Charge pump driven by attiny io doesnt work with limiting resistor.

Hey

So this dickson charge pump im driving, runs from an attiny with 60Khz tone function. It worked fine when there was no limiting resistor from the pin to the driver.
This screenshot is from the eevblog video i watched to make this, but my one has 2 stage instead of 1.


Im only powering a slow switching mosfet gate through a bjt push pull driver.

Problem.

1.The charge pump runs fine and gives 13 V when i short through the resistors with my multimeter and shows ( draws near 4 mA for a sec ) 0mA current flowing after a few seconds. why ?

  1. I tried making another bjt push-pull to drive the charge pump, but it failed. I suppose theres no way to control a 5V output line with a 5V input using transistors. Is it possible?

And also, i ran out of complimentary transistor pairs so all i have left is few b772 pnp and 2n2222A npn

The other aspects of the circuit works fine, i have made sure its the charge pump thats having trouble

Think we need the full circuit diagram , you mention lots of components that are not included in your diagram. Plus there are two square waves on there , how are they phrased ?

Isn’t this in the wrong part of the forum , there isn’t a programming question ?

Aww heck i just noticed this is the programming forum.. my mistake, ill be moving it.

Mods, can someone please move it?

Hey

So this dickson charge pump im driving, runs from an attiny with 60Khz tone function. It worked fine when there was no limiting resistor from the pin to the driver.


This screenshot is from the eevblog video i watched to make this, but my one has 2 stage instead of 1.
Im only powering a slow switching mosfet gate through a bjt push pull driver.

Problem.

1.The charge pump runs fine and gives 13 V when i short through the resistors with my multimeter and shows ( draws near 4 mA for a sec ) 0mA current flowing after a few seconds. why ?

  1. I tried making another bjt push-pull to drive the charge pump, but it failed. I suppose theres no way to control a 5V output line with a 5V input using transistors. Is it possible?

And also, i ran out of complimentary transistor pairs so all i have left is few b772 pnp and 2n2222A npn

The other aspects of the circuit works fine, i have made sure its the charge pump thats having trouble

kaseftamjid:
Mods, can someone please move it?

Click on 'report to moderator', there's a clue in the name.

1.The charge pump runs fine and gives 13 V when i short through the resistors with my multimeter and shows ( draws near 4 mA for a sec ) 0mA current flowing after a few seconds. why ?

Resistor? There is no resistor in your schematic. What value is this mystery resistor? Also, you show the output as 6V but then say it is 13V, which is it?

Please provide your actual schematic that you are using

Since you have not shown us what you mean by "when there was no limiting resistor from the pin to the driver", we have no idea whatsoever what you are doing. :astonished:

Just show us a proper circuit. :cold_sweat:


With component values.

Why did you start a new thread in a different forum section for the same query ?

Cross-posting is against the rules of the forum. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend 15 minutes (or more) writing a detailed answer on this topic, without knowing that someone else already did the same in the other topic.

Repeated cross-posting will result in a timeout from the forum.

In the future, please take some time to pick the forum board that best suits the topic of your question and then only post once to that forum board. This is basic forum etiquette, as explained in the sticky “How to use this forum - please read.” post you will find at the top of every forum board. It contains a lot of other useful information. Please read it.

Thanks in advance for your cooperation.

okay this


someone on Reddit pointed out that this creates an RC low pass filter, and at 250 ohms, that's about 63 hz...
now im confused if i even need a limiting resistor as i wont draw much from it, around a few mA. Ill update the schematic in a bit.

And this is what im driving.

Hello kaseftamjid,
Please will you post what you actually have and be consistent? Your first post showed a charge pump with 1 stage and a 6V output, then you mentioned 13V, which is correct?

What is the load in your circuit in reply #10? A charge pump cannot supply much current and I suspect that your problem is the load is far more than the charge pump can supply.

Your push-pull amplifier will not work as Q1 will always be on. This is because the PWM output is between 0 and 5V (or is it 3V as per your first post?), so there is always base current through R2.

PerryBebbington:
Hello kaseftamjid,
Please will you post what you actually have and be consistent? Your first post showed a charge pump with 1 stage and a 6V output, then you mentioned 13V, which is correct?

What is the load in your circuit in reply #10? A charge pump cannot supply much current and I suspect that your problem is the load is far more than the charge pump can supply.

Your push-pull amplifier will not work as Q1 will always be on.

kaseftamjid:


This screenshot is from the eevblog video i watched to make this, but my one has 2 stage instead of 1.

The load was a dummy load, about 10K for testing purposes.

PerryBebbington:
Your push-pull amplifier will not work as Q1 will always be on. This is because the PWM output is between 0 and 5V (or is it 3V as per your first post?), so there is always base current through R2.

weird, Because the push-pull controller works fine… i tested

kaseftamjid:
weird, Because the push-pull controller works fine.. i tested

But you did not test it using the charge pump, did you?


Look, the whole design of this system is useless.

The charge pump will charge the capacitors with the 250 Ohm resistor protecting the ATtiny, but not if you connect a load anywhere less than about 10k in value. Whatever your load is in the circuit above, I am sure it is far too low to be powered by the charge pump and even the mis-connected transistors alone provide a substantial load. :cold_sweat:

If you short out the protective resistor (220 Ohms as it should be), you clearly are overloading the microcontroller far beyond its maximum allowable output current just to charge the capacitors.

And as has been explained to you, while the circuit above may appear to function when you provide it with 13 V from a power supply which is capable of providing the necessary current, the upper "D882" transistor will always be biased on and in order to pull down the FET gate, the lower "B772" transistor must fight the upper.

The only reason it will "work" at all, is that to switch the FET to a state where it cannot supply much load current, it is probably sufficient to pull the IRF540 gate down to about 5 V and the "B772" transistor probably has just higher enough gain to do this. The FET may not actually switch off and will heat up but perhaps you do not notice that. :astonished:

You need a logic-level FET (IRL540) for the microcontroller to switch without the spurious transistors, and a switchmode "boost" regulator to provide your 13 V.

The capacitor values you're using are far too high when using a clock frequency of 60kHz. For example, I've designed a 3-stage dickson charge pump that uses 2 clocks running at 413kHz, but only it only uses 0.1uF capacitors. Max current is 10mA @ 12V with zener installed (16V without zener).

You need to drive a charge pump with a low impedance, so resistors are out.

A good device for this would be a MOSFET gate driver chip like the MIC4422 which can
deliver a few ohms of output impedance.

For your MOSFET switch just use a logic-level n-channel MOSFET, the IRF540 is not logic level.

Switched capacitor boost circuits are poor performers unless you only need tiny output
currents - a standard boost converter is the way to go otherwise, adjustable ones are
commonly available at low cost.

Hi,
What will your load eventually be?

Tom..... :slight_smile: