JP2000333469A - Power switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize highly accurate temperature keep control by selecting temperature information, related to detection temperature of an on-chip temperature detecting element preferentially, when the detection temperature exceeds a specified threshold level or when it is lower than the specified threshold level. SOLUTION: When a detected temperature is lower than a threshold level for deciding thermal overload, for example, the positive terminal input of an operational amplifier U1A has a voltage Vref, and a lowest voltage is selected from among thermistor output voltages VthU, VthV and VthW, i.e., the detection value of a thermistor detecting the highest temperature. It is then delivered externally from a buffer 600 as an analog voltage signal. When the threshold level for deciding thermal overload is exceeded, a constant voltage value VOLT indicative of that is inputted to the positive terminal input of the operational amplifier U1A, and the lowest voltage among the VOLTC, VthU, VthV and VthW is delivered externally as a detection temperature voltage. Consequently, an external controller can start lock protection control instantaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power switching device, and more particularly to a technique for protecting a semiconductor power switching element from overheating.

[0002]

2. Description of the Related Art A diode for detecting temperature (on-chip temperature detecting element) is formed on a chip on which a power switching element is formed, and a chip temperature is determined based on a change in a voltage drop of the diode due to a temperature change. On-chip temperature detection technology for detecting has been proposed. When this on-chip temperature detection type power switching element is used in an inverter device for driving a traveling motor of an electric vehicle or a hybrid vehicle,
Since the power switching element of this inverter device is supplied with a high power supply voltage of several hundred volts, a power supply formed based on this high power supply voltage is also provided to the on-chip temperature detection element to ensure insulation within the chip and reduce the number of terminals. Generally, a voltage is applied.

On the other hand, a control circuit which processes output signals from these temperature detecting circuits operates at a predetermined control power supply voltage, so that the temperature of each power switching element, particularly the power switching element on the high side of the inverter device, is controlled. The transmission of the temperature signal from each of the individually detected temperature detection circuits to the control circuit has involved an electrical insulation circuit such as a photocoupler.

[0004] Also, Japanese Patent Application Laid-Open No. 4-295278 discloses that
The temperature of the inverter circuit is detected by a temperature sensor (off-chip temperature detection element) such as a thermistor near the inverter circuit. If the temperature of the inverter circuit exceeds the allowable temperature, the output frequency of the inverter circuit is reduced and the main heat is generated. An inverter device that reduces the power loss of a device (power switching device), that is, the amount of heat generation has been proposed. In this case, the electrical insulation circuit such as the photocoupler can be omitted.

[0005]

However, since the above-mentioned thermistor (off-chip temperature detecting element) is mounted while ensuring electrical insulation with respect to the power switching element, the heat generated by the power element is determined by the thermal resistance between the two elements. And the temperature relationship between them changes non-linearly, and the thermal response is slower than that of the on-chip temperature sensor. It is not easy to cut off and protect the power switching element by the output signal of the chip temperature detecting element.

On the other hand, the above-mentioned diode (on-chip temperature detecting element) has a temperature detection sensitivity (SN ratio) of the element itself relatively lower than that of the off-chip temperature detecting element, and is used in the above-mentioned high voltage operation inverter circuit. In the power switching element, especially the on-chip temperature detection element of the power switching element on the high side, the transmission of the temperature signal to the control circuit further lowers the S / N ratio and the accuracy of the output signal is not sufficient. There is a problem that high-precision temperature control is not easy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and enables high-precision temperature maintenance control of a power switching element without deteriorating a protection function of the power switching element in a situation where the heat generation amount of the power switching element is rapidly increased. The problem to be solved is to provide a simple power switching device.

[0008]

According to a first aspect of the present invention, there is provided a power switching device, comprising:
For temperature monitoring, when the detected temperature of the on-chip temperature detecting element is equal to or higher than a predetermined threshold, the temperature information formed based on the detected temperature of the on-chip temperature detecting element is preferentially selected and adopted. When the detected temperature of the detecting element is lower than a predetermined threshold value, the temperature information linked to the detected temperature of the off-chip temperature detecting element is preferentially selected and adopted. When the temperature rises sharply, protection control of the device having excellent response can be realized by the temperature information from the on-chip temperature detection device. In other cases, the temperature control of the power switching device can be performed with high accuracy.

According to a second aspect of the present invention, in the power switching device according to the first aspect, when the detected temperature of the on-chip temperature detecting element is lower than a predetermined threshold, the power switching apparatus is linked to the detected temperature of the off-chip temperature detecting element. A predetermined analog voltage value indicating that the detected temperature of the on-chip temperature detecting element has reached the threshold value when the detected temperature of the on-chip temperature detecting element is equal to or higher than a predetermined threshold value.
Since the signal is output to the outside through the common signal line, the signal line for outputting the temperature information to the monitor unit can be simplified without lowering the protection function. More specifically, as the temperature information of the on-chip temperature detecting element, the temperature information on whether the detected temperature of the on-chip temperature detecting element has reached a predetermined alarm temperature value is referred to as the analog voltage range of the off-chip temperature detecting element. Since the analog voltage values are converted into analog voltage values of different levels, the output information of these two temperature detecting elements can be multiplexed and transmitted by the analog common signal line.

Further, since the temperature information from the on-chip temperature detecting element is converted into a binary signal, the temperature information may be reduced when the on-chip temperature detecting element circuit system and the off-chip temperature detecting element circuit operate at different power supply voltages. In addition, signal transmission from the on-chip temperature detecting element circuit system to the off-chip temperature detecting element circuit system while being electrically insulated can be realized by a simple circuit.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described based on the following examples.

[0012]

[Embodiment 1] An embodiment in which the power switching device of the present invention is applied to an inverter device for driving and controlling a traveling motor of an electric vehicle or a hybrid vehicle will be described below. (Overall Configuration) FIG. 1 shows the overall configuration of the inverter device of the embodiment.
This will be described with reference to FIG.

This inverter device is a vehicle-mounted three-phase inverter that performs 120-degree conduction control, and 51 is a high-voltage vehicle-mounted battery (DC power supply) that supplies power required for traveling.
53 is a smoothing capacitor for stabilizing the DC power supply voltage applied to the inverter, 54 is a motor serving as a load of the inverter, and 61 to 66 are power switching elements. In this embodiment, IGBTs are used. 71-76
Is a flywheel diode (FWD), 55 is a controller (control unit) including a control signal forming circuit for power switching element drive control and a protection circuit for the power switching element, 81 to 86 are element controllers, and 91 to 96 are element controllers. This is a signal line for connecting the controller 55 and each of the element controllers 81 to 86.

The element controllers 81 to 86 are modularized as a pair with the IGBTs 61 to 66 controlled by them, and power-amplify the gate control signal received from the controller 55 and apply it to the gate electrodes of the IGBTs 61 to 66. At the same time, the voltage, current and temperature of each of the IGBTs 61 to 66 are monitored, and when an abnormality occurs, an abnormality signal is output to the controller 55. When a certain kind of abnormal state is detected, the IGBT controlled by itself is shut off for a certain period of time. (Self-cut off). (Basic Operation of Inverter Device) In the 120-degree conduction control of this embodiment, the low-side IGBTs 64 to 66 are turned on with a shift of 120 degrees each by intermittently controlling the IGBTs 61 to 66, and the high-side IGBTs 61 to 63 are duty-controlled. Thus, pseudo three-phase AC voltages Vu, Vv, Vw are formed and applied to the motor 54. (Description of Temperature Detection Circuit in Element Controller) The gate control signals received from the controller 55 of the element controllers 81 to 86 are amplified by power and the IGBTs 61 to 66 are amplified.
Since the configuration and operation applied to the gate electrode and the circuit and operation for self-interruption are well known, the temperature detection circuit for detecting the temperature in the element controller 84 will be described below with reference to FIG. I do. The other element controllers have the same function as the element controller 84.

Reference numeral 100 denotes an on-chip temperature sensor (not shown) including a junction diode (not shown) formed on the main surface of the chip on which the IGBT 64 is formed and constituting an on-chip temperature detecting element according to the present invention. ) Output voltage Vdiode
(Corresponding to the on-chip temperature signal Tj) with the threshold voltage VO
This is a comparison circuit for comparing with VL. Although the on-chip temperature sensor utilizes the temperature characteristic of the forward voltage drop of the junction diode, it is different from the gist of the present invention, and therefore, the description is omitted.

The comparison circuit 100 has a threshold voltage VOVL
, A comparator including an operational amplifier OVCA, resistors R205, R206, and R207, a transistor Q1, resistors R208, R1, R2, and R
An amplifier circuit 30 on the input side of the photocoupler comprising the photocoupler 102, and an amplifier circuit on the output side of the photocoupler comprising the transistor Q2 and the resistors R3 and R5.

The output voltage Vdio of the on-chip temperature sensor
When de is larger than the threshold voltage VOVL2 input from the constant voltage source 101 to the comparator OVCA through the resistor R205 (at low temperature), the output of the comparator OVCA becomes low level, the transistor Q1 turns off, and the photocoupler 102 The high voltage Vref is input, and the photocoupler 102 outputs a low level voltage to the transistor Q2 to turn it on.

Output voltage Vdio of on-chip temperature sensor
When de is lower than the threshold voltage VOVL2 (low temperature)
The output of the comparator OVCA becomes high level,
The transistor Q1 turns on, a low voltage is input to the photocoupler 102, and the photocoupler 102
2 to output a high level voltage and turn it off. 200
Is a constant voltage source that generates a constant voltage VOLTC for indicating that the IGBT 64 is thermally overloaded.

Reference numerals 300 to 302 denote IGBT 64, respectively.
Off-chip temperature detection sensors provided in proximity to the chip of the IGBT 61 in the module of the above, each comprising a thermistor RthU, RthV, RthW and a resistor R2
4, a resistor voltage dividing circuit in which R25 and R26 are connected in series. Reference numerals 401 to 404 denote ideal diode circuits using an operational amplifier. The ideal diode circuit 401 includes resistors R9 and R10, a diode D3, and an operational amplifier U2A.
And the ideal diode circuit 402 includes resistors R11 and R11.
12, a diode D4 and an operational amplifier U3A. The ideal diode circuit 403 includes resistors R13 and R14, a diode D5, and an operational amplifier U4A, and the ideal diode circuit 404 includes resistors R7 and R6, a diode D1, and an operational amplifier U1A. These ideal diode circuits 401
The output of .about.404 is simply the high voltage Vref through resistor R8.
Is applied, the potential Vo at those output terminals becomes equal to the lowest one of the input potentials of the operational amplifiers U1A to U4A.

Reference numeral 500 denotes a low-pass filter for removing switching noise, and includes a resistor R19 and a capacitor C.
6. Reference numeral 600 denotes a voltage follower circuit as an output buffer. The power supply voltage Vcc1 of the comparator OCVA is a control power supply voltage used for driving the IGBT 4 and is set to +15 V with reference to the emitter potential of the IGBT 61. The power supply voltage VCC2 of the comparator 200 is a voltage of +15 V with reference to the GND of a low-voltage auxiliary battery (not shown). The lower power supply voltage Vref is a voltage that makes VCC2 and GND common, and is set to + 6V.

FIG. 3 shows an arrangement state in the module on which the on-chip temperature sensor, thermistor, IGBT 64 and flywheel diode 74 are mounted. Reference numerals 10 and 11 denote diode regions, two of which are connected in parallel to constitute the flywheel diode 74. 12 is I
Power switching element region where GBT 64 is formed, 1
3 is a ceramic insulating substrate such as aluminum nitride, 14 is fixed to the surface of the insulating substrate 13, and is an electrode connecting the cathodes of the diodes 10, 11 and the collector electrode of the IGBT 64, 15 is a thermistor (for example, RthU), 16, 1
Reference numeral 7 denotes an electrode for fixing the thermistor 15 by soldering and connecting an electrode for external connection. Reference numeral 18 denotes a temperature detecting diode in the power switching element region 12, which has a negative temperature characteristic in which the forward voltage decreases as the temperature increases. . Similarly, reference numerals 19 and 20 denote electrodes for mediating connection for outputting a signal from the temperature detecting diode to the outside. FIG. 3 shows an example in which the number of thermistors (off-chip temperature detecting elements) is one. (Description of Operation of Temperature Detection Circuit in Element Controller) The operation of this temperature detection circuit will be described with reference to a timing chart shown in FIG.

Until time t1, the element temperature Tj is within the allowable operating temperature range, so that the output voltage Vdiode of the temperature detecting diode is equal to the thermal overload determination threshold VOVL.
At this time, Q1 is off, Q3 is on,
Q2 is turned on, and V is applied to the positive input terminal of the operational amplifier U1A.
A voltage corresponding to ref is applied. Assuming that the motor as the inverter load is locked (locked) at time t1, a large lock current flows through IGBTs 61 to 66, and the junction temperature Tj of the chip, especially the IGBT, rises sharply. The temperature detected by the temperature detecting diode 18 changes rapidly following a rapid change in the chip temperature, but the output values VthU, Vt of the thermistors RthU, RthV, RthW are changed.
hV and VthW change slowly.

The junction region temperature Tj (power element temperature) continues to rise, and when the output voltage Vdiode falls below the thermal overload determination level VOVL2 at time t2, Q1 and Q2 are inverted, and the operational amplifier U1A has a positive input terminal. A constant voltage value VOLTC for outputting to the outside that the detected temperature of the on-chip temperature detecting element has exceeded the thermal overload determination level is applied.

Since the output terminals of the ideal diode circuits 401 to 404 are connected in common, the lowest value among the input voltages of the operational amplifiers U1A to U4A is output to this common output terminal. Therefore, the output voltage Vdiode
Is higher than the thermal overload determination threshold voltage VOVL2 (when the detected temperature is lower than the thermal overload determination threshold temperature), the positive terminal input of the operational amplifier U1A is set to Vref.
And the thermistor output voltages VthU, Vth
thV and VthW, the lowest voltage among the thermistor output voltages VthU, VthV and VthW, that is, the voltage which detects the highest temperature among the thermistor detection values, is selected, and the filter 500 is selected. After passing through, the buffer 600 sends the analog voltage signal to the outside. Based on this temperature information, the ECU performs output limiting control such as limiting the maximum output current when the power element temperature increases.

When the IGBT temperature exceeds the thermal overload judgment threshold temperature, a constant voltage value VOLTC indicating this is input to the positive terminal input of the operational amplifier U1A.
The lowest voltage among TC, VthU, VthV, and VthW is sent to the outside as detected temperature voltage VTOUT. This detected temperature voltage VTOUT is received by an external controller for motor control, and upon receiving the constant voltage value VOLTC, the controller immediately switches the control frequency to a low frequency, and controls the motor lock protection to suppress heat generation of the power element. To start.

Further, the controller is provided with VthU, Vth
Even if V and VthW are received, the value is the constant voltage value V
When it is almost equal to OLTC, the lock protection control is started. (Effect of the Embodiment) By the above operation, the external controller can start the lock protection control instantaneously only by monitoring the signal voltage from the thermistor, and the accuracy can be improved without monitoring the analog-insulated signal. Lock protection control is possible.

In addition, during steady-state operation in which the temperature changes gradually, a low-cost and high-precision thermistor signal is used, so that a high-precision temperature monitor can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an inverter device using a power switching device of the present invention.

FIG. 2 is a circuit diagram showing an example of a temperature detection circuit of the element controller shown in FIG.

FIG. 3 is a sensor arrangement diagram of a power module showing an example of an arrangement of an on-chip temperature detection element and an off-chip temperature detection element of the present invention.

FIG. 4 is a timing chart showing a potential change of each section of the circuit shown in FIG. 2;

[Explanation of symbols]

15 is a thermistor (off-chip temperature detecting element), 18 is a diode (on-chip temperature detecting element), 61 to 66 are IGBTs (power switching elements), and 401 to 404 are ideal diode circuits 403 (monitor unit).

Continued on the front page F-term (reference) 5H007 AA05 AA12 AA17 BB06 CA01 CB04 CB05 CC23 DB01 DC08 FA03 FA13 FA18 HA03 HA04 5H410 BB01 BB05 BB06 BB09 CC02 DD04 DD06 EA10 EA35 EA37 EB15 EB39 FF05 FF15 FF19 FF23 FF23 FF23 FF23 FF23 FF23 FF23 FF19 EE30 FF04 GG10 HA02 HB02 LL22 LL44 MM02 MM04 MM06 5H740 AA03 AA08 BA11 BB05 BB09 BB10 MM08 MM11 PP03

Claims (2)

[Claims] A power switching element, an on-chip temperature detection element integrated on the same chip as the power switching element, an off-chip temperature detection element provided in close proximity to the chip, and detection of the two temperature detection elements. A monitoring unit that monitors a temperature state of the power switching element based on a temperature, wherein the monitoring unit is configured to control the off-chip temperature detection element when the detected temperature of the on-chip temperature detection element is less than a predetermined threshold. Temperature information related to the detected temperature of the on-chip temperature detecting element is preferentially selected, and the temperature information related to the detected temperature of the on-chip temperature detecting element when the detected temperature of the on-chip temperature detecting element is equal to or higher than a predetermined threshold value A power switching device, wherein the power switching device is selected with priority. 2. The power switching device according to claim 1, wherein the monitor is configured to detect the detected temperature of the off-chip temperature detecting element when the detected temperature of the on-chip temperature detecting element is less than a predetermined threshold. An interlocking analog signal voltage is a predetermined analog signal indicating that the detected temperature of the on-chip temperature detecting element has reached the threshold value when the detected temperature of the on-chip temperature detecting element is equal to or higher than a predetermined threshold value. A power switching device wherein a voltage value is superimposed on a common signal line and output to the outside.