Household Appliance Circuit Isolation for Zero Off-State Power
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Solution Overview
Problem
Existing circuit arrangements for household appliances face inefficiencies in energy consumption and safety when switched off, as high-impedance bleeder resistors consume power and safety-critical loads can be unintentionally activated during a short circuit, and door lock mechanisms complicate wiring and design.
Innovation Solution
A circuit arrangement with a switched-mode power supply, a control unit, and safety-critical loads decoupled from the supply network on both sides via switches controlled by the unit, ensuring isolation when off, and an electrical contact element for door locking integrated with the control circuit to optimize wiring and reduce power consumption to zero when off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bleeder resistor is connected in parallel with the capacitor in the EMC mains filter, then residual charges are discharged and operator safety is improved, but power consumption occurs even when the household appliance is switched off
Solution Approach 1:
The patent applies the dynamics principle by making the bleeder resistor's connection dynamic rather than static. A switching element (transistor or thyristor) controls the connection of the bleeder resistor to the capacitor based on operational conditions. When the appliance is switched off, the switching element activates the bleeder resistor to discharge residual charges for safety. When operational, the switching element disconnects the bleeder resistor to eliminate unnecessary power consumption. This dynamic switching resolves the contradiction between maintaining operator safety and reducing power consumption.
2Speed
If safety-critical loads are coupled to the supply network when the household appliance is switched on, then immediate activation is achieved, but unintentional startup can occur during a short circuit even when switched off
Solution Approach 1:
The patent applies segmentation by dividing the power supply path into multiple independent sections controlled by separate switching elements. Instead of a single switch controlling all loads, the invention introduces: (1) a first switching element in the phase line controlled by a first control signal, and (2) a second switching element in the neutral line controlled by a second control signal. This segmentation allows independent control of safety-critical loads, enabling immediate activation when needed while preventing unintentional startup during short circuits by maintaining isolation through the dual-switching architecture.
Solution Approach 2:
The patent uses switching elements as intermediaries between the supply network and safety-critical loads. These switching elements (transistors or thyristors) act as controlled mediators that can isolate or connect loads based on operational state and safety conditions. The intermediaries provide precise control over power delivery, enabling fast activation when required while maintaining safety isolation during switched-off states or short circuit conditions.
3Reliability
If the motor current is routed via the door contact, then door locking safety is ensured, but the design of the door lock and wiring becomes more complex
Solution Approach 1:
The patent extracts the motor current path from the door contact circuit. Instead of routing motor current through the door contact, the invention separates these functions: the door contact maintains its simple safety-monitoring role, while motor current is supplied through dedicated power switching elements (transistors or thyristors) controlled by the control unit. This extraction simplifies the door lock design and wiring while maintaining safety, as the door contact only needs to provide a safety signal rather than carry high motor currents.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures safe and energy-efficient operation by preventing unintentional startup during a short circuit and optimizing the design of door locks and wiring, with zero power consumption when the appliance is switched off, and only supplying safety-relevant components when required.
Implementation Method 1
a switched-mode power supply (18) for converting a mains voltage (UN) of a supply network into a supply DC voltage
Implementation Method 2
the EMC filter has a capacitor (9) connected between a phase conductor pole (2) and a neutral conductor pole (3) of the supply network
Implementation Method 3
a bleeder resistor (10) connected in parallel with it, which is necessary to discharge residual charges in the capacitor
Data Source
AI summary
The invention relates to a circuit arrangement for operating a household appliance, in particular a household appliance for the care of laundry items, having a switched-mode power supply (18) for converting a power supply (UN) of a public power supply network into a direct supply voltage, having a control unit (21) for controlling processes of the household appliance, wherein said control unit is connected to the switching power supply (18) and can be supplied by the direct supply voltage, and having an EMC filter for protecting the public power supply network from interfering signals from the household appliance, wherein said filter has a condenser (9) connected between a phase conductor pole (2) and a neutral conductor pole (3) of the public power supply network and a bleeder resistor (10) connected parallel thereto, wherein the condenser (9) and the bleeder resistor (10) can be coupled to the neutral conductor pole (3) via a switch (11) which can be activated by the control unit (21). The invention further relates to other circuit arrangements for operating a household appliance.