LED Driving Circuit Frequency Adjustment
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Solution Overview
Problem
Conventional LED driving circuits require increasing inductance to match output current with duty cycles, leading to increased circuit area and cost due to the need for multiple series inductors, which results in spikes in switching signals and output currents.
Innovation Solution
A driving circuit that adjusts the frequency of the switching signal based on the duty cycle of the PWM signal to match the output current to LEDs, eliminating the need to change the inductance of the inductor or add series inductors, thereby reducing circuit area and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inductance of the inductor is increased to match the duty cycle and avoid spikes in switching signal and output current, then the stability of output current is improved, but the circuit area and cost increase due to requiring multiple series inductors
Solution Approach 1:
The patent changes the operating parameters of the existing inductor by dynamically adjusting the switching frequency based on the PWM duty cycle. When the duty cycle decreases, the switching frequency is increased, and vice versa. This parameter adjustment allows the same inductor to maintain appropriate impedance characteristics across different operating conditions, eliminating the need for multiple series inductors while preventing current spikes and maintaining output current stability.
2Reliability
If the inductance of the inductor is increased to match the duty cycle, then the reliability of output current is improved, but the device complexity increases due to requiring multiple series inductors
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the switching frequency according to the PWM duty cycle. This single parameter adjustment enables the existing inductor to adapt its effective impedance to match different operating conditions, eliminating the need for multiple inductors and simplifying the overall device structure while maintaining output current reliability.
Solution Approach 2:
The patent implements dynamics by making the switching frequency variable rather than fixed. The frequency automatically adjusts based on the duty cycle requirements, allowing the system to adapt to different operating conditions dynamically. This dynamic adjustment eliminates the need for static multiple inductor configurations and reduces device complexity.
3Area of stationary object
If the switching frequency is adjusted to match output current, then the circuit area is reduced, but the complexity of controlling frequency adjustment increases
Solution Approach 1:
The patent employs feedback by using the PWM duty cycle signal itself to control the switching frequency adjustment. The duty cycle information is fed back to the frequency control mechanism, creating a self-regulating system where the frequency automatically adapts to match the current output requirements. This feedback approach simplifies control complexity compared to external control methods.
Solution Approach 2:
The patent implements self-service by enabling the system to automatically adjust its own operating parameters based on its current state. The switching frequency is self-regulated according to the PWM duty cycle without requiring external intervention or complex control circuits, thereby reducing both circuit area and control complexity.
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
This approach allows for effective adjustment of LED light intensity without increasing inductance, preventing spikes and reducing circuit complexity and cost, while maintaining normal output current performance across varying duty cycles.
Implementation Method 1
an inductor L, a power switch M1... The inductor is used for producing an output current
Data Source
AI summary
The present invention relates to a driving circuit and a driving method for LED. The driving circuit for LED comprises an inductor used for producing an output current, a power switch coupled to the inductor and used for controlling the inductor to transmit the output current to a plurality of LEDs and drive the plurality of LEDs, an adjusting circuit receiving a PWM signal related to the output current, and a driving unit producing an adjusting impedance value according to the PWM signal. The driving unit generates a switching signal according to the adjusting impedance value. The switching signal switches the power switch and enables the inductor to produce the output current. The driving unit adjusts the frequency of the switching signal according to the adjusting impedance value.