JPS62236366A - Rectifying circuit - Google Patents

Abstract

PURPOSE:To sufficiently compensate a forward voltage of a rectifier irrespective of the amplitude of a load current by driving a field effect transistor by the output of an operational amplifier, and connecting a rectifier with the source of the transistor. CONSTITUTION:An operational amplifier l and an FET 2 are so operated as to compensate the forward voltage of a thyristor 3 by a feedback resistor 6. When the thyristor 3 is turned ON, a current flows through a bias power source 4, a diode 5, the FET 2 and the thyristor 3, and this circuit operates as a noninverting amplifier amplification factor 1. In this case, the power source 4 applies a bias voltage so that the FET 2 correctly operates. When the thyristor 3 is turned OFF, a leakage current determined by the resistor 6 merely flows so that an impedance between terminals A and K becomes very large. At this time, Zener diodes 7, 8 prevent the amplifier l from saturating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rectifier circuit having a compensation function for compensating for a forward voltage drop between an anode and a cathode of a rectifier element made of a thyristor or a diode.

[Technical background of the invention and its problems]

Generally, in a rectifier circuit using a thyristor, the output voltage is lower than the input voltage by the forward voltage value due to the forward voltage drop of the thyristor. Therefore, in a region where the forward voltage increases with respect to the input voltage, the rectified output voltage and the input voltage are no longer proportional, and undesirable effects such as forward voltage fluctuations depending on the magnitude of the load current occur.

Therefore, in the past, as shown in FIG. 15, an analog switch 11 with a small resistance value when turned on, a voltage detection circuit 13 that detects the magnitude of the anode voltage and cathode voltage of this analog switch 11, and a current detection circuit of the analog switch 11 are used. A current detection circuit 14 that detects that the cathode current flowing through the resistor 12 is positive, and a voltage detection circuit 13
When the anode voltage detected by the anode voltage and the cathode current detected by the current detection circuit 14 are input, and the anode voltage is positive, the analog switch 11 is turned on by a gate control signal.
A control circuit 15 that turns off the analog switch 11 when the cathode current is below zero is used to create a thyristor simulation circuit (Unexamined Japanese Patent Publication No. 5
9-148427@publication) to simulate a thyristor.

However, since this thyristor simulation circuit uses an electronic circuit to simulate the characteristics of a thyristor, it is difficult to simulate the unique characteristics of a thyristor, such as its gate trigger characteristics, turn-on and turn-off characteristics, and critical off-voltage characteristics. It is impossible to fully simulate the characteristics. Also, the resistance value when the analog switch 11 is turned on,
The series resistance value of the current detection circuit 14 cannot be ignored either.

In addition, other functions to compensate for the forward voltage of the cyrisk; 1. A compensating diode 17 with a constant current source 18 connected in parallel to the Some types of hooks are designed to reduce the forward voltage on the top, thereby reducing the voltage drop between the anode and the power source.

However, in such a configuration, thyristor 1
The current flowing through the compensation diode 17 varies greatly depending on the size of the load, but the current flowing through the compensation diode 111i is almost constant.
18 cannot accurately compensate for the forward voltage VF of the thyristor 16. This is true not only for thyristors but also for diodes.

[Purpose of the invention]

The present invention has been made to improve these problems, and its purpose is to provide a rectifier circuit that can sufficiently compensate for the forward voltage of a rectifier element regardless of the magnitude of the load current.

[Summary of the invention]

In order to achieve such an object, the present invention includes an operational amplifier whose non-inverting input terminal is connected to an input terminal and whose inverting input terminal is connected to an output terminal via a resistor, and which is driven by the output of this operational amplifier, and whose drain is biased by a power supply. a field effect transistor connected to the input terminal via the field effect transistor; and a rectifying element having one of an anode or a cande connected to the source of the field effect transistor and the other connected to the output terminal. It is characterized by compensating the voltage Vp.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration when a thyristor is used as a first embodiment of a rectifier circuit according to the present invention. In FIG. 1, A indicates the anode N pole of the thyristor, G indicates the cathode electrode, and G indicates the gate electrode. Further, 1 is an operational amplifier, whose non-inverting input terminal is connected to a terminal A corresponding to an anode electrode,
The inverting input terminal is connected via a feedback resistor 6 to a terminal K corresponding to a cathode electrode. Furthermore, two Zener diodes 7.8 are connected in series between the non-inverting input terminal and the output terminal of the operational amplifier 1 with polarities shown opposite to each other. Roughly speaking, the output end of the operational amplifier 1 is connected to the gate of a field effect transistor (hereinafter abbreviated as FET) 2. The drain of this FET2 is a diode 5. with the polarity shown. It is connected to a terminal A corresponding to an anode electrode via a bias power supply 4 in series. On the other hand, the source of FET2 is connected to the anode of thyristor 3.

In the above circuit configuration, the diode 5 prevents a reverse voltage from being applied to the FET 2, and the Zener diodes 7 and 8 connected in series with opposite polarity prevent the operational amplifier 1 from being applied during the non-conducting period of the thyristor 3. This is to prevent saturation.

Next, the operation of this embodiment will be explained.

In FIG. 1, the operational amplifier 1 and the FET 2 operate to compensate for the forward voltage Vp of the SIRISK 3 by means of the feedback resistor 6. When thyristor 3 is on, current flows through bias i[4, diode 5° FET 2 and thyristor 3, and the circuit operates as a non-inverting amplifier with an amplification factor of 1.

In this case, the bias power supply 4 applies a bias voltage so that the FET 2 operates correctly. Also, thyristor 3
When is off, only a leakage current determined by the feedback resistor 6 flows, and the impedance between terminal A- becomes extremely large. In this case, Zener diode 7.8 is op amp 1
works to prevent saturation.

Here, as shown in FIG. 2, the third example is about the operation of 59 cases in which AC power 19 is connected to terminal A corresponding to the anode electrode of the circuit in FIG. 1, and load 10 is connected to terminal K corresponding to the cathode bridge. This will be explained with reference to the time chart shown in the figure. Now, the AC power supply 9 connects terminal A to I! shown in FIG. 3(a). Assume that lightning voltage is applied. In this state, when the voltage at the terminal A corresponding to the anode electrode is higher than the voltage at the terminal corresponding to the cathode "l", the output voltage of the operational amplifier 1 is positively amplified, and the FET
2 to the anode of thyristor 3. When the thyristor 3 is off, this voltage V a is the Zener diode 7.8 as shown in Figure 3 (b).
You can take pictures up to the voltage VZ+ determined by .

Now, a gate drive signal Va sufficient to turn on the thyristor 3 as shown in FIG. 3(C) is applied to the gate electrode G.
, when applied between the cathode N pole, the thyristor 3 becomes conductive and the operational amplifier 1 operates as a non-inverting amplifier.
The voltage V at the cathode N pole is equal to the voltage VA at the anode electrode. That is, the forward voltage drop between the terminal A corresponding to the anode electrode and the terminal corresponding to the cathode electrode of the thyristor shown in this example is approximately Qv, and the load current i
is supplied from terminal A corresponding to the 7 node electrode through the drain-source of FET2. When the load current 1 becomes O, the thyristor 3 is turned off, and at this time the anode voltage Va swings up to Vz2. FIG. 3(d), (e) is an example of the voltage at the cathode electrode and the load current i when the load is a resistance component.

As is clear from the above explanation, the forward voltage VF- of the rectifier circuit using the thyristor shown in this embodiment is 0, and the on/off characteristics are the same as the original thyristor, and this is shown in FIG. The circuit is equivalent to the circuit shown in FIG.

On the other hand, as shown in FIG. 5, a power supply 9 is connected to the terminal K corresponding to the cathode electrode, and a load 1 is connected to the terminal A corresponding to the anode electrode.
A similar effect occurs when 0 is connected. That is, since the voltage at the terminal corresponding to the cathode electrode is applied to the inverting input terminal of the operational amplifier 1 through the feedback resistor 6, when the potential at the terminal corresponding to the cathode becomes lower than the terminal A corresponding to the anode, the operational amplifier 1 The output voltage of is positively amplified. When the thyristor 3 is conductive, a load Wi current i flows from the anode electrode A through the drain and source of the FET 2, and the operational amplifier 1 operates so that VA'-V becomes -.

Therefore, FIG. 5 is equivalent to FIG. 6, and the forward voltage Vp
It can be seen that - is an O thyristor.

As described above, according to the first embodiment, it is possible to realize a thyristor with a forward voltage drop of O during conduction while maintaining the on/off characteristics.

FIG. 7 shows a second embodiment of the rectifier circuit according to the present invention, and only the points different from FIG. 1 will be described here.

In Fig. 7, the difference from Fig. 1 is that FET2 is P
A channel FET is used, and the cathode of the thyristor 3 is connected to its source. In such a configuration, although the anode electrode and the cathode electrode are interchanged, a rectifier circuit having the same effect as the first embodiment can be obtained.

Further, FIG. 8 shows a third embodiment of the rectifier circuit according to the present invention, and here, points different from FIG. 1 will be described. The difference in FIG. 8 from FIG. 1 is that power supplies 19 and 20 are added to the operational amplifier 1.

With such a configuration, the following advantages can be obtained in addition to the effects of the first embodiment.

(a) The output voltage range of the operational amplifier 1 only needs to be a voltage sufficient to compensate the forward voltage VF of the thyristor 3, and the output current only needs to be able to drive the FET 2, so a general-purpose operational amplifier may be used.

(b) The bias power supply 4 can sufficiently flow the load current i, and the FE
Any device that can drive T2 may be used.

(c) Den! 19 and 20 need only be able to sufficiently drive the operational amplifier 1, so a small capacity one is sufficient.

FIG. 9 shows a fourth embodiment of the rectifier circuit according to the present invention, and here the differences from FIG. 1 will be described. 9th
The difference between the figure and FIG. 1 is that an IR configuration is used in which a voltage follower circuit including an operational amplifier 21 is connected between the terminal corresponding to the cathode electrode and the feedback resistor 6.

With such a configuration, the impedance of the thyristor 3 when it is off is equal to the input impedance of the operational amplifier 20, and has the advantage of being a very high value.

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40th Embodiment 0 First, a rectifier circuit using a +Nyristor will be described, but next, a rectifier circuit using a diode will be described.

FIG. 10 shows a fifth embodiment of the N-flow route according to the present invention, and here, the differences from FIG. 1 will be described. 10 differs from FIG. 1 in that a diode 31 is provided in place of the thyristor 3.

In a rectifier circuit using diodes with this configuration,
It is assumed that an AC power source 9 is connected to the coupling terminal A, and a load 10 is connected to the terminal K. In this state, when the voltage at the terminal A is higher than the voltage at the terminal, the output of the operational amplifier 1 is positively amplified and applied to the anode of the diode 31 through the source of the FET 2, so the diode 31 becomes conductive.

At this time, the load current flowing through the diode 31 is supplied from the drain of the FET 2 through the bias power supply 4 and the diode 5. This circuit operates as a non-inverting amplifier with an amplification factor of 1. That is, since the operational amplifier 1 operates to compensate for the VF of the diode 31, the voltage at the terminal becomes equal to the voltage at the terminal A, and a characteristic that compensates for the forward voltage drop VF of the diode 31 is obtained.

Next, when the voltage at the terminal A becomes lower than the voltage at the terminal, the output of the operational amplifier 1 is negatively amplified and applied to the anode of the diode 31 through the source of the FET 2, so the diode 31 becomes non-conductive.

Zener diodes 7 and 8 operate to prevent operational amplifier 1 from becoming saturated while diode 31 is open.

FIG. 11 shows a case in which the AC power source 9 is connected to the terminal side and the load 10 is connected to the terminal A side, contrary to the above case. Even in this case, the circuit between the terminals A and 31 has the same characteristics as the diode 31, which allows the load current to flow in only one direction from the terminal A to the terminal and compensates for the forward voltage of the diode 31. That is, since the voltage at the terminal is applied to the inverting input terminal of the operational amplifier 1 through the resistor 6, when the voltage at the terminal K becomes lower than that at the terminal A,
The output voltage of operational amplifier 1 is positively amplified and is connected to diode 3.
1 is conductive. Similarly to FIG. 10, the load current flows from the terminal A through the drain and source of the FET 2, and the operational amplifier 1 operates so that the voltages at the terminals A and Terminal A become equal.

As described above, in this embodiment, the terminal A has the same conductivity as the diode 31, and the voltage between the terminal A and the terminal becomes equal during conduction. In other words, the forward voltage drop is almost zero, and it is not affected by the magnitude of the load 'R current during conduction.]Il! It is possible to obtain ideal diode characteristics.

FIG. 12 shows the sixth to eighth embodiments corresponding to FIG. 7, FIG. 13 to FIG. 8, and FIG. 140 to FIG. 9, respectively. That is, in FIG. 12, the diode 31
, 5 and bias MWi4 are connected in the opposite direction to that in FIG. 10, and in this configuration, a rectifier circuit 1q using an ideal diode having a current polarity opposite to that in FIG. 10 is obtained. Furthermore, in FIG. 13, the driving type i1!19 and 20 are connected to the operational amplifier 1 in FIG.
l! Since it is supplied from 19 and 20, there is an advantage that an operational amplifier with a small width can be used. Furthermore, FIG. 14 shows a configuration in which an operational amplifier 21 having a voltage follower circuit configuration is provided in the feedback circuit of the feedback resistor 6 shown in FIG. 100 MΩ, and even better ideal diode characteristics can be obtained.

In each of the first to eighth embodiments described above, the case where the FET 2 is driven by the output of the operational amplifier 1 is shown, but instead of this FET, a transistor with a high current amplification factor or a Darlington transistor with a FET and a transistor are used. Even if a connected emitter follower circuit is used, the same effect as described above can be obtained.

(Effects of the Invention) As described above, according to the present invention, the operational amplifier has a non-inverting input terminal connected to an input terminal and a nine-inverting input terminal connected to an output terminal via a feedback resistor, and an output of this operational amplifier. a 1'' field effect transistor which is driven and whose drain is connected to the input terminal via a bias power supply;
One of the anode or the cathode is connected to the source of this field effect transistor, and the other is connected to the output terminal of the rectifying element to compensate for the forward voltage VF, so that the forward voltage of the rectifying element is It is possible to provide a rectifier circuit that can sufficiently compensate for the load current regardless of the magnitude of the load current.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram showing a rectifier circuit using a thyristor as a first embodiment of the present invention, and Fig. 2 shows a case where an AC 'IIi source is connected to the anode electrode and a load is connected to the cathode electrode K in Fig. 1. Figure 3 is a diagram showing its time chart, Figure 4 is an equivalent circuit diagram of the second factor, and Figure 5 is a circuit diagram of the circuit configuration.
6 and 6 are circuit configuration diagrams and equivalent circuit diagrams when a load is connected to the anode electrode and an AC power source is connected to the cathode electrode K in FIG. 1, and FIGS. FIG. 10 is a circuit diagram showing a rectifier circuit using diodes as a fifth embodiment of the present invention, and FIG. , circuit configuration diagrams when AC power sources are connected to the cathode electrodes, Figures 12 to 14
The figures are circuit diagrams showing sixth to eighth embodiments of the present invention, and FIGS. 15 and 16 are circuit diagrams showing different conventional rectifier circuits, respectively. 1...Operational amplifier, 2...FET, 3
... Thyristor, 31 ... Diode, 4 ... Bias power supply, 5 ... Diode, 6 ... Feedback resistor, 7.8. ...Zener diode, 9...AC power supply, 10...
...Load, A...Anode electrode, K...
...Cathode electrode, G...Gate electrode. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 5 Figure 10 Figure 11 Figure 14 Figure 15 Figure 16rXJ

Claims (3)

[Claims] (1) An operational amplifier whose non-inverting input terminal is connected to an input terminal and whose inverting input terminal is connected to an output terminal via a feedback resistor, and which is driven by the output of this operational amplifier and whose drain is connected to the input terminal via a bias power supply. A rectifier circuit comprising: a field effect transistor connected to the field effect transistor; and a rectifier element having one of an anode or a cathode connected to the source of the field effect transistor and the other connected to the output terminal. (2) The rectifying element uses a thyristor that is controlled on and off by a gate drive circuit (
The rectifier circuit described in item 1). (3) The rectifier circuit according to claim (1), wherein the rectifying element uses a diode.