1. Input Stage: DC Power from Battery
- Input: The inverter receives 48V DC from a battery bank (typically lead-acid, lithium-ion, or similar).
- Protection: The DC input passes through protective components like fuses, circuit breakers, or reverse polarity protection diodes to safeguard the inverter from overcurrent or incorrect wiring.
- Filtering: Capacitors smooth out any voltage ripple or noise from the battery to provide a stable DC input.
2. DC-DC Boost Conversion (High-Voltage DC Generation)
- Purpose: To generate split-phase 120/240V AC, the inverter first needs a higher DC voltage (typically 300-400V DC) because the peak voltage of a 240V AC sine wave is around 340V (240V × √2).
- Process:
- A boost converter or transformer-based H-bridge steps up the 48V DC to this high-voltage DC level.
- This is achieved using high-frequency switching (via MOSFETs or IGBTs) controlled by a pulse-width modulation (PWM) circuit.
- Inductors and capacitors store and release energy to facilitate the voltage increase.
- Topology: Some inverters use a high-frequency transformer here, while others rely on a transformerless design with a boost stage.
3. Inverter Stage: DC to AC Conversion
- H-Bridge Configuration:
- The high-voltage DC is fed into an H-bridge circuit made up of four high-power transistors (MOSFETs or IGBTs).
- The H-bridge switches rapidly (typically 20-50 kHz) to create a square wave or modified square wave approximation of AC.
- PWM Modulation:
- Pulse-width modulation refines this square wave into a smooth sine wave.
- A microcontroller or DSP (digital signal processor) generates PWM signals to control the transistors, adjusting the duty cycle to mimic a 60Hz sine wave (standard in North America).
- Split-Phase Output:
- The H-bridge is configured to produce two 120V AC outputs that are 180° out of phase with each other.
- These two "hot" legs (L1 and L2) are referenced to a neutral (N), providing 120V from L1-N or L2-N, and 240V from L1-L2.
4. Output Stage: Filtering and Stabilization
- LC Filter:
- The raw PWM AC signal contains high-frequency harmonics, so an inductor-capacitor (LC) low-pass filter smooths it into a clean sine wave.
- This removes switching noise and ensures the output meets power quality standards.
- Transformer (Optional):
- In some designs (especially older or lower-cost units), a low-frequency output transformer steps up or stabilizes the voltage and provides galvanic isolation between the DC input and AC output.
- Modern high-efficiency inverters often skip this, relying on transformerless designs for lighter weight and better efficiency.
5. Control and Monitoring
- Microcontroller/DSP:
- A central processor monitors input voltage, output voltage, current, temperature, and load conditions.
- It adjusts PWM signals in real-time to maintain stable output (e.g., 120/240V ±5%, 60Hz ±0.5Hz).
- Feedback Loop:
- Sensors measure the output waveform and feed data back to the controller to correct distortions or voltage drops under load.
- Cooling: Fans or heat sinks dissipate heat generated by switching losses and resistive elements.
6. Split-Phase Specifics
- Wiring:
- The inverter outputs three lines: L1 (hot), L2 (hot), and N (neutral).
- L1 and L2 are 180° out of phase, providing 240V across them, while either leg to neutral provides 120V.
- Load Balancing:
- The inverter can handle unbalanced loads (e.g., 120V appliances on L1-N and nothing on L2-N), though efficiency may drop slightly if heavily unbalanced.
- Power Capacity: At 6000W continuous output, the inverter can deliver up to 25A per 120V leg (6000W ÷ 240V = 25A across L1-L2), assuming perfect efficiency.
7. Efficiency and Losses
- Efficiency: Typically 90-95% for modern inverters. Losses occur due to:
- Switching losses in transistors.
- Resistive losses in inductors, capacitors, and wiring.
- Transformer losses (if present).
- Peak Power: Many inverters can handle short surges (e.g., 12,000W for motor startups) by drawing extra current from the battery (up to 250A at 48V for 12kW).
Simplified Internal Workflow
- 48V DC enters → Boosted to ~340V DC → H-bridge converts to raw AC → PWM refines to sine wave → LC filter smooths output → Split-phase 120/240V AC delivered.
Example Components
- MOSFETs/IGBTs: Handle high-current switching (e.g., 100A+ at 48V input).
- Capacitors: High-voltage electrolytic or film caps (e.g., 400V rated).
- Inductors: Toroidal or ferrite-core for filtering and boosting.
- Microcontroller: STM32, Texas Instruments DSP, or similar for PWM control.
And I was worried about providing too much detail!!! 
