JPS58196697A - Voltage holding device - Google Patents

Abstract

PURPOSE:To hold the voltage stably and for a long period of time, by detecting the potential of a capacitor and then feeding it back to a terminal at the other side of the capacitor after inversion and amplification. CONSTITUTION:The DV voltage V1 is applied to a terminal at one side of a capacitor 3, and then the potential of said terminal receives the voltage or current amplification through an amplifying means 4 and is amplified inversely by an amplifying means 7. Thus the potential -V1 is applied to a terminal at the other side of the capacitor 3. Therefore the capacitor 3 is charged up to potentials V1 and -V1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage holding device, and an object thereof is to provide a device that has a simple configuration and can stably hold a voltage for a long period of time.

A voltage holding device has the function of holding a voltage corresponding to a signal or information, and is often used in measuring instruments, audio equipment, and control devices. The maintained voltage level is used to control the above-mentioned devices or as a display power source.

An example of a conventional voltage holding device is shown in FIG. The disadvantage of this device is that it cannot hold voltage for long periods of time. Before explaining the reason, the configuration and operation of the device will be briefly described. The output of an axial signal source 1 that generates a DC signal or an AC signal is supplied as a DC voltage to a capacitor 3 via a diode 2, and the capacitor 3 holds the voltage. The first amplification means 4, which is made of a field effect semiconductor element or an integrated circuit incorporating a field effect semiconductor, has a high input impedance, and amplifies the voltage or current of the capacitor 3 and outputs it to the output terminal 5. Output to.

It then controls another device (not shown) or displays its level on another device. The constant current circuit 6 is used to set the number of current to be passed through the first amplifying means 4 when it is constituted by a field-effect semiconductor element. If configured, it may be omitted.

In this conventional device, there is a leakage current in the reverse direction of the diode 2, a self-discharge of the tip/strap 3, and a leakage current of the first amplification means 4, and even if each value is small, a long period of time has elapsed. Then (for example, after about 30 minutes to one hour), the voltage level of the capacitor 3 decreases, and the potential of the output terminal 6 also drifts. When the ambient temperature changes, the leakage current is affected by the change, and the drift of the output terminal 6 becomes even larger.

The present invention improves the above-mentioned conventional drawbacks, and -
The entire example is shown in FIG. Explanation of the components that overlap with those of the conventional example shown in FIG. 1 will be omitted, and only the differences will be described.

The second amplifying means 7 includes resistors 701 and 702 and an operational amplifier 703, and the gain is set by the ratio of the resistors 701 and 702. Terminal 704 is a terminal that supplies a reference voltage.

The output of the operational amplifier 703 is then connected to the other terminal or electrode of the capacitor 3.

The output of the first amplifying means 4 is reversed in polarity by the second amplifying means 7 and is supplied to the other terminal of the capacitor 3, so that a leakage current flows through the diode 2, the capacitor 3, and the first amplifying means 4. Even if , the second amplifying means 7 corrects the drift error of the output terminal 5, so that a long-time peak hold operation can be obtained. To facilitate understanding, FIG. 3 shows how the voltage changes.

1. When a DC voltage V as shown in Fig. 3 (A) is applied to one terminal (for example, the anode) of the capacitor 3, the potential of one terminal of the capacitor 3 becomes as shown in Fig. 3 (B). The potential is voltage or current amplified by the first amplifying means 4, further inverted and amplified by the second amplifying means 7, and then supplied to the other terminal (for example, the cathode) of the capacitor 3. In other words, the potential of -v1 as shown in Fig. 3(C) is the capacitor 3.
is supplied to the other terminal of The resulting capacitor
13 is charged to a potential of -v1. Note that charging of the capacitor 3 is instantaneous. In this state, when the voltage of the signal source 1 is decreased or made zero at time t, the potential of one side of the capacitor 3 decreases due to the leakage current of the diode 2, the capacitor 3, and the first amplifying means 4 as shown in FIG. ). However, the second
Since the amplifying means 7 inverts and amplifies the output of the output terminal 6 and supplies it to the other terminal of the capacitor 3, its potential is as shown in FIG.
As shown in C), the negative potential increases toward zero. This value is subject to potential changes at one terminal of the capacitor 3. As a result, the potential of the single terminal of the capacitor 3 as a whole is maintained at the value vl for a long time as shown in FIG. 3(D), and the voltage of the output terminal 6 also does not change. Further, since the second amplifying means 7 applies feedback to the other terminal of the capacitor 3, it is possible to stably hold the voltage for a long time without being affected by the ambient temperature.

The device shown in FIG. 2 is an embodiment of the present invention, and when the output of the signal source 1 is DC, the diode 2 may be replaced with an electronic switch (not shown).

Further, the second amplifying means 7 can change the charging time or charging response of the capacitor 3 by using impedance elements that set response characteristics in part of the resistors 701 and 702.

Further, although the output of the operational amplifier 703 is directly connected to the other terminal of the capacitor 3, it may be connected indirectly via an impedance element or other circuit (none of which is shown). .

As explained above, according to the device of the present invention, the potential of the capacitor is detected by the first amplifying means, inverted amplified by the second amplifying means, and fed back to the other terminal of the capacitor. However, even if there is a leakage current in the capacitor or the first amplifying means, the voltage can be stably maintained for a long time, and it has excellent effects in that it is not affected by the ambient temperature.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the same operation. 1... Signal source, 3... Capacitor, 4
.....first amplification means, 7.....-second amplification means.

Claims (1)

[Claims] a first amplification means comprising a capacitor for holding a DC voltage, a field effect semiconductor element or an integrated circuit incorporating a field effect semiconductor for detecting the voltage of the capacitor; and the first amplification means. A voltage holding device comprising second amplifying means for inverting and amplifying the output of the means and feeding it back directly or indirectly to the other terminal of the capacitor.