Offline Buck
Connector
Rocker Switch
Rocker switches create electrical connections and disconnect them again for currents of several amperes. A typical area of application here is the on/off switch for power supplies. Due to their exposure and safety-critical function, they often ensure compliance with stringent quality standards. IEC/UL 61058, glow wire, UV tests according to IEC60068-2-5, as well as additional reliability tests guarantee these claims.
Mains Filter
A line filter reduces interference between the device and the power supply. This means that, on the one hand, disturbances from the mains do not couple into the device (increasing immunity to interference), and on the other hand, disturbances from the device do not reach the mains (reducing emitted interference).
Switch
A higher switching frequency will enable smaller Inductors and smaller filter components. However, radiated EMI might increase.
Intermediate Circuit Capacitors
Due to the high voltages in the DC link circuit two different technolgies are suitable. Electrolytic capacitors offer a higher capacitance, DC link film capacitors withstand a higher ripple current.
Line Filter
Differential mode noise < 30MHz is best attenuated by ferrite based chokes.
Input Capacitor
Selecting the right input capacitor requires consider not only the rated voltage but also the impedance at the operating frequency of the switching regulator.
Thermal Management
Thermal management is of importance in order to guarantee reliability and longevity of electronic devices and components.
Thermal Management
Thermal management is of importance in order to guarantee reliability and longevity of electronic devices and components.
High Voltage Power Inductor
REDEXPERT helps you find the best power inductor for your SMPS and provide useful information regarding efficiency and temperature rise.
Output Capacitor
For lower ESR, aluminum polymer capacitors are recommended for bulk capacitors. Conventional electrolytic capacitors are suitable as well.
Connector
Schottky Diode
Diode‘s junction capacitance in combination with parasitic inductance of traces can lead to ringing.
Filter Cut-Off Frequency
The filter’s cut-off frequency should be about one tenth of the converter’s switching frequency. Please consider the SRF of all filter components. Use the REDEXPERT Filter Designer to design an EMI filter and evaluate the realistic response based on real components.
Short Introduction to Offline Buck
The buck converter, also called a step-down converter, is the switching regulator topology one of the most widely used.
Offline buck converterconverts rectified mains DC to a lower DC voltage. "Offline” in this context means, that the converter is not supplied directly from AC mains, but after rectification.
During the conduction phase the power inductor is exposed to the voltage difference between input and output of the regulator. Therefore a inductor with sufficient voltage isolation rating is required here. From an EMC point of view, the input line and the circuit node between the diode, switching controller and power inductor, the so-called "hot node", are particularly critical.
