JP2013192418A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device including a switching element that can immediately determine whether the switching element generating an overcurrent causes a short-circuit defect.SOLUTION: A power conversion device 5 uses a transistor 6 with a sensing function. A driver circuit 8 driving the transistor 6 is configured by a resistor 35, a first comparator 33, a second comparator 34, an AND circuit 32, and a driver IC 31. The resistor 35 has one end connected to a sense emitter E2 and the other end connected to the ground. The first comparator 33 compares a voltage of the sense emitter E2 with a first voltage Va. The second comparator 34 compares the voltage of the sense emitter E2 and a second voltage lower than the first voltage. The driver IC 31 outputs a signal indicating that the transistor 6 is short-circuited if an output of the second comparator 34 is High potential while applying Low potential to a gate of the transistor 6.

Description

  The technology disclosed in the present specification relates to a power conversion device including a switching element. In particular, the present invention relates to a power conversion device having a function of detecting a short-circuit failure of a switching element.

  A power conversion device such as a voltage converter or an inverter includes a transistor called a power element as a switching element. In electric vehicles including hybrid vehicles, the rated output of the motor is several tens of kilowatts, so the load on the switching element is also large. Therefore, the switching element may be broken. It is desirable to cope with a failure of the switching element promptly and to continue running with only a healthy switching element if possible. It is also desirable to avoid secondary failure of other elements / devices due to switching element failure. For example, in Patent Document 1, in an electric vehicle in which a plurality of motors are connected to a common output shaft, when an abnormality occurs in one motor, driving of the motor that has failed when the other motor is used to continue traveling is described. Techniques for protecting circuit elements are disclosed.

  Further, in order to continue traveling with only sound switching elements, it is necessary to identify which element has failed at an early stage. For example, Patent Document 2 discloses a technology that employs an IGBT with a sense function including a sense emitter as a switching element and detects the occurrence of a crack in the switching element. The IGBT with sense function is an IGBT in which a part (small part) of the emitter electrode in the element is divided. The small part is called a sense emitter. The remaining large portion may be referred to as a main emitter. The sense function means a function of diagnosing an IGBT (transistor) using a main emitter as a normal emitter electrode and utilizing a small current flowing through the sense emitter. The technique of Patent Document 2 measures the current flowing through the sense emitter, and determines that a crack has occurred if the magnitude of the current is outside a predetermined allowable range.

JP 2009-195026 A JP 2007-040817 A

  There are two types of failure of transistors used as switching elements: short-circuit failure and open failure. An open fault has little influence on other elements because current does not flow, but a short-circuit fault has a large influence on other elements because current continues to flow. The technology disclosed in this specification provides a power conversion device that can detect an overcurrent and quickly determine whether or not a transistor that has generated an overcurrent is a short-circuit fault.

  The technology disclosed in this specification also employs a transistor with a sense function including a sense emitter. Such a transistor is typically an IGBT. Usually, the power converter includes a driver (driver IC) that sends a PWM signal to the gate of the transistor as a set together with the transistor (IGBT). One driver is provided for each transistor. A power converter disclosed in the present specification includes a resistor having one end connected to a sense emitter and the other end connected to a ground, and a first comparator that compares the voltage of the sense emitter with a predetermined first voltage. And a second comparator for comparing the voltage of the sense emitter with a predetermined second voltage lower than the first voltage. When the driver outputs the signal indicating that the output of the second comparator is higher in voltage of the sense emitter than the second voltage while the low potential is applied to the gate of the transistor, the transistor Is configured to output a signal indicating that is short-circuited. Note that a driver (driver IC) for driving a transistor is a digital element, and “Low potential” and “High potential” mean binary signals in the digital circuit. In the following description, a circuit including the driver, the first and second comparators, and the resistor configured as described above may be referred to as a “short circuit detection circuit”.

  The above-described resistor is a so-called shunt resistor, and is provided for measuring the magnitude of the current flowing through the sense emitter as the magnitude of the voltage. That is, the voltage on the high potential side of the shunt resistor changes according to the change in the magnitude of the current flowing through the sense emitter. The voltage on the high potential side of the shunt resistor is referred to as “sense emitter voltage”. That is, the sense emitter voltage is used as a criterion for failure determination. The first comparator is provided for detecting an overcurrent. The first comparator compares the sense emitter voltage with a predetermined first voltage. Specifically, the sense emitter is connected to the non-inverting input of the first comparator, and the first voltage is applied to the inverting input. The first voltage is determined based on whether or not it is an overcurrent. When the output of the first comparator is at a high potential, that is, when the sense emitter voltage is higher than the first voltage, the driver Outputs a signal indicating that is in an overcurrent state.

  A sense emitter is connected to the non-inverting input of the second comparator, and a second voltage is applied to the inverting input. When the driver detects that the transistor (switching element) is overcurrent, the driver sets a command to be applied to the gate of the transistor to the low potential and monitors the output of the second comparator. If the command given to the gate of the transistor is a low potential but the output of the second comparator is high, that is, if the voltage of the sense emitter is higher than the second voltage, the driver will short-circuit the transistor. A signal indicating that there is a failure is output. When an overcurrent is detected, the driver immediately determines whether or not the IGBT is a short circuit failure.

  An example of a hardware configuration for determining a short-circuit fault is as follows. The driver includes another specific output terminal, and the short-circuit fault detection circuit further includes an AND circuit that inputs the output of the second comparator and the specific output of the driver. Then, when the output of the first comparator becomes a high potential and an overcurrent is detected, the driver sets a command to be applied to the gate of the transistor to the low potential and sets the high potential to the specific output. In this state, if the output of the AND circuit is a high potential, the driver outputs a signal indicating that the transistor is short-circuited. A signal indicating that an overcurrent has flowed through the transistor and a signal indicating that the transistor is short-circuited are transmitted to a host controller, for example. For example, the host controller executes emergency control for driving the motor while protecting circuits around the transistor in which the short circuit failure has occurred. Alternatively, a signal (data) indicating that an overcurrent has flowed through the transistor and a signal (data) indicating that the transistor is short-circuited are recorded in the nonvolatile memory and used for subsequent maintenance.

  Details of the technology disclosed in this specification and further improvements will be described in the embodiments of the present invention.

1 is a block diagram of a hybrid vehicle including a power conversion device according to an embodiment. It is a circuit diagram of a driver circuit (short circuit detection circuit).

  A power converter according to an embodiment will be described with reference to the drawings. The power conversion device according to the embodiment is a device that is mounted on a hybrid vehicle and converts the battery power into AC after boosting the power of the battery. FIG. 1 shows a block diagram of a hybrid vehicle 2 including a power conversion device 5. The hybrid vehicle 2 includes a motor 93 and an engine 91 as a driving source for traveling. The output torque of the motor 93 and the output torque of the engine 91 are appropriately distributed / combined by the power distribution mechanism 92 and transmitted to the axle 94 (that is, the wheel). It should be noted that FIG. 1 shows only parts necessary for the description of the technology disclosed in this specification, and some parts not related to the description are not shown.

  Electric power for driving the motor 93 is supplied from the main battery 3. The output voltage of the main battery 3 is, for example, 300 volts. The main battery 3 is connected to the power conversion device 5 via the system main relay 4. The system main relay 4 is a switch for connecting or disconnecting the main battery 3 and the drive system of the vehicle. The system main relay 4 is switched by the host controller 25.

  The power converter 5 includes a voltage converter circuit 21 that boosts the voltage of the main battery 3 to a voltage suitable for driving the motor 93 (for example, 600 volts), and an inverter circuit 22 that converts the boosted DC power into AC. In addition, although illustration is abbreviate | omitted, the power converter device 5 is the voltage (for example, 12 volts) suitable for the drive of the auxiliary machine (electric device driven with low voltage, such as a car navigation system and a room lamp), with the electric power of the main battery 3 It also includes a step-down converter that steps down the voltage.

  The hybrid vehicle 2 can also generate electric power with the motor 93 using the driving force of the engine 91 or the deceleration energy of the vehicle. When the motor 93 generates power, the inverter circuit 22 converts alternating current into direct current, and the voltage converter circuit 21 steps down to a voltage slightly higher than that of the main battery 3 and supplies it to the main battery 3.

  The voltage converter circuit 21 is a circuit mainly including a filter capacitor 12, a reactor 13, two switching elements 6a and 6b, and driver circuits 8a and 8b for driving these switching elements. The switching elements 6a and 6b are transistors and are typically IGBTs. In addition, although description is abbreviate | omitted, the diode is connected to each switching element in antiparallel. This diode is sometimes called a freewheeling diode. Since the above-described configuration of the voltage converter circuit and the mechanism of voltage conversion are well known, description thereof will be omitted. The driver circuits 8a and 8b receive a PWM signal from the controller (power controller 23) of the power conversion device 5 and supply it to the gate of the switching element, a function of detecting an overcurrent of the switching element, and a short circuit It has a function to detect a failure. The driver circuits 8a and 8b will be described in detail later.

  The inverter circuit 22 is a circuit mainly including six switching elements 6c-6h that repeat switching in order to generate alternating currents of U, V, and W phases of the motor 93. Similar to the switching elements 6a and 6c of the voltage converter circuit 21, the switching elements 6c-6h are also transistors, and are typically IGBTs. The driver circuit 8c-8h is also connected to each of the switching elements 6c-6h. The driver circuit 8c-8h also has a function of receiving a PWM signal from the power controller 23 and supplying it to the gate of the switching element, a function of detecting an overcurrent of the switching element, and a function of detecting a short-circuit fault. ing. In addition, a diode is connected in antiparallel to each of the switching elements 6c-6h.

  A smoothing capacitor 14 is connected in parallel to the high voltage side (that is, the inverter circuit side) of the voltage converter circuit 21. The smoothing capacitor 14 is inserted to smooth the current input to the inverter circuit 22. The high-potential side of the voltage converter circuit 21 and the high-potential side of the inverter circuit 22 are referred to as P lines. On the other hand, the electric wires on the low potential side of the voltage converter circuit 21 and the inverter circuit 22 are called N lines. The N line is connected to the ground Gnd.

  The power controller 23 receives a motor target output command from a higher-level controller 25 and transmits an abnormality of the power conversion device 5 to the higher-level controller 25. Further, the power controller 23 records operation history data including abnormality of the power converter 5 in the nonvolatile memory 24. The nonvolatile memory 24 is referred to by the service staff during vehicle maintenance and is used as a reference for maintenance. Data recorded in the nonvolatile memory 24 may be called diagnostic data (diagnosis data).

  Next, the driver circuit will be described in detail. As illustrated in FIG. 1, the power conversion device 5 includes a plurality of switching elements 6 a-6 h and driver circuits 8 a-8 h corresponding to the respective switching elements. Hereinafter, one switching element and a driver circuit are represented by reference numerals 6 and 8, respectively. Although not shown, the power conversion device 5 includes a step-down converter that steps down the voltage of the main battery 3 as described above, and a switching element and a driver circuit are also provided in the step-down converter. Yes.

  FIG. 2 shows a circuit diagram of the switching element 6 and the driver circuit 8. The switching element 6 is an IGBT with a sense function including a sense emitter E2 in addition to the main emitter E1. In the switching element 6, a part of the emitter electrode is divided from the other most part, and a small part of the emitter electrode corresponds to the sense emitter E2. The remaining most of the emitter electrode corresponds to the main emitter E1. When a predetermined voltage is applied to the gate G, most of the current flows from the collector C through the main emitter E1, while a small amount of current flows from the collector C through the sense emitter E2. The freewheeling diode 9 is connected between the main emitter E1 and the collector C. The collector C, the gate G, and the main emitter E1 function as normal switching elements, and the sense emitter E2 is used for failure diagnosis of the switching element 6.

  The driver circuit 8 includes a driver IC 31, two comparators 33 and 34 (comparators), a shunt resistor 35, and one AND circuit 32 (logical product circuit). The driver circuit 8 has a function of receiving a PWM signal from the power controller 23 and supplying it to the gate G of the switching element 6, a function of detecting an overcurrent of the switching element 6, and a function of detecting a short-circuit fault. Have. The function of supplying the PWM signal to the gate G of the switching element 6 is a function generally possessed by a normal driver IC.

  The driver IC 31 has four input terminals q1, q2, q3, and q4 and four output terminals p1, p2, p3, and p4. The driver IC 31 includes an input terminal and an output terminal in addition to that, but is not shown. The input terminal q3 is a terminal that receives a PWM signal from the power controller 23. Upon receiving the PWM signal, the driver IC 31 outputs the PWM signal from the output terminal p1. The PWM signal is supplied to the gate G of the switching element 6. The input terminal q4 is an inhibit terminal that stops the supply of the PWM signal. While the voltage at the terminal q4 is low, the driver IC 31 stops supplying the PWM signal from the output terminal p1 even if it receives the PWM signal at the input terminal q3. When any abnormality is detected in the system of the hybrid vehicle 2, the power controller 23 lowers the potential of the input terminal q4 of the driver IC 31 to the Low potential and stops the switching operation.

  A shunt resistor 35 is connected to the sense emitter E2 of the switching element 6. The other end of the shunt resistor 35 is connected to the ground Gnd. As is well known, the shunt resistor 35 is used when detecting the magnitude of the current as the magnitude of the voltage. Specifically, the shunt resistor 35 is a resistor whose small resistance value is precisely determined, and realizes a voltage on the high potential side that is exactly proportional to the magnitude of the current flowing through the sense emitter E2. The voltage at the connection point of the sense emitter E2 and the shunt resistor 35 is referred to as “the voltage of the sense emitter E2.”

  A mechanism of overcurrent detection in the driver circuit 8 will be described. The first comparator 33 is mainly responsible for overcurrent detection. The sense emitter E2 is connected to the non-inverting input of the first comparator 33. The first voltage Va is applied to the inverting input of the first comparator 33. The first voltage Va is set to the same value as the sense emitter voltage when an allowable limit current flows between the collector C of the switching element 6 and the main emitter E1. That is, while the current flowing between the collector C of the switching element 6 and the main emitter E1 is smaller than the allowable limit, the voltage of the sense emitter E2 is smaller than the first voltage Va, and the output of the first comparator 33 is the low potential. Become. When an overcurrent flows between the collector C of the switching element 6 and the main emitter E1, the voltage of the sense emitter E2 becomes higher than the first voltage Va, and as a result, the output of the first comparator 33 becomes a high potential. The output of the second comparator 33 is connected to the input terminal q2 of the driver IC. When the potential of the input terminal q2 becomes High, the driver IC sends a signal indicating that an overcurrent flows through the switching element 6 to the power controller 23 through the output terminal p3. The power controller 23 sends information indicating that an overcurrent is flowing through the switching element 6 to the higher-order controller 25 and records data indicating that fact in the nonvolatile memory 24.

  Next, the mechanism of short circuit detection in the driver circuit 8 will be described. The sense emitter E2 is also connected to the non-inverting input of the second comparator 34. The second voltage Vb is applied to the inverting input of the second comparator 34. The second voltage Vb is set to a value smaller than the first voltage Va for detecting overcurrent. The second voltage Vb is set to a value corresponding to the current flowing between the collector C and the sense emitter E2 when the switching element 6 is short-circuited. When the gate G of the switching element 6 is at a low potential (that is, when the switching element is in the OFF state), if the switching element 6 is short-circuited, a predetermined current flows through the collector C and the main emitter E1. The second voltage Vb is set to the same value as the sense emitter voltage corresponding to the predetermined current. That is, when the switching element 6 has a short circuit failure, the sense emitter voltage becomes larger than the second voltage Vb even if the voltage applied to the gate G is the low potential, and as a result, the output of the second comparator 34 Becomes a high potential. The output of the second comparator 34 is connected to one input of the AND circuit 32. The output terminal p2 of the driver IC 31 is connected to the other input of the AND circuit 32. The output terminal p2 of the driver IC 31 is normally set to a low potential. On the other hand, when the switching element 6 is in the ON state, a current also flows through the sense emitter E2, and the output of the second comparator 34 becomes High. However, as long as one input of the AND circuit 32 is at the low potential, the output of the AND circuit 32 is always low. The output of the AND circuit 32 is connected to the input terminal q1 of the driver IC 31.

  When the driver IC 31 detects an overcurrent by the first comparator 33, the driver IC 31 sets the output terminal p1 to the low potential. That is, a low potential is commanded to the gate G of the switching element 6. At the same time, the driver IC 31 switches the potential of the output terminal p2 from the low potential to the high potential. The output terminal p2 is connected to one input of the AND circuit 32. When one input terminal of the AND circuit 32 becomes a High potential, the output of the second comparator 34 is directly transmitted to the input terminal q1 of the driver IC 31. A low potential is applied to the gate G of the switching element 6. If the switching element 6 is normal, no current flows through the sense emitter E 2, and the output of the second comparator 34 becomes a low potential. The input terminal q1 is also at a low potential. On the other hand, if the switching element 6 is short-circuited, even if the potential of the gate G is low, a current flows between the collector C and the sense emitter E2, the output of the second comparator 34 becomes a high potential, and the AND circuit 32. Through this, the input terminal q1 becomes a high potential. That is, when the driver IC 31 detects an overcurrent, the driver IC 31 sets a command to be given to the gate G of the switching element 6 to the low potential, sets the high potential to the output terminal p2, and sets the output of the AND circuit 32 to the high potential. In addition, a short circuit failure of the switching element 6 is detected. When the potential of the input terminal q1 becomes High, the driver IC 31 sends a signal indicating that the switching element 6 is short-circuited to the power controller 23 through the output terminal p4. The power controller 23 sends to the higher-order controller 25 that the switching element has a short circuit failure, and records data indicating the short circuit failure in the nonvolatile memory 24. When the driver IC 31 sets the command to be given to the gate G of the switching element 6 to the Low potential and sets the High potential to the output terminal p2, the switching element 6 is short-circuited if the output of the AND circuit 32 is the Low potential. A signal indicating that no failure has occurred is sent to the power controller 23. The power controller 23 knows that an overcurrent has flowed through the switching element 6 but no short-circuit failure has occurred.

  As described above, when the driver circuit 8 detects an overcurrent of the switching element 6, it immediately checks whether or not the switching element has a short-circuit fault. The driver circuit 8 can be restated as a short circuit detection circuit. The driver circuit 8 outputs to the power controller 23 whether an overcurrent has passed through the switching element 6 and whether or not the switching element 6 has a short circuit fault. As described above, the power conversion device 5 includes a plurality of switching elements, and a driver circuit (that is, a short circuit detection circuit) is provided for each switching element. The power controller 23 receives signals from a plurality of driver circuits (short circuit detection circuits) and can grasp which switching element has a short circuit failure. The power controller 23 transmits data indicating that when any of the switching elements has a short-circuit fault to the host controller 25. The host controller 25 requests an abnormality check from the controller that controls the main battery 3 and other controllers. When a short circuit failure occurs in the switching element, the host controller 25 performs a system check of the hybrid vehicle and checks whether there is any other failure portion. The host controller 25 checks the presence or absence of a failure location, and then shifts to such emergency travel control when it is possible to continue travel using only other switching elements without using the short-circuit faulty switching element. At the same time, information indicating that is displayed on the console of the driver's seat. For example, when the switching element having a short circuit failure is an element of the inverter circuit 22, the host controller 25 drives the motor with two phases composed of healthy switching elements among the three UVW phases.

  Alternatively, if the host controller 25 checks the presence or absence of a failure location and determines that it cannot continue traveling without using a short-circuited switching element, it stops the drive system and simultaneously indicates that fact. Display information on the driver's console.

  When the overcurrent flows through the switching element, the power conversion device 5 immediately checks whether the switching element has a short-circuit fault. The power conversion device 5 can quickly identify the switching element that has a short circuit failure. The short circuit detection circuit mainly includes a driver IC 31, a second comparator 34, and an AND circuit 32. Since the short-circuit detection circuit is configured by hardware, it is possible to check whether a short-circuit failure has occurred promptly and reliably after overcurrent detection. In other words, the technology disclosed in this specification can configure a short circuit failure with a simple hardware circuit, so that the possibility that the detection circuit itself will fail is small, and the short circuit failure can be detected reliably.

  In the embodiment, the example in which the power conversion device 5 with the short-circuit detection function is applied to the hybrid vehicle has been described. The technology disclosed in this specification is not limited to a hybrid vehicle, and it is also suitable to apply to an electric vehicle not equipped with an engine or a fuel cell vehicle.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

2: Hybrid vehicle 3: Main battery 4: System main relay 5: Power converter 6a-6h: Switching element (transistor)
8a-8h: Driver circuit 9: Freewheeling diode 12: Filter capacitor 13: Reactor 14: Smoothing capacitor 21: Voltage converter circuit 22: Inverter circuit 23: Power controller 24: Non-volatile memory 25: Host controller 31: Driver IC
32: AND circuit (logical product circuit)
33: first comparator 34: second comparator 35: shunt resistor 91: engine 92: power distribution mechanism 93: motor 94: axle C: collector E1: main emitter E2: sense emitter G: gate Gnd: ground

Claims (5)

A power conversion device with a short circuit fault detection function of a switching element,
A transistor with a sense function including a sense emitter is used as the switching element,
A resistor having one end connected to the sense emitter and the other end connected to ground;
A first comparator for comparing the voltage of the sense emitter with a predetermined first voltage;
A second comparator for comparing the voltage of the sense emitter with a predetermined second voltage lower than the first voltage;
The transistor is short-circuited when the output of the second comparator outputs a signal indicating that the sense emitter voltage is higher than the second voltage while the low potential is applied to the gate of the transistor. A driver that outputs a signal indicating
A power conversion device comprising: The first comparator has a sense emitter connected to the non-inverting input, and a first voltage applied to the inverting input,
The second comparator has a sense emitter connected to the non-inverting input and a second voltage applied to the inverting input.
The power converter according to claim 1, wherein the driver outputs a signal indicating that the transistor is short-circuited when an output of the second comparator is a high potential.   The power converter according to claim 2, wherein the driver outputs a signal indicating that an overcurrent flows through the transistor when the output of the first comparator is a high potential.   When the output of the first comparator is a high potential, the driver sets a command to be given to the gate of the transistor to a low potential and monitors the output of the second comparator, and when the output of the second comparator is a high potential, the driver The power converter according to claim 2 or 3, wherein a signal indicating that the transistor is short-circuited is output. An AND circuit that receives the output of the second comparator and the specific output of the driver as inputs;
When an overcurrent is detected, the driver sets a command to be supplied to the gate of the transistor to a low potential, sets a high potential to a specific output, and shorts the transistor when the output of the AND circuit is a high potential. The power conversion device according to claim 4, wherein a signal indicating that the power is being output is output.

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