JP2831257B2 - 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 E
The class power amplifier circuit 3 represents a load. Class E power amplifier circuit 2
Is a switching element Qa connected in series to the DC power supply 7.
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, and a resonance coil L and a resonance capacitor C having a resonance point near the operating frequency. 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. 9 shows the waveform of the voltage Va across the switching element Qa and the waveform of the 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. 8 is increased, the loss in the switching element Qa also increases with the increase in the 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. 8, the increase in output may be limited.

Therefore, as shown in FIG. 10, 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 and a resonance capacitor are connected between the other ends of the inductors La and Lb. C series circuit is 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. 8 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. 10, the loss in the switching element can be reduced by two switching elements Qa,
Qb, and each switching element Q
Since the temperature rise due to the loss of a and Qb can be suppressed, the output of the class E power amplifier circuit can be increased.

FIG. 12 shows operating waveforms of the class E push-pull power amplifier circuit shown in FIG. 10 in an ideal state. As shown in FIG. 12, since the voltages Va and Vb applied to the respective switching elements Qa and Qb are 0 and the slopes 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 the design of 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. For this reason, when the class E push-pull power amplifier circuit of FIG. 10 is mounted, the two switching elements Q
As shown in FIG. 13, there may be a case where the operation state shifts 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. As a result, in the class E push-pull power amplifier circuit of FIG. 10, 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 the class E push-pull power amplifier circuit according to the present invention, as shown in FIG. 1, a center tap is connected to one electrode of a DC power supply 7 to solve the above-mentioned problem. A first inductor L1, second and third inductors L3 and L4 having one ends connected to one end and the other end of the first inductor L1, respectively,
And the first and second switching elements Q1, Q2 connected between the other electrode of the first and second ends of the second and third inductors L3, L4, respectively. 1 for alternately turning on / off
a, 1b and the first and second switching elements Q1, Q
2 and first and second capacitors C1 and C2 connected in parallel with each other, and second and third inductors L3 and L2.
4 and a load symmetrically coupled to the first inductor L1 or the second and third inductors L3 and L4. It is characterized by having a circuit.

[0010]

According to the present invention, as shown in FIG. 1, the class E push-pull power amplifier circuit is formed substantially symmetrically, so that when mounted on a printed circuit board, the impedance of the copper foil pattern of the printed circuit board is reduced by two switching elements. Q1, Q2
Can be made uniform. Also, since the circuit is substantially symmetric, the corresponding elements, ie, the second and third
Inductors L3, L4, first and second capacitors C
1, C2, the third and fourth capacitors C3 and C4, and the first and second switching elements Q1 and Q2 have substantially the same characteristics, and the operation of the entire circuit can be made extremely symmetric. . Therefore, the two switching elements Q1 and Q2 can be easily operated simultaneously in an ideal state or a state close to the ideal state as shown in FIG. Note that the circuit of FIG. 1 is different from the circuit of FIG. 10 in that the current flowing through the first inductor is supplied to each switching element through another second and third inductors. The class E power amplification operation can be performed according to the same principle as the class E push-pull power amplification circuit in FIG. 10, and high-efficiency power amplification becomes possible.

[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 Q1 and Q2 are composed of a power MOSFET, and a capacitor C1 and a capacitor C1 are provided between the drain and the source.
C2 is connected in parallel. These capacitors C1 and C2
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 both ends of the inductor L1 via the inductors L3 and L4, respectively. The center tap of the inductor L1 is connected to the positive electrode of the DC power supply 7. Vd
d represents the voltage of the DC power supply 7. Inductor L3
L4 supplies a direct current necessary for the class E operation to the switching elements Q1 and Q2. These inductors L
Capacitors C3 and C4 are connected in parallel to 3, L4, respectively. The parallel connection of the capacitor C3 and the inductor L3 and the parallel connection of the capacitor C4 and the inductor L4 are each set to a constant so as to exhibit substantially the same capacitive impedance near the operating frequency for class E operation. Make up the circuit. This resonance circuit includes switching elements Q1, Q2
Have a resonance point near the operating frequency. The switching elements Q1 and Q2 are alternately turned on and off.
The drive signal sources 1a and 1b are obtained, for example, by converting the output of the high-frequency oscillator 1 of FIG. 8 into two signals of opposite phases by a transformer with a center tap as shown in FIG. The constants are set so that each of the capacitors C1 and C2 also exhibits substantially the same capacitive impedance.
1 and Q2. 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.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. In this embodiment, the inductor L1 is connected to the output transformer T1.
Is configured using the leakage inductance of the above. The load R is connected to the secondary winding of the output transformer T1. One end of the load R is connected to the circuit ground. When the high-frequency output is extracted using an output transformer as in the present embodiment, one end of the extracted high-frequency output can be connected to the circuit ground, and the output can be easily handled with a coaxial cable, a connector, or the like. it can. On the other hand, FIG.
In the case where the load R is directly connected to the inductor L1 without using an output transformer as in the embodiment, there is an advantage that the number of components can be minimized among the configurations in which the effect of the present invention can be obtained.

FIG. 4 is a circuit diagram of a third embodiment of the present invention. In this embodiment, in the second embodiment shown in FIG.
Both ends of the inductor L1 are connected to the circuit ground by capacitors C5 and C6. Each capacitor C
The values of C5 and C6 are set substantially equal. Inductor L
1 and the combined impedance of the capacitors C5 and C6 are set to be inductive near the operating frequency and equal to the inductor L1 shown in FIG. In this embodiment, approximately two capacitors C5 and C6 are connected in series.
Since the midpoint of the equally divided inductor L1 is connected to the ground of the circuit, high-frequency noise radiated from the circuit can be reduced, and the terminal voltage of each element can be stabilized even at high frequencies. This has the effect of stabilizing the operation of the entire circuit.

FIG. 5 is a circuit diagram of a fourth embodiment of the present invention. In this embodiment, in the basic circuit shown in FIG. 1, the primary winding of the output transformer T3 is connected to the location of the inductor L3, and the primary winding of the output transformer T4 is connected to the location of the inductor L4. The secondary windings of the output transformers T3 and T4 are connected in series and connected to a load R. One end of the load R is connected to the circuit ground. In this embodiment, the leakage inductance of the output transformers T3 and T4 is used as the inductors L3 and L4.
Capacitors C3 and C4 are connected in parallel to each of the inductors L3 and L4, and constitute a capacitive element as a whole. Therefore, a low-pass filter is formed with respect to the output to reduce harmonic components of power appearing at the output. Has the effect of causing In addition, since high-frequency output can be taken out by using two output transformers T3 and T4, there is an effect of simplifying heat loss design for the output transformer, and high-efficiency amplification is realized in a class E push-pull power amplifier circuit. This is effective in simplifying the adjustment of the inductance value of the resonance circuit, which is important for performing the adjustment.

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention. In this embodiment, in the fourth embodiment shown in FIG.
Both ends of the inductor L1 are connected to the circuit ground by capacitors C5 and C6. Each capacitor C
The values of C5 and C6 are set substantially equal. Inductor L
1 and the combined impedance of the capacitors C5 and C6 are set to be inductive near the operating frequency and equal to the inductor L1 shown in FIG. In this embodiment, approximately two capacitors C5 and C6 are connected in series.
Since the midpoint of the equally divided inductor L1 is connected to the ground of the circuit, high-frequency noise radiated from the circuit can be reduced, and the terminal voltage of each element can be stabilized even at high frequencies. This has the effect of stabilizing the operation of the entire circuit.

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. 7 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.

[0017]

According to the present invention, in a class E push-pull power amplifier circuit using a resonance circuit, a center tap of a first inductor is connected to one electrode of a DC power supply, and one end of the first inductor and one end of the first inductor are connected. At the other end are the second and third
, And the first and second switching elements are connected between the other ends of the second and third inductors and the other electrode of the DC power supply, respectively.
The first and second capacitors are connected in parallel to the respective switching elements, and the third and fourth capacitors are respectively connected in parallel to the second and third inductors.
A resonance circuit is formed together with the first and second inductors, and the first and second switching elements are alternately turned on and off, so that the second and third inductors and the capacitor are connected in parallel or the load circuit is coupled to the first inductor. Since the output power is supplied to the first and second switching elements, the circuit configuration is symmetric with respect to the first and second switching elements, and the difference in the length of the copper foil pattern at the time of mounting can be eliminated.
The high frequency coupling between the circuits can also be made uniform, so that by simply designing the corresponding elements in the circuit to be substantially equal, a highly symmetric operation can be obtained and the two switching elements can be placed in the ideal state or It can be relatively easily operated in a state close to that.

Further, when the load circuit is connected to the secondary winding of the output transformer which also serves as the first inductor or the second and third inductors, the heat loss design for the output transformer for coupling can be simplified and the E.sub.E is reduced. In the class push-pull power amplifier circuit, there is an effect that the adjustment of the inductance value of the resonance circuit which is important for realizing high efficiency amplification can be simplified.

The first inductor at the center of the resonance circuit is connected to the second inductor by a series circuit of fifth and sixth capacitors.
If it is equally divided and its midpoint is connected to the circuit ground, high-frequency noise radiated from the circuit can be reduced, and the terminal voltage of each element can be stabilized even at high frequencies. This has the effect of stabilizing the overall operation.

Further, 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 first conventional example.

FIG. 9 is a waveform chart showing the operation of the first conventional example.

FIG. 10 is a circuit diagram of a second conventional example.

FIG. 11 is a circuit diagram of a drive signal source used in a second conventional example.

FIG. 12 is a waveform chart showing the operation of the second conventional example in an ideal state.

FIG. 13 is a waveform chart showing an operation of the second conventional example in a state deviated from an ideal state.

[Explanation of symbols]

 Q1, Q2 First and second switching elements C1 to C4 First to fourth capacitors L1 First inductor L3, L4 Second, third inductor 7 DC power supply

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Anan 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. 72) Inventor Fushi Okamoto 1048 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Works Co., Ltd. No. 1048, Kadoma, Kamon, Fumonma-shi Matsushita Electric Works, Ltd. (56) References JP-A-63-62190 (JP, A) JP-A-1-217895 (JP, A) JP-A-4-355505 (JP, A) JP-A-7-170129 (JP, A) JP-A-7-170133 (JP, A) JP-A-7-170132 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H03F 3/217 H05B 41/24- 41/29

Claims (9)

(57) [Claims] 1. A first inductor having a center tap connected to one electrode of a DC power supply, second and third inductors having one end connected to one end and the other end of the first inductor, respectively. The first and second switching elements connected between the other electrode of the DC power supply and the other ends of the second and third inductors, and the first and second switching elements are turned on / off alternately. Driving means, first and second capacitors connected in parallel to the first and second switching elements, respectively, and second and third capacitors connected in parallel to the second and third inductors to form capacitive elements, respectively. A class E push-pull power amplifier circuit comprising a third and a fourth capacitor and a load circuit symmetrically coupled in the circuit. 2. The class E push-pull power amplifier circuit according to claim 1, wherein the load circuit is coupled to the first inductor. 3. The class-E push-pull power amplifier circuit according to claim 1, wherein the load circuit is uniformly coupled to the second and third inductors. 4. The second and third inductors, the third and fourth inductors, the first and second capacitors, the third and fourth capacitors, and the first and second switching elements are substantially equal. The class-E push-pull power amplifier circuit according to claim 1, 2 or 3, having characteristics. 5. A method in which a series circuit of fifth and sixth capacitors is connected in parallel to a first inductor, and a connection point between a fifth capacitor and a sixth capacitor is connected to the other electrode of a DC power supply. The class E push-pull power amplifier circuit according to claim 1, wherein: 6. The first and second switching elements are elements having output capacitance, and the output capacitance is used as all or a part of the first and second capacitors, respectively. 6. The class-E push-pull power amplifier circuit according to any one of claims 1 to 5. 7. The class E push-pull power amplifier circuit according to claim 1, wherein the element having the output capacitance is a field effect transistor. 8. 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 a first inductor or second and third inductors. A class E push-pull power amplifier circuit as described. 9. The load circuit includes an electrodeless discharge lamp, an induction coil wound in the vicinity of the electrodeless discharge lamp, and a matching circuit for matching impedance and supplying power efficiently. 9. The class-E push-pull power amplifier circuit according to claim 1, wherein: