JPH0720950A - Temperature control circuit - Google Patents

Abstract

PURPOSE:To manufacture a temperature control circuit small in power consumption small in size and low in cost by applying a specific pulse signal to the base of a transistor(TR) and electric power to the collector, and interposing a diode between both emitters and a coil between the emitters and a thermomodule. CONSTITUTION:The output of a PID control part 11 is applied to a PWM circuit 21 and specific pulse width modulation is imposed to generate a PWM signal having duty corresponding to the deviation between a previously set temperature set value T0 and a temperature actually measured value T1. When the PWM signal is applied to the base of the TR 1, a cooling current ic having a specific waveform is obtained in the ON state of the TR 1 and specific energy is accumulated in the coil L1. In the OFF state of the TR 1, on the other hand, the energy accumulated in the coil L1 is discharged a circulating current flows through the diode D1. Therefore, the cooling current and circulating current are put together to obtain a DC current including a ripple on the whole. In this case, the power consumption corresponds to only the saturation voltages of the TR 1 and D1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control circuit using a thermo module.

[0002]

2. Description of the Related Art As a conventional device of this type, one shown in FIG. 10 is known.

In FIG. 1, a preset temperature set value T0 and a preset temperature measured value T1 are input to an adder unit 10, a deviation between them is calculated, and a PID control unit 11 is input. The PID control unit 11 performs a predetermined PID process and then applies the output to the VI conversion circuit 12. The V-I conversion circuit 12 performs voltage / current conversion to change the input voltage signal into a current signal, and outputs the output from the two parallel-connected transistors Tr1 in the temperature control circuit 20.
, Tr2. Due to this, when the output of the V-I conversion circuit 12 is positive, the transistor Tr1 becomes V-I.
It conducts according to the output level of the conversion circuit 12, and the cooling current i
c flows to the thermo module 14 side through the transistor Tr1 and the resistor 13, and when it is negative, the transistor Tr2
Becomes conductive in accordance with the output level of the V-I conversion circuit 12, and the heating current iH flows from the thermo module 14 through the resistor 13 to the transistor Tr2 side.

[0004]

However, in the conventional device as described above, when the maximum cooling current flowing through the thermomodule 14 is ic max and the maximum heating current is iH max, the cooling current is as shown in FIG. ic is 0 to ic max
And the heating current iH is linearly controlled in the range of 0 to iHmax to control the temperature.

Therefore, for example, the thermo module 14
When the transistor Tr1 is cooled,
As shown in, when the power supply voltage is Vc, the applied voltage to the transistor Tr1 is VTr1, the resistance of the resistor 13 is r, the resistance of the thermomodule 14 is R, and the cooling current is ic, Vc = VTr1 + ic (r + R) (1 ), VTr1 = Vc-ic (r + R) (2), and the power consumption PTr1 of the transistor Tr1 can be expressed by the following equation.

PTr1 = VTr1.ic = ic (Vc-ic (r + R)) (3) That is, since the equation (3) is expressed by a parabola as shown in FIG. 13, ic = Vc / 2 (r + R). It becomes the maximum when (4).

This also applies to the power PTr2 consumed on the transistor Tr2 side when the thermo module 14 is heated.

By the way, both transistors Tr as described above
The electric power PTr1 and PTr2 consumed by 1 and Tr2 are only consumed by both transistors Tr1 and Tr2, and do not contribute to cooling or heating of the thermo module 14. Therefore, wasteful power is consumed accordingly.

In addition, both such transistors Tr1,
Since the Tr2 consumes a considerable amount of power, a corresponding radiation fin is required on the substrate to which these transistors are attached, and especially when using multiple channels at the same time, cooling with a fan is also required, and the device becomes large. At the same time, there was a problem that the cost increased.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide a temperature control circuit which consumes less power and can be manufactured in a small size and at a low cost. is there.

[0011]

In order to achieve the above object, the present invention provides a temperature control circuit using a thermo module that heats or cools in response to an applied current. A pulse control signal forming means for forming a pulse control signal having a duty corresponding to the deviation; a transistor for forming a drive current for the thermo module which is on / off controlled by the pulse control signal formed by the pulse control signal forming means; And an inductance element interposed between the thermomodule and the thermomodule, and a diode forming a closed circuit for supplying a drive current from the inductance element to the thermomodule when the transistor is turned off. .

[0012]

According to the present invention, when a predetermined pulse control signal is applied to the transistor as a base current, a cooling current having a predetermined signal waveform is obtained when the transistor is turned on, and a predetermined energy is stored in the inductance element. Then, when the transistor is off, the energy stored in the inductance element is released and a circulating current flows through the diode. Therefore, the cooling current when the transistor is turned on and the circulating current when the transistor is turned off are combined, and a direct current including ripples is obtained as a whole. By the way, in this case, the power consumed by the transistor and the diode does not depend on the power supply voltage but only on the saturation voltage of the transistor and the diode. Therefore, by using a transistor and a diode having a low saturation voltage, the consumed power can be significantly reduced as compared with the conventional one.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
The same components as those used in the description of the above-mentioned conventional example will be described with the same reference numerals.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In this embodiment, the output of the PID control unit 11 is applied to the PWM circuit 21 and subjected to a predetermined pulse width modulation to form a PWM signal having a duty corresponding to the deviation between the preset temperature set value and the actual temperature measurement value. To be done. This PWM signal is applied to the bases of a first NPN transistor Tr1 used for cooling and a second PNP transistor Tr2 used for heating.

A first diode D1 and a second diode D2 are inserted between the emitter of the first transistor Tr1 and the emitter of the second transistor Tr2, and the connection point between the diode D1 and the diode D2 is grounded. .

A first power source Vc is applied to the collector of the first transistor Tr1 and a first coil L1 is inserted between the emitter and the thermo module 14.
A second power source is connected to the collector of the second transistor Tr2.
Vc is applied, and the second coil L2 is inserted between the emitter and the thermo module 14.

Any transistor can be used as the transistors Tr1 and Tr2 as long as it can be used as a high-speed switching element. For example, a bipolar transistor, a field effect transistor, a static induction type transistor or the like can be used.

Next, the operation of this embodiment will be described.

In the following description, for convenience of explanation, a circuit on the cooling side composed of the transistor Tr1, the diode D1 and the coil L1 shown in FIG. 2 will be described, but it is composed of the transistor Tr2, the diode D2 and the coil L2. The basic operation of the heating side circuit is exactly the same as that of the cooling side circuit.

First, at the base of the transistor Tr1,
A PWM signal whose pulse width is modulated to a predetermined duty ratio is input by the PWM circuit 21.

Now, when a PWM signal having a pulse width as shown by P1 in FIG. 3A is applied to the base of the transistor Tr1, a cooling current iTr1 as shown in FIG. 3C flows, but at this time. The signal waveform Q1 of is as shown in FIG. On the other hand, at this time, when the reactance is L, the energy of 1/2 L (iTrc) ² is stored in the coil L1.

Next, as indicated by P2 in FIG. 4 (c), when the PWM signal applied to the transistor Tr1 falls, the energy 1 / 2L (iTrc) ² stored in the coil L1 is reduced.
Is emitted and the circulating current iDIC flows through the diode D1 and the thermo module 14 as shown in FIG. 7C, and the signal waveform Q2 in this case has a gently falling waveform as shown in FIG.

Therefore, when the PWM signal as shown in FIG. 5A is continuously applied to the base of the transistor Tr1,
The cooling current iTrc shown in Fig. 3 (b) and the circulating current iDIC shown in Fig. 4 (b) are combined, and the DC current iTM with ripple as shown in Fig. 3 (b) is added to the thermo module 14. You can see it flowing.

Here, as shown in FIG. 6, when the pulse width (ON time) of the PWM signal is TON and the pulse interval is T,
The duty ratio q is q = TON / T (5)

Therefore, if the power supply voltage is Vc 1 and the voltage applied to the thermomodule 14 is VTM, then VTM = qVc (6), and if the power consumption of the cooling side circuit is Pvc, then Pvc = iTrcVc = iTM · VTM = iTM · q · Vc (7) Therefore, iTrc = q.iTM (8)

Therefore, if the saturation voltage of the transistor Tr1 is VF, the power consumption of the transistor Tr1 is PTr1 and the saturation voltage of the diode D1 is VDF, and the power consumption of the diode D1 is PD1, then PTr1 = iTrc.VF = q・ ITM ・ VF (9) PD 1 = iD 1 ・ VDF = (1-q) iTM ・ VDF (10), the total power consumption Pc is Pc = PTr1 + PD 1 = iTM {q ・ VF + (1 -q) VDF} (11)

When the above equation (11) is illustrated, as shown in FIG. 7, the power consumption PTr1 of the transistor Tr 1 and the power consumption PD 1 of the diode D1 are linear curves depending on the respective saturation voltages VF and VDF. It turns out that it becomes a formula.

That is, if the transistors Tr 1 and the diode D 1 are selected to have small saturation voltages VF and VDF,
The total power consumption Pc becomes smaller, and the power supply voltage V
do not depend on c.

A specific example will be described below. The power supply voltage is Vc, and the cooling current i flowing in the thermomodule 14 is i.
If TM is 1 A and the resistance of the thermo module 14 is 1 Ω, the power consumption Pc in the conventional example is the transistor Tr 1
However, the maximum power consumption PTrmax is the above-mentioned equation (3) and (4).
As is clear from the equation, PTrmax = Vc ² /4.R = 5 ² /4.1 = 25/4 = 6.3 (W).

On the other hand, in this embodiment, the total power consumption Pc is the sum of the power consumption PTr of the transistor Tr 1 and the power consumption PD of the diode D 1, so that the transistor is a bipolar transistor having a saturation voltage of 1.2 V and the diode is saturated. When a silicon diode with a voltage of 0.6 V is used, the power consumption Pc is, as is clear from the equation (11), Pc = PTr + Po = 1 * {q * 1.2 + (1-q) * 0.6} = 1 .2q + 0.6-0.6q = 0.6q + 0.6, and when q = 0, Pc = 0.6 (W) and when q = 1, Pc = 1.2 (W).

In the above example, a bipolar transistor and a silicon diode having a relatively high saturation voltage are used for the transistor and the diode, but if an FET or a Schottky diode having a low ON resistance and a low saturation voltage is used, the power consumption is further increased. It can be reduced to several times (however, it is calculated by ignoring switching loss).

In the above description, the cooling side circuit has been described, but the heating side circuit can also be calculated in exactly the same manner with respect to the electric power consumption only with the different polarities.

Next, FIG. 8 shows the power consumption in the conventional example,
FIG. 9 is a graph showing the experimental results of the power consumption in this example.

That is, FIG. 8 shows the cooling current Ic on the horizontal axis, and shows the power consumption PTr in the cooling side transistor when the power supply voltage Vc is 5 V, and 31 is the resistance of the thermomodule 0.2 Ω. , 32 shows the case where the resistance of the thermomodule is 0.6Ω, and 33 shows the case where the resistance of the thermomodule is 1.0Ω.
Is obtained by a parabola, and the power consumption P near the vertex is
You can see that Tr is quite large.

On the other hand, in the case of this embodiment shown in FIG. 9, cooling is performed when the frequency f of the PWM signal is taken on the horizontal axis under the condition that the power supply voltage Vc is 5V and the resistance of the thermomodule is 0.2Ω. The power consumption Pc of the entire side circuit is shown, 41 shows the case where the cooling current is 0.5A, 42 shows the case where the cooling current is 1.0A, and 43 shows the case where the cooling current is 1.5A. Although the reactance of the number coil of width is shown, the power consumption P is higher than that of the conventional example shown in FIG.
It can be seen that c is greatly reduced.

As is clear from the above description, in the present embodiment, the power consumption in the temperature control circuit depends only on the saturation voltage of the transistor and the diode and not on the power supply voltage. By selecting the one with a smaller value, the total power consumption can be reduced accordingly, and it is possible to obtain a temperature control circuit that consumes less power than before and does not require fins or fans for heat dissipation. You can do it.

[0037]

As described above, according to the present invention, the consumed power can be made to depend only on the saturation voltage of the transistor and diode used, so that the transistor or diode used has a small saturation voltage. By doing so, the power consumption can be significantly reduced compared to the conventional case.

Further, since the amount of heat generated from the transistor or the like can be greatly reduced by this, there is no need for a heat-radiating fin or fan as in the prior art, and the effect that this type of device can be obtained at a small size and low cost is obtained. Have.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment to which the present invention is applied.

FIG. 2 is a circuit diagram showing a cooling side circuit extracted from the circuit shown in FIG.

FIG. 3 is an explanatory diagram of a cooling current generated when the PWM signal is turned on and its waveform.

FIG. 4 is an explanatory diagram of a circulating current generated when the PWM signal is OFF and its waveform.

FIG. 5 is an explanatory diagram of a case where a cooling DC current having ripples is obtained by combining a cooling current generated when the PWM signal is turned on and off and a circulating current.

FIG. 6 is a diagram showing a duty ratio of a PWM signal.

FIG. 7 is an explanatory diagram of calculation of total power consumption.

FIG. 8 is a graph showing an experimental result when a power consumption amount in a conventional example is examined.

FIG. 9 is a graph showing an experimental result when the power consumption is examined in this example.

FIG. 10 is an explanatory diagram of a conventional temperature control circuit.

11 is a graph illustrating the operation of the circuit shown in FIG.

12 is a circuit diagram showing a cooling side circuit extracted from the circuit shown in FIG.

13 is a graph illustrating the operation of the circuit shown in FIG.

[Explanation of symbols]

 14 Thermo Module 20 Temperature Control Circuit Tr 1 First Transistor Tr 2 Second Transistor L1 First Coil L2 Second Coil D1 First Diode D2 Second Diode

Claims (2)

[Claims] 1. In a temperature control circuit using a thermo module that heats or cools in accordance with an applied current, pulse control signal formation for forming a pulse control signal having a duty corresponding to a deviation between a temperature set value and an actually measured temperature value. Means, a transistor that is on / off controlled by a pulse control signal formed by the pulse control signal forming means, and forms a drive current for the thermomodule; and an inductance element interposed between the transistor and the thermomodule. A temperature control circuit comprising a closed circuit for supplying a drive current from the inductance element to the thermo module when the transistor is turned off. 2. A temperature control circuit using a thermo module that heats or cools according to the polarity of an applied current, pulse control for forming a pulse control signal having a duty corresponding to a deviation between a temperature set value and an actual temperature measurement value. Signal forming means, an NPN first transistor to which the pulse control signal formed by the pulse control signal forming means is applied to the base, and a first power source is applied to the collector, formed by the pulse control signal forming means Connected between a PNP type second transistor having a base to which the generated pulse control signal is applied and a second power source being applied to the collector, and an emitter of the first transistor and a first terminal of the thermomodule. A first coil, between the emitter of the second transistor and the first terminal of the thermomodule A second coil connected to the first transistor; a first diode having a cathode connected to the emitter of the first transistor and an anode connected to the second terminal of the thermomodule via a ground terminal; A temperature control circuit comprising: a second diode having an anode connected to the emitter of the transistor and a cathode connected to the second terminal of the thermomodule through a ground terminal.