LED Driving Circuit Frequency Dithering Slope Compensation
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Solution Overview
Problem
Conventional lighting apparatuses for vehicles, particularly rear combination lamps using LEDs, face challenges in stabilizing output voltage during load changes, leading to prolonged stabilization times, increased power consumption, and potential EMI issues, along with difficulties in controlling sub-harmonic oscillations and maintaining effective dimming duties across varying switching frequencies.
Innovation Solution
The implementation of a driving circuit that performs frequency dithering on the driving signal, spreads the frequency of the driving signal, and dynamically adjusts the slope compensation voltage based on changing switching frequencies, allowing for quick voltage stabilization, reduced EMI, and effective dimming control without additional parts or terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional feedback voltage compensation and linear regulation are used to stabilize output voltage during load changes, then output voltage stability is improved, but stabilization time increases significantly
Solution Approach 1:
The patent applies preliminary action by predicting the required output voltage before load changes occur. The driving circuit calculates the necessary output voltage based on feedback voltages from LED channels and generates a preliminary driving signal that pre-compensates for upcoming load changes, thereby reducing stabilization time while maintaining voltage stability.
2Productivity
If switching frequency of the converter is increased to improve power conversion efficiency, then power conversion efficiency is improved, but EMI increases
Solution Approach 1:
The patent applies periodic action through frequency dithering, where the switching frequency is modulated with a small sinusoidal signal. This periodic variation spreads the EMI energy across a wider frequency spectrum, reducing peak EMI emissions while maintaining high power conversion efficiency through optimized average switching frequency.
3Power
If duty of driving signal is increased to improve power conversion, then power conversion capability is improved, but sub-harmonic oscillation occurs
Solution Approach 1:
The patent applies feedback by continuously monitoring the driving signal duty cycle and detecting sub-harmonic oscillation. When oscillation is detected, the system adjusts the duty cycle through feedback control, adding slope compensation to the driving signal to eliminate sub-harmonic oscillation while maintaining effective power conversion capability.
4Stability of the object's composition
If additional circuits are added to generate variable slope compensation voltage for variable switching frequency, then sub-harmonic oscillation control is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the driving circuit to generate the required slope compensation voltage internally using its existing components. The circuit utilizes the oscillation signal already present in the system to create a current that charges a capacitor, producing the frequency-dependent slope compensation voltage without requiring external circuits or additional terminals.
Data Source
AI summary
Provided is a lighting apparatus. The lighting apparatus may provide an output voltage to lighting loads, and include: a converter configured to generate the output voltage using a driving signal; and a driving circuit configured to provide the driving signal, and spread the frequency of the driving signal by performing frequency dithering on the driving signal while changing the shape of an oscillation signal.