I’ve got a bunch of these. Let’s say I need 3Amps. Can I hook two up in parallell or will bad things happen?
If yes, how close would the output voltage need to be? +- .1V ok?
They generally cannot work in parallel directly, as it may mess with the feedback loops of each other. There are ICs that can be used to load share, but they tend to be 10x more expensive than just getting a well-sized converter.
What you can do is divide the circuit into smaller chunks, and power each part off of a boost converter. Just make sure all grounds are connected.
Thanks. And it can’t be mitogated by adding some reverse current protection or similar on the individual outputs?
Diode ORing is what you're referring to, and I wouldn't recommend it. In a diode OR configuration, the higher voltage supply will take 100% of the load. If neither supply can power the load, this can result in one getting the load, the voltage sagging under too much of a load, the other taking over, the same thing happening, repeat. You need to properly split up the demand.
Thanks I think the answer is clear that this is a bad idea. Good to know.
could it be accomplished using 'ideal diodes' on both sides of the OR?
(spitballed from me, I wouldn't do it on my bench, when a Client returns an item because I played around that hurts My shop in both reputation and wallet.)
Not really, the issue is the same. Diodes (or FETs in ideal diode cases) can't "merge" current together this way.
The issue is really on the regulator's side, you need active communication between them to ensure both can handle the load: most of these are working where one is the master controller which monitors the voltage levels and controls the rest to constantly balance the current (and with it, the load) between ICs.
Diodes in OR or AND configuration or FETs can't do that, they just switch between two inputs based on their voltage.
With a smart control IC you can assemble a current control circuit where you constantly monitor the load on both regulators and use FETs to control the load levels but at that point, it is far cheaper and easier to buy a stronger regulator.
Yeah, you can address that by putting in resistors, but that reduces efficiency, making the whole thing more terrible. Better to just get a converter with greater power handling.
From what I see is connecting 2 boost converters in parallel with similar characteristics introduces a factor of 2 into the transfer function.
You shouldn't hook them in parallel directly, but you can add a low value series resistor to each one to keep them from fighting. It's not a great solution, but if you have the modules already, it's worth trying.
If you use 0.1 Ohms, You'll lose 150mV across the resistor at 3A (1.5A each) and each resistor will dissipate nearly 250mW.
You'll want to wire it so that the resistors can be disconnected so that you can set each module's output voltage independently before you connect them together. Try to get them within 25mV.
These modules probably can't sink much current at all (source only), so you may still have a problem if your load varies a lot. As the load gets near zero current, the module that is lower will not be able to pull its output terminal low enough and it may oscillate.
On the other hand, If the module design just shuts off when the output voltage is too high, it will work fine.
This is the way to do it OP.
These modules don't have the best load regulation making the output sag between full and partial load so getting them close and then running them with 0.1 ohm resistors should work great as the resistor will force balance in addition to the load sag.
They won't sink at all, the module just cuts off until the input voltage falls below threshold and it starts boosting again.
Boost converters can be paralleled as long as they don't have synchronous rectification. This one doesn't - there's clearly a diode between the inductor and the +ve output.
Paralleling multiple boost converters also requires that they have a simple overcurrent limit rather than a hiccup or shutdown, etc. Differences in their output voltages will mean that the converters don't share current equally and one will reach its current limit first, likely well before your desired output current.
You could ameliorate that by adding ballast resistors to improve current sharing, but the best way is to purchase a single boost converter that can drive your load.
That is the best answer so far. The balastresistors don't have to be that big, several hundreds of Milli ohms are sufficient
Not like this. There are circuits designed to share load like this, but they have one IC controlling all the mosfets, turning them on and off in sequence to spread the load evenly and reduce ripple.
Theoretically yes, however if one is set to a higher voltage than the other then it will take more of the load and it won't be balanced. You'd risk burning out one of the modules.
Set to exactly the same voltage as close as you can get (within 0.01v) would be the best you can do.
The best option would be to get a sufficiently rated converter instead.
Thanks. Yeah I’ll get an appropriate converter but now I know why.
Don't do it. If you need 3 amps at a certain voltage and you have a power supply that can supply it use a voltage regulator and a couple of caps. 3A is pretty common.
A buck converter has it's uses , is great actually but it varies along with the voltage provided. If you need a fixed voltage you can count on this might not be the way to go. I use buck converters a lot, as a first step down , then use a regulator later.
There's also plenty of buck converters on the chinese site that shall not be named for pennies. Getting a few and seeing what you get is always an option.
My answer also depends on the voltage you need though.
When you place two voltage sources in parallel what tends to happen is one runs full out until it current limits and the voltage drops, then the other takes up the slack. Not ideal for the long term.
Better if you add some impedance from each to the load to help them share better.
Use a different converter like xl6009 or ltc1871
In my experience this module is not recommended use more 1 amp of output.
As others have said, getting a different converter is the correct answer.
If you used a reverse current protection diode for each, as well as a series 1-ohm power resistor, I think it would be fine.
Let's say you get the output voltages within 0.1V. At low output, the higher voltage supply will take all of the load, but once it's putting out about 100mA, the drop across the resistor will decrease its output voltage enough for the other supply to start supplying current.
You can enter design parameters here: https://webench.ti.com/power-designer/
And a TI solution will be generated for you.
Have 2 separate 5v rails, one per supply. Switch between them every 5-10 milliseconds to keep the supplies balanced.
whit is your input output voltage amperage requeriments.
not a good idea. it would be easier to use a different converter with appropriate current rating. Generally, if you need to have several converters in parallel, they have to be synced.
Yes, it already has a diode on output. Get a precise multimeter to set them to the same output
is that <96% going from 1-95? or 95-96?
You should use a different converter instead. These boost converters instantly combust when short circuit. Don't ask me how I know.
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