Need schematics for 120Vdc supply

Sounds like the hard way ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| 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

An automotive 120 VAC inverter, a bridge rectifier, a capacitor, and a fuse.

Paul

"Paul E. Schonk"

** Gives about 170 volts DC and is not short circuit proof.

..... Phil

Ok, easy.

Yea... you forgot to mention what resistance. And inductance too. Any peculiar turn-on-surge current? Exactly how long are they on for?

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Hi,

I not sure all the project parameters are pertinent to the supply design, but here what I can give you:

Injector Coil DC Resistance: around 1 ohm

Injector Coil Inductance: Unknown

Injector Coil Pulse width: Variable between 50 microseconds and 5 milliseconds

Injector Coil Pulse frequency: Variable between 0 to 60 Hz

The motor use 6 injectors. They are pulsed in sequence, one by one.

The 6 injectors have a common path to the +120Vdc supply. They are return to ground using a power mosfet drive by a computer. (This is very similar to industrial unit).

Our prototype used a very typical 120Vac input power supply, using a simple transformer/bridge/capacitor design powered from the outlet. We add a 10 ohms power resistor in series with the +120Vdc to prevent the bridge from exploding in case of short, but this limit the current and heat up a lot.

We tried to use a commercial power inverter (400watts 13.8Vdc to 120Vac) to drive the 120Vac transformer to run the device from the 13.8Vdc power source. This is not working very well; the inverter is not powerful enough. We did not try with larger inverter. In any case, this concept is far than be efficient, and end up to being too voluminous to be used later.

I did try to use the power inverter as supply, but as mention we end up with

170Vdc. I modified the unit removing the DC to AC section and use only the 13.8Vdc to 170Vdc section. I also modified the loop back to lower the output at 120Vdc, but this is too limit for the unit transformer, it end up unstable and I still have no current limit protection. The prototype explodes a couple of time during test. The transformer should be modified, removing a few secondary turns, but it's impossible to rewire it without destroying it.

Looking at industrial units, I know they use something similar to a boost regulator. They use a PWM chip (unmark), a coil and a 220uf 160Vdc capacitor. The circuit is a bit complex, build on a multilayer PCB and difficult to reverse engineer. In any way, I do not wish to copy any proprietary design.

I need the short protection, in case one of the mosfet short, this can append. Also the end users are not very prudent to protect the circuit. They often short the coils or let wires touch the frame and so on. So it must be build to endure rough treatment.

Bye Jacques

You might be able to adapt a scheme such as shown in...

You need to measure the inductance of your injectors, then I could run the numbers.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| 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

It would be easier to get an inverter already made, with bridge rectifier on the output. 120 watts is a very small one. It would cost you lest in money and time. Or, you can try to build a simple thing like this and put a bridge rectifier on the output, along with some filter caps.

I'm not sure that the open circuit voltage is all that critical. It could be made relatively short-circuit proof by charging the capacitor through a relatively large resistor (150 ohms 100 watts) and then choosing a resistor for discharging into the injectors that will give the peak current required for a few mSec. I found the following injector driver kit:

It drives the injectors with a 4.1A pulse for up to 5 mSec and then drops the current to 1 amp. It does not specify the load resistance and inductance, or what the rise time of the pulse must be, but I doubt that

120 VDC is really necessary. The module described above is $333 and drives up to 10 injectors. I also found:

But this is only 3 channels and costs $2000! It does have an internal boost supply of 150 VDC and is capable of 30A peak and 15A hold, but that is probably for huge industrial engines, although I don't know what the OP really needs.

Here is an article about a new piezo injector that can operate on 12 VDC directly:

Information on patents by Delphi and others:

Here are some waveforms for driving fuel injectors:

Here are some detailed specs for an injector, showing resistance, inductance, and current:

Probably too much information, but I may have learned something...

Paul