Semiconductor device with substrate temperature monitor circuit

First and second circuits, a photocoupler and a substrate temperature monitor circuit are formed on a substrate. A photocoupler includes a primary-side light emitting diode that converts an electric signal received from the first circuit into an optical signal, and a light receiving device that converts the optical signal into an electric signal and outputs the electric signal to the second circuit. The substrate temperature monitor circuit reads a Vf voltage value of the primary-side light emitting diode of the photocoupler to monitor temperature of the substrate.

FIELD

The present invention relates to a semiconductor device capable of monitoring a substrate temperature without the need for adding any components.

BACKGROUND

A control system for a semiconductor device is required to achieve a high precision, a high functionality, and a high packaging density at a low cost. In the control system, an improvement in the precision of various sensing functions is one of important problems to be solved to achieve an improvement in the efficiency of the semiconductor device. One of impediments to the achievement of an improvement in precision is a variation in performance due to temperature characteristics of electronic components. Accordingly, it is necessary to take some measures to reduce the variation in performance.

Note that a photocoupler is an electronic component that is generally used to transmit signals from a logic part and a semiconductor device, while providing electrical isolation between the logic part and the semiconductor device. A technique in which a light emitting diode of a photocoupler detects abnormal heat generation in the photocoupler has been proposed (e.g., see PTL 1).

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

To reduce a variation in performance of sensing functions due to temperature characteristics of electronic components, it is necessary to monitor the temperature of a substrate and feed back the monitored temperature. Accordingly, monitoring the substrate temperature using a thermocouple or a thermistor causes a problem that the number of components and costs increase.

The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to obtain a semiconductor device capable of monitoring a substrate temperature without the need for adding any components.

Solution to Problem

A semiconductor device according to the present invention includes: a substrate; first and second circuits formed on the substrate; a photocoupler formed on the substrate and including a light emitting diode that converts an electric signal received from the first circuit into an optical signal, and a light receiving device that converts the optical signal into an electric signal and outputs the electric signal to the second circuit; and a substrate temperature monitor circuit reading a Vf voltage value of the light emitting diode of the photocoupler to monitor temperature of the substrate.

Advantageous Effects of Invention

In the present invention, the substrate temperature monitor circuit reads the Vf voltage value of the light emitting diode of the photocoupler to monitor the temperature of the substrate. Therefore, the photocoupler can monitor the temperature of the substrate, without the need for adding a component such as a thermocouple or a thermistor.

DESCRIPTION OF EMBODIMENTS

A semiconductor device according to the embodiments of the present invention will be described with reference to the drawings. The same components will be denoted by the same symbols, and the repeated description thereof may be omitted.

FIG. 1is a diagram showing a semiconductor device according to Embodiment 1 of the present invention. On a substrate1, first and second circuits2and3, a photocoupler4, and a substrate temperature monitor circuit5are formed. The photocoupler4includes a primary-side light emitting diode6that converts an electric signal received from the first circuit2into an optical signal, and a light receiving device7that converts the optical signal into an electric signal and outputs the electric signal to the second circuit3. The photocoupler4transmits signals from the first circuit2and the second circuit3, while providing electrical isolation between the first circuit2and the second circuit3.

FIG. 2is a graph showing Vf voltage characteristics of the light emitting diode of the photocoupler. As shown in the figure, the Vf voltage of the primary-side light emitting diode6has a temperature dependence. Accordingly, the substrate temperature monitor circuit5reads the Vf voltage value of the primary-side light emitting diode6of the photocoupler4, thereby monitoring the temperature of the substrate1. Since the photocoupler4is originally equipped in the device, the photocoupler4can monitor the temperature of the substrate1, without the need for adding a component such as a thermocouple or a thermistor. The monitored temperature is fed back to various sensing circuits to cancel a variation in circuit characteristics due to the temperature, thereby achieving an improvement in the precision of sensing functions.

FIG. 3is a diagram showing a semiconductor device according to Embodiment 2 of the present invention. A constant current circuit8is used as a drive circuit for the primary-side light emitting diode6. With this configuration, substrate temperature information can be accurately monitored.

FIG. 4is a diagram showing a semiconductor device according to Embodiment 3 of the present invention. A power supply circuit9supplies a voltage to each of the first and second circuits2and3. The substrate temperature monitor circuit5corrects a temperature variation in the output voltage value of the power supply circuit9according to the monitored temperature of the substrate1. Thus, the temperature information is fed back to the power supply circuit9and a variation in the power supply voltage value due to temperature characteristics is corrected, thereby making it possible to improve the precision of the drive system for the semiconductor device.

FIG. 5is a diagram showing a semiconductor device according to Embodiment 4 of the present invention. The substrate temperature monitor circuit5outputs an error signal when the monitored temperature of the substrate1has reached a threshold. A control circuit10which has received the error signal interrupts the operation of each of the first and second circuits2and3. Thus, the error signal is output during abnormal heat generation in the substrate1, thereby making it possible to properly protect the semiconductor device.

FIG. 6is a diagram showing a semiconductor device according to Embodiment 5 of the present invention. A signal output circuit11outputs a pulse width modulation (PWM) signal. The substrate temperature monitor circuit5corrects a PWM signal according to the monitored temperature of the substrate1and supplies the PWM signal to the photocoupler4. Thus, the temperature is monitored by the substrate temperature monitor circuit5and the monitored temperature is fed back, thereby making it possible to correct a variation in transmission of a duty of the PWM signal of the photocoupler4that is caused due to temperature characteristics.

FIG. 7is a diagram showing a semiconductor device according to Embodiment 6 of the present invention. The power supply circuit9includes an aluminum electrolytic capacitor12. The substrate temperature monitor circuit5refers to a preliminarily stored life curve of the aluminum electrolytic capacitor12, and accumulates thermal histories of the aluminum electrolytic capacitor12from the monitored temperature of the substrate1, to thereby predict the life of the aluminum electrolytic capacitor12.FIG. 8is a graph showing a life curve of the aluminum electrolytic capacitor. Based on this life curve, the life of the aluminum electrolytic capacitor12can be accurately predicted.

The substrate temperature monitor circuit5outputs an error signal when the predicted life of the aluminum electrolytic capacitor12has reached life criteria. An error output part13which has received the error signal notifies a user of the error by display, voice, or the like. Thus, the semiconductor device can be properly protected, and a time for replacement of the semiconductor device can be detected.

FIG. 9is a diagram showing a semiconductor device according to Embodiment 7 of the present invention. A plurality of photocouplers4is formed on the substrate1. Although the illustration of the first and second circuits2and3and the like is omitted, the configurations of these components are similar to those of any one of Embodiments 1 to 6.

The substrate temperature monitor circuit5reads the Vf voltage value of the primary-side light emitting diode6of each of the plurality of photocouplers4, and averages the read voltage values, thereby monitoring the temperature of the substrate1. Thus, the temperature of the substrate is monitored by the plurality of photocouplers4, thereby making it possible to more accurately monitor the temperature of the substrate1.

FIG. 10is a diagram showing a semiconductor device according to Embodiment 8 of the present invention. A plurality of photocouplers4is formed on the substrate1. Although the illustration of the first and second circuits2and3and the like is omitted, the configurations of these components are similar to those of any one of Embodiments 1 to 6.

The substrate temperature monitor circuit5reads the Vf voltage value of the primary-side light emitting diode6of the photocoupler4that is located at a position where the temperature of the substrate1is highest among the plurality of photocouplers4, thereby monitoring the temperature of the substrate1. Thus, one of the photocouplers4is monitored, thereby minimizing the cost and sensing processing.

REFERENCE SIGNS LIST