Power conversion device

Abstract

To provide a power conversion device that achieves insulation between an observation target system and an observation system with an inexpensive configuration.SOLUTION: An inverting input of a difference amplifier (8) is connected to the positive DC line (8a) via a first resistor (5a), and a non-inverting input of the difference amplifier (8) is connected to the negative DC line (5b) via a second resistor (21b), 8b 21p, in the power conversion device, the insulating property between a main circuit 2 and a voltage sensor 3 is secured based on at least a first resistor 5a and a second resistor 5b, and the input gain resistor of a differential amplifier 8 is constituted of the first resistor 5a and the second resistor 5b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device. [Background technology]

[0002] The semiconductor switching elements used in power conversion devices in fields such as power electronics, such as on-board chargers, step-down converters, and on-board inverters, are generally MOSFETs ( These include semiconductor switching elements such as Metal Oxide Semiconductor Field Effect Transistors (IGBTs), Insulated Gate Bipolar Transistors (IGBTs), and wide-gap semiconductors such as GaN (gallium nitride) and SiC (silicon carbide).

[0003] Furthermore, conventional power conversion devices are provided with a software shutdown protection device using software or a hardware shutdown protection device using hardware to prevent damage to the internal semiconductor switching elements or the connected load, etc. In particular, a hardware shutdown protection device is configured to stop the power conversion operation of the power conversion device before the semiconductor switching elements in the main circuit of the power conversion device are destroyed.

[0004] Generally, there is a failure mode in which a power supply line of the main circuit of a power conversion device, for example, a hot line (hereinafter referred to as a positive DC line) to which a high voltage is applied, or a cold line (hereinafter referred to as a negative DC line), grounds to a part of the control circuit system or the housing (case ground part). Even if such a failure occurs, the power conversion device is required to properly detect the occurrence of an overvoltage and stop the operation of the main circuit or properly activate a protective operation. For this reason, a power conversion device using a semiconductor switching element is required to be equipped with an appropriate voltage sensor.

[0005] Patent Document 1 discloses an AC voltage sensor circuit connected to an AC output section of an inverter circuit serving as a power conversion device. According to the disclosure, a control circuit and the inverter circuit are insulated from each other, the voltage sensor circuit includes a sense signal isolation circuit, the inverter circuit and the control circuit are insulated from each other by the voltage sensor circuit, the AC output section of the inverter includes first and second power supply lines, the inverter circuit includes a reference voltage node, and the AC voltage sensor circuit is configured to output a signal representing a voltage difference between the voltage of the first line relative to the reference voltage node and the voltage of the second line relative to the reference voltage node. Patent Document 1 claims that this configuration makes it possible to provide a voltage sensor circuit with a simpler circuit configuration than conventional ones.

[0006] The voltage sensor circuit in the conventional power conversion device disclosed in Patent Document 1 includes a sense signal isolation circuit that uses galvanic isolation, and insulation between the inverter circuit and the control circuit is ensured by the voltage sensor circuit.

[0007] If insulation between the input side and the output side is ensured by galvanic isolation, as in the voltage sensor circuit disclosed in Patent Document 1, even if a ground fault occurs between the positive DC line or negative DC line of the power conversion device and a part of the control circuit system or the housing of the power conversion device, the input / output characteristics of the voltage sensor will not be affected, and therefore even if an overvoltage occurs between the positive DC line and the negative DC line in a ground fault state, the overvoltage can be correctly detected. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2023-175392 Summary of the Invention [Problem to be solved by the invention]

[0009] According to the conventional device disclosed in Patent Document 1, in order to ensure insulation between the inverter circuit as the system to be observed and the control circuit as the observation system having a voltage sensor, it is necessary to provide a voltage sensor with galvanic isolation, such as an optical isolation circuit using a photocoupler, an isolation circuit using electrostatic capacitance coupling, a transformer circuit using magnetic coupling, an isolation amplifier, etc., which poses a problem of high component costs.

[0010] The present disclosure discloses a technology for solving the above-mentioned problems, and aims to provide a power conversion device that achieves isolation between the observed system and the observed system with an inexpensive configuration. [Means for solving the problem]

[0011] The power conversion device of the present disclosure includes: a main circuit that performs power conversion; a voltage sensor that detects a voltage between a positive DC line and a negative DC line of the main circuit; an abnormality determination circuit that determines whether or not there is an abnormality in the main circuit based on the output of the voltage sensor; Equipped with A power conversion device configured so that, when the abnormality determination circuit determines an abnormality in the main circuit, an operating state of the main circuit is changed, the voltage sensor is configured by a differential amplifier, the differential amplifier has an inverting input terminal connected to one end of a first resistor having the other end connected to the positive DC line, a non-inverting input terminal connected to the other end of a second resistor having one end connected to the negative DC line, and a bias power supply connected to the non-inverting input terminal; Insulation between the main circuit as an observation target system and the voltage sensor as an observation system is ensured based on at least the first resistor and the second resistor, an inverting input terminal of the differential amplifier is connected to the positive DC line via the first resistor, and a non-inverting input terminal of the differential amplifier is connected to the negative DC line via the second resistor, whereby an input gain resistor of the differential amplifier is composed of the first resistor and the second resistor. It is characterized by: [Effects of the Invention]

[0012] According to the power conversion device of the present disclosure, it is possible to obtain a power conversion device that achieves insulation between the observed system and the observed system with an inexpensive configuration. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 10 is an explanatory diagram showing the relationship between the input / output characteristics of a non-insulated voltage sensor and an overvoltage threshold value. [Figure 2] 1 is a circuit diagram showing a configuration of a power conversion device according to a first embodiment. [Figure 3] 3 is an explanatory diagram showing the relationship between the input / output characteristics of a voltage sensor and an overvoltage threshold in the power conversion device according to the first embodiment. FIG. [Figure 4] 3 is an explanatory diagram showing the offset characteristics of a single-power supply operational amplifier in the power conversion device according to the first embodiment. FIG. [Figure 5] FIG. 10 is a circuit diagram showing a configuration of a power conversion device according to a second embodiment. [Figure 6] FIG. 10 is a circuit diagram showing a configuration of a power conversion device according to a third embodiment. [Figure 7A] 10 is an explanatory diagram showing a response waveform of a comparator and an overdrive voltage in a power conversion device according to a third embodiment. FIG. [Figure 7B] 11 is an explanatory diagram showing the relationship between the overdrive voltage of the comparator and the response time in the power conversion device according to the third embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Underlying Technology 1 is an explanatory diagram showing the relationship between the input / output characteristics of a non-insulated voltage sensor and an overvoltage threshold, and shows the relationship between the input / output characteristics of the non-insulated voltage sensor as an observation system and the overvoltage threshold when a ground fault occurs in the positive DC line or negative DC line of the main circuit of a power conversion device as an observation target system, with the vertical axis representing the output voltage [V] and the horizontal axis representing the input voltage [V]. The input / output characteristics of the non-insulated voltage sensor have a positive characteristic.

[0015] The non-isolated voltage sensor is configured with a single-power operational amplifier as a differential amplifier, and its inverting input terminal is connected to the positive DC line of the main circuit of the power conversion device as the system to be observed, and its non-inverting input terminal is connected to the negative DC line of the main circuit. The voltage to be observed is the voltage between the positive and negative DC lines.

[0016] In Figure 1, when the main circuit is normal or when the positive DC line is grounded to the housing, the output voltage of the non-isolated voltage sensor changes in direct proportion to the input voltage, as shown by input-output characteristic X1. Therefore, when the output voltage of the non-isolated voltage sensor exceeds the overvoltage threshold Vth, an overvoltage in the system being observed can be detected. On the other hand, when the negative DC line is grounded to the housing, the output voltage becomes a constant value at the time t1 when the ground fault occurs, as shown by input-output characteristic X2. Even if the input voltage rises, the output voltage does not reach the overvoltage threshold Vth, and an abnormality in the system being observed cannot be detected.

[0017] Furthermore, when a non-isolated voltage sensor that does not use galvanic isolation is used to observe the voltage between the positive and negative DC lines in the main circuit of a power conversion device, which is the system under observation, if the positive or negative DC line is grounded to the housing, both ends of the resistor that determines the gain of the operational amplifier that serves as the differential amplifier in the non-isolated voltage sensor will be shorted, disrupting the potential balance between the inverting and non-inverting input terminals of the single-power-supply operational amplifier that serves as the differential amplifier. As a result, an offset voltage will be generated due to current leakage, preventing normal overvoltage detection.

[0018] Furthermore, when a single-power-supply operational amplifier is used as a non-isolated voltage sensor, the temperature characteristics of the single-power-supply operational amplifier cause the offset voltage to increase for input voltages where the output voltage reaches, for example, approximately 5 V. However, when a circuit is configured with a positive input / output characteristic for a non-isolated voltage sensor using a single-power-supply operational amplifier, in order to ensure the dynamic range of the non-isolated voltage sensor, the overvoltage threshold must be set near the point where the offset voltage increases, resulting in greater variation in the overvoltage threshold.

[0019] Therefore, in the case of a non-insulated voltage sensor using a single-power operational amplifier, measures are required to ensure that abnormality determination, particularly overvoltage abnormality determination, can be performed correctly even if the positive DC line or negative DC line of the system being observed is grounded to the housing that serves as the ground potential part of the power conversion device.

[0020] Embodiment 1, Next, a power conversion device according to a first embodiment will be described with reference to the drawings. FIG. 2 is a circuit diagram showing the configuration of the power conversion device according to the first embodiment. In FIG. 2, the power conversion device 1 is connected to a DC power supply 100 formed by a battery, and performs desired power conversion. The power conversion device 1 includes a main circuit 2, a voltage sensor 3, and an abnormality determination circuit 4.

[0021] The main circuit 2 may be configured as one of the following: (1) DC / AC converters in the range of several watts to several hundred kilowatts (2) DC / DC converter (3) AC / DC converters or step-down converters such as on-board chargers that consist of semiconductor switching elements such as MOSFETs or IGBTs, transformers, coils, diodes, capacitors, etc. (4) An inverter or converter consisting of a bridge circuit with semiconductor switching elements such as MOSFETs and IGBTs, smoothing capacitors, etc.

[0022] Here, the main circuit 2 constitutes the inverter described above in (4), and the inverter has a three-phase bridge circuit and is configured to convert DC power from the DC power supply 100 into three-phase AC power and supply the three-phase AC power to a three-phase AC motor serving as the load 200. The inverter can also operate as a converter that converts three-phase AC power generated during regenerative operation of the three-phase AC motor serving as the load 200 into DC power that charges a battery serving as the DC power supply 100.

[0023] The main circuit 2 constituting the inverter is configured with a three-phase bridge circuit including a U-phase arm consisting of a U-phase upper arm semiconductor switching element and a U-phase lower arm semiconductor switching element connected in series, a V-phase arm consisting of a V-phase upper arm semiconductor switching element and a V-phase lower arm semiconductor switching element connected in series, and a W-phase arm consisting of a W-phase upper arm semiconductor switching element and a W-phase lower arm semiconductor switching element connected in series.

[0024] The U-phase arm, V-phase arm, and W-phase arm are connected in parallel with each other, and one end of the parallel-connected U-phase arm, V-phase arm, and W-phase arm is connected to a positive-side DC line 21p connected to the positive side of the DC power supply 100, and the other end of the parallel-connected U-phase arm, V-phase arm, and W-phase arm is connected to a negative-side DC line 21n connected to the negative side of the DC power supply 100.

[0025] U-phase AC line 22u of main circuit 2 constituting the inverter is led out from a series connection portion of a U-phase upper arm semiconductor switching element and a U-phase lower arm semiconductor switching element, and is connected to a U-phase armature winding of a three-phase AC motor serving as load 200. V-phase AC line 22v of main circuit 2 constituting the inverter is led out from a series connection portion of a V-phase upper arm semiconductor switching element and a V-phase lower arm semiconductor switching element, and is connected to a V-phase armature winding of a three-phase AC motor serving as load 200. W-phase AC line 22w of main circuit 2 constituting the inverter is led out from a series connection portion of a W-phase upper arm semiconductor switching element and a W-phase lower arm semiconductor switching element, and is connected to a W-phase armature winding of a three-phase AC motor serving as load 200.

[0026] A gate driver circuit (not shown) included in the main circuit 2 supplies gate drive signals to the gates of all semiconductor switching elements in the main circuit 2 and controls the switching of each semiconductor switching element using PWM (Pulse Width Modulation). The gate driver circuit generates the gate drive signal based on a command from a control device (not shown) provided in an ECU (Electronic Control Unit), for example. The gate driver circuit is also configured to generate a gate drive stop signal that stops the switching operation of each semiconductor switching element based on a command from the control device.

[0027] When the abnormality determination circuit 4 described below determines an abnormality in the main circuit 2 and outputs the abnormality determination result to the control device, the control device controls the gate driver circuit to change the operating state of the main circuit 2 that constitutes the inverter. Changing the operating state of the main circuit 2 by the control device means, for example, stopping the operation of the inverter that is constituted by the main circuit, thereby protecting the semiconductor switching elements.

[0028] The voltage sensor 3 is a non-insulated voltage sensor that basically comprises a single-power-supply operational amplifier 8 as a differential amplifier, a first resistor 5a and a second resistor 5b each having a resistance value within a range of, for example, 2 MΩ to 6 MΩ, and a bias power supply 7, and further comprises a first gain resistor 6a and a second gain resistor 6b.

[0029] The single-power-supply operational amplifier 8 is supplied with power from a power supply 8e having an output voltage of, for example, 5 V, which is the same as the power supply of a microcontroller in the ECU.

[0030] An inverting input terminal 8a of the single-power-supply operational amplifier 8 is connected via a first resistor 5a to a positive DC line 21p of the main circuit 2, which is the system under observation. A non-inverting input terminal 8b of the single-power-supply operational amplifier 8 is connected via a second resistor 5b to a negative DC line 21n of the main circuit 2. A first gain resistor 6a is connected between the inverting input terminal 8a and the output terminal 8c, and a second gain resistor 6b and a bias power supply 7 are connected between the non-inverting input terminal 8b and the ground potential section GND. The ground potential section GND corresponds to the housing of the power conversion device 1, etc.

[0031] The control device (not shown) that controls the main circuit 2 must be insulated from the main circuit 2 to prevent accidents, and conventionally, galvanic isolation has been adopted as described above, but galvanic isolation has problems such as high component costs. In contrast, in the power conversion device according to the first embodiment, as described above, the voltage sensor 3 is composed of a single-power-supply operational amplifier 8 as a differential amplifier, a first resistor 5a and a second resistor 5b having resistance values ​​within a range of several MΩ, for example, from 2 MΩ to 6 MΩ, a bias power supply 7, a first gain resistor 6a, and a second gain resistor 6b.

[0032] The voltage sensor 3 monitors the voltage between the positive DC line 21p and the negative DC line 21n of the main circuit 2. When the main circuit generating the voltage to be monitored is the monitored system and the voltage sensor 3 is the monitored system, insulation between the monitored system and the monitored system is ensured by at least the high-resistance first resistor 5a and second resistor 5b. The first resistor 5a and second resistor 5b each have a resistance of several hundred kilohms (KΩ), for example, in the range of 200 to 600 KΩ, and are connected in series to provide a resistance of several megaohms (MΩ), for example, in the range of 2 to 6 MΩ.

[0033] As described above, insulation between the main circuit 2 as the system to be observed and the voltage sensor 3 as the observation system is ensured by at least the first resistor 5a and the second resistor 5b. Furthermore, the positive side DC line 21p of the main circuit 2 is connected to the inverting input terminal 8a of the differential amplifier formed by the single-power-supply operational amplifier 8, and the negative side DC line 21n is connected to the non-inverting input terminal 8b of the differential amplifier, so that the input gain resistance of the differential amplifier is formed by the first resistor 5a and the second resistor 5b.

[0034] The gain and offset voltage of the voltage sensor 3 are set by the bias power supply 7, the second gain resistor 6b connected to the non-inverting input terminal 8b, the first gain resistor 6a, which is also a feedback resistor connected between the inverting input terminal 8a and the output terminal 8c, the first resistor 5a, and the second resistor 5b.

[0035] Furthermore, the positive DC line 21p of the main circuit 2 is connected to the inverting input terminal 8a of the single-power-supply operational amplifier 8 via a high-resistance first resistor 5a, and the negative DC line 21n of the main circuit 2 is connected to the non-inverting input terminal 8b via a high-resistance second resistor 5b. As a result, the input / output characteristics of the voltage sensor 3 are realized as negative input / output characteristics with respect to changes in voltage, which is an electrical quantity between the positive DC line 21p and the negative DC line 21n of the main circuit 2 as the system to be observed.

[0036] FIG. 3 is an explanatory diagram showing the relationship between the input / output characteristics of the voltage sensor and the overvoltage threshold in the power conversion device according to embodiment 1, with the vertical axis representing the output voltage [V] and the horizontal axis representing the input voltage [V].

[0037] As described above, the input / output characteristics of the voltage sensor 3 are realized as negative input / output characteristics with respect to changes in voltage, which is an electrical quantity between the positive side DC line 21p and the negative side DC line 21n of the main circuit 2 as the system to be observed. As a result, even if the positive side DC line 21p or the negative side DC line 21n of the main circuit 2 is grounded to the housing, as shown in Fig. 3, the voltage sensor 3 can obtain normal output characteristics with respect to a high voltage input between the positive side DC line 21p and the negative side DC line 21n. Therefore, the abnormality determination circuit 4 downstream of the voltage sensor 3 can correctly determine that a voltage exceeding the overvoltage threshold Vth [V] is an overvoltage abnormality.

[0038] The bias power supply 7 is set based on the voltage of the power supply 8e of the single-power-supply operational amplifier 8, or is set according to the voltage range of the main circuit 2, which is the system under observation. For example, it is set based on the output voltage value of the voltage sensor 3 when the voltage of the system under observation is 0 [V].

[0039] The single-power supply operational amplifier 8 has a simple component configuration and is relatively robust against electrical stress. On the other hand, the single-power supply operational amplifier 8 has an offset characteristic with respect to the input voltage, as shown in a representative example in Fig. 4. That is, Fig. 4 is an explanatory diagram showing the offset characteristic of the single-power supply operational amplifier in the power conversion device according to embodiment 1, with the vertical axis representing the offset voltage [V] and the horizontal axis representing the input voltage [V].

[0040] In Figure 4, Y1 indicates the offset characteristics at 125°C, Y2 indicates the offset characteristics at 25°C, and Y3 indicates the offset characteristics at -40°C. As shown in Figure 4, a feature of single-power-supply operational amplifier 8 is that the common-mode input voltage range, which is the range of input voltages in which it operates normally, is narrow. In particular, because the input voltage maintains a linear region of the circuit up to the reference potential (ground potential), when considering the temperature drift characteristics of the offset voltage as the ground side as the lower input limit and the power supply voltage side as the upper input limit, the temperature drift characteristics on the upper input limit side are worse than those on the lower input limit side.

[0041] Therefore, if the voltage sensor 3 has a positive characteristic, the offset voltage will vary greatly near the overvoltage threshold and the temperature characteristic will also deteriorate. Therefore, by setting the voltage sensor 3 to a negative characteristic, the offset voltage near the overvoltage threshold can be suppressed, thereby improving the temperature characteristic. Furthermore, the gain and offset voltage of the voltage sensor 3 are set so that the upper limit of the guaranteed range of the operating voltage of the main circuit 2, which is the input to the voltage sensor 3, is the upper limit of the range of the common-mode input voltage of the voltage sensor 3, and the lower limit is a voltage higher than the overvoltage threshold Vth.

[0042] As a result, it is possible to ensure a dynamic range for the main circuit 2 as the system to be observed. For example, if the operating range of the voltage between the positive side DC line 21p and the negative side DC line 21n is 0 [V] to 950 [V], the power supply 8e of the voltage sensor 3 is 5 [V], and the power supply of the observation system, such as a microcomputer, is 5 [V], by setting the upper limit of the output voltage of the voltage sensor 3 to 3.5 [V] and the lower limit to about 1 [V], if the microcomputer is 5 [V] and 12 [bit], the observation system will have a dynamic range of about 0.5 [V / LSB (Least Significant Bit)], and it is possible to ensure a good dynamic range.

[0043] The abnormality determination circuit 4 determines that the voltage at any point in the main circuit 2 is abnormal based on the output from the voltage sensor 3, and transmits the abnormality to a downstream control device or the main circuit 2. When the abnormality is transmitted to the power conversion device 1, a software shutdown protection device using software or a hardware shutdown protection device using hardware prevents damage to the internal semiconductor switching elements or the connected load 200, etc.

[0044] Furthermore, in a protection device using a hardware shutdown method, it is necessary to stop the power conversion operation of the power conversion device 1 before the semiconductor switching elements in the main circuit 2 of the power conversion device 1 are destroyed. As described above, if the voltage sensor 3 is configured with a single-power supply operational amplifier 8 and has a positive input / output characteristic with respect to the system being observed, the error in the offset voltage near the overvoltage threshold Vth [VV] will increase, resulting in poor detection accuracy. However, with the configuration of the power conversion device of the first embodiment, the single-power supply operational amplifier 8 has a negative input / output characteristic with respect to the system being observed, and the voltage value of the overvoltage threshold Vth [V] is set near 1 [V] of the input / output characteristic of the voltage sensor 3, thereby making it possible to improve the error in the offset voltage near the overvoltage threshold Vth.

[0045] Furthermore, by configuring the abnormality determination circuit 4 as hardware, it is possible to quickly stop the gate drive of the semiconductor switching elements of the main circuit 2. Therefore, the protective operation of the power conversion device 1 can be quickly activated, thereby preventing damage to the semiconductor switching elements of the main circuit inside the power conversion device 1 or to the load outside the power conversion device 1 due to overvoltage. As a result, even when a ground fault occurs in the positive side DC line 21p or the negative side DC line 21n in the main circuit 2, it is possible to properly determine overvoltage and reliably protect the power conversion device 1 and the like with an inexpensive configuration.

[0046] According to the power conversion device of the first embodiment described above, even if either the positive side DC line 21p or the negative side DC line of the main circuit 2 of the power conversion device 1 is grounded to the housing, the input / output characteristics (particularly the high voltage side of the input voltage) of the voltage sensor 3 are not affected by the ground fault, so the subsequent abnormality determination circuit 4 can correctly detect the overvoltage. Therefore, an inexpensive voltage sensor configuration can reliably detect the overvoltage in the system under observation without using galvanic isolation.

[0047] Furthermore, since the differential amplifier of the voltage sensor is configured using an inexpensive single-power-supply operational amplifier, the cost of the circuit can be reduced.

[0048] Furthermore, by setting the gain and offset voltage of the voltage sensor 3 so that the upper limit of the guaranteed range of the operating voltage of the main circuit 2, which is the input to the voltage sensor 3, is the upper limit of the common-mode input range of the voltage sensor 3 and the lower limit is a voltage higher than the overvoltage threshold Vth [V], it is possible to ensure the dynamic range for the system under observation.In addition, overvoltage can be detected with high accuracy.

[0049] Embodiment 2 Next, a power conversion device according to embodiment 2 will be described with reference to the drawings. Fig. 5 is a circuit diagram showing the configuration of the power conversion device according to embodiment 2. In Fig. 5, a monitor circuit 11 receives the output voltage of the voltage sensor 3 from an output terminal branched from the output terminal 8c of the voltage sensor 3, and is configured to monitor, separately from the abnormality determination circuit 4, the voltage between the positive side DC line 21p and the negative side DC line 21n of the main circuit 2 as the system to be observed.

[0050] The monitor circuit 11 monitors the voltage between the positive side DC line 21p and the negative side DC line 21n of the main circuit 2, and if the voltage exceeds the overvoltage threshold Vth [V], the monitor circuit 11 transmits the monitoring result to the gate driver circuit of the main circuit 2 to stop the operation of the semiconductor switching elements, thereby making it possible to prevent erroneous driving of the semiconductor switching elements of the main circuit 2. Furthermore, by comparing the monitoring result of the monitor circuit 11 with the operating state of the abnormality determination circuit 4, it is also possible to detect a failure of the abnormality determination circuit 4.

[0051] By inputting the output of the monitor circuit 11 to, for example, an A / D board of a microcomputer that has the function of converting analog signals into digital signals, the above function can be performed by the microcomputer, and the output of the monitor circuit 11 can be used particularly effectively.

[0052] The other configurations are the same as those of the power conversion device according to the first embodiment, and the same effects as those of the first embodiment can be obtained.

[0053] Embodiment 3 Next, a power conversion device according to a third embodiment will be described with reference to the drawings. FIG. 6 is a circuit diagram showing the configuration of the power conversion device according to the third embodiment. In FIG. 6, the abnormality determination circuit 4 is made up of a comparator 9 and a reference power supply 10. An inverting input terminal 9a of the comparator 9 is connected to the output terminal 8c of the voltage sensor 3, and a non-inverting input terminal 9b is connected to the reference power supply 10. An input voltage Vin [V] from the voltage sensor 3 is input to the inverting input terminal 9a, and a reference voltage Vref [V] from the reference power supply 10 is input to the non-inverting input terminal 9b. A voltage is supplied to the comparator 9 from a power supply 9e.

[0054] Fig. 7A is an explanatory diagram showing the response waveform and overdrive voltage of the comparator in the power conversion device according to embodiment 3, and Fig. 7B is an explanatory diagram showing the relationship between the overdrive voltage and response time of the comparator in the power conversion device according to embodiment 3. In Fig. 7A, when the input voltage Vin [V] to the comparator 9 makes a step-like transition from high level H to low level L, the difference in level between the reference voltage Vref [V] and the input voltage Vin [V] is defined as overdrive voltage Vovr [V]. As indicated by Z in Fig. 7B, as the level of the overdrive voltage Vovr increases, the response time Tr [μs] becomes shorter.

[0055] 7A, Vcc [V] is the value of the high level H of the output voltage of the comparator 9, and the response time Tr [μs] corresponds to the time [μs] it takes for the output voltage Vout [V] of the comparator 9 to reach Vcc / 2 [V] from the low level L. Furthermore, the reference voltage Vref [V] as the output voltage of the reference power supply 10 corresponds to the overvoltage threshold Vth [V].

[0056] The output of the comparator 9 is used as a gate drive stop signal for the gate driver circuit that drives the semiconductor switching elements of the main circuit 2, and the semiconductor switching elements of the main circuit 2 stop switching operation in response to the gate drive stop signal from the gate driver circuit.

[0057] It is also possible to provide the monitor circuit 11 in the second embodiment and input the output of the comparator 9 to the monitor circuit 11 to monitor the occurrence of an overvoltage.

[0058] When an overvoltage occurs, a surge or pulse-like overvoltage occurs. Furthermore, the higher the overvoltage level, the lower the output voltage of the differential amplifier. In other words, the higher the overvoltage level, the lower the output voltage of the comparator 9. Therefore, by applying an overdrive characteristic to the input of the comparator 9 when an overvoltage occurs, the speed of the protection operation can be increased according to the overvoltage level. Specifically, if the input / output characteristics of the single-power-supply operational amplifier 8 serving as the differential amplifier constituting the voltage sensor 3 are as shown in FIG. 3, the value of the overdrive voltage Vovr shown in FIG. 7A increases as the overvoltage level increases. Therefore, as is clear from the overdrive voltage characteristics shown in FIG. 7B, the response time Tr decreases as the absolute value of the overdrive voltage Vovr increases, thereby increasing the speed of the protection operation according to the overvoltage level.

[0059] Furthermore, by configuring the abnormality determination circuit 4 as hardware, it is possible to quickly stop the gate drive of the semiconductor switching elements of the main circuit 2. Furthermore, the higher the overvoltage level, the lower the peak voltage output from the comparator 9, so the overdrive characteristics of the comparator 9 can speed up the speed of the protection operation according to the overvoltage level. Therefore, since the protection operation can be quickly activated, it is possible to prevent damage caused by overvoltage to the semiconductor switching elements of the main circuit 2 of the power conversion device 1 or to a load external to the power conversion device 1 (for example, a motor in the case of an inverter).

[0060] Although various exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are anticipated within the scope of the technology disclosed in this application. For example, modifications of at least one component, additions, or omissions, as well as extraction of at least one component and combinations with components of other embodiments, are also contemplated.

[0061] The other configurations are the same as those in the first and second embodiments.

[0062] Next, aspects of the power conversion device disclosed in the present application will be described below as supplementary notes. (Appendix 1) a main circuit that performs power conversion; a voltage sensor that detects a voltage between a positive DC line and a negative DC line of the main circuit; an abnormality determination circuit that determines whether or not there is an abnormality in the main circuit based on the output of the voltage sensor; Equipped with A power conversion device configured so that, when the abnormality determination circuit determines an abnormality in the main circuit, an operating state of the main circuit is changed, the voltage sensor is configured by a differential amplifier, the differential amplifier has an inverting input terminal connected to one end of a first resistor having the other end connected to the positive DC line, a non-inverting input terminal connected to the other end of a second resistor having one end connected to the negative DC line, and a bias power supply connected to the non-inverting input terminal; Insulation between the main circuit as an observation target system and the voltage sensor as an observation system is ensured based on at least the first resistor and the second resistor, an inverting input terminal of the differential amplifier is connected to the positive DC line via the first resistor, and a non-inverting input terminal of the differential amplifier is connected to the negative DC line via the second resistor, whereby an input gain resistor of the differential amplifier is composed of the first resistor and the second resistor. A power conversion device characterized by: (Appendix 2) The main circuit is configured by a bridge circuit having a plurality of semiconductor switching elements. 2. The power conversion device according to claim 1, (Appendix 3) When the abnormality determination circuit determines that an abnormality has occurred in the main circuit, the switching operation of the semiconductor switching element is stopped. 3. The power conversion device according to claim 2, (Appendix 4) The abnormality determination circuit is configured by a differential amplifier. 4. The power conversion device according to claim 1, wherein: (Appendix 5) a monitor circuit for monitoring the output voltage of the voltage sensor; 5. The power conversion device according to claim 1, wherein: (Appendix 6) The voltage sensor a gain and an offset voltage are set so that an upper limit value of the output voltage of the voltage sensor is the upper limit value of a common-mode input voltage range of the voltage sensor, and a lower limit value of the output voltage of the voltage sensor is a voltage value higher than an overvoltage threshold value set in the abnormality determination circuit; 6. The power conversion device according to any one of claims 1 to 5, (Appendix 7) The power supply voltage of the voltage sensor is substantially 5 [V], The upper limit of the output voltage of the voltage sensor is substantially 3.5 [V], The lower limit of the output voltage of the voltage sensor is substantially 1 [V]. 7. The power conversion device according to claim 1, wherein: (Appendix 8) The overvoltage threshold of the abnormality determination circuit is set to be substantially less than 1 [V]. 8. The power conversion device according to claim 7, (Appendix 9) The first resistor and the second resistor have resistance values ​​in the range of 2 MΩ to 6 MΩ. 9. The power conversion device according to any one of claims 1 to 8, (Appendix 10) the abnormality determination circuit is configured by a comparator, The output of the comparator is configured to be input to the monitor circuit. 6. The power conversion device according to claim 5, (Appendix 11) The output of the comparator is configured to be used as a gate drive stop signal for a gate driver circuit that drives a semiconductor switching element of the main circuit. 11. The power conversion device according to claim 10, [Explanation of symbols]

[0063] 1 power conversion device, 2 main circuit, 3 voltage sensor, 4 abnormality determination circuit, 5a first resistor, 5b second resistor, 6a first gain resistor, 6b second gain resistor; 7 bias power supply; 8 single-supply operational amplifier; 8a, 9a: inverting input terminals, 8b, 9b: non-inverting input terminals, 8c output terminal, 8e, 9e power supply, 9 comparator, 10 reference power supply, 11 monitor circuit, 100 DC power supply, 200 load, 21p positive side DC line, 21n negative side DC line, 22u U phase AC line, 22v V-phase AC line, 22w W-phase AC line, Vth overvoltage threshold, Vref Reference voltage

Claims

1. a main circuit that performs power conversion; a voltage sensor that detects a voltage between a positive DC line and a negative DC line of the main circuit; an abnormality determination circuit that determines whether or not there is an abnormality in the main circuit based on the output of the voltage sensor; Equipped with A power conversion device configured so that, when the abnormality determination circuit determines an abnormality in the main circuit, an operating state of the main circuit is changed, the voltage sensor is configured by a differential amplifier, the differential amplifier has an inverting input terminal connected to one end of a first resistor having the other end connected to the positive DC line, a non-inverting input terminal connected to the other end of a second resistor having one end connected to the negative DC line, and a bias power supply connected to the non-inverting input terminal; insulation between the main circuit as an observation target system and the voltage sensor as an observation system is ensured based on at least the first resistor and the second resistor; an inverting input terminal of the differential amplifier is connected to the positive DC line via the first resistor, and a non-inverting input terminal of the differential amplifier is connected to the negative DC line via the second resistor, whereby an input gain resistor of the differential amplifier is composed of the first resistor and the second resistor. A power conversion device characterized by:

2. The main circuit is configured by a bridge circuit having a plurality of semiconductor switching elements.

2. The power conversion device according to claim 1.

3. When the abnormality determination circuit determines that an abnormality has occurred in the main circuit, the switching operation of the semiconductor switching element is stopped.

3. The power conversion device according to claim 2.

4. The abnormality determination circuit is configured by a differential amplifier.

4. The power conversion device according to claim 1, wherein the power conversion device comprises: a power converter;

5. a monitor circuit for monitoring the output voltage of the voltage sensor; 4. The power conversion device according to claim 1, wherein the power conversion device comprises: a power converter;

6. The voltage sensor a gain and an offset voltage are set so that an upper limit value of the output voltage of the voltage sensor is the upper limit value of a common-mode input voltage range of the voltage sensor, and a lower limit value of the output voltage of the voltage sensor is a voltage value higher than an overvoltage threshold value set in the abnormality determination circuit; 4. The power conversion device according to claim 1, wherein the power conversion device comprises: a power converter;

7. The power supply voltage of the voltage sensor is substantially 5 V. The upper limit of the output voltage of the voltage sensor is substantially 3.5 [V], The lower limit of the output voltage of the voltage sensor is substantially 1 [V].

4. The power conversion device according to claim 1, wherein the power conversion device comprises: a power converter;

8. The overvoltage threshold of the abnormality determination circuit is set to be substantially less than 1 [V].

8. The power conversion device according to claim 7.

9. The first resistor and the second resistor have resistance values ​​within a range of 2 MΩ to 6 MΩ.

4. The power conversion device according to claim 1, wherein the power conversion device comprises: a power converter;

10. the abnormality determination circuit is configured by a comparator, The output of the comparator is configured to be input to the monitor circuit.

6. The power conversion device according to claim 5.

11. The output of the comparator is configured to be used as a gate drive stop signal for a gate driver circuit that drives a semiconductor switching element of the main circuit. The power conversion device according to claim 10 .

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