Project Description
Project description
In the modern home, a surprising number of appliances will operate on “high voltage” DC.
More and more appliances (computers, LCD monitors and TVs, compact fluorescent and LED lamps, phone charges etc) incorporate switch mode power supplies. These appliances will rectify the incoming 50/60 Hz mains, convert them to DC and then step the voltage down using a higher frequency and more efficient transformer. Typically they can be identified as having a wide input voltage range and frequency (e.g. 100 to 240V, 50-60Hz). Such appliances will operate at DC.
Many power tools and vacuum cleaners utilise what is called universal motors.
Heating appliances and incandescent lamps will also operate at DC voltage levels.
Operating appliances at DC is for educational experimentation only and not for the uneducated masses. Careful consideration must be taken into account when evaluating the appliance to be powered. One of many caveats is that many switches and thermostats are designed for AC and will have different, often lower DC current ratings.
A standard 12V to 220/240V Sine-wave inverter will consist of two distinct functional blocks. The first stage is the step up converter, converting the low voltage DC to a high voltage DC bus typically in the vicinity of 340 to 380V. The 2nd stage is the Sinusoidal Pulse Width Modulation (SPWM) that chops up the HV DC to construct a near pure sine wave with a bit of filtering.
When powering many appliances from a sine wave inverter, the HV DC is converted to AC only to be rectified back to DC in the appliance.
This inverter eliminates the SPWM stage and outputs DC only. This DC can be used to power appliances, or as a HV DC source for your SPWM, variable frequency drive (.. for your inverter fridge) or other project.
Ebay, AliExpress and other like stores have cheap 12VDC to 220-380VDC Converters (pictured above), ready for purchase under board names like QS-100 and GZF-02-Y.
These basic converter boards consist of a SG3525, four IRF3205 MOSFETs and a Transformer. They include no overload protection, output regulation/feedback or DC rectification. Nor do they include low voltage cutouts.
This project intends to build upon these boards and build in these other features and protection.
The converter uses a prewound 500W Transformer available from AliExpress.
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Design Files
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SWITCHMODE(TM) Power Rectifier, 2-Pin TO-220, Tube
D1, D2, D3, D4
IRF3205PBF
Q4, Q2, Q3, Q1
IC REG CTRLR PWM VM 16-SOIC
U1
Thick Film Resistors - SMD 5.11 OHM 1%
R4, R2
