JPH0549125B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drive circuit for a PWM power amplifier, and in particular to a bridge type drive circuit with a simplified circuit configuration.
PWM (Pulse Width Modulation) power amplifier
Provides PWM drive input. Regarding the drive circuit of PWM power amplifier.

[Conventional technology]

PWM power amplifiers have recently become popular due to their high power efficiency and low power consumption.

In addition, the power amplifier circuit in the PWM power amplifier configuration can double the applied power supply voltage compared to the push-pull power amplifier circuit, and therefore the power supply feeder can also be made thinner. There is a tendency for bridge-type power amplifier circuits, which have the following characteristics, to be used frequently. The basic form of this bridge-type power amplifier circuit that uses PWM is to place switching circuits that use semiconductor active elements, such as power-type MOSFETs, on the four sides of the bridge, and to connect the load to the neutral side and switch the power supply voltage. It operates in such a way that a binary amplified output is supplied to the load by applying the voltage and switching the switching circuit. In this case, the input gate signal for switching each switching circuit is a PWM type binary pulse signal. The drive circuit of a PWM amplifier generates and supplies sufficient drive voltage to switch, or drive, the bridge type amplifier circuit, and of course the signal waveform is PWM.
Waves are used.

[Problem that the invention seeks to solve]

However, the conventional PWM of this kind mentioned above
Since the PWM wave itself cannot pass through a transformer, the power amplifier drive circuit must be driven in a circuit format that is directly coupled to the power amplifier circuit. When driving in a format that is not separated from the power amplifier circuit in this way, there is a risk that unnecessary pulse components will be induced into the power amplifier circuit side through a common line such as a ground circuit that spans both, causing it to malfunction. Since the cost becomes extremely high, it is necessary to perform the drive operation on the premise that measures are taken to eliminate the occurrence of this problem.

For this reason, in the case of a drive circuit intended for a bridge-type power amplifier circuit, it is necessary to configure four channel driver circuits that are separate and independent from each other to drive the switching circuits that constitute the four sides of the bridge. In addition, regarding the power supply of the bridge type power amplifier circuit itself, three types of power supply circuits, including one common power supply, which are separated and independent from each other, are required for the switching circuit, and the configuration of the power amplifier circuit as well as the drive circuit is required. The disadvantage is that it is extremely complex.

The purpose of the invention is to eliminate the above-mentioned drawbacks and to
The signal itself is once tone bursted (tone burst).
An object of the present invention is to provide a PWM power amplifier drive circuit that greatly simplifies the circuit configuration by providing means for converting the signal into a burst signal and allowing it to pass through a transformer.

[Means for solving problems]

The drive circuit of the PWM power amplifier of the present invention is
Of the four switching circuits arranged on each side of a bridge circuit having four sides connected in phase, one set of two sets of opposing sides arranged are each switched by the first PWM drive input, and the other set is switched respectively by the first PWM drive input. A second PWM drive input with the polarity inverted from the first PWM drive input.
By switching with PWM drive input, the first
The first and second PWM drive inputs are supplied to a bridge type PWM power amplifier that obtains a power amplifier for a PWM signal with the same pulse train as the PWM drive input.
In a drive circuit of a PWM power amplifier, a first PWM signal generated as a modulating wave is a sine wave of a predetermined frequency, which is the load frequency, and the first PWM signal.
A second PWM signal with the polarity of the PWM signal inverted is applied to a first tone burst signal having the same frequency and the same pulse train configuration as the first PWM signal, and a second tone burst signal having the same pulse train configuration as the second PWM signal. tone burst converting means for converting and outputting a tone burst signal, and outputting the first tone burst signal and the second tone burst signal through a two-output coupling transformer, respectively, to generate the same pulse train as the first tone burst signal. two third tone burst signals having the same configuration and two fourth tone burst signals having the same pulse train configuration as the second tone burst signal; The tone burst signals are each full-wave rectified and input to the two first PWM drive inputs and the two second PWM drive inputs to the bridge type.
It has a configuration including a PWM drive input supply means for supplying to a PWM power amplifier.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The drive circuit of the embodiment shown in FIG.
A drive circuit consisting of 1 to 14, and a bridge power amplifier circuit 1 driven by this drive circuit.
5, a coil 16 and a capacitor 17 as an integrating circuit that receives the output of the bridge power amplifier circuit 15 and regenerates the input signal waveform input from the transformer 1, and a load 18 supplied with the regenerated input signal waveform. be done.

In FIG. 1, a transformer 1, a comparator 2, a triangular wave generator 3, an inverter 4, a square wave oscillator 5, 6, and an operational amplifier 7, 8 constitute tone burst conversion means, transformers 9, 10, full wave rectifiers 11- 14 constitutes a PWM drive input supply means.

Transformer 1, comparator 2, triangular wave generator 3
forms a PWM wave generation circuit.

First, we will explain the basics of PWM wave generation using a sine wave as a modulating wave. FIG. 4 is a block diagram showing the basics of PWM wave generation, and FIG. 5 is a waveform diagram for explaining PWM wave generation.

A sine wave input signal having a predetermined frequency is input to the comparator 21, and this and the triangular wave generator 22
By comparing the triangular wave output from the
PWM waves can be easily obtained. The PWM input and PWM output in FIG. 5 show the content of comparison processing by the comparator 21.

The PWM output from the comparator 21 is amplified to a predetermined level by a pulse amplifier 23, and then a reduction filter including a coil 24 and a capacitor 25 extracts only the input signal component and supplies it to a load 26. In this case, the pulse amplifier 8 in charge of power amplification targets a binary logical value of ON or OFF, and performs binary amplification using a switching element.
High power efficiency can be achieved with extremely low power consumption. It should be noted that the triangular wave pulse frequency used as the comparison signal needs to be several times to several ten times as high as the input signal, and therefore the switching element needs to be capable of high-speed switching.

Returning again to FIG. 1, the explanation of the embodiment will be continued. A sine wave as an input signal from transformer 1,
Further, the comparator 2 receives a triangular wave as a comparison wave from the triangular wave generator 3 and outputs a PWM wave.

FIG. 3 is a diagram of main waveforms in the embodiment of FIG. 1. The explanation of FIG. 1 will be continued below with reference to FIG. 3.

The comparator 2 output shown in Figure 3 is the first
It is output as a PWM signal to the inverter 4 and the square wave oscillator 5.

The inverter 4 inverts the polarity of the input first PWM signal and outputs it, and the output of the inverter 4 is supplied to the rectangular wave oscillator 6 as a second PWM signal.

The rectangular wave oscillator 5 operates as a rectangular wave oscillator that outputs a signal of a predetermined frequency f only when the input first PWM signal is positive, and supplies the output to the operational amplifier 7. The operational amplifier 7 amplifies this to a predetermined level and outputs it, and the output of the operational amplifier 7 is supplied to the transformer 9 as a first tone burst signal.

On the other hand, the square wave oscillator 6 also receives the second input signal.
It operates as a rectangular wave oscillator that outputs a signal of frequency f only when the PWM signal is positive, and supplies its output to the operational amplifier 8. The operational amplifier 8 amplifies the input to a predetermined level and outputs the amplified signal, and the output of the operational amplifier 8 is supplied to the transformer 10 as a second tone burst signal. The above-mentioned first and second
An example of both the PWM signal and the first and second tone burst signals is shown in FIG.

In this way, the first and second PWM signals are converted into first and second tone burst signals having the same pulse train configuration as the first and second PWM signals, respectively.

Both the transformer 9 and the transformer 10 are constructed as a two-output coupling transformer, and generate tone burst signals of the same level on two secondary sides having the same predetermined winding ratio. The outputs of the secondary sides of these transformers with intermediate taps are supplied to full-wave rectifiers 11 and 12 in the case of transformer 9 and to full-wave rectifiers 13 and 14 in the case of transformer 10.
The four full-wave rectified outputs are supplied to the bridge power amplifier circuit 15 as drive signals.

Among the four rectified outputs obtained on the secondary side of transformers 9 and 10, the rectified output obtained on the output side of full-wave rectifiers 11 and 12 is the rectified output corresponding to the portion exceeding the 0 level of the first PWM signal. , and as shown in the waveform diagram of Figure 3, the first level of the level range of P1
Similarly to the waveform of the PWM signal, the level itself has a value necessary for switching drive of the bridge power amplifier circuit 15.

In this way, one-to-two third tone burst signals are generated.

In addition, the output rectification of the full-wave rectifier circuits 13 and 14 is as follows:
This is a rectified output corresponding to the part of the first PWM signal that does not exceed the 0 level, and as shown in the waveform diagram in Figure 3.
Similarly to the waveform of the second PWM signal in the level range of P2, the level has the same value as the outputs of the full-wave rectifier circuits 11 and 12.

In this way, one-to-two fourth tone burst signals are generated.

The bridge power amplifier circuit 15 uses these two pairs of four full-wave rectified output pulses as drive voltages to switch the switching elements.
It generates an output with the same waveform as the PWM signal, but with only the level amplified to the required level for application to the load 18.

FIG. 2 is a block diagram showing in detail the bridge power amplifier circuit 15 of FIG. 1.

The bridge power amplifier circuit 15 has switching circuits 151 to 154 arranged on four sides, and a load 18 is connected to the neutral side via a coil 16 and a capacitor 17. The switching circuits 151 to 154 are
Power type with high switching speed and high voltage in mind
This is a switching circuit that uses MOSFET as a switching element, and each full-wave rectifier 11
~12 full-wave rectified output pulses are converted into power type
The signal is received by the gate electrode of the MOSFET and switched, and binary amplification is performed to generate a level-amplified PWM signal output with the same waveform as the first PWM signal to a low-pass filter consisting of a coil 16 and a capacitor 17.

A low-pass filter constituted by a coil 16 and a capacitor 17 extracts the sine wave of the original input signal from this PWM signal output and supplies it to a load 18.

In this way, it is possible to configure a drive circuit that can operate independently while being separated from the power amplifier circuit by the coupling transformers 9 and 10, and the drive circuit for driving the bridge power amplifier circuit 15 is extremely difficult to operate. A simplified two-channel configuration is required, and the bridge power amplifier circuit can also be configured with a single power supply. The reason why such simplification is possible is basically a feature of the present invention.
By tone burst processing of PWM signal.

〔Effect of the invention〕

As explained above, according to the present invention, in the drive circuit of a PWM power amplifier using a bridge type power amplifier circuit, a PWM signal is converted into a tone burst signal, outputted via a transformer, and then full-wave rectified. By using this as the drive voltage, it is possible to realize a PWM power amplifier drive circuit that can greatly simplify the circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a block diagram showing the details of the bridge power amplifier circuit shown in Fig. 1, Fig. 3 is a main waveform diagram in the embodiment of Fig. 1, Fig. 4 is a block diagram showing the basics of PWM wave generation, and Fig. 5 is a block diagram showing the basics of PWM wave generation. The figure is a waveform diagram for explaining PWM wave generation. 1,9,10...Transformer, 2,21...Comparator, 3,22...Triangular wave generator, 4...Inverter, 5,6...Square wave oscillator, 7,8...
Operational amplifier, 11-14...Full-wave rectifier, 15...
... Bridge power amplifier, 16, 24 ... Coil,
17, 25... Capacitor, 18, 26... Load, 23... Pulse amplifier, 151-154...
switching circuit.

Claims (1)

[Claims] 1. One set of two sets of opposing sides of four switching circuits placed on each side of a bridge circuit having four sides connected in phase is connected to the first side.
power amplification of the PWM signal of the same pulse train as the first PWM drive input by switching the PWM drive input, and switching the other set with a second PWM drive input whose polarity is inverted from the first PWM drive input. In a drive circuit of a PWM power amplifier that supplies the first and second PWM drive inputs to a bridge type PWM power amplifier that obtains an output, a first PWM that generates a sine wave of a predetermined frequency, which is the load frequency, as a modulating wave. signal and a second PWM signal with the polarity of the first PWM signal inverted.
the signals at the same frequency and the first
tone burst converting means for converting and outputting a first tone burst signal having the same pulse train configuration as the PWM signal and a second tone burst signal having the same pulse train configuration as the second PWM signal; A second tone burst signal is outputted through a two-output coupling transformer, respectively, and two third tone burst signals having the same pulse train configuration as the first tone burst signal and the same as the second tone burst signal are output. Two fourth tone burst signals having the same pulse train configuration are formed, and the third tone burst signal and the fourth tone burst signal are each full-wave rectified to the two first PWM drive inputs and the second tone burst signal. a PWM drive input supply means for supplying two second PWM drive inputs to the bridge type PWM power amplifier.