Peltier element control device, electrical device, and control method

Abstract

This Peltier element control device is equipped with a drive circuit, a voltage detector and a control circuit. The drive circuit supplies an electric current to the Peltier element. The voltage detector detects the voltage value of the voltage to be applied to the Peltier element. The control circuit controls the drive circuit so as to supply an electric current of a pre-determined fixed value to the Peltier element, and so as to reduce the size of the current to be supplied to the Peltier element when a value pertaining to the voltage value detected when the current of the fixed value is supplied to the Peltier element increases.

Description

[Technical Field]

[0001] The present disclosure relates to Peltier element control devices, electrical devices, and control methods. [Background technology]

[0002] Peltier elements are often used to cool heat sources contained in electrical devices, transferring heat from their heat-absorbing surface to their heat-dissipating surface in response to an electric current passing through them.

[0003] For example, Patent Document 1 discloses a Peltier element driving method that can drive a Peltier element using a power supply with a current capacity necessary and sufficient for a steady current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-353830 Summary of the Invention

[0005] The amount of heat transferred from the heat absorption surface to the heat dissipation surface by the Peltier element is proportional to the magnitude of the current flowing through the Peltier element. However, the greater the current flowing through the Peltier element, the greater the Joule heat generated by the Peltier element's electrical resistance. Furthermore, if the heat dissipation surface is insufficiently cooled, the generated Joule heat cannot be sufficiently transferred, causing the temperature of the heat absorption surface to rise, and an even greater current is required for the Peltier element to cool the heat absorption surface. Therefore, if the heat dissipation surface of the Peltier element is insufficiently cooled, the Peltier element will not be able to cool the heat source, and the Peltier element itself may generate heat and cause thermal runaway. For this reason, it is necessary to control the Peltier element so that thermal runaway is less likely to occur.

[0006] An object of the present disclosure is to provide a Peltier element control device and control method that can control a Peltier element so as to prevent thermal runaway with a simpler configuration than conventional devices, and to provide an electrical device equipped with such a Peltier element control device.

[0007] According to one aspect of the present disclosure, a Peltier element control device for controlling a Peltier element includes: a drive circuit for supplying a current to the Peltier element; a voltage detector for detecting a voltage value of the voltage applied to the Peltier element; and a control circuit that controls the drive circuit to supply a predetermined constant current to the Peltier element, and controls the drive circuit to reduce the magnitude of the current supplied to the Peltier element when a value related to the voltage value detected while the constant current is being supplied to the Peltier element increases.

[0008] According to one aspect of the present disclosure, it is possible to control a Peltier element so that thermal runaway is less likely to occur, with a configuration simpler than conventional configurations. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing the configuration of a Peltier element control device 1 according to a first embodiment. [Figure 2] 2 is a diagram schematically showing the current-voltage characteristics of the Peltier element 3 in FIG. 1 when the temperature difference between the heat absorption surface 3a and the heat radiation surface 3b of the Peltier element 3 is 10° C. FIG. [Figure 3] 2 is a diagram schematically showing the current-voltage characteristics of the Peltier element 3 in FIG. 1 when the temperature difference between the heat absorption surface 3a and the heat radiation surface 3b of the Peltier element 3 is 40° C. FIG. [Figure 4] 2 is a diagram schematically showing the current flowing through the Peltier element 3 and the voltage applied to the Peltier element 3 in FIG. 1 when the heat dissipation surface 3b of the Peltier element 3 is sufficiently cooled. [Figure 5]1. FIG. 2 is a diagram showing a first embodiment in which a control circuit 13 controls a drive circuit 11, and schematically shows a current flowing through the Peltier element 3 and a voltage applied to the Peltier element 3 when the heat dissipation surface 3b of the Peltier element 3 in FIG. 1 is not sufficiently cooled. [Figure 6] FIG. 10 is a diagram illustrating a second embodiment in which a control circuit 13 controls a drive circuit 11, and schematically illustrates a current flowing through the Peltier element 3 and a voltage applied to the Peltier element 3 when the heat dissipation surface 3b of the Peltier element 3 in FIG. 1 is not sufficiently cooled. [Figure 7] 1 is a block diagram showing the configuration of a video projection device 20 including a Peltier element control device 1 according to a first embodiment. [Figure 8] FIG. 10 is a block diagram showing the configuration of a Peltier element control device 1A according to a second embodiment. [Figure 9] FIG. 10 is a block diagram showing the configuration of a video projection device 20A including a Peltier element control device 1A according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed description than necessary may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

[0011] The inventors have provided the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0012] [First embodiment] [Configuration of the first embodiment] 1 is a block diagram showing the configuration of a Peltier element control device 1 according to the first embodiment. The Peltier element control device 1 receives power supply from a DC power supply device 2 and controls a Peltier element 3.

[0013] The Peltier element control device 1 includes a drive circuit 11, a voltage detector 12, and a control circuit 13. The drive circuit 11 receives power from a DC power supply 2 and supplies current to the Peltier element 3 under the control of the control circuit 13. The voltage detector 12 detects the voltage value of the voltage applied to the Peltier element 3. The control circuit 13 controls the drive circuit 11 based on the detected voltage value. For example, the drive circuit 11 is a constant current drive circuit, and the control circuit 13 controls the drive circuit 11 so as to supply a predetermined constant value of current to the Peltier element 3.

[0014] The Peltier element 3 has a heat absorption surface 3a and a heat dissipation surface 3b, and transfers heat from the heat absorption surface 3a to the heat dissipation surface 3b in response to a flowing current. The heat absorption surface 3a is arranged to be in contact with a heat source. The heat dissipation surface 3b may be arranged to be in contact with a heat sink, and may further be cooled by a cooling device such as a fan.

[0015] [Operation of the first embodiment] FIG. 2 is a diagram schematically showing the current-voltage characteristics of the Peltier element 3 of FIG. 1 when the temperature difference between the heat absorption surface 3a and the heat radiation surface 3b of the Peltier element 3 is 10°C. FIG. 3 is a diagram schematically showing the current-voltage characteristics of the Peltier element 3 of FIG. 1 when the temperature difference between the heat absorption surface 3a and the heat radiation surface 3b of the Peltier element 3 is 40°C. FIG. 2 shows a case where the temperature of the heat absorption surface 3a is 35°C and the temperature of the heat radiation surface 3b is 45°C. FIG. 3 shows a case where the temperature of the heat absorption surface 3a is 35°C and the temperature of the heat radiation surface 3b is 75°C. The voltage that must be applied to the Peltier element 3 to pass a predetermined amount of current through the Peltier element 3 varies depending on the temperature difference between the heat absorption surface 3a and the heat radiation surface 3b. As the temperature difference increases, a higher voltage must be applied. For example, in order to pass a current of 7 A through the Peltier element 3, in the example of Fig. 2, it is necessary to apply a voltage of 13 V to the Peltier element 3, and in the example of Fig. 3, it is necessary to apply a voltage of 18 V to the Peltier element 3. Therefore, when the Peltier element 3 is under constant current control, the temperature difference between the heat absorption surface 3a and the heat dissipation surface 3b can be estimated by detecting the voltage applied to the Peltier element 3.

[0016] 4 is a diagram schematically showing the current flowing through the Peltier element 3 and the voltage applied to the Peltier element 3 when the heat dissipation surface 3b of the Peltier element 3 in FIG. 1 is sufficiently cooled. When the Peltier element 3 is used to cool a heat source satisfactorily, the temperature difference between the heat absorption surface 3a and the heat dissipation surface 3b is a small, constant value, and the voltage applied to the Peltier element 3 is also a constant value. Therefore, when the voltage applied to the Peltier element 3 is a constant value, it can be determined that the heat source is being cooled satisfactorily.

[0017] 5 is a diagram showing a first embodiment in which the control circuit 13 controls the drive circuit 11 and schematically illustrates the current flowing through the Peltier element 3 and the voltage applied to the Peltier element 3 when the heat dissipation surface 3b of the Peltier element 3 shown in FIG. 1 is not sufficiently cooled, and illustrates a first embodiment in which the control circuit 13 controls the drive circuit 11. When the heat dissipation surface 3b is not sufficiently cooled, the temperature of the heat dissipation surface 3b increases rapidly, causing a rapid increase in the temperature difference between the heat absorption surface 3a and the heat dissipation surface 3b, and also a rapid increase in the voltage applied to the Peltier element 3. Therefore, when the voltage applied to the Peltier element 3 increases rapidly, it can be determined that the cooling of the heat dissipation surface 3b is insufficient and that the Peltier element 3 may experience thermal runaway.

[0018] Therefore, in the Peltier element control device 1 according to this embodiment, when a value related to the voltage value detected by the voltage detector 12 increases while a constant current is being supplied to the Peltier element 3, the control circuit 13 controls the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3. Specifically, as shown in FIG. 5, for example, when the temporal rate of change ΔV / Δt of the detected voltage value increases above a predetermined threshold (threshold value for the rate of change of the voltage value), the control circuit 13 controls the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3 or to stop the current supplied to the Peltier element 3. In this case, the threshold value may be set to 0.05 V / s, for example, when the Peltier element 3 has the characteristics shown in FIGS. 2 and 3. The temporal rate of change of the voltage value is an example of a value related to the voltage value.

[0019] According to the Peltier element control device 1 of this embodiment, by detecting the voltage applied to the Peltier element 3, it is possible to estimate the temperature difference between the heat absorption surface 3a and the heat dissipation surface 3b, and indirectly detect changes in the temperature of the heat dissipation surface 3b. The Peltier element control device 1 of this embodiment does not require a temperature sensor, so the size and cost of the device are reduced compared to conventional devices. Therefore, the Peltier element control device 1 of this embodiment can control the Peltier element 3 so as to prevent thermal runaway with a simpler configuration than conventional devices.

[0020] When attempting to protect a Peltier element from thermal runaway based on the current flowing through the Peltier element, it is not necessarily possible to protect the Peltier element under conditions where thermal runaway occurs. Thermal runaway in a Peltier element occurs due to insufficient cooling performance on the heat dissipation surface. The Peltier element control device 1 according to this embodiment can indirectly detect the temperature rise on the heat dissipation surface 3b, which is the cause of thermal runaway, and therefore can reliably protect the Peltier element 3 under conditions where thermal runaway occurs. Furthermore, the Peltier element control device 1 according to this embodiment can estimate the temperature of the heat dissipation surface 3b. Therefore, when the heat dissipation surface is liquid-cooled using a liquid-cooling type cooling device, the temperature of the coolant can be kept below the maximum value specified, thereby ensuring the reliability of the cooling device.

[0021] A change in the voltage applied to the Peltier element 3 can be detected more quickly than a change in the temperature of the Peltier element 3 detected by a temperature sensor. Therefore, according to the Peltier element control device 1 of this embodiment, by detecting the voltage applied to the Peltier element 3, a change in the temperature of the heat dissipation surface 3b can be detected more quickly than when a temperature sensor is used.

[0022] [Another Example of the First Embodiment] FIG. 6 is a diagram illustrating a second embodiment in which the control circuit 13 controls the drive circuit 11, and schematically illustrates the current flowing through the Peltier element 3 and the voltage applied to the Peltier element 3 when the heat dissipation surface 3b of the Peltier element 3 in FIG. 1 is not sufficiently cooled. When a constant current is being supplied to the Peltier element 3 and the voltage detected by the voltage detector 12 exceeds a predetermined threshold Vth (threshold voltage value), the control circuit 13 may control the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3 or to stop the current being supplied to the Peltier element 3. The threshold Vth may be set to 18 V, for example, when the Peltier element 3 has the characteristics shown in FIGS. 2 and 3. The voltage value is an example of a value related to the voltage value.

[0023] The control circuit 13 may control the drive circuit 11 using both the threshold value of the rate of change of the voltage value described with reference to FIG. 5 and the threshold value of the voltage value described with reference to FIG.

[0024] FIG. 7 is a block diagram showing the configuration of an image projection device 20 including a Peltier element control device 1 according to a first embodiment. The image projection device 20 includes a Peltier element control device 1, a power supply device 2, a Peltier element 3, a light source device 21, an illumination optical system 22, a light modulation device 23, a projection optical system 24, and a fan 25. The light source device 21 includes a light source element such as a laser diode and generates light of a predetermined wavelength, such as red light or blue light. Since the light source device 21 generates light and also functions as a heat source, the light source device 21 is cooled using a Peltier element 3. The Peltier element control device 1, power supply device 2, and Peltier element 3 in FIG. 7 are configured similarly to the corresponding components in FIG. 1. The heat absorption surface 3a of the Peltier element 3 is disposed so as to be in contact with the light source device 21. The illumination optical system 22 transmits light generated by the light source device 21 to the light modulation device 23. The light modulation device 23 includes a light modulation element such as a DMD (Digital Micromirror Device) and spatially modulates the light incident from the illumination optical system 22. The projection optical system 24 projects the light modulated by the light modulator 23 onto a screen. The fan 25 is arranged to cool the heat dissipation surface 3b of the Peltier element 3. In addition to or instead of the fan 25, a liquid-cooling type cooling device in contact with the heat dissipation surface 3b of the Peltier element 3 may be provided. As described above, the Peltier element control device 1 controls the Peltier element 3 so as to prevent thermal runaway.

[0025] Generally, when a video projection device is enclosed by an enclosure, the cooling radiator's exhaust port is blocked, resulting in reduced cooling performance compared to a device without an enclosure. In this case, the Peltier element cannot be cooled below a predetermined temperature, increasing the possibility of thermal runaway. Some conventional video projection devices, for example, have a protection function that stops current flowing through the Peltier element when a predetermined maximum current flows through the Peltier element for a predetermined period of time, in order to operate a liquid-cooled cooling device below the maximum specified value of the cooling liquid. This protection function often activates even when the temperature of the Peltier element's heat dissipation surface does not exceed the protection function's maximum specified value. In contrast, the Peltier element control device 1 of this embodiment indirectly detects changes in the temperature of the heat dissipation surface 3b of the Peltier element 3, which should be detected, and controls the Peltier element 3 based on this information, thereby reducing the likelihood of unnecessary current interruptions to the Peltier element.

[0026] The Peltier element control device 1 according to this embodiment is not limited to the video projection device 20, but can be applied to any electrical device equipped with a heat source.

[0027] [Advantages of the first embodiment] According to one embodiment of the Peltier element control device 1 of the present disclosure, the Peltier element control device 1 that controls the Peltier element 3 includes a drive circuit 11, a voltage detector 12, and a control circuit 13. The drive circuit 11 supplies a current to the Peltier element 3. The voltage detector 12 detects the voltage value of the voltage applied to the Peltier element 3. The control circuit 13 controls the drive circuit 11 to supply a predetermined constant current to the Peltier element 3, and controls the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3 when a value related to the voltage value detected while the constant current is being supplied to the Peltier element 3 increases.

[0028] This makes it possible to control the Peltier element 3 so that thermal runaway is less likely to occur, with a configuration simpler than conventional ones.

[0029] According to the Peltier element control device 1 of one embodiment of the present disclosure, the control circuit 13 may control the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3 when the rate of change over time of the voltage value detected while a constant current is being supplied to the Peltier element 3 becomes greater than a first threshold value.

[0030] This makes it possible to estimate the temperature difference between the heat absorbing surface 3a and the heat radiating surface 3b, and indirectly detect the change in temperature of the heat radiating surface 3b.

[0031] According to the Peltier element control device 1 according to one embodiment of the present disclosure, the control circuit 13 may control the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3 when the voltage value detected while a constant current is being supplied to the Peltier element 3 increases above the second threshold value.

[0032] This makes it possible to estimate the temperature difference between the heat absorbing surface 3a and the heat radiating surface 3b, and indirectly detect the change in temperature of the heat radiating surface 3b.

[0033] An electric device according to one aspect of the present disclosure includes a heat source, a Peltier element 3 in contact with the heat source, and the Peltier element control device 1 according to the above-described aspect.

[0034] This makes it possible to control the Peltier element 3 so that thermal runaway is less likely to occur, with a configuration simpler than conventional ones.

[0035] According to an embodiment of the electrical device of the present disclosure, the electrical device may be a video projection device 20. In this case, the heat source may be a light source device 21.

[0036] This makes it possible to control the Peltier element 3 so that thermal runaway is less likely to occur in order to cool, for example, the red laser diode of the light source device 21, which is the heat source of the video projection device.

[0037] A control method for controlling a Peltier element 3 according to one embodiment of the present disclosure includes the steps of supplying a predetermined constant current to the Peltier element 3, detecting a voltage value of a voltage applied to the Peltier element 3, and reducing the magnitude of the current supplied to the Peltier element 3 in response to an increase in the value of the voltage value detected when the constant current is being supplied to the Peltier element 3.

[0038] This makes it possible to control the Peltier element 3 so that thermal runaway is less likely to occur, with a configuration simpler than conventional ones.

[0039] [Second embodiment] FIG. 8 is a block diagram showing the configuration of a Peltier element control device 1A according to a second embodiment. The Peltier element control device 1A includes a control circuit 13A instead of the control circuit 13 in FIG. 1. The control circuit 13A may generate a control signal for controlling a cooling device separate from the Peltier element 3. If a value related to the voltage value detected by the voltage detector 12 increases while a constant current is being supplied to the Peltier element 3, the control circuit 13A sends a control signal to the cooling device to improve the cooling performance of the cooling device. For example, if the cooling device includes a fan, the cooling performance may be improved by increasing the rotation speed of the fan.

[0040] Fig. 9 is a block diagram showing the configuration of a video projection device 20A equipped with a Peltier element control device 1A according to the second embodiment. The video projection device 20A is equipped with a Peltier element control device 1A and a fan 25A instead of the Peltier element control device 1 and fan 25 in Fig. 7. The fan 25A operates in accordance with the Peltier element control device 1A.

[0041] When a value related to the voltage value detected by the voltage detector 12 increases while a constant current is being supplied to the Peltier element 3, the control circuit 13A in FIG. 8 may control the drive circuit 11 to reduce the magnitude of the current supplied to the Peltier element 3, and may also send a control signal to the cooling device to improve the cooling performance of the cooling device. This makes it possible to quickly cool the Peltier element 3 to a temperature at which the Peltier element 3 can operate again while reliably avoiding thermal runaway of the Peltier element 3. Alternatively, when a value related to the detected voltage value increases, the control circuit 13A may send a control signal to the cooling device to improve the cooling performance of the cooling device while maintaining the magnitude of the current supplied to the Peltier element 3. This makes it possible to operate the Peltier element 3 while making it less likely to experience thermal runaway.

[0042] [Advantages of the second embodiment] According to an embodiment of the electric device of the present disclosure, the electric device may further include a cooling device configured to reduce the temperature of the heat source, separate from the Peltier element 3. In this case, when a value related to the voltage value detected while a constant current is being supplied to the Peltier element 3 increases, the control circuit 13A sends a control signal to the cooling device to increase the cooling performance of the cooling device.

[0043] This makes it possible to reliably prevent thermal runaway of the Peltier element 3, and to cool the Peltier element 3 to a temperature at which the Peltier element 3 can operate again in a short time.

[0044] [Other embodiments] As described above, the embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which appropriate modifications, substitutions, additions, omissions, etc. are made. Furthermore, it is also possible to combine the components described in the above embodiments to create new embodiments.

[0045] As described above, the embodiments have been described as examples of the technology in the present disclosure, and for that purpose, the accompanying drawings and detailed description have been provided.

[0046] Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0047] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0048] A Peltier element control device according to an aspect of the present disclosure is applicable to electrical devices such as video projection devices. [Explanation of symbols]

[0049] 1,1A Peltier device control device 2 Power supply 3 Peltier element 3a Endothermic surface 3b Heat radiation surface 11 Drive circuit 12 Voltage detector 13,13A control circuit 20,20A Video Projection Device 21 Light source device 22 Illumination optical system 23 Optical Modulation Device 24 Projection optical system 25,25A fan

Claims

1. A Peltier element control device for controlling a Peltier element, a drive circuit for supplying a current to the Peltier element; a voltage detector for detecting a voltage value of the voltage applied to the Peltier element; a control circuit that controls the drive circuit to supply a desired current to the Peltier element, and controls the magnitude of the current supplied to the Peltier element by the drive circuit based on a change in the temporal rate of change of the voltage value detected when the desired current is supplied to the Peltier element, Peltier device control device.

2. the control circuit controls the drive circuit to reduce the magnitude of the current supplied to the Peltier element when a temporal change rate of the voltage value detected while the arbitrary current is being supplied to the Peltier element becomes greater than a first threshold value.

2. The Peltier device control device according to claim 1.

3. When the voltage value detected while the arbitrary current is being supplied to the Peltier element increases above a second threshold value, the control circuit controls the drive circuit to reduce the magnitude of the current supplied to the Peltier element.

2. The Peltier device control device according to claim 1.

4. A heat source and a Peltier element in contact with the heat source; and the Peltier element control device according to any one of claims 1 to 3. Electrical equipment.

5. the electrical device further comprising a cooling device separate from the Peltier element configured to reduce the temperature of the heat source; the control circuit sends a control signal to the cooling device to improve the cooling performance of the cooling device when a value related to the voltage value detected while the arbitrary current is being supplied to the Peltier element increases; 5. The electrical device of claim 4.

6. the electrical device is a video projection device; The heat source is a light source device.

5. The electrical device of claim 4.

7. A control method for controlling a Peltier element, comprising: supplying a given current to the Peltier element; detecting a voltage value of a voltage applied to the Peltier element; and controlling the magnitude of the current supplied to the Peltier element based on a change in the temporal rate of change of the voltage value detected while the arbitrary current is being supplied to the Peltier element. Control method.

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