Author Topic: 555 inverter brightness and over current issue  (Read 1001 times)

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Offline dave_j_fan

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555 inverter brightness and over current issue
« on: November 28, 2019, 05:14:26 am »
hi experts,
 I have used  this 555 circuit for very simple inverter
 
 https://www.eleccircuit.com/220-volts-power-inverter-using-ne555-and-mosfet
i am  running it  on dual 18650 i.e. approx 7.4v
for portability we cannot change this . It has to be 2 battery system .
MOSFETS are Z44.

observation
1) with 12 - 0-12 , 2 AMP transformer coil resistance 2.5E.  The inverter works very nicely
300mA current and ok brightness  ( just one winding i use 0-12 and one MOSFET )
so we get  7hour backup. This is fine

2) As the . 12-0-12 is bulky
  we used 0-6V/ 220V small 500ma transformer .
 coil resistance 12E
 But here it consumes 550mA 
 bulb is not bright too .


What can be the reason of increased current  .
i have  measured coil voltage to MOSFET its approx 3V







 

 
« Last Edit: November 28, 2019, 05:17:01 am by dave_j_fan »
 

Online Zero999

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Re: 555 inverter brightness and over current issue
« Reply #1 on: November 28, 2019, 10:31:36 am »
A schematic would help. The site you've linked to has two MOSFETs, yet the circuit you've describe only has one.

My guess is you're overloading the transformer causing core saturation, hence the higher current and lower output power.

What sort of light is it driving? LED or incandescent?

My advice is scrap the inverter and replace the mains lamp with one which can be powered directly from DC. Two white LEDs in series and a linear current regulator will be much more efficient than an inverter and a mains lamp. It can be made even more efficient with a switched mode power supply for the LEDs.
 

Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #2 on: November 28, 2019, 12:18:38 pm »
Reposting  the  same  ...
 here one MOSFET i use .  in  both cases

 1)with 12-0-12V 2 Amp transformer
 2)0-6 V ,500mA transformer

 load is  7W  led

 Both cases led is lit, in second case total current  550mA
 in 1  case its 300mA

 I want to make it work well in 500mA transformer. so that i can case it in smal case
 gets portable

 (Not interested to run DC LEDs .. so please dont advice )
 

Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #3 on: November 28, 2019, 12:31:33 pm »
DC lamps to avoided 

 1) need to be remotely mountable
 2)DC LED and  additional circuits are wastage of time and work
 3)All DC led bulbs  available in our countr are Junk and cant  be used
 --

 need to run 5w or 7W led as these are super reliable by all leading  brands
 comes with nice cases
 

Online Zero999

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Re: 555 inverter brightness and over current issue
« Reply #4 on: November 28, 2019, 12:40:10 pm »
Why post an oversized picture with loads of empty space?

Core saturation doesn't cause the iron core to heat up. It results in excess current being drawn through the primary winding. It may or may not cause noticeable heating of the transformer winding, depending on the power dissipation and mass of the transformer.

DC LEDs can be mounted wherever you like.

DC to AC circuits are a waste of time and just consume more power.

Just make your own DC LED lamps.
 

Offline JimRemington

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Re: 555 inverter brightness and over current issue
« Reply #5 on: November 29, 2019, 04:11:20 pm »
Quote
I want to make it work well in 500mA transformer.
The single MOSFET design is very inefficient and will never work well.
 
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Offline NiHaoMike

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Re: 555 inverter brightness and over current issue
« Reply #6 on: November 29, 2019, 05:30:29 pm »
Use a push pull PWM controller like the UC3525A, that way you get a symmetrical waveform with adjustable duty cycle.
Just make your own DC LED lamps.
Don't even need to make them, LED strips are cheap.
« Last Edit: November 29, 2019, 05:32:00 pm by NiHaoMike »
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Online Zero999

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Re: 555 inverter brightness and over current issue
« Reply #7 on: November 29, 2019, 07:11:38 pm »
Use a push pull PWM controller like the UC3525A, that way you get a symmetrical waveform with adjustable duty cycle.
Just make your own DC LED lamps.
Don't even need to make them, LED strips are cheap.
Yes, DC LEDs are widespread but they're normally rated to 12V or 24V, not 7.4V. A boost converter would be required to power to generate 12V.
 

Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #8 on: December 01, 2019, 11:08:13 am »
Use a push pull PWM controller like the UC3525A, that way you get a symmetrical waveform with adjustable duty cycle.
Just make your own DC LED lamps.
Don't even need to make them, LED strips are cheap.

led strips are not for bub replacement, they are just for corner lighting , come loaded with resistors
UC3525A not an option, cost issue
 

Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #9 on: December 01, 2019, 11:15:36 am »
i think the criteria is not clear to all .

1)cost is one factor here so designs like PWM ic are not a possibility
  BJT or basic 555 etc can be a possible choice
2)Regarding SIngle MOSFET inefficiency
3)forget DC lamps there re 100 reasons not to  use
   solutions do keep only to small inverter designs
   " same circuit works with  12 0 12  2AMP transformer .. low current  300mA "
   we have  used just one winding  0-12V

   but  same circuit with  0-6VSmaller  transformer  is 550mA approx

  We can live with  300mA but need to be ready with  smaller transformer
  so that cost of making  will be low and    we can put smaller case (cabinet)


 Any   alternate  circuit also  is fine  with lower parts cost.
 
« Last Edit: December 01, 2019, 11:17:26 am by dave_j_fan »
 

Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #10 on: December 01, 2019, 12:27:24 pm »
probably smaller core getting saturated , i will adapt to PNP NPN  design


http://pindiagram.blogspot.com/2012/02/dc-to-ac-inverter.html
 

Offline NiHaoMike

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Re: 555 inverter brightness and over current issue
« Reply #11 on: December 01, 2019, 01:08:28 pm »
UC3525A not an option, cost issue
How about TL494?
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Online Zero999

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Re: 555 inverter brightness and over current issue
« Reply #12 on: December 01, 2019, 01:54:22 pm »
probably smaller core getting saturated , i will adapt to PNP NPN  design


http://pindiagram.blogspot.com/2012/02/dc-to-ac-inverter.html
That design is very inefficient due to the huge losses with the 555 driving emitter followers.

If you use the original design posted at the start of the thread, with a centre tapped transforer two MOSFETs, the core is less likely to be saturated, since it will be alternately magnetised with opposite polarities, thus be used more efficiently.

If you need a smaller solution forget the bulky, inefficient inverter. Use a 12V LED and a small, lightweight, efficient boost converter.

 
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Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #13 on: December 04, 2019, 07:23:12 pm »
probably smaller core getting saturated , i will adapt to PNP NPN  design


http://pindiagram.blogspot.com/2012/02/dc-to-ac-inverter.html
That design is very inefficient due to the huge losses with the 555 driving emitter followers.

If you use the original design posted at the start of the thread, with a centre tapped transforer two MOSFETs, the core is less likely to be saturated, since it will be alternately magnetised with opposite polarities, thus be used more efficiently.

If you need a smaller solution forget the bulky, inefficient inverter. Use a 12V LED and a small, lightweight, efficient boost converter.


yes the core saturation was the issue
 --its resloved! ---
 8) 8) 8)
-- used Centertapped transformer and dual mosfets
-- Achieved good brightness at  230mA
 so 2200mAH pack will last 8-10hour
 with 2S4P we can get 20hour backup , which is huge


developed an ECO mode , slight less brightness at 155mA
on 2200mA ECO mode can pull till 12Long hours

All this with palm sized inverter.
test shown a 500mA transformer  can take  two 7Wbulbs ( lower brightness )
but this centertap is very good for one 7W

 

Offline dave_j_fan

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Re: 555 inverter brightness and over current issue
« Reply #14 on: December 04, 2019, 07:26:04 pm »
Will the LOGIC mosfets give even better brightness ?

AC was approx 185V and the  bulbs for 220V do very well now
 


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