JPH07212145A - E-class push-pull power amplifier circuit - Google Patents

Abstract

PURPOSE:To form a circuit configuration which easily to operates two switching elements in an ideal state or a in state near to it in an E-class push-pull power amplifier circuit. CONSTITUTION:The center tap of an inductor L1 is connected to a DC power source 7, and the parallel circuits of the switching elements Q1, Q2 and capacitors C1, C2 are connected to both terminals of the inductor L1 via inductor's L3, L4, and capacitors C3, C4 are connected in parallel with the inductors L3, L4, and also, a load circuit is connected in parallel with the inductors L3, L4 or the inductor L1. Therefore, it is possible to form the copper foil patterns of a printed circuit board symmetrically and to easily operate the switching element in the ideal state or the state near to it.

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, for example, it is used as a high-efficiency high-frequency power amplifier for a lighting device for 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 with the switching element Qa, a resonance coil L having a resonance point near the operating frequency, and a resonance capacitor C. It consists of a series circuit. Here, the capacitor Ca connected in parallel to the switching element Qa may substitute for or share a part of the output capacitance of the switching element Qa.

FIG. 9 shows waveforms of the voltage Va across the switching element Qa and the current Ia flowing through the switching element Qa when the ideal class E operation is performed. The characteristic of the class E operation is that the value Va and the slope of the voltage Va become 0 and the current Ia
Is flowing out, the switching loss when the switching element Qa shifts from OFF to ON becomes almost zero. Therefore, by using the class E power amplifier circuit, highly efficient power amplification can be realized even at high frequencies.

When the output of the class E single-ended power amplifier circuit of FIG. 8 is increased, the loss in the switching element Qa also increases as the output increases, and the heat generated causes the temperature of the switching element Qa to rise. Due to the temperature rise of the switching element Qa, the high output may be limited in the class E single-ended power amplifier circuit of FIG.

Therefore, based on the class E single-ended power amplifier circuit of FIG. 8, as shown in FIG. 10, a class E push-pull power amplifier circuit using two switching elements Qa and Qb has been devised. . 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 the operating frequency and a resonance capacitor are connected between the other ends of the inductors La and Lb. A series circuit of C 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 alternately turned on and off, and their drive signal sources 1a and 1b are used.
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 the class E push-pull power amplifier circuit as shown in FIG. 10, the loss in the switching element is reduced by the two switching elements Qa,
Qb can be shared 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 operation waveforms of the class E push-pull power amplifier circuit of 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 to flow into the respective switching elements Qa and Qb. , Switching element Q
The switching loss when a and Qb shift from OFF to ON can be made almost 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 or a state close thereto as shown in FIG. It is important to realize high efficiency power amplification. However, in a high frequency circuit, the copper foil pattern of the printed circuit board on mounting works as an inductance or a capacitance. Therefore, when the class E push-pull power amplifier circuit of FIG. 10 is mounted, the two switching elements Q are
As shown in FIG. 13, there may be a deviation in the operating state between a and Qb. Therefore, it tends to be difficult to adjust the two switching elements Qa and Qb so that they simultaneously operate in an ideal state or a state close thereto as shown in FIG. As a result, it is often difficult for the class E push-pull power amplifier circuit of FIG. 10 to obtain the power amplification efficiency of the ideal class E power amplifier circuit as shown in FIG.

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

[0009]

In the class E push-pull power amplifier circuit of the present invention, a center tap is connected to one electrode of a DC power source 7 as shown in FIG. 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 a DC power supply 7
Of the first and second switching elements Q1 and Q2 connected between the other electrode of the first and second ends of the second and third inductors L3 and L4, respectively, and the first and second switching elements Q1 and Q2. Drive means 1 for alternately turning on and off
a, 1b and the first and second switching elements Q1, Q
First and second capacitors C1 and C2, and second and third inductors L3 and L, which are connected in parallel to each other.
4 and third and fourth capacitors C3 and C4 respectively connected in parallel to form a capacitive element 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]

In the present invention, as shown in FIG. 1, since the class E push-pull power amplifier circuit is constructed substantially symmetrically, when mounted on a printed circuit board, the impedance due to the copper foil pattern of the printed circuit board is reduced to two switching elements. Q1, Q2
Can be made uniform with respect to. Also, since the circuit is substantially symmetrical, the corresponding elements, namely the second and third
Inductors L3, L4, first and second capacitors C
The operation of the entire circuit can be made extremely symmetrical only by making the characteristics of C1, C2, the third and fourth capacitors C3, C4, and the first and second switching elements Q1, Q2 substantially equal to each other. . Therefore, it becomes possible to easily operate the two switching elements Q1 and Q2 simultaneously in the ideal state or a state close to the ideal state as shown in FIG. The circuit of FIG. 1 is different from the circuit of FIG. 10 in that the current passing through the first inductor is supplied to each switching element through the other second and third inductors. A 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 is possible.

[0011]

FIG. 2 is a circuit diagram of the first embodiment of the present invention.
The circuit configuration will be described below. The pair of switching elements Q1 and Q2 are composed of power MOSFETs, and a capacitor C1 is provided between the drain and source thereof.
C2 is connected in parallel. These capacitors C1 and C2
May be shared or substituted for the output capacitance of the power MOSFET. The source of each power MOSFET is grounded and is connected to the negative electrode of the DC power supply 7, and the drain is connected to both ends of the inductor L1 via 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 required for class E operation to the switching elements Q1 and Q2. These inductors L
Capacitors C3 and C4 are connected in parallel to 3 and L4, respectively. The parallel connection between the capacitor C3 and the inductor L3 and the parallel connection between the capacitor C4 and the inductor L4 are set so as to exhibit substantially the same capacitive impedance near the operating frequency for class E operation, and the resonance is set along with the inductor L1. It constitutes the circuit. This resonance circuit includes switching elements Q1 and Q2.
Has 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. Further, the capacitors C1 and C2 are also set to have constant capacitances so that they have substantially the same capacitive impedance, so that the entire circuit has the switching element Q.
1 and Q2 are symmetrically configured. The printed circuit board on which this circuit is mounted is designed so that the copper foil patterns are substantially symmetrical and the circuit constants at high frequencies are symmetrical.

FIG. 3 is a circuit diagram of the second embodiment of the present invention. In this embodiment, the inductor L1 is the output transformer T1.
It is configured by using the leakage inductance of. A load R is connected to the secondary winding of the output transformer T1. One end of the load R is connected to the ground of the circuit. When the high frequency output is taken out by using the output transformer as in the present embodiment, one end of the taken out high frequency output can be connected to the ground of the circuit, and the output can be easily handled with a coaxial cable or a connector. it can. On the other hand, FIG.
When the load R is directly connected to the inductor L1 without passing through the output transformer as in the embodiment described above, there is an advantage that the number of parts is the smallest among the configurations in which the effects 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 5 and C6 are set to be substantially equal. Inductor L
The combined impedance of 1 and the capacitors C5 and C6 is set to be inductive near the operating frequency and equal to that of the inductor L1 shown in FIG. In this embodiment, the series circuit of the capacitors C5 and C6 makes it possible to obtain approximately 2
Since the midpoint of the equally divided inductor L1 is connected to the ground of the circuit, it is possible to reduce high frequency noise radiated from the circuit and stabilize the terminal voltage of each element even against high frequency. 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 the present embodiment, in the basic circuit shown in FIG. 1, the inductor L3 is connected to the primary winding of the output transformer T3, and the inductor L4 is connected to the primary winding of the output transformer T4. The secondary windings of the output transformers T3 and T4 are connected in series and connected to the load R. One end of the load R is connected to the ground of the circuit. In this embodiment, the leakage inductances of the output transformers T3 and T4 are used as the inductors L3 and L4.
Capacitors C3 and C4 are connected in parallel to the inductors L3 and L4 and form a capacitive element as a whole, so that a low-pass filter is formed for the output and harmonic components of the power appearing at the output are reduced. Has the effect of In addition, since high-frequency output can be taken out by using two output transformers T3 and T4, it has the effect of simplifying the design of loss heat for the output transformer and realizes high efficiency amplification 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 achieving this.

FIG. 6 is a circuit diagram of the 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 5 and C6 are set to be substantially equal. Inductor L
The combined impedance of 1 and the capacitors C5 and C6 is set to be inductive near the operating frequency and equal to that of the inductor L1 shown in FIG. In this embodiment, the series circuit of the capacitors C5 and C6 makes it possible to obtain approximately 2
Since the midpoint of the equally divided inductor L1 is connected to the ground of the circuit, it is possible to reduce high frequency noise radiated from the circuit and stabilize the terminal voltage of each element even against high frequency. This has the effect of stabilizing the operation of the entire circuit.

In the above embodiments, the load R is indicated by the symbol of resistance, but it may be a discharge lamp, for example. 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 an impedance matching circuit for the amplifier circuit and the discharge lamp 4 to supply electric power efficiently. It is a matching circuit. Needless to say, in each of the above embodiments, the constant of each circuit is adjusted so as to perform class E operation.

[0017]

According to the present invention, in the class E push-pull power amplifier circuit using the resonance circuit, the center tap of the first inductor is connected to one electrode of the DC power source, and one end of the first inductor and Second and third at the other end, respectively
Each of the inductors is connected to each other, 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 switching elements of, and the third and fourth capacitors are connected in parallel to the second and third inductors, respectively.
Load circuit that forms a resonance circuit together with the second inductor, alternately turns on and off the first and second switching elements, and connects the second and third inductors and the capacitor in parallel or is coupled to the first inductor. Since the output power is supplied to, the circuit configuration is symmetrical with respect to the first and second switching elements, and it is possible to eliminate the difference in the length of the copper foil pattern at the time of mounting,
The high frequency coupling between the circuits can also be made uniform, so that by designing the corresponding elements in the circuits to be approximately equal, a very symmetrical operation can be obtained and the two switching elements can be placed in the ideal state or It becomes relatively easy to operate in a state close to that.

If the load circuit is connected to the secondary winding of the output transformer that also serves as the first inductor or the second and third inductors, the design of loss heat for the output transformer for coupling can be simplified and E 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.

Further, the first inductor in the center of the resonance circuit is formed by a series circuit of fifth and sixth capacitors, and the first inductor is substantially two.
If the midpoint is equally divided and connected to the ground of the circuit, the high-frequency noise radiated from the circuit can be reduced, and the terminal voltage of each element can be stabilized against the high frequency. It has the effect of stabilizing the overall operation.

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 part of the first and second capacitors, or a load circuit is provided through a transformer. If the leakage inductance of this transformer is used as the inductive element of the resonance circuit, the number of parts can be reduced.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of the 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 diagram 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 diagram showing an operation of the second conventional example in an ideal state.

FIG. 13 is a waveform diagram showing the operation of the second conventional example in a state deviated from the 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 and third inductors 7 DC power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Anan 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor, Yuji Kumagai, 1048, Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Works, Ltd. (72) Inventor Taishi Okamoto 1048, Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor, Koji Nishimura, Kadoma, Osaka Prefecture 1048, Kadoma, Matsushita Electric Works, Ltd. (72) Shozo Kataoka, Kadoma, Osaka Prefecture 1048 Kadoma, Matsushita Electric Works, Ltd.

Claims (9)

[Claims] 1. A first inductor having a center tap connected to one electrode of a DC power source, and second and third inductors each having one end connected to one end and the other end of the first inductor, respectively. The first and second switching elements and the first and second switching elements respectively connected between the other electrode of the DC power source and the other ends of the second and third inductors are alternately turned on / off. Drive means, first and second capacitors respectively connected in parallel to the first and second switching elements, and second and third inductors respectively connected in parallel to form a capacitive element A class E push-pull power amplifier circuit comprising a load circuit symmetrically coupled in the circuit with a third and a fourth capacitor. 2. The class E push-pull power amplifier circuit of claim 1, wherein the load circuit is coupled to the first inductor. 3. The class E push-pull power amplifier circuit of claim 1, wherein the load circuit is evenly 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 to each other. The class E push-pull power amplifier circuit according to claim 1, 2 or 3, having characteristics. 5. A series circuit of fifth and sixth capacitors is connected in parallel to the first inductor, and a connection point of the fifth capacitor and the sixth capacitor is connected to the other electrode of the DC power supply. The class E push-pull power amplifier circuit according to any one of claims 1 to 4, which is characterized in that. 6. The first and second switching elements are elements having an output capacitance, and the output capacitance is used as all or part of the first and second capacitors, respectively. 6. A class E push-pull power amplifier circuit according to any one of 5 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 is connected via a transformer, and the leakage inductance of the transformer is used as the first inductor or the second and third inductors. The class E push-pull power amplifier circuit described. 9. The load circuit comprises an electrodeless discharge lamp, an induction coil wound in the vicinity of the electrodeless discharge lamp, and a matching circuit for matching impedance and efficiently supplying electric power. The class E push-pull power amplifier circuit according to any one of claims 1 to 8, wherein