JPS6016005A - Processing circuit for pulse width modulating wave - Google Patents

Abstract

PURPOSE:To improve remarkably a power consumption efficiency by providing a resonance circuit whose impedance is lowered to a modulating wave and increased to a carrier to a switching section of a power switching amplifier. CONSTITUTION:When a voltage of an input signal to a terminal 15 is positive, FETs 2, 3 are turned on and a current flows from a positive terminal 9 to a negative terminal 10 via the FET2, an output transformer 8, a series resonance circuit 5 and the FET3. When the voltage of the input signal is negative, FETs 1, 4 are turned on and a current flows from the positive terminal 9 to the negative terminal 10 via the FET1, the series resonance circuit 5, the output transformer 8 and the FET4. Thus, the current flowing to the output transformer 8 is reversed depending whether the voltage of the input signal is positive and negative, the impedance of the series resonance circuit 5 is lowered to the modulating wave and increased to the carrier, then the modulating wave whose power is amplified is obtained at an output terminal 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pulse width modulated wave processing circuit used in automatic train control devices, automatic train stopping devices, etc. The present invention relates to a pulse width modulated wave processing circuit that mainly amplifies the power of a wave component and outputs it.

Conventional technology As a power amplifier for pulse width modulated waves, B
A class-grade push-pull circuit is used.

However, push-pull circuits generally power amplify both the modulated wave component and the carrier wave component among the components in the pulse width modulated wave, so if only the modulated wave component is required, the power consumption efficiency is poor; Further, a bandpass filter, a demodulator, etc. must be provided at the next stage of the power amplifier to demodulate the modulated wave.

OBJECTS OF THE INVENTION An object of the present invention is to provide a pulse width modulated wave processing circuit that performs power amplification and demodulation of a modulated wave among the components in the pulse width modulated wave.

Structure of the Invention According to the present invention, a power switching amplifier is configured using a plurality of switching elements such as transistors, and the impedance of the switching part decreases for a modulated wave and increases for a carrier wave. This is achieved by inserting a resonant circuit to perform power amplification only on the modulated wave component and suppress power amplification on the carrier wave component.

Example The present invention will be explained below based on embodiments shown in the drawings.

Figure 1 shows four field effect transistors (1, 2=',
An example will be shown in which a power switching amplifier is formed using 3.4).

The field effect transistor (1) is a J type field effect transistor, and the field effect transistor (3, 4
) is a type of field effect transistor. The drain electrodes of the field effect transistors (1) and (3) and the drain electrodes of the field effect transistors (2) and (4) are short-circuited to each other, and the drain electrodes of the field effect transistors (1) and (4) are short-circuited to each other.
) and (3) and the middle point of the connection between field effect transistors (2) and (4) are the series resonant circuit (5) consisting of a coil (6) and a capacitor (7). and is connected via the primary coil of the output transformer (8).

Further, each source electrode of the J type field effect transistor (1, 2) is connected to the positive terminal (9) of the DC power supply,
Each source electrode of the K-type field effect transistor (3, 4) is connected to the negative side (ground side) terminal of the DC power supply 10).
It is connected to the.

Further, the gate electrodes of the field effect transistors (1, 3) are connected to the input terminal (15) via a drive buffer amplifier (11°13), and the gate electrodes of the field effect transistors (2, 4) are It is connected to the input terminal (15) via a drive buffer amplifier (12, 14) which also serves as an inverter.

The signal input to the input terminal (15) is a pulse width modulated wave as shown in FIG. 2 in which the pulse width of a carrier wave of a predetermined frequency is modulated by a modulated wave of a predetermined frequency.

The resonant circuit (5) has an impedance that decreases with respect to the modulated wave among the components of the pulse width modulated wave, and suppresses spurious and
In particular, increasing values are chosen for the harmonics of the modulated wave and the carrier wave.

The secondary coil of the output transformer (8) is connected to the output terminal (16,
16).

In this processing circuit, when the voltage of the input signal to the terminal (15) is positive, the field effect transistor (2) and (
3) is turned on and from the positive terminal (9), 3- field effect transistor (2), output transformer (8),
Series resonant circuit (5) and field effect transistor (3)
A current flows through the negative terminal (10). Further, if the voltage of the input signal is negative, the field effect transistor (
1) and (4) are turned on, and the negative voltage is transmitted from the positive terminal (9) through the field effect transistor (1), the series resonant circuit (5), the output transformer (8), and the field effect transistor (4). Current flows through the side terminal (10). Therefore, the current flowing through the output transformer (8) is in opposite directions when the voltage of the input signal is positive and when it is negative.

In this processing circuit, the current flowing through the primary coil of the output transformer (8) is reversed depending on the voltage polarity of the input signal, and the impedance of the series resonant circuit (5) is lowered for the modulated wave, and the carrier Since it increases for , the output terminal (
16, 16), a modulated wave whose power is amplified can be obtained.

Figure 3 uses a signal obtained by width-modulating a 235 KHz carrier wave with a 19.5 KH2 sine wave as a pulse width modulated wave, and also sets the impedance of the series 4-resonant circuit (5) in the processing circuit to a frequency of 19°5K.
The output waveform obtained at the output terminals (16, 16) and its frequency components are shown when the frequency component is set to be low only for the Hz component. Figure 4 shows the output waveform obtained when the series resonant circuit (5) is short-circuited. The output waveform obtained at the terminals (16, 16) and its frequency components are shown.

In Figures 3 and 4, Figure 3 (A) and Figure 4 (A)
) shows the output waveform, and FIGS. 3(B) and 4(B) show the frequency components. Further, (2o) indicates a modulated wave of 19.5 KHz (Z), and (21) indicates a carrier wave of 235 KHz.

As is clear from Figures 3 and 4, the series resonant circuit (
5), the modulated wave is demodulated into a clean sine wave, and the 19.5KH2 (7
) component, that is, the modulated wave (2o), is mainly power amplified, whereas the spurious component, especially the carrier wave of 235K)-12, is hardly power amplified, and therefore the series resonant circuit (
5), the power consumption efficiency will be significantly increased. On the other hand, if the series resonant circuit (5) is short-circuited, the output waveform will not demodulate the modulated wave even though the same pulse width modulated wave is used, and the modulated wave (20) in the pulse width modulated wave will not be demodulated. The power consumption efficiency of both the power amplification and spurious components is extremely poor.

In FIG. 5, a signal obtained by amplitude modulating a 19.5 KHz sine wave with a 721-1 z trapezoidal wave is used as a pulse width modulated wave, and a signal obtained by pulse width modulating a 235 KHz carrier wave with this modulated wave is used. In addition, the output waveform and frequency components obtained at the output terminals (16, 16) after inserting the series resonant circuit (5) are shown.

In Fig. 5, Fig. 5(A) shows the output waveform;
Figure (B) shows frequency components. Also, (20) is 19.5
It shows a modulated wave of KHz, and (21) shows a carrier wave of 235KH2.

As is clear from FIG. 5, even in the case of a pulse width modulated wave in which a signal obtained by amplitude modulating a sine wave with another signal is used as a modulating wave, and this modulated wave is further pulse width modulated, the modulated wave is demodulated cleanly. Furthermore, while the modulated wave is mainly power amplified and demodulated, spurious components are hardly power amplified, resulting in extremely high power consumption efficiency.

Note that the resonant circuit does not need to be a series resonant circuit; for example, a resonant circuit such as a parallel resonant circuit can be used.

Furthermore, the present invention can be applied not only to power switching amplifiers using field effect transistors, but also to power switching amplifiers using switching elements such as other types of transistors.

Effects of the Invention As described above, the present invention provides a resonant circuit in which the impedance decreases with respect to a modulated wave and increases with respect to a carrier wave, in the switching section of a power switching amplifier configured using a plurality of switching elements. Therefore, the modulated wave in the pulse width modulated wave is power amplified and demodulated, and the power amplification of the carrier wave is suppressed, so that the power consumption efficiency is significantly increased.

[Brief explanation of drawings]

Figure 1- is a diagram showing an embodiment of a pulse width modulated wave processing circuit according to the present invention; 7- Figure 2 is a diagram showing an example of a pulse width modulated wave; FIG. 5 is an explanatory diagram of electrical signals. (1, 2, 3, 4): Field effect transistor, (5
): Series resonant circuit, (8): Output transformer, (9): Positive side terminal, (10): Negative side terminal, (15): Input terminal,
(16): Output terminal. Patent applicant Nippon Signal Co., Ltd. 8- Figure 1 0 Figure 2

Claims (1)

[Claims] 1) A processing circuit for pulse width modulated waves, in which a power switching amplifier is configured using a plurality of switching elements, and a resonant circuit whose impedance decreases for modulated waves and increases for carrier waves is provided in the switching section. .