Switching power supplies are used to control these power supplies, and because of their significant advantages, switching power supplies have become the standard power source for most electronic products. Capacitors can be used to reduce ripple and absorb the noise generated by switching regulators. It can also be used for post-stage regulation to improve device stability and transient response. There should be no ripple noise or residual jitter in the Power Supply output. These circuits often use tantalum capacitors to reduce ripple, but tantalum capacitors can be affected by the noise of the switching regulator to create unsafe transients.
To ensure reliable operation, the rated voltage of the tantalum capacitor must be reduced. For example, a D-type tantalum capacitor rated at 10uF/35V should be operated down to 17V. If used to filter ripple at the input of the power supply, the rated 35V tantalum capacitor can operate reliably on voltage rails up to 17V.
High-voltage power bus systems are generally difficult to achieve a 50% reduction in rated voltage. This situation limits the use of tantalum capacitors for applications where the voltage rail is greater than 28V. Currently, since tantalum capacitors need to be derated, the only viable solution for high voltage filtering applications is to use larger, leaded electrolytic capacitors instead of tantalum capacitors.
New tantalum capacitor
In order to solve the problem of lowering the rated voltage, Vishay R&D has developed a new series of SMD solid tantalum capacitors with higher rated voltage levels. The rated voltage is up to 75WVDC.50V. The rated voltage capacitance is applied in 28V and higher voltage rails. The concern of the personnel, and the use of Vishay's new 63V and 75V tantalum capacitors, can achieve industry-recognized safety indicators with a 50% reduction in rated voltage. The dielectric forming is thinner and more uniform, enabling the SMD solid tantalum capacitor to be rated at 75V, thus achieving a technological breakthrough in increasing the rated voltage. The multi-step process has been improved in the forming process: the mechanical stress concentration generated 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 is rated at 75V and the 83 series is up to 63V.
Wireless inductively coupled charging
A large number of inductive chargers use a flyback converter. Inductive charging provides charging power to the medical device battery, while the inductive charger is also used in a large number of portable devices such as toothbrushes.
Reducing the size of the rechargeable battery helps to reduce the size of the implantable medical device with a wireless inductive charging circuit. The wireless inductive charger safely charges a tiny film (such as a Cymbet EnerChip) rechargeable energy storage device mounted on the device. The inductive charger uses the working principle of a parallel LC (inductor, capacitor) resonant tank circuit. Figure 1 shows Cymbet's CBC-EVAL-11 RF Inductive Charger Evaluation Kit.
The Vishay 595D Series 1000uF tantalum capacitor is used as the C5 capacitor for the Cymbet receiver board to provide pulsed current for loads such as radio emissions. This inductive charger has good isolation between the input and output, which is an important requirement for medical equipment.
In some high voltage inductive charger applications, high voltage stable capacitors are required as resonant capacitors. Since the primary coil of the inductive charger needs to be driven by an AC voltage, the capacitor must be adjusted accordingly. Inductive chargers require high breakdown voltage (VBD) performance and, in some applications, protection against high voltage arcing. In order to avoid arc discharge, the circuit board is generally coated with a protective coating, or by properly arranging the layout of the components to achieve the effect of isolating the high voltage side from other parts of the circuit board, and the like. However, this method often requires a large board space, because the high voltage circuit usually uses a large lead type through hole insertion capacitor.
High voltage arc protection capacitor solution
To solve this problem, Vishay introduced a series of HVArc (High Voltage Arc) protection MLCC (Multilayer Chip Ceramic Capacitor) to prevent arc discharge while saving space. These new devices have maximum capacity in higher voltage ratings and improve voltage breakdown tolerance. High voltage arcing can cause an open circuit and can damage other components. Standard high voltage SMD capacitors will eventually fail out, depending on the number of arc discharges and the problematic part. Vishay HVArc protection capacitors absorb all of the energy, so this capacitor can operate at high voltages, at least until a high voltage breakdown limit is reached without destructive arcing.
The VBD distribution of the HVArc protection capacitor is controlled by the unique design of the device, with VBD up to 3kV or more. This product uses NPO and X7R dielectrics.
New non-magnetic capacitor for MRI
Capacitors and other electronic components used in internal or peripheral circuits of magnetic resonance imaging (MRI) equipment need to be shielded or packaged outside the MRI. The dielectric, electrode material or termination material of the capacitor may contain iron or magnetic materials. In order to improve the image resolution, the magnetic field level of the MRI system is continuously increased, and the capacitance used in the MRI room causes magnetic field distortion. Therefore, it is necessary to reduce or completely eliminate the magnetic material in most of the capacitors.
The newly launched series of MLCCs use non-ferrous materials in the electrode and termination structures to meet the requirements for eliminating magnetization. Non-magnetic structures can be used with X7R and NPO dielectrics. Dimensions from 0402 to 1812, in line with EIA specifications. Vishay also used a dedicated capacitor sorting device in the final test to ensure that all non-magnetic capacitors meet the technical requirements.
Guangzhou Lufeng Electronic Technology Co. , Ltd. , https://www.lufengelectronics.com