To build a reliable 2000W 48V DC to 120V AC h bridge inverter, you need a 100Ah 48V LiFePO4 battery bank, an EGS002 SPWM driver board, and four IRFB4468PbF MOSFETs driving a 2000W toroidal step-up transformer. This low-frequency topology avoids the lethal 310V DC bus found in high-frequency commercial units, making it the safest and most robust architecture for bench and off-grid builders.
System Block Architecture: 48V DC Source to 120V AC Load
An h bridge inverter converts direct current into alternating current by rapidly switching four power semiconductors (the 'H' configuration) to reverse the polarity across the load. In a 48V low-frequency system, the architecture flows through five distinct stages:
- Source & Protection: 48V LiFePO4 bank feeds a 100A Class T fuse and a DC disconnect switch.
- Logic & Driver: An SPWM (Sinusoidal Pulse Width Modulation) generator creates the 50/60Hz switching signals with built-in dead-time to prevent shoot-through.
- H-Bridge Switching Stage: Four N-channel MOSFETs switch the 48V DC into a high-current 48V AC square/sine wave.
- Step-Up Transformation: A 48V-to-120V toroidal transformer steps the voltage up to standard mains level.
- Output Filtering: An LC low-pass filter smooths the high-frequency PWM carrier ripple, yielding a clean 120V RMS pure sine wave.
Battery Bank Sizing: Series vs. Parallel and Discharge Limits
Your inverter is only as capable as the DC source feeding it. For a 2000W continuous load, the choice between series and parallel battery wiring dictates your system's viability.
Series vs. Parallel Consequence for V and Ah
Wiring batteries in series increases voltage while maintaining the same Amp-hour (Ah) capacity. Wiring in parallel increases Ah capacity while maintaining the same voltage. For a 2000W load, a 12V parallel bank would require pulling over 166A continuously, demanding massive 2/0 AWG cabling and generating severe I²R heat losses. By wiring four 12V 100Ah batteries in series, you achieve a 48V nominal (51.2V actual) bank. The current drops to a manageable ~46A, allowing you to use standard 4 AWG THHN wire.
Charge/Discharge Limits and Peukert's Law
Peukert's Law dictates that a battery's effective capacity drops as the discharge current increases. For flooded lead-acid (FLA) batteries, the Peukert exponent is roughly 1.3, meaning heavy loads severely reduce runtime. LiFePO4 chemistry has an exponent near 1.05, effectively eliminating Peukert losses at typical inverter loads. However, you must apply an inverter efficiency derating factor (typically 0.85 to 0.90).
For our 100Ah 48V LiFePO4 bank:
- Max Discharge (C-Rate): 1C (100A). Our 46A draw is 0.46C, well within safe thermal limits.
- Depth of Discharge (DoD): Limit to 80% to preserve cycle life. Usable capacity is 4096Wh × 0.80 = 3276Wh.
- Runtime: 3276Wh / 2000W load = 1.63 hours of continuous full-load runtime.
Sizing the H-Bridge Inverter Stage for a 2000W Load
Sizing the semiconductors requires calculating the worst-case DC current and applying a safety margin for surge loads (like motor starting currents).
Inverter and Charger Sizing Math
Assume a 2000W continuous AC load and an 85% (0.85) inverter efficiency.
- DC Input Power: 2000W / 0.85 = 2352W
- Continuous DC Current: 2352W / 48V (low-voltage cutoff threshold) = 49A
- NEC Continuous Load Factor: 49A × 1.25 = 61.25A (Minimum wire and fuse rating)
- Surge Current (5 seconds): 49A × 2.0 = 98A
According to Texas Instruments gate driver fundamentals, MOSFETs must be sized not just for continuous current, but for peak pulsed current and thermal dissipation during the switching transitions. At a 20kHz PWM carrier frequency, switching losses dominate. We need MOSFETs rated for at least 100V (to handle 48V nominal + ringing spikes) and a pulsed drain current (IDM) exceeding 200A.
Decision Path: Selecting Your H-Bridge Driver and MOSFETs
Choosing the right components prevents catastrophic shoot-through (where high and low-side MOSFETs conduct simultaneously, shorting the battery). Use the decision matrix below to select your topology.
| Design Constraint | If True / Required | Component Path |
|---|---|---|
| Output Waveform | Pure Sine Wave (THD < 3%) | SPWM Driver Board (e.g., EGS002) |
| Output Waveform | Modified Sine / Square Wave | 555 Timer / CD4047 Astable Multivibrator |
| DC Bus Voltage | 12V / 24V / 48V (Low Freq) | N-Channel MOSFETs (Vds > 75V) |
| DC Bus Voltage | 310V+ (High Freq Boost) | IGBTs or High-Voltage SiC MOSFETs |
| Gate Drive Requirement | High-side floating drive needed | Half-bridge driver IC (IR2110 / IR2214) |
The Concrete Pick: EGS002 + IRFB4468PbF
For a 48V, 2000W pure sine wave h bridge inverter, terminate your design with this exact bill of materials:
| Component | Part Number | Key Specification |
|---|---|---|
| SPWM Driver | EGS002 Module | Integrated IR2110 drivers, 300ns-1.5us adjustable dead-time |
| H-Bridge MOSFETs (x4) | Infineon IRFB4468PbF | 100V Vds, 195A Id, 2.6mΩ Rds(on) at Vgs=10V |
| Gate Resistors (x4) | 10Ω 1W Metal Film | Prevents high-frequency ringing on the gate trace |
| Transformer | 2000W 48V-CT to 120V Toroidal | Center-tapped primary for push-pull, or standard 48V for full-bridge |
The IRFB4468PbF is the undisputed workhorse for low-frequency 48V bridges. Its exceptionally low 2.6mΩ on-resistance means that at 49A continuous, conduction losses per MOSFET are roughly I²R = (24.5A per leg)² × 0.0026Ω = 1.56W. This keeps the TO-220 packages cool enough to run on modest extruded aluminum heatsinks without forced air, provided you use high-quality thermal paste and insulating mica pads.
Output Filtering and Final Verification
The raw output of the H-bridge is a 48V RMS pulse-width modulated waveform. Before it hits the transformer, no filtering is required (the transformer's inductance naturally smooths the high-frequency carrier). However, on the 120V AC secondary side, you must filter out residual switching noise to protect sensitive electronics.
LC Filter Sizing
Place an LC low-pass filter on the 120V AC output. The cutoff frequency must be well above 60Hz but well below the 20kHz SPWM carrier frequency.
- Inductor (L): 1.5mH toroidal choke, rated for 20A AC.
- Capacitor (C): 4.7µF to 10µF AC-rated film capacitor (X2 safety rated, 275VAC minimum).
Verification Sequence
Before connecting any AC load, perform this bench verification sequence to prevent silicon vaporization:
- Dead-Time Check: Power the EGS002 logic with a 12V bench supply (do not connect the 48V high-power bus). Use an oscilloscope to probe the high-side and low-side gate signals. Verify a minimum 300ns dead-time where both signals are LOW. If dead-time is zero, the bridge will shoot-through and explode the MOSFETs upon applying power.
- Open-Circuit Voltage: Connect the 48V battery and turn on the bridge with no load. Measure the AC output of the transformer secondary. It should read 120V ± 5V RMS.
- Thermal Sweep: Connect a 1000W resistive load (like a space heater). Run for 15 minutes. Measure the MOSFET heatsink temperature. If it exceeds 60°C above ambient, upgrade the heatsink mass or add a 120mm cooling fan.
By strictly adhering to the 48V series battery architecture, respecting the 0.46C discharge limit, and utilizing the IRFB4468PbF/EGS002 combination, you eliminate the guesswork and thermal failures that plague most DIY inverter builds. Always verify your local electrical codes regarding standalone power systems and transfer switches before integrating this inverter into a permanent dwelling circuit.
