555boostvoltage
I found this circuit, a voltage doubler with 555.
The duty cycle of the 555 is 50%.
Does changing the duty cycle of the 555 timer affect the voltage output like in boost converter? Or does it not change anything except the charging rate of the capacitor?
If you need an accurate 50% duty cycle, a simple 555 circuit is not the way to go. A better method is to have an oscillator run at double frequency, where duty cycle is unimportant. Then feed that signal in a divide-by-two circuit and you'll have a perfect 50% duty cycle.
A simple divider can be made using a JK-flip flop where the J and K are high, like in this circuit:
simulate this circuit – Schematic created using CircuitLab
There are countless ways to create a 2-divider, all with their own advantages and disadvantages. A simple Google image search will give you pages full of them.
Use TL494 that has a reference and feedback loop to stabilize the voltage. http://www.ti.com/lit/an/slva001e/slva001e.pdf
If you can use microcontroller, use its PWM channel and ADC to achieve this. Any MCU can be used. For example, AtTiny series from Atmel. You need to program the MCU with what you want. MCU can also help you achieve temperature compensation of the charging voltage and many other things e.g. over-voltage and over-current protection.
Contrary to what has been said above, 555 is not unreliable and not inefficient. It can be used as a regulated booster than a simple booster (as it is in your case) but you need to modify your design. In your current design add a fixed reference voltage source and an op-amp. Let op-amp compare the voltage at the output to the reference voltage. If reference voltage is 1V, you need to divide the output voltage by 14.4 (using voltage divider network) and then let op-amp compare the voltages. Output of the op-amp should manipulate (increase or decrease) the duty factor so that the output voltage is fixed at 14.4V regardless of load or input voltage variations.
Best Answer
No, typically the duty cycle would not significantly affect the output voltage.
If you limit the duty cycle to a point where the capacitor can't fully charge/discharge to due on resistance of 555's output pin and diodes, you would see the output voltage sag low.
However, there is no duty cycle that will result in an output over 2x the input voltage.