JP6527267B2 - Motor control system - Google Patents

Description

  The present invention relates to an isolator, a semiconductor device, and a control method of the isolator, and can be suitably used, for example, in an isolator including first and second insulating elements, a semiconductor device, and a control method of the isolator.

  When a signal is transmitted between circuits having greatly different power supply voltages, when the signal is transmitted directly by wiring, the voltage difference generated in the DC voltage component of the transmitted signal may cause damage to the circuit or a defect in signal transmission. Therefore, isolators are widely used as circuits for transmitting signals while isolating circuits having different power supply voltages.

  As a conventional isolator, an isolator using a photocoupler is known, and in recent years, research on an isolator using an insulating element such as a coil (transformer) or a capacitor has been advanced. In an isolator using insulating elements, semiconductor chips having different power supply voltages are connected by an insulating element via an insulating film, and alternating current coupling (AC coupling) is performed between the insulating elements to transmit only an AC signal.

  Patent Documents 1 to 3 and Non-Patent Document 1 are known as related techniques.

JP, 2010-48746, A Unexamined-Japanese-Patent No. 2002-222477 JP, 2010-130325, A

Masayuki Hikita et al., "New Approach to Breakdown Study by Measuring Pre-Breakdown Current in Insulating Materials", Japanese Journal of Applied Physics (JJAP), vol.23, No.12, December, 1984, pp.L886-L888

  In recent years, isolators have begun to be used for various applications (application systems). In addition, since the use for applications such as in-vehicle systems is rapidly increasing, there is a strong demand for improving the reliability of isolators.

  However, in the prior art, in the isolator using the isolation element, the reliability has not been sufficiently considered. For example, when dielectric breakdown occurs in the insulating film between the insulating elements, an excessive short circuit current flows, which may lead to malfunction or destruction of the peripheral circuits. With conventional isolators, it is impossible to prevent insulation breakdown in actual use, so the system can not be used safely.

  As described above, there is a problem that it is difficult to improve the reliability in the conventional isolator.

  Other problems and novel features will be apparent from the description of the present specification and the accompanying drawings.

  According to one embodiment, the isolator includes a transmission circuit, a first insulation element, a second insulation element, a reception circuit, an impedance control unit, and a leak current detection unit.

  The transmission circuit generates an AC transmission signal using the first potential as a reference potential based on the input transmission data. The first isolation element is supplied with the generated alternating current transmission signal. The second insulating element is AC coupled to the first insulating element through the insulating film, whereby an AC received signal using a second potential different from the first potential as a reference potential according to the AC transmission signal. Generate The reception circuit reproduces the reception data based on the generated AC reception signal. The impedance control unit controls the impedance of the first or second insulating element to a higher impedance than before control. The leak current detection unit detects a leak current flowing between the first and second insulating elements through the first or second insulating element whose impedance is controlled.

  According to the one embodiment, the reliability of the isolator can be improved.

FIG. 1 is a configuration diagram showing a configuration of a semiconductor device including an isolator according to a first embodiment. FIG. 7 is a configuration diagram showing a configuration of a control system including an isolator according to Embodiment 2. FIG. 13 is a plan view schematically showing a mounting example of the isolator according to the second embodiment. FIG. 13 is a plan view schematically showing a mounting example of the isolator according to the second embodiment. FIG. 10 is a cross-sectional view schematically showing a mounting example of the isolator according to the second embodiment. FIG. 13 is a plan view schematically showing a mounting example of the isolator according to the second embodiment. FIG. 10 is a cross-sectional view schematically showing a mounting example of the isolator according to the second embodiment. 7 is a flowchart showing a control method of the isolator according to the second embodiment. 7 is a timing chart showing the operation of the isolator according to the second embodiment. FIG. 7 is a configuration diagram showing a configuration of a control system including an isolator according to Embodiment 3. 15 is a flowchart showing a control method of the isolator according to the third embodiment. FIG. 13 is a waveform chart showing the operation of the isolator according to the third embodiment. FIG. 13 is a configuration diagram showing a configuration of a control system including an isolator according to a fourth embodiment. 15 is a flowchart showing a control method of the isolator according to the fourth embodiment. FIG. 18 is a configuration diagram showing a configuration of a control system including an isolator according to Embodiment 5. FIG. 18 is a configuration diagram showing a configuration of a control system including an isolator according to Embodiment 6. FIG. 18 is a configuration diagram showing a configuration of a control system including an isolator according to a seventh embodiment. 21 is a flowchart showing a control method of the isolator according to the seventh embodiment. FIG. 18 is a configuration diagram showing a configuration of a control system including an isolator according to an eighth embodiment. It is a block diagram which shows the structure of the motor control system which concerns on the example of a premise of embodiment. It is a perspective view showing typically the example of mounting of the isolator concerning the example of premise of an embodiment. It is a graph which shows the relationship between the leak current described in the nonpatent literature 1 and the destruction of an insulating film.

(Example of premise of the embodiment)
Before describing the embodiment, a premise example before applying the embodiment will be described. FIG. 17 shows the configuration of a motor control system according to the premise example of the embodiment.

  As shown in FIG. 17, the motor control system 900 includes a plurality of isolators 910a and 910b (also referred to as 910), an MCU 920, a plurality of gate drivers 930a and 930b (also referred to as 930), and a plurality of IGBTs 940a. And 940 b (also referred to as 940) and a motor 950. For example, the MCU 920, the plurality of isolators 910a and 910b, and the plurality of gate drivers 930a and 930b are mounted on the semiconductor device 901 in one package.

  Motor 950 is a three-phase motor having U-phase, V-phase and W-phase coils. An IGBT 940a, which is a high side motor driver, and an IGBT 940b, which is a low side motor driver, are connected to each of the U, V, and W phases. Isolators 910a and 910b are connected to the IGBTs 940a and 940b and the motor 950 on the high side and low side of each phase via gate drivers 930a and 930b, respectively.

  The MCU 920 is connected to the isolators 910a and 910b, transmits control signals to the IGBTs 940a and 940b via the isolators 910a and 910b, and the gate drivers 930a and 930b, and alternately switches the IGBTs 940a and 940b. The high side IGBT 940 a supplies a current to the motor 950, and the low side IGBT 940 b draws the current from the motor 950 to drive the motor 950 to rotate.

  As shown in FIG. 17, the power supply voltage on the side of the MCU 920 is 3.3 V to 5 V, and the power supply voltage on the side of the IGBT 940 and the motor 950 is 1 kV. Therefore, the reference potential (corresponding to GND) on the MCU 920 side, the IGBT 940 and the motor 950 side has a difference of about several hundreds to several kilovolts depending on the difference of the power supply voltage, so that the control signal can not be transmitted directly. Therefore, in order to transmit a drive signal from the MCU 920 to the motor 950, an isolator 910 that isolates the different potential circuits in a DC manner is interposed. An inductor or a capacitor is used as the insulating element of the isolator 910, and the insulating elements transmit and receive signals by AC coupling through the insulating film, so that the difference in reference potential between the transmitting and receiving circuits can be absorbed.

  FIG. 18 schematically shows the mounting structure of the isolator 910 according to the premise example. As shown in FIG. 18, the isolator 910 included in the semiconductor device 901 has a transmitting chip 960 and a receiving chip 970 mounted on a mounting substrate 911 having an external terminal 912.

  The transmitting chip 960 includes a transmitting circuit 961, a transmitting coil (primary coil) 962a constituting the on-chip transformer 962, a receiving coil (secondary coil) 962b, and a pad 964 connected to the receiving coil 962b. And 965 are formed. The receiving chip 970 is formed with a receiving circuit 971 and pads 972 and 973 connected to the receiving circuit 971.

  Pad 964 and pad 972 are connected via bonding wire 981, and pad 965 and pad 973 are connected via bonding wire 982. That is, the receiving circuit 971 and the receiving coil 962 b are connected via the pad 972, the bonding wire 981 and the pad 964, and are connected via the pad 973, the bonding wire 982 and the pad 965.

  In the on-chip transformer 962, the transmitting coil 962a and the receiving coil 962b are respectively formed in the first wiring layer and the second wiring layer in the semiconductor chip, and between the transmitting coil 962a and the receiving coil 962b. An interlayer insulating film (also simply referred to as an insulating film) 963 is formed thereover.

  As described above, in the isolator 910, the transmitting coil 962a and the receiving coil 962b are AC-coupled through the interlayer insulating film 963 to transmit and receive signals. For this reason, the difference in reference potential which reaches several kV of the transmitting side circuit and the receiving side circuit is applied to the interlayer insulating film 963 between the insulating elements, so that the insulating film may be deteriorated along with the use of the isolator. It becomes a problem.

  The graph of FIG. 19 is the measurement result of the leak current flowing in the insulating film described in Non-Patent Document 1. In FIG. 19, in the insulating film formed of polyimide having a film thickness of 25 um, the time until the dielectric breakdown and the leak current at that time are observed.

  In FIG. 19, the applied voltage is monotonously increased at 30 V / s, and can be regarded as substantially constant in the time range of the graph. Although the absolute value of the applied voltage is unknown, the observation time is at least 3000 V because it is 100 s or more. Since the withstand voltage of 25 um thick polyimide is 5000 to 6000 V, it is expected to be in a relatively high stress state.

  The experimental results in FIG. 19 show that there is a phenomenon that the leak current increases with time under a substantially constant voltage of 10 us to 10 ns before the dielectric breakdown, and the increase of the leak current and the breakdown (progression of the dielectric degradation) ) Suggest that it is related.

  As described above, even in the rated voltage operation, the insulation property of the insulating film is reduced due to long-term use or the like. As a result, a short circuit occurs between the transmission side circuit and the reception side circuit of the isolator, resulting in the failure of peripheral devices. In motor control for automobiles and the like, ensuring reliability is regarded as particularly important since it may lead to a serious accident.

  Although it is conceivable to provide a fuse in the motor control system in order to prevent a malfunction or failure due to such a short circuit, the function of safely stopping the system at the time of dielectric breakdown is not realized. In addition, no measures against dielectric breakdown are taken at the isolator level.

  Therefore, in the embodiment to be described below, the condition immediately before the breakdown of the isolator is detected by utilizing the relationship between the increase of the leak current and the breakdown. That is, in the embodiment, the leak current detection function for detecting the leak current of the insulating film in the isolator and the control means are provided. According to the embodiment, it is possible to safely stop the operation of the system by detecting the leak current which increases due to the deterioration of the insulating film before the chip is broken. For example, in the example of FIG. 19, since the current rise is sustained for several us before dielectric breakdown, the current increase is detected during that time, and the system can be safely controlled.

Embodiment 1
The first embodiment will be described below with reference to the drawings. FIG. 1 shows the configuration of a semiconductor device including the isolator according to the present embodiment. As shown in FIG. 1, the semiconductor device 1 includes an isolator 100 and a controller 200 such as an MCU. Further, a controlled device 300 which is a control target of the controller 200 is connected to the semiconductor device 1.

  The isolator 100 includes a transmitting chip 120, a receiving chip 130, and external terminals T1 to T4. The isolator 100 is connected to the controller 200 via the external terminals T1 to T3, and is connected to the controlled device 300 via the external terminal T4.

  The external terminal T1 is a terminal for inputting an impedance control signal S1 for controlling the impedance from the controller 200. The external terminal T2 is a terminal for inputting transmission data VIN from the controller 200. The external terminal T3 is a terminal for outputting an error signal S2 that is a detection result of the leak current to the controller 200. The external terminal T4 is a terminal for outputting the reception data VOUT received via the insulating element to the controlled device 300.

  The transmission side chip 120 includes a transmission circuit 101, an insulation element (transmission side insulation element) 102, an insulation element (reception side insulation element) 103, pads P1 and P2 connected to the insulation element 103, an impedance control unit 105, and a leakage current detection The unit 106 is provided. The receiving chip 130 includes a receiving circuit 104 and pads P3 and P4 connected to the receiving circuit 104.

  The transmission circuit 101 receives transmission data VIN from the controller 200 via the external terminal T2, and generates an AC transmission signal based on the input transmission data VIN. The AC transmission signal is a signal based on the reference potential GND1 (first reference potential).

  The insulating elements 102 and 103 are, for example, a coil or a capacitor. The insulation element (first insulation element) 102 is supplied with an AC transmission signal from the transmission circuit 101 via the impedance control unit 105. An insulating film 107 is formed between the insulating element 102 and the insulating element 103.

  The insulating element (second insulating element) 103 generates an AC reception signal by AC coupling with the insulating element 102 through the insulating film 107. The AC reception signal is a signal based on a reference potential GND2 (second reference potential) different from the reference potential GND.

  The insulating element 103 and the receiving circuit 104 are connected via the pad P1 of the transmitting chip 120 and the pad P3 of the receiving chip 130, and the pad P2 of the transmitting chip 120 and the pad P4 of the receiving chip Connected through. The reception circuit 104 receives an AC reception signal via the pads P1 and P3 and the pads P2 and P4. The reception circuit 104 reproduces the reception data VOUT based on the input AC reception signal, and outputs the reception data VOUT to the controlled device 300 via the external terminal T4.

  The impedance control unit 105 receives an impedance control signal S1 from the controller 200 via the external terminal T1, and controls the impedance of the insulating element 102 to a high impedance based on the input impedance control signal S1. The leak current detection unit 106 detects a leak current flowing between the insulation elements. That is, leak current detection unit 106 detects a leak current through insulation element 102 whose impedance is controlled, and outputs error signal S2, which is a detection result according to the leak current, to controller 200 through external terminal T3. .

  In the example of FIG. 1, the impedance of the transmission-side insulating element 102 is controlled, and the leakage current is detected via the impedance-controlled insulation element 102. However, the impedance of the receiving-side insulation element 103 is controlled, Leakage current may be detected through the insulation element 103 whose impedance is controlled.

  When testing the leak current between the isolation elements, the controller 200 inputs a test preset signal which maintains a high level as the transmission data VIN. As a result, the reception data VOUT of the reception circuit 104 and the controlled device 300 are controlled to a constant state, and the reference potential GND2 becomes higher than the reference potential GND1, so that a leak current is generated. The controller 200 controls the impedance of the transmission-side insulating element 102 of the isolator 100 to a high impedance, and the leak current detection unit 106 detects a leak current through the transmission-side insulating element 102. The leak current detection unit 106 transmits an error signal S2 corresponding to the amount of leak current to the controller 200. The controller 200 determines the insulation (the deterioration state of the insulation film) from the received error signal S2, and controls the operation of the isolator 100.

  As described above, in the present embodiment, the isolator controls the impedance of the insulating element to detect a leak current, and outputs an error signal corresponding to the detected leak current. As a result, the deterioration of the insulating film can be detected before dielectric breakdown, and the isolator can be safely stopped, so that the reliability of the isolator can be improved.

Second Embodiment
The second embodiment will be described below with reference to the drawings. In this embodiment, more specific configuration and operation of the isolator described in Embodiment 1 will be described.

FIG. 2 shows the configuration of a motor control system including the isolator according to the present embodiment. The motor control system controls the rotational operation of the motor 301 as an example of the controlled device 300 to be controlled. The controlled device 300 may be a power supply circuit, a measuring instrument, a sensor or the like in addition to the motor. Other systems may be used as long as they are systems (applications) that can maintain the reference potential on the reception circuit side (secondary side) higher than the reference potential on the transmission circuit side, such as motors and IGBTs.
For example, the motor 301 is a three-phase motor, and as in FIG. 17, has IGBTs and isolators on the high side for each phase and IGBTs and isolators on the low side, and in FIG. Only the side IGBT and the isolator and the low side IGBT are illustrated. A gate driver may be provided as shown in FIG. 17 as needed.

  The semiconductor device 1 is connected to the motor 301 and the IGBTs 1 and 2 in order to control the rotation operation of the motor 301. The IGBT 1 is a high side motor driver, and the IGBT 2 is a low side motor driver. The IGBT 1 has a gate connected to the external terminal T 4, a collector supplied with a power supply VD 3 that is a DC power supply for IGBT, and an emitter connected to the motor 301 via the reference potential GND 2, the collector of IGBT 2 and the coil L 3.

  The semiconductor device 1 of FIG. 2 has the same configuration as the semiconductor device 1 of FIG. 1, and further includes specific circuit configurations of the insulating elements 102 and 103, the impedance control unit 105, and the leak current detection unit 106.

  That is, the semiconductor device 1 includes the isolator 100 and the controller 200 as in FIG. The isolator 100 is connected to the controller 200 via the external terminals T1 to T3, and is connected to the IGBT 1 via the external terminal T4. The isolator 100 includes a transmitting chip 120 and a receiving chip 130.

  The transmission side chip 120 includes a transmission circuit 101, an insulation element 102, an insulation element 103, pads P 1 and P 2, an impedance control unit 105, and a leak current detection unit 106. The power supply VD1 of several volts is supplied to the transmission circuit 101, and the reference potential GND1 on the transmission circuit 101 side from the insulating element 102 becomes approximately 0V.

  The receiving chip 130 includes a receiving circuit 104 and pads P3 and P4. The power supply VD2 of several volts is supplied to the reception circuit 104, and the power supply VD3 of several kilovolts is supplied to the IGBT 1 connected to the reception circuit 104. The reference potential GND2 of the isolation element 103 on the side of the reception circuit 104 is several kilovolts. It becomes degree.

  In the example of FIG. 2, the coil L1 on the transmission side and the coil L2 on the reception side are provided as the insulating elements 102 and 103. The impedance control unit 105 includes switches SW1 and SW2. As the leak current detection unit 106, a capacitor C1 (parasitic capacitance) and a comparator CMP1 are provided.

  The connection relationship of these configurations will be described. A first output terminal for outputting an AC transmission signal of the transmission circuit 101 is connected to one end of the coil L1 via the switch SW1, and a second output terminal for outputting the AC transmission signal of the transmission circuit 101 is a switch SW2. It is connected to the other end of the coil L1 via

  The switch SW1 is connected between the output terminal of the transmission circuit 101 and one end of the coil L1, and the control terminal is connected to the external terminal T1. The switch SW1 is turned on / off according to the impedance control signal S1 input from the controller 200 to the control terminal, and switches connection / disconnection between the first output terminal of the transmission circuit 101 and one end of the coil L1.

  The switch SW2 is connected between the second output terminal of the transmission circuit 101 and the other end of the coil L1, and the control terminal is connected to the external terminal T1. The switch SW2 is turned on / off according to the impedance control signal S1 input from the controller 200 to the control terminal, and switches connection / disconnection between the second output terminal of the transmission circuit 101 and the other end of the coil L1.

  One end of the capacitor C1 is connected to the other end of the coil L1, and the other end is connected to the reference potential GND1. The capacitor C1 charges the leak current flowing in the coil L1, and generates a leak voltage VL which is a voltage corresponding to the leak current.

  The comparator CMP1 has a positive input terminal connected to one end of the capacitor C1 (the other end of the coil L1), a threshold (threshold voltage) Vth input to the negative input terminal, and an output terminal connected to the external terminal T3. . The comparator CMP1 compares the leak voltage VL charged in the capacitor C1 with the threshold value Vth, and outputs the comparison result to the controller 200 as an error signal S2. The comparator CMP1 outputs a high level to the error signal S2 when the leak voltage VL is larger than the threshold value Vth.

  FIG. 3A is an example of a plan view of a wiring layer on which the transmission coil L1 is formed among the transmission chips 120 included in the isolator 100 of FIG. 2, and FIG. 3B is a drawing of the reception coil L2 of the transmission chip 120. 3C is an example of the top view of the wiring layer in which A is formed, FIG. 3C is an example of the AA 'sectional drawing of the transmission side chip | tip 120 of FIG. 3A and 3B.

  As shown in FIGS. 3A to 3C, in the transmission side chip 120, the gate electrode layer GL10 and the wiring layers WL11 to 18 are sequentially laminated and formed on the silicon substrate SUB1. In the gate electrode layer GL10 and the wiring layers WL11 to 18, gate electrodes and metal wires forming the circuit of the transmission side chip 120 are formed in a desired pattern, and an interlayer insulating film 107 is formed to fill the gate electrodes and metal wires. It is done.

  The transmission circuit 101 is formed in the gate electrode layer GL10 and the wiring layers WL11 to 18. A wiring is formed in the wiring layer WL15 so as to connect the external terminal T2 for inputting the transmission data VIN and the transmission circuit 101.

  The switch SW2 of the impedance control unit 105 is configured of a MOS transistor 105a. MOS transistor 105 a has two diffusion layers formed on the surface of silicon substrate SUB 1, and a gate electrode formed on gate electrode layer GL 10 on silicon substrate SUB 1.

  A wire of the wiring layer WL13 and a contact hole penetrating from the wiring layer WL13 to the gate electrode layer GL10 are formed to connect the transmission circuit 101 and one diffusion layer of the MOS transistor 105a. A contact hole penetrating from the wiring layer WL14 to the gate electrode layer GL10 is formed so as to connect the gate of the MOS transistor 105a and the external terminal T1 to which the impedance control signal S1 is input.

  Although the cross-sectional view is omitted, the switch SW1 of the impedance control unit 105 is formed of a MOS transistor as in the switch SW2, and the transmission circuit 101 and one diffusion layer of the MOS transistor are connected. The gate is connected to the external terminal T1, and the other diffusion layer of the MOS transistor is connected to the transmission side coil L1.

  The comparator CMP1 of the leak current detection unit 106 includes MOS transistors 106a and 106b. MOS transistors 106a and 106b have two diffusion layers formed on the surface of silicon substrate SUB1, and a gate electrode formed on gate electrode layer GL10 on silicon substrate SUB1.

  A contact hole penetrating from the wiring layer WL16 to the gate electrode layer GL10 is formed so as to connect one diffusion layer of the MOS transistor 106a to the external terminal T3 which outputs the error signal S2 for detecting the leak current. A wire of the wiring layer WL12 and two contact holes penetrating from the wiring layer WL12 to the gate electrode layer GL10 are formed so as to connect the gate of the MOS transistor 106a and one diffusion layer of the MOS transistor.

  The capacitor C1 of the leak current detection unit 106 is configured of the wiring formed in the wiring layer WL11 and the wiring layer WL13, and the insulating film 107 between the wirings. A contact hole passing through the gate electrode layer GL10 is formed to connect the wiring on the wiring layer WL11 side of the capacitor C1 and the silicon substrate SUB1.

  The transmission side coil L1 is formed of a wiring patterned in a spiral shape on the wiring layer WL14. A contact hole penetrating from the wiring layer WL13 to the gate electrode layer GL10 so as to connect the transmission side coil L1, the other diffusion layer of the MOS transistor 105a, the gate of the MOS transistor 106b and the wiring on the wiring layer WL13 side of the capacitor C1. A wiring of the wiring layer WL13, a contact hole penetrating from the wiring layer WL14 to the gate electrode layer GL10, and a wiring of the wiring layer WL14 are formed.

  The receiving coil L2 is formed of a wiring patterned in a spiral shape on the wiring layer WL18. The transmitting coil L1 and the receiving coil L2 are formed to face each other through the interlayer insulating film 107 formed in the wiring layers WL15 to WL17. The receiving coil L2 is connected to the pads P1 and P2 formed in the wiring layer WL18.

  FIG. 4A is an example of a plan view of the receiving chip 130 included in the isolator 100 of FIG. 2, and FIG. 4B is an example of a cross-sectional view of the receiving chip 130 of FIG.

  As shown in FIGS. 4A and 4B, in the receiving chip 130, the gate electrode layer GL20 and the wiring layers WL21 to 28 are sequentially formed on the silicon substrate SUB2 in the same manner as the transmitting chip 120. An interlayer insulating film 207 is formed.

  The receiving circuit 104 is formed in the gate electrode layer GL20 and the wiring layers WL21 to WL28. The pad P3 is formed in the wiring layer WL28, and a wiring is formed in the wiring layer WL28 so as to connect the pad P3 and the receiving circuit 104. Although the cross-sectional view of the pad P4 is omitted, the pad P4 is formed in the wiring layer WL28 similarly to the pad P3, and is connected to the receiving circuit 104 by the wiring of the wiring layer WL28. Further, a wiring is formed in the wiring layer WL27 so as to connect the external terminal T4 for outputting the reception data VOUT and the reception circuit 104.

  Next, a control method of the isolator according to the present embodiment will be described using FIGS. 5 and 6. FIG. 5 is a flowchart showing a control method of the isolator 100 (a test for detecting a leak current or a test method for testing an insulation film deterioration), and FIG. 6 is a timing chart showing an example of signal waveforms of the control method. is there.

  As shown in FIG. 5, first, the controller 200 transmits a signal so as to increase the high side voltage (S101). In order to detect the leak current between the isolation elements, first, the controller 200 connected to the outside of the isolator 100 transmits transmission data VIN (preset signal) maintaining the high level (Hi) to the isolator 100 (401 in FIG. 6). ). Then, the transmission circuit 101 applies a voltage to the transmission coil L1 in response to the rise of the transmission data VIN, and a current I1 in the positive direction temporarily flows in the transmission coil L1 (402 in FIG. 6). For this reason, in the reception side coil L2, an electromotive force corresponding to the change of the current I1 of the transmission side coil L1 is generated, and the induced voltage V2 temporarily rises (403 in FIG. 6). The receiving circuit 104 raises the reception data VOUT to the high level because the induced voltage V2 rises (404 in FIG. 6).

  As a result, the IGBT 1 connected to the rear stage of the isolator 100 is always on, and the reference potential GND2 is fixed to about the power supply voltage of the IGBT 1 (̃kV in FIG. 6) (405 in FIG. 6). After the change of the voltage V2, it is fixed at about the power supply voltage (.about.kV) (406 in FIG. 6).

  Subsequently, the controller 200 turns off the switches SW1 and SW2 (S102). The controller 200 raises the impedance control signal S1 to high level (407 in FIG. 6). As a result, the switch SW1 and the switch SW2 of the transmission side chip 120 of the isolator 100 are turned off, and the coil L1 which is the transmission side insulation element and the transmission circuit 101 are electrically disconnected, so both ends of the coil L1 which is the transmission side insulation element The child becomes high impedance.

  Subsequently, the isolator 100 detects the leak voltage VL of the coil L1 after a predetermined time (S103). By turning off the switches SW1 and SW2, inflow and outflow of current between the coil L1 as the transmission side insulating element and the transmission circuit 101 are blocked, and detection sensitivity of leakage current between the insulating elements of the coils L1 and L2 is improved. When the switches SW1 and SW2 are turned off, the coil L1, which is a transmission-side insulating element, is in the potential state immediately before the switch is turned off. Since the potential of the reception circuit 104 is higher than the potential of the transmission circuit 101 (several kV), a leak current according to the deterioration state of the insulating film 107 flows from the coil L2 which is the reception side insulation element to the coil L1 which is the transmission side insulation element. . This leakage current is charged into voltage detection means added to the coil L1 which is a transmission side insulating element, for example, a capacitor C1 which is a capacity (including a parasitic capacity) to convert it into a voltage (leakage voltage VL). Since the leak voltage VL is a value obtained by integrating the leak current, it rises with time (408 in FIG. 6).

  Subsequently, the isolator 100 determines whether the leak voltage LV of the coil L1 is less than or equal to the threshold value Vth (S104). The voltage of the capacitor C1 is input to the comparator CMP1, and insulation is established by setting the voltage value corresponding to the leak current value serving as the determination reference of normality / abnormality of the insulating film to the threshold voltage (reference voltage) Vth of the comparator CMP1. Detect membrane degradation. The comparator CMP1 compares the leak voltage VL obtained by integrating the leak current flowing while the impedance control signal S1 is at the high level with the threshold value Vth. The comparison result of the comparator CMP1 is output as an error signal S2 to the controller 200, and the controller 200 controls the operation of the isolator 100 according to the error signal S2.

  When the leak voltage VL of the coil L1 is equal to or less than the threshold value Vth, the controller 200 starts the normal operation (S105). The comparator CMP1 keeps the error signal S2 at the low level when the leak voltage VL is equal to or less than the threshold (409 in FIG. 6). The controller 200 determines that the isolator 100 is normal and starts the normal operation since the low level error signal S2 corresponding to the leakage current less than the specified value is input for a predetermined period (during which the impedance control signal S1 is high level). (410 in FIG. 6). The controller 200 inputs transmission data VIN for controlling the motor 301 into the isolator 100, drives the IGBT 1, and starts the rotation of the motor 301.

  When the leak voltage VL of the coil L1 is larger than the threshold value, the controller 200 outputs an alarm (S106) and performs a safety stop (S107). The comparator CMP1 raises the error signal S2 to high level when the leak voltage VL exceeds the threshold (411 in FIG. 6). The controller 200 determines that the insulating film of the isolator 100 is abnormal and stops the operation of the isolator 100 because the high level error signal S2 corresponding to the leak current equal to or more than the specified value is input within the predetermined period. 412 of FIG. The controller 200 inputs low level transmission data VIN to the isolator 100, turns off the IGBT 1, and stops the rotation of the motor 301. This prevents the destruction of the entire system in advance.

  Thus, in the present embodiment, as a specific example of the first embodiment, insulating elements 102 and 103 are configured by coils L1 and L2, impedance control unit 105 is configured by switches SW1 and SW2, and a leakage current detection unit 106 is composed of a capacitor C1 and a comparator CMP1. In this configuration, the impedance of the coil, which is an insulating element, is controlled to detect a leak current, and an error signal corresponding to the detected leak current is transmitted. Thus, the deterioration of the insulating film can be detected before the dielectric breakdown between the coils, and the isolator can be safely stopped, so that the reliability of the isolator can be improved.

Third Embodiment
The third embodiment will be described below with reference to the drawings. In this embodiment, a means for applying an initial potential to the isolation element for detecting a leak current is added to the isolator shown in the second embodiment, and the variation of the leak current is changed from the first threshold to the second threshold It is an example which determines whether it is in the range of a threshold value.

  FIG. 7 shows the configuration of a motor control system including the isolator according to the present embodiment. In FIG. 7, compared with FIG. 2 of the second embodiment, the transmission side chip 120 of the isolator 100 is provided with the switch SW0. In addition, the leak current detection unit 106 includes the comparators CMP1 and CMP2 and the logic circuit OR1. The other configuration is the same as that shown in FIG.

  The switch SW0 is connected between the third output terminal of the transmission circuit 101 and one end of the coil L1, and the control terminal is connected to the external terminal T0. The switch SW0 is turned on / off according to a bias control signal S0 input from the controller 200 to the control terminal, and switches connection / disconnection between the third output terminal of the transmission circuit 101 and one end of the coil L1.

  The comparator CMP1 has a positive input terminal connected between the other end of the coil L1 and the reference potential GND1, a first threshold Vth1 is input to the negative input terminal, and an output terminal connected to the logic circuit OR1. The comparator CMP1 compares the leak voltage VL according to the leak current of the coil L1 with the threshold value Vth1, and outputs the comparison result to the logic circuit OR1. The comparator CMP1 outputs a high level when the leak voltage VL is larger than the threshold value Vth1.

  The comparator CMP2 has a positive input terminal to which the second threshold Vth2 is input, a negative input terminal connected between the other end of the coil L1 and the reference potential GND1, and an output terminal connected to the logic circuit OR1. The comparator CMP2 compares the leak voltage VL according to the leak current of the coil L1 with the threshold value Vth2, and outputs the comparison result to the logic circuit OR1. The comparator CMP2 outputs a high level when the leak voltage VL is smaller than the threshold value Vth2.

  One input terminal of the logic circuit OR1 is connected to the output terminal of the comparator CMP1, the other input terminal is connected to the output terminal of the comparator CMP2, and the output terminal is connected to the external terminal T3. The logic circuit OR1 performs an OR logic operation on the inputs from the plurality of comparators and outputs an operation result. The logic circuit OR1 causes the error signal S2 to be high level when the output of the comparator CMP1 is high level or the output of the comparator CMP2 is high level. That is, the logic circuit OR1 sets the error signal S2 to the high level when the leak voltage VL is larger than the threshold Vth1 or when the leak voltage VL is smaller than the threshold Vth2.

  Next, a control method of the isolator according to the present embodiment will be described using FIGS. 8 and 9. FIG. 8 is a flow chart showing a control method of the isolator 100 (a test for detecting a leak current or a test method for testing an insulation film deterioration), and FIG. 9 is a graph showing the voltage VL of the transmission side isolation element in the control method. An example of a signal waveform is shown.

  As shown in FIG. 8, first, as in FIG. 5 of the second embodiment, the controller 200 transmits a signal so as to increase the high side voltage (S101). Similarly to FIG. 6, when the controller 200 transmits a high level preset signal to the isolator 100, the IGBT 1 is turned on via the coil L1 and the coil L2, and the reference potential GND2 rises.

  Subsequently, the controller 200 turns on the switch SW0 (S111), and then turns off the switches SW0, SW1 and SW2 (S112).

  In the second embodiment, after S101, the transmission-side insulating element and the transmission circuit are separated by the switches SW1 and SW2. At this time, since the transmission-side insulating element is in the potential state before the switch is turned off, the potential is indefinite. Since the initial potential of the insulating element largely affects the detection sensitivity of the leak current, in the present embodiment, the initial potential is controlled by the switch SW0.

  That is, in the present embodiment, before controlling the impedance of the insulating element, the controller 200 sets the bias control signal S0 to a high level to turn on the switch SW0 (501 in FIG. 9). Then, an arbitrary initial voltage (for example, VDD / 2) is applied in advance by the transmission circuit 101 and the power supply Vbias connected to the coil L1 of the transmission-side insulating element via the switch SW0. Thereafter, the controller 200 sets the bias control signal S0 to low level and the impedance control signal S1 to high level to turn off the switches SW0, SW1, and SW2 (502 in FIG. 9).

  Subsequently, the isolator 100 detects the leak voltage VL of the coil L1 after a predetermined time (S103), and determines whether the leak voltage VL of the coil L1 is larger than the first threshold Vth1 or not. It is determined whether it is smaller than the threshold value Vth (S113).

  In the present embodiment, two parallel connected comparators CMP1 and CMP2 are used as voltage detectors in detecting a leak current. Threshold values (reference voltages) Vth1 and Vth2 are input to these comparators CMP1 and CMP2, respectively. The first threshold voltage Vth1 is connected to the reference side of one comparator CMP1 and the second threshold voltage Vth2 is connected to the input side of the other comparator CMP2, and the leak voltage VL fluctuated by the leak current is in the range of Vth1 to Vth2 It is determined whether or not it is (503 in FIG. 9), and the determination result is output from the logic circuit OR1 to the controller 200 as an error signal S2.

  If the voltage of the coil L1 is within the range of the threshold values Vth1 to Vth2, the controller 200 determines that the isolator 100 is normal (no leak current), and starts the normal operation (S105). The comparator CMP1 outputs a low level signal when the leak voltage VL is equal to or less than the threshold value Vth1, and the comparator CMP2 outputs a low level signal when the leak voltage VL is equal to or more than the threshold value Vth2. OR1 keeps the error signal S2 low. Since the low level error signal S2 corresponding to the leak current within the specified value range is input for a predetermined period (during which the impedance control signal S1 is at high level), the controller 200 determines that the isolator 100 is normal and performs the normal operation. Start.

  When the voltage increase of the leak voltage VL of the coil L1 becomes larger than Vth1 or when the voltage drop becomes lower than Vth2, the controller 200 determines that it is abnormal (leakage current is present) and outputs an alarm (S106) And safety stop (S107). The comparator CMP1 sets the output signal to the high level when the leak voltage VL exceeds the threshold Vth1, and the comparator CMP2 sets the output signal to the high level when the leak voltage VL becomes lower than the threshold Vth2. The logic circuit OR1 raises the error signal S2 to high level.

  The controller 200 determines that the insulating film of the isolator 100 is abnormal and stops the operation of the isolator 100 since the high level error signal S2 corresponding to the leak current outside the specified value range is input within the predetermined period. . This prevents the destruction of the entire system in advance.

  As described above, in the present embodiment, with respect to the second embodiment, the initial potential of the insulating element is made constant by switch SW0, and the leakage within the range of threshold Vth1 and threshold Vth2 is achieved by comparators CMP1 and CMP2. I tried to detect the current. With such a configuration, the leak current can be detected not only when the current flows into the leak current detection unit 106 but also when the current flows out of the leak current detection unit 106. That is, there are cases where leakage current flows from coil L2 to coil L1 and leakage current flows from coil L1 to coil L2 depending on the potential difference between coil L1 and coil L2. In this embodiment, either case Leakage current can be detected accurately.

Embodiment 4
The fourth embodiment will be described below with reference to the drawings. The present embodiment is an example in which a storage means for storing a leak voltage is added to the isolator shown in the second embodiment.

  FIG. 10 shows the configuration of a motor control system including the isolator according to the present embodiment. In FIG. 10, compared to FIG. 2 of the second embodiment, the leak current detection unit 106 includes a memory circuit M1 in addition to the capacitor C1 and the comparator CMP1. The other configuration is the same as that shown in FIG.

  The memory circuit M1 is connected to the positive input terminal of the comparator CMP1 and to the negative input terminal of the comparator CMP1. The memory circuit M1 receives the leak voltage VL, which the comparator CMP1 has made a comparison this time, and stores the inputted voltage VL. In addition, the memory circuit M1 outputs the leak voltage VL + ΔV used and stored in the comparison of the comparator CMP1 in the previous time as the threshold value Vth of the comparator CMP1 this time.

  FIG. 11 is a flowchart showing a control method (a test for detecting a leak current or a test method for testing deterioration of an insulating film) of the isolator 100 according to the present embodiment.

  As shown in FIG. 11, first, as in FIG. 5 of the second embodiment, the controller 200 transmits a signal to increase the high side voltage (S101), and turns off the switches SW1 and SW2 (S102). .

  Subsequently, the isolator 100 detects the leak voltage VL of the coil L1 after a predetermined time (S103). Then, the isolator 100 reads the threshold value Vth from the memory circuit M1 (S121), and determines whether the leak voltage VL of the coil L1 is less than or equal to the read threshold value Vth (S104).

  The memory circuit M1 stores the leak voltage VL detected in the previous leak current test, reads this previous leak voltage VL + ΔV as the threshold value Vth, and inputs it to the negative input terminal of the comparator CMP1. Then, the comparator CMP1 compares the current leak voltage of the coil L1 with the previous leak voltage VL + ΔV.

  When the leak voltage VL of the coil L1 is equal to or less than the threshold value Vth, the memory circuit M1 stores the leak voltage of the coil L1 (S122), and the controller 200 starts the normal operation (S105). The comparator CMP1 keeps the error signal S2 at the low level when the current leak voltage VL is less than or equal to the previous leak voltage VL + ΔV. Then, the memory circuit M1 stores the leak voltage VL compared this time by the comparator CMP1. Further, since the low level error signal S2 is input for a predetermined period, the controller 200 determines that the isolator 100 is normal and starts the normal operation.

  When the leak voltage VL of the coil L1 is larger than the threshold value Vth, the controller 200 outputs an alarm (S106) and performs a safety stop (S107). The comparator CMP1 raises the error signal S2 to high level when the current leak voltage VL exceeds the previous leak voltage VL + ΔV. The controller 200 determines that the insulating film of the isolator 100 is abnormal and stops the operation of the isolator 100 because the error signal S2 at the high level is input within the predetermined period. This prevents the destruction of the entire system in advance.

  In the method of defining the abnormality judgment criteria of the insulating film with a constant leak current value, sufficient detection accuracy may not be obtained due to the influence of various variations and noise. Therefore, in the present embodiment, the state of the insulating film at the time of the previous test is used as a determination reference, and the abnormality is determined by observing the difference in leakage current from this state. When the leak voltage VL of the comparator CMP1 generated by charging the leak current exceeds the threshold (reference voltage) Vth, an error signal S2 is sent to the controller 200 as insulation film deterioration. Since the voltage applied between the insulating elements is substantially determined by the power supply voltage of the IGBT 1, the leak current value is approximately equal in each test unless the insulating film is deteriorated.

  Therefore, the leak current measurement result (VL) is held in the memory circuit M1 such as a register at the time of the test, and the previous leak voltage VL + ΔV read at the next test is set to the threshold value Vth. Here, ΔV is an arbitrary voltage margin, which may be introduced to eliminate the influence of variations and noise.

  As described above, in the present embodiment, the memory circuit M1 further storing the leak voltage according to the leak current is provided to the second embodiment, and the leak voltage used in the previous test is the next leak voltage. We decided to use as threshold for judging. Thereby, since the fluctuation of the leak current can be detected, the deterioration state of the insulating film can be detected accurately.

Fifth Embodiment
The fifth embodiment will be described below with reference to the drawings. The present embodiment is an example in which a means for stopping the isolator in accordance with the detection of the leak current is added to the isolator shown in the second embodiment.

  FIG. 12 shows the configuration of a motor control system including the isolator according to the present embodiment. In FIG. 12, as compared with FIG. 2 of the second embodiment, the transmission side chip 120 of the isolator 100 is provided with the switch SW4. The other configuration is the same as that shown in FIG.

  The switch SW4 is connected between the other end of the coil L1 and the reference potential GND1, and the control terminal is connected to the output terminal of the comparator CMP1. The switch SW4 is turned on / off according to the error signal S2 input from the comparator CMP1 to the control terminal, and switches connection / disconnection between the other end of the coil L1 and the reference potential GND1. The switch SW4 can also be said to be a reference potential supply circuit that sets the coil L1 to the reference potential GN1 according to the error signal S2.

  In each of the above embodiments, it is important to secure the detection accuracy of insulation deterioration and the feedback time of the detection result. For example, in the actual measurement result of Non-Patent Document 1, the time when the influence of the insulating film deterioration starts to appear is several us to several ns before the breakdown, and the leak current increases as it approaches the breakdown.

  As described above, as a large leak current is set as an error determination standard in order to improve the detection accuracy of insulation deterioration, there is a trade-off in which a time margin for feedback of the detection result to the controller 200 and control of the system becomes shorter. is there. For example, when the scale of the circuit / system is large, the system control time via the controller 200 can not be sufficiently secured, which may cause a problem.

  Therefore, in the present embodiment, not only the output signal from the comparator CMP1 is transmitted to the controller 200, but the isolator 100 is directly stopped.

  In the example of FIG. 12, the reference potential GND1 (.about.0 V) is connected to the coil L1, which is a transmission side insulating element, via the switch SW4. The switch SW4 is turned off only when the output of the comparator CMP1 is at high level (Hi), that is, when the insulation degradation error is output, and the potential level of the transmission side isolation element is forcibly dropped to low level (Low). As a result, the IGBT 1 is turned off and the high voltage application state between the insulating elements is released.

  As described above, in the present embodiment, in addition to the second embodiment, the switch SW4 that controls the potential of the coil in accordance with the detection of the leak current is provided. As a result, when the leak current before dielectric breakdown is detected, the controller 200 can stop the whole after emergency stop of the isolator main body. Thus, the system can be reliably shut down without causing a short circuit between the isolation elements.

Sixth Embodiment
The sixth embodiment will be described below with reference to the drawings. The present embodiment is an example in which a leak current is converted into a voltage by using an amplifier instead of a capacitor in the isolator shown in the second embodiment.

  FIG. 13 shows the configuration of a motor control system including the isolator according to the present embodiment. In FIG. 13, compared to FIG. 2 of the second embodiment, the leak current detection unit 106 includes a comparator CMP1 and an amplifier AMP1. The other configuration is the same as that shown in FIG.

  The amplifier AMP1 is a current-voltage conversion amplifier circuit that converts a leak current into a voltage and amplifies it. The amplifier AMP1 has a positive input terminal connected to the reference voltage Vth1, a negative input terminal connected to the other end of the coil L1, and an output terminal feedback-connected to the negative input terminal via the resistor R1. Connected to the input terminal.

As in the above embodiment, the capacitance may not necessarily be used to detect the leak current. In this embodiment, as shown in FIG. 13, the leak current is directly amplified by the amplifier AMP1, and then input to the error detection comparator CMP1. Assuming that the leak current is IL and the feedback resistance is R1, a difference voltage ΔVL between the output voltage of the amplifier AMP1 and the reference voltage Vth1 is given by (Expression 1) below.
[Equation 1]
ΔVL = IL × R1 (Equation 1)
It is preferable that the leak current IL be large enough to obtain the leak voltage VL corresponding to the leak current IL by amplification of the amplifier AMP1. Then, if a voltage corresponding to the leak current value without deterioration of the insulating film is set to the threshold value Vth2 of the comparator CMP1, an error can be detected when an abnormal increase of the leak current occurs.

  As described above, in the present embodiment, an amplifier is used instead of the capacitor as the current-voltage conversion unit of the leak current detection unit in the second embodiment. Even when an amplifier is used, the leak current can be detected as in the above embodiment. Therefore, an error signal can be generated according to the leak current, and the isolator can be stopped before breakdown of the insulating film, so that the reliability of the isolator can be improved.

Seventh Embodiment
The seventh embodiment will be described below with reference to the drawings. The present embodiment is an example in which the operation of all the isolators is controlled in accordance with the detection results of the plurality of isolators shown in the second embodiment.

  FIG. 14 shows the configuration of a motor control system including the isolator according to the present embodiment. As shown in FIG. 14, the semiconductor device 1 includes a controller 200 and a plurality of isolators 100 (100a to 100c), and a plurality of IGBTs (IGBT1 to IGBT3) are connected. The semiconductor device 1 further includes a logic circuit OR2 between the controller 200 and the plurality of isolators 100.

  A plurality of input terminals of the logic circuit OR2 are connected to an external terminal T3 for outputting an error signal (individual error signal) S2 of each isolator 100, and an output terminal is connected to an input terminal of an error signal (total error signal) SE of the controller 200. Connected The logic circuit OR2 performs an OR logic operation on the inputs from the plurality of isolators and outputs an operation result. The logic circuit OR2 outputs the error signal SE to the controller 200 as the high level when the error signal S2 of any of the plurality of isolators 100 is the high level.

  FIG. 15 is a flowchart showing a control method (a test for detecting a leak current or a test method for testing deterioration of an insulating film) of the isolator 100 according to the present embodiment.

  As shown in FIG. 15, first, the controller 200 selects the isolator 100 to be tested (S131). For example, the controller 200 sequentially selects the isolators 100a to 100c from the isolator 100a. Here, although the isolators are sequentially selected and tested, a plurality of isolators may be tested at the same time. In this case, S101 to S104 are simultaneously performed on all the isolators.

  Subsequently, as in FIG. 5 of the second embodiment, the controller 200 transmits a signal to the selected isolator 100 so as to increase the high side voltage (S101), and turns off the switches SW1 and SW2 ( S102). Furthermore, the selected isolator 100 detects the leak voltage VL of the coil L1 after a predetermined time (S103), and determines whether the leak voltage VL of the coil L1 is less than or equal to the threshold value Vth (S104).

  If the leak voltage VL of the coil L1 of the selected isolator 100 is less than or equal to the threshold value Vth, the controller 200 determines whether or not all the isolators 100 have been tested (S132). When testing the remaining isolators, the controller 200 returns to S131, selects the next isolator 100, and starts normal operation when all the isolators have been tested (S105).

  The comparator CMP1 of the isolator 100 outputs an error signal S2 that remains low when the leak voltage VL is less than or equal to the threshold value Vth. The logic circuit OR2 outputs an error signal SE, which remains low, to the controller 200 because the input error signal S2 is low.

  Since the low level error signal SE is input for a predetermined period, the controller 200 determines that the selected isolator 100 is normal, repeats the next isolator test, and normally completes all the isolator tests. Start operation.

  When the leak voltage VL of the coil L1 of the selected isolator 100 is larger than the threshold value Vth, the controller 200 outputs an alarm (S106), and safely stops all the isolators (S133).

  The comparator CMP1 of the isolator 100 raises the error signal S2 to high level when the leak voltage VL exceeds the threshold. The logic circuit OR2 raises the error signal SE because the input error signal S2 is at high level. The controller 200 determines that the insulating film of the selected isolator 100 is abnormal because the high level error signal SE is input within the predetermined period. Then, the controller 200 stops the operation of all the isolators 100. This prevents the destruction of the entire system in advance.

  Motor control requires isolators for three phases, and if any one of them is shorted, malfunction or system damage occurs. Therefore, in the present embodiment, it is decided to monitor all the isolators and to stop the operation of all the ICs (isolators) if the insulation property is deteriorated. This can further improve the reliability of the isolator.

Eighth Embodiment
The eighth embodiment will be described below with reference to the drawings. This embodiment is an example provided with an isolator for detecting the leak current of the receiving-side insulating element in addition to the isolator shown in the second embodiment.

  FIG. 16 shows the configuration of a motor control system including the isolator according to the present embodiment. As shown in FIG. 16, the semiconductor device 1 includes a controller 200, an isolator 100, an isolator 100-2, and a logic circuit OR3.

  The isolator 100 transmits a signal from the controller 200 to the motor 301. The isolator 100-2 transmits a signal from the motor 301 to the controller 200.

  The isolator 100-2 includes a transmitting chip 120-2 and a receiving chip 130-2. The transmitter chip 120-2 includes a transmitter circuit 101-2. The reception side chip 130-2 includes an insulation element 102, an insulation element 103, a reception circuit 104-2, an impedance control unit 105, and a leak current detection unit 106.

  The transmission circuit 101-2 receives the transmission data VIN from the error detection circuit 302 via the external terminal T4, and generates an AC transmission signal based on the input transmission data VIN. This AC transmission signal is a signal based on the reference potential GND2 (second reference potential).

  The insulating element 103 is supplied with an AC transmission signal from the transmission circuit 101. An insulating film 107 is formed between the insulating element 102 and the insulating element 103. The insulating element 102 generates an AC reception signal by AC coupling with the insulating element 103 via the insulating film 107. The AC reception signal is a signal based on a reference potential GND1 (first reference potential) different from the reference potential GND.

  The reception circuit 104 receives an AC reception signal from the isolation element 102 via the impedance control unit 105. The reception circuit 104 reproduces the reception data VOUT based on the input AC reception signal, and outputs the reception data VOUT to the controller 200 via the external terminal T2.

  Similar to the isolator 100, the impedance control unit 105 receives the impedance control signal S1 from the controller 200 via the external terminal T1, and controls the impedance of the insulating element 102 to a high impedance based on the input impedance control signal S1. Similar to the isolator 100, the leak current detection unit 106 detects a leak current through the insulation element 102 whose impedance is controlled, and controls an error signal S2 as a detection result according to the leak current through the external terminal T3. Output to 200.

  A plurality of input terminals of the logic circuit OR3 are connected to the external terminal T3 that outputs the error signal S2 of each isolator, and an output terminal is connected to the input terminal of the error signal SE of the controller 200. The logic circuit OR3 performs an OR logic operation on the inputs from the plurality of isolators and outputs an operation result. When the error signal S2 of any of the plurality of isolators 100 is at high level, the logic circuit OR3 outputs the error signal SE to the controller 200 as high level.

  In applications such as automotive motor control where reliability is important, not only the condition of the isolator but also the condition of the IGBT and motor are monitored. For example, as shown in FIG. 16, an error detection circuit 302 is provided which monitors and outputs isolator disconnection detection, IGBT overcurrent detection, overheat detection and the like. In this embodiment, another isolator 100-2 is provided to return the signal of the monitoring result to the primary side. A leakage current detector is also provided on the receiving side of the feedback isolator.

  As described above, even when the leak current detection unit is provided on the reception side, the leak current can be detected as in the above embodiment. Therefore, an error signal can be generated according to the leak current, and the isolator can be stopped before breakdown of the insulating film, so that the reliability of the isolator can be improved.

  As mentioned above, although the invention made by the present inventor was concretely explained based on an embodiment, the present invention is not limited to the above-mentioned embodiment, and can be variously changed in the range which does not deviate from the gist. Needless to say.

  An isolator is a circuit that can transmit signals in a noncontact manner between different potential circuits. The signal transmission system of the isolator includes the magnetic field (magnetic coupling) by the coil (L), the electric field (capacitive coupling) by the capacitor (C), light by the coupler, radio waves by the antenna, etc. Thus, the potential of the receiving circuit side (secondary side) can be controlled as in the above embodiment. If the isolator has an insulating element through at least an insulating film, by applying the above-described embodiment, the state before the insulating film is broken can be detected to improve the reliability.

Reference Signs List 1 semiconductor device 100 isolator 101 transmission circuit 102 isolation element (transmission side isolation element)
103 Insulating element (receiving side insulating element)
104 Reception circuit 105 Impedance control unit 105a MOS transistor 106 Leakage current detection unit 106a, 106b MOS transistor 107 Insulating film (interlayer insulating film)
120 transmission side chip 130 reception side chip 200 controller 207 interlayer insulating film 300 controlled device 301 motor 302 error detection circuit P1 to P4 pad T0 to T4 external terminal L1 coil (transmission side coil)
L2 coil (receiving side coil)
L3 coil SW0 to SW4 switch C1 capacitor CMP1 and CMP2 comparator OR1 to OR3 logic circuit M1 memory circuit AMP1 amplifier R1 resistor SUB1 and SUB2 silicon substrate GL10 and GL20 gate electrode layer WL11 to WL18 wiring layer WL21 to WL28 wiring layer

Claims (14)

A transmission circuit that generates an alternating current transmission signal based on the input transmission data;
A first coil to which the alternating current transmission signal is supplied;
A second coil that generates an AC reception signal according to the AC transmission signal by AC coupling with the first coil;
A receiving circuit that receives the alternating current reception signal and outputs reception data based on the alternating current reception signal;
An insulating film disposed between the first coil and the second coil;
A leak current detection unit that detects a leak current of the insulating film;
A first electronic device comprising
A second electronic device for controlling a motor based on the received data;
Motor control system. The first electronic device includes an impedance control unit configured to increase the impedance of the first coil or the second coil.
A motor control system according to claim 1. The impedance control unit is a switch circuit connected between the first coil and the transmission circuit, or a switch circuit connected between the second coil and the reception circuit.
The motor control system according to claim 2. The leak current detection unit detects an abnormality of the leak current according to a current flowing through the first or second coil whose impedance is controlled for a predetermined period.
The motor control system according to claim 2. The leak current detection unit
A current-voltage conversion circuit that converts a current flowing through the first or second coil whose impedance has been controlled, into the leak voltage during the predetermined period;
And a comparison circuit that detects an abnormality in the leakage current according to a comparison result between the leakage voltage and a predetermined threshold value.
The motor control system according to claim 4. The current-voltage conversion circuit is a capacitive element that charges a current flowing through the first or second coil whose impedance is controlled for the predetermined period.
The motor control system according to claim 5. A storage circuit for storing the leak voltage;
The comparison circuit uses the leak voltage stored in the storage circuit when the leak current detection unit detects the leak current last time as the threshold value, and the current-voltage conversion circuit has converted this time. Compare with voltage,
The motor control system according to claim 5. The threshold includes the leakage voltage and a voltage margin.
The motor control system according to claim 7. A bias circuit that supplies an initial potential to the first or second coil before controlling the impedance;
The motor control system according to claim 2. The leak current detection unit
According to the comparison result of the first threshold and the leak voltage corresponding to the current flowing to the first or second coil to which the initial potential is supplied and the impedance is controlled, A first comparison circuit that detects an abnormality;
And a second comparison circuit that detects an abnormality in the leak current according to a comparison result of the leak voltage and a second threshold smaller than the first threshold.
The motor control system according to claim 9. The first comparison circuit detects an abnormality of the leak current when the leak voltage is larger than the first threshold value;
The second comparison circuit detects an abnormality of the leak current when the leak voltage is smaller than the second threshold.
A motor control system according to claim 10. The potential of the first coil whose impedance is controlled is set as a first reference potential according to the detection result of the leak current, or the potential of the second coil whose impedance is controlled is a second. And a reference potential supply circuit for setting the reference potential
The motor control system according to claim 2. The reference potential supply circuit connects one end of the first coil and the first reference potential according to the detection result of the leak current, or one end of the second coil and the first A switch circuit connecting between two reference potentials,
A motor control system according to claim 12. The leak current detection unit
A current-voltage conversion amplifier circuit that converts and amplifies a current flowing through the first or second coil whose impedance has been controlled, into a leak voltage;
A comparison circuit that detects an abnormality in the leak current according to a comparison result between the amplified leak voltage and a predetermined threshold value;
The motor control system according to claim 2.

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