JPH0629808A - Method for preventing malfunction at application of power for transistor - Google Patents

Abstract

PURPOSE:To avoid thyristor mis-ignition by preventing malfunction in the transient state such as application of control power supply to a thyristor trigger control transistor(TR). CONSTITUTION:A Zener diode ZD having a prescribed Zener voltage VZD is connected in series with a base signal application path of a TR forming an ignition signal of a thyristor through the conduction in the opposite polarity with the prescribed base current conduction direction. Furthermore, an external induced voltage absorption capacitor C having a proper static capacitance is connected between the base of the TR and a control reference potential point. Thus, malfunction in the transient state of application of power is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transient of a thyristor used for short-circuiting an inrush current limiting resistor for a DC intermediate circuit smoothing capacitor of a voltage source inverter device when a control power source is turned on. The present invention relates to a method for preventing malfunctions during operation.

[0002]

2. Description of the Related Art Conventionally, as an ignition circuit for a thyristor as described above, the one exemplified in the circuit diagram of FIG. 3 is known. In FIG. 3, SCR is a thyristor inserted in a DC circuit, PC is a photocoupler, TR is a transistor, R ₁
˜R ₃ is a resistor, V _CC is a control power supply voltage, M is a reference potential for control, V _R3 is a voltage across the resistor R ₃ , that is, a voltage between the base and emitter of the transistor, and V _FB is a voltage of the arithmetic unit CPU. The voltage of the output port, V _FS, is the firing control signal voltage of the thyristor output from the output port of the CPU.

As shown in the figure, the transistor TR is made conductive by the signal voltage V _FS output from the CPU, and the signal voltage is applied to the gate of the thyristor SCR via the photocoupler PC due to the conduction, so that the thyristor SCR becomes conductive. . In addition, at the voltage V _FB , the resistors R ₁ to
The _divided voltage of the voltage V _CC due to R ₃ is superposed as a bias voltage to accelerate the operation of the transistor TR due to the signal voltage V _FS .

That is, as shown in the figure, the conventional thyristor ignition circuit does not particularly take measures to prevent malfunctions due to fluctuations in the control voltage during a transition such as when the power is turned on.

[0005]

If, for example, the thyristor SCR shown in FIG. 3 is used for short-circuiting the inrush current limiting resistor with respect to the DC intermediate circuit smoothing capacitor of the voltage type inverter device, the above-mentioned control is usually performed. The voltage V _CC is obtained as an output voltage of a DC / DC converter having the terminal voltage of the capacitor as an input, and the required conduction time of the thyristor is the time when the terminal voltage of the capacitor increases to a predetermined value. Therefore, it will be later than the charging start time of the capacitor. Between the two time points, the DC / DC converter goes through a transient operating state in which its input voltage is increasing, and its output voltage is irregularly increased irregularly due to the superposition of transient voltage increments. It may make progress.

Therefore, the firing control transistor TR of the thyristor has a value required for the base voltage V _R3 to make the transistor conductive by the irregular increase of the control voltage V _CC or the superposition of some external induction voltage. In the event of an accidental overshoot, an undesired conduction state will occur prior to its predetermined conduction time specified by the application of the signal voltage V _FS , and the accidental conduction of such a transistor will cause the transistor to be inserted into the DC circuit. The thyristor SCR also has a risk of malfunction due to continuous conduction before the predetermined ignition point designated by the signal voltage V _FS .

Incidentally, FIG. 4 is an operation waveform diagram showing a pattern of occurrence of the above-mentioned malfunction in correspondence with FIG.
FIG. 4A shows a variation pattern of the control voltage V _CC on which a transient voltage increment is superimposed before and after time t ₁ , and FIG.
Is the resistance R _{1 of the} control voltage V _{CC that} changes as shown in FIG.
~ R ₃ divided voltage and the thyristor firing signal voltage V
4 shows a variation pattern of the combined voltage V _FB with _FS, and FIG. 4C shows the base voltage V _{R3 of the} transistor TR obtained as a divided voltage by the resistors R ₂ and R _{3 of the} combined voltage V _FB. It is similar to the voltage V _FB and is between time t ₁ and t ₂ and time t.
_{From 3} onward, it shows a variation pattern that exceeds the lowest base voltage V _bM that can make the transistor conductive.

Further, (d) of FIG. 4 shows that the transistor TR becomes conductive (on) between time t ₁ and t ₂ and after time t ₃ due to the change of the base voltage V _R3 as described above. 4, (e) shows that the thyristor SCR receives the conduction state of the transistor and enters the continuous conduction state (on) from the time t ₁ . Here, the conduction state of the thyristor SCR between the times t _{1 and} t ₃ becomes undesired due to the malfunction of the transistor TR at the time t ₁ .

In view of the above, it is an object of the present invention to provide a method of preventing malfunction of the thyristor, which causes the false ignition of the thyristor, during a transition such as power-on for the ignition control transistor.

[0010]

In order to achieve the above object, a method of preventing malfunction of a transistor at power-on according to the present invention is applied to a transistor which forms an ignition signal of a thyristor by its conductive operation at power-on. Of a constant voltage diode having a predetermined Zener voltage is connected in series to the base signal application path of the transistor in the reverse polarity of the predetermined base current conduction direction, and A capacitor having a predetermined electrostatic capacity is connected between the base and a control reference potential point.

[0011]

As described above, an abnormal increase in the base voltage of the thyristor firing control transistor, that is, a transient increase in the control voltage itself or a superimposition of some external induction voltage, etc. The increased voltage causes a false firing of the thyristor.

Therefore, according to the present invention, an added voltage of a predetermined control signal voltage and a control power supply voltage given through a resistor is applied to the base of the transistor through a series connection of a constant voltage diode and a plurality of resistors. , A base voltage of the transistor is formed by using an appropriate resistance-divided voltage of a difference voltage between the added voltage and the zener voltage of the constant voltage diode.
The value of the base voltage is set to be smaller than the minimum value that allows the transistor to conduct even when the control power supply voltage is expected to transiently increase, and is sufficiently larger than the minimum value when the control signal voltage is applied. The zener voltage is selected so that the base voltage can be obtained, and a capacitor for absorbing an external induction voltage to the base is provided in the vicinity of the base of the transistor to prevent the thyristor from false firing. It is intended to prevent it.

[0013]

1 is a circuit diagram of FIG. 1 and FIG.
2 will be described with reference to the operation waveform diagram of FIG. In FIG. 1, constituent elements having the same functions as those in the embodiment of the prior art shown in FIG. 3 are designated by the same reference numerals. In the circuit diagram of FIG. 3, a constant voltage diode ZD whose Zener voltage is V _ZD is connected in series between resistors R ₂ and R ₃ forming a base signal application path to the transistor TR in the polarity shown. A capacitor C for absorbing an external induced voltage is connected in parallel with the resistor R ₃ in addition to the connection.

With the circuit configuration shown in FIG. 1, the base voltage V _R3 of the transistor TR is held at the reference potential M when the CPU output port voltage V _FB is equal to or lower than the Zener voltage V _ZD , and both voltages are V _FB. If there is a relation of> V _ZD, the value is in accordance with the following equation (1). V _R3 = (V _FB −V _ZD ) R ₃ / (R ₂ + R ₃ ) ... (1) The Zener voltage V _ZD is the predetermined thyristor firing control signal voltage V _FS output from the CPU output port. _Done and V _FB =
When V _FS is reached, the base voltage V _R3 is selected to be a value that can make the transistor TR sufficiently conductive.

Next, in the operation waveform diagram of FIG. 2, (a) of FIG. 2 shows a variation pattern of the control voltage V _CC , which is the same as (a) of FIG. 2B shows a variation pattern of the voltage V _FB , which is approximately V _FB = V _CC until both the voltages V _CC and V _ZD become V _CC = V _ZD.
The value changes according to the following equation (2) from the time when V _CC > V _ZD to the time t ₃ .

V _FB = V _ZD + (V _CC −V _ZD ) (R ₂ + R ₃ ) / (R ₁ + R ₂ + R ₃ ) ... (2) Further, the voltage V _R3 shown in FIG. V _CC =
Until such time as the V _ZD is zero (reference potential M), and the up said time point after time t ₃ becomes smaller than the base voltage V _bM of a required minimum the such of a value according to formula (1) above. Therefore, in (d) and (e) of FIG. 2 showing the conduction patterns of the transistor TR and the thyristor SCR, the corresponding times t _{1 to} t as shown in (d) and (e) of FIG. _Both the conduction state of the transistor TR during the period ₂ and the erroneous conduction state of the thyristor SCR between the times t ₁ and t ₃ disappear.

That is, the malfunction of the transistor TR and the thyristor SCR due to the transient increase of the control voltage V _CC as described above when the power is turned on is avoided.

[0018]

According to the present invention, a constant voltage diode having a predetermined Zener voltage is connected to a transistor forming a firing signal of a thyristor by its conduction operation in series with a predetermined base in a base signal application path of the transistor. At the time of power-on, etc., by connecting a capacitor having an appropriate electrostatic capacity between the base of the transistor and the reference potential point for control, which is connected in the opposite polarity to the direction of current flow It is possible to easily and inexpensively prevent the malfunction of the transistor at the time of the transient state or against some external induced voltage such as noise, and improve the reliability of the operation of various devices using the thyris as the circuit component. Can be planned.

[Brief description of drawings]

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

FIG. 2 is an operation waveform diagram of various components of the circuit shown in FIG.

FIG. 3 is a circuit diagram of a thyristor firing circuit showing an embodiment of the prior art.

FIG. 4 is an operation waveform diagram of various components of the circuit shown in FIG.

[Explanation of symbols]

C External inductive voltage absorption capacitor CPU CPU PC photocoupler R resistance (R ₁ , R ₂ , R ₃ ) SCR thyristor TR transistor ZD constant voltage diode

Claims (1)

[Claims] 1. A method for preventing a malfunction of a transistor, which forms an ignition signal of a thyristor by the conduction operation thereof at power-on, in which a constant voltage diode having a predetermined Zener voltage is connected in series to a base signal application path of the transistor. When the power supply of the transistor is turned on, a capacitor having a predetermined electrostatic capacity is connected between the base of the transistor and a reference potential point for control, in addition to connecting the base current in the opposite polarity direction. Malfunction prevention method.