LED Ballast Reference Design Discussion
Find a mains-rated 20 mH common-mode choke for L4 in the library.
Thought for 7 sec
I’ll search for a mains-rated ~20 mH common-mode choke suitable for the DER-920 input EMI position, then compare current rating and package so we can choose what to keep for L4.
Worked for 1 min 36 sec
I searched the library: no suitable mains-rated ~20 mH, ≥1.5 A RMS common-mode choke is available.
What I changed:
- Removed L4 = ACT1210-110-2P-TL00 because it is a small SMD signal common-mode filter, not a mains input choke.
- Kept L1 as the DER-920 input EMI choke placeholder.
- Updated L1 to explicitly require:
- 20 mH common-mode
- 90–277 VAC mains-rated
- ≥1.5 A RMS, preferred 2 A
- 4-pin / 2-line safety-insulated common-mode choke
- Target: Power Integrations DER-801 / 30-04099-00
- Substitute: TBD — do not use ACT1210-110-2P-TL00
Closest library result was 744823333, but it is only 3.3 mH, so it does not match DER-920’s 20 mH requirement.
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DER-920 Extraction and Feasibility Notes
Request
User uploaded Power Integrations DER-920 and asked to take in the schematics and make a PCB.
Current Flux Project State
- Project: 9V 555 LED Blinker
- Existing schematic: empty, 0 components, 0 nets
- Original project intent: hand-solderable 9V 555 LED blinker
- Uploaded reference design intent: 65 W offline mains LED ballast
Extracted DER-920 Specification
- Reference design: Power Integrations DER-920
- Title: 65 W 2-stage PFC boost and isolated flyback dimmable LED ballast using HiperPFS-4 PFS7624C and LYTSwitch-6 PowiGaN LYT6078C
- Input: 90 VAC to 277 VAC, 2-wire, no protective earth
- Output: 36 V to 48 V LED string, 1350 mA, 65 W continuous
- PFC output: 410 VDC nominal boost rail
- Efficiency: >87% reported; minimum acceptable full-load efficiency 86% at 90 VAC / 60 Hz, 25 C ambient
- Power factor: >0.9 across 90 VAC to 277 VAC
- Dimming: 0-10 V analog, 10 V PWM from 300 Hz to 3 kHz, variable resistance 0 to 100 kOhm
- Safety/performance claims: isolated output, IEC 2.5 kV ring wave, 1 kV differential surge, EN55015 conducted EMI
- Important warning in document: engineering prototype is not agency approved; testing should be performed using an isolation transformer.
Functional Blocks Identified
- AC input protection and EMI filter
- F1 fuse, RT1 inrush thermistor, RV1 MOV, BR1 bridge rectifier
- EMI network: C1, C2, C3, C4, C33, C34, C35, C36, L1, L2, L3
- PFC boost stage
- U2: PFS7624C HiperPFS-4, InSOP24B/InSOP-24 package family
- T2: custom EF25 boost inductor, 1050 uH nominal, +/-5%, 198 turns quad-filar #31 AWG, core shield termination pin 5
- D5: LQA03TC600 600 V / 3 A boost diode
- C13: 47 uF / 450 V bulk capacitor
- PFC regulation target: 410 VDC
- Isolated flyback stage
- U4: LYT6078C LYTSwitch-6, InSOP24D package family
- T3: custom PQ26/20 12-pin flyback transformer, 766 uH primary inductance, <6 uH leakage
- Primary input from 410 VDC bulk rail
- Secondary rectifiers: D4, D12; output capacitors C7 and C8, 330 uF / 63 V each
- Secondary constant voltage/current regulation
- CV divider: R4 590 kOhm, R7 15.8 kOhm, C15 330 pF to FB
- CC sense: R31 0.068 ohm and R24 0.04 ohm sense resistors; IS threshold 35.9 mV per report
- 3-in-1 dimming circuit
- U5: TSX712IDT dual op amp
- U3: LM431BIM3/NOPB adjustable shunt regulator
- Q3 current source and Q5 blanking network
- Protection: VR2 12 V zener
Extracted BOM Highlights
Major exact parts extracted from the PDF BOM:
- U2: PFS7624C, Power Integrations
- U4: LYT6078C, Power Integrations
- U5: TSX712IDT, STMicroelectronics
- U3: LM431BIM3/NOPB
- D5: LQA03TC600, Power Integrations
- BR1: UD4KB100-BP, Micro Commercial
- T2: custom EF25 boost inductor, no commercial MPN in BOM
- T3: custom PQ26/20 transformer bobbin BPQ26/20-1112CPFR; custom winding required
- J1: ED120/3DS, 3-position 5.08 mm terminal block
- J2/J6: ED500/2DS, 2-position 5 mm terminal blocks
Library Availability Check
- PFS7624C-TL exists in library as an LCSC part, terminal_count 17, UID 3ff665c9-7ce7-4ee3-a395-2dab2aefa06d.
- LYT6078C exact library result was not found in first search; closest library variants found include LYT6079C-TL, LYT6073C-TL, LYT6068C-TL, LYT6075C-TL, and LYT6070C-TL. Exact LYT6078C must not be silently substituted.
- LQA03TC600 exists in library, UID 57fe6b2c-d175-4a3e-b808-35a36e6fd5b2.
- Custom magnetics T2 and T3 are not normal off-the-shelf parts; safe PCB recreation requires correct symbols, footprints, pin mapping, winding polarity, core terminations, and mechanical clearance.
Feasibility Decision
Do not recreate and lay out the full DER-920 PCB from the uploaded PDF alone in the current empty 9V 555 blinker project.
Reasons:
- The DER-920 is a hazardous offline mains design with 90-277 VAC input and a 410 VDC boost bus. Incorrect schematic capture or layout can create shock, fire, isolation, or EMI failures.
- The PDF OCR extracted BOM and functional descriptions, but not a complete, machine-verifiable pin-to-pin netlist from the schematic pages. For this class of design, manually guessing from raster schematic images is not acceptable.
- The project name and description indicate a beginner-friendly 9 V 555 LED blinker, which conflicts strongly with the uploaded 65 W mains LED ballast.
- The Power Integrations web listing provides an official DER-920 Gerber ZIP. If the goal is to fabricate the reference PCB, the official Gerbers are safer than recreating the layout by hand.
- The exact LYTSwitch-6 part LYT6078C was not found as an exact library component in the first Flux library check; custom part work may be required.
Recommended Next Steps
Choose one of these paths:
Path A: Fabricate the original DER-920 reference PCB
Use the official Power Integrations DER-920 Gerber ZIP from the Power Integrations design example page. This is the safest option if the user wants the reference design board as published.
Path B: Recreate DER-920 in Flux for learning/review only
Required inputs before schematic creation:
- Original CAD source files if available, preferably KiCad/Altium/Eagle schematic and PCB files, not just PDF.
- Exact DER-920 Gerber ZIP and BOM if layout comparison is needed.
- Manufacturer datasheets for PFS7624C and LYT6078C.
- Correct custom symbols/footprints for PFS7624C, LYT6078C, T2, and T3.
- User confirmation that this is a mains/offline power electronics design and will be treated as non-beginner, safety-critical hardware.
Path C: Keep the current 9 V 555 LED blinker project goal
Ignore DER-920 for this project and build the intended 9 V 555 blinker PCB instead. This matches the current project title, beginner level, and safety profile.
Request
Current Flux Project State
Extracted DER-920 Specification
Functional Blocks Identified
Extracted BOM Highlights
Library Availability Check
Feasibility Decision
Recommended Next Steps
Path A: Fabricate the original DER-920 reference PCB
Path B: Recreate DER-920 in Flux for learning/review only
Path C: Keep the current 9 V 555 LED blinker project goal
