# CMOS DC booster - Start up circuit

1. ## CMOS DC booster - Start up circuit

Hello everybody,

I'm new in this forum and i have some questions about a dc-dc booster creating for my diploma thesis.

I have the above circuit. Mos-switch is designed in 0.13um. I want to have an output voltage to 1V coming from an input one of 50mV - 80mV. The problem I am facing is that i can achieve having this output voltage only when the width of mos-switch is some cm. However, in this case, the power consumption of mos-switch is nearly 100% of vdc's power.
Could you help me about that? How can I have both output voltage and least power consumption of mos?

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2. ## Re: CMOS DC booster - Start up circuit

Use a low threshold voltage MOS process and minimum drive voltage at the MOSFET gate.

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3. ## Re: CMOS DC booster - Start up circuit

You are asking for up to 20X increase. This means the duty cycle needs to be very high, on the order of 97 or 98% (according to my simulation). During that part of the cycle, current goes through the switching device (mosfet).

Hence only 2 or 3 percent of each cycle goes to the output stage.

It is normal operation in a boost converter, if you wish to get 20X increase.

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4. ## Re: CMOS DC booster - Start up circuit

I change duty cycle but power consumption in MOS is still to 100%. The only way i could decrease consumprion was by changing width of MOS to micrometers. However, in this way voltage boosting is nowhere. Any idea of how I could reach both targets?

5. ## Re: CMOS DC booster - Start up circuit

Change your topology; use a boost circuit which permits the use of a transformer—one with perhaps a 10:1 turns ratio.

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6. ## Re: CMOS DC booster - Start up circuit

What do you mean saying "use a transformer"?

Using, for example, model IRF034 and Vin=50m, L=22u, C=10u, RL=100k, the result of Vout=1.4V which is pretty good. However, power consumption in MOS switch is 100% of Vin's power. My Vpulse generator has Period=10m, PW=7.5m and V=1V. What changes could I make in these parameters?

7. ## Re: CMOS DC booster - Start up circuit

Come to think of it, if your power supply is .05V, then it is not able to turn on semiconductors, even if it has unlimited amperes available.

A flyback converter will perform with better efficiency. It uses a transformer which contains a primary and secondary. This is only theoretical talk of course. You will still need 1V or so, to turn on a switching device for a flyback.

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