JPS6130467Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a rectifier circuit that outputs a DC voltage or a DC current corresponding only to an AC component of an input voltage in which a DC component and an AC component are superimposed.

Conventionally, this type of rectifier circuit, as shown in Figure 1,
First, the DC component V _DC included in the input voltage Vi is removed by a coupling capacitor Cc, and the AC component V _AC is removed by an idealized diode circuit consisting of an operational amplifier OQ, diodes D ₁ and D ₂ , and resistors R ₁ and R ₂ . After half-wave rectification, it is smoothed by a filter circuit F to obtain a DC voltage Vo proportional to the _AC component VAC. However, the rectifier circuit having such a configuration has a drawback that a large capacity coupling capacitor Cc is required to remove the DC component V _DC included in the input voltage Vi. Furthermore, in order to obtain a current output, a voltage-current converter must be added, which has the disadvantage of complicating the overall configuration. Furthermore, when operating an operational amplifier, which normally requires two positive and negative power supplies, with a single power supply, complicated bias voltage calculations are required, which is impossible with the circuit shown in FIG.

The present invention has realized a novel rectifier circuit that does not have the above-mentioned drawbacks, so the rectifier circuit of the present invention will be explained below with reference to the drawings.

FIG. 2 is a connection diagram showing one embodiment of the rectifier circuit of the present invention. In the figure, the input voltage Vi is applied to the inverting input terminal (-) of operational amplifier OP via resistor R ₂ , and the input voltage Vi is applied to the non-inverting input terminal (+) via resistor R ₁ and capacitor C ₁ . It is added through a low-pass filter F1 consisting of _F1 . Also OP
A diode D and the base-emitter of the transistor Tr are connected between the output terminal and the inverting input terminal (-). The collector of the Tr is connected to the reference point via a filter F ₂ of a resistor R ₃ and a capacitor C ₂ . The voltage across the resistor _R3 is then taken out as the output voltage Vo. In addition, operational amplifier OP
Only the positive power supply +V is supplied as the power supply voltage.

The operation of the present invention constructed in this way will be explained below with reference to the waveform diagram of FIG. In FIG. 4, A is the waveform of the input voltage, B is the output waveform of the operational amplifier OP, and C is the waveform of the collector current of the transistor Tr. First, the non-inverting input terminal (+) of the operational amplifier OP has a DC component V as shown in Figure 4A.
Input voltage Vi _{( =} V _D
C + V _AC ) is smoothed by a filter F ₁ consisting of R ₁ C ₁ , and only the DC component V _DC of Vi is added. OP works so that the potential of the inverting input terminal (-) becomes V _DC through feedback by diode D or transistor Tr, so the output of OP is the same as that of the inverting input terminal (-).
The waveform shown in Figure 4B depends on the phase _of the alternating _current component of Vi applied to
The forward voltage of the transistor Tr, V _BE is the voltage between the base and emitter of the transistor Tr.
and diode D are turned on and off alternately. In other words, when V _AC is a positive half wave, Tr is on and D is off,
When it is a negative half wave, Tr is turned off and D is turned on. In this way, OP performs an inversion operation with an output phase difference of 180° with respect to V _AC , but since Vi includes the positive DC component V _DC , if V _DC - V _BE > 0, the OP output will be It is always positive and can operate with only one power supply (+). Also, the current i flowing through the resistor R ₂ is (Vi
-V _DC )/R ₂ , the DC component V _DC of Vi is removed and only the AC component V _AC is supported. This current i (=
V _AC /R ₂ ) flows through the turned-on diode D or transistor Tr. Therefore, the current flowing through the collector of the Tr is as shown in Fig. 4 (c), and V _AC
The waveform is obtained by extracting only the positive half wave of . This Tr
When the collector current of is smoothed by a filter F ₂ of C ₂ R ₃ , the smoothed voltage Vo is proportional to V _AC ·R ₃ /R ₂ . However, if the collector-emitter voltage of the Tr is V _CE , then R ₃ is V _DC - V _CE - V _AC・R ₃ /R ₂
>0. In other words, the conditions for the circuit in Figure 2 to operate normally are: if V _DC > 0, then V _DC - V _AC > 0, and V _DC - V _CE - _{V AC} R ₃ / R ₂ > 0. , this can be easily achieved.

In this way, the gain of the output voltage Vo is determined by R ³ /R ₂ and is stable, independent of active elements such as the transistor Tr and the diode D, and the DC component V _DC of the input voltage Vi. Further, since the DC component V _DC of the input voltage Vi also functions as a bias voltage as described above, the operational amplifier OP operates stably with a single power supply. Furthermore, to obtain the current force Io, it is sufficient to output the current flowing through the resistor R ₃ as shown in Figure 3.
No special voltage-current converter is required.

As described above, the present invention does not require a large-capacity coupling capacitor for removing the DC component contained in the input voltage Vi, and can provide a rectifier circuit with a simple overall configuration.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an example of the conventional circuit, Fig. 2 is a connection diagram showing one embodiment of the circuit of the present invention, Fig. 3 is a connection diagram showing another embodiment of the circuit of the present invention, and Fig. 4 is a connection diagram showing an example of the circuit of the present invention. FIG. 3 is a waveform diagram for explaining the operation of the circuit of the present invention. OP...Operation amplifier, _F1 , _F2 ...Filter, Tr
...Transistor, D...Diode.

Claims (1)

[Claims for Utility Model Registration] (1) Means for applying an input voltage in which a DC component and an AC component are superimposed to an inverting input terminal of an operational amplifier via a resistor; means for connecting a diode and the base-emitter of a transistor between the output terminal and the inverting input terminal of the operational amplifier, and means for smoothing the collector current of the transistor to A rectifier circuit comprising a stage for extracting a DC output voltage or a DC output current corresponding only to the AC component of the voltage. (2) The rectifier circuit according to claim 1 of the utility model registration claim, characterized in that the DC component included in the input voltage is used as the bias current of the operational amplifier, and the operational amplifier is operated with a single power supply. .