JPH11136958A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the stress of a switching element by reducing the current change rate of the switching element, to reduce ON loss by reducing the effective value of a current, and, furthermore, to maintain the input voltage waveform of a piezoelectric transformer in nearly a sinusoidal waveform, even when ambient temperature widely changes in a pull/push-type inverter device using the piezoelectric transformer. SOLUTION: In an inverter device provided with a DC power supply E, a pair of switching elements Q1 and Q2 that are alternately turned on and allow a current to alternately flow from the DC power supply E to an inductance element, a piezoelectric transformer 1 where electromotive force being generated at the inductance element is inputted by the switching operation, and a load 2 connected to the output of the piezoelectric transformer, capacitors CS1 and CS2 are connected between the terminal of a side that is not connected to the DC power supply E of the inductance element and at least one end of the DC power supply E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device using a piezoelectric transformer.

[0002]

2. Description of the Related Art In general, a piezoelectric transformer is a voltage conversion element that generates mechanical vibration by utilizing a piezo effect of a piezoelectric element and takes out a voltage converted to a secondary electrode side. It is a device that has attracted attention as a power source for backlights such as liquid crystals. Japanese Patent Application Laid-Open No. 8-275553 discloses an example of a driving circuit for a piezoelectric element of this type that can operate in a wide input voltage range and is suitable for miniaturization and thinning.

In this conventional example, as shown in FIG. 11, an electromagnetic transformer T ₁ , T
₂ are connected to each other, and the switching elements Q ₁ , Q ₂
Are turned on alternately, and one of the electromagnetic transformers T ₁ and T ₂
A current flows from the power supply E to the next side, and is charged as current energy. When the switching elements Q ₁ and Q ₂ are turned off, the charged energy is released, and a voltage higher than the power supply voltage is generated as voltage energy. This is FIG.
Vd ₁ and Vd ₂ in (a) and FIG. 12 (b), which are about three times the peak voltage of the power supply voltage E. These voltages Vd ₁ , V
d ₂ is the secondary side of the electromagnetic transformers T ₁ and T ₂ , as shown in FIG.
And will be converted to Vs _1, Vs ₂ in FIG. 12 (d), the turns ratio of the electromagnetic transformer T _1, T _{2 1:} When N, approximately 3 (N + 1) voltage of E [Vp-p] Peak. Since this pulse is alternately input to the input electrodes of the piezoelectric transformer 1, the pulse is equivalent to a sine wave of about 6 (N +
1) The piezoelectric transformer 1 is vibrated as a drive voltage of E [Vp-p].

FIG. 13 is an equivalent circuit viewed from the input side of the piezoelectric transformer 1. The load 2 converts a resistance component and a capacitance component of a cold cathode tube into a primary side of an ideal transformer in the equivalent circuit of the piezoelectric transformer 1. expressing. The waveforms of the current flowing through the piezoelectric transformer 1 and the electromagnetic transformers T ₁ and T ₂ will be described with reference to FIGS.

In FIG. 14A, the switching element Q ₁ is turned on and the switching element Q ₂ is turned off from t ₁ to t.
The current in the _second time will be described. First, the current charged before t ₁ generates a voltage resonance waveform on the primary side of the electromagnetic transformer T ₂ , which is further boosted on the secondary side. Thus, current Is ₂ in FIG. 14 (d) flows through the piezoelectric transformer 1 and the load 2, through the switching element Q ₁ from the secondary side of the electromagnetic transformer T _1. This current waveform is t
Set the capacitance of the electromagnetic transformer, piezoelectric transformer, and load so that the value becomes zero at ₂ .

Further, the primary inductance Lp ₁ electromagnetic transformer T _1, linearly current It flows which increases in proportion to the switching time, the same time electromagnetic transformer T
_On the primary side of 1, a current Is ₂ ′ whose turn ratio is N times higher by the current Is ₂ described above flows. Therefore, the switching element Q ₁ includes It, Is ₂ , Is
It will be synthesized current of ₂ 'flows, a lid-like current waveform Id ₁ grand piano shown in FIG 14 (b). Further, since a combined current of It and Is ₂ ′ flows on the primary side of the electromagnetic transformer T ₁ , the waveform is as shown in FIG. Then, past the t _2, the switching element Q ₁ is turned off, the switching element Q ₂ is turned on, current Is ₂
Flows in the opposite direction. Primary current Ip of the electromagnetic transformer T _1
1 Beyond t _2, the switching element Q ₁ is no current, It, is Ip ₂ 'becomes zero, the secondary I
It s ₁ flows.

[0007]

However, in the above-mentioned conventional example, the excitation current, the resonance current, and the load current of the inductance element all flow through the switching element peculiar to the push-pull circuit, and as shown in FIG. , current Id ₁ flowing through the switching element Q ₁ is, has become particularly large at the timing of t ₁ immediately after the switching element Q ₁ is the turns, di / dt is large, so that stress the switching element Q _1.

Further, the waveform of the current Id ₁ flowing through the switching element Q _1, the effective value is large in a lid-like current waveform of a grand piano, a large on loss of the switching element. For this reason, heat generation of the switching element increases.

The equivalent input capacitance Cd ₁ of the piezoelectric transformer
Varies greatly with changes in ambient temperature. For example, 1
With a change of 50 ° C., Cd ₁ changes by about ± 30%. Therefore, in the conventional example, when the ambient temperature changes, the piezoelectric transformer equivalent input capacitance Cd ₁ is changed, FIG. 12 (a) ~
Duration of _{Vd 1, Vd 2, Vs 1} , Vs 2 of the waveform of (d) is changed. These are Vd ₁ , Vd ₂ , Vd
This is because s ₁ and Vs ₂ are voltage resonance waveforms formed by the total inductance of the equivalent input capacitance Cd ₁ of the piezoelectric transformer, the primary inductance Lp on one side of the electromagnetic transformer, and the secondary inductance Ls. For example, if the ambient temperature becomes too high, the equivalent input capacitance Cd of the piezoelectric transformer
_{When 1} is increased by several tens of percent, the switching elements Q ₁ ,
The drain-source voltages Vd ₁ and Vd ₂ of Q ₂ are shown in FIG.
As shown in FIG. 5, during the off-period, the voltage cannot return to zero voltage, and the surge current flows immediately after the turn-on, thereby causing stress on the switching elements Q ₁ and Q ₂ and an increase in loss. On the other hand, when the ambient temperature becomes too low, the equivalent input capacitance Cd ₁ of the piezoelectric transformer becomes several tens%.
Also decreases, the drain-source voltages Vd ₁ , Vd ₂ of the switching elements Q ₁ , Q ₂ become as shown in FIG.
During the time until the switching element turns on after the voltage becomes zero in the middle of the off period, the switching elements Q ₁ ,
Current flows through the parasitic diode of Q _2, is clamped to zero voltage. As a result, extra current flows through the switching element and the electromagnetic transformer, causing an increase in loss (increase in heat generation).

In FIGS. 15 and 16, in each case, the voltage Vs ₁ -Vs ₂ input to both ends of the piezoelectric transformer has a waveform distorted compared to a sine wave, and the loss of the piezoelectric transformer increases. And causes an increase in harmonic noise.

In the conventional example, when the operation of the switching element is stopped and the oscillation is stopped in order to protect the circuit, the energy accumulated in the primary inductance Lp of the electromagnetic transformer is reduced by the parasitic capacitance Cp of the switching element.
However, there is a problem that a very large surge voltage is applied to the switching element due to emission through Cp≪Cd ₁ .

[0012]

According to the inverter apparatus of the present invention, in order to solve the above-mentioned problems, as shown in FIG.
The intermediate terminal is connected to the earth terminal of the DC power source E via the first and _second switching elements Q ₁ and Q ₂ and the first and second switching elements Q ₁ and Q _2, and the primary terminal is The first and second auto transformers T ₁ , T ₂ connected to the non-earth side terminal of the DC power source E, and the secondary side terminals of the first and _second auto transformers T ₁ , T ₂ are first and second. Piezoelectric transformers 1 respectively connected to the second input terminals
And a load 2 connected between an output terminal of the piezoelectric transformer 1 and a ground terminal of the DC power supply E, wherein the first input terminal of the piezoelectric transformer 1 and the DC power supply E A first capacitor Cs ₁ connected to a ground terminal; and a second capacitor Cs ₂ connected between a second input terminal of the piezoelectric transformer 1 and a ground terminal of the DC power supply E. And characterized in that:

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Embodiment 1 of the present invention is shown in FIG. In the figure, 1
Is a piezoelectric transformer, 2 is a load, T ₁ and T ₂ are electromagnetic transformers, E is a DC power supply, and Q ₁ and Q ₂ are switching elements that are turned on and off alternately. The electromagnetic transformers T ₁ and T ₂ are auto-transformers with a turns ratio of 1: N, and the primary inductances are Lp ₁ and Lp ₂ , respectively, and the secondary inductances are Ls ₁ and Ls ₂ , respectively. Where Cd and the resonance frequency are fo, fo = 1 / 2πｐLp ₁ · (1 + N) ² (Cd + Cs ₁ ) fo = 1 / 2π√ ｛Lp ₂ · (1 + N) ² (Cd + Cs ₂ )｝ ... capacitor Cs ₁ and Cs ₂ satisfying is connected between each other of the line and the ground connecting the electromagnetic transformer T _1, T ₂ and the piezoelectric transformer 1, respectively.

Switching element Q₁, Q_TwoTurns on alternately
State, the electromagnetic transformer T₁, T _TwoDC power to the primary side of
Apply current from source E and charge as current energy
You. Switching element Q₁, Q_TwoIs turned off,
Energy that is stored in the
Voltage Vd higher than source voltage₁, Vd_TwoOccurs. Voltage V
d₁, Vd_TwoResonates under the condition of
Zero voltage for each half cycle time of 1 resonance frequency fo
Is a half wave of the sine wave.

Here, as shown in FIG.
Element Q₁Is on, switching element Q_TwoTurned off
For the case, the switching element Q₁Current Id flowing through
₁Will be described. FIG. 3 shows a current waveform. switch
Element Q₁Turns on and the switching element Q_TwoIs off
Time t₁To t_TwoWill be described.
First, t₁Electromagnetic truck
Once T_TwoA voltage resonance waveform is generated on the primary side of
The voltage is further boosted on the next side. At this time, the current Is _TwoIs piezoelectric
Not only transformer 1 and load 2 but also capacitor Cs_TwoAlso
Flows. At this time, the capacitor Cs_TwoThe current flowing through
cs_TwoThen, the current passing through the piezoelectric transformer 1 and the load 2 is
Is_Two-Ics_TwoAnd the electromagnetic transformer T₁Secondary side of
Switching element Q₁Flows through. Also, this current
Tte electromagnetic transformer T₁Turns ratio N times on the primary side of
Current Is_Two'-Ics_Two’Flows and the switching element Q
₁Flows through. The electromagnetic transformer T₁Primary side inductor
Tance Lp₁Linear in proportion to switching time
A current It that gradually increases flows. In other words, switching
Element Q₁Contains It, Is_Two-Ics_Two, Is_Two'-I
cs_Two′ Will flow, and the waveform of FIG.
Become.

[0016] The current Id ₁ flowing through the switching element Q ₁
Is that di / dt at time t ₁ is smaller than in the conventional example. Also, it has fallen also the effective value of the current Id _1. This capacitance of the capacitor Cs ₂ becomes larger than the input capacitance Cd of the piezoelectric transformer 1, larger current Ics ₂ flowing to the capacitor Cs _2, the effect is increased. After the time t ₂ , the switching element Q ₁ is turned off and the switching element Q ₂ is turned on to perform an operation symmetrical to the above, and the switching element Q ₂ has the current Id during the time from the time t ₁ to t _2. will _{be 1} and approximately equal current Id ₂ flows.

Thus, the switching element di / d
t stress can be reduced, the effective value of the current is lowered,
The ON loss of the switching element can be reduced, the temperature of the switching element is prevented from rising, and the size of the switching element is reduced.
The cost can be reduced.

In this embodiment, as shown in the equation, the capacitance component that resonates with the inductance component of the electromagnetic transformer is not limited to the input capacitance Cd of the piezoelectric transformer as in the conventional example, but is connected in parallel with the input capacitance Cd of the piezoelectric transformer. The combined capacitance C with the capacitor Cs ₁ or Cs ₂ (= Cd + Cs
₁ or Cd + Cs ₂ > Cd), and even if the input capacitance Cd of the piezoelectric transformer greatly changes due to a temperature change, the change of the combined capacitance C to which the capacitance of the capacitor Cs ₁ or Cs ₂ is added is equal to the input capacitance Cd. It can be smaller than the change. For example, when the input capacitance Cd is 2 nF and changes by ± 50% due to a temperature change (1 nF ≦ Cd ≦ 3 nF),
When Cs ₁ = Cs ₂ = 4 nF is connected, the combined capacitance C is 5 nF from C = Cd + Cs ₁ , 1 nF ≦ Cd ≦ 3 nF.
? Input capacitance Cd of piezoelectric transformer
On the other hand, the effect increases as the values of the capacitors Cs ₁ and Cs ₂ connected in parallel are increased. The input capacitance C of the piezoelectric transformer is defined as the capacitors Cs ₁ and Cs _2.
By using a ceramic capacitor having a characteristic opposite to the temperature characteristic of d, the temperature change of the combined capacitance C can be made substantially zero.

[0019] Thus, even if the change in the ambient temperature (due to parallel with the input capacitance Cd of the piezoelectric transformer capacitor Cs ₁ or Cs ₂₎ combined capacitance C that resonates with electromagnetic transformer inductance components can substantially constant, the piezoelectric transformer The voltage at both ends of the input is maintained as a sine wave, so that it is possible to prevent an increase in the loss and temperature of the piezoelectric transformer, the electromagnetic transformer, and the switching element, and to suppress noise.

In this embodiment, the circuit protection
The switching element Q₁And Q _TwoTurn off both
When the oscillation is stopped, the electromagnetic transformer T₁, T_TwoTo
The stored energy is switched
Element Q₁, Q_TwoIs released only through the stray capacitance Cp
And Cs₁, Cs_TwoIf> Cp, it is released
Voltage energy (surge voltage) peak value can be reduced
You. This reduces the withstand voltage of the switching element.
To reduce the size and cost of switching elements
You.

(Embodiment 2) FIG. 4 shows Embodiment 2 of the present invention. The circuit configuration of FIG. 4 is such that the capacitors Cs ₁ and Cs ₂ of the _first embodiment shown in FIG. 1 are connected between the respective intermediate taps of the electromagnetic transformers T ₁ and T ₂ and the ground, and the resonance frequency fo of the piezoelectric transformer is Satisfies fo = 1 / 2π {Lp _1. ((1 + N) ² Cd + Cs ₁ )} fo = 1 / 2π {Lp _2. ((1 + N) ² Cd + Cs ₂ )} The effects are the same as in the first embodiment. Compared to the first embodiment, the capacitors Cs ₁ and Cs ₂ have the electromagnetic transformers T ₁ and Ts
Because it is connected to the low voltage side of _2, a capacitor with low withstand voltage can be used.

(Embodiment 3) FIG. 5 shows Embodiment 3 of the present invention. The circuit configuration of FIG. 5 is such that the capacitors Cs ₁ and Cs ₂ of the _first embodiment shown in FIG. 1 are connected between the respective intermediate taps of the electromagnetic transformers T ₁ and T ₂ and the DC power supply E (the non-ground side terminal). The resonance frequency fo of the piezoelectric transformer is as follows: fo = 1 / 2π√ ｛Lp ₁ · ((1 + N) ² Cd + Cs ₁ )｝ fo = 1 / 2π√ ｛Lp ₂ · ((1 + N) ² Cd + Cs ₂ )を 満 た す… is satisfied. The effect is the same as in the first and second embodiments.

(Embodiment 4) FIG. 6 shows Embodiment 4 of the present invention. In the circuit configuration of FIG. 6, the capacitors Cs ₁ and Cs ₂ of the _first embodiment shown in FIG. 1 are connected to the secondary output terminals of the electromagnetic transformers T ₁ and T ₂ and the DC power supply E (the non-earth side terminal). Connected between them, and the resonance frequency fo of the piezoelectric transformer
Satisfies fo = 1 / 2π {Lp ₁ · (1 + N) ² (Cd + Cs ₁ )} fo = 1 / 2π {Lp ₂ · (1 + N) ² (Cd + Cs ₂ )} The effect is the same as that of the first embodiment.

(Embodiment 5) FIG. 7 shows Embodiment 5 of the present invention.
You. The circuit configuration of FIG. 7 is similar to that of the first embodiment shown in FIG.
Lance T₁, T_TwoChokes 11 and 12 (inductors
Is Lp respectively ₁, Lp_Two) And the capacitor C
s₁, Cs_TwoAnd the output side of each of the chokes 11 and 12
This is connected between the ground and the resonance frequency of the piezoelectric transformer.
The wave number fo is: fo = 1 / 2π√ ｛Lp₁・ (Cd + Cs₁)｝… Fo = 1 / 2π√ ｛Lp_Two・ (Cd + Cs_Two)｝… The effect is the same as that of the first embodiment.

(Embodiment 6) FIG. 8 shows Embodiment 6 of the present invention. The circuit configuration of FIG. 8 is such that the capacitors Cs ₁ and Cs ₂ of the fifth embodiment shown in FIG. 7 are connected between the output side of each of the chokes 11 and 12 and the (non-ground side terminal) E of the DC power supply E. Thus, the resonance frequency fo of the piezoelectric transformer satisfies fo = １ ／ π√ ｛Lp ₁ · (Cd + Cs ₁ )｝ fo = π√ ｛Lp ₂ · (Cd + Cs ₂ )｝. The effect is the same as that of the first embodiment.

(Embodiment 7) FIG. 9 shows Embodiment 7 of the present invention. The circuit arrangement of Figure 9, is composed of a switching element Q _1, Q ₂ to turn on and off the inductor L ₀ and electromagnetic transformer 7 and the piezoelectric transformer 1 and the load 2 and the alternating current power source E,
The electromagnetic transformer 7 is a three-winding transformer having a number of turns of 1: 1: N. The inductors of the windings are respectively Lp ₁ , Lp ₂ , and Ls. _One side of Lp ₁ and Lp ₂ is connected to each other. Power supply E is connected. Also, Lp
₁ and Lp ₂ have switching elements Q ₁ ,
Q ₂ is connected between ground, which a capacitor Cs _1, Cs ₂ are connected in parallel. At this time, the resonance frequency fo of the piezoelectric transformer satisfies fo = １ ／ π√ ｛Lp ₁ · (N ² Cd + Cs ₁ )｝ fo =＝ π√ ｛Lp ₂ · (N ² Cd + Cs ₂ )｝. The effect is the same as that of the first embodiment.

(Eighth Embodiment) FIG. 10 shows an eighth embodiment of the present invention. The circuit configuration of FIG. 10 is different from the configuration of the seventh embodiment shown in FIG. 9 in that capacitors Cs ₁ and Cs ₂ are connected in parallel to _two primary windings Lp ₁ and Lp ₂ of a transformer, respectively. The resonance frequency fo of the transformer is
Satisfy the formula. The effects are the same as in the first embodiment. Also, in the circuit configuration shown in FIG. 9 or FIG. 10, the same effect can be obtained in an inverter device in which a ceramic capacitor is connected to both ends of the primary side of an electromagnetic transformer without using a piezoelectric transformer.

[0028]

According to the present invention, in a push-pull type inverter device using a piezoelectric transformer, the switching element is connected by connecting the first and second capacitors to reduce the current change rate of the switching element. Can be reduced, and the on-loss can be reduced by lowering the effective value of the current, so that the size and cost of the switching element can be reduced. Also, even if the ambient temperature changes over a wide range, the voltage waveform applied between the input terminals of the piezoelectric transformer is kept almost sinusoidal, suppressing an increase in the loss of the piezoelectric transformer, electromagnetic transformer or choke and switching element, and increasing the temperature. It is possible to suppress the occurrence of noise. Furthermore, for circuit protection, for example, when stopping the oscillation of the circuit for safety at no load or the like, the energy accumulated in the inductor is released through the stray capacitance of the switching element. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram for explaining the operation of the first embodiment of the present invention.

FIG. 3 is an operation waveform diagram according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a third embodiment of the present invention.

FIG. 6 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 8 is a circuit diagram according to a sixth embodiment of the present invention.

FIG. 9 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 10 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 11 is a circuit diagram of a conventional example.

FIG. 12 is an operation waveform diagram of a conventional example.

FIG. 13 is a circuit diagram for explaining the operation of the conventional example.

FIG. 14 is an operation waveform diagram showing a half-cycle current of the conventional example.

FIG. 15 is an operation waveform diagram of the conventional example when the ambient temperature is too high.

FIG. 16 is an operation waveform diagram of the conventional example when the ambient temperature is too low.

[Explanation of symbols]

E DC power supply Q ₁ Switching element Q ₂ Switching element 1 Piezo transformer 2 Load Cs ₁ Parallel capacitor Cs ₂ Parallel capacitor T ₁ Auto transformer T ₂ Auto transformer

Claims (18)

[Claims] 1. A DC power supply, an inductance element connected in series to the DC power supply, and one end connected to the DC power supply and alternately turned on to alternately supply current from the DC power supply to the inductance element. , A piezoelectric transformer applied between input terminals of an electromotive force generated in the inductance element by a switching operation of the pair of switching elements, and a load connected to an output terminal of the piezoelectric transformer. An inverter device comprising: a capacitor connected between a terminal of the inductance element that is not connected to the DC power supply and at least one end of the DC power supply. 2. A DC power supply, first and second switching elements that are alternately turned on and off, and first and second switching elements.
First and second autotransformers having an intermediate terminal connected to the ground terminal of the DC power supply and a primary terminal connected to the non-ground terminal of the DC power supply via the switching element of A piezoelectric transformer having a secondary terminal connected to the first and second input terminals, and a secondary terminal connected between the output terminal of the piezoelectric transformer and a ground terminal of the DC power supply. And a first capacitor connected between a first input terminal of the piezoelectric transformer and a ground terminal of the DC power supply, a second input terminal of the piezoelectric transformer, and the DC power supply. An inverter device comprising: a second capacitor connected between the power supply and a ground terminal of the power supply. 3. The piezoelectric transformer according to claim ₂ , wherein the capacitances of the first and second capacitors are Cs ₁ and Cs ₂ , the resonance frequency of the piezoelectric transformer is fo, and the input equivalent capacitance of the piezoelectric transformer is Cs ₁ .
d, the primary inductances of the first and second autotransformers are Lp ₁ and Lp ₂ , respectively, and the turns ratio is 1:
Assuming N, 1: n, fo ≒ 1 / 2π√ ｛Lp ₁ · (1 + N) ² (Cd + Cs
₁ )｝ fo ≒ 1 / 2π√ ｛Lp ₂ · (1 + n) ² (Cd + Cs
₂ ) An inverter device that satisfies the relationship of ( ₁ ). 4. A DC power supply, first and second switching elements that are alternately turned on and off, and a first and a second switching elements.
First and second autotransformers having an intermediate terminal connected to the ground terminal of the DC power supply and a primary terminal connected to the non-ground terminal of the DC power supply via the switching element of A piezoelectric transformer having a secondary terminal connected to the first and second input terminals, and a secondary terminal connected between the output terminal of the piezoelectric transformer and a ground terminal of the DC power supply. A first capacitor connected between an intermediate terminal of a first autotransformer and a ground terminal of the DC power supply, and an intermediate terminal of a second autotransformer and the DC power supply. The second terminal connected between the ground terminal
An inverter device comprising: a capacitor; 5. The piezoelectric transformer according to claim 4, wherein the capacitances of the first and second capacitors are Cs ₁ and Cs ₂ , the resonance frequency of the piezoelectric transformer is fo, and the input equivalent capacitance of the piezoelectric transformer is Cs ₁ .
d, the primary inductances of the first and second autotransformers are Lp ₁ and Lp ₂ , respectively, and the turns ratio is 1:
Assuming N, 1: n, fo√ ｛1 / 2π√ ｛Lp ₁ · (1 + N) ² Cd + C
s ₁ ｝ fo ≒ 1 / 2π ≒ Lp ₂ · (1 + n) ² Cd + C
An inverter device satisfying a relationship of s ₂ ｝. 6. A DC power supply, first and second switching elements which are alternately turned on and off, and first and second switching elements.
First and second autotransformers having an intermediate terminal connected to the ground terminal of the DC power supply and a primary terminal connected to the non-ground terminal of the DC power supply via the switching element of A piezoelectric transformer having a secondary terminal connected to the first and second input terminals, and a secondary terminal connected between the output terminal of the piezoelectric transformer and a ground terminal of the DC power supply. A first capacitor connected between an intermediate terminal of a first auto transformer and a non-ground side terminal of the DC power supply, an intermediate terminal of a second auto transformer, and the DC power supply. And a second capacitor connected between the non-ground side terminal of the inverter device. 7. The piezoelectric transformer according to claim 6, wherein the capacitances of the first and second capacitors are Cs ₁ and Cs ₂ , the resonance frequency of the piezoelectric transformer is fo, and the input equivalent capacitance of the piezoelectric transformer is Cs.
d, the primary inductances of the first and second autotransformers are Lp ₁ and Lp ₂ , respectively, and the turns ratio is 1:
Assuming N, 1: n, fo√ ｛1 / 2π√ ｛Lp ₁ · (1 + N) ² Cd + C
s ₁ ｝ fo ≒ 1 / 2π ≒ Lp ₂ · (1 + n) ² Cd + C
An inverter device satisfying a relationship of s ₂ ｝. 8. A DC power supply, first and second switching elements that are alternately turned on and off, and first and second switching elements.
First and second autotransformers having an intermediate terminal connected to the ground terminal of the DC power supply and a primary terminal connected to the non-ground terminal of the DC power supply via the switching element of A piezoelectric transformer having a secondary terminal connected to the first and second input terminals, and a secondary terminal connected between the output terminal of the piezoelectric transformer and a ground terminal of the DC power supply. And a first capacitor connected between a first input terminal of the piezoelectric transformer and a non-ground side terminal of the DC power supply; a second input terminal of the piezoelectric transformer; An inverter device comprising: a second capacitor connected between the non-earth terminal of the DC power supply. 9. The piezoelectric transformer according to claim 8, wherein the capacitances of the first and second capacitors are Cs ₁ and Cs ₂ , the resonance frequency of the piezoelectric transformer is fo, and the input equivalent capacitance of the piezoelectric transformer is Cs.
d, the primary inductances of the first and second autotransformers are Lp ₁ and Lp ₂ , respectively, and the turns ratio is 1:
Assuming N, 1: n, fo ≒ 1 / 2π√ ｛Lp ₁ · (1 + N) ² (Cd + Cs
₁ )｝ fo ≒ 1 / 2π√ ｛Lp ₂ · (1 + n) ² (Cd + Cs
₂ ) An inverter device that satisfies the relationship of ( ₁ ). 10. A DC power supply, first and second switching elements that are alternately turned on and off, and one end connected to a ground terminal of the DC power supply via the first and second switching elements. First and second chokes whose other ends are connected to the non-ground side terminal of the DC power supply;
A piezoelectric transformer having one ends of the first and second chokes connected to the first and second input terminals, respectively; and a load connected between an output terminal of the piezoelectric transformer and a ground terminal of the DC power supply. An inverter device comprising:
An inverter device comprising: a first capacitor connected in parallel with a first switching element; and a second capacitor connected in parallel with a second switching element. 11. The method according to claim 10, wherein the first and the second
Let Cs ₁ and Cs ₂ denote the capacitance of the capacitor, fo the resonance frequency of the piezoelectric transformer, Cd the input equivalent capacitance of the piezoelectric transformer, and Lp ₁ and Lp ₂ the inductance of the first and second chokes, respectively. An inverter device which satisfies a relationship of 1 / 2π {Lp ₁ · (Cd + Cs ₁ )} fo {1 / 2π {Lp ₂ · (Cd + Cs ₂ )}. 12. A DC power supply, first and second switching elements that are alternately turned on and off, and one end connected to a ground terminal of the DC power supply via the first and second switching elements. First and second chokes whose other ends are connected to the non-ground side terminal of the DC power supply;
A piezoelectric transformer having one ends of the first and second chokes connected to the first and second input terminals, respectively; and a load connected between an output terminal of the piezoelectric transformer and a ground terminal of the DC power supply. An inverter device comprising:
An inverter device comprising: a first capacitor connected in parallel with a first choke; and a second capacitor connected in parallel with a second choke. 13. The method according to claim 12, wherein:
Let Cs ₁ and Cs ₂ denote the capacitance of the capacitor, fo the resonance frequency of the piezoelectric transformer, Cd the input equivalent capacitance of the piezoelectric transformer, and Lp ₁ and Lp ₂ the inductance of the first and second chokes, respectively. An inverter device which satisfies a relationship of 1 / 2π {Lp ₁ · (Cd + Cs ₁ )} fo {1 / 2π {Lp ₂ · (Cd + Cs ₂ )}. 14. A DC power supply, first and second switching elements which are alternately turned on and off, and an intermediate terminal on the primary side are connected to a non-earth terminal of the DC power supply via a choke. An electromagnetic transformer having a pair of primary terminals connected to a ground terminal of the DC power supply via first and second switching elements;
In an inverter device including a piezoelectric transformer having a pair of secondary terminals connected between both ends of an input terminal, and a load connected between one input terminal and an output terminal of the piezoelectric transformer, a first switching element is provided. An inverter device comprising: a first capacitor connected in parallel; and a second capacitor connected in parallel with the second switching element. 15. The method according to claim 14, wherein:
Cs ₁ the capacity of the capacitor, Cs _2, wherein the piezoelectric transformer resonance frequency fo, the input equivalent capacitance of the piezoelectric transformer Cd, respectively Lp ₁ the inductance of the pair of the primary winding of the electromagnetic autotransformer, Lp _2, Assuming that the turns ratio of the primary winding and the secondary winding is 1: N and 1: n, respectively, fo {1 / 2π {Lp _1. (N ² Cd + Cs ₁ )} fo {1 / 2π} An inverter device which satisfies a relationship of Lp ₂ · (n ² Cd + Cs ₂ )｝. 16. A DC power supply, first and second switching elements that are alternately turned on and off, and an intermediate terminal on the primary side are connected to a non-ground side terminal of the DC power supply via a choke. An electromagnetic transformer having a pair of primary terminals connected to a ground terminal of the DC power supply via first and second switching elements;
An inverter device comprising: a piezoelectric transformer having a pair of secondary terminals connected between both ends of an input terminal; and a load connected between one input terminal and an output terminal of the piezoelectric transformer. And a second capacitor connected in parallel with the second primary winding and a first capacitor connected in parallel with the primary winding. 17. The method according to claim 16, wherein the first and second
Cs ₁ the capacity of the capacitor, Cs _2, wherein the piezoelectric transformer resonance frequency fo, the input equivalent capacitance of the piezoelectric transformer Cd, respectively Lp ₁ the inductance of the pair of the primary winding of the electromagnetic autotransformer, Lp _2, Assuming that the turns ratio of the pair of primary windings and secondary windings is 1: N and 1: n, respectively, fo ≒ 1 / 2π√ ｛Lp ₁ · (N ² Cd + Cs ₁ )｝ fo ≒ 1 / 2π An inverter device satisfying the relationship of {Lp ₂ · (n ² Cd + Cs ₂ )}. 18. The inverter device according to claim 1, wherein the first and second capacitors are ceramic capacitors having an inverse equivalent temperature characteristic to the input equivalent capacitance of the piezoelectric transformer.