Temperature Detection Device and Electronic Device

Abstract

Temperature detection device and electronic device. The change in the drive current supplied from the constant current circuit to the temperature detection element is monitored with high sensitivity. The temperature detection device (50) includes: a temperature detection element (15); a constant current circuit (55) that supplies a drive current (If) to the temperature detection element (15); and a temperature signal generation unit (75) that converts the voltage (Vp) of the temperature detection element (15) when the drive current (If) is supplied to the temperature detection element (15) into a temperature signal (Dt). The temperature detection device (50) has a drive current monitoring circuit (52), and the drive current monitoring circuit monitors the change in the drive current (If) output from the constant current circuit (55). The drive current monitoring circuit (52) has a current-voltage conversion unit (54) in which the voltage (Vg) changes corresponding to the change in the drive current (If), and the switching circuit (53) outputs the voltage (Vg) when the drive current (If) is supplied from the constant current circuit (55) to the current-voltage conversion unit (54).

Description

Technical Field

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

[0002] In electro-optical devices such as liquid crystal devices and organic electroluminescent display devices, when an image is displayed, the temperature of the electro-optical device rises. In particular, in a liquid crystal device used as a light valve in a projection display device among electro-optical devices, illumination light is irradiated onto the liquid crystal panel at a high intensity, and thus the temperature of the liquid crystal panel easily rises. In such a case, the modulation characteristics and response characteristics of the liquid crystal layer change. Therefore, if the projection display device is controlled based on the result obtained by detecting the temperature of the liquid crystal panel, the influence of temperature on the image can be mitigated. For example, if the control of a cooling fan provided in the projection display device can be performed based on the result obtained by detecting the temperature of the liquid crystal panel, the influence of temperature on the image can be mitigated.

[0003] On the other hand, as a temperature detection device, Patent Document 1 discloses a structure using a diode as a temperature detection element and a constant current circuit. Patent Document 2 discloses a structure using a resistance element as a temperature detection element and a constant voltage circuit.

[0004] Patent Document 1: Japanese Patent Laid-Open No. 8-29265

[0005] Patent Document 2: Japanese Patent Laid-Open No. 2009-236536

[0006] Patent Document 1 does not disclose a structure for monitoring the drive current from a constant current circuit. Therefore, when there are non-negligible temporal variations or faults in the drive current, there is a problem that appropriate temperature detection cannot be performed. Although the diode itself as a temperature detection element can also monitor the drive current to some extent, it is not practical because the diode needs to be placed in a specified temperature environment when monitoring the drive current. Moreover, since the diode is a non-linear element with a relatively small change in forward voltage with respect to the change in drive current, it is not suitable for monitoring the change in drive current. Patent Document 2 discloses the following structure: temperature detection is performed using the voltage division value of a resistance element as a temperature detection element, and a diagnostic resistance element having a resistance within the resistance value range of the temperature detection element is used for fault diagnosis of the temperature detection circuit. However, since it is a diagnostic resistance element having a resistance within the resistance value range of the temperature detection element, the sensitivity for detecting voltage variations of the constant voltage source is not greater than that of the temperature detection element. Even if the structure is extended to constant current driving of a resistance element as a linear element, the change in the voltage value of the diagnostic resistance element with respect to the change in drive current is not greater than the change in the voltage value of the temperature detection element. Therefore, for the case where a diode is used as the temperature detection element for constant current driving, a structure is required to monitor the change in drive current with high sensitivity. Summary of the Invention

[0007] To solve the above problems, the temperature detection device of the present invention includes: 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 that is electrically connected to the constant current circuit.

[0008] An electronic device having the temperature detection device of the present invention has an electro-optical device, and the electro-optical device has an electro-optical panel that detects temperature via the temperature detection element. Brief Description of the Drawings

[0009] Figure 1 It is a schematic structural diagram of an electronic device to which the present invention is applied.

[0010] Figure 2 It shows Figure 1 An explanatory diagram of one mode of the electro-optical panel of the electro-optical device shown.

[0011] Figure 3 It is provided in Figure 1 An explanatory diagram of a temperature detection device and the like of the electronic device shown.

[0012] Figure 4 It shows Figure 3 An explanatory diagram of the temperature characteristics of the temperature detection element shown.

[0013] Figure 5 It is an explanatory diagram showing the circuit structure of the temperature detection device according to Embodiment 1 of the present invention.

[0014] Figure 6 It shows Figure 5 an explanatory diagram of the current-voltage characteristics of the current-voltage conversion unit and the like shown.

[0015] Figure 7 It is an explanatory diagram showing the circuit structure of the temperature detection device according to a modified example of Embodiment 1 of the present invention.

[0016] Figure 8 It is an explanatory diagram showing the circuit structure of the temperature detection device according to Embodiment 2 of the present invention.

[0017] Figure 9 It is an explanatory diagram showing the circuit structure of the temperature detection device according to a modified example of Embodiment 2 of the present invention.

[0018] Figure 10 It is an explanatory diagram of the temperature detection device according to Embodiment 3 of the present invention.

[0019] Figure 11 It is an explanatory diagram of the temperature detection device according to Embodiment 4 of the present invention.

[0020] Reference Numeral Explanation

[0021] 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: Drive current monitoring circuit; 53: Switching circuit; 5: Current-voltage conversion section; 55: Constant current circuit; 60, 70: Wiring substrates; 71: Voltage detection unit; 72: Central control section; 73: Correction value storage unit; 74: Correction value storage unit; 75: Temperature signal generation section; 76: Alarm circuit; 77: Diagnostic result display unit; 78: Diagnostic command external input unit; 79: Temperature control section; 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 section; 542: Second current-voltage conversion section; 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: Voltages. Detailed implementation manners

[0022] The implementation manners of the present invention will be described with reference to the accompanying drawings. In addition, in the accompanying drawings referred to in the following description, each component and the like are set to a size that can be recognized on the drawings. Therefore, the scales of the components are different, and the number of components is reduced.

[0023] [Embodiment 1]

[0024] 1. Structural example of an electronic device

[0025] Figure 1 It is a schematic structural diagram of an electronic device 2100 to which the present invention is applied. In Figure 1 this, as an example of an electronic device 2100 to which the present invention is applied, a projection display device is shown. In addition, in Figure 1 this, illustrations of optical elements such as polarizing plates arranged on the incident side and the emission side of the electro-optical device 1 are omitted.

[0026] In Figure 1In [the device], the 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. The projection light emitted from the lamp unit 2102 is separated into light of three primary colors, red (R), green (G), and blue (B), by three reflecting mirrors 2106 and two dichroic mirrors 2108 arranged inside. The separated light is respectively guided to electro-optical devices 1(R), 1(G), and 1(B) corresponding to the respective colors. The electro-optical devices 1(R), 1(G), and 1(B) are all liquid crystal devices. The optical path of the blue (B) light is longer than those of the other red (R) and green (G) lights. Therefore, in order to prevent its loss, it is guided through a relay lens system 2121 having an incident lens 2122, a relay lens 2123, and an exit lens 2124.

[0027] In the electronic device 2100, after image signals specifying the gray levels of the respective colors are supplied to the electronic device 2100 from an external upper circuit, they are processed by the 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 according to the image signals. 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 (R) light and the blue (B) light are reflected at 90 degrees, and the green (G) light passes through. Therefore, after the modulated light of each color is combined by the dichroic prism 2112, it is projected as a color image onto a projection member such as a screen 2120 by a projection optical system 2114. In addition, regarding the projection display device, it may also 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 color light emitted from the LED light source or the like to the electro-optical devices 1(R), 1(G), and 1(B) respectively.

[0028] 2. Basic structure of the electro-optical panel 100

[0029] Figure 2 is an explanatory diagram showing Figure 1 one mode of the electro-optical panel 100 of the electro-optical device 1 shown. In Figure 2 it, a perpendicular coordinate system composed of the x-axis, y-axis, and z-axis is used to represent each direction. The z-axis direction is the thickness direction of the electro-optical panel 100, the y-axis direction is the extending direction of the wiring substrate included in the electro-optical device 1, and the x-axis direction is the width direction perpendicular to the extending direction of the wiring substrate. In addition, Figure 1 the electro-optical devices 1(R), 1(G), and 1(B) shown all have the same structure. Therefore, in the following description, when it is not necessary to distinguish the electro-optical devices 1(R), 1(G), and 1(B), the (R), (G), and (B) indicating the corresponding colors are omitted.

[0030] In Figure 2In this case, the electro-optical device 1 is a liquid crystal device and has a liquid crystal panel as the electro-optical panel 100. The electro-optical device 1 includes: a plurality of pixel electrodes 16 formed on the first substrate 10; a common electrode (not shown) formed on the second substrate 20; and an electro-optical layer (not shown) composed of a liquid crystal layer provided between the pixel electrode 16 and the common electrode. The pixel electrode 16 faces the common electrode across the electro-optical layer, thereby forming the pixel 17. In the electro-optical device 1, the second substrate 20 is attached to the first substrate 10 by a sealing material (not shown). In the electro-optical device 1, the electro-optical layer is provided in a region surrounded by the sealing material. In the electro-optical panel 100, the region where the pixels 17 are arranged in the x-axis direction and the y-axis direction is the display region 110.

[0031] The electro-optical device 1 of this embodiment is a transmissive liquid crystal device. Therefore, the substrate main bodies of the first substrate 10 and the second substrate 20 are made of a light-transmissive substrate such as heat-resistant glass or a quartz substrate. In the transmissive electro-optical device 1, for example, the illumination light incident from one of the first substrate 10 and the second substrate 20 is modulated during the period of exiting from the other substrate side and is emitted as display light. In this embodiment, the illumination light incident from the second substrate 20 is modulated during the period of exiting from the first substrate 10 and is emitted as display light.

[0032] The first substrate 10 has an overhanging portion 105 extending in the y-axis direction from the end of the second substrate 20. In the overhanging portion 105, a terminal region is provided in which a plurality of terminals 111 are arranged at a predetermined pitch along the first side 101 extending in the width direction of the first substrate 10, i.e., the x-axis direction. The electro-optical device 1 has a flexible wiring substrate 60 connected to the terminals 111, and the wiring substrate 60 extends in the y-axis direction in a manner separated from the first substrate 10.

[0033] As will be described later Figure 3 when constructing Figure 1 the electronic device 2100 shown Figure 2 the electro-optical devices 1 shown are respectively mounted as electro-optical devices 1(R), 1(G), and 1(B). At this time, the wiring substrates 60 of the three electro-optical devices 1(R), 1(G), and 1(B) are electrically connected to a common wiring substrate 70.

[0034] 3. Structure of the electro-optical device 1

[0035] Figure 3 is provided in Figure 1Explanatory drawing of the temperature detection device 50 of the electronic device 2100 shown. In addition, the temperature detection device 50 of this embodiment detects the temperature of each electro-optical panel 100(R), 100(G), 100(B) of the plurality of electro-optical devices 1(R), 1(G), 1(B). Therefore, for the structural elements of the temperature detection device 50, the reference numerals of the structural elements provided for each electro-optical device 1(R), 1(G), 1(B) are labeled with (R), (G), (B) indicating the corresponding colors, and the reference numerals of the structural elements common to the electro-optical devices 1(R), 1(G), 1(B) are not labeled with (R), (G), (B) indicating the corresponding colors. In addition, since the electro-optical devices 1(R), 1(G), 1(B) all have the same structure, in the following description, the electro-optical device 1(R) is taken as the center for description, and the detailed description of the electro-optical devices 1(G), 1(B) is omitted. However, when describing the electro-optical device 1(R), when it is not necessary to distinguish the electro-optical devices 1(R), 1(G), 1(B), the (R), (G), (B) indicating the corresponding colors are also omitted.

[0036] As Figure 3 shown, 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 becomes the display area 110. A plurality of inter-substrate conduction portions 106 are provided at positions where the first substrate 10 overlaps with the corner portions of the second substrate 20. The inter-substrate conduction portions 106 are electrically connected to each other through wirings 112 and are electrically connected to any one of the wirings and the terminals 111 (not shown). Therefore, a common voltage LCCOM is supplied to the common electrode on the second substrate 20 from the first substrate 10 side via the inter-substrate conduction portions 106.

[0037] In the first substrate 10, a data line driving circuit 108 is provided on the side of the protruding portion 105 with respect to the display area 110. The data line driving circuit 108 supplies an image signal to Figure 2 the plurality of pixel electrodes 16 shown via data lines (not shown) and pixel switching elements (not shown). Figure 2Each of the pixels 17 shown typically has a parasitic capacitance (not shown), one electrode of which is electrically connected to the pixel electrode 16 and the other electrode is electrically connected to the common voltage LCCOM. In the first substrate 10, an inspection circuit (not shown) is sometimes provided between the second side 102 opposite to the first side 101 and the display area 110. In the first substrate 10, a scan line driving circuit 109 is provided between the third side 103 extending in the y-axis direction from both ends of the first side 101 and the display area 110, between the third side 103 and the display area 110. The scan line driving circuit 109 supplies a scan signal to the pixel switching element via a scan line (not shown). The scan line driving circuit 109 is sometimes provided between both the third side 103 and the display area 110 and the fourth side 104 and the display area 110. In this embodiment, the data line driving circuit 108 and the scan line driving circuit 109 overlap with the light-shielding portion 25 in a plan view.

[0038] 3. Basic Structure of Temperature Detection Device 50

[0039] Figure 4 is a diagram showing Figure 3 the temperature characteristics of the temperature detection element 15 shown. As Figure 3 shown, Figure 1 the electronic device 2100 shown is provided with a temperature detection device 50 that detects the temperatures 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 includes: a temperature detection element 15(R) that detects the temperature of the electro-optical panel 100(R); a constant current circuit 55(R) that supplies a driving current If to the temperature detection element 15(R); and a temperature signal generation unit 75 that generates a temperature signal Dt(R) based on the output voltage from the temperature detection element 15(R) when the driving 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) that adjusts the temperature of the electro-optical panel 100 according to the temperature signal Dt(R) output from the temperature signal generation unit 75. In this embodiment, the driving 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 specified time.

[0040] The temperature detection element 15(R) is disposed in the first substrate 10 of the electro-optical panel 100(R) at a position that overlaps with the light-shielding portion 25 in a plan 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) near the display area 110 in the electro-optical panel 100(R).

[0041] The temperature detection element 15(R) is composed 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 substrate 60. Therefore, when a driving current If is applied to the temperature detection element 15(R), the output voltage from the temperature detection element 15(R) is a positive voltage Vp(R). This diode is formed using the process of forming pixel switching elements, etc. on the first substrate 10. In this mode, the temperature detection element 15(R) is composed of a plurality of diodes electrically connected in series to improve the detection sensitivity of temperature changes. Therefore, the voltage Vp(R) output from the temperature detection element 15(R) is equivalent to (the forward voltage of each diode) × (the number of diodes). The diode can be not only a PN junction but also a mode of diode-connecting a transistor.

[0042] In the temperature detection device 50 configured in this way, when a minute positive driving 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 driving current If flows through the temperature detection element 15(R). Here, as shown by the solid line P0 in Figure 4 , the positive voltage Vp of the temperature detection element 15(R) changes substantially linearly according to the temperature. For example, when five diodes are connected in series in the temperature detection element 15(R), when the temperature rises by 1 °C, the forward voltage drops by approximately 10 mV. Therefore, the voltage Vp of the temperature detection element 15(R) changes according to 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. 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.

[0043] As the temperature adjustment device 200(R), a mechanism for cooling the electro-optical panel 100(R) or a mechanism for heating the electro-optical panel 100(R) (not shown) can be used. In this mode, the temperature adjustment device 200(R) has a cooling fan 210 that supplies cooling air to the electro-optical panel 100 via the flow path 220. The temperature control unit 79 controls the rotation of the cooling fan 210 of the temperature adjustment device 200(R) and controls the flow rate of the cooling air supplied to the electro-optical panel 100(R). In addition, in Figure 3 , for the sake of convenience of explanation, it is depicted as blowing air from the fourth side 104 side of the electro-optical panel 100(R), but typically, air is blown to the electro-optical panel 100(R) from the second side 102. In addition, in the case of adopting a heating mechanism, according to the control signal from the temperature control unit 79, for example, the power supply to a heating wire or the like mounted on the holder holding the electro-optical panel 100(R) is controlled. In addition, in Figure 3In this case, for each electro-optical panel 100, an independent temperature adjustment device 200 is provided, but this is not mandatory. For example, a structure in which a cooling fan 210 and a flow path 220 are shared by three electro-optical panels 100 may also be adopted.

[0044] In addition, for the electro-optical device 1(R), sometimes the influence of temperature on the image is compensated by performing temperature correction on the image signal according to a control signal from the central control unit 72.

[0045] In this mode, the constant current circuit 55(R), the temperature signal generation unit 75, and the temperature control unit 79 are provided on a common wiring board 70. In addition, the electro-optical devices 1(G) and 1(B) are respectively configured in the same manner as the electro-optical device 1(R) together with the temperature detection elements 15(R) and the temperature adjustment devices 200(R), and thus the description thereof is omitted. In addition, a structure may be adopted in which at least a part of the function of the constant current circuit 55(R) is provided in a driving IC (not shown) mounted on the wiring board 60(R).

[0046] 4. Structure of the drive current monitoring circuit 52 etc.

[0047] Figure 5 It is an explanatory diagram showing the circuit structure of the temperature detection device 50 according to Embodiment 1 of the present invention. As Figure 5 shown, in this mode, the temperature detection device 50 of the present mode is provided with a plurality of constant current circuits 55(R), 55(G), and 55(B) corresponding to a 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 on the electro-optical panel 100(R) via the temperature detection circuit 51(R). In contrast, 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 generation unit 75.

[0048] The temperature signal generation unit 75 includes: a voltage detection unit 71 that detects the voltage Vp(R) of the temperature detection element 15(R); and a central control unit 72 that generates a temperature signal Dt(R) based on the detection result of the voltage detection unit 71. The voltage detection unit 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) according to a program pre-stored in a storage unit (not shown) such as an EEPROM.

[0049] In this method, the central control unit 72 calculates the temperature of the electro-optical panel 100(R) according to the following temperature calculation formula, and outputs a temperature signal Dt(R) corresponding to the calculation result of the temperature to the temperature control unit 79. In addition, the coefficients A and B of the temperature calculation formula are stored in the correction value storage unit 73 composed of an EEPROM or the like. The voltages Vp(G) and Vp(B) of the temperature detection elements 15(G) and 15(B) provided on the other electro-optical panels 100(G) and 100(B) are also processed in the same manner in the temperature signal generation unit 75. Since there are manufacturing deviations in the constant current circuit 55(R) and the temperature detection element 15(R), the temperature detection accuracy is improved by measuring the temperature characteristics using a constant temperature bath or the like and obtaining a correction value. As Figure 4 shown, in a diode, the voltage Vp(R) decreases as the temperature rises, so the coefficient A is typically negative.

[0050] Temperature = A × α(Vp(R)) + B

[0051] In the above formula,

[0052] A, B: Coefficients

[0053] α(Vp(R)): A / D converter value corresponding to the voltage Vp(R)

[0054] In addition, a drive current monitoring circuit 52(R) electrically connected to the constant current circuit 55(R) is provided in the temperature detection device 50. The drive current monitoring circuit 52(R) monitors the change in the drive current If output from the constant current circuit 55(R). In this mode, the drive current monitoring circuit 52(R) includes a current-voltage conversion unit 54(R) whose output voltage, i.e., voltage Vg(R), changes corresponding to the change 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 the voltage detection unit 71. Therefore, the drive current If generated by the constant current circuit 55(R) is supplied to the temperature detection element 15(R) and also to the current-voltage conversion unit 54(R). Accordingly, a switching circuit 53 is provided in the temperature detection device 50, and this switching circuit 53 switches the 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 the central control unit 72. Therefore, the central control unit 72 also controls the timing for sequentially monitoring the temperature by the temperature detection elements 15(R), 15(G), 15(B) and monitoring the drive current If by the current-voltage conversion units 54(R), 54(G), 54(B). These timing controls are executed by a program stored in an EEPROM or the like, but are sometimes executed by the diagnostic command external input unit 78. The switching circuit 53 can use, for example, a switch IC having a plurality of switching switches that can be controlled independently of each other built therein.

[0055] In this mode, the switching circuit 53 has a first switching circuit 531 and a second switching circuit 532. The first switching circuit 531 has: a switch SW1A provided at an intermediate position of the 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 at an intermediate position of the wiring in 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 has: a switch SW2A provided at an intermediate position of the output line from the temperature detection element 15 to the voltage detection unit 71; and a switch SW2B provided at an intermediate position of the output line from the current-voltage conversion unit 54(R) to the voltage detection unit 71.

[0056] In addition, the temperature detection device 50 has a diagnostic command external input unit 78 that inputs a diagnostic command for diagnosing the drive current If from the outside, and the diagnostic command external input unit 78 outputs an instruction for executing the diagnosis of the drive current If to the central control unit 72. The diagnostic command external input unit 78 is installed, 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.

[0057] 5. Example of operation

[0058] In this mode, the central control unit 72 outputs an instruction signal for performing temperature detection to the first switching circuit 531 and the second switching circuit 532 at a preset time starting from the waiting state in which all the switches SW1A, SW2A, SW1B, and SW2B are turned off. More specifically, the central control unit 72 outputs an instruction signal for turning on the switches SW1A and SW2A of the temperature detection circuit 51(R) and turning off the other switches to the first switching circuit 531 and the second switching circuit 532. 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 fixed period, and during this period, the voltage Vp(R) of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection unit 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 performs temperature adjustment of the electro-optical panel 100(R) by the temperature adjustment device 200(R). The detection of this temperature is periodically performed during the operation of the electro-optical device 1(R).

[0059] On the other hand, when a command such as monitoring the drive current If output from the constant current circuit 55(R) is input to the central control unit 72 via the diagnostic command external input unit 78, the central control unit 72 outputs an instruction signal for performing drive current monitoring to the first switching circuit 531 and the second switching circuit 532. More specifically, the central control unit 72 outputs an instruction signal for turning on the switches SW1B and SW2B of the drive current monitoring circuit 52(R) and turning off the other switches to the first switching circuit 531 and the second switching circuit 532. 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 fixed period. During this period, the voltage Vg(R) of the current-voltage conversion unit 54(R) is input to the central control unit 72 via the voltage detection unit 71. If the voltage Vg(R) at the time of the drive current If in the initial state is determined in advance, the central control unit 72 can calculate the change amount of the drive current If as a voltage value. The change amount of 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 is sometimes simply referred to as the change amount of the drive current If.

[0060] Here, the central control unit 72 corrects the coefficients A and B of the above temperature calculation formula based on the change amount of the drive current If, and then calculates the temperature of the electro-optical panel 100 using the corrected coefficients A and B. More specifically, the temperature signal generation unit 75 has a correction value storage unit 74 composed of an EEPROM or the like, and a relationship between the voltage value corresponding to the change amount of the drive current If and the correction values for the coefficients A and B is stored in the correction value storage unit 74 as a look-up table. For example, when the drive current If decreases, the calculated temperature rises above the true value, so a look-up table is created to reduce the coefficient B to offset the increase. In addition, when the drive current If strictly decreases, the sensitivity of the temperature detection element to temperature slightly increases, so the coefficient A should be changed, but in actual use, sometimes only changing the coefficient B is sufficient. Therefore, after detecting the change amount of the drive current If, the central control unit 72 corrects the coefficients A and B according to the look-up table stored in the correction value storage unit 74, and then calculates the temperature of the electro-optical panel 100(R) using the corrected coefficients A and B. In this way, a correction unit is formed in the temperature detection device 50, and the output voltage of the temperature detection element 15(R) is corrected by the correction value storage unit 74 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, in Figure 1 the electronic device 2100 shown, a higher-quality image can be displayed.

[0061] In addition, the temperature detection device 50 has an alarm circuit 76 that notifies an abnormality based on the monitoring result of the drive current If by the drive current monitoring circuit 52(R), and displays this result on the diagnostic result display unit 77. For example, when the change amount of the drive current If deviates from the set value prestored in the correction value storage unit 74 constituted by an EEPROM or the like, the central control unit 72 displays the occurrence of an abnormality on the diagnostic result display unit 77 through the alarm circuit 76. The diagnostic result display unit 77 can be set, for example, in the form of an LED (Light Emission Diode) provided on the wiring board 70 or the electronic device 2100, or a display item in the maintenance program menu displayed on the electronic device 2100. Therefore, the user can know that an abnormality has occurred in the drive current If through the lighting of these LEDs or the display of the maintenance program menu.

[0062] In addition, in the temperature detection device 50, a plurality of temperature detection elements 15(R), 15(G), 15(B) are provided corresponding to the plurality of electro-optical panels 100(R), 100(G), 100(B). Therefore, in the temperature detection device 50, a plurality of constant current circuits 55(R), 55(G), 55(B), a plurality of temperature detection circuits 51(R), 51(G), 51(B), and a plurality of drive current monitoring circuits 52(R), 52(G), 52(B) are provided corresponding to the plurality of temperature detection elements 15(R), 15(G), 15(B). In contrast, the temperature signal generation unit 75, the temperature control unit 79, the diagnostic command external input unit 78, and the diagnostic result display unit 77 are common to the plurality of electro-optical panels 100(R), 100(G), 100(B).

[0063] Therefore, under the control of the central control unit 72 and the switching circuit 53, the temperature detection of the plurality of electro-optical panels 100(R), 100(G), 100(B) is performed as follows, for example. For example, for the temperature detection circuit 51(R), a temperature measurement period of 0.5 seconds is set every 1 second during which the switches SW1A and SW2A of the switching circuit 53 are turned on and the switches SW1B and SW2B are turned off. The temperature detection circuit 51(G) is also switched and controlled in the same manner, 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 also switched and controlled in the same manner, 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 repeatedly performing the cycle of temperature detection by the temperature detection circuits 51(R), 51(G), 51(B) at 1-second intervals, the temperatures of the electro-optical panels 100(R), 100(G), 100(B) can be monitored. In addition, the temperature detection interval and the temperature measurement period are not limited to the above.

[0064] On the other hand, the monitoring of the drive current If is performed outside the temperature measurement period of the temperature detection circuit 51. For example, let 0.5 seconds after the end of the temperature measurement period of the temperature detection circuit 51(R) be the monitoring period of 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 opened, and the switches SW1B and SW2B are closed. Similarly, for the temperature detection circuit 51(G), let 0.5 seconds after the end of the temperature measurement period be the monitoring period of the drive current If of the constant current circuit 55(G). Similarly, for the temperature detection circuit 51(B), let 0.5 seconds after the end of the temperature measurement period be the monitoring period of the drive current If of the constant current circuit 55(B). That is, the cycle of the drive current monitoring circuits 52(R), 52(G), and 52(B) monitoring the drive current If is repeated at 1-second intervals. Thus, the drive currents If of the constant current circuits 55(R), 55(G), and 55(B) can be monitored. Therefore, the temperature measurement period and the monitoring period of the drive current If are staggered in time, so that the temperature measurement of the electro-optical panels 100(R), 100(G), and 100(B) and the monitoring of the drive currents If of the constant current circuits 55(R), 55(G), and 55(B) can be taken into account. In addition, the monitoring interval and monitoring period of the drive current If are not limited to the above. If the temperature measurement period and the monitoring period of the drive current If are staggered in time, they can be arbitrarily set.

[0065] 6. Structure of the current-voltage conversion unit 54

[0066] Figure 6 is an explanatory diagram showing Figure 5 the current-voltage characteristics of the current-voltage conversion unit 54 and the like as shown. In Figure 6 , the current-voltage characteristic of the temperature detection element 15 is represented by the solid line L15, and the current-voltage characteristic of the current-voltage conversion unit 54 is represented by the solid line L54.

[0067] In this embodiment, as Figure 6 shown, when the drive current If changes by ΔI, the change amount ΔVr of the voltage of the current-voltage conversion unit 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 conversion unit 54 is composed of a fixed resistor. For example, in the temperature detection element 15, five diodes are connected in series and have a non-linear characteristic in which the current increases sharply from around 3V. Therefore, even when 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 of the drive current If based on the voltage Vp when the drive current If is applied to the temperature detection element 15.

[0068] On the other hand, the current-voltage conversion unit 54 is, for example, a fixed resistor with a resistance value of 5 MΩ. Since the current has a linear characteristic proportional to the voltage, when the drive 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. To quantitatively describe the above characteristics, as shown below, the current-voltage conversion unit 54 can also be expressed as the change amount of the voltage with respect to the change of the drive current If being larger than n·N·K·T / q·If. In addition, in the equations used in the following description, the contents of each parameter are as described below. The saturation current Is and the emission 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 equation. For example, analysis tools such as solvers installed in spreadsheet calculation software represented by Excel manufactured by Microsoft Corporation can be used to obtain Is and N that minimize the sum of the squares of the errors between the measured values and the theoretical equation.

[0069] Is: Saturation current of the diode

[0070] If: Drive current (forward current of the diode)

[0071] Vf: Forward voltage of the diode

[0072] K: Boltzmann constant

[0073] T: Temperature [K]

[0074] q: Electric charge of an electron

[0075] N: Emission coefficient

[0076] n: Number of diodes connected in series

[0077] Vp: Total forward voltage of n diodes connected in series

[0078] First, the relationship between the forward voltage Vf and the forward current (drive current If) in the diode is expressed by the following equation (1).

[0079] If = Is{exp(q·Vf / N·K·T) - 1} ··· Equation (1)

[0080] If Equation (1) is approximated as follows and solved for Vf, Equation (2) is obtained.

[0081] If = Is{exp(q·Vf / N·K·T)}

[0082] Vf = N·K·T / q·In(If) - N·K·T / q·In(Is) ··· Equation (2)

[0083] If Equation (2) is partially differentiated with respect to If, Equation (3) is obtained.

[0084] δVf / δIf = N·K·T / q·If ·· Equation (3)

[0085] If five diodes are connected in series, the overall voltage Vp is given by the following equation, and thus Equation (4) is obtained.

[0086] Vp = n·Vf = 5·Vf

[0087] δVp / δIf = 5·N·K·T / q·If ·· Equation (4)

[0088] Here, if N = about 1.6 is used as the value in the diodes formed in the high-temperature polysilicon process used in the manufacture of the electro-optical panel 100 and T is set to room temperature (= 300 [K]), Equation (5) can be obtained.

[0089] 5·N·K·T / q ≈ 0.2 [V] ·· Equation (5)

[0090] Therefore, if the drive current If is set to 0.5 [μA], the change in the voltage Vp with respect to the change in the drive current If is as shown in Equation (6).

[0091] δVp / δIf = 0.2 [V] / 0.5 [μA] = 0.4 M [V / A] … Equation (6)

[0092] Therefore, when the drive current If changes by 10% (0.05 μA), the voltage Vp changes by approximately 20 mV. That is, when the temperature detection element 15 is composed of five diodes connected in series, the sensitivity of the voltage Vp with respect to the temperature change is approximately -10 mV / °C, and thus an error of approximately 2°C occurs.

[0093] When this is changed to the change in the voltage with respect to the change in the drive current If in the fixed resistor, as can also be seen from Equation (6), it becomes as shown in Equation (7).

[0094] R = 20 [mV] / 0.05 [μA] = 400 [kΩ] … Equation (7)

[0095] Therefore, when the drive current If is set to 0.5 uA and a 5 MΩ fixed resistor is used in the current-voltage conversion unit 54, the voltage change sensitivity with respect to a 10% change in the drive current If is more than 10 times that of the temperature detection element 15.

[0096] In addition, in the case of a fixed resistor, the change over time in the resistance value is about ±0.5%, which is extremely small. In addition, the temperature dependence of the fixed resistor is several 100 ppm, which is extremely small. Considering that the fixed resistor is arranged on the wiring board 70 where the temperature change is smaller than that of the electro-optical panel 100, the change in the resistance value of the fixed resistor mainly needs to consider the change amount over time. For example, in the case of a 5 MΩ fixed resistor, the change amount over time is about ±25 kΩ. If the drive current If is 0.5 μA, the influence caused by the change over time in the resistance value is less than ±15 mV. If it is at this level, it does not have a great influence 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.

[0097] [Modification Example of Embodiment 1]

[0098] Figure 7 FIG. is an explanatory diagram showing the circuit configuration of the temperature detection device 50 according to a modification example of Embodiment 1 of the present invention. In addition, since the basic structure of this embodiment is the same as that of Embodiment 1, the same reference numerals are given to the same parts, and their descriptions are omitted.

[0099] As Figure 7 shown, similar to Embodiment 1, the temperature detection device 50 of this embodiment is provided with temperature detection elements 15(R), 15(G), and 15(B) corresponding to the electro-optical panels 100(R), 100(G), and 100(B) of a plurality of electro-optical devices 1(R), 1(G), and 1(B), respectively. Therefore, temperature detection circuits 51(R), 51(G), and 51(B) and drive current monitoring circuits 52(R), 52(G), and 52(B) are provided corresponding to the electro-optical panels 100(R), 100(G), and 100(B), respectively. In addition, the temperature signal generation unit 75, the temperature control unit 79, the diagnostic command external input unit 78, and the diagnostic result display unit 77 are common to the three electro-optical panels 100(R), 100(G), and 100(B).

[0100] Here, the constant current circuit 55 supplies the drive current If to 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 structure can be simplified, and the probability of occurrence of defects caused by the constant current circuit 55 can be reduced. In addition, drive current monitoring circuits 52 are provided corresponding to the plurality of temperature detection elements 15, and the constant current circuit 55 supplies the drive current If to the current-voltage conversion units 54 of the plurality of drive current monitoring circuits 52, respectively.

[0101] In addition, the temperature detection device 50 has a switching circuit 53 that switches the current path between a state in which a 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 at an intermediate position of 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 at an intermediate position of the wiring from the constant current circuit 55 to the current-voltage conversion unit 54.

[0102] Therefore, when observing the voltage Vp of the temperature detection circuit 51, the voltage drop of SW1A is included, and when observing the voltage Vg of the current-voltage conversion unit 54, the voltage drop of SW1B is included. However, since the drive current If is very small and the on-resistance values of the switches SW1A and SW1B are also small enough, 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.

[0103] Therefore, when detecting the temperature, the central control unit 72 outputs an instruction signal that turns on the switch SW1A corresponding to the electro-optical panel 100(R) and turns off the other switches to the switching circuit 53. As a result, the drive current If is applied from the constant current circuit 55 to the temperature detection element 15(R) for a fixed period. During this period, the voltage Vp(R) of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection unit 71. Therefore, the central control unit 72 can detect the temperature of the electro-optical panel 100(R) based on the monitoring result in the temperature detection circuit 51(R). In addition, after detecting the temperature of the electro-optical panel 100(R), the temperature of the electro-optical panel 100(R) can be detected and then the temperature of the electro-optical panel 100(B) can be detected in sequence.

[0104] In addition, when monitoring the drive current, the central control unit 72 outputs an instruction signal that turns on the switch SW1B corresponding to the electro-optical panel 100(R) and turns off the other switches to the switching circuit 53. 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 fixed period. During this period, the voltage Vg(R) of the current-voltage conversion unit 54(R) is input to the central control unit 72 via the voltage detection unit 71. Therefore, the central control unit 72 can calculate the change amount of the drive current If based on the monitoring result in the drive current monitoring circuit 52(R). In addition, after monitoring the drive current If in the drive current monitoring circuit 52(R), the drive current If in the drive current monitoring circuit 52(G) and the drive current If in the drive current monitoring circuit 52(B) can be monitored in sequence.

[0105] In this method, 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 three current-voltage conversion units 54 can be used for monitoring, false determination caused by an abnormality of the current-voltage conversion unit 54 can be eliminated. For example, since the constant current circuit 55 is common, if the monitoring result of one current-voltage conversion unit 54 is abnormal and the monitoring results of the remaining two current-voltage conversion units 54 are normal, it is considered that one current-voltage conversion unit 54 has failed and false determination can be avoided. The abnormality determination of the current-voltage conversion unit 54 can be implemented as follows, for example. When the drive current If is 0.5 μA, as an example of the change over time of the output voltage of the current-voltage conversion unit 54 caused by the 5 MΩ fixed resistor, a change of about ±15 mV with respect to the initial state is illustrated. Therefore, for example, if a voltage change exceeding ±20 mV with respect to the initial state is detected, it can be determined that the current-voltage conversion unit 54 has failed.

[0106] In addition, since the voltage Vp of the temperature detection element 15 is input to the voltage detection unit 71 via the switch SW1A in each of the plurality of temperature detection circuits 51 and the drive current monitoring circuit 52, and the voltage Vg of the current-voltage conversion unit 54 is input to the voltage detection unit 71 via the switch SW1B, the number of switches of the switching circuit 53 can be reduced, etc., and the circuit structure can be simplified.

[0107] In addition, compared with the case where the constant current circuit 55 is provided separately, the temperature measurement error between the electro-optical panels 100 due to the difference in the drive current If disappears, and thus it is suitable for the case where relative temperature control between the electro-optical panels 100 is emphasized. For example, in order to improve the display fineness, there is pixel shift driving in which the display coordinates are shifted by the periodic swing of an optical component arranged on the emission optical path of a projector. In this case, when the temperature difference between the electro-optical panels 100 is large, problems such as coloring sometimes occur. However, as in this method, the constant current circuit 55 is common to the three temperature detection elements 15(R), 15(G), and 15(B), whereby the temperature measurement error between the electro-optical panels 100 due to the difference in the drive current If disappears and temperature management becomes easy.

[0108] [Embodiment 2]

[0109] Figure 8FIG. 0 is an explanatory diagram showing the circuit configuration of the temperature detection device 50 according to Embodiment 2 of the present invention. In addition, since the basic configuration of this embodiment is the same as that of Embodiment 1, the same reference numerals are given to the same parts, and the description thereof is omitted.

[0110] As Figure 8 shown, similar to Embodiment 1, in this embodiment, 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 the respective electro-optical panels 100(R), 100(G), 100(B) of the plurality of electro-optical devices 1(R), 1(G), 1(B). In addition, the temperature signal generation unit 75, the temperature control unit 79, the diagnostic command external input unit 78, and the diagnostic result display unit 77 are common to the three electro-optical panels 100(R), 100(G), 100(B).

[0111] In this embodiment, similar to the modification of Embodiment 1, the constant current circuit 55 supplies a drive current If to the plurality of temperature detection elements 15 via the temperature detection circuit 51. Therefore, the number of constant current circuits 55 is smaller than the number of temperature detection elements 15, and thus, the effect of simplifying the circuit configuration and the like can be achieved.

[0112] In this embodiment, a drive current monitoring circuit 52 is provided corresponding to any one of the plurality of temperature detection elements 15. In addition, a plurality of drive current monitoring circuits 52 are provided for any one of the plurality of temperature detection elements 15, and the constant current circuit 55 supplies the drive current If to 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 corresponding to the temperature detection element 15(R) among the plurality of temperature detection elements 15(R), 15(G), 15(B) as the first drive current monitoring circuit 521(R) and the second drive current monitoring circuit 522(R), and the constant current circuit 55 sequentially supplies the drive current If to 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 conversion unit 541(R) of the first drive current monitoring circuit 521(R) and the voltage Vg2(R) of the second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R) are both sequentially output to the common temperature signal generation unit 75.

[0113] In addition, in the first switching circuit 531 of the switching circuit 53, a switch SW1A is provided at an intermediate position of the wiring in the temperature detection circuit 51 from the constant current circuit 55 to the temperature detection element 15. Further, in the first switching circuit 531, a switch SW1B is provided at an intermediate position of the wiring in the first drive current monitoring circuit 521(R) from the constant current circuit 55 to the first current-voltage conversion section 541, and a switch SW1C is provided at an intermediate position of the wiring in the second drive current monitoring circuit 522(R) from the constant current circuit 55 to the second current-voltage conversion section 542.

[0114] In addition, in the second switching circuit 532 of the switching circuit 53, a switch SW2A is provided at an intermediate position of the wiring of the temperature detection circuit 51(R) from the temperature detection element 15 to the voltage detection unit 71. Further, in the second switching circuit 532, a switch SW2B is provided at an intermediate position of the wiring in the first drive current monitoring circuit 521(R) from the first current-voltage conversion section 541 to the voltage detection unit 71, and a switch SW2C is provided at an intermediate position of the wiring in the second drive current monitoring circuit 522(R) from the second current-voltage conversion section 542 to the voltage detection unit 71.

[0115] Therefore, when detecting the temperature, the central control unit 72 outputs an instruction signal for turning on the switches SW1A and SW2A corresponding to the electro-optical panel 100(R) and turning off the other switches to the first switching circuit 531 and the second switching circuit 532. As a result, a drive current If is applied from the constant current circuit 55 to the temperature detection element 15(R) for a fixed period. During this period, the voltage Vp of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection unit 71. Therefore, the central control unit 72 can detect the temperature of the electro-optical panel 100(R) based on the monitoring result in the temperature detection circuit 51(R). In addition, after detecting the temperature of the electro-optical panel 100(R), the temperature of the electro-optical panel 100(G) and the temperature of the electro-optical panel 100(B) can be detected in sequence.

[0116] In addition, when monitoring the drive current, the central control unit 72 outputs an instruction signal that turns on the switches SW1B and SW2B corresponding to the electro-optical panel 100(R) and turns off the other switches to the first switching circuit 531 and the second switching circuit 532. As a result, the 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 fixed period. During this period, the 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 unit 71.

[0117] Next, the central control unit 72 outputs an instruction signal that turns on the switches SW1C and SW2C and turns off the other switches to the first switching circuit 531 and the second switching circuit 532. As a result, in a state where the application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) is stopped, the drive current If is applied to the second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R) for a fixed period. During this period, the application of the drive current If to the first current-voltage conversion unit 541(R) of the first drive current monitoring circuit 521(R) is stopped. Therefore, the voltage Vg2(R) of the second current-voltage conversion unit 542 is input to the central control unit 72 via the voltage detection unit 71.

[0118] Therefore, the central control unit 72 calculates the change amount of the drive current If with respect to 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 change amount of the drive current If calculated based on the voltage Vg1 of the first current-voltage conversion unit 541 and the change amount of the drive current If calculated based on the voltage Vg2 of the second current-voltage conversion unit 542 as the change amount of the drive current If. In addition, when the difference between the change amount of the drive current If calculated based on the voltage Vg1 of the first current-voltage conversion unit 541 and the change amount of the drive current If calculated based on the voltage Vg2 of the second current-voltage conversion unit 542 is larger than a preset value, the central control unit 72 notifies an abnormality through an alarm circuit 76 such as the diagnostic result display unit 77. Other structures and operations are the same as those in the first embodiment, and thus the description thereof is omitted.

[0119] In this method, the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542 can each be either a fixed resistor with the same resistance value or a fixed resistor with a different resistance value. Here, it is preferable that the resistance values of the first current-voltage conversion unit 541 and the second current-voltage conversion unit 5642 are different. 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 set to 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. According to this structure, in addition to the change amount of the drive current If, it is also possible to monitor the stability of the constant-current characteristics when the operating point voltage of the constant-current circuit 55 is changed. Therefore, in addition to the case where the drive current If changes significantly, it is also possible to detect a failure of the constant-current circuit 55 in the case where the stability of the constant-current characteristics deteriorates, and repairs of the constant-current circuit 55 can be performed, etc.

[0120] [Modified Example of Embodiment 2]

[0121] Figure 9 FIG. is an explanatory diagram showing the circuit configuration of the temperature detection device 50 according to a modified example of Embodiment 2 of the present invention. In addition, since the basic structure of this method is the same as that of Embodiment 1, the same reference numerals are given to the same parts, and their descriptions are omitted.

[0122] As Figure 9 shown, similar to Embodiment 1, the temperature detection device 50 of this method is provided with a plurality of temperature detection elements 15(R), 15(G), 15(B) corresponding to the respective electro-optical panels 100(R), 100(G), 100(B) of a plurality of electro-optical devices 1(R), 1(G), 1(B). In addition, the temperature signal generation unit 75, the temperature control unit 79, the diagnostic command external input unit 78, and the diagnostic result display unit 77 are common to the three electro-optical panels 100(R), 100(G), 100(B). In this method, similar to the modified example of Embodiment 1, the constant-current circuit 55 supplies the drive current If to the plurality of temperature detection elements 15 via the temperature detection circuit 51. Therefore, the number of constant-current circuits 55 is smaller than the number of temperature detection elements 15, and thus, an effect of simplifying the circuit configuration can be achieved, etc.

[0123] In this mode, similar to the second embodiment, a drive current monitoring circuit 52 is provided corresponding to any one of the multiple temperature detection elements 15. Further, multiple drive current monitoring circuits 52 are provided for any one of the multiple temperature detection elements 15, and the constant current circuit 55 supplies drive currents If to the multiple current-voltage conversion units 54 of the drive current monitoring circuit 52 respectively. In this mode, as the first drive current monitoring circuit 521(R) and the second drive current monitoring circuit 522(R), a drive current monitoring circuit 52(R) is provided corresponding to the temperature detection element 15(R) among the multiple temperature detection elements 15(R), 15(G), and 15(B). The constant current circuit 55 sequentially supplies the drive current If to 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) respectively. Further, the voltage Vg1(R) of the first current-voltage conversion unit 541(R) of the first drive current monitoring circuit 521(R) and the voltage Vg2(R) of the second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R) are both output to the common temperature signal generation unit 75 sequentially.

[0124] In this mode, in the switching circuit 53, a switch SW1A is provided at an intermediate position of the wiring of the temperature detection circuit 51(R) from the constant current circuit 55 to the temperature detection element 15. Further, in the switching circuit 53, a switch SW1B is provided at an intermediate position of the wiring of the first drive current monitoring circuit 521(R) from the constant current circuit 55 to the first current-voltage conversion unit 541, and a switch SW1C is provided at an intermediate position of the wiring of the second drive current monitoring circuit 522(R) from the constant current circuit 55 to the second current-voltage conversion unit 542.

[0125] 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 observing the voltage Vg2(R) of the second current-voltage conversion unit 542(R), the voltage drop of the switch SW1C is included. However, since the drive current If is very small and the on-resistance values of the switches SW1A, SW1B, and SW1C are also small enough, it is possible to make 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) small.

[0126] Therefore, when detecting the temperature, the central control unit 72 outputs an instruction 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 fixed period. During this period, the voltage Vp(R) of the temperature detection element 15(R) is input to the central control unit 72 via the voltage detection unit 71. Therefore, the central control unit 72 can detect the temperature of the electro-optical panel 100(R) based on the monitoring result in the temperature detection circuit 51(R). In addition, after detecting the temperature of the electro-optical panel 100(R), the temperature of the electro-optical panel 100(G) and the temperature of the electro-optical panel 100(B) can be detected in sequence.

[0127] In addition, when monitoring the drive current, the central control unit 72 outputs an instruction signal to the switching circuit 53 to turn on the switch SW1B 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) 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 fixed period. During this period, the 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 unit 71.

[0128] Next, the central control unit 72 outputs an instruction signal to the switching circuit 53 to turn on the switch SW1C and turn off the other switches. As a result, in a state where the application of the drive current If from the constant current circuit 55 to the temperature detection element 15(R) is stopped, the drive current If is applied to the second current-voltage conversion unit 542(R) of the second drive current monitoring circuit 522(R) for a fixed period. During this period, the application of the drive current If to the first current-voltage conversion unit 541(R) of the first drive current monitoring circuit 521(R) is stopped. Therefore, the voltage Vg2(R) of the second current-voltage conversion unit 542(R) is input to the central control unit 72 via the voltage detection unit 71.

[0129] Therefore, the central control unit 72 can calculate the change amount of the drive current If relative to 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).

[0130] In this method, for the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542, either a fixed resistor with the same resistance value or fixed resistors with different resistance values can be used. Here, in the first current-voltage conversion unit 541 and the second current-voltage conversion unit 542, it is preferable that the resistance values are different. 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 set to 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 approximately 75°C. The voltage of 3.25 V is the operating point voltage when the temperature detection element 15(R) is approximately 0°C. According to this structure, in addition to the change amount of the drive current If, the stability of the constant current characteristics of the constant current circuit 55 when the temperature detection element 15(R) is placed at approximately 0°C to approximately 75°C can also be monitored. Therefore, in addition to the case where the drive current If changes significantly, in the case where the stability of the constant current characteristics deteriorates, it is also possible to detect a failure of the constant current circuit 55, and repair such as replacing components of the constant current circuit 55 can be performed.

[0131] [Embodiment 3]

[0132] Figure 10 It is an explanatory diagram of the temperature detection device 50 according to Embodiment 3 of the present invention. In Embodiments 1 and 2 and their modified examples, the current-voltage conversion unit 54 is a fixed resistor, but as Figure 10 shown, the current-voltage conversion unit 54 can also have a structure including 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 - have the same potential, a voltage Vg equivalent to -If × R1 is output from the operational amplifier 546 to the temperature signal generation unit 75. In addition, if the feedback resistor R1 is increased, the sensitivity to current changes can be improved. For example, in the case where a 10% change in the drive current If is output as a difference exceeding 20 mV, the following conditions are designed to be satisfied.

[0133] If × 0.1 × R1 > 20 [mV]

[0134] Therefore, when the drive current If is set to 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 greater than that of the temperature detection element 15. In addition, the operating point voltage of the constant current circuit 55 can be set by the input resistor R2. For example, when it is desired to set the drive current If to 0.5 μA and the operating point voltage to 3 V, the input resistor R2 may be set to 6 MΩ.

[0135] In Figure 10 this, the key points of the structure from the constant current circuit 55 to the temperature signal generation unit 75 are extracted and described, and the case of applying it to Embodiment 1 is described in detail. In addition, the description of the power supply connection of the operational amplifier 546 is omitted. In the case of having the Figure 10 operational amplifier 546 shown as the structure of the current-voltage conversion unit 54, for example, in Figure 5 Embodiment 1, the wiring between one end of SW1B and one end of SW2B is removed, and further, the symbol and wiring of the current-voltage conversion unit 54 are replaced with a three-terminal structure. 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 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.

[0136] The case of applying it to Embodiment 2 is described in detail. In addition, the description of the power supply connection of the operational amplifier 546 is omitted. In the case of having the Figure 10 operational amplifier 546 shown as the structure of the current-voltage conversion unit 54, in Figure 8 Embodiment 2, the wiring between one end of SW1B and one end of SW2B is removed, and the symbol and wiring of the first current-voltage conversion unit 541(R) are replaced with a three-terminal structure. 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 the 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 wiring between one end of SW1C and one end of SW2C is removed, and the symbol and wiring of the second current-voltage conversion unit 542(R) are replaced with a three-terminal structure. 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 the 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.

[0137] In the case of having Figure 10When the operational amplifier 546 shown is used as the current-voltage conversion unit 54, in Embodiment 1 Figure 5 , in Embodiment 2 Figure 8 , the voltage detection unit 71 is changed to a component corresponding to a negative voltage. For example, in an integrated circuit such as a microcomputer equipped with an A / D converter, there is an integrated circuit that can input a positive voltage and a negative voltage as a reference voltage, so it can be easily realized.

[0138] [Embodiment 4]

[0139] Figure 11 is an explanatory diagram of the temperature detection device 50 according to Embodiment 4 of the present invention. As Figure 11 shown, in this embodiment, the current-voltage conversion unit 54 has a capacitor 547 with a capacitance C. When the capacitor 547 is charged by a drive current If for a fixed time, the voltage Vg is output to the temperature signal generation unit 75 via a voltage follower 548. In this current-voltage conversion unit 54, after the voltage Vg is initialized to 0 V by turning off the switch SW1 and turning on the switch SW0 by a control signal from the central control unit 72, the switch SW0 is turned off and the switch SW1 is turned on to store the charge based on the drive current If in the capacitor 547.

[0140] Here, the voltage of the capacitor 547 after a fixed time t is obtained by Is·t / C. Therefore, the temperature signal generation unit 75 monitors the voltage equivalent to Is·t / C with respect to the ground level. Therefore, if the voltage Vg after a fixed time t is compared with a preset value, the change in the drive current If can be detected. In addition, to improve the sensitivity to the change in the drive current If, the time t is extended.

[0141] When a 10% change in the drive current If is output as a voltage difference exceeding 20 mV, it is designed to satisfy the following conditions.

[0142] If×0.1×t / C>20[mV]

[0143] Therefore, when the drive current If is set to 0.5 μA, it is sufficient to make t / C larger than 400 kV / A.

[0144] In Figure 11 , the key points of the structure from the constant current circuit 55 to the temperature signal generation unit 75 are extracted and described, but the case applied to Embodiment 1 is described in detail. In addition, the description of the power supply connection of the operational amplifier 546 is omitted. In the case of a structure having Figure 11 the operational amplifier 546 shown as the current-voltage conversion unit 54, for example, in Embodiment 1 Figure 5In this case, the wiring between one end of SW1B and one end of SW2B is removed, and thus the sign and wiring of the current-voltage conversion unit 54 are replaced with a three-terminal structure. 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 the terminal connecting one end of the capacitor 547 and one end of the switch SW0.

[0145] A case applied to the second embodiment will be described in detail. In addition, the description of the power supply connection of the operational amplifier 546 is omitted. When Figure 11 the operational amplifier 546 shown is adopted as the structure of the current-voltage conversion unit 54, in the second embodiment Figure 8 the wiring between one end of SW1B and one end of SW2B is removed, and the sign and wiring of the first current-voltage conversion unit 541(R) are replaced with a three-terminal structure. 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 the terminal connecting one end of the capacitor 547 and one end of the switch SW0. Similarly, the wiring between one end of SW1C and one end of SW2C is removed, and the sign and wiring of the second current-voltage conversion unit 542(R) are replaced with a three-terminal structure. 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 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 the terminal connecting one end of the capacitor 547 and one end of the switch SW0.

[0146] [Other Embodiments]

[0147] In the above embodiment, a plurality of temperature detection elements 15 are provided in the temperature detection device 50, but the present invention can also be applied to the case where one temperature detection element 15 is provided. For example, the present invention can also be applied to the case where a temperature detection element 15 is provided in any one of the plurality of electro-optical panels 100. In addition, the present invention can also be applied to the case where one electro-optical panel 100 is provided in the electronic device 2100.

[0148] In addition, for example, in Embodiment 1, a method of alternately and repeatedly performing temperature detection and drive current monitoring is adopted, but it is not limited thereto. The frequency of temperature detection may also be different from the frequency of drive current monitoring. The monitoring of the drive current may also be configured to be performed once at the time of power-on operation or power-off operation of the electronic device 2100, for example. Alternatively, the monitoring of the drive current may be executed by the diagnostic command external input unit 78 composed of control buttons provided in the electronic device 2100.

[0149] In addition, in Figure 8 In the shown Embodiment 2, the switch SW1C and the current-voltage conversion unit 542(R) may also be deleted, and the current-voltage conversion unit 542(R) may be a variable resistance element (also referred to as a digital volume unit) controlled by the central control unit 72. In this way, the behavior of the constant current circuit 55 at multiple operating point voltages can be monitored by the variable resistance element. Specifically, when monitoring the first drive current, the central control unit 72 turns on the switch SW1B and the switch SW2B and turns off the others. At this time, the central control unit 72 sets the variable resistance element of the current-voltage conversion unit 542(R) to the first resistance and performs the monitoring of the drive current. When monitoring the second drive current, the variable resistance element is similarly set to the second resistance having a resistance value different from that of the first resistance, and the monitoring of the drive current is performed. The behavior of the constant current circuit 55 can be investigated as a group by such first drive current monitoring and second drive current monitoring.

[0150] In the above embodiment, the electro-optical device 1 is a transmissive liquid crystal device, but the present invention can also be applied to the case where the electro-optical device 1 is a reflective liquid crystal device or the case where the electro-optical device 1 is an organic electroluminescent device. In addition, regarding the pixel, a structure adopting a display element (MEMS device) such as a DMD (Digital Micromirror Device) may also be used.

[0151] [Other electronic devices]

[0152] The electronic device having the electro-optical device 1 to which the present invention is applied is not limited to the electronic device 2100 in the above embodiment. For example, it can also 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 camera, and a liquid crystal television.

Claims

1. A temperature detection device, characterized in that, It has: 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; A drive current monitoring circuit that is electrically connected to the constant current circuit and includes a current-voltage conversion section whose output voltage changes corresponding to the change in the drive current, and outputs the voltage when the drive current is supplied to the current-voltage conversion section; And A switching circuit that switches the current path between a state in which the drive current is supplied from the constant current circuit to the temperature detection element and a state in which the drive current is supplied from the constant current circuit to the current-voltage conversion section.

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

3. The temperature detection device according to claim 1, wherein: The change amount of the output voltage of the current-voltage conversion section corresponding to the change in the drive current is greater than the change amount of the output voltage of the temperature detection element corresponding to the change in the drive current.

4. The temperature detection device according to claim 3, wherein: The current-voltage conversion section is a resistance element.

5. The temperature detection device according to claim 1 or 2, wherein: The temperature detection device has a correction unit that corrects the output voltage of the temperature detection element according to the monitoring result of the drive current by the drive current monitoring circuit.

6. The temperature detection device according to claim 1 or 2, wherein: The temperature detection device has an alarm circuit that notifies an abnormality according to the monitoring result of the drive current by the drive current monitoring circuit.

7. The temperature detection device according to claim 1 or 2, wherein: The temperature detection device has a plurality of the temperature detection elements, And the constant current circuit and the drive current monitoring circuit are respectively provided corresponding to the plurality of temperature detection elements.

8. The temperature detection device according to claim 1 or 2, wherein: The temperature detection device has a plurality of the temperature detection elements, The constant current circuit outputs the drive current to the plurality of temperature detection elements respectively, And the drive current monitoring circuit is respectively provided corresponding to the plurality of temperature detection elements.

9. The temperature detection device according to claim 1 or 2, wherein: The temperature detection device has a plurality of the temperature detection elements, The constant current circuit outputs the drive current to the plurality of temperature detection elements respectively, And the drive current monitoring circuit is provided corresponding to any one of the plurality of temperature detection elements.

10. The temperature detection device according to claim 1 or 2, wherein: A plurality of the drive current monitoring circuits are provided corresponding to the temperature detection element.

11. An electronic device, characterized in that, It has the temperature detection device according to any one of claims 1 to 10, The electronic device has an electro-optical device that has an electro-optical panel, and the temperature of the electro-optical panel is detected by the temperature detection element.

12. The electronic device according to claim 11, wherein: the electro-optical panel has a first substrate provided with a plurality of pixel electrodes in a display area; the temperature detection element is provided outside the display area in the first substrate.

13. The electronic device according to claim 12, wherein: the electro-optical panel has: a second substrate opposed to the first substrate; and an electro-optical layer disposed between the first substrate and the second substrate.

14. The electronic device according to any one of claims 11 to 13, wherein: the electro-optical device has a temperature adjustment device that adjusts the temperature of the electro-optical panel; the temperature adjustment device performs at least one of heating and cooling of the electro-optical panel according to the detection result of the voltage detection unit.

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