Three-phase power supply abnormity detection circuit and method and three-phase BLDC motor control circuit

Abstract

The invention relates to the technical field of motor manufacturing, and discloses a three-phase power supply abnormity detection circuit and method and a three-phase BLDC motor control circuit. The input end of a three-phase rectification step-down circuit is connected with three-phase input power supplies U, V and W. The output end of the three-phase rectification step-down circuit is connected with the first input end of a comparison circuit; the second input end of the comparison circuit is connected with direct current bus voltage, the output end of the comparison circuit is connected with the first input end of the microprocessor, and the first output end of the microprocessor is connected with the input end of the surge protection circuit. By setting the reference voltage of the comparison circuit as the bus voltage, the power failure and phase loss conditions of the three-phase power supply can be detected within 10mS, the action speed of the relay is further improved, the circuit is prevented from being impacted by surge, the second input end of the comparator is simultaneously connected to the microprocessor, the bus voltage of the three-phase power supply can be simultaneously detected, and the overvoltage and undervoltage of the three-phase power supply can be detected. And then corresponding protection actions are carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of motor manufacturing, and in particular to a three-phase power supply anomaly detection circuit and method and a three-phase BLDC motor control circuit. Background Art

[0002] ATS (Automatic Transfer Switch) is a dual power automatic transfer switch, mainly used in emergency power supply systems to automatically switch the load circuit from one power source to another (backup) power source to ensure continuous and reliable operation of important loads.

[0003] Many places have very high requirements for ATS switching, and some customers require extremely short switching time. During the switching time, the relay of the motor control circuit cannot be disconnected quickly due to capacitor discharge. When switching to the backup power supply, a huge impact current will be triggered to enter the motor controller. The relay cannot be disconnected in time, and the impact current will not pass through the PTC, which is very likely to damage the controller hardware, and the power supply will also have a certain probability of tripping.

[0004] In the existing solution, the level output by the three-phase power phase loss detection circuit to the microprocessor MCU is high or low, and there is no alternating state of high and low levels. When the power is disconnected, the level output by the three-phase power phase loss detection circuit to the microprocessor MCU is low, and when the power is closed, the level output by the three-phase power phase loss detection circuit to the microprocessor MCU is high. When the microprocessor MCU detects that the signal Vdp voltage is low, it will turn off the relay to protect the subsequent circuit. However, the above control method has the following shortcomings:

[0005] Since X capacitors are set at the three-phase input power supplies U, V, and W, when the external power supply is cut off, the voltages of the three-phase input power supplies U, V, and W are still at the values ​​before they are disconnected. The X capacitors need to discharge for a period of time before the three-phase power supply phase loss detection circuit can output a low level. The reaction is slow, causing the relay to remain in a closed state, and the PTC resistor cannot play a role in preventing current mutations. Summary of the invention

[0006] In view of this, the present invention provides a three-phase power supply abnormality detection circuit, method and a three-phase BLDC motor control circuit to solve the problem of relay shutdown delay caused by slow discharge of X capacitor in existing solutions.

[0007] In a first aspect, the present invention provides a three-phase power supply abnormality detection circuit, the detection circuit comprising: a three-phase rectifier and step-down circuit, a comparison circuit, a microprocessor and a surge protection circuit, wherein:

[0008] The input end of the three-phase rectifying and bucking circuit is connected to the three-phase input power supply U, V, and W respectively, the output end of the three-phase rectifying and bucking circuit is connected to the first input end of the comparison circuit, the second input end of the comparison circuit is connected to the DC bus voltage, the output end of the comparison circuit is connected to the first input end of the microprocessor, and the first output end of the microprocessor is connected to the input end of the surge protection circuit;

[0009] The three-phase rectifier and buck circuit transmits the voltage after rectification and bucking to the comparison circuit, the comparison circuit compares the voltage with the DC bus voltage, and outputs a detection signal to the microprocessor, the microprocessor determines whether the period of the detection signal is greater than a first preset time, and when the period of the detection signal is greater than the first preset time, the microprocessor outputs a drive signal to the surge protection circuit to turn off the relay in the surge protection circuit.

[0010] The present invention provides a three-phase power supply abnormality detection circuit, which processes the fixed phase difference of the three-phase input power supply through hardware to fit the high and low levels of a fixed period. It only needs to detect whether there is a rising edge or a falling edge of the level in a specific period. If it is detected, it belongs to the normal power supply state, and if the detection period becomes longer, it is in the abnormal power supply state. After the abnormal power supply state is detected, the microprocessor turns off the relay through the hardware circuit. By setting the reference voltage of the comparison circuit to a dynamic voltage, the generation speed of the detection signal Vdp can be increased, and then the action speed of the relay can be increased, thereby avoiding the relay shutdown delay caused by the slow discharge of the X capacitor.

[0011] In an optional implementation, the three-phase rectifier-step-down circuit includes: a first rectifier-step-down circuit, a second rectifier-step-down circuit and a third rectifier-step-down circuit, wherein:

[0012] The input end of the first rectifier-step-down circuit is connected to the U-phase input power supply, the input end of the second rectifier-step-down circuit is connected to the V-phase input power supply, the input end of the third rectifier-step-down circuit is connected to the W-phase input power supply, and the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit are connected together and then connected to the first input end of the comparison circuit.

[0013] In an optional embodiment, the comparison circuit includes a first comparator, the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit are connected together and then connected to the in-phase input end of the first comparator, the inverting input end of the first comparator is connected to the DC bus voltage, and the output end of the first comparator is connected to the first input end of the microprocessor.

[0014] By connecting the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit together and then connecting them to the first input end of the comparison circuit, the number of comparators used is reduced, the circuit structure is simplified, the anti-interference ability of the three-phase rectifier-step-down circuit is improved, and the probability of square wave interference is reduced.

[0015] In an optional implementation, the surge protection circuit includes: a relay drive circuit, a relay and a PTC resistor, wherein:

[0016] The input end of the relay drive circuit is connected to the first output end of the microprocessor, the output end of the relay drive circuit is connected to one end of the coil in the relay, the other end of the coil in the relay is connected to an external power supply, and the electromagnetic switch in the relay is connected in parallel with the PTC resistor and then connected in series between the three-phase rectifier circuit and the inverter circuit.

[0017] In an optional implementation, the relay drive circuit includes: a first capacitor, a second capacitor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first transistor, a second transistor and a first voltage stabilizing diode, wherein:

[0018] One end of the first capacitor and one end of the first resistor are both connected to an external power supply, the other end of the first resistor is respectively connected to the collector of the first transistor, one end of the second capacitor and the cathode of the first voltage-stabilizing diode, one end of the second resistor is connected to the first output end of the microprocessor, the other end of the second resistor is respectively connected to the base of the first transistor and one end of the third resistor, the anode of the first voltage-stabilizing diode is respectively connected to one end of the fourth resistor and the base of the second transistor, the collector of the second transistor is connected to the relay coil in the surge protection circuit, and the other end of the first capacitor, the other end of the third resistor, the emitter of the first transistor, the other end of the second capacitor, the other end of the fourth resistor and the emitter of the second transistor are all grounded.

[0019] In an optional embodiment, the detection circuit also includes: a bus voltage real-time detection circuit, one end of the bus voltage real-time detection circuit is connected to the DC bus voltage, and the other end of the bus voltage real-time detection circuit is connected to the second input terminal of the microprocessor.

[0020] In an optional implementation, the bus voltage real-time detection circuit includes: a third capacitor, a fourth capacitor, a Schottky diode and a fifth resistor, wherein:

[0021] One end of the third capacitor and the control end of the Schottky diode are both connected to the DC bus voltage, the cathode of the Schottky diode is connected to an external power supply, one end of the fifth resistor is connected to the control end of the Schottky diode, the other end of the fifth resistor is connected to one end of the fourth capacitor and then connected to the second input end of the microprocessor, and the other end of the third capacitor, the other end of the fourth capacitor and the anode of the Schottky diode are all grounded.

[0022] In a second aspect, the present invention provides a three-phase BLDC motor control circuit, comprising: a three-phase rectifier circuit, an inverter circuit, and a three-phase power supply abnormality detection circuit according to the first aspect or any corresponding embodiment thereof, wherein:

[0023] The input ends of the three-phase rectifier circuit are respectively connected to three-phase input power supplies U, V, and W, the output ends of the three-phase rectifier circuit are connected to a surge protection circuit and then connected in parallel with the inverter circuit, and the output end of the inverter circuit is connected to a motor.

[0024] By using a three-phase power supply abnormality detection circuit in a three-phase BLDC motor control circuit, it is only necessary to detect whether there is a rising edge or a falling edge in a specific period. If it is detected, it is a normal power supply state. If the detection period becomes longer, it is in an abnormal power supply state. After detecting the abnormal power supply state, the microprocessor turns off the relay through the hardware circuit. By setting the reference voltage of the comparison circuit to a dynamic voltage, the generation speed of the detection signal Vdp can be increased, thereby increasing the action speed of the relay, thereby avoiding the relay shutdown delay caused by the slow discharge of the X capacitor.

[0025] In a third aspect, the present invention provides a three-phase power supply abnormality detection method, based on the three-phase power supply abnormality detection circuit of the first aspect or any corresponding embodiment thereof, the three-phase power supply abnormality detection method includes:

[0026] The three-phase input power U, V, W is rectified and stepped down by using a three-phase rectifier and step-down circuit;

[0027] The rectified and stepped-down voltage is transmitted to a comparison circuit, where the voltage is compared with the DC bus voltage and a detection signal is output to a microprocessor;

[0028] The microprocessor determines whether the period of the detection signal is greater than a first preset time. When the period of the detection signal is greater than the first preset period, a signal is output to a relay drive circuit to turn off a relay in a surge protection circuit.

[0029] A three-phase power supply abnormal detection method provided by the present invention fits high and low levels with a fixed period through hardware processing of the fixed phase difference of the three-phase input power supply. Then, it only needs to detect whether there is a rising edge or a falling edge of the level within a specific period through software. If detected, it belongs to the normal power supply state; if the detection period becomes longer, it is in the abnormal power supply state. After detecting the abnormal power supply state, the microprocessor closes the relay through the hardware circuit. By setting the reference voltage of the comparison circuit as a dynamic voltage, the generation speed of the detection signal Vdp can be increased, thereby increasing the action speed of the relay, and avoiding the relay turn-off delay caused by the slow discharge of the X capacitor. And through the combined use of software and hardware, it can ensure normal operation under interference and reduce the misoperation rate.

[0030] In an alternative embodiment, the method further includes: T0 < T1 < T2, where T0 is the period of the square wave signal output by the comparison circuit when the three-phase input power supplies U, V, and W are input normally, T1 is the first preset period, and T2 is the period of the square wave signal output by the comparison circuit in the case of a three-phase power supply phase loss.

[0031] In an alternative embodiment, the method further includes: when the period of the detection signal is not greater than the first preset period, it is determined that the three-phase input power supplies U, V, and W are input normally.

[0032] In an alternative embodiment, the method further includes:

[0033] When the period of the detection signal is greater than the first preset period but not greater than the second preset period, it is determined that the three-phase input power supplies U, V, and W are in a phase loss state;

[0034] When the period of the detection signal is greater than the second preset period, it is determined that the three-phase input power supplies U, V, and W are in a power-off state. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 is a schematic block diagram of a three-phase power supply abnormal detection circuit according to an embodiment of the present invention;

[0037] Figure 2 is a schematic diagram of a three-phase rectification and step-down circuit and a bus voltage real-time detection circuit according to an embodiment of the present invention;

[0038] Figure 3is a voltage waveform diagram of a three-phase rectifier and buck circuit according to an embodiment of the present invention;

[0039] Figure 4 is a relay driving circuit diagram according to an embodiment of the present invention;

[0040] Figure 5 is a flow chart of a three-phase power supply abnormality detection method according to an embodiment of the present invention;

[0041] Figure 6 is another voltage waveform diagram of the three-phase rectifier and buck circuit according to an embodiment of the present invention;

[0042] Figure 7 is another voltage waveform diagram of the three-phase rectifier and buck circuit according to an embodiment of the present invention;

[0043] Figure 8 is another voltage waveform diagram of the three-phase rectifier and buck circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be noted that the terms “first”, “second” and “third” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] like Figure 1As shown, the present invention provides a three-phase power supply anomaly detection circuit, including: a three-phase rectifier and buck circuit, a comparison circuit, a microprocessor and a surge protection circuit. Among them, the input end of the three-phase rectifier and buck circuit is respectively connected to the three-phase input power supply U, V, W, the output end of the three-phase rectifier and buck circuit is connected to the first input end of the comparison circuit, the second input end of the comparison circuit is connected to the DC bus voltage, the output end of the comparison circuit is connected to the first input end of the microprocessor, and the first output end of the microprocessor is connected to the input end of the surge protection circuit. Among them, the surge protection circuit consists of Figure 1 The relay drive circuit, relay and PTC resistor are composed.

[0049] Specifically, the three-phase input power U, V, W is first rectified and stepped down by the three-phase rectifier and step-down circuit, and then the three-phase rectifier and step-down circuit transmits the voltage after rectification and step-down to the comparison circuit. The comparison circuit compares the voltage with the DC bus voltage and outputs a detection signal Vdp to the microprocessor. The microprocessor determines whether the period of the detection signal Vdp is greater than the first preset time. When the period of the detection signal Vdp is greater than the first preset time, the microprocessor outputs a drive signal to the surge protection circuit to turn off the relay in the surge protection circuit.

[0050] In an embodiment of the present invention, when the three-phase input power U, V, W is input normally, the comparison circuit outputs a detection signal Vdp of a specific period. When the three-phase input power U, V, W is input abnormally, the comparison circuit outputs a detection signal Vdp larger than the specific period or does not generate a detection signal Vdp. At this time, the microprocessor only needs to detect whether there is a rising edge or a falling edge of the level within a specific period. If it is detected, it belongs to a normal power supply state. If the detection period becomes longer or cannot be detected, it is in an abnormal power supply state. When it is detected that the three-phase input power U, V, W is in an abnormal power supply state. The microprocessor turns off the relay in the surge protection circuit through the hardware circuit.

[0051] In addition, by setting the reference voltage of the comparison circuit to a dynamic voltage, that is, a DC bus voltage, the generation speed of the detection signal Vdp can be increased, thereby increasing the action speed of the relay, thereby avoiding the relay shutdown delay caused by the slow discharge of the X capacitor. Among them, the DC bus voltage is taken from the output end of the three-phase rectifier circuit.

[0052] The present invention provides a three-phase power supply abnormality detection circuit, which processes the fixed phase difference of the three-phase input power supply through hardware to fit the high and low levels of a fixed period. It only needs to detect whether there is a rising edge or a falling edge of the level in a specific period. If it is detected, it belongs to the normal power supply state, and if the detection period becomes longer, it is in the abnormal power supply state. After the abnormal power supply state is detected, the microprocessor turns off the relay through the hardware circuit. By setting the reference voltage of the comparison circuit to a dynamic voltage, the generation speed of the detection signal Vdp can be increased, and then the action speed of the relay can be increased, thereby avoiding the relay shutdown delay caused by the slow discharge of the X capacitor.

[0053] In an optional embodiment, if Figure 2 As shown, the three-phase rectifier-step-down circuit includes: a first rectifier-step-down circuit, a second rectifier-step-down circuit and a third rectifier-step-down circuit. The input end of the first rectifier-step-down circuit is connected to the U-phase input power supply, the input end of the second rectifier-step-down circuit is connected to the V-phase input power supply, and the input end of the third rectifier-step-down circuit is connected to the W-phase input power supply. The output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit are connected together and then connected to the first input end of the comparison circuit.

[0054] Specifically, the three-phase input power supplies U, V, and W are rectified and stepped down by their respective rectifier and step-down circuits, and then input to the first input terminal of the comparison circuit. When the three-phase input is powered on normally, the voltage waveform of the three-phase input power supplies U, V, and W after being stepped down by the diode half-wave rectification is: Figure 3 Waveform 1. By connecting the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit together and then connecting them to the first input end of the comparison circuit, the number of comparators used is reduced, the circuit structure is simplified, the anti-interference ability of the three-phase rectifier-step-down circuit is improved, and the probability of square wave being interfered is reduced.

[0055] In an optional embodiment, if Figure 2 As shown, the comparison circuit includes a first comparator U104, the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit are connected together and then connected to the in-phase input end of the first comparator U104, the inverting input end of the first comparator U104 is connected to the DC bus voltage, and the output end of the first comparator U104 is connected to the first input end of the microprocessor.

[0056] Specifically, the three-phase input power U, V, W is input to the in-phase input terminal of the first comparator U104 after rectification and voltage reduction. The DC bus voltage is input to the reverse input terminal of the first comparator U104 after resistance voltage reduction and filtering. The first comparator U104 compares the two and outputs a detection signal Vdp to the microprocessor. Among them, the test waveform of the DC bus voltage after resistance voltage reduction and filtering is: Figure 3 The waveform 2 is the waveform of the two waveforms after being transformed by the first comparator U104, which is a square wave pulse waveform with a fixed frequency, and the frequency is 3 times the input AC frequency. The waveform is Figure 3 Medium waveform 3.

[0057] In an optional embodiment, if Figure 1 As shown, the surge protection circuit includes: a relay drive circuit, a relay and a PTC resistor. Among them, the input end of the relay drive circuit is connected to the first output end of the microprocessor, the output end of the relay drive circuit is connected to one end of the coil RY1 in the relay, the other end of the coil RY1 in the relay is connected to an external power supply, and the electromagnetic switch JK in the relay is connected in parallel with the PTC resistor and then connected in series between the three-phase rectifier circuit and the inverter circuit.

[0058] Specifically, when the microprocessor determines that the period of the detection signal Vdp is greater than the first preset time, the microprocessor outputs a high-level drive signal Vk to the relay drive circuit to control the coil RY1 in the relay to lose power, and then controls the electromagnetic switch JK to disconnect, thereby turning off the relay and putting the PTC resistor into use, thereby achieving the purpose of protecting subsequent circuits.

[0059] In an optional embodiment, if Figure 4 As shown, the relay driving circuit includes: a first capacitor C76, a second capacitor C77, a first resistor R93, a second resistor R134, a third resistor R136, a fourth resistor R135, a first transistor Q11, a second transistor Q3 and a first voltage stabilizing diode ZD7. Among them, one end of the first capacitor C76 and one end of the first resistor R93 are both connected to the external power supply, the other end of the first resistor R93 is respectively connected to the collector of the first transistor Q11, one end of the second capacitor C77 and the cathode of the first voltage-stabilizing diode ZD7, one end of the second resistor R134 is connected to the first output end of the microprocessor, the other end of the second resistor R134 is respectively connected to the base of the first transistor Q11 and one end of the third resistor R136, the anode of the first voltage-stabilizing diode ZD7 is respectively connected to one end of the fourth resistor R135 and the base of the second transistor Q3, the collector of the second transistor Q3 is connected to the relay coil in the surge protection circuit, and the other end of the first capacitor C76, the other end of the third resistor R136, the emitter of the first transistor Q11, the other end of the second capacitor C77, the other end of the fourth resistor R135 and the emitter of the second transistor Q3 are all grounded.

[0060] Specifically, the +15V power supply reaches the base of the second transistor Q3 through the first resistor R93 and the first voltage stabilizing diode ZD7. The microprocessor outputs a drive signal Vk that reaches the base of the first transistor Q11 through the second resistor R134. When the drive signal Vk is a low-level signal, the first transistor Q11 is turned off, the second transistor Q3 is turned on, the coil RY1 in the relay is energized, and the electromagnetic switch JK in the relay is closed. When the drive signal Vk is a high-level signal, the first transistor Q11 is turned on, the second transistor Q3 is turned off, the coil RY1 in the relay is de-energized, and the electromagnetic switch JK in the relay is disconnected.

[0061] In an optional embodiment, if Figure 1 As shown, the detection circuit also includes: a bus voltage real-time detection circuit, one end of the bus voltage real-time detection circuit is connected to the DC bus voltage, and the other end of the bus voltage real-time detection circuit is connected to the second input end of the microprocessor.

[0062] Specifically, Figure 2 As shown, the bus voltage real-time detection circuit includes: a third capacitor C72, a fourth capacitor C75, a Schottky diode BAT54 and a fifth resistor R131. Among them, one end of the third capacitor C72 and the control end of the Schottky diode BAT54 are both connected to the DC bus voltage, the cathode of the Schottky diode BAT54 is connected to the external power supply, one end of the fifth resistor R131 is connected to the control end of the Schottky diode BAT54, the other end of the fifth resistor R131 is connected to one end of the fourth capacitor C75 and then connected to the second input end of the microprocessor, and the other end of the third capacitor C72, the other end of the fourth capacitor C75 and the anode of the Schottky diode BAT54 are all grounded.

[0063] In the embodiment of the present invention, the bus voltage real-time detection circuit is used to detect abnormal conditions such as DC bus phase loss, power failure, overvoltage and undervoltage in real time. When the DC bus has the above abnormal conditions, the bus voltage real-time detection circuit outputs an abnormal signal Vdc to the microprocessor. The microprocessor turns off the relay according to the abnormal signal Vdc to avoid the relay being unable to be disconnected in time due to the abnormal DC bus voltage, thereby affecting the use of the PTC resistor.

[0064] The present invention provides a three-phase BLDC motor control circuit, such as Figure 1As shown, it includes: a three-phase rectifier circuit, an inverter circuit and the three-phase power supply abnormality detection circuit in the above embodiment. Among them, the three-phase power supply abnormality detection circuit in the above embodiment includes: a three-phase rectifier step-down circuit, a comparison circuit, a microprocessor and a surge protection circuit. The input end of the three-phase rectifier circuit is respectively connected to the three-phase input power supply U, V, and W, the output end of the three-phase rectifier circuit is connected to the surge protection circuit and then connected in parallel with the inverter circuit, and the output end of the inverter circuit is connected to the motor.

[0065] Specifically, when the three-phase input power supply U, V, and W are normal, the three-phase BLDC motor control circuit controls the motor to operate normally, and when the external power supply is within the rated voltage range, Vdp is a square wave pulse waveform with a fixed frequency. The microprocessor detects a rising edge or a falling edge in a specific period, and outputs a low-level drive signal Vk to the relay drive circuit, the relay saves the energized state, and the motor maintains a normal operating state.

[0066] By using a three-phase power supply abnormality detection circuit in a three-phase BLDC motor control circuit, it is only necessary to detect whether there is a rising edge or a falling edge in a specific period. If it is detected, it is a normal power supply state. If the detection period becomes longer, it is in an abnormal power supply state. After detecting the abnormal power supply state, the microprocessor turns off the relay through the hardware circuit. By setting the reference voltage of the comparison circuit to a dynamic voltage, the generation speed of the detection signal Vdp can be increased, thereby increasing the action speed of the relay, thereby avoiding the relay shutdown delay caused by the slow discharge of the X capacitor.

[0067] The present invention provides a three-phase power supply abnormality detection method based on the three-phase power supply abnormality detection circuit in the above embodiment. Figure 5 As shown, the three-phase power supply abnormality detection method includes the following steps:

[0068] Step S11, using a three-phase rectifying and step-down circuit to rectify and step-down the three-phase input power U, V, W.

[0069] Step S12, the rectified and stepped-down voltage is transmitted to a comparison circuit, where the voltage is compared with the DC bus voltage and a detection signal is output to a microprocessor.

[0070] Step S13, the microprocessor determines whether the period of the detection signal is greater than a first preset time. When the period of the detection signal is greater than the first preset period, a signal is output to the relay drive circuit to turn off the relay in the surge protection circuit.

[0071] Specifically, the three-phase input power supplies U, V, and W first undergo rectification and voltage reduction by a three-phase rectifier and voltage reduction circuit, and then the three-phase rectifier and voltage reduction circuit delivers the voltage after rectification and voltage reduction to a comparison circuit. The comparison circuit compares the voltage with the DC bus voltage and outputs a detection signal Vdp to a microprocessor. The microprocessor determines whether the period of the detection signal Vdp is greater than a first preset time. When the period of the detection signal Vdp is greater than the first preset time, the microprocessor outputs a drive signal to a surge protection circuit to turn off the relay in the surge protection circuit.

[0072] In an embodiment of the present invention, when the three-phase input power supplies U, V, and W are input normally, the comparison circuit outputs a detection signal Vdp with a specific period. When the three-phase input power supplies U, V, and W are input abnormally, the comparison circuit outputs a detection signal Vdp greater than the specific period or does not generate a detection signal Vdp. At this time, the microprocessor only needs to detect whether there is a rising edge or a falling edge of the level within the specific period. If detected, it belongs to the normal power supply state. If the detection period becomes longer or not detected, it is in the abnormal power supply state. After detecting that the three-phase input power supplies U, V, and W are in the abnormal power supply state, the microprocessor turns off the relay in the surge protection circuit through a hardware circuit.

[0073] In addition, by setting the reference voltage of the comparison circuit to a dynamic voltage, that is, the DC bus voltage, the generation speed of the detection signal Vdp can be increased, thereby increasing the operation speed of the relay, and thus avoiding the relay turn-off delay caused by the slow discharge of the X capacitor.

[0074] A three-phase power supply abnormal detection method provided by the present invention fits high and low levels with a fixed period through hardware processing of the fixed phase difference of the three-phase input power supply. Then, it only needs to detect whether there is a rising edge or a falling edge of the level within a specific period through software. If detected, it belongs to the normal power supply state. If the detection period becomes longer, it is in the abnormal power supply state. After detecting the abnormal power supply state, the microprocessor turns off the relay through a hardware circuit. By setting the reference voltage of the comparison circuit to a dynamic voltage, the generation speed of the detection signal Vdp can be increased, thereby increasing the operation speed of the relay, and thus avoiding the relay turn-off delay caused by the slow discharge of the X capacitor. And through the combined use of software and hardware, it can ensure normal operation under interference and reduce the misoperation rate.

[0075] In an alternative embodiment, the method further includes: T0 < T1 < T2, where T0 is the period of the square wave signal output by the comparison circuit when the three-phase input power supplies U, V, and W are input normally, T1 is the first preset period, and T2 is the period of the square wave signal output by the comparison circuit in the case of a three-phase power supply phase loss.

[0076] Specifically, the waveform period T0 detected by the microprocessor is related to the power frequency. In the normal mode of the three-phase input power supply U, V, and W, when the frequency of the three-phase input power supply U, V, and W is 50 Hz, the waveform period T0 detected by the microprocessor is approximately 6.7 ms, and T0 = 1 / (50×3); when the frequency of the three-phase input power supply U, V, and W is 60 Hz, the waveform period T0 detected by the microprocessor is T0 = 1 / (60×3).

[0077] In the phase-loss mode of the three-phase input power supply U, V, and W, when the frequency of the three-phase input power supply U, V, and W is 50 Hz, the waveform period T2 detected by the microprocessor is approximately 10 ms, and T2 = 1 / (50×2); when the frequency of the three-phase input power supply U, V, and W is 60 Hz, the waveform period T2 detected by the microprocessor is T2 = 1 / (60×2).

[0078] Therefore, when the microprocessor only needs to determine whether there are two rising-edge inputs every T1 (T0 < T1 < T2), if there are two rising-edge inputs, it can be determined that the three-phase input is normal; if the rising-edge input is abnormal, it can be determined that the three-phase input is abnormal, and then the relay is turned off.

[0079] In an alternative embodiment, the method further includes:

[0080] Step S131, when the period of the detection signal is not greater than the first preset period, it is determined that the three-phase input power supply U, V, and W is input normally.

[0081] Step S132, when the period of the detection signal is greater than the first preset period but not greater than the second preset period, it is determined that the three-phase input power supply U, V, and W is in a phase-loss state.

[0082] Step S133, when the period of the detection signal is greater than the second preset period, it is determined that the three-phase input power supply U, V, and W is in a power-off state.

[0083] Specifically, when the three-phase power is disconnected, since the voltage waveforms of the three-phase input power supply U, V, and W are continuously fluctuating voltages, the X capacitor between any two of the three-phase inputs will discharge from any voltage value in the fluctuation range at the moment of disconnection. Therefore, there are two states. The first: the voltage of the X capacitor discharge voltage passing through the voltage-dividing resistor and entering the first comparator U104 is higher than the reference voltage of the inverting input terminal of the first comparator U104, and the first comparator U104 outputs a high level. The second: the voltage of the X capacitor discharge voltage passing through the voltage-dividing resistor and entering the first comparator U104 is lower than the reference voltage of the inverting input terminal of the first comparator U104, and the first comparator U104 outputs a low level. However, regardless of whether a high level or a low level is output, the microprocessor cannot recognize two rising edges of the square wave within the T0 time. The waveform test is as Figure 6 and Figure 7 shown.

[0084] When the three-phase input power supply U, V, and W is missing a phase, due to the 120-degree phase difference of the input voltage, the output period T0 of the square-wave signal output by the first comparator U104 will increase by 1 / 2. At this time, T0 is about 10.5 ms. The test waveform is shown in Figure 8 the following figure.

[0085] It can be summarized that when the input is normal, the period T0 of the square wave output by the first comparator U104 is about 7 ms. When the input is missing a phase, the period T0 of the square wave output by the first comparator U104 is about 10 ms. When the input is disconnected instantaneously, the first comparator U104 has no square-wave output. Therefore, it only needs to be determined whether there are two rising edges input within every T1 (T0 < T1) time by the microprocessor. If the two rising-edge inputs are abnormal, it can be determined that the three-phase input is abnormal, and then the relay is turned off, avoiding the problem that the relay turn-off delay caused by the slow discharge of the X capacitor set at the three-phase input power supply U, V, and W, resulting in the PTC resistor being unable to play the role of preventing current mutation. Thus, the relay can be turned off at the 10-ms level, meeting the market demand and improving its versatility.

[0086] It can be seen from the above conclusion that the hardware circuit outputs pulses with a specific period under normal power supply, and generates pulses with a period larger than the specific period or does not generate pulses under abnormal power supply. At this time, the microprocessor only needs to detect whether there is a rising edge or a falling edge of the level within a specific period (that is, the period of the detection signal is not greater than the first preset period). If detected, it belongs to the normal power supply state. If the detection period becomes longer (that is, the period of the detection signal is greater than the first preset period but not greater than the second preset period), it is in the phase-loss state. If not detected (that is, the period of the detection signal is greater than the second preset period), it is in the power-off state. After detecting the power-off state, the microprocessor closes the relay through the hardware circuit. Among them, the second preset period is determined according to specific circumstances.

[0087] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A three-phase power supply abnormality detection circuit, characterized in that: The detection circuit includes: a three-phase rectifier and step-down circuit, a comparison circuit, a microprocessor and a surge protection circuit, wherein: The input end of the three-phase rectifying and bucking circuit is connected to the three-phase input power supply U, V, and W respectively, the output end of the three-phase rectifying and bucking circuit is connected to the first input end of the comparison circuit, the second input end of the comparison circuit is connected to the DC bus voltage, the output end of the comparison circuit is connected to the first input end of the microprocessor, and the first output end of the microprocessor is connected to the input end of the surge protection circuit; The three-phase rectifier and buck circuit transmits the voltage after rectification and bucking to the comparison circuit, the comparison circuit compares the voltage with the DC bus voltage, and outputs a detection signal to the microprocessor, the microprocessor determines whether the period of the detection signal is greater than a first preset time, and when the period of the detection signal is greater than the first preset time, the microprocessor outputs a drive signal to the surge protection circuit to turn off the relay in the surge protection circuit.

2. The three-phase power supply abnormality detection circuit according to claim 1, characterized in that: The three-phase rectifier and buck circuit comprises: a first rectifier and buck circuit, a second rectifier and buck circuit and a third rectifier and buck circuit, wherein: The input end of the first rectifier-step-down circuit is connected to the U-phase input power supply, the input end of the second rectifier-step-down circuit is connected to the V-phase input power supply, the input end of the third rectifier-step-down circuit is connected to the W-phase input power supply, and the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit are connected together and then connected to the first input end of the comparison circuit.

3. The three-phase power supply abnormality detection circuit according to claim 2, characterized in that: The comparison circuit includes a first comparator, wherein the output end of the first rectifier-step-down circuit, the output end of the second rectifier-step-down circuit and the output end of the third rectifier-step-down circuit are connected together and then connected to the in-phase input end of the first comparator, the inverting input end of the first comparator is connected to the DC bus voltage, and the output end of the first comparator is connected to the first input end of the microprocessor.

4. The three-phase power supply abnormality detection circuit according to claim 1, characterized in that: The surge protection circuit comprises: a relay drive circuit, a relay and a PTC resistor, wherein: The input end of the relay drive circuit is connected to the first output end of the microprocessor, the output end of the relay drive circuit is connected to one end of the coil in the relay, the other end of the coil in the relay is connected to an external power supply, and the electromagnetic switch in the relay is connected in parallel with the PTC resistor and then connected in series between the three-phase rectifier circuit and the inverter circuit.

5. The three-phase power supply abnormality detection circuit according to claim 4, characterized in that: The relay drive circuit comprises: a first capacitor, a second capacitor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first triode, a second triode and a first voltage stabilizing diode, wherein: One end of the first capacitor and one end of the first resistor are both connected to an external power supply. The other end of the first resistor is respectively connected to the collector of the first triode, one end of the second capacitor, and the cathode of the first voltage stabilizing diode. One end of the second resistor is connected to the first output end of the microprocessor. The other end of the second resistor is respectively connected to the base of the first triode and one end of the third resistor. The anode of the first voltage stabilizing diode is respectively connected to one end of the fourth resistor and the base of the second triode. The collector of the second triode is connected to the relay coil in the surge protection circuit. The other end of the first capacitor, the other end of the third resistor, the emitter of the first triode, the other end of the second capacitor, the other end of the fourth resistor, and the emitter of the second triode are all grounded.

6. The three-phase power supply abnormality detection circuit according to claim 3, characterized in that: The detection circuit further includes: a bus voltage real-time detection circuit, one end of which is connected to the DC bus voltage, and the other end is connected to the second input end of the microprocessor.

7. The three-phase power supply abnormality detection circuit according to claim 6, characterized in that: The bus voltage real-time detection circuit includes: a third capacitor, a fourth capacitor, a Schottky diode, and a fifth resistor, where One end of the third capacitor and the control terminal of the Schottky diode are both connected to the DC bus voltage. The cathode of the Schottky diode is connected to the external power supply. One end of the fifth resistor is connected to the control terminal of the Schottky diode. The other end of the fifth resistor is connected to one end of the fourth capacitor and then connected to the second input end of the microprocessor. The other end of the third capacitor, the other end of the fourth capacitor, and the anode of the Schottky diode are all grounded.

8. A three-phase BLDC motor control circuit, characterized in that: including: a three-phase rectifier circuit, an inverter circuit, and the three-phase power supply abnormal detection circuit according to any one of claims 1-7, where The input ends of the three-phase rectifier circuit are respectively connected to the three-phase input power supplies U, V, and W. The output end of the three-phase rectifier circuit is connected to the surge protection circuit and then connected in parallel with the inverter circuit. The output end of the inverter circuit is connected to the motor.

9. A three-phase power supply anomaly detection method, characterized in that: Based on the three-phase power supply abnormal detection circuit according to any one of claims 1-7, the three-phase power supply abnormal detection method includes: Performing rectification and step-down processing on the three-phase input power supplies U, V, and W by using a three-phase rectification step-down circuit; Transmitting the voltage after rectification and step-down processing to a comparison circuit, comparing the voltage with the DC bus voltage in the comparison circuit, and outputting a detection signal to the microprocessor; Judging by the microprocessor whether the period of the detection signal is greater than a first preset time. When the period of the detection signal is greater than the first preset period, output a signal to the relay drive circuit to turn off the relay in the surge protection circuit.

10. The three-phase power supply anomaly detection method according to claim 9, characterized in that: The method further includes: T0 < T1 < T2, where T0 is the period of the square wave signal output by the comparison circuit when the three-phase input power supplies U, V, and W are input normally, T1 is the first preset period, and T2 is the period of the square wave signal output by the comparison circuit in the case of a three-phase power supply phase loss.

11. The three-phase power supply anomaly detection method according to claim 9, characterized in that: The method further includes: when the period of the detection signal is not greater than a first preset period, determining that the three-phase input power U, V, W is input normally.

12. The three-phase power supply abnormality detection method according to claim 9, characterized in that: The method further comprises: When the period of the detection signal is greater than the first preset period but not greater than the second preset period, it is determined that the three-phase input power U, V, W is in a phase-loss state; When the period of the detection signal is greater than the second preset period, it is determined that the three-phase input power U, V, W is in a power-off state.

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