PWM Load Controller Circuit for Lighting Dimming
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Solution Overview
Problem
Linear amplifier circuits used for dimming lighting systems are inefficient due to their inability to both sink and source current and require positive and negative power supplies, leading to inherent power losses.
Innovation Solution
A PWM load controller circuit that uses a single common circuit element, an inductor-capacitor filter, to generate a time-averaged direct current output voltage, allowing for both current sourcing and sinking, eliminating the need for dual power supplies and reducing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If linear amplifier circuits are used for dimming control, then current control capability is provided, but power losses increase and dual power supplies are required
Solution Approach 1:
The patent employs pulse width modulation (PWM) technique where a switching element operates at high frequency, periodically connecting and disconnecting the power supply to the load. This periodic switching action allows the circuit to control average power delivery without requiring continuous current flow through linear amplifiers, thereby eliminating the need for dual power supplies and reducing power losses significantly.
Solution Approach 2:
The patent replaces the linear amplifier-based mechanical/electronic continuous control system with a switching-based system. Instead of using linear amplifiers that continuously dissipate power, the invention uses electronic switching elements (transistors) that operate in saturation or cutoff regions, substituting continuous analog control with pulsed digital-like control to achieve the same dimming function with higher efficiency.
2Adaptability or versatility
If linear amplifier circuits are used for dimming control, then current control capability is provided, but the circuit can only sink or source current, not both
Solution Approach 1:
The patent merges the functions of current sourcing and current sinking into a single H-bridge circuit configuration. The H-bridge combines four switching elements arranged in a specific topology that allows the circuit to bidirectionally control current flow through the load, enabling both sourcing and sinking capabilities within one integrated circuit structure rather than requiring separate circuits.
Solution Approach 2:
The H-bridge circuit serves multiple functions simultaneously: it can source current to the load, sink current from the load, and control the direction of current flow. This universal circuit configuration provides adaptability for various lighting load types and control requirements, replacing the need for separate dedicated sourcing and sinking circuits.
3Loss of energy
If PWM switching circuit is used, then power efficiency is improved, but output voltage ripple increases
Solution Approach 1:
The patent introduces an LC filter circuit as an intermediary element between the PWM switching output and the lighting load. The inductor and capacitor in the filter circuit work together to smooth the pulsed voltage output from the switching elements, attenuating the high-frequency ripple while maintaining the average voltage level required for proper LED operation, thus eliminating the harmful voltage ripple effect.
Solution Approach 2:
The patent carefully selects and adjusts the parameters of the LC filter components (inductance value L and capacitance value C) to optimize the filtering performance. By changing these parameters, the cutoff frequency of the filter is set appropriately below the PWM switching frequency, ensuring effective ripple attenuation while maintaining the desired voltage output characteristics for the lighting load.
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 enables precise control of lighting loads with high efficiency, reducing thermal drift and component count, and eliminating the need for negative power supplies, resulting in improved operational efficiency and cost savings.
Implementation Method 1
an inductor that is part of a passive low pass inductor capacitor filter
Implementation Method 2
a passive low pass inductor capacitor filter adapted to generate a time-averaged direct current output voltage
Data Source
AI summary
Provided herein is a lighting load control assembly, comprising: a circuit adapted to source a first lighting load controlling current to a lighting load and sink a second lighting load controlling current from the lighting load through a single common circuit element. Further provided herein is a method for controlling a lighting load, the method comprising: receiving a pulse width modulated (PWM) control signal with a predetermined duty cycle and frequency; generating complementary gate output signals based on the received PWM control signal; generating a pulse train output signal based on the complementary gate output signals with substantially the same duty cycle and frequency as the received PWM control signal; receiving the generated pulse train output signal at an LC filter; and generating an LC output signal that is substantially equal to the time-averaged product of a maximum voltage of the received pulse train output signal and the duty cycle of the received pulse train output signal, which is also substantially equal to the duty cycle of the PWM input signal.