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Rigol DS1054Z DC Power Supply – Linear Post Regulation

Finally, here’s the last part of the Rigol 12v DC Power Supply project, the linear post regulation section to remove some of the ripple.

I have made a couple of layout adjustments since the last post about this part of the project – a little more filtering on the DC outputs. As usual the Eagle project files are at the bottom of the post for those who might find them useful.

Updated PCB
Updated PCB
Updated Schematic
Updated Schematic

 

Completed PCB
Completed PCB

Here’s the completed PCB, partially installed in the back of the scope. The missing regulator is the 5v one, since I already have a source of clean 5v from my original attempt at the supply, it’s not a problem not using a linear after the switcher. The filtering is the same on all channels, input from the switchers is on the right, outputs to the scope on the left.

PCB Bottom
PCB Bottom

Here’s the bottom of the PCB, with the common mode input chokes. The design of this board has allowed me to remove a couple of the switching modules as well, as I can use a single bipolar supply to run both sets of bipolar regulators on this board. This should help remove some of the noise also.

The ripple level has now dropped to lower than it was originally on the mains supply! Current draw at 13.8v DC is about 1.75A.

Scope Ripple
Scope Ripple

[download id=”5589″]

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Rigol DS1054Z 12v Power Supply Noise Filtering

Since I fitted my scope with a SMPS based 12v input supply, there has been a noise problem on very low volts/div settings, this noise isn’t present on the mains supply, so I can only think it’s coming from the switching frequencies of the various DC-DC modules I’ve used.

Scope Ripple
Scope Ripple

Because of this I’ve designed a linear post-regulation stage for the supply, to remove the RFI from the DC rails.
This board takes the outputs from the DC-DC converters, removes all the noise & outputs clean DC onto the mainboard of the scope.

As the scope internally uses regulation to get the voltages lower, I’ve found that I don’t have to match the outputs of the mains supply exactly, for the +/-17.5v rails, 12v is perfectly fine instead.

Scope Linear PSU
Scope Linear PSU

Here’s the PCB layout, with the 6ย  common mode filters on the input (left), linear regulator ICs in the centre & the output filters on the right.

Scope Linear PSU
Scope Linear PSU

Here’s the schematic layout, as usual the Eagle Project files are in the link below, I’ll update when I have built the board & tested!

[download id=”5589″]

73s for now ๐Ÿ™‚

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Rigol DS1054Z 12v Power Supply Project – Completion

All of the parts I required to complete the supply arrived this morning. After several hours of building, here’s what I came up with:

12v Power Supply
12v Power Supply

I’ve mounted everything on a piece of FR4 PCB, with it’s copper plane grounded to the case. This backing board is the same size as the original PSU PCB to allow it to be screwed into the same location in the scope.

The power comes in via the converter on the right, which outputs a single 24v rail for the rest of the supplies. The other 6 supplies then generate the individual voltage rails that the scope requires. The use of a single input supply allows this system to operate at voltages up to 30v DC, so it’s good for both 12v & 24v systems.

Scope Ripple
Scope Ripple

At present the only issue is with some ripple on one of the supplies, this is showing up on the scope display with no input connected at the lowest volts/division. Parts are on order from Farnell to build some common mode filters to remove this from the DC output.

On a 13.8v supply, the scope draws about 1.5A total from the supply, giving a total power consumption of 20.7W. This is with all 4 channels enabled.

My wiring assignments & DC-DC converter ratings are in the table below

Connector PinPCB PinSignalMainboardDC-DC RatingWire Colour
110GNDGNDN/ABLACK
22+9v_GNDFAN --NABLACK
38+7.5V6.3V6AORANGE
414-7.5V-7.5V2AGREEN
51NOT USEDAC_TRIGN/ANOT USED
64+5V5V5A6ARED
76GNDGNDN/ABLACK
87GNDGNDN/ABLACK
912-17.5V-17.5V3APURPLE
109+7.5V6.3V6AORANGE
113+9VFAN +1AGREY
121117.5V17.5V3ABLUE
135+5V5V5A6ARED
1413GNDGNDN/ABLACK

Stay tuned for the final section of this build with the power supply filtering & main DC input connections!

73s for now ๐Ÿ™‚