This patent describes a new refrigeration devices especially conceived for home and commercial purposes, equipped with thermoelectric elements controlled by a Pulse With Modulation (PWM) electronic circuit, replacing the traditional gas compression system, allowing the production of easy and fast assemblage refrigeration apparatus, cheaper than conventional models. This new system enables the construction of hybrid devices, in which operational life and reliability are strongly increased, reducing the need of preventive and corrective maintenance.

Refrigeration is the cooling of substances within enclosed spaces which provides low-temperature environments. A common example is the home refrigerator, in which foods can be stored for days at low temperatures.

Refrigeration is also used commercially for storing food in warehouses and for transporting foodstuffs, biological materials and certain chemicals.

Today, mechanical gas-compression refrigerators are by far the most commonly used household refrigerators all over the world.

On these devices, a special fluid (the refrigerant) is vaporized recirculates through a so-called closed cycle, which has four basic components: a compressor, a condenser, an expansion valve, and an evaporator. In home and commercial refrigerators the evaporator section is the food compartment and its surrounding coils, which contain the refrigerant. The vapor leaving the evaporator section is compressed. The compressed gas is then condensed into a liquid by the condenser, which transfers heat to the external surroundings, trough coils at the back or bottom or the refrigerator. The liquid is then passed through an expansion valve and fed back into the cold-chamber evaporator, where absorbs heat as it is vaporized.

These apparatus are heavy, expensive and relatively complex, demanding periodic maintenance.

On the other side, when occurs a leakage of the refrigerant gas (especially the most common : CFC, or chlorofluorocarbon), it drift up slowly into the stratosphere, where, under the influence of ultraviolet radiation from the

Sun they break down into chlorine atoms which destroy the ozone layer and ailow harmful radiation from the Sun to reach the Earth's surface For a continuously running refrigerator, a steady cold state is reached when the heat transferred from the unit equals the heat absorbed by the refrigerant.

In practice, however, most refrigerators work only intermittently. If the temperature in the food compartment slightly exceeds the desired temperature, a thermostat with a double pair of electric contacts activates the compressor motor and the compartment is cooled to just below the required temperature.

The compressor is then shut off, to be restarted when the compartment warms up.

During the day, the door of the refrigeration apparatus is opened many times, and the compressors shut on and off very frequently. The repetition of this cycle the operation life of the system.

The object of this patent is to provide an alternative for that system. A thermoelectric refrigeration circuit capable to replace the conventional gas- compression system, and enabling the construction of a special hybrid refrigeration device, using both systems on a single apparatus, in order to increase the operational life of the mechanical components and the overall reliability, and reducing the need of preventive and corrective maintenance operations.

The new system uses a one or more Peltier cells, which is controlled by a Pulse With Modulation (PWM) electronic circuit specifically developed for it.

Thermoelectric cells basically consist of a pile of thermocouples (cells) made up of two different types of semi-conductors and subjected to an imposed direct current flow. Electrical energy received at the junction (cell) produces cold in one side and heat in the another one. The cold side is connected to the area in which cold is required and the hot one is linked to a heat exchanger.

The new refrigeration apparatus is composed by thermoelectric cells disposed in the wall of a refrigeration chamber, being controlled by a single PWM electronic circuit, maintaining the voltage and frequency of the electric

current flowing across the cells on a narrow optimized range, while the work cycle varies in according with the required thermal power.

The system can works simultaneously or alternatively, according with the refrigeration power needed.

A thermoelectric refrigeration device is composed by one or more Peltier cells, each of them disposed on the wall of the refrigeration chamber, the "cold"face of this cell being on the inside of the chamber, while the other face ("warm") is on the outside and presents a plated thermal exchanger, the cell being electrically connected to a electronic circuit board which has a Pulse- With-Modulation (PWM) circuit comprising a pulse generator, a cycle controller and a power module, the circuit being supplied by direct current from a battery or an alternative current rectifier, the control circuit being connected or disconnected to the battery or to the rectifier by means of a thermostat having a double pair of electric contacts, respectively for maximum and minimum temperatures.

An hybrid refrigeration apparatus has the thermoelectric device described below and a complete gas compression unit, equipped with the compressor, powered by an electric motor, a condenser, an expansion valve, and an evaporator, both energized by a special thermostat with three pair of double contacts, operating at three correspondent temperature setpoints.

When the temperature inside the refrigeration chamber equals the lower setpoint of the thermostat, both systems are turned off.

Then, the temperature slowly increases, to reach the medium setpoint, when the thermoelectric device is turned on.

If the temperature decreases, reaching the minimum, this device is turned off. Otherwise, happening a rise of internal temperature, it reaches the maximum setpoint, turning on the gas compression unit.

If desired, both systems can operate simultaneously, fastening the fall of the temperature inside the chamber.

For better understanding of the invention, the drawings referred bellow show the essential characteristics of a device equipped with the new electronic circuit, as described bellow: Fig. 1 : schematic drawing of a refrigeration apparatus constructed in

accordance with this patent ; Fig. 2 : simplified block diagram of the refrigeration electronic circuit used in the device showed on fig. 1; Fig. 3: schematic drawing of a hybrid refrigeration apparatus, combining on a single device a compressed gas refrigeration circuit and the new thermoelectric electronic controlled circuit.

According with these drawings, a thermoelectric refrigeration device is composed by one or more Peltier cells (1), each of them disposed on the wall of the refrigeration chamber (4), the"cold"face (2) of these cells being put inside of this chamber, presenting a heat exchanger (3) while the other face ("warm") (5) is on the outside and presents a second heat exchanger (6), said cell being electrically connected to a electronic circuit board (7) which has a Pulse-With-Modulation (PWM) circuit comprising a pulse generator (8), a cycle controller (9) and a power module (10), said circuit being supplied by direct current from a battery or from an alternative current rectifier, the control circuit being connected or disconnected to the battery or the rectifier by means of a thermostat having a double pair of electric contacts (11) and (12), respectively for maximum and minimum temperatures.

A further evolution of this equipment is an hybrid refrigeration apparatus that has the thermoelectric device described bellow plus a complete gas compression unit, equipped with the compressor (13) powered by an electric motor (14), a condenser (15), an expansion valve (16) and an evaporator (17), both energized by a special thermostat with three pair of double contacts (11), (12) and (18), operating at three correspondent temperature setpoints.

All refrigeration devices equipped with thermoelectric elements and an PWM electronic control circuit, like the apparatus above described, differing only by their design, materials, size or other secondary characteristics, will be attached to he scope of this patent.