Power Factor Correcting Circuit for AC Direct Lighting
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Solution Overview
Problem
AC direct drive circuits for LED lighting devices face challenges with phase differences between input voltage and output current, leading to reactive power generation and increased power dissipation, especially due to frequency drift of the AC input voltage signal.
Innovation Solution
A power factor correcting circuit that adjusts the frequency of the drive current signal by varying a reference voltage signal, reducing the phase difference between the AC input voltage and drive current signals, and automatically selecting the input voltage frequency without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If AC direct drive circuits are used to power LED lighting devices, then weight and space restrictions are reduced, but phase difference between input voltage and output current increases, leading to reactive power generation and increased power dissipation
Solution Approach 1:
The patent adjusts the frequency of the drive current signal to match the frequency of the AC input voltage signal. By dynamically changing the operating parameters (frequency) of the drive circuit, the phase difference between input voltage and output current is minimized, thereby reducing reactive power and power dissipation while maintaining the benefits of AC direct drive architecture
2Device complexity
If AC direct drive circuits are used to power LED lighting devices, then device complexity is reduced, but phase difference between input voltage and output current increases, resulting in reactive power generation
Solution Approach 1:
The patent employs frequency adjustment of the drive current signal to synchronize with the AC input voltage frequency. This parameter change approach allows the simple AC direct drive circuit to operate efficiently by minimizing phase difference, thereby reducing reactive power generation without adding significant circuit complexity
3Ease of operation
If fixed frequency drive current is used in AC direct drive circuits, then circuit operation is simplified, but frequency drift of AC input voltage signal cannot be compensated
Solution Approach 1:
The patent transitions from a fixed frequency drive current approach to a dynamic frequency adjustment mechanism. The drive current frequency is continuously adapted to match the AC input voltage frequency, enabling the circuit to automatically compensate for frequency drift while maintaining operational simplicity through automated control
Data Source
AI summary
A circuit for correcting a power factor for an AC direct lighting apparatus that includes a valley signal generating unit configured to receive a full-wave rectified AC input voltage signal and configured to compare an internal reference voltage signal and the AC input voltage signal to generate a valley signal, a reference voltage control unit configured to receive the generated valley signal and count clock cycles of an internal clock to detect a frequency of the AC input voltage signal and configured to determine a frequency of a drive current to control a reference voltage signal based on the determined frequency of the drive current and a reference voltage control clock generating unit configured to generate a pulse width modulation signal associated with a pulse width of the reference voltage signal and configured to generate the reference voltage control clock signal based on the generated pulse width modulation signal and the controlled reference signal. Thus, the circuit may control a phase of a drive current and adjust a variation of the reference voltage signal to improve the power factor of the circuit.