Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Reexamination Certificate
1999-10-12
2001-09-11
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
C327S432000, C327S403000, C327S405000, C327S478000
Reexamination Certificate
active
06288597
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a temperature sensing circuit and a temperature sensing method for a voltage drive type semiconductor device.
As one of the protective functions typically provided for a conventional IGBT (Insulated Gate Bipolar Transistor) module containing IGBTs, representing a kind of voltage drive type semiconductor device, temperature sensing using a temperature sensing circuit is employed for detecting a temperature rise of the IGBT module in order to switch off the IGBT before it becomes damaged. For example, such a conventional IGBT module is disclosed in Japanese Patent Application laid-open No. 7-67389.
The temperature rise of an IGBT module is detected by a temperature sensing circuit using a thermistor, and the signal produced by the temperature sensing circuit is transmitted to a control circuit to control the operation of the IGBT. The thermistor is attached on a cooling fin on which the IGBT module is mounted; and so, when the temperature of the cooling fin rises, the resistance of the thermistor is decreased and the terminal voltage thereof is also decreased. When the temperature exceeds a preset temperature, the temperature sensing circuit operates to switch off the IGBT by making use of this characteristic.
FIG. 6
shows a temperature sensing circuit
31
using a thermistor
29
attached to a cooling fin, a control circuit
26
for controlling an IGBT module
9
a
, and a gate drive circuit
12
.
In the temperature sensing circuit
31
, one end of the thermistor
29
is connected in series with a resistor
30
and a voltage source, and the junction between the thermistor
29
and the resistor
30
is connected to an input terminal of a voltage comparing circuit
13
. The other end of the thermistor
29
is connected to ground potential. A second input terminal of the voltage comparing circuit
13
is connected to a constant voltage circuit
18
, and the output terminal thereof is connected to the control circuit
26
.
In
FIG. 6
, since the thermistor for temperature sensing is a part mounted on the cooling fin, a temperature change of the IGBT is sensed by the temperature of the cooling fin. Therefore, when an IGBT element
1
a
generates heat due to an over-current or the like, there arises a problem in that the temperature transmitted to the thermistor differs depending on the position of the element which is generating heat. In this regard, the temperature sensing accuracy is decreased as the distance between the element and the thermistor increases.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly reliable temperature sensing circuit and a highly reliable temperature sensing method by taking the above-mentioned problem into consideration.
A temperature sensing circuit and a temperature sensing method in accordance with the present invention are applied to a voltage drive type semiconductor device comprising a semiconductor element for controlling current flowing between a pair of main electrodes in response to a voltage applied to an insulated gate electrode of the semiconductor device; a gate terminal electrically connected to the insulated gate electrode; another terminal electrically connected to one main electrode among the pair of main electrodes. As the semiconductor element, there are various kinds of semiconductor elements having an insulated gate electrode, such as an MOSFET and so on, in addition to an IGBT. As the voltage drive type semiconductor device, there are, for example, a power semiconductor module, a resin seal type semiconductor device and so on.
In the temperature sensing circuit in accordance with the present invention, a resistor having a positive temperature coefficient is connected between the gate terminal and the insulated gate electrode of a voltage drive type semiconductor device. Further, the temperature sensing circuit comprises a means for receiving a voltage, representing a voltage drop across the resistor disposed in a circuit portion between the gate terminal and said other terminal, and for sensing the temperature of the voltage drive type semiconductor device based on the received voltage.
The temperature sensing circuit in accordance with the present invention, as described above, makes use of the fact that, when a resistor having a positive temperature coefficient is connected between the gate terminal and the insulated gate electrode of a semiconductor device, a voltage representing a voltage drop across the resistor disposed in a circuit portion between the gate terminal and said other terminal is changed by the temperature of the voltage drive type semiconductor device. Therefore, the sensing response to a temperature change in the voltage drive type semiconductor device becomes fast. Accordingly, by sensing the temperature based on the received voltage, a temperature sensing circuit having a high reliability can be obtained.
In the temperature sensing method in accordance with the present invention, a resistor having a positive temperature coefficient is connected between the gate terminal and the insulated gate electrode of the semiconductor element; and a temperature is sensed based on a voltage representing a voltage drop across the resistor disposed in a circuit portion between the gate terminal and said other terminal during a mirror effect condition which is generated when the semiconductor element turns off.
The temperature sensing method in accordance with the present invention, as described above, makes use of the fact that, when a resistor having a positive temperature coefficient is connected between the gate terminal and the insulated gate electrode of the semiconductor device, a voltage including a voltage drop across the resistor disposed in a circuit portion between the gate terminal and said other terminal during a mirror effect condition which is generated when the semiconductor element turns off. Accordingly, similar to the temperature sensing circuit in accordance with the present invention, as described above, the sensing response becomes fast and a temperature sensing circuit having a high reliability can be obtained.
It is preferable when the resistor connected between the gate terminal and the insulated gate electrode in the voltage drive type semiconductor device is contained in the voltage drive type semiconductor device. By doing so, since the resistor is placed in a position near the semiconductor element, which represents the heat generating source, the temperature sensing accuracy can be improved. Further, as the resistor, it is possible to use a resistor which is contained in the voltage drive type semiconductor device primarily for a purpose other than temperature sensing, such as a gate resistor.
A drive device for a voltage drive type semiconductor device in accordance with the present invention comprises a drive circuit connected to the gate terminal through another resistor and to said other terminal; and the temperature sensing circuit in accordance with the present invention as described above.
The drive device for a temperature sensing circuit in accordance with the present invention, as described above, makes use of the fact that, when a resistor having a positive temperature coefficient is connected between the gate terminal and the insulated gate electrode and another resistor is connected between the drive circuit and the gate terminal, a voltage corresponding to a voltage drop across the resistor disposed in a circuit portion between the gate terminal and said other terminal is changed by the temperature of the voltage drive type semiconductor device. Therefore, by controlling the drive device based on the output signal of the temperature sensing circuit, a highly accurate protective operation relative to the temperature can be performed.
In a case where the voltage drive type semiconductor device comprises a plurality of semiconductor elements, the voltage drive type semiconductor device having the following structure is suitable for use of the temperature sensing circuit and the temperature
Hasegawa Hiroyuki
Kurosu Toshiki
Sugayama Shigeru
Antonelli Terry Stout & Kraus LLP
Cunningham Terry D.
Hitachi , Ltd.
Nguyen Long
LandOfFree
Temperature sensing circuit for voltage drive type... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature sensing circuit for voltage drive type..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature sensing circuit for voltage drive type... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2455117