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Forum: µC & Digital Electronics TC1044 theory questions


Author: qbgjklssd (Guest)
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First off, Hi, and thank you for making such a cool pedal. I am using 
this project
as my electronics lab project. Since I have full use of oscilloscopes, 
function generators, and various testing equipment, i thought it would 
be fun to poke around at various smaller components of your design and 
see if there is any room for improvement. As i am brand new to this, i 
was hoping you could help me out a bit. The first component i built was 
the power supply. I noticed you decided on the TC1044 chip, which was a 
very interesting little chip to use.
So looking at this datasheet,
http://www.kynix.com/uploadfiles/pdf8827/TC1044SEOA.pdf

I find..
"Theoretical Power Efficiency
Considerations
In theory, a capacitive charge pump can approach
100% efficiency if certain conditions are met:
(1) The drive circuitry consumes minimal power.
(2) The output switches have extremely low ON
resistance and virtually no offset.
(3) The impedances of the pump and reservoir
capacitors are negligible at the pump frequency.
The TC1044S approaches these conditions for negative
voltage multiplication if large values of C1 and C2 are
used. Energy is lost only in the transfer of charge
between capacitors if a change in voltage occurs. "

Basically, it says if you use 100uF caps, you can obtain 100% 
efficiency. So my question is, would using 100uF caps in this design 
have any negative effect on the pedal?

Further on down the page, i also came across this section,

"Paralleling Devices
Any number of TC1044S voltage converters may be
paralleled to reduce output resistance (Figure 4). The reservoir
capacitor, C2, serves all devices, while each device
requires its own pump capacitor, C1. The resultant output
resistance would be approximately:
R out= R out(of TC1044s)/n(number of devices)"

So running these chips in parallel will lower the output impedance. 
This, of course is mostly for academic curiosity, and i realize that a 
serious modification to the final pc board would be the result if it 
worked, but is this actually going to affect my overall sound when 
completed?
I have a few more questions, but since they are not related to the 
TC1044 chip, I think i will just email you instead.
BTW, the troubleshooting guide is a great focus on helping me test this 
project as i go, THANK YOU!!!
Anyways, happy  :guitarsg:  :guitargibso and whatnot,

Author: kowals (Guest)
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qbgjklssd wrote:
> So looking at this datasheet,
> http://www.kynix.com/uploadfiles/pdf8827/TC1044SEOA.pdf
This is a "Selection Guide" - the original datasheet you are citing from 
is located at
http://ww1.microchip.com/downloads/en/DeviceDoc/21348a.pdf.

> I find..
> "Theoretical Power Efficiency
> Considerations
> In theory, a capacitive charge pump can approach
> 100% efficiency if certain conditions are met:
Only if there is exactly zero load current and therefore no need to 
transfer any charge. Unfortunately, at this operating point the 
efficiency reaches 0%.

There is no way to avoid the problem of the missing energy, known as 
"Capacitor Paradoxon".
http://www.physics.princeton.edu/~mcdonald/example...

> Basically, it says if you use 100uF caps, you can obtain 100%
> efficiency. So my question is, would using 100uF caps in this design
> have any negative effect on the pedal?
It will increase the time to reach the steady state condition. Initial 
power loss rises too.

The LTspice example shows a steady state efficiency η=33% (@Il=500nA).
p_in:  AVG(v(v+)*i(v1))=  -7.64875e-006 FROM 0.99 TO 1
p_out: AVG(v(vout)*i(rl))= 2.49959e-006 FROM 0.99 TO 1
eta:   p_out/p_in=        -0.326798
Feel free to improve it ;)

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