H bridge inverters

Thread Starter

falade47

Joined Jan 24, 2017
176
How are these designs built to handle high current looking at the size of the high frequency transformer in comparison with the basic transformer inverters
 

Alec_t

Joined Sep 17, 2013
11,640
They inlude power MOFETs or IGBTs switching at a high frequency (typically hundreds of kHz), thus only requiring small high-frequency transformers instead of chunky mains-frequency transformers. The high frequency signal is pulse-width modulated with a low frequency (usually 50Hz or 60Hz) sinusoidal modulation envelope. When demodulated by low-pass filtering, the result is a 50/60Hz sine wave.
 

Thread Starter

falade47

Joined Jan 24, 2017
176
They inlude power MOFETs or IGBTs switching at a high frequency (typically hundreds of kHz), thus only requiring small high-frequency transformers instead of chunky mains-frequency transformers. The high frequency signal is pulse-width modulated with a low frequency (usually 50Hz or 60Hz) sinusoidal modulation envelope. When demodulated by low-pass filtering, the result is a 50/60Hz sine wave.
Can I get a simple circuit diagram of one..the ones I see online are a bit complex..I would love to build one
 

Alec_t

Joined Sep 17, 2013
11,640
Would you recommend any for me?
I don't know of any. I can only recommend that you start with a simpler project, to avoid frustration/disappointment.
With only 6V input, a 500W 220V output will require an input current of about 90A. How do you plan to source that?
 

Thread Starter

falade47

Joined Jan 24, 2017
176
I don't know of any. I can only recommend that you start with a simpler project, to avoid frustration/disappointment.
With only 6V input, a 500W 220V output will require an input current of about 90A. How do you plan to source that?
Yeah ..I missed that.. I'm currently working on an power bank project and was looking at incorporating a low power transformer less inverter
 

Reloadron

Joined Jan 15, 2015
5,646
A Google of "500 Watt inverter circuit" should get you a few dozen circuits to look over.

As to an:
H-bridge inverter circuit
Featured snippet from the web
An H-bridge is an electronic circuit that switches the polarity of a voltage applied to a load. ... Most DC-to-AC converters (power inverters), most AC/AC converters, the DC-to-DC push–pull converter, most motor controllers, and many other kinds of power electronics use H bridges.

You are describing a DC to AC power inverter.

Ron
 

Thread Starter

falade47

Joined Jan 24, 2017
176
A Google of "500 Watt inverter circuit" should get you a few dozen circuits to look over.

As to an:
H-bridge inverter circuit
Featured snippet from the web
An H-bridge is an electronic circuit that switches the polarity of a voltage applied to a load. ... Most DC-to-AC converters (power inverters), most AC/AC converters, the DC-to-DC push–pull converter, most motor controllers, and many other kinds of power electronics use H bridges.

You are describing a DC to AC power inverter.

Ron
Maybe I was wrong with my description..but I needed a mini inverter just like those used in car cigarettes lighter.. obviously they do not have those chunky transformer in them..I want to incorporate that into my multipurpose power bank design
 

DickCappels

Joined Aug 21, 2008
6,587
What are the expected capabilities of your power bank and how long do you want to run you inverter on a full charge (For example, 1 kW of 10 nanoseconds is no problem).

We know your power bank will be 6V to 12V -how many peak amps can it source and how many amp-hours does it store?
 

Reloadron

Joined Jan 15, 2015
5,646
You have a few other considerations like what output you want or need?
6-12v input and 220vac output..max power 500w
That does not mention the output frequency? Another consideration is the output waveform? Cheap simple designs might output a MSW (Modified Sine Wave) rather than a TSW (True Sine Wave) and some just output a square wave. Next power is power expressed in watts. Therefore 500 watts / 220 volts = 2.37 amps. Your primary side will require 500 watts / 6 volts = 84 amps on your battery and that assumes 100% efficiency which is not possible. With 12 volts it gets down to about 42 amps and 24 volts about 21 amps. A 24 volt 100 AH battery won't even get you 4 hours of operation.

You are also not likely to find a way around a large clunky transformer if you want a 50/60 Hz output frequency, it's just the nature of the beast. Another option is to buy a kit which will give you what is commonly plugged into a 12 VDC cigarette lighter or utility plug.

Ron
 

Thread Starter

falade47

Joined Jan 24, 2017
176
That does not mention the output frequency?
I'm in Africa where our equipment uses 50/60 Hz
Another consideration is the output waveform?
The output waveform is not really a problem to me ..a modified sine wave would do the job..my laptop charger is smart enough I guess as it has a complex smps circuitry
You are also not likely to find a way around a large clunky transformer if you want a 50/60 Hz output frequency, it's just the nature of the beast.
I don't understand this..are you saying I can't get 50Hz with such circuitry ?
 

Reloadron

Joined Jan 15, 2015
5,646
I don't understand this..are you saying I can't get 50Hz with such circuitry ?
I am saying that if you require 50/60 Hz the transformer will be large and bulky. Years before inverters were gaining in popularity all of the AC systems on aircraft were 400 Hz. The reasoning was 3 phase 400 Hz power could use smaller lighter transformers in aircraft electrical systems. The 50/60 Hz designs come with a price of weight and cost.

If you look at the current required for 500 watts at the low voltage DC side your transformer will have thick wire gauge windings making for bulk and weight. Additionally if you look close at some basic 500 watt inverters you will notice the use of aluminum in a heat sink design and they use fans to remove excess heat. All things considered this is why even in an electrical engineering forum most people familiar with these things suggest buy over build. You may also notice that when inverters start getting above 300 watts they get away from the 12 volt utility (cigarette lighter) plugs and use heavier wire gauges for power. I can buy a simple 500 watt inverter 12 VDC in for about $50 USD and I certainly can't build one that inexpensive. The Google suggestion I posted earlier has several schematics and designs if you wish to roll your own.

Ron
 

Reloadron

Joined Jan 15, 2015
5,646
You would be surprised at the number of people on this website that don't believe that. Most of them long time members here. I got reported for arguing it wasn't possible in another thread.
If power in is equal to power out where does the heat come from that I need to remove? Wow, maybe it's free? :)

Ron
 
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