Step-down PFC Power Supply for LED Lighting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing AC-DC converters for LED lighting face challenges such as increased part cost and size due to the need for high-voltage components, distorted AC current waveforms leading to reduced power factor and harmonic currents, and lower power conversion efficiency in flyback converters.
Innovation Solution
A power supply device with a rectifying circuit, switch element, inductor, current detection resistor, control circuit, and output capacitor that improves the power factor by controlling the switch element's on/off cycles, using a semiconductor device with a multiplication circuit, square circuit, and comparator circuits to shape the input current waveform closer to sinusoidal, thereby reducing the size and cost of the power supply system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a step-up converter with PFC circuit is used to avoid harmonic current, then power factor is improved, but output voltage becomes higher than input voltage requiring high breakdown voltage parts
Solution Approach 1:
The patent inverts the conventional step-up converter topology by using a step-down converter configuration where the output voltage is lower than the input voltage. This inversion allows the use of low breakdown voltage parts throughout the circuit, including the PFC circuit and subsequent stages, while still achieving power factor correction and reducing harmonic current through the same control mechanisms.
2Reliability
If high breakdown voltage parts are used to handle high output voltage, then voltage requirements are met, but part cost and device size increase
Solution Approach 1:
The patent changes the voltage parameter relationship by implementing a step-down converter where Vout < Vin, allowing all circuit components to operate at low voltage levels. This parameter change eliminates the need for high breakdown voltage parts, thereby reducing both part cost and device size while maintaining reliable operation through appropriate voltage selection for each component.
3Ease of operation
If a step-down converter is added after step-up converter for LED driving, then voltage is reduced to suitable level, but power supply system size and cost further increase
Solution Approach 1:
The patent extracts and removes the unnecessary step-up converter stage from the power supply system. By directly using a step-down converter configuration where Vout < Vin, the design eliminates the need for a subsequent step-down stage, thereby reducing the overall power supply system size and component count while still achieving the required voltage level for LED operation.
4Device complexity
If flyback converter is used for AC-DC conversion, then circuit simplicity is achieved, but power conversion efficiency is reduced
Solution Approach 1:
The patent segments the power conversion function into two separate stages: a rectifying circuit for AC-DC conversion and a step-down converter for voltage regulation. This segmentation allows each stage to be optimized independently, with the rectifying circuit focusing on efficient AC-to-DC conversion and the step-down converter focusing on voltage regulation, thereby improving overall power conversion efficiency compared to a single-stage flyback converter.
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 solution enables a compact, cost-effective power supply with improved power factor, reduced harmonic components, and enhanced power conversion efficiency, suitable for LED lighting applications.
Implementation Method 1
The inductor stores the power of the first node when a switch element driven on, and discharges the stored power when the switch element driven off
Implementation Method 2
A power supply device with a rectifying circuit, switch element, inductor, current detection resistor, control circuit, and output capacitor that improves the power factor by controlling the switch element's on/off cycles, using a semiconductor device with a multiplication circuit, square circuit, and comparator circuits to shape the input current waveform closer to sinusoidal
Data Source
AI summary
A power supply topology is used in which a transistor is provided on the side of an output node of a rectifying circuit. An inductor is provided on the side of a reference node, a resistor is inserted between the transistor and the inductor, and one end of the resistor is coupled to a ground power supply voltage of a PFC circuit. The PFC circuit includes a square circuit which squares a result of multiplication of an input voltage detection signal and feedback information (output voltage of an error amplifier circuit). The PFC circuit drives on the transistor when a detection voltage developed at the resistor reaches zero, and drives off the transistor when the detection signal reaches an output signal of the square circuit.