JP4078754B2 - Power switching device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power switching device, and more particularly to an overheat protection technology for a semiconductor power switching element.
[0002]
[Prior art]
An on-chip temperature is formed by forming a diode for temperature detection (on-chip temperature detection element) on the chip on which the power switching element is formed, and detecting the chip temperature based on the change in the voltage drop of the diode due to the temperature change. Detection techniques have been proposed.
When this on-chip temperature detection type power switching element is employed in an inverter device for driving a traveling motor of an electric vehicle or a hybrid vehicle, the power switching element of this inverter device is fed with a high power supply voltage such as several hundred volts. In general, a power supply voltage formed based on this high power supply voltage is applied to the on-chip temperature detection element in order to ensure insulation within the chip and reduce the number of terminals.
[0003]
On the other hand, since the control circuit that processes the output signal from each temperature detection circuit operates with a predetermined control power supply voltage, the temperature of each power switching element, particularly the power switching element on the high side of the inverter device, is individually detected. In order to transmit the temperature signal from each temperature detection circuit to the control circuit, an electrical insulation circuit such as a photocoupler is interposed.
[0004]
Japanese Laid-Open Patent Publication No. 4-295278 discloses an inverter circuit in which an element temperature of an inverter circuit is detected by a temperature sensor (off-chip temperature detection element) such as a thermistor provided in the vicinity of the inverter circuit, and the temperature exceeds an allowable temperature. Has been proposed to reduce the power loss of the main heating element (power switching element), that is, the amount of heat generated. In this case, the electric insulation circuit such as the photocoupler can naturally be omitted.
[0005]
[Problems to be solved by the invention]
However, since the above-described thermistor (off-chip temperature detection element) is mounted with electrical insulation secured to the power switching element, the temperature relationship between the two changes nonlinearly depending on the amount of heat generated by the power element due to the thermal resistance between them. In addition, the thermal response is slow compared to the on-chip temperature sensor, so power is generated by the output signal of the off-chip temperature detection element in situations where the amount of heat generated by the power switching element increases rapidly, such as when the motor is locked. It has not been easy to cut off and protect the switching element.
[0006]
On the other hand, the above-described diode (on-chip temperature detection element) has a temperature detection sensitivity (SN ratio) of the element itself relatively lower than that of the off-chip temperature detection element, and power switching used in the high voltage operation inverter circuit described above. In the on-chip temperature detection element of the power switching element on the high side thereof, the SN ratio is further reduced by the transmission of the temperature signal to the control circuit, and the accuracy of the output signal is not sufficient. There was a problem that temperature control was not easy.
[0007]
The present invention has been made in view of the above problems, and power switching capable of high-precision temperature maintenance control of the power switching element without degrading the protection function of the power switching element in a situation where the heat generation amount of the power switching element is rapidly increased. Providing a device is a problem to be solved.
[0008]
[Means for Solving the Problems]
The power switching device according to claim 1, wherein the temperature of the power switching element is the on-chip temperature when the detected temperature of the on-chip temperature detecting element is equal to or higher than a predetermined threshold value for temperature protection and temperature monitoring of the power switching element. The temperature information formed based on the detection temperature of the detection element is preferentially selected and adopted, and when the detection temperature of the on-chip temperature detection element is lower than a predetermined threshold , the temperature of the power switching element is set as the temperature of the off-chip temperature detection element. Since the temperature information linked to the detected temperature is selected and adopted with priority, when the temperature rises rapidly due to a rapid increase in the amount of heat generated in the high temperature region of the power switching element, the element has excellent response due to the temperature information from the on-chip temperature detection element Protection control can be realized, and in other cases, high-precision temperature maintenance control of the power switching element is possible It made.
[0009]
According to the configuration of claim 2, in the power switching device according to claim 1, an analog signal that is linked to the detection temperature of the off-chip temperature detection element when the detection temperature of the on-chip temperature detection element is less than a predetermined threshold value. When the detected temperature of the on-chip temperature detecting element is equal to or higher than a predetermined threshold value, a predetermined analog voltage value indicating that the detected temperature of the on-chip temperature detecting element has reached the threshold value is obtained via a common signal line. Since it outputs to the exterior, the signal line which outputs temperature information to a monitor part can be simplified, without reducing a protective function. More specifically, as the temperature information of the on-chip temperature detection element, the temperature information indicating whether or not the detection temperature of the on-chip temperature detection element has reached a predetermined warning temperature value is the analog voltage range of the off-chip temperature detection element. Since the analog voltage values are converted to different levels, the output information of both the temperature detecting elements can be multiplexed and transmitted by the analog common signal line.
[0010]
In addition, since the temperature information from the on-chip temperature detection element is converted into a binary signal, when the on-chip temperature detection element circuit system and the off-chip temperature detection element circuit system operate with different power supply voltages, It is possible to realize signal transmission from the temperature detection element circuit system to the off-chip temperature detection element circuit system while being electrically insulated with 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]
[Example 1]
An embodiment in which the power switching device of the present invention is applied to an inverter device that drives and controls a traveling motor of an electric vehicle or a hybrid vehicle will be described below.
(overall structure)
The overall configuration of the inverter device of the embodiment will be described with reference to FIG.
[0013]
This inverter device is an in-vehicle three-phase inverter that performs 120-degree energization control, 51 is a high-voltage on-vehicle battery (DC power supply) that supplies power necessary for traveling, and 53 is a DC power supply voltage applied to the inverter device. Is a smoothing capacitor for stabilizing the voltage, 54 is a motor serving as a load of the inverter device, 61 to 66 are power switching elements, and an IGBT is used in this embodiment. Reference numerals 71 to 76 denote flywheel diodes (FWD), 55 denotes 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 denote element controllers, 91 Reference numerals -96 denote signal lines for connecting the controller 55 and the element controllers 81-86.
[0014]
The element controllers 81 to 86 are modularized in pairs with the IGBTs 61 to 66 that they control. The gate controllers received from the controller 55 are amplified and applied to the gate electrodes of the IGBTs 61 to 66. The voltage, current, and temperature of the IGBTs 61 to 66 are monitored, and an abnormality signal is output to the controller 55 when an abnormality occurs, and the IGBT controlled by itself when an abnormality of a certain type is detected is shut off for a certain period (self-interruption) )
(Basic operation of the inverter device)
In the 120-degree energization control of the present embodiment, the IGBTs 61 to 66 are intermittently controlled, so that the low-side IGBTs 64 to 66 are turned on by 120 degrees, and the high-side IGBTs 61 to 63 are DUTY controlled to perform the pseudo three-phase AC voltage Vu. , Vv, Vw are formed and applied to the motor 54.
(Explanation of temperature detection circuit in element controller)
Since the configuration and operation of power-amplifying the gate control signal received from the controller 55 of the element controllers 81 to 86 and applying them to the gate electrodes of the IGBTs 61 to 66 and the circuit and operation for self-interruption are well known. A portion of the temperature detection circuit for detecting the temperature in the controller 84 will be described below with reference to FIG. The other element controllers have the same function as the element controller 84.
[0015]
Reference numeral 100 denotes an output of an on-chip temperature sensor (not shown) including a junction diode (not shown) that is formed on the main surface of the chip on which the IGBT 64 is formed and constitutes the on-chip temperature detecting element referred to in the present invention. This is a comparison circuit that compares the voltage Vdiode (corresponding to the on-chip temperature signal Tj) with the threshold voltage VOVL. The on-chip temperature sensor uses the temperature characteristics of the forward voltage drop of the junction diode, but the description is omitted because it differs from the gist of the present invention.
[0016]
The comparison circuit 100 includes a constant voltage source 101 that generates a threshold voltage VOVL, an operational amplifier OVCA, a comparator that includes resistors R205, R206, and R207, and a photocoupler input side that includes a transistor Q1 and resistors R208, R1, R2, and R30. It comprises an amplifier circuit, a photocoupler 102, and an amplifier circuit on the photocoupler output side comprising a transistor Q2 and resistors R3 and R5.
[0017]
When the output voltage Vdiode of the on-chip temperature sensor is larger than the threshold voltage VOVL2 input to the comparator OVCA from the constant voltage source 101 through the resistor R205 (at low temperature), the output of the comparator OVCA becomes low level and the transistor Q1 is turned off. The high voltage Vref is input to the photocoupler 102. The photocoupler 102 outputs a low level voltage to the transistor Q2 and turns it on.
[0018]
When the output voltage Vdiode of the on-chip temperature sensor is lower than the threshold voltage VOVL2 (at low temperature), the output of the comparator OVCA becomes high level, the transistor Q1 is turned on, and a low voltage is input to the photocoupler 102. The coupler 102 outputs a high level voltage to the transistor Q2 and turns it off.
A constant voltage source 200 generates a constant voltage VOLTC for indicating that the IGBT 64 is in a thermal overload.
[0019]
300 to 302 is an off-chip temperature sensor provided near the tip of the IGB T at each I GB T within the module, each thermistor RthU, RthV, and RthW, a resistor R24, R25, R26 It consists of a resistance voltage dividing circuit formed by connecting in series.
401 to 404 are ideal diode circuits using operational amplifiers. The ideal diode circuit 401 includes resistors R9 and R10, a diode D3, and an operational amplifier U2A. The ideal diode circuit 402 includes resistors R11 and R12, 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. The ideal diode circuit 404 includes resistors R7 and R6, a diode D1, and an operational amplifier U1A. Since the outputs of these ideal diode circuits 401 to 404 are simply applied with the high voltage Vref through the resistor R8, the potential Vo at their output terminals is the lowest of the input potentials of the operational amplifiers U1A to U4A. Is equal to
[0020]
Reference numeral 500 denotes a low-pass filter that removes switching noise, and includes a resistor R19 and a capacitor C6.
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 that is also used for driving the IGBT 4, and is set to + 15V with respect to the emitter potential of the IGBT 61. The power supply voltage VCC2 of the comparator 200 is set to a voltage of + 15V with reference to GND of a low voltage auxiliary machine battery (not shown). The low power supply voltage Vref is a voltage that makes VCC2 and GND common, and is + 6V.
[0021]
FIG. 3 shows an arrangement state in a 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, which are connected in parallel to constitute the flywheel diode 74. 12 is a power switching element region in which the IGBT 64 is formed, 13 is a ceramic insulating substrate such as aluminum nitride, 14 is fixed to the surface of the insulating substrate 13, and connects the cathodes of the diodes 10 and 11 and the collector electrode of the IGBT 64. Electrode, 15 is a thermistor (for example, RthU), 16 and 17 are electrodes for soldering the thermistor 15 and connecting electrodes for external connection, and 18 is a diode for temperature detection in the power switching element region 12, It has a negative temperature characteristic that the forward voltage decreases. Similarly, reference numerals 19 and 20 denote electrodes that mediate connection for outputting a temperature detection diode signal to the outside. FIG. 3 shows an example in which there is one thermistor (off-chip temperature detection element).
(Explanation of operation of temperature detection circuit in element controller)
The operation of this temperature detection circuit will be described with reference to the timing chart shown in FIG. 4 showing the potential change of each part of the temperature detection circuit.
[0022]
Until the time t1, since the element temperature Tj is within the allowable dynamic temperature range, the output voltage Vdiode of the temperature detecting diode is equal to or higher than the thermal overload determination threshold VOVL. At this time, Q1 Is off, Q3 is on, Q2 is on, and a voltage equivalent to Vref is applied to the positive input terminal of the operational amplifier U1A.
Assuming that the motor as the inverter load is locked (restrained) at time t1, a large lock current flows through the IGBTs 61 to 66, and the junction region temperature Tj of the chip, particularly the IGBT, rapidly increases. The detected temperature of the temperature detecting diode 18 changes rapidly following the sudden change in the chip temperature, but the output values VthU, VthV, VthW of the thermistors RthU, RthV, RthW change slowly.
[0023]
When the junction region temperature Tj (power element temperature) continues to rise and 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 an on-chip on the positive input terminal. A constant voltage value VOLTC for outputting to the outside that the detected temperature of the temperature detecting element has exceeded the thermal overload determination level is applied.
[0024]
Since the ideal diode circuits 401 to 404 have their output terminals connected in common, the lowest value among the input voltages of the operational amplifiers U1A to U4A is output to the common output terminal.
Therefore, when 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 becomes Vref. Since the thermistor output voltages VthU, VthV, and VthW are always higher than the thermistor output voltages VthU, VthV, and VthW, the lowest voltage among the thermistor output voltages VthU, VthV, and VthW, that is, the highest temperature among the thermistor detection values is detected. The selected voltage is passed through the filter 500, and then sent to the outside as an analog voltage signal by the buffer 600. Based on this temperature information, the ECU performs output limiting control such as limiting the maximum output current when the power element temperature increases.
[0025]
Further, when the IGBT temperature exceeds the thermal overload determination threshold temperature, the constant voltage value VOLTC indicating the same is input to the positive terminal input of the operational amplifier U1A, so the lowest voltage among VOLTC, VthU, VthV, and VthW Is sent to the outside as the detected temperature voltage VTOUT.
The detected temperature voltage VTOUT is received by an external controller for motor control. Upon receiving the constant voltage value VOLTC, the received controller immediately switches the control frequency to a low frequency and controls motor lock protection to suppress power element heat generation. To start.
[0026]
Even when VthU, VthV, and VthW are received, the controller starts the lock protection control if the value is substantially equal to the constant voltage value VOLTC.
(Example effect)
With the above operation, the external controller can start the lock protection control instantly only by monitoring the signal voltage from the thermistor, and the lock protection control with high accuracy without monitoring the analog isolated signal. Is possible.
[0027]
Further, since the thermistor signal is inexpensive and highly accurate during steady operation where the temperature change is gradual, it is possible to monitor the temperature with high accuracy.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an inverter device using a power switching device of the present invention.
2 is a circuit diagram showing an example of a temperature detection circuit of the element controller shown in FIG. 1. FIG.
FIG. 3 is a sensor arrangement diagram of a power module showing an example of arrangement of an on-chip temperature detection element and an off-chip temperature detection element of the present invention.
4 is a timing chart showing potential changes in various parts of the circuit shown in FIG. 2;
[Explanation of symbols]
15 is a thermistor (off-chip temperature detection element), 18 is a diode (on-chip temperature detection element), 61 to 66 are IGBTs (power switching elements), and 401 to 404 are ideal diode circuits 403 (monitor unit).

Claims (2)

Power switching element,
An on-chip temperature detection element integrated on the same chip as the power switching element;
An off-chip temperature detecting element provided close to the chip, and
A monitor unit for monitoring the temperature state of the power switching element based on the detected temperatures of the two temperature detecting elements;
With
The monitor unit, the detected temperature is the detection temperature of the off-chip temperature sensing element preferentially select as the temperature of the chip in the case of less than a predetermined threshold of the on-chip temperature sensing element, power switching device, characterized in that the detected temperature of the on-chip temperature sensing element is preferentially selected the detected temperature of the on-chip temperature sensing element as a temperature of the chip in the case of more than the threshold value. The power switching device according to claim 1, wherein
The monitor unit outputs an analog signal voltage linked to 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 value. When the detected temperature is equal to or higher than a predetermined threshold, a predetermined analog voltage value indicating that the detected temperature of the on-chip temperature detecting element has reached the threshold is superimposed on a common signal line and output to the outside A power switching device.

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