EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Simon on April 26, 2018, 02:03:35 pm
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I am doing a charge pump (18-36V @ 25mA) I am not certain if I can use an electrolytic capacitor due to the ripple current. Even putting a resistor in series with the capacitor to control current spikes I still have peaks of 600mA in a simulation which is beyond the spec of most small electrolytics at 120Hz never mind 1-10KHz. Is a ceramic a the best choice here ? I could of course use tantalum as I am putting 33R in series with the flying capacitor so it won't be prone to the typical failures of tantalums.
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Little experience from few days ago:
TC7660 charge pump operating with three (input, floating, output) MLCC 1u/25V ceramic capacitors produces audible sound (10kHz).
Not very loud but sometimes irritating.
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Little experience from few days ago:
TC7660 charge pump operating with three (input, floating, output) MLCC 1u/25V ceramic capacitors produces audible sound (10kHz).
Not very loud but sometimes irritating.
Don't worry there will be more noise to worry about than that ;)
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I have used this appnote before when adding charge pumps to boost converters:
http://www.ti.com/lit/an/slva398a/slva398a.pdf (http://www.ti.com/lit/an/slva398a/slva398a.pdf)
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Well I came up with the attached, it uses a mosfet driver and will be pulsed from a micro controller and I will try and introduce some current measurement on the main regulator this is driving so that I can cut the pulses off, reduce duty to lower the output voltage.