JPH0326673Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention relates to an astable multivibrator with variable duty.

<Prior Art> Conventionally, there has been a variable duty astable multivibrator as shown in FIG. In Fig. 1, 1 is a DC power supply, 2 is a first resistor 3, a second resistor is
a reference voltage generation circuit consisting of a resistor 4 and a third resistor 5; 6 a delay circuit consisting of a variable resistor 7, a resistor 8, and a delay capacitor 9; 10 a first comparator; 11 a second comparator 12; 1 is a flip-flop, and 13 is a discharge transistor. Note that there is a timer IC 555 as an IC that integrates the reference voltage generation circuit 2, first and second comparators 10 and 11, flip-flop 12, and discharge transistor 13.

The resistance values of the first resistor 3, the second resistor 4, and the third resistor 5 are the same, the voltage of the DC power supply 1 is E, the resistance value of the variable resistor 7 is RVR (variable), and the resistance value of the resistor 8 is The operation will be explained assuming that the capacitance values of R8 and the delay capacitor 9 are C. The time delay capacitor 9 is charged through the variable resistor 7 and the resistor 8, and when the voltage exceeds 2E/3, the first comparator 10 becomes "H" level, the flip-flop 12 is reset, and the output Q _U- becomes "H". level, transistor 13
is turned on, and the charge in the delay capacitor 9 is discharged through the resistor 8. When the voltage of the time delay capacitor 9 is discharged and becomes less than E/3, the output of the second comparator 11 becomes "H" level, the flip-flop 12 is set, and the output Q _U- becomes "L" level. , the transistor 13 is turned off, the discharge of the delay capacitor 9 is stopped, and the variable resistor 7 and the resistor 8 are turned off.
The time delay capacitor 9 is charged through the time delay capacitor 9. This repetition causes oscillation. The charging time of the time delay capacitor 9 (the period in which the output of the flip-flop 12 is at the “L” level) is 1n2・(RVR+R8)・
The discharge time (the period during which the output of the flip-flop 12 is at the "H" level) is 1n2.R8.C. As a result, the duty D is R8/(RVR
+2・R8), and the duty range that can be controlled by variable resistor 7 is narrow: O<D<0.5. Also, the oscillation frequency f is 1/(1n2・(RVR+2・R8)・C)
Therefore, if the duty is changed by the variable resistor 7, the oscillation frequency will also change.

<Problems to be Solved by the Invention> The purpose of the invention is to eliminate the drawbacks of the prior art described above.

<Means and operations for solving the problems> The present invention is devised so that there is no resistance that affects both charging and discharging of the delay capacitor by combining a variable resistor and a diode.

<Example> FIG. 2 shows an astable multivibrator of the present invention. In the figure, reference numeral 14 is a delay circuit consisting of a variable resistor 15, a diode 9, and a delay capacitor 9. Charging the time delay capacitor 9 is done by variable resistor 1
However, the effect on the charging time constant due to the resistance between the sliding terminal of the variable resistor 15 and the terminal of the variable resistor 15 on the time delay capacitor 9 side is eliminated by the diode 16 connected in parallel. On the other hand, the discharge is caused by the variable resistor 15 on the time delay capacitor 9 side.
This is done from the terminal to the sliding terminal and through the transistor 13.

The resistance values of the first resistor 3, the second resistor 4, and the third resistor 5 are the same, the voltage of the DC power supply 1 is set to E, and the resistance value between the variable resistor 15 terminal on the positive side of the DC power supply and the sliding terminal is set to R _A (variable), sliding terminal and time delay capacitor 9
The resistance value between the variable resistor 15 terminals on the side is R _B (variable),
The resistance value between the variable resistor 15 terminal on the positive side of the DC power supply and the variable resistor 15 terminal on the time delay capacitor 9 side is R (=
R _A + R _B (constant), the capacitance value of the delay capacitor 9 is C, and if the forward voltage drop of the diode 16 and the saturated collector-emitter voltage of the transistor 13 are ignored, the charging time of the delay capacitor 9 is (the period in which the flip-flop output is “H” level) is 1n2・R _A・C, and the discharge time (the period in which the flip-flop output is “L” level) is
1n2・R _B・C. As a result, the duty D
is R _B /((R _A + R _B )・C) = R _B /R, and the duty range that can be controlled by moving the sliding terminal of the variable resistor 15 expands to O<D<1, and the oscillation frequency f
is 1/(1n2・(R _A +R _B )・C)=1/(1n2・R・
C), and even if the duty is changed by moving the sliding terminal of the variable resistor 15, the oscillation frequency does not change.

<Effects of the invention> According to the invention, the duty can be changed without changing the frequency. Furthermore, the duty can be varied over a wide range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional variable duty astable multivibrator, and FIG. 2 is a circuit diagram of an astable multivibrator of the present invention. In the figure, 2 is a reference voltage setting circuit, 10 is a first comparator, 11 is a second comparator,
12 is a flip-flop, 13 is a discharge transistor, 14 is a time delay circuit, 15 is a variable resistor, and 16 is a diode.

Claims (1)

[Scope of utility model registration request] A series reference voltage setting circuit connected in series to a DC power source and consisting of first to third resistors having the same resistance value, a variable resistor connected to the DC power source, a delay capacitor, and an anode of the variable resistor. A time delay circuit consisting of a diode whose cathode is connected to the connection point of the variable resistor and the time delay capacitor on a sliding terminal, and a (-) side input terminal is connected to the connection point of the first resistor and the second resistor. a first comparator that is connected to the first comparator, the (+) side input terminal of which is connected to the connection point of the variable resistor and the time delay capacitor; and the (-) side input terminal connected to the connection point of the variable resistor and the time delay capacitor. a second comparator whose (+) side input terminal is connected to the connection point of the second and third resistors; a reset input terminal connected to the output of the first comparator; and a set terminal connected to the output of the first comparator. It consists of a flip-flop connected to the output of the second comparator, and a discharging transistor whose collector is connected to the sliding terminal of the variable resistor, whose emitter is connected to the negative side of the DC power supply, and whose base is connected to the output of the flip-flop. Astable multivibrator.