JPS5990407A - Peak detecting circuit - Google Patents

Abstract

PURPOSE:To detect a peak position at an input voltage being a negative voltage below zero by deciding the polarity of the 1st and the 2nd diodes being at the same polarity between an output and a non-inverting input of an operational amplifier and giving an input voltage between the non-inverting input and a common. CONSTITUTION:The output of the operational amplifier OP1 is connected to an anode of a diode D1. The input voltage (ei) is applied between the non-inverting input and a common of the operational amplifier OP1, and an output voltage l0 is extracted between the output of the operational amplifier OP1 and the common. As the input voltage (ei) increases, a voltage between an inverting input and the non-inverting input of the operational amplifier OP1 is decreased gradually less than the forward voltage of the diode D2 and reaches the voltage finally, and when the voltage exceeds the value, the output voltage (eo) of the operational amplifier OP1 rises positively, the diode D1 is conductive, the diode D2 is nonconductive, the circuit restores to the state similar to the first state. Thus, the peak position is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a peak detection circuit for detecting the peak position of input voltage.

Conventionally, this type of circuit has a configuration as shown in Figures 1 and 2. Figure 1 is used to detect one-time peak positions, and Figure 2 is used to detect continuous AC peak positions. It is used to detect.

The conventional peak detection circuit shown in Fig. 1 consists of an operational amplifier O
Connect the output terminal of PI to the anode of diode D, connect the cathode of diode D to one terminal of capacitor C and the non-inverting input terminal of operational amplifier OP2, and connect the other terminal of capacitor C to the common terminal (ground). Connect it and release it between the terminals of the capacitor! A switch S is provided for the operational amplifier O.
The inverting input terminal and output terminal of P2 are connected to form a buffer, and this output terminal is connected to the inverting input terminal of operational amplifier OP1. And operational amplifier OP
An input voltage ei is applied between the non-inverting input terminal of the operational amplifier WOPI and the common terminal (earth), and an output voltage eo is taken out between the output terminal of the operational amplifier WOPI and the common terminal (earth).

Note that Q is the connection point between the cathode of the diode D, one terminal of the capacitor C, and the non-inverting input terminal of the operational amplifier OP2.

In such a circuit, when a pulsed voltage e+ as shown in FIG. 3(a) is input, the voltage at point Q and the output voltage eo in FIG. ,eo
The position of the peak P of the input voltage ei is detected by the output voltage eo. However, the input voltage e
At i, the first
Following the peak P1, a second peak with a smaller imaging width than the peak P1
When the peak P2 of is reached, the charge in the capacitor O has not been completely discharged, so the operational amplifier OPI does not operate, and the second peak P2 is not detected as the output voltage eo. For this reason, the switch S must be closed in a timely manner by a discharge starting circuit (not shown) to discharge the charge in the capacitor C immediately after detecting the first peak P1. Therefore, the circuit of FIG. 1 has the disadvantage that a discharge starting circuit is required.

Furthermore, in the circuit of Figure 1, as shown by ei' in Figure 3(d), a negative DC voltage is superimposed on the input pulse voltage, and when the peak P is a negative voltage, the diode D becomes reverse biased. This has the drawback that the peak P is not detected because the current becomes non-conductive.

Next, I will explain the circuit in Figure 2.The circuit in Figure 2 is the first circuit.
The difference from the circuit shown in the figure is that instead of the discharging switch S connected in parallel to the capacitor C, a resistor R is connected in parallel to the capacitor C. 3. Input voltage e1 in Fig. 2
As shown by ei in Figure 4(a), if a repeated signal with period T is input, then if the time constant CR of capacitor C and resistor R is sufficiently large compared to period T, the voltage at point Q in Figure 2 will be It becomes like Q in FIG. 4(b). This is because when the input voltage ei has a positive slope, the output impedance of the operational amplifier OPI is low, so the capacitor C is rapidly charged, and the waveform becomes almost the same as that of the input voltage, but when the input voltage e1 passes through the peak P, the input voltage e1 becomes As the voltage decreases due to the charge stored in capacitor C, diode D becomes reverse biased and becomes non-conducting, and the time constant C of capacitor C and resistor R increases.
This is because the capacitor C is discharged with a discharge characteristic determined by R.

As a result, the output voltage eo has a waveform like eO in FIG. 4(C), and the position of the peak P is detected.

If the period T of the input voltage ei is made thicker and approaches the time constant CR, the waveform at point Q in FIG.
′, near the peak the input voltage ei (4th
(see figure (a)), the output voltage e
As shown in the signal eo' in FIG. 4(e), O causes a delay error of time t in the position of the detected peak P. This means that the period T of the input voltage e1 with respect to the time constant CR
This indicates that it has the disadvantage that it must be within a certain range.

Furthermore, as shown in ei' in FIG. 4(f), the input voltage e1
occurs in the negative voltage range, the diode D is always reverse biased and non-conductive, as in the case of FIG. 1, and the position of the peak P cannot be detected.

The present invention solves these drawbacks, has small frequency dependence (5), can handle pulsed inputs and repeated input voltages, and can detect the peak position even when the input voltage is a negative voltage of zero volts or less. The purpose of this study is to obtain a peak detection circuit that is possible.

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

FIG. 5 shows a first embodiment of the present invention, in which an operational amplifier OPI
The output terminal of the capacitor C is connected to the anode of the diode D1, the cathode of the diode DI is connected to one terminal of the capacitor C, the anode of the diode D2, and the inverting input terminal of the operational amplifier OPI, and the other terminal of the capacitor C is connected to the common terminal (
ground), connect the cathode of diode D2 to the output terminal of operational amplifier OP2, connect the non-inverting input terminal of operational amplifier OP2 to the non-inverting input terminal of operational amplifier OPI, and connect the inverting input terminal of operational amplifier OP2 to connected to its output terminal. In the circuit of Fig. 5, the operational amplifier O
Input voltage ei between the non-inverting input terminal of PI and the common terminal
is applied, and an output voltage (6) eo is taken out from between the output terminal of the operational amplifier OP1 and the common terminal. Note that Q is the connection point between the cathode of the diode D1, one terminal of the capacitor C, the anode of the diode D2, and the inverting input terminal of the operational amplifier OP1.

In the above circuit, when the repetition signal ei as shown in FIG. 6(a) is input as the input voltage ei, the operational amplifier OP2
It goes without saying that the same voltage as the input voltage ei is generated at the output terminal of . On the other hand, in the operational amplifier OPI, since the charge on the capacitor C starts from zero, the diode D1 becomes conductive, and the Q point increases with the same amplitude as the input voltage el, as shown in FIG. 6(b). The output voltage eo of the operational amplifier OPl up to the point where the input voltage ei reaches the peak P is the input voltage ei
On the other hand, as shown in FIG. 6(c), the voltage changes to a higher voltage by the forward voltage Vf1 of the diode D1.

Also, the voltage across the diode D2 is the input voltage e1, respectively.
The diode D2 does not contribute to the operation. When the input terminal ei passes the position of the peak P, the capacitor C is charged to the peak voltage, so the inverting input terminal of the operational amplifier OPI also becomes the peak voltage.

Subsequently, the input voltage e+ begins to decrease, so the operational amplifier OP
The voltage at the non-inverting input terminal of I becomes lower than the voltage at the inverting input terminal, and its output voltage eO drops to the minus saturation voltage 8 of the operational amplifier OPI, as shown in FIG. 6(c). As a result, diode D1 becomes reverse biased and non-conducting. Then, when the input voltage ei further decreases and the voltage at the output terminal of the operational amplifier OP2 drops below the voltage at point Q to the forward voltage f2 of the diode D2, the diode D2 becomes conductive, and the charge on the capacitor C is transferred to the diode D.
2 to the output terminal of the operational amplifier OP2, and then the voltage at the Q point changes by a voltage 712 times better than the input voltage ei. This situation is shown in FIG. 6(b). The two-dot chain line in the same figure shows the conventional C'R discharge characteristic (see Figure 4 (b)). In this way, after passing the position of the peak P, the voltage of the capacitor C is different from the conventional one, and the voltage of the diode D2 is Since the input voltage ei is followed with a difference of only the forward voltage Vf2, there is no accumulation of excess charge, and the state is such that it is easy to follow subsequent input changes.

In other words, there is little frequency dependence.

Subsequently, when the input voltage ei starts to increase, the operational amplifier OPI
The voltage between the inverting input terminal and the non-inverting input terminal of is the voltage Vf,
It gradually became smaller than the box of
1 point in Figure (b)), the output voltage eO of the operational amplifier OPI rises in the positive direction, and the diode D1 becomes conductive and the diode D2 becomes non-conductive, returning to the same state as at the beginning. Become. In this way, the beak position P is detected.

Furthermore, as shown in FIG. 6(d) as the input voltage e1,
Even when the overall voltage is negative, the relative voltage between each element is the same as described above, so the position of the peak P can be detected in the same way.

However, the output voltage eO at that time is as shown in FIG. 6(e).

In this way, according to the circuit shown in Figure 5, there is little dependence on the frequency of the input voltage, and it is possible to detect the bias position even in the negative voltage range, which could not be detected with conventional circuits. There is an advantage to having one.

In addition, in the above embodiment, a buffer using the operational amplifier OP2 was used, but it goes without saying that if a voltage is input from a signal source with low output impedance, a configuration as shown in FIG. 7 without using a buffer may also be used. Nor. The operation of FIG. 7 showing the second embodiment of the present invention is completely the same as that of FIG. 5, so the same parts are given the same numbers and the explanation will be omitted.

In addition, in FIGS. 5 and 7, diodes D1 and D2
It goes without saying that the minimum position of the input voltage can be detected by reversing the connection direction.

Furthermore, as shown in FIG. 8, by adding an operational amplifier OP2' to the circuit in FIG. 7, the signal e in FIG.
i, e', ei" In any case, the position of the beak P is detected as a rectangular wave at the output terminal of the operational amplifier OP2 as shown in FIG. 9(b). In addition, as shown in FIG. 9(e) shows the voltage eO at the output terminal of the operational amplifier OPI.

Of course, the circuit of FIG. 9 can also be used for pulsed inputs as shown in FIG. 3(a).

(10) As described above, according to the present invention, not only can each peak position be detected even for pulsed inputs and repetitive inputs, but also the frequency dependence is small, and even for signals containing a large amount of DC component. There is an advantage that the peak position can be detected every time.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams of conventional peak detection circuits, Figure 3 is a waveform diagram of each part in Figure 1, Figure 4 is a waveform diagram of each part in Figure 2, and Figure 5 is a diagram of the waveform of each part in Figure 2. A circuit diagram of one embodiment, FIG. 6 is a waveform diagram of each part in FIG. 5, FIGS. 7 and 8 are circuit diagrams of other embodiments of the present invention, and FIG. 9 is a waveform diagram of each part in FIG. 8. It is a diagram. [Explanation of symbols of main parts] OPI・・・・・・・・・Operational amplifier C・・・・
・・・・・・・・・・・・・・・Capacitor D1, D2・
·······diode. (]1) 5 figures, t-6 figures/-1 = ″7 figures, q prisoner

Claims (1)

[Claims] A capacitor is connected between the inverting input terminal of the operational amplifier and a common terminal, a first diode is provided between the inverting input terminal and the output terminal of the operational amplifier, and a first diode is provided between the inverting input terminal and the common terminal of the operational amplifier. a second diode is provided between the non-inverting input terminal, and the first diode and the second diode are oriented in the same direction between the output terminal and the non-inverting input terminal; A peak detection circuit characterized in that an input voltage is applied between the non-inverting input terminal and a common terminal, and an output voltage is extracted from between the output terminal and the common terminal.