BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a semiconductor device, and more particularly, to a semiconductor device performing stitching control, on a high voltage side of a power supply, of a load that is arranged on a ground side of the power supply.

Background Art

Automobiles typically are equipped with many semiconductor devices that perform switching control of loads, such as a motor. As such semiconductor devices to be mounted in automobiles, a high-side IPS (intelligent Power Switch) is often used. The high-side IPS integrates a power semiconductor switch arranged on the high-voltage side of the load to supply power to the load, and a control circuit therefor. Typically, an N-channel MOSFET (Metal-Oxide-Semiconductor Filed-Effect Transistor) having a small ON resistance per unit area is used as the power semiconductor switch of the high-side IPS.

FIG. 6shows a configuration example of a conventional high-side IPS.FIG. 7is a logic table of a logic circuit of the logic circuit of the high-side IPS. In explainingFIG. 6, the name of a terminal and the voltage or signal that is associated with the terminal may be referred to by the same reference numerals/characters.

As shownFIG. 6, the conventional high-side IPS100includes a main MOSFET110, a logic circuit120, and a driver circuit130. The high-side IPS100further includes, as protection circuits, an overcurrent detection circuit140, an overheat detection circuit150, and an overvoltage detection circuit160, and has an IN terminal, a VCC terminal, an OUT terminal, and a GND terminal.

The IN terminal of the high-side IPS100is connected to an input terminal of the logic circuit120, an output terminal of the logic circuit120is connected to an input terminal of the driver circuit130, and an output terminal of the driver circuit130is connected to a gate terminal of the main MOSFET110. A drain terminal of the main MOSFET110is connected to the VCC terminal, and the VCC terminal in turn is connected to a battery of an automobile to provide the voltage VCC. A source terminal of the main MOSFET110is connected to the OUT terminal and the OUT terminal is connected to the load200.

The OUT terminal is also connected to the overcurrent detection circuit140, and an output terminal of the overcurrent detection circuit140is connected to a terminal of the logic circuit120that receives an overcurrent detection signal OC. An output terminal of the overheat detection circuit150is connected to a terminal of the logic circuit120that receives an overheat detection signal OH. The overvoltage detection circuit160is connected to the VCC terminal and the GND terminal, and an output terminal of the overvoltage detection circuit160is connected to a terminal of the logic circuit120that receives an overvoltage detection signal OV.

When the high-side IPS100is operating normally, as shown inFIG. 7, when the IN terminal is inputted with the low-level (“L-level”) logic input signal, the logic circuit120generates and outputs the L-level logic output signal. This logic output signal is supplied to the gate terminal of the main MOSFET110via the driver circuit130to control the main MOSFET110to be OFF, thereby not supplying the voltage VCC to the load200.

When the high-level (“H-level”) logic input signal is inputted to the IN terminal, the logic circuit120generates and outputs the H-level logic output signal. This logic output signal is supplied to the gate terminal of the main MOSFET110via the driver circuit130to control the main MOSFET to be ON, thereby supplying the voltage VCC to the load200.

When the overcurrent detection circuit140is detecting an overcurrent at the main MOSFET110, if the L-level logic input signal is inputted to the IN terminal, the logic circuit120generates and outputs the L-level logic output signal to control the main MOSFET110to be OFF.

When the overcurrent detection circuit140is detecting an overcurrent at the main MOSFET110, if the H-level logic input signal is inputted to the IN terminal, the logic circuit120outputs a chopping operation signal. This chopping operation signal is a periodic High and Low signal train having a prescribed duty cycle. Due to the chopping signal, the main MOSFET is not maintained to be in the OFF state, but is controlled to be turned ON intermittently and periodically. Because of this, if the overcurrent situation is resolved to the normal situation during the chopping operation, the logic circuit120returns to the normal operation mode.

When the overheat detection circuit150is detecting an overheat of the main MOSFET, if the L-level logic input signal is inputted to the IN terminal, the logic circuit120generates and outputs the L-level logic output signal, thereby controlling the main MOSFET110to be OFF.

When the overheat detection circuit150is detecting an overheat of the main MOSFET, if the H-level logic input signal is inputted to the IN terminal, the logic circuit120still generates and outputs the L-level logic output signal, thereby controlling the main MOSFET110to be OFF.

When the overvoltage detection circuit160is detecting an abnormally high voltage, if the L-level logic input signal is inputted to the IN terminal, the logic circuit120generates and outputs the L-level logic output signal, thereby controlling the main MOSFET110to be OFF.

When the overvoltage detection circuit160is detecting an abnormally high voltage, if the H-level logic input signal is inputted to the IN terminal, the logic circuit120still generates and outputs the L-level logic output signal, thereby controlling the main MOSFET110to be OFF.

As described above, when the overcurrent detection circuit140is detecting an overcurrent due to, for example, a short-circuit at the load, if the H-level logic input signal is inputted to the IN terminal, the load200is intermittently provided with current due to the chopping operation, thereby reducing stress applied to the main MOSFET110. However, this overcurrent situation may not be resolved (and the normal condition thereby resumed) in a short period of time. If the chopping operation continues for a long period of time, the temperature of the main MOSFET110will continue to rise until the overheat detection circuit150detects an overheat. When the temperature rises due to the overcurrent, the main MOSFET110is under greater stress than when the temperature rises due to a rise of the ambient temperature. Thus, the overcurrent situation causes greater damages to the main MOSFET110.

To solve this issue, in the conventional art, a threshold that is used in determining the overcurrent is changed based on the duration in which the overcurrent situation continues. See Patent Document 1, for example. In the technology described in Patent Document 1, the longer the period of the overcurrent situation, the progressively lower the threshold for the overcurrent is changed to, thereby protecting the main power semiconductor switch from the overcurrent situation.

RELATED ART DOCUMENT

Patent Document

Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2014-158326

SUMMARY OF THE INVENTION

In the conventional semiconductor device, however, when the overcurrent situation, the overheating situation, and a high-voltage situation (a situation with a high voltage, but not as high as the abnormally high voltage (overvoltage)) respectively continue for only a short period of time, stress to the power semiconductor switch is small, but when the overheat situation occurs due to the overcurrent or the high voltage situation, the power semiconductor switch is subject to greater stress.

Accordingly, the present invention is directed to a semiconductor device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. An object of the present invention is to provide a semiconductor device in which a power semiconductor switch does not suffer great damage, such as burnout, even if the overheat situation occurs due to the overcurrent or high voltage situation.

Additional or separate features and advantages of the invention will be set forth in the descriptions that follow and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in one aspect, the present disclosure provides a semiconductor device having an input terminal to receive an input signal, an output terminal to be connected to a load, and a power supply terminal to receive a power supply voltage, the semiconductor device comprising: a power semiconductor switch connected between the power supply terminal and the output terminal; a logic circuit connected to the input terminal, the logic circuit generating a logic output signal in accordance with the input signal inputted to the input terminal, the logic output signal causing the power semiconductor switch to turn ON or OFF; an overheat detection circuit that outputs to the logic circuit an overheat detection signal when a temperature of the power semiconductor switch exceeds an overheat detection threshold; and an overcurrent detection circuit that monitors a current that flows through the power semiconductor switch and that outputs to the logic circuit and to the overheat detection circuit an overcurrent detection signal when the current that flows through the power semiconductor switch exceeds a prescribed threshold, wherein in the overheat detection circuit, the overheat detection threshold is set to a first threshold value when semiconductor device is operating normally, and the overheat detection threshold values is changed to a second threshold value that is lower than the first threshold value when the overheat detection circuit receives the overcurrent detection signal from the overcurrent detection circuit.

In another aspect, the present disclosure provides a semiconductor device having an input terminal to receive an input signal, an output terminal to be connected to a load, and a power supply terminal to receive a power supply voltage, the semiconductor device comprising: a power semiconductor switch connected between the power supply terminal and the output terminal; a logic circuit connected to the input terminal, the logic circuit generating a logic output signal in accordance with the input signal inputted to the input terminal, the logic output signal causing the power semiconductor switch to turn ON or OFF; an overheat detection circuit that outputs to the logic circuit an overheat detection signal when a temperature of the power semiconductor switch exceeds an overheat detection threshold; and a high-voltage detection circuit that monitors the power supply voltage on the power supply terminal and outputs to the overheat detection circuit a high-voltage detection signal when the power supply voltage exceeds a prescribed voltage, wherein in the overheat detection circuit, the overheat detection threshold is set to a first threshold value when semiconductor device is operating normally, and the overheat detection threshold values is changed to a second threshold value that is lower than the first threshold value when the overheat detection circuit receives the high-voltage detection signal from the high-voltage detection circuit.

In at least some of the aspects of the semiconductor devices described above, when an overheat condition occurs as a result of an overcurrent or a higher voltage of the power supply, the overheat detection circuit determines that the overheat occurs at a temperature lower than a temperature at which the overheat would be determined to occur under the normal situation (i.e., situation where no overcurrent or higher voltage situation occurs). This protects the power semiconductor switch from damages significantly.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed.

