1

Is it ok to tie the battery pack (in my case 3s1p) to a SPST switch to turn it on/off or I should need a series resistor after the switch to limit current and a big fat cap to smooth the on/off transition?

Something like this:

schematic

simulate this circuit – Schematic created using CircuitLab

If so how can I calculate the wattage for R1?

This is what the supply is going to power: enter image description here

Status Re
  • 223
  • 1
  • 7
  • 1
    What kind of load is connected to the battery that requires this kind of "soft start"? What is the purpose of the diode and why this specific diode (with a max current of noy 300mA)? – StarCat Aug 11 '23 at 12:37
  • This is the power supply to a ~4W AB amp. The diode prevents C1 to discharge to the battery. this is the diode I found in this schematic program. I guess It should be a schottky. But the question remains. Do I need such a circuit or I can just use a switch? – Status Re Aug 11 '23 at 12:39
  • 1
    The LM4952 prevents pops and clicks during turn on and turn off so your resistor and diode are not needed. use a 1000uF battery decoupling capacitor. The volume control you are using has an "A" audio taper but the LM4952 also has an audio taper. Then use a "B" linear taper. The NE5532 is not needed and use 1uF film capacitors feeing the LM4952. The lithium battery cells will be damaged if they discharge less than 3V each, add a voltage monitor/disconnect circuit. – Audioguru Aug 11 '23 at 18:28
  • @Audioguru: ok UVLO circuit, ok 1000uF decoupling capacitor. Not sure what do you mean that the LM4952 has an audio taper. Also I think it is a good idea to use a voltage follower at the input to provide a low impedance output to the LM input – Status Re Aug 14 '23 at 05:22

2 Answers2

1

What you need is precharge: two switches, one through a resistor and one directly. First you turn the switch through the resistor, then, 1 second or so later, you turn on the direct switch.

I wrote a white paper on that: http://liionbms.com/php/precharge.php

Another approach is to use an ICL (inrush current limiter) in series.

Davide Andrea
  • 21,104
  • 6
  • 34
  • 73
0

Your volume control has an audio taper so that when turned to 50% the volume is reduced a fair amount. But the LM4952 also has a non-linear taper then adding them makes the volume control wrong, turning down the volume control to 50% causes the sound to be very very low volume.

volume control

Audioguru
  • 4,348
  • 6
  • 10