Semiconductor Light Source Driving Apparatus PWM Rectangular Waveform
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Solution Overview
Problem
Existing semiconductor light source driving apparatuses face challenges in achieving high power efficiency and accurately delivering a pulse width modulation current with a rectangular waveform, particularly due to issues with temperature fluctuations and unstable source voltages.
Innovation Solution
A semiconductor light source driving apparatus is designed with a switching power supply, a first switching device, an inductor, a second switching device, and a free-wheeling diode, which together provide a DC voltage and switch the semiconductor light source with a PWM signal to produce an accurate rectangular current waveform, utilizing a snubber circuit and surge protection diode to minimize noise and ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LED drive circuit with error signal generating means and signal retaining means is used, then constant pulse current can be output by reducing influences of temperature fluctuations and unstable source voltage, but the circuit complexity increases and power efficiency decreases
Solution Approach 1:
The patent extracts and eliminates the complex error signal generating means, signal retaining means, and switching power supply control means from the conventional circuit. Instead, it uses a simple PWM signal input that directly controls the first switching device, achieving constant pulse current output without the need for error signals or signal retention mechanisms. This dramatically simplifies the circuit while maintaining the reliability of constant current output.
Solution Approach 2:
The inductor in the circuit automatically performs current smoothing and waveform shaping functions. When the first switching device switches on/off the PWM signal, the inductor inherently generates a rectangular current waveform through its electromagnetic properties, eliminating the need for external control mechanisms. The circuit components serve their basic functions without requiring complex coordination or control logic.
2Reliability
If a conventional drive circuit with multiple control components is used, then temperature fluctuations and voltage instability can be compensated, but power efficiency is reduced
Solution Approach 1:
The patent removes the switching power supply control means and error signal generating means that consume additional power. The simplified circuit uses only basic switching devices and passive components (inductor, diode, capacitor) that have minimal power loss. The PWM-based direct control approach eliminates the need for continuous error signal processing and signal retention, significantly improving power efficiency while maintaining stability through the inherent properties of the inductor and PWM control.
3Loss of energy
If PWM switching is implemented without proper waveform control, then power efficiency can be improved, but the current waveform accuracy deteriorates
Solution Approach 1:
The inductor automatically generates the rectangular current waveform through its electromagnetic properties when subjected to PWM switching. The second switching device and free-wheeling diode work together to ensure clean current transitions. This self-organizing behavior of the circuit components produces accurate rectangular waveforms without requiring complex waveform control mechanisms, thereby maintaining both power efficiency and waveform accuracy.
Solution Approach 2:
The circuit uses periodic PWM switching at a fixed frequency to drive the semiconductor light source. The regular on/off cycling of the first switching device, combined with the inductor's energy storage and release characteristics, naturally produces a stable rectangular current waveform. This periodic action ensures consistent waveform accuracy across different operating conditions while maintaining high power efficiency through minimal switching losses.
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 apparatus achieves high power efficiency and accurately drives semiconductor light sources with a rectangular pulse width modulation current, reducing distortions and maintaining stability across varying junction temperatures.
Implementation Method 1
an inductor (1310) having a first end connected to an output of the first switching device (1200)
Implementation Method 2
a free-wheeling diode (1320) connected between the first end of the inductor (1310) and a negative terminal of the switching power supply (110)
Implementation Method 3
switching power supply (110) that supplies a DC voltage, a first switching device (1200) that switches on/off an output of a positive terminal of the switching power supply (110) in accordance with an input signal
Data Source
AI summary
A semiconductor light source driving apparatus of the present disclosure includes a switching power supply that supplies a DC voltage, a power source switching FET, a coil, an inverting FET driver, a semiconductor light source device, and a free-wheeling diode. The power source switching FET switches on/off an output of a positive terminal of the switching power supply in accordance with an input PWM signal. The coil has a first end connected to the output of the power source switching FET. The inverting FET driver is connected between a second end of the coil and a negative terminal of the switching power supply and switched on/off in accordance with an input signal. The semiconductor light source device is connected between the second end of the coil and the negative terminal of the switching power supply. The first end of the coil and the negative terminal of the switching power supply are connected to the free-wheeling diode.