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
While most PlayStation 2 (PS2) games typically range from 2GB to 4GB, several titles were originally released on CDs rather than DVDs, making them naturally smaller
. Through high compression (stripping non-essential data like FMVs or audio), these can often be reduced to under 200MB. Top PS2 Games Under 200MB (Highly Compressed)
Below are notable games that fit your size requirement when highly compressed or in their native CD format: : A legendary shooter that compresses to approximately SOCOM U.S. Navy SEALs : This tactical shooter can be found as small as : A unique flight combat game that compresses down to Phantasy Star: Generation 1
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You can find these small-sized files on archive and community-driven platforms. Always look for files in formats to ensure maximum compression. Internet Archive Internet Archive PS2 Essentials
: A directory containing a variety of PS2 titles with direct size listings. Internet Archive Sony PS2 U-Collection highly compressed ps2 games under 200mb
: Useful for finding regional versions and beta releases that often have smaller footprints.
: Frequently cited by enthusiasts as a top source for "small size" or "highly compressed" PS2 ROMs. Internet Archive Essential Emulation Tools
To play these games, you will need an emulator and potentially extraction software:
playstation2_essentials directory listing - Internet Archive
Here’s a feature concept for a custom emulation frontend / archival tool called: While most PlayStation 2 (PS2) games typically range
A fighting game legend. The PS2 version includes the "Groove" system and hundreds of sprite frames. While the Japanese version has anime intros that bloat the size, the "Milky" or "US" rip removes the FMV, leaving just the gameplay. It squeezes in just under the 200MB wire.
The PlayStation 2 remains one of the greatest consoles ever made, boasting a library of over 10,000 titles. However, for retro gamers using emulators like PCSX2 on low-spec PCs, handhelds (Steam Deck, Anbernic), or older Android devices, storage space and file size are major hurdles. A standard PS2 DVD ISO weighs in at 4.7GB, while dual-layer discs hit 8.5GB.
But here’s the secret: thanks to aggressive compression techniques (CSO, ZSO, GZip) and the removal of dummy files, language packs, and FMV (Full Motion Video) cutscenes, a handful of PS2 classics can be shrunk down to under 200MB.
Let’s explore the best "micro" PS2 games that defy logic.
Before we list the games, it helps to understand why these files get so small: Refers to PlayStation 2 game disk images (ISOs)
Remember the golden era of the PlayStation 2? The console that gave us Shadow of the Colossus, God of War, and Final Fantasy X? It was a time of 4.7GB DVDs and memory cards the size of a cracker.
Fast forward to 2026. You’ve got a powerful PC, an Android handheld, or a Steam Deck. You want to relive the nostalgia, but your hard drive is screaming for mercy. Modern games are 100GB+. Even PS2 "backups" usually weigh in at 3-4GB per title.
Enter the niche world of Ultra-Compressed PS2 ROMs (under 200MB).
Is it magic? Black magic? Actually, it’s just clever file compression, dummy files removed, and a focus on games that weren't full of FMV (Full Motion Video) bloat. Let’s dive into why these tiny files are a retro gamer’s secret weapon.
