Checking HV Ingnition Coil Drver Ckt

A 2N3055, particularly driven as shown, is quickly go to emit the magic smoke... and it won't even be visible.

Your drive mechanism needs to pull the base of the power device to ground when turning off to ensure HV stand-off.

With a conventional ignition coil you need a device capable of at least 350V... unless so heavily snubbed that you get miniscule HV. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     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.

2n3055 is rated for 60V not much used for ignition google "ignition igbt" will find lots of better parts

or to make it easy get one of the many model igntion coils that have the igbt driver build in

-Lasse

Thanks for the reply, but we are not looking at the same circuit. There are several on the linked page. Please follow the description above to find the one I am refering to.

It uses an IRF740, not a 2N3055.

Kevin Summers

Stock up on 393's >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     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.

Can you recommend any improvements to the circuit? Or is is fairly standard "as is", with no viable remedy for the built-in in failure risk?

Kevin Summers

Pad series R's, with diodes to rail, so that the Cdg spike doesn't kill your driver ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | 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

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Should the diodes be placed:

1) Between the rails and the op amp's V+/V- 2) Across the rails with the op amp output as center point. 3) Between all device connections to the rails.

By "series R's", I assume you mean the ones already shown in the schematic(?)

Kevin Summers

Diode A at OpAmp Out, K to V+ Diode K at OpAmp Out, A to V- Resistor from OpAmp Out to NMOS gate ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     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.

Thanks Jim. Now ready to fire it up.