Super Capacitor Power Supply Circuit for LED Flashlight Peak Current
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Solution Overview
Problem
White LEDs in portable devices, such as mobile phones with integrated digital cameras, require high peak power when used as flashlights, leading to excessive current draw from the battery, which is inefficient and demanding for the power supply.
Innovation Solution
A power supply circuit with a DC-DC converter and charge pump, coupled with a super capacitor, that charges during one mode and discharges through LEDs in another mode, minimizing peak current from the battery, and includes a control stage for switching between modes and limiting inrush current with a soft-start scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If white LEDs are switched on to provide instantaneous flashlight, then illumination intensity is improved, but power consumption increases causing excessive current draw from battery
Solution Approach 1:
The super capacitor is pre-charged during normal operation when the LEDs are not active. When the flashlight function is activated, the pre-charged super capacitor immediately discharges to provide the high peak current needed for the LEDs, eliminating the need for the battery to supply excessive current during the brief flashlight activation.
Solution Approach 2:
The super capacitor acts as an intermediary energy storage device between the battery and the LEDs. It absorbs excess energy during low-power periods and releases it during high-power需求的 moments, decoupling the battery from direct high-current demands and protecting the power supply system from current spikes.
2Illumination intensity
If multiple white LEDs are provided in series, then illumination intensity is improved, but power consumption increases further
Solution Approach 1:
The super capacitor is pre-charged during normal operation when the LEDs are not active. When the flashlight function is activated, the pre-charged super capacitor immediately discharges to provide the high peak current needed for the LEDs, eliminating the need for the battery to supply excessive current during the brief flashlight activation.
Solution Approach 2:
The circuit dynamically changes the operating voltage and current parameters by switching between battery-powered mode and super capacitor-powered mode. During flashlight operation, the super capacitor provides elevated voltage and current to drive multiple series LEDs at high brightness, while during normal operation, the battery supplies only the low current needed for standby or low-power modes.
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 circuit provides sufficient power to white LEDs while minimizing battery current usage, making it suitable for portable devices without high power demands, allowing efficient operation of multiple LEDs in series as a flashlight.
Implementation Method 1
A super capacitor is coupled to the charge pump and is adapted to be charged to a voltage on top of the voltage at the converter output during a first mode of operation. In a second mode of operation, the super capacitor is discharged through the LEDs
Implementation Method 2
The circuit comprises a DC-DC power converter and a charge pump coupled to an output of the DC-DC power converter
Implementation Method 3
A charge pump coupled to an output of the DC-DC power converter. The full output voltage of the converter is therefore used as an input to the charge pump and the voltage generated by the charge pump is added to the output voltage of the converter
Data Source
AI summary
A power supply circuit is proposed for supplying current to a pair of white LEDs connected in series. The circuit comprises a DC-DC power converter, with a charge pump coupled to the output of the DC-DC power converter. A super capacitor is coupled to the charge pump to be charged to a voltage on top of the converter output in a first mode of operation. The super capacitor is discharged through the pair of LEDs during a second mode of operation. A control stage is provided for switching between the first mode of operation and the second mode of operation.