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Old 09-18-2012, 11:16 AM #1
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Default 555 timer boost drive?

Hi,
I was wondering - I saw that most boost drivers have a small IC that outputs PWM signals to the rest of the circuit.
I guess all these IC's do is PWM the voltage.. The ones that I saw are quite rear and pricey. I know that a 555 timer, can also generate PWM, and it is much cheaper. Why not use it for boost drivers?


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Old 09-18-2012, 11:42 AM #2
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Default Re: 555 timer boost drive?

The problem is that nonlinear converters (boost, buck, etc) require control of PWM between 10 and 90% at minimum, and the 555 timer chip can only adjust pwm between 50 and 90%, and it also cannot adjust pwm independant of frequency.
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Old 09-18-2012, 02:18 PM #3
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Default Re: 555 timer boost drive?

Quote:
Originally Posted by Sigurthr View Post
the 555 timer chip can only adjust pwm between 50 and 90%
Not true. A couple of diodes can be used to allow faster discharge of the timing cap. It can also go up to 100%.

It's possible, but not ideal. Here's one example.
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