Signal conversion device and motor drive system

Abstract

The present invention provides a signal conversion device and a motor drive system. The signal conversion device of one embodiment of the present invention has: a first signal input terminal, which is provided with a first AC signal from a signal source; a second signal input terminal, which is provided with a second AC signal from the signal source, the second AC signal including an in-phase signal in the same phase as the first AC signal and an inverted signal in an inverted phase with the first AC signal, and the phase is switched according to the switching of the in-phase signal and the inverted signal; and a detection unit, which uses the provided first AC signal to detect whether the provided second AC signal is the in-phase signal or the inverted signal.

Description

Technical Field

[0001] The invention relates to a signal conversion device and a motor driving system. Background Art

[0002] Research and development are being conducted on technologies related to systems that control motors and the like that are controlled objects (motor drive systems).

[0003] In this regard, there is described a device that performs on / off control of a plurality of controlled objects using switches provided outside the controlled objects (see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2010-43854

[0005] In the prior art, for example, when multiple control objects are turned on / off, the device sometimes detects a portion of the current flowing in a specific control object, and the device controls other control objects based on the detection result. However, the current flowing in the control object sometimes takes various values ​​depending on the type, power consumption, number, working state, etc. of the control object. In such a case, it is difficult to determine the reference value (threshold) for detecting the magnitude of the current flowing in the control object to an appropriate value, and it is difficult to detect the current flowing in the control object with high accuracy and control the control object. Summary of the invention

[0006] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a signal conversion device and a motor drive system capable of switching the operating state of a controlled object by a simpler method using a provided signal.

[0007] According to the first embodiment of the present invention, a signal conversion device is provided, which comprises: a first signal input terminal, to which a first AC signal is provided from a signal source; a second signal input terminal, to which a second AC signal is provided from the signal source, the second AC signal comprising an in-phase signal that is in phase with the first AC signal and an inverted signal that is in phase with the first AC signal, and the phase is switched according to the switching of the in-phase signal and the inverted signal; and a detection unit, which uses the provided first AC signal to detect whether the provided second AC signal is the in-phase signal or the inverted signal.

[0008] According to a second aspect of the present invention, there is provided a motor drive system including: a motor body; the above-mentioned signal conversion device; and a drive circuit that controls the motor body based on a detection result of the signal conversion device.

[0009] According to one embodiment of the present invention, it is possible to provide a signal conversion device and a motor drive system that can switch the operating state of a controlled object by a simpler method using a provided signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing an example of the configuration of the motor drive system according to the first embodiment.

[0011] Figure 2 This is a diagram for explaining the operation of the signal detection circuit in state A3.

[0012] Figure 3 A diagram for explaining simulation results of a signal detection circuit.

[0013] Figure 4 This is a diagram for explaining a state in which a leakage current exists through a load device.

[0014] Figure 5 This is a diagram for explaining the operation of the signal detection circuit.

[0015] Figure 6 It is a diagram showing an example of the configuration of a motor drive system according to the second embodiment.

[0016] Description of symbols

[0017] 1: Motor drive system; 2: AC / DC motor; 3: Interface device; 4: Switch; 5: Load device; 21: Motor body; 34: Signal detection circuit (detection unit); 341: Diode (first rectifier circuit); 343: Diode (second rectifier circuit, rectifier circuit); 344: LP filter; 345: Comparison circuit; 346: Bias circuit; 346A: First bias circuit; 347: Second bias circuit; 381: Terminal (first signal input terminal); 384: Terminal (second signal input terminal). DETAILED DESCRIPTION

[0018] <First embodiment>

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, in this embodiment, the conductor that transmits the electrical signal is referred to as a power supply line, a ground line, a wiring, a control signal line, etc. The power supply line and the ground line may be, for example, a cord, a conductor printed on a substrate, or a conductor of any shape such as a bus bar. The "connection" in the embodiment includes electrical connection.

[0020] <Motor drive system structure>

[0021] Figure 1It is a diagram showing an example of the configuration of the motor drive system 1 according to the first embodiment.

[0022] The motor drive system 1 includes an AC / DC motor 2 (referred to as “AC / DC motor” in the figure), an interface device 3, a switch 4, and a load device 5 (referred to as “LED” in the figure). The interface device 3 is an example of a signal conversion device.

[0023] Reference numeral PS denotes a power source for supplying AC power to the motor drive system 1. The power source PS is an example of a signal source.

[0024] The load device 5 includes a load that receives AC power from the power supply PS together with the motor drive system 1. The load device 5 may be, for example, a lighting device having an LED module. As shown in the figure, the power supply PS, the switch 4, and the load device 5 are connected in series. When the switch 4 is turned on, a closed circuit is formed, and power from the power supply PS is supplied to the load device 5. In addition, the load device 5 may not be included in the motor drive system 1, but may be associated with the motor drive system 1.

[0025] Next, the AC / DC motor 2 will be described.

[0026] The AC / DC motor 2 includes, for example, a motor body 21 (referred to as “DCM” in the drawing), a drive circuit 22 , and terminals 291 , 292 , and 294 to 296 .

[0027] The motor body 21 is connected to a drive circuit 22 to be described later, and is a DC motor that is rotated by power supplied from the drive circuit 22 .

[0028] The drive circuit 22 includes, for example, a power supply unit 23 , an inverter unit 24 , and a control circuit 25 .

[0029] First, the power supply unit 23 will be described.

[0030] The power supply unit 23 includes, for example, a capacitor 231 , a rectifier 232 , a capacitor 233 , direct current power supply devices 234 and 235 (referred to as “DC / DC” in the figure), a fuse 236 , and a surge voltage limiting element 237 .

[0031] The power supply side terminal of the power supply unit 23 also serves as terminals 291 and 292 for supplying AC power to the AC / DC motor 2. The power supply side terminal of the rectifier 232, the capacitor 231, and the surge voltage limiting element 237 are connected in parallel to the terminals 291 and 292 via a pair of power supply lines. The power supply side terminal of the DC power supply device 234 is connected in parallel to the DC side terminal of the rectifier 232. The power supply side terminal of the DC power supply device 235 is connected in parallel to the load side terminal of the DC power supply device 234. A fuse 236 is provided on the power supply line connected to the terminal 291. The position where the fuse 236 is provided is, for example, a position closer to the terminal 291 side than the connection point where the rectifier 232, the capacitor 231, and the surge voltage limiting element 237 are connected.

[0032] The negative electrode of the DC side terminal of the rectifier 232 is connected to the ground electrode 2G in the drive circuit 22. The ground electrode 2G is the reference potential of the DC power supply device 23. In the following description, the potential of the ground electrode 2G is described as the reference potential of the drive circuit 22.

[0033] For example, the rectifier 232 has four diodes connected in a bridge type, and performs full-wave rectification on the alternating current. The positive electrode of the DC side terminal of the rectifier 232 provides power for the motor body 21, and provides control power to the DC power supply device 234 described later. A capacitor 233 is connected in parallel to the DC side terminal of the rectifier 232. The capacitor 233 smoothes the pulsating current output by the rectifier 232, and its DC voltage is called voltage VM. The DC power supply device 234 and the DC power supply device 235 are regulators that generate different DC voltages by constant voltage control. The DC power supply device 234 and the DC power supply device 235, for example, generate a first DC voltage (e.g., DC 15V) and a second DC voltage (e.g., DC 3.3V), and provide them to the drive circuit 22.

[0034] Next, the inverter unit 24 will be described.

[0035] The inverter unit 24 has, for example, an inverter body 241 (represented as "IPM" in the figure), a shunt resistor 242, and a bypass capacitor 243. The inverter body 241 has at least one switching element not shown. The inverter body 241 is connected to the coil of the motor body 21. The inverter body 241 drives the motor body 21 using the DC power (voltage VM, DC15V) provided from the power supply unit 23. The inverter body 241 rotates the motor body 21 according to the signal provided from the controller 257. The shunt resistor 242 is connected to the inverter body 241 and the ground electrode 2G to detect the driving current of the motor body 21. The bypass capacitor 243 is connected to the power terminal of the voltage VM and the ground electrode 2G.

[0036] Next, the control circuit 25 will be described.

[0037] The control circuit 25 includes, for example, a current detection circuit 251 , a temperature detection circuit 252 , a bypass capacitor 253 , a VM power supply detection circuit 254 , a pull-up circuit 255 , and a controller 257 .

[0038] In the control circuit 25, terminals 294 to 296 are allocated as terminals connected to the external circuit of the drive circuit 22. Terminal 294 is connected to the ground electrode 2G inside the drive circuit 22. Terminals 295 and 296 are input terminals for control signals of the drive circuit 22. Terminals 295 and 296 are connected to signal lines for control signals. In addition, terminal 296 may be omitted, and the following description will focus on the control signal input to terminal 295.

[0039] The current detection circuit 251 is connected to the non-grounded side of the shunt resistor 242 of the inverter unit 24, and detects the voltage generated in the shunt resistor 242. This voltage represents the current flowing in the shunt resistor 242. The temperature detection circuit 252 includes a temperature sensor for detecting temperature abnormalities, etc. The bypass capacitor 253 is connected to the ground electrode 2G and the power supply terminal with a potential of DC 3.3V. The VM power supply detection circuit 254 is connected to the positive electrode of the power supply side terminal of the DC power supply device 234 of the power supply unit 23, and detects the power supply voltage of the voltage VM. The outputs of the current detection circuit 251, the temperature detection circuit 252, and the VM power supply detection circuit 254 are connected to the controller 257.

[0040] The pull-up circuit 255 includes a signal line connected to the terminal 295 and the controller 257, a pull-up resistor for pulling the signal line to DC3.3V, and an RC filter circuit. The RC filter circuit is, for example, a primary filter composed of a capacitor connected to the signal line and the ground electrode 2G and a resistor provided on the signal line. The filter circuit is not limited to the structure shown in the figure, and can be appropriately changed, including deletion.

[0041] The controller 257 includes, for example, a CPU (Central Processing Unit) 2570, a storage unit 2571 such as a semiconductor memory, and a signal input / output circuit 2572. The controller 257 may be an FPGA (Field Programmable Gate Array) having a processor or the like, or may be hardware.

[0042] The controller 257 has, for example, a signal acquisition unit 2573 and an inverter control unit 2574. The signal acquisition unit 2573 acquires the detection results of the current detection circuit 251, the temperature detection circuit 252, and the VM power supply detection circuit 254 via the signal input / output circuit 2572. The signal acquisition unit 2573 acquires the logic state of the control signal provided from the interface device 3 via the signal input / output circuit 2572. The inverter control unit 2574 controls the inverter unit 24 based on the detection results of the current detection circuit 251, the temperature detection circuit 252, and the VM power supply detection circuit 254. For example, when the control signal from the interface device 3 is at an H (high) level, the inverter control unit 2574 outputs a control signal for energizing the motor body 21 from the signal input / output circuit 2572 to the inverter unit 24, so that the motor body 21 is driven. When the control signal from the interface device 3 is at an L (low) level, the inverter control unit 2574 outputs a control signal for interrupting the power supply to the motor body 21 from the signal input / output circuit 2572 to the inverter unit 24, thereby stopping the rotation of the motor body 21. As described above, the controller 257 can decide whether to energize or cut off the motor body 21 according to the logic of the control signal from the interface device 3. In addition, the controller 257 can not only be used to stop the drive of the motor body 21 according to the logic of the control signal from the interface device 3, but also can use the control signal when changing the internal setting parameters of the controller 257 to change the speed, torque parameters, etc. when the motor body 21 is driven.

[0043] Next, the interface device 3 will be described.

[0044] The interface device 3 includes, for example, a fuse 31 , a filter unit 32 , a fuse 33 , a signal detection circuit 34 (detection unit), a surge voltage limiting element 35 , and a resistor 36 .

[0045] The interface device 3 has, for example, terminals 381 to 384 as terminals on the power supply PS side, and terminals 391 to 395 as terminals on the AC / DC motor 2 side.

[0046] First, the connection on the power supply PS side of the interface device 3 will be described.

[0047] Terminals 381 to 383 are power supply terminals and ground terminals provided to be exposed to the outside of the interface device 3. Terminal 384 is similarly a control signal terminal. In the case of the circuit shown in the figure, terminal 381 also serves as a control signal terminal.

[0048] For example, outside the interface device 3, the terminal 381 is connected to the first pole of the power supply PS via the wiring PSL. The terminal 382 is connected to the second pole of the power supply PS via the wiring PSN. The second pole of the power supply PS is sometimes grounded. The terminal 383 is used as a grounding terminal for safety. For example, Figure 1 The upper pole of the power supply PS shown is the above-mentioned first pole, and the lower pole is the above-mentioned second pole.

[0049] The terminal 384 is connected to the first pole of the power supply PS via the control signal line PSS. The switch 4 is provided on the control signal line PSS. The control signal line PSS connecting the terminal 384 and one end of the switch 4 is connected to one end of the load device 5, and the other end of the load device 5 is connected to the second pole of the power supply PS. According to the above connection, the power supply control to the load device 5 can be linked with the switching control of the working state of the AC / DC motor 2 by operating the switch 4.

[0050] Next, the internal structure of the interface device 3 will be described.

[0051] One end of the power supply line L, the power supply line N, and the ground line PE are connected to the terminals 381 to 383, respectively. The other ends of the power supply line L, the power supply line N, and the ground line PE are connected to the terminals 391 to 393, respectively. The filter unit 32 is provided on the power supply line L and the power supply line N. The fuse 31 is provided at a position of the power supply line L closer to the terminal 381 than the filter unit 32. The connection point of the power supply line L where the filter unit 32 and the fuse 31 are connected is called a connection point LP.

[0052] The filter unit 32, for example, has a coil and a plurality of capacitors for reducing common mode noise and normal mode noise, and a protection element for limiting surge voltage. Some of the capacitors are connected to the ground line PE. In addition, the internal structure of the filter unit 32 is a structure representing an example, and is not limited thereto, and may also be changed to other structures. Alternatively, the filter unit 32 may not be set in the interface device 3, and may also be set outside the interface device 3.

[0053] Terminal 384 is connected to the input terminal of signal detection circuit 34 via the control signal line provided with fuse 33. One end of surge voltage limiting element 35 is connected to the control signal line between fuse 33 and the input terminal of signal detection circuit 34. The other end of surge voltage limiting element 35 is connected to terminal 382.

[0054] The terminal 394 is connected to the ground electrode 3G inside the interface device 3 .

[0055] The terminal 395 is an output terminal for the control signal output by the signal detection circuit 34 .

[0056] Next, the signal detection circuit 34 will be described.

[0057] The signal detection circuit 34 includes, for example, a diode 341 , a resistor 342 , a diode 343 , an LP filter 344 , a comparison circuit 345 , and a bias circuit 346 .

[0058] The anode of the diode 341 is connected to the input terminal of the signal detection circuit 34, the cathode of the diode 341 is connected to one end of the resistor 342 and one end of the resistor 36, the other end of the resistor 342 is connected to the anode of the diode 343, the cathode of the diode 341 is connected to the input end of the LP filter 344, the output end of the LP filter 344 is connected to the input end of the comparison circuit 345, and the output end of the comparison circuit 345 is connected to the terminal 395. The other end of the resistor 36 is connected to the power supply line N.

[0059] Among the above-mentioned connection points, the connection point where the other end of the resistor 342 is connected to the anode of the diode 343 is referred to as a connection point BP, and the input end of the comparison circuit 345 is referred to as a test terminal TP.

[0060] LP filter 344 is a low-pass filter composed of a resistor and a capacitor. LP filter 344 is an example of a smoothing circuit that smoothes the half-wave signal generated by diode 343. LP filter 344 can reduce the pulsation of the above-mentioned half-wave signal so that the comparison circuit 345 of the subsequent stage will not make an erroneous detection. For example, a circuit in which two groups of resistors and capacitors are combined and connected in cascade is illustrated. As the frequency characteristic of LP filter 344, the cut-off frequency of the low-pass filter characteristic is determined in such a way that the cut-off frequency is lower than the basic frequency of the AC. In addition, the structure of LP filter 344 is not limited to this and can be appropriately changed. For example, it can also be replaced by an averaging circuit, a peak holding circuit, etc.

[0061] The comparison circuit 345 includes at least one switching element. The comparison circuit 345 shown in the figure includes, for example, an emitter-grounded comparison circuit including one transistor and a first resistor and a second resistor for defining a base potential of the transistor.

[0062] For example, the base of the transistor of the comparison circuit 345 is connected to the connection point of the first resistor and the second resistor. The other end of the first resistor is connected to the input end of the comparison circuit 345. The other end of the second resistor is connected to the ground electrode 3G. The emitter of the transistor is grounded to the ground electrode 3G, and the collector is connected to the output end of the comparison circuit 345, that is, the terminal 385. In the structure in the signal detection circuit 34, the transistor has an open collector output. The structure of the comparison circuit 345 is not limited to the structure shown in the figure, and can also be other types of switching elements or a so-called comparator.

[0063] The bias circuit 346 includes a first diode 346a, a resistor 346b, and a second diode 346c connected in series. For example, the connection point BP is connected to the anode of the first diode 346a, the cathode of the first diode 346a is connected to one end of the resistor 346b, the other end of the resistor 346b is connected to the anode of the second diode 346c, and the cathode of the second diode 346c is connected to the connection point LP.

[0064] The above-mentioned interface device 3 is used in a state of being connected to the AC / DC motor 2. At this time, the terminals 291 to 295 are respectively connected to the terminals 391 to 395 except the terminal 393. Since the terminal 393 is not connected to the AC / DC motor 2, the ground electrode 2G of the AC / DC motor 2 and the ground electrode 3G of the interface device 3 are capacitively coupled to the ground electrode on the power supply PS side through the capacitor in the filter unit 32.

[0065] The interface device 3 is connected to the AC / DC motor 2 , and the output terminal (terminal 395 ) of the comparison circuit 345 is pulled up to DC 3.3 V by the pull-up circuit 255 of the control circuit 25 . The terminal 394 has the same potential as the terminal 294 .

[0066] For example, when a voltage exceeding a predetermined positive voltage (referred to as a threshold voltage VTH) is applied to the terminal 384, the transistor of the comparison circuit 345 detects the voltage and becomes an ON state. This state is simply referred to as "the comparison circuit 345 outputs an ON signal". Conversely, when a voltage below the threshold voltage VTH is applied to the terminal 384, or when the terminal 384 is in an open state, the transistor of the comparison circuit 345 becomes an OFF state. This state is simply referred to as "the comparison circuit 345 outputs an OFF signal".

[0067] The controller 257 functions by supplying power from the power supply unit 23 while the desired AC power is supplied from the power supply PS. The controller 257 detects whether the switch 4 is in the on state or the off state based on the voltage of the control signal (on signal or off signal) supplied from the interface device 3 to the terminal 385, and determines whether to energize the motor body 21 to drive it or not energize it to stop it based on the detection result.

[0068] <Motor drive system operation>

[0069] The following describes the operation of the signal detection circuit 34 of the motor drive system 1 by exemplifying several typical usage modes. For convenience, the description is divided and performed corresponding to the combination of the state (on state / off state) of the switch 4 and the phase (first phase / second phase) of the AC. In addition, it is assumed that the switch 4 is turned on when the motor body 21 is energized, and the switch 4 is turned off when the motor body 21 is not energized.

[0070] The phase in which the alternating current flows in the first direction is called the "first phase", and the phase in which the alternating current flows in the opposite direction is called the "second phase". For example, in the first phase, the potential of the pole on the power supply line PSL side is higher than the potential of the pole on the power supply line PSN side, and in the second phase, the opposite is true.

[0071] (Use form A)

[0072] The usage form A is an example of a structure in which the load device 5 is not provided. Figure 1 The case of load device 5.

[0073] (State A1: switch 4 is in the open state and the AC is in the first phase)

[0074] Since the load device 5 is not provided, when the switch 4 is in the off state, no current flows into the terminal 384 and the signal detection circuit 34 outputs an off signal.

[0075] (State A2: switch 4 is in the open state and the AC is in the second phase)

[0076] Similar to the state A1, the signal detection circuit 34 outputs an OFF signal.

[0077] (State A3: switch 4 is on and the AC is in the first phase)

[0078] Reference Figure 2 , the operation of the signal detection circuit 34 in state A3 is described. Figure 2 This is a diagram for explaining the operation of the signal detection circuit 34 in the state A3 of the embodiment.

[0079] The switch 4 is in the on state, a voltage exceeding the threshold voltage VTH is supplied to the terminal 384, and a current Ion flows to the terminal 384 via the switch 4. The signal detection circuit 34 detects this and outputs an on signal.

[0080] In addition, there may be a period during which a voltage exceeding the threshold voltage VTH is not supplied to the terminal 384. During this period, the current Ion does not flow through the terminal 384, and the signal detection circuit 34 detects this and outputs an OFF signal.

[0081] (State A4: switch 4 is on and the AC is in the second phase)

[0082] Since the switch 4 is in the on state, the potential of the signal supplied to the terminal 384 is negative. In this case, the diode 341 is reverse biased, so no current flows in the terminal 384. Since no current flows into the signal detection circuit 34, the signal detection circuit 34 outputs an off signal.

[0083] Reference Figure 3 , the actions in the above-mentioned (state A3) and (state A4) are explained.

[0084] Figure 3 It is a diagram for explaining the simulation results of the signal detection circuit 34 according to the embodiment. Figure 3 The waveform diagram shown relates to the above-mentioned (state A3) and (state A4). The signal Scont in the waveform diagram represents the voltage of the test terminal TP, and the signal Sout represents the voltage of the terminal 395. In the initial state, the switch 4 is in the off state, and the signal Sout is a potential representing the H (high) level. At this time, the transistor of the comparison circuit 345 is in the off state.

[0085] When the switch 4 is switched from the off state to the on state at time 0, the voltage indicated by the signal Scont rises accordingly. Since there is impedance in the path of the current Ion and there is the LP filter 344, a delay in transient response occurs in the change of the voltage of the signal Scont. The delay time from time 0 to time t1 depends on the capacitance of the capacitor of the LP filter 344 and the circuit provided in series between the power supply PS and the capacitor of the LP filter 344.

[0086] Since a voltage exceeding the threshold voltage VTH is supplied to the terminal 384 , the comparison circuit 345 detects this at time t1 and inverts the logic of the output signal, outputting a signal Sout indicating a potential of an L (low) level to the terminal 395 .

[0087] When the switch 4 is switched from the on state to the off state at time t2, the voltage indicated by the signal Scont drops. Although the current Ion is cut off, the voltage indicated by the signal Scont (the terminal voltage of the capacitor) gradually decreases because the capacitor of the LP filter 344 is charged. The rate of change depends on the capacitance of the capacitor of the LP filter 344 and the circuit connected in parallel with the capacitor. When the voltage of the signal Scont drops to a predetermined voltage, the comparison circuit 345 detects this and inverts the logic of the output signal, making the signal Sout become an H level.

[0088] The above is the description of using form A.

[0089] (Use form B)

[0090] (Usage form B) is an example of a structure in which a load device 5 is provided. This is different from the above-mentioned (Usage form A). Except for the provision of a load device 5, the conditions from (State B1) to (State B4) are the same as the conditions from (State A1) to (State A4). The following description will focus on the differences from (Usage form A).

[0091] (State B1: switch 4 is in the open state and the AC is in the first phase)

[0092] The switch 4 in the off state cuts off the current. The interface device 3 in this (state B1) does not have a path for the current (referred to as "leakage current IL") to flow through the load device 5, and is therefore not affected by it. Therefore, the signal detection circuit 34 outputs an off signal.

[0093] (State B2: switch 4 is in the open state and the AC is in the second phase)

[0094] Although the switch 4 in the off state cuts off the current, the leakage current IL may flow to the interface device 3 (signal detection circuit 34 ) via the load device 5 .

[0095] Reference Figure 4 , the operation when the leakage current flows into the signal detection circuit 34 is described. Figure 4 This is a diagram for explaining a state of the embodiment in which a leakage current exists through the load device 5. The leakage current IL flows along a path along the arrow.

[0096] The signal detection circuit 34 in this (state B1) outputs an OFF signal without being affected by the leakage current IL by satisfying the required conditions described later.

[0097] (State B3: switch 4 is on and the AC is in the first phase)

[0098] The signal detection circuit 34 in this (state B3) outputs an on signal regardless of the presence or absence of the load device 5. Refer to the description of the above (state A3).

[0099] (State B4: switch 4 is on and the AC is in the second phase)

[0100] The switch 4 is in the on state, and the diode 341 is reverse biased, so that similarly to the case of the above-mentioned (state A4), no current flows through the terminal 384. The signal detection circuit 34 outputs an off signal.

[0101] exist Figure 5 In the above, the operation of the signal detection circuit 34 is organized. Figure 5This is a diagram for explaining the operation of the signal detection circuit 34 of the embodiment. This diagram shows the relationship between the AC signal (one cycle) input to the signal detection circuit 34 and the signal output by the signal detection circuit 34. The waveform of the AC (first AC signal) input to the terminal 381 and the waveform of the AC (second AC signal) input to the terminal 384 are shown by comparing when the switch 4 is in the on state and when it is in the off state.

[0102] The signal detection circuit 34 in the above-mentioned usage form B does not erroneously detect a false signal caused by the leakage current IL, and detects a normal control signal.

[0103] When comparing the pseudo signal and the regular control signal, the common point is that their signal sources are the AC power supply PS, but the poles of the AC as the signal source are different, so the phases of the respective signals are opposite. That is, when the regular control signal and the pseudo signal are half-wave rectified using the common half-wave rectifier circuit (diode 341), the phases of the half-waves left without restriction are different.

[0104] Therefore, if Figure 5 As shown in the "voltage at the connection point BP", the signal detection circuit 34 uses the negative voltage of the first AC signal to limit the amplitude of the signal input to the signal detection circuit 34, so that a half-wave generated according to the regular control signal is left, and a half-wave generated according to the pseudo signal is not left. In the limited signal, the positive voltage of the pseudo signal is limited. As a result, the signal detection circuit 34 can detect the positive voltage of the regular control signal without being affected by the pseudo signal, and output the result from the terminal 395.

[0105] More specifically, at a phase in which the current of the false signal (leakage current IL) flows into the terminal 384 of the signal detection circuit 34, the bias circuit 346 of the signal detection circuit 34 causes the leakage current IL to flow to the power supply line L and return to the power supply PS. Thus, even if the leakage current IL flows, the potential of the test terminal TP is restricted so as not to rise higher than the comparison potential (threshold voltage VTH).

[0106] Next, the necessary conditions for the signal detection circuit 34 to output an OFF signal in the above-mentioned (state B2) and not to erroneously detect a false signal due to the influence of the leakage current IL are described. For example, the signal detection circuit 34 can be formed to satisfy the following necessary conditions.

[0107] The signal detection circuit 34 causes the leakage current IL flowing into the terminal 384 to flow to the power supply line L through the bias circuit 346 (see Figure 4). The diodes 346a and 346c provided in the bias circuit 346 are arranged so that the forward direction is toward the direction in which the leakage current IL flows. The diodes provided on the path through which the leakage current IL flows can determine the constants of each part so that they are continuously in the on state during the period in which the leakage current IL flows. The period in which the leakage current IL flows is a period of about half a cycle of the AC.

[0108] For example, resistor 36 is a resistor for impedance matching with the impedance of load device 5, and adjusts the impedance of load device 5 and the voltage division of resistor 342. Resistor 36 is an example of a circuit for making each of the above-mentioned diodes continue to be in an on state while leakage current IL flows. Resistor 36 flows a dark current for making diodes 346a and 346c continue to be in an on state while leakage current IL flows. The above-mentioned dark current flows through resistor 36, and the potential of connection point BP and test terminal TP is stabilized. In addition, by providing resistor 36, even if the leakage current IL changes due to the operation of load device 5, the above-mentioned dark current can flow without being affected by the change. In the following description, the description of the dark current is sometimes omitted.

[0109] The comparison circuit 345 of the signal detection circuit 34 detects the positive amplitude of the smoothed half-wave signal to detect the phase of the signal provided to the terminal 384. In other words, the comparison circuit 345 detects whether the signal provided to the terminal 384 (the second AC signal) and the signal provided to the terminal 381 are in-phase or inverted by detecting the positive amplitude of the smoothed half-wave signal. Such a comparison circuit 345 is not easily affected by the surge voltage accompanying the switching of the diode. In addition, the signal detection circuit 34 detects the phase of the second AC signal using the amplitude of the smoothed signal instead of detecting the presence or absence of the second AC signal.

[0110] Therefore, the diode 341, the resistor 342, and the bias circuit 346 can be configured so that the potential of the connection point BP can be maintained at a potential lower than the comparison potential of the comparison circuit 345 even if the leakage current IL flows. In addition, the potential of the connection point BP is a voltage obtained by dividing a voltage twice the peak voltage of the AC by the combination of the diode 341 and the resistor 342 and the bias circuit 346, but the constants of each part can be determined so as to satisfy the above conditions. The comparison potential of the comparison circuit 345 and the threshold voltage VTH for identifying the potential of the connection point BP are strictly different, but can also be regarded as being substantially the same.

[0111] The signal detection circuit 34 formed to satisfy the above-mentioned necessary conditions can output an OFF signal even in a situation where the leakage current IL flows into the terminal 384 .

[0112] In addition, although the signal detection circuit 34 of this embodiment uses the leakage current IL in the above-mentioned operation, it does not detect the presence or absence of the leakage current IL flowing in. Figure 4 As shown, although the leakage current IL flows from the load device 5, the load device 5 is not energized via the switch 4. The load device 5 is not driven by power supplied via the switch 4. Therefore, the leakage current IL is not a part of the current flowing to drive the load device 5.

[0113] According to the above-mentioned embodiment, a first AC signal is provided from a power supply PS (signal source) to a terminal 381 (first signal input terminal) of an interface device 3. A second AC signal is provided from a power supply PS to a terminal 384 (second signal input terminal). The second AC signal includes a same-phase signal in phase with the first AC signal and an opposite-phase signal in phase with the first AC signal. The second AC signal provided to the terminal 384 is a signal in which the above-mentioned same-phase signal and the opposite-phase signal are switched by a switch 4, and the phase is switched according to the state of the switch 4. The signal detection circuit 34 uses the first AC signal provided to the terminal 381 to detect whether the second AC signal provided to the terminal 384 is a same-phase signal or an opposite-phase signal of the first AC signal. Thus, the interface device 3 can switch the operating state of the AC / DC motor 2 (control object) by a simpler method using the provided signal. In addition, the LP filter 344 and the comparison circuit 345 of the embodiment are an example of a detection unit.

[0114] For example, in the interface device 3, the diode 341 (first rectifier circuit) generates a half-wave signal obtained by half-wave rectification of the second AC signal provided to the terminal 384. The bias circuit 346 applies a negative bias to the half-wave signal generated by the diode 341 during a period in which the first AC signal provided to the terminal 381 has a negative amplitude. The diode 343 (second rectifier circuit) generates a second half-wave signal obtained by half-wave rectification of the second AC signal to which the bias circuit 346 applies a negative bias. For example, the comparison circuit 345 can detect whether the second AC signal provided to the terminal 384 is an in-phase signal or an inverted signal of the first AC signal by detecting the positive amplitude of the second half-wave signal generated by the diode 343. Thus, the interface device 3 can detect whether the second AC signal provided to the terminal 384 is a false signal caused by the leakage current IL or a regular control signal by a simple method.

[0115] <Second embodiment>

[0116] Reference Figure 6 , a motor drive system 1 according to a second embodiment will be described.

[0117] <Motor drive system structure>

[0118] Figure 6This is a configuration diagram of a motor drive system 1 according to the second embodiment. Therefore, the description will be mainly focused on the differences from the first embodiment.

[0119] The interface device 3 of the motor drive system 1 includes a signal detection circuit 34A instead of the signal detection circuit 34 .

[0120] The signal detection circuit 34A is different from the signal detection circuit 34 in that the diode 341 and the resistor 342 are deleted, a first bias circuit 346A is provided in place of the bias circuit 346 , and a second bias circuit 347 is added.

[0121] The first bias circuit 346A includes a first diode 346a, a resistor 346d, and a first constant voltage diode 346e connected in series. For example, the connection point BP is connected to the anode of the first diode 346a, the cathode of the first diode 346a is connected to one end of the resistor 346d, the other end of the resistor 346d is connected to the cathode of the first constant voltage diode 346e, and the anode of the first constant voltage diode 346e is connected to the connection point LP.

[0122] The second bias circuit 347 includes a third diode 347a, a resistor 347d, and a second constant voltage diode 347e connected in series. For example, the connection point BP is connected to the cathode of the third diode 347a, the anode of the third diode 347a is connected to one end of the resistor 347d, the other end of the resistor 347d is connected to the anode of the second constant voltage diode 347e, and the cathode of the second constant voltage diode 347e is connected to the ground electrode 3G.

[0123] In the case of the signal detection circuit 34A, since a part of the circuit elements are omitted from the signal detection circuit 34, only the fuse 33 (circuit protection element) is left between the terminal 384 and the connection point Bp. As a result, the potential of the connection point Bp is roughly consistent with the potential of the terminal 384. In addition, the connection destination of one end of the resistor 36 in the signal detection circuit 34A becomes the connection point Bp. In addition, the resistor 36 continuously causes the diode 346a and the first constant current diode 346e to flow dark current during the period when the leakage current IL flows. For other descriptions of the resistor 36, refer to the first embodiment.

[0124] As described above, in the signal detection circuit 34A, the circuit for limiting the potential of the connection point Bp is different from the circuit of the signal detection circuit 34 .

[0125] <Motor drive system operation>

[0126] Next, the operation of the signal detection circuit 34A of the motor drive system 1 is described by classifying the operation into four states according to the combination of the on / off state of the switch 4 and the phase of the AC.

[0127] In addition, in the second embodiment, although the description corresponding to the above-mentioned (use form A) is omitted, it is also applicable to the (use form A).

[0128] (Use form B)

[0129] (State B1: switch 4 is in the open state and the AC is in the first phase)

[0130] Similar to the first embodiment, the signal detection circuit 34A outputs an OFF signal.

[0131] (State B2: switch 4 is in the open state and the AC is in the second phase)

[0132] Since the switch 4 is in the off state, the current passing through the switch 4 is cut off, but it may be affected by the installation of the load device 5.

[0133] For example, if the load device 5 does not flow leakage current, it will not be affected. In this case, it is the same as the use mode A, so the detailed description is omitted. On the other hand, in the load device 5, leakage current IL may flow depending on the structure of its internal circuit.

[0134] Next, an operation when the leakage current IL flows into the signal detection circuit 34 via the load device 5 will be described. Figure 6 The arrows shown indicate the leakage current IL and the bias current IB. Each current flows in a path along the arrows.

[0135] The bias current IB flows from the ground electrode 3G toward the power supply line L through the second bias circuit 347 and the first bias circuit 346A. When the bias current IB flows, the potential of the connection point BP is limited to the following voltage range: a voltage that is higher than the potential of the power supply line L by at least the voltage of the first constant voltage diode 346e, and a voltage that is lower than the potential of the ground electrode 3G by at least the voltage of the second constant voltage diode 347e. In addition to the above-mentioned constant voltage diode, a diode and a resistor are also provided in the path where the bias current IB flows, so the above-mentioned voltage range is further narrowed. The voltage (operating point) of the connection point BP is determined by the constants of the circuit connected to the connection point BP, and the magnitude of the leakage current IL and the bias current IB.

[0136] In this (state B2), the signal detection circuit 34A is also required to output an OFF signal without being affected by the leakage current IL. The signal detection circuit 34A may satisfy the following necessary conditions.

[0137] The signal detection circuit 34A allows the leakage current IL flowing into the terminal 384 to flow to the power supply line L through the bias circuit 346A. The diode 346a provided in the bias circuit 346A is arranged so that the forward direction faces the direction in which the leakage current IL flows. The diodes provided on the path where the leakage current IL flows can determine the constants of each part so that the leakage current IL and the bias current IB are turned on.

[0138] The constants of the elements of the second bias circuit 347 and the first bias circuit 346A are determined so that the potential of the connection point BP is maintained at a potential lower than the comparison potential (threshold potential) of the comparison circuit 345 even when the leakage current IL flows.

[0139] Through the above, the signal detection circuit 34A outputs an OFF signal.

[0140] (State B3: switch 4 is on and the AC is in the first phase)

[0141] The signal detection circuit 34 in this (state B3) outputs an OFF signal regardless of the presence or absence of the load device 5. Refer to the description of the (state A3) of the first embodiment described above.

[0142] (State B4: switch 4 is on and the AC is in the second phase)

[0143] Since the switch 4 is in the on state, the diode 343 is reverse biased, and therefore no current flows from the terminal 384 to the comparison circuit 345. The signal detection circuit 34 outputs an off signal.

[0144] According to the above-mentioned embodiment, the bias circuit 346A and the bias circuit 347 apply a negative bias to the second AC signal supplied to the terminal 384 during the period when the first AC signal supplied to the terminal 381 has a negative amplitude. The diode 343 (rectifier circuit) generates a half-wave signal obtained by half-wave rectification of the second AC signal biased by the bias circuit 346 and the bias circuit 347. For example, the comparison circuit 345 can detect whether the second AC signal supplied to the terminal 384 is a same-phase signal or an opposite-phase signal of the first AC signal by detecting the positive amplitude of the half-wave signal generated by the diode 343. In this way, in the bias circuit 346A and the bias circuit 347, a negative bias is selectively applied to the second AC signal supplied to the terminal 384 during the period when the first AC signal supplied to the terminal 381 has a negative amplitude. As a result, the comparison circuit 345 can easily identify the second AC signal supplied to the terminal 384.

[0145] As described above, the signal conversion device of the embodiment has: a first signal input terminal, which is provided with a first AC signal from a signal source; a second signal input terminal, which is provided with a second AC signal from the signal source, the second AC signal including an in-phase signal in the same phase as the first AC signal and an inverted signal in an inverted phase with the first AC signal, and the phase is switched according to the switching of the in-phase signal and the inverted signal; and a detection unit, which uses the provided first AC signal to detect whether the provided second AC signal is the in-phase signal or the inverted signal. Thus, the signal conversion device can switch the working state of the control object by a simpler method using the provided signal.

[0146] In addition, the detection unit may also include: a first rectifier circuit that generates a half-wave signal obtained by half-wave rectification of the second AC signal provided; a bias circuit that applies a negative bias to the generated half-wave signal during a period when the first AC signal provided has a negative amplitude; a second rectifier circuit that generates a second half-wave signal obtained by half-wave rectification of the biased second AC signal; and an amplitude detection unit that detects whether the second AC signal provided is an in-phase signal or an anti-phase signal by detecting the positive amplitude of the generated second half-wave signal. In this case, during a period when the first AC signal provided has a negative amplitude, the first rectifier circuit performs half-wave rectification on the second AC signal provided, and further applies a negative bias to the signal. Regardless of the amplitude of the first AC signal, the second rectifier circuit performs half-wave rectification on the signal that has been half-wave rectified and negatively biased during the period when the first AC signal has a negative amplitude, thereby being able to detect the positive amplitude of the second half-wave signal after half-wave rectification, and easily detecting whether the provided second AC signal is an in-phase signal or an anti-phase signal of the first AC signal.

[0147] In addition, the detection unit may also include: a bias circuit that applies a negative bias to the second AC signal provided during a period when the first AC signal provided has a negative amplitude; a rectifier circuit that generates a half-wave signal obtained by half-wave rectification of the biased second AC signal; and an amplitude detection unit that detects whether the second AC signal provided is an in-phase signal or an anti-phase signal by detecting the positive amplitude of the generated half-wave signal. In this case, the second AC signal provided is biased to be negative during a period when the first AC signal provided has a negative amplitude, and then half-wave rectification is performed by the second rectifier circuit, thereby making it easy to detect the positive amplitude of the second half-wave signal after half-wave rectification.

[0148] In addition, the amplitude detection unit may include a smoothing circuit for smoothing the generated half-wave signal, and detects whether the provided second AC signal is an in-phase signal or an anti-phase signal by detecting the positive amplitude of the smoothed half-wave signal. Thus, regardless of the phase of the generated half-wave signal, the amplitude of the smoothed half-wave signal can be detected, and it is possible to detect whether the provided second AC signal is an in-phase signal or an anti-phase signal without using a synchronization circuit that generates a synchronization signal based on the provided first AC signal or the provided second AC signal.

[0149] In addition, the motor may include a motor body, the signal conversion device, and a drive circuit for controlling the motor body according to the detection result of the signal conversion device. If it is such a motor, the detection result of the signal conversion device can be used for its control.

[0150] As mentioned above, although the embodiment of the present invention is described in detail with reference to the drawings, the specific structure is not limited to this embodiment, and changes, replacements, deletions, etc. may be made without departing from the gist of the present invention.

[0151] For example, the drive circuit 22 may be modified as follows: The drive circuit 22 may receive a control signal from the interface device 3 using a relay, and control the drive state of the motor body by opening and closing the contact of the relay.

[0152] In addition, the number and arrangement positions of the fuses, surge voltage limiting elements 35, 237, etc., which function as a protection circuit, are not limited thereto and can be changed as appropriate.

Claims

1. A signal conversion device, comprising: a first signal input terminal to which a first AC signal is supplied from a signal source; a second signal input terminal to which a second AC signal is supplied from the signal source, the second AC signal including an in-phase signal in the same phase as the first AC signal and an anti-phase signal in anti-phase with respect to the first AC signal, and a phase is switched according to switching of the in-phase signal and the anti-phase signal; as well as a detection unit that uses the provided first AC signal to detect whether the provided second AC signal is the in-phase signal or the anti-phase signal, The detection unit has: a first rectifier circuit for generating a half-wave signal by half-wave rectifying the provided second AC signal; a bias circuit for applying a negative bias to the generated half-wave signal during a period in which the provided first AC signal has a negative amplitude; a second rectifier circuit for generating a second half-wave signal obtained by half-wave rectifying the second AC signal to which the bias is applied; as well as The amplitude detection unit detects whether the provided second AC signal is the in-phase signal or the anti-phase signal by detecting the positive amplitude of the generated second half-wave signal.

2. A signal conversion device, comprising: a first signal input terminal to which a first AC signal is supplied from a signal source; a second signal input terminal to which a second AC signal is supplied from the signal source, the second AC signal including an in-phase signal in the same phase as the first AC signal and an anti-phase signal in anti-phase with respect to the first AC signal, and a phase is switched according to switching of the in-phase signal and the anti-phase signal; as well as a detection unit that uses the provided first AC signal to detect whether the provided second AC signal is the in-phase signal or the anti-phase signal, The detection unit has: a bias circuit for applying a negative bias to the second AC signal provided during a period in which the first AC signal provided has a negative amplitude; a rectifier circuit for generating a half-wave signal obtained by half-wave rectifying the second AC signal to which the bias is applied; as well as The amplitude detection unit detects whether the provided second AC signal is the in-phase signal or the anti-phase signal by detecting the positive amplitude of the generated half-wave signal.

3. The signal conversion device according to claim 1 or 2, wherein: The amplitude detection unit includes a smoothing circuit for smoothing the generated half-wave signal. The amplitude detection unit detects whether the provided second AC signal is the in-phase signal or the anti-phase signal by detecting the positive amplitude of the smoothed half-wave signal.

4. A motor drive system, comprising: Motor body; The signal conversion device according to any one of claims 1 to 3; and A driving circuit controls the motor body according to the detection result of the signal conversion device.

Images