The history of the creation of the mains transformer, classical rectifiers based on it. power conversion - from transformers to transformerless

This is part of the fascinating story of how humanity tamed electricity, traveling the path from huge humming coils to tiny chargers that fit in our pockets!

1. The Birth of the Mains Transformer: The Battle of Currents.

The history of the transformer began in the 1830s with the discoveries of Michael Faraday and Joseph Henry, who discovered the phenomenon of electromagnetic induction. However, the first devices (Rhumkorff coils) operated on direct current and produced only spark discharges.

The real breakthrough occurred in the 1880s:

The transmission of electrical energy by high-voltage alternating current became possible after the creation of a single-phase transformer with a closed magnetic system, which had sufficiently good operational characteristics.

The first transformers of the Budapest plant of "Ganz & Co": a) toroidal; b) shell type; c) serial core type.

Such a transformer, in several modifications (ring, shell, and core types), was developed in 1884–1885 by Hungarian electrical engineers Miklós Déri, Otto Bláthy (1860–1938), and Károly Zipernowsky (1853–1942), who were the first to propose the very term “transformer.”

In their patent application (February 1885), they noted the important significance of a closed laminated core, especially for powerful transformers.

Fig. 1 shows the first samples of the ring and shell transformers, as well as the general view of a serial transformer of the Bláthy–Déri–Zipernowsky system, which was manufactured by the electromechanical plant of the Ganz & Co. company in Budapest.

These transformers contained all the main elements of modern single-phase transformer designs.

2. Classical Rectifiers: From Tubes to Semiconductors.

A transformer outputs alternating current (AC), but most devices (and the first radio stations) required direct current (DC).

Thus arose the need for a “valve” that allows current to flow in only one direction.

The Era of Tubes: In the early 20th century, vacuum diodes (kenotrons) were used. They were huge, produced a lot of heat, and required time to “warm up.”

The Era of Selenium and Copper: In the 1930s, selenium rectifiers appeared — bulky stacks of plates. If they burned out, they smelled like rotten eggs.

The Silicon Revolution (1950s): The appearance of semiconductor diodes changed everything. They became tiny and reliable.

The Classical Circuit:

Transformer (steps down 220 V to the required 12 V).
Diode bridge (rectifies the current).
Electrolytic capacitor (smooths ripples).

Fig. 2. Diagram of a simple classical rectifier

3. Switching Power Supplies (SPS): The End of the “Copper Era”

Classical transformers had a huge drawback: the higher the power, the heavier the copper and iron.

To make power supplies lighter, engineers used a clever trick — they decided to increase the operating frequency.

The idea: Instead of 50 Hz (the standard mains frequency), use 50,000 Hz and above. At such a frequency, to deliver the same power, a transformer tens of times smaller is sufficient:

Fig. 3. Circuit board of a switching power supply, output 1 A, 50 V

1960s: The first developments were for the aerospace industry (NASA needed to save every gram on rockets).
1970s: Apple was one of the first companies to implement a switching power supply in a personal computer (Apple II). This allowed them to eliminate the heavy transformer and fan, as efficiency increased sharply.

How it works: First, current from the mains is rectified into high-voltage DC, then a power transistor switch “chops” it into ultra-fast pulses, which pass through a tiny high-frequency transformer and are rectified again.

The result of evolution:

If an old Soviet television weighed 30–50 kg (largely due to the huge transformer), a modern flat-screen TV or smartphone charger weighs only grams, thanks to the transition from mains transformers to switching power supplies.

However, powerful (500 W and above) switching power supplies (SPS), used in particular as Cathodic Protection Stations (CPS), cannot withstand operation in hot climates.

Often, manufacturers, despite all careful design and production measures, indicate that when operating at elevated temperatures (for example, just above +40 °C!), the maximum output current (power) of the power supply must be reduced (so-called derating) to avoid component overheating and preserve their service life.

For example, at +55 °C, a power supply rated at 100 W at +25 °C may be limited to 80 W.

Also, they often do not satisfy requirement 1.2 — they are not reliable during mains voltage surges.

Although switching power supplies have a wider input voltage range (for example, 85–265 V) and are generally more resistant to voltage fluctuations than traditional ones, they are nevertheless vulnerable to:

Powerful impulse surges (overvoltages): These are short-duration but very high voltage spikes (for example, up to 600 V and above) caused by lightning strikes or switching processes in the grid.

Such surges can lead to the failure of fuses, varistors (protective elements), or even damage to the capacitors at the input of the power supply.

Prolonged exceeding of permissible input voltage: If the mains voltage significantly and for a long time exceeds the upper limit specified by the manufacturer (for example, 265 V), this can cause overheating and failure of power-supply components.

In the event of a powerful surge, the power supply may fail to handle the load and fail itself, and in some cases may also cause failure of connected equipment.

4. Transformerless Power Supplies: The Mains Transformer is Completely Eliminated!

Another way to combat the excessive weight of single-phase (or other mains) transformers, which consume a lot of copper and/or aluminum during manufacturing, is to eliminate them entirely from the rectifier circuit, thereby allowing the design and manufacture of a transformerless rectifier.

The history of transformerless power supplies (TPS) is the history of the struggle for compactness and low cost, where the main price paid was safety.

If a classic transformer is a “diplomat” that transfers energy through a magnetic field, preventing the wires from the mains from touching your device, then a transformerless circuit is a “suicide conductor” that connects the electronics directly to the 220 V mains.

History of emergence:

From tubes to savings.

The idea of getting rid of the transformer arose almost simultaneously with its invention, but it became widespread in two cases:

1930s–1950s (Radio and TV):

To make radios cheaper and lighter, engineers began connecting the filaments of the tubes in series and plugging them directly into the mains. These devices were called “AC/DC”, because it did not matter to them which type of current was in the mains. However, one of the wires in the circuit was always connected to the mains line.
The era of the “dropping capacitor”: With the advent of semiconductors, it became popular to use the reactive impedance of a capacitor. The capacitor does not burn off the “excess” voltage (as a resistor does) but simply limits the current due to its capacitance. This made it possible to produce tiny power supplies for LED lamps, motion sensors, and cheap chargers.

Fig. 4. Transformerless power supply (TPS) with a dropping capacitor.

Do they “shock” with the phase?

Yes, and this is their main problem!

In a conventional power supply, there is galvanic isolation. In a transformerless power supply, there is none.

This means that any point in your circuit (even where it is supposed to be “safe” 5 V) is directly connected to the mains.

How exactly they “shock”:

Direct contact with the phase:

If you plug in the device so that the phase goes through the dropping element, then the entire low-voltage line will have a potential of 220 V relative to ground.

If you touch a wire (or the case, if it is metal), current will flow through you to the ground.

“Divider effect”:

Even if there is a rectifier bridge at the output, it does not isolate you.

One of the diodes in the bridge will always be conducting, creating a “bridge” for current from the mains directly to your fingers.

Where are they used today, and why don’t they kill us all?

Despite the danger, TPS surrounds us everywhere. You will encounter them in:

LED lamps: The entire casing is plastic, so it is impossible to touch the circuit.
Smart switches: They are hidden deep inside the wall.
Cheap nightlights.

Golden rule:

Transformerless power supplies can be used only where the user can never touch live parts.

The enclosure must be completely insulated (plastic), and there must be no external connectors (USB, audio, etc.).

Transformerless circuits are “marathon runners of small tasks”.

They are extremely efficient and cheap, but only as long as high power is not required.

In short: the typical power (excluding a small number of other TPS types) of such devices is 0.1 to 5 W.

This is a major limitation, but of course their main disadvantage is the lack of galvanic isolation, which creates a risk of electric shock and limits their broader applications.

In the article “The Story of the Development of TAPS”, it is described how we managed to:

Eliminate the heavy mains transformer, that is, to develop a powerful (up to 3000 W and higher) transformerless power supply using a new method, which provides excellent galvanic isolation.

This unique and unexpected result was achieved for the first time 95 years after the appearance of the first transformerless power supplies, which emerged in 1930.

Go to article >

Page updated

Google Sites

Report abuse