LED Driving Apparatus with Charging Capacitor for Light Output
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Solution Overview
Problem
Existing LED driving circuits using AC power face challenges in achieving a balance between power supply efficiency, power factor, LED usage efficiency, and light output crest factor, often resulting in low efficiency and perceived flicker due to pulsating current rectification.
Innovation Solution
A light-emitting diode driving apparatus with a rectifying circuit, charging/discharging capacitor, and separate charging and discharging constant current circuits allows the LED section to emit light during both charging and discharging periods, improving the light ON period and efficiency, while also controlling current paths to optimize power supply and LED usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the sum of Vf values of LED devices is set low, then the power supply efficiency is improved, but the LED usage efficiency decreases
Solution Approach 1:
The LED devices are divided into multiple series-connected strings, where each string has a different number of LED devices. This segmentation allows the circuit to selectively activate different strings based on the input voltage level, thereby optimizing both power supply efficiency and LED usage efficiency across varying operating conditions.
Solution Approach 2:
The constant current circuit dynamically adjusts the operating current based on the detected input voltage level. When input voltage is high, the circuit reduces the current to prevent excessive power loss, and when input voltage is low, it increases the current to maintain adequate LED brightness, thus resolving the contradiction between efficiency and usage effectiveness.
2Loss of energy
If the sum of Vf values of LED devices is set high, then the power supply efficiency is improved, but the driving efficiency decreases and light ON period is shortened
Solution Approach 1:
By dividing LED devices into multiple series strings with different LED counts, the circuit can select appropriate strings based on input voltage. This ensures that the total forward voltage matches the available input voltage, maximizing the light ON period while maintaining efficient power supply operation.
Solution Approach 2:
The circuit changes the effective forward voltage parameter by selectively activating different LED string configurations. This adaptation allows the system to maintain optimal operating conditions across varying input voltages, preventing both excessive power loss and premature LED turn-off.
3Stability of the object's composition
If a large-capacitance capacitor is used for smoothing pulsating current, then the light output crest factor is improved, but the power factor is reduced due to quick charge current
Solution Approach 1:
A capacitor is introduced as an intermediary energy storage element between the rectified power supply and the LED driving circuit. This capacitor smooths the pulsating current to improve light output stability while the constant current circuit controls the charging current to maintain acceptable power factor, thus resolving the contradiction between output quality and input power quality.
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 solution enhances driving efficiency, reduces power loss, and improves the light output crest factor, leading to better lighting quality and efficiency, with a power factor improvement of about 5% compared to conventional systems.
Implementation Method 1
a rectifying circuit 2 which is connected to AC power supply AP and rectifies an AC voltage of the AC power supply AP to generate a rectified voltage
Implementation Method 2
a charging/discharging capacitor 3 which is serially connected to the first LED section 11
Implementation Method 3
LEDs emit light only when applied with a current in the forward direction
Implementation Method 4
LEDs are devices driven by DC power. LEDs emit light only when applied with a current in the forward direction
Data Source
AI summary
A charging diode 6 is connected to the capacitor 3 and the anode of a first LED 11, and limits the direction of the charging current. A discharging diode 7 is connected to the capacitor 3 and the cathode of the first LED 11, and limits the direction of the discharging current. A charging path CP is provided which includes the capacitor 3, the charging diode 6, and the charger 5. The capacitor 3 is charged through the charging path CP. A discharging path DP is provided which includes the capacitor 3, the discharging diode 7 and a discharger 4. The capacitor 3 is discharged through the discharging path DP. A transient path TP is provided which does not include the capacitor 3 but includes the first LED 11, the charger 5 and the discharger 4.