EL Driver 1

The EL Driver 1 will be an EL wire driver, that can be plugged into the EL Shield (revision 2+) or used standalone as a regular inverter.

• Generates 80VDC @ ~50-150mA from 4.5-20V in using the LT1737 IC
• Converts the 80VDC into 160v p-p using an H bridge
  • H bridge is driven from a PIC10F microcontroller
  • Can be set to low frequency, high frequency, or fed a pulse train from an external device

Status

• 2012-03-31: Proper FET and transistor ordered/received, will assemble today and re-test.
• 2012-03-22: Troubleshot more, found some board stuffing issues. Fixed and now it puts out ~80VDC with no load and the output filter disconnected, but output collapses under any load. FET still getting hot and drawing way too much current.
• 2012-03-21: Assembled DC-DC side, controller chip got very hot. Found two missing caps, added them and it puts out ~0.5VDC with high current draw, FET gets hot.
• 2012-03-19: PCBs arrived.
• 2012-03-04: Digikey parts ordered.
• 2012-02-26: Completed PCB layout and CAM, sent off to Laen for manufacturing. Transformer samples ordered, still need to do the Digikey order.
• 2012-02-25: Completed design and simulation runs, started schematic entry and BOM creation.
• 2012-02-21: Decided that the tolerances were just too tight on the existing design, and scrapped it. DC-AC converter can stay, but the DC-DC side needs redesigning. Started a redesign around the LT1737, which is similar to the LT3575 I was using, but uses an external MOSFET, which is a lot more flexible.
• 2012-02-20: Built the AC converter, troubleshot the software a bunch. Now the built-in high/low frequency modes work fine, the external-sync mode works mostly, but there's a weird short pulse right before it goes into the off-time. Attempted to test, but since the HVDC side isn't generating enough voltage, it won't work yet.
• 2012-02-18: Lots more troubleshooting, at a reduced current level so nothing gets damaged. Lowered the zener voltage in the snubber which helped a lot, but the snubber still acts too slowly. Will replace the diode in the snubber with a Schottky on Tuesday to avoid the response time associated with p-n diodes, see if that fixes it.
• 2012-02-04: Lots more troubleshooting. No real progress other than blowing up more controller chips.
• 2012-01-25: Symbol wasn't wrong, transformer had the mark on the wrong side (my fault, I took it apart and reassembled it wrong). Found that the voltage spike on the primary upon turn-off is blowing up the controller chip's switch.
• 2012-01-23: Did a lot of troubleshooting. Found the transformer was in backwards, and the symbol must be wrong as once it's in right, the secondary is wired up backwards. Green-wiring the board now to fix that.
• 2012-01-18: Assembled DC-DC section. Connected to 5V it pulls 250mA and outputs nothing. Troubleshooting needs to be done.
• 2011-12-04: Completed board layout, finished silkscreen, CAM files output and sent to Laen. Parts still need to be ordered.
• 2011-12-03: Completed 95% of board, 4 airwires left, then silkscreen/CAM.
• 2011-12-02: Completed schematic and BOM.
• 2011-12-01: Completed most of the schematic and BOM, LEDs still remaining to be done.
• 2011-11-30: Design of flyback converter based around LT3575 finalized. Started the schematic entry.
• 2011-11-29 and prior: LTspice simulations to finalize design.

Revision 1 Issues

• Fixed in rev. 2 - Secondary of transformer is backwards
• Fixed in rev. 2 - HFREQ/SYNC and HV_SHDN pins are reversed

Revision 2 Issues

• 3.3v regulator for logic has max. 6V input, but module is supposed to take up to 20 (replace with MCP1804)
• ID pins are connected to raw input, should be off the regulated supply or to GND
• Fixed on rev. 1 BOM - Q2/Q3 missing from BOM
• Fixed on rev. 1 BOM - C8/C9 listed as C6/C7 on BOM
• Fixed on rev. 1 BOM - R19 on BOM as 1.8k, s/b 20k (also on as 20k)
• Fixed on rev. 1 BOM - R20/21 stuffed wrong, double check BOM is correct (wasn't)
• D1 backwards on schematic