Diodes are indispensable components in switching power supplies, serving multiple critical functions across different topologies. One of their primary roles is rectification, converting alternating current (AC) input into direct current (DC) in the front-end stage. Bridge rectifiers, composed of four diodes, are commonly used to convert full-wave AC to DC, ensuring that both halves of the AC waveform contribute to the output.

In DC-DC converters, diodes act as free-wheeling diodes, providing a path for current when the main switching transistor is turned off. This is especially important in buck (step-down) converters, where the diode conducts current through the inductor during the transistor’s off-state, maintaining a continuous current flow to the load and preventing voltage spikes across the switch. Schottky diodes are often preferred for this role due to their low forward voltage drop and fast switching speed, which minimize power losses.

Diodes also serve as clamping devices to protect sensitive components from voltage transients. For example, in flyback converters, a catch diode across the primary winding of the transformer clamps the voltage spike generated when the switching transistor turns off, redirecting energy back to the input capacitor. Additionally, transient voltage suppressor (TVS) diodes are used to absorb voltage surges from the input line, safeguarding the power supply from damage caused by lightning or grid fluctuations.

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