JPH1015670A - Method for compensating capacitor capacity in capacity type welding power source, and circuit therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the variation of capacity of a capacitor due to temp. etc., by turning off charging current of the capacitor when the actual measured value becomes a reference voltage of the therely measuring the voltage of the capacitor. SOLUTION: A reference energy Er stored in the capacitor 52 from a reference capacity Cr and the reference voltage Vr of the capacitor 52 is calculated by a CPU. The actual measured capacity value Ct of the capacitor 52 is calculated at each charging of the capacitor 52 from a voltage ΔVt obtained by integrating the voltage of the capacitor 52 for an arbitrary time Δt and a constant current I from a fixed current source 2. A correction coefficient of the capacitor is calculation from this actual measured capacity Ct and the reference energy Er is calculated and the reference voltage Vr corresponding to the reference energy Er is calculated. The actual measured voltage Vt is calculated from the correction coefficient and the reference voltage Vr, and it is judged that this actual measured voltage value V is equal to the reference voltage Vr of the capacitor. Then, at this time, the variations of the voltage and the capacity can be removed by turning off the charging to the capacitor 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor compensation method for compensating for a change in the capacitance of a capacitor for supplying a welding current in a capacitor-type welding power source, and a capacitance compensation circuit therefor.

[0002]

2. Description of the Related Art Conventionally, in a capacitor type welding power source,
As shown in FIG. 3, after the current from the AC 100 V power supply 50 is full-wave rectified by the full-wave rectifier circuit 51, the rectified current is charged to the capacitor 52 connected in series to the full-wave rectifier circuit 51. . The discharge current from the capacitor 52 is supplied to the work 54 via the external transformer 53 as a welding current.

[0003] The voltage across the capacitor 52 is
When the reference voltage set on the panel is reached, as shown in FIG. 4, a delay signal according to each timing signal from the timing generator 55 based on an ACT signal (Actuator Signal) for discharging the capacitor 52. As a result, a gate signal (discharge signal) of the SCR 56 is generated with a certain delay from the ACT signal, the capacitor 52 is discharged, a current flows to the primary side of the external transformer 53, and as a result, the welding current flows to the secondary side. Is configured to occur. Next, the switch circuit 57 operates to generate a reset signal, and the SCR 56 is extinguished.

The HOFF1 signal is a timing signal for inhibiting the capacitor 52 from being charged while the welding current is being supplied to the work, and is an integration circuit 59 of the addition amplification circuit 58 having a long time constant. Capacitor 5
The generation of the second voltage control voltage CV is suppressed. HOFF
The two signals are timing signals from the integrating circuit 59, and integrate the panel information and the voltage control voltage CV obtained from the feedback voltage of the capacitor 52 added by the amplifier circuit 60 and the extracted component of the error component. The time constant of the integrating circuit 59 and the HOFF2 signal determine the charging speed of the capacitor 52.

The output voltage of a D / A converter 61 for converting panel setting information into a digital signal and the output of an amplifier circuit 62 for detecting and amplifying a feedback gain are input to a summing amplifier 58, and the output voltage of the capacitor 52 is output. Is input to the triac gate pulse generator 63 and input to the triac as a charging voltage control signal, whereby the charging voltage of the capacitor 52 is controlled.

The voltage of the capacitor 52 is supplied to a feedback gain circuit 67.
When the setting condition is switched by comparing with the set value on the panel side, the amplifier circuit 68 compares the reference voltage detected by the resistor R69 with the voltage from the amplifier circuit 60,
FET 70 that operates as a switch based on the result
Is controlled.

With this configuration, the voltage of the capacitor 52 is compared with the set value on the panel side by the feedback gain circuit 67, and the feedback voltage is amplified by the amplifier circuit 71 to control the voltage. The generator 63 generates a gate pulse signal to turn off the AC 100 V power supply 50 and cut off the charging current to the capacitor 52.

[0008]

As described above, the charging voltage of the capacitor 52 is controlled so that the capacitor 52 is charged with a constant voltage. However, the capacitance of the capacitor 52 varies from 20 to 30%, and sometimes as much as 50%, due to differences in capacitance due to variations among individual components, temperature changes in the use environment, temperature fluctuations of the capacitor itself, and the like. Therefore, there is a problem that the energy charged in the capacitor 52 fluctuates, and the device as a welding power source varies, and the welding quality also varies.

[0009]

According to a first aspect of the present invention, there is provided a capacitor type welding power supply having a capacitor for rectifying a current from an AC power supply and charging the rectified current to supply a welding current to a work. In the capacity compensation method, the reference capacity Cr and the reference voltage Vr of the capacitor are input to the CPU as initial conditions to determine the reference energy Er stored in the capacitor, and the reference energy Er and the reference voltage Vr are one-to-one. The voltage is displayed on the panel and the capacitor is charged with the constant current I from the constant current source, and the measured voltage ΔVt at the time when the capacitor voltage is at the arbitrary time ΔT is determined. The actual measured value capacity Ct for each charge of the capacitor is obtained from the current I and the actual measured value energy E at this time.
t, a correction coefficient (Cr / Ct) ^1/2 of the capacitor is obtained from the reference energy Er, the measured energy Et and the measured capacitance Ct displayed on the panel, and a reference voltage corresponding to the reference energy Er displayed on the panel. An actual measurement voltage Vt is obtained from Vr and a correction coefficient (Cr / Ct) ^1/2 . When the actual measurement voltage Vt becomes the reference voltage Vr of the capacitor, the charging current to the capacitor is turned off. It is.

According to a second aspect of the present invention, the panel includes a reference voltage Vr
, The reference energy Er and the reference current Ir are displayed in a one-to-one correspondence, and the capacitor is directly charged by the rectified current instead of the constant current from the constant current source, and the constant current I
Instead of the measured voltage ΔVt, the arbitrary time ΔT, and this Δ
From the current 容量 IdT at the time T, an actually measured value capacity Ct at each time of charging of the capacitor is obtained, an actually measured value energy Et at this time is obtained, and a reference current Ir corresponding to the reference energy Er displayed on the panel and a correction coefficient (Cr / Ct)
^The actual measured value current It is obtained from ^1/2 and the actual measured value current It is obtained.
Is turned off when the reference current Ir of the capacitor is reached.

A third invention is a capacitor compensating circuit in a capacitor type welding power supply having a capacitor for rectifying a current from an AC power supply and charging the rectified current to supply a welding current. A constant current source for supplying the current I and a reference capacitance Cr of the capacitor
And a reference voltage Vr to calculate a reference energy Er stored in the capacitor, and charge the capacitor for an arbitrary time ΔT, and charge the capacitor from the voltage ΔVt obtained by integrating the ΔT time and the current ∫IdT each time. A calculation function for calculating the measured capacitance Ct of the capacitor, a calculation function for calculating a correction coefficient (Cr / Ct) ^1/2 of the capacitor from the measured capacitance Ct and the reference energy Er, and a function corresponding to the reference energy Er. An arithmetic function for calculating the reference voltage Vr, an arithmetic function for calculating the actually measured voltage Vt from the correction coefficient (Cr / Ct) ^1/2 and the reference voltage Vr, and the actually measured voltage Vt is equal to the reference voltage Vr of the capacitor CPU having a judgment function for judging that
and a panel for displaying the r and the reference voltage Vr in one-to-one correspondence, and means for turning off the constant current from the constant current source when the actually measured voltage Vt becomes equal to the reference voltage Vr to the capacitor. This is provided with a capacitance compensating circuit.

According to a fourth aspect of the present invention, the constant current source is removed, and the capacitor is directly charged by the rectified current.
Instead of the current ∫IdT integrated over the ΔT time and the voltage ΔVt integrated over the ΔT time, the measured capacitance C
t, an arithmetic function for calculating the reference current Ir instead of the reference voltage Vr corresponding to the reference energy Er, a correction coefficient (Cr / Ct) ^1/2 and the reference current Ir instead of the reference voltage Vr. And a judgment function for judging that the actually measured current It is equal to the reference current Ir of the capacitor.
r, the reference energy Er and the reference current Ir are displayed in one-to-one correspondence, and when the measured current It becomes equal to the reference current Ir of the capacitor instead of the measured voltage Vt, the constant current source is displayed. And a means for turning off a rectified current instead of a constant current from the power supply.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 An embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is a block diagram showing an embodiment of the present invention. The same components as those in the conventional example are denoted by the same names and the same reference numerals, and description thereof is omitted.

In FIG. 1, 50 is an AC power supply, 1 is a smoothing circuit, 2 is a constant current source, and 52 is a capacitor for charging a welding current. Reference numeral 3 denotes a dummy resistor, which forms a discharge circuit when the capacitor 52 is overcharged. 4 is a CPU,
An arithmetic function for calculating the reference energy Er stored in the capacitor 52 from the reference capacitance Cr and the reference voltage Vr of the capacitor 52, a voltage ΔVt obtained by integrating the voltage of the capacitor 52 for an arbitrary time ΔT, and a constant current I from the constant current source 2 And a calculation function for calculating the measured capacitance Ct of the capacitor 52 each time the capacitor 52 is charged,
A calculation function for calculating a correction coefficient of the capacitor from the reference energy Er, a calculation function for calculating a reference voltage Vr corresponding to the reference energy Er, a correction coefficient and the reference voltage V
r and a function of determining that the measured voltage Vt is equal to the reference voltage Vr of the capacitor, and controls each unit.

Reference numeral 5 denotes a clock oscillator for generating a CPU clock, and reference numeral 6 denotes an A / D converter, which measures the voltage of the capacitor 52, amplifies it with an amplifier circuit 7, and converts it to a digital signal. 8 is an I / O port, 9 is a panel, 10 is A
An amplifier circuit for amplifying the CT signal, 11 is a switch circuit,
The charging current to the capacitor 52 is turned on and off.
It may be driven directly by the PU 4 or driven via a drive circuit (not shown).

With this configuration, after the current from the AC power supply 50 is full-wave rectified by the full-wave rectifier circuit 51,
This rectified current is smoothed by the smoothing circuit 1 and further converted to a constant current I in the constant current source 2, and the capacitor 52 is charged by the constant current I. The charge voltage of the capacitor 52 is detected, amplified by the amplifier circuit 7, converted into a digital signal by the A / D converter 6, and stored in the CPU 4.

Here, in general, assuming that the charge Q stored in the capacitor 52 and the capacitance C of the capacitor 52, Q = CV (1) Then, the charge charged during the dT time with the constant current i is ∫dQ = ∫idt, so that Q = it...
(2) Here, i is a constant.

On the other hand, the energy E stored in the capacitor is expressed as follows: E = (１ ／) CV ² (3) As is apparent from the equation (3), the voltage V
Is constant, the energy E changes when the capacitance C of the capacitor fluctuates.

Therefore, in equation (3), the capacitor 5
If the measured value capacity Ct of 2 is known, the energy E can be calculated. Therefore, when the voltage value ΔV of the capacitor 52 at a certain time ΔT is determined,
Is charged by the constant current I from the constant current source 2, the capacitance C of the capacitor 52 at that time can be obtained as C = (ΔT / ΔV) × I (4) .

Here, the reference capacitance of the capacitor 52 is C
r, the reference voltage Vr, the reference energy Er when the capacitor 52 has the reference capacitance Cr is Er = (1/2) CrV ² ... (5). When the capacitance changes due to variations in parts, the reference energy Et also changes.

Therefore, when the capacitance of the capacitor 52 changes, in order to obtain the same reference energy Et as in the case of the reference capacitance Cr, (1/2) CrVr ² = (1/2) CtVt ^2. When the voltage Vt of the capacitor 52 that satisfies (6) is reached, the constant current I from the constant current source 2 supplied to the capacitor 52 is turned off to stop charging the capacitor 52. (6) can be satisfied.

Accordingly, from equation (6), Vt = (Cr / Ct) ^1/2 Vr (7) holds. (Cr / Ct) ^1/2 in this equation (7)
Is the correction coefficient, the measured capacitance Ct of the capacitor 52 is
When the measured value voltage Vt of the capacitor 52 becomes the reference voltage Vr, if the charging of the capacitor 52 is turned off, the fluctuation of the voltage and the capacitance of the capacitor 52 can be removed.

The capacitor 52 is charged by the constant current I during the time ΔT, and its voltage becomes ΔV. Therefore, the measured capacitance Ct of the capacitor 52 at this time is calculated from the expression (4) by (ΔT /
ΔV) × I. Each time the capacitor 52 is charged, the actually measured capacitance Ct is calculated and obtained by the CPU 4.

The measured capacitance Ct of the capacitor 52
, A correction coefficient represented by (Cr / Ct) ^1/2 is calculated for each charge, and the capacitor 52 calculated by the equation (7) is calculated.
When the actually measured voltage Vt reaches the reference voltage Vr displayed on the panel 9, the switch 1
1 is turned off to cut off the constant current I, which is the charging current.

As the switch 11, a MOSFET is appropriate because of the response speed. Incidentally, by averaging the actually measured capacitance Ct charged in the capacitor 52 every time the charging operation is performed and obtaining a correction coefficient based on the average value, it is possible to eliminate the influence of noise on the AC line.

The panel 9 has a capacitor 5 as an initial value.
2 and the reference energy Er are one-to-one.
When the corrected actual measurement voltage Vt becomes the reference voltage Vr based on the reference voltage Vr, a drive signal from the CPU 4 is input to the switch 11 and cut off. , The charging of the capacitor 52 by the constant current I is stopped.

[0027]

Second Embodiment FIG. 2 shows another embodiment of the present invention. Unlike the first embodiment, the rectifier which is full-wave rectified by the full-wave rectifier 51 without using the constant current source 2 is shown. The current is
It is configured to directly charge the capacitor 52 via the smoothing circuit 1.

Accordingly, the CPU 4 has an arithmetic function for calculating the reference energy Er stored in the capacitor 52 from the reference capacitance Cr and the reference voltage Vr of the capacitor 52, and a voltage ΔVt obtained by integrating the voltage of the capacitor 52 for an arbitrary time ΔT. The rectified current from the wave rectifier circuit 51
Calculation function for calculating the measured capacitance Ct of the capacitor 52 each time the battery is charged, a calculation function for calculating a correction coefficient of the capacitor from the measured capacitance Ct and the reference energy Er, and a reference current corresponding to the reference energy Er. A calculation function for calculating Ir, a calculation function for calculating the measured current It from the correction coefficient and the reference current Ir, and a calculation function for calculating the measured current It
Is determined to be equal to the reference current Ir of the capacitor, and each section is controlled.

Further, the panel 9 displays the reference energy Er and the reference current Ir in one-to-one correspondence, instead of the reference voltage Vr in the first embodiment.

With such a configuration, the first embodiment
Instead of the constant current I, the CPU 4 obtains the measured value capacity Ct for each charging of the capacitor 52 from the measured value voltage ΔVt, the arbitrary time ΔT, and the measured value current に よ り IdT, and calculates the measured value energy Et at this time. calculate.

Since the reference current Ir corresponding to the reference energy Er is displayed on the panel 9 in a one-to-one correspondence, the reference current Ir corresponding to the reference Er displayed on the panel 9 and the correction coefficient (Cr / Ct) ^1/2 , the actual measured current It is calculated as follows.
When the reference current Ir becomes 2, the CPU 4 outputs a signal for turning off the charging current of the capacitor 52, and the switch 11 is turned off.

[0032]

The present invention relates to a method of compensating for a capacitor in a capacitor type welding power supply having a capacitor for rectifying a current from an AC power supply and supplying a welding current to a work by charging the rectified current. As a condition, the reference capacitance Cr and the reference voltage Vr of the capacitor are input to the CPU to determine the reference energy Er stored in the capacitor, and the reference energy Er and the reference voltage Vr are displayed on the panel in one-to-one correspondence. And
The capacitor is charged with the constant current I from the constant current source, and the measured voltage ΔVt is obtained when the voltage of the capacitor is at the arbitrary time ΔT. When the capacitor is charged from the measured voltage ΔVt, the arbitrary time ΔT and the constant current I, The actual measured value capacity Ct is determined for each of the measured values, and the actual measured value energy Et at this time is determined.
From the measured capacitance Ct to the correction coefficient (Cr
/ Ct) ^1/2 is determined, and a reference voltage Vr corresponding to the reference energy Er displayed on the panel and a correction coefficient (Cr / Ct)
^The actual measured voltage Vt is obtained from ^1/2 and the actual measured voltage Vt is obtained.
When the voltage of the capacitor becomes the reference voltage Vr, the charging current of the capacitor is turned off. By measuring the voltage of the capacitor, the capacitance of the capacitor due to temperature and the like, which could not be controlled conventionally, was measured. Fluctuations can be eliminated.

Further, according to the present invention, the reference voltage V
The reference energy Er and the reference current Ir are set to 1 instead of r.
The capacitor is directly displayed by the rectified current instead of the constant current from the constant current source.
Instead of the measured voltage ΔVt, the arbitrary time ΔT, and this Δ
From the current 容量 IdT at the time T, an actually measured value capacity Ct at each time of charging of the capacitor is obtained, an actually measured value energy Et at this time is obtained, and a reference current Ir corresponding to the reference energy Er displayed on the panel and a correction coefficient (Cr / Ct)
^The actual measured value current It is obtained from ^1/2 and the actual measured value current It is obtained.
When the current reaches the reference current Ir of the capacitor, the charging current to this capacitor is turned off. Therefore, the same effect as described above is obtained, and there is no need to provide a constant current source, so that the cost is reduced accordingly.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a timing chart for explaining an operation state.

[Explanation of symbols]

 50 AC power supply 51 Rectifier circuit 52 Capacitor 2 Constant current source 4 CPU 9 Panel 11 Switch

Claims (4)

[Claims] 1. A method for compensating a current from an AC power supply, and supplying a welding current to a work by charging the rectified current and supplying a welding current to a work. Is input to the CPU to determine the reference energy Er stored in the capacitor, and the reference energy Er and the reference voltage Vr are displayed on the panel in one-to-one correspondence. ,
The capacitor is charged with a constant current I from a constant current source, and the voltage of the capacitor is measured at an arbitrary time ΔT.
Vt is obtained, and the actually measured voltage ΔVt and the arbitrary time ΔT
And the constant current I, the actual measured value capacity Ct at each time of charging the capacitor is obtained, the actual measured value energy Et at this time is obtained, and the reference energy Er, the actual measured value energy Et, and the reference energy displayed on the panel are obtained. Correction coefficient (Cr / Ct) of the capacitor from the measured capacitance Ct
^The reference voltage Vr corresponding to the reference energy Er displayed on the panel and the correction coefficient (Cr / C
t) ^1/2 , the measured voltage Vt is obtained, and when the measured voltage Vt becomes the reference voltage Vr of the capacitor,
A method for compensating for the capacitance of a capacitor in a capacitor-type welding power source, comprising turning off a charging current of the capacitor. 2. The panel displays a reference energy Er and a reference current Ir in a one-to-one correspondence instead of the reference voltage Vr, and uses the rectified current instead of the constant current from the constant current source. The capacitor is directly charged, and in place of the constant current I, an actually measured value capacitance Ct for each charge of the capacitor is obtained from the actually measured voltage ΔVt, the arbitrary time ΔT, and the current ΔIdT during the ΔT time, The actual measured value energy Et at this time is obtained, and the actual measured value current It is obtained from the reference current Ir corresponding to the standard energy Er displayed on the panel and the correction coefficient (Cr / Ct) ^1/2. 2. The capacitor according to claim 1, wherein the charging current of the capacitor is turned off when the current It becomes the reference current Ir of the capacitor. Capacitor compensation method. 3. A capacitor compensating circuit in a capacitor type welding power supply having a capacitor for rectifying a current from an AC power supply and charging the rectified current to supply a welding current, wherein a constant current I is supplied to the capacitor. A constant current source to supply power, an arithmetic function for calculating a reference energy Er stored in the capacitor from a reference capacitance Cr and a reference voltage Vr of the capacitor, and charging the capacitor for an arbitrary time ΔT and integrating the Δ time Voltage ΔVt
Calculation function for calculating the measured capacitance Ct of the capacitor each time the capacitor is charged from the current and the current ΔIdT, and the correction coefficient (Cr / Ct) ^{1 of the} capacitor based on the measured capacitance Ct and the reference energy Er. ^{/ 2} , an arithmetic function for calculating a reference voltage Vr corresponding to the reference energy Er, and a correction function (Cr / C
t) a CPU having an arithmetic function for calculating an actual measurement voltage Vt from ^1/2 ) and the reference voltage Vr, and a determining function for judging that the actual measurement voltage Vt is equal to the reference voltage Vr of the capacitor; Reference energy Er and reference voltage V
and a means for displaying a one-to-one correspondence between r and r, and means for turning off the constant current from the constant current source when the actually measured voltage Vt becomes equal to the reference voltage Vr of the capacitor. A capacitance compensation circuit for a capacitor in a capacitor-type welding power supply. 4. The constant current source is removed and the capacitor is directly charged by the rectified current. Instead of the constant current I, the CPU replaces the current ΔIdT integrated by ΔT time and
An arithmetic function for calculating the measured capacitance Ct of the capacitor from the voltage ΔVt obtained by integrating the T time, an arithmetic function for calculating a reference current Ir instead of the reference voltage Vr corresponding to the reference energy Er, An arithmetic function for calculating a reference current Ir instead of the correction coefficient (Cr / Ct) ^1/2 and the reference voltage Vr;
The panel has a judgment function of judging that t is equal to the reference current Ir of the capacitor. The panel has a one-to-one correspondence between the reference energy Er and the reference current Ir instead of the reference voltage Vr. And the measured current It is replaced with the reference current I of the capacitor instead of the measured voltage Vt.
4. The capacitor compensation circuit according to claim 3, further comprising means for turning off the rectified current instead of the constant current from the constant current source when the value becomes equal to r.