JP7252004B2 - power converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power converter, and more particularly to a power converter with a thyristor.

2. Description of the Related Art In a power converter that receives AC power and converts it to DC power by a rectifier circuit and then converts it to AC power by an inverter, the rectifier circuit section is converted to DC power by a diode and a capacitor. In this circuit configuration, when the power is turned on, an excessive charging current flows into the power supply system and the diode toward the capacitor. ing. When the power is turned on, the switch is turned off and the capacitor is temporarily charged through the resistor to suppress the charging current. After charging is completed, the switch is turned on to bypass the resistor, and the current during normal operation is supplied to the inverter through the switch.

Mechanical contacts such as electromagnetic contactors and relays may be used for these switches, and thyristors, which are power semiconductors, may also be used. Patent Document 1 is known as a conventional technique in which a thyristor is connected in parallel with a current-limiting resistor.

Patent Document 1 is an invention relating to an inverter device and a motor drive device having a rush prevention circuit for preventing rush current from flowing into a smoothing circuit when power is turned on. Among them, the rush prevention circuit has current limiting means for limiting the rush current, a plurality of semiconductor switching elements, and a rush prevention circuit drive circuit for driving the semiconductor switching elements, and the semiconductor switching elements are connected in parallel. It discloses a connecting configuration.

JP 2001-112265

A thyristor is generally provided as a module enclosed in a package, and the package is provided with a gate terminal for applying a gate signal.

On the other hand, a control circuit for controlling the power conversion device and a circuit for controlling the switching elements are generally mounted on the board. A thyristor drive circuit for driving the thyristor is also generally mounted on the board.

Wires are often used to connect gate signals between thyristors and substrates on which circuits for controlling and driving power converters are mounted.

If there is a problem with the wiring, the thyristor will not turn on, and the current will pass through the resistors connected in parallel, causing excessive thermal stress and potentially leading to failure of the resistors.

Further, when the power capacity of the power conversion device is large, it is necessary to increase the capacity of the thyristors as well. As a method of increasing the capacity of the thyristors, thyristors may be used in parallel. When thyristors are connected in parallel, if one of the thyristor gate wirings in parallel has a defect in the gate signal wiring as described above, the thyristor on the defective side cannot turn on the gate signal. No current flows, and the entire current flows only through the thyristor on the other side where the wiring is normal.

Therefore, the thyristor on the normal side is used in a state in which a current exceeding the capacity flows, which may lead to failure. In Patent Document 1, no consideration is given to preventing failures due to wiring defects as described above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power conversion device that prevents failures due to faulty wiring between a thyristor and a thyristor drive circuit.

A preferred example of the present invention includes a rectifier, smoothing means for smoothing the output voltage of the rectifier, a resistor for suppressing rush current to the smoothing means when power is turned on, a thyristor, and a substrate, wherein the substrate is has a thyristor drive circuit for driving the thyristor and a control circuit for controlling the thyristor drive circuit, the substrate and the thyristor are connected by wiring,
The thyristor drive circuit is a power conversion device having a switch for passing a gate signal of the thyristor according to a signal from the control circuit, and a voltage detector for detecting an abnormality in the voltage between the gate and the cathode of the thyristor. be.

Advantageous Effects of Invention According to the present invention, it is possible to realize a power conversion device that prevents failures due to faulty wiring between a thyristor and a thyristor drive circuit.

1 is a diagram showing an overall circuit of a power conversion device of Example 1; FIG. 1 is a diagram showing the overall structure of Example 1. FIG. 1 is a diagram showing a circuit of Example 1; FIG. 4 is a timing chart of Example 1. FIG. FIG. 10 is a diagram showing a circuit of Example 2; FIG. 10 is a diagram showing a circuit of Example 3; FIG. 10 is a diagram showing a circuit of Example 4; FIG. 10 is a diagram showing a circuit of Example 5; FIG. 10 is a circuit diagram of Modification 1 of Embodiment 2; FIG. 10 is a circuit diagram of Modification 2 of Embodiment 2;

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the overall circuit configuration of a power conversion device 1 of Example 1. As shown in FIG. A power conversion device 1 receives power from an AC power supply 2, and includes a diode 3 as a rectifier, a switching element 5 as an inverter, a resistor 7 and a thyristor 8, a capacitor 4, and a switching element drive circuit 13 that controls the switching element 5. , a thyristor drive circuit 12 for controlling the thyristor 8 , a control circuit 11 for controlling the switching element drive circuit 13 and the thyristor drive circuit 12 , a control power supply circuit 14 , and an operation panel 15 . Power converter 1 supplies power to load 6 .

The current supplied from the AC power supply 2 is full-wave rectified by the bridge-connected diode 3 acting as a rectifier. The voltage output from the rectifier is smoothed by capacitor 4 . The output of capacitor 4 is DC power.

By switching ON or OFF the plurality of switching elements 5, it functions as an inverse converter that converts DC power into AC power of any frequency and any voltage. AC power is then output to the load 6 . Power semiconductors such as IGBTs and MOS FETs are used as switching elements.

The thyristor 8 and the resistor 7 are provided to suppress rush current flowing as charging current to the capacitor 4 as smoothing means when power is turned on. When the power is turned on, the thyristor 8 is turned off. In that case, the charging current flows through the resistor 7, so the rush current is suppressed by the resistor 7.

After the capacitor 4 is fully charged, the thyristor 8 is turned on and the resistor 7 is bypassed. Current that a normal power converter passes during operation passes through thyristor 8 and is supplied to capacitor 4 and switching element 5 .

A control circuit 11 such as a microcomputer that controls the power conversion device 1, a thyristor drive circuit 12 that drives the gate of the thyristor 8, a switching element drive circuit 13 that drives the gate of the switching element 5, and a control that supplies power to each circuit. A power supply circuit 14 and the like are mounted on the board 9 . This embodiment is characterized by the configuration of the thyristor drive circuit 12 provided on the substrate 9. FIG.

FIG. 2 is a diagram showing the overall structure of the power conversion device of Example 1. As shown in FIG.

Power semiconductors such as diodes, thyristors and switching elements are often provided in packaged modules in a bridge-connected configuration. FIG. 2 shows an example using power semiconductors in the form of modules.

A diode 3 as a rectifier, a thyristor 8, and a switching element 5 as an inverter are arranged on the cooling fins 21 as cooling means, and the cooling fins 21 cool the heat generated from these power semiconductors. .

Power semiconductors such as diodes 3, thyristors 8 and switching elements 5, capacitors 4, and resistors 7 are wired with wiring materials 22 such as electric wires and copper bars. The substrate 9 on which the control circuit 11, the thyristor drive circuit 12, the switching element drive circuit 13, etc. are mounted, the thyristor 8, and the switching element 5 are wired by wiring materials 24 and 25 such as electric wires.

FIG. 3 is a diagram showing a circuit of Example 1 comprising a thyristor 8, a thyristor drive circuit 12, and a control circuit 11. As shown in FIG. In FIG. 3, parts such as the resistor 7 of the power converter 1 are omitted. 5 to 10 are the same.

The thyristor drive circuit 12 includes a DC power supply 31, a switch 32 that is turned on according to a thyristor-on signal S from the control circuit 11, a gate resistor 33, and a voltage detector 35 that monitors the state of the voltage between the gate and cathode of the thyristor.

A DC power supply 31 feeds a driving power supply Vs. The switch 32 is turned on by the thyristor-on signal S from the control circuit 11, supplies current to the gate terminal of the thyristor 8 via the gate resistor 33, and turns the thyristor 8 on. A transistor or a relay is generally used for the switch 32 .

The voltage detector 35 monitors the state of the voltage between the gate and cathode of the thyristor, and sends a detection signal f to the control circuit 11 assuming that an abnormality has occurred when the voltage exceeds a predetermined voltage. Upon receiving the detection signal f, the control circuit 11 stops the operation of the switching element drive circuit 13, and stops the operation of the operation panel 15 or the operation of the switching element drive circuit 13 due to the abnormality. display that

Next, the operation of the circuit of FIG. 3 will be described. FIG. 4 is a diagram showing a timing chart of the thyristor drive circuit shown in FIG. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the signal states of the thyristor-on signal S, the detection voltage V1 between the gate and cathode of the thyristor, and the detection signal f from the voltage detector 35 in the circuit of FIG. .

At time t1, the thyristor-on signal S is turned on, the switch 32 is turned on, a gate current flows from the gate of the thyristor to the cathode, and the thyristor is turned on. The detected voltage V1 of the voltage detector 35 at this time becomes the normal voltage V _GT between the gate and the cathode of the thyristor.

Here, if the gate wiring 24 between the thyristor 8 and the substrate 9 is disconnected at time t2, the gate current stops flowing and V1 rises to the power supply voltage Vs.

A predetermined threshold voltage Vth selected from an arbitrary value in the range from the gate-cathode voltage _VGT to the power supply voltage Vs is set in the voltage detector 35, and compared with the detection voltage V1, the detection voltage is obtained. is equal to or less than the threshold voltage, that is, when V1≤Vth, it is judged to be normal. When the detected voltage exceeds the threshold voltage, that is, when V1>Vth, it is determined that there is an abnormality due to a wiring defect.

The Vth value should have a margin greater than the voltage _VGT between the gate and cathode of the thyristor during normal operation, considering the maximum value due to variations in _VGT and temperature changes, as well as variations and fluctuations in Vs to prevent operation under normal conditions. It is better to set the value as

According to the first embodiment, it is possible to detect wiring defects between the substrate 9 on which the thyristor drive circuit is mounted and the thyristors 8, thereby preventing secondary failures such as failures in resistors and thyristors. can be done.

FIG. 5 is a diagram showing a circuit in Example 2 comprising the thyristor drive circuit 12, the thyristor 8, and the control circuit 11. As shown in FIG. Descriptions overlapping those of the first embodiment are omitted.

The voltage detector 35 is configured by connecting a constant voltage diode 51 and a photocoupler 52 in series. A secondary side of the photocoupler 52 is connected to a control circuit.
It is assumed that the voltage Vz of the constant voltage diode 51 and the forward voltage Vf of the primary side of the photocoupler 52 are assumed.

Here, when the voltage of V1 rises and becomes higher than Vz+Vf, the constant voltage diode 51 and the photocoupler 52 become conductive, current flows, the secondary side of the photocoupler 52 turns on, and the detection signal f is sent to the control circuit 11. to transmit. Vth in Example 1 can be set by Vz+Vf.

In the second embodiment, by configuring the voltage detector 35 with the constant voltage diode 51 and the photocoupler 52, it is possible to reduce the number of parts and cost compared to a normal comparator. Then, wiring defects between the substrate 9 and the thyristor 8 can be detected.

FIG. 9 shows a circuit diagram of Modification 1 of Embodiment 2. As shown in FIG. In FIG. 9, the connection positions of the zener diode 51 and the photocoupler 52 are arranged in the opposite direction compared to the circuit of FIG. Such a configuration also has the same effect as the circuit shown in FIG.

FIG. 10 shows a circuit diagram of Modification 2 of Embodiment 2. As shown in FIG. 9 shows a circuit configuration in which a current limiting resistor 53 and an operation stabilizing resistor 54 are added to the circuit of FIG.

By providing the operation stabilizing resistor 54 and the current limiting resistor 53 as shown in FIG. 10, it is possible to prevent voltage detection from malfunctioning due to leakage current.

FIG. 6 is a diagram showing a circuit example of Example 3, in which thyristor modules are used in a two-parallel configuration. A description that overlaps with the above-described embodiment will be omitted. In FIG. 6, an OR circuit 64 outputs the OR of the signals from the voltage detector 1 indicated by reference numeral 35 and the voltage detector 2 indicated by reference numeral 63, so that it is possible to detect if one of them has an abnormality. and

In this embodiment, an example in which two thyristors are arranged in parallel has been described, but it is also applicable to three or more parallel thyristors. Also, in this embodiment, one switch 32 is shared, but a plurality of switch units may be arranged in parallel according to the number of thyristors.

According to the third embodiment, it is possible to detect a wiring defect between the substrate 9 and the thyristor 8 in a power conversion device having two or more thyristors connected in parallel, and to Failures can be prevented.

FIG. 7 is a diagram showing a circuit of Example 4, which is an example of using two thyristor modules in parallel as in Example 3. In FIG. A description that overlaps with the above-described embodiment will be omitted.

Example 4 is based on the circuit of Example 2, and has two thyristors in parallel. A zener diode 51 and a photocoupler 52 are connected between the gate and cathode of one thyristor 8 . A voltage regulator diode 71 and a photocoupler 72 are connected between the gate and cathode of the other thyristor 62 .

The secondary side of the photocoupler 52 and the secondary side of the photocoupler 72 are connected to a wired OR, and the output signal of the wired OR is sent to the control circuit 11 . A wired OR is a circuit having a resistor connected to a DC voltage source, and one end of the resistor is connected to the two secondary outputs of the photocouplers 52 and 72 .

According to the fourth embodiment, a wiring fault between the substrate 9 and the thyristors 8, 62 in a power conversion device having two or more thyristors 8, 62 connected in parallel can be detected with a simple circuit. can be done.

FIG. 8 is a diagram showing a voltage detector of Example 5. FIG. In a circuit modified from the fourth embodiment, diodes 81 and 82 are connected to the gates of thyristors 8 and 62, respectively. This is the configuration to apply. A description that overlaps with the above-described embodiment will be omitted.

The forward voltage Vd of the diodes 81 and 82, the voltage Vz of the constant voltage diode 51, and the forward voltage Vf of the primary side of the photocoupler 52 are assumed. When the voltage V1 between the gate and cathode of thyristor 8 rises and becomes higher than Vd+Vz+Vf, current flows through diode 81, voltage regulator diode 51, and photocoupler 52, turning on the secondary side of photocoupler 52. , to the control circuit 11 and the like.

The detection threshold voltage Vth can be set by Vd+Vz+Vf. On the other hand, when the voltage on the side of voltage V2 between the gate and cathode of thyristor 62 becomes larger than Vd+Vz+Vf, a current similarly flows through photocoupler 52, turning on the secondary side of photocoupler 52 and controlling circuit 11. etc.

According to the fifth embodiment, when two thyristors are connected in parallel, an abnormality can be detected with one zener diode 51 and one photocoupler 52, and the circuit is simpler than the fourth embodiment. There is an effect that it can be configured.

DESCRIPTION OF SYMBOLS 1... Power converter, 3... Diode, 4... Capacitor, 5... Switching element, 6... Load, 7... Resistance, 8... Thyristor, 9... Substrate, 11... Control circuit, 12... Thyristor drive circuit, 13... Switching element Drive circuit 15 Operation panel 35 Voltage detector 51 Constant voltage diode 52 Photocoupler

Claims (9)

a rectifier;
smoothing means for smoothing the output voltage of the rectifier;
a thyristor that cuts off current flowing from a power source to the smoothing means ;
a resistor bypassing the thyristor ;
and a substrate for determining an abnormality when the voltage between the gate and cathode of the thyristor exceeds a threshold voltage . In the power converter according to claim 1,
The substrate is
a zener diode;
and a photocoupler connected in series with the constant voltage diode,
A power converter, wherein the threshold voltage is set by the voltage of the constant voltage diode and the voltage of the primary side of the photocoupler. In the power converter according to claim 2 ,
The power conversion device, wherein the substrate has an operation stabilization resistor connected in parallel to the photocoupler, and a current limiting resistor connected in series with the voltage regulator diode. In the power converter according to claim 1,
A plurality of the thyristors are connected in parallel,
the substrate,
a plurality of voltage detectors for detecting a voltage between the gate and the cathode of each of the plurality of thyristors;
and a logical sum circuit that takes a logical sum of output signals from a plurality of voltage detectors. In the power converter according to claim 4 ,
the logical sum circuit is a wired OR,
A power conversion device, wherein the voltage detector has a constant voltage diode and a photocoupler connected in series with the constant voltage diode. In the power converter according to claim 1,
A plurality of the thyristors are connected in parallel,
A plurality of diodes connected to each of the plurality of thyristors are connected in series to one voltage regulator diode and one photocoupler,
A power converter , wherein the substrate has a plurality of voltage detectors for detecting voltages between the gates and the cathodes of the plurality of thyristors . In the power converter according to claim 1,
A power converter, characterized in that , when the board detects the abnormality, the operation panel displays that the abnormality has occurred. In the power converter according to claim 1,
Having a switching element drive circuit that drives a switching element as an inverse converter,
A power converter, wherein the switching element drive circuit stops operating when the substrate detects the abnormality. In the power converter according to claim 1,
Having a switching element as an inverse converter,
A power converter comprising cooling means for cooling the rectifier, the thyristor, and the switching element.

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