JPH0335883A - Charging and discharging circuit for capacitor - Google Patents

Abstract

PURPOSE:To improve stability and reproducibility of welding conditions by charging at a value slightly lower than the specified voltage by a main charging circuit to execute phase control charging from an AC power source, superimpos ing the voltage of the difference from an auxiliary charging circuit to execute charging. CONSTITUTION:The set voltage of the main charging circuit 100 is set lower by several ten % than the desired charging voltage of a capacitor 300. The auxiliary charging circuit 210 is then set at the voltage of the difference between the desired charging voltage and the set voltage of the main charging circuit 100. The sum of a current of these two charging circuits charges the capacitor 300. The change in the lapse of time of the charging voltage of the capacitor 300 is controlled so that the sum of the current of the two charging circuits is made to the desired charging voltage. When the inputted voltage rises sudden ly, although the charging voltage rises, the set voltage of the main charging circuit 100 is set lower by several ten % than the desired charging voltage, so it does not exceed the desired charging voltage. At this time, the output voltage of the auxiliary charging circuit 210 drops responsibly quickly and the desired charging voltage of the main charging circuit 100 is maintained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to charging and discharging a capacitor, which charges a large capacitor from a relatively small power source and instantly discharges it to obtain a steep discharge current. Regarding circuits.

[Prior art/problems to be solved by the invention] Devices using this type of capacitor charging/discharging circuit 7 For example, a phase control charging circuit using a thyristor is used in a capacitor storage type welding machine. . An example of this is shown in FIG. 3, where an AC power source I is connected to a primary winding 21 of a transformer 2. The secondary winding 22 is connected to a rectifier circuit consisting of a diode 104. The output of this rectifier circuit is
A capacitor 3°O is charged via a thyristor 105 and a resistor 106. The thyristor 105 is controlled by the phase control pulse generation circuit 120 so that the voltage across the capacitor 300 becomes a predetermined voltage. The other secondary winding 23 of the transformer 2 is connected to the auxiliary power supply 200 and supplied to the one-phase control pulse generation circuit 120. Charging capacitor 300 1
! As shown in FIG. 4, the voltage change over time is phase-controlled so that the average value becomes a desired charging voltage Bo. That is, the thyristor 105 is conductive from 1=mouth to 1=12, and the primary conduction is from t=t3 to [4].

Then, conduction occurs from t=t5 to t6. by the way.

Immediately after conduction at t=t3, when the input voltage suddenly increases as shown by the broken line, the charging voltage increases because the thyristor 105 cannot be turned off midway.

In this way, with only the phase control method using non-self-extinguishing switches such as thyristors, AC
[If the source voltage increases for some reason, there is no way to control overcharging of the capacitor.

[Means to solve the problem]

This invention aims to solve such problems.

Uses a non-self-extinguishing switch element from an AC power supply.

The main charging circuit performs phase control charging and continuous DC current.
We propose a circuit that is composed of both a sub-charging circuit and a sub-charging circuit that responds and charges faster than the main charging circuit.

[Effect]

I- Therefore, the main charging circuit that performs phase control charging from an AC power source charges to a value slightly lower than the predetermined voltage, and the sub-charging circuit charges the battery by superimposing the voltage difference.
It can be charged to the required predetermined voltage, and even if the non-self-extinguishing switch element of the main charging circuit cannot be turned off in the event of excessive input! 1 The charging circuit can be stopped and the output voltage value can be limited.

〔Example〕

The present invention will be explained below based on the drawings. , FIG. 1 is a diagram showing an embodiment of the present invention.

First, the configuration will be explained.The AC power source I is connected to the second primary winding of the transformer 2, and the secondary winding 1m22 is connected to the rectifier circuit of diodes 101 to 104. The 111 power of this rectifier circuit is charged to 91 nden-)+300 via the thyristor 105 and the resistor [06. This charging system is the main charging circuit 1 (IQ). The other secondary winding 23 of the transformer 2 is connected to a bridge rectifier circuit composed of diodes 2 (N to 204). This output is connected to a smoothing capacitor 207ε is connected to the regulator 206 and its output; it is stabilized by the Noden G207.

This output is used as an auxiliary power source 200 for the sub charging circuit 210 and the phase 11 control pulse generating circuit 120.

The main charging circuit 100 includes the following phase control pulse generation circuit 12
The phase is controlled by 0. First, the voltage across capacitor 300 is connected to resistor 161. Variable resistor 162. It is detected by a voltage detection circuit consisting of a resistor 163 and a capacitor 164, and is connected to the inverting input terminal of the operational amplifier 141 via the resistor 142. Here, the capacitor 164 functions to enhance stability and prevent hunting in the feedback system. On the other hand, reference voltage source 150 is connected to the non-inverting input terminal of operational amplifier +41 via resistor 143. This compared and amplified output voltage is passed through a resistor 145 to a transistor +4.
6. It is then divided by resistors 147 and 148 and connected to transistor +25 via resistor 127. Transistor 125 provides a charge il[ to capacitor 124 in response to its base signal. A circuit composed of a capacitor 124, a unijunction transistor 121, a resistor 123, and a pulse transformer +22 is a well-known pulse generating circuit. And from the secondary winding Ia23 of the transformer 2 to the synchronous circuit 1
A signal is connected to the base of transistor 1 through 10 to generate a pulse synchronized with the frequency of AC type 1.

Next, regarding the auxiliary charging circuit 210, the capacitor 30 is connected to the auxiliary power supply 200 using the transistor 211 as a series control element.
Charge 0. Its control is in the form of a well-known series regulated power supply. The voltage detected by resistors 261 and 262 is passed through resistor 243 to the inverting input terminal of operational amplifier 24! , T-connected 7 The reference voltage source +50 is connected to the non-inverting input terminal of the τ operational amplifier 241 via a resistor 242. The output voltage of the comparison amplifier 241 is amplified by a transistor 246 via a resistor 245. There is a P between the base and emitter of the transistor 246.
The emitter and collector of the I4P l-run raster 282 are connected in parallel. A Schmitt trigger circuit 280 is connected to the base of the PNP transistor 282 from the collector of the transistor 146 in the phase control pulse generation circuit 120.
A signal is supplied via the resistor 281. This signal is sent to the sub charging circuit 21 when the main charging circuit +00 is lower than a predetermined value.
Force 0 off.

When the main charging circuit 10 is higher than the predetermined value, the sub charging circuit 21
0 causes the setting value to be maintained independently.

And the Schmitt trigger circuit 280 is the main charging circuit +00
This is effective in giving history characteristics to the above-mentioned signal so as to maintain more stable control coordination between the charging circuit and the sub-charging circuit 210.

The output of transistor 246 is divided by resistors 247 and 248 and connected to transistor 2!2.

Transistor 212 controls current output to transistor 211, which is a series control element, according to its base signal.

Transistor 2!3 and resistor 215 are transistor 2
It acts to limit the drooping of the output current of No. 11.

In this circuit configured in this way, the main charging circuit 10
The set voltage of 0 is the desired charging voltage of the capacitor 300 [!
It is set at EII+, which is several tens of percent lower than 0. The sub-charging circuit 210 is set to a voltage difference between the desired charging Tl1l pressure Eo and the set voltage I'm of the main charging circuit 100.

The sum of the currents of these two charging circuits charges the capacitor 300. Charging capacitor 300T! ! Looking at the change in voltage over time in FIG. 2, it is controlled so that the sum of IItIL of the two charging circuits becomes the desired charging voltage EO. That is,
The main charging circuit 100 conducts from t=tl to 1=12, and the 0th order conducts from t=ta to t4, and then t=
Successively conducts from L5 to t6. By the way, t=t3
If the input voltage suddenly increases as shown by the broken line immediately after conduction, the charge is 111! Although the pressure increases, the main charging circuit 10
The set voltage of 0 is the desired charge 1! The desired charging voltage F is set at l11m, which is several tens of percent lower than the voltage IIO.
i.

not exceed. At this time, the output voltage of the auxiliary charging circuit 210 quickly decreases in response to 100% of the desired charging pressure F,
Keep o.

The output setting voltage Em of the main charging circuit is selected to be lower than the setting voltage Ha of the auxiliary charging circuit, but if this difference is made small,
1s force efficiency becomes higher. However, if H+w is chosen too close to Eo, it will not be possible to cope with sudden fluctuations in the AC input power supply. Therefore, it is necessary to find an appropriate value between the efficiency and the predicted value of the input fluctuation range.

In the embodiment, the rectifier circuit of the main charging circuit is a single-phase full-wave type, but it can also be made into a three-phase type, and can be configured as either a full-wave type or a half-wave type. It is also possible to replace some or all elements of the arms of the rectifier circuit with thyristors. Furthermore, the sub-charging circuit can be controlled not only in series but also in parallel. The main charging circuit can also be configured by providing an AC phase control element such as a triac on the AC side and then rectifying it with a diode.

〔Effect of the invention〕

As explained above, according to the present invention, charging efficiency is maintained high by the main charging circuit using a non-self-extinguishing switching element, and the response speed is continuously controlled at high speed by the sub-charging circuit, which is capable of controlling commercial power frequency. It can be done as quickly as within one period. The response speed is so fast that fluctuations in the capacitor voltage value are not displayed even on a digital voltmeter. Therefore, when the capacitor charging/discharging circuit according to the present invention is used in a welding machine, the stability and reproducibility of welding conditions are improved, and the operator's inconvenience is eliminated.

Since the auxiliary charging circuit requires only 1710 times the power loss of the main charging circuit, it requires only a slight extension of the printed circuit board of the conventional phase control circuit in terms of implementation, making it compact and economical.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows its charging characteristics over time, Fig. 3 shows an example of a conventional charging/discharging circuit, and Fig. 4 shows its charging characteristics over time. shows. ! ...AC power supply, 2...Transformer, Ioo...Main charging circuit 101-104...Diode, 105...
Thyristor. HO...Synchronization circuit 120...Phase control pulse generation circuit 121...Unijunction transistor 150...
... Reference voltage source 200 ... Kamisuke power supply, 206 ... Regulator 21
0... False charging circuit 280... Schmit trigger circuit 300... Capacitor 301... Diode, 302... Transformer, 303
...cysta, 304...-discharge control circuit, 305.
・・Welding electrode

Claims (1)

[Scope of Claims] A main charging circuit that charges a capacitor in phase control from an AC power supply, a sub-charging circuit that charges the capacitor with a DC current energized from the AC power supply, and a switch means that discharges the capacitor. A capacitor charging/discharging circuit comprising: