Patent Publication Number: US-2022231505-A1

Title: Circuit arrangement for controlling a plurality of electrical loads

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2021 200 507.1, filed Jan. 21, 2021; the prior application is herewith incorporated by reference in its entirety. 
     FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a circuit arrangement for controlling a plurality of electrical loads, such as for example power switching elements. 
     A household appliance, such as for example a washing machine or a dishwasher, typically has different electrical loads, such as for example electric motors, valves, pumps, switching elements, etc., which are arranged for example in the FELV range (functional extra-low voltage) of the household appliance. On the other hand, the different electrical loads are typically controlled by means of one or several microcontrollers which are arranged in the SELV range (safety extra-low voltage) or in the PELV range (protective extra-low voltage). 
     SUMMARY OF THE INVENTION 
     The galvanic isolation between a control module, in particular a microcontroller, in the PELV/SELV range and several different electrical loads in the FELV range is typically associated with a relatively high outlay. The present document is concerned with the technical object of enabling electrical loads in an electrical appliance to be controlled efficiently (in terms of cost, weight and/or installation space) and in a galvanically isolated manner. 
     With the above and other objects in view there is provided, in accordance with the invention, a circuit arrangement for controlling a plurality of loads of an electrical appliance, the circuit arrangement comprising: 
     a main control module arranged in a first voltage range of the circuit arrangement and configured to generate control data for controlling a first load of the plurality of loads; wherein the plurality of loads are arranged in a second voltage range; 
     a galvanic isolation unit configured to transfer the control data via a galvanically isolated connection from the first voltage range to the second voltage range; 
     at least one auxiliary control module configured to receive the control data and having a plurality of control outputs for the plurality of loads; 
     said at least one auxiliary control module comprising:
         a light-emitting diode driver configured to operate a corresponding plurality of LED arrangements via said plurality of control outputs; and/or   a general-purpose input/output expansion circuit having a plurality of programmable control outputs; and       

     said at least one auxiliary control module being configured, based on the control data:
         to identify a first control output from the plurality of control outputs for controlling a first load of the plurality of loads; and   to cause the first load of the plurality of loads to be controlled via the first control output.       

     In other words, according to one aspect of the invention, a circuit arrangement (also referred to as circuit apparatus) for controlling a plurality of loads of an electrical appliance, in particular a household appliance, is described. Exemplary household appliances are a washing machine, a dishwasher, a dryer, a fridge, a cooker, an oven, etc. An electrical load of an electrical appliance can be configured to provide a function of the electrical appliance, for example a heating function, a cooling function, a drive function, etc. Exemplary electrical loads are: an electrically driven valve, an electrically driven motor, an electrically driven heater, an electrically driven pump and/or an electrical switching element, in particular a relay, a TRIAC, a transistor, a MOSFET. An electrical switching element can be used in particular to switch (i.e., to activate or deactivate) another load, for example a valve, a motor, a heater, a pump, etc. 
     The circuit arrangement comprises a main control module (e.g. a microcontroller), which is arranged in a first voltage range of the circuit arrangement, and which is configured to generate control data for controlling a first load of the plurality of loads. The control data can comprise a control instruction for a specific load of the electrical appliance, for example in order to activate or deactivate the load or in order to set and/or change the power consumption or the power output of the load. The first voltage range can be a safety extra-low voltage (SELV) or a protective extra-low voltage (PELV) range. 
     The plurality of loads can be arranged in a second voltage range which differs from the first voltage range. Here, the second voltage range may belong to a different protection class than the first voltage range. In particular, the second voltage range can be a functional extra-low voltage (FELV) range. 
     Furthermore, the circuit arrangement comprises a galvanic isolation unit, which is configured to transfer the control data via a galvanically isolated connection from the first voltage range to the second voltage range. The galvanic isolation unit can comprise for example an optocoupler, a capacitive coupler and/or an inductive coupler. 
     The circuit arrangement further comprises at least one auxiliary control module, which comprises a plurality of control outputs for the corresponding plurality of loads. The at least one auxiliary control module can be configured to control the plurality of control outputs independently of one another, in particular to switch them independently of one another. 
     The auxiliary control module can have a data input via which the control data from the galvanic isolation unit can be received. The received control data can then be used to operate one or several of the control outputs. In particular, the current and/or the voltage can be set at at least one control output as a function of the control data. 
     The auxiliary control module can comprise a light-emitting diode (LED) driver or the auxiliary control module can be embodied as an LED driver. The LED driver can be embodied to operate a corresponding plurality of LED arrangements (e.g. LEDs or LED chains) via the plurality of control outputs. In particular, the plurality of control outputs can be provided for controlling LED arrangements with different colors, in particular a red (R), a green (G) and/or a blue (B) LED arrangement. 
     Alternatively or in addition, the auxiliary control module can comprise a general-purpose input/output (GPIO) expansion circuit or expander, or can be embodied as a GPIO expansion circuit or expander. The GPIO circuit or expander can be embodied such that the behavior of the plurality of control outputs can be programmed (by a user, possibly freely). 
     In this way, one or several cost-efficient auxiliary control modules can be used in the second voltage range, in particular in a manner departing from their original purpose, in order to control the individual electrical (power) loads. Here, the one or several auxiliary control modules can be configured in each case to identify, on the basis of the control data, a first control output from the plurality of control outputs for controlling the first load. The control data can have for example an identifier (such as a bit code) for the first load or for the first control output. The auxiliary control module can be embodied to assign the control data, in particular a control instruction contained in the control data, to the first control output on the basis of the identifier. 
     Furthermore, the one or several auxiliary control modules can be configured to cause the first load to be controlled via the first control output. The control data can comprise a control instruction for the first load (in addition to the identifier of the first load). The auxiliary control module can be configured to operate the first control output as a function of the control instruction. In particular, the voltage level and/or the current can be set to or at the first control output as a function of the control instruction. 
     A circuit arrangement is thus described which uses one or several auxiliary control modules (in particular one or several LED driver chips and/or one or several GPIO expander chips) in the second voltage range in order to control different loads of an electrical appliance. This can enable several different loads in the second voltage range to be controlled in an efficient manner using a single galvanic isolation unit. Furthermore, LED driver chips and/or GPIO expander chips are used in large quantities for other purposes (in particular for controlling LED-based light elements), and can thus be provided in a cost-efficient manner for controlling the electrical loads of an electrical appliance (in a manner departing from their original purpose). 
     The auxiliary control module can be embodied to set the voltage level of the first control output to high or low as a function of the control data, in particular as a function of the control instruction for the first load. In this way, the first load can be controlled, in particular activated or deactivated, or opened or closed, in a reliable manner. When the auxiliary control module, in particular the LED driver, is used in accordance with its original purpose, the voltage level at the first control output can be used to activate or deactivate an LED arrangement connected to the first control output. 
     Alternatively or in addition, the auxiliary control module, in particular the LED driver of the auxiliary control module or the auxiliary control module implemented by way of an LED driver, can be embodied to set the (first) current at the first control output by means of pulse-width modulation (PWM) as a function of the control data, in particular as a function of the control instruction for the first load, in particular in order to set the power, for example the mechanical power, the heating power, etc. of the first load. 
     The LED driver can be configured to dim an LED arrangement connected to a control output of the LED driver by means of PWM. Here, the pulse width can be reduced or increased in order to reduce or increase the strength of the current at the control output in a corresponding manner. This dimmer mechanism of the LED driver can be used in the circuit arrangement for controlling an electrical load of the electrical appliance. In this way, a particularly efficient and precise control of different electrical loads in an electrical appliance can be enabled. 
     The circuit arrangement can comprise a first auxiliary control module and a second auxiliary control module which are arranged, for instance in a cascaded connection, within the second voltage range. Here, the auxiliary control modules can be of identical design. The auxiliary control modules can in each case have a data input (in particular a data input pin) via which the control data can be received by the respective auxiliary control module. Furthermore, the auxiliary control modules can in each case have a data output, in particular a cascading pin, via which the control data can be forwarded to a downstream auxiliary control module. The auxiliary control modules can thus be embodied for a cascading, in which the data input of a downstream auxiliary control module is connected to the data output of an upstream auxiliary control module. The control data can thus be forwarded in a cascaded manner from one auxiliary control module to an auxiliary control module disposed directly downstream. In this way, the number of electrical loads which can be controlled in the second voltage range via the main control module (which is arranged in the first voltage range) can be adjusted, in particular increased, in an efficient and flexible manner. 
     When a first and a second auxiliary control module are used, the first auxiliary control module can comprise a plurality of first control outputs for a corresponding plurality of first loads. The second auxiliary control module can comprise a plurality of second control outputs for a corresponding plurality of second loads. For example, each auxiliary control module can be configured to control two or more, or three or more, or four or more electrical loads of the electrical appliance. Here, the individual control outputs can be constructed identically in each case. 
     The first auxiliary control module can be embodied to forward the control data received via the galvanic isolation unit, in particular via the cascading pin of the first auxiliary control module, to the second auxiliary control module. In particular, the first auxiliary control module can be embodied as a shift register, which forwards the control data to the second auxiliary control module as a function of a cycle time. 
     The main control module can be embodied to transmit the control data to the auxiliary control module by means of a line code, in particular by means of a binary line code, for example a non-return-to-zero (NRZ) code. In this way, a particularly efficient control of several different loads can be enabled. 
     According to a further aspect, a household appliance (e.g. a washing machine, a dishwasher, an oven, a cooker, a kitchen appliance, a vacuum cleaner, a dryer, a fridge, etc.) is described which comprises the circuit arrangement described in this document. The household appliance can comprise a mains connection for connecting the household appliance to an AC supply voltage. Furthermore, the household appliance can comprise a switched mode power supply and/or one or several voltage transformers, which are embodied to provide several different voltage ranges in the household appliance on the basis of the AC supply voltage (e.g. for operating a main control module on the one hand and for operating several different electrical loads on the other hand). 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     It should be noted that any aspects of the circuit arrangement described in this document can be combined with one another in a wide variety of ways. In particular, the features of the claims can be combined with one another in a wide variety of ways. In other words, although the invention is illustrated and described herein as embodied in circuit arrangement for controlling a plurality of electrical loads, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  shows a block diagram of an exemplary household appliance; 
         FIG. 1B  shows an exemplary galvanic isolation between control modules and loads of a household appliance; and 
         FIG. 2  shows an exemplary circuit arrangement for controlling several electrical loads of an electrical appliance, in particular a household appliance. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As noted above, the present invention concerns itself with the efficient, galvanically isolated control of different loads, in particular of different switching elements, of an appliance, in particular a household appliance. In this context,  FIG. 1A  shows an exemplary household appliance  100 , for example a washing machine, with a mains connection  102 , in particular with a switched mode power supply, via which the household appliance  100  can be connected to an AC supply voltage  103 . 
     As shown by way of example in  FIG. 1B , the household appliance  100  typically comprises one or several control modules  121 , which are configured to control different electrical loads  123 , in particular different electrical switching elements, of the household appliance  100 . In particular, a control instruction  124  can be transmitted from a control module  121  to an electrical load  123 , for example in order to activate the electrical load  123  or to deactivate the electrical load  123 . 
     The control module  121  for an electrical load  123  can be arranged in the SELV/PELV (safety/protective extra low voltage) range  131  of the household appliance  100 , while the electrical load  123  is arranged in the FELV (functional extra low voltage) range  132  of the household appliance  100 . The expression that a given element is “arranged in” a given range, or voltage range, is partly meant to be understood as an indication of its location and partly meant to be understood as an indication of its supply voltage or operating voltage. The term “galvanic isolation” is informed by the different (voltage) ranges and, accordingly, a separation in terms of location and/or an insulation in terms of protecting against the transmission or bleed of the respective voltages between the ranges. A galvanic isolation unit  122  is therefore arranged between the control module  121  and the electrical load  123  and is configured to transfer the control instruction  124  via a galvanically isolated communication connection from the control module  121  to the electrical load  123 . 
     A household appliance  100  can thus comprise different electrical loads  123 , such as for example several valves, one or several motors, a heater, one or several pumps, etc., which can be switched as necessary via a corresponding one or several relays, TRIACs, transistors, MOSFETs, etc. The one or several switching elements  123  are actuated by one or several control modules  121 , in particular microcontrollers. 
     The actuation of the switching elements  123  takes place typically in a galvanically isolated manner for safety reasons and/or as a protective measure and/or to avoid ground loops and/or to avoid shifts in potential. The galvanic isolation of the actuation of a power switching element  123  takes place for example optically (by means of an optocoupler, optotriac, etc.), inductively (by means of a transformer), or capacitively (by means of a capacitive coupler, a capacitor, etc.). In this way, the individual switching elements  123  can be switched via a microcontroller that is supplied by SELV or PELV. 
     The galvanic isolation between a control module  121  and the different loads  123  can be effected through the use of a dedicated galvanic isolation unit  124  for each individual load  123 . Alternatively, an additional control module (in particular an additional microcontroller) can be used, which communicates with the main control module  121  via a separate data bus. The galvanically isolated actuation of the individual loads  123  can be effected by the additional control module. 
     The above-cited measures for galvanic isolation are typically associated with relatively high costs, in particular for installing a dedicated isolation unit  124  for each individual load  123 , or for installing an additional microcontroller. Furthermore, a relatively large isolation trench is typically required between the SELV/PELV range  131  and the FELV range  132 . 
       FIG. 2  shows a circuit arrangement  200  with a main control module  121 , which is arranged in a first voltage range  131  (in particular in a SELV range or in a PELV range). The main control module  121  is connected to one or several auxiliary control modules  201  via a galvanic isolation unit  122 . Here, an auxiliary control module  201  is configured to control one or several loads  123 . In particular, an auxiliary control module  201  can have one or several control outputs  204  for controlling a corresponding one or several loads  123 . The one or several auxiliary control modules  201  of the circuit arrangement  200  are arranged in a second voltage range  132  (in particular in an FELV range). 
     The main control module  121  is configured to transmit control data  202  to one of the auxiliary control modules  201  via the isolation unit  122 . Here, the control data  202  can indicate an identifier for the load  123 , in particular for the auxiliary control module  201  and for the control output  204 , to which the load  123  is connected, for which the control data  202  is intended. Furthermore, the control data  202  can have a control instruction  124  for the load  123  indicated by the identifier (e.g., a control instruction  124  for activating or deactivating the load  123  or a control instruction  124  for setting the power of the load  123 ). 
     An auxiliary control module  201  of the circuit arrangement  200  can be configured to check control data  202 , which has been transmitted by the main control module  121 , in order to determine whether the control data  202  is intended for a load  123  which is connected to a control output  204  of the auxiliary control module  121 . If this is not the case, the control data  202  can be ignored by the auxiliary control module  121 . If this is the case, the control instruction  124  can be forwarded to the identified control output  204  of the auxiliary control module  121 . This can enable different loads  123  to be controlled in an efficient manner across different voltage ranges  131 ,  132 . 
     In a preferred example, an auxiliary control module  121  is or comprises an LED (light-emitting diode) driver, in particular a single-line LED driver, or a GPIO (general-purpose input/output) expander. In this way, a particularly efficient circuit arrangement  200  can be provided. The GPIO has a plurality of programmable outputs ( 204 ); that is, the behavior of the plurality of control outputs ( 204 ) can be programmed. 
     The use of single-line LED drivers or GPIO expanders  201  enables not only LEDs but also other loads  123  to be actuated. Here, just a single galvanic isolation element  122  is required. Furthermore, a control output  204 , in particular a chip pin, can be used in each case for the individual loads  123 . The use of LED drivers or GPIO expanders  201  in the FELV range  132  makes it possible to reduce the PCB (printed circuit board) area or footprint of the circuit arrangement  200 , as the number of isolation elements  122  between SELV/PELV  131  and FELV  132  can be reduced. The main microcontroller  121  can transmit a line code  202 , for example a non-return-to-zero code, as an actuation signal  123  via the galvanic isolation element  122  to a driver  201 . The driver  201  can then switch a load  123  directly or via a power switch. 
     A driver  201  can be configured to switch several outputs  204  independently of one another. It is also possible to cascade several drivers  201 . Here, a cascade of drivers  201  can work in the manner of a shift register, in which the cycle time is generated by the drivers  201  themselves and/or transmitted separately. As a result, an almost unlimited multiplicity of drivers  201  can be linked to one another and can in turn actuate a corresponding number of loads  123 . 
     The use of LED drivers  201  for actuating loads  123  in an electrical appliance  100  enables the loads  123  to be actuated in a particularly efficient manner in terms of costs and installation space, in particular on account of the fact that fewer galvanic isolation elements  122  can be used and/or on account of the fact that LED drivers  201  are manufactured in high quantities. Furthermore, the cascading of drivers  201  enables the number of controlled loads  123  to be adjusted flexibly. Moreover, the required PCB (printed circuit board) area for the isolation trench between the voltage ranges  131 ,  132  can be reduced. 
     Once more in a summary of the disclosure, there is provided a circuit arrangement ( 200 ) for controlling a plurality of loads ( 123 ) of an electrical appliance ( 100 ). The circuit arrangement ( 200 ) comprises a main control module ( 121 ), which is arranged in a first voltage range ( 131 ) of the circuit arrangement ( 200 ), and which is configured to generate control data ( 202 ) for controlling a first load ( 123 ) from the plurality of loads ( 123 ); wherein the plurality of loads ( 123 ) is arranged in a second voltage range ( 132 ). The circuit arrangement ( 200 ) further comprises a galvanic isolation unit ( 122 ), which is configured to transfer the control data ( 202 ) via a galvanically isolated connection from the first voltage range ( 131 ) to the second voltage range ( 132 ). In addition, the circuit arrangement ( 200 ) comprises at least one auxiliary control module ( 201 ), which comprises a plurality of control outputs ( 204 ) for the corresponding plurality of loads ( 123 ). The auxiliary control module ( 201 ) comprises a light-emitting diode (LED for short) driver, which is embodied to operate a corresponding plurality of LED arrangements via the plurality of control outputs ( 204 ), and/or a general-purpose input/output (GPIO for short) expansion circuit, in which a behavior of the plurality of control outputs ( 204 ) can be programmed. The auxiliary control module ( 201 ) is configured, on the basis of the control data ( 202 ), to identify a first control output ( 204 ) from the plurality of control outputs ( 204 ) for controlling the first load ( 123 ); and to cause the first load ( 123 ) to be controlled via the first control output ( 204 ). 
     It will be understood that the present invention is not restricted to the exemplary embodiments described. It should be noted that the description and the figures are only intended to illustrate the principle of the proposed circuit arrangement.