuit diagram of a switching circuit.

[0022] Figure 6 is a circuit diagram of a frequency-sensitive circuit.

[0023] Figure 7 is a circuit diagram of a frequency-changing circuit.

[0024] Figure 8 is a circuit diagram of a switching execution circuit. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] The technology, methods and devices known to those skilled in the relevant art can not be discussed in detail, but should be considered as part of the authorized description when appropriate.

[0027] It should be noted that the following implementation method is not unique, and the implementation parameters are not fixed. The rectifier switching circuit provided by the present application allows the motor to access the low-speed winding at low speed to close the high-speed winding and work through the low-speed winding, and to cut off the low-speed winding at high speed to work through the high-speed winding.

[0028] The two sets of independent windings of the motor are connected to two three-phase rectifier bridges, the positive poles of the two three-phase rectifier bridges are directly connected to each other as the output positive pole of the motor, the negative poles of the two rectifier bridges are connected to each other through an N-channel field effect transistor Q13 (the field effect transistor Q13 is used to realize switching of the two rectifier bridges), the drain end of the field effect transistor Q13 is used as the output negative pole of the motor, forming a common positive pole output mode, and of course, a common negative pole output mode can also be formed through a P-channel field effect transistor.

[0029] When the motor works, the polarity of any phase voltage of the motor relative to the neutral point alternates between positive and negative, and the unidirectional conductivity of the light emitting diode inside the optocoupler is used to connect the phase voltage of a phase (such as phase A) of the winding to the base of the optocoupler and the neutral point to the emitter of the optocoupler, so that a square wave signal proportional to the frequency and the rotating speed of the motor can be obtained, the square wave signal passes through an RC charging and discharging circuit composed of a transistor and a resistor and a capacitor, so that a sawtooth wave with a period varying with the rotating speed can be obtained, the sawtooth wave passes through an amplification circuit and a filtering circuit, so that a direct current voltage proportional to the rotating speed can be obtained, the direct current voltage is compared with a reference voltage, so that a switching signal corresponding to a certain rotating speed of the reference voltage can be obtained, the signal controls the on-off work of the N-channel field effect transistor Q13, so that the switching of the working rectifier bridge, that is, the switching of the working winding, can be realized.

[0030] The use of the high-speed winding or the low-speed winding to extract the rotating speed signal does not affect the realization of the above functions, but since the terminal voltage of the high-speed winding doubles when switching to the low-speed winding, in order to reduce the voltage withstand requirement of the components, the high-speed winding is used for sampling in the utility model.

[0031] There are not less than one scheme in the circuit implementation of the comparison between the phase voltage of the winding and the neutral point voltage, the first scheme is a three-phase four-wire system, which needs to draw a fourth wire as the neutral point, and the manufacturing complexity is increased in structure. Another scheme is to connect three equivalent resistors in star type on the three-phase lines of the motor, and the connection points of the three resistors form the neutral point, and the scheme is relatively simple in structure, and the utility model adopts the scheme. The third scheme is to connect two voltage dividing resistors with the same resistance in series between the positive and negative electrodes of the motor, and the connection point of the two voltage dividing resistors is the neutral point of the motor.

[0032] Generally, a power diode is used in a three-phase rectifier bridge, but the existing power diode adopts a large-size package, so it is difficult to realize the miniaturization design of the product, the utility model uses the body diode existing in the field effect transistor to realize the diode replacement of the field effect transistor by short-circuiting the gate and the source of the N-channel field effect transistor, the miniaturization of the field effect transistor is realized, the miniaturization of the three-phase rectifier bridge is realized, and the arrangement effect of two three-phase rectifier bridges in limited space is realized.

[0033] The motor applied in the utility model is composed of two sets of three-phase windings (a high-speed winding used for high rotating speed working conditions and a low-speed winding used for low rotating speed working conditions), and the two neutral points of the two sets of three-phase windings are not connected to each other.

[0034] The three-phase winding of each set of motor utilizes six field effect tubes to form a three-phase full-wave rectification circuit, and when N-channel field effect tubes are specially adopted, the source and the gate of the field effect tube are directly connected, and the internal body diode is utilized to realize the rectification purpose. Generally, a power diode is adopted to realize the three-phase rectification bridge, and compared with the diode, the field effect tube scheme adopted by the utility model has small size, compact structure and high integration, and can save space.

[0035] The positive poles of the two three-phase rectification bridges are directly connected as the output positive pole of the motor, the negative poles of the two rectification bridges are connected through N-channel field effect tube Q13, the drain end of the field effect tube Q13 is used as the output negative pole of the motor, and the output mode of common positive pole is formed. The output mode of common negative pole can also be realized through the P-channel field effect tube: the negative poles of the two three-phase rectification bridges are directly connected as the output negative pole of the motor, the positive poles of the two rectification bridges are connected through the P-channel field effect tube, the source end of the field effect tube is used as the output positive pole of the motor, and the output mode of common negative pole is formed. The utility model adopts the scheme of N-channel field effect tube.

[0036] The full-wave rectification switching output circuit obtains a square wave signal through the comparison of the voltage of a phase of the winding and the neutral point voltage, the unidirectional conductivity of the light emitting diode inside the optocoupler, the RC charging and discharging circuit, the amplifying circuit and the filtering circuit, and the direct current voltage proportional to the amplitude and the rotating speed can be obtained, the switching signal corresponding to the rotating speed can be obtained by comparing the direct current voltage with the set reference voltage, the signal controls the on-off work of the N-channel field effect tube Q13, and the switching of the working winding is realized.

[0037] The comparison of the voltage of a phase of the winding and the neutral point voltage in the switching circuit is realized by connecting three equivalent resistors in star type on the three-phase line of the motor, and the neutral point is formed by the connecting points of the three resistors. The comparison of the voltage of a phase of the winding and the neutral point voltage is used to obtain the rotating speed signal.

[0038] Two voltage dividing resistors with the same resistance value can also be connected in series between the positive pole and the negative pole of the motor, and the connecting point of the two voltage dividing resistors is the neutral point of the motor.

[0039] The utility model adopts the star type connection of three equivalent resistors on the three-phase line of the high-speed winding of the motor, and compared with the low-speed winding, the adoption of the high-speed winding can reduce the voltage requirement of the components.

[0040] The field effect tube Q13 is controlled to be turned on through the optocoupler U3, realizes the level isolation, and plays the role of switching of the two rectification bridges in the circuit, so that the switching of the winding and the switching of the rotating speed are realized.

[0041] The rectification switching circuit provided by the embodiment of the utility model includes a full-wave rectification circuit and a switching circuit; the full-wave rectification circuit includes two three-phase rectification bridges connected with two sets of three-phase windings respectively; the switching circuit includes three equivalent resistors connected in star type on three-phase lines of the motor, a frequency sensitive circuit, a frequency change circuit and a switching execution circuit.

[0042] The positive poles of the two three-phase rectification bridges are directly connected in communication as the output positive pole of the motor, the negative poles of the two rectification bridges are connected in communication through an N-channel field effect transistor Q13, the drain end of the field effect transistor Q13 is taken as the output negative pole of the motor, and a common positive pole output mode is formed.

[0043] The frequency sensitive circuit: three equivalent resistors are connected in star type on three-phase lines of the motor, and a neutral point is formed by using the connection points of the three resistors. The voltage of an arbitrary phase (C phase is taken as an example in the utility model) of a high-speed winding is compared with the voltage of the neutral point. When the motor works, the polarity of the motor neutral point voltage and the phase voltage will change alternately, and through an RC charging and discharging loop formed by a photocoupler U4 and resistors R32 and a capacitor C18, a sawtooth wave with a period changing with the speed can be obtained. By selecting appropriate RC parameters, within the working speed range, the higher the speed is, the shorter the charging time of the capacitor C18 is, and the lower the sawtooth peak value of the C18 voltage is, that is, the amplitude of the sawtooth wave and the speed are inversely related. Resistors R33-R35, R38-R40 and an operational amplifier U5A constitute a differential amplification circuit. The amplification circuit intercepts the peak part of the sawtooth wave for subsequent comparison (the part below the bias voltage is discarded) through the bias voltage of the inverting input end, so as to improve the sensitivity of the frequency sensitive circuit, and the output impedance of the frequency sensitive circuit is also improved through the operational amplifier, so as to ensure the stability of the system.

[0044] The frequency change circuit: a direct current voltage is obtained through a filter circuit formed by a diode D18 and resistors R41 and a capacitor C19. When the motor speed is low, the direct current voltage is high, the voltage is input to the inverting terminal of the operational amplifier U5B through the resistor R47, when the potential of the inverting terminal of the operational amplifier U5B is higher than the potential of the set non-inverting terminal (corresponding to the switching speed), the U5B outputs a low level, when the motor speed is high, the direct current voltage is low, the voltage is input to the inverting terminal of the operational amplifier U5B through the resistor R47, when the potential of the inverting terminal of the operational amplifier U5B is lower than the potential of the set non-inverting terminal (corresponding to the switching speed), then the U5B outputs a high level, and a frequency signal is output to the switching execution circuit after delay.

[0045] Switching execution circuit: when the operational amplifier U5B outputs low level, the photo-coupler U3 is cut off, the gate voltage of the field effect transistor Q13 is higher than the conduction voltage, Q13 is turned on, the second rectifier bridge is connected to close the first rectifier bridge to work through the second rectifier bridge, the low-speed winding works, and the motor works in the low-speed mode. When the operational amplifier U5B outputs high level, the photo-coupler U3 is turned on, the gate voltage of the field effect transistor Q13 is the same as the source voltage, Q13 is cut off, the second rectifier is cut off to work through the first rectifier bridge, the high-speed winding works, and the motor works in the high-speed mode.

[0046] As shown in Figures 1-8 The full-wave rectification switching output circuit provided by the utility model includes a full-wave rectification circuit and a switching circuit. The full-wave rectification circuit includes two three-phase rectifier bridges connected with two sets of three-phase windings respectively. The switching circuit includes three equivalent resistors connected in star on three-phase lines of a motor, a frequency sensitive circuit, a frequency changing circuit and a switching execution circuit.

[0047] The first rectifier bridge includes field effect transistors Q1-Q6.

[0048] The second rectifier bridge includes field effect transistors Q7-Q12.

[0049] The frequency sensitive circuit includes resistors R31, diode D21, photo-coupler U4, resistor R32, capacitor C18, resistor R33, resistor R35, resistor R34, resistor R38, resistor R39, resistor R40, operational amplifier U5A and capacitor C14.

[0050] The frequency changing circuit includes resistors R45, R44, R41, R43, R42, R47, R48, variable resistor R46, operational amplifier U5B, diode D18 and diode D20, and capacitor C19.

[0051] The switching execution circuit includes resistor R23, photo-coupler U3, resistor R24, resistor R22, voltage stabilizing tube D17, field effect transistor Q13, capacitor C15 and resistor R27.

[0052] The high-speed winding A-phase output line is connected with the gate of the field effect transistor Q1, the source of the field effect transistor Q1 and the drain of the field effect transistor Q4 respectively. The winding B-phase output line is connected with the gate of the field effect transistor Q2, the source of the field effect transistor Q2 and the drain of the field effect transistor Q5 respectively. The winding C-phase output line is connected with the gate of the field effect transistor Q3, the source of the field effect transistor Q3 and the drain of the field effect transistor Q6 respectively.

[0053] The low-speed winding U-phase output line is connected with the gate of the field effect transistor Q7, the source of the field effect transistor Q7 and the drain of the field effect transistor Q10 respectively. The winding V-phase output line is connected with the gate of the field effect transistor Q8, the source of the field effect transistor Q8 and the drain of the field effect transistor Q11 respectively. The W-phase output line is connected with the gate of the field effect transistor Q9, the source of the field effect transistor Q9 and the drain of the field effect transistor Q12 respectively.

[0054] The drains of the field effect transistors Q1-Q6 are connected together. The gates and the sources of the field effect transistors Q4, Q5, Q6, Q10, Q11 and Q12 are connected to the common ground.

[0055] The voltage of any one phase of a winding is compared with the midpoint voltage. At this time, the C-phase voltage of the low-voltage winding is compared with the midpoint voltage.

[0056] The sources of the field effect transistors Q1, Q2 and Q3 are connected with the first ends of the resistors R28, R25 and R26 respectively. The second ends of the resistors R28, R25 and R26 are connected with the anode of the diode D21. The C-phase output line of the low-voltage winding is connected with the first end of the resistor R31. The second end of the resistor R31 is connected with the cathode of the diode D21.

[0057] The cathode of the diode D21 is connected with the anode of the optocoupler U4. The anode of the diode D21 is connected with the cathode of the optocoupler U4. The collector of the optocoupler U4, the first end of the resistor R32, the first end of the capacitor C18 and the first end of the resistor R38 are connected together. The second end of the resistor R32, the first end of the resistor R33, the positive power supply of the operational amplifier U5A and the first end of the capacitor C14 are connected together. The second end of the capacitor C14 is connected to the common ground.

[0058] The second end of the resistor R33, the first end of the resistor R34 and the first end of the resistor R35 are connected together.

[0059] The second end of the resistor R34, the first end of the resistor R40 and the inverting input terminal of the operational amplifier U5A are connected together. The second end of the resistor R38, the second end of the resistor R39 and the non-inverting input terminal of the operational amplifier U5A are connected together. The negative power supply of the operational amplifier U5A is connected to the ground. The output terminal of the operational amplifier U5A, the second end of the resistor R40 and the anode of the diode D18 are connected together.

[0060] The emitter of the optocoupler U4, the second end of the capacitor C18, the second end of the resistor R35 and the second end of the resistor R39 are connected to the common ground.

[0061] The cathode of the diode D18 is connected with the first end of the resistor R41. The second end of the resistor R41, the first end of the capacitor C19, the first end of the resistor R42 and the first end of the resistor R47 are connected together.

[0062] The second end of the capacitor C19 and the second end of the resistor R42 are connected to the common ground.

[0063] The second end of the resistor R27 is connected with the reverse input end of the operational amplifier U5B, the output end of the B5B is connected with the anode of the diode D20 and the first end of the resistor R48, the second end of the resistor R48 is connected with the same phase input end of the operational amplifier U5B and the first end of the resistor R43, the second end of the resistor R43 is connected with the adjusting end of the variable resistor R46, the first end of the resistor R46 is connected with the first end of the resistor R44, the second end of the R44 is connected with +15V, the second end of the variable resistor R46 is connected with the first end of the resistor R45, and the second end of the R45 is grounded.

[0064] The cathode of the diode D20 is connected with the first end of the resistor R23, the second end of the R23 is connected with the positive electrode of the photo-coupler U3, the negative electrode of the photo-coupler U3 is grounded, the collector of the U3, the first end of the resistor R24, the first end of the resistor R22, the negative electrode of the voltage stabilizing tube D17 and the gate of the field effect transistor Q13 are connected together.

[0065] The source of the field effect transistor Q13 and the first end of the resistor R27 are grounded, the second end of the resistor R27 is connected with the first end of the capacitor C15, and the second end of the C15 and the drain of the field effect transistor Q13 are grounded.

[0066] The emitter of the photo-coupler U3, the second end of the resistor R22 and the positive electrode of the voltage stabilizing tube D17 are grounded.

Claims

1. A rectifier switching circuit, characterized by: The application relates to a full-wave rectification circuit and a switching circuit, wherein the full-wave rectification circuit comprises two three-phase rectification bridges for connecting with high-speed windings and low-speed windings of a motor respectively; the switching circuit comprises three equivalent resistors in star connection on three-phase lines of the motor, a frequency sensitive circuit for comparing a neutral point voltage formed by connecting points of the three equivalent resistors with an arbitrary phase voltage of the high-speed windings and outputting a frequency sensitive signal, a frequency changing circuit for converting the frequency sensitive signal into a frequency signal, and a switching execution circuit for switching the working windings according to the frequency signal; the switching execution circuit comprises an N-channel field effect transistor Q13; the positive poles of the two three-phase rectification bridges are directly connected as output positive poles of the motor, the negative poles of the two three-phase rectification bridges are connected through the N-channel field effect transistor Q13, and the drain end of the N-channel field effect transistor Q13 is connected as an output negative pole of the motor, so that a common positive pole output mode is formed; the switching of the working rectification bridge, i.e. the high-speed windings and the low-speed windings, is realized through the on-off of the N-channel field effect transistor Q13.

2. The rectifier switching circuit of claim 1, wherein: The frequency sensitive circuit comprises a charge-discharge circuit and a differential amplification circuit; the charge-discharge circuit is composed of an optical coupler U4 and resistors R32 and a capacitor C18, the sawtooth wave with a period varying with the rotating speed is obtained through the charge-discharge circuit between the neutral point voltage and the phase voltage of the motor; the differential amplification circuit is composed of resistors R33-R35, R38-R40 and an operational amplifier U5A, the sensitivity of the frequency sensitive circuit is improved by intercepting the peak part of the sawtooth wave, so that the system stability is ensured.

3. The rectifier switching circuit of claim 2, wherein: The frequency changing circuit receives the frequency sensitive signal output by the frequency sensitive circuit, the frequency sensitive signal obtains a direct current voltage through a filter circuit in the frequency changing circuit, the voltage varies with the change of the rotating speed of the motor, the direct current voltage becomes high when the rotating speed of the motor is low, the operational amplifier U5B in the frequency changing circuit outputs a low level; the direct current voltage becomes low when the rotating speed of the motor is high, the U5B in the frequency changing circuit outputs a high level, and the frequency signal is output to the switching execution circuit after time delay.

4. The rectifier switching circuit of claim 3, wherein: The switching execution circuit comprises an optical coupler U3; the N-channel field effect transistor Q13 is controlled to be conductive through the optical coupler U3, the level isolation is realized, and the switching of the two rectification bridges is realized in the circuit; when the operational amplifier U5B outputs a high level, the optical coupler U3 is conductive, the field effect transistor Q13 is cut off, the high-speed windings work, and the motor works in a high rotating speed mode; when the operational amplifier U5B outputs a low level, the optical coupler U3 is cut off, the field effect transistor Q13 is conductive, the low-speed windings work, and the motor works in a low rotating speed mode.

5. The rectifier switching circuit of claim 4, wherein: When the motor speed is higher than the set threshold, the optocoupler U4 is on for a long time, the capacitor C18 voltage is lower than the threshold, the operational amplifier U5A output voltage is lower than the threshold, the operational amplifier U5B outputs high level, the optocoupler U3 is on, the field effect transistor Q13 gate voltage is lower than the source voltage, the field effect transistor Q13 is cut off, the high speed winding works, and the motor is in high speed working mode; when the motor speed is lower than the set threshold, the optocoupler U4 is on for a short time, the capacitor C18 voltage is higher than the threshold, the operational amplifier U5A output voltage is higher than the threshold, the operational amplifier U5B outputs low level, the optocoupler U3 is cut off, the field effect transistor Q13 gate voltage is higher than the source voltage, the field effect transistor Q13 is on, the low speed winding works, and the motor is in low speed working mode.

6. The rectifier switching circuit of claim 1, wherein: The full-wave rectification switching output circuit further comprises a filter circuit and a sampling voltage regulation circuit.

7. The rectifier switching circuit of claim 4, wherein: The three equivalent resistors are connected to three-phase lines of the high speed winding.

8. The rectifier switching circuit of claim 1, wherein: The three-phase rectification bridge comprises six field effect transistors.

9. The rectifier switching circuit of claim 8, wherein: The high speed winding A-phase output line is connected to the gate of the field effect transistor Q1, the source of the field effect transistor Q1 and the drain of the field effect transistor Q4; the B-phase output line is connected to the gate of the field effect transistor Q2, the source of the field effect transistor Q2 and the drain of the field effect transistor Q5; the C-phase output line is connected to the gate of the field effect transistor Q3, the source of the field effect transistor Q3 and the drain of the field effect transistor Q6; the low speed winding U-phase output line is connected to the gate of the field effect transistor Q7, the source of the field effect transistor Q7 and the drain of the field effect transistor Q10; the V-phase output line is connected to the gate of the field effect transistor Q8, the source of the field effect transistor Q8 and the drain of the field effect transistor Q11; the W-phase output line is connected to the gate of the field effect transistor Q9, the source of the field effect transistor Q9 and the drain of the field effect transistor Q12; the drains of the field effect transistors Q1-Q6 are connected; the gates and sources of the field effect transistors Q4, Q5, Q6, Q10, Q11 and Q12 are connected to the ground.

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