JP2003348849A - Current detector for rectifier circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an input current without use of a direct current detector when a rectifier circuit is operated with a high power factor. <P>SOLUTION: Resistors 11 and 12 are connected in serial with both semiconductor switch circuits, and a first current computing circuit 20 computes the input current IIN of the rectifier circuit from the voltages of both resistors 11 and 12. The first current computing circuit 20 is composed of a first adder 25 which subtracts a negative voltage detection value from a second negative voltage detector 24 connected with the second resistor from a negative voltage detection value from a first negative voltage detector 23 connected with the first resistor 11. Alternatively, an alternating current detector 31 is installed on the input side of the rectifying circuit, and the resistors 11 and 12 are connected in series with both the semiconductor switch circuits. A second current computing circuit 30 computes the input current IIN of the rectifier circuit from the voltages of both resistors 11 and 12 and a detection value from the alternating current detector 31. The second current computing circuit 30 is composed of a second adder 32 which subtracts the voltage of the second resistor 12 from the voltage of the first resistor 11; an average value computing unit 33 which determines the average value of the results of the computation by the second adder; and a third adder 34 which adds the computed average value and the detection value from the alternating current detector 31. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier circuit current detector for detecting a current input to a rectifier circuit capable of converting AC power into DC power at a high power factor.

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram showing a conventional rectifier circuit capable of converting AC power into DC power at a high power factor. FIG.
In the conventional circuit of FIG.
A series circuit in which a series diode 2 is connected to a semiconductor switch circuit 1 composed of an OSFET 1A and a built-in diode 1B and a series circuit in which a series diode 4 is connected to a semiconductor switch circuit 3 composed of a MOSFET 3A and a built-in diode 3B are connected to the positive electrode of a DC circuit. An AC power supply 6 is connected between the connection point between the semiconductor switch circuit 1 and the series diode 2 and the connection point between the semiconductor switch circuit 3 and the series diode 4 via a reactor 5. By that
A rectifier circuit for converting AC power to DC power is formed.
Further, a DC current detector 7 for detecting an input current of the rectifier circuit is inserted in series with the reactor 5, and a smoothing capacitor 8 for removing a pulsating component contained in the DC power output from the rectifier circuit is connected to the DC circuit. Connect between positive and negative electrodes.

When the input voltage V _{IN of the} rectifier circuit is positive,
When the MOSFET 1A is turned on, the current flows while increasing along the path of the AC power supply 6 → reactor 5 → MOSFET 1A → built-in diode 3B → AC power supply 6. So MOSF
When the ET1A is turned off, the current flowing through the reactor 5 is changed from the reactor 5 → the series diode 2 → the smoothing capacitor 8 → the built-in diode 3B → the AC power supply 6 → the reactor 5
Commutation to the path.

When the input voltage V _IN is negative, the MOS
By turning on FET3A, the current is changed from AC power supply 6 to MO.
It flows while increasing along the path of SFET 3A → built-in diode 1B → reactor 5 → AC power supply 6. So MOSF
When the ET3A is turned off, the current flowing through the reactor 5 is changed from the reactor 5 → AC power supply 6 → series diode 4 →
Smoothing capacitor 8 → Built-in diode 1B → Reactor 5
Commutation to the path.

That is, when the input voltage V _IN is positive, MO
The control pulse width of the SFET 1A is controlled.
By controlling the control pulse width of the OSFET 3A,
AC input power at the time of conversion to DC power can be controlled to a high power factor. However, this requires the input current I _IN
And the MOSFET 1A and the MOSFET 3A so as to have the same waveform as the sine wave voltage having the same phase as the input voltage V _IN.
, The input current I _IN needs to be detected. Therefore, in the conventional circuit, the input current I _IN is detected by installing the DC current detector 7 on the input side of the rectifier circuit.

FIG. 8 is a waveform diagram showing the waveforms of the input voltage and input current of the rectifier circuit in the conventional circuit shown in FIG. 7, and FIG. 8 shows the waveform of the input voltage V _IN of the rectifier circuit.
Is a waveform of the input current I _IN detected by the DC current detector 7, and shows a state where the voltage and the current are in phase, that is, the power factor is 100%.

[0007]

As described above, in order to maintain the input power of the rectifier circuit at a high power factor, it is necessary to detect the input current I _IN. However, in controlling the rectifier circuit shown in FIG. Generally, the negative electrode N on the DC output side is set to the reference potential. Therefore, the current detector for detecting the input current I _IN in the control circuit must be insulated, and this current detector must also be able to detect the DC component included in the input current I _IN . This is because the current transformer that detects the AC current cannot detect the DC current component superimposed on the input current I _IN , and if there is any control error when controlling the rectifier circuit, the current transformer is included in the input current I _IN . Cannot correct the DC current component. As a result, the DC current component increases and an excessive current may be caused to damage the device. Therefore, in order to avoid such danger, the DC current detector 7 is used.
Use However, the DC current detector 7 has a drawback that the circuit is complicated and expensive compared to the current detection based on the voltage drop of the resistance and the current detection using the AC current detector.

An object of the present invention is to make it possible to detect an input current without using a DC current detector when operating a rectifier circuit at a high power factor.

[0009]

In order to achieve the above object, a current detecting device for a rectifier circuit according to the present invention comprises a semiconductor switch element having a built-in diode or a semiconductor comprising an anti-parallel connection of a semiconductor switch element and a diode. A series diode having a different conduction direction is connected to the switch circuit, and two sets of the series circuit are connected in parallel between the positive and negative electrodes of the DC circuit, and two sets of the semiconductor switch circuit and the series diode are connected.
An AC power supply is connected between the two connection points via a reactor, and the voltage of the AC power supply turns on / off one semiconductor switch circuit during a positive half cycle, and the other semiconductor switch circuit during a negative half cycle. In a rectifier circuit that converts AC power into DC power by turning on and off the first semiconductor switch circuit in series with the one semiconductor switch circuit.
A resistor is connected, and a second resistor is connected in series with the other semiconductor switch circuit. From the voltage drop value of the first resistor and the voltage drop value of the second resistor, the first input current operation circuit determines the input of the rectifier circuit. Calculate the current.

The first input current calculation circuit detects a value when the voltage drop of the first resistor is negative, and detects a value when the voltage drop of the second resistor is negative. Second
The rectifier comprises a negative voltage detector and a first adder which uses a result obtained by subtracting a detection value of the second negative voltage detector from a detection value of the first negative voltage detector as an input current of the rectifier. Alternatively, an AC current detector is inserted into an input circuit of the rectifier, a first resistor is connected in series with the one semiconductor switch circuit, and a second resistor is connected in series with the other semiconductor switch circuit. The second input current calculation circuit calculates the input current of the rectifier circuit from the voltage drop value of the second resistor, the voltage drop value of the second resistor, and the detection value of the AC current detector.

The second input current operation circuit includes a first voltage detector for detecting a voltage drop of a first resistor, a second voltage detector for detecting a voltage drop of a second resistor, and the first voltage detector. Subtracting the detection value of the second voltage detector from the detection value of
An adder, an average calculator for calculating an average value of the operation result of the second adder, and a result obtained by adding the average calculation value and a detection value of the AC current detector as an input current of the rectifier. It is composed of a third adder.

[0012]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. The circuit of the first embodiment shown in FIG. 1 is different from the conventional example shown in FIG. The difference is that the detector 7 is removed, a first resistor 11 is connected in series to the semiconductor switch circuit 1, and a second resistor 12 is connected in series to the semiconductor switch circuit 3. Since the circuit is the same as the conventional circuit of FIG. 7, the description of the same part is omitted.

FIG. 2 is an operation waveform diagram showing the operation of the circuit of the first embodiment shown in FIG. 1. FIG. 2 shows the waveform of the input voltage V _IN of the rectifier circuit, and FIG. Voltage V
FIG. 2 shows the waveform of _R1 ; FIG. 2 shows the waveform of the voltage V _R2 generated in the second resistor 12; and FIG. 2 shows the waveform of the input current I _IN of the rectifier circuit. The contents of the embodiment will be described below.

As in the conventional circuit, the MOS shown in FIG.
FET1A to a switching operation at t ₁ ~t ₂ period the input voltage V _IN is positive. Therefore, during this period, MOSFE
When T1A is turned on, the first resistor 11 has the MOSFET 1
A current flows from A to the negative electrode N, and a voltage V _{R1 in the} direction of the arrow is drawn.
Although but occurs, current to the first resistor 11 if the off MOSFET1A does not flow, does not occur voltage V _R1. Therefore t
Intermittent voltage (see FIG. 2) is generated in the ₁ ~t ₂ period. Also, during the period from t _{2 to} t ₃ when the input voltage V _IN is negative,
Regardless of whether the MOSFET 3A is on or off, the first resistor 11 always has the MOSFET 1A
, A continuous voltage in the direction opposite to the arrow (see FIG. 2) is generated.

During the period from t _{2 to} t ₃ when the input voltage V _IN is negative, the MOSFET 3A performs a switching operation.
When the MOSFET 3A turns on during this period, the second resistor 1
The second current in the direction of the negative electrode N is generated, the arrow direction of the voltage V _R2 flows from MOSFETs but, MOSFETs
Is turned off, no current flows through the second resistor 12, so that no voltage _VR2 is generated. Therefore intermittent voltage (see FIG. 2) is generated in the t ₂ ~t ₃ periods. Further, during the period from t _{1 to} t ₂ when the input voltage V _IN is positive, a current always flows from the negative electrode N to the MOSFET 3A through the second resistor 12 regardless of whether the MOSFET 1A is on or off. Generates a continuous voltage in the reverse direction (see FIG. 2).

Therefore, a period in which the voltage V _R1 generated in the first resistor 11 is negative (ie, a period from t ₂ to t _{3 in} FIG. 2) and a period in which the voltage V _R2 generated in the second resistor 12 is negative (ie, FIG. in t ₁ ~t ₂ period) was removed, if calculating the difference between the former voltage and the latter voltage, the waveform shown in FIG. 2, that is, the input current I _iN is obtained. Or, by inverting the polarity of the latter voltage and calculating the sum of it and the former voltage,
The input current I _IN shown in FIG. 2 is obtained.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. In the circuit of the first embodiment shown in FIG. 1, the first current operation circuit 20 for obtaining the input current I _IN already described in FIG. It shows the configuration. In the circuit of the second embodiment, a first current calculation circuit 20 includes a first voltage detector 21 that insulates and detects a voltage across the first resistor 11 and a first voltage detector 21 that outputs only a negative value of the detected voltage. A negative voltage detector 23, a second voltage detector 22 for detecting the voltage across the second resistor 12 while insulating the voltage, and a second negative voltage detector 24 for outputting only a negative value of the detected voltage
And a first adder 25 for subtracting the output value of the second negative voltage detector 24 from the output value of the first negative voltage detector 23. The output of the first adder 25 is shown in FIG. The input current I _IN is shown.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention. The circuit of the third embodiment shown in FIG. 4 is different from the conventional example shown in FIG. Instead, an AC current detector 31 is provided, the semiconductor switch circuit 1 is connected in series with the first resistor 11, and the semiconductor switch circuit 3 is connected in series with the second resistor 12, Other than this, the circuit is the same as the conventional circuit of FIG. 5, and the description of the same parts will be omitted.

FIG. 5 is an operation waveform diagram showing the operation of the circuit of the third embodiment shown in FIG. 4. FIG. 5 is a waveform of the input voltage V _IN of the rectifier circuit, and FIG. Voltage V
_R1 waveforms 5 the waveform of the voltage V _R2 generated in the second resistor 12, FIG. 5 is a waveform obtained by subtracting a voltage V _R2 from voltage V _R1, Figure 5 by subtracting a voltage V _R2 from voltage V _R1 Represents the DC component included in the value. The contents of the third embodiment of the present invention will be described below with reference to FIGS.

[0020] Similar to the first embodiment circuit described above, MOSFET1A shown in FIG. 4 is positive input voltage V _IN is t ₁
And a switching operation in ~t ₂ period, the input voltage V _IN is in the t ₂ ~t ₃ periods is negative, MOSFETs to the switching operation. Therefore, the voltage V generated in the first resistor 11
_R1 has the waveform shown in FIG. 5, which is the same as the waveform already described in FIG.
The waveform of the voltage V _R2 represented by is also the same as the waveform already described in FIG.

In the third embodiment, the voltage V _{R1 is changed} from the voltage V _R1 to the voltage V _R2.
Is subtracted, and the waveform of the subtraction result is shown in FIG.
It becomes. The average value of the waveform shown in FIG. 5 should be zero, but if there is any control error, it does not become zero because a direct current component is included. The magnitude of the DC current I _DC (see FIG. 5) can be detected by calculating the average value of the waveform shown in FIG. The DC current I _DC thus obtained is
By adding the _AC current I _AC detected by the AC current detector 31 installed in the input circuit of the rectifier circuit, the input current I _IN (I _IN = I _AC + I _DC ) to the rectifier circuit can be obtained.

FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention. The input current I _{IN in the} circuit of the third embodiment described with reference to FIG.
2 shows the configuration of the second current calculation circuit 30 for obtaining the following equation. In the circuit of the fourth embodiment, the second current operation circuit 30
A first voltage detector 21 for insulating and detecting the voltage between both ends of the first resistor 11, a second voltage detector 22 for insulating and detecting the voltage between both ends of the second resistor 12, and an output of the first voltage detector 21 A third adder 32 for subtracting the output value of the second voltage detector 22 from the value, an average value calculator 33 for calculating an average value of the operation result of the third adder 32, And a third adder 34 for adding the detection value of the AC current detector 31. The output of the third adder 34 is the input current I _{IN of the} rectifier circuit.

[0023]

In order to convert AC power into DC power at a high power factor, a semiconductor switch circuit constituting a rectifier circuit is controlled. However, a slight control error at this time causes an increase in the input current of the rectifier circuit. If a direct current component is included, the direct current component increases without correcting this, and there is a possibility that the device may be damaged. Therefore, a DC current detector has conventionally been used for detecting an input current including a DC current component. However, this DC current detector has a drawback that the device is complicated and expensive. Therefore, in the present invention, a resistor is inserted in series with a semiconductor switch circuit constituting a rectifier circuit, and the input current I _{IN is} calculated by a first current operation circuit constituted by a negative voltage detector, an adder, etc., based on a voltage drop generated in the resistor. Is obtained, it is possible to detect an input current I _{IN including} a DC component without using an expensive DC current detector.

Alternatively, a second current calculation for detecting an input current by adding a voltage drop of a resistor inserted in series to a semiconductor switch circuit and a DC current component obtained by an average value calculation and an AC current component obtained by an AC current detector. The circuit has an effect that the input current I _{IN including the} DC component can be detected without using an expensive DC current detector.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram showing the operation of the first embodiment circuit shown in FIG.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention.

FIG. 5 is an operation waveform diagram showing the operation of the circuit of the third embodiment shown in FIG. 4;

FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a conventional example of a rectifier circuit capable of converting AC power to DC power at a high power factor.

8 is a waveform diagram showing the waveforms of the input voltage and the input current of the rectifier circuit in the conventional circuit shown in FIG.

[Explanation of symbols]

1,3 semiconductor switch circuit 1A, 3A MOSFET 1B, 3B Built-in diode 2,4 series diode 5 reactor 6 AC power supply 7 DC current detector 11 1st resistance 12 Second resistance 20 1st current calculation circuit 21 1st voltage detector 22 Second voltage detector 23 1st negative voltage detector 24 Second negative voltage detector 25 First adder 30 Second current operation circuit 31 AC current detector 32 Second adder 33 Average calculator 34 Third adder

Claims (4)

[Claims] 1. A semiconductor switch circuit comprising a semiconductor switch element having a built-in diode, or a semiconductor switch circuit comprising an anti-parallel connection of a semiconductor switch element and a diode, connected to a series diode having a different conduction direction. A series circuit is formed, and two sets of the series circuit are connected in parallel between the positive and negative electrodes of a DC circuit, and an AC power supply is connected via a reactor between two connection points of the semiconductor switch circuit and the series diode. During the positive half cycle of the voltage of the AC power supply, one semiconductor switch circuit is turned on and off, and during the negative half cycle, the other semiconductor switch circuit is turned on and off to convert AC power into DC power. In the rectifier circuit for conversion, a first resistor is connected in series with the one semiconductor switch circuit and a first resistor is connected in series with the other semiconductor switch circuit. A current detection device for a rectifier circuit, comprising: a first input current calculation circuit that connects two resistors and calculates an input current of the rectifier circuit from a voltage drop detection value of the first resistor and the second resistor. 2. The current detection device for a rectifier circuit according to claim 1, wherein the first input current calculation circuit detects a value when the voltage drop of the first resistor is negative. A second negative voltage detector for detecting a value when the voltage drop of the second resistor is negative, and adding or subtracting a detection value of the second negative voltage detector from a detection value of the first negative voltage detector And a first adder for calculating the result of calculation as an input current of the rectifier circuit. 3. A semiconductor switch circuit comprising a semiconductor switch element having a parasitic diode, or a semiconductor switch circuit comprising an anti-parallel connection of a semiconductor switch element and a diode, connected to a series diode having a different conduction direction. A series circuit is formed, and two sets of the series circuit are connected in parallel between the positive and negative electrodes of a DC circuit, and an AC power supply is connected via a reactor between two connection points of the semiconductor switch circuit and the series diode. During the positive half cycle of the voltage of the AC power supply, one semiconductor switch circuit is turned on and off, and during the negative half cycle, the other semiconductor switch circuit is turned on and off to convert AC power into DC power. In the rectifier circuit for conversion, an AC current detector is inserted into an input circuit of the rectifier circuit, and a first resistor is connected in series with the one semiconductor switch circuit. A second resistor is connected in series with the other semiconductor switch circuit, and an input current of the rectifier circuit is calculated from a detected value of the AC current detector and a detected voltage drop of the first resistor and the second resistor. A current detection device for a rectifier circuit, comprising a second input current calculation circuit. 4. The current detection device for a rectifier circuit according to claim 3, wherein the second input current calculation circuit detects a voltage drop of the first resistor, and a voltage of the second resistor. A second voltage / voltage detector for detecting a drop, a second adder for subtracting a detection value of the second voltage detector from a detection value of the first voltage detector, and an average of operation results of the second adder An average value calculator for calculating a value, and a third adder that adds the average value calculation value and the detection value of the AC current detector and uses the result of the calculation as an input current of the rectifier circuit. Characteristic rectifier circuit current detection device.