1000V rectifier for 24V linear power supply? - Page 1
Forum section: electronics / beginners

author: webgiorgio
author_rank: Regular Contributor
timestamp: February 04, 2018, 04:09:33 pm
content: I am selecting the H bridge rectifier for the low voltage side of a transformer 220/24Vac 5A.I would pick a 100-200V rectifier, and I want to minimize the thermal loss of the H bridge.I would expect that the silicon is thicker for a diode with higher reverse voltage, but if you look at this datasheet (https://www.diodes.com/assets/Datasheets/ds21221.pdfGBJ2510), you see that the Vforward=1.05V for any Vreverse from 50V to 1000V.Why diodes with different reverse voltage have the same Vforward?I see that 1000V bridge rectifiers are more easily available on ebay than 100-200V. Is it a bad design if I use a 1000V version? (as far of the datasheet I would say no).

author: danadak
author_rank: Super Contributor
timestamp: February 04, 2018, 04:14:29 pm
content: Not a bad design to use 1000V, just overkill.Look at diode theory for answer to Vbr vs Vf on diodes, these parametersare predicted by different physical properties.Google "diode theory" or look at the books onwww.archive.orgRgards, Dana.

author: SeanB
author_rank: Super Contributor
timestamp: February 04, 2018, 04:40:00 pm
content: Forward voltage is always given as "typical", and generally also depends on the current flow, so it is given at the full rated current. As you are using a 25A bridge, the peak current through it will be nicely derated, so the actual forward voltage drop will be lower, probably at around 0.9V, being roughly the forward voltage at the 10A mark, when used as a full bridge rectifier with capacitive load. As to the actual unit, the forward voltage difference between a 50V and a 1000V is likely to be zero, as they make only one diode design for the units, and bin them during test for forward voltage drop ( to find those that are super leaky and get rid of them) and reverse voltage drop at around 0.5mA with a 1000V compliance voltage, to get an idea as to breakdown voltage, and then bin them for voltage. The binning generally, with a known process with good history and well known equipment, tends to be towards the top, 1000V devices being all that comes out, so while there might be devices made with lower voltage ratings in the part number, they all will probably pass the 1000V mark in most cases, unless they had a poor day at the foundry and actually made a not too good load of wafers by accident that did not meet the 1kV spec, but tested out lower. They all start off as GBJ2510 devices, but some either failed final voltage test and were labelled appropriately, or they had an order for the part and simply used the good stock with a lower label, as they do meet or exceed the required spec.Poorly kept secret is that a 1kV diode like 1N4007 could be any die that exceeds 1kV, some might be 1500V, some 1800V but all will be 1000V capable at 125C die temperature. You can be reasonably sure that at room temp all will withstand 1200V though, but make no assumptions on that, they make terrible voltage reference avalanche diodes.

author: davy peleman
author_rank: Regular Contributor
timestamp: February 04, 2018, 06:41:53 pm
content: the same in my country. the 1000 volt ones are more common and less expensive than the weaker bridge rectifiers. really unlogical. so i also buy the 1000 volt ones. really strange a strange fact.