[SOLVED] Help me with charge pump DC to DC design

[jiangwp]

Charge pump DC to DC

Now i want to design a charge pump DC2DC.

I want to know how to determine the frequency of oscillator, the value of

capacitor and the size of switch. Maybe there are some equations among them.

 

[vdaniel]

Re: Charge pump DC to DC

Do you mean a IC design?
If not, then use one of a lot of ICs. Very nice one, with very low noise
and internal regulator is LTC1550L from Linear Technology. There are a lot of
other types for different voltages and polarities from the most manufacturers and availabe, for example, from Digi-Key.
For the swithching frequency the more, the best for smaller capacitors and lower
noise (easier for filtering).

Varuzhan

 

[jiangwp]

Re: Charge pump DC to DC

Yeath, i want to discuss the IC design.

Also it can work well at the range form 2.7 to 3.3 voltage.

So it consists of the doubler and tripler .

Therefore, we must design a logic control to control the selection of doubler and tripler.

 

[dog1357]

Re: Charge pump DC to DC

may i ask whether the double and triple power supply will be consisitent when driving a current let say 50mA.
i think for normal DCDC charge pump, the frequency is not very high so they normally use abstable oscilator, later i will upload an file to discribe abstable circuit will you can do your own search. the RC can be find and the simulation results is quite close to calculated one, fine tune capacitor will shift the frequency quite big, the resistor will not contribute much.

duanlian@pmail.ntu.edu.sg

 

[jiangwp]

Re: Charge pump DC to DC

To dog1357:

Because the charge pump DC2DC is wide range for work.

So i do the double and triple together with a logic control to control the selection.

 

[li-jerry]

Charge pump DC to DC

1MegHz will be OK most time, for a concrete load, say 50mA, we need to calculate deltaV * C=I*T. We can choose DeltaV, for example 50mV, then we get T, 1/T is our frequency and C is our Cap value.

 

[JPR]

Re: Charge pump DC to DC

The three design variables that you mentioned, frequency, capacitor value, and switch resistance will all have primary impact on the output resistance of yor converter.

If you are running open-loop, none of these parameters will vary with output voltage, so they will directly impact output voltage. If you know your input voltage and output voltage specifications, you can determine an output resistance specification. From this, you will be able to determine how the design variables constrain each other. From other design considerations (available clocks, available capacitor sizes, etc.), you may be able to further constrain the design variables in order to determine your solution.

If you are running closed-loop, one or more of the parameters will vary with output voltage, usually either switch resistance (in one or both phases) or switching frequency. This will effectively modulate the output resistance to give you a more consistent output voltage. The solution for this case would be similar to the first case, only one of the design variables would be variable when in use.

 

[mikechiang]

Re: Charge pump DC to DC

Charge Pump paper

 

[andy2000a]

Charge pump DC to DC

if input from 0.9 ~ 1.5v .. and charge_pump to 3.3v
and fix 3.3v ( not double/triple volt)
how to control switch freq ?

1. use VCO detect Vin
if Vin < 1v clock spped up
if Vin > 1.3v clock speed down
but I think VCO is mode complex

another design is use double/triple conv
when Vin < 1v use triple
when vin > 1.5 use double , but Vout will not continue output .

which method use in IC design ?

 

[xuel]

Re: Charge pump DC to DC

agree with Li-jerry, C=I*T/delt V. To use on-chip or off-chip cap is deternmined by C's value. For example, I=4mA, f=100Mhz， deltV=0.4V, C=100p is too large for 0n-chip, so must choose off-chip C.

 

[naisare]

Re: Charge pump DC to DC

if input from 0.9 ~ 1.5v .. and charge_pump to 3.3v
and fix 3.3v ( not double/triple volt)
how to control switch freq ?

You can use PWM or PFM methods to regulate the output voltage to 3.3V.