(19) TZZ ¥_T

(11) EP 2 589 973 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.: 08.05.2013 Bulletin 2013/19 G01R 31/02 (2006.01) G01R 31/28 (2006.01) H02H 3/16 (2006.01) D06F 39/00 (2006.01) (21) Application number: 11187665.2

(22) Date of filing: 03.11.2011

(84) Designated Contracting States: • Driussi, Paolo AL AT BE BG CH CY CZ DE DK EE ES FI FR GB 33080 Porcia (PN) (IT) GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO •Lorenzi,Marco PL PT RO RS SE SI SK SM TR 33080 Porcia (PN) (IT) Designated Extension States: • Dorigo, Hubert BA ME 33080 Porcia (PN) (IT)

(71) Applicant: Electrolux Home Products Corporation (74) Representative: Maccalli, Marco et al N.V. Maccalli & Pezzoli S.r.l. 1130 Brussel (BE) Via Settembrini 40 20124 Milano (IT) (72) Inventors: • Cecco, Alessandro 33080 Porcia (PN) (IT)

(54) Ground power leakage detection for peripheral printed circuit boards

(57) The present invention relates to an electric ap- board (220m) comprises a detection device(R SENSE, pliance (100) comprising an electric load(225), and a T1SENSE,T2SENSE) for detecting a dispersion of electric printed circuit board assembly(115) for electronically power towards ground of the electric load (225) and/or managing the electric appliance (100); the printed circuit of the slave printed circuit board (220s) when the oper- board assembly comprises a slave printed circuit board ative electric power is not provided to said slave printed (220s) operatively associated with the electric load (225) circuit board (220s), and for providing, in response to the for driving it, and a master printed circuit board (220m) detecting, a control parameter indicative of the dispersion operatively associated with the slave printed circuit board of electric power towards ground. The master printed cir- (220s) and arranged for receiving an electric power sup- cuit board (220m) further comprises a control unit (250) ply (L,N) of the electric appliance and for selectively pro- configured for receiving the control parameter, compar- viding/stoppingthe provision ofan operative electric pow- ing the control parameter to a preset threshold value or er to the slave printed circuit board (220s) for energiza- range of values, and enabling provision of the operative tion/de-energization thereof. The master printed circuit electric power to the slave printed circuit board(220s) according to a result of such comparison. EP 2 589 973 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 2 589 973 A1 2

Description and the electric resistor. [0008] In such conditions, when the electric resistor is Field of the invention energized, an undesired flow of electric current (leakage current), may leak from, e.g., the AC electric power sup- [0001] The present invention generally relates to elec- 5 ply and the ground, at which the electric resistor case is tric appliances, such as washing machines, washers/dry- typically kept. ers, dryers, dishwashers, refrigerators, ovens, both for [0009] The dispersion of electric power towards domestic and professional use. More particularly, the ground is to be avoided, since in case the AC distribution present invention relates to detection of electrical faults, network in the user premises where the electric appliance such as power dispersion towards earth or ground, in 10 is installed is properly protected, the protection devices such electric appliances. intervene and cause the de-energization of all or at least sectionsof the userpremises; even worse,when no prop- Background of the invention er protection exists, the risk of electric shock for the user is very high. [0002] Each electric household and professional ap- 15 [0010] Some solutions known in the art make use of a pliance (hereinafter, appliance, for the sake of concise- substantially common approach according to which fault ness) comprises various electric, electro-mechanical of the insulator material is tried to be prevented by and/or electro-hydraulic components that need to be pre-emptively acting on one or more specific parameters properly powered for performing specific functionalities identified as being among the most important ones to of the appliance, as well as electronic components (such 20 determine the fault. For example, being an uncontrolled as dedicated and/or shared printed circuit boards) for over-temperature of the electric resistor a possible cause powering and/or driving such electric, electro-mechani- of physical breakage or crack of the insulator material or cal and/or electro-hydraulic components (the latter thus of an at least partial detaching thereof from the electric acting as corresponding electric loads). resistor, many appliances are provided with overheating [0003] For example, a class of appliances make use 25 protection circuits for monitoring a temperature of the of treatment fluids that need to be heated during the ap- heating element or a temperature of the treatment fluid pliance operation for accomplishing the intended tasks, and aborting the operation of the appliance (possibly, such as washing and/or drying of laundry or dishware. displaying a proper error code) in case the monitored [0004] For this reason, such appliances are usually temperature rises a critical temperature. provided with one or more electric loads for heating the 30 [0011] Another solution is disclosed in EP 0 677 908 treatment fluids (heating elements), which are able to A2, which generally relates to an apparatus for automat- convert electric energy into heat to be released to the ically coupling an internal ground of an appliance to an treatment fluid to heat it up. external ground. Such document also discloses an ap- [0005] In many appliances, the heating element com- paratus for automatically detecting a leakage current, prises an electric resistor that by Joule effect generates 35 comprising a power supply for supplying an AC input volt- heat from an electric current flowing therethrough; the age to an electric load of the appliance, switching means electric resistor is encased in a case of conductive ma- coupled between the electric load and the power supply, terial with interposition of an insulator material, thereby ground connection means for automatically coupling the the electric resistor is not in electrical contact with, i.e. is internal ground of the appliance to a line of the power insulated from the treatment fluid to be heated. When the 40 supply, current sensing means coupled between the in- treatment fluid has to be heated, line and neutral poten- ternal ground and said line for detecting a current flowing tials of an AC electric power supply are fed to respective therethrough to generate a current detection signal when terminals of the electric resistor (for example, by closing the current is greater than a predetermined value, and proper switching elements) for allowing the latter to be switch drive means for generating, in response to the energized. 45 current detection signal, a switch drive signal to separate [0006] As known, the electric loads may be affected the power supply from the electric load. by phenomena of dispersion of electric power towards earth or ground, which apart from increasing the power Summary of invention consumption, may pose safety problems. [0007] Considering for example the case of heating el- 50 [0012] The Applicant has realized that the known so- ements for heating treatment fluids, insulation faults may lutions are not satisfactory for modern technological re- affect the insulator material that insulates the electric re- quirements. sistor from the case, as a result of production defects or [0013] In particular, according to the Applicant, the ap- as a consequence of usage wear (particularly for wash- proach providing overheating protection circuits does not er-dryers, whose operation cause the electric resistors 55 protect the user and/or the appliance from dispersion of to be subjected to significant mechanical stress that may electric power towards ground of the heating element, impair the electric insulation), thereby originating low re- but at most provisionally avoids that the insulator material sistance paths or even a short-circuit between the case of the heating element breaks or cracks because of an

2 3 EP 2 589 973 A1 4 excessive thermal stress. Moreover, such an approach printed circuit board and arranged for receiving an elec- is not effective for protecting the user/appliance against tric power supply of the electric appliance (for example, dispersions of other electric loads present in the appli- through line and neutral conductors) and for selectively ance (e.g. motors, pumps, and the like). providing/stopping the provision of an operative electric [0014] As far as EP 0 677 908 A2 is concerned, the 5 power to the slave printed circuit board for energiza- Applicantbelieves that the solutiondisclosed insuch doc- tion/de-energization thereof (and hence, for energiza- ument is not efficient in terms of safety, since it allows tion/de-energization of the electric load). detecting the leakage current only after a certain time [0021] The master printed circuit board comprises a period the electric power supply has been coupled to the detection device (for example, an electric sensing resis- electric load, as well as in terms of power wastes. 10 tor) for detecting a dispersion of electric power towards [0015] Moreover, suchsolution checksif a leakage cur- ground of the electric load and/or of the slave printed rent exists between the electric power supply and ground circuit board when the operative electric power (i.e. the without distinguishing the origin of such leakage current, whole power necessary to the slave printed board for thereby making the tracing of the failure cause of the completely and correctly performing its functions, and in appliance difficult. 15 particular for providing to the electric load the electric [0016] Finally, the disclosed solution, having a high cir- power necessary to the latter for completely and correctly cuit complexity, is not easy to implement in modern ap- performing its functions) is not provided to said slave pliances wherein the higher and higher number of func- printed circuit board, and for providing, in response to tions for the same, or even lower, space occupation the detecting, a control parameter ( e.g., voltage, current, makes features like circuit simplicity and low-component 20 electric power and the like) indicative of the dispersion circuits mandatory. of electric power towards ground. The master printed cir- [0017] The Applicant has tackled the problem of de- cuit board comprises also a control unit (for example, a vising a satisfactory solution able to overcome the microcontroller) configured for receiving the control pa- above-discussed drawbacks. rameter, comparing the control parameter to a preset [0018] The Applicant has found that by providing op- 25 threshold value or range of values, and enabling provi- erative electric power (i.e. the whole electric power nec- sion of the operative electric power to the slave printed essary for performing its functions) to a slave printed cir- circuit board according to a result of such comparison. cuit board and hence to an electric load powered by the [0022] Preferably, the preset threshold value or range slave printed circuit board only if a master printed circuit of values are preset ( e.g., by the microcontroller) accord- board who power-supplies the slave printed circuit board 30 ing to a value of a chosen electric parametere.g ( . the evaluates that a power dispersion towards ground is not amplitude of the voltage provided by the electric power present or is low, it is possible to ensure the electrical supply, which value may be inputted by the user for ex- safety of the appliance comprising such load and boards. ample by a suitable input device, or which may be for [0019] In other words, the Applicant has found that example detected by the master printed circuit board it- electrical safety of an appliance, in relation to the power 35 self, for example by a suitable detecting circuit comprised dispersion towards ground of one of its electric loads in the board). Moreover, the preset threshold value or (and/or slave printed circuit boards), may be ensured if, range of values may be ( e.g., automatically) updated ac- before providing the whole power supply (or operative cording to any proper criterion (such as according to var- electric power) to such slave printed circuit board, the iations of the chosen electric parameter, for example the possible power dispersion towards ground of the electric 40 value of the amplitude of the voltage provided by the elec- load (and/or of the slave printed circuit board power-sup- tric power supply, measured by the master printed circuit plying the electric load) is evaluated/detected, and the board). operative electric power is supplied to such slave printed [0023] According to an embodiment of the present in- circuit board (and hence to the electric load) only if the vention, the control unit may be either configured for en- evaluated/detected power dispersion towards ground is 45 abling provision of the operative electric power to the not present or is low. slave printed circuit board only if the control parameter [0020] The solution according to one or more embod- is within the preset range of values, or the control unit iments of the present invention relates to an electric ap- may be configured for enabling provision of the operative pliance (for example, a laundry washing machine, a laun- electric power to the slave printed circuit board only if the dry washer/dryer, a laundry dryer, a dishwasher, a oven, 50 control parameter is outside a preset range of values. a refrigerator, or the like). The electric appliance com- [0024] According to another embodiment of the prises an electric load (e.g, one or more electric heating present invention, the control unit may be either config- elements, a motor, a pump, and the like), and a printed ured for enabling provision of the operative electric power circuit board assembly for electronically managing the to the slave printed circuit board only if the control pa- electric appliance. The printed circuit board assembly 55 rameter has a value above the preset threshold value, comprises a slave printed circuit board operatively asso- or the control unit may be configured for enabling provi- ciated with the electric load for driving it, and a master sion of the operative electric power to the slave printed printed circuit board operatively associated with the slave circuit board only if the control parameter has a value

3 5 EP 2 589 973 A1 6 below the preset threshold value. er, a case for housing the at least one electric resistor [0025] Preferably, the master printed circuit board (with the case that is preferably connected to the ground comprises a first switching element for connecting/dis- of the electric appliance), and an insulating coating be- connecting a first conductor of the electric power supply tween the at least one electric resistor and the case for to a first terminal of the slave printed circuit board, and 5 electrically insulating the at least one electric resistor the slave printed circuit board comprises a second from the case. The detection device may be configured switching element for connecting/disconnecting a sec- for detecting the dispersion of electric power towards ond conductor of the electric power supply to a second ground through the insulating coating for checking insu- terminal of the slave printed circuit board; in this way, the lation degree thereof. control unit may enable/ disable provision of the operative 10 [0033] Without losing of generality, the electric appli- electricpower tothe slave printed circuitboard by closing/ ance may be a laundry washing machine, a laundry opening the first switching element and the second washer/dryer, a laundry dryer, a dishwasher, a oven, or switching element thereby connecting/ disconnecting the a refrigerator. first conductor and the second conductor to the first ter- [0034] Thanks to the present invention, the dispersion minal and the second terminal, respectively, of the slave 15 of electric power towards ground affecting a selected printed circuit board, and the detection device may detect electric load (and/or a selected slave printed circuit the dispersion of electric power towards ground and pro- board, e.g. the slave printed circuit board associated with vide the control parameter when the first switching ele- the selected electric load) is precisely and easily detected ment and the second switching element are both opened. as soon as it takes place, but always before the operative [0026] Advantageously, the detection device is config- 20 electric power is fed to the electric load (and/or to the ured for being run through by a leakage current indicative slave printed circuit board). Therefore, the present inven- of the dispersion of electric power towards ground. tion prevents electric power from dispersing towards [0027] In a preferred but not limiting embodiment, the ground when the electric load is energized, which avoids detection device is placed between a first terminal of the to the user annoyances deriving by de- energization of all first switching element connected to a first portion of the 25 or at least sections of the user premises wherein the ap- first conductor and a second terminal of the first switching pliance is installed due to intervention of protection de- element connected to a second portion of the first con- vices, as well as makes the user safe from electric shock ductor;in this way,the detection devicecan be configured when no proper protection devices exist. such as to detect the leakage current flowing through the [0035] Moreover, the present invention allows tracing first portion of the first conductor, the detection device, 30 the cause of the failure, since the origin of the dispersion the second portion of the first conductor, the electric load, of electric power towards ground is univocally associated and a ground of the electric appliance. to the selected electric load. [0028] Advantageously, the detection device compris- es a sensing resistor having a first terminal and a second Brief description of the annexed drawings terminal connected to the first terminal and the second 35 terminal of the first switching element, respectively. [0036] These and other features and advantages of [0029] The control parameter may be a current, an the present invention will be made apparent by the fol- electric power, a photon intensity, or a voltage depending lowing description of some exemplary and non limitative on the dispersion of electric power towards ground de- embodiments thereof; for its better intelligibility, the fol- tected by the detection device. 40 lowing description should be read making reference to [0030] In an embodiment of the present invention, the the attached drawings, wherein: control unit is connected to the detection device for re- ceiving said voltage depending on the dispersion of elec- Figure 1 schematically shows an electric appliance tric power towards ground, and is configured to compare wherein the solution according to one or more em- said voltage to a voltage threshold value or range of value 45 bodiments of the present invention may be applied, corresponding to the preset threshold value or range of and values. Figure 2 schematically shows in terms of functional [0031] In a non limiting arrangement, the electric load blocks the solution according to an embodiment of comprises at least one electric heating element for heat- the present invention. ing treatment fluids during heating operations of the elec- 50 tric appliance; for example, such at least one electric Detaileddescription of preferred embodiments of the heating element may be configured for being powered invention by the operative electric power and for generating heat therefrom. [0037] Referring now to the drawings, Figure 1 sche- [0032] Such at least one electric heating element may 55 matically shows an electric appliance or, shortly, appli- comprise at least one electric resistor connected be- ance 100, for example for domestic use (i.e., a household tween a first terminal and a second terminal of the electric appliance), wherein the solution according to one or more heating element for receiving the operative electric pow- embodiments of the present invention may be applied.

4 7 EP 2 589 973 A1 8

Theappliance 100 mayfor example be a laundrywashing [0043] The slave PCB 220s is associated with (i.e., it machine, a laundry washer/dryer or a laundry dryer, e.g. drives, controls, and/or monitors) an electric load225, a tumble dryer (as generically illustrated in the figure, and which may comprise one or more heating elements, like to which reference will be made in the following by way washing liquid heating resistors, or for example a motor, of a non-limiting example only), but the principle of the 5 a pump, a compressor, etc. In the embodiment illustrated present invention also apply to dishwashers, ovens, re- inthe enclosedfigures the electricload 225 isfor example frigerators and any other appliance generally equipped an electric heating element ( e.g. an electric resistor). Ad- with electric loads that, powered by an electric power vantageously the master PCB 220m, which receives the supply, could be intrinsically subjected to phenomena of electric power supply (typically, an AC electric power sup- dispersion of electric power towards ground. 10 ply, not shown) of the appliance, preferably selectively [0038] The appliance 100 preferably comprises a sub- enables a selected slave PCB (the slave PCB 220s, in stantially parallepiped-shaped cabinet 105, which en- the case at issue) for driving (i.e. providing/stopping an closes an inner compartment 107 apt to contain items to operative electric power, such as an operative electric be treated (such as laundry to be washed and/or dried), current) to the electric load 225 (a heating element in the and accessible through an access door 110 (shown in 15 example of enclosed drawings) for energization/de-en- an open configuration) provided preferably on a front ergization thereof. panel of the cabinet 105 for loading/unloading the items. [0044] In the illustrated example the term "operative [0039] The inner compartment 107 of the household electric power" is intended to identify the electric power appliance 100 also preferably accommodates, not visible fed to the slave PCB 220s and hence to the electric load in such figure, electro-mechanical components, such as 20 225 for energization/de-energization thereof, and there- motor for causing a rotating drum to rotate, or solenoid fore the whole electric power necessary to the electric valves, as well as electric components, such as heating load for correctly and completely performing its functions elements for causing treatment fluids ( e.g., water-based (e.g. heatingin thecase of an electric heater), as opposed cleaning solutions, rinsing water and/or air) to be heated, to the dispersion of electric power towards ground and electro-hydraulic components, such as valves for 25 through the slave PCB 220s and/or the electric load 225, causing the treatment fluids to be loaded and discharged which in the example at issue is in the form of a current during the washing/drying cycle. leaking through the slave PCB 220s (and the electric load [0040] The inner compartment 107 of the appliance 225) or leakagecurrent, whenno operative electric power 100 further accommodates electronic components 115 is provided to the slave PCB 220s (and hence to the (schematically represented by a generic rectangle hav- 30 electric load 225). ing dashed perimeter lines) for causing both the elec- [0045] If the electric load 225 is a heating element, it tro-mechanical components, the electric components is able to generate heat (from electric energy, such as andthe electro- hydraulic components to be electronically an electric current) to be released to the treatment fluid, controlled, driven (e.g., powered or energized) and/or thereby heating it up to a desired temperature (typically monitored (thus acting as corresponding electric loads). 35 depending on preferred appliance settings). [0041] Modern electronic components 115 are typical- [0046] In the embodiment illustrated in enclosed fig- ly in the form of a printed circuit board (or PCB) assembly, ures, preferably, the heating element comprises one (as whose implementation according to an embodiment of in the shown example) or more electric resistors 230 that, the present invention is schematically shown in terms of by Joule effect, allows generating heat from the operative functional blocks in Figure 2. The PCB assembly 115 is 40 electric power fed thereto by the slave PCB220s; the advantageously configured for electronically managing electric resistor 230 is encased in a case 235 of conduc- theoperation of theappliance, such as controlling,driving tive material (typically grounded at a reference voltage, and/or monitoring the various electric loads; however, for e.g., 0V, or ground), with interposition (partial or total, as the sake of conciseness and clarity, in the following only exemplarily shown in the figure) of an insulator material functional blocks of the PCB assembly 115 directly in- 45 240 apt to prevent the electric resistor 230 from being in volved in heating operations by which the treatment fluid electrical contact with the treatment fluid to be heated. is properly heated will be considered. [0047] In operation, the electric load 225 can be ener- [0042] In this regard, the PCB assembly 115 may com- gized by feeding it with the required operative electric prise twoor more, e.g.a pluralityof PCBs; advantageous- power by line and neutral potentials of the AC electric ly, the PCB assembly 115 comprises PCBs 220s (one, 50 powersupply, preferably through correspondingline con- in the example in the figure) acting as "slave" PCBs ( i.e., ductor L and neutral conductor N. Advantageously, the peripheral or secondary PCBs whose operation is re- line conductor L and the neutral conductor N can be con- quested only if there is a need for the specific operations nected to/disconnected from terminals of other electric, they are designed to perform), and further PCBs 220m electronic and/or electro-mechanic components (not (one, in the example in the figure) acting as "master" 55 shown) of (or associated with) the slave PCB220s. In PCBs (i.e., main or primary PCBs coordinating the slave the example herein disclosed, the line conductor L and PCBs and activating them individually, for example the neutral conductor N can be connected to/ disconnect- based on a proper communication protocol). ed from a terminal T1LOAD and another terminal T2LOAD

5 9 EP 2 589 973 A1 10 of the electric load 225 (and hence to/from respective may be configured for enabling provision of the operative terminals of the electric resistor 230), respectively, pref- electric power to the slave PCB 220s (hence to the elec- erably by means of corresponding electrically-operated tric load 225) only if the control parameter is within the switching elements ( e.g.,relays) 245Land 245N mechan- preset range. ically supported by and electrically connected to the mas- 5 [0052] Without losingof generality,alternatively the mi- ter PCB 120m and the slave PCB 120s, respectively (al- crocontroller 250 may be configured for enabling provi- beit other arrangements of the relays 245L and 245N are sion of the operative electric power to the electric load possible without departing from the principles of the 225 only if the control parameter is outside the preset present invention). range. In another embodiment, the microcontroller 250 10 [0048] Each relay 245L,245N preferably comprises a may be configured for enabling provision of the operative first terminal T1L,T1N connected to a first portion of the electric power to the slave PCB 220s only if the control line conductor L and to a first portion of the neutral con- parameter has a value above the preset threshold value. ductor N, respectively, and a second terminalT 2L,T2N In a still another embodiment, the microcontroller250 preferably connected to a second portion of the line con- may be configured for enabling provision of the operative 15 ductor L (in turn connected to the terminal T1LOAD) and electric power to the slave PCB 220s only if the control to a second portion of the neutral conductorN (in turn parameter has a value below the preset threshold value. connected to the terminal T2LOAD), respectively; in this [0053] Preferably, the preset threshold value or range way, a closure/opening of the relay 245L,245N causes of values are preset e.g( ., by the microcontroller 250) the first terminal T1L, T1N (and hence the first portions of according to a value of a chosen electric parameter ( e.g., line conductor L and neutral conductor N) to be connect- 20 the electric power supply). Moreover, the preset thresh- ed to/disconnected from the respective second terminal old value or range of values may be ( e.g., automatically) T2L,T2N (and hence to/from the second portions of line updated according to any proper criterion (such as ac- conductor L and neutral N conductor, respectively), and cording to variations of the chosen electric parameter). thus the electric load 225 (in this example a heating el- [0054] In the exemplary but not limiting disclosed em- ement) to be connected to/disconnected from the electric 25 bodiment, the detection device is a sensing electric re- power supply (and hence to be provided/not provided sistor (or sensing resistor) RSENSE, and the dispersion of with the operative electric power). electric power towards ground is detected as leakage [0049] The master PCB 120m further comprises a mi- current flowing therethrough, and the control parameter crocontroller 250 which in general accomplishes man- is a voltage depending on the leakage current flowing 30 agement, processing and control functions. Amongst through the sensing resistor RSENSE. Preferably, but not other things, the microcontroller250 is configured for necessarily, the sensing resistor RSENSE has a terminal controlling the relays 245L and 245N thus enabling/disa- T1SENSE connected to the terminal T1L of the relay 245L bling the provision of the operative electric power to the and another terminal T2SENSE connected to the terminal slave PCB 220s (hence to the electric load 225). T2L of the relay 245L (i.e., the sensing resistor RSENSE 35 [0050] Moreover, as will be discussed shortly, if the is placed in parallel to the relay 245L). In such configu- electric load 225 is a heating element comprising an in- ration, although the relays 245L,245N are open, the sens- sulator material 240, the microcontroller 250 may be pref- ing resistor RSENSE can still establish an electrical cou- erably also configured for checking an insulation degree pling from electric power supply to ground (for example (i.e., a dispersion of electric power towards ground) of through the first portion of the line conductor L, the sens- 40 the insulator material 240 when the relays 245L and 245N ing resistor RSENSE itself, the second portion of the line are both opened (and thus the electric load225 is not conductor L, the electric resistor 230, the insulator ma- energized). terial 240 and the case 235) according to an insulation [0051] In this respect, according to the present inven- degree of the insulator material 240. tion, the master PCB 120m further comprises a detection [0055] In this way, if the insulator material 240 is not device for detecting a possible dispersion of electric pow- 45 perfectly insulating, a leakage current will flow through er towards ground when the operative electric power is the sensing resistor RSENSE and a voltage will develop not yetprovided to the electric load 225, and for providing, atthe terminal T2SENSE; as should be understood, in such in response to said detecting, a control parameter indic- condition the voltage at the terminal T2SENSE will be lower ative of the dispersion of electric power towards ground, than the voltage at the terminal T1SENSE (that is forced whereas the microcontroller 250 cooperates with such 50 to the line potential) to an extent depending on the value detection element for receiving the control parameter, of the leakage current flowing through the sensing resis- comparing the control parameter to a preset threshold tor RSENSE and the resistance value thereof. Otherwise, value or range of values (depending on the admitted dis- no leakage current will flow through the sensing resistor persion of electric power towards ground), and enabling RSENSE, condition wherein the detection voltage sub- 55 provision of the line and neutral potentials (hence of the stantially equals the voltage at the terminalT1SENSE operative electric power) to the slave PCB 220s (e.g. by (safety condition), or has a prefixed value, different form closing the relays 245L,245N) according to a result of the voltage at the terminalT 1SENSE, (for example be- such comparison. For example, the microcontroller 250 cause of the low current circulating through the sensing

6 11 EP 2 589 973 A1 12 resistor RSENSE towards the microcontroller 250) but also [0061] Moreover, although in the present description different form the voltage at the terminal T2SENSE in case explicit reference has been made to distinct and sepa- of a power dispersion. rated master and slave PCBs, this should not be con- [0056] The microcontroller 250 monitors the voltage at strued limitatively. In fact, the same considerations apply 5 the terminal T2SENSE (and hence at the terminal T2L of if the master and slave PCBs are identifiable functional- the relay 245L). In this way, the microcontroller 250 can ly-different portions of a same PCB. Furthermore, as compare such voltage to a voltage threshold value or herein considered, the term "slave PCB" is intended in range of values corresponding to the preset value or its widest meaning of any group of electric, electro-me- range of values, and thereby enable provision of the op- chanic and/or electronic components carrying out func- erative electric power to the heating element 225 if the 10 tions related to the driving of the electric load. voltage has a specific relation with said threshold value [0062] The slave PCB may also be associated with a or range of values ( e.g. if the voltage is within- or without, plurality of different or equivalent electric loads, which according to the chosen implementation- a preset voltage can be individually selected and/or activated by means range ); the microcontroller 250 commands the closure of additional switching elements. Moreover, the slave 15 of both the relays 245L,245N only if such condition is ver- PCB may have a different circuit configuration; for exam- ified. ple, the slave PCB may be provided with additional [0057] As visible in Figure 2, the slave PCB 220s may switching elements (e.g., properly controlled by the mi- further comprise a processing and control unit255 co- crocontroller and/or the processing and control unit). Ad- operating with the relay 245N for commanding the closure ditionally or alternatively, the slave PCB may be provided thereof thereby enabling provision of the line and neutral 20 with further electric, electronic and/or electro-mechanic potentials (hence of the operative electric power) to the components for being powered only if no power disper- slave PCB 220s (thus, to the electric load 225). For in- sion towards ground is detected, and for driving the elec- stance, the processing and control unit 255 may be pow- tric load only if such condition is verified. ered by the voltage provided by (or derived from) the line [0063] The switching elements are not necessarily re- 25 conductor L (for example, taken from the terminalT 2L, lays, but also, for example, electronic switches such as connection not shown) and the neutral conductor N (for power (BJT, MOS, and the like) transistors, as well as example, taken from the terminalT 1N, connection not they can be in any number. Moreover, the arrangement shown). In this way, if no power dispersion towards of the switching elements herein described is not strictly ground is detected by the microcontroller 250, the micro- necessary, and several modifications are possible; in this 30 controller 250 closes the relay 245L (thereby enabling respect, the switching elements may be arranged and/or provisionof the operative electric powerto theprocessing distributed differently in the master and/or slave PCBs. and control unit 255), and the processing and control unit For example, although in the present description the 255 closes the relay 245N, thereby enabling provision of switching element within the master PCB has been de- the operative electric power to the electric load 225. Con- scribed as "insulating" the electric load from the line con- versely, if power dispersion towards ground is detected 35 ductor, whereas the switching element within the slave by the microcontroller 250, the relay 245L is open, there- PCB has been described as "insulating" the electric load by provision of the operative electric power to the from the neutral conductor, the present invention may be processing and control unit 255 is disenabled (since the equivalently configured such as the switching element latter is electrically connected only to the neutral conduc- within the master PCB "insulates" the electric load from 40 tor through the terminal T1N); then, the relay 245N is open the neutral side and the switching element within the as well (thereby the provision of the operative electric slave PCB "insulates" the electric load from the line con- power to the electric load 225 is disenabled). ductor). [0058] Preferably, but not necessarily, the sensing re- [0064] The same considerations apply if the detection sistor RSENSE has a high resistance value (e.g., grater device is implemented differently; for example, it is pos- than 100 KΩ, such as 1 MΩ), so that the voltage at the 45 sible to provide more sensing resistors ( e.g., arranged in terminal T2L is responsive also to very small leakage cur- series or parallel configurations), and/or other electric el- rents (however, as will be readily understood, the resist- ements, for example according to the provided control ance value of the sensing resistor RSENSE may be chosen parameter. In fact, the control parameter may be a volt- according to specific design parameters). age (asexemplarily described in thepresent description), [0059] Clearly, the appliance according to the inven- 50 or a current depending on the leakage current flowing tion may comprise more slave or master PCBs. through the sensing resistor; in this respect, the detection [0060] In addition, although in the present description device and/or the microcontroller may comprise transis- explicit reference has been made to slave and master tor current mirrors for taking such current and properly PCBs, this should not be understood in a restrictive way; processing it. Analogous considerations apply if the con- in fact, according to the used communication protocol, 55 trol parameter is an electric power, or a photon intensity the slave PCBs may also perform master functions, depending on the leakage current flowing through the whereas the master PCBs may also perform slave func- sensing resistor. In the latter case, the detection device tions. and/or the microcontroller may comprise a light emitting

7 13 EP 2 589 973 A1 14 diode for converting the leakage current into light and a said slave printed circuit board (220s) only if the con- photodector (such as a photodiode) for re-converting trol parameter has a value above the preset thresh- such light into a corresponding current (e.g., equal to or old value,or the controlunit is configuredfor enabling proportional to the leakage current). provision of the operative electric power to said slave 5 printed circuit board (220s) only if the control param- eter has a value below the preset threshold value. Claims 4. The electric appliance (100) according to any of the 1. An electric appliance (100) comprising an electric preceding Claims, wherein the master printed circuit load (225), and a printed circuit board assembly10 board (220m) comprises a first switching element (115) for electronically managing the electric appli- (245L) for connecting/ disconnecting a first conductor ance (100), the printed circuit board assembly com- (L) of the electric power supply (L,N) to a first terminal

prising: (T1LOAD) of the electric load(225), and the slave printed circuit board (220s) comprises a second 15 - a slave printed circuit board (220s) operatively switching element (245N) for connecting/ disconnect- associated with said electric load (225) for driv- ing a second conductor (N) of the electric power sup-

ing it, and ply (L,N) to a second terminal (T2LOAD) of the electric - a master printed circuit board (220m) opera- load (225), the control unit (250) enabling/disabling tively associated with said slave printed circuit provision of the operative electric power to the elec- board (220s) and arranged for receiving an elec- 20 tric load (225) by closing/opening the first switching tric power supply (L,N) of the electric appliance element (245L) and the second switching element and for selectively providing/stopping the provi- (245N) thereby connecting/disconnecting the first sion of an operative electric power to the slave conductor (L) and the second conductor (N) to the printed circuit board (220s) for energization/de- first terminal and the second terminal, respectively, energization thereof, 25 of the electric load (225), and the detection device characterized in that (RSENSE,T1SENSE,T2SENSE) detecting the dispersion of electric power towards ground of the electric load the master printed circuit board (220m) comprises: (225) and/or of the slave printed circuit board (220s) and providing the control parameter when the first 30 - a detection device (RSENSE,T1SENSE,T2SENSE) switching element (245L) and the second switching for detecting a dispersion of electric power to- element (245N) are both opened. wards ground of the electric load (225) and/or of the slave printed circuit board(220s) when 5. The electric appliance (100) according to any of the the operative electric power is not provided to preceding Claims, wherein the detection device 35 said slave printed circuit board (220s), and for (RSENSE,T1SENSE,T2SENSE) is configured for being providing, in response to said detecting, a con- run through by a leakage current indicative of the trol parameter indicative of the dispersion of dispersion of electric power towards ground. electric power towards ground, and - a control unit (250) configured for receiving the 6. The electric appliance (100) according to Claim 4, control parameter, comparing the control pa- 40 wherein

rameter to a preset threshold value or range of the detection device (RSENSE,T1SENSE,T2SENSE) is values, and enabling provision of the operative configured for being run through by a leakage current electric power to the slave printed circuit board indicative of the dispersion of electric power towards (220s) according to a result of such comparison. ground of the electric load (225) and/or of the slave 45 printed circuit board (220s), and 2. The electric appliance (100) according to Claim 1, the detection device (RSENSE,T1SENSE,T2SENSE) is wherein the control unit ( 250) is either configured for placed between a first terminal(T 1L) of the first enabling provision of the operative electric power to switching element (245L) connected to a first portion said slave printed circuit board ( 220s) only if the con- of the first conductor (L) and a second terminal (T2L) 50 trol parameter is within the preset range of values, of the first switching element (245L) connected to a or the control unit is configured for enabling provision second portion of the first conductor (L), the detec- of the operative electric power to said slave printed tion device (RSENSE,T1SENSE,T2SENSE) being config- circuit board (220s) only if the control parameter is ured to detect the leakage current flowing through outside a preset range of values. the firstportion of thefirst conductor (L), the detection 55 device (RSENSE,T1SENSE,T2SENSE), the second por- 3. The electric appliance (100) according to Claim 1, tion of the first conductor (L), the electric load (225), wherein the control unit (250) is either configured for and a ground of the electric appliance (100). enabling provision of the operative electric power to

8 15 EP 2 589 973 A1 16

7. The electric appliance (100) according to Claim 6, for receiving the operative electric power, wherein the detection device(R SENSE,T1SENSE, a case (235) for housing the at least one electric T2SENSE) comprises a sensing resistor (RSENSE), a resistor, the case being connected to the ground first terminal (T1SENSE) and a second terminal of the electric appliance, 5 (T2SENSE) of the sensing resistor being connected an insulating coating (240) between the at least to the first terminal(T 1L) and the second terminal one electric resistor (230) and the case (235) for (T2L) of the first switching element (245L), respec- electrically insulating the at least one electric re- tively. sistor (230) from the case (235), the detection device detecting the dispersion of electric power 8. The electric appliance (100) according to any Claim 10 towards ground through the insulating coating from 1 to 7, wherein the control parameter is a current (240) for checking insulation degree thereof depending on the dispersion of electric power to- wards ground detected by the detection device 15. The electric appliance (100) according to any of the

(RSENSE,T1SENSE,T2SENSE). preceding Claims, wherein the electric appliance 15 (100) is a laundry washing machine, a laundry wash- 9. The electric appliance (100) according to any Claim er/dryer, a laundry dryer, a dishwasher, a oven, or a from 1 to 7, wherein the control parameter is an elec- refrigerator. tric power depending on the dispersion of electric power towards ground detected by the detection de- 20 vice (RSENSE,T1SENSE,T2SENSE).

10. The electric appliance (100) according to any Claim from 1 to 7, wherein the control parameter is a photon intensity depending on thedispersion of electric pow- er towards ground detected by the detection device 25 (RSENSE,T1SENSE,T2SENSE).

11. The electric appliance (100) according to any Claim from 1 to 7, wherein the control parameter is a volt- age depending on the dispersion of electric power 30 towards ground detected by the detection device (RSENSE,T1SENSE,T2SENSE).

12. The electric appliance (100) according to Claim 11, wherein the control unit (250) is connected to the 35 detection device (RSENSE,T1SENSE,T2SENSE) for re- ceiving said voltage depending on the dispersion of electric power towards ground, the control unit (250) being configured to compare said voltage to a volt- age threshold value or range of value corresponding 40 to the preset threshold value or range of values.

13. The electric appliance (100) according to any of the preceding Claims, wherein the electric load(225) comprises at least one electric heating element for 45 heating treatment fluids during heating operations of the electric appliance (100), the at least one electric heating element being configured for being powered by the operative electric power and for generating heat therefrom. 50

14. The electric appliance (100) according to Claim 13, wherein the at least one electric heating element comprises: 55 at least one electric resistor (230) connected be- tween a first terminal(T 1LOAD) and a second terminal (T2LOAD) of the electric heating element

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• EP 0677908 A2 [0011] [0014]

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