How to Make an IPS (Inverter Power Supply)
A concise 5-page step-by-step guide
Generated: 2025-08-09
Purpose:
This short guide shows the basic steps and key considerations to build a low-voltage DC → AC
inverter (commonly called an IPS or inverter power supply). It explains the system blocks, parts,
safe assembly, testing and troubleshooting. This is an educational guide — working with batteries
and mains voltages is hazardous. If you are not experienced with electrical safety, ask a qualified
technician.
Overview, Block Diagram & Safety
What is an IPS?
An IPS (Inverter Power Supply) converts DC battery power (e.g., 12V) into AC mains voltage
(e.g., 220–240V, 50Hz). Typical uses: backup home power, off-grid systems and powering AC
appliances where mains is unavailable.
High-level block diagram (textual):
Battery (12V/24V) -> Input fuse & switch -> DC smoothing capacitors -> Inverter driver
(oscillator / MCU) -> Gate drivers -> Power stage (H-bridge or push-pull MOSFETs) -> Step-up
transformer -> Output protective components -> Load
Essential safety notes:
- Working with batteries and mains voltages is dangerous. Always disconnect power before
changing wiring.
- Use proper insulated tools, eye protection and avoid loose clothing.
- Include fuses on the battery positive and at the AC output. Use properly rated circuit
breakers.
- Provide a reliable earth ground for the AC output and metal enclosure.
- When testing, use an isolation transformer or double-check all connections; never work on
live mains unless qualified.
Components (BOM) and Circuit Topology
Suggested Parts (example for a small 300–500W inverter):
- Battery: 12V lead-acid or LiFePO4 (capacity depends on run-time needed, e.g., 100Ah for long
run-time).
- MOSFETs: 4 x N-channel power MOSFETs (choose low Rds(on), high current rating; e.g., IRF3205
or similar with proper specs).
- Gate driver / driver IC: e.g., IR2110 or dedicated high-side driver, or use MOSFET driver ICs
for safe switching.
- Control: small MCU (Arduino/ATtiny) or discrete oscillator + flip-flop for complementary 50Hz
drive.
- Transformer: step-up transformer designed for the inverter's low-voltage primary (12V or
2×12V CT) and rated for target power.
- Input capacitors: low-ESR electrolytics (several 10s to 100s of µF at 25–50V) to smooth
battery transients.
- TVS/surge protection, output choke (optional), mains filter, fuses, heat sinks, cooling fan,
cabling (thick battery cables).
- Auxiliary: PCB, terminal blocks, enclosure, AC socket, transfer relay (for automatic
switching between mains and inverter).
Circuit topology (conceptual):
1. Control generates two complementary 50Hz signals with a small deadtime to avoid shoot-
through.
2. Gate drivers translate logic signals to gate voltages appropriate for the MOSFETs.
3. MOSFETs are arranged in an H-bridge (4 MOSFETs) or a push-pull pair with a center-tapped
transformer low-voltage winding.
4. The transformer's low-voltage side sees an alternating polarity created by switching; the
high-voltage side delivers AC mains.
5. Add an output fuse and optionally an LC filter to reduce switching noise.
Assembly — Step-by-step
1) Plan & Safety: Gather all parts and prepare a workspace. Verify MOSFET datasheets for gate
drive and Rds(on).
2) Build the control circuit: Use an MCU or oscillator to produce complementary 50Hz signals.
If using MCU, implement deadtime (few µs).
3) Gate drivers & protection: Place gate resistors (10–100Ω), gate diodes if needed, and pull-
down resistors on gates to prevent floating.
4) Mount power MOSFETs on heatsinks: Securely bolt MOSFETs to the heatsink with insulating pads
if required. Ensure thermal compound is applied.
5) Connect DC supply: Use a heavy-duty fuse on battery positive. Keep low-resistance short
battery leads. Add input capacitors near the MOSFETs.
6) Wire transformer & output: Connect the transformer low-voltage winding to the MOSFET bridge
outputs as per topology chosen. Add output fuse and AC outlet.
7) Initial no-load checks: Verify gate waveforms with a multimeter or oscilloscope (no-load).
Check for shorts between supply rails and MOSFET drains/sources.
8) First power-up: Use a current-limited power source or a fuse. Power the control only first,
then apply MOSFET drive. Observe for smoke/heating.
9) Test with a resistive lamp: Connect a low-wattage incandescent lamp as first load. Gradually
increase load while monitoring temperatures and battery voltage.
10) Enclosure & finishing: Mount everything in a ventilated metal enclosure, earth the chassis,
install a fan, label terminals and provide service access.
Testing, Troubleshooting & Final Tips
Testing checklist:
- Check continuity and correct polarity for all battery connections.
- Verify gate signals: complementary 50Hz with deadtime; no gates floating when control is off.
- Monitor MOSFET temperature under load; ensure heatsinks and fan keep temps safe.
- Measure output RMS voltage with a true-RMS meter; tune PWM or transformer winding choice to
approach desired AC voltage.
Troubleshooting common issues:
- No output: check fuses, gate drive, and transformer connections.
- MOSFET overheating: insufficient heatsink, poor gate drive, or incorrect deadtime causing
shoot-through.
- Low output voltage under load: battery voltage sag, undersized transformer, or inadequate
MOSFET current rating.
- High noise or harmonics: add output LC filter or use PWM with filtering; use snubbers and TVS
diodes for spikes.
Final tips & safety reminder:
- Always include over-current protection and an emergency disconnect switch.
- Avoid connecting the inverter to the mains distribution without an appropriate transfer
switch and interlock.
- If you plan a grid-tie or automatic transfer setup, consult a licensed electrician or
certified installer.
This document is an educational 5-page overview and not a substitute for detailed engineering
schematics for commercial-grade designs.
