Temperature detection device and electronic device

Abstract

To provide a temperature detection device, an electro-optical device, and an electronic apparatus that can monitor, with good sensitivity, a change in a driving current supplied from a constant current circuit to a temperature detection element.SOLUTION: A temperature detection device 50 has: a temperature detection element 15; a constant current circuit 55 that supplies a driving current If to the temperature detection element 15; and a temperature signal generation unit 75 that converts a voltage Vp of the temperature detection element 15 when the driving current If is supplied to the temperature detection element 15 into a temperature signal Dt. The temperature detection device 50 includes a driving current monitoring circuit 52 that monitors a change in the driving current If output from the constant current circuit 55. The driving current monitoring circuit 52 has a current-voltage conversion unit 54 whose voltage Vg changes in correspondence with the change of the driving current, and with a switching circuit 53, outputs the voltage Vg when the driving current If is supplied from the constant current circuit 55 to the current-voltage conversion unit 54.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a temperature detection device including a constant current circuit that supplies a drive current to a temperature detection element, and to an electronic device. [Background technology]

[0002] In electro-optical devices such as liquid crystal devices and organic electroluminescence display devices, the temperature of the electro-optical device rises when an image is displayed. In particular, in electro-optical devices such as liquid crystal devices used as light valves in projection display devices, the temperature of the liquid crystal panel is likely to rise because illumination light is irradiated to the liquid crystal panel at a high intensity. In such cases, the modulation characteristics and response characteristics of the liquid crystal layer change. Therefore, if the projection display device is controlled based on the result of detecting the temperature of the liquid crystal panel, the effect of temperature on the image can be mitigated. For example, if the cooling fan provided in the projection display device is controlled based on the result of detecting the temperature of the liquid crystal panel, the effect of temperature on the image can be mitigated.

[0003] Meanwhile, as a temperature detection device, Patent Document 1 discloses a configuration using a diode as a temperature detection element and a constant current circuit, and Patent Document 2 discloses a configuration using a resistance element as a temperature detection element and a constant voltage circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-29265 [Patent Document 2] JP 2009-236536 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 does not disclose a configuration for monitoring the drive current from the constant current circuit. Therefore, there is a problem that if the drive current has a non-negligible aging variation or failure, appropriate temperature detection cannot be performed. Although it is possible to monitor the drive current using the diode itself as the temperature detection element, it is not practical because the diode needs to be placed in a specified temperature environment when monitoring the drive current. Furthermore, since the diode is a nonlinear element in which the change in forward voltage is small with respect to the change in drive current, it is not suitable for monitoring the change in drive current. Patent Document 2 discloses a configuration in which temperature is detected by the divided voltage value of a resistor element that serves as a temperature detection element, and a fault diagnosis of the temperature detection circuit is performed using a diagnostic resistor element having a resistance within the resistance value range of the temperature detection element. However, since the diagnostic resistor element has a resistance within the resistance value range of the temperature detection element, the sensitivity of detecting the voltage fluctuation of the constant voltage source is not greater than that of the temperature detection element. Even if the configuration is extended to constant current drive of a resistor element that is a linear element, the voltage value change of the diagnostic resistor element with respect to the change in drive current is not greater than the voltage value change of the temperature detection element. Therefore, there has been a demand for a configuration that uses a diode as the temperature detection element and is capable of monitoring changes in the drive current with high sensitivity when the device is driven with a constant current. [Means for solving the problem]

[0006] In order to solve the above problems, the temperature detection device of the present invention is characterized in that it comprises a temperature detection element, a constant current circuit that supplies a drive current to the temperature detection element, a voltage detection unit that detects the voltage of the temperature detection element when the drive current is supplied to the temperature detection element, and a drive current monitoring circuit electrically connected to the constant current circuit.

[0007] The electronic device equipped with the temperature detection device according to the present invention detects temperature via the temperature detection element. The present invention is characterized in that it has an electro-optical device including an electro-optical panel. [Brief description of the drawings]

[0008] [Figure 1]FIG. 1 is a schematic configuration diagram of an electronic device to which the present invention is applied. [Diagram 2] 2 is an explanatory diagram showing one embodiment of an electro-optical panel of the electro-optical device shown in FIG. 1. [Diagram 3] 2 is an explanatory diagram of a temperature detection device and the like provided in the electronic device shown in FIG. [Figure 4] 4 is an explanatory diagram showing the temperature characteristics of the temperature detection element shown in FIG. 3. [Diagram 5] FIG. 1 is an explanatory diagram showing a circuit configuration of a temperature detection device according to a first embodiment of the present invention. [Figure 6] 6 is an explanatory diagram showing the current-voltage characteristics of the current-voltage conversion unit and the like shown in FIG. 5. [Figure 7] FIG. 4 is an explanatory diagram showing a circuit configuration of a temperature detection device according to a modified example of the first embodiment of the present invention. [Figure 8] FIG. 6 is an explanatory diagram showing a circuit configuration of a temperature detection device according to a second embodiment of the present invention. [Figure 9] FIG. 11 is an explanatory diagram showing a circuit configuration of a temperature detection device according to a modified example of the second embodiment of the present invention. [Figure 10] FIG. 11 is an explanatory diagram of a temperature detection device according to a third embodiment of the present invention. [Figure 11] FIG. 11 is an explanatory diagram of a temperature detection device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiments of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the scale of each component is different and the number of components is reduced so that each component can be recognized on the drawing.

[0010] [Embodiment 1] 1. Example of electronic device configuration Fig. 1 is a schematic diagram of an electronic device 2100 to which the present invention is applied. Fig. 1 shows a projection display device as an example of the electronic device 2100 to which the present invention is applied. Note that optical elements such as polarizing plates arranged on the entrance side and exit side of the electro-optical device 1 are omitted in Fig. 1.

[0011] In FIG. 1, electronic device 2100 is a projection display device, and a lamp unit 2102 having a white light source such as a halogen lamp is provided as a light source unit. Projection light emitted from lamp unit 2102 is separated into three primary colors of light, red R, green G, and blue B, by three mirrors 2106 and two dichroic mirrors 2108 arranged inside. The separated light is guided to electro-optical devices 1(R), 1(G), and 1(B) corresponding to each color, respectively. All of electro-optical devices 1(R), 1(G), and 1(B) are liquid crystal devices. Since blue B light has a longer optical path than other colors, red R and green G, it is guided through a relay lens system 2121 having an input lens 2122, a relay lens 2123, and an output lens 2124 to prevent loss of blue B light.

[0012] In the electronic device 2100, image signals specifying the gradation levels of each color are supplied to the electronic device 2100 from an external higher-level circuit, processed by a processing circuit of the electronic device 2100, and supplied to the electro-optical devices 1(R), 1(G), and 1(B). Then, the electro-optical devices 1(R), 1(G), and 1(B) modulate the incident light based on the image signal. The modulated light emitted from the electro-optical devices 1(R), 1(G), and 1(B) is incident on the dichroic prism 2112 from three directions. In the dichroic prism 2112, the red light R and the blue light B are reflected at 90 degrees, and the green light G is transmitted. Therefore, the modulated light of each color is combined by the dichroic prism 2112, and then projected as a color image by the projection optical system 2114 onto a projection member such as a screen 2120. In addition, the projection type display device may be configured to use an LED light source or the like that emits light of each color as the light source unit, and supply the colored light emitted from the LED light source or the like to the electro-optical devices 1(R), 1(G), and 1(B), respectively.

[0013] 2. Basic configuration of the electro-optical panel 100 FIG. 2 is an explanatory diagram showing one embodiment of the electro-optical panel 100 of the electro-optical device 1 shown in FIG. 1. In FIG. 2, each direction is represented using an orthogonal coordinate system consisting of an x-axis, a y-axis, and a z-axis. The z-axis direction is the thickness direction of the electro-optical panel 100, the y-axis direction is the extension direction of the wiring board included in the electro-optical device 1, and the x-axis direction is the width direction perpendicular to the extension direction of the wiring board. Since the electro-optical devices 1(R), 1(G), and 1(B) shown in FIG. 1 all have the same structure, in the following description, when there is no need to distinguish between the electro-optical devices 1(R), 1(G), and 1(B), the (R), (G), and (B) indicating the corresponding colors are omitted.

[0014] In FIG. 2, the electro-optical device 1 is a liquid crystal device, and includes a liquid crystal panel as an electro-optical panel 100. The electro-optical device 1 includes a plurality of pixel electrodes 16 formed on a first substrate 10, a common electrode (not shown) formed on a second substrate 20, and an electro-optical layer (not shown) made of a liquid crystal layer provided between the pixel electrodes 16 and the common electrode. The pixel electrodes 16 face the common electrode via the electro-optical layer to form pixels 17. In the electro-optical device 1, the second substrate 20 is bonded to the first substrate 10 by a sealant (not shown). In the electro-optical device 1, the electro-optical layer is provided in a region surrounded by the sealant. In the electro-optical panel 100, a region in which the pixels 17 are arranged in the x-axis direction and the y-axis direction is a display region 110.

[0015] The electro-optical device 1 of this embodiment is a transmissive liquid crystal device. Therefore, the substrate body of the first substrate 10 and the substrate body of the second substrate 20 are made of a light-transmitting substrate such as a heat-resistant glass substrate or a quartz substrate. In the transmissive electro-optical device 1, for example, illumination light incident from one of the first substrate 10 and the second substrate 20 is modulated while exiting from the other substrate, and is output as display light. In this embodiment, illumination light incident from the second substrate 20 is modulated while exiting from the first substrate 10, and is output as display light.

[0016] The first substrate 10 has a protruding portion 105 that protrudes in the y-axis direction from an end of the second substrate 20. The protruding portion 105 is provided with a terminal area in which a plurality of terminals 111 are arranged at a predetermined pitch along a first side 101 that extends in the x-axis direction, which is the width direction of the first substrate 10. The electro-optical device 1 has a flexible wiring board 60 connected to the terminals 111, and the wiring board 60 extends in the y-axis direction so as to be spaced apart from the first substrate 10.

[0017] As will be described later with reference to Fig. 3, when configuring the electronic device 2100 shown in Fig. 1, the electro-optical devices 1 shown in Fig. 2 are mounted as electro-optical devices 1(R), 1(G), and 1(B), respectively. At that time, the wiring boards 60 of the three electro-optical devices 1(R), 1(G), and 1(B) are each electrically connected to a common wiring board 70.

[0018] 3. Configuration of the electro-optical device 1 FIG. 3 is an explanatory diagram of the temperature detection device 50 and the like provided in the electronic device 2100 shown in FIG. 1. The temperature detection device 50 of this embodiment detects the temperature of each of the electro-optical panels 100(R), 100(G), and 100(B) of the multiple electro-optical devices 1(R), 1(G), and 1(B). Therefore, among the components of the temperature detection device 50, the components provided for each of the electro-optical devices 1(R), 1(G), and 1(B) are marked with (R), (G), and (B) indicating the corresponding colors, and the components common to the electro-optical devices 1(R), 1(G), and 1(B) are not marked with (R), (G), and (B) indicating the corresponding colors. In addition, since the electro-optical devices 1(R), 1(G), and 1(B) all have the same configuration, the following description will focus on the electro-optical device 1(R), and a detailed description of the electro-optical devices 1(G) and 1(B) will be omitted. However, even when describing the electro-optical device 1(R), if there is no need to distinguish between the electro-optical devices 1(R), 1(G), and 1(B), the (R), (G), and (B) indicating the corresponding colors will be omitted.

[0019] 3, in the electro-optical panel 100(R), a frame-shaped light-shielding portion 25 is formed on the second substrate 20, and the inside of the light-shielding portion 25 is a display region 110. A plurality of inter-substrate conductive portions 106 are provided at positions of the first substrate 10 overlapping with corners of the second substrate 20. The inter-substrate conductive portions 106 are electrically connected to each other by wiring 112, and are electrically connected to any of the terminals 111 by wiring not shown. Therefore, a common voltage LCCOM is supplied to the common electrode of the second substrate 20 from the first substrate 10 side via the inter-substrate conductive portions 106.

[0020] In the first substrate 10, a data line driving circuit 108 is provided on the side of the overhanging portion 105 with respect to the display area 110. The data line driving circuit 108 supplies image signals to the plurality of pixel electrodes 16 shown in FIG. 2 via data lines (not shown) and pixel switching elements (not shown). Each pixel 17 shown in FIG. 2 typically includes an auxiliary capacitance (not shown) having one electrode electrically connected to the pixel electrode 16 and the other electrode electrically connected to a common voltage LCCOM. In the first substrate 10, a test circuit (not shown) may be provided between the second side 102 facing the first side 101 and the display area 110. In the first substrate 10, a scanning line driving circuit 109 is provided between the third side 103 and the display area 110 among the third side 103 and the fourth side 104 extending from both ends of the first side 101 in the y-axis direction. The scanning line driving circuit 109 supplies scanning signals to the pixel switching elements via scanning lines (not shown). The scanning line driving circuit 109 may be provided both between the third side 103 and the display area 110 and between the fourth side 104 and the display area 110. In this embodiment, the data line driving circuit 108 and the scanning line driving circuit 109 overlap with the light shielding portion 25 in a plan view.

[0021] 3. Basic configuration of temperature detection device 50 FIG. 4 is an explanatory diagram showing the temperature characteristic of the temperature detection element 15 shown in FIG. 3. As shown in FIG. 3, the electronic device 2100 shown in FIG. 1 is provided with a temperature detection device 50 for detecting the temperature of each of the electro-optical panels 100(R), 100(G), and 100(B) of the electro-optical devices 1(R), 1(G), and 1(B). The temperature detection device 50 has a temperature detection element 15(R) for detecting the temperature of the electro-optical panel 100(R), a constant current circuit 55(R) for supplying a drive current If to the temperature detection element 15(R), and a temperature signal generation unit 75 for generating a temperature signal Dt(R) based on an output voltage from the temperature detection element 15(R) when the drive current If is applied to the temperature detection element 15(R). In addition, the electro-optical device 1(R) is provided with a temperature adjustment device 200(R) for adjusting the temperature of the electro-optical panel 100 based on the temperature signal Dt(R) output from the temperature signal generation unit 75. In this embodiment, the drive current If output from the constant current circuit 55(R) is supplied to the temperature detection element 15(R) by the switching circuit 53 at a predetermined timing.

[0022] The temperature detection element 15(R) is provided on the first substrate 10 of the electro-optical panel 100(R) at a position overlapping with the light-shielding portion 25 in a planar view, and is close to the display area 110. Therefore, the temperature detection element 15(R) can detect the temperature of the electro-optical panel 100(R) in the vicinity of the display area 110 of the electro-optical panel 100(R).

[0023] The temperature detection element 15(R) is made of a diode, the constant current circuit 55(R) is electrically connected to the anode side of the diode, and the cathode side of the diode is electrically connected to ground via the wiring board 60. Therefore, when a drive current If is applied to the temperature detection element 15(R), the output voltage from the temperature detection element 15(R) is a forward voltage Vp(R). Such a diode is formed by utilizing the process of forming pixel switching elements and the like on the first substrate 10. In this embodiment, the temperature detection element 15(R) is made of a plurality of diodes electrically connected in series to increase the detection sensitivity of temperature changes. Therefore, the voltage Vp(R) output from the temperature detection element 15(R) is calculated as follows: (forward voltage per diode)× (number of diodes). The diodes are not limited to PN junctions, and may be transistors connected in a diode configuration.

[0024] In the temperature detection device 50 configured as above, when a minute forward drive current If of about 100 nA to several μA is supplied from the constant current circuit 55 to the temperature detection element 15(R), the drive current If flows through the temperature detection element 15(R). Here, the forward voltage Vp of the temperature detection element 15(R) changes approximately linearly with temperature as shown by the solid line P0 in FIG. 4. For example, in the temperature detection element 15(R), when five diodes are connected in series, the forward voltage decreases by about 10 mV when the temperature rises by 1° C. Therefore, the voltage Vp of the temperature detection element 15(R) changes with the temperature of the electro-optical panel 100(R). Therefore, the temperature signal generation unit 75 can generate a temperature signal Dt(R) based on the voltage Vp of the temperature detection element 15(R) and output it to the temperature control unit 79, and the temperature adjustment device 200(R) adjusts the temperature of the electro-optical panel 100(R) under the control of the temperature control unit 79.

[0025] As the temperature adjustment device 200(R), a mechanism for cooling the electro-optical panel 100(R) or a mechanism (not shown) for heating the electro-optical panel 100(R) is used. In this embodiment, the temperature adjustment device 200(R) has a cooling fan 210 that supplies cooling air to the electro-optical panel 100 through a flow path 220, and the temperature control unit 79 controls the rotation of the cooling fan 210 of the temperature adjustment device 200(R) to control the flow rate of the cooling air supplied to the electro-optical panel 100(R). Note that, for the sake of explanation, FIG. 3 shows air being blown from the fourth side 104 of the electro-optical panel 100(R), but typically air is blown to the electro-optical panel 100(R) from the second side 102. Note that, in the case where a heating mechanism is employed, the temperature control unit 79 controls the supply of power to, for example, a heater wire attached to a holder that holds the electro-optical panel 100(R) based on a control signal from the temperature control unit 79. 3, an independent temperature adjustment device 200 is provided for each electro-optical panel 100, but this is not mandatory. For example, the cooling fan 210 and the flow path 220 may be shared by three electro-optical panels 100.

[0026] Incidentally, for the electro-optical device 1(R), temperature correction may be performed on the image signal based on a control signal from the central control unit 72, thereby compensating for the effect of temperature on the image.

[0027] In this embodiment, the constant current circuit 55(R), temperature signal generating unit 75, and temperature control unit 79 are provided on a common wiring board 70. Note that the electro-optical devices 1(G) and 1(B) are each configured similarly to the electro-optical device 1(R), including the temperature detection element 15(R) and temperature adjustment device 200(R), and therefore a description thereof will be omitted. Note that at least a part of the functions of the constant current circuit 55(R) may be provided in a driving IC (not shown) mounted on the wiring board 60(R).

[0028] 4. Configuration of the drive current monitoring circuit 52, etc. 5 is an explanatory diagram showing a circuit configuration of a temperature detection device 50 according to the first embodiment of the present invention. As shown in FIG. 5, the temperature detection device 50 according to this embodiment is provided with a plurality of constant current circuits 55(R), 55(G), and 55(B) corresponding to the plurality of temperature detection elements 15(R), 15(G), and 15(B), respectively. Therefore, the drive current If generated by the constant current circuit 55(R) is supplied to the temperature detection element 15(R) provided in the electro-optical panel 100(R) via the temperature detection circuit 51(R). In response to this, the voltage Vp(R) of the temperature detection element 15(R) when the drive current If is applied, the voltage Vp(G) of the temperature detection element 15(G) when the drive current If is applied, and the voltage Vp(B) of the temperature detection element 15(B) when the drive current If is applied are all output to the temperature signal generating unit 75.

[0029] The temperature signal generating unit 75 detects the voltage Vp(R) of the temperature detecting element 15(R). The device includes a voltage detection means 71 and a central control unit 72 that generates a temperature signal Dt(R) based on the detection result by the voltage detection means 71. The voltage detection means 71 includes, for example, a voltage follower using an operational amplifier and an A / D converter, and the central control unit 72 performs processing such as generating the temperature signal Dt(R) based on a program previously stored in a storage unit (not shown) such as an EEPROM.

[0030] In this embodiment, the central control unit 72 calculates the temperature of the electro-optic panel 100(R) based on the following temperature calculation formula, and outputs a temperature signal Dt(R) corresponding to the temperature calculation result to the temperature control unit 79. The coefficients A and B of the temperature calculation formula are stored in a calibration value storage means 73 consisting of an EEPROM or the like. The voltages Vp(G) and Vp(B) of the temperature detection elements 15(G) and (B) provided in the other electro-optic panels 100(G) and 100(B) are similarly processed in the temperature signal generating unit 75. Since there are manufacturing variations in the constant current circuit 55(R) and the temperature detection element 15(R), the temperature characteristics are measured using a thermostatic bath or the like to obtain a calibration value and improve the temperature detection accuracy. As shown in FIG. 4, in a diode, the voltage Vp(R) decreases with an increase in temperature, so the coefficient A is typically a negative value. Temperature=A×α(Vp(R))+B In the above formula, A, B: Coefficients α(Vp(R)): A / D converter value corresponding to voltage Vp(R)

[0031] The temperature detection device 50 is also provided with a drive current monitoring circuit 52(R) electrically connected to the constant current circuit 55(R), and the drive current monitoring circuit 52(R) monitors changes in the drive current If output from the constant current circuit 55(R). In this embodiment, the drive current monitoring circuit 52(R) includes a current-voltage conversion unit 54(R) whose output voltage Vg(R) changes in response to changes in the drive current If, and outputs the voltage Vg(R) when the drive current If is supplied to the current-voltage conversion unit 54(R). This voltage Vg(R) is input to the central control unit 72 via a voltage detection means 71. Therefore, the drive current If generated by the constant current circuit 55(R) is supplied to the temperature detection element 15(R) and is also supplied to the current-voltage conversion unit 54(R). Therefore, the temperature detection device 50 includes a constant current circuit 55(R) A switching circuit 53 is provided for switching a current path between a state in which the drive current If is supplied from the constant current circuit 55(R) to the temperature detection element 15(R) and a state in which the drive current If is supplied from the constant current circuit 55(R) to the current-voltage conversion unit 54(R). The switching circuit 53 is controlled by a central control unit 72. The central control unit 72 therefore also controls the timing of sequentially monitoring the temperature by the temperature detection elements 15(R), 15(G), and 15(B) and the drive current If by the current-voltage conversion units 54(R), 54(G), and 54(B). These timing controls are executed by a program stored in an EEPROM or the like, but may also be executed by a diagnostic command external input means 78. The switching circuit 53 may be, for example, a switch IC incorporating a plurality of transfer switches that can be controlled independently of each other.

[0032] In this embodiment, the switching circuit 53 includes a first switching circuit 531 and a second switching circuit 532. The first switching circuit 531 includes a switch SW1A provided in a wiring of the temperature detection circuit 51(R) from the constant current circuit 55(R) to the temperature detection element 15(R), and a switch SW1B provided in a wiring of the drive current monitoring circuit 52(R) from the constant current circuit 55(R) to the current-voltage conversion unit 54(R). The second switching circuit 532 includes a switch SW2A provided in a wiring of the output line from the temperature detection element 15 to the voltage detection means 71, and a switch SW2B provided in a wiring of the output line from the current-voltage conversion unit 54(R) to the voltage detection means 71.

[0033] The temperature detection device 50 also has a diagnostic command external input means 78 for inputting a diagnostic command for diagnosing the drive current If from the outside. The diagnostic command external input means 78 is 2 to execute diagnosis of the drive current If. The diagnostic command external input means 78 is implemented, for example, as a control switch provided on the wiring board 70, a control switch provided on the electronic device 2100, or a selection item of a control program menu of the electronic device 2100 displayed by the electronic device 2100.

[0034] 5. Example of operation In this embodiment, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to execute temperature detection at a preset timing from a standby state in which all the switches SW1A, SW2A, SW1B, and SW2B are turned off. More specifically, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to turn on the switches SW1A and SW2A of the temperature detection circuit 51(R) and turn off the other switches. As a result, a drive current If is applied from the constant current circuit 55(R) to the temperature detection element 15(R) for a certain period, during which the voltage Vp(R) of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection means 71. Therefore, the central control unit 72 outputs a temperature signal Dt(R) corresponding to the temperature of the electro-optical panel 100(R) to the temperature control unit 79, and the temperature adjustment device 200(R) adjusts the temperature of the electro-optical panel 100(R). Such temperature detection is performed periodically while the electro-optical device 1(R) is in operation.

[0035] On the other hand, when a command to monitor the drive current If output from the constant current circuit 55(R) is input to the central control unit 72 via the external diagnostic command input means 78, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to execute drive current monitoring. More specifically, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to turn on the switches SW1B and SW2B of the drive current monitoring circuit 52(R) and turn off the other switches. As a result, the application of the drive current If from the constant current circuit 55(R) to the temperature detection element 15(R) is stopped, and the drive current If is applied to the current-voltage conversion unit 54(R) for a certain period of time. During that time, the voltage Vg(R) of the current-voltage conversion unit 54(R) is input to the central control unit 72 via the voltage detection means 71. If the voltage Vg(R) at the initial drive current If is determined in advance, the central control unit 72 can calculate the amount of change in the drive current If as a voltage value. The amount of change in the drive current If is a voltage value calculated with reference to the output voltage of the current-voltage conversion unit 54, but in the following description, it may be simply referred to as the amount of change in the drive current If.

[0036] Here, the central control unit 72 corrects the coefficients A and B of the temperature calculation formula based on the amount of change in the drive current If, and thereafter calculates the temperature of the electro-optical panel 100 using the corrected coefficients A and B. More specifically, the temperature signal generating unit 75 has a correction value storage means 74 made of an EEPROM or the like, and the relationship between the voltage value corresponding to the amount of change in the drive current If and the correction value for the coefficients A and B is stored in the correction value storage means 74 as a lookup table. For example, when the drive current If decreases, the calculated temperature rises above the true value, so a lookup table is created in which the coefficient B is decreased to offset the increase. Strictly speaking, when the drive current If decreases, the sensitivity of the temperature detection element to the temperature increases slightly, so the coefficient A should be changed, but in practice, there are cases where only changing the coefficient B is sufficient. Therefore, after detecting the amount of change in the drive current If, the central control unit 72 corrects the coefficients A and B based on the lookup table stored in the correction value storage means 74, and thereafter calculates the temperature of the electro-optical panel 100(R) using the corrected coefficients A and B. In this way, the temperature detection device 50 is configured with a correction means that uses the correction value storage means 74 to correct the output voltage of the temperature detection element 15(R) based on the monitoring result of the drive current If by the drive current monitoring circuit 52(R). Therefore, even if the drive current If changes to some extent, the temperature of the electro-optical panel 100(R) can be appropriately adjusted. Therefore, the electronic device 2100 shown in FIG. 1 can display a high-quality image.

[0037] The temperature detection device 50 also includes an alert circuit 76 that notifies of an abnormality based on the monitoring result of the drive current If by the drive current monitoring circuit 52(R), and the result is displayed on the diagnosis result display means 77. For example, when the amount of change in the drive current If deviates from a set value previously stored in the correction value storage means 74 made of an EEPROM or the like, the central control unit 72 displays the occurrence of an abnormality on the diagnosis result display means 77 through the alert circuit 76. The diagnosis result display means 77 can be, for example, an LED (Light Emission Diode) provided on the wiring board 70 or the electronic device 2100, or a display item in a maintenance program menu displayed by the electronic device 2100. Therefore, the user can know the occurrence of an abnormality in the drive current If by lighting up the LED or displaying the maintenance program menu.

[0038] The temperature detection device 50 is provided with a plurality of temperature detection elements 15(R), 15(G), and 15(B) corresponding to the plurality of electro-optical panels 100(R), 100(G), and 100(B). Therefore, the temperature detection device 50 is provided with a plurality of constant current circuits 55(R), 55(G), and 55(B), a plurality of temperature detection circuits 51(R), 51(G), and 51(B), and a plurality of drive current monitoring circuits 52(R), 52(G), and 52(B) corresponding to the plurality of temperature detection elements 15(R), 15(G), and 15(B). In contrast, the temperature signal generation unit 75, the temperature control unit 79, the external diagnostic command input means 78, and the diagnostic result display means 77 are common to the plurality of electro-optical panels 100(R), 100(G), and 100(B).

[0039] Therefore, under the control of the central control unit 72 and the switching circuit 53, the temperature of the multiple electro-optical panels 100(R), 100(G), 100(B) is detected, for example, as follows. For example, for the temperature detection circuit 51(R), the switches SW1A and SW2A of the switching circuit 53 are turned on, and the switches SW1B and SW2B are turned off, and a temperature measurement period is set for 0.5 seconds every second. The temperature detection circuit 51(G) is similarly switched and the temperature measurement period starts 0.5 seconds after the end of the temperature measurement period of the temperature detection circuit 51(R). The temperature detection circuit 51(B) is similarly switched and the temperature measurement period starts 0.5 seconds after the end of the temperature measurement period of the temperature detection circuit 51(G). That is, by repeating the cycle of temperature detection by the temperature detection circuits 51(R), 51(G), 51(B) at one second intervals, it is possible to monitor the temperatures of the electro-optical panels 100(R), 100(G), 100(B). Note that the temperature detection interval and temperature measurement period are not limited to those described above.

[0040] On the other hand, the drive current If is monitored outside the temperature measurement period by the temperature detection circuit 51. For example, the period of 0.5 seconds after the end of the temperature measurement period for the temperature detection circuit 51(R) is set as the monitoring period for the drive current If of the constant current circuit 55(R). During this monitoring period, the switches SW1A and SW2A of the switching circuit 53 are turned off, and the switches SW1B and SW2B are turned on. Similarly, the temperature detection circuit 51(G) monitors the drive current If of the constant current circuit 55(G) for 0.5 seconds after the end of the temperature measurement period. Similarly, the temperature detection circuit 51(B) monitors the drive current If of the constant current circuit 55(B) for 0.5 seconds after the end of the temperature measurement period. That is, the drive current If of the constant current circuits 55(R), 55(G), and 55(B) can be monitored by repeating the cycle of monitoring the drive current If by the drive current monitoring circuits 52(R), 52(G), and 52(B) at 1-second intervals. Therefore, since the temperature measurement period and the monitoring period of the drive current If are shifted in time, it is possible to measure the temperature of the electro-optical panels 100(R), 100(G), and 100(B) and monitor the drive current If of the constant current circuits 55(R), 55(G), and 55(B). Note that the monitoring interval and monitoring period of the drive current If are not limited to those described above. As long as the temperature measurement period and the monitoring period of the drive current If are shifted in time, they can be set arbitrarily.

[0041] 6. Configuration of current-voltage conversion unit 54 FIG. 6 is an explanatory diagram showing the current-voltage characteristics of the current-voltage conversion unit 54 and the like shown in FIG. In FIG. 6, the current-voltage characteristic of the temperature detection element 15 is shown by a solid line L15, and the current-voltage characteristic of the current-voltage conversion unit 54 is shown by a solid line L54.

[0042] In this embodiment, as shown in FIG. 6, when the drive current If changes by ΔI, the change amount ΔVr of the voltage of the current-voltage converter 54 is larger than the change amount ΔVd of the voltage of the temperature detection element 15. In this embodiment, the temperature detection element 15 is a diode, and the current-voltage converter 54 is made of a fixed resistor. For example, the temperature detection element 15 has five diodes connected in series and has a nonlinear characteristic in which the current increases rapidly from around 3V. Therefore, even if the drive current If changes by ΔI, the change amount ΔVd of the voltage Vp of the temperature detection element 15 is small. Therefore, it is difficult to monitor the change in the drive current If from the voltage Vp when the drive current If is applied to the temperature detection element 15.

[0043] On the other hand, the current-voltage conversion unit 54 is a fixed resistor with a resistance value of, for example, 5 MΩ, and has a linear characteristic in which the current is proportional to the voltage. Therefore, when the driving current If changes by ΔI, the change amount ΔVr of the voltage Vg of the current-voltage conversion unit 54 is larger than the change amount ΔVd of the voltage Vp. Quantitatively explaining the above feature, as shown below, the current-voltage conversion unit 54 can also be expressed as having a voltage change amount with respect to a change in the driving current If that is larger than n·N·K·T / q·If. In the formulas used in the following explanation, the contents of each parameter are as follows. The values ​​of the saturation current Is and the radiation coefficient N can be obtained, for example, by measuring the electrical characteristics of the diode at room temperature (300 K) and fitting them to a theoretical formula. For example, using an analysis tool such as a solver implemented in spreadsheet software such as Microsoft Excel, it is possible to obtain Is and N that minimize the sum of squares of the error between the measured value and the theoretical formula. Is: Diode saturation current If: Drive current (forward current of the diode) Vf: forward voltage of the diode K: Boltzmann constant T: Temperature [K] q: charge of electron N: Radiation coefficient n: number of diodes in series Vp: Total forward voltage of n series diodes

[0044] First, the relationship between the forward voltage Vf and the forward current (drive current If) in a diode is expressed by the following formula (1). If=Is{exp(q Vf / N K T)-1}...Equation (1)

[0045] By approximating equation (1) as shown below and solving Vf, we obtain equation (2). If=Is{exp(q Vf / N K T)} Vf=N K T / q ln(If)-N K T / q ln(Is) Formula (2)

[0046] By partially differentiating equation (2) with respect to If, we obtain equation (3). δVf / δIf=N K T / q If...Equation (3)

[0047] If five diodes are connected in series, the total voltage Vp is given by the following equation, so we obtain equation (4). Vp=n Vf=5 Vf δVp / δIf=5 N K T / q If Equation (4)

[0048] Here, the electro-optic panel 100 is manufactured using a high-temperature polysilicon process. If we use a value of about N = 1.6 for the diode and set T to room temperature (= 300 [K]), we obtain equation (5). 5 N K T / q≒0.2[V] Formula (5)

[0049] Therefore, if the drive current If is 0.5 [μA], the change in voltage Vp with respect to the change in drive current If is as shown in equation (6). δVp / δIf=0.2[V] / 0.5[μA]=0.4M[V / A]...Equation (6)

[0050] Therefore, when the drive current If changes by 10% (0.05 μA), the voltage Vp fluctuates by about 20 mV. In other words, when the temperature detection element 15 is composed of five diodes connected in series, the sensitivity of the voltage Vp to temperature changes is approximately -10 mV / °C, resulting in an error of about 2°C.

[0051] If this is rewritten as a change in voltage relative to a change in drive current If in a fixed resistor, then it becomes as shown in equation (7), as is clear from equation (6). R=20[mV] / 0.05[μA]=400[kΩ]...Equation (7)

[0052] Therefore, when the drive current If is 0.5 μA and a fixed resistor of 5 MΩ is used in the current-voltage converter 54 , the voltage change sensitivity to a 10% change in the drive current If is 10 times or more that of the temperature detection element 15 .

[0053] Moreover, in the case of a fixed resistor, the change in resistance value over time is about ±0.5%, which is extremely small. In addition, the temperature dependency of the fixed resistor is several hundreds of ppm, which is extremely small. Considering that the fixed resistor is disposed on the wiring board 70, which has a smaller temperature change than the electro-optical panel 100, the fluctuation in the resistance value of the fixed resistor may be mainly considered to be the change over time. For example, in the case of a fixed resistor of 5 MΩ, the change over time is about ±25 kΩ. If the drive current If is 0.5 μA, the influence of the change in resistance value over time is less than ±15 mV. At this level, it does not have a large effect on the detection of the voltage change amount (200 mV or more) corresponding to a 10% change in the drive current If. Therefore, it is suitable for the current-voltage conversion unit 54 for detecting the change in the drive current If. Therefore, since the change in the drive current If can be monitored with high sensitivity, appropriate temperature detection can be managed for the electro-optical panel 100.

[0054] [Modification of the first embodiment] 7 is an explanatory diagram showing a circuit configuration of a temperature detection device 50 according to a modified example of the first embodiment of the present invention. Since the basic configuration of this embodiment is similar to that of the first embodiment, the same reference numerals are used for common parts and their description will be omitted.

[0055] 7, in the temperature detection device 50 of this embodiment, similarly to the first embodiment, temperature detection elements 15(R), 15(G), 15(B) are provided corresponding to each of the electro-optical panels 100(R), 100(G), 100(B) of the plurality of electro-optical devices 1(R), 1(G), 1(B). Therefore, temperature detection circuits 51(R), 51(G), 51(B) and drive current monitoring circuits 52(R), 52(G), 52(B) are provided corresponding to each of the electro-optical panels 100(R), 100(G), 100(B). In addition, the temperature signal generating unit 75, the temperature control unit 79, the external diagnostic command input means 78, and the diagnostic result display means 77 are common to the three electro-optical panels 100(R), 100(G), 100(B).

[0056] Here, the constant current circuit 55 supplies a drive current If to each of the plurality of temperature detection elements 15 via the temperature detection circuit 51. Therefore, since the number of constant current circuits 55 is smaller than the number of temperature detection elements 15, the circuit configuration can be simplified and the probability of occurrence of a malfunction caused by the constant current circuit 55 can be reduced. A driving current monitoring circuit 52 is provided correspondingly, and a constant current circuit 55 supplies a driving current If to each of the current-voltage conversion units 54 of the plurality of driving current monitoring circuits 52 .

[0057] The temperature detection device 50 also includes a switching circuit 53 that switches a current path between a state in which the drive current If is supplied from the constant current circuit 55 to the temperature detection element 15 and a state in which the drive current If is supplied from the constant current circuit 55 to the current-voltage conversion unit 54. More specifically, in the temperature detection circuit 51, a switch SW1A is provided in a position midway along the wiring from the constant current circuit 55 to the temperature detection element 15, and in the drive current monitoring circuit 52, a switch SW1B is provided in a position midway along the wiring from the constant current circuit 55 to the current-voltage conversion unit 54.

[0058] Therefore, the voltage drop across SW1A is included when observing the voltage Vp of the temperature detection circuit 51, and the voltage drop across SW1B is included when observing the voltage Vg of the current-voltage conversion unit 54. However, the drive current If is extremely small and the on-resistance values ​​of the switches SW1A and SW1B are also sufficiently small, so that the errors imparted to the voltage Vp of the temperature detection circuit 51 and the voltage Vg of the current-voltage conversion unit 54 can be made small.

[0059] Therefore, during temperature detection, the central control unit 72 outputs a command signal to the switching circuit 53 to turn on the switch SW1A corresponding to the electro-optical panel 100(R) and turn off the other switches. As a result, a drive current If is applied from the constant current circuit 55 to the temperature detection element 15(R) for a certain period, during which the voltage Vp(R) of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection means 71. Therefore, the central control unit 72 can detect the temperature of the electro-optical panel 100(R) based on the monitoring result of the temperature detection circuit 51(R). After detecting the temperature of the electro-optical panel 100(R), the central control unit 72 can sequentially detect the temperature of the electro-optical panel 100(R) and the temperature of the electro-optical panel 100(B).

[0060] During the drive current monitoring, the central control unit 72 outputs a command signal to the switching circuit 53 to turn on the switch SW1B corresponding to the electro-optical panel 100(R) and turn off the other switches. As a result, the application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) and the like is stopped, and the drive current If is applied to the current-voltage conversion unit 54(R) for a certain period of time. During that time, the voltage Vg(R) of the current-voltage conversion unit 54(R) is input to the central control unit 72 via the voltage detection means 71. Therefore, the central control unit 72 can calculate the amount of change in the drive current If based on the monitoring result of the drive current monitoring circuit 52(R). After monitoring the drive current If in the drive current monitoring circuit 52(R), the drive current If can be monitored in the drive current monitoring circuit 52(G) and the drive current If can be monitored in the drive current monitoring circuit 52(B) in sequence.

[0061] In this embodiment, the constant current circuit 55 is common to the three temperature detection elements 15(R), 15(G), and 15(B), but three drive current monitoring circuits 52(R), 52(G), and 52(B) are provided corresponding to the temperature detection elements 15(R), 15(G), and 15(B). Therefore, if monitoring is performed using three current-voltage conversion units 54, it is possible to eliminate erroneous determination due to an abnormality in the current-voltage conversion unit 54. For example, since the constant current circuit 55 is common, if the monitoring result by one current-voltage conversion unit 54 is abnormal and the monitoring results by the remaining two current-voltage conversion units 54 are normal, it is possible to avoid erroneous determination that one current-voltage conversion unit 54 has failed. The abnormality determination of the current-voltage conversion unit 54 can be performed, for example, as follows. As an example of the change over time in the output voltage of the current-voltage conversion unit 54 with a fixed resistance of 5 MΩ when the drive current If is 0.5 μA, a change of about ±15 mV with respect to the initial state as a reference has been described. Therefore, for example, if a voltage fluctuation exceeding ±20 mV with respect to the initial state as a reference is detected, it can be determined that the current-voltage conversion unit 54 has failed.

[0062] Furthermore, in each of the multiple temperature detection circuits 51 and drive current monitoring circuit 52, the voltage Vp of the temperature detection element 15 is input to the voltage detection means 71 via switch SW1A, and the voltage Vg of the current-voltage conversion unit 54 is input to the voltage detection means 71 via switch SW1B. This makes it possible to simplify the circuit configuration, for example by reducing the number of switches in the switching circuit 53.

[0063] In addition, compared to the case where the constant current circuits 55 are provided individually, there is no temperature measurement error between the electro-optical panels 100 due to the difference in the drive current If, so this is suitable when placing importance on relative temperature control between the electro-optical panels 100. For example, there is pixel shift driving in which the display coordinates are shifted by periodic oscillation of optical components arranged on the emission light path of the projector in order to improve the display resolution. In this case, if the temperature difference between the electro-optical panels 100 is large, coloring and the like may become a problem. However, by sharing the constant current circuit 55 for the three temperature detection elements 15(R), 15(G), and 15(B) as in this embodiment, there is no temperature measurement error between the electro-optical panels 100 due to the difference in the drive current If, and temperature management becomes easier.

[0064] [Embodiment 2] 8 is an explanatory diagram showing the circuit configuration of a temperature detection device 50 according to a second embodiment of the present invention. Since the basic configuration of this embodiment is similar to that of the first embodiment, the same reference numerals are used for common parts and their description will be omitted.

[0065] 8, the temperature detection device 50 of this embodiment is provided with a plurality of temperature detection elements 15(R), 15(G), 15(B) corresponding to each of the electro-optical panels 100(R), 100(G), 100(B) of the plurality of electro-optical devices 1(R), 1(G), 1(B) in the same manner as in the embodiment 1. In addition, the temperature signal generation unit 75, the temperature control unit 79, the external diagnostic command input means 78, and the diagnostic result display means 77 are common to the three electro-optical panels 100(R), 100(G), 100(B).

[0066] In this embodiment, similarly to the modified example of the first embodiment, the constant current circuit 55 supplies a drive current If to each of the temperature detection elements 15 via the temperature detection circuit 51. Therefore, since the number of constant current circuits 55 is smaller than the number of temperature detection elements 15, an effect such as simplification of the circuit configuration can be achieved.

[0067] In this embodiment, a drive current monitoring circuit 52 is provided corresponding to any one of the plurality of temperature detection elements 15. Also, a plurality of drive current monitoring circuits 52 are provided corresponding to any one of the plurality of temperature detection elements 15, and a constant current circuit 55 supplies a drive current If to each of a plurality of current-voltage conversion units 54 of the drive current monitoring circuit 52. In this embodiment, a drive current monitoring circuit 52(R) is provided as a first drive current monitoring circuit 521(R) and a second drive current monitoring circuit 522(R) corresponding to the temperature detection element 15(R) of the plurality of temperature detection elements 15(R), 15(G), and 15(B), and the constant current circuit 55 sequentially supplies a drive current If to each of a first current-voltage conversion unit 541(R) of the first drive current monitoring circuit 521(R) and a second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R). In addition, the voltage Vg1(R) of the first current-voltage converter 541(R) of the first drive current monitoring circuit 521(R) and the voltage Vg2(R) of the second current-voltage converter 542(R) of the second drive current monitoring circuit 522(R) are both output sequentially to a common temperature signal generating unit 75.

[0068] In the first switching circuit 531 of the switching circuit 53, a switch SW1A is provided in a position midway along the wiring from the constant current circuit 55 to the temperature detection element 15 in the temperature detection circuit 51. In the first switching circuit 531, a switch SW1A is provided in a position midway along the wiring from the constant current circuit 55 to the first current-voltage conversion unit 541 in the first drive current monitoring circuit 521(R). 1B is provided, and a switch SW1C is provided midway along the wiring from the constant current circuit 55 to the second current-voltage converter 542 in the second drive current monitoring circuit 522(R).

[0069] In the second switching circuit 532 of the switching circuit 53, a switch SW2A is provided in a position midway along the wiring of the temperature detection circuit 51(R) extending from the temperature detection element 15 to the voltage detection means 71. In the second switching circuit 532, a switch SW2B is provided in a position midway along the wiring from the first current-voltage conversion unit 541 to the voltage detection means 71 in the first drive current monitoring circuit 521(R), and a switch SW2C is provided in a position midway along the wiring from the second current-voltage conversion unit 542 to the voltage detection means 71 in the second drive current monitoring circuit 522(R).

[0070] Therefore, during temperature detection, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to turn on the switches SW1A and SW2A corresponding to the electro-optical panel 100(R) and turn off the other switches. As a result, a drive current If is applied from the constant current circuit 55 to the temperature detection element 15(R) for a certain period, during which the voltage Vp of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection means 71. Therefore, the central control unit 72 can detect the temperature of the electro-optical panel 100(R) based on the monitoring result of the temperature detection circuit 51(R). After detecting the temperature of the electro-optical panel 100(R), the central control unit 72 can sequentially detect the temperature of the electro-optical panel 100(G) and the temperature of the electro-optical panel 100(B).

[0071] Also, during drive current monitoring, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to turn on the switches SW1B and SW2B corresponding to the electro-optical panel 100(R) and turn off the other switches. As a result, application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) is stopped, and the drive current If is applied to the first current-voltage conversion unit 541(R) of the first drive current monitoring circuit 521(R) for a certain period of time. During that time, application of the drive current If to the second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R) is stopped. Therefore, the voltage Vg1(R) of the first current-voltage conversion unit 541(R) is input to the central control unit 72 via the voltage detection means 71.

[0072] Next, the central control unit 72 outputs a command signal to the first switching circuit 531 and the second switching circuit 532 to turn on the switches SW1C and SW2C and turn off the other switches. As a result, the drive current If is applied to the second current-voltage converter 542(R) of the second drive current monitoring circuit 522(R) for a certain period of time while the application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) is stopped. During that time, the application of the drive current If to the first current-voltage converter 541(R) of the first drive current monitoring circuit 521(R) is stopped. Therefore, the voltage Vg2(R) of the second current-voltage converter 542 is input to the central control unit 72 via the voltage detection means 71.

[0073] Therefore, the central control unit 72 calculates the amount of change in the drive current If from a preset current value based on the voltage Vg1(R) of the first current-voltage conversion unit 541(R) and the voltage Vg2(R) of the second current-voltage conversion unit 542(R). For example, the central control unit 72 determines the average value of the amount of change in the drive current If calculated based on the voltage Vg1 of the first current-voltage conversion unit 541 and the amount of change in the drive current If calculated based on the voltage Vg2 of the second current-voltage conversion unit 542 as the amount of change in the drive current If. Furthermore, when the difference between the amount of change in the drive current If calculated based on the voltage Vg1 of the first current-voltage conversion unit 541 and the amount of change in the drive current If calculated based on the voltage Vg2 of the second current-voltage conversion unit 542 is greater than a preset value, the central control unit 72 notifies of an abnormality by the alert circuit 76 such as the diagnosis result display means 77. Other configurations and operations are the same as those of the first embodiment, and therefore will not be described.

[0074] In this embodiment, the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542 may be fixed resistors having the same resistance value or fixed resistors having different resistance values. Here, it is preferable that the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542 have different resistance values. For example, the resistance value of the first current-voltage conversion unit 541 is 5 MΩ, and the resistance value of the second current-voltage conversion unit 542 is 7 MΩ. Therefore, if the drive current If is 0.5 μA, an output of 2.5 V can be obtained from the first current-voltage conversion unit 541, and an output of 3.5 V can be obtained from the second current-voltage conversion unit 542. With this configuration, in addition to the amount of change in the drive current If, the stability of the constant current characteristic when the operating point voltage of the constant current circuit 55 is changed can be monitored. Therefore, in addition to when the drive current If changes significantly, even when the stability of the constant current characteristic decreases, a failure of the constant current circuit 55 can be detected, and the constant current circuit 55 can be repaired, etc.

[0075] [Modification of the second embodiment] 9 is an explanatory diagram showing a circuit configuration of a temperature detection device 50 according to a modified example of the second embodiment of the present invention. Since the basic configuration of this embodiment is similar to that of the first embodiment, the same reference numerals are used for common parts and their description will be omitted.

[0076] 9, the temperature detection device 50 of this embodiment is provided with a plurality of temperature detection elements 15(R), 15(G), and 15(B) corresponding to each of the electro-optical panels 100(R), 100(G), and 100(B) of the electro-optical devices 1(R), 1(G), and 1(B) in the same manner as in the first embodiment. In addition, the temperature signal generating unit 75, the temperature control unit 79, the diagnostic command external input means 78, and the diagnostic result display means 77 are common to the three electro-optical panels 100(R), 100(G), and 100(B). In this embodiment, the constant current circuit 55 supplies a drive current If to each of the plurality of temperature detection elements 15 via the temperature detection circuit 51 in the same manner as in the modified example of the first embodiment. Therefore, since the number of constant current circuits 55 is smaller than the number of temperature detection elements 15, an effect such as simplification of the circuit configuration can be achieved.

[0077] In this embodiment, similarly to the second embodiment, a drive current monitoring circuit 52 is provided corresponding to any one of the plurality of temperature detection elements 15. Also, a plurality of drive current monitoring circuits 52 are provided corresponding to any one of the plurality of temperature detection elements 15, and a constant current circuit 55 supplies a drive current If to each of the plurality of current-voltage conversion units 54 of the drive current monitoring circuit 52. In this embodiment, a drive current monitoring circuit 52(R) is provided as a first drive current monitoring circuit 521(R) and a second drive current monitoring circuit 522(R) corresponding to the temperature detection element 15(R) among the plurality of temperature detection elements 15(R), 15(G), and 15(B), and the constant current circuit 55 sequentially supplies a drive current If to each of the first current-voltage conversion unit 541(R) of the first drive current monitoring circuit 521(R) and the second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R). In addition, the voltage Vg1(R) of the first current-voltage converter 541(R) of the first drive current monitoring circuit 521(R) and the voltage Vg2(R) of the second current-voltage converter 542(R) of the second drive current monitoring circuit 522(R) are both output sequentially to a common temperature signal generating unit 75.

[0078] In this embodiment, in the switching circuit 53, a switch SW1A is provided in the temperature detection circuit 51(R) at a midpoint of the wiring from the constant current circuit 55 to the temperature detection element 15. Also, in the switching circuit 53, a switch SW1B is provided in the first drive current monitoring circuit 521(R) at a midpoint of the wiring from the constant current circuit 55 to the first current-voltage conversion unit 541, and a switch SW1C is provided in the second drive current monitoring circuit 522(R) at a midpoint of the wiring from the constant current circuit 55 to the second current-voltage conversion unit 542.

[0079] Therefore, when observing the voltage Vp of the temperature detection circuit 51, the voltage drop of the switch SW1A is included, and when observing the voltage Vg1(R) of the first current-voltage conversion unit 541(R), the voltage drop of the switch SW1B is included. When the drive current If is observed, the voltage drop of the switch SW1C is included. However, since the drive current If is extremely small and the on-resistance values ​​of the switches SW1A, SW1B, and SW1C are also sufficiently small, the errors given to the voltage Vp(R) of the temperature detection circuit 51, the voltage Vg1(R) of the first current-voltage conversion unit 541(R), and the voltage Vg2(R) of the second current-voltage conversion unit 542(R) can be made small.

[0080] Therefore, during temperature detection, the central control unit 72 outputs a command signal to the switching circuit 53 to turn on the switch SW1A corresponding to the electro-optical panel 100(R) and turn off the other switches. As a result, a drive current If is applied from the constant current circuit 55 to the temperature detection element 15(R) for a certain period, during which the voltage Vp(R) of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection means 71. Therefore, the central control unit 72 can detect the temperature of the electro-optical panel 100(R) based on the monitoring result of the temperature detection circuit 51(R). After detecting the temperature of the electro-optical panel 100(R), the central control unit 72 can sequentially detect the temperature of the electro-optical panel 100(G) and the temperature of the electro-optical panel 100(B).

[0081] Furthermore, during drive current monitoring, the central control unit 72 outputs a command signal to the switching circuit 53 to turn on the switch SW1B and turn off the other switches. As a result, application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) is stopped, and the drive current If is applied to the first current-voltage converter 541(R) of the first drive current monitoring circuit 521(R) for a certain period of time. During that time, application of the drive current If to the second current-voltage converter 542(R) of the second drive current monitoring circuit 522(R) is stopped. Therefore, the voltage Vg1(R) of the first current-voltage converter 541(R) is input to the central control unit 72 via the voltage detection means 71.

[0082] Next, the central control unit 72 outputs a command signal to the switching circuit 53 to turn on the switch SW1C and turn off the other switches. As a result, the drive current If is applied to the second current-voltage converter 542(R) of the second drive current monitoring circuit 522(R) for a certain period of time while the application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) is stopped. During that time, the application of the drive current If to the first current-voltage converter 541(R) of the first drive current monitoring circuit 521(R) is stopped. Therefore, the voltage Vg2(R) of the second current-voltage converter 542(R) is input to the central control unit 72 via the voltage detection means 71.

[0083] Therefore, the central control unit 72 can calculate the amount of change in the drive current If from a preset current value based on the voltage Vg1(R) of the first current-voltage conversion unit 541(R) and the voltage Vg2(R) of the second current-voltage conversion unit 542(R).

[0084] In this embodiment, the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542 may be fixed resistors having the same resistance value or fixed resistors having different resistance values. Here, it is preferable that the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542 have different resistance values. For example, the resistance value of the first current-voltage conversion unit 541 is 5 MΩ, and the resistance value of the second current-voltage conversion unit 542 is 6.5 MΩ. Therefore, if the drive current If is 0.5 μA, an output of 2.5 V can be obtained from the first current-voltage conversion unit 541, and an output of 3.25 V can be obtained from the second current-voltage conversion unit 542. The voltage of 2.5 V is the operating point voltage when the temperature detection element 15 (R) is about 75° C. The voltage of 3.25 V is the operating point voltage when the temperature detection element 15 (R) is about 0° C. According to this configuration, in addition to the amount of change in the drive current If, it is possible to monitor the stability of the constant current characteristics of the constant current circuit 55 when the temperature detection element 15(R) is placed at a temperature between about 0° C. and about 75° C. Therefore, in addition to a large change in the drive current If, a decrease in the stability of the constant current characteristics can also be detected as a failure of the constant current circuit 55, and repairs such as replacing parts of the constant current circuit 55 can be performed.

[0085] [Embodiment 3] FIG. 10 is an explanatory diagram of a temperature detection device 50 according to a third embodiment of the present invention. In the first and second embodiments and their modified examples, the current-voltage conversion unit 54 is a fixed resistor. However, as shown in FIG. 10, the current-voltage conversion unit 54 may be configured to include an operational amplifier 546. More specifically, the non-inverting input terminal + of the operational amplifier 546 is electrically connected to the ground, and a feedback resistor R1 is electrically connected between the inverting input terminal - and the output terminal of the operational amplifier 546. Here, since the non-inverting input terminal + and the inverting input terminal - are at the same potential, a voltage Vg equivalent to -If / R1 is output from the operational amplifier 546 to the temperature signal generating unit 75. In addition, if the feedback resistor R1 is made larger, the sensitivity to current changes can be increased. For example, when a 10% change in the drive current If is output as a difference of more than 20 mV, the following conditions are satisfied. If x 0.1 x R1>20 [mV]

[0086] Therefore, when the drive current If is 0.5 μA, if the feedback resistor R1 is made larger than 400 kΩ, the sensitivity to changes in the drive current If can be made larger than that of the temperature detection element 15. The operating point voltage of the constant current circuit 55 can be set by the input resistor R2. For example, when the drive current If is set to 0.5 μA and the operating point voltage is desired to be 3 V, the input resistor R2 should be set to 6 MΩ.

[0087] In FIG. 10, the essential points of the configuration from the constant current circuit 55 to the temperature signal generating unit 75 are extracted and explained, but the case where it is applied to the first embodiment will be explained in detail. The explanation of the power supply connection of the operational amplifier 546 is omitted. In the case of a configuration including the operational amplifier 546 shown in FIG. 10 as the current-voltage conversion unit 54, for example, in FIG. 5 of the first embodiment, the connection between one end of SW1B and one end of SW2B is deleted, and further, the symbol and connection of the current-voltage conversion unit 54 are replaced with a three-terminal configuration. That is, the first terminal is connected to one end of SW1B, the second terminal is connected to one end of SW2B, and the third terminal is connected to ground. Here, the first terminal is the inverting input terminal - of the operational amplifier 546, the second terminal is the output terminal of the operational amplifier 546, and the third terminal is the non-inverting input terminal + of the operational amplifier 54.

[0088] A detailed description will be given of the case where the present invention is applied to the second embodiment. Note that the description of the power supply connection of the operational amplifier 546 will be omitted. In the case where the current-voltage conversion unit 54 includes the operational amplifier 546 shown in FIG. 10, the connection between one end of SW1B and one end of SW2B is deleted in FIG. 8 of the second embodiment, and the symbol and connection of the first current-voltage conversion unit 541(R) are replaced with a three-terminal configuration. That is, the first terminal is connected to one end of SW1B, one end of the second terminal is connected to SW2B, and the third terminal is connected to ground. Here, the first terminal is the inverting input terminal - of the operational amplifier 546, the second terminal is the output terminal of the operational amplifier 546, and the third terminal is the non-inverting input terminal + of the operational amplifier 54. Similarly, the connection between one end of SW1C and one end of SW2C is deleted, and the symbol and connection of the second current-voltage conversion unit 542(R) are replaced with a three-terminal configuration. That is, the first terminal is connected to one end of SW1C, the second terminal is connected to one end of SW2C, and the third terminal is connected to ground. Here, the first terminal is the inverting input terminal − of the operational amplifier 546, the second terminal is the output terminal of the operational amplifier 546, and the third terminal is the non-inverting input terminal + of the operational amplifier 54.

[0089] When the current-voltage conversion unit 54 is configured to include the operational amplifier 546 shown in Fig. 10, the voltage detection means 71 in Fig. 5 of the first embodiment and Fig. 8 of the second embodiment is changed to one that supports negative voltages. For example, this can be easily realized because there are integrated circuits such as microcomputers equipped with A / D converters that can input positive and negative voltages as reference voltages.

[0090] [Embodiment 4] 11 is an explanatory diagram of a temperature detection device 50 according to a fourth embodiment of the present invention. As shown in FIG. 11, in this embodiment, the current-voltage conversion unit 54 includes a capacitor 547 having a capacitance C, and a voltage Vg obtained when the capacitor 547 is charged for a certain time by the drive current If is output to the temperature signal generation unit 75 via a voltage follower 548. In the current-voltage conversion unit 54, a control signal from the central control unit 72 is used to turn off the switch SW1 and turn on the switch SW0 to initialize the voltage Vg to OV, and then turn off the switch SW0 and turn on the switch SW1 to accumulate the charge due to the drive current If in the capacitor 547.

[0091] Here, the voltage of capacitor 547 after a certain time t has elapsed is calculated as Is·t / C. Therefore, temperature signal generating unit 75 monitors a voltage equivalent to Is·t / C from the ground level. Therefore, by comparing voltage Vg after a certain time t has elapsed with a preset value, it is possible to detect a change in drive current If. Also, to increase the sensitivity to changes in drive current If, time t is increased.

[0092] When a 10% change in drive current If is output as a voltage difference exceeding 20 mV, the following conditions must be satisfied: If×0.1×t / C>20[mV]

[0093] Therefore, if the drive current If is 0.5 μA, t / C should be made greater than 400 kV / A.

[0094] In FIG. 11, the main points of the configuration from the constant current circuit 55 to the temperature signal generating unit 75 are extracted and explained, but the case where it is applied to the first embodiment will be explained in detail. Note that the explanation of the power supply connection of the operational amplifier 546 is omitted. In the case of a configuration including the operational amplifier 546 shown in FIG. 11 as the current-voltage conversion unit 54, for example, in FIG. 5 of the first embodiment, the connection between one end of SW1B and one end of SW2B is deleted, and further, the symbol and connection of the current-voltage conversion unit 54 are replaced with a three-terminal configuration. That is, the first terminal is connected to one end of SW1B, the second terminal is connected to one end of SW2B, and the third terminal is connected to ground. Here, the first terminal is the non-inverting input terminal + of the operational amplifier 546, the second terminal is the output terminal of the operational amplifier 546, and the third terminal is a terminal to which one end of the capacitor 547 and one end of the switch SW0 are connected.

[0095] A detailed description will be given of the case where the present invention is applied to the second embodiment. Note that the description of the power supply connection of the operational amplifier 546 will be omitted. In the case where the current-voltage conversion unit 54 is configured to include the operational amplifier 546 shown in FIG. 11, the connection between one end of SW1B and one end of SW2B is deleted in FIG. 8 of the second embodiment, and the symbol and connection of the first current-voltage conversion unit 541(R) are replaced with a three-terminal configuration. That is, the first terminal is connected to one end of SW1B, the second terminal is connected to one end of SW2B, and the third terminal is connected to the ground. Here, the first terminal is the non-inverting input terminal + of the operational amplifier 546, the second terminal is the output terminal of the operational amplifier 546, and the third terminal is a terminal to which one end of the capacitor 547 and one end of the switch SW0 are connected. Similarly, the connection between one end of SW1C and one end of SW2C is deleted, and the symbol and connection of the second current-voltage conversion unit 542(R) are replaced with a three-terminal configuration. That is, the first terminal is connected to one end of SW1C, the second terminal is connected to one end of SW2C, and the third terminal is connected to ground. Here, the first terminal is the non-inverting input terminal + of the operational amplifier 546, the second terminal is the output terminal of the operational amplifier 546, and the third terminal is a terminal to which one end of the capacitor 547 and one end of the switch SW0 are connected.

[0096] [Other embodiments] In the above embodiment, the temperature detection device 50 is provided with a plurality of temperature detection elements 15, but the present invention may be applied to a case where only one temperature detection element 15 is provided. For example, the present invention may be applied to a case where a temperature detection element 15 is provided in any one of a plurality of electro-optical panels 100. The present invention may also be applied to a case where one electro-optical panel 100 is provided in the electronic device 2100.

[0097] Also, for example, in the first embodiment, the temperature detection and the drive current monitoring are repeated alternately, but the present invention is not limited to this. The frequency of the temperature detection and the frequency of the drive current monitoring may be different. The drive current monitoring may be performed once when the power of the electronic device 2100 is turned on or off. Alternatively, the drive current monitoring may be performed by the external diagnostic command input means 78 configured by a control button provided on the electronic device 2100.

[0098] In the second embodiment shown in FIG. 8, the switch SW1C and the current-voltage converter 542(R) may be deleted, and the current-voltage converter 542(R) may be a variable resistance element (also called a digital volume) controlled by the central control unit 72. In this way, the behavior of the constant current circuit 55 at a plurality of operating point voltages can be monitored by the variable resistance element. Specifically, when the first drive current is monitored, the central control unit 72 turns on the switches SW1B and SW2B and turns off the others. At that time, the central control unit 72 sets the variable resistance element of the current-voltage converter 542(R) as the first resistor and monitors the drive current. When the second drive current is monitored, the variable resistance element is set to a second resistor having a resistance value different from the first resistor in a similar manner and monitors the drive current. The behavior of the constant current circuit 55 can be examined by combining such first drive current monitoring and second drive current monitoring.

[0099] In the above embodiment, the electro-optical device 1 is a transmissive liquid crystal device. However, the present invention may be applied to a case where the electro-optical device 1 is a reflective liquid crystal device or an organic electroluminescence device. A display element (MEMS device) such as a Micromirror Device may also be used.

[0100] [Other electronic devices] An electronic device including the electro-optical device 1 to which the present invention is applied is not limited to the electronic device 2100 of the above embodiment. For example, the present invention may be used in electronic devices such as a projection type HUD (head-up display) or a direct-view type HMD (head-mounted display), a personal computer, a digital still camera, and a liquid crystal television. [Explanation of symbols]

[0101] 1...electro-optical device, 10...first substrate, 15...temperature detection element, 16...pixel electrode, 17...pixel, 20...second substrate, 50...temperature detection device, 51...temperature detection circuit, 52...driving current monitoring circuit, 53...switching circuit, 5...current-voltage conversion unit, 55...constant current circuit, 60, 70...wiring substrate, 71...voltage detection means, 72...central control unit, 73...calibration value storage means, 74...correction value storage means, 75...temperature signal generation unit, 76...alert circuit, 77...diagnosis result display means, 78...external diagnosis command input means, 79...temperature control unit, 100...electro-optical panel, 110...display area, 200...temperature adjustment device, 210...cooling Fan, 220...flow path, 521...first drive current monitoring circuit, 522...second drive current monitoring circuit, 531...first switching circuit, 532...second switching circuit, 541...first current-voltage conversion unit, 542...second current-voltage conversion unit, 546...operational amplifier, 547...capacitor, 548...voltage follower, 2100...electronic device, 2102...lamp unit, 2114...projection optical system, R1...feedback resistor, R2...input resistor, If...drive current, SW0, SW1, SW1A, SW1B, SW1C, SW2A, SW2B, SW2C...switches, Dt...temperature signal, Vg, Vg1, Vg2, Vp...voltage.

Claims

1. A temperature detection element; a constant current circuit for supplying a drive current to the temperature detection element; A voltage of the temperature detection element is detected when the driving current is supplied to the temperature detection element. A voltage detection means for detecting a voltage A voltage regulator is electrically connected to the constant current circuit, and an output voltage of the voltage regulator varies in response to a change in the drive current. and the driving current is supplied to the current-voltage converter. a drive current monitoring circuit that outputs a voltage corresponding to the drive current; A state in which the drive current is supplied from the constant current circuit to the temperature detection element, A current path is switched to a state in which the drive current is supplied from the circuit to the current-voltage converter. A switching circuit for A temperature detection device comprising:

2. 2. The temperature detection device according to claim 1, The temperature detection device, wherein the temperature detection element is a diode.

3. 3. The temperature detection device according to claim 1, The current-voltage converter determines a change in output voltage corresponding to a change in the drive current based on the temperature. The change in the output voltage of the detector element is greater than the change in the drive current of the detector element. Temperature detection device.

4. 4. The temperature detection device according to claim 3, The temperature detection device is characterized in that the current-voltage conversion section is a resistive element.

5. The temperature detection device according to any one of claims 1 to 4, The output of the temperature detection element is determined based on the monitoring result of the drive current by the drive current monitoring circuit. A temperature detection device comprising: a correction means for correcting an output voltage.

6. The temperature detection device according to any one of claims 1 to 5, An alarm that notifies an abnormality based on the monitoring result of the drive current by the drive current monitoring circuit. A temperature detection device comprising a temperature detection circuit.

7. The temperature detection device according to any one of claims 1 to 6, A plurality of the temperature detection elements are provided, The constant current circuit and the drive current monitoring circuit are provided corresponding to each of the plurality of temperature detection elements. A temperature detection device comprising:

8. The temperature detection device according to any one of claims 1 to 6, A plurality of the temperature detection elements are provided, the constant current circuit outputs the drive current to each of the plurality of temperature detection elements; The drive current monitoring circuit is provided corresponding to each of the plurality of temperature detection elements. A temperature detection device comprising:

9. The temperature detection device according to any one of claims 1 to 6, A plurality of the temperature detection elements are provided, the constant current circuit outputs the drive current to each of the plurality of temperature detection elements; The drive current monitoring circuit is provided corresponding to any one of the plurality of temperature detection elements. A temperature detection device comprising:

10. A temperature detection element; a constant current circuit for supplying a drive current to the temperature detection element; A voltage of the temperature detection element is detected when the driving current is supplied to the temperature detection element. A voltage detection means for detecting a voltage A plurality of driving circuits are provided corresponding to the temperature detection elements and electrically connected to the constant current circuit. A dynamic current monitoring circuit; A temperature detection device comprising:

11. 11. The temperature detection device according to claim 10, The drive current monitoring circuit is a current-voltage detector that detects a change in output voltage in response to a change in the drive current. a voltage converter, and outputs a voltage when the driving current is supplied to the current-voltage converter. A temperature detection device comprising:

12. 12. The temperature detection device according to claim 11, The current-voltage converter determines a change in output voltage corresponding to a change in the drive current based on the temperature. The change in the output voltage of the detector element is greater than the change in the drive current of the detector element. Temperature detection device.

13. 13. The temperature detection device according to claim 11, A state in which the drive current is supplied from the constant current circuit to the temperature detection element and a current path for supplying the drive current to the current-voltage converter from the first path to the second path. A temperature detection device comprising a switching circuit.

14. The temperature detection device according to any one of claims 10 to 13, The output of the temperature detection element is determined based on the monitoring result of the drive current by the drive current monitoring circuit. A temperature detection device comprising: a correction means for correcting an output voltage.

15. The temperature detection device according to any one of claims 10 to 14, An alarm that notifies an abnormality based on the monitoring result of the drive current by the drive current monitoring circuit. A temperature detection device comprising a temperature detection circuit.

16. An electronic device comprising the temperature detection device according to any one of claims 1 to 15, The present invention provides an electro-optical device having an electro-optical panel in which temperature is detected via the temperature detection element. The electronic device according to claim 1,

17. 17. The electronic device according to claim 16, The electro-optical panel includes a first substrate having a plurality of pixel electrodes provided in a display area, The temperature detection element is provided outside the display area of ​​the first substrate.

2. The electronic device according to claim 1 .

18. 18. The electronic device according to claim 17, The electro-optical panel includes a second substrate facing the first substrate, and a first substrate and a second substrate. and an electro-optic layer disposed between the substrate and the electro-optic layer.

19. 19. The electronic device according to claim 16, the electro-optical device includes a temperature adjustment device that adjusts a temperature of the electro-optical panel, The temperature adjustment device adjusts the temperature of the electro-optic panel based on the detection result of the voltage detection means.

23. An electronic device comprising: an electronic device that performs at least one of heating and cooling.

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