1 Fundamental Roles of Electrolytic Capacitors in Chargers

Electrolytic capacitors are indispensable components in chargers, performing critical functions such as filtering, energy storage, and voltage stabilization. In switching power supplies like chargers, alternating current (AC) from the mains is rectified into pulsating direct current (DC), which contains significant ripple. Electrolytic capacitors smooth this pulsating DC into a stable voltage, ensuring proper operation of subsequent circuits and charging efficiency .

In chargers, high-voltage electrolytic capacitors are typically placed on the primary side, directly connected to the rectifier circuit. For chargers designed for global voltage ranges (100-240V AC), the peak voltage after rectification can exceed 300V. Therefore, capacitors with 400V-450V ratings are commonly selected to provide sufficient margin for grid fluctuations and surge impacts . The Equivalent Series Resistance (ESR) and ripple current handling capability directly affect the charger's conversion efficiency and heat generation. Low-ESR capacitors reduce energy loss and temperature rise, thereby improving overall efficiency and lifespan .

2 Capacitor Selection Strategies for Different Power Chargers

2.1 Capacitor Selection for Ultra-Slim Fast Chargers

Ultra-slim fast chargers, with their extremely limited internal space, impose stringent requirements on high-voltage filter capacitors. These products often adopt a flat design, with thickness typically controlled under 18mm, making traditional cylindrical electrolytic capacitors difficult to accommodate .

For instance, the BPOWER 65W GaN ultra-slim charger uses two JSH Wan Jingyuan 400V 47μF capacitors in parallel, totaling 94μF. Many CUKTECH models utilize two BERYL 400V 27μF capacitors. A more radical approach is seen in the OPPO 50W GaN charger, which abandons traditional electrolytic capacitors entirely, innovatively using Murata high-voltage MLCCs for filtering .

Table: Capacitor Selection Examples in Ultra-Slim Fast Chargers

2.2 Capacitor Demands for High-Power PD3.1 Fast Chargers

With the adoption of the PD3.1 fast charging standard, output power has increased to 140W, 240W, and even higher, placing greater demands on the voltage rating and capacitance of high-voltage filter capacitors .

In high-power PD3.1 chargers, the withstand voltage rating of high-voltage electrolytic capacitors is generally increased to the 420V-450V range, and capacitance selection is more diverse. For example, the Ugreen 300W GaN charger uses Xinzhongyuan 450V 100μF capacitors; the Anker 140W PD3.1 GaN charger uses Yongming 450V 120μF capacitors .

3 Jiangxi Fulong Electronic Technology Co., Ltd. Capacitor Solutions

Jiangxi Fulong Electronic Technology Co., Ltd. is a high-tech enterprise certified with IATF16949, ISO9001, ISO14001, and ISO45001. It specializes in the R&D, manufacturing, and sales of aluminum electrolytic capacitors. The company boasts 70 fully automated production lines with an annual output of approximately 1.2 billion capacitors, covering various sizes .

Fulong Electronic possesses an international professional R&D team focused on the core technology of aluminum electrolytic capacitors. It can produce various chip aluminum electrolytic capacitor series according to customer requirements, including products with special needs like high-frequency low impedance, low leakage current, wide temperature range, very low impedance, non-polar, and ultra-long life. The company's products can withstand a soldering temperature of 260℃, meeting the requirements of lead-free reflow soldering technology for OEMs .

For the fast-charging market, Fulong Electronic has launched a series of innovative products, such as the FVM series ultra-small chip aluminum electrolytic capacitors, which can be as small as 5mm*4.5mm, making them ideal for high-end applications with size constraints. Compared to imported brands, these products have significant advantages in price and delivery time, meeting the needs for domestic substitution .

Fulong Electronic's capacitor products excel in voltage withstand capability, temperature characteristics, and service life. For example, its FVU series wide-temperature long-life products can operate stably within a temperature range of -55℃ ~ +105℃, while the FVD series high-voltage long-life products have a lifespan of up to 3000～5000 hours .

4 Core Parameters for Capacitor Selection

Key parameters must be considered when selecting capacitors for charger design :

• Voltage Rating: The nominal withstand voltage should be 20%-30% higher than the peak operating voltage. For example, choose a 400V rated capacitor for an application with a 320V actual peak voltage.

  
  

• Capacitance Selection: Larger capacitance offers better filtering but requires balancing volume and cost. A 65W PD fast charger typically requires about 40-100μF of total capacitance.

  
  

• ESR and Ripple Current: Low ESR reduces energy loss and improves efficiency. High ripple current withstand capability prevents capacitor overheating failure.

  
  

• Temperature and Lifespan: Capacitor lifespan follows the "10℃ rule" - for every 10℃ decrease in operating temperature, the lifespan approximately doubles. High-quality chargers typically select electrolytic capacitors with temperature ratings of 105℃ or even 125℃.

  
  

5 Summary

The selection of electrolytic capacitors directly affects the performance, reliability, and service life of chargers. There are significant differences in capacitor requirements across different power levels, from standard 20W fast chargers to advanced 240W PD3.1 chargers. As an important representative of domestic capacitor manufacturers, Jiangxi Fulong Electronic Technology Co., Ltd., with its advanced production technology and diverse product lines, provides the fast-charging industry with various high-performance, miniaturized capacitor solutions, effectively promoting the development of fast-charging technology towards higher efficiency and more compact sizes .