Two-Wire MOSFET Dimmer Circuit With Floating AC/DC Supply
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Solution Overview
Problem
Existing AC power control systems in facility electrical systems are inefficient, prone to wear, and can cause electrical noise and health issues, particularly when controlling large loads or LED lighting, and often require three wires for operation.
Innovation Solution
A bidirectional switch using power MOSFETs with a floating AC/DC power supply, allowing for efficient control of AC power with only two wires, enabling both on-off and phase-control functions through a novel configuration that incorporates a back-to-back arrangement of MOSFETs and a periodically refreshed AC/DC power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical outlets and switches are used for AC power control, then simple on-off control is provided, but the devices wear out and can cause short circuits or dangerous arcing
Solution Approach 1:
The patent replaces mechanical switches and outlets with solid-state electronic switches that use semiconductor devices to control AC power flow. This substitution eliminates mechanical wear, contact arcing, and the associated reliability issues while maintaining the on-off control function.
Solution Approach 2:
The invention changes the control parameter from mechanical position to electrical signal, using electronic switching devices that can be controlled by low-power signals. This allows for more reliable control without the physical wear inherent in mechanical systems.
2Ease of operation
If triacs are used for phase control of AC power, then cycle-by-cycle control is achieved, but electrical noise is induced back into the facility electrical system
Solution Approach 1:
The patent replaces triac-based phase control with solid-state electronic switching that uses MOSFETs or IGBTs controlled by microprocessors. This substitution provides phase control capability while significantly reducing electrical noise generation compared to triac-based systems.
Solution Approach 2:
The invention introduces microprocessor-based control circuits as intermediaries between the user interface and the power switching elements. This intermediary layer enables precise phase control while filtering and minimizing electrical noise injection into the facility electrical system.
3Loss of energy
If triacs are used for AC power control, then efficiency is improved compared to rheostats, but the devices are too inefficient for small enclosures controlling large electrical loads
Solution Approach 1:
The patent changes the switching device parameters by using MOSFETs or IGBTs with much lower on-resistance compared to triacs. This enables highly efficient control of large electrical loads while generating minimal heat, making the devices suitable for small enclosure installations.
Solution Approach 2:
The invention segments the power control function into separate optimization zones: high-power MOSFETs/IGBTs for load control and low-power microprocessors for signaling and timing. This segmentation allows each component to operate in its optimal efficiency range.
4Reliability
If state-of-the-art three-wire systems are used for AC control, then reliable electronic control is provided, but installation complexity increases requiring all three wires
Solution Approach 1:
The patent makes the control circuitry universal by designing it to operate with only two wires (hot and neutral), eliminating the requirement for a separate ground wire for control circuit operation. The microprocessor and associated circuits are powered and controlled through the existing two-wire AC connection, simplifying installation while maintaining reliability.
Solution Approach 2:
The invention merges the power delivery function and the control signal function into the same two-wire connection. The control circuit draws power and receives control signals through the hot and neutral wires, eliminating the need for separate control wiring and reducing installation complexity.
5Ease of operation
If conventional AC/DC power supplies are used with transistorized control circuits, then control functionality is achieved, but the system requires access to all three wires in a typical single-phase circuit
Solution Approach 1:
The patent inverts the traditional approach by using the AC mains waveform itself to periodically refresh the floating AC/DC power supply, rather than requiring a separate DC power source. This inversion eliminates the need for a dedicated ground reference and enables operation with only two wires.
Solution Approach 2:
The control circuitry serves itself by using the existing AC power lines to provide both power and control signals. The microprocessor and associated circuits are powered from the AC/DC converter that is periodically refreshed by the AC mains, eliminating external power requirements and simplifying the wire configuration.
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
The solution provides reliable, efficient, and wide-ranging control of AC power, reducing wear and noise, and allowing for the dimming of electrical loads with improved safety and efficiency, while simplifying installation and reducing the number of wires required.
Implementation Method 1
power MOSFETs as electronic switches having very low 'on' resistance connected between the AC mains supply and the desired load
Implementation Method 2
typical power MOSFETs intrinsically incorporate a body diode in parallel with the conducting channel
Implementation Method 3
a novel floating AC/DC power supply is included that is periodically refreshed through operation of the MOSFET switches
Data Source
AI summary
A bidirectional switch and dimmer for the control of power from an AC source to a load is described. The approach uses power MOSFETs in a bidirectional switch subcircuit configuration that includes a floating AC/DC power supply and a solid state double pole switch that alternates between connection of the AC source to the load and periodic connection of the AC source to the AC/DC power supply. The switch and dimmer circuit configuration allows insertion into an existing single-phase circuit using only two wires. The design allows for manufacturing the entire circuit on a single chip.