PWM Control for Series-Connected Variable Color-Temperature Lamp Beads
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Solution Overview
Problem
Existing color temperature adjustment methods for color-temperature-variable lamp beads are limited by mechanical switches, leading to large transition values and difficulty in achieving precise and smooth color temperature adjustments.
Innovation Solution
A color temperature adjustment apparatus using a single-chip microcomputer (STC89C51) to control PWM signals, adjusting current flow through transistors Qa and Qb to achieve precise color temperature adjustments by varying duty ratios, with a diode conductive path for current distribution and a common conductive path for mixing colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a toggle switch is used for color temperature adjustment, then the control structure is simple, but the color temperature transition value is large and smooth adjustment is difficult
Solution Approach 1:
The patent replaces the mechanical toggle switch system with an electronic control system using a single-chip microcomputer and PWM signals. This substitution eliminates the discrete switching mechanism that causes large transition values, enabling continuous and precise color temperature adjustment through electronic duty cycle control of the PWM signal.
Solution Approach 2:
The patent introduces dynamic control through PWM (pulse-width modulation) signaling, where the duty ratio of the PWM signal dynamically adjusts the effective current through the lamp beads. This dynamic adjustment mechanism allows smooth transitions between color temperatures by varying the duty cycle, overcoming the static nature of toggle switches.
2Device complexity
If diodes and resistors are used for current adjustment, then the circuit structure is simple, but the color temperature transition is not smooth
Solution Approach 1:
The patent replaces the passive component-based current adjustment (diodes and resistors) with an active electronic control system using transistors Qa and Qb controlled by PWM signals from a microcomputer. This replacement enables dynamic and continuous current adjustment, producing smooth color temperature transitions while maintaining relatively simple circuit structure.
Solution Approach 2:
The patent changes the control parameter from discrete component selection to continuous PWM duty cycle variation. By adjusting the duty ratio parameter of the PWM signal, the effective current through the lamp beads can be continuously varied, enabling smooth color temperature transitions without the limitations of fixed resistor and diode values.
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
Enhances precision in color temperature adjustments by minimizing smooth transitions, allowing for precise control of luminous intensities and improved color mixing in lamp beads.
Implementation Method 1
a pin of the single-chip microcomputer outputs a pulse-width modulation (PWM) signal, the PWM signal is a square-wave signal, or a sinusoidal signal, or a cosine signal
Implementation Method 2
one terminal of the LED lamp unit is connected to a positive electrode of a power supply
Implementation Method 3
when the PWM signal is at the high level, small currents are output through a transistor Qa and a transistor Qb; when the PWM signal is at the low level, large currents are output through the transistor Qa and the transistor Qb
Implementation Method 4
a collector of the transistor Qa is connected to a diode Da adjustment conductive path, one terminal of the diode Da adjustment conductive path is connected to a mechanical switch group, a downstream terminal of the resistor Rb is connected to a base of the transistor Qb, a collector of the transistor Qb is connected to a diode Db adjustment conductive path
Data Source
AI summary
A color temperature adjustment apparatus and a color temperature adjustment method for color-temperature-variable lamp beads connected in series are provided. The provided includes control manners such as single-chip microcomputer-based control and switch-based control. In switch-based control, switches on different lines are switched on to turn on lamp beads on the lines to achieve a mixed color effect. In single-chip microcomputer-based control, a PWM signal is output by using a pin of a single-chip microcomputer, where the PWM signal is at a high level or a low level; when the PWM signal is at the high level, small currents are output through a transistor Qa and a transistor Qb; when the PWM signal is at the low level, large currents are output through the transistor Qa and the transistor Qb; and the adjustment apparatus includes a resistor Ra and a resistor Rb.