Dimmer Pre-regulator with Adjustable Resistor for Inrush Current Control
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Solution Overview
Problem
2-wire dimmer configurations face challenges in controlling current to LED loads due to limited power budgets and high inrush currents, leading to inefficient power conversion and potential LED activation issues, while prior solutions with fixed resistors result in inefficiencies and heating.
Innovation Solution
A dimmer with a pre-regulator comprising an adjustable resistor and sensor, controlled by a microcontroller, which senses current and adjusts resistance to manage power efficiently, preventing unwanted LED activation and optimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed value resistor is added in the current path to reduce inrush current and prevent LED flashing, then LED activation issues are improved, but power efficiency deteriorates and heating increases
Solution Approach 1:
The patent replaces the fixed value resistor with a dynamically controllable resistor whose resistance value can be adjusted in real-time. The resistor is controlled by a microcontroller that monitors current conditions and adjusts the resistance accordingly - using higher resistance during startup to limit inrush current, and lower resistance during normal operation to minimize power loss and heating.
Solution Approach 2:
The patent changes the resistance parameter of the resistor from a fixed value to a variable value that can be modified based on operating conditions. This allows the system to optimize the resistance value for different scenarios - high resistance for inrush current limiting, low resistance for efficient power conversion during steady-state operation.
2Object-affected harmful factors
If the power budget for the dimmer is limited to 150 mW or below to prevent LED glow, then unwanted LED activation is prevented, but current control capability deteriorates
Solution Approach 1:
The patent implements a pre-regulator stage before the main power conversion circuit that proactively controls the current flowing to the dimmer electronics. This preliminary current regulation ensures that the power consumption remains within the 150 mW budget while still providing adequate current to the LED load, separating the power needs of the dimmer control circuitry from the LED driving circuitry.
Solution Approach 2:
The patent introduces a pre-regulator as an intermediary component between the AC input and the main power conversion stage. This intermediary stage acts as a buffer that limits power to the dimmer electronics while allowing full power to the LED load, effectively mediating between the power budget constraint and the current control requirement.
3Use of energy by moving object
If high voltage capacitors are used in the switched mode power supply for efficient AC to DC conversion, then power efficiency is improved, but inrush current increases causing LED flashing
Solution Approach 1:
The patent applies preliminary anti-action by placing a controllable resistor in series with the AC input before the high voltage capacitor. During startup, this resistor limits the inrush current that would otherwise charge the capacitor and cause LED flashing. Once the capacitor is charged, the resistor value is reduced or bypassed to minimize its impact on power efficiency during normal operation.
Solution Approach 2:
The patent makes the series resistor dynamic rather than fixed, allowing it to provide strong current limiting during capacitor charging while minimizing power loss during steady-state operation. The microcontroller adjusts the resistor value based on the charging state of the high voltage capacitor, maintaining both protection against inrush current and efficiency during normal operation.
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 effectively controls current to the DC power supply, reducing inefficiencies and heating, enabling smooth dimming and adapting to varying power conditions, while ensuring the dimmer operates within safe current limits.
Implementation Method 1
The sensor is adapted for sensing the current between the switch terminal and the DC terminal
Implementation Method 2
The pre-regulator is adapted for controlling the resistance of the adjustable resistor based on the sensed current
Implementation Method 3
The adjustable resistor comprises a first transistor having a first and a second main electrode and a control electrode
Implementation Method 4
the dimmer and the load are connected in series with an AC voltage source
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A pre-regulator (120) for controlling the current from an AC voltage source (170) to a DC power supply (140) of a dimmer (100). The pre-regulator (120) comprises an adjustable resistor (121) and a sensor (122) wherein the sensor (122) and the adjustable resistor (121) are adapted to be connected in series between a switch unit of the dimmer and the DC power supply by means of a switch terminal (163) and a DC terminal (164). The sensor (122) is adapted for sensing the current between the switch terminal (163) and the DC terminal (164) and the pre-regulator (120) is adapted for controlling the resistance of the adjustable resistor (121) based on the sensed current when the AC voltage source is connected to the dimmer.