With around 300 watts of continuous power inverter you can run items like desktop computers, monitors, full size fax machines, battery chargers and AC adapters for notebook computers, cellular phones, camcorders, small power tools, drills, mid-sized TVs, soldering guns, and a variety of rechargeable equipment on the road. If you have a higher power inverter, you can run more devices or more powerful devices. With a lower power converter you can use only devices which use less power. Power inverters are also very useful in solar power system which generally use low voltage batteries (usually 12V DC) to be able to run mains powered devices in them.
The three most common outputs for inverters are square wave, modified sinewave (sometimes called a quasi sinewave), and sinewave outputs. Most devices with variable speeds such as electric drills, or devices with chargers such as cordless drills or screwdrivers, can behave irrationally when operating with modified sine or square wave inverters. Small wall based chargers (called wall warts) can have overheating problems with modified sine or square wave inputs. Some computers and stereo equipment use switching power supplies that utilize SCR's and Triacs as well. These pieces of equipment may experience the same troubles with non-sinewave power. True sine wave output allows connected loads and equipment to operate the same as they would from utility supplied power. Unfortunately the true sine wave output inverters are more expensive than the ones which use square wave or modified sinewave.
Generally you can buy a small 150- or 300-watt quasi-sine-wave inverter for about $50. Higher power or true sinewave models cost generally more.
An Uninterruptible Power Supply (UPS) is a device that sits between a power supply (e.g. a wall outlet) and a device (e.g. a computer) to prevent undesired features of the power source (outages, sags, surges, bad harmonics, etc.) from the supply from adversely affecting the performance of the device. UPS devices generally consist of some form of internal battery, inverter and intelligent switching electronics. When normal mains power is available, it is supplied to the devices connected to UPS. When mains power is not available, the devices connected to UPS output are powered by the inverter circuit inside the UPS. UPS devices aren't designed to let you keep working for a long period of time after power outage; they're designed to give you enough time to shut your system down in the normal manner.
NOTE: Most of the circuits below have square wave output and are not suitable for driving sensitive electronics equipments. The AC from those inverters can damage some equipments connected to them.
- A Simple Tool for Interactive Design of Inverters - this paper presents a simple method to predict the losses in the power semiconductors of an inverter where the output sinewave is obtained by pulse-width modulation of a high frequency carrier
- How Emergency Power Systems Work - A wide variety of natural disasters can cause long-term power outages. An UPS or battery and inverter can provide emergency power for some time, but there are also other alternatives for this.
- Modified Sinewave and Sinewave Waveforms - three most common outputs for inverters are square wave, modified sinewave and sinewave outputs, this paper will look at these waveforms, and how different types of loads behave when operating from them
- Power Converter Survives High-Energy, Low-Frequency Surges - article on UPS design
- 24 Volt DC to 110 Volt AC Power Inverter - Converts the power from two 12 volt batteries to AC to power a drill or whatever
- 5W Inverter - A single transistor is all you need for this simple inverter. The main aim of this circuit is to provide a suitable supply for all kind of low power battery chargers that normally connect to the mains such as mobile phones, electric shavers, etc, even an electronic neon light rated at 5W.
- Basic 200 W power inverter - 12V DC to 110V 60 Hz AC, up to 200W continunous, square wave output
- Building a dc to ac converter - Otherwise known as a dual axis drive corrector, this unit is intended to provide 240 volts/50 Hz (or 120 volts/60 Hz with minor modifications) for a right ascension (ra) drive and a reversible declination motor. The supply requirement is from 11 to 16 volts d.c. at 500 mA. The overall output frequency is adjustable from 47.5 Hz to 52.5 Hz or from 40 Hz to 60 Hz on the remote unit. This frequency is stabilised against voltage or temperature change.
- DC/AC inverter - 12V DC to 110V AC
- DC to AC power inverter - convert 12V DC to 120V AC, based on SCRs and FETs
- Inverter - takes 12 VDC and steps it up to 120 VAC
- Inverter offers design flexibility - works from a 12V car battery and produces mains voltage with closed-loop voltage regulation
- SCR Inverter - outputs 300V 400Hz, waveform is vaguely sinusoidal, 5W output power
- The I2K Power Inverter - This circuit is a 2kVA 12VDC to 120VAC inverter for power backup. This description of the inverter is preliminary and incomplete.
- Uninterruptible Power Supply (UPS) FAQ - This is a FAQ document on Uninterruptible Power Supplies. It is intended to provide a starting point for those people that want to find out what they are, what they do, and what's available. Most of this document is very US-centric. The power numbers, companies and services all emphasize US consumer needs.
- Uninterruptable Power Supply Reference Design - Application note from Microchip
- Uninterruptible Power Supply Types - Most people know that UPSes exist, but many seem to think that there is just one kind of device that goes by that name. In fact, there are several different major designs in use for UPS models. Those who sell these devices share much of the blame for this situation, because too often, the different kinds of UPS are all called the same, generic name.
- UPS Semiconductor Technologies
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