Welding inverter is an alternative to a conventional welding transformer. Modern semiconductors allow to replace the traditional mains transformer with a
switching power supply, which is much lighter, smaller and allows easy current adjustment via a potentiometer. The advantege is
also that the output current is DC. DC current is less dangerous than AC and prevents arc extinction.
For this inverter i chose topology, which is the most common in welding inverters - forward converter with two switches.
In my article about switchning supplies it is a topology II.D.
Input mains voltage passes through an EMI filter and is smoothed with high capacity capacitors. Since the inrush current of those capacitors would be too high,
there's a softstart circuit. After switching ON, the primary smoothing capacitors are charging via resistors, which are later bypassed
by the contact of a relay. As power switches, IGBT transistors IRG4PC40W are used.
They are driven through a forward gate-drive transformer TR2 and shaping circuits with BC327 PNP transistors.
The control integrated circuit is UC3844. It's similar to UC3842, but it has its pulse-width limited to 50%. Working frequency is 42kHz.
Control circuit is powered by an auxiliary power supply of 17V.
Current feedback, due to high currents, is using a current transformer Tr3. Voltage drop accros the sensing resistor 4R7/2W is approximately proportional to the output current.
Output current can be controlled by potentiometer P1, which determines the threshold of the current feedback. Threshold voltage of the pin 3 of UC3844 (current sensing) is 1V.
Power semiconductors require cooling. Most of the heat is dissipated in output diodes. Upper diode, consisting of 2x DSEI60-06A, must in worst
case handle the average current of 50A and the dissipation of 80W (total of both diodes).
Lower diode STTH200L06TV1 (doube diode package with both internal diodes connected in parallel) must in worst
case handle an average current of 100A and the dissipation of nearly 120W. Maximum total dissipation of the secondary rectifier is 140W. The heatsink must be able to handle it.
To the thermal resistance you must include the junction-case Rth, case-sink Rth and sink-ambient Rth.
DSEI60-06A diodes don't have insulation pads and the cathode is connected to the the heatsink. Output choke L1 is therefore in the negative rail. It
is advantageous because in this configuration, there's no high-frequency voltage on the heatsink.
You can use another type of diodes, for example a parallel combination of a sufficient number of the most accessible diodes,
such as MUR1560 or FES16JT. Note that the maximum average current of the lower diode is twice the current of the upper diode.
Calculation of the power dissipation of the
IGBTs is more complicated because in addition to conductive losses there are also switching losses. Loss of each transistor is up to about 50W.
It is also necessary to cool the reset diodes UG5JT and the mains bridge rectifier. The power dissipation of the reset diodes depends on the construction of Tr1
(inductance, stray inductance), but is much lower than the dissipation of the IGBTs. The rectifier bridge has a power dissipation of up to about 30W.
UG5JT diodes and the rectifying bridge are placed on the same heatsink as the IGBTs. UG5JT diodes
also can be replaced with MUR1560 or FES16JT or other ultrafast diodes.
During construction it is also necessary to decide the maximum loading factor of the welding inverter, and accordingly select size of heatsinks, winding gauges and so on.
It is also good to add a fan.
Switching transformer Tr1 is wound on two ferrite EE cores, each with a central column cross section 16x20mm. The total cross section is therefore
16x40mm, the core must have no air gap. 20 turns primary winding is wound using 14 wires of a 0.5 mm diamater. It would be better to use 20 wires, but they
didn't fit into my core.
Secondary winding has 6 turns of a copper strip (36 x 0.5 mm). Forward gate-drive transformer Tr2 is made with an emphasis on low stray inductance. It is trifillary wound,
using three twisted insulated wires of 0.3 mm diameter, and all the windings have 14 turns. Core is made of material H22, middle column has a diameter of 16mm, with no gaps.
Current sensing transformer Tr3 is made from an EMI suppression choke on a toroidal core. The original winding with 75 turns of 0.4 mm wire works as a secondary.
Primary has just 1 turn. Polarity of all the transformer windings must be kept (see dots in schematic)!
L1 inductor has a ferrite EE core, middle column has cross section 16x20mm. It has 11 turns of a copper strip (36 x 0.5mm) and the total air gap in the magnetic circuit is 10mm.
Its inductance is cca 12uH.
The auxiliary 17V switching power supply, including Tr4, is described in more detail
here.
The simplest welding inverter on Pic 1 has no voltage feedback. Voltage feedback does not affect the welding, but affects the power consumption and heat losses in the idle state.
Without the output voltage feedback there is quite high output voltage (approximately 100V)
and the PWM controller ia running at its max duty cycle, thereby increasing the power consumption and heating of components.
Therefore, it is better to implement the voltage feedback. You can inspire on Pic 2. The feedback can be connected directly because the controll circuit is
isolated from mains. The reference voltage is 2.5V. Select the R2 to set the open circuit voltage.
You can find useful info in datasheet of UC3842, 3843, 3844, 3845 or in its another datasheet.
Inspiration for modifications you can also find in 3-60V 40A supply.
Interesting links from which I drew:
http://svarbazar.cz/phprs/index.php?akce=souvis&tagid=3
http://leo.wsinf.edu.pl/~leszek/spawarki/
http://www.y-u-r.narod.ru/Svark/svark.htm
http://www.emil.matei.ro/weldinv3.php
http://nexor.electrik.org/svarka/barmaley/kosoy/shema.gif
and a little modified: http://nexor.electrik.org/svarka/barmaley/kosoy1/shema.gif
To vent her frustrations without ruining her "perfect wife" image, she "purchases" a young man named Jun Setsuna
Often a young woman facing immense societal or familial pressure. She might be dealing with debt, a looming arranged marriage, or a career crisis. The Solution: To solve her immediate problem, she enters a financial agreement—taking out a loan to "rent" or "buy" a boyfriend. The Twist: The "boyfriend" is never who he seems. In the tradition of the "secret billionaire" trope, the purchased boyfriend is usually a CEO, a hidden heir, or a powerful figure in disguise.
[ادرج هنا رابط حقيقي إن وجد]
اللقطة الفيروسية التي بحثت عنها ( fydyw lfth ) موجودة في الحلقة الأولى، الدقيقة 23:17 – لكنني أنصحك بمشاهدة كامل الحلقة لتفهم السياق. To vent her frustrations without ruining her "perfect
في عالم الدراما الذي لا يتوقف عن ابتكار قصص صادمة وجذابة، برز مؤخراً مسلسل يحمل عنواناً استفزازياً: (اشتريت صديقاً بقرض بنكي). العمل ليس مجرد قصة حب عابرة، بل نقد لاذع للاستهلاكية، وعلاقات العصر الحديث، ويأس بعض النساء من الوحدة.
The "loaner boyfriend" who works to pay off his debts by being completely submissive to Tae. Shunpei Shiraishi Yasushi Fuchikami
يبدو أن كاتب المسلسل استوحى الفكرة من قصص حقيقية لنساء أقدمن على قروض لتمويل حفلات زفاف خيالية أو شراء هدايا مبالغ فيها لحبيب وهمي. لكن بجرأة درامية، حوّل الفكرة إلى علاقة . The Twist: The "boyfriend" is never who he seems
However, the coherent part — — suggests a dramatic, possibly fictional or clickbait-style story. The rest ( mshahdt mslsl = "watching series"? mtrjm kaml = "fully translated"? fydyw lfth = "video clip"?) seems to point to a viral video or translated series episode with a shocking plot.
On its surface, the idea of taking out a loan to “buy” a boyfriend is absurd. Loans are instruments for houses, education, or business—assets that appreciate or generate future value. A boyfriend, however, is a person with autonomy, feelings, and the potential to leave. By framing a human relationship as a purchase, the series (or concept) satirizes the commodification of intimacy. In many modern societies, dating apps present potential partners as profiles to be swiped, ranked, and discarded—a marketplace where people market themselves. The loan adds a layer of financial desperation, suggesting that the protagonist cannot “attract” a partner through conventional means (charisma, looks, status) and thus resorts to a simulated relationship bought with borrowed money.
Why would someone borrow money to have a boyfriend? The answer points to deep-seated loneliness and social pressure. In many cultures, being single past a certain age is stigmatized, and relationship status becomes a marker of success. The loan-funded boyfriend is a desperate performance of normalcy—a way to show friends, family, or social media followers that one is “chosen.” Yet, the arrangement is inherently unstable. The boyfriend, being “bought,” might act out affection, but genuine emotional reciprocity is absent. The series would likely explore the protagonist’s growing realization that purchased performance cannot fill an internal void, leading to a spiral of greater debt and deeper isolation. often designed for platforms like TikTok
The series explores the high-pressure social expectations placed on Japanese women. The Dual Life: Protagonist Tae Ukishima
The demand for highlights
In the vast and rapidly expanding universe of digital entertainment, a new genre has silently conquered the screens of millions: the vertical micro-drama. These bite-sized series, often designed for platforms like TikTok, Reels, and dedicated apps, pack the emotional punch of a full-length soap opera into episodes lasting barely two minutes. Among the myriad of titles vying for attention, one specific search term has piqued the curiosity of a diverse, multilingual audience:
