High Powered DC circuit

Are you asking if there is a chip that can provide and analog siganl between +-10 volts with a voltage rail of 0 to 54 Volts? If this is what you want do you want, what is the ouput power you need?

Hi thanks for the reply,

No, I need a chip to provide an output of up to 54v, 4.5Amps depending on the size of the control signal which is up to 10V.

thanks

Yes, there are a number of high power op amps in fact I have half a dozen here that I'm experimenting with...

The larger version is capable of 8 Amps and 60 volts swing, it is a dual device so it can be used in a bridge configuration for dc motor control etc...

They come in a multi watt package... sorry must go and find out their part numbers ....

John.

Burr-Brown OPA549

Its rated at 8 Amps continuous and 10 Amps peak - that should do the job!!

John.

Thanks John, that sounds perfect, how did you find that? I searched globalspec, but nothing would come up with both the current and voltage requirements.

Guest, to be honest.... I hadn't come across them before until I saw 6 for sale on ebay and quickly bought them!!!

The data sheet is available from :

http://www.alldatasheet.com.kr

I would recommend you keep that address in your favourites, as it contains data sheets for just about every type of transistor diode and ic ever made!!!

John.

http://www.alldatasheet.com/?gclid=CMSZqpmW1okCFQlsTAodMy9Q5A-- -instead of

http://www.alldatasheet.com.kr/

Shd. get you the page.

Indeed a goldmine!

To make it even easier here's the features of this device, it really is quite amazing....

FEATURES

l HIGH OUTPUT CURRENT:

8A Continuous

10A Peak

l WIDE POWER SUPPLY RANGE:

Single Supply: +8V to +60V

Dual Supply: ±4V to ±30V

l WIDE OUTPUT VOLTAGE SWING

l FULLY PROTECTED:

Thermal Shutdown

Adjustable Current Limit

l OUTPUT DISABLE CONTROL

l THERMAL SHUTDOWN INDICATOR

l HIGH SLEW RATE: 9V/ms

l CONTROL REFERENCE PIN

l 11-LEAD POWER ZIP PACKAGE

APPLICATIONS

l VALVE, ACTUATOR DRIVER

l SYNCHRO, SERVO DRIVER

l POWER SUPPLIES

l TEST EQUIPMENT

l TRANSDUCER EXCITATION

l AUDIO POWER AMPLIFIER

Another technique is to use scr's with phase control. Your circuit drives an isolating pulse transformer. Or you can use photo isolators with a clever gate circuit.

Just another common way to use AC for DC motor control.

You may be disappointed, check the data sheet carefully. The Burr-Brown op-amp has transistors in it's output circuit. Transistors (bipolar) exhibit a phenomenon called second breakdown. What this means is that the transistor will sustain a voltage of whatever, say 60 volts and it will sustain a current of say 10 amps but, it's one or the other. If you expect it to drop 60 volts while it is putting out 10 amps (600 watts!) it will fail catastrophically. If you need 10 amps at 2 volts and then maybe 10 amps at 60 volts you should look into a switching amplifier. I don't know offhand who makes them but I am certain they exist and they can source that kind of range of power gracefully.

I second that. I was drueling over these untill I found out what you mentioned. I was hoping to drive a DC motor with one... no luck as the power demand increased the voltage plummeted.

Repeat! 'State your problem and add the circuit diagram and point with arrow-what/how/when u want to control'

Otherwise nobody can comment.

Try LM12CLK. Find it in www.alldatasheet.com

Do they still make those? I remember seeing a data sheet but never actually saw one. Anyway, second breakdown limits would apply.

Thanks for the info, indeed I do need to run 54V at 4.5A, so I take it that opamp wont work..

Its an eddy current dyno, you control the amount of voltage to the coils, which in turn controls the current, controlling the magnetic field so that it can meet the torque of the engine, the reactive force is then measured using the load cell.

I have a digitial signal processor to control it, so my control signal can be anywhere from -10V to +10V, I will most likely just use from 0V to +10V to make it easier.

the rest is up to me.

The other dyno I have seen runs ac, but I was of the belief that coils are much better run through dc.

I will post my theoretical circuit shortly...

thanks

cool project!

Since you are powering a coil (large inductor, ie choke or filter) a PWMed switching regulator should work sweet. I assume, and hope, that your DSP (digital signal processor) has at least one PWM channel in hardware. Just take that PWM output and feed it to a MOSFET driver circuit (isolation would be a good idea) and use that MOSFET to handle the current.

I suggest another way out.

Buy the smallest TIG inverter welderDC machine $100-$200. Hundreds of types-search Globalspec. Choose V and I ratings to suit your application.

Modify the Current contol knob circuit to receive a 'Request'DC signal ( otherwise stick to the knob setting as the Input). Your job is done.

I have now registered, (formerly guest IE thread starter), thanks for your reply, but I would prefer to build/buy components than pull apart another item.

Battery1 and switch to be replaced by dsp PWM signal

Battery 2 to be replaced by ac rectified and smoothed to approximately 54v dc.

The circuit looks more complicated that expected cause I had to keep the voltage down across the optocoupler, but keep the voltage up at the MOSFET.

Cory

<What this means is that the transistor will sustain a voltage of whatever, say 60 volts and it will sustain a current of say 10 amps but, it's one or the other. If you expect it to drop 60 volts while it is putting out 10 amps (600 watts!) it will fail catastrophically. If you need 10 ---->

Would#1 please restate his problem once again

"I WANT electronicallyVARIABLE CURRENT" or

"I WANT electronically Variable VOLTAGE?"