JPS5849046B2 - Waveform shaping circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waveform shaping circuit that converts slowly changing analog signals into rectangular waves for inputting into digital circuits, and particularly relates to a circuit for shaping a plurality of similar signal waveforms. It is something.

Conventionally, there has been a circuit of this type as shown in FIG.

In the figure, 1 to 3 are buffer amplifiers, 4 to 6 are comparators, and R1 and R2 are resistors for determining a comparison reference voltage Vs.

As shown in FIG. 2, signals input from L1 to L3 are input to comparators 4 to 6 via buffer amplifiers 1 to 3.

This signal is shaped into a waveform such as Cl-C3 with reference voltage vs as a boundary.

In this example, the signals input to L1 to L3 have three phases, and as shown in the figure, the beginning of L2 wraps around the end of the pulse of L1, and the beginning of L3 wraps around the end of L2. It is designed so that one of the phases is always in an ON and OFF state at the same time, and for example, a step motor or the like is driven by a power meter in proportion to the usage amount.

It is transmitted as a pulse.

The conventional waveform shaping circuit is configured as described above.
Since the value of the comparison reference voltage s is constant, if the entire three-phase signal is induced by the power frequency, or if continuous external noise invades, the comparators 4 to 6 will be affected as shown in Figure 3. Not only does the level of the input signal fluctuate and the expected output may not be obtained, but the value of the reference voltage ■s depends on the power supply voltage of the circuit, so due to fluctuations in the power supply voltage, ■It had many drawbacks, such as changing the s or requiring precise adjustment of the power supply voltage.

This invention was made in view of the above-mentioned drawbacks of conventional circuits, and it combines the input signal levels and uses it as a comparison reference voltage for a comparator, and waveform shaping that does not output erroneous pulses even if the input signal level fluctuates. The purpose is to provide a circuit.

A description will be given below based on FIG. 4, which is an embodiment of the present invention.

In the figure, 7 to 12 are diodes, and 7 to 9 are low level ORs, and 10 to 12 are low level ORs.

That is, in the three-phase pulses applied to L1 to L3, one of the phases has a low level and a high level at the same time, and a low level always appears on Va and a high level appears on Vb.

R3R4 is the comparison voltage Vs of comparators 4 to 6, va
Resistance determined from vb, here resistors R3 and R4
The constants of are chosen to be the same value.

5 and 6 are diagrams showing the operation of this embodiment.

In FIG. 5, when signals in which stable low level and high level states alternate as shown are applied to inputs L and L3, voltages as shown appear at Va and Vb, respectively.

This voltage is divided by resistors R3 and R4, and is used as the comparison reference voltage Vs of the comparators 4-6.

Now, since resistors R3 and R4 have the same value, the reference voltage Vs
is a voltage between Va and vb.

Therefore, the outputs of the comparators 4 to 6 become C, to C3.

As shown in Fig. 6, when the entire L1 to L3 signals fluctuate,
Along with this, Va and vb also change.

Therefore, since the reference voltage Vs is always maintained at a voltage intermediate between Va and vb, it follows input fluctuations.

In other words, as the level of the entire input signal increases, the reference voltage Vs also increases, and conversely, as the overall input signal decreases, the reference voltage Vs also decreases, so that it is possible to always maintain the optimal comparison reference voltage Vs. Therefore, even when the overall input signal fluctuates as shown in FIG. 6, the same output as shown in FIG. 5 when the overall level is stable can be obtained.

In the above explanation, the voltage between Va and vb is the reference voltage Vs
However, by changing the ratio of the constants of the resistors R3 and R4, the reference voltage Vs can be set to any voltage between Va and vb.

In addition, although this embodiment describes only the case where the input signal has three phases, as mentioned above, one of the phases always has a low level and one of the other phases has a high level at the same time. If so, it is not limited to only three phases.

Furthermore, it goes without saying that by providing hysteresis to the operating characteristics of the comparators 4 to 6, it is possible to obtain an output with a more stable waveform.

As described above, according to the present invention, although it is a simple circuit, not only can stable waveform shaping be performed even when the level of the input signal fluctuates, but also the comparison reference voltage is lower than that of the conventional circuit. Since it is not dependent on the power supply voltage, even if the power supply voltage fluctuates slightly, it will not have any effect.
Furthermore, it is possible to provide an inexpensive and highly accurate waveform shaping circuit that does not require precise adjustment of the power supply voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional waveform shaping circuit, FIGS. 2 and 3 are explanatory diagrams explaining the operation of FIG. 1, and FIG. 4 is a circuit showing an embodiment of the present invention. 5 and 6 are explanatory diagrams for explaining the operation of FIG. 4. In the figure, 1 to 3 are buffer amplifiers, 4 to 6 are comparators, 7 to 12 are diodes, and R3 to R4 are resistors. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A pulse in which a high level and a low level always arrive alternately, each pulse partially wrapping around the other pulse, and the pulse in either phase is always at a low level. In a device that uses a comparator to compare a multiphase pulse in which one of the other phases is at a high level with a reference voltage and shape the waveform, the high level OR and low level OR of each phase are taken. A waveform shaping circuit characterized in that a reference voltage for comparison of the comparator is determined from these levels. 2. The waveform shaping circuit according to claim 1, wherein the comparator has a hysteresis characteristic.