Is the 100 mV a maximum, or a constant desired voltage?
edit: reading the post again and the schematic, it looks like you want a swinging or switcheable output voltage between -100 and +100 mV?
There's a few things to take into account:
- even with low Ron for the secondary fets, the voltage drop is going to be significant at 10 A. In particular in relation to the 100 mV output.
- the output capacitor needs to filter ripple on a 10 A signal, and it has to be bipolar - that may be hard to find. It may be better to outsource the majority of the ripple filtering to an inductor. But then that makes polarity shifting tricky ....
I have a 48 V to 0.5 V design here (but without polarity selection on the secondary side). And it uses a number of measures to get to a reasonable efficiency.
100mV is only a maximum, I need to regulate the current, so the voltage will depend on the load.
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Can I summarise it like this?
- you need a device that can control a DC current between -10 A and + 10 A. That current has to be configurable and maintained by the circuit.
- it's derived from the load that within these ranges, the output voltage will stay between -100 mV and 100 mV
- The input voltage has to be 5 V DC.
- a switch mode design.
Thank you for your hints, Jan. I will definitely use an inductor in series with the load.
I found that the minimum Ron of commercial NMOS is about 1mOhm, so at the maximum current of 10A, the voltage drop will be 10mV, with 100mW of dissipation.
The voltage on the load (about 10-100mV) will be comparable to the voltage drop on the transistor, but will this be a problem? I will measure the voltage in parallel to the load (from FEEDBACK signal to GND), or even better the current with an hall effect sensor (like ACS712), so I think I can ignore the voltage drop on the mosfet in series.
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If you kick up your input control voltage to about 20V, you could use an IGBT module.
I've used them to get hundreds of amps for solid state Tesla Coils.
They use them for arc welders also.
Look into induction heater circuits, you might find what you're looking for.
Thank you, Scott.
Unfortunately, I can't have 20V of voltage. I have 5V of main power source and 3.3V for digital control signals (the voltage of my microcontroller).
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How accurately must you control the voltage/current ?
How much noise is acceptable on the output.
What sort of signal will you drive the load with ? (AC, slowly varying DC etc)
(Can you tell us what the load is ?)
I'm thinking that the best bet would be a 5V to 1V switching converter and then a linear bridge type power amplifier.
Alternatively you could re-purpose the LT1923 which is a switching Thermo electric cooler driver. Even if you don't use this chip it would be worth reading the data sheet and app note to get some background information.
I've used this chip and it works quite well, (although it's very expensive).
Since the power FETs and sense resistor are off chip you can tune it up for whatever you want.
I need to control the current with a resolution of 10mA, preferably 1mA.
A little noise won't be a big deal.
The load will be controlled by a slowly varying DC, with a maximum variation of 10A in 1s.
The load is a solenoid.
Thank you for the suggested LT1923, I'm reading the datasheet now.
I'm dealing with a quite strange design. I have a single 5V power source with few amps of current (about 3A) and I need to drive a load (about 0.8mOhm of resistance, but variable in function of voltage/current) with a current from -10A to 10A, at 100mV of maximum voltage.
I'm searching for an IC which can help me, but I don't found any suitable device, at this moment.
I would try a discrete configuration like the following schematic:
I can send an alternate (square wave) current with one or another direction in the transformer, using a PWM signal on CTRL1 or CTRL2, with 50% duty cycle.
If i use a 10:1 ratio transformer (for example), I will have a reduced maximum voltage, but with more current (about 10 times). Correct?
And then, with another PWM on CTRL3 or CTRL4, I can modulate the output from zero to positive maximum and to negative minimum voltage, measuring the voltage to the feedback point, or the current in series of the load (R1) with an hall effect sensor.
I probably don't even need two input windings, but I can send a single square wave in input and activate Q3 or Q4 to obtain a positive or negative output. And perhaps one of the two outgoing mosfets should be type P?
What do you think about this solution? Anyone have alternative ideas or suggestions?