Elenos Power Supplies

We consider in this article a functional block of extreme importance for Elenos equipment: switching power supplies.
The majority of electronic equipment, in fact, requires a regulated voltage, which can be provided precisely by the stabilized power supplies.
There are 3 types of stabilized power supplies: parallel, series and switching.
The first two are called “linear”, because the stabilization is generated by an element (variable resistor) that, placed between the source and the load, maintains constant voltage, changing linearly its value.
Switching power supplies, however, are divided into CC/CC converters and inverters CC/CA.
They are an updated version of the “vibrator” used many years ago to feed the car radio, where contacts were replaced by modern solid-state devices.

Starting from a continuous voltage input, obtained by righting-levelling of an alternating voltage, split it at high speed through a power transistor, which changes from run to total prohibition, and then straighten and filter it.
The stabilization of the output voltage is achieved by varying appropriately the relationship between the time when the transistor is in conduction and the frequency of repetition.
Elenos switching power supplies are at high frequency with input from single-phase supply, forced ventilation and modular structure redundant, so that the failure of a single power supply does not cause either short-circuit on power, control and communication bus. The efficiency are very high.
To understand the great value of Elenos power supplies see the development of models currently in use and those who soon would enter on field.
Elenos acquired, several years ago, the known-how from a company specialized in building such systems. The types were by analog control and analog-digital control.
The first version is now totally outdated (may return only when repair older equipment), while the second is still used.
It provides both types of communication to and from the outside, and a communication between the power supplies, placed in parallel, only digital.
Initially, about the basic design(from which it was born the first model: the 2KW), the challenge, which Elenos designers faced, was a sudden failure of power supplies.
Following extensive testing, main causes have been identified: the power components (such as MOSFETs and diodes), the layout (PCB) and assembly processes.
These aspects are all mainly related to negligence and specialization lack of external suppliers.
It’s important to remember that, despite dimensions and specialization of companies in this sector, the characteristics and performance required at power supplies are extremely critical and thrusts.
Therefore, the suppliers substitution, the definition of clear assembly phases and the introduction of ATE test(Automatic Test Equipment), gave a significant change to the situation: the reliability of systems is largely increased and failures have been reduced almost to zero.
In particular, the ATE testing process allowed the identification of erroneous and / or missing components and to track critical or partial welds. In fact, in the meantime, the technology used was from solder with tin / lead to lead-free, more complex and critical.
After resolving these issues, other measures have been introduced in order to achieve a new project, which, after a short time, has resulted in a higher power: 3KW model.
The most significant changes were: PCB from 2 to 4 layers (more efficient in handling high currents and less “noisy” to the outside thanks to its geometric shape), introduction of additional finned heatsink inside equipment (to solve the heating problem, increasing significantly the dissipation), the redesign of the power transformer, the redesign of straightening output system.
This was made possible through the use of Schottky diode technology instead of planar/epitaxial diode technology, which guarantees lower voltage drop and higher efficiency in switching.
The experience and robustness obtained, and the birth of new transmitters (such as ETG3500) have led to evolve the 2KW model to the new 2.5KW.
In it there are lower operating temperatures and output currents much higher.
Other strengths are visible seeing the structure in detail.

The main blocks are four:
EMI FILTER _ Filter which has the aim to mitigate and / or to delete the radio interference conduced to the network, generated by converters in the unit.
PFC (Power Factor Corrector) _ It’s composed, first, from the soft-start circuit that, at the closure of the switch line, has the function a precharge of the capacitors on the Bus (+300 V), limiting the peak charging current of capacitors and avoiding the intervention of magneto thermal switch.
Then, there are regulating and control power circuit sections, with BOOST topology, the top for this application. PFC has not only the aim to correct the power factor, but is also useful for the attainment of powers. In fact, the input current has a sinusoidal trend and not impulsive, as the voltage. This current, therefore, overloads the distribution line and deforms the sinusoidal voltage.
The use of an active correction circuit, with continued monitoring of the current, achieves a high power factor and reduces harmonic distortion, maintaining the value within the permitted limits for Class D equipment of EN 61000-3-2.
The BOOST stage, then, raises the voltage of the bridge rectifier at 400Vcc and keeps it constant at the AC input voltage varies.
DC/DC CONVERTER _ It’s composed by full bridge phase-shift, which, unlike that of some competitors like half-bridge variable modulation, allows for much lower currents at equal power.
Here we adopt the technology PowerMOS, switched Zero Voltage Switch (ZVS).
PowerMOS are driven by special modules, designed to make them immune from noise and disturbance.
The control circuit of this stage is completely isolated from the network, and it’s on the same potential of the output ground.
It makes the limitation of maximum output current and voltage regulation, settable through external analog signal 0¸5Vcc, or through serial bus IEE485. It allows the enabling / disabling (ENA) of the converter stage. It provides outwards analog signals proportional to the voltage and current output.
There are, then, rectifiers and output filtering, to obtain a continuous voltage with low ripple, driver circuits and driving circuits.
AUX SUPPLY _ Discontinuous flyback type. It provides power service to the various control sections and sent out an auxiliary voltage to power any devices to manage information (such as voltage, current, temperature, diagnostics, etc.).
All this it’s contained in very small dimension.

Finally, the youngest it’s the 1KW power supply, used in ETG up to 500W. It has more compact size (in terms of length).
The technology used is different and less complex. Even here there is the PFC circuit, but more simple and suitable for low-medium power rating.
It provides only an analog communication, but perfectly compatible with other models more powerful.
New versions of power supplies would also have the protection fuses on the network filter and the container is not in aluminium colour, but anodized black.
Today Elenos uses, to realize power supplies, the most advanced technologies and better components, and it solves the critical aspects of production process by carrying out a rigorous test of power (power run-in) on the total production (each 3 power supplies), before their use on the RF apparatus.