JPS592210B2 - Parallel operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parallel operation system for a plurality of AM modulators (AM transmitters) that always maintains good synthesis balance and operates redundantly.

The first example of parallel operation of conventional AM modulators (AM transmitters)
As shown in the figure. Generally, in solid-state radio broadcasting equipment, the outputs of a plurality of amplitude modulators are combined and operated in parallel in order to obtain high output and redundant operation.

FIG. 1 is an example of parallel operation of two AM transmitters using the serial modulation method. In FIG. 1, 11 is a modulation signal input terminal, 12 is a carrier wave oscillator, and 131 and 132 are carrier wave excitation circuits, which amplify the output of the carrier wave oscillator 12 and excite the modulated power amplifiers 151 and 152. The modulated power amplifiers 151 and 152 include a series voltage drop type series modulator 1.
41 and 142 reduce the voltage of the power supplies 161 and 162 according to the amplitude of the modulation signal input terminal 11 and supply power. ITI and 1T2 are tuning circuits including impedance matching, and the outputs from 151 and 152 are I
The impedance is transformed by TI, 1T2 and the synthesizer 1
8, and the combined amplitude modulated power can be obtained at the output terminal 19. In this case, if the operating point (output, phase) settings of the two transmitters are not equal, a composite loss will occur, so accurate adjustment is required, and the modulation characteristics (modulation frequency characteristics, etc.) of the two transmitters are required. If there is a difference between the
If there is a phase difference in the carrier waves, including the combining circuit, there is a drawback that a phase modulation component may occur. The purpose of the present invention is to solve these drawbacks, and its feature is that a loop is provided to automatically equalize each amplitude modulation operation, and if one unit does not perform amplitude modulation operation at all due to a malfunction or the like, or A limiting circuit (or switch circuit) is provided to limit the loop from responding beyond a certain value when the difference is significant, so as not to damage the redundant operation, which will be described in detail below. FIG. 2 shows a first embodiment of the present invention, in which 21 is a modulation signal input terminal, 22 is a carrier wave oscillator, 2
31, 232 are carrier wave excitation circuits, 241, 242 are series modulators, 251, 252 are modulated power amplifiers, 261,
262 is a power supply, 27 is an output tuning circuit, 28 is an output synthesis circuit, 29 is an output terminal, 30 is a differential intensifier, 311, 31
2 is a resistor, and 321, 322, 323, and 324 are Zener diodes.

The operation of FIG. 2 is as follows.

As is well known, the output of the carrier oscillator 22 is transmitted to the carrier wave excitation circuit 2.
31, 232, modulated power amplifiers 251, 252
are excited in the same phase. Power supply 261 and modulated power amplifier 2
A series modulation amplifier 24 is inserted between the power supply terminals 51, and similarly a power supply 262 and a modulated power amplifier 252.
A series modulation amplifier 242 is also inserted between the power supply terminals. The series modulator is simply a bipolar transistor or F
A conventional series modulator that uses an ET or the like as a variable voltage drop resistance element may be used, but it has a lot of loss, so a series modulator that uses PWM (pulse width modulation) switching operation as shown in the system diagram in Figure 3 is generally used. used for. In FIG. 3, 41 is a modulation signal input terminal, 42 is a pulse width modulation circuit, 43 is a sample carrier wave oscillator, 44 is a 1 drive circuit,
45 is a high-speed power switching circuit, 46 is a power supply terminal, 4
7 is a low-pass filter, 48 is an output terminal, and 49 is a damper diode. The operation of this circuit will be briefly explained next. The output of the pulse width modulator 42 has a pulse width of
A PWM (pulse width modulation) signal proportional to the signal amplitude at the modulation input terminal 41 is obtained.

Generally, when the modulation signal is an audio signal, that is, 10KH
If it is necessary to modulate up to about z, the frequency of the sample carrier wave is on a 50 KHz sphere. Reference numeral 45 denotes a high-speed power switching circuit using switching elements such as bipolar transistors and FETs, which tips the current from the power supply terminal 46 in accordance with the input PWM1 drive signal.

At this time, since a high-speed switching diode 49 is connected between the input of the low-pass filter 47 and the ground as a damper diode, the 0 of the switching circuit 45
During the FF period, the low-pass filter input current flows from the damper diode 49, and the continuity of the current is satisfied by the energy stored in the coil of the low-pass filter input stage. A PWM signal can be obtained. If the low-pass filter 47 has a characteristic of passing the modulated signal but blocking the sample carrier wave, the average value of the input PWM waveform will be output as the output of the low-pass filter. That is, the voltage at the output terminal 48 can be changed without loss according to the modulation input signal, and by connecting the power supply terminal of the modulated power amplifier as a load to the output terminal, it can be operated as a modulator. Further, as is well known, the DC voltage at the output terminal 48 can be controlled by the DC bias of the input signal. In FIG. 2, the outputs of the modulated power amplifiers 25, 252 are combined by the output combining circuit 28; Assuming the circuit, the modulated power amplifier 251,
If the output voltages of 252 are made equal, the power supplied to the output combining circuit will be equal, and no loss will occur.

That is, in FIG. 4, 51 and 52 are input terminals, and 53
is an output terminal, and 54 is a high-frequency transformer with a high degree of coupling and an equal turn ratio for the next and second orders (n1=N2). Since the currents in the primary and secondary windings are equal (11-12), the input If the amplitudes are made equal, the synthesis will be balanced, and the reflection absorption resistance 5
No power is absorbed by 5.

The same applies to the case of Fig. 5, where 51 and 52 are input terminals, and 5
3 is an output terminal, 541 and 542 are high frequency transformers with a high degree of coupling, and the turns ratio of 541 and 542 should be equal (
As is well known, (N2=N4), the Nln3 input currents are equal.

By the way, the modulated power increases. If the width switch is configured with a voltage switching type circuit as shown in the circuit example shown in Fig. 6, if the saturated ON resistance of the switching element is ignored, there is a one-to-one correspondence between the source voltage and the high-frequency output voltage. . That is, the high frequency output amplitude is determined only by the supply voltage, regardless of the load current. In FIG. 6, 61 is an excitation input terminal, 62
is a positive power supply terminal, 63 is a negative power supply terminal, 64 is an output terminal, 65, 66 are power MOS-FETs 67, 68,
69 is a capacitor exhibiting sufficiently small impedance at the switching frequency, and 70 is an inverting human-powered transformer that excites the gates of 65 and 66 in opposite phases. When a square wave excitation waveform is input to 61, the power MOS-FET 65
, 66 alternately repeat 0N and 0FF operations, and a square wave output having an amplitude equal to the turtle current voltage is obtained at the output terminal 64, which is efficiently converted into high frequency energy.

Based on the above explanation, in order to always maintain the composition balance,
It is understood that the supply voltages of the modulated power amplifiers 251 and 252 should always be made equal.

30 to 32 in FIG. 2 constitute a feedback circuit for equalizing the voltages of the modulated power amplifier, and the operation of the feedback circuit will be explained below. First, two modulated power amplifiers 2
By applying the supply voltages EO, , EO2 to the differential amplifier circuit 30 to the differential amplifier circuit 30, the voltage difference between them is obtained.

The differential amplifier circuit has a gain of β and has inverted and non-inverted outputs. The gains of the modulation amplification sections 241 and 242 are α1 and α2, respectively, and the respective input voltages are Ei
l, Ei2, α1=ξGL, α2=? ? , and the non-inverted output has (EO, -EO2)β=(Ei pi α1
−Ei2・α2)β For the inverted output, (EO2−EOl)β
= (Ei2・α2−Eil・α1) Let Ei be the modulated input signal voltage that is outputted by β, and let the DC weight that sets the carrier wave level of each amplitude modulator be expressed by the input side bias voltages Ea and eb, When the non-inverting output of the differential amplifier is subtracted from the input signal or the inverted output is fed back to each input with the polarity of adding it to the input signal, the following relational expression is established.

{Ei-(EOl-EO2)β+Ea}α12EO,・
...(1) {Ei+(EOl-EO2)β+Eb
}α2=EO2...(2) From (1) and (2)...(3)...(4) If α1β>1, α2β>1, then 1+α1β Since Ki α1β, 1 + α2β Ki α2β・
...(3Y...(4γ).

In other words, the settings of the two circuits are different (E.Sb). Even if the characteristics do not match (α1\α2), EOl=E
It is understood that it will be O2.

Second, if one of the two circuits fails, EOl - EO2 becomes very large, and even in that case, if the loop operates so that it becomes EO,2 EO2, the feedback amount Redundant operations may be impaired due to an inappropriate amount of output, too much output, or too little output. In order to prevent this, an amplitude limiting circuit is provided at the output of the differential amplifier to limit the control width to approximately ±10 (fl).
Resistors 311, 312 and Zener diodes 321-32
. constitutes an amplitude limiting circuit. By inserting an amplitude limiting circuit, an imbalance within about 10% is always absorbed (both dynamically and statically), and even if one of the differential amplifiers fails, the output of the differential amplifier is clipped, making it possible to It has a redundant operation comparable to that of parallel operation. As explained above, the first
In this embodiment, firstly, the feedback loop is configured so that the two modulated power amplifier supply voltages (modulating voltages) are always equal, so the synthesis balance is always good, and secondly,
If one of them fails, the operation of the feedback loop is restricted and there is an advantage that redundant operation is not impaired. In the first embodiment, a case has been described in which a feedback circuit is configured using a circuit with equal input currents as a composite circuit so that the supply voltages of the modulated power amplifiers are equal, but as shown in FIG. Similarly, even if a circuit with equal input voltages (in this case, simply parallel connection) is used as a synthesis circuit, and a feedback circuit is configured so that the supply currents of the modulated power amplifiers are equal, The balance of synthesis is maintained.

In FIG. 7, 71 is a modulation signal input terminal, 72 is a carrier wave oscillator, 731, 732 are carrier wave excitation circuits, 74, .
742 is a series modulator, 751 and 752 are modulated power amplifiers, 76, 762 are power supplies, and 77 is an output tuning circuit.

731, 741, 751, 76, and 732, 742
, 752, and 762 constitute two AM modulators, No. 1 and No. 2, and their respective operations are the same as in the first embodiment.

In order to combine the outputs of these two AM modulators, if their outputs are connected in parallel, their output voltages will be equal, so if their output currents are equal, the power combination will be balanced. In other words, as described in the first embodiment, if a voltage switching type power amplifier circuit is used as the modulated power amplifier circuit, the magnitude of the power supply current and the high frequency output current will be 1:1.
If the power supply currents are made equal to accommodate this, the power combination will be balanced. In Figure 7, 821, 82
2 is a current shunt for converting the supply current of the modulated power amplifier into a voltage with respect to ground, and includes a differential amplifier 80 and a resistor 8.
As in the first embodiment, a good composite balance is always maintained so that the voltages of the shunts 11 and 812 are equal to each other.

However, if a failure occurs in either No. 1 or No. 2 and the power supply current becomes extremely different, the room amplifiers 83 and 841, 84
2, the smoothing circuit 8 applies a voltage proportional to the absolute value of the difference.
5 and is compared with a certain constant voltage by a voltage comparator 86, and the comparison output is used as a control signal to control an analog switch 87, thereby stopping the operation of the feedback circuit and preventing the redundant system from being lost. It is also possible to prevent
This is similar to the first embodiment. FIG. 8 is a system diagram of the third embodiment. In the first and second embodiments, the case of combining two transmitters (final stage series modulation method) was described, but as shown in the system diagram of FIG. 8, two transmitters?
Even in the case of parallel operation of the above arbitrary number n, the input signal of the differential amplifier is its own output voltage (or a voltage proportional to the output current o (5n output voltage (or voltage proportional to the output current) As in the first and second embodiments, if the average value of n is given, the composite balance of n pieces is maintained well, and even if one piece fails, its control (feedback amount) is limited. It is possible to operate without compromising redundancy.
In FIG. 8, 931 to 93n are modulation amplifiers, and only input terminals and output terminals are shown, and power supplies and modulated amplifiers are omitted. 91 is a modulation signal input terminal, and the signal is distributed to n systems by a divider 92, and is connected to n modulation amplifiers 9.
31-93n (M1-Mn).

Since each output is connected to a common point by resistors 941 to 94n, the common point is connected to a common point by resistors 941 to 94n.
If the resistance values of 42 are equal, the voltage will be average. 95,～
95n is a differential amplifier, and in order to feed back to the input side a voltage proportional to the voltage difference between the voltage at the common point and the output, the feedback loop is set so that each output is equal to the voltage at the common point. act.

In this way, as in the first and second embodiments, it is possible to maintain good synthesis balance, and even if a small number of modulation amplifiers fail, the resistors 961-96n and 971-9
Since the output of the differential amplifier is limited by the 7n Zener diode, the amount of feedback does not become inappropriate. In other words, redundant operations are not damaged. The present invention has the advantage of combining AM modulation power in a very well-balanced manner and enabling redundant operation, and can be used in high-output radio broadcasting equipment that requires high reliability.

[Brief explanation of the drawing]

Fig. 1 is an example of parallel operation of a conventional AM modulator, Fig. 2 is a first embodiment of the present invention, Fig. 3 is a system diagram of a series modulator using a pulse width modulation method, and Fig. 4 is an input current FIG. 5 is an example of another combining circuit where the input currents are equal, FIG. 6 is an example of a circuit of a voltage switching type modulated power amplifier, and FIG. 7 is a second embodiment of the present invention. Example, FIG. 8 is a third embodiment of the present invention. 11, 21, 41, 71, 91...Modulation signal input terminal, 12, 22, 72...Carrier wave oscillator,
131, 132, 231, 232, 731, 732...
...Carrier wave excitation circuit, 14,,142,24,,2
42,741,742,93,~93n...Modulation (power) amplifier, 151,152,251,252,
75,,752...Modulated (power) amplifier, 1
6,,162,26,,262,761,762...
...Power supply, 17,,172,27,77...
Output tuning circuit, 18, 28...Synthesizing circuit, 19
, 29, 48, 53, 64, 79... Output terminal, 30, 80, 83, 951-95n... Differential amplifier, 311, 312, 811, 822, 96, - 9
6n, 941-94n...Resistor, 321-3
2,,97,~97n...Zena diode,
42...Pulse width modulation circuit, 43...
Sample carrier wave oscillator, 44...1 drive circuit,
45... Switching circuit, 46...
Power supply terminal, 47...Low pass filter, 49.
...Diode, 51,52...Input terminal, 55...Reflection absorption resistor, 54,541,
542...High frequency transformer, 61...
Excitation input terminal, 62...Power terminal (+), 63
...Power terminal (to), 65, 66...
MOS-FET, 67-69... Capacitor 70... Phase inversion input transformer, 821, 82
2...Shunt, 841, 842...Diode, 85...Smoothing circuit, 86...
・Voltage comparator, 87...Analog switch, 9
2...Distribution circuit.

Claims (1)

[Claims] 1. In a parallel operation system of a plurality of AM modulators, each AM modulator is a DC-coupled system in which the supply voltage of the modulated power amplifier can be controlled by controlling the low level part of the input. a combination circuit that combines the respective modulated outputs, and a differential amplifier that obtains an output that is proportional to the difference between the output of a modulated power amplifier and the output of another modulated power amplifier or the average value of the outputs of a plurality of modulated power amplifiers. The output of the differential amplifier is fed back to the input of each AM modulator with a polarity that reduces the difference, and a limiting circuit or a switch circuit is provided to limit the amount of control. Parallel operation method. 2. The parallel operation method according to claim 1, in which a combining circuit in which the input currents are equal is used as the combining circuit, and an amount proportional to the output voltage, that is, the supply voltage of the modulated power amplifier is used as the output of the modulated power amplifier. . 3. The parallel operation method according to claim 1, in which a combining circuit in which the input voltages are equalized is used as the combining circuit, and an amount proportional to the output current, that is, the supply current of the modulated power amplifier is used as the modulated power amplifier output. .