# Project Specification — 3 kW Programmable CV/CC Supply ## Project Overview - Status: Draft schematic start - Device: Programmable isolated-output CV/CC bench/lab supply architecture targeting 0.5–100 V output, 0–40 A current limit, and 3 kW maximum output power. - Current scope: full four-phase system schematic. Mean Well AC/DC power modules, matrix contactors, high-current fuses, busbars, enclosure wiring, fans, and emergency-stop mains hardware are represented as off-board interfaces rather than PCB-mounted parts. ## Intended Use - Prototype/validation platform for a high-power programmable DC supply. - Intended development sequence starts with schematic capture and design review, followed by one-phase power-stage validation before committing to a full 3 kW layout and enclosure. ## What the Device Should Do - Generate programmable CV and CC output from 0.5 V to 100 V. - Deliver up to 40 A below the power-limit knee, constrained to 3 kW maximum. - Switch between LOW bus mode (~26.4 V, four supplies in parallel) and HIGH bus mode (~105.6 V, four supplies in series) with output interruption. - Provide hard/firmware protection for overcurrent, overvoltage, phase imbalance, overtemperature, failed contactor states, and discharge/precharge sequencing. ## Main Features - Four interleaved synchronous buck phases at 100 kHz/phase. - Off-board supply/contactors modeled via connectors and control/feedback interfaces. - C2000 controller with PWM, trip-zone, ADC, and sigma-delta filter inputs. - Isolated per-phase current measurement plus independent total-current hardware trip. - Precision monitoring ADC for calibration and telemetry. - Dedicated auxiliary rails independent of the reconfigurable high-power bus. ## System Architecture ```mermaid flowchart TD AC[Off-board AC/DC Modules\n4x 26.4 V calibrated] --> MATRIX[Off-board Series/Parallel\nContactor Matrix] MATRIX --> BUS[PCB HV Bus Interface\nPrecharge / brake / bus caps] BUS --> P1[Phase 1 Buck] BUS --> P2[Phase 2 Buck] BUS --> P3[Phase 3 Buck] BUS --> P4[Phase 4 Buck] P1 --> OUT[Output Bus + Capacitor Banks] P2 --> OUT P3 --> OUT P4 --> OUT OUT --> LOAD[Output Terminals] SENSE[Voltage + Current Sensing] --> MCU[C2000 Controller] MCU --> DRV[Gate Drivers + Trips] DRV --> P1 DRV --> P2 DRV --> P3 DRV --> P4 AUX[Off-board 24 V Aux Supply] --> RAILS[12 V / 5 V / 3.3 V Rails] RAILS --> MCU RAILS --> SENSE RAILS --> DRV ``` ## Hardware Subsystems - Off-board power-source interface: four 24 V/960 W AC/DC modules adjusted to 26.4 V, represented by module terminal/control connectors. - Off-board contactor matrix: series/parallel mode contactors, output contactor, precharge bypass, and LV capacitor-bank contactor represented by coil-drive and auxiliary-feedback connectors. - Four-phase buck stage: 200 V MOSFET half-bridges, gate drivers, inductors, phase shunts, local input capacitors, bootstrap networks, and output bus combining. - Sensing/protection: per-phase isolated delta-sigma modulators, total-current Hall sensor/comparator, remote/local voltage sense, bus OVP/brake, output discharge. - Control: TI C2000 controller, precision ADC, isolated CAN, watchdog, debug/programming. - Auxiliary rails: off-board 24 V auxiliary input; onboard 12 V, 5 V, and 3.3 V regulators. ## Interfaces and Connections - High-power bus: BUS+, BUS− from off-board matrix. - Output: OUT+, OUT− high-current terminals and remote-sense pair. - Off-board controls: AC/DC enable, contactor coil drives, auxiliary contact feedback, current-share relay controls. - Communications: isolated CAN. - Debug: C2000 programming/debug interface. ## Power and Runtime Expectations - Main output: ≤3 kW, up to 100 V and 40 A depending on setpoint. - Auxiliary input: 24 V off-board supply, target ~150 W class. - Onboard rails: 12 V gate-driver rail, 5 V analog/sensor/relay logic rail, 3.3 V MCU/digital rail. ## Power Tree and Power Budget | Rail / Path | Source | Estimated Load / Rating Basis | |---|---|---| | Main HV bus | Off-board supply matrix | 26.4 V LOW or 105.6 V HIGH; ~30 A bus current at 3 kW/95% in HIGH mode | | Output | Four-phase buck | 0.5–100 V, 0–40 A, 3 kW max | | 12 V | Onboard buck from 24 V aux | Gate drivers and analog protection circuits; provisional sizing pending datasheet-current summation | | 5 V | Onboard buck from 24 V aux | ADCs, current modulators, sensors, CAN side support; provisional sizing pending datasheet-current summation | | 3.3 V | LDO/buck-derived from 5 V | MCU and digital logic; provisional sizing pending datasheet-current summation | ## Manufacturing and Assembly Expectations - Professional SMD PCB for control and power electronics. - High-current AC/DC modules, contactors, fuses, copper busbars, mains wiring, fans, and enclosure hardware are off-board. - High-current PCB copper, creepage/clearance, thermal relief, gate-drive layout, current-sense Kelvin routing, and snubber tuning require prototype validation. ## Firmware-Relevant Hardware Requirements - Four synchronized PWM phases with 0/90/180/270° phase offsets. - Hardware trip inputs must disable PWM without firmware latency. - ADC/SDFM measurement channels for phase currents, total current, bus voltage, output voltage, temperatures, contactor feedback, and auxiliary rail telemetry. - Sequenced state machine for precharge, range changes, output contactor, discharge, and fault handling. ## Physical Design Expectations - Board size, enclosure, airflow, heatsinking, busbar interfaces, and connector locations are TBD. - Layout must treat switch nodes, gate loops, shunt Kelvin signals, isolated boundaries, and high-current planes as critical. ## Important Design Decisions - Use four fixed AC/DC modules off-board rather than designing the mains front end on the PCB. - Use two bus modes only: LOW 4P and HIGH 4S. - Keep contactors off-board and represent them through control/feedback connectors. - Use one common controller supervising all four phases rather than paralleling independent converters. - Build the schematic for the full system now, but validate a one-phase prototype before full-power assembly. ## Assumptions - Mains AC handling remains outside the PCB/enclosure wiring model for this schematic pass. - The first schematic revision is architectural and will require datasheet-backed refinement, loop compensation calculation, thermal analysis, and prototype test results. - Exact connector families and board mechanical constraints are not yet specified. ## Change Notes - Initial specification created from the provided Rev A reference implementation and user request to start the full four-phase schematic with power modules/contactors off-board.