Power conversion device

Abstract

In the power conversion device of the present invention, a temperature-sensing diode (Td) is provided near a U-phase lower arm semiconductor element (Tul). A gate control circuit (131) outputs an on-state signal to a conduction-side gate resistor (Rg1) in response to a drive signal inputted from a microcomputer (151), thereby conducting the U-phase lower arm semiconductor element (Tul). The switching characteristics of the U-phase lower arm semiconductor element (Tul) are determined by two gate resistors consisting of a conduction-side gate resistor (Rg1) and a disconnection-side gate resistor (Rg2). The resistance value of the gate resistor for determining the switching characteristics of the U-phase lower arm semiconductor element (Tul) whose temperature is detected by a temperature detection unit (14) is set to a value at which heat generation due to switching loss becomes greater than that of the gate resistor for determining the switching characteristics of other semiconductor elements whose temperature is not detected.

Description

Technical Field

[0001] The present invention relates to a power conversion device. Background Art

[0002] The power conversion device has a semiconductor element for converting DC power into AC power. As the semiconductor element, an IGBT (Insulated Gate Bipolar Transistor) or the like is used. The semiconductor element that switches high voltage and large current generates heat due to switching losses and the like. Therefore, a temperature detection element such as a temperature-sensing diode is provided near the semiconductor element to detect the temperature of the semiconductor element, and control is performed so that the semiconductor element does not exceed the allowable temperature. When driving a three-phase motor, for example, the power conversion device uses two semiconductor elements for each of the UV and W phases, for a total of six semiconductor elements, and multiple temperature detection units are also required for the semiconductor elements of each phase.

[0003] Patent Document 1 describes a power conversion device that includes a temperature-sensing diode for detecting the temperature of one IGBT and estimates the temperature of a semiconductor element whose temperature is not detected through calculation processing.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-186968 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] The device described in Patent Document 1 has a problem in that complicated calculation processing is required to estimate the temperature.

[0009] Technical solutions used to solve technical problems

[0010] The power conversion device of the present invention includes: a power conversion circuit unit, which has multiple semiconductor elements that convert DC power into multi-phase AC power; and a temperature detection unit, which is used to detect the temperature of the semiconductor element corresponding to any phase of the multi-phase AC power. The power conversion device drives the semiconductor element whose temperature is detected by the temperature detection unit so that the heat caused by the switching loss becomes larger than that of other semiconductor elements whose temperature is not detected.

[0011] Effects of the Invention

[0012] According to the present invention, the temperature detection unit is provided to the minimum required level, and complicated calculation processing for estimating the temperature is unnecessary. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a circuit diagram of a power conversion device.

[0014] Figure 2 1 is a circuit diagram showing a main portion of a drive circuit unit.

[0015] Figure 3 (A) Figure 3 (B) is a graph showing the relationship between motor current, temperature, and loss. DETAILED DESCRIPTION

[0016] [Implementation Method 1]

[0017] Figure 1 2 is a circuit diagram of the power conversion device 1 .

[0018] Power conversion device 1 is composed of a circuit with semiconductor elements for converting direct current into alternating current. Using battery 2 as a power source, power conversion device 1 switches the semiconductor elements on and off to ensure the desired current flows, thereby controlling the drive of motor 3. Furthermore, conversion between DC power and AC power is performed between battery 2 and motor 3. Battery 2 and power conversion device 1 are connected via relay 4. A higher-level control unit 5 is also connected to power conversion device 1.

[0019] The power conversion device 1 includes a power conversion circuit 10 for performing power conversion, a capacitor 11 for filtering DC current, a drive power supply 12, a drive circuit 13, a temperature detector 14, and a control unit 15. The control unit 15 is powered by an external power supply 6.

[0020] The power conversion circuit unit 10 includes upper and lower arm series circuits for the U, V, and W phases. The U-phase upper and lower arm series circuit comprises a U-phase upper arm semiconductor device Tuu and a U-phase upper arm diode Duu, and a U-phase lower arm semiconductor device Tui and a U-phase lower arm diode Dul. The V-phase upper and lower arm series circuit comprises a V-phase upper arm semiconductor device Tvu and a V-phase upper arm diode Dvu, and a V-phase lower arm semiconductor device Tvl and a V-phase lower arm diode Dvl. The W-phase upper and lower arm series circuit comprises a W-phase upper arm semiconductor device Twu and a W-phase upper arm diode Dwu, and a W-phase lower arm semiconductor device Twl and a W-phase lower arm diode Dwl.

[0021] The driving power supply unit 12 is connected to the positive bus bar P and the negative bus bar N for power supply, has a built-in DC-AC converter, a transformer, and an AC-DC converter, and outputs the power supply voltages Vuu, Vvu, Vwu, Vul, Vvl, and Vwl of the driving circuit for driving the semiconductor elements of each phase.

[0022] The drive circuit unit 13 includes a drive circuit Guu, which is supplied with a power supply voltage Vuu and controls the U-phase upper arm semiconductor element Tuu on / off; a drive circuit Gvu, which is supplied with a power supply voltage Vvu and controls the V-phase upper arm semiconductor element Tvu on / off; and a drive circuit Gwu, which is supplied with a power supply voltage Vwu and controls the W-phase upper arm semiconductor element Twu on / off. The drive circuit unit 13 also includes a drive circuit Gul, which is supplied with a power supply voltage Vul and controls the U-phase lower arm semiconductor element Tul on / off; a drive circuit Gvl, which is supplied with a power supply voltage Vvl and controls the V-phase lower arm semiconductor element Tvl on / off; and a drive circuit Gwl, which is supplied with a power supply voltage Vwl and controls the W-phase lower arm semiconductor element Twl on / off.

[0023] The temperature detection unit 14 includes a temperature detection circuit 141 that detects temperature using a temperature sensing diode Td. In this embodiment, the temperature sensing diode Td is disposed near the U-phase lower arm semiconductor element Tu1, while no temperature sensing diode is disposed near other semiconductor elements.

[0024] The control unit 15 includes a microcomputer 151. The current value supplied to the motor 3, detected by the current sensor 16, is input. In response to a command value from the host control unit 5, the microcomputer 15 outputs a drive signal to the drive circuits Guu to Gwl. Furthermore, the temperature detected by the temperature detection unit 14 is input to the control unit 15, which controls the semiconductor elements so that they do not exceed the allowable temperature.

[0025] Figure 2 1 is a circuit diagram showing a main portion of the drive circuit unit 13 .

[0026] like Figure 2 As shown, the temperature sensing diode Td is arranged near the U-phase lower arm semiconductor element Tu1. The temperature detection unit 14 includes a temperature detection circuit 141 that detects the temperature based on the temperature sensing diode Td, and the detected temperature is input to the microcomputer 151.

[0027] The microcomputer 151 outputs a drive signal to the drive circuit Gul. The drive circuit Gul includes the gate control circuit 131, an on-side gate resistor Rg1, an off-side gate resistor Rg2, and a gate-emitter capacitor Cge. Furthermore, the drive power supply unit 12 supplies a power supply voltage Vul as a driving power source to the gate control circuit 131 and the temperature detection circuit 141.

[0028] The gate control circuit 131 turns on the U-phase lower arm semiconductor element Tu1 by outputting an on signal to the on-side gate resistor Rg1 in response to a drive signal input from the microcomputer 151. The gate control circuit 131 outputs a zero potential to the off-side gate resistor Rg2.

[0029] exist Figure 2 Figure 1 shows the drive circuit Gul for driving the U-phase lower arm semiconductor element Tul. The drive circuits Guu, Gvu, and Gwl for the other phases have similar structures. However, in this embodiment, as described later, the resistance values of the on-side gate resistor Rg1 and the off-side gate resistor Rg2 of the drive circuit Gul differ from those of the drive circuits Guu, Gvu, and Gwl for the other phases. Furthermore, the capacitance of the capacitor Cge for each phase is the same.

[0030] The switching characteristics of the U-phase lower arm semiconductor element Tul are determined by two gate resistors, namely the on-side gate resistor Rg1 and the off-side gate resistor Rg2. When the resistance value of the gate resistor is increased, the switching loss of the U-phase lower arm semiconductor element Tul increases, but the peak value of the surge voltage generated by the switch decreases. Generally, the resistance value of the gate resistor is set so that the switching loss is minimized within the range where the surge voltage does not exceed the rated voltage of the semiconductor element. In this embodiment, the resistance value of the gate resistor for determining the switching characteristics of the U-phase lower arm semiconductor element Tul, whose temperature is detected by the temperature detection unit 14, is set to a value such that the heat generated by the switching loss becomes larger than the gate resistor for determining the switching characteristics of other semiconductor elements whose temperature is not detected. That is, the gate resistance of the U-phase lower arm semiconductor element Tul is increased so that its temperature is higher than that of the semiconductor elements of other phases, thereby intentionally creating a phase with increased switching loss and detecting the temperature of this phase.

[0031] The switching loss of the phase where temperature detection is performed is set in consideration of the variation in temperature detection so that the minimum temperature value of the phase where temperature detection is performed is greater than the maximum temperature value of the phase where temperature detection is not performed.

[0032] Temperature detection variation is primarily due to the cooling efficiency of the structure, the characteristics of the semiconductor elements, and the characteristics of the temperature detection circuit. Therefore, for example, a temperature variation of ±10% can increase switching losses in the phase performing temperature detection, causing a temperature rise of +20% or more.

[0033] Figure 3 (A) Figure 3 (B) is a graph showing the relationship between the motor current, temperature, and loss when this embodiment is applied.

[0034] Figure 3In (A), the horizontal axis shows the motor current, and the vertical axis shows the temperature. When the gate resistance of the U-phase lower arm semiconductor element T11 is increased to increase its temperature above that of the semiconductor elements in other phases, its temperature rises above that of other phases, such as the W phase. This temperature difference increases in proportion to the magnitude of the motor current.

[0035] Figure 3 In (B), the horizontal axis shows the motor current, and the vertical axis shows the loss. When the gate resistance of the U-phase lower arm semiconductor element Tul is increased to raise its temperature above that of the semiconductor elements in other phases, the loss increases compared to other phases, such as the W-phase. This loss difference increases in proportion to the magnitude of the motor current.

[0036] According to this embodiment, by detecting the temperature of the semiconductor element of a specific phase, overtemperature protection of semiconductor elements of other phases can be achieved at low cost while maintaining reliability.

[0037] [Implementation Method 2]

[0038] Next, embodiment 2 will be described. Figure 1 The circuit structure diagram of the power conversion device shown in FIG. Figure 2 The circuit structure diagram of the driving circuit and temperature detection part shown in the figure, Figure 3 The graphs of the temperature and loss of the U-phase and the V-phase shown are also the same in this embodiment.

[0039] In this embodiment, for Figure 2 In the illustrated gate-emitter capacitor Cge, the capacitance of capacitor Cge for the phase undergoing temperature detection is set larger than that of the other phases not undergoing temperature detection. Specifically, by increasing the capacitance of capacitor Cge, the temperature of the U-phase lower arm semiconductor element Tul is increased relative to the semiconductor elements of the other phases. This intentionally creates a phase with increased switching losses, and the temperature of that phase is then detected. Furthermore, the gate resistors of all phases have the same resistance value.

[0040] Taking into account the variation in temperature detection, the switching loss of the phase where temperature detection is performed is set so that the minimum temperature value of the phase where temperature detection is performed is greater than the maximum temperature value of the phase where temperature detection is not performed.

[0041] Temperature detection variation is primarily influenced by the cooling efficiency of the structure, the characteristics of the semiconductor device, and the characteristics of the temperature detection circuit. Therefore, for example, a temperature variation of ±10% increases switching losses in the phase performing temperature detection, causing the temperature to rise by more than +20%.

[0042] According to this embodiment, by detecting the temperature of the semiconductor element of a specific phase, overtemperature protection of semiconductor elements of other phases can be achieved at low cost while maintaining reliability.

[0043] [Implementation Method 3]

[0044] Next, embodiment 3 will be described. Figure 1 The circuit structure diagram of the power conversion device shown in FIG. Figure 2 The circuit structure diagram of the driving circuit and temperature detection part shown in the figure, Figure 3 The graphs of the temperature and loss of the U-phase and the V-phase shown are also the same in this embodiment.

[0045] In this embodiment, Figure 1 The power supply voltage Vul supplied to the drive circuit Gul by the drive power supply unit 12 is set to a lower voltage than the power supply voltages Vuu, Vvu, Vwu, Vvl, and Vwl supplied to the other drive circuits. This voltage reduction increases switching losses using the gate resistors consisting of the on-side gate resistor Rg1 and the off-side gate resistor Rg2. Specifically, by driving the drive circuit Gul at a low voltage, the temperature of the U-phase lower arm semiconductor element Tul is higher than that of the semiconductor elements of the other phases. This intentionally creates a phase with increased switching losses, and the temperature of that phase is then detected. Furthermore, the gate resistors and capacitors Cge are identical for each phase.

[0046] Taking into account the variation in temperature detection, the switching loss of the phase where temperature detection is performed is set so that the minimum temperature value of the phase where temperature detection is performed is greater than the maximum temperature value of the phase where temperature detection is not performed.

[0047] Temperature detection variation is primarily influenced by the cooling efficiency of the structure, the characteristics of the semiconductor device, and the characteristics of the temperature detection circuit. Therefore, for example, a temperature variation of ±10% increases switching losses in the phase performing temperature detection, causing the temperature to rise by more than +20%.

[0048] According to this embodiment, by detecting the temperature of the semiconductor element of a specific phase, overtemperature protection of semiconductor elements of other phases can be achieved at low cost while maintaining reliability.

[0049] According to the embodiment described above, the following effects can be obtained.

[0050] (1) A power conversion device 1 includes a power conversion circuit unit 10 having a plurality of semiconductor elements for converting DC power into multi-phase AC power; and a temperature detection unit 14 for detecting the temperature of the semiconductor element corresponding to any one phase of the multi-phase AC power. The power conversion device 1 drives the semiconductor element whose temperature is detected by the temperature detection unit 14 so that the heat generated by the semiconductor element due to switching loss is greater than that of the other semiconductor elements whose temperature is not detected. Thus, the temperature detection unit is provided to the minimum required level, and complex calculation processing for estimating the temperature is not required.

[0051] (Variation)

[0052] The present invention can be implemented by modifying the above-described first to third embodiments as follows.

[0053] (1) In each embodiment, the example of detecting the temperature of a specific phase is described, but the temperature of a plurality of specific phases may be detected. In this case, control is performed based on the higher temperature of the detected temperatures so as not to exceed the allowable temperature.

[0054] (2) The power conversion circuit portion of each embodiment has been described as being applied to three phases, ie, UV and W phases. However, the power conversion circuit portion is not limited to three phases and can be applied to multiple phases.

[0055] The present invention is not limited to the above-described embodiment, and other embodiments that can be considered within the scope of the technical concept of the present invention are also included in the scope of the present invention as long as the characteristics of the present invention are not impaired. In addition, a structure combining the above-described embodiment and multiple modified examples is also possible.

[0056] Description of labels

[0057] 1 Power conversion device

[0058] 2 Batteries

[0059] 3. Electric Motor

[0060] 4 relays

[0061] 5. Upper control unit

[0062] 6 External power supply

[0063] 10 Power conversion circuit

[0064] 11 Capacitor

[0065] 12. Drive power supply unit

[0066] 13. Drive circuit unit

[0067] 14 Temperature detection unit

[0068] 15 Control Unit

[0069] 16 Current sensor

[0070] 131 Gate Control Circuit

[0071] 141 Temperature Detection Circuit

[0072] 151 Microcomputer

[0073] Tuu U-phase upper arm semiconductor device

[0074] Tu1 U-phase lower arm semiconductor element

[0075] Tvu V phase upper arm semiconductor device

[0076] Tv1 V-phase lower arm semiconductor device

[0077] Twu W-phase upper arm semiconductor device

[0078] Tw1 W-phase lower arm semiconductor device

[0079] Duu U-phase upper arm diode

[0080] Du1 U-phase lower arm diode

[0081] Dvu V phase upper arm diode

[0082] Dv1 V-phase lower arm diode

[0083] Dwu W phase upper arm diode

[0084] Dw1 W phase lower arm diode

[0085] Cge gate-emitter capacitor

[0086] Td temperature sensing diode

[0087] Rg1 On-side gate resistance

[0088] Rg2 Off-side gate resistor

[0089] Guu, Gvu, Gwu, Gul, Gvl, Gwl drive circuits.

Claims

1. A power conversion device, characterized in that: include: a power conversion circuit portion having a plurality of semiconductor elements for converting DC power into multi-phase AC power; as well as a temperature detection unit for detecting a temperature of the semiconductor element corresponding to any one phase of the multi-phase AC power; The semiconductor element whose temperature is detected by the temperature detection unit is driven so that the heat generated by the switching loss becomes larger than that of the other semiconductor elements whose temperature is not detected. Furthermore, a minimum temperature value of the semiconductor element whose temperature is detected by the temperature detection unit is greater than a maximum temperature value of the other semiconductor elements whose temperature is not detected.

2. The power conversion device according to claim 1, wherein: The gate resistor for determining switching characteristics of the semiconductor element whose temperature is detected by the temperature detection unit is set to a value that increases heat generation due to switching loss compared to the gate resistor for determining switching characteristics of the other semiconductor elements whose temperature is not detected.

3. The power conversion device according to claim 1, wherein: The gate-emitter capacitance of the semiconductor element whose temperature is detected by the temperature detection unit is set to a value that increases switching loss compared to the gate-emitter capacitance of the other semiconductor elements whose temperature is not detected.

4. The power conversion device according to claim 1, wherein: A driving voltage of a driving circuit of the semiconductor element whose temperature is detected by the temperature detection unit is set to a value lower than a driving voltage of a driving circuit of another semiconductor element whose temperature is not detected.

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