High side protection cirruit + resonance circuit suggestion

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#1
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Hi all ,

 

below , Q10 is the low side protection circuit in the case of over current of Q7 (NPN Transistor)

1 - can you suggest a high side protection circuit for a PNP transistor

2 - can a combination of NPN and PNP transistor be used for resonance circuit (125khz) instead of 2 mosfets ?

 

Thanks in advanced

 

 

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Just flip everything upside down, flip the juice and gnd,  and use pnps?  Show us the resonance circuit. Transistors might work fine. Easy to test.

Imagecraft compiler user

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Besides of the Q10 the R29 is protecting too the low side, you can add a TVS or Zener.

For high side, a varistor, TVS or Zener between collector and GND.

Regards,

Bruno Muswieck

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The rfid reader in the taxi on the blink?

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It's my idea

Is it correct ?

 

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Probably a Real Bad Idea to turn em both on at the same time.

 

Imagecraft compiler user

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bobgardner wrote:
Probably a Real Bad Idea to turn em both on at the same time.
Indeed, but... isn't that the point of the high-side and low-side protection circuits in the first place?

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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Designing a Class D amp?

 

JC

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A l293 should do the job?

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Thanks

 

l293 is too expensive for mass production

What about the circuit I mentioned ?

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Aren't R1 and R2 really going to hurt your efficiency?  I'd consider what might happen to Q3 and Q4 if they both turn on.

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You cant expect a bunch of engineers to comment on the suitablity of a circuit to do a job that has not been specified. What does it do? What drives the inputs? What does the output do? After the prototype is debugged, will there be production? 100? 1000? 10000? Now saving 1 cent on a resistor or diode starts saving money. If there are 10 ways to shake an output on and off, you need to tell us a lot more about whats most important. Price? Speed? Temperature range? Is there a power supply? So many questions.

 

Imagecraft compiler user

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No, over-current protection is NOT to prevent problems with cross conduction (both on at same time). It is to prevent damage if the output  is shorted. 

 

It is a really bad idea to design with possible cross conduction. It kills your efficiency and your transistors.

 

There are LOTs of parts there. It will be more expensive to assemble than you realize. And even more expensive when you deal with returns from dead equipment from customers. There are gobs of half-H bridge ICs out there. There must be a low-end one that will meet your needs. Try STMicro, Infineon, TI, On Semi, Fairchild, and lots of others. You don't need a lot of power, I would guess, but you do need reliable, non-overlapping drive. Another advantage of the half-H solution is that it will take only one drive pin from the micro - they have the necessary delays built in to prevent cross-conduction.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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thanks a lot