JP2831252B2 - Class E push-pull power amplifier circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a class E push-pull power amplifier circuit, and is used, for example, as a high-efficiency high-frequency power amplifier for a lighting device of an electrodeless discharge lamp.

[0002]

2. Description of the Related Art A conventional class E single-ended power amplifier circuit is shown in FIG. In the figure, 1 is a high-frequency oscillator, 2 is a class E power amplifier circuit, and 3 is a load. The class E power amplifier circuit 2 includes a switching element Q connected in series to a DC power supply 7.
a, an inductor La for making the input current from the DC power supply 7 substantially constant, a capacitor Ca connected in parallel to the switching element Qa, a resonance coil L having a resonance point near the operating frequency, and a resonance capacitor C Consists of a series circuit. Here, the capacitor Ca connected in parallel to the switching element Qa may be used as a substitute or part of the output capacitance of the switching element Qa.

FIG. 16 shows waveforms of a voltage Va across the switching element Qa and a current Ia flowing through the switching element Qa when an ideal class E operation is performed. The characteristic of the class E operation is that the value of the voltage Va and the slope become 0 and the current Ia
Is flowing out, so that the switching loss when the switching element Qa shifts from off to on becomes substantially zero. Therefore, when a class E power amplifier circuit is used, highly efficient power amplification can be realized even at a high frequency.

When the output of the class E single-ended power amplifier circuit shown in FIG. 15 is increased, the loss in the switching element Qa also increases with the increase in output, and the temperature of the switching element Qa rises due to generated heat. Due to the temperature rise of the switching element Qa, in the class E single-ended power amplifier circuit of FIG. 15, the increase in output may be limited.

Therefore, as shown in FIG. 17, a class E push-pull power amplifier circuit using two switching elements Qa and Qb has been devised based on the class E single-ended power amplifier circuit shown in FIG. . In this circuit, a circuit in which an inductor La is connected in series to a parallel circuit of a switching element Qa and a capacitor Ca, and a circuit in which an inductor Lb is connected in series to a parallel circuit of a switching element Qb and a capacitor Cb are connected in parallel to the DC power supply 7. Connected.
One end of each of the inductors La and Lb is connected to one electrode of the DC power supply 7, and a resonance coil L having a resonance point near an operating frequency is provided between the other ends of the inductors La and Lb.
And a series circuit of a resonance capacitor C are connected. The resonance coil L uses the leakage inductance of the output transformer T. A load R is connected to the secondary winding of the output transformer T. The switching elements Qa and Qb are turned on and off alternately, and their drive signal sources 1a and 1b
Is obtained, for example, by converting the output of the high-frequency oscillator 1 of FIG. 15 into two signals of opposite phases by a transformer with a center tap as shown in FIG. By using a class E push-pull power amplifier circuit as shown in FIG.
a, Qb can be shared, and the temperature rise due to the loss of each switching element Qa, Qb can be suppressed, so that the output of the class E power amplifier circuit can be increased.

FIG. 19 shows operation waveforms of the class E push-pull power amplifier circuit in FIG. 17 in an ideal state. As shown in FIG. 19, since the voltages Va and Vb applied to the respective switching elements Qa and Qb are 0 and the gradients of the voltages Va and Vb become 0, the currents Ia and Ib start flowing through the respective switching elements Qa and Qb. , Switching element Q
The switching loss when a and Qb change from off to on can be made substantially zero, and high-efficiency power amplification can be realized even at high frequencies.

[0007]

In designing a power amplifier circuit using a resonance system such as a class E push-pull power amplifier circuit, it is necessary to operate in an ideal state as shown in FIG. This is important for achieving high efficiency power amplification. However, in a high-frequency circuit, a copper foil pattern on a printed circuit board on mounting functions as inductance or capacitance. Therefore, when the class E push-pull power amplifier circuit of FIG. 17 is mounted, the two switching elements Q
As shown in FIG. 20, the operation state may be shifted between a and Qb. Therefore, it is likely that it becomes difficult to adjust the two switching elements Qa and Qb to operate simultaneously or in an ideal state as shown in FIG. Thus, in the class E push-pull power amplifier circuit of FIG. 17, it is often difficult to obtain the power amplification efficiency of the class E power amplifier circuit in an ideal state as shown in FIG.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to operate two switching elements in an E-class push-pull power amplifier circuit in or near an ideal state. It is an object of the present invention to provide an easy circuit configuration.

[0009]

In order to solve the above-mentioned problems, a class E push-pull power amplifier circuit according to the present invention has one end connected to one electrode of a DC power supply 7 as shown in FIG. The first and second inductors La and Lb, the other electrode of the DC power supply 7 and the first and second inductors La and Lb.
First and second switching elements Qa and Qb respectively connected between the other ends of Lb, driving means 1a and 1b for turning on and off the first and second switching elements Qa and Qb alternately, First and second switching elements Q
a and Qb respectively connected in parallel to the first and second capacitors Ca and Cb, and the first and second inductors L and L
a, a class-E push-pull power amplifier circuit comprising a resonance circuit connected between the other ends of the a and Lb, and a load circuit connected in parallel to one of the elements constituting the resonance circuit. The circuit comprises first, second, and third elements Z1, Z2, and Z3 in the order in which they are connected in series, and the first and third elements Z1 and Z3 at both ends have substantially equal impedance. Things. Here, when the first and third elements Z1 and Z3 have a capacitive impedance, the second element Z2 has an inductive impedance and the first element Z2 has a first impedance.
When the third elements Z1 and Z3 have inductive impedance, the second element Z2 has capacitive impedance. However, the capacitive element and the inductive element only need to have the capacitive and inductive properties near the operating frequency of each internal impedance, and the internal configuration is not limited.

[0010]

In the conventional class-E single-ended power amplifier circuit, the resonance circuit constituted by the two elements of the capacitor C and the inductor L shown in FIG. 17 is replaced by the class-E push-pull power amplifier circuit of the present invention. As shown in the figure, the first, second, and third elements Z1, Z2, and Z3 are connected in series, the impedances of the first and third elements Z1 and Z3 on both sides are substantially equal, and First and third elements Z1, Z
When one of the third element Z2 and the second element Z2 is capacitive and the other is inductive, a class E push-pull power amplifier circuit can be configured and mounted substantially symmetrically, and the two switching elements Qa and Qb Can be easily operated in an ideal state or a state close to the ideal state as shown in FIG.

[0011]

FIG. 2 is a circuit diagram of a first embodiment of the present invention.
Hereinafter, the circuit configuration will be described. The pair of switching elements Qa and Qb are composed of a power MOSFET, and a capacitor Ca,
Cb are connected in parallel. These capacitors Ca, Cb
May be shared or substituted by the output capacitance of the power MOSFET. The source of each power MOSFET is grounded and connected to the negative electrode of the DC power supply 7, and the drain is connected to the positive electrode of the DC power supply 7 via inductors La and Lb. Vdd means the voltage of the DC power supply 7. Between the drains of the power MOSFETs, there is connected a resonance circuit formed by serially connecting a capacitor C1, an inductor L2, and a capacitor C3 in series. Capacitors C1 and C3 on both sides have substantially the same capacitance, and the center inductor L
2, a load R is connected in parallel. This resonance circuit
The switching elements Qa and Qb have a resonance point near the operating frequency. The switching elements Qa and Qb are turned on and off alternately, and their drive signal sources 1a and 1b
Is obtained, for example, by converting the output of the high-frequency oscillator 1 of FIG. 15 into two signals of opposite phases by a transformer with a center tap as shown in FIG. Further, each of the inductors La and Lb has substantially the same inductive impedance, and each of the capacitors Ca and Cb has substantially the same capacitive impedance. Thus, the entire circuit is configured symmetrically with respect to the switching elements Qa and Qb.
The printed circuit board on which this circuit is mounted is designed so that the copper foil pattern is substantially symmetrical, and is designed so that high-frequency circuit constants are symmetrical. This circuit has the advantage of requiring the least number of components among the configurations in which the effects of the present invention can be obtained.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. In this embodiment, in the first embodiment shown in FIG.
The primary winding of the output transformer T is connected to the inductor L2, and the load R is connected to the secondary winding. One end of the load R is connected to the circuit ground. In this embodiment, the leakage inductance of the output transformer T is used as the inductor L2, and is used as the second element exhibiting inductive impedance. In addition, capacitors C1, C
3 constitutes first and third elements having substantially equal capacitive impedance. In this embodiment, as compared with the first embodiment shown in FIG. 2, since the high-frequency output is extracted using the output transformer T, one end of the extracted high-frequency output can be connected to the ground of the circuit, and The output can be easily handled with a cable or a connector.

FIG. 4 is a circuit diagram of a third embodiment of the present invention. In this embodiment, in the second embodiment shown in FIG.
The primary winding of the output transformer T is divided into approximately two equal parts, and the center tap is connected to the circuit ground. About 2
Leakage inductances L2a and L2 of the equally divided primary winding
When b is combined, it becomes equal to the inductor L2 of the second embodiment shown in FIG. In the present embodiment, as compared with the second embodiment shown in FIG. 3, since the midpoint of the approximately equally divided inductor L2 is connected to the circuit ground, high-frequency noise radiated from the circuit is reduced. In addition to this, the terminal voltage of each element can be stabilized even at a high frequency, and the operation of the entire circuit is stabilized.

FIG. 5 is a circuit diagram of a fourth embodiment of the present invention. In the present embodiment, a resonance circuit is formed by sequentially connecting the primary winding of the output transformer T1, the capacitor C2, and the primary winding of the output transformer T3 in series. Output transformers T1 and T
The secondary winding No. 3 is connected in series and connected to the load R. One end of the load R is connected to the circuit ground. The leakage inductances of the output transformers T1 and T3 are used as inductors L1 and L3, and are used as first and third elements exhibiting inductive impedance. In the present embodiment, since high-frequency output can be taken out using the two output transformers T1 and T3, there is an effect of simplifying heat loss design for the output transformer, and high efficiency is achieved in the class E push-pull power amplifier circuit. This has the effect of simplifying the adjustment of the inductance value of the resonance circuit, which is important for realizing amplification.

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention. In this embodiment, in the fourth embodiment shown in FIG.
The capacitor C2 as the second element at the center is divided into approximately two equal parts to form a series circuit of two capacitors C2a and C2b, and the connection point of the capacitors C2a and C2b is connected to the circuit ground. Almost equally divided capacitor C
The combination of 2a and C2b becomes equal to the capacitor C2 of the fourth embodiment shown in FIG. In the present embodiment, compared to the fourth embodiment shown in FIG. 5, since the midpoint of the approximately equally divided capacitor C2 is connected to the circuit ground, high-frequency noise radiated from the circuit is reduced. In addition to this, the terminal voltage of each element can be stabilized even at a high frequency, and the operation of the entire circuit is stabilized.

FIG. 7 is a circuit diagram of a sixth embodiment of the present invention. In this embodiment, a pair of switching elements Qa, Qb
L between the drains of the MOSFETs
1, a capacitor C2 and an inductor L3 are connected in series in this order. Central capacitor C
2 are connected to the primary winding of an output transformer T2. The load R is connected to the secondary winding of the output transformer T2. One end of the load R is connected to the circuit ground. The combined inductance of the leakage inductance of the output transformer T2 and the capacitor C2 constitutes a second element, and the circuit constant is set so as to be capacitive near the operating frequency. In this circuit, the capacitor C
2, the inductor L
1, a capacitor C2 and an inductor L3 form a low-pass filter, which has the effect of reducing harmonic components of power appearing at the output. Further, even if the secondary circuit of the output transformer T2 is in a no-load state and the impedance seen from the primary circuit is in a short-circuit state, the current flowing through the resonance circuit is limited by the leakage inductance, and the switching elements Qa and Qb This has the effect of preventing breakdown due to a large current.

FIG. 8 is a circuit diagram of a seventh embodiment of the present invention. In the present embodiment, in the sixth embodiment shown in FIG.
The capacitor C2 as the second element at the center is divided into approximately two equal parts to form a series circuit of two capacitors C2a and C2b, and the connection point of the capacitors C2a and C2b is connected to the circuit ground. Almost equally divided capacitor C
When 2a and C2b are combined, they become equal to the capacitor C2 of the sixth embodiment shown in FIG. The inductor L2 due to the leakage inductance exists in the primary winding of the output transformer T2, but the circuit constant is set so that the impedance combined with the capacitors C2a and C2b becomes capacitive near the operating frequency. In the present embodiment, as compared with the sixth embodiment shown in FIG. 7, the midpoint of the capacitor C2, which is approximately equally divided into two, is connected to the ground of the circuit. Because it is connected to the ground, the effect as the low-pass filter increases, the harmonic suppression effect increases, and high-frequency noise radiated from the circuit can be reduced, and
It is possible to stabilize the terminal voltage of each element even at high frequencies, which has the effect of stabilizing the operation of the entire circuit.

FIG. 9 is a circuit diagram of an eighth embodiment of the present invention. In this embodiment, a pair of switching elements Qa, Qb
Between the drains of the MOSFETs constituting the capacitor C
1, a resonance circuit formed by serially connecting an inductor L2 and a capacitor C3 in series. Capacitor C at both ends
1 and C3 are connected to primary windings of output transformers T1 and T3, respectively. The secondary windings of the output transformers T1 and T3 are connected in series and connected to a load R. One end of the load R is connected to the circuit ground. The inductors L1 and L3 due to the leakage inductance of the output transformers T1 and T3 are connected in parallel with the capacitors C1 and C3, and their combined impedance is set to a circuit constant so as to be capacitive near the operating frequency.
In this circuit, a high-frequency output is taken out from both ends of the two capacitors C1 and C3, so that a low-pass filter is formed for the output similarly to the circuits in FIGS. And an effect of preventing the switching element from being destroyed. Further, since the output transformer is divided into two parts, there is an effect that the heat loss and the inductance value of the output transformer can be easily designed as in the circuits of FIGS.

FIG. 10 is a circuit diagram of a ninth embodiment of the present invention. In the present embodiment, in the eighth embodiment shown in FIG.
The inductor L2 as the second element at the center is divided into approximately two equal parts to form a series circuit of two inductors L2a and L2b, and a connection point of the inductors L2a and L2b is connected to the ground of the circuit. At this time, a DC path is formed from the DC power supply through the inductor La, the inductor L1, the inductor L2a or the inductor Lb, the inductor L3, and the inductor L2b and leading to the circuit ground. Capacitors C2a and C2 are connected to the inductances L2a and L2b, respectively.
b are connected in series. Each capacitor C2a, C2
The value of b is set substantially equal. The combined impedance of the inductors L2a and L2b and the capacitors C2a and C2b approximately divided into two equal parts becomes inductive near the operating frequency and is set to be equal to the inductor L2 of the eighth embodiment shown in FIG. Also, the eighth line shown in FIG.
As compared with the embodiment, since the midpoint of the inductor L2, which is approximately bisected, is connected to the ground of the circuit, the high-frequency noise radiated from the circuit can be reduced, and the high-frequency noise can also be reduced for the high frequency. The terminal voltage of the element can be stabilized, and the operation of the entire circuit can be stabilized.

In the above embodiment, the load R is indicated by the symbol of resistance, but may be, for example, a discharge lamp. As an example, FIG. 11 shows an embodiment in which an electrodeless discharge lamp that discharges and emits light by a high-frequency electromagnetic field is used as a load.
In the figure, 4 is an electrodeless discharge lamp, 5 is an induction coil wound in the vicinity of the electrodeless discharge lamp 4, and 6 is a device for matching the impedance of the amplifier circuit and the discharge lamp 4 to efficiently supply power. It is a matching circuit. In each of the above embodiments, it is needless to say that the constant of each circuit is adjusted so as to perform the class E operation.

In the design of a class E push-pull power amplifier circuit, the design of the resonance frequency is important to obtain ideal voltage and current waveforms as shown in FIG. Therefore, fine adjustment of the constant is often required. As one example, there is a case where the inductance of the resonance coil is adjusted. In the case of a single-ended circuit as shown in FIG. 17, an air-core coil is often used as the inductor L at a high frequency, and the adjustment is relatively easy. However,
In the class E push-pull circuit as shown in FIG. 12, since the resonance inductor L2 is shared with the output transformer T wound around the iron core, it is difficult to adjust the inductance. Also, at the time of design, the inductance value must be designed in consideration of the leakage inductance, and it is very difficult to achieve both the function of the transformer and the inductance value. Therefore, if the output transformer T is designed as an ideal transformer, and the resonance inductor L2 is provided between the transformer T and the resonance capacitor C1 or C3 as shown in FIG. 13, for example, the resonance inductor L2 can be an air-core coil. And fine-tuning becomes easier. However, this figure 1
With the configuration as in No. 3, the symmetry is broken when the class E push-pull power amplifier circuit is mounted. In a circuit that handles high frequencies, as described above, the copper foil pattern of the printed circuit board sometimes acts as an inductance, and the fact that it is not symmetric in mounting is equivalent to the fact that the element constant is not symmetric. Therefore, in the push-pull circuit as shown in FIG. 12, it is ideal to configure the drive circuit to the output resonance circuit symmetrically. Therefore, it is conceivable to provide resonance coils on both sides of the transformer. However, it is difficult not only to increase the number of elements but also to adjust the balance in a well-balanced manner. Therefore, as shown in FIG. 14, it is preferable to provide a resonance air core coil L2 in the circuit on the secondary winding side of the ideal transformer T. Thus, since the symmetric configuration does not need to be broken, it is possible to prevent the circuit constant from being asymmetric due to the copper foil pattern. Adjustment of the circuit operation can be easily performed by the air-core coil L2. Further, since it is not necessary to provide the leakage inductance of the output transformer T, the design of the output transformer T becomes easy.

[0022]

According to the present invention, a class E push-pull power amplifier circuit using a resonance circuit includes a resonance circuit including first, second, and third elements in the order of serial connection. Since the first and third elements have substantially the same impedance, the resonance circuit becomes symmetric, and if the central second element is inductive, the first and third elements on both sides become capacitive, If the second element in the center is capacitive, the first and third elements on both sides are inductive. By thus symmetrically configuring the resonance circuit, the copper foil at the time of mounting can be obtained. The difference in pattern length can be eliminated, and high-frequency coupling between circuits can be made uniform.
It is relatively easy to operate the two switching elements in or near an ideal state.

Further, if the load circuit is connected to the central second element, there is an advantage that switching noise hardly appears in the load circuit. Furthermore, if the load circuit is connected in parallel to the first and third elements on both sides, the heat loss design for the output transformer for coupling can be simplified, and high efficiency amplification can be achieved in the class E push-pull power amplifier circuit. This has the effect of simplifying the adjustment of the inductance value of the resonance circuit, which is important for realization.

Further, among the three elements of the resonance circuit,
The center second element is replaced with fourth and fifth elements connected in series such that the impedance is substantially equal to the second element, and the connection point of the fourth and fifth elements is connected to the circuit ground. , The middle point of the second element in the center is connected to the ground of the circuit, so that high-frequency noise radiated from the circuit can be reduced and each The terminal voltage of the element can be stabilized, and the operation of the entire circuit can be stabilized.

Also, an element having an output capacitance such as a field effect transistor is used as a switching element, and the output capacitance is used as all or a part of the first and second capacitors, respectively, or a load circuit is connected via a transformer. If the leakage inductance of the transformer is used as the inductive element of the resonance circuit, the number of components can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.

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

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

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

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

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention.

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

FIG. 8 is a circuit diagram of a seventh embodiment of the present invention.

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

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

FIG. 11 is a circuit diagram of a tenth embodiment of the present invention.

FIG. 12 is a circuit diagram showing a circuit example in which a load is not grounded according to a second embodiment of the present invention.

FIG. 13 is a circuit diagram of a resonance circuit shown as a comparative example to the present invention.

FIG. 14 is a circuit diagram of an eleventh embodiment of the present invention.

FIG. 15 is a circuit diagram of a first conventional example.

FIG. 16 is a waveform chart showing the operation of the first conventional example.

FIG. 17 is a circuit diagram of a second conventional example.

FIG. 18 is a circuit diagram of a drive signal source used in a second conventional example.

FIG. 19 is a waveform chart showing the operation of the second conventional example in an ideal state.

FIG. 20 is a waveform diagram showing an operation of the second conventional example in a state deviated from an ideal state.

[Explanation of symbols]

 Qa first switching element Qb second switching element La first inductor Lb second inductor Ca first capacitor Cb second capacitor Z1 first element Z2 second element Z3 third element R load

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Anan 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Inventor Yuji Kumagai 1048 Kadoma Kadoma Kadoma City Osaka Prefecture Matsushita Electric Works Co., Ltd. ( 72) Inventor Fushi Okamoto 1048 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Works Co., Ltd. (72) Inventor Koji Nishimura 1048 Odaka Kazuma Kadoma City Osaka Prefecture Inside Matsushita Electric Works Co., Ltd. (72) Inventor Shozo Kataoka Osaka 1048, Okadoma, Kamon, Fumonma-shi, Japan Matsushita Electric Works, Ltd. (72) Inventor Derek Bray 94022 Los Altos, Hawson Avenue, California, USA 41 (56) References JP-A 1-217895 (JP, A) JP 63-62190 (JP, A) JP-A-4-355505 (JP, A) JP-A-7-170133 (JP, A) JP-A -170129 (JP, A) (58 ) investigated the field (Int.Cl. ^6, DB name) H03F 3/217 H05B 41/24 - 41/29

Claims (13)

(57) [Claims] 1. A first and a second inductor having one ends connected to one electrode of a DC power supply, and a first and a second inductor connected between the other electrode of the DC power supply and the other ends of the first and second inductors, respectively. First and second switching elements,
Driving means for alternately turning on / off the second and third switching elements, first and second capacitors connected in parallel to the first and second switching elements, respectively, and first and second inductors. In a class E push-pull power amplifier circuit including a resonance circuit connected between the other ends and a load circuit connected in parallel to any of the elements constituting the resonance circuit, the resonance circuits are connected in series. The first, second, and third elements are connected in the order in which they are connected.
And a class E push-pull power amplifier circuit, wherein the third element has substantially equal impedance. 2. The method according to claim 1, wherein the first element of the resonance circuit is capacitive,
The class E push-pull power amplifier circuit according to claim 1, wherein the second element is an inductive element, and the third element is a capacitive element. 3. The method of claim 1, wherein the first element of the resonant circuit is inductive,
2. The class E push-pull power amplifier circuit according to claim 1, wherein the second element is a capacitive element and the third element is an inductive element. 4. The resonance circuit according to claim 1, wherein a load circuit is connected in parallel to a second element of the first, second, and third elements of the resonance circuit. Class E push-pull power amplifier circuit. 5. The load circuit according to claim 1, wherein a load circuit is connected in parallel to the first and third elements of the first, second and third elements of the resonance circuit. A class E push-pull power amplifier circuit according to any one of claims 1 to 4. 6. The three elements of the resonance circuit, wherein a central second element is replaced with fourth and fifth elements connected in series such that impedance is substantially equal to the second element. 2. A connection point between the fourth, fifth and fifth elements is connected to the other electrode of the DC power supply.
6. The class-E push-pull power amplifier circuit according to any one of claims 1 to 5. 7. The device according to claim 1, wherein the first and second switching elements are elements having an output capacitance, and the output capacitance is used as all or a part of the first and second capacitors, respectively. 7. A class-E push-pull power amplifier circuit according to any one of claims 1 to 6. 8. The device according to claim 7, wherein the element having the output capacitance is a field effect transistor.
Class push-pull power amplifier circuit. 9. The load circuit according to claim 1, wherein the load circuit is connected via a transformer, and a leakage inductance of the transformer is used as an inductive element of the resonance circuit.
9. A class E push-pull power amplifier circuit according to any one of claims 1 to 8. 10. The load circuit is connected via a transformer, wherein the transformer has substantially zero leakage inductance.
10. The class E according to claim 1, wherein the transformer is a substantially ideal transformer having a substantially infinite mutual inductance, and an air-core coil is connected to a secondary winding of the transformer in series with a load circuit. Push-pull power amplifier circuit. 11. The load circuit includes an electrodeless discharge lamp, an induction coil wound near the electrodeless discharge lamp, and a matching circuit for matching impedance and supplying power efficiently. The class-E push-pull power amplifier circuit according to any one of claims 1 to 10, wherein: 12. The printed circuit board according to claim 1, wherein the first and second switching elements have a uniform impedance by a copper foil pattern. Class E push-pull power amplifier circuit. 13. The method according to claim 1, wherein the first and second inductors have substantially equal inductive impedances, and the first and second capacitors have substantially equal capacitive impedances. A class E push-pull power amplifier circuit as described.