LED Driving System with Closed-Loop Capacitor Control
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Solution Overview
Problem
Existing LED driving systems face challenges in meeting ERP standards due to inefficiencies and increased costs associated with complex de-ripple circuits and separate control of charging and discharging modules, which result in narrow input voltage ranges and efficiency losses.
Innovation Solution
An LED driving system employing a closed-loop control method utilizing an addition and subtraction counter for digital loop compensation, eliminating the need for large external compensation capacitors, and integrating a constant-current control module with a discharging-voltage measuring module and a charging-current control module to adjust electrolytic capacitor charging currents based on measured voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a de-ripple circuit is added to a traditional linear LED driver, then strobing is reduced, but device complexity and efficiency loss increase
Solution Approach 1:
The patent combines the constant current control and de-ripple functions into a single integrated control circuit. The controller simultaneously regulates LED current and manages capacitor charge/discharge operations, eliminating the need for separate de-ripple circuitry while maintaining strobing reduction performance.
Solution Approach 2:
The controller is designed to perform multiple functions: constant current regulation for LED driving, de-ripple operation through capacitor management, and adaptive charging current adjustment. This multi-functional approach replaces multiple dedicated circuits with a single versatile control unit, reducing overall system complexity.
2Device complexity
If the charging current of the electrolytic capacitor is not adjusted, then the control circuit is simple, but efficiency decreases due to charging loss at high input voltage
Solution Approach 1:
The controller monitors input voltage levels and uses this feedback to dynamically adjust the charging current of the electrolytic capacitor. When input voltage is high, the controller reduces charging current to minimize conduction losses in the switching transistor. This closed-loop control optimizes efficiency across varying input conditions without requiring overly complex circuitry.
Solution Approach 2:
The charging current is made dynamic rather than fixed. The controller adaptively modulates the charging current based on real-time input voltage conditions, allowing the system to operate efficiently across a wide voltage range. This dynamic adjustment transforms a static, simple circuit into an adaptive system that maintains optimal performance.
3Loss of time
If the electrolytic capacitor charges quickly at low input voltage, then charging time is reduced, but the LED experiences frequency ripple due to sudden current drops
Solution Approach 1:
The controller continuously monitors the operational state and uses feedback to regulate the charging current waveform. At low input voltages, the controller increases charging current to maintain adequate charge levels, while simultaneously modulating the discharge timing to prevent sudden current drops that would cause frequency ripple. This feedback control balances charging speed with output stability.
Solution Approach 2:
The controller employs periodic charge-discharge cycles of the electrolytic capacitor to smooth out current variations. By carefully timing the discharge operations to coincide with natural voltage troughs and controlling the recharge phases, the system maintains continuous current flow to the LED, eliminating frequency ripple while achieving fast charging when needed.
4Ease of manufacture
If separate control circuits are used for charging and constant current modules, then each module can be optimized independently, but the modules cannot cooperate to achieve best performance
Solution Approach 1:
The patent merges the separate control circuits into a single integrated controller that manages both constant current regulation and capacitor charge/discharge operations. This unified control architecture enables coordinated operation between modules, allowing the system to achieve optimal performance by considering the interaction between charging and LED driving functions rather than treating them as independent, potentially conflicting processes.
Data Source
AI summary
An LED driving system and a closed-loop control method for LED driving are provided; the LED driving system includes an LED load, a constant-current control module, an electrolytic capacitor, a discharging-voltage measuring module, a bus-voltage measuring module and a charging-current control module, wherein the charging-current control module is connected to an output of the discharging-voltage measuring module, the bus-voltage measuring module and a lower plate of the electrolytic capacitor; the charging current of the electrolytic capacitor is adjusted based on the control signal of the discharging-voltage measuring module and the measured voltage of the bus-voltage measuring module, wherein the charging current of the electrolytic capacitor is reduced by an subtraction operation performed by the addition and subtraction counter, and the charging current of the electrolytic capacitor is increased by an addition operation performed by the addition and subtraction counter.