FR2595882A1 - Mains adaptor unit with multiple protection - Google Patents

Abstract

Double mains adaptor unit intended for connecting up and protecting two distinct appliances, connected up to the network outlets A and B. The protection obtained results from the insertion, into the body of the plug, of various components such as earth bypass capacitors 1 and 2 as well as of a varistor 6 connected directly in parallel with the pins 3 and 4. The invention is furthermore characterised in that the plug 23, fastened on to the casing 25 by clamping, is provided in order to be able to perform a 180 DEG rotation about its axis, with positionings at 0, 90 and 180 DEG . One individual means of interference suppression per path is ensured by the inductance coils 9 and 10, by a capacitor 11 in parallel with the outputs A and B, moreover, so as to limit the possible couplings between the outlets A and B, and by common earthing, an inductance 15 and 16 has been inserted on each wire connecting the earth jack 13, of each outlet A and B to the earth pin of the socket 5. Protection from excessive currents is ensured on each path by a thermal circuit breaker with reset 8.

Description

The number of electrical or electronic devices supplied on low voltage networks is constantly increasing and
the observation could have been made, that the disturbances conveyed by these networks had two distinct origins: one giving rise to transient overvoltages, the other to electromagnetic parasites.

 Transient overvoltages can, in some cases, reach several KV, for times ranging from a few microseconds to a few milllseconds. The incidences of these transient voltages are very numerous and can be at the origin of the destruction of the apparatuses connected on the network and, mainly, if they comprise electronic, loglques or other systems.

 In the absence of destruction, these transient overvoltages can cause erratic operation of the connected equipment, inadvertently trigger power circuits or cause premature wear of the equipment.

 The origin of transient overvoltages is either atmospheric, or resulting from untimely or voluntary operations, such as the destruction of a fuse or the connection to the network of inductive circuits.

 Electromagnetic interference does not develop high voltages on networks and rarely reaches a volt; on the other hand, their spectrum extending from a few KHz to a few MHz, disturbances of this kind are very often repetitive, even permanent, and these voltages act on electronic circuits, without destroying them, but by distorting the information stored or during storage.

Considering what is developed above, it is obvious * that a protection, to be effective, will have to be operated, simultaneously against transient overvoltages and on electromagnetic parasites. This protection must be made as close as possible to the connection point on the network, for the following reasons
The clipping of transient overvoltages, due to the specificity of the latter, which may last only a few, it is therefore essential that the absorbent element has a very fast response time, and a high absorption capacity. Zinc oxide varistors meet these criteria.

 However, in order for the action of the varistor to be effective, it must in no case be connected to the network via connections behaving like a self, and would have the effect of delaying the function of this varistor, the latter being liable to react only too late, with respect to the speed of the logic circuits, for example.

 With regard to electromagnetic interference, their attenuation must be such that the remaining balance cannot have an unfortunate influence on the apparatus; beyond the need for a direct connection to the network.

 Disturbances of this type are either common mode (asymmetric) or differential mode (symmetrical).

 For the attenuation of asymmetric voltages, the filter will therefore comprise, according to the well known principle, inductive elements connected in series, capacitive elements connected in parallel, and bypass elements mounted between network and earth wires.

The components of noise filters are therefore
inductors and capacitors, the latter particularly
vulnerable to transient overvoltages.

 The object of the present invention is to provide a device allowing both the clipping of transient overvoltages, and acting simultaneously as a noise filter.

 Assembly comprising a box, fitted with a plug, according to the chosen standard, but comprising, on the other face, the possibility of simultaneously connecting two devices, respectively on the sockets A and B, while ensuring the same protection and avoiding possible parasitic couplings.

 The basic assembly consists of a noise filter, comprising two inductance coils (9 and 10) one per channel, earth derivation capacitors (1 and 2), of value normally included, depending on the uses, between 1 and 30 nF, a capacitor (11) with a capacity of the order of 0.05 to 0.5 uF, in parallel on the use outputs (12 and 14), the network being connected by pins ( 3 and 4). In parallel on these two pins is connected, directly, the varistor (6), intended for the absorption of transient overvoltages.

The two sockets A and B are integral with the cover (26) shown in Figure 2 PI 2/2. The schematic diagram is shown on Plate 1/2. This diagram highlights the use of a common trunk comprising the socket outlet of Figure 1 (23)
PL 2/2. This sheet contains the components identified from 1 to 6, it is fixed to the housing (25) which, in the invention, is integral with the housing (26).

 The invention further provides that the socket (23) is clamped on the housing (25) and that it can rotate 1800 around its axis, in order to make it possible to use the assembly in hard to reach places.

 On the conductor connecting the pins or earth contacts (13) to the contact (15), two protective chokes (15 and 16) have been inserted, intended to limit the crosstalk phenomena as well as the transmission of the disturbances brought about or generated by common grounding, these inductors (15 and 16) may consist of a winding of a few turns on a ferrite core.

 The assembly described has the property of providing common protection by the varistor (6) against transient overvoltages in the network, and interference protection, also common, provided by the bypass capacitor to ground (1 and 2).

 The two separate channels A and B include filtering specific to each channel, the values of the inductive components (9 and 10) were not mentioned, because they can be different from one channel to another, and also according to , for example, current flowing through each channel.

 FIG. 2, of plate 2/2, highlights, on each channel, the safety device (8), of diagram 2, which, as shown in FIG. 2 (PI 2/2), is a small thermal circuit breaker, with reset, inserted on the phase wire, and calibrated according to the admissible current in each channel.

Claims (8)

1- Power adapter block, with multiple protections, intended for  connection of two devices using the same socket  network, characterized in that it includes a clipping device  transient overvoltage and interference filtering, intended  to provide the same protection individually and to avoid  parasitic couplings, if any, between the two sockets,  all of these elements being incorporated in a housing,  which is attached to the plug (23), intended for connection  on the network; the sockets A and B being integral with the face  front of the case. 2- AC adapter block according to claim 1, characterized  in that the interference filtering device comprises,  for each channel, 2 inductors (9 and 10), a condensa  tor (11), in parallel on the use outputs (12 and  14), as well as two ground bypass capacitors  (1 and 2) forming part of the common core, the network being connected  by pins (3 and 4) and, in that the clipping device  transient overvoltages consists of a varistor  (6), part of the common core, connected in parallel  on the two pins (3 and 4). 3- adapter block according to claims 1 and 2, characterized  in that the components of the common core are enclosed  in the male plug (23), which is itself fixed on  the housing (25), which is integral with the cover (26). 4- Adapter block according to any one of the claims  previous, characterized in that the plug (23) is mounted  by clamping on the housing (25) and, in that it is susceptible  to turn 1800 around its axis. 5- Adapter block according to any one of the claims  previous, characterized in that two inductors are inserted  (15 and 16) on the conductor connecting the pins (13) of each  taken at socket or earth contacts (5), plug  (23). 6- Adapter block according to the preceding claim, characterized  in that each of the inductors (15 and 16) is made up  by winding a few turns on a ferrite core. 7- Power adapter block according to any one of the claims  tions above, characterized in that it comprises, on each  track, a safety device (8). 8- adapter block according to the preceding claim, characterized  in that the safety device consists of a circuit breaker  reset thermal calibrator according to the current  admissible in each channel.