JP2692331B2 - Inverter protection circuit using voltage-controlled element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an inverter using voltage-controlled elements such as FETs and IGBTs that are used in electric vehicles, electric trains, and other electric devices that use an electric motor as a drive source. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit, and more particularly to an inverter protection circuit using a voltage control type element that converts a direct current of a power supply into an alternating current through inverter control through a smoothing capacitor.

[Prior Art] Conventionally, an inverter drive device that includes a smoothing capacitor to smooth a DC power supply voltage and uses the smoothed DC power supply voltage as an inverter drive source is known, and this type of device is a three-phase system using a DC voltage of an in-vehicle battery, for example. It is used as a drive device for an electric vehicle that drives an induction motor.

In this inverter driving device, a DC voltage is charged to the smoothing capacitor in a short time at the time of starting, and a starting device including a current limiting resistor is used to limit the inrush current at this time.

A conventional general starting device has a resistor that limits an inrush current of a smoothing capacitor, a timer that measures, for example, an elapsed time sufficient to charge the smoothing capacitor, and a resistor that burns the resistor when supplying power to a load. And a relay that protects the resistor from being burnt out by turning on the relay after a predetermined time elapses.

Also, detecting the voltage of the resistor that limits the inrush current,
A starting device has been proposed which operates the relay to prevent the resistor from burning when the voltage drops and when the smoothing capacitor has been charged (JP-A-56-58774).

On the other hand, FIG. 4 shows an example of a conventional inverter protection circuit of this type, which is disclosed in Japanese Patent Laid-Open No. 63-1145.
No. 01 publication.

This inverter protection circuit consists of a parallel circuit consisting of a resistor and a GTO thyristor installed between the inverter power supply lines, and limits and controls overcurrent.

That is, as shown in the figure, in a conventional protection circuit, for example, a current is supplied from a power feeding line 2 by a pantograph 1 of a train, and the current is limited by an electromagnetic connection path 4 and a filter reactor 6 which are connected in series. Resistor 8 and GTO for short circuit
The filter capacitor 14 is charged through the changeover switch unit 12 formed by connecting the thyristors 10 in parallel.

Then, the charging current of the filter capacitor 14 is supplied to the thyristor inverter 16 to drive the induction motor 18.

As described above, in the protection circuit of the inverter, the current limiting resistor 8 and the short-circuit GTO as the changeover switch unit 12 are provided between the filter capacitor 14 and the filter reactor 6.
The thyristor 10 is connected to limit the short-circuit current flowing into the inverter 16 when energized.

[Problems to be Solved by the Invention] However, in such a conventional inverter protection circuit shown in FIG. 4, an OFF state of a device such as a FET or an IGBT is becoming faster as a voltage-controlled device becomes faster. There was a tendency for the element to be damaged or destroyed when a current was supplied.

Especially, when the inverter 16 is in an unlimited state or stopped,
Even if the current from the power supply side is cut off by the change-over switch unit 12, the residual charge voltage of the capacitor 14 is added to the element of the inverter 16, so that there is a high possibility that the element will erroneously fire, There was a problem that it was destroyed by it.

That is, in the protection circuit of the inverter, the changeover switch unit 12 connected in parallel with the current limiting resistor 8 and the GTO thyristor 10 is simply connected between the reactor 6 and the capacitor 14, and the capacitor 14 And the inverter circuit 16 are always directly connected.

For this reason, even if the short-circuit current flowing from the power supply line 2 to the element of the inverter at the time of energization is limited by the current limiting resistor 8 and the supply current can be interrupted by the changeover switch unit 12, the capacitor 14 is charged at the time of OFF. A high voltage due to the residual charge is applied to the inverter 16, which prevents the current from flowing into the inverter 16 at all and damages or destroys the voltage input device.

Therefore, in the related art, it is not possible to take complete measures for protection of the elements constituting such an inverter circuit, which is insufficient, and there is a problem in reliability in the operation of the inverter circuit.

OBJECT OF THE INVENTION The present invention has been made in view of the above conventional problems,
The purpose thereof is to prevent the residual charge charged in the smoothing capacitor from flowing into the inverter circuit when the inverter circuit is in a stopped state, and to surely prevent damage and destruction of the voltage controlled element. It is to provide a protection circuit for an inverter using an element.

[Means for Solving the Problem] In applying a DC voltage from a DC power supply to a DC input terminal of an inverter circuit for exchanging a DC voltage with an AC current, via a smoothing capacitor connected between the DC input terminals, In a protection circuit that protects the inverter circuit from damage due to voltage or current, first and second current limiting circuits that are provided between the DC input terminals to limit a flowing current, and the first and second current limiting circuits. Of the current limiting circuit is electrically disconnected or bypassed from the DC input terminal, and the parallel connection body of the second current limiting circuit and the smoothing capacitor is connected via the first current limiting circuit. And a second state connected between the DC input terminals according to a control signal, and a state of the contactor when the inverter circuit is stopped. And a control means for switching the state from the first state up to that time to the second state.

[Operation] According to the present invention having the above-described configuration, the control means issues a control signal when the inverter circuit is in a stop state in which there is a high possibility that the element falls into an uncontrolled state and the element is erroneously fired
As a result, the smoothing capacitor and the inverter circuit are connected via the first current limiting circuit and the smoothing capacitor is also connected to the second current limiting circuit. Therefore, it becomes possible to reliably prevent the residual charge charged in the smoothing capacitor from flowing into the inverter circuit.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an example of a circuit configuration of an inverter protection circuit using a voltage control type element according to the present invention.

A feature of the present invention is that when the inverter circuit is in a stopped state, the connection between the smoothing capacitor and the inverter circuit is cut off to prevent inflow of residual charge to be charged into the inverter circuit.

The circuit configuration and operation of this embodiment shown in FIG. 1 will be described below.

In the figure, the main circuit configuration of the protection circuit of the inverter using the voltage control type element, the main contactor 26 for intermittently supplying the DC current from the main battery E1 to the inverter through the fuse, and the load as the drive source. An inverter circuit 20 connected to the motor 18 and having FETs, IGBTs, etc. as voltage input type elements, a charging resistor Rc connected in series, a smoothing capacitor C, and a discharge resistor connected in parallel with the smoothing capacitor C via a sub-contactor 22. A smoothing circuit section 23 composed of Rb and the stop state of the inverter circuit 20 are detected, and the smoothing capacitor C and the inverter circuit 20 are detected.
And a control circuit 24 for controlling connection and disconnection by the sub-contactor 22.

The sub-contactor 22 as a connecting / disconnecting means is provided so as to be connected between the inverter circuit 20 and the smoothing capacitor C, and the connection between them can be connected / disconnected.

Therefore, the connection can be cut off by the control circuit 24, which prevents the residual charge charged in the smoothing capacitor from flowing into the inverter circuit 20.

Further, the control circuit 24 turns on and off the power source E2 and the power source.
An IG switch 28 for switching and a control signal 32a for controlling the inverter circuit 20 which is supplied with a power source E2 when the IG switch 28 is turned on, and then outputs a start signal 32b for controlling the main conductor 26. A controller 32 that outputs, a transistor Tr1 that performs switching control by the activation signal 32b, a timer circuit 30 that inputs the activation signal 32b and outputs an activation signal for controlling the sub-contactor 22 after a predetermined time, and the timer circuit. The transistor Tr2 is switching-controlled by a start signal output from 30.

FIG. 2 shows the operation sequence of the inverter protection circuit of this embodiment shown in FIG. 1 by the rising or falling of the pulse. Also, in FIG. 3, the operation sequence of the timer circuit 30 is similarly shown by a pulse,
The operation of this embodiment will be described below with reference to FIGS.

In FIG. 2, the control circuit 24 is activated when the inverter is started.
When the IG switch 28 is turned on, the controller 32 is operated by the power supply E2, and the controller 32 outputs the control signal 32b for controlling the inverter circuit 20 (shown in FIG. 2 (a)). Pulse rise).

The control signal 32a turns off all the voltage control elements of the inverter circuit 20 in the initial stage of startup, and causes each element to perform a switching operation after completion of charging of the smoothing capacitor described later (after t3). It is what is input to the gate.

Then, after a predetermined time t1 from the ON of the IG switch, the activation signal 32a is input from the controller 32 to each base input terminal of the Tr2 via the Tr1 and the timer circuit 30.

At the same time, the Tr1 is turned on to turn on the main contactor 26 (rising of the pulse shown in FIG. 2A), and Tr2 is also turned on to turn on the timer circuit 30 to start the timer operation. .

Here, when the main contactor 26 is turned on, the power supply voltage E1 is supplied to the smoothing circuit 23 via a fuse.
At this time, the power supply voltage E1 is charged in the smoothing capacitor C via the charging resistor Rc.

However, at this time, the switch of the sub-contactor 22 is on the B side as shown in FIG. 1, so that the smoothing capacitor C and the inverter circuit 20 are not directly connected.

Therefore, as shown in FIG. 3, by the operation of the timer circuit 30 described above, a timer output signal is output to the Tr2 at a predetermined timer time t2 after the start signal 32b is input, so that the Tr2 is turned on. As a result, the switch of the sub-conductor 22 shown in FIG. 1 is switched from the B side to the A side (the rising edge of the pulse shown in FIG. 2A).

This is the main contactor 26 shown in FIG. 2 (a).
It is understood that the time from the turning on of the sub contactor 22 to the turning on of the sub-contactor 22 is the timer time t2 and corresponds to the charging time t3 for charging the smoothing capacitor C (t2 = t.
3).

That is, as in the operation sequence of FIG. 3, after the smoothing capacitor C is charged to a predetermined voltage level at time t2, the sub-contactor 22 is activated (A side), whereby the charging resistor Rc is short-circuited. The smoothing capacitor C is directly connected to the inverter circuit 20 without the charging resistor Rc.

The specific setting of the timer time t2, that is, the charging time t3 for charging the smoothing capacitor C is determined based on the smoothing capacitor C, the charging resistance Rc, and the discharging resistance Rb, and generally Rc <Rb ( VRc <VRb).

When the inverter circuit 20 is stopped, the controller 32 stops the output of the start signal 32b to stop the timer circuit 30 (rising of the pulse shown in FIG. 3), and by turning off Tr1 and Tr2, The main contactor
At the same time as turning off 26, the sub-contactor 22 is switched from the A side to the B side. Therefore, as shown in FIG. 2B, the pulses fall at the same time.

As a result, the direct connection between the smoothing capacitor C and the inverter circuit 20 is cut off, and the inflow of the residual charge charged in the smoothing capacitor C into the voltage control type element is caused by the resistor Rc.
Is limited by Further, the electric charge will be discharged by the discharge resistor Rc.

As described above, it is possible to reliably prevent the charge residual charge from flowing into the voltage input type element, and prevent damage or destruction to the element.

Further, in this embodiment, since the charging resistor Rc is provided in the input portion of the smoothing circuit 23, it is possible to limit the inrush current to the smoothing capacitor at the time of startup, and the smoothing circuit 23 and the inverter. By providing the sub-contactor 22 with the circuit 20, the smoothing capacitor C when stopped
It is possible to prevent the residual charge that has been charged due to flowing into the device.

Therefore, in the present embodiment, the smoothing circuit 23 can be simply configured by only the combination of the sub-contactor 22 and Rc, C, and Rb, and the smoothing circuit 23 can be easily formed by the flow of the residual charge when charging is stopped. The protection of the inverter circuit is reliably achieved.

[Advantages of the Invention] As described above, according to the protection circuit of the present invention,
By blocking the direct connection between the smoothing capacitor and the inverter circuit when the inverter is stopped, it is possible to surely prevent the charge residual charge from flowing from the smoothing capacitor to the inverter circuit.

Further, according to the present invention, the circuit configuration of the inverter protection circuit itself is greatly simplified.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an inverter protection circuit using a voltage control type device according to the present invention, FIG. 2 is a time chart of starting and stopping in the inverter protection circuit shown in FIG. 1, and FIG. 1 is a time chart of the operation of the control circuit shown in FIG. 1, and FIG. 4 is a circuit configuration diagram of a conventional inverter protection circuit using a voltage-controlled element. 20 ... Inverter circuit 22 ... Sub contactor 23 ... Smoothing circuit 24 ... Control circuit 30 ... Timer circuit 32 ... Controller Rc ... Charging resistance C ... Smoothing capacitor Tr1, Tr2 ... Switching transistor

Claims (1)

(57) [Claims] 1. When applying a DC voltage from a DC power supply to a DC input terminal of an inverter circuit for converting a DC voltage into an AC current through a smoothing capacitor connected between the DC input terminals, the inverter circuit is provided. In a protection circuit that protects from damage due to voltage or current, first and second current limiting circuits that are arranged between the DC input terminals and that limit the flowing current, and the first and second current limiting circuits Is electrically disconnected or bypassed from the DC input terminal, and the parallel connection body of the second current limiting circuit and the smoothing capacitor is connected to the DC input via the first current limiting circuit. A contactor that switches between a second state connected between the terminals according to a control signal, and the state of the contactor when the inverter circuit is stopped. Protection circuit characterized in that it comprises from 1 state and control means for switching to the second state, the.