How To Choose Capacitors For Switching Power Supply Design?

- Dec 27, 2019-

Switching power supplies are used to control these power supplies. Due to their significant advantages, switching power supplies have become the standard power supply for most electronic products. Capacitors can be used to reduce ripple and absorb noise generated by switching regulators. It can also be used in subsequent stage voltage regulation to improve the stability and transient response of the device. There should be no ripple noise or residual jitter in the power output. These circuits often use tantalum capacitors to reduce ripple, but tantalum capacitors may be affected by the noise of the switching regulator and cause unsafe transients.


To ensure reliable operation, the rated voltage of the tantalum capacitor must be reduced. For example, a D-type tantalum capacitor with a rated value of 10uF / 35V should be reduced to 17V. If it is used to filter the ripple at the power input, a rated 35V tantalum capacitor can reliably work on voltage rails up to 17V.


The high-voltage power bus system is generally difficult to achieve the target of reducing the rated voltage by 50%. This situation limits the use of tantalum capacitors for applications with voltage rails greater than 28V. At present, because tantalum capacitors need to be derated, the only feasible method for high-voltage filtering applications is to use larger electrolytic capacitors with leads instead of tantalum capacitors.


New tantalum capacitor


In order to solve the problem of reducing the rated voltage, Vishay's R & D department has developed a new series of SMD solid tantalum capacitors with higher rated voltage levels. The rated voltage is as high as 75WVDC. The application of 50V rated voltage capacitors in 28V and higher voltage guides has caused design People's worry, and the use of Vishay's new 63V and 75V tantalum capacitors can achieve industry-recognized safety indicators that reduce the rated voltage by 50%. The dielectric forming is thinner and more consistent, enabling the rated voltage of SMD solid tantalum capacitors to reach 75V, thereby achieving a technological breakthrough in increasing the rated voltage. In the forming process, several processes have been improved: the mechanical stress concentration during the forming process is reduced, the local overheating of the electrolyte during the capacitor forming process is reduced, and the consistency of the electrolyte concentration and purity during the dielectric forming process is improved. The new capacitor T97 series has a rated voltage of 75V and 83 series reaches 63V.


Wireless inductive coupling charging


A large number of inductive chargers use flyback converters. Inductive charging provides charging power for medical device batteries, and inductive chargers are also used in a large number of portable devices such as toothbrushes.


Reducing the size of rechargeable batteries helps reduce the size of implantable medical devices that use wireless inductive charging circuits. Wireless inductive chargers can safely charge tiny thin-film (such as CymbetEnerChip) rechargeable energy storage devices installed on the device. The inductive charger uses the working principle of a parallel LC (inductive, capacitive) resonant energy storage circuit.