Even with a reasonable switcher you're going to end up with >200 Watts dissipation. ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
What is the alternator's output current capability?
Since we now know that it's a vehicle with a battery, how much load current (accessories) on the battery?
Is the 14.5V/300A you develop only available with alternator running, or must it come from battery when alternator stopped? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
+2. He can say no though.
NT
Its almost tempting to look at a linear reg. Fixed-ish V drop with diodes followed by a regulated drop.
OP needs to consider load dump though, or it will fry his every effort.
NT
I've done that on several occasions... usually followed a year or two later by the customer returning begging me to fix the mess created by the consultant that agreed to their premise >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
That's good advice, you first.
Jamie
Did you follow the link?
Not if you use synchronous rectification, though it might be difficult to get much lower than that.
-- Bill Sloman, Sydney
I misremembered the size it was this one.
approx 16"x10"x3"
here's a 1KW inverter in the approximate size you gave.
In a buck converter the power circuit only sees the voltage difference. but it passes the full current.
-- \_(?)_
Hi jim The source is an alternator with a max current of 340 amp. And no it does not charge the batteries when the engin is off. Do i still need an inductor. Can it be done solely with semiconductors to reduce size?
This is already rectified, so I cant do synchronous rectification. Ive been told the DC level varies slightly if the alternator is ideling or at full capacity, just like most car alternator. K
Well, let's see... The largest mica capacitor Digikey has stock of is .091uF. So he'll need 2,417 of them.
Ouch. Well, the cost each is $57.60. However since this is a rather large quantity, the price drops to $39.20 so the total cost will only be $94,746.40. Certainly *that* won't break the budget! Thank heavens for quantity discounts, right AW?
Digikey only has 4 in stock so this may take awhile. They're 30mm long x 23mm high. Man, is this going to need a big PCB!
Good job, AW! This is one of your best suggestions yet!
*rolls eyes*
ssipative power being 1kw. But the output is 300amp x 14.5v = 4350watt.
sto get much lower than that.
een told the DC level varies slightly if the alternator is idling or at ful l capacity, just like most car alternator.
Jim's conversion from 300A to 200W implies that he's thinking of a diode dr op somewhere.
The simplest way of doing what you ask is to stick the current through an i nductor. Most of the time the 18V in to 14.5V is generating an increasing c urrent through the inductor, but if you disconnect the 18V from the inducto r for about 20% of the time, and connect the inductor to 0V instead, the in ductor current will fall for that interval.
This is called a switching buck converter
and the classic example (which is what Jim may have been thinking of) does have a diode to connect the inductor to ground when it's not connected to t he 18V, and you do have an diode drop through the diode for that period.
You can use active switches to return the 300A to ground through a lower vo ltage drop than a diode can offer.
The catch is that 300A through an inductor will saturate anything that isn' t both big and very carefully designed.
Transformer-based schemes can have less nett flux in the magnetic circuit ( but even more current in the windings) which is presumably where the SEPIC reference in your original post came from.
I don't understand much about any of them, but the transformer version of t he Cuk converter might be another thing to look at
-- Bill Sloman, Sydney
Further proof, if any were needed, of AW's imbecility.
And why is that?
joe
You didn't quite answer the questions... does the alternator charge a battery? Are accessory devices powered from the battery? Where is the 14.5V/300A used... i.e. what kind of load?
Depending on ripple requirements you _might_ be better off with an analog drop from the battery, otherwise you'll need HUGE capacitance. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Yes, I saw it.
Regards, Allan
How about posting a drawing/schematic of the hook-up on Dropbox or whatever?
It's abundantly unclear what you're trying to accomplish. ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
Jim. The load is lithium batteries. I have the client for some specifics ab out charging those batteries. Apparently not. He can just tell me i dont ne ed to. Bother with that. As far as is there a load connec5ed to the batteri es.. I would assume so. I will ask what type of load. But most probably a m otor as it is an electric vehicle. K
Jim. The load is lithium batteries. I have the client for some specifics ab out charging those batteries. Apparently not. He can just tell me i dont ne ed to. Bother with that. As far as is there a load connec5ed to the batteri es.. I would assume so. I will ask what type of load. But most probably a m otor as it is an electric vehicle. K
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