2 kW active power factor correction circuit design - Power Circuit - Circuit Diagram

Abstract: Active power factor correction reduces harmonic pollution from power equipment to the grid while improving the power factor at the input of electrical devices. The principle of the active power factor corrector (APFC) is thoroughly analyzed. A 2 kW active power factor correction circuit was designed using the average current control mode. Experimental results demonstrate that the active power factor corrector, with TDA16888 at its core, can produce a stable 380 V DC voltage output across an input voltage range of 90-270 V, achieving a power factor as high as 0.99. This system performance is exceptional. Keywords: average current control; power factor correction; harmonic pollution; active power factor correction (APFC) Introduction: Most home appliances currently use diode full-bridge rectification, which leads to harmonic pollution of the power grid, reduced power factor, and increased reactive components, primarily high-order harmonics. The third harmonic amplitude is approximately 95% of the fundamental frequency, the fifth harmonic amplitude is around 70%, and the seventh harmonic amplitude is roughly 45%. These higher harmonics can harm the power grid, decrease input power factors, and generate strong electromagnetic interference (EMI), posing risks to the safe operation of the grid and other electrical devices. The Active Power Factor Corrector (APFC) ensures the input current of the power supply matches the input mains in phase, thus enhancing the equipment's power factor and reducing harmonic pollution to the grid. In theory, various converter topologies such as Buck, Boost, Boost-Buck, and Flyback can serve as the primary circuit for APFC. Among these, Boost APFC offers simplicity, high power factor values, low total harmonic distortion, and efficiency. It is suitable for power supplies ranging from 75 to 2,000 watts and is widely applied. Due to its continuous inductor current, the energy storage inductor acts as a filter, suppressing RF interference (RFI) and EMI noise while protecting the main circuit from high-frequency transient shocks from the grid. The Boost APFC circuit boosts the output voltage above the input voltage peak, expanding the allowable input voltage range up to 90-270 V. This enhances the adaptability of the power supply, simplifies control, and broadens the applicable power range. Consequently, a 2 kW active power factor correction circuit based on Boost topology with TDA16888 as the control core was proposed, achieving a power factor of 0.99 or higher. Boost APFC Circuit Principle: There are three methods for controlling Boost APFC: (1) Current peak control maintains a fixed switch frequency, operating in continuous conduction mode (CCM). Using the Boost circuit structure, the peak value of the inductor current (as the control reference) is sensitive to noise and prone to control errors. (2) Current hysteresis control operates under variable switch frequencies in CCM, utilizing the Boost circuit structure. Load size significantly impacts the switching frequency. Given the large variation range of the switching frequency, designing the output filter requires considering the minimum switching frequency, making it challenging to achieve the smallest volume and weight. (3) Average current control maintains a fixed switch frequency and operates in arbitrary modes. By detecting the inductor current, the current error signal must be amplified. The peak value of the power frequency current in this method is the average of the high-frequency current, resulting in smaller total harmonic distortion (THD), insensitivity to noise, and minimal error between the peak value of the inductor current and its average values. It can operate in both CCM and discontinuous conduction mode (DCM) and is suitable for any topology. [3][4] In conclusion, the proposed Boost APFC circuit using TDA16888 demonstrates excellent performance, providing a stable output voltage and high power factor, effectively addressing harmonic pollution and ensuring efficient power usage. Future developments may explore further optimizations and alternative topologies to enhance overall system efficiency and reliability.

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