Two-Stage LED Power Conversion with Adaptive PFC Voltage Control
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Solution Overview
Problem
High power LED switching power supplies face inefficiency and increased thermal dissipation issues due to the wide range of output voltage requirements, leading to higher power loss and costs.
Innovation Solution
A power conversion device with a first stage circuit generating an adjustable output voltage and a second stage circuit generating an output current and voltage, controlled by a unit that adjusts the first stage circuit based on the set output current value to optimize voltage and reduce inefficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the output voltage range of the power supply is widened to satisfy different LED load requirements, then the adaptability is improved, but the efficiency of the second stage Buck circuit deteriorates due to increased voltage difference
Solution Approach 1:
The first stage PFC circuit dynamically adjusts its output voltage based on the actual output voltage requirements of the second stage Buck circuit. The control unit receives feedback from the output voltage detection circuit and modifies the PFC output voltage accordingly, enabling the system to adapt to different LED load voltage requirements while maintaining optimal operating conditions for the Buck circuit
Solution Approach 2:
A feedback control mechanism is implemented where the output voltage of the second stage Buck circuit is detected and fed back to the control unit. This feedback signal is used to adjust the output voltage of the first stage PFC circuit, creating a closed-loop control system that optimizes efficiency while maintaining adaptability to various output voltage requirements
2Adaptability or versatility
If the output voltage of the Buck circuit is reduced to match lower LED load voltage requirements, then the adaptability is improved, but the duty cycle becomes small causing increased switch loss and thermal dissipation
Solution Approach 1:
The PFC circuit output voltage is dynamically adjusted upward when the Buck circuit operates at lower output voltages. This dynamic voltage adjustment compensates for the reduced duty cycle operation of the Buck circuit, maintaining larger voltage margins that improve switch efficiency and reduce thermal dissipation while still meeting the lower voltage requirements of specific LED loads
Solution Approach 2:
The system changes the operating parameters of the PFC circuit based on the operating conditions of the Buck circuit. When the Buck output voltage is low, the PFC output voltage is increased to maintain optimal voltage difference ratios, which improves the effective duty cycle and reduces switch losses and thermal dissipation in the Buck circuit
3Device complexity
If the first stage PFC circuit output voltage is fixed to simplify control, then the device complexity is reduced, but the efficiency deteriorates when adapting to wide voltage ranges
Solution Approach 1:
A feedback control loop is established where the output voltage of the Buck circuit is continuously monitored and used to adjust the PFC circuit output voltage. This feedback mechanism enables automatic optimization of the voltage relationship between stages without requiring complex manual configuration or multiple fixed-voltage modes, achieving improved efficiency with manageable control complexity
Data Source
AI summary
The invention discloses a power conversion device and a voltage control method. The power conversion device includes a first stage circuit configured to generate a first output voltage, a second stage circuit configured to receive the first output voltage and generate an output current and a second output voltage, and a control unit configured to control the first stage circuit according to a set value of the output current, thereby adjusting the first output voltage. The invention can be adapted to a wide range load voltage by adjusting the first output voltage of the first stage circuit according to the set value of the output current of the second stage circuit.