Semiconductor device

Abstract

To provide a semiconductor device capable of detecting a state of a semiconductor light source at a low cost.SOLUTION: A semiconductor device 1 comprises: an output terminal OUT connected to a semiconductor light source 2; a current driving part 10 that switches a current flown to the output terminal OUT into a current value that is different in each of a plurality of first driving segments; a measurement part 40 that measures a voltage of the output terminal OUT; and a state detection part 50 that detects a state of the semiconductor light source 2 from the voltage of the output terminal OUT detected in each of the plurality of first driving segments.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor device having a function of detecting the state of a semiconductor light source. [Background technology]

[0002] The light emission control device disclosed in Patent Document 1 includes a forward voltage detection unit that detects the forward voltage of an LED (Light Emitting Diode) element, and a temperature calculation unit that calculates the ambient temperature of the LED element from the detected forward voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-129598 A

[0004] [overview] The light emission control device disclosed in Patent Document 1 includes a first terminal connected to a first end of an LED element and a second terminal connected to a second end of the LED element, and detects the forward voltage of the LED element from the voltage applied to the first terminal and the voltage applied to the second terminal. Then, the ambient temperature of the LED element is calculated from the detected voltage. In this case, the light emission control device requires the first terminal and the second terminal.

[0005] The semiconductor device disclosed in this specification comprises a terminal configured to be connected to a semiconductor light source, a current driving unit configured to switch a current flowing through the terminal to a different current value for each of a plurality of first driving sections, a measurement unit configured to measure a voltage of the terminal, and a state detection unit configured to detect a state of the semiconductor light source from the voltage of the terminal detected for each of the plurality of first driving sections. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an overall configuration diagram of a sensor system according to a reference example of the present disclosure. [Diagram 2] FIG. 2 is a block diagram of the semiconductor device according to the first embodiment of the present disclosure. [Diagram 3] FIG. 3 is a detailed block diagram of a semiconductor device according to a first example belonging to the first embodiment of the present disclosure. [Figure 4] FIG. 4 is a waveform diagram of the drive current and the voltage at the output terminal according to the first example belonging to the first embodiment of the present disclosure. [Diagram 5] FIG. 5 is a block diagram of a semiconductor device according to a second example belonging to the first embodiment of the present disclosure. [Figure 6] FIG. 6 is a block diagram of a semiconductor device according to the second embodiment of the present disclosure. [Figure 7] FIG. 7 is a waveform diagram showing an example of a driving current. [Figure 8] FIG. 8 is a waveform diagram showing another example of the driving current. [Figure 9] FIG. 9 is a block diagram showing a configuration in which an operation selection unit is added to the semiconductor device according to the first embodiment. [Figure 10] FIG. 10 is a block diagram showing a configuration in which an internal state monitoring unit is added to the semiconductor device according to the first embodiment. [Figure 11] FIG. 11 is a block diagram showing a configuration in which an external signal monitoring unit is added to the semiconductor device according to the first embodiment.

[0007] [Detailed Description] <<Reference example>> 1 is an overall configuration diagram of a proximity sensor system SYS according to a reference example of the present disclosure. The proximity sensor system SYS includes a semiconductor device 1, a semiconductor light source 2, and an MPU (Micro Processing Unit) 3. The operation of each component of the proximity sensor system SYS will be described below.

[0008] The semiconductor device 1 includes a current driver 10, a light receiver 20, and a controller 30. The current driver 10 is connected to an output terminal OUT, and supplies a drive current IDRV to the semiconductor light source 2 at a required timing under the control of the controller 30. Light emitted from the semiconductor light source 2 is reflected by an object OBJ. The reflected light from the object OBJ is received by the light receiver 20, and a signal indicating the light reception result is output from the light receiver 20 to the controller 30.

[0009] The semiconductor light source 2 emits light upon receiving a drive current IDRV. An LED or a semiconductor laser can be used as the semiconductor light source 2. The semiconductor laser may be, for example, a vertical cavity surface emitting laser. The semiconductor light source 2 has a first end and a second end, and the first end of the semiconductor light source 2 is connected to an output terminal OUT. The second end of the semiconductor light source 2 is connected to a terminal TVDRV to which a drive voltage VDRV is applied. The drive current IDRV flows from the second end to the first end of the semiconductor light source 2, causing the semiconductor light source 2 to emit light. For example, if the semiconductor light source 2 is an LED, the anode of the LED is connected to the terminal TVDRV, and the cathode of the LED is connected to the output terminal OUT. The wavelength of the light emitted from the semiconductor light source 2 is arbitrary. The light emitted from the semiconductor light source 2 may be visible light or infrared light.

[0010] The light receiving unit 20 includes a light receiving element 21, a current-voltage conversion circuit 22, and an ADC (Analog-to-Digital Converter) 23. The light receiving element 21 receives reflected light from the object OBJ and generates a current according to the intensity of the reflected light. The light receiving element 21 can be formed of a photodiode or a phototransistor. The current-voltage conversion circuit 22 converts the current generated by the light receiving element 21 into a voltage and outputs the voltage obtained by the conversion. The output voltage of the current-voltage conversion circuit 22 is an analog voltage. The ADC 23 is an analog / digital conversion circuit, and executes AD conversion processing to convert the output voltage of the current-voltage conversion circuit 22 into a digital signal. The digital signal obtained by the AD conversion processing is output from the light receiving unit 20 to the control unit 30 as a light receiving result signal. Note that the configuration of the light receiving unit 20 can be modified in various ways as long as a light receiving result signal can be obtained. The light receiving unit 20 can also be placed outside the semiconductor device 1.

[0011] The control unit 30 is connected to the MPU 3 through the communication terminals SCL and SDA, and performs bidirectional communication with the MPU 3 through the communication terminals SCL and SDA. The control unit 30 includes an interface circuit for realizing bidirectional communication with the MPU 3. Here, bidirectional communication between the control unit 30 and the MPU 3 is realized by two-wire serial communication according to the I2C standard. However, as long as bidirectional communication between the control unit 30 and the MPU 3 can be realized, the connection method and communication method between the control unit 30 and the MPU 3 are arbitrary. The control unit 30 can control the state of the current driver 10 based on a command received from the MPU 3. The control of the state of the current driver 10 includes control of the magnitude of the drive current IDRV and control of whether or not the drive current IDRV is supplied to the semiconductor light source 2. The control unit 30 can also transmit to the MPU 3 a signal indicating the light reception result from the light receiver 20 or a signal based on the light reception result signal.

[0012] The above is the operation of each component of the proximity sensor system SYS. The semiconductor device of the present disclosure described below detects the state of a semiconductor light source in addition to the basic functions of a sensor system. Naturally, the present disclosure can be implemented not only in a proximity sensor system, but also in any semiconductor device to which a semiconductor light source is connected.

[0013] <<First embodiment>> 2 is a diagram showing the semiconductor device 1 according to the first embodiment. The semiconductor device 1 according to the present embodiment includes an output terminal OUT connected to a semiconductor light source 2, a current driving unit 10 that switches a current flowing through the output terminal OUT to a different current value for each of a plurality of first driving sections, a measurement unit 40 that measures the voltage of the output terminal OUT, and a state detection unit 50 that detects the state of the semiconductor light source 2 from the voltage of the output terminal OUT detected for each of the plurality of first driving sections.

[0014] The measuring unit 40 measures the voltage at the output terminal OUT. An ADC is one example of the configuration of the measuring unit 40. The voltage at the output terminal OUT is converted into a finite digital code by the ADC.

[0015] The state detection section 50 instructs the current driving section 10 and the measurement section 40 to perform current driving and measurement operations according to a predetermined procedure, receives voltage measurement values ​​from the measurement section 40, and detects the state of the semiconductor light source 2.

[0016] As described above, the semiconductor device 1 detects the state of the semiconductor light source 2 only through the output terminal OUT. Generally, the cost of a semiconductor device is proportional to the number of terminals. Therefore, compared to the light emission control device disclosed in Patent Document 1, the cost of the semiconductor device of the present disclosure is lower.

[0017] <First Example> FIG. 3 is a detailed block diagram of a semiconductor device according to a first example belonging to the first embodiment of the present disclosure. The semiconductor device 1 according to this example detects the temperature of the semiconductor light source 2. In this example, the state detection unit 50 includes a state detection control unit 51, a measurement result holding unit 52, and a temperature calculation unit 53. A procedure for detecting the temperature of the semiconductor light source 2 will be described with reference to FIG. 4. All procedures are controlled by the state detection control unit 51. First, the current driving unit 10 draws a current of a current value IDRV1 from the output terminal OUT. At that time, the voltage of the output terminal OUT drops from the drive voltage VDRV to become a voltage VOUT1, and the measurement unit 40 measures the voltage VOUT1 and transmits it to the state detection unit 50 as a voltage measurement value. The measurement result holding unit 52 holds the voltage measurement value VOUT1. After a predetermined time has elapsed, the current driving unit 10 draws a current of a current value IDRV2 from the output terminal OUT. At this time, the voltage at the output terminal OUT drops from the drive voltage VDRV to voltage VOUT2, which is measured by the measurement unit 40 and transmitted as a measured voltage value to the state detection unit 50. The measurement result holding unit 52 holds the measured voltage value VOUT2.

[0018] In general, the current I when a forward voltage V is applied to a diode can be approximated as I = I0 × exp(qV / kT), where q = 1.6 × 10 -19 Coulomb, k = Boltzmann's constant, T = absolute temperature, and I0 = reverse current.

[0019] From the two voltage measurements of the output terminal OUT, IDRV1=I0×exp{q(VDRV-VOUT1) / kT} IDRV2=I0×exp{q(VDRV-VOUT2) / kT} These equations are respectively IDRV1 / I0=exp{q(VDRV-VOUT1) / kT} IDRV2 / I0=exp{q(VDRV-VOUT2) / kT} and transforms.

[0020] Furthermore, taking the natural logarithm of both sides, we get ln(IDRV1 / I0)=q(VDRV-VOUT1) / kT ln(IDRV2 / I0)=q(VDRV-VOUT2) / kT Taking the difference between the above two equations from top to bottom, we get ln(IDRV1 / I0)-ln(IDRV2 / I0) =q(VDRV-VOUT1) / kT-q(VDRV-VOUT2) / kT It becomes.

[0021] To summarize, ln(IDRV1 / IDRV2)=q(VOUT2-VOUT1) / kT From this, T={q(VOUT2-VOUT1)} / {k×ln(IDRV1 / IDRV2)}...(1) The temperature of the semiconductor light source 2 can be calculated from the drive current IDRV1, the drive current IDRV2, the measured voltage VOUT1, and the measured voltage VOUT2.

[0022] Temperature calculation unit 53 calculates detected temperature value T of semiconductor light source 2 from the held measured voltage values ​​VOUT1 and VOUT2 and drive currents IDRV1 and IDRV2 driven by current driver 10 using equation (1).

[0023] <Second Example> 5 is a diagram showing a semiconductor device according to a second example belonging to the first embodiment of the present disclosure. In this example, the state detection unit 50 includes a state detection control unit 51, a measurement result storage unit 52, a temperature calculation unit 53, and an abnormality determination unit 54. The temperature calculation unit 53 calculates a detected temperature value T of the semiconductor light source 2. The abnormality determination unit 54 outputs a determination result indicating whether or not the semiconductor light source 2 is abnormal based on T and threshold information. For example, when T=100 degrees absolute temperature and the operating temperature range of the semiconductor device 1 is from 220 degrees absolute temperature to 390 degrees absolute temperature, the abnormality determination unit 54 outputs a determination result indicating an abnormality.

[0024] The abnormality determination unit 54 may determine whether or not the semiconductor light source 2 is abnormal based on the measurement result rather than the detected temperature value T of the semiconductor light source 2. For example, if the digital code received from the measurement unit 40 is 0 volts, the abnormality determination unit 54 determines that the first end of the semiconductor light source 2 is short-circuited to ground, which is an abnormal state. Also, if the voltage value indicated by the digital code received from the measurement unit 40 is the drive voltage VDRV, for example, the abnormality determination unit 54 determines that the semiconductor light source 2 has failed and is in a short-circuit state.

[0025] <<Second embodiment>> 6 is a diagram showing a semiconductor device according to the second embodiment. The semiconductor device 1 according to this embodiment includes a temperature sensor 60. A state detection unit 50 detects the temperature of the semiconductor light source 2. An abnormality determination unit 54 generates a comparison result between the output of the temperature sensor 60 and the detected temperature of the semiconductor light source 2, and detects an abnormality in the semiconductor light source 2 based on the comparison result. As in the first example of the first embodiment, a temperature calculation unit 53 calculates a detected temperature value T1 of the semiconductor light source 2.

[0026] Meanwhile, the temperature sensor 60 also outputs the temperature T2 of the semiconductor device 1. Although the temperature T2 is the temperature of the semiconductor device 1, since the semiconductor device 1 is not used for power supply, it does not generate much heat and the temperature T2 may be approximated as being equal to the temperature around the semiconductor device 1. Therefore, if there is no abnormality in the semiconductor light source 2, the detected temperature value T1 and the temperature T2 are almost equal. When the absolute value of the difference between the detected temperature value T1 and the temperature T2 exceeds a certain threshold value, the abnormality determination unit 54 outputs a determination result indicating an abnormality.

[0027] <<First operation example of the current driver>> The current driver 10 passes a current through the output terminal OUT in a second driving section that is longer than the first driving section. Fig. 7 is a diagram showing an example of a change in the driving current IDRV over time in each of the first and second embodiments described above. The first current value IDRV1 and the second current value IDRV2 are used to detect the temperature of the semiconductor light source 2, as in the second embodiment, and the third current value IDRV3 is a current value used for the original sensor function.

[0028] Since the first drive section is shorter than the second drive section, the sensor does not interfere with its normal operation to detect the temperature of the semiconductor light source 2. Furthermore, if the semiconductor light source 2 is an LED that emits visible light, then if the first drive section is appropriately set, the temperature of the semiconductor light source 2 can be detected without being seen.

[0029] <<Second operation example of the current driver>> 8 is a diagram showing another example of the change over time of the drive current IDRV in each of the first and second embodiments described above. In this example, the current driver 10 causes a plurality of first driving sections to continuously pass a current to the output terminal OUT. Since the first current value IDRV1 and the second current value IDRV2 are continuously driven, the original sensor operation is not hindered and the operation of detecting the temperature of the semiconductor light source 2 is less likely to be visually recognized compared to the first operation example.

[0030] <<Examples of using detection results>> In each of the first and second embodiments described above, the semiconductor device 1 may have an operation selection section 70 that selects the operation of the semiconductor device 1 based on the detection result of the state detection section 50. Fig. 9 is a diagram showing a configuration in which the operation selection section 70 is added to the semiconductor device according to the first embodiment. For example, if the state detection section 50 conveys to the operation selection section 70 that the temperature of the semiconductor light source 2 is absolute 450 degrees, the operation selection section 70 outputs a signal to start a shutdown of the semiconductor device 1 as the operation selection result, thereby preventing the sensor system from going out of control.

[0031] <<First example of starting status detection operation>> In each of the first and second embodiments described above, the semiconductor device 1 may have an internal state monitoring unit 80 that monitors the internal state of the semiconductor device 1, and the state detection unit 50 may start a state detection operation in response to the monitoring result of the internal state monitoring unit 80. FIG. 10 is a diagram showing a configuration in which the internal state monitoring unit 80 is added to the semiconductor device according to the first embodiment. For example, when the semiconductor device 1 has a timer and the timer reaches the end of a predetermined time, the internal state monitoring unit 80 receives a signal notifying the timer of the expiration and transmits a detection start signal to the state detection unit 50. Then, the state detection unit 50, having received the detection start signal, starts a state detection operation. This enables periodic (every time a predetermined time has elapsed) state detection.

[0032] <<Second example of starting status detection operation>> In each of the first and second embodiments described above, the semiconductor device 1 has an external signal monitoring unit 90 that monitors an external signal of the semiconductor device 1, and the state detection unit 50 may start a state detection operation according to a monitoring result of the external signal monitoring unit 90. FIG. 11 is a diagram showing a configuration in which the external signal monitoring unit 90 is added to the semiconductor device according to the first embodiment. For example, when a signal for starting a state detection operation is applied from an input terminal of the semiconductor device 1 to the external signal monitoring unit 90, the external signal monitoring unit 90 transmits a detection start signal to the state detection unit 50. Then, the state detection unit 50 that has received the detection start signal starts a state detection operation. This enables external control of the state detection start timing.

[0033] <<Other>> In addition to the above-mentioned embodiment, the configuration of the invention can be modified in various ways without departing from the spirit of the invention. The above-mentioned embodiment should be considered to be illustrative in all respects and not restrictive, and the technical scope of the present invention is indicated by the claims, not by the description of the above-mentioned embodiment, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims. For example, like the semiconductor device 1 according to the reference example of the present disclosure, the semiconductor device 1 according to the first embodiment and the semiconductor device 1 according to the second embodiment may each include a light receiving unit 20.

[0034] <<Additional Notes>> Regarding the present disclosure, specific configuration examples of which have been shown in the above-mentioned embodiments, additional notes will be provided.

[0035] (Appendix 1) A terminal (OUT) configured to be connected to a semiconductor light source (2); A current driving unit (10) configured to switch a current flowing through the terminal to a different current value for each of a plurality of first driving sections; A measuring unit (40) configured to measure the voltage of the terminal; a state detection unit (50) configured to detect a state of the semiconductor light source from a terminal voltage of the terminal detected for each of the plurality of first driving sections; A semiconductor device comprising:

[0036] According to the semiconductor device described in Supplementary Note 1, it is possible to detect the state of the semiconductor light source with only a single terminal. Generally, the cost of a semiconductor device is proportional to the number of terminals. Therefore, the semiconductor device described in Supplementary Note 1, which requires a small number of terminals to detect the state of the semiconductor light source, can achieve low costs.

[0037] (Appendix 2) 2. The semiconductor device according to claim 1, wherein the state detection unit is configured to detect a temperature of the semiconductor light source.

[0038] (Appendix 3) 2. The semiconductor device according to claim 1, wherein the state detection unit is configured to detect an abnormality in the semiconductor light source.

[0039] (Appendix 4) 4. The semiconductor device according to claim 3, wherein the state detection unit is configured to detect a temperature of the semiconductor light source and detect an abnormality in the semiconductor light source based on the temperature of the semiconductor light source.

[0040] (Appendix 5) A temperature sensor (60), The state detection unit detects a temperature of the semiconductor light source, generating a comparison result between the output of the temperature sensor and the temperature of the semiconductor light source; 2. The semiconductor device according to claim 1, further comprising: a semiconductor light source configured to detect an abnormality in the semiconductor light source based on a result of the comparison.

[0041] (Appendix 6) 6. The semiconductor device according to claim 1, wherein the current driver is configured to cause a current to flow through the terminal in a second driving interval that is longer than the first driving interval.

[0042] (Appendix 7) 7. The semiconductor device according to claim 1, wherein the plurality of first driving sections are continuous.

[0043] (Appendix 8) 8. The semiconductor device according to claim 1, further comprising a selection unit configured to select an operation of the semiconductor device based on a detection result of the state detection unit.

[0044] (Appendix 9) an internal state monitoring unit configured to monitor an internal state of the semiconductor device; 9. The semiconductor device according to any one of claims 1 to 8, wherein the state detection unit is configured to start a detection operation in response to a monitoring result of the internal state monitoring unit.

[0045] (Appendix 10) an external signal monitoring unit configured to monitor an external signal of the semiconductor device; 9. The semiconductor device according to any one of claims 1 to 8, wherein the state detection unit is configured to start a detection operation in response to a monitoring result of the external signal monitoring unit. [Explanation of symbols]

[0046] 1 Semiconductor device 2. Semiconductor light source 3. MPU 10 Current driver 20 Light receiving section 21 Photodetector 22 Current-to-voltage conversion circuit 23 ADC 30 Control section 40 Measuring part 50 Status detection unit 51 Status detection control section 52 Measurement result holding section 53 Temperature calculation section 54 Abnormality determination section 60 Temperature Sensor 70 Operation selection section 80 Internal condition monitoring unit 90 External signal monitoring unit

Claims

1. a terminal configured to be connected to a semiconductor light source; a current driving unit configured to switch a current flowing through the terminal to a different current value for each of a plurality of first driving sections; A measurement unit configured to measure a voltage at the terminal; a state detection unit configured to detect a state of the semiconductor light source from a voltage of the terminal detected for each of the plurality of first driving sections; A semiconductor device comprising:

2. The semiconductor device according to claim 1 , wherein the state detector is configured to detect a temperature of the semiconductor light source.

3. The semiconductor device according to claim 1 , wherein the state detection unit is configured to detect an abnormality in the semiconductor light source.

4. 4. The semiconductor device according to claim 3, wherein the state detection section is configured to detect a temperature of the semiconductor light source and to detect an abnormality in the semiconductor light source based on the temperature of the semiconductor light source.

5. Equipped with a temperature sensor, The state detection unit detects a temperature of the semiconductor light source, generating a comparison result between the output of the temperature sensor and the temperature of the semiconductor light source; 2. The semiconductor device according to claim 1, further comprising: a step of detecting an abnormality in the semiconductor light source based on a result of the comparison.

6. The semiconductor device according to claim 1 , wherein the current driver is configured to cause a current to flow through the terminal in a second driving section that is longer than the first driving section.

7. The semiconductor device according to claim 1 , wherein the plurality of first driving sections are continuous.

8. 2. The semiconductor device according to claim 1, further comprising a selection section configured to select an operation of the semiconductor device based on a detection result of the state detection section.

9. an internal state monitoring unit configured to monitor an internal state of the semiconductor device; 2. The semiconductor device according to claim 1, wherein the state detection section is configured to start a detection operation in response to a monitoring result of the internal state monitoring section.

10. an external signal monitoring unit configured to monitor an external signal of the semiconductor device; 2. The semiconductor device according to claim 1, wherein the state detection section is configured to start a detection operation in response to a monitoring result of the external signal monitoring section.

Images