JPS6292516A - Pulse width modulation system - Google Patents

Abstract

PURPOSE:To realize a pulse width modulation circuit suitable even to a high frequency by inputting a modulation signal to a controller and obtaining a pulse modulation signal output having a pulse width corresponding to the modulation signal from a monostable multivibrator. CONSTITUTION:A trigger signal (a) is inputted to a terminal B of a monostable multivibrator 2 from a trigger signal generating circuit 1. The monostable multivibrator 2 has an operation time decided normally by a time constant circuit 3 comprising a resistor R1 and a capacitor C, but in this circuit, the charge/discharge time of the circuit 3 is controlled by an emitter follower circuit using a transistor (TR) 4. That is, in inputting a modulation signal (b) from a modulation signal input terminal 5, the charge/discharge current of the circuit 3 by the monostable multivibrator 2 is controlled by the emitter follower circuit comprising the TR 4, resulting that the operation time is controlled. Thus, a pulse signal (c) whose pulse width is changed corresponding to the signal (b) in the same period as that of the trigger signal (a) is outputted at the output terminal 6 of the monostable multivibrator 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulse width modulation method for obtaining a pulse width modulation signal having a pulse width corresponding to a modulation signal.

[Prior Art] A conventionally used pulse width modulation circuit is configured by a combination of a triangular wave generation circuit and a comparator.

FIG. 3 is a block diagram showing an example of a conventionally used pulse width modulation circuit, which utilizes a triangular wave generation process using an OP amplifier. FIG. 4 is a signal waveform diagram of each part of the above circuit.

In FIG. 3, 11 is an input terminal to which the modulation signal es is inputted, 12 is an integrating circuit, 13 is a comparator, 14 is an inverter, 15 and 16 are switches, 17 is a reference voltage generation circuit, and 18 is a pulse width modulation signal input terminal. Output terminals R8 and R9 are resistors, and C is a capacitor.

Next, the operation will be explained.

To make the operation easier to understand, first, the input modulation signal e5 is set to 0V (e5=OV).

At this time, as shown in Fig. 4(i), the legal voltage eR is +5V (e, l-+5V) or -5V (ep--5■).
When the switch 15 controlled by the output of the comparator 13 is ON in either of →-5■, the switch 16 is ON
When the voltage is -5V.

Now, if the reference voltage e8 is 15V, the comparison voltage e of the comparator 13 is. becomes -2,5■, and the output e0 of the integrating circuit 12 increases linearly in the positive direction. and,
Output e of the integrating circuit 12. However, when the voltage reaches +2.5 V, the comparator 13 is inverted, and the switch 15 is turned on to set the reference voltage e8 to +5■ and the comparison voltage e. Set to +2.5V. Then, we start integrating in the opposite direction and repeat this operation one after another.

Therefore, the time constant of this circuit is determined by R2XC, and when the eight modulation signals are OV (e, , = OV), a pulse width modulation signal output with a duty cycle of 50% is generated.

On the other hand, when the modulation signal e8 is applied, since R1=R2 as shown in FIG. 3, the modulation signal eS and the basic voltage eA
The sum <es+eR) becomes the integral input, and the modulated signal eS
The pulse width is modulated by

In other words, when + 5 V > e S > OV, (
(see FIG. 4(ii)), e of the integral output. (the upward slope becomes slower and the downward slope becomes faster. Also, 0 ■ > a
, , > -5V (see Fig. 4 (iii))) The opposite operation occurs.

Therefore, since a pulse width modulation signal with a pulse width corresponding to the modulation signal e5 inputted from the input terminal 11 is configured as output, it is necessary to generate a triangular wave signal by the integrating circuit 12, so a low frequency pulse Although it is suitable for width modulation, it has a problem in that it is not suitable for high frequency pulse width modulation.

This invention was made to solve the above-mentioned problems, and is a method that can realize a pulse width modulation circuit suitable for high frequency pulse width modulation without using a triangular wave generation circuit using an integrating circuit. The purpose is to obtain.

[Means for solving problems]

The pulse width modulation method according to the present invention includes a monostable multi-high break, a signal generating means for generating a trigger signal for operating the monostable multi-high break, and a time constant circuit that determines the operation time of the monostable multi-high break. control means for controlling the charging and discharging current of based on the input signal, and by inputting a modulation signal to the control means, a pulse width modulation signal output with a pulse width corresponding to the modulation signal is obtained from the monostable multivibrator. By immediately inputting a modulation signal, it is possible to control the charging and discharging current of the time constant circuit that determines the operation time of the monostable multivibrator, so that the monostable multivibrator generates a pulse with a pulse width corresponding to the modulation signal. A width modulated signal output can be obtained.

(Example〕 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a signal waveform diagram of each part of the circuit shown in the figure.

In FIG. 1, 1 is a trigger signal generation circuit that generates a negative trigger pulse at a constant cycle as shown in FIG. 2(a);
2 is a monostable multi-high break, and this monostable multivibrator 2 may be of any type, but here, as an example, a 74LS configured with a standard $T TL is used.
123, and a time constant circuit 3 consisting of a resistor R1 and a capacitor C is attached externally. Reference numeral 4 denotes a PNP junction type transistor, the emitter side of which is connected to the time constant circuit 3 and also connected to the +5■ power supply via a resistor R2. Here, the trigger signal generation circuit 1 and transistor 4 correspond to the signal generation means and control means of the present application, and in this circuit, the base of the transistor 4 serves as the input terminal 5 of the modulation signal, and the Q The terminal becomes the output terminal 6 of the pulse width modulation signal C.

Next, the operation will be explained.

The trigger signal shown in FIG. 2(a) is generated from the trigger signal generation circuit 1! ;j, a are input to the 13 terminal of the monostable multi-high break 2. In general, monostable Marzano\1゛Norta2
has an operation time determined by a time constant circuit 3 made up of m anti-R+ and a capacitor C, but in this circuit, this time constant circuit 3 is determined by an emitter follower circuit using a transistor 4.
The charging and discharging time of the battery is controlled.

That is, when a modulation signal as shown in FIG. 2(b) is inputted from the modulation signal input terminal 5, the charging/discharging current of the time constant circuit 3 of the monostable multivibrator 2 is controlled by the emitter follower circuit of the transistor 4. As a result, the operating time can be controlled.

Therefore, the output terminal 6 of the monostable multivibrator 2 has the same period as the trigger signal a, and the pulse width changes as shown in FIG. Signal 0 is output.

As described above, this method is more suitable for high-frequency pulse width modulation than the conventional method using an integrating circuit, and has a simpler circuit configuration.

In the above embodiment, standard TTI was used as the monostable multi-high break, but it goes without saying that other types may be used.

Although current control using a transistor emitter follower circuit is used as a control means based on the modulation signal manually, other means may also be used. For example, a method using a change in the resistance value between the collector and emitter of an L transistor, In short,
It is sufficient if the charging and discharging current of the time constant circuit of the monostable multivibrator can be controlled externally.

〔Effect of the invention〕

As described above, according to the method of the present invention, there is provided a monostable multivibrator, a signal generating means for generating a trigger signal for operating the substable multivibrator, and a time constant circuit that determines the operating time of the substable multivibrator. control means for controlling the charging and discharging current of the battery based on the input signal,
"By manually inputting a modulation signal to the bipedal control means, a pulse width modulation signal output with a pulse width corresponding to the modulation signal is obtained from the monostable multivibrator, thereby making it possible to use an integrating circuit like the conventional system. Zuni,.

In order to control the charging and discharging current of the time constant circuit of a monostable multivibrator, it is possible to realize a pulse width modulation circuit that is also suitable for high frequencies.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The signal waveform diagram of each part of the circuit shown in the figure, Figure 3 is a configuration diagram showing a conventionally used pulse width modulation circuit, and Figure 4 is a diagram of the pulse width modulation circuit used in the past.
FIG. 3 is a signal waveform diagram of each part of the circuit shown in the figure. 1...Trigger signal generation circuit (signal generation means),
2... Monostable multi-high break, 3...
...Time constant circuit, 4...Transistor (control means), 5...Input terminal, 6...Output terminal. Agent Masuo Oon (and 2 others) 2 ・Gunchusadama IL/Kebai 9-ta No. 2 F (C) cho-nanshita] cho-hai-ti,'-old-fLflJ procedural correction power (1 Showa year month day

Claims (2)

[Claims] (1) Controlling the charging and discharging currents of a monostable multivibrator, a signal generating means that generates a trigger signal to operate the monostable multivibrator, and a time constant circuit that determines the operating time of the monostable multivibrator based on input signals. 1. A pulse width modulation method, comprising: a control means for inputting a modulation signal to the control means to obtain a pulse width modulation signal output from the monostable multivibrator with a pulse width corresponding to the modulation signal. (2) The pulse width modulation method according to claim 1, wherein the control means comprises a transistor whose base serves as an input terminal for a modulation signal.