JP3441622B2 - Peltier element drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Peltier element driving circuit for driving a Peltier element that generates or absorbs heat by flowing an electric current. 2. Description of the Related Art A Peltier element is an element that generates or absorbs heat other than Joule heat at a junction by connecting two kinds of metals or a metal and a semiconductor and passing a current to the two.
Heat generation or absorption occurs by changing the current in a forward or reverse direction. FIG. 3 shows an example of the configuration of a Peltier device driving circuit for supplying a current to such a Peltier device. In FIG. 3, 1 is a commercial power supply, 2 is an input-side rectifier for rectifying the commercial power supply 1, 3 is a capacitor for smoothing the rectified DC, and 4 is high-frequency switching by a switching element having a built-in rectified and smoothed DC. A high-frequency converter that outputs high-frequency AC, 5 is a transformer that inputs high-frequency AC and transforms it to a desired voltage, 6 is an output rectifier that rectifies the transformed high-frequency AC, and 7 is rectified by the output rectifier 6. A reactor for smoothing direct current, 8 is a switching circuit for switching a direct current flowing through the Peltier element in a forward direction or a reverse direction, and 9 is a Peltier element of a load. The switching circuit 8 includes power switching elements 11 and 1 such as IGBTs, MOSFETs, and power transistors connected in series to a DC output obtained by rectifying a high-frequency AC.
And power switching elements 12 and 14 connected in series, such as IGBTs, MOSFETs, and power transistors.
And diodes 15, 17, 1 connected in antiparallel to power switching elements 11, 13, 12, 14, respectively.
6 and 18. Next, the operation will be described. The commercial power supply 1 is rectified by the input side rectifier 2, and the rectified DC is smoothed by the capacitor 3. The rectified and smoothed DC is converted into a high-frequency AC by a high-frequency converter 4, and the high-frequency AC is transformed into a desired voltage by a transformer 5. The transformed high-frequency AC is rectified by the output rectifier 6 and smoothed by the reactor 7. The rectified and smoothed DC is input to the switching circuit 8. Now, when a forward drive command signal is applied to the gates of the power switching elements 11, 14, the power switching elements 11, 14 are turned on. When the power switching elements 11 and 14 are turned on, a forward current flows through the power switching element 11, the load 9, and the switching element 14, and the Peltier element of the load 9 generates heat. When the reverse drive command signal is applied to the gates of the power switching elements 12, 13, the power switching elements 12, 13 are turned on. When the power switching elements 12 and 13 are turned on, a reverse current flows through the power switching element 12, the load 9, and the power switching element 13, and the Peltier element of the load 9 absorbs heat. In the above-mentioned Peltier element driving circuit, since the high-frequency AC is output by the high-frequency converter 4, the impedance of the reactor 7 is designed to be small. By the way, when a forward current flows from a state in which a forward current flows to a Peltier element, or when a forward current flows from a state in which a reverse current flows,
That is, when switching the current direction, the power switching elements 11 and 13 or 12 connected in series with the DC power supply are used.
And 14 may be turned on at the same time. In this case, a short-circuit current flows in the DC power supply, and the reactor 7 is small, so that the power switching element may be damaged. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and a Peltier device driving circuit of the present invention performs high-frequency switching of a rectified DC of an AC power supply and a high-frequency AC. A high-frequency converter that outputs a signal, a transformer that transforms the high-frequency alternating current, an output rectifier that rectifies the transformed high-frequency alternating current, and a power switching element that passes the current flowing from the DC output of the output rectifier to the Peltier element of the load. A driving circuit for driving the high-frequency converter is turned on when a forward drive command signal and a reverse drive command signal are input, respectively. A signal switching element and a second signal switching element, and the first and second signal switches The output increases when the first signal switching element is on, and decreases when the second signal switching element is on. An integrator, a first comparator and a second comparator which are provided at the output of the integrator and compare the positive reference signal and the negative reference signal, respectively, and the output of the integrator is a positive reference signal. An OR circuit for stopping a drive signal from the first comparator and the second comparator to the high frequency converter when the output is smaller than the negative reference signal and when the output of the integrator is larger than the negative reference signal. is there. The rectified DC of the AC power supply is subjected to high-frequency switching to obtain high-frequency AC, and the high-frequency AC is transformed into a desired voltage by a transformer. The transformed high-frequency AC is rectified by an output rectifier, and the rectified DC is input to a switching circuit. By turning on the forward power switching element incorporated in the switching circuit, a current flows in the Peltier element of the load in the forward direction, and the Peltier element generates heat. When the reverse power switching element built in the switching circuit is turned on, a reverse current flows through the Peltier element of the load, and the Peltier element absorbs heat. Now, when the forward drive command signal is input to the first signal switching element, the first signal switching element is turned on, and the output of the integrator rises. Then, the first and second comparators compare the positive reference signal and the negative reference signal with the output of the integrator, respectively. When the output of the integrator starts to rise, the output of the integrator is smaller than the negative reference signal, and the second comparator outputs a signal for driving the high-frequency converter. When the output of the integrator becomes larger than the negative reference signal and the output of the integrator does not reach the positive reference signal, the outputs of the first comparator and the second comparator become high frequency. The drive signal of the converter is stopped, and the output from the high-frequency converter is stopped. Further, when the output of the integrator becomes larger than the positive reference signal, the output of the first comparator outputs a signal for driving the high-frequency converter. Next, when the forward drive command signal is turned off and the reverse drive command signal is input to the second signal switching element, the second signal switching element is turned on, and the output of the integrator falls. When the output of the integrator is larger than the positive reference signal, the first comparator outputs a signal for driving the high-frequency converter. When the output of the integrator is smaller than the positive reference signal and the output of the integrator is larger than the negative reference signal, the outputs of the first and second comparators are the driving signals of the high-frequency converter. Is stopped, and the output from the high-frequency converter is stopped. Further, when the output of the integrator becomes smaller than the negative reference signal, the output of the second comparator outputs a signal for driving the high frequency converter. FIG. 1 is a schematic block diagram of a Peltier device driving circuit according to an embodiment of the present invention. In FIG. 1, those having the same reference numerals as those in FIG. 3 indicate those having the same functions. The difference between FIG. 1 and FIG. 3 is that FIG. 1 of the present invention is provided with a function for preventing a short circuit from occurring in the power switching elements connected in series. That is, 20
Are drive circuits for driving the high-frequency converter, 21 and
Reference numeral 2 denotes a first signal switching element to which a forward drive signal is input and a second signal switching element to which a reverse drive signal is input, which are connected in series to positive and negative bias power supplies via resistors 23 and 24. . Reference numeral 25 denotes an operational amplifier, and reference numeral 26 denotes a capacitor. The operational amplifier 25, the capacitor 26, and the resistors 23 and 24 form an integrator 27. 33 and 34 are comparators for comparing the integrated output signal with the reference signals of the reference power supplies 31 and 32. In the comparator 33, the output signal of the operational amplifier 25 is input to an inverting input terminal, and the reference signal of the reference power supply 31 is input to a non-inverting input terminal. On the other hand, in the comparator 34, the output signal of the operational amplifier 25 is input to the non-inverting input terminal, and the reference signal of the reference power supply 32 is input to the inverting input terminal. Reference numerals 35 and 36 denote OR circuits provided at the outputs of the comparators 33 and 34, and reference numerals 38 and 37 denote resistors. The output signal of the OR circuit 38 is input to the high frequency converter 4. Now, as shown in FIG. 2A, when a forward drive command signal is applied to the first signal switching element 21 at time t1, the first signal switching element 21
Is turned on, the first signal switching element 21, the resistor 2
The charging current flows through the capacitor 26 through the capacitor 3, and the output of the operational amplifier 25 rises as shown in FIG. 2C and is input to the comparators 33 and 34. When the output of the operational amplifier 25 is lower than the reference value of the reference power supply 32, the output of the comparator 34 becomes low and the diode 36 is turned on. Therefore, the output of the OR circuit is turned on as shown in FIG. The output of the OR circuit becomes a drive command signal for the high-frequency converter 4 and the high-frequency converter 4 outputs a high-frequency alternating current. On the other hand, the reverse drive command signal is input to the power switching elements 12 and 13 of the switching circuit 8 until the output signal of the operational amplifier 25 changes from negative to 0, and the power switching elements 12 and 13 are turned on. As shown in e), the reverse current continues to flow through the Peltier element of the load. Next, the output of the operational amplifier 25 is
Is higher than the reference value, the output of the comparator 34 is at a high level, and the diode 36 is off. When the output of the operational amplifier 25 is lower than the reference value of the reference power supply 31, the output of the comparator 33 becomes high level,
Is off. Therefore, the output of the OR circuit 38 is shown in FIG.
It is off as shown in (d). Since the output of the OR circuit is off, the high frequency converter 4 turns off the output and outputs 0. Therefore, the output of the switching circuit 8 is off as shown in FIG. The output of the operational amplifier 25 is connected to the reference power source 3
When the value becomes higher than the reference value of 1, the output of the comparator 33 becomes low and the diode 35 is turned on. Therefore, the output of the OR circuit 38 is on as shown in FIG. The output of the OR circuit 38 is used as a drive command signal for the high-frequency converter 4 to output a high-frequency AC from the high-frequency converter 4. On the other hand, when the output signal of the operational amplifier 25 is 0
, The positive direction drive command signal is input to the switching circuit 8 to turn on the power switching elements 11 and 14, and a positive current flows through the Peltier element of the load as shown in FIG. 2 (e). Next, as shown in FIG. 2A, at time t2, the forward drive command signal input to the first switching element 21 is turned off, and as shown in FIG. When the reverse drive command signal is input to the element 22, the second switching element 22 turns on. When the second switching element 22 is turned on, the electric charge charged in the capacitor 26 is discharged through the resistor 24 and the second switching element 22, and the output of the operational amplifier 25 is as shown in FIG. , And its output is input to the comparators 33 and 34. At this time, the output of the operational amplifier 25 is
When it is higher than the reference value of 1, the output of the comparator 33 becomes low level and the diode 35 is turned on. Accordingly, the output of the OR circuit 38 turns on as shown in FIG. 2D, and the output of the OR circuit 38 becomes a drive command signal for the high-frequency converter 4 to output a high-frequency AC from the high-frequency converter 4. Further, the forward drive command signal is input to the power switching elements 11 and 14 of the switching circuit 8 until the output signal of the operational amplifier 25 changes from positive to 0, and the power switching 11 and 14 continue to be turned on. As shown in (e), the forward current continues to flow through the Peltier element of the load. Next, the output of the operational amplifier 25 is supplied to the reference power supply 31.
Becomes lower than the reference value, the output of the comparator 33 becomes high level and the diode 35 is turned off. On the other hand, the operational amplifier 2
5 is higher than the reference value of the reference power supply 32, the comparator 3
4 is at a high level, and the diode 36 is off. Therefore, the OR circuit is off as shown in FIG. Since the output of the OR circuit 38 is off, the high-frequency converter 4 is off and outputs 0.
Therefore, the output of the switching circuit 8 is off as shown in FIG. Further, when the output of the operational amplifier 25 becomes lower than the reference value of the reference power supply 32, the output of the comparator 34 becomes low and the diode 36 is turned on. Accordingly, the output of the OR circuit 38 is turned on as shown in FIG. 2D, and the output of the OR circuit becomes a drive command signal for the high-frequency converter 4 and the high-frequency converter 4 outputs high-frequency AC. On the other hand, the output signal of the operational amplifier 25 changes from 0 to negative, a reverse drive command signal is input to the switching circuit 8, and the power switching elements 12 and 13 are turned on.
As shown in (e), a reverse current flows through the Peltier element of the load. As described above, when the drive command signal of the switching circuit 8 is switched from the reverse direction to the forward direction or from the forward direction to the reverse direction, the high-frequency converter 4 is turned off during the period T. Therefore, no DC voltage is applied to the switching circuit. For this reason, even if a command signal is erroneously input to the power switching elements connected in series in the switching circuit 4, no current flows through the power switching elements and there is no risk of destruction. As described above, according to the Peltier device driving device of the present invention, when the switching circuit is switched, the high-frequency converter is turned off for a short period of time and no DC voltage is applied to the switching circuit. Even if a drive command signal is erroneously input to the power switching elements connected in series, no current flows through the power switching elements and there is no risk of damage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of an embodiment of a Peltier device driving circuit according to the present invention. FIG. 2 is a time chart of each part in FIG. 1; FIG. 3 is a schematic block diagram of a conventional Peltier device drive circuit. [Description of Signs] 2 Input-side rectifier 4 High-frequency converter 5 Transformer 6 Output-side rectifier 8 Switching circuit 11, 12, 13, 14 Power switching element 20 Drive circuit 21 (First) Signal switching element 22 (Second ) Signal switching elements 23, 24 Resistance 25 Operational amplifier 26 Capacitor 27 Integrator 31, 32 Reference power supply 33 (First) comparator 34 (Second) comparator 35, 36 Diode 38 OR circuit 40 Inverter

Claims (1)

(1) A high-frequency converter that performs high-frequency switching of a rectified DC of an AC power supply and outputs a high-frequency AC,
A transformer for transforming the high-frequency AC, an output rectifier for rectifying the transformed high-frequency AC, and a switching circuit for switching the current flowing from the DC output of the output rectifier to the Peltier element of the load using a power switching element. When the drive circuit for driving the high-frequency converter receives a forward drive command signal and a reverse drive command signal,
A first signal switching element and a second signal switching element that are respectively turned on, and an output when the first signal switching element is on, provided at outputs of the first and second signal switching elements. Rises, the output falls when the second signal switching element is on, the integrator serving as a switching command signal for the switching circuit, and the output of the integrator are provided with a positive reference signal and a negative reference signal, respectively. A first comparator and a second comparator for comparing with a reference signal of
When the output of the integrator is smaller than the positive reference signal and when the output of the integrator is larger than the negative reference signal, the drive signal is stopped from the first comparator and the second comparator to the high frequency converter. A Peltier element driving circuit, comprising: