CN116508256A

CN116508256A - Temperature estimation device and control device

Info

Publication number: CN116508256A
Application number: CN202180075384.1A
Authority: CN
Inventors: 茂木拓也; 塚越英斗
Original assignee: Hitachi Astemo Ltd
Current assignee: Hitachi Astemo Ltd
Priority date: 2020-11-09
Filing date: 2021-11-04
Publication date: 2023-07-28
Also published as: JP2022089339A

Abstract

In an inverter circuit provided with 1 or more switch legs each having an upper arm and a lower arm each provided with a return diode, the temperature estimation device estimates the operating temperature based on the forward voltage and the forward current of the return diode obtained from the inverter circuit in an extended time width in which the dead time of the upper arm and the lower arm is extended from a predetermined time width.

Description

Temperature estimation device and control device

Technical Field

The present invention relates to a temperature estimation device and a control device.

The present application claims priority based on japanese patent application publication nos. 2020-186355 at 11/9 of 2020, the contents of which are incorporated herein by reference. The present application claims priority based on japanese patent application No. 2020-201669 at 12/4/2020, the contents of which are incorporated herein by reference.

Background

Patent document 1 discloses a power converter. The power converter is intended to estimate the junction temperature (Junction Temperature) of a switching element following a rapid temperature rise with high accuracy, and is a power converter using a semiconductor switching element, and includes: a current detection unit that detects a current flowing through the semiconductor switching element; a voltage detection unit that detects a saturation voltage and a forward voltage of the semiconductor switching element; and a control unit that estimates the junction temperature of the semiconductor switching element from the saturation voltage, the forward voltage, and the current (forward current).

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2019-216571

Disclosure of Invention

Problems to be solved by the invention

However, in the above-described power converter, the junction temperature of the semiconductor switching element is estimated as the operation temperature of the semiconductor switching element based on the saturation voltage, the forward voltage, and the forward current, which are characteristic amounts of the semiconductor switching element. However, in the above-described power converter, it is necessary to detect the characteristic amount of the semiconductor switching element in a relatively short time, and thus high-speed operation is required, and thus noise toughness (noise toughness) becomes low.

The present invention has been made in view of the above circumstances, and an object thereof is to estimate an operation temperature of a semiconductor switching element without requiring high-speed operation.

Means for solving the problems

(1) In an inverter circuit provided with 1 or more switching arms each having semiconductor switching elements of the upper arm and the lower arm each provided with a return diode, the temperature estimation device estimates the operating temperature from the forward voltage and the forward current of the return diode obtained from the inverter circuit within an extended time width in which the dead time of the upper arm and the lower arm is extended to be greater than a predetermined time width.

(2) In the temperature estimation device according to (1), the expansion time width may be set by making the other on time of the gate signals for controlling one of the upper arm and the lower arm and the other one of the upper arm and the lower arm, respectively, shorter than the one on time.

(3) In the temperature estimation device according to (1), the expansion time width may be set by removing an on pulse of the other gate signal out of the gate signals that control one of the upper arm and the lower arm and the other one of the upper arm and the lower arm, respectively.

(4) In the temperature estimation device according to any one of (1) to (3) above, the operating temperature of the semiconductor switching element may be estimated based on a forward voltage and a forward current of the reflux diode obtained from the inverter circuit when the reflux diode is operated in a linear region.

(5) In the temperature estimation device according to any one of (1) to (4), the inverter circuit may be a three-phase inverter circuit including 3 switching legs, and the operation temperature may be estimated based on the forward voltage and the forward current obtained from the three-phase inverter circuit.

(6) In the temperature estimation device according to any one of (1) to (5), when the inverter circuit includes a plurality of the semiconductor switching elements, the operation temperature of a part of the semiconductor switching elements may be estimated based on heat radiation performance of the plurality of the semiconductor switching elements.

(7) The temperature estimation device is provided with: the temperature estimation device according to any one of the above (1) to (6); and a gate signal generating unit that generates gate signals for controlling the upper arm and the lower arm based on the operation temperature estimated by the temperature estimating device.

Effects of the invention

According to the present invention, the operating temperatures of the upper arm and the lower arm are estimated based on the forward voltage and the forward current acquired in the extended time width, so that the operating temperatures can be estimated without requiring a high-speed operation.

Drawings

Fig. 1 is a block diagram showing the functional configuration of a temperature estimation device and a control device according to a first embodiment.

Fig. 2 is a flowchart showing the overall operation of the temperature estimation device and the control device according to the first embodiment.

Fig. 3 is a timing chart showing operations of the temperature estimation device and the control device according to the first embodiment.

Fig. 4 is a flowchart showing detailed operations of the temperature estimation device and the control device according to the first embodiment.

Fig. 5 is a block diagram showing the functional configuration of the temperature estimation device and the control device according to the second embodiment.

Fig. 6 is a graph showing a relationship between forward current and forward voltage of a BODY DIODE (BODY DIODE) according to the second embodiment.

Fig. 7 is a flowchart showing the overall operation of the temperature estimation device and the control device according to the second embodiment.

Fig. 8 is a flowchart showing detailed operations of the temperature estimation device and the control device according to the second embodiment.

Fig. 9 is a timing chart showing operations of the temperature estimation device and the control device according to the second embodiment.

Fig. 10 is a schematic diagram showing a cooling structure of a three-phase inverter circuit according to a second embodiment.

Detailed Description

(first embodiment)

As shown in fig. 1, a control device a according to the first embodiment is a device that is a control target of a three-phase inverter circuit B, and includes a temperature estimating unit a1 and a gate signal generating unit a2 as functional components.

The three-phase inverter circuit B is configured by MOS transistors 1 to 6, and converts dc power supplied from a dc power supply 7 into three-phase ac power to supply the three-phase ac power to the motor 8. The three-phase inverter circuit B includes switching arms (switching legs) Ru, rv, and Rw corresponding to the respective switching arms, and additionally includes voltage sensors 9 to 12 and current sensors 13 to 15.

Of these switching legs Ru, rv, rw, switching leg Ru is a U-phase switching leg corresponding to U. The switching leg Rv is a V-phase switching leg corresponding to V. The switching leg Rw is a W-phase switching leg corresponding to W.

These switching legs Ru, rv, rw include MOS transistors 1, 3, 5 constituting upper arms and MOS transistors 2, 4, 6 constituting lower arms, respectively. These MOS transistors 1 to 6 correspond to the semiconductor switching element of the present invention.

That is, U-phase switching arm Ru includes upper-arm MOS transistor 1 and lower-arm MOS transistor 2. The V-phase switching arm Rv includes an upper-arm MOS transistor 3 and a lower-arm MOS transistor 4. The W-phase switching arm Rw includes an upper-arm MOS transistor 5 and a lower-arm MOS transistor 6.

When the U-phase switching leg Ru, the V-phase switching leg Rv, and the W-phase switching leg Rw are further described, in the U-phase switching leg Ru, the MOS transistor 1 of the upper arm and the MOS transistor 2 of the lower arm are connected in series with the dc power supply 7.

That is, in the upper-arm MOS transistor 1, the drain terminal is connected to the positive electrode of the dc power supply 7, the source terminal is connected to the drain terminal of the lower-arm MOS transistor 2, and the gate terminal is connected to the gate signal generating unit a 2. The upper-arm MOS transistor 1 controls an ON state (ON state)/OFF state (OFF state) by the first gate signal input from the gate signal generating section a 2.

The lower-arm MOS transistor 2 has a drain terminal connected to the source terminal of the upper-arm MOS transistor 1, a source terminal connected to the negative electrode of the dc power supply 7, and a gate terminal connected to the gate signal generating unit a 2. The MOS transistor 2 of the lower arm controls an ON state (ON state)/OFF state (OFF state) by the second gate signal inputted from the gate signal generating section a 2.

Similarly to the U-phase switching arm Ru, the V-phase switching arm Rv has the MOS transistor 3 of the upper arm and the MOS transistor 4 of the lower arm connected in series with the dc power supply 7.

That is, in the upper-arm MOS transistor 3, the drain terminal is connected to the positive electrode of the dc power supply 7, the source terminal is connected to the drain terminal of the lower-arm MOS transistor 4, and the gate terminal is connected to the gate signal generating unit a 2. The MOS transistor 3 of the upper arm controls an ON state (ON state)/OFF state (OFF state) by the third gate signal inputted from the gate signal generating section a 2.

The drain terminal of the MOS transistor 4 of the lower arm is connected to the source terminal of the MOS transistor 3 of the upper arm, the source terminal is connected to the negative electrode of the dc power supply 7, and the gate terminal is connected to the gate signal generating unit a 2. The MOS transistor 4 of the lower arm controls an ON state (ON state)/OFF state (OFF state) by the fourth gate signal inputted from the gate signal generating section a 2.

The W-phase switching arm Rw is connected in series with the dc power supply 7, as is the case with the U-phase switching arm Ru and the V-phase switching arm Rv described above, to the MOS transistor 5 of the upper arm and the MOS transistor 6 of the lower arm.

That is, in the MOS transistor 5 of the upper arm, the drain terminal is connected to the positive electrode of the dc power supply 7, the source terminal is connected to the drain terminal of the MOS transistor 6 of the lower arm, and the gate terminal is connected to the gate signal generating unit a 2. The MOS transistor 5 of the upper arm controls an ON state (ON state)/OFF state (OFF state) by the fifth gate signal inputted from the gate signal generating section a 2.

The MOS transistor 6 of the lower arm has a drain terminal connected to the source terminal of the MOS transistor 5 of the upper arm, a source terminal connected to the negative electrode of the dc power supply 7, and a gate terminal connected to the gate signal generating unit a 2. The MOS transistor 6 of the lower arm controls an ON state (ON state)/OFF state (OFF state) by the sixth gate signal inputted from the gate signal generating section a 2.

In the U-phase switching leg Ru, the source terminal of the MOS transistor 1 of the upper arm and the drain terminal of the MOS transistor 2 of the lower arm, which are connected to each other, are output terminals of the U-phase switching leg Ru. The output is a U-phase output in the three-phase inverter circuit B and is connected to a U-phase input of the motor 8.

In the V-phase switching arm Rv, the source terminal of the MOS transistor 3 of the upper arm and the drain terminal of the MOS transistor 4 of the lower arm, which are connected to each other, are output terminals of the V-phase switching arm Rv. The output is a V-phase output in the three-phase inverter circuit B and is connected to a V-phase input of the motor 8.

In the W-phase switching leg Rw, the source terminal of the MOS transistor 5 of the upper arm and the drain terminal of the MOS transistor 6 of the lower arm, which are connected to each other, are output terminals of the W-phase switching leg Rw. The output is a W-phase output in the three-phase inverter circuit B, and is connected to a W-phase input of the motor 8.

The MOS transistors 1 to 6 constituting the three-phase inverter circuit B are additionally provided with body diodes D1 to D6, respectively. These body diodes D1 to D6 function as recirculation diodes (refluxdiodes) for recirculating a regenerative current based on the back electromotive force of the motor 8 to the dc power supply 7.

That is, the MOS transistor 1 of the upper arm of the U-phase switching arm Ru includes a first body diode D1. The body diode D1 has a cathode terminal connected to the drain terminal of the MOS transistor 1 of the upper arm and an anode terminal connected to the source terminal of the MOS transistor 1 of the upper arm as shown.

The MOS transistor 2 of the lower arm of the U-phase switching arm Ru includes a body diode D2. The body diode D2 has a cathode terminal connected to the drain terminal of the MOS transistor 2 of the lower arm, and an anode terminal connected to the source terminal of the MOS transistor 2 of the lower arm, as shown.

The MOS transistor 3 of the upper arm of the V-phase switching arm Rv includes a body diode D3. The body diode D3 has a cathode terminal connected to the drain terminal of the MOS transistor 3 of the upper arm, and an anode terminal connected to the source terminal of the MOS transistor 3 of the upper arm, as shown.

The MOS transistor 4 of the lower arm of the V-phase switching arm Rv includes a fourth body diode D4. The body diode D4 has a cathode terminal connected to the drain terminal of the MOS transistor 4 of the lower arm, and an anode terminal connected to the source terminal of the MOS transistor 4 of the lower arm, as shown.

The MOS transistor 5 of the upper arm of the W-phase switching arm Rw includes a body diode D5. The body diode D5 has a cathode terminal connected to the drain terminal of the MOS transistor 5 of the upper arm, and an anode terminal connected to the source terminal of the MOS transistor 5 of the upper arm, as shown.

The MOS transistor 6 of the lower arm of the W-phase switching arm Rw includes a body diode D6. The body diode D6 has a cathode terminal connected to the drain terminal of the MOS transistor 6 of the lower arm, and an anode terminal connected to the source terminal of the MOS transistor 6 of the lower arm, as shown.

Such a three-phase inverter circuit B corresponds to the switching circuit of the present invention, and the MOS transistors 1 to 6 correspond to the semiconductor switching element of the present invention. That is, the three-phase inverter circuit B is an inverter circuit provided with a plurality of switching arms each having a semiconductor switching element provided with an upper arm and a semiconductor switching element provided with a lower arm of a return diode.

In addition, the MOS transistors 1 to 6 in the three-phase inverter circuit B are set to on/off states based on the gate signal input from the control device a. The gate signals are control pulse signals generated by the control device a for the MOS transistors 1 to 6, respectively. The control pulse signal is, for example, a PWM (Pulse Width Modulation: pulse width modulation) signal.

In the voltage sensors 9 to 12 provided in the three-phase inverter circuit B, the voltage sensor 9 detects the input voltage of the three-phase inverter circuit B, that is, the output voltage (power supply voltage V _D ) And will represent the supply voltage V _D The detection signal (power supply voltage signal) of (a) is output to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a.

The voltage sensor 10 is a sensor that detects an output voltage (U-phase voltage) of the U-phase switching arm Ru, and outputs a detection signal (U-phase voltage signal) indicating the U-phase voltage to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a. The voltage sensor 11 is a sensor that detects an output voltage (V-phase voltage) of the V-phase switching arm Rv, and outputs a detection signal (V-phase voltage signal) indicating the V-phase voltage to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a. The voltage sensor 12 is a sensor that detects an output voltage (W-phase voltage) of the W-phase switching arm Rw, and outputs a detection signal (W-phase voltage signal) indicating the W-phase voltage to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a.

Of the current sensors 13 to 15, the current sensor 13 is a sensor that detects an output current (U-phase current) of the U-phase switching arm Ru, and outputs a detection signal (U-phase current signal) indicating the U-phase current to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a. The current sensor 14 is a sensor that detects an output current (V-phase current) of the V-phase switching arm Rv, and outputs a detection signal (V-phase current signal) indicating the V-phase current to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a. The current sensor 15 is a sensor that detects an output current (W-phase current) of the W-phase switching arm Rw, and outputs a detection signal (W-phase current signal) indicating the W-phase current to the temperature estimating unit a1 and the gate signal generating unit a2 of the control device a.

The control device a estimates the operating temperature of the MOS-type transistors 1 to 6 based on the above-described power supply voltage signal of the voltage sensor 9, the U-phase voltage signal of the voltage sensor 10, the V-phase voltage signal of the voltage sensor 11, the W-phase voltage signal of the voltage sensor 12, the U-phase current signal of the current sensor 13, the V-phase current signal of the current sensor 14, and the W-phase current signal of the current sensor 15, and generates a gate signal based on a state quantity input from an external device and a control instruction according to the estimated value (temperature estimated value).

That is, the temperature estimating unit a1 of the control device a obtains the power supply voltage V obtained from the voltage sensor 9 _D U-phase voltage V obtained from voltage sensor 10-12 _u V-phase electricityPressure V _v W-phase voltage V _w U-phase current I obtained from current sensors 13-15 _u Current I of V phase _v W-phase current I _w . The temperature estimating unit a1 obtains the junction temperatures T of the body diodes D1 to D6 based on the state signal indicating the state of the gate signal input from the gate signal generating unit a2 ₁ ～T ₆ . The junction temperature of the body diode D1 is the junction temperature T ₁ . The junction temperature of the body diode D2 is the junction temperature T ₂ . The junction temperature of the body diode D3 is the junction temperature T ₃ . The junction temperature of the body diode D4 is the junction temperature T ₄ . The junction temperature of the body diode D5 is the junction temperature T ₅ . The junction temperature of the body diode D6 is the junction temperature T ₆ 。

Here, the body diodes D1 to D6 are integrated with the 6 MOS transistors 1 to 6, and thus are in a thermally tight relationship. Namely, junction temperature T with respect to body diodes D1 to D6 ₁ ～T ₆ The operating temperatures of the MOS transistors 1 to 6 can be regarded as. Therefore, the temperature estimation unit a1 obtains (estimates) the junction temperature T ₁ To T ₆ As the operating temperature of the MOS type transistors 1 to 6.

That is, the temperature estimation unit a1 obtains the junction temperature T of the first body diode D1 in the U-phase switching leg Ru based on the power supply voltage signal of the voltage sensor 9, the U-phase voltage signal of the voltage sensor 10, and the U-phase current signal of the current sensor 13 ₁ And the junction temperature T ₁ The operating temperature of the MOS transistor 1 as the upper arm.

The temperature estimation unit a1 obtains the junction temperature T of the body diode D2 in the U-phase switching leg Ru based on the U-phase voltage signal of the voltage sensor 10 and the U-phase current signal of the current sensor 13 ₂ And the junction temperature T ₂ The operating temperature of the MOS transistor 2 as the lower arm.

The temperature estimation unit a1 obtains the junction temperature T of the body diode D3 in the V-phase switching arm Rv based on the power supply voltage signal of the voltage sensor 9, the V-phase voltage signal of the voltage sensor 11, and the V-phase current signal of the current sensor 14 ₃ And the junction temperature T ₃ The operating temperature of the MOS transistor 3 as the upper arm.

In addition, the control device A is based onThe V-phase voltage signal of the voltage sensor 11 and the V-phase current signal of the current sensor 14 obtain the junction temperature T of the body diode D4 in the V-phase switching leg Rv ₄ And the junction temperature T ₄ The operating temperature of the MOS transistor 4 as the lower arm.

The temperature estimation unit a1 obtains the junction temperature T of the body diode D5 in the W-phase switching leg Rw based on the power supply voltage signal of the voltage sensor 9, the W-phase voltage signal of the voltage sensor 12, and the W-phase current signal of the current sensor 15 ₅ The junction temperature T is set ₅ The operating temperature of the MOS transistor 5 as the upper arm.

Further, the control device a obtains the junction temperature T of the body diode D6 in the W-phase switching leg Rw based on the W-phase voltage signal of the voltage sensor 12 and the W-phase current signal of the current sensor 15 ₆ The junction temperature T is set ₆ The operating temperature of the MOS transistor 6 as the lower arm.

Here, it is known that a forward current I flows through a junction (junction) of a pn junction diode _F The impact type diode equation shown in the following formula (1) is followed. In the formula (1), I _S Is a saturated current, V _F Is a forward voltage, q is a meta-charge, n is an ideal coefficient, K _B Is Boltzmann constant, T is junction temperature, R _S Is the series resistance of the junction diode. Among these various physical quantities, the saturation current I _S The meta-charge quantity q, the Boltzmann constant K _B Series resistor R of junction diode _S Is a known constant.

[ number 1]

In this formula (1), if the first term in brackets is assumed to be sufficiently larger than 1 of the second term, then formula (2) is established as an approximation formula. Then, when this approximation formula (2) is solved for the junction temperature T, formula (3) is obtained.

[ number 2]

[ number 3]

That is, the forward currents I of the body diodes D1 to D6 are obtained ₁ ～I ₆ And a forward voltage V _F1 ～V _F6 And thus obtained. Forward currents I of body diodes D1-D6 ₁ ～I ₆ Forward current I of body diode D1 associated with U-phase switching leg Ru ₁ And the forward current I of the second body diode D2 ₂ Corresponds to the U-phase current Iu detected by the current sensor 13.

Forward current I ₁ Is the forward current of the body diode D1. Forward voltage V _F1 Is the forward voltage of the body diode D1. Forward current I ₂ Is the forward current of the body diode D2. Forward voltage V _F2 Is the forward voltage of the body diode D2. Forward current I ₃ Is the forward current of body diode D3. Forward voltage V _F3 Is the forward voltage of the body diode D3. Forward current I ₄ Is the forward current of the body diode D4. Forward voltage V _F4 Is the forward voltage of the body diode D3. Forward current I ₅ Is the forward current of body diode D5. Forward voltage V _F5 Is the forward voltage of the body diode D5. Forward current I ₆ Is the forward current of the body diode D6. Forward voltage V _F6 Is the forward voltage of the body diode D6.

Forward current I of body diode D3 associated with V-phase switching leg Rv ₃ Forward current I of body diode D4 ₄ Corresponds to the V-phase current I detected by the current sensor 14 _v . And, the forward current I of the body diode D5 related to the W-phase switching leg Rw ₅ Forward current I of body diode D6 ₆ Corresponds to W-phase current I detected by current sensor 15 _w 。

Forward voltages V of body diodes D1-D6 _F1 -V _F6 Forward voltages V of the body diodes D2, D4, D6 in (a) _F2 、V _F4 、V _F6 Corresponding to the output voltages of the respective phases detected by the voltage sensors 10 to 12. Further, the forward voltages V of the body diodes D1, D3, D5 _F1 、V _F3 、V _F5 By the supply voltage V detected from the voltage sensor 9 _D The forward voltages V of the body diodes D2, D4, D6 are subtracted _F2 、V _F4 、V _F6 And thus obtained.

The temperature estimation unit a1 stores forward voltages V representing the body diodes D1 to D6 in advance _F1 ～V _F6 Forward current I ₁ ～I ₆ Junction temperature T ₁ ～T ₆ Mapping data of the relation with (3), that is, junction temperature T based on formula (3) ₁ ～T ₆ A plurality of temperature data associated therewith.

When the temperature estimation unit a1 takes in the voltage corresponding to the forward voltage V from the voltage sensor 10-12 _F2 U-phase voltage V of (2) _u Corresponding to the forward voltage V _F4 V phase voltage V of (2) _v Corresponding to the forward voltage V _F6 W-phase voltage V of (2) _w And draw in the current corresponding to the forward current I from each of the current sensors 13-15 ₁ 、I ₂ U-phase current I of (2) _u Corresponding to forward current I ₃ 、I ₄ V-phase current I of (2) _v Corresponding to forward current I ₅ 、I ₆ W-phase current I of (2) _w Then based on these U-phase voltages V _u V phase voltage V _v And W phase voltage V _w U-phase current I _u Current I of V phase _v And W phase current I _w To retrieve the map data to obtain the junction temperature T ₁ ～T ₆ 。

Such a temperature estimation portion a1 corresponds to the temperature estimation device of the present invention, and operates the MOS transistors 1 to 6, that is, junction temperature T of the body diodes D1 to D6 ₁ ～T ₆ (temperature estimated value) is output to the gate signal generation section a2. The gate signal generating unit a2 generates gate signals for controlling the MOS transistors 1 to 6, respectively, based on the operating temperatures of the MOS transistors 1 to 6, and on the state amounts and control commands input from the external device.

The gate signal generating unit a2 outputs the first gate signal to the gate terminal of the MOS transistor 1 of the upper arm, and outputs the second gate signal to the gate terminal of the MOS transistor 2 of the lower arm. The gate signal generating unit a2 outputs the third gate signal to the gate terminal of the MOS transistor 3 of the upper arm, and outputs the fourth gate signal to the gate terminal of the MOS transistor 4 of the lower arm. Further, the gate signal generating unit a2 outputs a fifth gate signal to the gate terminal of the MOS transistor 5 of the upper arm, and outputs a sixth gate signal to the gate terminal of the MOS transistor 6 of the lower arm.

The first gate signal of the MOS transistor 1 constituting the upper arm and the second gate signal of the MOS transistor 2 constituting the lower arm of the U-phase switching arm Ru are paired with each other, and a Dead time (Dead time) of a time width Δt is provided at a transition point, which will be described in detail later. The third gate signal of the MOS transistor 3 constituting the upper arm of the V-phase switching arm Rv and the fourth gate signal of the MOS transistor 4 constituting the lower arm are paired with each other, and a dead time of a time width Δt is provided at the transition point.

Further, the fifth gate signal of the MOS transistor 5 constituting the upper arm of the W-phase switching arm Rw and the sixth gate signal of the MOS transistor 6 constituting the lower arm are paired with each other, and a dead time of the time width Δt is provided at the transition point. The time width Δt of the dead time is a predetermined value set in advance to prevent the through current in the switching arm of each phase.

Here, among the gate signals, the first, third, and fifth gate signals corresponding to the MOS transistors 1, 3, and 5 of the upper arm correspond to one gate signal, and the second, fourth, and sixth gate signals corresponding to the MOS transistors 2, 4, and 6 of the lower arm correspond to the other gate signal.

Regarding such dead time, the gate signal generating section a2 sufficiently secures the junction temperature T of the body diodes D1 to D6 in the temperature estimating section a1 ₁ ～T ₆ During the junction temperature T ₁ ～T ₆ In the estimation process of (2), an expansion time width obtained by temporarily expanding a predetermined time width Δt is set. The details of the amplification process for the predetermined time period Δt will be described later.

When the expansion process of the time width Δt is performed, the gate signal generating unit a2 refers to the U-phase voltage signal, the V-phase voltage signal, the W-phase voltage signal, the U-phase current signal, the V-phase current signal, and the W-phase current signal, and calculates the output power of the three-phase inverter circuit B based on the U-phase voltage signal, the V-phase voltage signal, the W-phase voltage signal, the U-phase current signal, the V-phase current signal, and the W-phase current signal.

The gate signal generating unit a2 outputs the state signal to the temperature estimating unit a1. The state signal is a signal indicating the state of the gate signal, that is, the ON state (ON state) or the OFF state (OFF state), and is thus a switching state signal indicating the ON/OFF of each MOS transistor 1-6.

Next, the operation of the control device a of the first embodiment will be described in detail with reference to fig. 2 to 4.

As shown in fig. 2, the gate signal generating unit a2 first determines whether or not temperature estimation should be performed (step S1). For example, in the case where temperature estimation is periodically performed, the gate signal generating unit a2 determines the period of performing temperature estimation based on the temperature response time constant grasped by itself. The gate signal generating unit a2 refers to a timer value (timer value) for counting time, and determines in step S1 whether the timer value has reached a preset value (execution time).

If the determination in step S1 is no, that is, if the temperature estimation is not performed, the gate signal generating unit a2 generates a normal gate signal based on the control command and the state quantity and outputs the generated signal to the three-phase inverter circuit B (step S2). The normal gate signal is used for feedback control of the three-phase inverter circuit B based on the control command and the state quantity, and the estimation process of the operation temperature of each MOS transistor 1 to 6 by the temperature estimation unit a1 is not considered at all.

Here, fig. 3 shows an example of the first gate signal and the second gate signal input to the gate terminal of the upper arm MOS transistor 1 and the gate terminal of the lower arm MOS transistor 2, which are semiconductor switching elements of the U-phase upper arm and the U-phase lower arm. Fig. 3 shows 3 types of first gate signals and second gate signals, and waveforms shown in the second and third stages from the top correspond to the above-described normal gate signals.

As shown in the uppermost stage of fig. 3, the gate signal generating unit a2 generates the gate signal by comparing a voltage command value generated based on a control command and a state quantity with a carrier wave using a triangular wave having a predetermined repetition period, but sets a dead time of a time width Δt at a transition point of the gate signal in order to prevent a through current in a switching arm of each phase.

The dead time is a period in which both the gate signal for the U-phase upper arm and the gate signal for the U-phase lower arm are turned off, and is set to a timing of turning from the off state to the on state and a timing of turning from the on state to the off state, respectively. The time width Δt of the dead time is a predetermined value set in consideration of the performance of the semiconductor switching element and the like.

However, when the determination in step S1 is yes, that is, when the temperature estimation is performed, the process in step S3 is performed. That is, the gate signal generating unit a2 compares the output power of the three-phase inverter circuit B with the predetermined power threshold value Rw to determine whether or not the output power of the three-phase inverter circuit B is equal to or lower than the predetermined power threshold value Rw (step S3).

More specifically, the gate signal generating unit a2 calculates the phase power of each phase based on the U-phase voltage signal, the V-phase voltage signal, the W-phase voltage signal, the U-phase current signal, the V-phase current signal, and the W-phase current signal, and calculates the output power of the three-phase inverter circuit B based on each phase power. Then, the gate signal generating unit a2 compares the output power thus calculated with the power threshold Rw stored in advance to perform the judgment processing of step S3.

When the determination at step S3 is yes, the gate signal generating unit a2 performs the above-described shortening process of the ON pulse (ON pulse) in the normal gate signal (step S4). That is, as shown in the fourth and fifth stages of fig. 3, the gate signal generating unit a2 shortens the time width of the on pulse in the second gate signal to expand the dead time from the predetermined time width Δt to the time width Δ2t (expanded time width).

On the other hand, when the determination in step S3 is no, that is, when the output power of the three-phase inverter circuit B is greater than the power threshold Rw, the above-described removal process of the on pulse in the normal gate signal is performed (step S5). That is, as shown in the sixth and seventh stages of fig. 3, the gate signal generating unit a2 expands the dead time from a predetermined time width Δt to a time width Δ6t (expanded time width) by removing the on pulse in the second gate signal.

In this way, the gate signal generating unit a2 switches the method of setting the dead time according to the magnitude of the output power of the three-phase inverter circuit B with respect to the power threshold Rw. That is, when the output power of the three-phase inverter circuit B is equal to or less than the power threshold value Rw, the gate signal generating unit a2 sets the time width Δ2t (the expansion time width) of the dead time by making the ON time (ON time) of the second gate signal (the other gate signal) shorter than the ON time of the first gate signal (the one gate signal), whereas when the output power of the three-phase inverter circuit B is greater than the power threshold value Rw, the ON pulse of the second gate signal (the other gate signal) is removed to set the time width Δ6t (the expansion time width) of the dead time.

Here, in fig. 3, the expansion process of the dead time width Δt concerning the first gate signal for the U-phase, i.e., the MOS transistor 1 of the upper arm, and the second gate signal for the MOS transistor 2 of the lower arm is described, but the expansion process of the dead time width Δt is similarly performed concerning the third gate signal for the MOS transistor 3 of the V-phase and the W-phase, i.e., the MOS transistor 3 of the upper arm, the fourth gate signal for the MOS transistor 4 of the lower arm, the fifth gate signal for the MOS transistor 5 of the upper arm, and the sixth gate signal for the MOS transistor 6 of the lower arm.

After completing such expansion processing of the time width Δt of the dead time related to three phases, the gate signal generating portion a2 executes estimation processing of the operating temperature of the MOS transistors 1 to 6 in the expanded time width Δ2t or the time width Δ6t (step S6). This process of estimating the operating temperature is realized by the temperature estimating section a1 executing a series of processes shown in fig. 4.

Further, the order of estimation of the operating temperatures of the MOS transistors 1 to 6 in the U-phase, V-phase, and W-phase is substantially the same. Therefore, the order of estimating the operating temperatures of the U-phase upper arm MOS transistor 1 and the U-phase lower arm MOS transistor 2 will be described in detail below with reference to fig. 4.

In estimating the operation temperatures of the upper-arm MOS transistor 1 and the lower-arm MOS transistor 2 of the U-phase, the temperature estimating unit a1 first determines the U-phase current I based on the U-phase current signal input from the current sensor 13 _u Whether the polarity of (a) is positive (step Sa 1).

In the case where the determination at step Sa1 is yes, i.e., U-phase current I _u When the polarity of (a) is positive, the temperature estimation unit a1 determines whether or not the MOS transistor 1 constituting the upper arm of the U-phase upper arm is in the off state based on the state signal (the switching state signal) input from the gate signal generation unit a2 (step Sa 2).

Then, when the determination at step Sa2 is yes, that is, when the MOS transistor 1 of the upper arm is in the off state, the temperature estimating unit a1 determines whether or not the MOS transistor 2 of the lower arm constituting the U-phase lower arm is in the off state based on the state signal (on-off state signal) (step Sa 3).

When the determination at step Sa3 is yes, that is, when the upper-arm MOS transistor 1 and the lower-arm MOS transistor 2 are both in the off-state dead time as shown in fig. 3, the temperature estimating unit a1 obtains the U-phase current I _u (step Sa 4), and obtains the U-phase voltage V based on the U-phase voltage signal input from the voltage sensor 10 _u (step Sa 5).

Then, the temperature estimating section a1 uses the U-phase current I _u U-phase voltage V _u To retrieve the mapping data to obtain the current I of the phase U _u U-phase voltage V _u The corresponding mapping value, namely the junction temperature T of the body diode D2 ₂ (step Sa 6). Then, the temperature estimation unit a1 calculates the junction temperature T of the body diode D2 thus obtained ₂ The operation temperature of the MOS type transistor 2 as the lower arm (step Sa 7).

When the operating temperature of the lower-arm MOS transistor 2 (junction temperature T2 of the body diode D2) is thus obtained, the temperature estimating unit a1 determines the U-phase current I from the U-phase current signal input from the current sensor 13 _u Whether the polarity of (a) is negative (step Sa 8).

Then, in the case where the determination at step Sa8 is yes, that is, the U-phase current I _u When the polarity of (a) is negative, the temperature estimation unit a1 determines whether or not the MOS transistor 1 constituting the upper arm of the U-phase upper arm is in the OFF (OFF) state based on the state signal (switching state signal) input from the gate signal generation unit a2 (step Sa 9).

Then, when the determination at step Sa9 is yes, that is, when the MOS transistor 1 of the upper arm is in the off state, the temperature estimating unit a1 determines whether or not the MOS transistor 2 of the lower arm constituting the U-phase lower arm is in the off state, based on the state signal (on-off state signal) (step Sa 10).

When the determination at step Sa10 is yes, that is, as shown in fig. 3, in the dead time in which both the MOS transistor 1 of the upper arm and the MOS transistor 2 of the lower arm are in the off state, the temperature estimating unit a1 obtains the U-phase current I _u (step Sa 11), additionally, by supplying the voltage V from the power supply _D Subtracting the U-phase voltage V obtained from the U-phase voltage signal input from the voltage sensor 10 _u Obtain the forward voltage V of the body diode D1 ₁ (step Sa 12).

Then, the temperature estimating section a1 uses the U-phase current I _u Forward voltage V ₁ To retrieve the mapping data to obtain the current I of the phase U _u Forward voltage V ₁ Corresponding mapping value, i.e. junction temperature T of body diode D1 ₁ (step Sa 13). Then, the temperature estimation unit a1 calculates the junction temperature T of the body diode D1 thus obtained ₁ The operation temperature of the MOS type transistor 1 as the lower arm (step Sa 14).

The temperature estimation unit a1 obtains the respective operation temperatures of the upper-arm MOS transistor 1 and the lower-arm MOS transistor 2 in this manner, but the same applies to the upper-arm MOS transistor 3 and the lower-arm MOS transistor 4 constituting the V-phase switching arm Rv, and the upper-arm MOS transistor 5 and the lower-arm MOS transistor 6 constituting the W-phase switching arm Rw.

That is, the temperature estimation unit a1 obtains the respective operation temperatures for all of the MOS transistors 1 to 6. Then, the temperature estimating unit a1 outputs the operating temperatures of the MOS transistors 1 to 6 to the gate signal generating unit a2.

When the operating temperatures of the MOS transistors 1 to 6 are within a preset allowable range, the gate signal generating unit a2 generates gate signals for controlling the MOS transistors 1 to 6 regardless of the operating temperatures of the MOS transistors 1 to 6. When the operating temperature of any one of the MOS transistors 1 to 6 is out of the allowable range, that is, when an abnormal temperature MOS transistor is generated, the gate signal generating unit a2 generates a gate signal that forcibly turns off the abnormal temperature MOS transistor, thereby suppressing the output of the abnormal temperature MOS transistor and reducing heat generation.

According to the first embodiment, the forward current and the forward voltage of the body diodes D1 to D6 are obtained in the time width Δ2t or the time width Δ6t of the dead time which is larger than the time width Δt of the dead time in the normal gate signal, and the operating temperature of the MOS transistors 1 to 6 is estimated, so that the operating temperature of the MOS transistors 1 to 6 (semiconductor switching elements) can be estimated without requiring a high-speed operation.

In addition, according to the first embodiment, the gate signal is generated based on the operation temperature of the MOS type transistors 1 to 6 (semiconductor switching elements) thus obtained, and therefore the MOS type transistors 1 to 6 can be reliably controlled.

The present invention is not limited to the first embodiment, and for example, the following modifications can be considered.

In the first embodiment, the three-phase inverter circuit B (switching circuit) is configured by 6 MOS transistors 1 to 6 (semiconductor switching elements), but the present invention is not limited to this. The present invention can also be applied to a three-phase inverter circuit configured by using semiconductor switching elements of different types from MOS transistors, such as IGBTs (Insulated Gate Bipolar Transistor: insulated gate bipolar transistors).

For example, in the case of using an IGBT as a semiconductor switching element, in an RC-IGBT (reverse-turn-on IGBT) integrated as a body diode, the temperature of the semiconductor switching element can be estimated based on the junction temperature of the body diode estimated from the forward current and the forward voltage at the time of operation, similarly to a MOS transistor.

In addition, in an IGBT that does not include a body diode as a parasitic diode like a MOS transistor, the body diode needs to be provided in close proximity to the body diode due to heat of the same DCB substrate or the like, but the temperature of the semiconductor switching element can be estimated from the junction temperature of the reflux diode estimated from the forward current and the forward voltage.

In the first embodiment, the three-phase inverter circuit B, which is one type of switching circuit, is described, but the present invention can be applied to switching circuits other than the three-phase inverter circuit B. The present invention can be applied to a switching circuit including, for example, 1 semiconductor switching element. That is, the present invention can be applied to estimation of the operating temperature of 1 or more semiconductor switching elements that constitute a switching circuit and are respectively provided with a reflux diode.

In the first embodiment, the operation temperatures of all the MOS transistors 1 to 6 (semiconductor switching elements) constituting the three-phase inverter circuit B (switching circuit) are estimated, but the present invention is not limited to this. For example, the operating temperature of a part of the MOS type transistors 1 to 6 (semiconductor switching elements) can also be estimated.

In the first embodiment, the case where the implementation condition of the temperature estimation is the time condition was described, but the present invention is not limited to this. That is, the operation temperature of the MOS-type transistors 1 to 6 may be estimated based on implementation conditions other than the time conditions.

(second embodiment)

A second embodiment will be described below with reference to the drawings. In the following description, portions having the same functions as those described in the first embodiment are given the same names and reference numerals, and detailed description about the functions is omitted.

As shown in fig. 5, the control device 100 of the present embodiment is a device that is controlled by a three-phase inverter circuit X. As shown in the figure, the three-phase inverter circuit X is a switching circuit configured by 6 MOS transistors 1 to 6, and converts dc power supplied from a dc power supply 7 into three-phase ac power to supply the three-phase ac power to a motor 8 (load).

Describing this three-phase inverter circuit X in more detail, the three-phase inverter circuit X includes 3 switching arms Ru, rv, and Rw corresponding to each. Of these switching legs Ru, rv, rw, switching leg Ru is a U-phase switching leg corresponding to U. The switching leg Rv is a V-phase switching leg corresponding to V. The switching leg Rw is a W-phase switching leg corresponding to W.

The 3 switching legs Ru, rv, and Rw include MOS transistors 1, 3, and 5 constituting upper arms and MOS transistors 2, 4, and 6 constituting lower arms, respectively. These 6 MOS transistors 1 to 6 correspond to the semiconductor switching element of the present invention.

Further describing each of the switching arms Ru, rv, and Rw, in the U-phase switching arm Ru, the MOS transistor 1 of the upper arm and the MOS transistor 2 of the lower arm are connected in series with respect to the dc power supply 7.

That is, in the upper-arm MOS transistor 1, the drain terminal is connected to the positive electrode of the dc power supply 7, and the source terminal is connected to the drain terminal of the lower-arm MOS transistor 2. The drain terminal of the MOS transistor 2 of the lower arm is connected to the source terminal of the MOS transistor 1 of the upper arm, and the source terminal is connected to the negative electrode of the dc power supply 7.

The V-phase switching arm Rv is connected in series with the dc power supply 7, as is the case with the U-phase switching arm Ru, with the MOS transistor 3 on the upper arm and the MOS transistor 4 on the lower arm.

That is, in the upper-arm MOS transistor 3, the drain terminal is connected to the positive electrode of the dc power supply 7, and the source terminal is connected to the drain terminal of the lower-arm MOS transistor 4. The drain terminal of the MOS transistor 4 of the lower arm is connected to the source terminal of the MOS transistor 3 of the upper arm, and the source terminal is connected to the negative electrode of the dc power supply 7.

The W-phase switching arm Rw is connected in series with the dc power supply 7, as is the case with the U-phase switching arm Ru and the V-phase switching arm Rv described above, with the MOS transistor 5 of the upper arm and the MOS transistor 6 of the lower arm.

That is, in the upper-arm MOS transistor 5, the drain terminal is connected to the positive electrode of the dc power supply 7, and the source terminal is connected to the drain terminal of the lower-arm MOS transistor 6. The drain terminal of the MOS transistor 6 of the lower arm is connected to the source terminal of the MOS transistor 5 of the upper arm, and the source terminal is connected to the negative electrode of the dc power supply 7.

In the U-phase switching leg Ru, the source terminal of the MOS transistor 1 of the upper arm and the drain terminal of the MOS transistor 2 of the lower arm, which are connected to each other, are output terminals of the U-phase switching leg Ru. The output terminal is a U-phase output terminal of the three-phase inverter circuit X, and is connected to a U-phase input terminal of the motor 8.

In the V-phase switching arm Rv, the source terminal of the MOS transistor 3 of the upper arm and the drain terminal of the MOS transistor 4 of the lower arm, which are connected to each other, are output terminals of the V-phase switching arm Rv. The output terminal is a V-phase output terminal of the three-phase inverter circuit X, and is connected to a V-phase input terminal of the motor 8.

In the W-phase switching leg Rw, the source terminal of the MOS transistor 5 of the upper arm and the drain terminal of the MOS transistor 6 of the lower arm, which are connected to each other, are output terminals of the W-phase switching leg Rw. The output terminal is a W-phase output terminal of the three-phase inverter circuit X, and is connected to a W-phase input terminal of the motor 8.

The 6 MOS transistors 1 to 6 constituting the three-phase inverter circuit X are additionally provided with body diodes D1 to D6, respectively. These body diodes D1 to D6 function as return diodes for returning the regenerative current based on the back electromotive force of the motor 8 to the dc power supply 7.

That is, the MOS transistor 1 of the upper arm of the U-phase switching arm Ru includes a body diode D1. The body diode D1 has a cathode terminal connected to the drain terminal of the MOS transistor 1 of the upper arm and an anode terminal connected to the source terminal of the MOS transistor 1 of the upper arm as shown.

The MOS transistor 4 of the lower arm of the V-phase switching arm Rv includes a body diode D4. The body diode D4 has a cathode terminal connected to the drain terminal of the MOS transistor 4 of the lower arm, and an anode terminal connected to the source terminal of the MOS transistor 4 of the lower arm, as shown.

Each MOS transistor 1-6 in the three-phase inverter circuit X sets an ON/OFF state based ON a gate signal input from the control device 100. The gate signal is a PWM (Pulse Width Modulation: pulse width modulation) signal generated by the control device 100 for each of the MOS transistors 1 to 6.

Such a three-phase inverter circuit X is additionally provided with 4 voltage sensors 9 to 12 and 3 current sensors 13 to 15. Of the 4 voltage sensors 9 to 12, the voltage sensor 9 is a sensor that detects an input voltage of the three-phase inverter circuit X, that is, an output voltage (power supply voltage VD) of the dc power supply 7, and outputs a detection signal (power supply voltage signal) indicating the power supply voltage VD to the control device 100.

The voltage sensor 10 is a sensor that detects an output voltage (U-phase voltage) of the U-phase switching arm Ru, and outputs a detection signal (U-phase voltage signal) indicating the U-phase voltage to the control device 100. The voltage sensor 11 is a sensor that detects an output voltage (V-phase voltage) of the V-phase switching arm Rv, and outputs a detection signal (V-phase voltage signal) indicating the V-phase voltage to the control device 100. The voltage sensor 12 is a sensor that detects an output voltage (W-phase voltage) of the W-phase switching arm Rw, and outputs a detection signal (W-phase voltage signal) indicating the W-phase voltage to the control device 100.

Of the 3 current sensors 13 to 15, the current sensor 13 is a sensor that detects an output current (U-phase current) of the U-phase switching arm Ru, and outputs a detection signal (U-phase current signal) indicating the U-phase current to the control device 100. The current sensor 14 is a sensor that detects an output current (V-phase current) of the V-phase switching arm Rv, and outputs a detection signal (V-phase current signal) indicating the V-phase current to the control device 100. The current sensor 15 is a sensor that detects an output current (W-phase current) of the W-phase switching arm Rw, and outputs a detection signal (W-phase current signal) indicating the W-phase current to the control device 100.

The control device 100 estimates the operation temperature of each MOS type transistor 1-6 based on the above-described power supply voltage signal, U-phase voltage signal, V-phase voltage signal, W-phase voltage signal, U-phase current signal, V-phase current signal, and W-phase current signal, and controls the three-phase inverter circuit X based on a value (temperature estimated value) according to the estimation and a state quantity and a control instruction input from an external apparatus.

That is, the control device 100 includes a temperature estimating unit 16 and a gate signal generating unit 17. The temperature estimation unit 16 calculates junction temperatures T1 to T6 of the respective body diodes D1 to D6 as operation temperatures of the respective MOS transistors 1 to 6 based on the power supply voltage VD acquired from the voltage sensor 9, the U-phase voltage Vu, the V-phase voltage Vv, and the W-phase voltage Vw acquired from the voltage sensors 10 to 12, the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw acquired from the current sensors 13 to 15, and the state signal indicating the state of the gate signal input from the gate signal generation unit 17 when the respective body diodes D1 to D6 are operated in the linear region.

Here, the body diodes D1 to D6 are integrated with the MOS transistors 1 to 6, and thus are in close thermal relationship. That is, junction temperatures T1 to T6 associated with the body diodes D1 to D6 can be regarded as operating temperatures of the MOS transistors 1 to 6. Therefore, the temperature estimation section 16 obtains (estimates) junction temperatures T1 to T6 as the operating temperatures of the MOS transistors 1 to 6.

That is, the temperature estimation unit 16 estimates the junction temperature T1 of the body diode D1 in the U-phase switching leg Ru as the operation temperature of the upper-arm MOS transistor 1 based on the power supply voltage signal, the U-phase voltage signal, and the U-phase current signal. Further, the control device 100 estimates the junction temperature T2 of the body diode D2 in the U-phase switching leg Ru as the operation temperature of the MOS transistor 2 of the lower arm based on the U-phase voltage signal and the U-phase current signal.

The temperature estimation unit 16 estimates the junction temperature T3 of the body diode D3 in the V-phase switching arm Rv as the operating temperature of the upper-arm MOS transistor 3 based on the power supply voltage signal, the V-phase voltage signal, and the V-phase current signal. Further, the control device 100 estimates the junction temperature T4 of the body diode D4 in the V-phase switching leg Rv as the operation temperature of the MOS transistor 4 of the lower arm based on the V-phase voltage signal and the V-phase current signal.

Further, the temperature estimation unit 16 estimates the junction temperature T5 of the body diode D5 in the W-phase switching leg Rw as the operation temperature of the upper-arm MOS transistor 5 based on the power supply voltage signal, the W-phase voltage signal, and the W-phase current signal. Further, based on the W-phase voltage signal and the W-phase current signal, control device 100 estimates junction temperature T6 of body diode D6 in W-phase switching leg Rw as the operation temperature of MOS transistor 6 of the lower arm.

Here, the forward current IF flowing through the junction (junction) of the pn junction diode follows the impact diode equation shown in the above equation (1). In the above equation (1), if the first term in parentheses is assumed to be sufficiently larger than 1, the above equation (2) is established as an approximation equation. Then, when the above formula (2) is solved for the junction temperature T, the above formula (3) is obtained.

Fig. 6 shows a graph of the relationship between the forward current IF and the forward voltage VF based on the above equation (3) using the junction temperature T as a parameter. Here, since the forward current IF is expressed in equation (3) as a natural logarithm variable, fig. 6 is a logarithmic graph showing the logarithm of the vertical axis (current axis).

As shown in fig. 6, in a current region where the logarithmic value of the forward voltage VF and the forward current IF are in a linear relationship, the forward current IF is equal to or lower than the current threshold Ri. In a current region where the forward current IF exceeds the current threshold Ri, a voltage drop due to the series resistance RS of the pn junction diode occurs, and the linearity of the logarithmic value of the forward voltage VF and the forward current IF is greatly deteriorated.

In consideration of such a relationship between the forward voltage VF and the logarithmic value of the forward current IF with the junction temperature T as a parameter, when it is desired to determine (estimate) the junction temperature T (parameter) based on the forward voltage VF and the forward current IF, it is preferable to increase the estimation accuracy in a linear region of the relationship between the forward voltage VF and the logarithmic value of the forward current IF, that is, in a current region where the forward current IF is equal to or lower than the current threshold Ri.

That is, the forward currents I1 to I6 and the forward voltages VF1 to VF6 of the respective body diodes D1 to D6 are obtained. The forward current I1 of the body diode D1 and the forward current I2 of the body diode D2, which are related to the U-phase switching leg Ru, among the forward currents I1 to I6 of the body diodes D1 to D6 correspond to the U-phase current Iu detected by the current sensor 13.

The forward current I3 of the body diode D3 and the forward current I4 of the body diode D4 associated with the V-phase switching arm Rv correspond to the V-phase current Iv detected by the current sensor 14. The forward current I5 of the body diode D5 and the forward current I6 of the body diode D6 associated with the W-phase switching arm Rw correspond to the W-phase current Iw detected by the current sensor 15.

The forward voltages VF2, VF4, and VF6 of the 3 individual diodes D2, D4, and D6 among the forward voltages VF1 to VF6 of the individual diodes D1 to D6 correspond to the output voltages of the respective phases detected by the respective voltage sensors 10 to 12. The forward voltages VF1, VF3, and VF5 of the 3 individual diodes D1, D3, and D5 are obtained by subtracting the forward voltages VF2, VF4, and VF6 of the individual diodes D2, D4, and D6 from the power supply voltage VD detected by the voltage sensor 10.

The temperature estimation unit 16 stores map data indicating the relationship between the forward voltages VF1 to VF6, the forward currents I1 to I6, and the junction temperatures T1 to T6 of the respective body diodes D1 to D6, that is, a plurality of temperature data related to the junction temperatures T1 to T6 based on the formula (3) in advance.

When the U-phase voltage Vu corresponding to the forward voltage VF2, the V-phase voltage Vv corresponding to the forward voltage VF4, and the W-phase voltage Vw corresponding to the forward voltage VF6 are taken in from the voltage sensors 10 to 12, and the U-phase current Iu corresponding to the forward currents I1 and I2, the V-phase current Iv corresponding to the forward currents I3 and I4, and the W-phase current Iw corresponding to the forward currents I5 and I6 are taken in from the current sensors 13 to 15, the junction temperature T1 to T6 is obtained by searching the map data based on the U-phase voltage Vu, the V-phase voltage Vv, the W-phase voltage Vw, and the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw.

In a state where the body diodes D1 to D6 are operated in the linear region, the temperature estimation unit 16 takes in the U-phase voltage Vu (forward voltage VF 2), the V-phase voltage Vv (forward voltage VF 4), the W-phase voltage Vw (forward voltage VF 6), the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw.

The linear region is an operation region in which the U-phase voltage Vu (forward voltage VF 2) and the U-phase current I1 are in linear relation, an operation region in which the V-phase voltage Vv (forward voltage VF 4) and the U-phase current I2 are in linear relation, and an operation region in which the W-phase voltage Vw (forward voltage VF 6) and the W-phase current I3 are in linear relation, and is an operation region in which the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw are smaller than a predetermined current threshold value Ri.

Such a temperature estimation unit 16 corresponds to a temperature estimation device according to the present invention, and outputs the operating temperature of each MOS transistor 1 to 6, that is, the junction temperature T1 to T6 (temperature estimation value) of each body diode D1 to D6, to the gate signal generation unit 17. The gate signal generating unit 17 generates first to sixth gate signals for controlling the 6 MOS transistors 1 to 6, respectively, based on the operating temperatures of the MOS transistors 1 to 6, and on the state amounts and control commands input from the external device.

The gate signal generating unit 17 outputs the first gate signal to the gate terminal of the MOS transistor 1 of the upper arm and outputs the second gate signal to the gate terminal of the MOS transistor 2 of the lower arm. The gate signal generating unit 17 outputs a third gate signal to the gate terminal of the MOS transistor 3 of the upper arm and outputs a fourth gate signal to the gate terminal of the MOS transistor 4 of the lower arm. Further, the gate signal generating unit 17 outputs a fifth gate signal to the gate terminal of the MOS transistor 5 of the upper arm, and outputs a sixth gate signal to the gate terminal of the MOS transistor 6 of the lower arm.

The gate signal generating unit 17 outputs the state signal to the temperature estimating unit 16.

The state signal is a signal indicating the ON (ON) state or the OFF (OFF) state, which is the state of the first to sixth gate signals, and is thus a switching state signal indicating the ON/OFF of each MOS transistor 1 to 6.

Next, the operation of the control device 100 of the second embodiment will be described in detail with reference to fig. 7 to 9.

As shown in fig. 7, the temperature estimating section 16 (temperature estimating means) in the control device 100 estimates the operating temperature of each MOS transistor 1-6 in the order of U-phase temperature estimation (step S11), V-phase temperature estimation (step S12), W-phase temperature estimation (step S13).

That is, the temperature estimation unit 16 estimates the operating temperatures of all the MOS transistors 1 to 6 in the three-phase inverter circuit X (switching circuit) by obtaining all the junction temperatures T1 to T6 in the order of junction temperatures T1, T2 of the body diodes D1, D2, junction temperatures T3, T4 of the body diodes D3, D4, and junction temperatures T5, T6 of the body diodes D5, D6 based on the above-described formula (3).

Here, the estimation steps of the operation temperatures of the respective MOS transistors 1 to 6 in the U phase, V phase, and W phase are substantially the same. Therefore, the order of estimating the operating temperatures of the upper arm MOS transistor 1 and the lower arm MOS transistor 2 of the U-phase will be described in detail below with reference to fig. 8.

When estimating the operating temperatures of the upper arm MOS transistor 1 and the lower arm MOS transistor 2 of the U-phase, the temperature estimating unit 16 first determines whether or not the polarity of the U-phase current Iu is positive based on the U-phase current signal input from the current sensor 13 (step Sb 1).

When the determination at step Sb1 is yes, that is, when the polarity of the U-phase current Iu is positive, the temperature estimating unit 16 determines whether or not the MOS transistor 1 constituting the upper arm of the U-phase upper arm is in the OFF (OFF) state based on the state signal (switching state signal) input from the gate signal generating unit 17 (step Sb 2).

Then, when the determination of step Sb2 is yes, that is, when the MOS transistor 1 of the upper arm is in the OFF state, the temperature estimating unit 16 determines whether or not the MOS transistor 2 of the lower arm constituting the U-phase lower arm is in the OFF (OFF) state based on the state signal (on-OFF state signal) (step Sb 3).

When the determination at step Sb3 is yes, that is, when both the upper arm MOS transistor 1 and the lower arm MOS transistor 2 are in the off state, the temperature estimating unit 16 determines whether or not the absolute value of the U-phase current Iu is equal to or less than the current threshold Ri based on the U-phase current signal (step Sb 4).

Here, fig. 9 is a timing chart showing the operation states of the MOS transistors 1 to 6 in the three-phase inverter circuit X, a carrier wave (triangular wave) that determines the repetition period of the gate signal, and time variations of the respective phase currents Iu to Iw. The off state of the MOS transistor 1 of the upper arm and the MOS transistor 2 of the lower arm corresponds to the period Δp1 to Δp6 in fig. 9.

These periods Δp1 to Δp6 are dead times set by the gate signal generating unit 17 in order to prevent through currents from flowing in the U-phase switching leg Ru, the V-phase switching leg Rv, and the W-phase switching leg Rw. In the three-phase inverter circuit X, such dead time is provided for each of the U-phase switching arm Ru, the V-phase switching arm Rv, and the W-phase switching arm Rw, thereby preventing abnormal heat generation of the MOS transistors 1 to 6 due to the through current.

The period Δp1 to Δp3 among these periods Δp1 to Δp6 is a time zone in which the absolute value of the U-phase current Iu is equal to or less than the current threshold Ri. That is, these periods Δp1 to Δp3 are time zones in which the reflux current flows as the U-phase current Iu through the body diode D2 of the MOS transistor 2 of the lower arm. These periods Δp1 to Δp3 are included in the linear region in which the aforementioned reflux current in the operation region of the body diode D2 is relatively small.

The temperature estimation unit 16 obtains the U-phase current Iu in the period Δp1 to Δp3 (step Sb 5), and obtains the U-phase voltage Vu based on the U-phase voltage signal input from the voltage sensor 10 (step Sb 6). These U-phase current Iu and U-phase voltage Vu are characteristic amounts of the body diode D2 at the time of linear region operation, and the linearity of the correlation is excellent.

Then, the temperature estimation unit 16 searches for map data using the U-phase current Iu and the U-phase voltage Vu, thereby obtaining a junction temperature T2 of the body diode D2, which is a map value corresponding to the U-phase current Iu and the U-phase voltage Vu (step Sb 7). Then, the temperature estimation unit 16 uses the junction temperature T2 of the body diode D2 thus obtained as the operating temperature of the MOS transistor 2 of the lower arm (step Sb 8).

When the operating temperature of the MOS transistor 2 of the lower arm (junction temperature T2 of the body diode D2) is obtained in this way, the temperature estimating section 16 determines whether the polarity of the U-phase current Iu is negative or not from the U-phase current signal input from the current sensor 13 (step Sb 9).

Then, when the determination at step Sb9 is yes, that is, when the polarity of the U-phase current Iu is negative, the temperature estimating unit 16 determines whether or not the MOS transistor 1 constituting the upper arm of the U-phase upper arm is in the OFF (OFF) state based on the state signal (switching state signal) input from the gate signal generating unit 17 (step Sb 10).

Then, when the determination of step Sb10 is yes, that is, when the MOS transistor 1 of the upper arm is in the OFF state, the temperature estimating unit 16 determines whether or not the MOS transistor 2 of the lower arm constituting the U-phase lower arm is in the OFF (OFF) state based on the state signal (on-OFF state signal) (step Sb 11).

When the determination at step Sb11 is yes, that is, when both the upper arm MOS transistor 1 and the lower arm MOS transistor 2 are in the off state, the temperature estimating unit 16 determines whether or not the absolute value of the U-phase current Iu is equal to or less than the current threshold Ri based on the U-phase current signal input from the current sensor 13 (step Sb 12).

Although not shown in fig. 9, there is necessarily a period Δpx during which the absolute value of the U-phase current Iu is equal to or less than the current threshold Ri in the dead time in which both the MOS transistor 1 in the upper arm and the MOS transistor 2 in the lower arm are turned off.

The period Δpx is a time zone in which the reflux current flows as the U-phase current Iu through the body diode D1 of the MOS transistor 1 of the upper arm, and is included in the linear zone in which the reflux current is relatively small in the operation zone of the body diode D1.

The temperature estimation unit 16 obtains the U-phase current Iu in the period Δpx (step Sb 13), and subtracts the U-phase voltage Vu obtained from the U-phase voltage signal input from the voltage sensor 10 from the power supply voltage VD, thereby obtaining the forward voltage V1 of the body diode D1 (step Sb 14). These U-phase current Iu and forward voltage V1 are characteristic amounts of the body diode D1 when operated in the linear region, and the correlation is excellent in linearity.

Then, the temperature estimation unit 16 searches the map data by using the U-phase current Iu and the forward voltage V1, thereby obtaining a junction temperature T1 of the body diode D1, which is a map value corresponding to the U-phase current Iu and the forward voltage V1 (step Sb 15). Then, the temperature estimation unit 16 uses the junction temperature T1 of the body diode D1 thus obtained as the operating temperature of the MOS transistor 1 of the lower arm (step Sb 16).

The temperature estimation unit 16 obtains the operating temperatures of all the MOS transistors 1 to 6 by performing the processing of steps S11 to S13 in fig. 7. Then, the temperature estimation section 16 outputs the operating temperature of the MOS transistors 1 to 6 to the gate signal generation section 17.

When the operating temperature of the MOS transistors 1 to 6 is within a preset allowable range, the gate signal generating unit 17 generates first to sixth gate signals for controlling the MOS transistors 1 to 6, regardless of the operating temperature of the MOS transistors 1 to 6, but when the operating temperature of any one of the MOS transistors 1 to 6 is out of the allowable range, that is, when an abnormal temperature MOS transistor is generated, the gate signal generating unit 17 generates a gate signal for forcibly turning off the abnormal temperature MOS transistor.

According to the second embodiment, the junction temperatures T1 to T6 of the body diodes D1 to D6 are estimated using the forward currents and the forward voltages at the time of the linear region operation of the body diodes D1 to D6, and the junction temperatures T1 to T6 are set as the operation temperatures of the MOS transistors 1 to 6, so that the operation temperatures of the MOS transistors 1 to 6 (semiconductor switching elements) can be estimated with higher accuracy than ever.

According to the second embodiment, the first to sixth gate signals are generated based on the operating temperatures of the MOS transistors 1 to 6 (semiconductor switching elements) thus obtained, and therefore the MOS transistors 1 to 6 can be reliably controlled.

The present invention is not limited to the above-described embodiments, and the following modifications are conceivable, for example.

In the second embodiment described above, the three-phase inverter circuit X (switching circuit) is configured by 6 MOS transistors 1 to 6 (semiconductor switching elements), but the present invention is not limited to this. The present invention can also be applied to a three-phase inverter circuit configured by using semiconductor switching elements of different types from MOS transistors, such as IGBTs (Insulated Gate Bipolar Transistor: insulated gate bipolar transistors).

In addition, for example, in the case of employing an IGBT as the semiconductor switching element, in an RC-IGBT (reverse-turn-on IGBT) integrated as a body diode, the temperature of the semiconductor switching element can be estimated from the junction temperature of the body diode estimated from the forward current and the forward voltage at the time of operation, similarly to the MOS transistor. In addition, in an IGBT that does not include a body diode as a parasitic diode like a MOS transistor, the body diode needs to be provided in close proximity to the body diode due to heat of the same DCB substrate or the like, but the temperature of the semiconductor switching element can be estimated from the junction temperature of the reflux diode estimated from the forward current and the forward voltage.

In the second embodiment described above, the three-phase inverter circuit X, which is one type of switching circuit, is described, but the present invention can also be applied to switching circuits other than the three-phase inverter circuit X. The present invention can be applied to a switching circuit including, for example, 1 semiconductor switching element. That is, the present invention can be applied to estimation of the operating temperature of 1 or more semiconductor switching elements that constitute a switching circuit and are respectively provided with a reflux diode.

In the second embodiment described above, the operating temperatures of all the MOS transistors 1 to 6 (semiconductor switching elements) constituting the three-phase inverter circuit X (switching circuit) were estimated, but the present invention is not limited to this. For example, the operation temperature of a part of the MOS type transistors (semiconductor switching elements) may also be estimated based on the heat radiation performance of a plurality of (6) MOS type transistors 1 to 6 (semiconductor switching elements).

Fig. 10 schematically shows a cooling configuration of a three-phase inverter circuit X (switching circuit) in the second embodiment. As shown in fig. 10, each MOS transistor 1-6 is a heat generating component configured as a semiconductor module, and a cooling jacket C is mounted via a heat sink or the like.

That is, heat generated by each MOS transistor 1-6 is dissipated by heat conduction to the refrigerant flowing through the cooling jacket C via the radiator or the like. Each MOS transistor 1-6 is maintained within a predetermined operating temperature by successive heat removal from the cooling jacket C.

Here, the refrigerant flows into the cooling jacket C from an inflow port C1 provided at one end of the cooling jacket C, and is discharged to the outside of the cooling jacket C from an outflow port C2 provided at the other end of the cooling jacket C. That is, the entire flow direction of the refrigerant in the cooling jacket C is, as indicated by the arrow, a direction from one end of the cooling jacket C, which is the inflow port C1, toward the other end of the cooling jacket C, which is the outflow port C2.

In such a cooling structure of the three-phase inverter circuit X, among the plurality of (6) MOS transistors 1 to 6, i.e., the U-phase switching leg Ru, the V-phase switching leg Rv, and the W-phase switching leg Rw, the U-phase switching leg Ru closest to the inflow port c1 has the highest heat radiation performance, and the W-phase switching leg Rw closest to the outflow port c2 has the lowest heat radiation performance.

That is, the heat dissipation performance of the three-phase inverter circuit X is a relationship of the U-phase switching leg Ru > V-phase switching leg Rv > W-phase switching leg Rw. As a result, the operating temperatures of the upper-arm MOS transistor 5 and the lower-arm MOS transistor 6 of the W-phase switching arm Rw tend to be higher than those of the other upper-arm MOS transistors 1 and 3 and the lower-arm MOS transistors 2 and 4.

Considering the tendency concerning the operation temperatures of the MOS transistors 1 to 6, it is considered that the operation temperatures of only the MOS transistor 5 of the upper arm and the MOS transistor 6 of the lower arm of the W-phase switching arm Rw are estimated as the operation temperatures of a part of the MOS transistors.

According to such a modification, the operating temperatures of not all the MOS transistors 1 to 6 but a part of the MOS transistors are estimated, so that the processing load of the temperature estimating unit 16 related to the estimation of the operating temperatures of the MOS transistors can be reduced.

In the second embodiment described above, as shown in fig. 7, the operation temperatures of all the MOS transistors 1 to 6 are estimated in the order of U-phase temperature estimation, V-phase temperature estimation, and W-phase temperature estimation, but the present invention is not limited to this. As described above, regarding the heat radiation performance of the three-phase inverter circuit X, there may be a phase having a tendency of an operation temperature to become higher in each phase than other phases. In view of this, it is preferable to estimate the operating temperature sequentially from the phase having a tendency of the operating temperature to become high.

The first embodiment may include the structure described in the second embodiment. For example, the temperature estimating unit a1 of the first embodiment may also have the function of the temperature estimating unit 16 of the second embodiment. As an example, the temperature estimating unit a1 may have a function of estimating the operating temperature of the semiconductor switching element based on the forward voltage and the forward current of the reflux diode obtained from the switching circuit when the reflux diode is operated in the linear region.

Symbol description

A100 control device

a1, 16 temperature estimation unit

a2, 17 grid signal generating part

B. X three-phase inverter circuit (switch circuit)

D1-D6 body diode (reflow diode)

Ru U-phase switch bridge arm

Rv V phase switch bridge arm

Rw W phase switch bridge arm

1. 3, 5 upper arm MOS type transistor (semiconductor switch element)

2. MOS type transistors (semiconductor switching element) of 4 and 6 lower arms

7. DC power supply

8. Motor with a motor housing having a motor housing with a motor housing

9-12 voltage sensor

13-15 current sensor

C cooling jacket

c1 Inflow port

c2 Outflow opening

Claims

1. A temperature estimation device is characterized in that,

in an inverter circuit provided with 1 or more switch legs having semiconductor switching elements of the upper and lower legs provided with return diodes respectively, the operating temperatures of the upper and lower legs are estimated,

the temperature estimation device estimates the operating temperature based on the forward voltage and the forward current of the reflux diode obtained from the inverter circuit in an extended time width in which dead time of the upper arm and the lower arm is extended from a predetermined time width.

2. The apparatus according to claim 1, wherein,

the expansion time width is set so that the on time of the other of the gate signals for controlling the one and the other of the upper arm and the lower arm is shorter than the one on time.

3. The apparatus according to claim 1, wherein,

the expansion time width is set by removing an on pulse of the other gate signal of the gate signals respectively controlling one of the upper arm and the lower arm.

4. A temperature estimation device according to any one of claims 1 to 3, wherein,

the operating temperature of the semiconductor switching element is estimated from a forward voltage and a forward current of the flyback diode taken from the inverter circuit when the flyback diode is operated in a linear region.

5. The apparatus according to any one of claims 1 to 4, wherein,

the inverter circuit is a three-phase inverter circuit provided with 3 of the switch legs, and the operating temperature is estimated based on the forward voltage and the forward current obtained from the three-phase inverter circuit.

6. The apparatus according to any one of claims 1 to 5, wherein,

in the case where the inverter circuit includes a plurality of the semiconductor switching elements, the operation temperature of a part of the semiconductor switching elements is estimated based on heat radiation performance of the plurality of the semiconductor switching elements.

7. A control device is characterized by comprising:

the temperature estimation device of any one of claims 1 to 6; and

and a gate signal generating unit that generates a gate signal for controlling the upper arm and the lower arm based on the operation temperature estimated by the temperature estimating device.