【 Weak current College 】 high frequency rectifier diode characteristics and parameters 】

Switching power supply rectifier diode must have positive pressure reduction, quick resume feature, you should have sufficient output power, you can use the following three types of rectifier diode: fast recovery rectifier diodes; ultra-fast recovery rectifiers; Schottky rectifier diode. Quick recovery, and blazing fast recovery rectifier diodes with moderate and high forward voltage drop, which range from 0.8 ~ 1.2V. Both rectifier diode also has higher cutoff voltage parameters. Therefore, they are particularly suited to low-power, output voltage 12V auxiliary power supply circuit around.

Because modern switching power supply operating frequency is above the 20kHz than General rectifier diode, fast recovery rectifier diodes and an ultra fast recovery rectifier diode reverse recovery time was reduced to Shakespearean Ⅱ nanosecond level, therefore, greatly improving power efficiency. According to experience, at the choice of fast recovery rectifier diodes, its reverse recovery time, at least, should be the switch transistor's rise time of 1/3. Both rectifier diode also reduces the switching voltage spikes, and this spike directly affects the output DC voltage ripple. In addition, although some are known as soft recovery-rectifier diode of the noise is small, but the reverse recovery time longer, reverse current are large, thus making the switching loss increases, and does not meet the job requirements of switching power supply.

Fast recovery rectifier diodes and blazing fast recovery rectifier diodes in switching power supply when used as Rectifiers parts radiator is required, according to the circuit of maximum power. In General, these diodes in manufacturing is allowed at 175 ° c junction temperature, manufacturers on the technical description of the index has to offer to designers to calculate the maximum output current, voltage and temperature, the shell.

Schottky rectifier diode even in large forward current, the forward voltage drop isalso very low, with only about 0.4V and as junction temperature increases, the forward voltage drop even lower, therefore, makes the Schottky Diode is especially suitable for the 5V or so low voltage output circuit. Schottky rectifier diode reverse recovery time is negligible, because this device is the majority carrier semiconductor devices, devices of the switching process, no clear minority carrier storage charge.

Schottky rectifier diode has two major drawbacks: first, reverse cutoff voltage tolerance level is low, the current product is approximately 100V; second, reverse leakage current is large, so the device than any other type of rectifier easier heating breakdown. Of course, these disadvantages can increase transient overvoltage protection circuit and appropriate control TJ to overcome. Represents a typical high speed rectifier diode characteristics and parameters.