Power conversion device

Abstract

The present invention provides a power conversion device capable of accurately estimating the main current of a power device based on sensing current observation. The power conversion device includes: an inverter circuit (22) comprising a device having a main element and a sensing element; a temporary main current estimator (43) which estimates the current flowing through the main element as a temporary main current based on the sensing current flowing through the sensing element; a temperature difference estimator (44) which estimates the temperature difference between the main element and the sensing element based on a gate drive signal for the main element and the temporary main current; a main current corrector (45) which corrects the temporary main current using the estimated temperature difference and the on-resistance temperature characteristics of the main element, and outputs the corrected main current; and an inverter control circuit (24) which outputs a gate drive signal based on the corrected main current.

Description

Technical Field

[0001] This invention relates to a power conversion device with power devices, and more particularly to a power conversion device that requires high-precision current measurement. Background Technology

[0002] As next-generation vehicles, hybrid electric vehicles, which combine an internal combustion engine and an electric motor to drive the wheels, and electric vehicles, which drive the wheels solely through an electric motor, are attracting attention. Furthermore, among the automotive motors used in these vehicles, small, high-torque synchronous motors with permanent magnets embedded in the rotor are employed. Vector control is typically used to maximize the torque of these synchronous motors.

[0003] Such vector control calculates a current command based on the torque command and speed generated by the accelerator or braking command, and generates a PWM signal based on this current command to drive the power devices of the inverter. Furthermore, vector control requires a current sensor to measure the output current of the inverter. Therefore, a dedicated current sensing element is provided separately from the main control element such as the IGBT or MOSFET constituting the power devices. The current flowing through this sensing element (sensing current) is detected, and the main current flowing through the main control element is estimated. For example, such a power conversion circuit is disclosed in Patent Document 1.

[0004] The power device composed of the aforementioned sensing element and main control element is temperature-dependent, thus exhibiting a problem where the sensing current characteristics change with temperature, making it impossible to measure the accurate current. Therefore, in Patent Document 1, a temperature sensing diode is formed on the semiconductor substrate constituting the power device, and the current characteristics are corrected using this temperature sensing diode.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-271098 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, when using temperature-sensing elements such as temperature-sensing diodes to measure the temperature of power devices, only the temperature of the portion of the power device containing the temperature-sensing element can be measured. Power devices are sometimes large semiconductor chips with an area exceeding 1 mm square, which themselves become heat-generating elements during operation. Therefore, the temperature within the chip is uneven, resulting in a temperature difference between the center and the edges of the chip. Typically, the temperature in the center of the chip, where heat is more easily concentrated, is higher than that at the edges. The suitable location for placing the temperature-sensing element is at the chip edge. The reason is that, to improve low on-resistance and cooling efficiency, both sides of the power device chip serve as drain or source terminals. Since these terminals are held together by a metal electrode that also acts as a heat sink, it is impossible to place the pads for connecting the temperature-sensing element to the bonding wires in the center of the chip. Furthermore, if the temperature-sensing element itself is placed in the center away from the pads, and wiring connects the temperature-sensing element to the pads at the chip edge, the wiring portion becomes a non-active area that is not part of the power device, resulting in poor area efficiency and increased cost. The same applies to sensing elements. It can be said that configuring them together with temperature sensing elements at the chip end is essential to achieving low on-resistance, low thermal resistance, and low cost as power devices.

[0010] In chip temperature measurement using the temperature-sensing element exemplified in Patent Document 1, the measured temperature is only the temperature at the chip's edge, i.e., the temperature of the sensing element. The temperature of the main control element (hereinafter referred to as the main element) cannot be measured, and there is a temperature difference relative to the sensing element's temperature. Here, since power devices such as IGBTs or MOSFETs are semiconductors, their on-resistance is temperature-dependent. Because the main element and the sensing element are connected in parallel, the ratio of the main current (hereinafter referred to as the main current) to the sensing current (sensing ratio) changes when the temperature difference between the main element and the sensing element changes. That is, as in Patent Document 1, without considering the temperature difference between the main element and the sensing element, errors occur in the estimation of the main current, leading to accuracy degradation and becoming a problem.

[0011] The purpose of this invention is to provide a power conversion device that, in a power device with sensing elements, can accurately estimate the main current based on sensing current observation by taking into account the temperature difference.

[0012] Technical means to solve the problem

[0013] To achieve the above objectives, the present invention provides a power conversion device comprising: an inverter circuit including a device having a main element and a sensing element; a temporary main current estimator that estimates the current flowing through the main element as a temporary main current based on the sensing current flowing through the sensing element; a temperature difference estimator that estimates the temperature difference between the main element and the sensing element based on a gate drive signal for the main element and the temporary main current; a main current corrector that corrects the temporary main current using the estimated temperature difference and the on-resistance temperature characteristics of the main element, and outputs the corrected main current; and an inverter control circuit that outputs a gate drive signal based on the corrected main current.

[0014] The effects of the invention

[0015] According to the present invention, in a device equipped with a sensing element, the main current flowing through the device can be accurately estimated using the chip temperature and sensing current detected at the chip tip. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating an example of the system configuration of a hybrid electric vehicle.

[0017] Figure 2 It means Figure 1 A circuit configuration example of a power conversion device in a system is shown in the figure.

[0018] Figure 3 This is a diagram illustrating one configuration of the power devices used in the power conversion apparatus of various embodiments.

[0019] Figure 4 It is a characteristic graph representing the time-varying values ​​of the main component temperature, the sensing element temperature, and the sensing ratio.

[0020] Figure 5 This is a characteristic diagram showing the typical on-resistance temperature characteristics of a power device.

[0021] Figure 6 This is a diagram illustrating one configuration example of the power conversion device of Embodiment 1.

[0022] Figure 7 This is a thermal equivalent circuit diagram representing a model example of the thermal resistance of a power device.

[0023] Figure 8 This is a diagram illustrating one configuration example of the temperature difference arithmetic unit of the power conversion device in Embodiment 1.

[0024] Figure 9 This is a diagram illustrating one configuration example of the power conversion device of Embodiment 2.

[0025] Figure 10This is a diagram illustrating one configuration example of the temperature difference arithmetic unit of the power conversion device in Embodiment 2.

[0026] Figure 11 This is a diagram illustrating one configuration example of the power conversion device of Embodiment 3. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. Various modifications and applications are also included within the scope of the technical concept of the present invention.

[0028] First, various embodiments of the power conversion apparatus to which the present invention is applied will be described with reference to the accompanying drawings. The power conversion apparatuses of each embodiment are representatively applicable to hybrid vehicles and electric vehicles; however, the following description focuses on the application to hybrid vehicles as an example. However, the power conversion apparatuses of each embodiment are not limited to hybrid vehicles and electric vehicles, and can also be used for power conversion of electric motors used in other types of industrial equipment.

[0029] Figure 1 In the example of a hybrid vehicle system configuration, the internal combustion engine 10 and the electric generator 11 are the power sources that generate the driving torque of the vehicle. In addition, the electric generator 11 not only generates rotational torque as an electric motor, but also has the function of generating electricity by converting the mechanical energy, i.e., rotational force, applied to the electric generator 11 into electrical electricity.

[0030] In this way, the electric generator 11 operates as either an electric motor or a generator, depending on how the car is operated.

[0031] The output of the internal combustion engine 10 is transmitted to the electric generator 11 via the power distribution mechanism 12. The rotational torque from the power distribution mechanism 12 or the rotational torque generated by the electric generator 11 is transmitted to the wheels 15 via the transmission 13 and the differential gear 14.

[0032] On the other hand, during regenerative braking, rotational torque is transmitted from wheel 15 to electric generator 11, which generates alternating current (AC) power based on the transmitted torque. The generated AC power is converted into direct current (DC) power by power conversion device 20 to charge high-voltage battery 21, and the charged power is then used again as driving energy.

[0033] The power conversion device 20 includes an inverter circuit 22 and a smoothing capacitor 23. The inverter circuit 22 is electrically connected to the battery 21 via the smoothing capacitor 23, and power is transferred between the battery 21 and the inverter circuit 22. The smoothing capacitor 23 smooths the DC power supplied to the inverter circuit 22.

[0034] The control circuit 24 of the inverter circuit 22 of the power conversion device 20 receives commands from the upper-level control device via a communication connector 25, or sends data indicating the operating status to the upper-level control device. Based on the input commands, the control circuit 24 calculates the control quantity of the electric generator 11, generates a control signal based on the calculation result, and provides a control signal to the gate drive circuit 26. Based on this control signal, the gate drive circuit 26 generates a drive signal for controlling the inverter circuit 22.

[0035] When the electric generator 11 is operated as a motor, the inverter circuit 22 generates AC power based on the DC power supplied from the battery 21 and supplies it to the electric generator 11. The drive mechanism consisting of the electric generator 11 and the inverter circuit 22 operates as an electric / generator unit.

[0036] Figure 2 This is a diagram showing the circuit configuration of the power conversion device 20 in the system. The following description illustrates an example of a power device using MOSFETs. The power conversion device 20 has upper and lower arms corresponding to the three phases (U, V, and W) of the AC power, each upper and lower arm equipped with a MOSFET 31 and a diode 32 for controlling the power device 30.

[0037] The upper and lower arms of these three phases constitute inverter circuit 22. Here, the control MOSFET 31 is sometimes also referred to as "main control element" due to its relationship with the sensing element.

[0038] The drain terminal of the upper arm control MOSFET 31 is electrically connected to the capacitor terminal on the positive side of the smoothing capacitor 23, and the source terminal of the lower arm MOSFET 31 is electrically connected to the capacitor terminal on the negative side of the smoothing capacitor 23. Thus, the control MOSFET 31 has a drain terminal, a source terminal, and a gate terminal. Additionally, a diode 32 is connected in parallel between the drain terminal and the source terminal.

[0039] The gate drive circuit 26 is disposed between the source terminal and the gate terminal of the control MOSFET 31, and controls the conduction and disconnection of the control MOSFET 31. The inverter control circuit 24 provides control signals to the multiple gate drive circuits 26.

[0040] The power device 30 of the lower arm is equipped with a current sensing element configured in parallel with the control MOSFET 31. This sensing element is also composed of a MOSFET, and the sensing current flowing through its source terminal is input to the current sensing circuit 33. Then, based on the current detected by the current sensing circuit 33 and the voltage separately measured therefrom, the rotor speed and magnetic pole position are calculated, and these are used to control the rotational torque and rotational speed.

[0041] Thus, the control circuit 24 of the inverter circuit 22 receives control commands from the host control device, and based on these commands, generates control signals to control the power devices 30 constituting the upper and lower arms of the inverter circuit 22, and provides these control signals to the gate drive circuit 26. The gate drive circuit 26 then provides drive signals to the power devices 30 of each phase to drive the power devices 30 constituting the upper and lower arms of each phase based on the control signals.

[0042] The MOSFET 31, used for controlling the power device 30, turns on or off based on a drive signal from the gate drive circuit 26, converting the DC power supplied by the battery 21 into three-phase AC power, which is then supplied to the electric generator 11. Such power conversion devices are well known.

[0043] However, as Figure 3 As shown in (a), the power device 30 is a large-area semiconductor chip, such as Figure 3 As shown in (b), the chip has a temperature sensing element 37 and a sensing element 39 at its end. The temperature sensing element 37 is connected to the outside of the chip via pads 37a and 37b, and the sensing element 39 has its source terminal connected to the outside via pad 36. Additionally, the gate is connected to the gate drive circuit 26 via pad 35. The source terminal of the main element is pad 34, and the common drain terminal of the main element and the sensing element is connected via pad 38 on the back of the chip.

[0044] Here, at the output of inverter circuit 22 Figure 4 In the case of a sinusoidal current as described above, because current flows through the power device 30 due to its switching action, power losses are generated in the power device 30 synchronously with the output current. Consequently, the power device 30 heats up, as... Figure 4 As shown by the solid line in the middle section, the main component temperature Tm changes synchronously with the output current. On the other hand, because the sensing element located at the end of the chip has high cooling efficiency, the heat transfer from the center of the chip is delayed, so as... Figure 4 As illustrated by the dashed line in the middle section, the amplitude of the sensing element temperature Ts is smaller than that of Tm and changes with a delay. That is, the temperature difference ΔT between the main component and the sensing element changes with time. Furthermore, ΔT represents different values ​​depending on the frequency and amplitude of the inverter output current.

[0045] This section explains the effect of the temperature difference ΔT on the accuracy of current estimation. First, let T be the component temperature, the on-resistance of the sensing element be Rs(T), and the on-resistance of the main component be Rm(T). The on-resistance of each component, when the power device is a SiC-MOSFET, typically has the following characteristics: Figure 5 The characteristic shown is that it increases with increasing temperature. The sensing ratio M can be described as in equation (1).

[0046] [Formula 1]

[0047]

[0048] The relationship between Ts and Tm is shown in equation (2) using ΔT.

[0049] [Formula 2]

[0050] T M =T S +ΔT…(2)

[0051] Here, the information about the sensing ratio prepared in advance to estimate the main current based on the sensing current is the sensing ratio at a fixed temperature difference ΔT0. For example, when the temperature characteristics of the sensing ratio are obtained in advance using a constant temperature bath, ΔT0 is 0 because the sensing element and the main element are heated to a uniform temperature from the outside. If the sensing ratio at this time is set as M0(T), it becomes Equation (3).

[0052] [Formula 3]

[0053]

[0054] become.

[0055] On the other hand, the sensing ratio of the device when it heats up during operation is Mreal.

[0056] [Formula 4]

[0057] .

[0058] If the actual temperature difference ΔT is different from the temperature difference ΔT0 when the sensing ratio is obtained in advance, then M0(T)≠Mreal(T). Thus, due to the difference between ΔT and ΔT0, the sensing ratio changes compared to the assumption, causing an error in the current estimation caused by the temperature difference.

[0059] As shown in equation (5), the deviation of the sensing ratio caused by ΔT can be expressed as the coefficient K of M0(T).

[0060] [Formula 5]

[0061] M real (T S )=K·M0(T S (5)

[0062] Here, K is a coefficient defined by equation (6).

[0063] [Formula 6]

[0064]

[0065] As shown in equation (6), K is the ratio of the on-resistance of the main element at temperature Ts+ΔT0 to that at temperature Ts+ΔT. That is, if the temperature characteristic Rm(T) of the on-resistance of the main element, the temperature difference ΔT0 between the main element and the sensing element when the sensing ratio is obtained in advance, and the temperature difference ΔT when the actual operation occurs, then K can be known, that is, the correct sensing ratio Mreal can be obtained, and the main current can be estimated with high accuracy.

[0066] Here, Rm(T) can be known beforehand by acquiring its characteristics, and ΔT0 can also be zero by setting the device to an isothermal state when the sensing ratio is acquired beforehand. As long as ΔT, which changes over time with the operating state of the power device, can be known in real time, the coefficient K can be derived, and the correct sensing ratio Mreal can be obtained in real time. That is, by using the pre-stored on-resistance temperature characteristics of the power device to correct the sensing ratio, the main current can be accurately estimated based on the sensing current.

[0067] Example 1

[0068] Example 1 is an example of a power conversion device that derives the aforementioned coefficient K and corrects the current estimate based thereon. Specifically, Example 1 is an example of a power conversion device comprising: an inverter circuit including a device having a main element and a sensing element; a temporary main current estimator that estimates the current flowing through the main element as a temporary main current based on the sensing current flowing through the sensing element; a temperature difference estimator that estimates the temperature difference between the main element and the sensing element based on a gate drive signal for the main element and the temporary main current; a main current corrector that corrects the temporary main current using the estimated temperature difference and the on-resistance temperature characteristics of the main element, and outputs the corrected main current; and an inverter control circuit that outputs a gate drive signal based on the corrected main current.

[0069] In the power conversion device of this embodiment, such as Figure 6 As shown, the sensing current of the power device 30 is detected by the sensing current detector 42. In the temporary main current estimator 43, a temporary main current value Ime', which includes the error caused by the previously explained temperature difference, is obtained from this sensing current Is. Then, using this temporary main current and the gate drive signal, the temperature difference estimator 44 calculates the estimated temperature difference value ΔTe between the main element and the sensing element. Finally, the main current corrector 45 calculates a correction coefficient based on the estimated temperature difference ΔTe and the temperature characteristics of the on-resistance. This correction coefficient yields the main current Ime, which has been corrected for the temperature difference error, and it is input to the inverter control circuit 24 for real-time control of the inverter circuit. The temporary main current estimator 43, the temperature difference estimator 44, and the main current corrector 45 will be described sequentially below.

[0070] The temporary main current estimator 43 has a memory 432 that stores the previously acquired sensing ratio M0. The temporary main current arithmetic unit 431 performs the following multiplication operation on the sensing current Is acquired by the sensing current detector 42, and outputs the temporary main current Ime'.

[0071] [Formula 7]

[0072] I ME ′=M0I S …(7)

[0073] That is, the temporary main current estimator 43 estimates the temporary main current Ime' based on the ratio of the main current to the sensing current obtained in advance, i.e. the sensing ratio and the sensing current Is.

[0074] Here, since the sensing ratio sometimes exhibits temperature characteristics due to the non-uniformity of the power device 30's construction, the sensing ratio stored in the memory 432 can also be a temperature-dependent table. In this case, the temporary main current estimator 43 can also use the sensing element temperature Ts obtained by the sensing element temperature detector 41 for temperature correction. Additionally, there are also cases where the sensing ratio is current-dependent, so it can also be a table of sensing ratios dependent on the sensing current. In summary, since the power device 30 includes a temperature-sensing element, the temporary main current estimator 43 can perform temperature correction of the temporary main current based on the sensing element temperature Ts detected by the sensing element temperature detector 41 from the output of the temperature-sensing element.

[0075] The temperature difference estimator 44 is used to estimate the temperature difference ΔT between the main component and the sensing element. It includes a chip loss calculator 442 that calculates the estimated loss Ee based on the temporary main current Ime', and a temperature difference calculator 441 that calculates the estimated temperature difference based on the estimated loss. The temperature difference ΔT is the internal temperature difference of the chip. As mentioned above, it is difficult to obtain the temperature at the center of the chip. Therefore, the temperature difference ΔT is obtained by estimating based on the operating state of the power device 30. Specifically, in the temperature difference estimator 44, the losses generated in the power device 30 are estimated, and ΔT is calculated in real time using the pre-obtained thermal resistance from the losses to the temperature difference.

[0076] First, an example of the estimated loss of power device 30 will be explained. The loss of power device 30 consists of conduction loss caused by the main current flowing through the main element with conduction resistance, and switching loss generated in each PWM switch during power conversion operation. If the duty cycle of PWM is set to D, the PWM frequency is set to FPWM, the turn-on loss is set to Eon, and the turn-off loss is set to Eoff, then Eloss in 1 PWM cycle is expressed by equation (8).

[0077] [Formula 8]

[0078]

[0079] The first term represents the conduction loss, and the second and third terms represent the switching loss. The chip loss calculator 442 calculates the loss according to equation (8) and outputs an estimated loss Ee for each PWM switch. The duty cycle and frequency of the PWM required for the conduction loss calculation can be obtained by monitoring the gate drive signal output by the inverter control circuit 24. The duty cycle and frequency do not necessarily need to be obtained from the gate drive signal, and can also be obtained separately from the inverter control as data. In addition, the main current IM can be approximated by using the already obtained temporary estimated value Ime' of the main current. The on-resistance Rm of the main element obtained in advance is stored in memory 445 for conduction loss calculation. Regarding the switching loss, it is usually proportional to the main current value, so the previously obtained Eon+Eoff is stored in memory 444 as a table for the main current. Since the on-resistance and the turn-on and turn-off losses are sometimes temperature dependent, the temperature Ts of the sensing element detected by the sensing element temperature detector 41 can also be used for temperature correction by the chip loss calculator 442. In this case, the temperature dependence data of on-resistance, on-loss, and off-loss can be stored in memory 445 and memory 444.

[0080] Next, an example of a configuration using the estimated temperature difference ΔT derived from the estimated loss Ee will be described. ΔT is calculated and estimated using the estimated loss Ee and a previously obtained thermal resistance. The power device 30 itself is a heat source due to losses caused by current conduction during operation, and has a thermal structure that dissipates heat to the outside via a heat sink mounted on the power device 30.

[0081] Figure 7 It is represented using a thermal equivalent circuit. Figure 7 The left end represents the heat source generated by the power device 30's losses. The heat flow from the heat source is dissipated to the periphery of temperature T0 via the thermal resistances θ0~θN of the chip and the heat capacity C0~CN of the heat sink. In this thermal equivalent circuit, the time waveform q(t) of the heat flow from the heat source is expressed as equation (9).

[0082] [Formula 9]

[0083] q(t)=F PWM E LOSS …(9)

[0084] When the heat transfer impedance from the heat source to the main component is set as Zm and the heat transfer impedance from the heat source to the sensing element is set as Zs, the temperature Tm(s) of the main component and the temperature Ts(s) of the sensing element in the frequency region s are expressed as equations (10) and (11).

[0085] [Formula 10]

[0086] T M (s)=Z M Q(s)+T0…(10)

[0087] [Equation 11]

[0088] T S (s)=Z S Q(s)+T0…(11)

[0089] Here, Q(s) is q(t) in the frequency region. The temperature difference ΔT is...

[0090] [Formula 12]

[0091] ΔT(s)=(Z M -Z S )Q(s)…(12)

[0092] That is, it can be seen that the time waveform of the temperature difference ΔT is the result of filtering the loss q(t) by the thermal impedance of (Zm-Zs). In the temperature difference estimator 44, the estimated loss Ee for each PWM switch output is passed through the temperature difference arithmetic unit 441, which is a discrete-time filter, to obtain the estimated value of the temperature difference ΔTe.

[0093] Here, in order to obtain the corrected main current Ime in real time, ΔTe is required in real time; therefore, the digital filter constituting the temperature difference calculator needs low latency. When the digital filter is configured as an FIR filter, a delay of more than half the number of taps is generated, which is therefore undesirable. Preferably, as follows... Figure 8 The configuration shown enables a low-delay IIR filter. The tap coefficients An and Bn (n = 1, 2, 3, ...) of the IIR filter that realizes thermal impedance (Zm-Zs) are stored in memory 443 and used by the temperature difference estimator 441.

[0094] Finally, an example of the configuration of the main current corrector 45 will be explained. The main current corrector 45 has a correction coefficient calculator 451 that calculates the correction coefficient based on the estimated temperature difference, and multiplies the calculated correction coefficient by the temporary main current to obtain the corrected main current. The temporary main current Ime' output by the temporary main current estimator 43 is already the value of the sensing ratio M0 when the sensing current Is is multiplied by the temperature difference ΔT = 0. Therefore, by multiplying Ime' by the correction coefficient K, the estimated value of the main current Ime is obtained by multiplying Is by the sensing ratio Mreal with the temperature difference added. Here, the correction coefficient K can be calculated according to equation (6) or according to equation (13), which is its first approximation.

[0095] [Formula 13]

[0096]

[0097] The correction coefficient calculator 451 of the main current corrector 45 uses the estimated temperature difference ΔTe, which is the output of the temperature difference estimator 44, as ΔT. When the correction coefficient K is calculated according to equation (13), the temperature coefficient of the on-resistance of the main component, which is obtained in advance, is stored in the memory 453. The correction coefficient K is obtained by multiplying ΔTe by the correction coefficient calculator 451. That is, by using the pre-stored temperature characteristics of the on-resistance of the power device to correct the sensing ratio, the main current can be accurately estimated based on the sensing current. The corrected main current, obtained by multiplying the temporary main current by the correction coefficient K calculated in the main current corrector 45, is output to the inverter control circuit 24.

[0098] Thus, according to the power conversion device of this embodiment, by estimating the main current taking into account the temperature difference, the current estimation of the power device based on the current observation of the detection sensor can be performed correctly.

[0099] Alternatively, in the case of a configuration that allows for more accurate calculation of equation (6), the on-resistance of the main components at each temperature, obtained in advance, can be stored in memory 453. However, in this case, since a divider is required in the correction coefficient arithmetic unit 451, the configuration according to equation (13) is preferred when hardware size and calculation speed are insufficient.

[0100] Example 2

[0101] Example 2 is an embodiment of a power conversion device equipped with an arithmetic unit that performs main current correction processing at a higher speed than Example 1. That is, it is an embodiment of a power conversion device in which the temperature difference estimator estimates the temperature difference between the main element and the sensing element based on predetermined driving conditions for the device, such as a predetermined main current value and its pulse width in the next switching.

[0102] Since the estimated main current is used for real-time control of the inverter circuit, the calculation of estimating the main current based on the sensed current needs to be performed with low latency. As shown in this invention, when seeking high accuracy and performing more correction calculations, the calculation may not be fast enough depending on the speed of the arithmetic unit. The correction calculation is basically a product summation operation accompanied by memory access, and one of the most time-consuming arithmetic units is the temperature difference arithmetic unit 441 of the temperature difference estimator 44. This is because in the temperature difference arithmetic unit 441, such as Figure 8 The illustrated IIR filter requires multiple product sum operations.

[0103] Figure 9This embodiment describes a configuration of a power conversion device that predicts chip losses and calculates temperature differences in advance to achieve low delay in temperature difference estimation. In this embodiment, the inverter control circuit 24 transmits predetermined drive conditions, namely, the predetermined main current value and its pulse width for the next PWM1 cycle of switching, to the temperature difference estimator 44. In the inverter control circuit 24, the target current value for the next switch and the predetermined pulse width are known as drive conditions predetermined before driving the gate, so by using this information, the loss value for the next switch can be predicted in advance in the temperature difference estimator 44. Figure 9 The temperature difference estimator 44 shown has a chip loss prediction arithmetic unit 446 for this prediction. Except for the input of a predetermined main current value and its pulse width for the next switch as predetermined driving conditions, its configuration is the same as that of the chip loss arithmetic unit 442. The loss value Ep predicted by the chip loss predictor 446 for the next switch, together with the estimated loss value Ee of the already generated switch, is output to the temperature difference prediction arithmetic unit 441b.

[0104] Figure 10 This illustrates a configuration example of the temperature difference prediction calculator 441b. In the temperature difference prediction calculator 441b, the predicted value ΔTep of the estimated temperature difference ΔTe for the next switch is calculated using the predicted loss Ep. As a configuration, it internally incorporates the features described in Embodiment 1. Figure 8 The temperature difference arithmetic unit 441 has a second temperature difference arithmetic unit 4411 that performs calculations using the internal state signal derived therefrom and the predicted loss Ep. Here, the tap coefficient Cn (n = 1, 2, 3, ...) is defined according to equation (14).

[0105] [Formula 14]

[0106] C n =B n +A n B0…(14)

[0107] By constructing the power conversion circuit of this embodiment, a power conversion device with an arithmetic unit can be provided. This arithmetic unit can obtain the temperature difference as a predicted value before switching, and after sensing the current, the corrected main current Ime can be obtained with only the delay of the temporary main current estimator 43 and the main current corrector 45. This enables low-delay current sensing and high-speed main current correction processing.

[0108] Example 3

[0109] Example 3 is an embodiment of a power conversion device equipped with an arithmetic unit that performs main current correction processing with higher accuracy compared to the power conversion device of Example 1. Specifically, it is an embodiment of a power conversion device equipped with a second temperature difference estimator and a second main current corrector. The second temperature difference estimator estimates a temperature difference based on the corrected main current, and the second main current corrector calculates a second correction coefficient based on the second estimated temperature difference estimated by the second temperature difference estimator and multiplies the second correction coefficient by the corrected main current.

[0110] In Example 1, a temporary main current Ime', incorporating error, is used to calculate chip losses in the temperature difference estimator 44. Since conduction losses in chip losses are proportional to the square of the current, the error between the temporary main current Ime' and the actual main current Im has a significant impact on the chip loss error. This chip loss error becomes the error in the estimated temperature difference ΔTe, and consequently, the error in the final estimated main current value Ime. Conversely, the higher the accuracy of the main current value used by the temperature difference estimator, the higher the accuracy of Ime. Therefore, by repeatedly performing temperature difference estimation and main current correction, a high-accuracy main current can be obtained.

[0111] Figure 11 This diagram illustrates one configuration of this embodiment when it is repeated twice. In this diagram, the second temperature difference estimator 44b and the second main current corrector 45b operate by taking the corrected main current output by the main current corrector 45, i.e., the second temporary main current Ime”, as input. Compared to Ime’, Ime” is correspondingly more accurate as a quantity that has had the influence of temperature difference removed. Therefore, the second estimated temperature difference ΔTe’ output by the second temperature difference estimator 44b is more accurate than the original estimated temperature difference ΔTe, and the corrected main current Ime output by the second main current corrector 45b is more accurate than the second temporary main current Ime”.

[0112] In addition, Figure 11 In this configuration, the temperature difference estimator 44 and the second temperature difference estimator 44b, which are identical in configuration, and the main current corrector 45 and the second main current corrector 45b, which are identical in configuration, are connected in series, but this configuration is not necessarily required. By preparing a separate sequencer and reusing the same temperature difference estimator and main current corrector, the memory size and arithmetic unit size can be reduced. In addition, the number of repetitions is not limited to 2 times, but can be performed 3 times or more.

[0113] In the above embodiments, a power conversion device for controlling an electric motor has been described, but the present invention can also be applied to other power conversion devices. For example, in a power conversion device composed of a MOSFET that controls the current flowing in an electromagnetic coil of an electromagnetic drive mechanism, an overcurrent detection device that detects overcurrent flowing in the MOSFET to protect the MOSFET can also be applied. Here, as an electromagnetic drive mechanism, examples include an electromagnetic flow control valve that controls the amount of fuel in a continuously variable transmission (CVT) in an automobile, and a direct injection fuel injection valve that directly injects fuel into the combustion chamber of an internal combustion engine.

[0114] Furthermore, the present invention is not limited to the above-described embodiments, but also includes various modifications.

[0115] For example, the above detailed description of the embodiments is provided for ease of understanding and explanation of the present invention, and is not necessarily limited to having all the described configurations. Furthermore, a portion of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Additionally, for a portion of the configuration of each embodiment, other configurations can be added, deleted, or replaced.

[0116] Symbol Explanation

[0117] 10…Internal Combustion Engine (EGN), 11…Electric Generator (MG), 12…Power Distribution Mechanism (TSM), 13…Transmission (TM), 14…Differential Gear (DEF), 15…Wheel (WH), 20…Power Conversion Device, 21…Battery (BAT), 22…Inverter Circuit, 23…Smoothing Capacitor, 24…(Inverter) Control Circuit, 25…Connector, 26…Gate Drive Circuit, 30…Power Device, 31…MOSFET for Control 32…Diode, 33…Current detection circuit, 34…35, 36, 38 Pads, 37…Temperature sensing element, 39…Sensing element, 41…Sensing element temperature detector, 42…Sensing current detector, 43…Temporary main current estimator, 431…Temporary main current calculator, 44…Temperature difference estimator, 441…Temperature difference calculator, 442…Chip loss calculator, 446…Chip loss prediction calculator, 45…Main current corrector, 451…Correction coefficient calculator.

Claims

1. A power conversion device, characterized in that, have: An inverter circuit includes a device having a main element, a temperature sensing element, and a sensing element, wherein the temperature sensing element and the sensing element are arranged adjacent to each other and are separated from the main element. A temporary main current estimator estimates the main current flowing through the main element as a temporary main current based on the sensing current flowing through the sensing element, and performs temperature correction of the temporary main current based on the sensing element temperature detected from the output of the temperature sensing element. A temperature difference estimator outputs an estimated temperature difference between the main element and the sensing element based on the gate drive signal for the main element and the temporary main current. A main current corrector that uses the estimated temperature difference and the on-resistance temperature characteristics of the main component to correct the temporary main current and outputs the corrected main current. as well as The inverter control circuit outputs the gate drive signal based on the corrected main current.

2. The power conversion device according to claim 1, characterized in that, The temporary main current estimator estimates the temporary main current based on the pre-obtained ratio of the main current to the sensing current (i.e., the sensing ratio) and the sensing current.

3. The power conversion device according to claim 2, characterized in that, The temperature difference estimator has the following features: A chip loss calculator that calculates and estimates losses based on the temporary main current; and A temperature difference calculator that calculates the estimated temperature difference based on the estimated loss.

4. The power conversion device according to claim 3, characterized in that, The main current corrector has a correction coefficient calculator that calculates correction coefficients based on the estimated temperature difference.

5. The power conversion device according to claim 4, characterized in that, The main current corrector multiplies the correction coefficient by the temporary main current to obtain the corrected main current.

6. The power conversion device according to claim 5, characterized in that, The main current corrector multiplies the on-resistance temperature coefficient of the main element at the temperature of the sensing element by the estimated temperature difference to obtain the correction coefficient.

7. The power conversion device according to claim 1, characterized in that, The temperature difference estimator estimates the temperature difference between the main element and the sensing element based on predetermined driving conditions for the device.

8. The power conversion device according to claim 7, characterized in that, The predetermined driving conditions are the predetermined main current value and its pulse width in the next switching.

9. The power conversion device according to claim 1, characterized in that, It includes: a second temperature difference estimator, which estimates the temperature difference based on the corrected main current; and The second main current corrector calculates a second correction coefficient based on the second estimated temperature difference estimated by the second temperature difference estimator, and multiplies the second correction coefficient by the corrected main current.

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