Your current limiting, can't you scale up the resistors in order to avoid these 22 uF caps?
C109, 1 uF plastic, polyester
R126, 1 kohms
R124 1.5 kohms
With my suggestion you will get approx 600 us time constant, maybe this is somewhat fast but I'll guess you can increase the resistors even more,
I'll guess you don't have so big demands of base current to Q108?
C109, 1 uF plastic, polyester
R126, 1 kohms
R124 1.5 kohms
With my suggestion you will get approx 600 us time constant, maybe this is somewhat fast but I'll guess you can increase the resistors even more,
I'll guess you don't have so big demands of base current to Q108?
I see that you are trying to eliminate the use of the 22uF caps...perhaps that might be possible...but why try to save on a lessthanadollar part?? Maybe one day we can forget about the out-put transistors...lolx
peranders
Yes you can do that😉
However the proportion between the two resistors R124/R126
defines the level where the current limiter sets in.
With your suggestion of resistor values, you have changed it from 3.6A to 4.5A (per output transistor)🙂
Yes you can do that😉
However the proportion between the two resistors R124/R126
defines the level where the current limiter sets in.
With your suggestion of resistor values, you have changed it from 3.6A to 4.5A (per output transistor)🙂
Yuk....that would mean better transistors...would be needed...and more $$$ plus bigger/better heatsinks...just because I dun wan the cap...
How do you get so much difference? OK, this is only a "tweaking" thing.
Anyway, I'll try to avoid electrolythics as much as I can. This is the last resort for me becuase they last not so long (especially in warm places) and also the performance is worse.
Anyway, I'll try to avoid electrolythics as much as I can. This is the last resort for me becuase they last not so long (especially in warm places) and also the performance is worse.
Hmmm...maybe there is a poly or mylar cap that is 22uF?? I dun think so...too big a value...so wads the next best thing to do??
peranders
The current limiter circuit measures the voltage across the emitter resistor of the first output transistor. This voltage is then devided by the resistors R124 and R126 before it goes to the base of Q108. When base of Q108 reaches 0.6V the transistor goes on and limits the signal voltage to the predriver transistor Q106.
When using equal value resistors as suggested in my schematic, the voltage on the connection of the two resistors are = half the voltage across the output transistor emitter resistor.....
Meaning that when there are 0.6V on base of Q108, there will be 1.2V over the 0,33R emitter resistor = 3,6363A 😉
The current limiter circuit measures the voltage across the emitter resistor of the first output transistor. This voltage is then devided by the resistors R124 and R126 before it goes to the base of Q108. When base of Q108 reaches 0.6V the transistor goes on and limits the signal voltage to the predriver transistor Q106.
When using equal value resistors as suggested in my schematic, the voltage on the connection of the two resistors are = half the voltage across the output transistor emitter resistor.....
Meaning that when there are 0.6V on base of Q108, there will be 1.2V over the 0,33R emitter resistor = 3,6363A 😉
Just for your information!
If have choosen these values for the current limiter circuit from good experience... You are free to change the values as you like, but please keep in mind, how many A's are really necessary???
Taking the costs of output transistors into conciderations😉
If have choosen these values for the current limiter circuit from good experience... You are free to change the values as you like, but please keep in mind, how many A's are really necessary???
Taking the costs of output transistors into conciderations😉
Yeah...that's what I was thinking of as well...so maybe Peranders can suggest better types of caps that go all the way to 22uF...
I dont use Poly-Caps, when it's over 1uF.....
(to expencive according to my paycheck 😀 )
And since I never uses caps in the direct signal path, the type of cap is less important 😉
(to expencive according to my paycheck 😀 )
And since I never uses caps in the direct signal path, the type of cap is less important 😉
I ment polyester, not polypropulene or some other "poly"-type.ACD said:
Polyester 1 uF/63V rather small. I don't either use larger than 1 uF plastic if I don't have to.
Ok...seems like my waiting time just increased...lolx...so I would go along with Elect. caps...cheaper and easier to find...is there a 22uF Poly cap?? Peranders...???
As I said earlier, use a 1 uF/63 V polyester and also change resistor values. 22 uF plastic (of any kind) isn't very good idea, adds nothing but size, costs much also.li_gangyi said:
The only thing to think about is that the transistor gets sufficiently with base current (R124, R126) when you have over current condition.
If you still want to use a 22 uF, a 22 uF/16 V (or more). The place where it is, is very "kind", just 0-0.7 V only across it and no reverse polarity at all (according to me).
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