JP5937985B2 - Dielectric device and method for controlling dielectric device - Google Patents

Description

  The present invention relates to a dielectric device and a method for controlling a dielectric device.

  Various functions are developed by applying an alternating voltage such as a sine wave to a dielectric such as an electro-optic crystal or an electrostrictive crystal. For example, in Non-Patent Document 1, an electro-optic crystal is arranged in an optical resonator, and a wavelength swept light source is realized by applying a 150 kHz sine wave voltage to the electro-optic crystal.

Shogo Yagi, Tadayuki Imai, Yasuo Shibata, Shigeo Ishibashi, Masahiro Sasaura, Kazutoshi Kato, Kazunori Naganuma, Yuzo Sasaki, and Kazuo Fujiura, “A mechanical-free 150-kHz repetition swept light source incorporated a KTN electro-optic deflector”, Proc of SPIE, 2011, Vol. 7889, 78891J-1 to 78891J-6 Masahiro Ueno and five others, "Power consumption of 200 kHz optical deflector for OCT using KTN crystal", Proceedings of Electronics Lecture 1, Electronics Society Conference of IEICE, 2012, p.124

However, when a high-frequency, large-amplitude AC voltage is continuously applied to the dielectric, heat is generated in the dielectric and the temperature of the dielectric rises. For example, Non-Patent Document _{2, KTa 1-x Nb x} O 3 crystal 200kHz, when applying an AC voltage of 600Vpp (peak to peak voltage), the power consumption of KTa _1-x Nb x O ₃ crystal about It is 1 W, and it is noted that the temperature rises.

  FIG. 6 shows a configuration of a conventional dielectric device 600. In the conventional dielectric device 600 shown in FIG. 6, the dielectric 601 is interposed between the upper metal electrode block 602 and the lower metal electrode block 603 so that the dielectric 601 is sandwiched between the upper metal electrode block 602 and the lower metal electrode block 603. Is provided. A temperature sensor 604 and a Peltier element 605 are attached to the lower metal electrode block 603. A heat sink 606 is attached to the Peltier element 605. A power source 608 is connected to the upper metal electrode block 602 and the lower metal electrode block 603, and a Peltier controller 607 is connected to the temperature sensor 604 and the Peltier element 605.

  A temperature sensor 604 attached to the lower metal electrode block 603 measures the temperature of the lower metal electrode block 603. The Peltier controller 607 performs control to keep the temperature of the lower metal electrode block 603 at a predetermined set temperature. Specifically, the Peltier controller 607 controls the temperature of the lower metal electrode block 603 by adjusting the current passed through the Peltier element 605, thereby controlling the temperature of the dielectric 601. When the dielectric 601 is not generating heat, the temperature of the lower metal electrode block 603 (set temperature) and the temperature of the dielectric 601 are approximately equal.

  However, when an AC voltage is applied to the dielectric 601 via the upper metal electrode block 602 and the lower metal electrode block 603 by the power source 608, the dielectric 601 generates heat. In such a case, the temperature of the dielectric 601 becomes higher than the set temperature of the temperature sensor 604 due to the thermal resistance of the dielectric 601 itself and the thermal resistance between the dielectric 601 and the lower metal electrode block 603. This is shown in FIG.

  FIG. 7 shows the relationship between the voltage applied to the dielectric and the temperature of the dielectric. As shown in FIG. 7, when an AC voltage is applied to the dielectric, the temperature of the dielectric gradually becomes higher than the set temperature as time elapses.

  FIG. 8 shows an example of the temperature dependence of the dielectric constant of the dielectric. As shown in FIG. 8, the dielectric constant decreases as the temperature of the dielectric increases. That is, when the temperature of the dielectric increases, the capacitance of the dielectric decreases. This is undesirable if a large dielectric constant is required.

  For example, in the optical deflector used in the wavelength swept light source disclosed in Non-Patent Document 1, since the deflection angle is proportional to the dielectric constant, there is a problem that the decrease in the deflection angle, that is, the wavelength sweep width is caused by the decrease in the dielectric constant. there were. Further, in the electro-optical device other than the optical deflector, since the secondary electro-optic coefficient is proportional to the square of the dielectric constant, there is a problem that the electro-optic effect is reduced when the dielectric constant is reduced.

  As a means for obtaining a large dielectric constant in a dielectric having the characteristics shown in FIG. 8, it is conceivable to lower the temperature of the dielectric in advance. However, if the temperature drops as a result of lowering the temperature in order to obtain a large dielectric constant, the dielectric changes from the paraelectric phase to the ferroelectric phase, and the dielectric is damaged by voltage application. After that, there was a problem that voltage could not be applied.

  FIG. 9 shows the temperature dependence of the dielectric constant of the dielectric near the ferroelectric-paraelectric phase transition. As shown in FIG. 9, many dielectrics have a large dielectric constant in the vicinity of the ferroelectric-paraelectric phase transition point. In order to obtain a dielectric constant larger than that obtained at the dielectric temperature Tx, when the dielectric temperature is lowered to a temperature Ty (dielectric phase transition temperature Tc <Ty <Tx), the temperature Ty is the phase. When the temperature is in the vicinity of the transition temperature Tc, the dielectric constant increases rapidly when the temperature is lowered, and the dielectric constant becomes very large in the vicinity of the ferroelectric-paraelectric phase transition point. There is a problem that the AC power source cannot operate and the AC voltage cannot be applied by the resonance type power source.

  Here, an exemplary configuration of a resonance type power supply will be described with reference to FIG. A resonance type power supply is a power supply that generates a sine wave voltage, and generates a sine wave by inputting a rectangular wave into a resonance circuit. As illustrated in FIG. 10, the resonance type power supply 1000 includes a rectangular wave generation unit 1001, a part of the resonance circuit 1003, and output ports 1002-1 and 1002-2. The output ports 1002-1 and 1002-2 are connected to the dielectric 1004. A resonance circuit 1005 is formed by a part 1003 of the resonance circuit and the dielectric 1004.

  The resonance circuit 1005 has a resonance angular frequency ω0. Further, if the repetitive angular frequency of the rectangular wave generated by the rectangular wave generating unit 1001 is ωs, the cycle is 2π / ωs as shown in the upper diagram of FIG. here,

Since the angular frequency ωs component is extracted from the rectangular wave, a sine wave voltage having the angular frequency ωs can be applied to the dielectric 1004 as shown in the lower diagram of FIG.

  FIG. 12 shows the temperature dependence of the dielectric constant of the dielectric in the vicinity of the ferroelectric-paraelectric phase transition and the range of the dielectric constant at which the resonance type power supply operates. As shown in FIG. 12, when the temperature of the dielectric is Tz (Tc <Tz <Tx), the dielectric constant becomes very large, so that the capacitance becomes very large. When a high-frequency, large-amplitude AC voltage is continuously applied to the dielectric device, heat is generated in the dielectric, the temperature becomes Tz + ΔT, and the dielectric constant decreases. That is, the capacitance decreases.

  Here, as shown in FIG. 12, since the resonance type power supply does not operate unless the capacitance of the connected dielectric is within a predetermined range, the dielectric constant (or capacitance) is increased in the process of increasing the temperature. ) Drastically decreases, and when the dielectric capacitance deviates from the predetermined range, no voltage is applied to the dielectric.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a dielectric device capable of reliably applying an alternating voltage to a dielectric and obtaining a large dielectric constant. It is in providing the control method.

A dielectric device according to claim 1 of the present invention includes a dielectric provided between an upper electrode block and a lower electrode block, a Peltier element, and a path of heat flowing between the dielectric and the Peltier element. A temperature sensor disposed in the middle of the temperature sensor, a Peltier controller connected to the temperature sensor and the Peltier element, and controlling the temperature of the temperature sensor using the Peltier element, via the upper electrode block and the lower electrode block wherein a power supply of resonant for applying a voltage to the dielectric, the dielectric device and a said Peltier controller and connected to said power source of the resonance controller Te, the control unit, the measured temperature of the temperature sensor After the first command is sent to the Peltier controller so that becomes the first set temperature, and the measured temperature becomes the first set temperature An AC voltage feeding the second instruction to the power of the resonant to apply to the dielectric, the amplitude of the predetermined or between the alternating voltage amplitude of the AC voltage is gradually increased to a predetermined amplitude After the amplitude is increased , the third command is sent to the Peltier controller so that the measured temperature becomes the second set temperature, and the first set temperature is set to the dielectric before the application of the AC voltage. Is higher than a phase transition temperature at which the dielectric transitions from a paraelectric phase to a ferroelectric phase so that the dielectric is paraelectric, after the application of the AC voltage. a temperature to maintain the phase, the rather low than the first predetermined temperature, said second set temperature, characterized in that a temperature in the range of power of the resonant operates.

A dielectric device according to a second aspect of the present invention is the dielectric device according to the first aspect of the present invention, wherein the control unit sends a DC voltage to the dielectric after sending the first command. A fourth command is sent to the resonance type power supply so as to be applied, a charge is injected into the dielectric, and then the second command is sent.

A dielectric device according to a third aspect of the present invention is the dielectric device according to the first or second aspect of the present invention, wherein the dielectric is potassium tantalate niobate (KTa _1-x Nb _x O ₃ ( 0 <x <1)) crystal, or lithium from the doped _{(K 1-y Li y Ta} 1-x Nb x O 3 (0 <x <1,0 <y <0.1)) crystal KTN It is configured.

According to a fourth aspect of the present invention, there is provided a dielectric provided between the upper electrode block and the lower electrode block, a Peltier element, and a path of heat flowing between the dielectric and the Peltier element. A temperature sensor disposed in the Peltier controller, connected to the temperature sensor and the Peltier element, and controlling the temperature of the temperature sensor using the Peltier element, and via the upper electrode block and the lower electrode block A method of controlling a dielectric device comprising: a resonance type power supply for applying a voltage to a dielectric; and a control unit connected to the Peltier controller and the resonance type power supply, wherein the control unit includes the temperature A step of sending a first command to the Peltier controller so that the measured temperature of the sensor becomes a first set temperature; After a serial first set temperature, and sending a second instruction to the AC voltage to the power supply of resonant to apply to the dielectric, the control section, the amplitude of the AC voltage given Sending a third command to the Peltier controller so that the measured temperature becomes a second set temperature while gradually increasing the amplitude or after increasing the amplitude of the AC voltage to the predetermined amplitude The first set temperature is higher than a phase transition temperature at which the dielectric transitions from a paraelectric phase to a ferroelectric phase so that the dielectric is a paraelectric phase before application of the AC voltage. the second predetermined temperature is a temperature at which the dielectric after application of the AC voltage to maintain the paraelectric phase, the rather low than the first predetermined temperature, the second set temperature is the resonance this power of the mold is at a temperature in the range that works The features.

A method according to claim 5 of the present invention is the method according to claim 4 of the present invention, wherein after the step of sending the first command and before the step of sending the second command, the control unit The method further comprises the step of sending a fourth command to the resonant power supply to apply a DC voltage to the dielectric to inject charge into the dielectric.

The method according to claim 6 of the present invention is the method according to claim 4 or 5 of the present invention, wherein the dielectric is potassium tantalate niobate (KTa _1-x Nb _x O ₃ (0 <x < 1)) crystal, or doped with lithium _{KTN (K 1-y Li y} Ta 1-x Nb x O 3 (0 <x <1,0 <y <0.1)) and a crystal It is characterized by that.

  According to the dielectric device and the control method thereof according to the present invention, the dielectric becomes a ferroelectric phase by lowering the temperature of the dielectric after starting the application of the AC voltage with the dielectric set to a predetermined temperature. Thus, it is possible to reliably apply an AC voltage to the dielectric, and to obtain a remarkable effect that the dielectric constant can be increased. In addition, since the electro-optic effect increases as the dielectric constant increases, the remarkable effect that the applied voltage of the dielectric device can be reduced can be achieved. Furthermore, since the dielectric constant of the dielectric can be kept within a predetermined range, there is a remarkable effect that a voltage can be reliably applied to the dielectric even when a resonance type power supply is used. Can do.

It is the figure which showed the structure of the dielectric device of this invention. FIG. 4 is a diagram showing temperature dependency of dielectric constant of a dielectric and an operating range of a resonance type power supply in the present invention. It is the figure which showed the flow of control in the dielectric material based on this invention. In the dielectric device according to the present invention, it is a diagram illustrating a case where the amplitude of the alternating voltage is gradually increased and the set temperature is lowered after reaching the desired amplitude. In the dielectric device according to the present invention, it is a diagram for explaining a case where the amplitude of the AC voltage is gradually increased and the set temperature is lowered before reaching the desired amplitude. It is the figure which showed the structure of the conventional dielectric device. It is the figure which showed the relationship between the voltage applied to a dielectric material, and the temperature of a dielectric material. It is the figure which showed an example of the temperature dependence of the dielectric constant of a dielectric material. It is the figure which showed the temperature dependence of the dielectric constant of a dielectric material. It is a figure which shows the structure of a resonance type power supply. It is a figure which shows the relationship between the voltage which the short wave generation part of a resonance type power supply produces | generates, and the voltage applied to a dielectric material. It is the figure which showed the temperature dependence of the dielectric constant of a dielectric material, and the operating range of a resonance type power supply.

  FIG. 1 shows a configuration of a dielectric device 100 according to the present invention. As shown in FIG. 1A, in the dielectric device 100 according to the present invention, the upper metal electrode block 102 and the lower metal so that the dielectric 101 is sandwiched between the upper metal electrode block 102 and the lower metal electrode block 103. It is provided between the electrode block 103. Although not shown in FIG. 1A, an insulator may be further provided between the upper metal electrode block 102 and the lower metal electrode block 103. A temperature sensor 104 that measures the temperature of the lower metal electrode block 103 and a Peltier element 105 that adjusts the temperature of the lower metal electrode block 103 are attached to the lower metal electrode block 103. A heat sink 106 is attached to the Peltier element 105. A power source 108 is connected to the upper metal electrode block 102 and the lower metal electrode block 103, a Peltier controller 107 is connected to the temperature sensor 104 and the Peltier element 105, and a control unit 109 is connected to the Peltier controller 107 and the power source 108. Yes. FIG. 1A shows a configuration in which the temperature sensor 104 is attached to the lower metal electrode block 103, but an insulator is provided between the upper metal electrode block 102 and the lower metal electrode block 103. In the above, the temperature sensor 104 may be attached to the upper metal electrode block 102. Further, an insulator may be provided between the Peltier element 105 and the lower metal electrode block 103, and the temperature sensor 104 may be attached to the insulator. The temperature sensor 104 only needs to be in the middle of a path of heat flowing between the dielectric 101 and the Peltier element 105.

  FIG. 1 (b) shows another configuration 100 'of a dielectric device according to the present invention. As shown in FIG. 1B, Peltier elements 105 may be attached to both the upper metal electrode block 102 and the lower metal electrode block 103. Further, an insulator may be provided between the upper metal electrode block 102 and the lower metal electrode block 103 and the Peltier element 105, and the temperature sensor 104 may be attached to the insulator. Similarly, in the other configuration 100 ′ of the dielectric device shown in FIG. 1B, the temperature sensor 104 may be in the middle of the path of the heat flowing between the dielectric 101 and the Peltier element 105.

  The Peltier controller 107 can control the temperature of the lower metal electrode block 103 by controlling the current flowing through the Peltier element 105. The power supply 108 can apply a voltage to the dielectric 101 via the upper metal electrode block 102 and the lower metal electrode block 103. The control unit 109 controls the Peltier controller 107 and the power source 108 as will be described later.

  A control flow in the dielectric device 100 according to the present invention will be described with reference to FIGS. As shown in FIG. 3, in step 301, the control unit 109 sends a first command to the Peltier controller 107 so that the temperature of the temperature sensor 104 becomes the first set temperature T0. Upon receiving the first command, the Peltier controller 107 adjusts the temperature using the Peltier element 105 so that the temperature of the temperature sensor 104 becomes T0, whereby the temperature of the dielectric 101 also becomes T0.

  Next, in step 302, the control unit 109 sends a second command to the power supply 108 so as to start application of the AC voltage. The power supply 108 that has received the second command applies an AC voltage to the dielectric 101 via the upper metal electrode block 102 and the lower metal electrode block 103. After application of the AC voltage, the temperature of the dielectric 101 rises by ΔT0 due to heat generation of the dielectric 101, and the temperature of the dielectric 101 becomes T0 + ΔT0 as shown in FIG. Further, as the temperature of the dielectric 101 increases, the dielectric constant of the dielectric 101 decreases and the capacitance decreases.

  Next, in Step 303, the control unit 109 sends a third command to the Peltier controller 107 so that the temperature of the temperature sensor 104 becomes the second set temperature T1 (<T0). The Peltier controller 107 having received the third command adjusts the temperature using the Peltier element 105 so that the temperature of the temperature sensor 104 becomes T1, thereby lowering the temperature of the dielectric 101 by ΔT1 and the temperature of the dielectric 101 Becomes T0 + ΔT0−ΔT1. Further, as the temperature of the dielectric 101 decreases, the dielectric constant of the dielectric 101 increases and the capacitance increases. Note that the temperature sensor cannot measure ΔT0 and ΔT1. Therefore, it should be noted that the temperature sensor 104 cannot measure the temperature T0 + ΔT0−ΔT1 of the dielectric 101.

  In addition, after sending the first command, the control unit 109 sends a fourth command to the power supply 108 so as to apply a DC voltage to the dielectric 101 and injects electric charge into the dielectric 101, It may be configured to send instructions.

  T1 can be selected to satisfy ΔT0 = ΔT1, for example. In that case, the temperature of the dielectric 101 is T0 + ΔT0−ΔT0 = T0. However, it is not always necessary to set ΔT0 = ΔT1. Even if a voltage is applied when the temperature of the temperature sensor 104 is lowered to T1, the crystal is not damaged.

  Further, as the power source 108, a resonance type power source as exemplified in FIG. 10 can be used. In that case, the dielectric constant (capacitance) of the dielectric 101 when the temperature of the temperature sensor 104 is lowered to T1 in step 303 is within the range where the resonance type power supply operates, and the crystal must be damaged. It ’s fine. In FIG. 2, the case of Tc <T1 is shown, but T1 <Tc may be satisfied. That is, even if the temperature T1 of the temperature sensor 104 is lower than Tc, the temperature T0 + ΔT0−ΔT1 of the dielectric 101 can be higher than Tc.

In the dielectric device 100 shown in FIG. 1A, a KTa _1-x Nb _x O ₃ crystal (4.0 × 3.2 × 1.0 mm, x = 0.4) is used as the dielectric 101. . The first set temperature T0 was set to 51.8 ° C., which is the temperature at which the dielectric constant becomes 17500 and the crystal structure becomes cubic (paraelectric phase). A Ti electrode was deposited on a 4.0 mm × 3.2 mm surface, and a KTa _1-x Nb _x O ₃ crystal was sandwiched between the upper metal electrode block 102 and the lower metal electrode block 103. In this case, the capacitance of the dielectric 101 is 8.854 * 10 ⁻¹² * 17500 * 4.0 * 10 ⁻³ * 3.2 * 10 ⁻³ /(1.0*10 ⁻³ ) = 1.98 nF. is there.

After allowing light having a wavelength of 1.3 μm to enter the dielectric 101, applying a DC voltage (+300 V (10 seconds), −300 V (10 seconds)), and injecting electrons into the KTa _1-x Nb _x O ₃ crystal When a sinusoidal voltage having a frequency of 350 kHz and 600 V (peak-to-peak) was applied to the dielectric 101, the deflection angle of the emitted light was 39.6 mrad. When the second set temperature T1 = 48.8 ° C. was applied after applying the sine wave voltage, the deflection angle was 55.2 mrad. When the second set temperature T1 = 45.8 ° C. was applied after the sine wave voltage was applied, the deflection angle was 69.9 mrad. When the second set temperature T1 = 44.8 ° C. was applied after the sine wave voltage was applied, the deflection angle was 75.0 mrad.

  FIG. 4 shows the dielectric device 100 according to the first embodiment applied to the dielectric when the set temperature is lowered after gradually increasing the amplitude of the AC voltage (sinusoidal voltage) to reach the desired amplitude. It is the figure which showed the relationship between the voltage to be performed and preset temperature. Here, the reason why the amplitude is gradually increased is that, by adopting such a method, a rapid heat generation / temperature rise of the dielectric 101 is suppressed, so that temperature control by the control unit 109 becomes easy. is there.

  FIG. 5 shows an application to the dielectric in the dielectric device 100 according to the first embodiment when the set temperature is decreased before the amplitude of the AC voltage (sine wave voltage) is gradually increased to reach the desired amplitude. It is the figure which showed the relationship between the voltage to be performed and preset temperature. The timing for lowering the set temperature may be before or after the voltage reaches the desired amplitude as long as the crystal is not damaged. Further, when using a resonance type power supply, the timing for lowering the set temperature is such that the dielectric constant (capacitance) of the dielectric 101 is within the range in which the resonance type power supply operates and the crystal is not damaged. It may be before or after the voltage reaches the desired amplitude.

In the dielectric device 100 according to the first embodiment, KTa _1-x Nb _x O ₃ crystal (x = 0.4) is used as the dielectric 101, but other x (0 <x <1) Alternatively, KTa _1-x Nb _x O ₃ crystal may be used. Alternatively, the dielectric 101 may be a K _1-y Li _y Ta _1-x Nb _x O ₃ crystal (0 <y <1, 0 <x <1).

101, 601, 1004 Dielectric 102, 602 Upper metal electrode block 103, 603 Lower metal electrode block 104, 604 Temperature sensor 105, 605 Peltier element 106, 606 Heat sink 107, 607 Peltier controller 108, 608 Power supply 109 Control unit 1000 Resonance type Power source 1001 rectangular wave generator 1002 output port 1003 part of resonant circuit 1005 resonant circuit

Claims (6)

A dielectric provided between the upper electrode block and the lower electrode block;
Peltier element,
A temperature sensor disposed in the middle of a path of heat flowing between the dielectric and the Peltier element;
A Peltier controller connected to the temperature sensor and the Peltier element and controlling the temperature of the temperature sensor using the Peltier element;
A resonant power source for applying a voltage to the dielectric through the upper electrode block and the lower electrode block;
A dielectric device comprising: the Peltier controller and a control unit connected to the resonance type power supply.
The controller sends a first command to the Peltier controller so that the measured temperature of the temperature sensor becomes a first set temperature, and after the measured temperature becomes the first set temperature, A second command is sent to the resonance type power supply so as to be applied to the dielectric and the amplitude of the AC voltage is gradually increased to a predetermined amplitude or the amplitude of the AC voltage is set to the predetermined amplitude. After increasing, a third command is sent to the Peltier controller so that the measured temperature becomes the second set temperature,
The first set temperature is higher than a phase transition temperature at which the dielectric transitions from a paraelectric phase to a ferroelectric phase so that the dielectric is a paraelectric phase before application of the AC voltage,
The second predetermined temperature, the dielectric after application of the AC voltage is a temperature to maintain the paraelectric phase, rather lower than the first predetermined temperature,
The dielectric device according to claim 2, wherein the second set temperature is a temperature in a range where the resonance type power supply operates . The controller, after sending the first command, sends a fourth command to the resonance type power supply so as to apply a DC voltage to the dielectric, and injects charges into the dielectric, The dielectric device of claim 1, wherein the second command is sent. The dielectric is a potassium tantalate niobate (KTa _1-x Nb _x O ₃ (0 <x <1)) crystal, or KTN doped with lithium (K _1-y Li _y Ta _1-x Nb _{x 3.} The dielectric device according to claim 1, wherein the dielectric device is made of an O ₃ (0 <x <1, 0 <y <0.1) crystal. A dielectric provided between the upper electrode block and the lower electrode block;
Peltier element,
A temperature sensor disposed in the middle of a path of heat flowing between the dielectric and the Peltier element;
A Peltier controller connected to the temperature sensor and the Peltier element and controlling the temperature of the temperature sensor using the Peltier element;
A resonant power source for applying a voltage to the dielectric through the upper electrode block and the lower electrode block;
A method of controlling a dielectric device comprising: the Peltier controller and a control unit connected to the resonant power source,
The controller sends a first command to the Peltier controller so that the temperature measured by the temperature sensor becomes a first set temperature;
The controller sends a second command to the resonant power supply to apply an AC voltage to the dielectric after the measured temperature reaches the first set temperature;
While the controller gradually increases the amplitude of the AC voltage to a predetermined amplitude or after increasing the amplitude of the AC voltage to the predetermined amplitude, the measured temperature becomes the second set temperature. Sending a third command to the Peltier controller,
The first set temperature is higher than a phase transition temperature at which the dielectric transitions from a paraelectric phase to a ferroelectric phase so that the dielectric is a paraelectric phase before application of the AC voltage,
The second predetermined temperature, the dielectric after application of the AC voltage is a temperature to maintain the paraelectric phase, rather lower than the first predetermined temperature,
2. The method according to claim 1, wherein the second set temperature is a temperature in a range where the resonance type power supply operates . After the step of sending the first command and before the step of sending the second command, the control unit applies a DC voltage to the dielectric to inject charge into the dielectric. The method of claim 4 , further comprising sending a fourth command to the resonant power source. The dielectric is a potassium tantalate niobate (KTa _1-x Nb _x O ₃ (0 <x <1)) crystal, or KTN doped with lithium (K _1-y Li _y Ta _1-x Nb _{x O 3 (0 <x <1,0} <y <0.1)) the method of claim 4, characterized in that it is composed of crystals.

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