Power conversion device

Abstract

A new power conversion device is provided, which can estimate the temperature of a power device without using a temperature detection diode, and can accurately estimate the temperature and current of a current sensing element that observes a main current. The temperature of a power device (30) is estimated based on the current (Ib) flowing between the source terminals (31s, 49s) of the main control element (31) and the current sensing element (49), by using the fact that the resistance value of a semiconductor substrate between the source terminals of a main control element (31) and a current sensing element (49) has temperature dependence. When the main control element (31) and the current sensing element (49) are disconnected, a measurement voltage (Vref) is applied between the source terminals (31s, 49s) of the main control element (31) and the current sensing element (49).

Description

Technical Field

[0001] The present invention relates to a power conversion device including a power device such as an IGBT or a MOSFET, and in particular to a power conversion device requiring high-precision current measurement. Background Art

[0002] As the next generation of automobiles, hybrid vehicles that rotate the drive wheels by combining an internal combustion engine and an electric motor, and electric vehicles that rotate the drive wheels only by an electric motor are attracting attention. Moreover, the automobile motors used in these vehicles are small and capable of generating high torque, and the permanent magnets are embedded in the rotor. In order to maximize the torque of the synchronous motor, vector control is generally used.

[0003] Such vector control generates a PWM signal based on a torque command and a speed calculation current command generated by an accelerator or brake command to drive the power device of the inverter. In addition, in vector control, a current sensor for measuring the output current of the inverter is required. Therefore, unlike the main control element of the IGBT or MOSFET constituting the power device, a current sensing element dedicated to current detection is provided, and the current flowing through the current sensing element is detected to estimate the main current flowing through the main control element. Such a power conversion circuit is well known, for example, as disclosed in Japanese Patent Publication No. 2006-271098 (Patent Document 1).

[0004] However, since the power device composed of the current sensing element and the main control element has temperature dependence, there is a problem that the sensing current characteristics vary with temperature and the correct current cannot be measured. Therefore, a temperature detection diode is formed on the semiconductor substrate constituting the power device, and the current characteristics are corrected using the temperature detection diode.

[0005] However, when the temperature detection diode is used for temperature measurement, a temperature detection diode, wiring connected to the temperature detection diode, and a pad for connecting to an external circuit are required on the semiconductor substrate, and accordingly the area of ​​the semiconductor substrate increases, which increases the product cost. In addition, since a process for making the temperature detection diode on the semiconductor substrate is required, the manufacturing process becomes complicated and the manufacturing cost increases.

[0006] Therefore, a power conversion device capable of measuring the temperature of a power device without using a temperature detection diode has been proposed. For example, Japanese Patent Application Laid-Open No. 2016-225695 (Patent Document 2) shows a current detection circuit having the following configuration.

[0007] In Patent Document 2 Figure 1In the embodiment, FET and IGBT are connected in parallel, IGBT is a power device constituting the main control element and current detection element mentioned in the present invention, and FET is an element added for temperature detection. Moreover, the FET driver operates in a manner that changes the gate voltage of the FET during the period when the IGBT is turned on. Here, the drain current flowing through the FET changes according to the gate voltage, and the current detection unit detects the collector current of the IGBT that changes inversely to the change in the drain current of the FET. Here, since the gate voltage of the FET has temperature dependence, the temperature estimation unit can estimate the temperature of the FET based on the change characteristics of the drain current relative to the change in the gate voltage.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2006-271098

[0011] Patent Document 2: Japanese Patent Application Publication No. 2016-225695 Summary of the invention

[0012] Problem that the invention aims to solve

[0013] However, in the above-mentioned Patent Document 2, based on the premise of utilizing the temperature dependence of the gate voltage of the FET, the change of the drain current when the FET is turned on is observed using the IGBT, and the gate voltage (Vth) of the FET at the moment of turning on is observed, thereby observing the temperature of the FET. However, the temperature of the IGBT that is observing the original current is not taken into consideration, which is an insufficient configuration. In addition, during the on-time period of the IGBT where the current should be measured, the current is changed for temperature observation, which hinders the observable period and accuracy of the current observation.

[0014] An object of the present invention is to provide a new power conversion device that can observe the temperature of a power device having a current sensing element without using a temperature detection diode and can accurately estimate the current of the power device based on current sensing current observation.

[0015] Technical means of solving problems

[0016] The first feature of the present invention is to utilize the fact that the resistance value of the semiconductor substrate between the source terminals of the main control element and the current sensing element has temperature dependence, and when the main control element and the current sensing element are disconnected, a measurement voltage is applied between the source terminals of the main control element and the current sensing element, and the temperature of the power device is estimated based on the current flowing between the respective source terminals of the main control element and the current sensing element at this time.

[0017] In addition, a second feature of the present invention is that, by utilizing the fact that the resistance value of the semiconductor substrate between the source terminals of the main control element and the current sensing element has temperature dependence, when the main control element and the current sensing element are disconnected, a constant current flows from a constant current source to between the source terminals of the main control element and the current sensing element, and the temperature of the power device is estimated based on the terminal voltage between the source terminals of the main control element and the current sensing element at this time.

[0018] Effects of the Invention

[0019] According to the present invention, in a power device equipped with a current sensing element, the temperature of the power device can be accurately estimated with reduced area without using a temperature detection diode, and current observation by the current sensing element is not hindered. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a block diagram showing the system configuration of a hybrid vehicle.

[0021] Figure 2 Yes means Figure 1 A circuit diagram showing the circuit configuration of the power conversion device shown.

[0022] Figure 3 It is a cross-sectional view showing the structure of a power device used in the embodiment of the present invention.

[0023] Figure 4 Yes means Figure 3 The characteristic diagram of the relationship between the resistance between the source terminals of the current sensing element and the main control element and the temperature is shown.

[0024] Figure 5 This is a circuit diagram showing the configuration of a main current detection unit according to the first embodiment of the present invention.

[0025] Figure 6 Yes means Figure 5 A circuit diagram showing the configuration of a power switching unit.

[0026] Figure 7 This is an explanatory diagram for explaining the operation in the temperature detection mode and the current detection mode.

[0027] Figure 8 This is an explanatory diagram for obtaining the temperature-corrected main current from the output voltage of the current measuring unit.

[0028] Fig. 9 This is an explanatory diagram for explaining the relationship between the output voltage of the current measuring unit and the temperature of the power device.

[0029] Fig.10 : is an explanatory diagram showing the relationship between the output voltage of the current measuring unit and the sense current.

[0030] Fig.11 This is an explanatory diagram for explaining the relationship between the sense current of the current detection MOSFET and the main current of the control MOSFET.

[0031] Fig.12 This is a circuit diagram showing the configuration of a main current detection unit according to a second embodiment of the present invention.

[0032] Fig.13 This is an explanatory diagram for explaining the operation in the temperature detection mode and the current detection mode.

[0033] Fig.14 This is an explanatory diagram for obtaining the main current after temperature correction from the output of the current measuring unit.

[0034] Fig.15 This is an explanatory diagram for explaining the relationship between the terminal voltage of the source terminal of the current detection MOSFET and the temperature of the power device.

[0035] Fig.16 This is an explanatory diagram for explaining the relationship between the output voltage of the current measuring unit and the sense current.

[0036] Fig.17 This is an explanatory diagram for explaining the relationship between the sense current of the current detection MOSFET and the main current of the control MOSFET. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present invention will be described in detail using the drawings, but the present invention is not limited to the following embodiments, and various modifications and application examples are also included in the technical concept of the present invention.

[0038] First, the power conversion device to which the present invention is applied is described with reference to the accompanying drawings. The power conversion device of the present invention can be typically applied to a hybrid vehicle or an electric vehicle, and the case where it is applied to a hybrid vehicle is described below as an example. However, the present invention is not limited to hybrid vehicles or electric vehicles, and can of course be used for a power conversion device of an electric motor used in other industrial equipment.

[0039] Figure 1 The system configuration of a hybrid vehicle is shown, and the internal combustion engine 10 and the motor generator 11 are power sources for generating torque for driving the vehicle. In addition, the motor generator 11 not only generates rotation torque as a motor, but also has a power generation function of converting mechanical energy (rotational force) applied to the motor generator 11 into electric power. The motor generator 11 can operate as either a motor or a generator depending on the operation method of the vehicle.

[0040] The output of the internal combustion engine 10 is transmitted to the motor generator 11 via the power split mechanism 12 , and the rotational torque from the power split 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 .

[0041] On the other hand, during the operation of regenerative braking, the rotation torque is transmitted from the wheel 15 to the motor generator 11, and the motor generator 11 generates AC power based on the transmitted rotation torque. The generated AC power is converted into DC power by the power conversion device 20, and the high voltage battery 21 is charged, and the charged power is used again as driving energy.

[0042] 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 transmitted and received between the battery 21 and the inverter circuit 22. The smoothing capacitor 23 smoothes the DC power supplied to the inverter circuit 22.

[0043] The control circuit 24 of the power conversion device 20 receives a command from a higher-level control device or sends data indicating an operation 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 according to the input command, generates a control signal according to the calculation result, and supplies the control signal to the gate drive circuit 26. The gate drive circuit 26 generates a drive signal for controlling the inverter circuit 22 according to the control signal.

[0044] When the motor 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 the AC power to the motor generator 11. The drive mechanism composed of the motor generator 11 and the inverter circuit 22 operates as a motor / generator unit.

[0045] Figure 2 2 is a diagram showing a circuit configuration of the power conversion device 20. In the following description, an example using a power device of MOSFET is described.

[0046] The power conversion device 20 includes an upper arm and a lower arm corresponding to three phases consisting of the U phase, V phase, and W phase of the AC power, and the upper arm and the lower arm are formed by including a control MOSFET 31 and a diode 32 constituting the power device 30. The upper and lower arms of these three phases constitute the inverter circuit 22. Here, the control MOSFET 31 is sometimes expressed as a "main control element" because of the relationship with the current sensing element described later.

[0047] The drain terminal of the control MOSFET 31 of the upper arm is electrically connected to the capacitor terminal on the positive side of the smoothing capacitor 23, and the source terminal of the MOSFET 31 of the lower arm is electrically connected to the capacitor terminal on the negative side of the smoothing capacitor 23. In this way, the control MOSFET 31 has a drain terminal, a source terminal, and a gate terminal. In addition, the diode 32 is electrically connected in parallel between the drain terminal and the source terminal.

[0048] Gate drive circuit 26 (see Figure 1 ) is provided between the source terminal and the gate terminal of the control MOSFET 31, and performs on / off control of the control MOSFET 31. The control circuit 24 provides a control signal to the gate drive circuit 26.

[0049] The power device 30 of the lower arm is provided with a current sensing element for current detection arranged in parallel with the control MOSFET 31. The current sensing element is also composed of a MOSFET, and the sense current flowing through its source terminal is input to the current detection circuit 33. In this embodiment, the current sensing element is described as a "current detection MOSFET".

[0050] Then, the rotor speed and the magnetic pole position are calculated based on the current detected by the current detection circuit 33 and the voltage measured separately therefrom, and the rotation torque and the rotation speed are controlled using these.

[0051] In this way, the control circuit 24 receives a control instruction from the upper control device, generates a control signal for controlling the power devices 30 of the upper arm and the lower arm constituting the inverter circuit 22 according to the control instruction, and provides the control signal to the gate drive circuit 26. The gate drive circuit 26 provides a drive signal for driving the power devices 30 of the upper arm and the lower arm constituting each phase to the power devices 30 of each phase according to the control signal.

[0052] The control MOSFET 31 of the power device 30 is turned on or off according to a drive signal from the gate drive circuit 26 , and converts DC power supplied from the battery 21 into three-phase AC power. The converted power is supplied to the motor generator 11 .

[0053] A power conversion device having such a configuration is already well known, and thus further description thereof will be omitted.

[0054] However, as described above, since the power device 30 has temperature dependence, the current characteristics vary according to the temperature, and the current cannot be measured accurately. Therefore, it is necessary to be able to estimate the temperature of the power device without using a temperature detection diode, and to be able to accurately estimate the temperature of the current sensing element that observes the sense current.

[0055] Example 1

[0056] Therefore, in the present embodiment, the following structure is proposed: utilizing the fact that the resistance value of the semiconductor substrate between the source terminals of the control MOSFET and the current detection MOSFET has temperature dependence, a prescribed measurement voltage is applied between the source terminals of the control MOSFET and the current detection MOSFET when the control MOSFET and the current detection MOSFET are disconnected, and the temperature of the power device is estimated based on the current flowing between the source terminals of the control MOSFET and the current detection MOSFET at this time.

[0057] Thus, by utilizing the fact that the semiconductor substrate between the source terminals of the control MOSFET and the current detection MOSFET has temperature dependence, the temperature of the current detection MOSFET for observing the sense current can be accurately estimated without using a temperature detection diode.

[0058] Figure 3 The cross section of the power device 30 in which the control MOSFET 31 and the current detection MOSFET 49 are assembled is shown. Here, the current detection MOSFET 49 may also be expressed as a "current sensing element" because of its relationship with the above-mentioned main control element.

[0059] Hereinafter, a case where a silicon substrate is used as a semiconductor substrate will be described, but other semiconductor substrates, such as a silicon carbide substrate, may also be used. Figure 3 As shown, on a silicon substrate, a control MOSFET 31 and a current detection MOSFET 49 are formed in an electrically parallel connection relationship with an imaginary dividing line D as a boundary.

[0060] Furthermore, drain electrodes 40m and 40s are provided on the silicon substrate, N+ layers 41m and 41s are formed on the drain electrodes 40m and 40s, and N- layers 42m and 42s are formed on the N+ layers.

[0061] P layers 43m and 43s are formed on N-layers 42m and 42s. In addition, N layers 44m and 44s are formed on P layers 43m and 43s. Gate oxide films 45m and 45s are formed across N-layers 42m and 42s, P layers 43m and 43s, and N layers 44m and 44s, and gate electrodes 46m and 46s are formed on gate oxide films 45m and 45s. In addition, ohmically connected source electrodes 47m and 47s are formed on P layers 43m and 43s, and N layers 44m and 44s. Source electrodes 47m and 47s and gate oxide films 45m and 45s are insulated and separated by insulating films 48m and 48s. Here, N+ layers 41m and 41s are ohmically connected to drain electrodes 40m and 40s.

[0062] In this way, the drain electrode 40m, the N+ layer 41m, the N- layer 42m, the gate oxide film 45m, the gate electrode 46m, the insulating film 48m, and the source electrode 47m form the control MOSFET 31. Similarly, the drain electrode 40s, the N+ layer 41s, the N- layer 42s, the gate oxide film 45s, the gate electrode 46s, the insulating film 48s, and the source electrode 47s form the current detection MOSFET 49. In addition, according to the description, the electrode can be replaced with a terminal.

[0063] Here, as an important configuration in this embodiment, the source electrode 47m of the control MOSFET 31 and the source electrode 47s of the current detection MOSFET 49 are electrically connected via the P layer 43m on the control MOSFET 31 side and the P layer 43s on the current detection MOSFET 49 side. That is, the P layer 43m on the control MOSFET 31 side and the P layer 43s on the current detection MOSFET 49 side are formed as a common P layer.

[0064] Therefore, a temperature-dependent P layer made of a semiconductor substrate is formed between the source electrode 47m of the control MOSFET 31 and the source electrode 47s of the current detection MOSFET 49, and thus the source electrodes 47m and 47s are connected via a temperature-dependent resistor 50. In addition, for the sake of convenience, the temperature-dependent resistor 50 will be described as a "body resistor 50" in the following description.

[0065] Figure 4 The relationship between the resistance value (Rb) of the bulk resistor 50 formed by the P layers 43m and 43s themselves and the temperature (T) has a negative characteristic that the resistance value decreases as the temperature increases. Thus, the temperature of the current detection MOSFET 49 can be estimated with high accuracy.

[0066] Next, a configuration for estimating the temperature of the power device 30 using the bulk resistance 50 and performing temperature correction on the main current will be described.

[0067] Figure 5 The circuit configuration of the main current detection unit provided in the lower arm of one phase is shown in FIG. The same main current detection unit is provided in the lower arms of other phases. Therefore, since the main current detection units of all lower arms operate in the same manner, Figure 5 The circuit structure and operation of the main current detection unit are described in detail.

[0068] exist Figure 5In the embodiment, the power device 30 is formed with a control MOSFET 31 and a current detection MOSFET 49, and these MOSFETs 31 and 49 are electrically connected in parallel. Therefore, if an on signal of a gate signal is applied to the gates of the control MOSFET 31 and the current detection MOSFET 49, the main current (Im) flows through the control MOSFET 31, and the sense current (Is) after the diversion flows through the current detection MOSFET 49.

[0069] The control MOSFET 31 includes a drain terminal 31 d connected to the upper arm and the one-phase coil of the motor generator 11 , a gate terminal 31 g to which a gate signal is input, and a source terminal 31 s connected to the negative electrode of the battery 21 .

[0070] Similarly, the current detection MOSFET 49 includes a drain terminal 49 d connected to the drain terminal 31 d of the control MOSFET 31 , a gate terminal 49 g to which a gate signal is input, and a source terminal 49 s connected to the negative electrode of the battery 21 .

[0071] Furthermore, the source terminal 31s of the control MOSFET 31 and the source terminal 49s of the current detection MOSFET 49 are both connected to the negative electrode of the battery 21. In addition, a body resistor 50 is connected between the source terminal 31s of the control MOSFET 31 and the source terminal 49s of the current detection MOSFET 49. Figure 3 As described above, the bulk resistor 50 is formed by the P layers 43m and 43s of the silicon substrate itself, and has a resistance value (Rb) that depends on temperature. (See Figure 4 )

[0072] Here, a main current detection unit 51 is provided between the source terminal 49s of the current detection MOSFET 49 and the negative electrode of the battery 21. The main current detection unit 51 is composed of at least a current measurement unit 52, a measurement voltage switching unit 53, and a main current temperature correction unit 54. Here, the main current temperature correction unit 54 has a function of performing temperature correction by table conversion processing using a conversion table built in the microcomputer.

[0073] The current measuring unit 52 is composed of an operational amplifier 55 and a parallel resistor (feedback resistor) 56 connected in parallel to the output side and the inverting input (-) side of the operational amplifier 55. The inverting input (-) side is connected to the source terminal 49s of the current detection MOSFET 49. The parallel resistor 56 has a resistance value (Rref).

[0074] On the other hand, the non-inverting input (+) side of the operational amplifier 55 is connected to the measurement voltage switching unit 53. The measurement voltage switching unit 53 applies the measurement voltage (Vref) from the measurement power supply 57 to the current measurement unit 52 in accordance with the switching of the gate signal input to the power device 30. The measurement voltage switching unit 53 will be described later. The output of the current measurement unit 52 is an output voltage (Vo) output from the output side of the operational amplifier 55. The main current (Im) can be estimated from the sense current (Is) by the output voltage (Vo).

[0075] in addition, Figure 6 1 shows an example of the voltage switching unit 53, but the present embodiment is not limited thereto, and various voltage switching units can be used. Figure 6 As shown, the measurement voltage switching unit 53 is connected between the non-inverting input (+) side of the operational amplifier 55 of the current measuring unit 52 and the negative electrode of the battery 21, and a power switching switch 58 composed of a FET is arranged in the middle. The power switching switch 58 is turned on and off by a power switching signal corresponding to the gate signal input to the power device 30, and is turned on when the power switching signal is turned on, and is not turned on when the power switching signal is turned off.

[0076] In addition, the current from the battery 21 is supplied to the resistor 59 to supply the measurement voltage (Vref) between the non-inverting input (+) side of the operational amplifier 55 and the power supply switching switch 58. Therefore, when the power supply switching switch 58 is turned on, the measurement voltage (Vref) is not applied to the current measuring unit 52, and when the power supply switching switch 58 is not turned on, the measurement voltage (Vref) is applied to the current measuring unit 52.

[0077] The main current temperature correction unit 54 also has a function of switching the conversion table according to a table switching signal corresponding to the gate signal input to the power device 30. That is, when the temperature detection mode is executed, it has a function of estimating the temperature of the power device 30 using the temperature conversion table based on the output voltage (Vo) of the current measurement unit 52.

[0078] Similarly, when the current detection mode is executed, the main current (Im) flowing through the control MOSFET 31 is estimated from the sense current (Is) flowing through the current detection MOSFET 49 using a current conversion table based on the output voltage (Vo) of the current measuring unit 52 .

[0079] The main current temperature correction unit 54 has a function of performing temperature correction on the main current (Im) by reflecting the temperature estimated in the temperature detection mode. The main current temperature correction unit 54 will be described in detail later.

[0080] Next, Figure 5The operation of the main current detection unit 51 shown in FIG. 5 is described below. The basic operation of the main current detection unit 51 is to execute the current detection mode to estimate the current value of the main current (including temperature correction) when the gate signal turns on the power device 30, and to execute the temperature detection mode to estimate the temperature of the power device 30 when the gate signal turns off the power device 30. In addition, Figure 7 The following diagram shows changes in main parameters of the main current detection unit 51 when the current detection mode and the temperature detection mode are executed in synchronization with the on and off of the gate signal.

[0081] First, use Figure 5 , Figure 6 and Figure 7 The normal current detection mode is described below. When the gate signal is turned on, the control MOSFET 31 and the current detection MOSFET 49 are turned on, the main current (Im) flows through the control MOSFET 31 , and the sense current (Is) flows through the current detection MOSFET 49 .

[0082] In addition, if Figure 6 As shown in FIG. 1 , since the power switching signal turns on the power switching switch 58 in synchronization with the gate signal to the power device 30, the measurement voltage (Vref) is not applied to the current measuring unit 52. Figure 7 As shown, in the current detection mode, the main current (Im) performs an action corresponding to the action of the control MOSFET 31. At this time, the voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 is 0V. In addition, in this state, since the voltage difference between the two ends of the body resistor 50 is 0V, the existence of the body resistor 50 can be ignored. That is, the detection accuracy of the sense current (Is) will not be degraded due to the existence of the body resistor 50.

[0083] Here, the sense current (Is) flowing through the current detection MOSFET 49 is detected by the current measuring unit 52. Since the input impedance of the operational amplifier 55 is high, almost no sense current (Is) flows on the inverting input (-) side, and the sense current (Is) flows through the parallel resistor 56, so the output voltage (Vo) is "Vo = Is*Rref".

[0084] In addition, if Figure 7 As shown in FIG. 1 , the output voltage (Vo) is displayed in the negative direction because the inverting input (-) side of the operational amplifier 55 is used as the input. In addition, when the output voltage (Vo) needs to be on the positive side, the output can be inverted. Then, the output voltage (Vo) is input to the main current temperature correction unit 54 at the subsequent stage.

[0085] Next, use Figure 5 , Figure 6 and Figure 7The temperature detection mode is described. When the gate signal is turned off, the control MOSFET 31 and the current detection MOSFET 49 are turned off, the main current (Im) does not flow through the control MOSFET 31, and similarly, the sense current (Is) does not flow through the current detection MOSFET 49. In addition, in this state, since the control MOSFET 31 and the current detection MOSFET 49 are turned off, the body resistance 50 acts as described below.

[0086] like Figure 6 As shown, the power switching signal makes the power switching switch 58 non-conductive in synchronization with the gate signal of the power device 30, so that the measurement voltage (Vref) is applied to the current measuring unit 52. Therefore, in the temperature detection mode, the current based on the measurement voltage (Vref) flows to the negative electrode of the battery 21 through the current measuring unit 52, the source terminal 49s of the current detection MOSFET 49, the body resistor 50, and the source terminal 31s of the control MOSFET 31. Here, as described above, since the body resistor 50 has temperature dependence, the body current (Ib) flowing therethrough also has temperature dependence.

[0087] At this time, if Figure 7 As shown in FIG. 1 , the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 is "Vref". That is, the operational amplifier 55 becomes the measurement voltage (Vref) on the inverting input (-) side and the non-inverting input (+) side due to the virtual short circuit. Therefore, Figure 7 As shown, the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 also becomes the measurement voltage (Vref).

[0088] Here, the body current (Ib) flowing through the body resistor 50 is detected by the current measuring unit 52. If the body resistor 50 is focused on, "Vref = Rb*Ib". Here, "Rb" is the resistance value of the body resistor 50. In addition, almost no current flows through the inverting input (-) side and the non-inverting input (+) side of the operational amplifier 55, so the current flowing through the parallel resistor 56 also becomes the body current (Ib).

[0089] Therefore, the output voltage (Vo) of the operational amplifier 55 is a voltage obtained by adding the voltages of the parallel resistor 56 and the body resistor 50, which is "Vo = Rb*Ib+Rref*Ib". Then, the output voltage (Vo) is input to the main current temperature correction unit 54 of the subsequent stage. As described above, since the body current (Ib) has temperature dependence, the output voltage (Vo) of the operational amplifier 55 also has temperature dependence.

[0090] For example, the following can be understood from the above two formulas.

[0091] Vref=Rb*Ib…(1)

[0092] Vo=Rb*Ib+Rref*Ib…(2)

[0093] Here, according to equation (1), Ib=Vref / Rb.

[0094] Next, formula (2) is expressed as follows.

[0095] Vo=Vref+Rref*Vref / Rb

[0096] Then, the difference (ΔV) between the output voltage and the measured voltage (Vref) due to temperature change is:

[0097] ΔV=Vo-Vref=Vref*Rref / Rb...(3).

[0098] Therefore, from formula (3) and Figure 7 It can be seen from the output voltage (Vo) of the current measuring unit 52 that the difference between the output voltage (Vo) and the measured voltage (Vref) is a voltage change (current change) corresponding to the temperature change, which is caused by the resistance value (Rb) of the temperature-dependent body resistor 50. Then, the output voltage (Vo) of the current measuring unit 52 is input to the main current temperature correction unit 54 of the subsequent stage.

[0099] Here, if Figure 4 As shown, the resistance value (Rb) of the bulk resistor 50 increases as the temperature decreases. Therefore, the value of "Rref / Rb" in the equation (3) decreases, and the difference in output voltage (Vo-Vref) corresponding to the temperature change also decreases.

[0100] Therefore, by making the resistance value (Rref) of the parallel resistor 56 variable (the lower the temperature, the larger the resistance value (Rref)), a sufficient output voltage difference (Vo-Vref) can be obtained. In other words, the amplification factor (Vo / Vref) of the current measuring unit 52 can be improved. In addition, when changing the resistance value (Rref) of the parallel resistor 56, it can be achieved by switching a plurality of resistors.

[0101] The temperature detection mode described above is a mode performed during the period when the control MOSFET 31 and the current detection MOSFET 49 are turned off, so it is performed exclusively in the current detection mode which is a necessary and sufficient condition to perform during the period when the control MOSFET 31 and the current detection MOSFET 49 are turned on. That is, in the configuration of the present invention, there is a feature that the configuration and operation for temperature detection do not interfere with the current detection mode and do not impair the observation accuracy of the sensed current (Is).

[0102] In the main current temperature correction unit 54, the temperature correction is performed by the control function of the microcomputer, and the output voltage (Vo) is input to the A / D converter of the input / output circuit. Then, the temperature correction function of the microcomputer executes Figure 8 In addition, although control is actually performed by a control program, the following description will be given as a control function block.

[0103] First, when a table switching signal synchronized with the gate signal of the power device 30 is input, the output voltage (Vo) in the temperature detection mode or the output voltage (Vo) in the current detection mode is taken in by the switching function unit 60. In the temperature detection mode, as described above, since the power device 30 is in the off state, the switching function unit 60 performs the control function of the voltage / temperature conversion function unit 61. On the other hand, in the current detection mode, as described above, since the power device 30 is in the on state, the switching function unit 60 performs the control function of the voltage / current conversion function unit 62.

[0104] For example, when the temperature detection mode is selected, the switching function unit 60 performs the control function of the voltage / temperature conversion function unit 61 to estimate the temperature (T) of the power device 30 from the output voltage (Vo). As described above, the output voltage (Vo) in the temperature detection mode has temperature dependence.

[0105] Therefore, by having Fig. 9 The voltage / temperature conversion table of the conversion characteristics shown can estimate the temperature (T) of the power device 30 from the output voltage (Vo). Fig. 9 The voltage / temperature conversion table shown is a table schematically showing the relationship between the output voltage (Vo) and the temperature (T).

[0106] The voltage / temperature conversion table is a conversion table determined by the characteristics of the body resistance 50 and the current measuring unit 52. In the voltage / temperature conversion table, the horizontal axis represents the output voltage (Vo) and the vertical axis represents the temperature (T) of the power device 30. In addition, the dotted line is the measured voltage (Vref). And, the temperature of the power device 30 increases as the output voltage (Vo) increases (= the body resistance (Rb) decreases).

[0107] Here, the characteristics of the voltage / temperature conversion table may be characteristics obtained by experiment, characteristics obtained by simulation, or characteristics obtained by conversion formula. The information of temperature (T) obtained by the voltage / temperature conversion function unit 61 is used by the subsequent sense current / main current conversion function unit 63.

[0108] Next, when the current detection mode is selected, the switching function unit 60 executes the control function of the voltage / current conversion function unit 62 to estimate the sense current (Is) flowing through the current detection MOSFET 49 based on the output voltage (Vo). In addition, the output voltage (Vo) at this time is not affected by the resistor 50.

[0109] Therefore, by having Fig.10 The voltage / current conversion table of the conversion characteristics shown in the figure can estimate the sense current (Is) flowing through the current detection MOSFET 49 from the output voltage (Vo). Fig.10 The voltage / temperature conversion table shown is also a table schematically showing the relationship between the output voltage (Vo) and the sense current (Is).

[0110] The voltage / current conversion table is a conversion table determined by the characteristics of the current measuring unit 52 . In the voltage / current conversion table, the horizontal axis represents the output voltage (Vo) and the vertical axis represents the sense current (Is) flowing through the current detection MOSFET 49 .

[0111] As described above, the sense current (Is) can be obtained from the relationship "Vo = Is*Rref". That is, since the output voltage (Vo) is measured and the resistance value (Rref) of the parallel resistor 56 is known, the sense current (Is) can be obtained. Therefore, the greater the output voltage (Vo), the greater the sense current (Is) flowing through the current detection MOSFET 49.

[0112] The information of the sense current (Is) obtained by the voltage / current conversion function unit 62 is used by the subsequent sense current / main current conversion function unit 63. In addition, the characteristics of the voltage / current conversion table may be characteristics obtained by experiment, characteristics obtained by simulation, or characteristics obtained by conversion formula.

[0113] Next, the sense current / main current conversion function unit 63 performs a control function of estimating the main current (Im) based on the information of the sense current (Is). Since the current division ratio of the current flowing through the control MOSFET 31 and the current detection MOSFET 49 is predetermined, if the sense current (Is) is known, the main current (Im) can be estimated.

[0114] Therefore, by having Fig.11 The sense current / main current conversion table with conversion characteristics as shown can estimate the main current flowing through the control MOSFET 31 based on the sense current (Is) flowing through the current detection MOSFET 49. Fig.11 The sense current / main current conversion table shown is also a table schematically showing the relationship between the sense current (Is) and the main current (Im).

[0115] The sense current / main current conversion table is a conversion table determined by the characteristics of the current detection MOSFET 49 and the control MOSFET 31 . In the sense current / main current conversion table, the horizontal axis represents the sense current (Is) and the vertical axis represents the main current (Im).

[0116] Furthermore, when the main current (Im) is obtained from the sense current (Is), the main current (Im) can be temperature-corrected based on the information of the temperature (T) of the power device 30 obtained by the voltage / temperature conversion function unit 61. For example, Fig.11 The example shows an example in which the current characteristic representing the relationship between the sense current (Is) and the main current (Im) is corrected by the temperature (T), and the slope of the current characteristic is corrected by the temperature (T).

[0117] Alternatively, the temperature correction coefficient corresponding to the temperature (T) may be multiplied by the sensing current (Is), and the main current (Im) may be obtained based on the temperature-corrected sensing current (Is). Furthermore, the main current (Im) obtained based on the sensing current (Is) may be multiplied by the temperature correction coefficient corresponding to the temperature (T), and the main current (Im) may be obtained by temperature correction.

[0118] Furthermore, the voltage / temperature conversion table, the voltage / current conversion table, and the sense current / main current conversion table described above are respectively provided as different conversion tables, but may be provided as a conversion table in which these are combined.

[0119] In the above-mentioned embodiment, the main current detection unit 51 used for vector control is described, but the present embodiment can also be applied to an overcurrent detection device that detects an overcurrent flowing through the power device 30 to protect the power device 30 .

[0120] Thus, in this embodiment, the following configuration is used: utilizing the fact that the resistance value of the semiconductor substrate between the source terminals of the control MOSFET and the current detection MOSFET has temperature dependence, a measurement voltage is applied between the source terminals of the control MOSFET and the current detection MOSFET when the control MOSFET and the current detection MOSFET are disconnected, and the temperature of the power device is estimated based on the current flowing between the respective source terminals of the main control MOSFET and the current detection MOSFET at this time.

[0121] This makes it possible to accurately estimate the temperature of the current sensing element without hindering observation of the sense current, without using a separate temperature detection diode.

[0122] Example 2

[0123] Next, a second embodiment of the present invention will be described. In the second embodiment, a configuration is proposed for estimating the temperature of the power device 30 using a constant current source.

[0124] exist Fig.12 1 also shows the circuit structure of the main current detection unit provided on the lower arm of one phase, and the same main current detection unit is also provided on the lower arms of other phases. Therefore, since the main current detection units of all lower arms operate in the same way, Fig.12 The circuit configuration and operation of the main current detection unit will be described.

[0125] exist Fig.12 In the embodiment, the configuration of the power device 30 is the same as that of the first embodiment, so the description is omitted. In addition, a main current detection unit 70 is provided between the source terminal 49s of the current detection MOSFET 49 and the negative electrode of the battery 21. The main current detection unit 70 is composed of at least a current measurement unit 71, a constant current source switching unit 72, and a main current temperature correction unit 73. Here, the main current temperature correction unit 73 has a function of performing temperature correction by table conversion processing using a conversion table built in a microcomputer, as in the first embodiment.

[0126] The current measuring unit 71 is composed of an operational amplifier 74 and a parallel resistor (feedback resistor) 75 connected in parallel to the output side of the operational amplifier 74 and the inverting input (-) side, and the inverting input (-) side is connected to the source terminal 49s of the current detection MOSFET 49. The parallel resistor 75 has a resistance value (Rref). The output of the current measuring unit 71 is an output voltage (Vo) output from the output side of the operational amplifier 74. The main current (Im) can be estimated from the sense current (Is) through the output voltage (Vo).

[0127] The constant current source switching unit 72 is composed of a constant current source 76, a first switch SW1, and a second switch SW2. Here, the two switches SW1 and SW2 are composed of semiconductor elements such as FETs.

[0128] Furthermore, a first switch SW1 is connected between the inverting input (-) side of the operational amplifier 74 of the current measuring unit 71 and the source terminal 49s of the current detecting MOSFET 49. Furthermore, a constant current source 76 is connected between the source terminal 49s of the current detecting MOSFET 49 and the first switch SW1. Furthermore, the constant current source 76 is configured to selectively flow a constant current (Iref) through the source terminal 49s of the current detecting MOSFET 49 via the second switch SW2. This will be described later.

[0129] Here, the first switch SW1 and the second switch SW2 are configured to operate in accordance with a switch switching signal corresponding to a gate signal input to the power device 30, and the first switch SW1 and the second switch SW2 operate in opposite directions. For example, if the first switch SW1 and the second switch SW2 are FETs of the same type, then if the switch switching signal of one is inverted by the inverter 77, the first switch SW1 and the second switch SW2 can operate in opposite directions.

[0130] The main current temperature correction unit 73 also has a function of switching the conversion table according to a table switching signal corresponding to the gate signal input to the power device 30. That is, when the temperature detection mode is executed, it has a function of estimating the temperature of the power device 30 using the temperature conversion table based on the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49.

[0131] On the other hand, when the current detection mode is executed, the main current (Im) flowing through the control MOSFET 31 is estimated from the sense current (Is) flowing through the current detection MOSFET 49 using the current conversion table based on the output voltage (Vo) of the current measuring unit 71. In addition, the main current temperature correction unit 73 has a function of performing temperature correction on the main current (Im) by reflecting the temperature estimated in the temperature detection mode. In addition, the details of the main current temperature correction unit 73 will be described later.

[0132] Next, Fig.12 The operation of the main current detection unit 70 shown in FIG. 1 is described below. The basic operation of the main current detection unit 70 is to execute the current detection mode to estimate the current value of the main current (including temperature correction) when the gate signal turns on the power device 30, and to execute the temperature detection mode to estimate the temperature of the power device 30 when the gate signal turns off the power device 30. In addition, Fig.13 The following diagram shows changes in main parameters of the main current detection unit 70 when the current detection mode and the temperature detection mode are executed in synchronization with the on and off of the gate signal.

[0133] First, use Fig.12 and Fig.13 The normal current detection mode is described below. When the gate signal is turned on, the control MOSFET 31 and the current detection MOSFET 49 are turned on, the main current (Im) flows through the control MOSFET 31, and the sense current (Is) flows through the current detection MOSFET 49. In addition, as described above, the existence of the body resistance 50 can be ignored in this state.

[0134] In addition, since the first switch SW1 is turned on and the second switch SW2 is turned off in synchronization with the gate signal to the power device 30, the constant current (Iref) from the constant current source 76 does not flow through the source terminal 49s of the current detection MOSFET 49. Fig.13 As shown, in the current detection mode, the main current (Im) operates in accordance with the operation of the control MOSFET 31. At this time, the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 is 0V.

[0135] Here, the sense current (Is) flowing through the current detection MOSFET 49 is detected by the current measuring unit 71. Since the input impedance of the operational amplifier 74 is high, almost no sense current (Is) flows on the inverting input (-) side, and the sense current (Is) flows through the parallel resistor 75, so the output voltage (Vo) becomes "Vo = Is*Rref".

[0136] In addition, here, Fig.13 As shown in FIG. 1 , the output voltage (Vo) is shown as a negative direction because the inverting input (-) side of the operational amplifier 74 is used as an input. In addition, when the output voltage (Vo) needs to be positive, the output can be inverted. And, the output voltage (Vo) is used in the main current temperature correction unit 54 of the subsequent stage.

[0137] Next, use Fig.12 and Fig.13 The temperature detection mode is described. When the gate signal of the power device 30 is turned off, the control MOSFET 31 and the current detection MOSFET 49 are turned off, the main current (Im) does not flow through the control MOSFET 31, and similarly, the sense current (Is) does not flow through the current detection MOSFET 49. In addition, in this state, since the control MOSFET 31 and the current detection MOSFET 49 are turned off, the body resistance 50 acts as described below.

[0138] like Fig.12 As shown, the switch switching signal makes the first switch SW1 non-conductive and the second switch SW2 conductive in synchronization with the gate signal of the power device 30. Therefore, the current measuring device 71 and the source terminal 49s of the current detection MOSFET 49 are disconnected, and a constant current (Iref) flows from the constant current source 76 to the source terminal 49s of the current detection MOSFET 49.

[0139] Therefore, in the temperature detection mode, the constant current (Iref) based on the constant current source 76 flows to the negative electrode of the battery 21 through the source terminal 49s of the current detection MOSFET 49, the body resistor 50, and the source terminal 31s of the control MOSFET 31. Here, as described above, since the resistance value (Rb) of the body resistor 50 has temperature dependence, the terminal voltage (Vs) between the source terminal 49s of the current detection MOSFET 49 and the source terminal 31s of the control MOSFET 31 also has temperature dependence.

[0140] At this time, if Fig.13 As shown, the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 becomes "Vs = Iref * Rb". Here, "Rb" is the resistance value of the body resistor 50. And, the terminal voltage (Vs) of the source terminal 49s is used in the main current temperature correction unit 73 of the subsequent stage.

[0141] Here, even when the value of the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 is small, the voltage of the source terminal 49s and the source terminal 31s, which are both ends of the body resistor 50, can be input to the inverting input (-) side and the non-inverting input (+) side of the voltage amplifier for amplification. In addition, the voltage of the source terminal 31s becomes a reference voltage.

[0142] In the main current temperature correction unit 73, temperature correction is performed by the control function of the microcomputer, and the output voltage (Vo) of the current measuring unit 71 and the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49 are input to the A / D converter of the input / output circuit. Then, the temperature correction function of the microcomputer is executed. Fig.14 In addition, although control is actually performed by a control program, the following description will be made as a control function block.

[0143] First, when a table switching signal synchronized with a gate signal of the power device 30 is input, the terminal voltage (Vs) in the temperature detection mode or the output voltage (Vo) in the current detection mode is taken in by the switching function section 78 .

[0144] In the temperature detection mode, as described above, since the power device 30 is in the off state, the switching function unit 78 takes in the terminal voltage (Vs) in the temperature detection mode, but does not take in the output voltage (Vo) of the current measuring unit 71. Then, in the temperature detection mode, the control function of the voltage / temperature conversion function unit 79 is executed.

[0145] On the other hand, in the current detection mode, as described above, the power device 30 is in the on state, so the switching function unit 78 takes in the output voltage (Vo) in the current detection mode, but does not take in the terminal voltage (Vs) of the source terminal 49s of the current detection MOSFET 49. Then, in the current detection mode, the control function of the voltage / current conversion function unit 80 is executed.

[0146] For example, when the temperature detection mode is selected, the switching function unit 78 performs the control function of the voltage / temperature conversion function unit 79 to estimate the temperature (T) of the power device 30 from the terminal voltage (Vs). As described above, the terminal voltage (Vs) in the temperature detection mode has temperature dependence.

[0147] Therefore, by having Fig.15 The voltage / temperature conversion table of the conversion characteristics shown in FIG. 1 can estimate the temperature (T) of the power device 30 from the terminal voltage (Vs). Fig.15 The voltage / temperature conversion table shown is a table schematically showing the relationship between the output voltage (Vo) and the temperature (T).

[0148] The voltage / temperature conversion table is a conversion table determined by the characteristics of the body resistor 50 and the constant current power supply 76. In the voltage / temperature conversion table, the horizontal axis represents the terminal voltage (Vs) and the vertical axis represents the temperature (T) of the power device 30. Figure 4 The characteristic is that the lower the terminal voltage (Vs) (= the lower the body resistance (Rb)), the higher the temperature of the power device 30. Therefore, the closer the temperature (T) of the power device 30 on the vertical axis is to the origin, the higher the temperature.

[0149] In addition, the characteristics of the voltage / temperature conversion table may be characteristics obtained by experiment, characteristics obtained by simulation, or characteristics obtained by conversion formula. The information of temperature (T) obtained by the voltage / temperature conversion function unit 79 is used in the subsequent sense current / main current conversion function unit 81.

[0150] Next, when the current detection mode is selected, the switching function unit 78 performs the control function of the voltage / current conversion function unit 80, and estimates the sense current (Is) flowing through the current detection MOSFET 49 based on the output voltage (Vo). In addition, the output voltage (Vo) at this time is not affected by the resistor 50.

[0151] Therefore, by having Fig.16 The voltage / current conversion table of the conversion characteristics shown in the figure can estimate the sense current (Is) flowing through the current detection MOSFET 49 from the output voltage (Vo). Fig.16The voltage / temperature conversion table shown is also a table schematically showing the relationship between the output voltage (Vo) and the sense current (Is).

[0152] The voltage / current conversion table is a conversion table determined by the characteristics of the current measuring unit 71 . In the voltage / current conversion table, the horizontal axis represents the output voltage (Vo) and the vertical axis represents the sense current (Is) flowing through the current detection MOSFET 49 .

[0153] As described above, the sense current (Is) can be obtained from the relationship "Vo = Is*Rref". That is, since the output voltage (Vo) is measured and the resistance value (Rref) of the parallel resistor 75 is known, the sense current (Is) can be obtained. Therefore, the larger the output voltage (Vo), the larger the sense current (Is) flowing through the current detection MOSFET 49.

[0154] The information of the sense current (Is) obtained by the voltage / current conversion function unit 80 is used by the subsequent sense current / main current conversion function unit 63. In addition, the characteristics of the voltage / current conversion table may be characteristics obtained by experiment, characteristics obtained by simulation, or characteristics obtained by conversion formula.

[0155] Next, the sense current / main current conversion function unit 81 performs a control function of estimating the main current (Im) based on the sense current (Is) information. Since the current split ratio of the current flowing through the control MOSFET 31 and the current detection MOSFET 49 is predetermined, if the sense current (Is) is known, the main current (Im) can be estimated.

[0156] Therefore, by having Fig.17 The sense current / main current conversion table with conversion characteristics as shown can estimate the main current flowing through the control MOSFET 31 based on the sense current (Is) flowing through the current detection MOSFET 49. Fig.17 The sense current / main current conversion table shown is also a table schematically showing the relationship between the sense current (Is) and the main current (Im).

[0157] The sense current / main current conversion table is a conversion table determined by the characteristics of the current detection MOSFET 49 and the control MOSFET 31 . In the sense current / main current conversion table, the horizontal axis represents the sense current (Is) and the vertical axis represents the main current (Im).

[0158] Furthermore, when the main current (Im) is obtained from the sense current (Is), the main current (Im) can be temperature-corrected based on the information of the temperature (T) of the power device 30 obtained by the voltage / temperature conversion function unit 79. For example, Fig.17The example shows an example in which the current characteristic representing the relationship between the sense current (Is) and the main current (Im) is corrected by the temperature (T), and the slope of the current characteristic is corrected by the temperature (T).

[0159] Alternatively, the temperature correction coefficient corresponding to the temperature (T) may be multiplied by the sensing current (Is), and the main current (Im) may be obtained based on the temperature-corrected sensing current (Is). Furthermore, the main current (Im) obtained based on the sensing current (Is) may be multiplied by the temperature correction coefficient corresponding to the temperature (T), and the main current (Im) may be obtained by temperature correction.

[0160] Furthermore, the voltage / temperature conversion table, the voltage / current conversion table, and the sense current / main current conversion table described above are respectively provided as different conversion tables, but may be provided as a conversion table in which these are combined.

[0161] Of course, as described in the first embodiment, the present embodiment can also be applied to an overcurrent detection device that detects an overcurrent flowing through the power device 30 to protect the power device 30 .

[0162] Thus, in this embodiment, the following configuration is used: utilizing the fact that the resistance value of the semiconductor substrate between the source terminals of the control MOSFET and the current detection MOSFET has temperature dependence, when the control MOSFET and the current detection MOSFET are disconnected, a prescribed constant current flows from a constant current source between the source terminals of the control MOSFET and the current detection MOSFET, and the temperature of the power device is estimated based on the source terminal voltage between the source terminals of the main control MOSFET and the current detection MOSFET at this time.

[0163] Thus, the temperature of the current sensing element that observes the sense current can be accurately estimated without using a temperature detection diode.

[0164] In the first and second embodiments, the power conversion device for controlling the electric motor is 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 the electromagnetic coil of the electromagnetic drive mechanism, it can also be applied to an overcurrent detection device that detects the overcurrent flowing in the MOSFET to protect the MOSFET. Here, as the electromagnetic drive mechanism, there is, for example, an electromagnetic flow control valve that adjusts the oil amount of the continuously variable transmission (CVT) of the automobile, and there is also a direct injection fuel injection valve that directly injects fuel into the combustion chamber of the internal combustion engine.

[0165] In addition, the present invention is not limited to the above-mentioned embodiments, but also includes various modified examples. For example, the above-mentioned embodiments are detailed descriptions for easily understanding the present invention, and are not necessarily limited to having all the described structures. In addition, a part of the structure of some embodiments can be replaced by the structure of other embodiments, and the structure of some embodiments can be added to the structure of other embodiments. In addition, for a part of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0166] Explanation of symbols

[0167] 30…power device, 31…control MOSFET, 31d…drain terminal, 31g…gate terminal, 31s…source terminal, 49…current detection MOSFET, 49d…drain terminal, 49g…gate terminal, 49s…source terminal, 50…body resistance, 51…main current detection unit, 52…current measurement unit, 53…measurement voltage switching unit, 54…main current temperature correction unit, 55…operational amplifier, 56…parallel resistor, 57…measurement power supply, 58…power supply switching switch, 59…resistance, 60…switching function unit, 61…voltage / temperature conversion function unit, 62…voltage / sensing current conversion function unit, 63…sensing current / main current conversion function unit.

Claims

1. A power conversion device comprising a current detection unit for estimating a current flowing through a power device, wherein: The power device is composed of at least a main control element formed on a semiconductor substrate and a current sensing element electrically connected in parallel with the main control element. The current detection unit applies a predetermined measurement voltage between the source terminals of the main control element and the current sensing element when the main control element and the current sensing element are disconnected, and estimates the temperature of the power device based on the current flowing between the source terminals of the main control element and the current sensing element at this time. The main control element is formed by a control MOSFET, and the current sensing element is formed by a current detection MOSFET. The source terminal of the control MOSFET and the source terminal of the current detection MOSFET are connected via a body resistance which is a temperature-dependent resistance formed by the semiconductor substrate. The current detection unit executes a current detection mode and a temperature detection mode in accordance with a gate signal for controlling the power device. In the temperature detection mode in which the gate signal is in an OFF state, the current detection unit estimates the temperature of the power device based on the current flowing through the body resistor. In the current detection mode in which the gate signal is in an on state, the current detection unit estimates a main current flowing through the control MOSFET based on a sense current flowing through the current detection MOSFET and information on the temperature of the power device.

2. The power conversion device according to claim 1, characterized in that: The bulk resistor is formed by a P layer connected to the source terminal of the control MOSFET and a P layer connected to the source terminal of the current detection MOSFET, and the P layers are a common P layer.

3. The power conversion device according to claim 1, characterized in that: In response to the temperature detection mode in which the power device is turned off, the measurement voltage is applied to the source terminal of the current detection MOSFET.

4. The power conversion device according to claim 1, characterized in that: A current measuring unit and a measurement voltage switching unit are connected to the source terminal of the current detection MOSFET. The current measuring unit is composed of an operational amplifier and a parallel resistor connecting the output unit and the inverting input (-) side of the operational amplifier. The inverting input (-) side of the operational amplifier is connected to the source terminal of the current detection MOSFET, and the non-inverting input (+) side of the operational amplifier is connected to the measurement voltage switching unit to apply the measurement voltage.

5. The power conversion device according to claim 4, characterized in that: The output section of the operational amplifier outputs a first output voltage based on the current flowing through the bulk resistor in the temperature detection mode, and outputs a second output voltage based on the current flowing through the current detection MOSFET in the current detection mode.

6. The power conversion device according to claim 5, characterized in that: The current detection unit includes a main current temperature correction unit, and the first output voltage and the second output voltage are input from the current measurement unit to the main current temperature correction unit. The main current temperature correction unit estimates the temperature of the power device based on the first output voltage, estimates the sense current flowing through the current detection MOSFET based on the second output voltage, and estimates the main current flowing through the control MOSFET based on information on the temperature of the power device and the sense current.

7. The power conversion device according to claim 4, characterized in that: The resistance value of the parallel resistor connected in parallel to the operational amplifier constituting the current measuring unit is variable according to the temperature of the power device.

8. The power conversion device according to claim 7, characterized in that: The parallel resistor connected in parallel with the operational amplifier is set so that the resistance value increases as the temperature of the power device decreases.

9. A power conversion device comprising a current detection unit for estimating a current flowing through a power device, wherein: The power device is composed of at least a main control element formed on a semiconductor substrate and a current sensing element electrically connected in parallel with the main control element. When the main control element and the current sensing element are disconnected, the current detection unit flows a predetermined constant current from a constant current source between the source terminals of the main control element and the current sensing element, and estimates the temperature of the power device based on the terminal voltage between the source terminals of the main control element and the current sensing element at this time. The main control element is formed by a control MOSFET, and the current sensing element is formed by a current detection MOSFET. The source terminal of the control MOSFET and the source terminal of the current detection MOSFET are connected via a body resistance which is a temperature-dependent resistance formed by the semiconductor substrate. The current detection unit executes a current detection mode and a temperature detection mode in response to a gate signal for controlling the power device. In the temperature detection mode in which the gate signal is in an OFF state, the current detection unit estimates the temperature of the power device based on the body resistance and the terminal voltage determined by the constant current flowing through the body resistance. In the current detection mode in which the gate signal is in an on state, the current detection unit estimates a main current flowing through the control MOSFET based on a sense current flowing through the current detection MOSFET and information on the temperature of the power device.

10. The power conversion device according to claim 9, characterized in that: The constant current source and the current measuring unit are connected to the source terminal of the current detecting MOSFET via a current switching unit. Corresponding to the gate signal of the power device, the current switching unit performs the following actions: When the source terminal of the current detection MOSFET and the constant current source are turned on, the source terminal of the current detection MOSFET and the current measuring unit are turned off, and the terminal voltage between the source terminals of the current detection MOSFET and the control MOSFET is output, When the source terminal of the current detection MOSFET and the constant current source are not conducted, the source terminal of the current detection MOSFET and the current measuring unit are conducted, and the current measuring unit outputs an output voltage.

11. The power conversion device according to claim 10, characterized in that: The current detection unit includes a main current temperature correction unit, the terminal voltage and the output voltage are input to the main current temperature correction unit, and The main current temperature correction unit estimates the temperature of the power device based on the terminal voltage, estimates the sense current flowing through the current detection MOSFET based on the output voltage, and estimates the main current flowing through the control MOSFET based on information on the temperature of the power device and the sense current.

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