JPH0884494A - Failure detector for semiconductor bridge main circuit - Google Patents

Abstract

PURPOSE: To detect conduction failure of a semiconductor bridge main circuit element under shutdown state by providing a small circuit additionally. CONSTITUTION: Under a state where the upper arms U, V of a semiconductor bridge main circuit 1 are turned ON by a control circuit 7, voltage between the input terminals is detected by means of a voltage detection circuit 11. When the detected voltage is lower than a set voltage, the control circuit 7 makes a decision that a conduction failure is present in lower arm X, Y. On the contrary, a decision is made that a conduction failure is present in the upper arm based on a voltage detected when the lower arm is turned ON. The decisions are made under shutdown state of a unit comprising the semiconductor bridge main circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detecting device for a semiconductor bridge main circuit for supplying direct current power by switching positive and negative polarities to a direct current load.

[0002]

2. Description of the Related Art A DC electric vehicle (forklift, unmanned vehicle, etc.) is equipped with a DC motor for traveling, a DC motor for power steering, and a DC motor for cargo handling. A driving circuit including a circuit is provided.

FIG. 3 shows a drive circuit of a DC motor for power steering of an electric vehicle. Semiconductor bridge main circuit 1
Has a configuration in which power transistors U, V, X, Y and respective free wheeling diodes D are connected in anti-parallel and upper and lower arms are bridge-connected, and the DC motor 2 is connected to the output terminal thereof.
Is connected.

At the input terminal of the semiconductor bridge main circuit 1,
DC power is supplied from the battery 3 through the key switch 4, the fuse 5 and the power steering contactor 6.

The control device 7 has a microcomputer configuration, performs on / off control of the power transistor Tr according to the operation direction (or operation command) and the operation amount of the steering wheel of the direct current electric vehicle, and applies it to the direct current electric motor 2. The polarity of DC is switched between positive and negative and the DC voltage is controlled by the chopper operation.

For example, as shown in the example of the gate waveform in FIG. 4, during the forward rotation period T ₁ of the DC motor 2, the power transistor U is continuously turned on and the power transistor Y is controlled according to the steering operation amount. ON / OFF control is repeated at the conductivity rate.

In the reverse rotation period T ₂ of the DC motor 2,
The power transistor V is continuously ON-controlled, and the power transistor X is ON / OFF-controlled at a conduction rate according to the steering operation amount.

The driving of the electric motor of the electric vehicle and the driving of the cargo handling motor are performed in the same manner. Further, instead of the power transistor, a power semiconductor element having a self-extinguishing ability such as a GTO or SI transistor is used. Further, the power semiconductor and the diode D may be integrated into the same substrate to form a module.

Further, it is also used for various industrial devices that require forward and reverse rotations using a DC motor as a drive source, and also for DC loads that require positive and negative rotations. In these cases, a control method may be adopted in which the chopper operation is omitted and the paired power semiconductor elements remain in the ON state.

[0010]

In the conventional semiconductor bridge main circuit, when a failure occurs in a semiconductor element, the failure may spread to other semiconductor elements and peripheral circuits.

For example, in the configuration of FIG. 3, when the power transistor Y has a conduction failure, the power transistors V and Y are short-circuited when the power transistors V and X are turned on, and the power transistor V is also damaged. Further, the fuse 5 is blown and the contactor 6 is burnt out.

Further, when the power transistor Y has a conduction failure, the power transistor U is ON-controlled,
When the power transistor Y is chopper-controlled, the DC voltage of the DC motor 2 is reduced by the conduction failure of the power transistor Y.
Is applied to the electric motor 2, and a large current flows through the electric motor 2, resulting in sudden acceleration, sudden steering wheel operation, or steering wheel operation failure, which may cause an accident or mechanical failure.

In order to solve these problems, in order to protect the semiconductor element from a short-circuit failure, a method may be considered in which the power is cut off when an overcurrent of the element or the input / output terminal of the main circuit is detected. It requires complicated and expensive protective devices such as high speed circuit breaker.

Further, the protection by overcurrent detection is subject to the condition that the device is in operation, and there is a risk of causing an accident due to a delay in response of the protection operation.

An object of the present invention is to provide a failure detecting device capable of detecting a conduction failure of a main circuit element by adding a few circuits.

Another object of the present invention is to provide a failure detecting apparatus capable of detecting a conduction failure of a main circuit element when the operation of the apparatus is stopped.

[0017]

In order to solve the above-mentioned problems, the present invention has a bridge connection structure of power semiconductor elements, a DC power source is applied between input terminals, and the ON / OFF control of the elements is performed. In a semiconductor bridge main circuit that inverts the DC polarity of an output terminal to positive and negative and supplies it to a DC load, a voltage detection circuit that applies a DC voltage between the input terminals to detect a voltage between the input terminals, and the semiconductor bridge. When the upper arm of the main circuit is on-controlled or the lower arm is on-controlled and the detection voltage of the voltage detection circuit is lower than a set voltage, it is determined that the power semiconductor element has a conduction failure and protection processing is performed. It is characterized by comprising processing means for performing.

[0018]

When the upper arm of the semiconductor bridge main circuit is on-controlled, when the lower arm has a conduction failure, the voltage between the input terminals becomes low, so that the determination of the conduction failure of the lower arm can be obtained. On the contrary, when the lower arm is on-controlled, the voltage between the input terminals becomes low when the upper arm has a conduction failure, so that the determination of the conduction failure of the upper arm can be obtained.

These failure determinations are obtained in the operation stop state of the device having the semiconductor bridge main circuit.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of the present invention, and the same components as those in FIG. 3 are designated by the same reference numerals.

The voltage detection circuit 11 applies a power supply voltage between the power supply input terminals of the semiconductor bridge main circuit 1 and detects the voltage between the power supply input terminals of the semiconductor bridge main circuit 1 in response to this voltage application.

This voltage is applied by bypassing the power steering switch 6 and the fuse 5 and from the battery 3 through the key switch 4 by the resistor 11 ₁ . Further, voltage detection is performed by connecting the resistor 11 ₁ and the power input terminal of the semiconductor bridge main circuit 1 to the series connection circuit of the voltage dividing resistors 11 ₂ and 11 ₃ between the power input terminals of the semiconductor bridge main circuit 1. Is taken out as the divided voltage of the voltage dividing resistors 11 ₂ and 11 ₃ . Zener diode 11 ₄ limits the detection voltage becomes excessive. The capacitor 11 _5, to prevent the detection voltage varies pulsation and noise.

The A / D converter 12 converts the voltage detected by the voltage detection circuit 11 into a digital value and supplies it to the control circuit 7 having a microcomputer as detection data. The A / D converter 12 can use an existing one for the control circuit 7 to take in steering operation angle data and accelerator depression amount data for controlling the electric vehicle.

Further, the voltage detection circuit 11 detects the voltage between the power supply input terminals of the semiconductor bridge main circuit 1, and this detection detects whether or not the voltage exceeds a set level as will be described later. Instead of the / D converter 12, it may be replaced with a comparator, and this comparator may detect in advance whether or not the level exceeds a set level.

The control circuit 7 contains programs and data for various controls of the electric vehicle, and as one of them, software for detecting a failure of the semiconductor bridge main circuit is provided.

Further, the control circuit 7 takes in the detected voltage data of the voltage detection circuit 11 which has passed through the A / D converter 12 by the parallel input / output device 7 ₁ , and further outputs a failure display output to the display 13 as a failure display means. To occur. Further, the semiconductor bridge main circuit 1 is provided with an interface 7 ₂ and a drive circuit 7 ₃ for gate control of each power transistor.

FIG. 2 shows a processing flow of the failure detection software provided in the control circuit 7, and this processing will be described below.

First, when the key switch 4 of the electric car is turned on, all of the power transistors U, V, X and Y that are the initial settings for various controls of the electric car and the upper and lower arms of the semiconductor bridge main circuit 1 are turned off. Initialization for controlling the state is performed (S1).

Next, the voltage V _PN between the input terminals detected by the voltage detection circuit 11 is _fetched and it is determined whether or not the voltage is equal to or higher than the set voltage V _C (S2). If V _PN ≧ V _C in this judgment, the voltage V _PN between the input terminals is too low (despite all the power transistors U, V, X, Y of the semiconductor bridge main circuit 1 being in the OFF control state). Failure display processing is performed as a possibility of continuity failure).

This process is performed by turning off the upper and lower arms (S
3), the protection output (S4), and the failure display (S5) by the display unit 13. Of these, the protection output (S4) controls the opening of the protection relay 14 that prohibits the power supply connection to the semiconductor bridge main circuit 1 by turning on the power steering switch 6.

When it is determined in the determination process S2 that V _PN ≧ V _C , the upper arm (power transistor U,
V) is on-controlled (S6), and in this state, the voltage detection circuit 1
The detected voltage V _PN from 1 is fetched again and it is determined whether or not it is equal to or higher than the set voltage V _C (S7).

At this time, if a conduction failure occurs in the lower arm (power transistors X, Y), the voltage of the semiconductor bridge main circuit (detection voltage V
_PN ) becomes a very low value compared to the set voltage, and it is possible to detect the conduction failure of one or both of the lower arms. When this continuity failure is determined, failure processing (S3 to S5) is performed.

When it is determined in the determination process S7 that V _PN ≧ V _C , the initial state for controlling the upper arm to be turned off is returned (S8), and the lower arm is controlled to be turned on (S9). The detection voltage V _PN from the voltage detection circuit 11 is fetched again and it is determined whether or not it is equal to or higher than the set voltage V _C (S1).
0).

At this time, if a conduction failure occurs in the upper arm, the voltage (detection voltage V _PN ) of the semiconductor bridge main circuit becomes extremely lower than the set voltage due to the ON state of the lower arm. A conduction fault on one or both arms can be detected. Even when the determination of the conduction failure is made, the failure processing (S3 to S5) is performed.

When it is determined in the determination process S10 that V _PN ≧ V _C , it means that there is no conduction failure in the upper and lower arms, and the lower arm is returned to the initial state of OFF control ( S11), the operation is started by turning on the power steering switch 6 (S12).

Since the failure determination is performed in the operation stop state of the apparatus, the determination in the process S2 may be omitted depending on the applied apparatus. Further, the design of the protection process and the failure display process is appropriately changed.

Also, in the case where hardware dedicated to failure detection is provided in place of software for failure detection using a control circuit, simple hardware called a logic circuit configuration having an ON / OFF control procedure for a comparator and elements It's done.

[0038]

As described above, according to the present invention, in detecting the failure of the semiconductor bridge main circuit, the voltage between the input terminals is detected and the voltage when the upper arm is ON-controlled or the lower arm is ON-controlled. Since it is possible to determine whether or not there is a conduction failure in the power semiconductor device from the detection voltage of the detection circuit, it is possible to add a simple voltage detection circuit and a simple failure detection software or hardware to the control circuit. There is an effect that judgment and protection processing can be easily performed.

In particular, the failure determination can be made when the device having the semiconductor bridge main circuit is in the operation stopped state, and when it is applied to, for example, power steering, there is an effect that safety can be improved by eliminating a steerable steering wheel and an inability to handle.

[Brief description of drawings]

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

FIG. 2 is a processing flow of an embodiment.

FIG. 3 is a drive circuit of a DC motor.

FIG. 4 is an example of the gate waveform of FIG.

[Explanation of symbols]

 1 ... Semiconductor bridge main circuit 2 ... DC motor 7 ... Control circuit 11 ... Voltage detection circuit 12 ... A / D converter 13 ... Failure indicator

Claims (1)

[Claims] 1. A power semiconductor element is connected in a bridge structure, a direct current power source is applied between input terminals, and the on / off control of the element reverses the direct polarity of the output terminal to positive or negative and supplies it to a direct current load. In the semiconductor bridge main circuit, a voltage detection circuit that applies a DC voltage between the input terminals to detect the voltage between the input terminals, and when the upper arm of the semiconductor bridge main circuit is ON-controlled or the lower arm is ON-controlled When the detected voltage of the voltage detection circuit at that time is lower than a set voltage, the semiconductor bridge main circuit is provided with a processing unit that determines that the power semiconductor element has a conduction failure and performs a protection process. Failure detection device.