JP2003116263A - Gate drive circuit of voltage-driven semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an actual output voltage match a command voltage of an inverter while the oscillation phenomenon of a voltage waveform, in an antiparallel recovery time of a diode connected in parallel with a device such as an IGBT or the like constituting an inverter or the like, is avoided. SOLUTION: A gate drive circuit of an IGBT comprises a filter circuit 18, a one-shot circuit 20, a logic operation circuit 22, etc. If the pulse period width of a gate command signal is shorter than 1/2 of a minimum off-period T, an off-operation is prohibited by the circuit 18 and, if the pulse period width is T/2-T, an off-period is forcibly changed to be T by the circuit 20, and, if the pulse period width is not shorter than T, the operation is continued as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate drive circuit for a voltage drive type semiconductor device such as an IGBT (insulated gate type bipolar transistor).

[0002]

2. Description of the Related Art FIG. 2 shows a main circuit diagram of an inverter using an IGBT. 1 is a DC power supply circuit (in the case of an AC input inverter, it is a rectifier + electrolytic capacitor), 2 is an inverter section composed of an IGBT and a diode for converting DC to AC, 3 and 4 are IGBT drive circuits, 5 Is an IGBT, 6 is a diode connected in anti-parallel to the IGBT, and 7 is a load such as a motor.

FIG. 3 shows details of the drive circuit. This circuit is provided corresponding to each of the IGBT 5a and the diode 6a and the IGBT 5b and the diode 6b, but one circuit will be described below. Reference numeral 8 is a power supply for a drive circuit, 9 and 10 are switch elements for turning on and off the IGBT, respectively.
Reference numerals 1 and 12 denote turn-on and turn-off gate resistors, respectively, which are turned on signal S1 from the host and control unit 13.
Alternatively, it operates by being supplied with the off command signal S2. Also,
The inverting circuit 14 includes an upper arm side IGBT and a lower arm side IGBT.
It is connected to alternately turn on and off T. It should be noted that in reality it is necessary to provide a dead time so that the upper and lower arms do not turn on at the same time, but since it is not directly related here, it was decided to ignore it.

[0004]

FIG. 4 shows an example of the voltage (V _F ) waveform at the time of reverse recovery of the opposing arm diode at the time of IGBT turn-on (time t ₀ ). FIG. 4A shows a case where the diode is on (the IGBT of the opposing arm is off) for a sufficiently long period in a normal case.
(B) shows the case where the period is shortened. That is, when the diode is on for a sufficiently long period, the V _F waveform becomes smooth as shown in FIG. 4A, whereas when the diode is on for a short period, as shown in FIG. 4B. Vibrate violently,
In the worst case, the device is destroyed.

Therefore, conventionally, as shown in FIG. 3, filter circuits 17 and 18 are provided so as not to pass an ON or OFF pulse within a fixed time (T) at which an oscillation phenomenon does not occur, or Japanese Patent Laid-Open No. 2000-023471. Less than,
(Also referred to as a cited document), the minimum value of the off time is set to be a constant time T to deal with the problem. However, in this case, the command voltage value and the actual output voltage value may be different from each other, which causes a problem that accurate control cannot be performed, such as occurrence of uneven rotation at low motor speed. Therefore, an object of the present invention is to avoid the vibration phenomenon and enable accurate control.

[0006]

In order to solve such a problem, according to the invention of claim 1, in a gate drive circuit of a voltage drive type semiconductor element constituting a power converter, a pulse width within a fixed time width is set. A filter circuit that blocks passage of the gate command signal that it has, a one-shot circuit that generates a one-shot pulse signal for a fixed time by using the output signal of this filter circuit as a trigger, and this one-shot pulse signal and the output signal from the filter circuit And a logic operation circuit for performing a logic operation on the logic circuit, and an output signal from the logic operation circuit is used as a gate command signal. In the invention of claim 1, when the minimum time width of the allowable off period of the voltage driven semiconductor element is T, the pulse width of the gate command signal blocked by the filter circuit is T / 2,
The pulse width of the one-shot pulse signal can be T (the invention of claim 2).

[0007]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This is because the setting time of the filter circuit 18 is set to T / 2 (T: a fixed time in which the vibration phenomenon does not occur, or the minimum width of the allowable off period) in comparison with the conventional example shown in FIG.
In addition, the one-shot circuit (one-shot is T) 20 triggered by the rising edge of the output signal S3 of the filter circuit 18, and the logic operation (logical sum) of the output signal S4 and the signal S3. Arithmetic circuit 22
It is configured by adding and. The ON side is basically the same, and the output of the logical operation circuit 22 may be inverted and used instead of the illustrated circuit.

With the above structure, the off operation is not performed by the filter circuit 18 when the off period is short (within T / 2), and by the one-shot circuit 20 when the off period is T / 2 to T. The off period is forcibly set to T, and when the off period is equal to or longer than T, it is output as it is as in the conventional case. Incidentally, in the case of the conventional example of FIG. 3, it is said that when the off period is T or less, it is set to “0”, and in the case of the cited publication, when the off period is T or less, it is set to be “T”. According to the present invention, by dividing the period T into within T / 2 and within T / 2 to T, the command voltage value and the actual inverter output voltage value are made more equal on average as compared with the above. Can be said to be a thing.

[0009]

According to the present invention, the command voltage value and the actual inverter output voltage value can be made equal on average while avoiding the vibration phenomenon due to the short off pulse, and as a result, the motor output voltage value at the time of low motor speed can be made equal. It is possible to obtain the advantage that high-precision motor control can be performed by eliminating the occurrence of uneven rotation.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a general example of an inverter using an IGBT.

FIG. 3 is a circuit diagram showing the gate driver of FIG. 2 in detail.

FIG. 4 is an operation explanatory diagram of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply circuit, 2 ... Inverter circuit, 3, 4 ... Gate drive part, 5 ... IGBT (insulated gate type bipolar transistor), 6 ... Diode, 7 ... Load (motor), 8
... Drive power supply, 9, 10 ... Switch element, 11, 12 ...
Resistors, 13 ... Control unit, 14 ... Inversion circuit, 17, 18 ... Filter circuit, 20 ... One-shot circuit, 22 ... Logical operation circuit.

Claims (2)

[Claims] 1. A gate drive circuit for a voltage-driven semiconductor element that constitutes a power conversion device, wherein a filter circuit that blocks passage of a gate command signal having a pulse width within a fixed time width, and an output signal of this filter circuit are provided. A one-shot circuit that generates a one-shot pulse signal for a certain period of time as a trigger and a logical operation circuit that logically operates the one-shot pulse signal and the output signal from the filter circuit are provided, and the output signal from the logical operation circuit Is a gate command signal, which is a gate drive circuit for a voltage drive type semiconductor device. 2. When the minimum time width of the allowable off period of the voltage-driven semiconductor element is T, the pulse width of the gate command signal blocked by the filter circuit is T / 2, and the pulse of the one-shot pulse signal is The gate drive circuit for a voltage-driven semiconductor device according to claim 1, wherein the width is T.