JPH08237063A - Output composition circuit - Google Patents

Abstract

PURPOSE: To attain the composition of large electric powers regardless of the use of small sized cores by connecting in parallel secondary windings of transformer systems each comprising plural unit transformers where the output of a high frequency electric power amplifier is applied to each primary winding and their secondary windings are connected in series. CONSTITUTION: A high frequency signal outputted from power amplifier circuits 111-11n of a 1st group 11 is fed to primary windings of unit transformers T11-T1n. Furthermore, the high frequency signal outputted from power amplifier circuits 121-12n of a 2nd group 12 is fed to primary windings of unit transformers T21-T2n. Moreover, a 1st transformer system T1 is made up of the transformers T11-T1n and secondary windings of the transformers T11-T1n are connected in series. A 2nd transformer system T2 is made up of the transformers T21-T2n and secondary windings of the transformers T21-T2n are connected in series. Secondary windings of the 1st transformer system T1 and the 2nd transformer system T2 are connected in parallel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output synthesizing circuit used for a power amplifying circuit of a series synthesizing type digital amplitude modulation transmitter used in medium-wave radio broadcasting and the like.

[0002]

2. Description of the Related Art A conventional output synthesizing circuit will be described with reference to FIG. 9, taking a case where it is used in a power amplifying circuit of a serial synthesizing type digital amplitude modulation transmitter as an example.

Reference numeral 91 is a signal wave generation circuit for generating a signal wave, and the signal wave generated by the signal wave generation circuit 91 is added to an A / D converter 92. Then, in the A / D converter 92, it is converted into, for example, a 12-bit digital signal. This digital signal is applied to the encoder 93 and converted into a code corresponding to the magnitude of the digital signal.

At this time, when the digital signal is at the maximum level, 4095 signals corresponding to 12 bits are output from the encoder 9.
3 is output, and if there is no digital signal, the encoder 93 outputs nothing. In this way, the encoder 93 outputs the number of signals corresponding to the magnitude of the digital signal. The output of the encoder 93 is applied to each of the switches SW to set the switches SW to the ON state.
Further, a high frequency signal from the carrier wave generator 94 is applied to the switch SW. This high frequency signal passes through the switch SW in the ON state and the power amplifier circuits 95a to 95a.
n is added and amplified.

The signals amplified by the power amplifier circuits 95a to 95n are added to the primary windings of the transformers Ta to Tn. The secondary windings of the transformers Ta to Tn are connected in series. Further, one end thereof forms the output terminal OUT and the other end is grounded. The output terminal OUT is connected to a load impedance (not shown).

According to the above configuration, in the case of medium-wave radio broadcasting, for example, the power amplifier circuits 95a to 95n are operated in the number corresponding to the magnitude of the signal wave to be broadcast. Therefore, when the signal wave is large, many power amplification circuits 95a to 95n are provided.
And a small number of power amplifier circuits 95a to 95n operate when the signal wave is small. Then, the outputs of the power amplification circuits 95a to 95n in the operating state are the transformers
Applied to the primary winding of Tn. The outputs of the power amplifier circuits 95a to 95n added to the primary windings are the transformers Ta to Tn.
Are combined on the secondary side of and output to the output terminal OUT. At this time, the output terminal OUT outputs an amplitude-modulated wave having an amplitude according to the magnitude of the signal wave.

By the way, in the output combining circuit described above, the transformer T having the structure shown in FIG. 10 is used. 101 is
It has a ring shape with a so-called toroidal core. A primary winding 102 is wound around the core 101, and a copper pipe is passed through the hollow portion of the core 101 to form a secondary winding 103. The secondary winding 103 is the core 101 or the primary winding 1.
It is arranged so as not to touch 02. In the case of this configuration, the potential difference v between the primary and secondary windings 102 and 103 of the transformer T is maximized.

Here, the output voltage of the secondary winding 103 is v
Further, when the output current is i, the output power P of the transformer T
0 is represented by P0 = v · i (1). The primary and secondary windings 10 of the transformer T
The voltage applied between 2 and 103 must be smaller than the withstand voltage determined by the material, shape, and size of the transformer T. Further, since the conductivity of the secondary winding 103 is finite,
When the current flowing through the secondary winding 103 increases, the secondary winding 1
03 temperature rises. Therefore, since it is necessary to suppress the temperature rise of the secondary winding 103, the current flowing through the secondary winding 103 also has an upper limit.

[0009]

When a large amount of electric power is taken out from the secondary side of the transformer T, it is necessary to increase one or both of the voltage v and the current i, as can be seen from the equation (1). Here, it is assumed that the voltage v and the current i have the upper limit values. To further increase the output power from this state, consider the case where the current i is increased. At this time, if the radius d of the copper pipe of the secondary winding is increased so that a large amount of current i can flow, the gap between the primary winding and the secondary winding is narrowed, and the voltage v is lowered. On the contrary, the voltage v
Considering the case of increasing the temperature, in this case, it is necessary to reduce the radius d of the copper pipe and the current i must be reduced.

As can be seen from the above relation, when a large amount of electric power is taken out from the secondary side of the transformer T, the radius d of the copper pipe has an optimum value. The electric power determined by the voltage v and the current i that can be taken out at the optimum value is the maximum electric power obtained by using the transformer. Therefore, in order to obtain more power than that, the number of transformers connected in series is increased. However, when the number of transformers is increased, a large voltage is applied to the transformer located on the output end side. Therefore, the inner diameter of the core itself becomes large so as to withstand a high voltage.

By the way, a core used in a high frequency band,
For example, a ferrite core becomes difficult to manufacture if it exceeds a certain size, and the price rises sharply. In addition, since it is necessary to provide an insulation interval, the size and volume of the output combining circuit composed of a plurality of transformers are increased.

The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide an output synthesizing circuit which can synthesize a large amount of electric power by using a small core which can be obtained at a low cost.

[0013]

The output combining circuit of the present invention comprises a plurality of unit transformers each having a primary winding to which the output of the high frequency power amplifier is applied and whose secondary windings connected in series. The transformer device is configured, and the secondary windings of the respective transformer devices are connected in parallel.

Further, the unit transformer includes an annular core, a primary winding wound around an annular portion of the core, and a secondary winding of a conductor passing through the hollow portion of the core.

A switch is connected between both terminals of the primary winding of the unit transformer.

Further, the output of one power amplifier is applied to the primary windings of a plurality of unit transformers constituting different transformer devices.

Further, different unit transformers are connected to each other between the unit transformers.

[0018]

According to the above construction, one transformer device is constituted by a plurality of unit transformers in which the output of the high frequency power amplifier is applied to the primary winding and the secondary windings are connected in series with each other. There is. The transformer devices having such a configuration are connected in parallel. Therefore, even when a large output is obtained, the number of unit transformers constituting one transformer device can be reduced. Therefore, the voltage applied to the unit transformer located on the output side of each transformer device does not need to be high, and a small unit transformer core can be used. As a result, a compact and inexpensive output synthesis circuit can be realized. Also, the unit transformer has an annular core,
The core is composed of a primary winding wound around an annular portion and a secondary winding of a conductor passing through the hollow portion of the core. In this way, when the conductor passing through the hollow portion of the core is used as the secondary winding, the configuration in which the secondary windings of each unit transformer are connected in series can be easily realized.

When a switch is connected between both terminals of the primary winding of the unit transformer, for example, when the primary winding is opened due to an abnormality in the power amplifier circuit connected to the primary winding, the switch is turned on. The conduction makes it possible to prevent the primary winding from becoming an open state. Further, in the case of a configuration in which the output of one power amplifier is applied to the primary windings of a plurality of unit transformers that form different transformer devices,
The output per power amplifier can be increased.

Further, when different unit transformers are connected to each other, the conductors connecting the unit transformers function as a reinforcing member, and the strength of the entire unit can be increased.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

Reference numerals 111 to 11n are power amplification circuits forming the first group 11, and 121 to 12n are power amplification circuits forming the second group 12. A high-frequency signal is applied to the power amplifier circuits of the groups 11 and 12 from a switch (not shown) set to the ON state as described in the related art. Then, the power amplification circuits 111 to 11 of the first group 11
The high frequency signal output from n is a unit transformer (hereinafter,
Applied to the primary winding of T11-T1n (simply referred to as transformer). In addition, the power amplifier circuits 121 to 1 of the second group 12
The high frequency signals output from 2n are transformers T21 to T2.
n primary winding. The transformers T11 to T
1n constitutes the first transformer device T1, and the transformer T1
Secondary windings 1 to T1n are connected in series. Also,
The transformers T21 to T2n form a second transformer device T2, and the secondary windings of the transformers T21 to T2n are connected in series.

The secondary windings of the first transformer device T1 and the second transformer device T2 are connected in parallel. In this case, the secondary windings of the transformer T1n and the transformer T2n are connected to form the output terminal OUT. The secondary windings of the transformer T11 and the transformer T21 are connected and grounded.

In the above-mentioned configuration, for example, in the case of medium-wave radio broadcasting, the number of power amplifier circuits 111 to 11 according to the magnitude of the signal wave to be broadcast is the same as described in the prior art.
A high frequency signal is applied to n, 121 to 12n. Therefore, when the signal wave is large, many power amplifier circuits 111
To 11n and 121 to 12n operate, and the power amplifier circuits 111 to 11n and 121 are small when the signal wave is small.
~ 12n works. The outputs of the power amplifier circuits 111 to 11n in the operating state are the transformers T11 to T1n,
Applied to the primary winding of T21-T2n. Power amplifier circuits 111 to 11n and 121 to 12n added to the primary winding
Are combined on the secondary sides of the transformers T1 to Tn. Further, the outputs of the transformers T1 to Tn are combined and output to the output terminal OUT. At this time, the output terminal OUT outputs an amplitude-modulated wave having an amplitude according to the magnitude of the signal wave.

According to the above configuration, the two transformers T1 and T2 are connected in parallel to obtain a large electric power.
When the two transformer devices T1 and T2 are connected in parallel in this way, a large amount of electric power can be obtained even if the number of transformers connected in series to one transformer device T1 and T2 is small. Therefore, compared with a configuration in which a plurality of transformers are simply connected in series, even when the same electric power is obtained, the output terminal O
The voltage of the transformer located on the UT side becomes low. Therefore, a small core can be used, and the overall structure can be reduced. In this case, if the number of transformer devices connected in parallel is increased, a large output can be obtained without increasing the voltage of the transformer located on the output terminal OUT side.

In each transformer device, a plurality of transformers having the same structure are connected in series. Here, one transformer will be described with reference to FIG.

Reference numeral 21 is a toroidal core formed in an annular shape, and a primary winding 22 is wound around each annular portion. The terminals 23a and 23b of the primary winding 22 are connected to a power amplifier circuit (not shown). In addition, a conductor such as a copper pipe 2 is provided in the hollow portion of the toroidal core 21.
4 is passed. In this case, the copper pipe 24 forms a secondary winding corresponding to the primary winding 22. The copper pipe 24 is commonly used as a secondary winding of an adjacent transformer, and the secondary windings are connected in series.

Next, another embodiment of the present invention will be described with reference to FIG. Note that, in FIG. 3, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted. In this embodiment, a switch S is connected between both ends of the primary windings of the transformers T11 to T1n and T21 to 2n.

As described above, in the case of an output combining circuit having a structure in which a high frequency signal is applied to the primary windings of a plurality of transformers to obtain a combined output from the secondary windings connected in series, for example, the primary winding of the transformer is used. When even one line is open, there is a characteristic that signals are not combined. Therefore, when an abnormality occurs in the power amplification circuit 41 and the primary winding is likely to open, the primary winding is short-circuited by the switch S so that the signals can be combined.

The configuration and operation of the switch S will be described with reference to FIG. Since each switch S has the same configuration, only one of them will be described. 41 is a power amplifier circuit, and the power amplifier circuit 41 is the primary winding t of the transformer T.
Connected to 1. In addition, t2 is a secondary winding. The switch S is connected between both ends of the primary winding t1. The switch S is composed of a gas discharge circuit S1 and a short circuit switch S2. With this configuration, when an abnormality occurs in the power amplification circuit 41 and, for example, a high voltage is generated in the primary winding t1, the gas discharge circuit S1 is discharged and becomes a short-circuited state. At this time, if a short-circuit current flows through the gas discharge circuit S1 for a long time, the temperature becomes high. Therefore, when the abnormal state of the power amplification circuit 41 appears as an increase in voltage or current, for example, the abnormality detection circuit 42 detects it and short-circuits the short-circuit switch S2. As a result, it is possible to prevent a short-circuit current from flowing through the short-circuit switch S2 for a long time, and prevent the gas discharge circuit S1 from generating heat. Although the gas discharge circuit S1 has a quick response, it has a characteristic that it becomes highly heated when a short-circuit current flows for a long time. It prevents the fever of.

Next, another embodiment of the present invention will be described with reference to FIG. Reference numerals 511 to 51n denote power amplification circuits. The output of one power amplification circuit is divided and added to the primary windings of the transformers of the transformer devices T1 and T2 connected in parallel with each other. In addition, each of the transformer devices T1 and T2 includes a plurality of transformers T11 to T1n and T21 to T21.
T2n, the secondary side of which is connected in series. Then, one ends of the transformer devices T1 and T2 form an output terminal OUT, and the other ends are grounded. With this configuration, the output per power amplifier circuit can be increased, and the power can be increased.

Next, another embodiment of the present invention will be described with reference to FIG. 611 to 61n are power amplifier circuits,
T1 and T2 are transformer devices connected in parallel. One ends of the transformer devices T1 and T2 form an output terminal OUT, and the other ends are grounded. In addition, each transformer device T
1, T2 are a plurality of transformers T11 to T1n,
It is composed of T21 to T2n, and its secondary side is connected in series.

In this embodiment, each transformer device T1, T
2 is connected by short bars 62 not only to both ends on the secondary side but also to each other between unit transformers. Short bar 62
Is made of, for example, aluminum and is used for positioning and reinforcement when the copper pipe forming the secondary winding is long. If the position where the short bar 62 is connected is selected between the points where the potentials are equal on the secondary sides of the transformers T1 and T2, no current will flow through the short bar 62 and the electrical operation will not be affected.

Incidentally, FIG. 7 schematically shows a structure in which transformer devices connected in parallel are connected by a short bar. T1 and T2 are transformer devices, and each transformer device T
1, T2 are a plurality of transformers T11 to T1n,
The secondary windings t1 and t2 are connected in series. In addition, the transformer devices T1, T
One end of 2 is connected in parallel with the output conductor 71, and the output terminal O
It constitutes the UT. The other ends of the transformers T1 and T2 are connected to the ground conductor 72 and grounded. The transformers T1 and T2 are connected by a short bar 73.

Next, another embodiment of the present invention will be described with reference to FIG. 811 to 81n are power amplifier circuits,
T1 to T3 are transformer devices connected in parallel. One end of the transformer devices T1 to T3 forms an output terminal OUT, and the other end is grounded. In addition, each transformer device T1
To T3 are a plurality of transformers T11 to T1n and T1, respectively.
21 to T2n and T31 to T3n, and their secondary sides are connected in series. And the transformer device T1
Up to T3 are connected between the transformers by the short bar 81. Further, the transformers T11 to T1n and T2
1 to T2n and T31 to T3n have a switch S between the primary windings.
Is connected.

According to this structure, by increasing the transformer devices T1 to T3 connected in parallel, the output power can be increased without increasing the voltage or current handled by one transformer. Further, the switch S connected between both ends of the primary winding prevents the primary winding from being opened. The secondary windings of the transformer devices T1 to T3 are reinforced by the short bar 81. Therefore, it is suitable as an output synthesizing circuit for a transmitter used in a high-power medium-wave digital amplitude modulation method.

In the above embodiments, the output of each power amplifier is the same. However, the output of each power amplifier is weighted so that the output of each power amplifier is different. When connecting the transformer devices with a short bar, it is desirable that the potentials at the points where the short bars are connected are the same between the transformer devices during the operation. Therefore, for example, the outputs of the power amplifiers added to the transformers of the respective transformer devices are controlled to be balanced.

As described above, according to the present invention, the output power can be increased without increasing the voltage and current handled by the transformers constituting the transformer devices connected in parallel with each other. Further, by appropriately selecting the number of transformer devices connected in parallel, the number of transformers forming each transformer device, etc., for example, a transmitter of all output power required for medium-wave band radio broadcasting can be obtained. Can be manufactured. Further, even when the output power is increased, it is not necessary to increase the core size of the transformer, so that an inexpensive and compact output combining circuit can be realized.

[0039]

According to the present invention, an inexpensive and compact output synthesis circuit can be realized.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram showing a transformer used in the present invention.

FIG. 3 is a circuit configuration diagram illustrating another embodiment of the present invention.

FIG. 4 is a diagram illustrating a switch used in the present invention.

FIG. 5 is a circuit configuration diagram illustrating another embodiment of the present invention.

FIG. 6 is a circuit configuration diagram illustrating another embodiment of the present invention.

FIG. 7 is a diagram for explaining the present invention, showing a schematic configuration in which transformer devices are connected by short bars.

FIG. 8 is a circuit configuration diagram illustrating another embodiment of the present invention.

FIG. 9 is a circuit configuration diagram illustrating a conventional example.

FIG. 10 is a diagram illustrating a switch used in a conventional example.

[Explanation of symbols]

 111-11n, 121-12n ... Power amplification circuit T1, T2 ... Transformer device T11-T1n, T21-T2n ... Unit transformer

Claims (5)

[Claims] 1. A respective transformer device is composed of a plurality of unit transformers to which an output of a high frequency power amplifier is applied to a primary winding and secondary windings are connected in series with each other. An output combining circuit in which the secondary windings of a transformer device are connected in parallel. 2. The unit transformer comprises an annular core, a primary winding wound around an annular portion of the core, and a secondary winding of a conductor passing through a hollow portion of the core. The output combining circuit according to claim 1. 3. The output combining circuit according to claim 1, wherein a switch is connected between both terminals of the primary winding of the unit transformer. 4. The output of one power amplifier is applied to the primary windings of a plurality of unit transformers constituting different transformer devices.
An output combining circuit according to any one of 1. 5. The output combining circuit according to claim 1, wherein different transformer devices are connected to each other between respective unit transformers.