Current detection device for power devices and power conversion device

Abstract

To provide a current detection device and a power conversion device that accurately estimate the main current flowing from the sense current to a power device.SOLUTION: A current detection device 50 for a power conversion device 20 comprises: a sense element temperature estimation unit 64 that estimates the sense element temperature, which is the temperature of a sense element 42 of a power device, based on the output of a temperature-sensitive element 44; a reference temperature acquisition unit 53 that obtains the reference temperature of the power device; a main element temperature estimation unit 62 that estimates the main element temperature, which is the temperature of a main element 43, based on the sense element temperature and the reference temperature; and a main current estimation unit 63 that estimates the main current value flowing through the main element based on the sense current value detected by the sense element, the sense element temperature, and the main element temperature. The main element temperature estimation unit estimates the main element temperature using a thermal impedance ratio, which is the ratio of the mutual thermal impedance of the sense element to the self-thermal impedance of the main element with respect to heat generation of the main element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current detection device for a power device and a power conversion device. [Background technology]

[0002] With the aim of realizing a carbon-free society and taking measures to combat air pollution caused by exhaust gases, efforts to electrify automobiles are attracting attention. Interior permanent magnet synchronous motors, which have permanent magnets embedded in the rotor, are used in the motors used to rotate the drive wheels of electric and hybrid vehicles because they are small and can generate high torque. Highly efficient and precise torque control is required in automobiles from the perspective of ride comfort and quietness inside the vehicle, and vector control is commonly used as a motor control method for this purpose.

[0003] Vector control calculates a current command from the torque command generated by the accelerator or brake command and the speed, and generates a PWM signal based on this current command to drive the inverter's power device. At this time, the PWM signal is calculated using the measured inverter output current and controls the actual current so that it follows the command value. For this reason, a current sensor is required to measure the inverter output current.

[0004] A commonly used measurement method is to install a Hall element type current sensor at the inverter output and convert the magnetic field generated by the current into a voltage for detection.

[0005] Another measurement method is to provide a sense element dedicated to current detection on the same chip as a power semiconductor element such as an IGBT or MOSFET that constitutes a power device, and estimate the current (main current) flowing through the power semiconductor element (hereinafter referred to as the main element) by detecting the current (sense current) flowing through the sense element. Such a power conversion circuit is disclosed, for example, in Patent Document 1. Patent Document 1 describes a method for estimating current with high accuracy by correcting the deviation in the sense ratio due to the temperature difference between the main element and the sense element, taking into account that the temperature inside the chip becomes uneven due to self-heating of the power semiconductor element when current is applied.

[0006] Patent Document 2 describes a method of using the temperature characteristics of the body resistance of a power semiconductor as a temperature-sensitive element. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-97435 [Patent Document 2] Patent Publication No. 2021-35232 Summary of the Invention [Problem to be solved by the invention]

[0008] In Patent Document 1, in order to estimate the temperature difference ΔT between the main element and the sense element due to heat generation during operation, the loss Q of the main element and the heat transfer impedance Z from the heat source (loss of the main element) to the main element are used. M and the heat transfer impedance Z from the heat source to the sense element S is acquired in advance and stored in memory. At this time, the temperature difference ΔT between the main element and the sense element can be calculated from equation (1) in the frequency domain s.

[0009]

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[0010] Patent Document 1 further describes the sense ratio M, which is calculated by correcting the deviation based on the temperature difference ΔT between the main element and the sense element according to equations (2) and (3). real It is described that the main current is estimated from the sense current by calculating the above equation (4).

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[0014] In these equations, ΔT is the main element temperature T M and the temperature of the sense element T S temperature difference, M real is the sense ratio corrected for deviation due to temperature difference ΔT, and M0 is the main element temperature T M = temperature of the sensing element T S The sense ratio measured in advance in the environment, I M_E is the estimated main current, I S is the sense current.

[0015] However, the method of Patent Document 1 has the following two issues with the measurement of loss Q obtained in advance. The first is a deterioration in the accuracy of estimating the main current due to loss measurement errors. Measurement of switching loss, which occurs during switching, is particularly susceptible to individual differences in current and voltage probes, as well as magnetic noise generated by current changes, and can contain large errors. The impact of loss errors is reduced in the process of converting them into the main current using equations (1) to (4), so no significant errors in estimating the main current occur (in one example, the main current estimation error relative to switching loss measurement errors is estimated to be less than 1%). However, in vehicles, highly accurate torque control is required from the perspective of ride comfort, so current errors of less than 1% may not be negligible in some cases.

[0016] The second issue is the increased development man-hours required to acquire loss data. Because loss data varies depending on factors such as temperature, voltage, current, and gate drive conditions, it is necessary to acquire a wide range of loss table data under the various expected operating conditions when the product is used and store it in memory, which increases the man-hours required for evaluation and implementation in a microcontroller.

[0017] Furthermore, if it becomes necessary to change the operating conditions (for example, gate drive conditions) outside the range of the table data during development or after commercialization, additional man-hours will be required to perform additional loss data evaluations, implementation, and verification of current estimation accuracy, which may increase the development period and make it difficult to flexibly change the operating conditions.

[0018] In view of the above, the present invention aims to provide a current detection device for a power device that can improve the problems associated with obtaining the loss data described above and accurately estimate the main current flowing through the power device from the sense current. [Means for solving the problem]

[0019] In view of the above, the present invention provides a current detection circuit for a power device equipped with a power semiconductor having a main element, a sense element for detecting current, and a temperature-sensitive element for detecting temperature, the current detection circuit comprising: a sense element temperature estimation unit that estimates the sense element temperature, which is the temperature of the sense element, based on the output of the temperature-sensitive element; a reference temperature acquisition unit that acquires a reference temperature of the power device; a main element temperature estimation unit that estimates the main element temperature, which is the temperature of the main element, based on the sense element temperature and the reference temperature; and a main current estimation unit that estimates the main current value flowing through the main element based on the sense current value detected by the sense element, the sense element temperature, and the main element temperature, the main element temperature being characterized in that the main element temperature estimation unit estimates the main element temperature using a thermal impedance ratio, which is the ratio between the mutual thermal impedance of the sense elements with respect to the heat generation of the main element and the self-thermal impedance of the main element.

[0020] The present invention is also described as "a power conversion apparatus comprising a power device equipped with a power semiconductor having a main element, a sense element for detecting current, and a thermosensitive element for detecting temperature, and a control circuit for driving the gate of the power device, wherein the control circuit generates a gate signal for the power device in accordance with a main current estimated value estimated by a current detection device for the power device, and drives the gate of the power device." [Effects of the Invention]

[0021] According to the present invention, the main current flowing through the power device can be accurately estimated from the sense current.

[0022] Furthermore, according to the embodiments of the present invention, the number of product development steps required to acquire loss data can be reduced, shortening the development period and enabling flexible design changes to suit the conditions of use. The principles and effects of the invention will be described in detail below in the explanation of the embodiments. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing an example of the overall configuration of a power conversion device that employs a current detection device for a power semiconductor element according to a first embodiment of the present invention; [Figure 2] FIG. 1 is a diagram showing an example of the cross-sectional structure of a double-sided cooling type power device. [Figure 3a] FIG. 2 is a diagram showing an example of a power semiconductor plane. [Figure 3b] A diagram showing a cross section of a power device and its thermal equivalent circuit. [Figure 4] This diagram summarizes the heat equivalent circuit of Figure 3b with the direction of heat flow added. [Figure 5a] FIG. 10 is a diagram showing the relationship between the main current and the sense element temperature TS over time. [Figure 5b] FIG. 10 is a graph showing the relationship between the sense element temperature TS and the sense ratio Mreal. [Figure 6] 10A and 10B are diagrams showing alternative examples of the setting position and method of the reference temperature point 120. [Figure 7]10A and 10B are diagrams showing alternative examples of the setting position and method of the reference temperature point 120. [Figure 8] 10A and 10B are diagrams showing alternative examples of the setting position and method of the reference temperature point 120. [Figure 9] 10A and 10B are diagrams showing alternative examples of the setting position and method of the reference temperature point 120. [Figure 10] FIG. 10 is a diagram showing an example of the overall configuration of a power conversion device employing a current detection device for a power semiconductor element according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a diagram showing an example of the overall configuration of a power conversion device employing a current detection device for a power semiconductor element according to a third embodiment of the present invention. [Figure 12] FIG. 1 is a diagram showing an example of a system configuration of a hybrid vehicle. [Figure 13] FIG. 2 is a diagram showing a circuit configuration of a power conversion device 20 in the system. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] Before proceeding to the description of the embodiments, examples of application of a power conversion device to which the present invention is preferably applied and examples of the configuration of the power conversion device will be described with reference to the drawings.

[0026] The power semiconductor current detection device according to the present invention can be applied to general power conversion devices, but in recent years it has been typically applied to hybrid vehicles and electric vehicles, so the following will explain its application to a hybrid vehicle as an example. However, the power conversion device is not limited to hybrid vehicles and electric vehicles, and it can of course also be used as a power conversion device for electric motors used in other industrial equipment.

[0027] Fig. 12 shows an example of the system configuration of a hybrid vehicle, in which an internal combustion engine 10 and a motor generator 11 are power sources that generate torque for driving the vehicle. The motor generator 11 not only generates rotational torque as an electric motor, but also has a power generation function that converts rotational force, which is mechanical energy applied to the motor generator 11, into electric power. In this way, the motor generator 11 operates as both an electric motor and a generator depending on how the vehicle is driven.

[0028] The output of the internal combustion engine 10 is transmitted to the motor generator 11 via the power distribution mechanism 12, and the rotational torque from the power distribution mechanism 12 or the rotational torque generated by the motor generator 11 is transmitted to the wheels 15 via the transmission 13 and the differential gear 14.

[0029] On the other hand, during regenerative braking, rotational torque is transmitted from the wheels to motor generator 11, and motor generator 11 generates AC power based on the transmitted rotational torque. The generated AC power is converted to DC power by power conversion device 20 and charges high-voltage battery 21, and the charged power is used again as driving energy.

[0030] The power conversion device 20 includes an inverter circuit 22 and a smoothing capacitor 23. The inverter circuit 22 is electrically connected to a battery 21 via the smoothing capacitor 23, and power is exchanged between the battery 21 and the inverter circuit 22. The smoothing capacitor 23 smoothes the DC power supplied to the inverter circuit 22.

[0031] A control circuit 24 of the inverter circuit 22 of the power conversion device 20 receives commands from a higher-level control device and transmits data indicating the operating state to the higher-level control device via a communication connector 25. The control circuit 24 calculates the control amount of the motor generator 11 based on the input command, generates a control signal based on the calculation result, and supplies the control signal to a gate drive circuit 26. Based on this control signal, the gate drive circuit 26 generates a drive signal for controlling the inverter circuit 22.

[0032] When the motor generator 11 is operated as an electric motor, the inverter circuit 22 generates AC power based on DC power supplied from the battery 21 and supplies it to the motor generator 11. The drive mechanism consisting of the motor generator 11 and the inverter circuit 22 operates as an electric motor / power generation unit.

[0033] FIG. 13 is a diagram showing one circuit configuration of a power conversion device 20 in a system. In the following explanation, an example of a power device using a MOSFET will be described. The power conversion device 20 has upper and lower arms each including a control MOSFET 31 and a diode 32 that constitute the power device 30, corresponding to three phases consisting of the U phase, V phase, and W phase of AC power. These upper and lower arms for these three phases constitute an inverter circuit 22. Here, the control MOSFET 31 is sometimes referred to as a "main control element" in relation to the sense element.

[0034] The drain terminal of the upper-arm control MOSFET 31 is electrically connected to the positive capacitor terminal of the smoothing capacitor 23, and the source terminal of the lower-arm MOSFET 31 is electrically connected to the negative capacitor terminal of the smoothing capacitor 23. Thus, the control MOSFET 31 has a drain terminal, a source terminal, and a gate terminal. In addition, a diode 32 is electrically connected in parallel between the drain terminal and the source terminal.

[0035] The gate drive circuit 26 is provided between the source terminal and gate terminal of the control MOSFET 31, and controls the on / off of the control MOSFET 31. The inverter control circuit 24 supplies control signals to the plurality of gate drive circuits 26.

[0036] The lower arm power device 30 is provided with a current detection sense element arranged in parallel with the control MOSFET 31. This sense element is also made up of a MOSFET, and the sense current flowing through its source terminal is input to a current detection circuit 33. Then, based on the current detected by the current detection circuit 33 and a voltage measured separately, the rotor speed and magnetic pole position are calculated, and the rotational torque and rotational speed are controlled using these.

[0037] In this way, the control circuit 24 of the inverter circuit 22 receives a control command from a higher-level control device, generates control signals for controlling the power devices 30 that constitute the upper and lower arms of the inverter circuit 22 based on the control commands, and supplies these control signals to the gate drive circuit 26. The gate drive circuit 26 supplies drive signals to the power devices 30 of each phase based on the control signals, for driving the power devices 30 that constitute the upper and lower arms of each phase.

[0038] The control MOSFET 31 of the power device 30 is turned on or off based on a drive signal from the gate drive circuit 26, converting the DC power supplied from the battery 21 into three-phase AC power, which is then supplied to the motor generator 11. A power conversion device having such a configuration is already well known.

[0039] The inverter configuration example can be IGBT instead of MOSFET. It can also be applied to other semiconductor materials such as Si, SiC, GaN, and gallium oxide. It can be used for power conversion devices in general, not just hybrid or electric vehicles. Furthermore, the electric vehicle configuration example can be applied not only to hybrids but also to EVs without internal combustion engines.

[0040] The present invention is applicable to, for example, the power conversion device described above, but is not limited to this and can be widely used. [Example]

[0041] FIG. 1 shows an example of the overall configuration of a power conversion device employing a power semiconductor current detection device according to a first embodiment of the present invention. In FIG. 1, a power conversion device 20 is configured with power devices 30 and a control circuit 24 (often implemented by a microcontroller unit (MCU)) that controls the power devices. A power semiconductor current detection device 50 is implemented by combining a hardware area configured with an electrical circuit and a software area within the MCU. Although not shown in FIG. 1, an inverter circuit 22 is configured by electrically connecting multiple power devices 30. For example, in the case of a three-phase inverter circuit as shown in FIG. 13, one phase of the inverter circuit is configured by connecting two power devices 30 in series, and the inverter circuit 22 is configured by connecting three one-phase circuits in parallel.

[0042] Of these, the power device 30 is configured with a power semiconductor 130 as its main element, which has a main element 43, a sense element 42, and a temperature-sensitive element 44 whose body resistance changes depending on the temperature of the sense element.

[0043] The microcontroller unit (hereinafter referred to as MCU) 24 contains the power semiconductor current detection device 50 according to the first embodiment of the present invention as well as an ignition control device for the inverter circuit 22, but in Figure 1, the components other than the current detection device 50 are not shown.

[0044] The current detection device 50 ultimately obtains an estimated main current value, and for this estimation calculation, it is equipped with a sense current detection circuit 51 that detects the sense current of the power semiconductor 130, a sense element temperature detection circuit 52 that detects the body resistance corresponding to the sense element temperature using a temperature sensor 44, and a reference temperature acquisition unit 53 that obtains the reference temperature for calculating the main temperature from a reference temperature point 120, and is connected to the input unit of the MCU 24.

[0045] Furthermore, the current detection device 50 refers to the body resistance temperature characteristic data D1 from the detected body resistance value (sense element temperature) in the MCU 24 to calculate the sense element temperature T Sa sense element temperature estimator 61 for estimating the sense element temperature T S The main element temperature T M a main element temperature estimator 62 that estimates the sense current and the sense element temperature T S , main element temperature T M The MCU 24 provides a gate signal to the gate drive circuit 26 via a gate signal generator 67 that generates a gate signal based on the main current estimated value, thereby controlling the firing of the power device 30 and the inverter circuit 22 that includes the power device 30.

[0046] 2 shows an example of the cross-sectional structure of a double-sided cooling type power device 30. Both surfaces (source electrode, drain electrode) of a vertical MOSFET, which is a power semiconductor 130, are connected to the respective lead terminals (source lead terminal 221, drain lead terminal 217) by solder or sintered material 216.

[0047] The lead terminals 221 and 217 are connected to a finned base plate 212 with an insulating sheet 214 sandwiched therebetween, and are inserted into a water-cooling jacket 211. By flowing a coolant 213 through a water channel formed by the base plate 212 and the water-cooling jacket 211, the heat generated by the power semiconductor 130 is cooled from both sides.

[0048] In the first embodiment, the temperature of the coolant 213 is acquired as the reference temperature. In this case, the position of the reference temperature point 120 is not limited to the position shown in Fig. 2. If there is no inflow of heat from a heat source other than the power semiconductor between the power semiconductor 130 and the reference temperature point 120 (or if the influence on the temperature rise of the power semiconductor 130 is negligibly small), the reference temperature point 120 may be at any position in the coolant 213. In addition, it does not have to be at one point, and may be the average temperature within a certain volume range (for example, within the water-cooled jacket 211).

[0049] The acquisition method may be to attach a water temperature sensor directly to the reference temperature point 120, or to indirectly estimate the temperature of the reference temperature point 120 from the value of a water temperature sensor attached to the water cooling jacket 211, part of the base plate 212, or a water channel outside the water cooling jacket 211 (for example, the radiator inlet / outlet temperature).

[0050] The scope of the MCU 24 of the present invention is not limited to the configuration shown in Figure 1. For example, the sense element temperature estimator 61 and the main element temperature estimator 62 may be configured as circuits separate from the MCU 24, or the gate drive circuit 26, sense current detection circuit 51, sense element temperature detection circuit 52, and MCU 24 may be integrated into a single integrated circuit. Furthermore, as described in Patent Document 2, the sense current detection circuit 51 and the sense temperature detection circuit 52 may be configured as a common circuit, and the detection target may be switched in synchronization with the gate signal. Various combinations are possible as methods for implementing each block.

[0051] A method for estimating the main current in the above configuration shown in Figures 1 and 2 will be described in detail. In the power conversion device 20 of Figure 1, when the power semiconductor 130 is in the on state, the sense current detection circuit 51 detects the sense current and outputs it to the MCU 24. When the power semiconductor 130 is in the off state (i.e., when no sense current is flowing), the sense element temperature detection circuit 52 detects the body resistance value and outputs it to the MCU 24. In addition, the reference temperature acquisition unit 53 outputs the temperature of the coolant 213 at the reference temperature point 120 shown in Figure 2 to the MCU 24.

[0052] Upon receiving these data, in the MCU 24, the sense element temperature estimator 64 in the sense element temperature estimator 61 refers to the temperature characteristic data D1 of the body resistance stored in advance in the memory in the form of a table, and calculates the sense element temperature T S Estimate.

[0053] The main element temperature calculation unit 65 in the main element temperature estimator 62 calculates the heat transfer function data D2 (ZthM / ZthS) stored in advance in the memory and the estimated sense element temperature value T obtained by the sense element temperature estimator 61. SThe reference temperature acquired by the reference temperature acquisition unit 53 is used to calculate the main element temperature T M Estimate.

[0054] The main current calculation unit 66 in the main current estimator 63 refers to the sense ratio table data D4 and the temperature characteristic table data D3 of the on-resistance stored in advance in the memory, and calculates the sense current, the sense element temperature T S , main element temperature T M The main current is estimated from

[0055] The gate signal generator 67 uses the main current estimate value to output a gate signal to the gate drive circuit 26, and the gate drive circuit 26 drives the power semiconductor 130, thereby performing real-time control of the inverter circuit 22.

[0056] In the present invention, the calculation methods of the main element temperature estimator 62 and the main current estimator 63 in the configuration of FIG. 1 are new, so the processing therein will be described in detail below.

[0057] First, the main element temperature estimator 62 calculates the detected sense element temperature T S It has the role of estimating the average temperature of the main element from the detected reference temperature. Main element temperature T M The calculation method will be explained in detail below.

[0058] FIG. 3a shows a plan view of the power semiconductor, and FIG. 3b shows a cross section of the power device and a thermal equivalent circuit, which correspond to the power device in FIG.

[0059] Of these, the main element source pad 131, gate pad 132, Kelvin source pad 133, and sense element source pad 134 are arranged on the power semiconductor plan view of Figure 3a, and the AA cross section including the main element source pad 131 and sense element source pad 134 in this planar region is shown as Figure 3b.

[0060] The power device cross section in Figure 3b shows the cross-sectional structure of one side of the power device cross section in Figure 2, from the power semiconductor 130 to the water-cooled jacket 211, and also shows a simplified thermal equivalent circuit of heat transfer from the power semiconductor 130 to the water-cooled jacket 211 for ease of explanation.

[0061] The power semiconductor 130 includes a main element region 141 and a sense element region 142. Here, the reference temperature T Ref and the estimated value T of the sense element temperature in the sense element region 142 obtained by the sense element temperature estimator 61. S Therefore, the main element temperature T M We are trying to estimate the following.

[0062] This thermal equivalent circuit shows that the heat generation Q of the main element of the power semiconductor 130 directly converts into the main element temperature T M This heat generation Q acts on the thermal impedance Z Sh The estimated temperature T of the sense element in the sense element region 142 is calculated via S On the other hand, this heat generation Q acts on the cooling heat in the coolant 213 with an impedance Z com , Z Mv , Z Sv This shows the flow of heat when acting through a

[0063] The thermal equivalent circuit will be explained in more detail. First, the main element and the sense element are connected by thermal impedance Z, which corresponds to the heat generation Q of the main element. Sh is the thermal impedance in the plane direction of the power semiconductor between the main element region 141 and the sense element region 142, and Z Mv , Z Sv are the longitudinal thermal impedances of the main element and the sense element, respectively, and Z com indicates the thermal impedance common to the main element and the sense element from the main element and the sense element to the reference temperature point 120, respectively.

[0064] At this time, the main element temperature TM , the sense element temperature T S , reference temperature T Ref is expressed by the relationship between equations (5) and (6).

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[0067] Figure 4 is a diagram in which the heat flow direction is added to the thermal equivalent circuit of Figure 3b. In Figure 4 and equations (5) and (6), R represents the ratio of the heat generated by the main element Q flowing to the sense element. In this case, the terms other than Q on the right side of equations (5) and (6) are the intrinsic thermal impedance Z determined by the structure of the power device. M―Ref , Z S―Ref Therefore, it can be rewritten as equations (7), (8), (9), and (10).

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[0072] In these formulas, Z M―Ref is called self-thermal impedance because it represents the temperature rise caused by the heat generated by the main element itself, and Z S―Refis called the mutual thermal impedance because it represents the temperature rise of the sense element relative to the heat generated by the main element.

[0073] From the definitions of equations (9) and (10), Z M―Ref , Z S―Ref is the main element temperature T M , the sense element temperature T S , reference temperature T Ref It is possible to obtain this in advance by measuring the relationship between the heat generation Q and the temperature. In Patent Document 2, T is calculated by taking the difference between equations (7) and (8). Ref The term is removed, and the difference between the heat generation (∝ loss) Q and the thermal impedance (Z M―Ref )―(Z S―Ref ) so ΔT=T M -T S This caused problems with taking losses.

[0074] Therefore, in the present invention, the heat generation Q is eliminated by taking the ratio of equations (7) and (8), and the thermal impedance ratio (Z M―Ref ) / (Z S―Ref ) and the sense element temperature T S and reference temperature T Ref to the main element temperature T M This makes it possible to estimate the main element temperature without being affected by errors associated with loss acquisition.

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[0076] When considering the double-sided cooling structure and three-dimensional structure, the circuit becomes more complex than the thermal equivalent circuit diagrams shown in Figs. 3 and 4. However, the main element temperature T M , the sense element temperature T S , reference temperature T Ref If there is no heat flow from a heat source other than Q (or the main element temperature T M , the sense element temperature T SIf the influence on the rise of the temperature is negligibly small, it can be expressed in the form of equations (7) to (10). Therefore, the present invention using equation (11) can be applied.

[0077] Next, the calculation method of the main current estimator 63 in Fig. 1 will be described. The processing of the main current estimator 63 is similar to the sense ratio correction processing of Patent Document 1. That is, the sense ratio data M0 when the previously acquired main element temperature and sense element temperature are equal (temperature difference ΔT = 0) is corrected using the temperature difference during operation, the previously acquired on-resistance temperature characteristic data, and equations (2) and (3), to obtain the corrected sense ratio M real Calculate the sense current and sense ratio M real Using equation (4), the main current estimate I M-E Output.

[0078] The difference between Patent Document 1 and the present invention is that the main element temperature used to calculate the temperature difference ΔT is calculated from equation (11) instead of equation (1). In implementing equation (11), the thermal impedance is implemented using a transfer function, similar to the method described in Patent Document 2. The thermal impedance ratio (Z M―Ref ), (Z S―Ref ) is composed of a thermal circuit network of thermal resistance and thermal capacity, and therefore has a time-delay response component (i.e., frequency response) to the time change Q(t) of the heat pulse. The main element temperature T M Since the frequency response must also be taken into account when estimating, the time change Q(t) of the heat pulse is calculated in advance as T M -T Ref , T M -T Ref and calculate the heat transfer function Z, which represents the frequency response in the s-domain. M―Ref (s), Z S―Ref Convert it to (s).

[0079] Thus, the thermal impedance ratio (Z M―Ref ) / (Z S―Ref) in memory as the thermal transfer function data D2, it is possible to estimate the main current taking into account such a time-delay response. A well-known method for performing transfer function calculation processing on the MCU 124 is to implement it as a digital filter.

[0080] Next, the sense ratio M real This section explains an example of calculation results that show hysteresis due to the fact that the main current has a time-delay response component relative to the reference temperature. Figure 5a shows the relationship between the main current and the sense element temperature T S The time relationship between the sense element temperature T S Figure 5b shows the change over time in the sense element temperature T S and sense ratio M real FIG.

[0081] According to these, during the period (I) of FIG. 5a, a constant main current continues to flow from an external current source to the power device, and the sense element temperature T S In period (II), the current source is given as an ON / OFF pulse, and the current-carrying period is reduced, so the sense element temperature T S Period (III) shows a state in which the main current is again supplied at a constant value and the temperature of the sense element is rising.

[0082] When the temperature of the power semiconductor changes due to changes in heat generation as in periods (II) and (III), the main element temperature T M and the sense element temperature T S The time response of the sense ratio M real For example, the main element temperature T M If the time response of the sensor is faster than that of the sense element, the main element temperature T M The temperature drops faster in the case of real By the same principle, the sense ratio M real decreases.

[0083] In this way, the sense element temperature T S The sense ratio M real Similarly, the sense ratio M real shows hysteresis. In order to consider this time-delay response, the heat transfer function is used to calculate the main element temperature T M It is best to estimate

[0084] The configuration of the above-described first embodiment does not use losses, so it is possible to estimate the main current with high accuracy without being affected by measurement errors when acquiring losses. Furthermore, it reduces the product development man-hours required to acquire loss data, shortens development time, and enables flexible design changes to suit usage conditions.

[0085] In addition, in realizing the present invention, several modifications and alternatives can be adopted. First, in this embodiment, an example in which the cooling liquid 213 is used as a refrigerant on the premise of a water-cooling system has been described, but a cooling system that uses gas as a refrigerant, such as air-cooling or a heat pipe, may also be used.

[0086] Furthermore, the setting position and method of the reference temperature point 120 of the power semiconductor 130 may be at a location or by a method other than those shown in Fig. 1. Fig. 6 shows an example in which the temperature of a portion of the base plate 212 is measured by a temperature sensor such as a thermistor or a thermocouple and used as the reference temperature, Fig. 7 shows an example in which the temperature of a portion of the insulating sheet 214 is measured by a temperature sensor such as a thermistor or a thermocouple and used as the reference temperature, Fig. 8 shows an example in which the temperature of a portion of the lead terminal 121 is measured by a temperature sensor such as a thermistor or a thermocouple and used as the reference temperature, and Fig. 9 shows an example in which the forward voltage VF of the temperature sensing diode 45 on the power semiconductor 130 is measured by a VF detection circuit which is the reference temperature acquisition unit 53 and used as the reference temperature. [Example]

[0087] In the first embodiment, the main current is estimated by mathematically expanding the reference temperature obtained by the reference temperature acquisition unit 53. In contrast to this, in the second embodiment, processing is performed taking into account time-series changes in the reference temperature.

[0088] In the second embodiment, the sense element temperature and the main element temperature one sampling period before are used as the reference temperature. The main element temperature one sampling period before, the heat generation temperature, and the reference temperature (for example, the coolant temperature) are respectively represented by T M(n-1) , Q (n-1) , T Ref(n-1) , the main element temperature, heat generation, and reference temperature of the current cycle are T M(n) , Q (n) , T Ref(n) , the thermal impedance between the main element and the reference temperature is Z M―Ref Then, equations (12) and (13) hold.

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[0091] Furthermore, equations (12) and (13) assume that the reference temperature is a constant value T Ref When the temperature can be controlled precisely, or when the change in the reference temperature is negligibly small, the temperature can be expressed by the following equations (14) and (15).

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[0094] Calculate equations (14) and (15) to obtain the reference temperature T Ref By removing, we obtain equation (16).

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[0096] Similarly, equation (17) also holds true for the sense element.

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[0098] Next, calculate equation (16) / (17) to remove the heat generation Q, and the main element temperature T M(n) can be calculated using equation (18).

[0099]

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[0100] Equation (18) is the thermal impedance ratio (Z M―Ref ) / (Z S―Ref ) to calculate the main element temperature T M From another perspective, since the formula is similar to formula (11) in the first embodiment, the sense element temperature and main element temperature one sampling period before can be calculated as the reference temperature T Ref1 , T Ref2 and can be regarded as an equation for estimating the main element temperature.

[0101] Since the initial value is not determined in equation (18), it is assumed that there is no temperature difference between the main element and the sense element due to self-heating at the start of operation, and processing is performed as in equation (19) below. However, T S-initial is the detected temperature value of the sense element at the start of operation.

[0102]

number

[0103] The thermal impedance ratio (Z M―Ref ) / (Z S―Ref ) for measuring the reference temperature T Ref does not have to be the coolant temperature. M , TS , T Ref There is no heat inflow from any heat source other than the heat generation Q of the power semiconductor between them (i.e., equations (12) and (13) must hold). Also, as a difference from Example 1, if the temperature is constant, equation (18) holds, and the method of Example 2 can be applied.

[0104] 10 shows an example of the configuration of a power conversion device according to a second embodiment of the present invention. The difference from the configuration of the first embodiment shown in FIG. 1 is that the reference temperature acquisition unit 53 acquires the sense element temperature T S and the main element temperature T M That is, the sense element temperature T calculated by the sense element temperature estimator 61 and the main element temperature estimator 62 is acquired and stored in the memory. S and the main element temperature T M is stored in memory and is used to calculate equation (18) in the next sampling period.

[0105] The configuration of this embodiment has the effect of eliminating the need to create a reference temperature point or a detection circuit for acquiring the reference temperature of the power device as in the first embodiment. [Example]

[0106] In the third embodiment, the temperature of a plurality of power semiconductors connected in parallel is used as the reference temperature.

[0107] 11 shows an example of the configuration of a power conversion device in which two power semiconductors 130A and 130B are connected in parallel within a power device 30. A sense element 42A and a temperature sensor 44A of the power semiconductor 130A are used to detect a sense current and a sense element temperature, similar to the first embodiment.

[0108] In contrast, the sense element 42B and the temperature sensing element 44B of the power semiconductor 130B are used to detect the reference temperature by treating the temperature sensing element 44B as the reference temperature point 120. A reference temperature acquisition unit 53 (sense element temperature detection circuit 2) detects the body resistance 2 of the sense element and outputs it as a reference temperature signal to the MCU 24. A sense element temperature estimator of the MCU 24 refers to temperature characteristic table data of the body resistance stored in advance in memory, and estimates the reference temperature from the value of the detected body resistance 2. The rest of the configuration is the same as in the first embodiment, so a description thereof will be omitted.

[0109] The estimation method of the main element temperature estimator 62 of the third embodiment will be described. The main element temperature and the sense element temperature of the power semiconductor 130A are respectively T M1 , T S1 The main element temperature and sense element temperature of power semiconductor 130B are T M2 , T S2 Then, the relationships in equations (20) to (23) hold true in the same way as equations (7) to (10).

[0110]

number

[0111]

number

[0112]

number

[0113]

number

[0114] Here, Q represents the total heat dissipation of the parallel chips. M1-S2 , Z S1-S2is the thermal impedance determined by the structure of the power device, and can be measured in advance using the relationship in equations (22) and (23). By removing Q from equations (20) and (21), the relationship in equation (24) is obtained.

[0115]

number

[0116] Therefore, T S2 The reference temperature T Ref By considering this as the case, the formula becomes the same as equation (11) in Example 1, and the main element temperature 1 (T M1 ) can be calculated.

[0117] In addition, the roles of the temperatures of the power semiconductor 130A and the power semiconductor 130B are interchanged, and the sense element temperature 1 (T S1 ) is regarded as the reference temperature, and the main element temperature 2 (T M2 ) can also be calculated.

[0118]

number

[0119] The main element temperature estimated value output by the main element temperature estimator is T M1、 T M2 You can calculate and output either T M1、 T M2 Alternatively, the average value of the above may be calculated and output.

[0120] 11 has been described using an example of two chips connected in parallel, this embodiment can also be applied to a case where three or more chips are connected in parallel. For example, among N chips connected in parallel, the (N-1) chip may be regarded as the power semiconductor 130A in FIG. 11, and the remaining chip may be regarded as the power semiconductor 130B. [Explanation of symbols]

[0121] 22: Inverter circuit 24: Control circuit, microcontroller unit 26: Gate drive circuit 30: Power devices 42: Sense element 43: Main element 44: Thermosensitive element 50: Current detection device 51: Current detection circuit 52: Sense element temperature detection circuit 53: Reference temperature acquisition section 61: Sense element temperature estimator 62: Main element temperature estimator 63: Main current estimator 67: Gate signal generator 130: Power semiconductors 120: Reference temperature point

Claims

1. A current detection device for a power device equipped with a power semiconductor having a main element, a sense element for current detection, and a temperature-sensing element for temperature detection, a sense element temperature estimation unit that estimates a sense element temperature, which is the temperature of the sense element, based on an output of the temperature sensitive element; a reference temperature acquisition unit that acquires a reference temperature of the power device; a main element temperature estimating unit that estimates a main element temperature, which is the temperature of the main element, based on the sense element temperature and the reference temperature; a main current estimating unit that estimates a main current value flowing through the main element based on a sense current value detected by the sense element, the sense element temperature, and the main element temperature, A current detection device for a power device, characterized in that the main element temperature estimation unit estimates the main element temperature using a thermal impedance ratio, which is the ratio between the mutual thermal impedance of the sense element with respect to the heat generation of the main element and the self-thermal impedance of the main element.

2. 2. The power device current detection device according to claim 1, The main element temperature estimation unit estimates the main element temperature based on the product of the temperature difference between the sense element temperature and the reference temperature and the thermal impedance ratio.

3. 3. The power device current detection device according to claim 2, The current detection apparatus for a power device, wherein the reference temperature acquisition unit acquires, as the reference temperature, the temperature of a refrigerant that cools the power device.

4. 3. The power device current detection device according to claim 2, The current detection device for a power device, wherein the reference temperature acquisition unit acquires the temperature of a thermistor mounted on the power device as the reference temperature.

5. 3. The power device current detection device according to claim 2, The current detection apparatus for a power device, wherein the reference temperature acquisition unit acquires a base plate temperature of the power device as the reference temperature.

6. 3. The power device current detection device according to claim 2, The current detection apparatus for a power device, wherein the reference temperature acquisition unit acquires an insulator temperature of the power device as the reference temperature.

7. 3. The power device current detection device according to claim 2, The current detection apparatus for a power device, wherein the reference temperature acquisition unit acquires a terminal temperature of the power device as the reference temperature.

8. 3. The power device current detection device according to claim 2, The current detection device for a power device, wherein the reference temperature acquisition unit acquires the sense element temperature and the main element temperature from one sampling period or more ago as the reference temperature.

9. 3. The power device current detection device according to claim 2, the sense element temperature estimation unit acquires temperatures of the temperature sensing elements of some of the power semiconductors connected in parallel within the power device, The current detection device for a power device, wherein the reference temperature acquisition unit acquires, as the reference temperature, the temperatures of the thermosensitive elements of some of the remaining power semiconductors connected in parallel within the power device.

10. A power conversion apparatus including a power device having a power semiconductor including a main element, a sense element for detecting current, and a temperature-sensing element for detecting temperature, and a control circuit for driving a gate of the power device, 10. A power conversion device, characterized in that the control circuit generates a gate signal for the power device in accordance with a main current estimated value estimated by the power device current detection device according to any one of claims 1 to 9, and drives a gate of the power device.

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