TL Inverter


 TL(Transformer Less) Inverter is based on Texas Instrument Technology. The design principles and the circuit operation of the 800VA pure Sine Wave Inverter. The pure Sine Wave inverter has various applications because of its key advantages such as operation with very low harmonic distortion and clean power like utility-supplied electricity, reduction in audible and electrical noise in Fans, fluorescent lights and so on, faster, quieter and cooler running of Inductive loads like microwaves and motors. 
Contents
                                                           Introduction 
Pure Sine Wave Inverter's Design Transformer Less Inverter
Power inverter is a device that converts electrical power from DC form to AC form using electronic circuits. It is typical application is to convert battery voltage into conventional household AC voltage allowing you to use electronic devices when an AC power is not available. There are basically three kinds of Inverter out of which, the first set of inverters made, which are now obsolete, produced a Square Wave signal at the output. The Modified Square Wave also known as the Modified Sine Wave Inverter produces square waves with some dead spots between positive and negative half-cycles at the output.  The cleanest Utility supply like Power source is provided by Pure Sine Wave inverters.
The present Inverter market is going through a shift from traditional Modified Sine Wave Inverter to Pure Sine Wave inverters because of the benefits that these inverters offer. 
 Semiconductors used :
1   TMS320F280270  T I Micro Controller
2.  Full Gate Driver   SM72295
3.  Bridge Mosfet  CSD18502
4.  TPS 54231 3.3V Supply Regulator
5.  LM339 for Current Sensing
6. AMC1100  Main Voltage sense

There is a dual mode of operation in a residential Inverter, ie Mains mode and Inverter modes shown in Figure 2. An Inverter not only converts the DC Voltage of battery to 220V/120 V AC Signals but also charge the Battery when the AC mains is present. The block diagram shown above is a simple depiction of the way an Inverter Works.  Inverter Mode: The method, in which the low voltage DC power is inverted, is completed in two steps.   The   first step is the conversion of the low voltage DC power to a high voltage DC source, and the   second step is the conversion of the high DC source to an AC waveform using pulse width   modulation. Another method to complete the desired outcome would be to first convert the low   voltage DC power to AC, and then use a transformer to boost the voltage to 120/220 volts. The   widely used method in the current residential inverter is the second one and hence this reference design is based on this method. The AC input is sensed through isolated amplifier (AMC1100) and the isolated replica of the AC input is given to the TI’s Picolo Lite Microcontroller ADC. When the AC input is not present in Valid range (Inverter mode) or AC fails ,  the   relay    between    Mains  AC  Input    and  the Inverter  Output   remain  open, the microcontroller generates  PWMs and send  four drives output to Gate Driver (SM72295) . Now the Gate Driver accepts low-power inputs from the controller and produces the appropriate high-current gate drive for the power MOSFETs placed in Full Bridge Topology.  Here H-bridge circuit converts battery DC voltage into AC using high frequency PWM (6 kHz to 20 KHz) thus feeding the 50 Hz transformer which Boost it to 120V/220V AC. The output of transformer contains a capacitor which filters it to make clean 50Hz AC.(Details of Switching can be found in the sections to come).