Voltage Booster Module Current

[michan]

Hi guys,

Recently I bought what I think is a boost converter on ebay ( http://www.ebay.com.au/itm/172105952906?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT ) To convert 3.5V to 450V.
I was wondering if a resistance was necessary on the output to prevent a circuit from drawing too much current when connected to the module (in other words shorting the output of the module). OR would the boost converter have a resistance on the primary side of the module already built in that prevents too much current anyway? Even if there was a resistor on the primary side would it still be possible to somehow draw too much current on the output?

The fact that the module is stepping up the voltage using an inductor is the bit that leads me to believe a resistor on the primary side of the module wouldn't matter, and you would need a resistor on the output as well to prevent the connected circuit from drawing too much current when the current is being generated by the collapsing magnetic field in the inductor.

The reason i ask all this is because if i do need a resistor on the output, then it would need to dissipate something like 20 Watts of power and have a resistance of something like 10Kohm which ends up being rediculously beefy and expensive for me being a broke uni student.

 

[(*steve*)]

the simple answer is to limit your load to something sensible.

 

[michan]

the simple answer is to limit your load to something sensible.

But if the resistor is anything but those values that I mentioned before then it would be drawing too much current and/or the resistor wouldn't be handling the amount of heat it needs to dissipate? The module is going to be charging a bank of capacitors so it will be acting like a short circuit unless there's a resistor onboard the module already, or i add my own onto the circuit but then we are back at the problem of too big and beefy?

unless you meant something else by limit the load to something sensible?

 

[Alec_t]

it would need to dissipate something like 20 Watts of power

How do you get that figure? I think you've misread the spec .
According to the module's spec the operating current with a 3.5V supply is 48mA (so the power input is 168mW). Allowing for inefficiencies the output power is likely to be ~140mW, so at 450V you could draw only 0.3mA.

 

[michan]

How do you get that figure? I think you've misread the spec .
According to the module's spec the operating current with a 3.5V supply is 48mA (so the power input is 168mW). Allowing for inefficiencies the output power is likely to be ~140mW, so at 450V you could draw only 0.3mA.

Oh I assumed that was the output current because it was so low? hmmmm