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bki

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inverting Boost converter
Apr 17^th, 2014, 2:03am

Hi,

i am circuit design beginner (student) and have a little problem.
I need to design an integrated inverting boost converter that is able to generate -70V (negative voltage) at the output from 5V input supply.

The technology that i use only allows me to use NMOS transistors and the source of those transistors need to be connected to ground.
Therefore, i can not use a regular inverting Boost Converter topology, where the switch connects the input voltage to the inductor node.

Any ideas how to implement the circuit instead?

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loose-electron

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Re: inverting Boost converter
Reply #1 - Apr 22^nd, 2014, 3:39pm

Are you inside an IC or on a PCB?

You can generate the V+ (say 80V with a LC boost circuit) and then use sequenced switches to take that voltage and invert it to -80V

Charge the capacitor to 80V, and then sequence switches on a holding capacitor to make it -80V, where you use a diode (needs to float from substrate) to dump it into a holding capacitor.

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Jerry Twomey
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Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical

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bki Community Member Offline Posts: 32	Re: inverting Boost converter Reply #2 - Apr 23^rd, 2014, 4:53am Hi, thanks for your message. It is for an IC. I am not a native english speaker, therefore i don�t really understand what do you mean with sequence switches ? Maybe do you have a picture example? Thank a lot for your help!
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: inverting Boost converter Reply #3 - Apr 23^rd, 2014, 3:00pm http://www.linear.com/products/Inverting_Regulators Take a look at the above devices, this is what you are trying to do.
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bki Community Member Offline Posts: 32	Re: inverting Boost converter Reply #4 - Apr 24^th, 2014, 5:39am exactly, but i am doing it integrated. So, i can not use another IC. My big problem is that my technology offers no PMOS transistors - only NMOS.
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: inverting Boost converter Reply #5 - Apr 24^th, 2014, 4:25pm you may have to create what are called "boot power" to bias the NMOS transistors above the power supply rail to use NMOS switches only. see: http://4.bp.blogspot.com/-GZBCM0xlSbk/UPvnSo5w4rI/AAAAAAAAAZo/YUTt0KpFnPA/s1600/... which shows an example of how to control an NMOS transistor to switch a large positive voltage.
Back to top	Jerry Twomey www.effectiveelectrons.com Read My Electronic Design Column Here Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical IP Logged