RFB-01 - The ultra fast rectifier bridge
Interesting features
- Possible to use fast diodes
- High current pcb, thick copper traces
- "Snubberized", each diodes has snubbers
- Wago cage clamp connector
Why did I design this?
Some people feel that they need a faster rectifier bridge than the normal 1-50 µs in 50/60 Hz applications. I have seen on the internet that there are few products out there which can take max 2-3 A because the don't have any cooling arrangements.
My design can take a lot more current because I have four heatsinks, one for each diode.
The schematic
The schematic. Please download it if you want to take a closer look.
The rectifier bridge is built by four ultra fast recovery diodes plus four heavy duty polypropulene capacitors PHE450 from the famous swedish company EVOX-RIFA. As an option you can choose to have only a capacitor or a capacitor plus a resistor. The values can go from 1-100 nF and 1-100 ohms and to really determine the exact value you must have spectrum analyzer which no DIY'er have I suppose. 100 ohms and 100 nF is a good start I think. You don't have to use the type of capacitor I have suggested. The pcb has holes for almost any type with pin spacing, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 and 0.6"inch, from 5 to 15 mm.
Top view of the RFB-01. Note that you only have to solder one type of connectors.
Virtually any diode, especially if they have TO220 case, fits. You can even use regular round ones. MUR820 (200V, 25 ns) and MUR860 (600V, 45 ns IR, 25 ns ON-Semi) seem to be good choices. I have chosen MUR820 because ELFA has it.
Two manufactures of diodes can be found here:
If you plan to use this bridge in a preamp, you won't probably need any heatsinks. If you plan use this bridge in a heavy duty application you must use heat compound between the diode and the heatsink. This compound is usually white and I recommend you to use a silicone free product because the silicone has the tendency to creep all over the place and collect dust.
You can connect the bridge with ordinary cables but max 2.5 square millimeters if you use Wago-connector. Other screw terminals may take bigger cables. As an option I have added lug connectors. Then you can use cables with an area of 6-10 square millimeters.
As a general rule for this project, use any component, audiophilic or not. As long as it's fits for the application it's OK to use it.
The pcb layout
The component print.
Note that the caps has two optional positions.
The component side
The component side.
The solder side
The solder side viewed from above, therefore the mirrored text.
Build directions
It's really easy to build this bridge. Start with mounting the diodes on the heatsinks. You don't need any insulation because the heatsinks aren't connected to anything. Solder the heatsink with a very small drop of tin, just so it won't fall off. Then solder the diode. When the whole bridge is finished and tested you may solder the heatsinks a little bit better. This is just a precaution if you want to remove the heatsinks of some reason before you are completely finished. Once you have soldered them in they will be impossible to remove without damaging the pcb.
Mount caps and optionally the resistors. Just solder them in.
Mount connectors, the type you have chosen.
Soldering
Some parts are demanding in terms of heat. The pcb has thick copper which cools good. Therefore you must "fire up" some pads. Those pads with wide traces demands lot's of heat. If you have a temperature controlled soldering iron turn up the temperature to max, maybe 450 deg C! Stop warming when the tin has start to flow up on the component side. See the picture above. Note also that the lug had a thick oxide layer. The soldering joint isn't perfect. The tin hasn't wet the surface of the lug but still, the quality is fair.
Test
To be extra sure test this bridge with low voltage and small currents. Use max 24 VAC and 1-2.2 kohms load. Measure that you get correct voltage. 24 VAC will generate 24/1.11 = 21.6 V if you don't have any smoothing caps. If you don't get fullwave rectification you will get only 10.8 V. Don't use any smoothing capacitors for this first test because you won't be able to notice if you have full or halfwave rectification.
Connect this ultra high performance rectifier bridge in your amp now and good luck. You won't be disappointed.
Technical data
| MUR820 | MUR820 | Unit | ||
| Peak repetitive reverse voltage: | 200 | 600 | Volts | |
| Average rectified forward current: | 8 | 8 | Amps | |
| Peak rectified forward current: | 16 | 16 | Amps | |
| Non-repetitive peak rectified forward current: | 100 | 100 | Amps | |
| Maximum reverse recovery time: | 25-35 | 25-35, 50-60 | ns |
For complete data, please read the datasheet. Different brands aren't 100% identical in performance. ON seems to be better than International Rectifier, the MUR860 type.