Suppose you have a circuit which has a current requirement of 2 Amp, but the input diode has a current capacity of 1 Amp. What do you do then? Put two diodes in parallel as shown?
This is not advisable. The reason is as follows:
When current passes through a diode, it heats up and it's resistance decreases. So if the two diodes are not matched properly, which is usually the case, the diode with the smaller resistance ends up taking more current. As a result, it heats up more and the resistance decreases further. This is an endless cycle and soon the other diode will be effectively cut-off from the circuit. If provided sufficient current, the active diode would end up burning out.
If pairing diodes is inevitable, then the most common way out is to calculate the V-I characteristics of diodes and take only the ones that match. Further, the diodes must be coupled with the same heat sink so as to reduce the effect of difference in heating.
It's always advisable to replace the combination with a diode with a higher current rating rather than multiple smaller ones in parallel. As a general rule, each diode or LED in parallel should have it's own bias resistor.
This is not advisable. The reason is as follows:
When current passes through a diode, it heats up and it's resistance decreases. So if the two diodes are not matched properly, which is usually the case, the diode with the smaller resistance ends up taking more current. As a result, it heats up more and the resistance decreases further. This is an endless cycle and soon the other diode will be effectively cut-off from the circuit. If provided sufficient current, the active diode would end up burning out.
If pairing diodes is inevitable, then the most common way out is to calculate the V-I characteristics of diodes and take only the ones that match. Further, the diodes must be coupled with the same heat sink so as to reduce the effect of difference in heating.
It's always advisable to replace the combination with a diode with a higher current rating rather than multiple smaller ones in parallel. As a general rule, each diode or LED in parallel should have it's own bias resistor.
No comments:
Post a Comment