Selection of power adapter output rectifier

Issue Time:2006-04-24
The output rectifier diode of the 1.5V power adapter output is selected. The peak current of the output rectifier is about 4 times of the average value of the output current. Since the average current of the output is 4A, the peak current flowing through the output rectifier is about 16A, so the extra current is selected as 16A. Withstand voltage, for the 5V output, you can choose not less than 5 times the output voltage, that is, no lower than the output rectifier diode of the 25V12V power adapter output.

The voltage requirement of the rectifier diode output from the 12V power adapter is not less than 65V. The forward voltage of the Schottky diode with a withstand voltage above 65V can reach 0.7V, and the Schottky diode leakage current is significantly larger than the ultrafast reverse. Recovery of the diode, if the Schottky diode is not properly selected, its total loss is not necessarily lower than that of the ultra-fast reverse recovery diode, so in this case it is necessary to select an ultra-fast reverse recovery diode. The extra voltage is chosen to be 100V, and the extra current can pick about 3 times the average value of the output current, and pick 1A extra current.

Selection of 12V power adapter output rectifier filter capacitor.

The 12u output rectification filter capacitor selects 10uF to fully satisfy the ripple current requirement, and the withstand voltage can select 16V.

All output rectifying and filtering capacitors require the selection of "high frequency, low resistance" electrolytic capacitors.

L1: inductance at 15A is 15μH; l2, l3: inductance at 25A is 25uH.

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