The service life of ultra-small aluminum electrolytic capacitors
Release time:
2022-07-15
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Although small- and medium-power switching power supplies and high-power switching power supplies differ in their switching frequencies, the role of rectifier filter capacitors is essentially the same: they primarily use filter capacitors to absorb current flows at the switching frequency and its higher harmonic frequencies, thereby filtering out ripple voltage.
Although small- and medium-power switching power supplies and high-power switching power supplies differ in their switching frequencies, the role of rectifier filter capacitors is essentially the same: they primarily use filter capacitors to absorb the current flowing at the switching frequency and its higher harmonic frequencies, thereby filtering out the ripple voltage.
Ultra-small electrolytic capacitor The capacitor is one of the key components in the first- and second-circuit filtering networks of power modules. Its equivalent circuit can be modeled as an ideal capacitor connected in series with parasitic inductance and an equivalent series resistance. Most electrolytic capacitors adopt a wound structure, which makes them relatively bulky yet offers an exceptionally high capacitance per unit volume—several to dozens of times greater than that of other types of capacitors. Since capacitance is directly proportional to volume, and switching power supplies are becoming increasingly modular, we need to find new approaches to develop capacitors with both large and small capacitance values.
Once an active filter circuit is applied to the primary side of a switching power supply, the operating environment for aluminum ultra-small electrolytic capacitors will become more severe. For example, the high-frequency pulsed current—primarily pulsating currents in the range of 20 kHz to 100 kHz—will significantly increase. The heat generated by the main switching devices in the power converter will cause the temperature around the aluminum electrolytic capacitors to rise.
Most power converters use voltage step-up and step-down circuits, which require high-voltage-resistant aluminum. Ultra-small electrolytic capacitor components. If aluminum electrolytic capacitors are manufactured using previous technologies, larger-sized capacitors must be selected, as they need to handle significantly greater ripple currents than before. Consequently, the power supply capacity increases, making it difficult to use such capacitors in compact electronic devices. Therefore, to meet the requirements of power supply modules, we must develop new electrolytic capacitors that feature small size, high capacitance, high voltage resistance, high-frequency performance, low impedance, and withstand high current ratings. Moreover, these capacitors must have an extended service life when operating in high-temperature environments.
In the design process of switch-mode power supplies, it is inevitable to select appropriate capacitors. Aluminum electrolytic capacitors are inexpensive and widely used in high-capacitance products above 100 μF. However, in recent years, aluminum... Ultra-small electrolytic capacitor The use of capacitors is increasing steadily. Since the service life of aluminum electrolytic capacitors significantly impacts product performance, many power module manufacturers aim to avoid using them as much as possible, given their relatively short lifespan.
The service life of electrolytic capacitors is directly related to the operating ambient temperature: the higher the temperature, the shorter the capacitor’s service life. When the ambient temperature reaches 90°C, conventional electrolytic capacitors will start to suffer damage. However, nowadays many types of electrolytic capacitors are designed to operate in much higher ambient temperatures. At an ambient temperature of 90°C, even when the AC current and rated pulse current passing through the electrolytic capacitor reach a ratio of 0.5, the capacitor’s service life still remains at 10,000 hours. But once the temperature rises to 95°C, the electrolytic capacitor will also begin to suffer damage.
When selecting capacitors, it’s important to take into account the specific ambient temperature and other relevant parameters. If the impact of ambient temperature on the capacitor’s service life is overlooked, the reliability and stability of the power supply will be significantly reduced, and the equipment could even be damaged. Generally speaking, when the ambient temperature is 80℃, the service life of electrolytic capacitors can reach up to 10,000 hours.
Keywords:
Ultra-small electrolytic capacitor
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