JP2005278370A - Transistor control method and control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transistor control method and a control device excellent in usability by extending a current control range. <P>SOLUTION: A 31m long wiring and a 51m long wiring are provided for a pulse transformer 51a. An offset voltage in a reverse direction to an output voltage of the 31m long wiring is produced from the 51m wiring using a rectification circuit 52 and a Zener diode 54. When a transistor Tr21a is turned on, the offset voltage is applied to the output voltage of the 31m long wiring, and the output voltage offset to a minus side is applied to between a gate terminal g1 and a source terminal s1 of the transistor Tr21a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transistor control method and a control circuit for controlling conduction between a source terminal and a drain terminal by applying an output voltage of a pulse transformer between a source terminal and a gate terminal.

  For example, in an inverter-controlled DC arc welding power source, in order to improve welding quality, an output voltage value detection means is provided, and an inverter circuit is provided so that the output voltage value supplied to the welded part approaches a preset value. I have control.

  FIG. 3 is a connection diagram of a conventional inverter-controlled DC arc welder.

  The AC voltage supplied from the commercial power source 1 is rectified to a DC voltage by the rectifier circuit 2, converted to a high-frequency AC voltage by the inverter circuit 3, and converted to a voltage suitable for welding by the transformer 4.

  The AC voltage output from the transformer 4 is rectified to DC again by the rectifier circuit 5. The output current (welding current) is smoothed by the reactor 6 and supplied to the external output terminals 7 and 8.

  The + side external output terminal 7 is connected to the welding wire 10 via the tip 9. The negative side external output terminal 8 is connected to the base material 11. The welding wire 10 is fed by a pair of rollers 12.

  The voltage detection circuit 13 connected between the external output terminals 7 and 8 outputs the welding voltage Va to the control circuit 14.

  The control circuit 14 controls the inverter circuit 3 via the PWM control device 20 so that the welding voltage Va becomes the voltage set by the setting device 15.

  Next, the inverter circuit 3 will be described.

  FIG. 4 is a connection diagram of the inverter circuit 3, and FIG. 5 is a connection diagram of the transistor control circuit in the inverter circuit 3.

  As shown in FIG. 4, the inverter circuit 3 includes four transistors (power transistors; hereinafter referred to as “Tr”) 21a to 21d, and four transistor control circuits 30a to 30d surrounded by dotted lines in the figure. It is composed of

  The drain terminal d1 of Tr21a is connected to the + side of the rectifier circuit 2, the source terminal s1 is connected to the drain terminal d2 of Tr21b and the terminal 4a of the transformer 4, and the source terminal s2 of Tr21b is connected to the-side of the rectifier circuit 2. .

  The drain terminal d3 of Tr21c is connected to the + side of the rectifier circuit 2, the source terminal s3 is connected to the drain terminal d4 of Tr21d and the terminal 4b of the transformer 4, and the source terminal s4 of Tr21d is connected to the-side of the rectifier circuit 2. .

  As shown in FIG. 5, one of the output side windings 31m of the pulse transformer 31a constituting the transistor control circuit 30a is connected to the gate terminal g1 of the Tr 21a via the resistor 32a, and the other is connected to the source terminal s1 of the Tr 21a. . A resistor 33a and a capacitor 34a are connected in parallel between the source terminal s1 and the gate terminal g1.

  The configuration of the transistor control circuits 30b to 30d is the same as that of the transistor control circuit 30a, and is connected to the Tr 21b to 21d, respectively.

  As shown in FIG. 4, the input sides of the pulse transformer 31a and the pulse transformer 31d are connected to the first output terminal 20a of the PWM controller 20 with the same polarity, and the input sides of the pulse transformer 31b and the pulse transformer 31c are The polarity is matched and connected to the second output terminal 20b of the PWM controller 20.

  FIG. 6 is a time chart showing the output voltages output from the terminals 20a and 20b of the PWM control device 20, the voltage Vsg between the gate terminals and the source terminals of the Trs 21a to 21d, and the output voltage of the transformer 4.

  As shown in the figure, when a positive voltage is supplied from the terminals 20a and 20b, the inter-terminal voltage Vsg becomes a positive voltage, the transistor becomes conductive (ON), and current is supplied to the welded portion. The In this case, if the output period T of the voltage output from the PWM control device 20 is lengthened, the welding voltage is increased (the welding current is increased), and if it is shortened, the welding voltage is decreased (the welding current is decreased).

  Therefore, the PWM control device 20 controls the output period T so that the welding voltage becomes a value set by the setting device 15. An alternating current of about 20 kHz is output from the transformer 4 and electric power is supplied to an arc load formed between the welding wire 10 and the base material 11.

  As described above, when the transistor control circuits 30a to 30d using the pulse transformer are used for the on / off control of the Trs 21a to 21d, the configuration can be simplified.

  By the way, the wider the control range of the welding current, the more various workpieces can be machined and the usability is improved.

  However, when the transistor is controlled by a transistor control circuit using a pulse transformer, the welding voltage (that is, the welding current) cannot be reduced. Hereinafter, the reason will be described.

  FIG. 7 is a diagram showing the relationship between the output voltage of the PWM controller 20 and the inter-terminal voltage Vsg, where (a) shows a case where the voltage output period T (on period) is sufficiently long, and (b) shows an on period. The cases where are short are shown respectively. The upper stage is the output voltage of the PWM controller 20, and the lower stage is the inter-terminal voltage Vsg.

  As can be seen from the figure, when the on period is sufficiently long, the voltage Vsg in the off period is negative.

  On the other hand, when the on period is short, a period in which the voltage Vsg in the off period is positive occurs. When the voltage Vsg becomes positive, for example, the Tr 21a becomes conductive during the ON period of the Tr 21b, so that both ends of the rectifier circuit 2 are short-circuited, and Tr 21a and Tr 21b are damaged by the short-circuit current.

  Therefore, conventionally, the minimum value of the output period T is set to a value at which the voltage Vsg in the off period does not become positive. For this reason, the minimum control range of the current is about 20% of the rating.

  An object of the present invention is to provide a transistor control method and a control device that expands a current control range and is excellent in usability.

  The reason why the off-period voltage becomes positive in the transistor control circuit using the pulse transformer is that energy stored in the iron core of the pulse transformer is released in the off-period. In order to solve the above problems, the first means of the present invention is a transistor control that controls conduction between the source terminal and the drain terminal by applying an output voltage of the pulse transformer between the source terminal and the gate terminal. In the method, a negative offset voltage is added to the output voltage.

  According to a second means of the present invention, an output voltage of a pulse transformer is applied between the source terminal and the gate terminal of a transistor comprising a source terminal, a drain terminal, and a gate terminal. In the transistor control circuit for controlling conduction between the drain terminals, offset voltage adding means for offsetting the output voltage to the minus side is provided, and conduction between the source terminal and the drain terminal by the output voltage offset to the minus side is provided. It is characterized by controlling.

  According to the present invention, since it is configured as described above, the current control range is widened and the usability is improved.

  FIG. 1 is a connection diagram of a transistor control circuit according to the present invention, and the same or the same functions as those in FIGS. The connection diagram of the inverter circuit 3 is obtained by replacing the transistor control circuits 30a to 30d in FIG.

  The transistor control circuit 50a is a transistor control circuit that controls the Tr 21a. In addition to the first winding 31m, a second winding 51m is provided on the output side of the pulse transformer 51a. One end of the winding 51m is connected to one of the AC terminals of the rectifier circuit 52, and the other end is connected to the other of the AC terminals of the rectifier circuit 52. The + side output terminal 52a of the rectifier circuit 52 is connected to the source terminal s1 of the Tr 21a via the resistor 53, and the − side output terminal 52b is connected to the gate terminal g1 of the Tr 21a via the winding 31m and the resistor 32a.

  A Zener diode 54 and a capacitor 55 are connected in parallel between the output terminal 52b and the source terminal s1. The voltage clamped by the Zener diode 54 is about 1 to 2 volts.

  In addition, transistor control circuits 50b to 50d that are not shown in detail control Tr21b to Tr21d, respectively.

  Next, the operation of this circuit will be described.

  FIG. 2 shows the output voltage output from the terminal 20a of the PWM controller 20 and the voltage Vsg between the gate terminal g1 (g4) and the source terminal s1 (s4) of the Tr21a (Tr21d) when the output period T is short. It is a time chart which shows.

  As shown in the figure, the voltage output from the winding 51m is offset to the minus side by the rated voltage Vz of the Zener diode 54.

  As a result, after the voltage output period T elapses and until the next output period T starts, the inter-terminal voltage Vsg is maintained negative, and Tr21a (Tr21d) does not become conductive.

  Therefore, the ON period can be shortened, and for example, the minimum control range of the welding current can be expanded to about 10% of the rating.

  In this embodiment, since the offset voltage is generated from the second winding provided in the pulse transformer, it is not necessary to provide a special drive source, and the apparatus configuration is simplified.

  For example, a battery can be used instead of the offset circuit.

  The present invention can be applied not only to the inverter type DC welding machine but also to other devices.

  Thus, when the present invention is applied to, for example, a welding machine, usability is improved.

It is a connection diagram of a transistor control circuit according to the present invention. It is operation | movement explanatory drawing of this invention. It is a connection diagram of a conventional inverter-controlled DC arc welding machine. It is a connection diagram of a conventional inverter circuit. It is a connection diagram of a conventional transistor control circuit. It is operation | movement explanatory drawing of a prior art. It is operation | movement explanatory drawing of a prior art.

Explanation of symbols

21a transistor 31m winding 51a pulse transformer 51m winding 52 rectifier circuit 53 Zener diode g1 gate terminal s1 source terminal

Claims (3)

In a transistor control method for controlling conduction between the source terminal and the drain terminal by applying an output voltage of a pulse transformer between the source terminal and the gate terminal,
A transistor control method comprising adding a negative offset voltage to the output voltage. Transistor control for controlling conduction between the source terminal and the drain terminal by applying an output voltage of a pulse transformer between the source terminal and the gate terminal of a transistor having a source terminal, a drain terminal, and a gate terminal In the circuit
A transistor control circuit comprising offset voltage adding means for offsetting the output voltage to the minus side, and controlling conduction between the source terminal and the drain terminal by the output voltage offset to the minus side. 3. The transistor control circuit according to claim 2, wherein the offset voltage adding means is generated from an output voltage of a second winding arranged on the output side of the pulse transformer.

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