high voltage charge pump

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   Anyone familiar with a high voltage charge pump designed as a step down  
power supply? The voltage is between 175 & 200. Numerous high voltage  
versions exist using inductors, (Onsemi has one that is "self supplied"  
which is attractive) but not a one that works with just a capacitor. Are  
there any out there I've missed?

Hul

Re: high voltage charge pump
On 12/30/19 8:53 AM, Hul Tytus wrote:
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Most charge pump designs will multiply voltages (invert or step up), not  
divide.

While a step down configuration is possible, I think it requires much  
more careful choices of values and control law to keep the output from  
getting too high of a voltage.

Also, all charge pumps that I know use MULTIPLE capacitors, they  
generally work moving charge in a controlled way, so generally require  
at least one 'moving' capacitor to transfer with and one fixed output  
capacitor to store the output charge.

One reason you don't generally use a charge pump for step down is that  
charge pumps are best used at very low current. For very low current  
steo down, the simple linear regulator is normally a perfect solution  
and often is as efficient or even better than a switched capacitor step  
down system.

Re: high voltage charge pump
Richard - what I'm looking for is an ic similar in results to Microchips  
tc7662 with an input voltage limit above 200 volts. The output current  
needed is only 60 ma. which is in the range of charge pump ic that I've  
seen so far.

Hul

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Re: high voltage charge pump
On 12/31/19 11:35 AM, Hul Tytus wrote:
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Yes, a doubler configuration can be reversed to become a halfer, if that  
is the voltage you need. 60 mA is also on the high range of what these  
supplies are considered good for, due to the somewhat high output  
impedance of a charge pump.

I am not familiar with devices in that range, so can't suggest what  
might work up there. One issue that you may run into is that a lot of  
things likely need to scale in the wrong directions. Higher voltages  
means more charge transferred for equivalent percentage ripple, which up  
the energy involved, so you may need to reduce the capacitance, or the  
switching frequency which drops the current capacity of the system.

Re: high voltage charge pump
On Tuesday, December 31, 2019 at 11:36:01 AM UTC-5, Hul Tytus wrote:
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There is nothing to stop you from creating your own design.  The switches a
re just FETs and need some drive circuitry to make them do their job.  I ha
ven't looked at the details, but you might be able to use H-drivers.  I exp
ect you can find them in high voltages.  

--  

  Rick C.

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