JP2013246687A - Temperature control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature control circuit that prevents occurrence of mechanical distortion of a Peltier element to prolong the service life thereof, and satisfactorily operates even in a region with a low voltage.SOLUTION: A temperature control circuit 10 for executing temperature control using a Peltier element 6 includes: a driver unit 14 for changing a supply voltage supplied to the Peltier element 6; and a control unit 36 that controls the driver unit 14 so as to change, from 0 V to a predetermined voltage, the duty ratio of a pulse voltage whose amplitude is the voltage value of the predetermined voltage to output the supply voltage, and so as to output, from the predetermined voltage to a rated voltage, a direct current voltage corresponding to each voltage as the supply voltage.

Description

  The present invention relates to a control circuit for controlling temperature, and more particularly to a temperature control circuit for controlling a Peltier element.

A temperature control device using a Peltier element is generally well known as a small and precise temperature control device capable of precise temperature control.
A Peltier element is an element that utilizes the Peltier effect in which heat is transferred from one metal to the other by joining two different metals and passing a current between them.

Patent Document 1 discloses a temperature control device that performs temperature control of a laser diode. This temperature control device uses a Peltier element, and the temperature controller controls the Peltier element.
The temperature control part of patent document 1 detects the temperature of the laser diode used as temperature control object with a thermistor, and controls the voltage applied to a Peltier element based on this detected temperature. Specifically, the calculation processing circuit calculates the deviation between the temperature detected by the thermistor and the target temperature, and further calculates the optimum on-time of the Peltier element according to the calculated deviation. Then, the pulse generation circuit generates a pulse voltage obtained by dividing the ON time of the Peltier element into a plurality, and the control of the Peltier element is executed by the pulse voltage generated by the pulse generation circuit.

  Patent Document 2 also discloses a temperature control device using a Peltier element. According to this temperature control device, the Peltier element is controlled to be energized for a predetermined energization period based on the temperature data detected by the temperature detector.

JP 2003-31892 A JP 2007-79893 A

As disclosed in Patent Document 1 and Patent Document 2 described above, conventional Peltier element control is so-called PWM control in which an applied voltage is divided into a predetermined pulse width and the pulse width is changed with respect to a target temperature. Often done by.
In the PWM control, a pulse voltage having a predetermined cycle is generally obtained by turning on and off the FET at a predetermined timing using an FET or the like. Changing the temperature of the Peltier element is performed by changing the duty ratio.

However, when controlling a Peltier element with a pulse voltage that is PWM-controlled, if it is attempted to control everything from 0 V to the rated voltage with a pulse voltage, the Peltier element is mechanically distorted in a high voltage region, and the lifetime is shortened. There is a problem that it becomes shorter and causes damage and failure.
In the case where control is performed using a DC voltage instead of a pulse voltage, there is a problem that if the FET is used as a control circuit, the FET does not operate in a region where the drain-source voltage is lower than the saturation voltage. That is, there is a problem that temperature control becomes difficult in a region where the applied voltage is low near 0V.

  Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent the occurrence of mechanical distortion of the Peltier element, to extend the life, and to operate well even in a low voltage region. It is to provide a control circuit.

According to the temperature control circuit of the present invention, in the temperature control circuit that performs temperature control by the Peltier element, the driver unit that changes the supply voltage supplied to the Peltier element, and the driver unit are set to 0 V to a predetermined value set in advance. Until the voltage, the supply voltage is output by changing the duty ratio of the pulse voltage whose amplitude is the voltage value of the predetermined voltage, and the DC voltage corresponding to each voltage is output as the supply voltage from the predetermined voltage to the rated voltage. And a control unit for controlling.
By adopting this configuration, the supply voltage is generated by changing the duty ratio of the pulse voltage in the range from 0 V to a predetermined voltage. Since the voltage value of the pulse voltage at this time is a voltage value of a predetermined voltage, it is not necessary to control the driver unit with a low voltage in the vicinity of 0 V, so that the unstable operation part of the driver unit is not used. be able to.
Further, in the range from the predetermined voltage to the rated voltage, a DC voltage is applied to the Peltier element instead of using the pulse voltage as the supply voltage. By doing so, no pulse voltage is applied on the high voltage side within the rated voltage, so that mechanical distortion of the Peltier element can be prevented. For this reason, damage and failure of the Peltier element can be prevented.

The predetermined voltage may be set to have a voltage value that is 1/3 of the rated voltage.
According to this configuration, for example, when the rated voltage is 15 V, the Peltier element is controlled by changing the duty ratio of the pulse voltage having an amplitude of 5 V or −5 V in the range of 0 V to 5 V or 0 V to −5 V. . And in the range of 5V-15V or -5V-15V, it controls by supplying the DC voltage of the voltage value.

  According to the present invention, the mechanical distortion of the Peltier element can be prevented and the operation can be satisfactorily performed even in a low voltage region.

1 is a block diagram showing a schematic overall configuration of a temperature control circuit according to the present invention. It is a graph which shows the supply voltage supplied to a Peltier device.

The overall configuration of the temperature control circuit according to the present invention is shown in FIG.
Note that the temperature control object, the Peltier element, and the radiator shown in FIG. 1 are not included in the temperature control device of the present invention.
The temperature control object 5 may be any object, for example, a thermostatic bath used in the field of physics and chemistry or semiconductor manufacturing. The temperature control object 5 is provided with a temperature sensor 8 and measures the temperature of the temperature control object 5.
The Peltier element 6 is an element for electronically controlling the temperature of the temperature control object 5. A known Peltier element 6 itself is employed.

  Note that one surface of the Peltier element 6 is in contact with the temperature control object 5, and a radiator 9 is provided on the other surface. When the temperature of the temperature control object 5 is controlled in the cooling direction, the other surface of the Peltier element 6 has a high temperature. As shown in FIG. 1, the radiator 9 may be an air-cooled radiating fin or a water-cooled type. Even when the temperature is controlled in the heating direction, it is preferable to provide the radiator 9.

The temperature control circuit 10 includes a temperature controller 12, a driver unit 14, and a DC power supply 16.
Based on the actual temperature and the target temperature of the temperature control object 5, the temperature controller 12 calculates what percentage of the supply voltage is supplied with respect to the rated voltage of the Peltier element 6 in order to reach the target temperature. .
Specifically, the temperature controller 12 is provided with an AD converter 21, a CPU 22, and a target temperature input unit 23. Temperature data measured by the temperature sensor 8 is input to the AD converter 21. The AD converter 21 converts the temperature data input as an analog value into a digital value. The target temperature input unit 23 is configured such that the operator can input the target temperature as a touch panel or an operation panel. The input target temperature is input to the CPU 22.

  The temperature data converted into a digital value by the AD converter 21 is input to the CPU 22. In the CPU 22, a supply voltage output from the driver unit 14 to the Peltier element 6 is determined. In determining the supply voltage, the CPU 22 compares the target temperature input from the target temperature input unit 23 with the measured temperature data, and determines the supply voltage value by PID control. The CPU 22 outputs the determined supply voltage value to the driver unit 14 as a control signal.

The driver unit 14 is connected to one of both sides of the Peltier element 6 to supply a supply voltage, and the second switching circuit is connected to the other side of the Peltier element 6 to supply a supply voltage. 32.
The first switching circuit 30 is configured by connecting the drain of the P-channel FET 26 and the drain of the N-channel FET 28. A connection line 31 is connected to one side of the Peltier element 6 from between the drain of the P-channel FET 26 and the drain of the N-channel FET 28. A supply voltage is supplied to one side of the Peltier element 6 by the connection line 31.

  The second switching circuit 32 also has the same configuration as the first switching circuit 30. That is, the second switching circuit 32 is configured by connecting the drain of the P-channel FET 27 and the drain of the N-channel FET 29. A connection line 33 is connected to the other side of the Peltier element 6 from between the drain of the P-channel FET 27 and the drain of the N-channel FET 29. A supply voltage is supplied to the other side of the Peltier element 6 by the connection line 33.

The driver unit 14 is provided with a control unit 36 that receives a control signal from the temperature controller 12 and controls the first switching circuit 30 and the second switching circuit 32 based on the control signal.
And the control part 36 can perform ON / OFF of each FET by outputting the gate voltage applied to the gate of each FET of the 1st switching circuit 30 and the 2nd switching circuit 32. FIG.
In addition, the control unit 36 outputs a DC voltage output variable instruction signal to the DC power supply 16. The DC power supply 16 supplies a predetermined DC voltage between the drain and source of the first switching circuit 30 and the second switching circuit 32 based on the DC voltage output variable instruction signal.
Such an operation of the control unit 36 is executed based on a control program P1 stored in advance in a memory 38 such as a ROM or a RAM.

  The DC power supply 16 is a power supply device that can receive a commercial power supply AC100V or AC200V and output a predetermined DC voltage.

Next, the control operation of the control unit 36 will be described.
FIG. 2 shows the relationship of the supply voltage actually supplied to the Peltier element 6 with respect to the operating voltage (voltage to be supplied) of the Peltier element 6. In this graph, the horizontal axis represents the operating voltage (voltage to be supplied) of the Peltier element, and the vertical axis represents the actual supply voltage. Specifically, FIG. 2 shows a case where a Peltier element with a rated voltage of −15V to 15V is controlled.
However, in the present invention, the rated voltage of the Peltier element is not limited to -15V to 15V.

As shown in FIG. 2, the temperature control circuit 10 of the present embodiment uses a pulse voltage having a voltage value with a preset amplitude as a supply voltage from 0 V to a preset voltage. 6 is supplied.
In the present embodiment, the preset voltage is ± 5 V, which is 1/3 of ± 15 V. Therefore, a pulse voltage with an amplitude of ± 5 V is supplied to the Peltier element 6 in the range of 0 V to ± 5 V.

First, for example, a case where a voltage value in the range of 0 V to 5 V is supplied to the Peltier element 6 as a supply voltage will be described.
When the necessary supply voltage is in the range of 0 V to 5 V, the control unit 36 inputs a DC voltage having a preset voltage value of 5 V between the drains and the sources of the first switching circuit 30 and the second switching circuit 32. The DC power supply 16 is instructed to do so.
The DC power supply 16 inputs a DC voltage of 5V between the drain and source of the first switching circuit 30 and the second switching circuit 32.

Further, the control unit 36 outputs a gate signal to the first switching circuit 30 and the second switching circuit 32 so that the supply voltage becomes a pulse voltage. Since the first switching circuit 30 and the second switching circuit 32 are turned on and off by turning on and off the gate signal, a pulse voltage with an amplitude of 5 V can be generated.
Further, the duty ratio is changed depending on the ON / OFF timing of the gate signal. Even between 0V and 5V, when close to 0V, the duty ratio is changed so that the on time of the pulse voltage is shortened and the off time is lengthened. When the voltage is close to 5 V, the pulse voltage is controlled by increasing the ON time of the pulse voltage and decreasing the OFF time.

  For example, when a voltage of 0 V to +5 V is applied when the connection line 31 is + and the connection line 33 is −, the control unit 36 controls the FET 26 of the first switching circuit 30 while being on, and controls the FET 28. Control is left off. On the other hand, the control unit 36 performs on / off control of the FET 29 at a predetermined timing while keeping the FET 27 of the second switching circuit 32 off. For this reason, a pulse voltage of 5 V is applied between the connection line 31 and the connection line 33.

  In addition, when supplying the voltage value of the range of 0V--5V to the Peltier device 6 as a supply voltage, the point that the control part 36 outputs a gate signal to the 1st switching circuit 30 and the 2nd switching circuit 32 is the same. Control is performed by switching the polarities of the first switching circuit 30 and the second switching circuit 32 from the case of 0V to + 5V described above.

  That is, when a voltage of 0 V to −5 V is applied when the connection line 31 is + and the connection line 33 is −, the control unit 36 keeps the FET 26 of the first switching circuit 30 off, and the FET 28 On / off control is performed at a predetermined timing. On the other hand, the control unit 36 controls the FET 27 of the second switching circuit 32 while keeping it on, and controls the FET 29 while keeping it off. For this reason, a pulse voltage of −5 V is applied between the connection line 31 and the connection line 33.

  Also, when a voltage value in the range of 0 V to −5 V is supplied to the Peltier element 6 as a supply voltage, the duty ratio is changed depending on the on / off timing of the gate signal. Even between 0V and -5V, when it is close to 0V, the duty ratio is changed so that the ON time of the pulse voltage is short and the OFF time is long. When the voltage is close to −5 V, the pulse voltage is controlled by increasing the ON time of the pulse voltage and decreasing the OFF time.

  As described above, when the operating voltage is in the range of 0 V to ± 5 V, a pulse voltage having an amplitude of 5 V is supplied to the Peltier element 6. For this reason, since the state between the drain and source of each FFT of the first switching circuit 30 and the second switching circuit 32 of the driver unit 14 is saturated, that is, the FET can operate normally, it is supplied to the Peltier element 6. Even when the power voltage is low, temperature control can be reliably performed.

Next, a case where a voltage value in the range of 5V to 15V is supplied to the Peltier element 6 as a supply voltage will be described.
When the necessary supply voltage is in the range of 5V to 15V, the control unit 36 inputs a DC voltage having a necessary voltage value between each drain and source of the first switching circuit 30 and the second switching circuit 32. Directs to DC power supply 16.
The DC power supply 16 inputs the instructed DC voltage between the drain and source of the first switching circuit 30 and the second switching circuit 32.

Further, the control unit 36 outputs a gate signal so that the first switching circuit 30 and the second switching circuit 32 are kept on so that the voltage from the DC power supply 16 is supplied to the Peltier element 6 as it is. That is, the control unit 36 outputs a gate signal that does not turn on / off so that the first switching circuit 30 and the second switching circuit 32 remain on.
Thereby, in the range of 5V to 15V, the supply voltage necessary to reach the target temperature is supplied to the Peltier element 6 as a DC voltage.

  For example, when a voltage of 5 V to 15 V is applied when the connection line 31 is + and the connection line 33 is-, the control unit 36 keeps the FET 26 of the first switching circuit 30 on and the FET 28 is off. Control as is. On the other hand, the control unit 36 controls the second switching circuit 32 with the FET 27 turned off and the FET 29 turned on. For this reason, a DC voltage of 5V to 15V is applied between the connection line 31 and the connection line 33.

  When the necessary supply voltage is in the range of −5 V to −15 V, the control unit 36 performs control by switching the polarities of the first switching circuit 30 and the second switching circuit 32 from the case of +5 V described above.

  That is, when a voltage of −5 V to −15 V is applied when the connection line 31 is + and the connection line 33 is −, the control unit 36 keeps the FET 26 of the first switching circuit 30 off, Control while on. On the other hand, the control unit 36 controls the FET 27 of the second switching circuit 32 with the FET 27 on and the FET 29 off. For this reason, a DC voltage of −5 V to −15 V is applied between the connection line 31 and the connection line 33.

  As described above, the Peltier element 6 is controlled by the DC voltage between the preset predetermined voltage and the rated voltage. If the pulse voltage is controlled during this time, the mechanical distortion of the Peltier element 6 increases, but a mechanical burden is imposed on the Peltier element 6 by controlling with a DC voltage that does not turn on and off. There is no control.

In the embodiment described above, the temperature controller 12 and the driver unit 14 have been described as separate bodies. However, the temperature controller 12 and the driver unit 14 may be integrated.
Furthermore, the CPU 22 of the temperature controller 12 and the control unit 36 of the driver unit 14 do not have to be provided separately. Calculation and determination of the voltage value to be supplied to achieve the target temperature, and control of the switching circuits 30 and 32 And an instruction to the DC power supply 16 may be executed by one control unit.

  While the present invention has been described above with reference to a preferred embodiment, the present invention is not limited to this embodiment, and it goes without saying that many modifications can be made without departing from the spirit of the invention. .

5 Temperature control object 6 Peltier element 8 Temperature sensor 9 Radiator 10 Temperature control circuit 12 Temperature controller 14 Driver unit 16 DC power source 21 A / D converter 23 Target temperature input unit 26, 27 P channel FET
28, 29 N-channel FET
30 first switching circuit 32 second switching circuit 31, 33 connection line 36 control unit 38 memory P1 control program

Claims (2)

In a temperature control circuit that performs temperature control by a Peltier element,
A driver unit for changing a supply voltage supplied to the Peltier element;
The driver unit outputs a supply voltage by changing the duty ratio of a pulse voltage whose amplitude is a voltage value of the predetermined voltage from 0 V to a predetermined voltage, and each voltage from the predetermined voltage to the rated voltage And a control unit that controls to output a DC voltage corresponding to the supply voltage as a supply voltage.   The temperature control apparatus according to claim 1, wherein the predetermined voltage is set to be a voltage value of 1/3 of the rated voltage.

Images