JPS63109607A - Signal processing circuit for pulse generator - Google Patents

Abstract

PURPOSE:To surely prevent malfunction even with a noise component such as jumping peak or the like in a signal by keeping an input signal to a Schmitt circuit to a potential not reaching the next threshold level for a prescribed time after its output is inverted. CONSTITUTION:A trigger circuit 14 outputting a set signal when an output signal from a Schmitt circuit 14 is inverted, a delay circuit outputting a reset signal at a prescribed time after the set signal is outputted and a sample and hold circuit 13 are provided. The sample and hold circuit 13 keeps the level of the input signal to the Schmitt circuit 14 to a potential where the input signal to the Schmitt circuit 14 does not reach the next threshold level while the reset signal is outputted after the set signal is outputted. Thus, even if a noise component is included in the signal from the pulse generator, malfunc tion of the Schmitt circuit 14 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a signal processing circuit for a pulse generator that applies a signal from the pulse generator to a Schmitt circuit to shape the waveform.

(Prior Art) A pulse generator is used, for example, to control the rotational phase of a motor. Its schematic structure is as shown in FIG. That is, a magnetic ring 1 is placed on the outer periphery of the rotor (not shown).
A pair of magnetic pole portions 2 having different polarities are formed at radially symmetrical positions. Further, a magnetic head 3 having a core with a gap is fixed on the stator side, and the magnetic pole part 2 crosses in front of the magnetic head 3 as the rotor rotates. In this case, the magnetic herad 3 of the pulse generator outputs a detection signal as shown in FIG. 4(A). On the other hand, the signal processing circuit is basically constituted by a well-known Schmitt circuit, although not shown, and the level of the positive direction peak p of the signal from the pulse generator is the first.
The same figure (B
), the output signal is inverted to high level, and at the same time, the state is switched to a negative level monitoring state. and,
When the rotor further rotates by 180° and the next magnetic pole part 2 comes to face the magnetic head 3, and the level of the negative direction peak n reaches the second threshold level ■2, the output signal is inverted to low level. , At the same time, the state switches to a positive level monitoring state. In this way, the rotational phase of the rotor is detected according to the pulse width of the output signal obtained from the Schmitt circuit.

However, the output signal of this type of pulse generator has a fourth
As shown in Figure (A), each peak p in the positive direction and negative direction
It is known that so-called rebound peaks occur that are located before and after , n and go in the opposite direction to each peak. For this reason, when the output level is increased especially to improve the S/N ratio, the level of the rebound peak also increases and exceeds the hysteresis width of the Schmitt circuit. level v1
A problem arises in that the rebound peak n' in the negative direction is erroneously detected after the state is switched to the monitoring state at the negative direction level. To avoid this, conventional methods have been to suppress the rebound peak level of pulse generators to below the hysteresis width of the Schmitt circuit, which requires extremely strict inspection and production control of pulse generators. There was a problem of low productivity.

(Problems to be Solved by the Invention) As described above, in the signal processing circuit of a conventional pulse generator, malfunctions are likely to occur due to noise components other than the peak to be detected. There was a problem in that it was necessary to take measures such as improving accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a signal processing circuit for a pulse generator that can prevent malfunctions caused by noise components such as rebound peaks included in signals from the pulse generator.

[Structure of the Invention] (Means for Solving the Problems) A signal processing circuit for a pulse generator according to the present invention includes a trigger circuit that outputs a set signal when the output signal from the Schmitt circuit is inverted, and this set. a delay circuit that outputs a reset signal a predetermined time after the signal is output; and a delay circuit that causes the input signal to the Schmitt circuit to reach the next threshold level only from the time the set signal is output until the reset signal is output. This is characterized by the provision of a level hold circuit that maintains the potential at a certain level.

(Function) When the signal from the pulse generator exceeds the first threshold level of the Schmitt circuit, the output signal of the Schmitt circuit is inverted, and based on this, first a set signal is output from the trigger circuit, and then a reset signal is output from the delay circuit. is output. The level hold circuit, after the set signal is output until the reset signal is output,
Since the input signal to the Schmitt circuit is maintained at a potential that does not reach the next threshold level, this prevents the Schmitt circuit from malfunctioning even if the signal from the pulse generator contains noise components. can.

(Embodiment) An embodiment in which the present invention is applied to a rotational phase detection circuit for a motor will be described below with reference to FIGS. 1 and 2.

Reference numeral 11 denotes a magnetic head of a pulse generator, which has a well-known configuration in which an induction coil is wound around a ring-shaped core with a gap, and when a rotor (not shown) rotates, magnetic poles provided at symmetrical positions in the radial direction of the rotor The section crosses just in front of the magnetic herad 11 and outputs a detection signal vpg as shown in FIG. 2(A) every rotation. 12 is a switching enclosure;
This is for selectively providing either the detection signal Vl)g from the pulse generator 11 or the output signal vh from the sample hold circuit 13, which will be described later, to the Schmitt circuit 14. The Schmitt circuit 14 has a well-known configuration and has first and second threshold levels V1. V2 (1>v2), a high-level square wave signal is output during a period in which the input signal has a potential equal to or higher than both levels v1*V2. Reference numeral 15 denotes a trigger circuit, which applies a set signal Ss as shown in FIG. 2(B) to the sample and hold circuit 13 and the delay circuit 16 when the output signal of the Schmitt circuit 14 is inverted. When the delay circuit 16 receives the set signal Ss, it outputs a reset signal Sr as shown in FIG. There is. The time point at which this reset signal S is output depends on the rotational speed of the rotor.
It is set to occur after a rebound peak occurs in the output signal from 1 and before the next negative direction peak n or positive direction peak p occurs. When the sample and hold circuit 13 receives the set signal Ss from the trigger circuit 15, it samples the output signal vpg from the pulse generator 11 at that time, maintains the output signal vh at that level, and resets it from the delay circuit 16. When receiving the signal Sr, the output signal vh is changed to 0 level. Therefore, the output signal v from the sample and hold circuit 13
h becomes as shown in FIG. 2(D). Further, the switching circuit 12 constitutes a level hold circuit 17 in the present invention together with the sample hold circuit 16, and when the output signal vh of the sample hold circuit 13 is at 0, the output signal Vpg from the pulse generator 11 is Schmitt circuit 1
4, and when the output signal vh of the sample hold circuit 13 is other than 0, the output signal vh is switched to be applied to the Schmitt circuit 14. Therefore, the output signal Va applied from the level hold circuit 17 to the Schmitt circuit 14 becomes as shown in FIG. 2(E).

To describe the operation of the above configuration, the rotor rotates and the detection signal vpg from the pulse generator 11 is transmitted to the Schmitt circuit 1.
4, the output signal of the Schmitt circuit 14 is inverted and the set signal Ss is output from the trigger circuit 15 to the sample hold circuit 13. . Then, the sample hold circuit 13 outputs the detection signal V I from the pulse generator 11 at the time tl until the reset signal S' is output from the delay circuit 16 at the time t2 delayed by a predetermined delay time from the time t1. )g(V'1) is maintained and output.As a result, the switching circuit 12 outputs the second threshold level, which is the next threshold level, to the Schmitt circuit 14.
A potential (high) that does not reach the threshold level v2 is applied.

Therefore, during that time, the detection signal Vp from the pulse generator 11
Even if a rebound peak n' occurs in g, the Schmitt circuit 14 malfunctions and does not invert, and the output signal of the Schmitt circuit 14 maintains a high level. After that, at time t2, the delay circuit 16 outputs a reset signal S'',
As a result, the output signal vh of the sample and hold circuit 13 changes to O, so that the detection signal vpg from the pulse generator 11 is thereafter supplied to the shot circuit 14. Then, when the detection signal Vpg becomes lower than the second threshold level v2 of the Schmitt circuit 14, the output signal of the Schmitt circuit 14 is inverted, and based on this, the trigger circuit 15 outputs the set signal Ss. (time t3), detection voltage V9g at that time
is sampled and sent from the sample hold circuit 13 to the detection signal vpg from the pulse generator 11 at time t3.
is output. As a result, a potential v2, that is, a potential (low) that does not reach the first threshold level V1, which is the next threshold level, is applied from the switching circuit 12 to the Schmitt circuit 14, and this state is applied from the delay circuit 16 to the sample and hold circuit 13. This continues until time t4 when the reset signal S" is output. As a result, during this period, the pulse generator 1
Even if a bounce peak p' occurs in the detection signal Vpg from 1, malfunction of the Schmitt circuit 14 can be reliably prevented. Thereafter, by repeating this process, a phase detection signal as shown in FIG. 2(F) synchronized with the rotational phase of the rotor is obtained from the Schmitt circuit 14.

Therefore, according to this embodiment, it is not necessary to strictly control the manufacturing of the pulse generator 11 in order to suppress the rebound peak of the pulse generator 11, and productivity can be improved accordingly. Further, according to this embodiment, while the input voltage to the Schmitt circuit 14 is maintained at a potential that does not reach the next threshold level (1, ~-t2, t3-ta
), the SZN
It is also very effective in improving the ratio.

In the above embodiments, the level hold circuit 17 maintains the potential of the input signal of the Schmitt circuit 14 at the level of the detection signal vpg from the pulse generator 11 when its output is inverted. The invention is not limited to this, and it may be maintained at a constant level regardless of the level of the detection signal vpg at that time, and even if the potential fluctuates as long as the potential does not reach the next threshold level. good.

[Effects of the Invention] As described above, the present invention has a configuration in which the input signal to the Schmitt circuit is maintained at a potential that does not reach the next threshold level for a predetermined period of time after the output is inverted. Even if the signal from the generator contains noise components such as rebound peaks, it has the excellent effect of reliably preventing malfunctions.

[Brief explanation of the drawing]

Figure 1 and Figure 2 show an embodiment of the present invention, Figure 1 is an overall block diagram, Figure 2 is a voltage and waveform diagram of each part, Figure 3 is a schematic plan view of a pulse generator, FIG. 4 is a voltage waveform diagram of the output signal from the pulse generator. In the drawing, 11 is a pulse generator, 13 is a sample hold circuit, 14 is a Schmitt circuit, 15 is a trigger circuit, 1
6 is a delay circuit, and 17 is a level hold circuit. Applicant Toshiba Corporation (A) (B) Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. Waveform shaping is performed by applying a signal from a pulse generator to a Schmitt circuit that outputs a square wave signal during a period in which the input signal has a potential equal to or higher than two threshold levels, wherein the Schmitt circuit a trigger circuit that outputs a set signal when the output signal from the circuit is inverted; a delay circuit that outputs a reset signal a predetermined time after the set signal is output; and a delay circuit that outputs a reset signal after the set signal is output. A signal processing circuit for a pulse generator, comprising a level hold circuit that maintains the input signal to the Schmitt circuit at a potential that does not reach the next threshold level only until the signal is output. 2. The level hold circuit maintains the input signal to the Schmitt circuit at the level of the signal from the pulse generator when its output is inverted. A signal processing circuit for a pulse generator described in .