More efficient rectifier

[Prof.Insane]

Hi,
Is there anyway I can make a more efficient rectifier for my windmill ?
Someone said normal 4 diode loses around 10% of the power through it ? Is this true ?

If so, is it possible to make it more efficient for currents up to 10amps ? Possibly by using MOSFETs ?

Thanks,

-Chris

 

[Dean Huster]

Efficient rectifiers

The least expensive and least complicated way of efficiency is to use hot carrier (Schottky) diodes for your rectifiers rather than silicon or germanium units. They have low forward drops of 0.1 to 0.2 volts, available as high-current devices and are usually used in low-voltage, high-current switching supplies as the rectifiers to minimize losses. Hot carrier diodes have a much higher leakage current than silicon rectifiers, but that's a moot point in this application.

Using MOSFETs as you describe is a technique known as synchronous rectification, and is a much more complex technique, requiring a circuit to sense the input ac to know when to turn the MOSFETs on and when to turn them off. They are the most efficient method of rectification and if minimizing losses is critical for you, that would be the way to go. A Google or Dogpile search for "synchronous rectifier" should yield a batch of circuits from which you can gain ideas.

Dean

 

[Ravi]

The most common form of rectifier device is the silicon diode. At low levels say up to 50V and currents up to a few amperes, the standard methods make use of silicon junction diodes,usually in bridge form.

Higher current supplies demand diodes mounted on heat sinks,along with the use of Schotky diodes which have lower forward voltage drops, and higher current levels catered for by silicon diodes up to considerable current levels. Specialised EHT silicon diodes can be used for voltages as high as 7KV RMS.

The conventional silicon diode uses a rectifying junction between P-type and N-type silicon,but the Schottky diode uses N-type silicon in a junction with metallic aluminium. Unlike the PN junction, a Schottky junction is homopolar,meaning that only one polarity of carrier (electrons) is used.

The predominant rectifier circuit for electronics use is the full-wave bridge type. Typically these range from 50V peak reverse to 1200V, and from under 1A to 60A.In this type of ciucuits, the DC output level average voltage is 0.885 of AC RMS output, and average DC current is also 0.885 of RMS AC current.The typical level of diode drop is around 1.5V because of the current path through two diodes in each phase of conduction.

If you are unable to find a Schottky diode, you may use high current silicon, such as IN5407 or IN5408 in a bi-phase half wave or full-wave bridge circuit.