Circuit diagram of a capacitive power supply: The vector diagram makes it clear: The majority of the input voltage drops out at the reactance of the capacitor with virtually no power dissipation being created in the capacitor. As the capacitor is directly connected to the power supply, very high demands are made on its reliability.
In contrast to conventional designs, the capacitive power supplies are short-circuit-proof at the output. The vector diagram makes it clear: The majority of the input voltage drops out at the reactance of the capacitor with virtually no power dissipation being created in the capacitor.
In theory class X2 capacitors are electrically suited for that but this is not the intended use of X2 capacitors as defined by IEC-60664-1. Many capacitor manufacturers do not recommend X2 capacitors for these applications, while some permit the use or offer alternative series for capacitive power supply.
The value and type of capacitor used will depend upon the bandwidth of the power supply, the magnitude of the load transient, the frequency components of the load transient, and the acceptable level of voltage excursion caused by the load transients.
When we look at almost any power supply application circuit there will be capacitors on the output of the power supply located at the load. One question often asked of power supply vendors is “Why are the output capacitors required on a power supply and how are the capacitors selected?”.
INTRODUCTION A capacitive power supply is a very low-cost AC/DC converter without a transformer or switching components. With a very small parts count, these circuits can provide a DC voltage for low-power applications. In addition, because no high-speed switching is occurring, no EMI noise is generated.