Replacement Components and Methods - HV Arbitrary Waveform Amplifier
Purpose
This file resolves the current blocking items for the HV arbitrary waveform amplifier by separating them into:
- Direct component replacements
- Library/import actions
- Architecture-level replacement methods when a direct component is not practical
Current baseline:
- Power input: fixed 220 VAC mains only
- External interfaces: only power input, signal input, signal output
- Output: +/-1000 V peak differential
- Load: 1.5 nF
- Frequency target: 0 to 500 kHz
- Current limit: 6 A peak
- Topology baseline: floating differential BTL fixed-HV-rail linear amplifier
- Suggested internal rails: +/-600 V to +/-650 V per output leg
Updated architecture implication
The previous idea of using external +/-600 V to +/-650 V lab supplies is no longer allowed because the user confirmed the only power interface is 220 VAC mains. Therefore, the design must include an internal mains-derived power subsystem.
The replacement method is:
220 VAC input -> protection/EMI/inrush -> rectifier/PFC or HV DC bus -> isolated HV conversion -> internal +/-600 V to +/-650 V rails and low-voltage auxiliary rails.
No external HV rail connector is allowed.
Blocking item 1 - Output-stage SiC MOSFET
Problem
A true Flux-library match for a 1700 V TO-247-4 / Kelvin-source SiC MOSFET was not found. The earlier Flux-library closest part, C3M0030090K, is 900 V and is not suitable for final +/-600 V to +/-650 V rail operation.
Direct replacement candidates
Preferred final path: 1700 V TO-247-4 SiC MOSFET
Candidate families found externally:
-
Navitas / GeneSiC G3R20MT17K
- 1700 V SiC MOSFET
- TO-247-4
- Web result indicates Kelvin-source pin and 1700 V class
- Recommended as a final-voltage-margin candidate
-
Wolfspeed / equivalent 1700 V TO-247-4 SiC MOSFETs
- Search confirms TO-247-4 1.7 kV SiC MOSFETs exist through distributors
- Exact MPN was not found in Flux library
-
Sansha FMG50AQ170N6 class
- 1700 V TO-247-4L SiC MOSFET family appears externally
- Requires datasheet, availability, and SOA review
Use case: final HV output stage where each device may see high rail-to-rail stress and voltage transients.
Acceptable interim library path: Microchip MSC025SMA120B4N
Flux library found:
- MSC025SMA120B4N
- 1200 V SiC MOSFET
- 113 A class
- TO-247-4 / 4 terminals
- Library part UID: 7d8e744c-06f1-49a0-a00b-3c7584e98c29
Use case: lower-risk first schematic placeholder or reduced-rail prototype. It is not as safe as 1700 V for +/-650 V rails unless actual VDS stress and transient margin are proven acceptable.
China supply-chain candidate: Tokmas CI90N120SM4
External search found:
- Tokmas CI90N120SM4
- 1200 V SiC MOSFET
- TO-247-4
- LCSC listing found
- Requires import/library creation before use in Flux
Use case: domestic / China supply-chain candidate. Must not be frozen until datasheet SOA, gate charge, thermal resistance, pinout, and package footprint are verified.
Method replacement if 1700 V part is unavailable
Use a stacked-device linear output leg:
- Stack two 1200 V SiC MOSFETs per high-voltage device position
- Add static voltage-sharing resistors
- Add dynamic voltage-sharing capacitors / RC snubbers
- Use isolated or level-shifted gate drive per device
- Add per-device VDS clamps and thermal sensing
Advantages:
- Uses more available 1200 V parts
- Better derating than a single 1200 V device on high rails
Disadvantages:
- Much more complex gate drive and compensation
- More parasitics, more stability risk
- Needs detailed simulation before schematic freeze
Recommendation: for final voltage margin, import/create a 1700 V TO-247-4 SiC MOSFET. Do not use 900 V parts for final +/-650 V rail output stage.
Blocking item 2 - HV output connector
Problem
No usable SHV/MHV 5 kV-class connector was found in the Flux library.
Direct replacement candidates
External search confirmed SHV connector families are intended for high-voltage coax applications. Common ratings found in search results:
- SHV: typically up to about 5 kV DC or 3.5 kV RMS depending series
- Some references state standard SHV is 5 kV / 5 A class
- TE Connectivity 5051494-1 appears as an SHV connector candidate externally but was not found in Flux library
Recommended connector strategy
Use a panel-mount SHV connector and wire it to the PCB/output network internally, instead of relying on a PCB-mount HV coax connector.
Why:
- Panel-mount SHV parts are easier to source and mechanically safer
- The enclosure can provide strain relief and creepage/clearance control
- The PCB does not need to support connector mating force directly
- Output cable shield bonding and HV spacing are easier to manage
Implementation:
- Treat the HV output interface as a panel connector plus internal short HV-rated cable or bus wire
- Put the PCB output node on a guarded HV pad or terminal region
- Add output damping resistor and discharge network on PCB before the connector feed
- Keep connector shield/chassis bonding strategy explicit
Do not use ordinary BNC/SMA connectors.
Blocking item 3 - Internal 220 VAC to HV/LV power subsystem
Problem
Because the only power interface is 220 VAC, the product must internally generate all rails:
- Isolated +/-600 V to +/-650 V HV rails for BTL output stage
- Low-voltage analog/control rails: +/-15 V, 5 V, 3.3 V
- Isolated gate-driver rails as required
Required internal power chain
-
220 VAC input protection
- Fuse
- MOV/surge absorber
- NTC or active inrush limiting
- Common-mode choke and EMI filter
- X/Y safety capacitors as appropriate
- Protective earth/chassis bonding strategy
-
Rectifier and bulk DC bus
- Bridge rectifier
- Bulk capacitor bank
- Bleeder/discharge resistors
- HV DC bus sensing
- Optional/likely PFC depending power level and compliance target
-
Isolated HV converter
- Candidate topologies: LLC resonant, phase-shift full bridge, or dual isolated converters for +HV and -HV
- Output: regulated or semi-regulated +/-600 V to +/-650 V rails
- Must include soft-start, OVP, UVP, current limit, isolation feedback, and energy dump/regeneration path
-
Auxiliary low-voltage supplies
- Mains-derived isolated low-voltage AC/DC for housekeeping
- Secondary DC/DC rails for analog/control/gate drive
Replacement methods
Method A - Certified front-end plus custom isolated HV converter
Use a certified AC/DC front-end or PFC module to create a safe intermediate DC bus, then design an isolated HV converter.
Pros:
- Best safety path
- Reduces offline mains design burden
- Allows dedicated HV conversion optimization
Cons:
- Still requires custom HV converter and transformer design
Recommendation: preferred first integrated architecture.
Method B - Full custom 220 VAC offline HV supply
Design the entire AC/DC and isolated HV conversion chain on the board.
Pros:
- Most integrated
- Best cost control at production scale
Cons:
- Highest safety/EMI risk
- Requires full isolation, magnetics, creepage, thermal, and compliance design
- Not recommended as the first unvalidated prototype path
Method C - Commercial HV module inside enclosure
Use a commercial HV DC/DC module internally, powered from an internal isolated low-voltage bus.
Pros:
- Fastest internal-only architecture
- Keeps external interface as 220 VAC only
Cons:
- Many HV modules are low power and may not support reactive load energy
- May only work for limited-duty or reduced-performance prototypes
Updated recommendation
Do not use external lab +/-HV supplies as user-facing power inputs. If lab supplies are used temporarily during bench bring-up, they must be treated as a development fixture only, not a project interface. The schematic architecture should show internal 220 VAC input and internal generation of HV/LV rails.
Blocking item 4 - Gate driver
Usable Flux-library candidates
-
STGAP1AS
- Flux library part found
- Galvanically isolated 5 A advanced single gate driver
- Miller clamp, desaturation, UVLO/OVLO, SPI
- Recommended first candidate for protected SiC gate-drive channel
-
STGAP2SCM
- Galvanically isolated 4 A single gate driver
- Miller clamp
- Useful when compact drive is preferred
-
2ED1324S12P
- 1200 V half-bridge driver with active Miller clamp and protection features
- More suitable for switching half-bridge style drive than fully isolated per-device linear/stacked drive
Recommendation: use STGAP1AS for schematic-level protected isolated driver channel, pending datasheet confirmation of CMTI, isolation rating, DESAT timing, supply range, and gate-drive bias compatibility.
Blocking item 5 - HV feedback divider
Usable Flux-library candidates
-
CRMV2512AF100KFKEF
- Vishay 100 kOhm, 1 W, 2512 SMD high-voltage thick-film resistor
- Candidate for series divider string
-
HVC4020V5007JET
- Ohmite 5 GOhm HV resistor
- Useful for very high impedance paths but not ideal for precision feedback due to tolerance
Method
Use a resistor string, not a single resistor:
- Split HV across many 100 kOhm to 1 MOhm high-voltage resistors
- Keep each resistor below its voltage rating with margin
- Add compensation capacitors in parallel with selected divider sections
- Guard the high-impedance nodes on PCB
- Validate divider phase response to >500 kHz
Recommended path forward
Preferred updated prototype path
- Keep BTL differential linear topology.
- Use internal 220 VAC input protection and internal isolated HV/LV rail generation.
- Use panel-mount SHV output connector, not PCB-mount low-voltage coax.
- Import/create one 1700 V TO-247-4 SiC MOSFET part, or use MSC025SMA120B4N only for reduced-voltage prototype validation.
- Use STGAP1AS as the first gate-driver candidate after datasheet check.
- Build schematic in functional blocks:
- 220 VAC input protection and EMI filter
- Rectifier/PFC/intermediate DC bus
- Isolated HV supply (+/-600 V to +/-650 V)
- Isolated LV supplies
- Signal input conditioning
- Controller/error amplifier/slew limiter
- HV feedback/current sensing/protection
- BTL output leg template
- Output damping/discharge/SHV panel connector
If continuous full-scale 500 kHz is mandatory
Switch from fixed-rail linear prototype toward:
- Multilevel / cascaded H-bridge output stage
- Tracking or regenerative rails
- Custom isolated HV power supply with dump/regeneration
This is more complex but likely required if continuous full-scale 500 kHz operation is mandatory.
Action items
- Import or request library part for G3R20MT17K or another 1700 V TO-247-4 SiC MOSFET.
- Import or request library part for Tokmas CI90N120SM4 if China supply-chain priority is strict.
- Select exact SHV panel connector MPN and create/import its symbol/footprint or represent it with a rated connector placeholder plus mechanical note.
- Select the internal 220 VAC to HV/LV supply architecture before freezing the power schematic.
- Begin schematic with mains input protection, discharge, interlock, signal input, feedback, current sense, and one BTL output-leg template.