In this post we learn how to build 3 unique power inverter circuits using the IC SG3525. All these inverters will produce 220 V or 110 V AC from any 12 V automobile lead acid battery
On camping grounds, automobile repairs in the heart of nowhere, and picnics or party gatherings in the woods, the unavailability of a main supply power outlet is often felt acutely. In certain situations, bringing mains electricity to a distant location necessitates installing a very long cable, which is either unsafe, difficult, or not feasible. Whatever the situation, intentional or accidental, having a power inverter capable of converting the I 2V vehicle battery voltage to 230 volts AC is invaluable.
1) Circuit Description
The circuit is perhaps the easiest way to create a power outlet for use on the road. During the design process, the goal was to create a completely basic circuit.
An inexpensive IC SG3526 switch-mode regulator serves as the circuit's core component. Figure 1 depicts the power inverter's fundamental functionality. The SG3526 alternates switching current through the 12-V windings of a mains transformer, with the two centre terminals of the windings hooked up to the positive pole of the battery (+12 V). The path of the current varies with each switching operation, as does the path of the magnetic field in the transformer core. At the 230-V side of the transformer, the output is a square-wave (type) AC voltage.
Transformer
The project's transformer could be a toroidal design with a 230 V primary and two 12-V secondary windings. Users in areas employing mains voltages of 117 V should, obviously, use a corresponding 200-watt transformer. If you have an unused toroidal transformer hanging around in a closet or a trash box,'retro-fitting' a couple of 12-V windings may not be too tough. Connect the primary to the mains by winding 10 rounds of litze wire around the core. Compute how many turns you'll need at 12 V by measuring the voltage over your new winding.
With a 200-watt output, the average current would be around 10 A, thus the litze wire you're utilizing must have a cross-sectional width (c.s.a.) of 1.5 mm2 or more. It's critical that both 12-volt windings possess the identical number of turns. If there is only a single-turn variation, the transformer core might saturate as soon as the 12-volt battery is attached, forcing the regulator IC to 'stall' in lockdown mode.
The windings' sensing orientation is likewise significant. Hookup the ends of the two 12-volt windings in series and supply 230 Vac to the primary prior to installing the transformer. The open ends of the secondaries must have a voltage of 24 Vac.
MOSFETs
The FETs utilised in the circuit have an RDs(on) of just 12 milliohm and capable of withstanding up to 72 A at 55 V. Other varieties might, however, be utilised as long as these are able to take at least 40 A at 40 V and have an RDs(oN) of less than 50 milliohm.
Power FETs could generally be interconnected in parallel, however each one should have its separate gate resistor. If you want to set the inverter for output powers larger than 200 watts, you should use the parallel arrangement. In such scenario, the current limiter must be adjusted, which is best accomplished by lowering the value of shunt R8 and/or changing the voltage divider R16-R17.
Most power inverters will have problems with conventional bulbs and halogen (flood) lights. Both have an extremely low 'cold' resistance, which causes the inverter to lower its output voltage or possibly shut down. As a result, there is little voltage to preheat the filaments to their usual working temperature, resulting in a lock-up. Thankfully, the 200-watt version of the inverter detailed in this article should have no trouble turning on bulbs with a maximum power of 150 watts. If difficulties emerge, the value of capacitor C6 can be raised — but only to some level, because the circuit's capacity to tolerate short-circuits would be compromised.
Soft Start and Shut Down
It's also feasible to enhance the soft-start duration significantly or eliminate it entirely with C5. That is, without a doubt, the smartest option.
Comparator IC1 measures the battery voltage and ambient temperature, then compares the values to the SG3526's 5-V reference voltage. In the event of a mistake, the two open-collector outputs drive the shutdown control input (pin 8) to ground. The switch-off temperature is determined by the
PTC utilized. R6 may need to be resized somewhat depending on the specific kind in your circuit.
A simple wire connection can be employed in place of the PTC if a sufficiently large heatsink is utilised. The voltage monitoring switches on at around 12 volts, and R1 and R5 may be changed to suit different values. R2 and R4 on the comparators specify the level of hysteresis that inhibits the power inverter from restarting after a breakdown situation.
The reference voltage climbs gradually after turning on, as defined by the charge time of C2, thus the monitors are only enabled after a few seconds.
Battery
Batteries in automobiles deliver incredibly high currents. To keep the inverter from catching fire and creating a catastrophe, use a vehicle fuse rated between 25 and 35 amps. Although it is generated by a battery, the 230 Vac output voltage can be quite hazardous.
2) SG3525 Inverter Circuit with Automatic Voltage Correction
The second article shows how to build a reasonably powerful SG3535 inverter circuit with output correction and also with other protection features such as battery regulation and mosfet overheat protection.
The discussed inverter is actually a system that enables power equipment needing 220V AC during the circumstances of a power outage or scenarios that result in virtually no accessibility to it.
The many included features of this inverter will be liked by folks spending vacation in a outdoor tents or bivouac.
The proposed SG3535 inverter circuit with output correction has been tested practically and worked well with outstanding accuracy.
The prototype was tested with the below mentioned appliances:
• televisions and radio
• bulbs, fluorescent lamps,
• circulation pumps furnace CO,
• power tools (drills, grinders)
• computers,
• Power.
PRINCIPLE OF OPERATION
Schematic diagram of the inverter exhibits the Fig.1. Voltage 220VAC acquired by means of alternately switching windings of the transformer TS1.
The crucial job is peformed by a couple of MOSFET power transistors from the n channel - T2 and T3. These are operated specifically by the IC US3 (SG 3524).
This set up is IC PWM generator intended specifically for use in voltage converters. The frequency with which it runs correctly is fairly wide and varies from 10 Hz to 300 kHz.
In the scenario explained in this article, this frequency inverter is 50Hz, or responds to the frequency from the power main grid.
This frequency is determined by by the parts R15 and C6. Variable pulse width US3 created through the technique has been employed for voltage stabilization 220VAC output.
Among the voltage stabilizing stages are components D6, D7 and divider Resistance R12 and R13, through which voltage signal moves to the input of the amplifier error (ending IN-) of the US3.
This specific voltage is analyzed with an suitably a divided reference voltage located on the Vref port. This lets "Self Adjust" the generator into the terminal voltage of the battery.
An additional clamping circuit tend to be components D8, R6, PR1, US2, R7, R8, and C4, that happen to be in control of offering a feedback signal relative to load malfunction applicable at the output of the inverter. Inverter with no stabilization might allow the output voltage depend directly soon load power and the degree of discharge of the battery.
The voltage might range from 170V to 270V ~ ~. As a consequence of these protection circuits the unit is able to stabilize voltage at the inverter output in practically any conditions enabling a constant 220 V ~.
Supposing essentially the most undesirable scenario, which may be partial discharge the battery as well as the load of the inverter at 100 % power of 250 W output voltage is probably not going to tumble under 220 V ~.
Switching transistors T2 and T3 are blocking capacitors in the form of C8 and C9, whose job would be to limit the voltage spikes created during the switching of T2 and T3. Further safeguard is delivered by the in-built configurations of the MOSFET diode reverse.
With a load of the order of 200W or 250W, the transistors tend to work with significant amounts of current, causing notable rise in temperatures. For that reason, the inverter is geared up with an active cooling system. As soon as the temperature extends to 40 ° C (which often roughly signifies that the core temperature of the device is 70 ° C), causes the resistance of the sensor which is a PTC thermistor to increase.
This in turn cause the comparator US5 alter the status of the output towards the to a triggering of the transistor T4 whose collector is attached with a cooling fan installed near the heatsink.
Converter system protected against incorrect connection battery terminals. This particular safeguard is accomplished using a diode D1 in the control relay PK1. This circuit stage is additionally utilized as collateral protection against abnormal battery discharge.
In case the value of the input voltage the power supply drops beneath 10.5 V at the end of the 6 US1 voltage begins to develop, thus inhibiting the operation of transistor T1 and, this results in the disconnection of the relay contacts PK1.
LED D5 indicates the triggering of the inverter, while the D4 notifies that the battery is actually overly discharged. Forced to quit in the situation, the inverter system now begins operating only with a single load whose power is optimized appropriately. while protection against short-circuit by means of fuses B1 and B2 appears to be adequate.
INSTALLATION AND COMMISSIONING OF WARNING!!
The inverter generates AC voltage 220V, which can be extremely hazardous to life and health. The inverter system is assembled on one single printed circuit board which can be found in Fig.2. Figure 3 exhibits the distribution of components.
Switching transistors T2 and T3 are placed on a plate yet needs to be mounted on a individual heat sink and coupled to the transformer.
Immediately within the heat sink is actually fitted is a PTC thermistor. It appears like with regard to fuses B1 and B2, which may be accessible externally. The inverter is built with quality and standard components so that they work optimally after connecting wth the battery.
All manipulations to the system pertains to your setting potentiometers PR1 and PR2. By using PR1 set output of the inverter voltage to precisely 220V ~. It has to be taken into account that the criticality of right measurement associated with RMS voltage 220V from the inverter is vital.
Because the output waveform will not be a sine wave nevertheless in close proximity to rectangular A number of appliances might have difficulties coping with the RMS value of the output voltage.
For that reason, to measure the voltage go for the meters equipped with "True RMS" measurement feature or employ the oscilloscope. The subsequent potentiometer PR2 needs to be set for the heat sink at a temperature of about 40 ° C. in order to switch ON the connected cooling fan.
The transformer which is used is a toroidal transformer with a couple of set of winding having symmetrical V 10 (secondary winding) and a 220 V (the primary winding).
The inverter no-load really should charge at the rate of current of approx. 300 mA. In case the current drawn tends to be much higher that could indicate asymmetrical winding activation of the transformer TS1 or causing varyations in the triggering of the switching transistors T2, T3.
At the conclusion a few words on the compatibility of the inverter battery. Finding the right battery for the inverter must be paid consideration regarding two parameters.
The first being the highest current drawn from the battery, which might depend on the equipment powered by the inverter.
Each load 10 converter means 1A current usage through the battery. The 2nd aspect is battery capacity or the AH which determines the operating period of the inverter and this must be taken into consideration too.
PCB track and component overlay designs for the proposed SG3535 inverter circuit with output correction can be seen in the following diagrams
Parts List for the 220V inverter circuit using SG3525 and output voltage correction feature
3) Inverter Circuit Using IC SG3524
This 3rd design is easy to build, the output power of 150W, the present simple inverter circuit using IC SG 3524 design frequency of about 300HZ, the purpose is to reduce the volume of the inverter transformer, the weight, the output waveform is a square wave. The inverter can be used in other aspects of home lighting, electronic ballasts for fluorescent lamps, household appliances, switching power supply when the power fails.
The inverter is relatively easy to make, can be 12V DC supply voltage of 220V mains voltage inverter, multivibrator circuit composed by the BG2 and BG3 driven through BG1 and BG2 driver to control BG6 and BG7 work. Wherein the oscillation circuit from the regulated power supply BG5 and DW group, this could make the output frequency stable. In the production, there is an optional transformer dual 12V output common mains transformer. As needed, to select the appropriate 12V battery capacity.
The circuit uses 12V battery. First with a voltage module times the pressure of the op amp power supply. You can select, IC sg3524, ICL7660 or MAX1044. Amplifier 1 generates 50Hz sine wave as a reference signal. Operational amplifier 2 as an inverter. 3 op amp and the op amp as a comparator with hysteresis 4.
In fact, the op amp 3 and switch 1 is the ratio of the switching power supply configuration. 4 op amps and switch 2 also. Its switching frequency instability. In the op-amp output signal is positive phase, the operational amplifier 3 and switch work. 2 then the op amp output is negative phase. Then the positive input of operational amplifier 4 potential (fixed to 0) than the negative input potential is high, so the output of the operational amplifier 4 fixed to 1, the switch is turned off. In the op-amp output is 1 when the negative phase, and vice versa. This enables the two switches alternately work.
When the reference signal ratio detection signal, that is, the op amp negative input 3 or 4 signal is high a small value than the positive input signal, the comparator output is 0, the switch to open, followed by the detection signal is rapidly increasing, when the detection signal a small high value than the reference signal, the comparator output 1, switch off.
Here we should note that, in the comparator circuit has a flip positive feedback process, which is characteristic of the hysteresis comparator. For example, in the reference signal is lower than the detection signal of the premise, as they continue to close the difference, at the moment they are equal, and the reference signal immediately detected signal higher than a certain value. This "certain value" influence the switching frequency. The lower the frequency the greater it. Here it is selected 0.1 ~ 0.2V.
C3, C4's role is to make a high frequency current through the freewheeling switch, while the lower frequency of 50Hz signal generating large impedance. C5 by the formula: = 50 is calculated. L generally 70H, measured at the production of the best. Thus C is about 0.15μ. The ratio of R3 and R4 must be strictly equal to 0.5, a large waveform distortion obviously, not a small start-up, but rather a number of large, non-small. Maximum switch current is: I == 25A.
Existing inverters have square wave output sine wave output and two kinds. High efficiency of the inverter square wave output, designed for the use of sine wave power for appliances, except for a few outside the majority of electrical appliances NA can be applied, the output sine wave inverter is no disadvantage in this regard, but there low efficiency, how to choose according to their needs which requires the.
This article describes simple inverter using SG3524 IC, and the concrete circuit diagram and principle analysis. We are in a "mobile" era, mobile office, mobile communications, mobile leisure and entertainment. In the mobile state, people not only need low-voltage direct current from the battery or battery supply, but we need more indispensable in everyday environments 220 volts AC inverter that meet our needs.