Illumination device for a space exposed to ionising radiation

Abstract

The invention relates to an illumination device for illuminating a space exposed to ionising radiation, the device comprising: a power supply circuit having an input for receiving alternating current from a mains electricity grid and an output suitable for delivering a direct current in response to receiving the alternating current, the power supply circuit comprising a diode bridge, and an illumination circuit (50) connected to the output of the power supply circuit, the illumination circuit comprising: a plurality of light-emitting diodes (51) connected in series, a plurality of Zener diodes (52), each connected in parallel with one or more light-emitting diodes of the plurality of light-emitting diodes and at least one resistor (53) connected in series with the plurality of light-emitting diodes, wherein a cumulative nominal supply voltage of the plurality of light-emitting diodes connected in series is adapted to a nominal voltage of the mains electricity grid.

Description

Lighting device for a room exposed to ionizing radiation

[0001] The invention relates to the field of lighting devices for illuminating a room exposed to ionizing radiation. Technological background

[0002] In the state of the art, several types of lighting are known for use in a room exposed to ionizing radiation.

[0003] In particular, lighting devices are known comprising a power supply circuit adapted to receive as input an alternating current from a mains electricity network and a lighting circuit adapted to be powered by said power supply circuit and comprising a plurality of light-emitting diodes.

[0004] However, the electrical circuits of these lighting devices known from the prior art include one or more electrical components with poor resistance to ionizing radiation, such as a step-down transformer or an integrated circuit (a transistor or an operational amplifier). For example, CN-A-114143932 uses SM2315 chips which are integrated circuits containing, in a small space, several Mosfet transistors and operational amplifiers which function as comparators. For example, CN-A-112867197 uses a step-down transformer and transistors, as well as electrolytic capacitors. Such a step-down transformer uses windings whose turns are insulated from each other by an insulator, such as the enamel covering the wires.The action of ionizing radiation is likely to damage the insulation and create short circuits between the turns, all the more quickly as the insulation thicknesses are thin. CN-A-109219183 also uses a step-down transformer. In the case of such a transformer, a short circuit will lead to the end of the component's life and may even cause a fire.

[0005] These electrical components are only able to withstand a low dose of ionizing radiation without degrading their operation.

[0006] The duration of use of these lighting devices in a room exposed to ionizing radiation, with reliable operation, is therefore likely to be very limited. Summary

[0007] An idea underlying the invention is to provide a lighting device for illuminating a room exposed to ionizing radiation having increased resistance to ionizing radiation and consequently an extended duration of use subjected to ionizing radiation.

[0008] As a preamble, we will note the following definitions.

[0009] The nominal value of an electrical quantity relating to a particular electrical component is a theoretical value or, in other words, an ideal value, of the electrical quantity for which the operation of the electrical component is optimized. In the case of electrical components, the nominal values ​​of certain electrical quantities are indicated by the manufacturer and often written by the latter on the electrical component.

[0010] The nominal voltage Unom of an electrical device is the theoretical potential difference for which an electrical device is designed. This nominal voltage guarantees satisfactory operation of the electrical device, for example, optimal efficiency. The adjective "nominal" indicates that this voltage is generally used to characterize the device.

[0011] In the case of a mains-type electrical network, hereinafter referred to as a mains electrical network or mains network, providing a mains voltage, the nominal voltage of the electrical network, also hereinafter referred to as the nominal mains voltage, is the one used to name or identify the network. In practice, electricity suppliers provide a mains voltage within a range around this nominal mains voltage value.

[0012] The effective value Ueff of a time-varying voltage is equal to the value of the direct voltage that would generate the same thermal energy in the same ohmic conductor during the same time as this variable voltage. For an alternating voltage with a sinusoidal variation in time, the effective value Ueff is equal to Umax / √(2), where Umax is the maximum value of the variable voltage during the sinusoidal variation. In the following, the maximum value of the variable voltage during the sinusoidal variation Umax will be called the peak voltage.

[0013] The invention thus relates to a lighting device for illuminating a room exposed to ionizing radiation, comprising: at least one support card, a power supply circuit mounted on the at least one support card, the power supply circuit having an input for receiving an alternating current from a mains electricity network and an output adapted to deliver a direct current in response to the reception of the alternating current, the power supply circuit comprising a diode bridge, and a lighting circuit mounted on the at least one support card and connected to the output of the power supply circuit, the lighting circuit comprising: a plurality of light-emitting diodes mounted in series, a plurality of Zener diodes each mounted in parallel with one or more light-emitting diodes of the plurality of light-emitting diodes and at least one resistor mounted in series with the plurality of light-emitting diodes,wherein a cumulative nominal supply voltage of the plurality of series-connected light-emitting diodes is matched to a nominal voltage of the mains electricity network.,

[0014] The "cumulative nominal supply voltage" of the plurality of light-emitting diodes is the sum of the nominal forward voltages of the light-emitting diodes connected in series in the lighting circuit. The nominal forward voltage of a light-emitting diode is also known as the "forward voltage" and is available from the manufacturer.

[0015] Because the series-connected LEDs have a cumulative nominal supply voltage that matches the nominal mains voltage of the mains electricity network, the power supply circuit can be designed as a rectifier circuit without producing a substantial reduction in voltage, thus eliminating the need for any voltage transformer.

[0016] According to one embodiment, the cumulative nominal supply voltage of the plurality of light-emitting diodes is greater than or equal to 80% of the nominal effective voltage of the mains electricity network, preferably greater than or equal to 90% of the nominal effective voltage of the mains electricity network.

[0017] Preferably, the cumulative nominal supply voltage of the plurality of light-emitting diodes is less than or equal to 120% of the nominal effective voltage of the mains electricity network, preferably less than or equal to 100% of the nominal effective voltage of the mains electricity network.

[0018] Preferably, the lighting circuit consists solely of: the plurality of light-emitting diodes connected in series, the plurality of Zener diodes each connected in parallel with one or more light-emitting diodes of the plurality of light-emitting diodes and the at least one resistor connected in series with the plurality of light-emitting diodes.

[0019] Thus, the lighting circuit of the lighting device has only a minimum of electrical components. The electrical components used are simple and can be selected to have optimized resistance to ionizing radiation.

[0020] Thanks to the invention, a lighting device having improved resistance to ionizing radiation can be obtained economically, using commercial electrical components.

[0021] According to one embodiment, the direct current delivered by said power supply circuit is a pulsed direct current which has a peak voltage of between 85 and 100% of a peak voltage of the mains electricity network delivering the alternating current received at the input of the power supply circuit.

[0022] Thus, in the power supply circuit, no voltage transformer is used to decrease the supply voltage received by the lighting circuit.

[0023] According to one embodiment, the power supply circuit is intended to be connected to a single-phase mains electricity network having a nominal effective voltage greater than 110VAC, for example equal to 230VAC.

[0024] Thus the lighting device is suitable for being powered by a standard single-phase mains network available in most countries.

[0025] As a reminder, in Europe, the single-phase mains voltage is generally 230 VAC 50 HZ. For many countries around the world, it is between 220 VAC and 240 VAC, usually at 50 Hz, sometimes 60 Hz. In many countries in the Americas and other countries, the single-phase mains voltage is 110 to 127 VAC, at 60 HZ, or 50 Hz. In Japan, it is 100 VAC, 60 Hz or 50Hz.

[0026] According to one embodiment, the power supply circuit and the lighting circuit are adapted to withstand without loss of functionality a dose of ionizing radiation greater than or equal to 8.8 kiloGray (kGy), preferably greater than 10 kGy, preferably greater than 20 kGy, preferably greater than 50 kGy, preferably greater than 100 kGy and preferably greater than 250 kGy.

[0027] Thus, advantageously, the lighting device according to the invention can be used for at least ten years in premises exposed to high intensity ionizing radiation, for example in a reactor building of a nuclear power plant, or even several decades in less highly exposed premises.

[0028] According to one embodiment, said power supply circuit consists solely of the diode bridge and one or more electrical components selected from: a fuse, and one or more resistors. Thus, the resistance to ionizing radiation of the power supply circuit is optimized.

[0029] According to another embodiment, the power supply circuit consists solely of the diode bridge and one or more electrical components selected from: a fuse, resistors and capacitors.

[0030] The capacitors of the power supply circuit, when present, are chosen from the following types of capacitors: plastic-insulated capacitors, in particular metallized polypropylene film capacitors, metallized polyester film capacitors, or others, excluding electrolytic capacitors.

[0031] The resistors of the power supply circuit are for example chosen from metal film anti-surge resistors (“Metal Electrode Leadless Face” or MELF resistor) or carbon film resistors, and thick film resistors, for example from “High Pulse Load Carbon Film MELF Resistors”, “Pulse Proof in MELF”, and “High Power Thick Film Chip Resistors in 1206 case”.

[0032] A Transil diode is preferably arranged after the diode bridge, in parallel with it. This transient voltage suppression diode is suitable for protecting sensitive electronic components from rapid transient overvoltages induced, for example, by lightning or other events. This transient voltage suppression diode comprises, for example, a glass-passivated pn junction (GPP) arranged in a plastic or glass enclosure. Such diodes are, for example, marketed by the company SMC.

[0033] According to one embodiment, said power supply circuit comprises an overvoltage protection circuit, the overvoltage protection circuit consisting solely of one or more electrical components selected from: one or more coils of conductive wire, one or more capacitors, and one or more varistors. Thus, the resistance to ionizing radiation of the power supply circuit is optimized while integrating overvoltage protection.

[0034] The varistors in the surge protection circuit are chosen, for example, from metal oxide varistors encapsulated in an epoxy resin casing. These are disc varistors with radial leads. Varistors are, for example, arranged upstream and downstream of the coil(s) of conductive wire. Their role is to protect the circuit against high surges. They have a high nominal peak surge current and a high energy absorption capacity.

[0035] The coils of the surge protection circuit are chosen, for example, from common-mode chokes. These common-mode chokes comprise, for example, two coils that are separated by an insulator. If the insulating sheath of the conductor wire wound to form one of the coils is damaged, the performance of the chokes is reduced, but the chokes remain functional and reliable. These include, for example, coils designed with high-permeability ferrite cores. They have a high inductance. Each common-mode choke comprises two coils that are insulated from each other. These coils are useful for protection against fast and high transient overvoltages in combination with the varistors and transient voltage suppression diodes described previously.

[0036] According to one embodiment, said power supply circuit comprises, downstream of the diode bridge, one or more capacitors, and / or one or more resistors and / or a Transil diode. Preferably, the power supply circuit does not comprise any other component downstream of the diode bridge.

[0037] According to one embodiment, the at least one support card is a printed circuit card comprising a layer of electrically conductive material and a supporting structure, in which the supporting structure is made of one or more materials chosen from: aluminum, copper, fiberglass-reinforced epoxy resin composite, epoxy resin, ceramic.

[0038] According to one embodiment, a said light-emitting diode of said plurality of light-emitting diodes, i.e. one, each, all or some of the light-emitting diode(s) of said plurality of light-emitting diodes, comprises a semiconductor element and a phosphor, not covered with an optical lens. Thus, the resistance to ionizing radiation of the light-emitting diode is optimized because opacification or darkening of the optical lens is avoided.

[0039] The size of the semiconductor element of the light-emitting diode allows it to satisfactorily resist ionizing radiation.

[0040] According to one embodiment, a said light-emitting diode of said plurality of light-emitting diodes, i.e. one, each, all or some of the light-emitting diode(s) of said plurality of light-emitting diodes, has a nominal forward supply voltage greater than 2V, preferably between 2.7V and 3V for a current of 200mA. At the end of the life of the light-emitting diode, the forward voltage may reach a higher value.

[0041] According to one embodiment, suitable for example for an effective mains voltage of 230V, the lighting circuit comprises more than 50 light-emitting diodes, preferably more than 60 light-emitting diodes, preferably more than 70 light-emitting diodes.

[0042] Thus, it is possible to power the lighting circuit with the pulsed direct current delivered at the output of the power supply circuit, this pulsed direct current having a peak voltage of between 85 and 100% of the peak voltage of the mains network supplying the alternating current received at the input of the power supply module.

[0043] According to one embodiment, a so-called Zener diode, i.e. one, each, all or some of the Zener diode(s), is of the type comprising an inorganic glass housing, without the use of plastic, polymer or silicone material. Thus, the resistance to ionizing radiation of the Zener diode is optimized because the degradation of its housing is limited.

[0044] According to one embodiment, a said Zener diode, or each or some of the Zener diode(s), is connected directly in parallel to a said light-emitting diode. Thus, the lighting circuit is protected against malfunction of this light-emitting diode. In the event of malfunction of the light-emitting diode, if the lighting circuit opens at this light-emitting diode, the Zener diode becomes conductive and allows current to bypass the light-emitting diode which no longer operates.

[0045] According to one embodiment, the Zener diode has a breakdown voltage at least 5% higher than the nominal supply voltage of said light-emitting diode with which it is connected directly in parallel, preferably at least 15% higher, or even at least 25% higher than the nominal supply voltage.

[0046] According to one embodiment, a said Zener diode, or each or some of the Zener diode(s), is connected directly in parallel to a set of light-emitting diodes whose number is between 2 and 5. Thus, the Zener diode protects the lighting circuit against the malfunction of one of the light-emitting diodes in this set. The number of Zener diodes used is further reduced.

[0047] According to one embodiment, the Zener diode has a breakdown voltage at least 5% higher than the nominal supply voltage of said set of light-emitting diodes, preferably at least 15% higher, or even at least 25% higher than the nominal supply voltage.

[0048] Preferably, each light emitting diode is connected in parallel to one of said Zener diodes.

[0049] According to one embodiment, said at least one resistor connected in series with said plurality of light-emitting diodes comprises a plurality of resistors distributed between the light-emitting diodes of said plurality of light-emitting diodes. Thus, the dissipation of thermal energy produced by the Joule effect in the resistors is improved.

[0050] According to one embodiment, the power supply circuit is implemented in the form of a power supply module comprising a first support board and the lighting circuit is implemented in the form of a lighting module comprising a second support board, the lighting module comprising a power supply input connected to the output of the power supply circuit to power the lighting circuit. Thus, the lighting device according to the invention is in a modular form having two modules.

[0051] According to one embodiment, the power supply circuit is a first power supply circuit, the lighting module is a first lighting module and the lighting device comprises a second lighting module connected to the output of the power supply circuit in parallel with said first lighting module, the second lighting module comprising a second lighting circuit mounted on the at least one support board and connected to the output of the power supply circuit, the second lighting circuit comprising: another plurality of light-emitting diodes connected in series, another plurality of Zener diodes each connected in parallel with one or more light-emitting diodes of the other plurality of light-emitting diodes and at least one other resistor connected in series with the other plurality of light-emitting diodes,wherein a cumulative nominal supply voltage of the other plurality of series-connected light-emitting diodes is also matched to the nominal effective voltage of the mains electricity network.,

[0052] According to one embodiment, the lighting device further comprises a battery adapted to be connected to the lighting circuit so as to power said plurality of light-emitting diodes or a subset of the plurality of light-emitting diodes, the subset comprising a number of light-emitting diodes strictly less than the total number of light-emitting diodes of said plurality of light-emitting diodes. Thus, an autonomous power source is provided for the lighting device in the event of a failure of the mains electricity network. The lighting device thus performs an emergency lighting function.

[0053] According to one embodiment, the lighting circuit comprises an intermediate input adapted to receive the direct current delivered by the battery, the intermediate input being connected to an intermediate point of said plurality of light-emitting diodes to power the subset of the plurality of light-emitting diodes.

[0054] In this case, the cumulative nominal supply voltage of the subset of the plurality of light-emitting diodes is preferably adapted to a nominal voltage of the battery. Thus, the battery which delivers a voltage lower than that delivered by the electrical network can supply the subset of the plurality of light-emitting diodes satisfactorily. Brief description of the figures

[0055] The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

[0056] is a schematic representation of a first embodiment of the lighting device.

[0057] is a schematic representation of a second embodiment of the lighting device.

[0058] is a schematic representation of a first example of embodiment of a power supply circuit suitable for the lighting devices of figures 1 and 2.

[0059] is a schematic representation of a second exemplary embodiment of the power supply circuit suitable for the lighting devices of Figures 1 and 2.

[0060] is a schematic representation of the variation over time of the mains voltage supplied at the input of the power supply circuits of Figures 3 and 4 and of the corresponding variation over time of the voltage delivered at the output of these power supply circuits.

[0061] is a schematic representation of an exemplary embodiment of the lighting circuit suitable for the lighting devices of Figures 1 and 2.

[0062] is a schematic cross-sectional representation of a printed circuit board that can be used to make the lighting devices of Figures 1 and 2.

[0063] is a schematic cross-sectional representation of a light-emitting diode suitable for use in the lighting circuit of the.

[0064] A lighting device 1; 2 for illuminating a room exposed to ionizing radiation will be described below.

[0065] Some radiation is called ionizing because the energy it carries is sufficient to strip electrons from the atoms it passes through, forming ions. This phenomenon causes atomic changes in the materials exposed to the radiation.

[0066] There are several types of ionizing radiation:

[0067] – alpha radiation emitted by an atom by losing protons and neutrons,

[0068] – beta minus or beta plus radiation emitted by an atom by transforming a neutron into a proton or vice versa,

[0069] – X-rays and gamma rays which are high-energy photon emissions.

[0070] Depending on the energy transported, ionizing radiation penetrates more or less deeply into the materials it encounters and is more or less likely to ionize the atoms of these materials.

[0071] Alpha and beta ionizing radiation are easily stopped by an external casing surrounding the lighting device 1; 2 or any other obstacle placed between the radiation source and the lighting device 1; 2. Gamma ionizing radiation, on the other hand, has a very long range (several hundred meters) and is highly penetrating. It is only blocked by significant thicknesses of dense materials such as steel or concrete. These gamma ionizing radiations are not blocked by an external casing surrounding the lighting device. The lighting device 1; 2 will therefore be exposed to them. The same is true for X-rays.

[0072] The effects of ionizing radiation on materials are of two types:

[0073] – the dose or cumulative effect: the ions formed in the material by the ionizing radiation cause premature aging of the material by modifying its physical structure,

[0074] – the singular effect: the ions formed in the material by the ionizing radiation create a transient and parasitic current in the electronic components until their destruction.

[0075] Many materials thus see their physical properties, particularly mechanical or optical, modified by exposure to ionizing radiation. Organic materials are particularly sensitive to this type of radiation.

[0076] The functioning of electronic components is also degraded by ionizing radiation, eventually rendering them completely unusable.

[0077] The dose of ionizing radiation physically "absorbed" by matter is measured in Gray, which represents the energy absorbed by a kilogram exposed to ionizing radiation providing an energy of 1 joule: 1 Gy = 1 J / kg.

[0078] Premises exposed to ionising radiation include those of nuclear power plants or research laboratories such as CERN.

[0079] Two embodiments of the lighting device are shown schematically in Figures 1 and 2.

[0080] Generally, the lighting device 1 or 2 comprises a power supply circuit 30 or 40 and a lighting circuit 50 and at least one support card 10, 11; 20 on which the power supply circuit 30 or 40 and the lighting circuit 50 are mounted.

[0081] In the first embodiment shown in the, the lighting device 1 comprises two support cards 10 and 11, while in the second embodiment shown in the, the lighting device according to the invention only comprises a single support card 20.

[0082] For example, as many support cards as there are power supply circuits and lighting circuits are provided.

[0083] Then, as is the case in the lighting device 1, the power supply circuit 30 or 40 is mounted on a first support card 10 and the lighting circuit 50 is mounted on a second support card 11, distinct and separate from the first support card 10.

[0084] The assembly of the first support card 10 with the power supply circuit 30 or 40 then forms a power supply module 1A and the assembly of the second support card 11 with the lighting circuit 50 forms a lighting module 1B.

[0085] Alternatively, as is the case in the lighting device 2 shown in the, the power supply circuit 30 or 40 and the lighting circuit 50 are mounted on the same single support board 20.

[0086] In practice, each carrier board takes the form of a printed circuit board, which will be described in more detail later.

[0087] The power supply circuit 30 or 40 has an input E1; E1' for receiving an alternating current from a single-phase mains network and an output S1; S1' adapted to deliver a direct current in response to the reception of the alternating current from the single-phase mains network.

[0088] The input E1; E1' of the power supply circuit 30 or 40 in practice comprises connection terminals adapted to receive electrical wires 16 or connection pins connected to the single-phase mains network.

[0089] In the lighting device 1 shown in the, the output S1 of the power supply circuit 30 is in the form of connection terminals adapted to receive electrical wires 17 or connection pins for connecting the power supply circuit 30 to the lighting circuit 50. In the lighting device 2 shown in the, the output S1' of the power supply circuit 40 is part of conductive tracks 27 arranged on the support board 20 and which electrically connect the power supply circuit 40 and the lighting circuit 50.

[0090] The power supply circuit 30 or 40 further comprises a diode bridge 33.

[0091] The diode bridge 33 is an assembly of four diodes connected in a bridge that rectify the single-phase alternating current into direct current, i.e., current flowing in only one direction. More specifically, this is a full-wave rectifier bridge. The diode bridge has a high nominal supply voltage, for example equal to the nominal mains voltage. At the nominal voltage, the diode bridge is powered by a low current, for example a nominal current of less than 200 mA, for example approximately 170 mA, or a peak current of less than 230 mA, which limits the heating of the diode bridge. Each diode of the diode bridge comprises, for example, a glass-passivated pn junction. The four glass-passivated pn junctions of the diode bridge are enclosed in a plastic or glass envelope. The diode bridge is adapted to receive a current of greater intensity than the current present in the power supply circuit described.For robustness reasons, each diode is, for example, designed to withstand 1000V, a nominal current of 2 Amperes (A) and a peak current of 50A. This limits the heating of the diode bridge and avoids additional stress on the plastic or glass enclosure. In addition, the diode bridge is designed to withstand a high peak surge current.

[0092] According to a first exemplary embodiment, shown in the, said power supply circuit 30 is solely made up of the diode bridge 33 and one or more electrical components selected from a fuse 34, one or more varistors 35A and one or more resistors 35, 36.

[0093] According to a second embodiment shown in the, the power supply circuit 40 comprises the diode bridge 33, a fuse 44, resistors 45, capacitors 46, varistors 435A and 435B, coils 431, and a Transil diode 47. It comprises in particular a protection circuit 43 against overvoltages consisting of the coils 431, the capacitors 436A, 436B, and the varistors 435A, 435B. Preferably, the coils 431 constitute a common mode inductor of the “Common mode SSR coil” type with high impedance.

[0094] The power supply circuit 30 or 40 does not include any transistors, operational amplifiers, switches, or integrated circuits. The power supply circuit is also made without a voltage transformer.

[0095] Thus, whatever the embodiment of the power supply circuit 30 or 40, only electrical components that are not very sensitive to ionizing radiation are used.

[0096] In the power supply circuit 30 shown in the, it comprises the diode bridge 33, a fuse 34, a varistor 35A and four resistors 35, 36. The resistors 35, 36 are connected in series to the input and output terminals of the diode bridge 33 (). The varistor 35A is arranged in parallel with the diode bridge 33, upstream of the resistors 35 located upstream of the diode bridge 33 and the fuse 34 is arranged upstream of the varistor 35A, at the input of the circuit. This first embodiment of the power supply circuit is simple and economical. Its resistance to rapid and high transient overvoltages is limited.

[0097] The power supply circuit 30 has the advantage of comprising a minimum of electrical components.

[0098] Fuse 34 protects the power supply circuit in the event of significant surges when the 35A varistor begins to be damaged. Fuse 34 is, for example, a slow-blow fuse of the through-wire type. This is, for example, a Bel Fuse ® fuse with reference number 0697H40000-02, between 2 and 4 Amps, for example at 4 Amps. Diode bridge 33 is, for example, a Taiwan Semiconductor DBLS209G ® diode bridge. Resistors 35, 36 are, for example, 20 ohm metal film anti-surge resistors (MELF).

[0099] In the power supply circuit 40 (), a fuse 44 is provided at the input, then the protection circuit 43, the diode bridge 33 connected in parallel with a Transil diode 47, two resistors 45 and two capacitors 46 in parallel at the output S1; S1' of the power supply circuit 40. This second example of embodiment corresponds to a more complex version of the lighting device 1 or 2.

[0100] Fuse 44 protects the power supply circuit in the event of significant overvoltages and in the event of a short circuit at the end of the life of the varistor or the printed circuit.

[0101] The protection circuit 43 protects the lighting device 40 against voltage peaks on the single-phase mains network.

[0102] At the input and output of the coils 431 are arranged a varistor 435A, 435B and a capacitor 436A, 436B in parallel with each other.

[0103] Varistors are used to protect the light-emitting diodes 51 of the lighting circuit 50 against overvoltages, particularly high and short overvoltages, and electrostatic discharges.

[0104] The common mode choke is used to protect the Transil diode 47 and the second varistor 435B against high currents. High overvoltages will be eliminated or reduced by the first varistor 435A at the input. The second varistor 435B protects the light-emitting diodes of the lighting circuit against overvoltages. The capacitors 436A, 436B located upstream and downstream of the diode bridge 33 are intended to improve the behavior in the event of electrostatic discharge (ESD) and to ensure satisfactory electromagnetic compatibility (EMC).

[0105] The protection circuit 43 may also optionally include one or more resistors in parallel with the common mode inductor, to the exclusion of any other electrical component.

[0106] In combination with protection circuit 43, Transil diode 47 helps protect the power supply circuit against electrostatic discharges: it protects against very rapid transient overvoltages.

[0107] The varistors 435A, 435B of the protection circuit 43 protect against high overvoltages longer than those acted on by the Transil diode 47, for example due to lightning, and against overloads. The two resistors 45 have the function of reducing the input current of the two capacitors 46. These may be varistors having a nominal voltage between 387 and 473 V.

[0108] Capacitors 436A, 436B and 46 arranged before and after the diode bridge 33 are intended to improve behavior in the event of electrostatic discharge (ESD) and to ensure satisfactory electromagnetic compatibility (EMC).

[0109] The capacitors 46 arranged in parallel at the output of the power supply circuit 40 are optional. Alternatively, a power supply circuit identical to that of the, without the capacitors 46, can be envisaged.

[0110] When present, these capacitors 46 make it possible to limit the flickering of the light-emitting diodes. They also make it possible to reduce the output current of the power supply circuit 40 in the event of overvoltages to protect the light-emitting diodes of the lighting circuit 50 powered by the power supply circuit 40.

[0111] Fuse 44 is, for example, a slow-blow fuse of the through-wire type. This is, for example, a Bel Fuse ® fuse with reference 0697H40000-02, from 2 to 4 Amps. Diode bridge 33 is, for example, a Taiwan Semiconductor DBLS209G ® diode bridge. The resistors are, for example, 20 ohm metal film anti-surge resistors (MELF).

[0112] The 435A, 435B varistors are for example Littelfuse ® Ultramov varistors with reference V20E320P for the first 435A varistor and V14E275P for the second 435B varistor; the 436A and 436B capacitors are for example 0.1 microFarad and have reference R523I310050P0K, 0.1µF, 275V. The coils are for example a Kemet SSR10H ® common mode choke of 22 milliHenry. The Transil diode is for example a Littelfuse SMCJ400A ® TVS diode.

[0113] The 40 power supply circuit has the advantage of being more resistant to voltage spikes. Its use allows for more stable and generally better quality lighting.

[0114] The capacitors 46 provide better lighting performance, in particular by reducing the flicker of the light-emitting diodes. More specifically, the two capacitors 46 reduce flicker at the 100 Hz frequency of the electric current. They reduce the turn-off time of the light-emitting diodes to a few milliseconds, which improves the flicker index of the lighting device. For this purpose, the capacitance of a capacitor 46 may be less than 10 µF, for example 1 µF or less.

[0115] The diode bridge 33 allows full-wave rectification to be carried out as shown schematically in the figure.

[0116] The left graph shows the variation over time of the AC voltage Uin of the single-phase mains network applied to the input of the power supply circuit 30;40. The right graph shows schematically the variation over time of the output voltage Uout of the power supply circuit 30 or 40 supplied by the AC voltage from the right graph. The output voltage Uout of the power supply circuit 30 or 40 is a pulsed DC voltage.

[0117] The frequency of the alternating voltage Uin is for example 50 Hz. The frequency of the output voltage Uout is twice the frequency of the alternating voltage Uin, here for example 100 Hz.

[0118] The direct current delivered by said power supply circuit 30 or 40 is a pulsed direct current. This pulsed direct current has a peak voltage VmaxDC equal to or lower than a peak voltage VmaxAC of the alternating current received at the input of the power supply circuit. Thus, the peak voltage VmaxDC of the pulsed direct current is for example between 85 and 100% of the peak voltage VmaxAC of the alternating current received at the input of the power supply circuit, preferably between 90 and 100% of the peak voltage VmaxAC of the alternating current received at the input of the power supply circuit, i.e. between 85 and 100%, preferably between 90 and 100% of the peak voltage of the mains network. The output voltage of the power supply circuit is applied to the input of the lighting circuit: the output voltage of the power supply circuit is therefore the power supply voltage of the lighting circuit.

[0119] In the lighting device 1 or 2, the lighting circuit 50 is powered by a high voltage, greater than 110V, and a low current, less than 250mA, preferably less than 200mA.

[0120] In practice, the power supply circuit 30 or 40 is intended to be connected to a single-phase mains network having a nominal effective voltage greater than or equal to 110 VAC, for example a nominal effective voltage equal to 230 VAC. The actual effective voltage delivered by the mains is for example preferably between the nominal effective voltage minus 15% and the nominal effective voltage of the mains plus 15%, for example here between 210 and 260 VAC, corresponding to a peak voltage between 296 and 364 V. For the nominal effective voltage of the mains equal to 230 VAC, the peak voltage is for example equal to 325 V. For use with a single-phase 110 V mains network, the number of light-emitting diodes is reduced compared to the number used with a 230 V mains.

[0121] The lighting circuit 50 is connected to the output S1; S1' of the power supply circuit 30 or 40.

[0122] For this purpose, in the lighting device 1, the lighting circuit 50 comprises connection terminals 50A adapted to receive the electric wires 17 or connection pins for connecting the lighting circuit 50 to the power supply circuit 30.

[0123] In the lighting device 2, the lighting circuit 50 is connected to the output S1' of the power supply circuit 40 by conductive tracks 50B arranged on the support board 20 and connected to the conductive tracks 27 of which the output S1' of the power supply circuit 40 forms part.

[0124] The lighting circuit 50 comprises:- a plurality of light-emitting diodes 51 connected in series,- a plurality of Zener diodes 52 each connected in parallel with one or more light-emitting diodes 51 of the plurality of light-emitting diodes 51 and- resistors 53 connected in series with the plurality of light-emitting diodes 51.

[0125] The voltage drop in the lighting circuit 50 results from the sum of the voltage drops across all the components connected in series. The voltage drop in the lighting circuit 50 can therefore be divided into a contribution from all the resistors 53 and a contribution from all the light-emitting diodes 51.

[0126] The contribution of the light-emitting diodes 51 can be determined from the nominal forward voltage of each. This voltage varies slightly with the current. A cumulative nominal voltage of the plurality of light-emitting diodes 51 connected in series is adapted to a nominal voltage of the single-phase mains network.

[0127] The number of light-emitting diodes 51 and the nominal voltage of each light-emitting diode 51 are determined so that the cumulative nominal voltage of the plurality of light-emitting diodes is greater than or equal to 80% of the nominal voltage of the mains network, preferably greater than or equal to 90% of the nominal voltage of the mains network.

[0128] Further, preferably, the cumulative nominal voltage of the plurality of light-emitting diodes is less than or equal to 120% of the nominal voltage of the mains network, preferably less than or equal to 100% of the nominal voltage of the mains network.

[0129] The nominal voltage of the mains network in question here is the nominal effective voltage of 230 V.

[0130] To select these thresholds, a safety margin was taken into account because the single-phase mains voltage can have transient overvoltages. In order to make the lighting circuit robust against these overvoltages, an overvoltage less than or equal to 15% of the nominal voltage of the single-phase mains network was taken into account.

[0131] Regarding the cumulative rated supply voltage of LEDs, the higher it is, the more resistant the lighting circuit will be to surges. However, the lighting quality will be lower because the flicker will be greater (higher flicker index) than for LEDs with a lower cumulative rated supply voltage.

[0132] Therefore, preferably, the cumulative nominal supply voltage of the plurality of light-emitting diodes is less than or equal to 120% of the nominal voltage of the mains network, preferably less than or equal to 100% of the nominal voltage of the mains network.

[0133] The choice of the cumulative nominal voltage of the light-emitting diodes and the sizing of the associated resistors in the lighting module results from a compromise between tolerance to instabilities in the mains electricity network, in particular to occasional overvoltages, and the quality of the lighting.

[0134] . As for the power supply circuit, only electrical components that are not very sensitive to ionizing radiation are used in the lighting circuit 50.

[0135] Preferably, the lighting circuit 50 is only made up of: the plurality of light-emitting diodes 51 connected in series, the plurality of Zener diodes 52 each connected in parallel with one or more light-emitting diodes 51 of the plurality of light-emitting diodes and the at least one resistor 53 connected in series with the plurality of light-emitting diodes 51.

[0136] An example of such a lighting circuit 50 is shown schematically in the. The output voltage Uout of the power supply circuit 30; 40 is applied to the input of the lighting circuit 50, between an input point of the circuit C1 and an output point C2.

[0137] The supply voltage of the lighting circuit 50 may here be greater than or equal to the nominal voltage of the single-phase mains network. For example, it is greater than the nominal voltage of the network during transient overvoltages.

[0138] The lighting circuit 50 preferably comprises more than 50 light-emitting diodes. For example, between 65 and 80 light-emitting diodes 51 are provided.

[0139] The nominal current flowing in each light-emitting diode 51 is low, of the order of 50 to 250 mA, preferably between 50 and 200 mA. Thus, the heating of the light-emitting diodes 51 is limited. The nominal current flowing through each light-emitting diode preferably remains less than 250 mA, preferably less than 240 mA, preferably less than or equal to 200 mA, for example equal to 120 mA. The peak current may be higher during transient overvoltages.

[0140] The resistors 53 connected in series to the light-emitting diodes 51 have the role of dissipating energy in the form of heat and of limiting the current passing through the light-emitting diodes 51.

[0141] Groups of two resistors 53 in parallel can be provided to maintain the operation of the lighting circuit 50 when one of the two resistors in parallel is damaged.

[0142] The total equivalent resistance of all 53 resistors reduces the current in the event of transient overvoltages. The peak current intensity preferably remains below the maximum current intensity that can flow through each light-emitting diode.

[0143] The choice of the total equivalent resistance of all the resistors 53 is a compromise between the robustness of the lighting circuit 50 to overvoltages on the one hand, and its energy efficiency on the other hand.

[0144] Example 1

[0145] The power supply circuit 40 shown in is used and the nominal effective voltage of the mains is equal to 230VAC, which corresponds to a peak voltage of approximately 325V. The output voltage Uout of the power supply circuit 40 has a peak voltage of approximately 320V, or 98% of the peak voltage of the mains. A plurality of resistors 53 are provided distributed between the light-emitting diodes 51 whose equivalent overall resistance is between 500 and 1200 ohms. Here, 35 groups of two resistors 53 of 33 ohms (corresponding to 500mW) can be provided, each arranged in parallel with each other and in series with the light-emitting diodes 51. The equivalent resistance of all the resistors of the lighting circuit 50 is then equal to 577 ohms. The lighting circuit 50 then comprises 75 light-emitting diodes 51. The light-emitting diodes are, for example, Nichia NE2B757GT_B1 or NVSLE21A ® reference diodes.Their nominal direct voltages are given in Table 1.

[0146] The cumulative nominal supply voltage of all the light-emitting diodes is, for example, equal to 210V at a nominal current of 200mA.

[0147] The use of 75 LEDs as described above is suitable when the nominal mains voltage is 230V. This number will be reduced if the nominal mains voltage used is lower than 230V, for example 110VAC.

[0148] In this example, each light-emitting diode 51 is arranged in parallel with a single Zener diode and each Zener diode is arranged in parallel with a single light-emitting diode 51.

[0149] Table 1: Forward voltages of light-emitting diodesReference LEDU F, min (SEEN F, m ax(V)Nichia®NE2B757GT_B12,53,3Seoul®SZ8Y222,63,05Nichia®NVS E21A 2,83,0Nichia®NFSL757 GT 2,43,3Nichia®NVSL219 CT 2,63,4Seoul ®Z5M4-SZ52,553,0

[0150] Example 2

[0151] Alternatively, it is also possible to provide 68 resistors of 33 ohms distributed between the light-emitting diodes in 34 groups of two resistors in parallel. The equivalent resistance of all the resistors of the lighting circuit 50 is then equal to 561 ohms. The lighting circuit 50 then comprises 75 light-emitting diodes 51 of reference Seoul SZ8Y22 ®.

[0152] In this example, each LED is arranged in parallel with a single Zener diode, and each Zener diode is arranged in parallel with a single LED 51. The LEDs in Example 1 (Nichia®) are molded from plastic. Those in Example 2 (Seoul®) are made entirely of ceramic. The difference lies in the possibility of a higher maximum current and better stability in Example 2. For example, the LEDs in Examples 1 and 2 have different maximum current ratings: the Nichia® LEDs in Example 1 have a maximum current of 250mA, and the LED in Example 2 (Seoul®) has a maximum current of 2.0A. Another difference is the luminous efficiency: mid-power LEDs like the one in Example 1 have an improved luminous efficiency that can be greater than 60%.The choice of LEDs depends on maximum heat and maximum input voltage versus higher efficiency and lower stability. Ceramic diodes have greater radiation resistance and longer life, but higher cost.

[0153] Alternatively, it is possible to distribute the resistive components differently depending on the environment and in particular its ability to dissipate the heat produced by the circuit. For example, it is possible to use a single resistor of approximately 560 ohms, for example, or a smaller number of resistors having values ​​greater than 33 ohms, as in the examples given above. It is also possible to use a larger number of resistors having smaller values ​​than the example described above. It is advantageous for the lighting device 1; 2 to have a larger number of resistors of smaller value to allow better dissipation of the thermal energy produced by the Joule effect in these resistors.

[0154] For example, it is possible to provide a number of resistors at least equal to a quarter or half of the number of light-emitting diodes 51, preferably between a quarter of the number of light-emitting diodes and the number of light-emitting diodes.

[0155] Furthermore, it is useful to increase the number of resistors provided in series with the light-emitting diodes in the lighting circuit 50 when it is intended to operate with a less stable mains electricity network, which implies that the variations in the supply voltage of the lighting circuit increase.

[0156] In the example shown in the, each Zener diode 52 of the lighting circuit 50 of the lighting device is connected directly in parallel to a single light-emitting diode 51.

[0157] Alternatively, a so-called Zener diode 52, here each Zener diode, is connected directly in parallel to a set of light-emitting diodes whose number is between 2 and 5.

[0158] Each Zener diode 52 is designed to start conducting electric current in response to an electrical voltage above a threshold value called the breakdown voltage. It acts as a switch controlled by the voltage applied to it.

[0159] Each Zener diode 52 here has a breakdown voltage at least 5% higher than the nominal supply voltage of the light-emitting diode 51, preferably at least 15% higher.

[0160] For example, the nominal supply voltage of each light-emitting diode 51 is between 2.8 and 3.3V and the breakdown voltage of each Zener diode 52 arranged in parallel with a single light-emitting diode 51 is between 3.4 and 3.8V, for example equal to 3.5V.

[0161] Thus, in response to the failure of one of said light-emitting diodes 51, the opening of the lighting circuit 50 at the faulty light-emitting diode 51 causes the application of a voltage greater than or equal to the breakdown voltage across the terminals of the Zener diode 52 arranged in parallel with the faulty light-emitting diode. The corresponding Zener diode 52 becomes conductive and allows current to flow. The Zener diode 52 allows current to bypass the faulty light-emitting diode.

[0162] This allows the lighting circuit 50 to continue to operate, even when one or more diodes fail and open the lighting circuit 50.

[0163] The power supply circuit 30; 40 and the lighting circuit 50 are adapted to withstand without loss of functionality a dose of ionizing radiation greater than 5000 gray (Gy), preferably greater than 10000 Gy, preferably greater than 20000 Gy, preferably greater than 50000 Gy, preferably greater than 100000 Gy, preferably greater than 250 kGy.

[0164] “Resist without loss of functionality” means that the lighting device emits, after irradiation, a luminous flux substantially equal to the luminous flux emitted before irradiation.

[0165] Generally speaking, the lighting device 1; 2 is free from any electrical component particularly sensitive to ionizing radiation.

[0166] In particular, the lighting device 1; 2 is free of transistors, operational amplifiers, switches and any integrated circuits. The power supply circuit is made without a voltage transformer, which avoids the use of conventional voltage transformer coils, the insulating sheath of which is likely to be vulnerable to ionizing radiation and cause a short circuit which would lead to a premature end of life of the power supply circuit.

[0167] Each electrical component used is selected to provide optimized resistance to ionizing radiation.

[0168] Generally, large, bulky electrical components are selected. These are preferably discrete, non-integrated, non-miniaturized electrical components. The lighting device 1; 2 is free of any integrated or miniature electrical component or any component comprising control electronics. In each family of electrical components, resistors, capacitors, diodes, etc., the largest components compatible with their use in the lighting device are chosen.

[0169] Furthermore, the use of organic materials such as plastics, polymers, silicone, is limited. The electrical components of the lighting device 1; 2 are made of materials as insensitive as possible to the effects of ionizing radiation.

[0170] In particular, each light-emitting diode 51 of said plurality of light-emitting diodes 51 comprises a semiconductor element 511 and a phosphor 512 mounted on a support plate 514, as shown for example in the. The semiconductor element 511 emits blue light at a wavelength of approximately 450 nm when passed through by the electric current. The phosphor illuminated by this blue light emits yellow light which mixes with the blue light to give a substantially white light.

[0171] This semiconductor element 511 and the phosphor 512 are or are not covered with an optical lens.

[0172] Preferably, each light-emitting diode 51 is free of an optical lens, as in the example shown in the. The optical lens is in fact generally made of silicone and risks becoming opaque or darkening in response to exposure to ionizing radiation.

[0173] Furthermore, the light emitted by the LED without a lens is less directional than in the presence of the optical lens. In practice, the LED emits in an emission cone with an apex angle equal to 160°; compared to 60 to 120° in the presence of the optical lens.

[0174] Each Zener diode 52 is preferably of the type comprising a housing 521 made of inorganic glass, without the use of plastic or polymer material. Alternatively, the Zener diodes may also comprise a housing made of plastic or polymer material.

[0175] Generally speaking, Zener diodes are power components with relatively large structures that promote material stability. The 52 Zener diode equipped with a 521 glass package also has greater resistance to ionizing radiation than other Zener diodes with a plastic or polymer material package. Zener diodes with a glass-passivated junction are preferably used, as they are stable and robust. Using other types of diodes using a silicone plate and glue may lead to more failures due to a mismatch between the glue and the silicone plate.

[0176] The support board 10, 11 or 20 is a printed circuit board, a schematic sectional view of which is shown in the figure. It comprises a layer of electrically conductive material 12 and a supporting structure 13.

[0177] The layer of electrically conductive material 12 is for example a layer of copper or another metal preferably having an electrical conductivity greater than 20×10 6 S / m at 20°C. It preferably has a thickness greater than 50 micrometers, for example between 50 and 150 micrometers thick, for example 70 micrometers.

[0178] The conductive tracks of the printed circuit are arranged in this layer of conductive material. The conductive tracks are obtained, for example, by photolithography.

[0179] The supporting structure 13 is, for example, in the form of a rectangular plate. It is made of one of the following materials: aluminum, copper, fiberglass-reinforced epoxy resin composite, epoxy resin, ceramic. It is, for example, an aluminum plate. The thickness of the plate forming the supporting structure is, for example, 2 millimeters.

[0180] The supporting structure is advantageously made of a material having high thermal conductivity in order to quickly evacuate heat and reduce the temperature of the light-emitting diodes in order to avoid premature aging thereof. In addition, the heating of the light-emitting diodes 51 is limited thanks to the low current passing through them.

[0181] In the lighting devices 1 and 2 for which the supporting structure is made of an electrically conductive material (aluminum or copper), the printed circuit board further comprises a layer of insulating material 14 interposed between the layer of conductive material 12 and the supporting structure 13. In the example of 1a, the layer of insulating material 14 is bonded to the supporting structure 13 by a layer of glue 15. This layer of glue 15 measures for example between 20 and 50 micrometers in thickness. Here, the term insulating material means an electrically insulating material.

[0182] The layer of insulating material 14 is, for example, a dielectric material made of ceramic, comprising, for example, ceramic fibers. It measures, for example, between 50 and 100 micrometers in thickness.

[0183] The thickness of the insulating material layer and the insulating material used are determined by taking into account a compromise between effective electrical insulation and limited thermal insulation. Indeed, the printed circuit board preferably has heat dissipation properties in order to dissipate the heat produced by the light-emitting diodes 51 and the resistors 53 during the passage of current. The material of the supporting structure therefore preferably has an optimized thermal conductivity, preferably greater than 3 Wm -1 K -1. The thickness of the insulating material layer is greater than 90 µm to avoid failures in the ionizing environment. The thickness of the insulating material layer 14 is for example equal to 100 µm.

[0184] The light-emitting diodes 51, the Zener diodes 52 and the resistors 53 are for example soldered onto the conductive material layer 12. The figure shows generic electrical components M soldered onto the conductive material layer 12 which may be light-emitting diodes 51, Zener diodes 52 or resistors 53.

[0185] As can be seen in the, each light-emitting diode 51 comprises two electrical connection wires 513 connecting the semiconductor element 511 to the layer of conductive material 12 of the printed circuit board forming the support board 10, 11; 20. They are thus electrically connected to the conductive tracks of the printed circuit.

[0186] Alternatively, several layers of conductive material separated by layers of electrically insulating materials may be provided. These layers of conductive material separated by layers of insulating material form a front face of the printed circuit. The layers of insulating material preferably have a thickness greater than 90 µm. The rear face is formed by a layer of metal such as aluminum.

[0187] According to a variant not shown, the lighting circuit described above is a first lighting circuit and the lighting device according to the invention comprises a second lighting circuit connected to said power supply circuit as described above, in parallel with said first lighting circuit.

[0188] The second lighting circuit is similar to the first: it comprises another plurality of light-emitting diodes connected in series, another plurality of Zener diodes each connected in parallel with one or more light-emitting diodes of the other plurality of light-emitting diodes and at least one other resistor connected in series with the other plurality of light-emitting diodes, a cumulative nominal voltage of the other plurality of light-emitting diodes connected in series being adapted to the peak voltage of the alternating current of the single-phase mains network.

[0189] In the case of the embodiment of the, there is provided for example a second lighting module connected to the output of the power supply circuit in parallel with a first lighting module comprising said first lighting circuit. The second lighting module is for example identical to the first lighting module.

[0190] In the case of the embodiment of the, the second lighting circuit is supported by the same support board. The second lighting circuit is for example identical to the first lighting circuit.

[0191] Alternatively, the second lighting circuit differs from the first lighting circuit, for example, in the type of light-emitting diodes used. The light-emitting diodes of the second lighting circuit, for example, emit light of a different color than the light emitted by the light-emitting diodes of the first circuit.

[0192] For example, we can consider the use of light-emitting diodes producing white or yellow light.

[0193] According to one embodiment, the lighting device further comprises a battery (not shown) adapted to be connected to the lighting circuit 50.

[0194] For example, the battery delivers a direct voltage of 120 V.

[0195] In this case, each light-emitting diode 51 is supplied with a voltage lower than its nominal supply voltage and will emit a luminous flux lower than the luminous flux obtained by a power supply with the nominal supply voltage.

[0196] Alternatively, the battery may be adapted to be connected to the lighting circuit 50 so as to power a subset 57 of the light-emitting diodes 51 of the lighting circuit 50 ().

[0197] The number of light-emitting diodes in subassembly 57 is adapted to the direct voltage delivered by the battery.

[0198] In practice, the number of light-emitting diodes 51 of the sub-assembly 57 is determined so that the cumulative nominal supply voltage of the light-emitting diodes of this sub-group 57 is greater than or equal to 80% of the voltage applied to the terminals of the lighting circuit 50, preferably greater than or equal to 90% of the voltage applied to the terminals of the lighting circuit 50. Consequently, the number of light-emitting diodes 51 of the sub-assembly 57 is determined so that the cumulative nominal supply voltage of the light-emitting diodes of this sub-group 57 is greater than or equal to 80%, preferably 85 or 90%, of the DC voltage delivered by the battery.

[0199] Furthermore, the number of light-emitting diodes 51 of the sub-assembly 57 is determined so that the cumulative nominal supply voltage of the light-emitting diodes of this sub-assembly 57 is less than or equal to 120%, preferably 115 or 100%, of the direct voltage delivered by the battery.

[0200] As shown schematically in the, the lighting circuit 50 then comprises for this purpose an intermediate input C3 adapted to receive the direct current Ubatt delivered by the battery, the intermediate input C3 being located between two light-emitting diodes 51 so as to supply said subassembly 57 by bypassing the rest of the light-emitting diodes 51.

[0201] Furthermore, the power supply circuit 30 or 40 and the lighting circuit 50 of the lighting device 1 or 2 do not have harmonic distortion. The power factor of the lighting device may be greater than 85%, for example between 90 and 99%.

[0202] Irradiation tests conducted by the applicant have shown the resistance of the lighting device according to the invention to irradiation by ionizing radiation.

[0203] Lighting device 1 has been tested.

[0204] The power supply module comprising the power supply circuit 30 and the power supply module comprising the power supply circuit 40 were irradiated as well as the lighting module 50 produced with different commercial models of light-emitting diodes 51.

[0205] The irradiation conditions were as follows.

[0206] The power supply and lighting modules were exposed 1 m from the radiation source to an X-ray field of up to 3 MeV.

[0207] The tests are carried out under normal conditions of temperature, pressure and humidity. Irradiation is interrupted 10 times to respect the levels and check the operation of certain modules at each irradiation dose level.

[0208] Reference dosimeters (Alanine pellets) are placed at several points on the equipment in order to determine the dose mapping with an expanded relative uncertainty of 3.4%.

[0209] The temperature, pressure and humidity conditions during all the tests were such that:

[0210] • 18.4 °C < T < 18.6 °C

[0211] • 995.8 hPa < P < 1014.5 hPa

[0212] • 64.1% < H < 70.0%.

[0213] The results are as follows.

[0214] The power supply module 1A comprising the power supply circuit 30 still exhibits fault-free operation after an actual absorbed dose of 6040 Gy corresponding to a dose emitted by the X-ray source of 10000 Gy. The irradiation was carried out on two power supply modules not connected to the AC mains network and on two power supply modules connected to the network. The results are identical for the four modules conforming to the first embodiment.

[0215] The power supply module 1A comprising the power supply circuit 40 still exhibits fault-free operation after an actual absorbed dose of 6040 Gy corresponding to a dose emitted by the X-ray source of 10000 Gy. The irradiation was carried out on three power supply modules not connected to the AC mains network and on a fourth power supply module connected to the network. The results are identical for the four power supply modules.

[0216] The lighting module 1B comprising the lighting circuit 50 in accordance with the embodiment described above still exhibits fault-free operation after an actual absorbed dose of approximately 8.8 kiloGray (kGy) corresponding to a dose emitted by the X-ray source of 10,000 Gy. The irradiation was carried out on different unpowered lighting modules, produced with different models of light-emitting diodes: a lighting module equipped with 75 Nichia® light-emitting diodes of reference NVS E21A; a lighting module equipped with 75 Nichia® light-emitting diodes of reference NFSL757 GT; a lighting module equipped with 75 Nichia® light-emitting diodes of reference NVSL219 CT; a lighting module equipped with 75 Samsung® light-emitting diodes of reference LM281B Plus; a lighting module equipped with 75 Seoul light-emitting diodes ® reference Z5M4-SZ5; a lighting module equipped with 75 Seoul ® light-emitting diodes reference Y22.The Zener diodes used here are reference BZT55C6V6, voltage 3.6V produced by Taiwan Semiconductor. The resistors of the power supply circuit are 33 Ohm resistors, reference 33RCRCW120633ROFKEAHP, marketed by Vishay®. The resistors of the lighting circuit are 20 Ohm resistors, reference 20RCMB02070X2009GB200, marketed by Vishay®. After irradiation, each lighting module tested is connected to a power supply module powered by the mains and the operation of the light-emitting diodes is checked. All the lighting modules tested show a fault-free operation after the actual absorbed dose of 8.8 kGy.

[0217] A dose of 8.8 kGy is considered to correspond to the maximum dose of ionizing radiation received by equipment spending 10 years in a highly irradiated area of ​​a reactor building of a nuclear power plant. This area is commonly referred to as the "inaccessible zone" of the reactor building.

[0218] The lighting device according to the invention is therefore particularly suitable for use in this context.

[0219] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0220] The use of the verb "comprise", "comprise" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

[0221] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Lighting device (1; 2) for illuminating a room exposed to ionizing radiation, comprising:at least one support card (10, 11; 20),a power supply circuit (30; 40) mounted on the at least one support card (10, 11; 20), the power supply circuit (30; 40) having an input (E1) for receiving an alternating current from a mains electricity network and an output (S1) adapted to deliver a direct current in response to the reception of the alternating current, in which the direct current delivered by said power supply circuit (30; 40) is a pulsed direct current which has a peak voltage of between 85 and 100% of the peak voltage of the alternating current of the mains electricity network received at the input of the power supply circuit (30; 40), the power supply circuit (30; 40) comprising a diode bridge (33), anda lighting circuit (50) mounted on the at least a support card (11;20) and connected to the output (S1) of the power supply circuit, the lighting circuit (50) comprising:a plurality of light-emitting diodes (51) connected in series,a plurality of Zener diodes (52), each connected directly in parallel to one or more light-emitting diodes (51) of the plurality of light-emitting diodes (51) andat least one resistor (53) connected in series with the plurality of light-emitting diodes (51),wherein a cumulative nominal supply voltage of the plurality of light-emitting diodes connected in series is adapted to a nominal voltage of the mains electricity network, the lighting device being free of transistors.; The lighting device of claim 1, wherein the cumulative nominal supply voltage of the plurality of light emitting diodes is greater than or equal to 80% of the nominal effective voltage of the mains electricity network and less than or equal to 120% of the nominal effective voltage of the mains electricity network. Lighting device according to one of claims 1 to 2, in which the power supply circuit (30; 40) is intended to be connected to a single-phase mains electricity network having a nominal effective voltage greater than 110VAC. Device according to one of claims 1 to 3, in which the power supply circuit (30; 40) and the lighting circuit (50) are adapted to withstand without loss of functionality a dose of ionizing radiation greater than or equal to 8.8 kilogray. Lighting device according to one of claims 1 to 4, wherein said power supply circuit (30) consists solely of the diode bridge (33) and one or more electrical components selected from: a fuse (34) and resistors (35, 36). Lighting device according to one of claims 1 to 4, wherein said power supply circuit (40) comprises an overvoltage protection circuit (43), the overvoltage protection circuit (43) being solely made up of one or more electrical components selected from: one or more coils of conductive wire (431), one or more capacitors (436A, 436B), and one or more varistors (435A, 435B). Lighting device according to one of claims 1 to 6, wherein the at least one support card (10, 11; 20) is a printed circuit card comprising a layer of electrically conductive material (12) and a supporting structure (13), wherein the supporting structure (13) is made of one or more materials chosen from: aluminum, copper, fiberglass-reinforced epoxy resin composite, epoxy resin, ceramic. A lighting device according to one of claims 1 to 7, wherein a said light-emitting diode (51) of said plurality of light-emitting diodes (51) comprises a semiconductor element (511) and a phosphor (512), not covered with an optical lens. Lighting device according to one of claims 1 to 8, wherein a said light-emitting diode (51) of said plurality of light-emitting diodes (51) has a nominal forward voltage greater than 2V, preferably between 2.7 and 3V for a current of 200 mA, and wherein the lighting circuit comprises more than 50 light-emitting diodes (51). Lighting device according to one of claims 1 to 9, wherein a said Zener diode (52) is of the type comprising an inorganic glass housing, without the use of plastic material, polymer material or silicone. Lighting device according to one of claims 1 to 10, wherein a said Zener diode (52) is connected directly in parallel to a said light-emitting diode (51). A lighting device according to claim 11, wherein each Zener diode (52) has a breakdown voltage at least 5% higher than the nominal forward voltage of the light emitting diode, preferably at least 15% higher. Lighting device according to one of claims 1 to 12, wherein said at least one resistor connected in series with said plurality of light-emitting diodes (51) comprises a plurality of resistors (53) distributed between the light-emitting diodes (51) of said plurality of light-emitting diodes (51). Lighting device according to one of claims 1 to 13, wherein the power supply circuit (30; 40) is implemented in the form of a power supply module (1A) comprising a first support board (10) and the lighting circuit (50) is implemented in the form of a lighting module (1B) comprising a second support board (11), the lighting module (1B) comprising a power supply input (50A) connected to the output (S1) of the power supply circuit (30; 40) for powering the lighting circuit (50). Lighting device according to one of claims 1 to 14, further comprising a battery adapted to be connected to the lighting circuit so as to power said plurality of light-emitting diodes (51) or a sub-assembly (57) of the plurality of light-emitting diodes (51), the sub-assembly (57) comprising a number of light-emitting diodes (51) strictly less than the total number of light-emitting diodes (51) of said plurality of light-emitting diodes (51). Lighting device according to claim 15, wherein the lighting circuit (50) comprises an intermediate input (55) adapted to receive the direct current delivered by the battery, the intermediate input (55) being connected to an intermediate point of said plurality of light-emitting diodes (51) to power the sub-assembly (57) of the plurality of light-emitting diodes (51).

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