Hello,
I have a couple of miscellaneous questions - if somebody would mind taking some time to answer them (or whatever help they can provide), it would be appreciated.
1) Note: I got 3x RMS value from the page at http://www.kpsec.freeuk.com/powersup.htm#rectifier
When building a regulated AC to DC power supply, why does bridge rectifiers Vrrm have to be 3x the RMS value? I'm in the UK, so the AC RMS here is 230V (see below for further question on this), giving a peak of (1.414*230) 325.22V, so why should I need a Vrrm of 690V if the peak is only 325.22V?
Actually, come to mention that, take a transformer with the following stats:
2) It seems that the Max Vf for bridge rectifiers don't seem to really go beyond 3.3V - the most common values seem around the 1V mark, so how can this be used on a microchip that may require say 5V?
3) Why would a bridge rectifier ever have more than 4 pins, although they aren't common at all looking at Farnells stock, I'm not seeing how there even can be anything other than 4 pins?
4) The UK mains is 230V ± 10% (207V - 253V), does this mean any equipment that I design (or rather the DC power supplies) should really work at the top end of 253V, so when buying a transformer I should get one rated at least 253V rather than 230V?
That should keep me going a while.
Thanks in advance,
Gump.
I have a couple of miscellaneous questions - if somebody would mind taking some time to answer them (or whatever help they can provide), it would be appreciated.
1) Note: I got 3x RMS value from the page at http://www.kpsec.freeuk.com/powersup.htm#rectifier
When building a regulated AC to DC power supply, why does bridge rectifiers Vrrm have to be 3x the RMS value? I'm in the UK, so the AC RMS here is 230V (see below for further question on this), giving a peak of (1.414*230) 325.22V, so why should I need a Vrrm of 690V if the peak is only 325.22V?
Actually, come to mention that, take a transformer with the following stats:
If the output voltage is only 6V, then why should a bridge rectifier Vrrm need to be more than (1.414*6) 8V? Similarly, the transformer has a current rating of 167mA, yet it seems the vast majority of bridge rectifiers start from 1A, why?Input Voltage:230V;
Output Voltage:6V;
Current Rating:167mA;
Power Rating:1VA;
2) It seems that the Max Vf for bridge rectifiers don't seem to really go beyond 3.3V - the most common values seem around the 1V mark, so how can this be used on a microchip that may require say 5V?
3) Why would a bridge rectifier ever have more than 4 pins, although they aren't common at all looking at Farnells stock, I'm not seeing how there even can be anything other than 4 pins?
4) The UK mains is 230V ± 10% (207V - 253V), does this mean any equipment that I design (or rather the DC power supplies) should really work at the top end of 253V, so when buying a transformer I should get one rated at least 253V rather than 230V?
That should keep me going a while.
Thanks in advance,
Gump.