POWER|SUPPLY FROM A BATTERY WHEN THE BATTERY VOLTAGE IS BELOW A

THRESHOLD, AND DEVICE|COMPRISING SUCH AN ELECTRICAL CIRCUIT

The present invention relates to an electrical circuit comprising a load supplied by an electric cell.

The invention relates more particularly to an electrical circuit comprising a load supplied by an electric cell and a means avoiding too considerable a discharging of the electric cell.

The invention also relates to a device for cosmetic treatment, in particular for massage or for applying a cosmetic product, said device comprising such an electrical circuit.

The expression "cosmetic product" is understood to mean any product as defined in Regulation (EC) No 1223/2009 of the European Parliament and Council of 30 November 2009 relating to cosmetic products.

The design of electrical circuits comprising a load supplied by an electric cell can sometimes bring about considerable discharging of the cell, also called "deep discharge" or "over-discharge".

This phenomenon can cause impairment of the cell, its chemical components then being able to spill out of their confinement enclosure. Another risk caused by this phenomenon is the exploding of the cell. Certain electric cells are more sensitive to this phenomenon than others, such being the case in particular for alkaline cells for example of the LR44 type whose voltage can fall from about 1 .5Volts to less than 0.6Volts between the start and the end of life of the cell, and wherein risks related to deep discharge can appear below a cell voltage of about OJVolts.

In general, electrical devices comprise electronic components which cease to operate as soon as the supply voltage of the cell becomes low. Thereafter, the current demanded is very low and there is little chance of the deep discharge phenomenon occurring.

In the case of devices not comprising any electronic component, for example when the load is linked directly to the cell, the current demanded is always considerable even if the voltage of the cell falls below a threshold onward of which the load ceases to operate. The cell may then suffer deep discharge and risk leaking or exploding.

A circuit comprising a load linked to a power supply battery is known from document WO2007/079868 A1 . When the voltage across the terminals of the battery becomes low, electronic components control the power supply of a luminous telltale to inform the user that he must recharge the battery. However, the electronic components do not make it possible to interrupt the circuit so as to prevent the current from flowing in the load.

Complex electrical circuits comprising rechargeable batteries intended to be connected to loads are known from documents US4086525, EP0588615 A2, EP0525744 A1 and EP0512340 A1 . These circuits comprise electronic components commanding the interruption of the circuit when the voltage across the terminals of the battery becomes low. These electronic components are expensive electronic comparators which are not suitable for operating with electric cells whose voltages may reach fairly low values.

The object of the present invention is therefore to provide an improved electrical circuit so as to alleviate the aforementioned drawbacks.

For this purpose the invention proposes an electrical circuit comprising an electric cell, a load supplied by the electric cell, and an interruption component for the circuit exhibiting a threshold voltage value above which it is passing and below which it is blocking.

According to the invention, the interruption component is arranged in the electrical circuit in such a way that it is passing when the voltage of the electric cell is above said threshold voltage value and in such a way that it is blocking when the voltage of the electric cell is below said threshold voltage value.

The invention makes it possible advantageously to obtain a simple and inexpensive circuit for preventing the cell from discharging below a certain value. This threshold value being advantageously defined by the intrinsic characteristics of the interruption component without needing other electronic components. According to other characteristics of the invention, the interruption component can be a transistor. The transistor can be a field-effect transistor, comprising a Gate terminal, a Source terminal and a Drain terminal.

The transistor can be an N-channel MOFSET transistor, whose Gate terminal is linked directly to a first terminal of the electric cell, whose Source terminal is linked directly to the second terminal of the electric cell, and whose Drain terminal is linked downstream of the load, the load being linked upstream to the first terminal of the electric cell.

The threshold voltage value of the interruption component can lie between 0.45Volts and 1Volt, or indeed between OJVolts and 1Volt.

The electric cell can be an alkaline cell.

The electric cell can exhibit a nominal voltage of less than or equal to 3Volts, or indeed of less than or equal to 1 .5Volts.

The load can be at least one of the following elements: a motor, a heating element, and/or a luminous element.

The electrical circuit can also comprise a switch allowing a user to turn the electrical circuit on or off manually.

According to a characteristic of the invention the electrical circuit can consist solely of an electric cell, of a load supplied by the electric cell, of an interruption component for the circuit exhibiting a threshold voltage value above which it is passing and below which it is blocking, and of a switch, these elements being linked together by electrical conductors. Thus the circuit is particularly simple and can accommodate to a large number of devices at reduced cost.

The invention also relates to a device for massage and/or application of cosmetic product comprising such an electrical circuit.

The invention will be understood better from reading the following description of non-limiting examples of the implementation thereof with reference to the appended drawings, in which:

- Figure 1 represents a diagram of an exemplary electrical circuit according to the invention; - Figure 2 is a partial cutaway view of a first exemplary device comprising the electrical circuit of the invention;

- Figure 3 is a partial cutaway view of a second exemplary device comprising the electrical circuit of the invention.

With reference to Figure 1 , an electrical circuit 1 comprises an electric cell 2 linked to a load 3.

The various elements of the circuit are conventionally linked together by electrical conductors which can be electrical wires or tracks of a printed circuit.

The terms "upstream" and "downstream" used in the subsequent description are defined by the conventional sense of the electric current, that is to say by considering that the current flows from upstream to downstream, exiting the electric cell via the positive terminal and passing through the electrical circuit heading for the negative terminal of the electric cell.

The electric cell 2 can be composed of a single electric cell as in the circuit represented, or by several electric cells for example mounted in series one after another.

The electric cell is preferably an alkaline cell, however as a variant the electric cell can be a lithium cell, or a zinc/silver cell.

The electric cell exhibits a nominal voltage of less than or equal to 3Volts, or indeed of less than or equal to 1 .5Volts.

The cell may be an electric cell of "stick cell" type or of "button cell" type. For example the electric cell can be chosen from among the following formats defined by the International Electrotechnical Commission (IEC): LR03, LR06, LR41 , LR42, LR43, LR44, LR54, LR55, LR57, LR58, LR59, LR60, LR63, LR66, LR68, LR69. The electric cell of the circuit of Figure 1 is an LR44 cell.

Preferably the electric cell is not rechargeable. However as a variant the cell can be a rechargeable accumulator for example of the nickel-cadmium (NiCd) type or nickel-metal hydride (NiMH) type.

The load 3 is for example a motor that can bring about a rotation motion. The load can in particular be a motor of the "coin motor" type whose very high rotation speed associated with a flyweight makes it possible to generate vibrations.

As a variant the load can be a heating element such as a resistive wire, or a luminous element such as a light-emitting diode (LED) or a liquid- crystal display screen.

The load can be composed of a single load as in the circuit represented, or by several loads for example mounted in series one after another, or in parallel.

An upstream terminal of the load is linked to a first terminal of the cell in particular by an electrical conductor. The first terminal of the cell is the positive terminal.

Preferably the upstream terminal of the load 3 is linked directly to the first terminal of the cell 2, that is to say no component giving rise to a potential difference between the positive terminal of the cell 2 and the upstream terminal of the load 3 is inserted between these two points.

A switch 4 allowing the user to open or close the electrical circuit can be positioned in series between the load and the cell . The switch 4 can be positioned upstream or downstream of the cell. Indeed a switch is not considered to be a component giving rise to a potential difference since it acts as a simple electrical conductor consuming no energy in the closed position.

According to the invention, the electrical circuit 1 comprises an interruption component 5 for the circuit exhibiting a value of threshold voltage (Vth) measured between two terminals of said interruption component 5 and above which it is passing and below which it is blocking. This threshold voltage value (Vth) is an intrinsic characteristic of said interruption component 5.

This interruption component 5 is mounted in series between the load 3 and the electric cell 2. In the example represented in Figure 1 , the interruption component 5 is mounted downstream of the load 3.

Moreover this interruption component 5 is arranged in the circuit in such a way that it is passing when the voltage of the electric cell 2 is above said threshold voltage value (Vth) and in such a way that it is blocking when the voltage of the electric cell is below said threshold voltage value (V _t h). Advantageously the threshold voltage value (V _t h) lies between 0.45Volts and 1 Volt, or indeed between OJVolts and 1 Volt, for example substantially equal to OJVolts. These values correspond in general to the values below which the deep discharge phenomenon occurs according to the type of the electric cell used in the circuit.

The interruption component 5 of the example is a field-effect transistor of N-channel MOFSET type. However, other types of interruption components can be used and, in particular, other types of transistors.

By way of example, the interruption component 5 is a PMR280-UN- 1 15 transistor from the company NXP whose threshold voltage value (V _t h) is substantially equal to OJVolts. This transistor is advantageously chosen since its threshold voltage value corresponds to the value below which the deep discharge phenomenon occurs for an LR44 cell.

The transistor forming the interruption component 5 comprises a Gate terminal (G), a Source terminal (S) and a Drain terminal (D).

The Gate terminal (G) is linked directly to the first terminal of the electric cell 2, that is to say the positive terminal. The Source terminal (S) is linked directly to the second terminal of the electric cell 2, that is to say the negative terminal. Thus the voltage (V _gs ) measured between the Gate terminal (G) and the Source terminal (S) is equal to the voltage across the terminals of the electric cell 2.

Finally, the Drain terminal (D) is linked to the downstream terminal of the load 3.

When the switch 4 is in the closed position, the circuit 1 operates as follows.

As long as the voltage of the electric cell 2, that is to say V _gs , is above the threshold voltage value (V _t h), the transistor 5 is closed and the current can flow freely between the Drain terminal (D) and the Source terminal (S), the load 3 can therefore be supplied by the electric cell 2. Having regard to the low resistance in the closed state of the transistor 5, the loss caused by this additional component is negligible. On the other hand if the voltage of the electric cell 2, that is to say Vg _S , falls below the threshold voltage value (V _t h), the transistor 5 is opened and the current can no longer flow between the Drain terminal (D) and the Source terminal (S), the load 3 therefore cannot be supplied by the electric cell 2. The electric cell 2 hardly discharges any longer and its voltage is kept at a value substantially equal to the value of the threshold voltage (V _t h), the deep discharge phenomenon is thus avoided.

By virtue of this electrical circuit 1 , the transistor is controlled directly by the voltage across the terminals of the electric cell 2, instead of being controlled by a setpoint originating from electronic components, for example of comparator type.

A device 1 10 onboard which is embedded an electrical circuit described hereinabove is described with reference to Figure 2.

This device 1 10 is a cosmetic product application apparatus such as a mascara applicator. It comprises a gripping cap 1 1 1 also serving as closure element for a recipient 1 12 containing the cosmetic product.

The cap 1 1 1 is prolonged by a rod 1 13 which dips into the recipient 1 12 when the cap 1 1 1 is positioned on the recipient 1 12. The rod 1 13 comprises at its free end a product application member 1 14, for example a brush for applying mascara.

The cap 1 1 1 also contains a part of the electrical circuit which is not visible in the figure. The cap 1 1 1 contains for example the cell, the interruption element and a switch 104 such as a push-button.

The load 103 is a resistive wire wound around the application member 1 14 so as to heat the product during application.

As a variant, not represented, the cap 1 1 1 can furthermore comprise a vibrating motor, or a rotary motor driving the rod in rotation about its elongation axis. The cap 1 1 1 can also comprise a luminous telltale.

Another exemplary device 210 onboard which is embedded an electrical circuit described hereinabove is described with reference to Figure 3. The electrical circuit is mounted on a printed circuit comprising a cell 202, a transistor 205 and a load 203. This device 210 is a massage apparatus in particular for a cosmetic treatment. The device comprises a gripping portion 21 1 and an application surface 212. The application surface 212 is for example made of metal to afford a cold effect when it is placed in contact with the user's skin. The load 203 of the circuit is a vibrating motor for producing a massage effect when the application surface 212 is placed in contact with the user's skin. A cosmetic product can be applied independently before, during or after massage with the device.

The invention is not limited to the examples illustrated. The features of the various examples can in particular be combined as parts of variants which are not illustrated.

The expression "comprising a" should be understood as meaning "comprising at least one", unless specified to the contrary.