DISHWASHERS

The present invention relates to the field of electric motors. More particularly, the present invention relates to power supply regulation of electric motors of laundry treatment machines, such as laundry washing machines, laundry washing/drying machines and laundry drying machines, and of dishwashers.

Laundry washing machines, laundry washing/drying machines and laundry drying machines (hereinafter referred to as "laundry treatment machines") and dishwashers typically comprises a number of devices (e.g., pumps and/or fans) adapted to be operated by or comprising electric motors.

For example, laundry washing machines and laundry washing/drying machines are equipped with a drain pump operable to cause washing liquid (e.g., water, water mixed with washing products and/or water mixed with rinsing products) located inside the washing tub to be discharged into the water drain network system at the end of a washing phase. Some laundry washing machines and laundry washing/drying machines are also provided with a recirculation pump which, during a washing liquid loading phase and/or a washing phase and/or a rinsing phase, is operable to take some washing liquid from the bottom of the washing tub, and reintroduce this liquid into a different region of the washing tub, or directly into the drum, so as to deliver the washing liquid to the laundry from more than one directions, and not only from the bottom of the tub.

Moreover, laundry drying machines and laundry washing/drying machine are equipped with recirculation fans adapted to blow drying air into the drum and to suck out from the drum the moisturized air. Laundry drying machines and laundry washing/drying machines having a heat exchanger of the heat pump type are also equipped with a fan adapted to cool down the heat pump compressor. Laundry drying machines and laundry washing/drying machines having a heat exchanger of the air-air type are equipped with a fan for blowing air for the condensation of the moisturized air.

Different types of electric motors can be used to operate the devices of the type mentioned above, such as for example three phase motors or synchronous motors.

Electric motors are designed to operate within corresponding safe operating conditions, which may greatly vary based on the type, materials and structure thereof.

On this regard, electric motors are typically designed to operate when supplied by a supply voltage (e.g., the mains voltage) not higher than a maximum threshold (herein referred to as "maximum safe voltage"). Making reference to a synchronous motor, if the supply voltage exceeds said maximum safe voltage, the synchronous motor starts to heat up. If the temperature of the synchronous motor goes above a certain limit for a sufficiently long amount of time and/or for a sufficiently high number of times, the motor itself may be damaged.

In order to prevent the occurrences of damages, synchronous motors are usually coupled with thermal protection systems adapted to turn off the supply of power to the motor itself (e.g., by interrupting the supply of the supply voltage to the motor) before the temperature of the latter rises above a certain limit (depending on the type, materials and structure of the motor).

In order to avoid the activation of the thermal protection system (and therefore the turning off of the motor), synchronous motors to be installed in a laundry treatment machine or a dishwasher are usually chosen having a sufficiently high maximum safe voltage, capable of withstanding the supply voltages even considering the unavoidable and unpredictable variations the mains voltage may be subject to.

However, synchronous motors with high maximum safe voltages are expensive, being designed to have electromagnetic and/or mechanic characteristics requiring and are power consuming, being designed to operate with high supply voltages. Since a laundry treatment machine or a dishwasher is usually provided with several synchronous motors, the resulting cost and the resulting power consumption may become very high.

In view of the above, the Applicant has faced the problem of reducing the cost and the power consumption of a laundry treatment machine or a dishwasher comprising devices adapted to be operated by or comprising electric motors, such as synchronous motors. Another problem is to prevent at the same time that such electric motors heat up to an extent such to cause the thermal protection system intervention.

Moreover, electric motors in a laundry treatment machine or a dishwasher may operate with different electric power levels based on the washing/drying cycle actually carried out, such as for example the motor of the drain pump of a laundry treatment machine. For this purpose, the Applicant has also faced the problem of supplying the electric motors with an amount of electric power based on the specific operation actually carried out by the laundry treatment machine or dishwasher.

Applicant realized that for some purposes, electric motors - such as synchronous electric motors- installed in a laundry treatment machine or a dishwasher supplied with a given mains voltage (e.g., 230 V) may be supplied with supply voltages that are lower than the mains voltage itself (e.g., 180 V or 160 V).

Moreover, Applicant realized that for some purposes, in a laundry treatment machine or a dishwasher supplied with a given mains voltage (e.g., 230 V) it is possible to install electric motors - such as synchronous electric motors- which are specifically designed to safely operate with supply voltages lower than the mains voltage itself.

Supply voltages may be subjected to unpredictable variations, for example because of unpredictable mains voltage fluctuation. Therefore, during such unpredictable variations, an electric motor may be supplied with a supply voltage having an RMS value different from the one required by the specific operation actually carried out by the laundry treatment machine or dishwasher. For this purpose, the Applicant has also faced the problem of correctly setting the actual level of electric power supplied to the motor to desired values irrespective of possible unpredictable supply voltage variations.

An aspect of the present invention proposes a laundry treatment machine or a dishwasher comprising a washing and/or drying assembly configured to carry out washing and/or drying cycles, and an electronic unit configured to drive the washing and/or drying assembly to carry out the washing and/or drying cycles. The washing and/or drying assembly comprises a device adapted to be operated by, or comprising, an electric motor. The electronic unit comprises a power supply apparatus for supply electric power to the electric motor. The power supply apparatus comprises a TRIAC comprising a first anode terminal coupled with a first terminal of an AC electric power supply and a second anode terminal coupled with a first terminal of the electric motor. The electric motor comprises a second terminal coupled with a second terminal of the AC electric power supply for receiving a supply voltage. The power supply apparatus further comprises a controller configured to generate a driving signal, and a triggering circuit for activating the TRIAC by providing triggering pulse signals to a third, gate terminal of the TRIAC based on the driving signal received from the controller. The electronic unit further comprises a sensing unit configured to sense the supply voltage at the second terminal of the AC electric power supply and to provide a corresponding sensed voltage to the controller. The electronic unit further comprises a current monitoring circuit configured to sense the current flowing across the TRIAC and comprising a mean absolute value circuit configured to generate a corresponding processed signal based on the mean absolute value of said current. The controller is further configured to set the driving signal for activating the TRIAC with a firing angle based on the sensed voltage, based on the processed signal, and based on an electric motor target voltage in such a way to supply the electric motor with a corresponding operating voltage. Such operating voltage is lower than or substantially equal to said supply voltage.

According to an embodiment of the present invention, such electric motor target voltage is based on electromagnetic and/or mechanic characteristics of the electric motor, and/or the washing and/or drying cycle carried out by the washing and/or drying assembly.

Thanks to this solution, the electric motor is supplied with an operating voltage set taking into consideration both the actual value of the supply voltage and the electromagnetic and/or mechanic characteristics of the motor (i.e., the type of the motor) and/or the washing and/or drying cycle actually carried out by the laundry treatment machine or the dishwasher.

According to an embodiment of the present invention, electric motor target voltage values may be directly programmed by the controller or may be stored in a memory unit coupled therewith.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a voltage not higher than a maximum safe voltage, and the controller is configured to temporally supply the electric motor with an operating voltage higher than the maximum safe voltage for a corresponding time period.

This time period is sufficiently short to avoid that the temperature of the motor goes above a limit for which the motor itself may be damaged. In this way, with this solution, even if a cheap electric motor is installed, capable of safely sustaining only a relatively low maximum safe voltage, a higher supply voltage can be temporarily provided to promote the starting of the motor without damaging the latter.

According to an embodiment of the present invention, said time period may have a duration which depends on the supply voltage. For example, the duration of said time period may be inversely proportional to the value of the supply voltage.

According to an embodiment of the present invention, the controller is configured to supply the electric motor during said time period with an operating voltage corresponding to the supply voltage.

According to an embodiment of the present invention, the controller is configured to supply the electric motor after said time period is elapsed with an operating voltage lower than the maximum safe voltage.

This is advantageous for the electric motors which require to be supplied with a relatively high power only during the starting thereof, such as for example an electric motor designed to rotate devices which are immersed in liquids (e.g. a drain pump), in which the motor requires a substantially high supply of power only during the starting thereof (in order to overtake the liquid friction), in the steady state being sufficient a lower supply of power. Supplying the electric motor with a high supply of power only for a short period of time is advantageous not only from a manufacturing cost point of view - since it is possible to use a cheaper electric motor -, but also from the power consumption point of view. Indeed, after the initial, short, starting period, the electric power delivered to the motor may be advantageously reduced for the entire duration of the steady state period, which is usually much longer than the starting period. Such temporary relatively high power may be also supplied to the electric motor following the occurrence of particular events, such as for example an anomalous temperature increasing, an insufficient water level decreasing, and so on.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a voltage not higher than a maximum safe voltage, and the controller is configured to supply the electric motor with a first operating voltage not higher than the maximum safe voltage for a corresponding time period, and then with a second operating voltage lower than the first operating voltage after said time period is elapsed. According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a voltage not higher than a maximum safe voltage, and the controller is configured to supply the electric motor with an operating voltage lower than the maximum safe voltage.

This is advantageous for the electric motors which does not require to be supplied with a high power at the starting thereof, such as for example an electric motor designed to rotate devices which are not immersed in liquids (e.g., a fan).

According to an embodiment of the present invention, said maximum safe voltage substantially corresponds to the supply voltage or it is lower than the supply voltage.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a safe voltage substantially corresponding to the supply voltage, and the controller is configured to supply the electric motor with an operating voltage lower than the safe voltage. Then, according to an embodiment of the present invention, based on the washing and/or drying cycle which is actually carried out by the laundry treatment machine or dishwasher, the controller may be configured to further reduce the operating voltage to a still lower value.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a safe voltage lower than the supply voltage, and the controller is configured to supply the electric motor with an operating voltage corresponding to the safe voltage. As in the previous case, then, according to an embodiment of the present invention, based on the washing and/or drying cycle which is actually carried out by the laundry treatment machine or dishwasher, the controller may be configured to further reduce the operating voltage to a still lower value.

According to an embodiment of the present invention, the laundry treatment machine or dishwasher is a laundry washing machine, a laundry washing/drying machine, or a dishwasher, and said device comprises at least one among a drain pump and a recirculation pump.

In the case of a recirculation pump, the proposed solution allows to reduce both the power consumption and the noise generated because of the electromagnetic forces acting on the windings of the motor. For example, compared to know solutions it is possible to reduce the power consumption of about the 25% (e.g., 9 Wh). This solution is very interesting, since the recirculation pump is usually turned on for a long time during a washing cycle, and the overall power consumption reduction is sensibly high.

In the case of a drain pump, the proposed solution allows to strongly reduce the noise generated during operation, as well as a reduction in the power consumption.

According to an embodiment of the present invention, the laundry treatment machine or dishwasher is a laundry drying machine or a laundry washing/drying machine, and said device comprises a drying air recirculation fan.

According to an embodiment of the present invention, said electric motor is a synchronous electric motor.

According to an embodiment of the present invention, the washing and/or drying assembly comprises at least a further device in addition to said device and configured to safely operate by being supplied with a voltage corresponding to the supply voltage.

For example, the drain pump of a washing machine may be operated by a synchronous electric motor designed to safely operate with a maximum safe voltage of about 160 V, while the washing machine (and such further device as well) is supplied with a supply voltage of 220 V.

According to an embodiment of the present invention, said further device is a heating device.

For example, while the drain pump of a washing machine may be operated by a synchronous electric motor having a maximum safe voltage of about 160 V, the heating device adapted to heat the washing liquid may be supplied with the supply voltage of 220 V.

According to an embodiment of the present invention, the laundry treatment machine is a laundry drying machine or a laundry washing/drying machine comprising a rotatable drum, and said further device comprises a further electric motor in addition to said electric motor and operable to rotate the rotatable drum.

For example, while the drain pump of a washing machine may be operated by a synchronous electric motor having a maximum safe voltage of about 160 V, the electric motor operable to rotate the drum may be supplied with the supply voltage of 220 V.

According to an embodiment of the present invention, the controller is further configured to estimate an indication of the voltage difference across the electric motor terminals based on said sensed supply voltage and based on said processed signal, and to set the driving signal for activating the TRIAC with a firing angle based on a comparison between said indication of the voltage difference across the electric motor terminals and the electric motor target voltage.

According to an embodiment of the present invention, the controller is further configured to estimate an indication of the voltage difference across the electric motor terminals by scaling the processed signal according to said sensed supply voltage.

According to an embodiment of the present invention, said current monitoring circuit comprises a resistor connected between the first anode terminal of the TRIAC and the first terminal of the AC electric power supply for being crossed by the current flowing across the TRIAC to generate a corresponding first AC voltage, wherein the mean absolute value circuit is configured to receive the first AC voltage and accordingly generate said processed signal based on the mean absolute value of said first AC voltage.

According to an embodiment of the present invention, said mean absolute value circuit comprises a rectifier section configured to rectify the first AC voltage to generate a corresponding unipolar signal, and a converter section configured to convert the unipolar signal into a DC signal. Said DC signal has value based on the mean absolute value of the first AC voltage. Said processed signal corresponds to said DC signal.

Another aspect of the present invention provides for a method for operating a laundry treatment machine or a dishwasher. The laundry treatment machine or dishwasher comprises a washing and/or drying assembly configured to carry out washing and/or drying cycles. The washing and/or drying assembly comprises a device adapted to be operated by, or comprising, an electric motor adapted to be supplied with electric power from a supply voltage corresponding to the AC electric power supply of the laundry treatment machine or dishwasher through a TRIAC. The method comprises sensing the supply voltage, sensing the current flowing across the TRIAC, generating a processed signal based on the mean absolute value of said current, and setting a firing angle of the TRIAC based on the sensed supply voltage, based on the processed signal, and based on an electric motor target voltage in such a way to supply the electric motor with a corresponding operating voltage lower than or substantially equal to said supply voltage. According to an embodiment of the present invention, said electric motor target voltage is based on electromagnetic and/or mechanic characteristics of the electric motor, and/or based on the washing and/or drying cycle carried out by the washing and/or drying assembly.

According to an embodiment of the present invention, the electric motor target voltages are directly available at a controller adapted to implement the method, or stored in a memory unit coupled therewith.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a voltage not higher than a maximum safe voltage. The method further comprises temporally supplying the electric motor with an operating voltage higher than the maximum safe voltage for a corresponding time period.

According to an embodiment of the present invention, the method further comprises supplying the electric motor during said time period with an operating voltage corresponding to the supply voltage.

According to an embodiment of the present invention, the method further comprises supplying the electric motor after said time period is elapsed with an operating voltage lower than the maximum safe voltage.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a voltage not higher than a maximum safe voltage. The method further comprises supplying the electric motor with first operating voltage not higher than the maximum safe voltage for a corresponding time period, and supplying the electric motor with a second operating voltage lower than the first operating voltage after said time period is elapsed.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a voltage not higher than a maximum safe voltage. The method further comprises supplying the electric motor with an operating voltage lower than the maximum safe voltage.

According to an embodiment of the present invention, said maximum safe voltage substantially corresponds to the supply voltage or it is lower than the supply voltage.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a safe voltage substantially corresponding to the supply voltage. The method further comprises supplying the electric motor with an operating voltage lower than the safe voltage.

According to an embodiment of the present invention, the electric motor is configured to safely operate by being supplied with a safe voltage lower than the supply voltage. The method further comprises supplying the electric motor with an operating voltage corresponding to the safe voltage.

According to an embodiment of the present invention, the washing and/or drying assembly comprises at least a further device in addition to said device. The method further comprises supplying said further device with a voltage corresponding to the supply voltage.

According to an embodiment of the present invention, the method further comprises estimating an indication of the voltage difference across the electric motor terminals based on said sensed supply voltage and based on said processed signal, and setting the driving signal for activating the TRIAC with a firing angle based on a comparison between said indication of the voltage difference across the electric motor terminals and the electric motor target voltage.

According to an embodiment of the present invention, said estimating an indication of the voltage difference across the electric motor terminals comprises scaling the processed signal according to said sensed supply voltage.

These, and others, features and advantages of the solution according to the present invention will be better understood by reading the following detailed description of some embodiments thereof, provided merely by way of exemplary and non- limitative examples, to be read in conjunction with the attached drawings, wherein:

Figure 1 is a schematic view of a laundry washing machine in which embodiments of the present invention may be implemented, and

Figure 2A schematically illustrates in terms of circuit elements a power supply regulation apparatus according to an embodiment of the present invention;

Figure 2B shows exemplary evolution over time of some voltages and currents of the circuit illustrated in Figure 2A;

Figure 3 schematically illustrates in terms of circuit elements a MAV circuit of the power supply regulation apparatus of Figure 2 according to an embodiment of the present invention, and

Figure 4 is a schematic view of a laundry drying machine in which embodiments of the present invention may be implemented.

With reference to the drawings, Figure 1 illustrates a laundry treatment machine

100 (briefly, "laundry machine") in which embodiments of the present invention may be implemented. The laundry machine 100 may be for example a laundry washing machine or a laundry washing/drying machine. The laundry machine illustrated in Figure 1 is a laundry machine for treating (washing, or washing/drying) laundry of the front-loading type. Anyway, it should be apparent from the following description that the invention can be applied, without any substantial modification, to a laundry washing machine of the top-loading type.

In the example at issue, the laundry machine 100 advantageously comprises a casing 105, preferably substantially parallelepiped-shaped, that encloses a washing tub 107 wherein laundry is treated, along with any other components of the washing machine 100 necessary for the operation (e.g., hydraulic, electronic and electromechanical apparatuses). The washing tub 107 has preferably a substantially cylindrical shape and it is made of waterproof material which is also able to withstand operating temperatures and chemicals reactions promoted by washing liquids during the washing machine operation, such as a plastic polymer.

The washing tub 107 houses a rotatable drum 110, preferably perforated, preferably substantially cylindrical- shaped, in which laundry 112 to be washed can be loaded. The rotatable drum 110 is adapted to be selectively rotated, preferably at variable rotation speeds, by an electric motor, only conceptually depicted in figure and denoted, as a whole, by the reference 115. The concepts of the present invention may be applied both to laundry washing machines of the type having a drum which rotates about an horizontal or semi-horizontal axis, as well as to the ones having a drum which rotates about a vertical or semi- vertical axis.

In order to allow a user to access the washing tub and the inside of the drum 110 (for loading/unloading the laundry), a loading/unloading opening, closable by a door, not illustrated, is advantageously provided, preferably on a front side of the laundry machine 100.

A water supply system 120 and a detergent supply system 122 are arranged preferably in the upper part of the laundry machine 100 for supplying washing liquid into the washing tub 107. The detergent supply system 122 advantageously comprises a removable drawer 123 provided with compartments suited to be filled with washing and/or rinsing products.

Water flowing through the water supply system 120 is advantageously supplied into the washing tub 107 by making it flow through the drawer 123 and through an inlet line 125 in fluid communication with the washing tub 107. Advantageously, the water supply system 120 further comprises a main pipe 130 f uidly connecting the drawer 123 to an external water supply line 135, preferably by means of a controlled input supply valve 140.

Washing liquid which reaches the washing tub 107 may selectively contain one of the products (e.g., detergent, softener, bleach) contained in the compartments of the drawer 123, or may be clean water (i.e., which does not contain any product), depending on the washing program which is actually performed. Alternative arrangements may be provided, for example with a separate water inlet line adapted to supply exclusively clean water into the washing tub 107.

A heating element 144, such as an electric resistor, is located on the bottom portion of the washing tub 107, for heating the washing/rinsing liquid inside the washing tub 107 when activated.

The laundry machine 100 is provided with a discharge system 145 adapted to selectively remove (or drain) washing/rinsing liquid from the washing tub 107.

The discharge system 145 comprises a discharge duct 150 fluidly connected to the washing tub 107 for receiving the washing/rinsing liquid to be discharged. The discharge duct 150 may be made of a rigid material, such as plastic. Anyway, the discharge duct 150 may be a flexible hose, for example made of a flexible material, such as rubber. The discharge duct 150 is arranged to be, preferably selectively, in fluid communication with the washing tub 107 through a discharge hole 155 provided at the bottom of the washing tub 107. Preferably, a valve 160 is provided for selectively opening/closing the discharge hole 155, in order to selectively allow/block liquid to flow between the washing tub and 107 the discharge duct 150. Downstream the valve 160, an anti-fluff / anti-clog filter 165 is preferably provided.

Downstream the anti-fluff / anti-clog filter 165, a drain pump 170 is provided, which is operable to selectively cause liquid located into the discharge duct 150 to be discharged through a drain duct 175 adapted to be connected to a water drain network system (not illustrated).

A recirculation pump 177, for example in parallel with the drain pump 170, may be also provided, which is operable to selectively cause liquid located into the discharge duct 150 to be conveyed back into the washing tub 107 through a recirculation conduit 180, preferably for being sprayed inside the drum 110, e.g., by means of nozzle(s) 185 located on the drum 110 in proximity of the rotation axis thereof.

According to an embodiment of the present invention, the drain pump 170 and - if present - the recirculation pump 177, comprise synchronous motors each one driven by a respective power supply regulation apparatus comprising a TRIAC (TRIode for Alternating Current) arranged to selectively couple said synchronous motor to line and neutral terminals of an AC electric power supply {e.g., the mains voltage). Said power supply regulation apparatuses (not illustrated in Figure 1) are preferably located on the electronic control unit 190 {e.g., a programmable electronic board) of the laundry machine 100.

Figure 2A schematically illustrates in terms of circuit elements the power supply regulation apparatus, identified with the reference 200, designed to drive the synchronous motor of the drain pump 170 according to an embodiment of the present invention.

The power supply regulation apparatus 200 comprises a TRIAC 205 having a first anode terminal Ml coupled with the neutral terminal (identified in Figure 2 with reference TN) of the AC electric power supply providing a reference signal Vn, a second anode terminal M2 connected to a first terminal of the motor of the drain pump 170, and a gate terminal G connected to a triggering circuit 208 adapted to generate triggering pulse signals for activating the TRIAC 205. The motor of the drain pump 170 comprises a second terminal connected to the line terminal (identified in Figure 2 with reference TL) of the AC electric power supply providing an AC supply signal VI with respect to the reference signal Vn. In the example at issue, the AC supply signal VI is a 230V or 125V alternating voltage at a 50Hz or 60Hz frequency, having a full- wave periodic, e.g., sinusoidal, waveform. The concepts of the present invention also apply if further electric components (not illustrated), such as for example switches or relays, are provided between the first anode terminal Ml of the TRIAC 205 (and/or the second terminal of the motor of the drain pump 170) and the terminals of the AC electric power supply.

An AC-DC conversion circuit (only conceptually illustrated in the figure and denoted, as a whole, by the reference 210) is provided, comprising transforming, rectifying and regulation components for receiving the (AC) electric power supply (from line TL and neutral TN terminals) and providing one or more DC voltages, such as a ground voltage GND and a DC supply voltage Vcc {e.g., a 3V, 5V or 12V DC voltage with respect to the ground voltage GND). The DC voltages generated by the AC-DC conversion unit 210 are used for supplying the electric and electronic components included in the electronic control unit 190, such as a controller, e.g., a microcontroller, 215 directed to manage the operation of the laundry machine 100. For this purpose, the microcontroller 215 is connected between a DC supply terminal Th for receiving the DC supply voltage Vcc and a ground terminal GND for receiving the ground voltage GND. As visible in Figure 2, the neutral terminal TN is preferably coupled with the terminal of the AC-DC conversion unit 210 providing the DC supply voltage Vcc, and therefore to the DC supply terminal Th of the microcontroller 215, so that the reference signal Vn is set to the DC supply voltage Vcc for allowing proper driving of power components, such as the TRIAC 205.

The triggering circuit 208 for activating the TRIAC 205 is driven by the microcontroller 215. For example, the triggering circuit 208 comprises a bipolar transistor 220 having a base terminal coupled with the microcontroller 215 for receiving a driving signal Vd capable of selectively taking a high value corresponding to the DC supply voltage Vcc and a low value corresponding to the ground voltage GND, an emitter terminal connected to the ground terminal GND for receiving the ground voltage GND, and a collector terminal connected to a first terminal of a resistor R. The resistor R has a second terminal connected to the gate terminal G of the TRIAC 205.

Making reference to Figure 2A together with Figure 2B, when the microcontroller 215 sets the driving signal Vd to the low value, the transistor 220 is off, and the gate terminal G of the TRIAC 205 is floating. In this condition, the TRIAC 205, and therefore the motor of the drain pump 170, are off.

In order to trigger the activation of the TRIAC 205 for turning on the drain pump 170, the microcontroller 215 sets the driving signal Vd to the high value, turning on the transistor 220. In this condition, a current pulse flows from the gate terminal G toward the ground terminal GND flowing across the resistor R and the transistor 220, triggering the activation of the TRIAC 205, and then turning on the motor of the drain pump 170, which is in turn crossed by a current Ip. The delay at which the current pulse is generated with respect to the start of the half-cycles of the AC supply signal VI at the line terminal TL - also referred to as TRIAC "firing angle" - sets the actual voltage difference waveform applied across the drain pump 170 motor terminals, thus determining its RMS effective value (which sets in turn the actual flow rate of the drain pump 170).

According to an embodiment of the present invention, the microcontroller 215 is configured to monitor the RMS value of the voltage difference waveform Vp actually applied across the drain pump 170 motor terminals, and set the firing angle of the TRIAC 205 based on a comparison between the monitored RMS value and a target voltage Vt indicative of the target {e.g., RMS) value of the voltage difference Vp to be provided across the terminals of the motor of the pump 170 (and therefore indicative of the actual level of electric power supplied to the motor) through a feedback control loop.

According to an embodiment of the present invention, during operation of the laundry machine 100, the microcontroller 215 calculates indications of the RMS value of the monitored voltage difference waveform Vp actually applied across the drain pump 170 motor terminals, and compares said indications with the target voltage Vt corresponding to the specific phase of the washing program the laundry machine 100 is carrying out. If the RMS value of the monitored voltage difference waveform Vp is higher than the target voltage Vt - meaning that the electric power actually supplied to the drain pump 170 motor is too high -, the microcontroller 215 is configured to increase the firing angle of the TRIAC 205 for reducing the supply of electric power. If instead the RMS value of the monitored voltage difference waveform Vp is lower than the target voltage Vt - meaning that the electric power actually supplied to the drain pump 170 motor is too low -, the microcontroller 215 is configured to reduce the firing angle of the TRIAC 205 for increasing the supply of electric power.

According to an embodiment of the present invention, the microcontroller 215 is configured to calculate the target voltage Vt based on predefined settings depending on electromagnetic and/or mechanic characteristics of the motor and/or the washing program and the specific phase thereof the laundry machine 100 is actually performing.

According to an embodiment of the present invention, target voltage Vt values may be directly programmed by the microcontroller 215, or may be stored in a memory unit coupled therewith.

According to an embodiment of the present invention, a washing program carried out by the laundry machine 100 may provide for a starting phase in which the drain pump 170 is supplied with a first electric power level, followed by a phase in which the drain pump 170 is supplied with a second electric power level lower than the second power level. In this case, the microcontroller 215 may firstly set the target voltage Vt to a first value, such as 230 V, during the starting phase, and then set the target voltage Vt to a second value lower than the first value, such as 160 V, during the following phase.

According to an embodiment of the present invention, the starting phase may have a duration which depends on the supply voltage. For example, the duration of the starting phase may be inversely proportional to the value of the supply voltage.

According to an embodiment of the present invention, the microcontroller 215 may firstly set the target voltage Vt to a value that is higher than the highest voltage the motor of the drain pump 170 is able to safely sustain (maximum safe voltage) for a period of time sufficiently short to avoid that the temperature of the motor goes above a limit for which the motor itself may be damaged (such as 2-3 seconds), and then lower the target voltage Vt to a value that may be safely sustained for a subsequent (longer) period. This is particularly useful for starting the drain pump motor 170, which requires a relatively high amount of power to overtake the liquid friction at the starting, and then a lower amount of power is sufficient to maintain the rotation during the steady state. In this way, with this solution, even if a cheap electric motor is installed, capable of safely sustaining only a relatively low maximum safe voltage, a higher supply voltage can be temporarily provided to promote the starting of the motor without damaging the latter. The duration of the steady state may be either predetermined, for example based on the specific operation cycle the laundry machine 100 is carrying out, or may be dynamically determined, for example based on information collected by sensors (such as for example a sensor adapted to measure the washing liquid level inside the washing tub, so as to stop the drain pump 170 when the washing tub has been assessed to be empty).

As mentioned above, the microcontroller 215 may be also configured to calculate the target voltage Vt based on predefined settings depending on electromagnetic and/or mechanic characteristics of the motor, which depends in turn on the type, materials and structure of the motor. For example, different models of motors may safely sustain different maximum voltages. For example, during the starting phase of a motor having a maximum safe voltage of 180 V, the microcontroller 215 may set the target voltage Vt to the supply voltage {e.g. , 220 V), and then to a lower voltage such as for example to the maximum safe voltage of the motor itself or also to a lower value. In this way, it is possible to strongly reduce the noise generated during the pump operation, as well as to reduce the power consumption. According to another example, in a laundry machine 100 supplied with a mains voltage of 220 V, and with the drain pump 170 that is operated by an electric motor designed to safely operate with a safe voltage of 160 V, the microcontroller 215 may set the target voltage Vt to said safe voltage or to a lower voltage.

According to an embodiment of the present invention, the microcontroller 215 is configured to calculate (an indication of) the RMS value of the voltage difference waveform Vp actually applied across the drain pump 170 motor terminals by jointly monitoring the current Ip flowing across the TRIAC 205 and the motor of the drain pump 170, and the AC supply signal VI. As will be described in greater detail in the following of the present description, the microcontroller 215 is configured to receive a processed signal Iv having a value based on the mean absolute value of the monitored current Ip and to infer an indication of the RMS value of the voltage difference waveform Vp actually applied across the drain pump 170 motor terminals by scaling such value of the processed signal Iv according to the actual AC supply signal VI.

For this purpose, according to an embodiment of the present invention, a monitoring circuit is provided, which is adapted to monitor the current Ip flowing across the TRIAC 205 and the motor of the drain pump 170 and accordingly generate a processed signal Iv having a value based on the mean absolute value of the monitored current Ip, and to monitor the AC supply signal VI at the line terminal TL.

According to an embodiment of the present invention, said monitor circuit comprises the microcontroller 215, a resistor Ri connected between the terminal Ml of the TRIAC 205 and the neutral terminal TN and a Mean Absolute Value (MAV) circuit 235 coupled between the terminal Ml of the TRIAC 205 and the microcontroller 215 to provide said processed signal Iv to the latter.

Moreover, said monitoring circuit comprises a supply voltage sensing unit 260 configured to periodically sense values actually taken by the AC supply signal VI. Advantageously, the supply voltage sensing unit 260 may be coupled to the line terminal TL for receiving the AC supply signal VI and to the microcontroller 215 for providing a supply signal sensed value Vs corresponding to the voltage value actually taken by the AC supply signal VI every a corresponding period of time - such as for example every period or every half period of the AC supply signal VI. According to an embodiment of the present invention, the supply voltage sensing unit 260 is configured to sense the peak value taken by the AC supply signal VI at every period or half period of the AC supply signal VI, for example by generating a supply signal sensed value Vs indicative of, e.g. , proportional to, the peak value of the AC supply signal VI. However, similar considerations apply if the supply signal sensed value Vs is generated by considering AC supply signal VI values different from the peak values.

Figure 3 schematically illustrates in terms of circuit elements the MAV circuit 235 according to an embodiment of the present invention.

The MAV circuit 235 comprises a rectifier section 310, an AC-DC converter section 320 and an (optional) filter section 321 connected in series to each other.

The rectifier section 310 comprises an operational amplifier 322 having a non- inverting input terminal coupled to the DC supply terminal Th (which is connected in turn to the neutral terminal TN) through a resistor 324, an inverting input terminal coupled to the terminal Ml of the TRIAC 205 through a resistor 326, and an output terminal connected to the anode terminal of a diode 328. The rectifier section 310 further comprises a further diode 330 having the anode terminal connected to the inverting input of the operational amplifier 322 and the cathode terminal connected to the output terminal of the operational amplifier 322. The rectifier section 310 further comprises a resistor 332 having a first terminal connected to the inverting input of the operational amplifier 322 and a second terminal connected to the cathode terminal of the diode 328 (circuit node 334).

The AC-DC converter section 320 comprises a further operational amplifier 336 having a non-inverting input terminal connected to the DC supply terminal Th (which is connected in turn to the neutral terminal TN), and a non-inverting input terminal coupled to the circuit node 334 through a resistor 338. The AC-DC converter section 320 further comprises a resistor 340 having a first terminal connected to the inverting input terminal of the operational amplifier 336 and a second terminal connected to the output terminal of the operational amplifier 336. The AC-DC converter section 320 further comprises a capacitor 342 having a first terminal connected to the inverting input terminal of the operational amplifier 336 and a second terminal connected to the output terminal of the operational amplifier 336.

A further resistor 343 is provided, having a first terminal connected to the terminal Ml and a second terminal connected to the inverting input terminal of the operational amplifier 336.

The filter section 321 comprises a resistor 344 having a first terminal connected to the output terminal of the operational amplifier 336 and a second terminal connected to the ground terminal GND. The filter section 321 further comprises a resistor 346 having a first terminal connected to the output terminal of the operational amplifier 336 and a second terminal connected to a first terminal of a capacitor 348 (circuit node 350). The capacitor 348 has a second terminal connected to the ground terminal GND. The circuit node 350 is connected to an input terminal of the microcontroller 215 to provide the processed signal Iv to the latter, as described hereinbelow.

The generation of the processed signal Iv will be now described according to an embodiment of the present invention.

During operation, the current Ip flowing across the TRIAC 205 and the motor of the drain pump 170 generates a corresponding voltage signal Vin corresponding to the voltage drop across the terminals of the resistor Ri. The voltage signal Vin is an AC signal which periodically reverses direction and has an RMS which depends on the TRIAC firing angle (see Figure 2B).

The voltage signal Vi is fed to the rectifier section 310 of the MAV circuit 235. The MAV circuit 235 blocks the positive half of the voltage signal Vi, while passes the negative half thereof (converting its polarity to the positive one), generating a corresponding unipolar signal Viu at the circuit node 334.

The AC-DC converter section 320 of the MAV circuit 235 converts the unipolar signal Viu generated by the rectifier section 310 into a DC signal having a value based on the mean absolute value of the voltage signal Vi, i.e., that has a value based in turn on the mean absolute value of the current Ip flowing across the TRIAC 205 and the motor of the drain pump 170. For example, according to an embodiment of the present invention, the higher the mean absolute value of the current Ip, the lower the amplitude of said DC signal, and vice versa.

Said DC signal, after being optionally filtered by means of the filter section 321, is the abovementioned processed signal Iv having a value based on the mean absolute value of the monitored current Ip.

The processed signal Iv is provided to the microcontroller 215, which infers an indication of the RMS value of the voltage difference waveform Vp actually applied across the drain pump 170 motor terminals by scaling such value of the processed signal Iv according to the supply signal sensed value Vs provided by the supply voltage sensing unit 160.

Thanks to the proposed solution, the microcontroller 215 is able to efficiently calculate the actual RMS value of the voltage difference waveform Vp applied across the drain pump 170 motor terminals. The RMS value of Vp is calculated taking into account the actual value of the AC supply signal VI, which is updated every period (or half- period) thereof through the supply voltage sensing unit 260. If the AC supply signal VI is subjected to an unpredictable fluctuation during one or more periods thereof, said fluctuation causes a corresponding variation in the sensed value Vs, which causes in turn a variation in the RMS value of the voltage difference waveform Vp calculated by the microcontroller 215.

Thanks to the feedback control carried out by the microcontroller 215, the firing angle is dynamically updated in such a way to maintain the RMS value of the voltage difference waveform Vp across the terminals of the motor close to the desired target voltage Vt, preventing any heating up of the motor pump if the AC supply signal VI rises because of unpredictable fluctuations, avoiding at the same time the intervention of thermal protection systems which may cause the interruption of the washing process.

Although in the description reference has been explicitly made to a power supply regulation apparatus 200 directed to regulate the supply of power to the synchronous motor of the drain pump 170 of the laundry machine 100, the concepts of the present invention directly apply to motors of different devices of the laundry machine 100, such as for example the synchronous motor of the recirculation pump 177.

Moreover, although in the description reference has been explicitly made to a power supply regulation apparatus for motors of pumps of a laundry washing machine or a laundry washing/drying machine, similar considerations apply if the previously described power supply regulation apparatus is employed for regulating the power supply to motors designed to operate devices of a laundry drying machine, such as the laundry drying machine 400 schematically illustrated in Figure 4.

With reference to Figure 4, the laundry drying machine 400 comprises a laundry treatment chamber 405 for accommodating the laundry to be dried. Preferably the laundry treatment chamber 405 includes a drum rotatably mounted inside the machine casing or cabinet 410.

The cabinet 410 is generically a parallelepiped in shape, and has a front wall, two side walls, a rear wall, a basement and a top. The front wall is provided with an opening for accessing the laundry treatment chamber 405 and with an associated door 415 for closing the opening. The top closes the cabinet 410 from above, and may also define a worktop.

Drying air is typically caused to flow through the laundry treatment chamber 405, where the laundry to be dried is contained, and is caused to tumble by the drum rotation. After exiting the laundry treatment chamber 405, the flow of moisture-laden drying air passes through a moisture condensing system, where the humid, moisture-laden drying air is (at least partially) dried, dehydrated, and the dehydrated air flow is then heated and caused to pass again through the laundry treatment chamber 405, repeating the cycle.

Reference numeral 420 denotes a compressor of the heat pump forming the moisture condensing system for the moisture- laden drying air; reference numeral 425 denotes a first heat exchanger, which in the example here considered forms the heat pump evaporator for cooling the drying air and heating the refrigerant; reference numeral 430 denotes a second heat exchanger, which in the example here considered forms the heat pump condenser for heating the drying air and cooling the refrigerant; reference numeral 435 denotes expansion means (e.g., capillary tube, expansion valve) between the evaporator 425 and the condenser 430 of the heat pump; the dashed lines 440 denote the heat pump refrigerant fluid circuit. More generally, the compressor 420, the first heat exchanger 425, the expansion means 435 and the second heat exchanger 430 form a refrigerant circuit of the heat pump, which is subdivided into a high pressure portion and a low pressure portion: the high pressure portion extends from the outlet of the compressor 420 via the first heat exchanger 425 to the inlet of the expansion means 435, whereas the low pressure portion extends from the outlet of the expansion means 435 via the second heat exchanger 430 to the inlet of the compressor 420. In the considered example, the first heat exchanger 425 acts as an evaporator, and the second heat exchanger 430 acts as a condenser.

Reference numeral 445 denotes a drying-air recirculation path. Reference numeral 450 denotes a drying-air recirculation fan, which promotes the recirculation of the drying air in the laundry treatment chamber 405 and the drying-air recirculation path 445. Reference numeral 455 denotes a Joule-effect drying air heater, for example one (or, possibly, more than one) electric resistor that is provided in the drying-air recirculation path 445 for boosting the drying air heating and arranged downstream the second heat exchanger 430. The heat pump used as a means for condensing the moisture contained in the drying air returning from the laundry treatment chamber 405 is also able to heat up the drying air after it has been de-humidified (the condenser 430 downstream the evaporator 415 has such a function). Preferably, but not limitatively, the recirculation fan 450 is a variable-speed fan.

According to an embodiment of the present invention, a power supply regulation apparatus equivalent to the power supply regulation 200 illustrated in Figure 2 is employed for regulating the power supply to a motor of the recirculation fan 450 (for example a synchronous motor directly coupled with the recirculation fan 450), or to a, e.g., synchronous, motor of a fan (not illustrated in figures) adapted to cool down the compressor 420.

According to an embodiment of the present invention, the microcontroller 215 may set the target voltage Vt to a value lower than the maximum safe voltage of the motor of the recirculation fan 450. The maximum safe voltage may substantially correspond to the supply voltage {e.g., 230 V) or may be lower {e.g., 160 V).

The present invention has been hereabove described by presenting some exemplary and non- limitative embodiments thereof. Several modifications to the embodiments described in the foregoing can be envisaged.

For example, even if in the detailed description reference has been explicitly made to a laundry treatment machine comprising a washing machine, a drying machine and/or a washing/drying machine, the concepts of the present invention may be applied as well to motors adapted to operate devices of other appliances, such as for example a motor adapted to operate the drain pump of a dishwasher.