Relay driver circuit using ULN2003. ULN2003 is very famous relay driver integrated circuit. Relay driver IC uln2003 is high voltage and high current integrated IC which used Darlington array. Its contains seven Darlington pair of transistor which have high voltage and high current carrying capability. This all about pin configuration and working of TLP250. Now i will talk about how to used isolated mosfet driver tlp250 as low side MOSFET driver and high side mosfet driver. TLP250 as a low side MOSFET driver. Circuit diagram of low side mosfet driver using tlp250 is shown below. I'm embarrassed to say that I've had this very elementary problem for weeks now, without finding the solution by my self. I have a micrcontroller device producing a 1kHz PWM signal that I would like to use to switch a power circuit on and off*. This is primarily being used as an LED-dimmer device. The 1kHZ PWM apparently precludes the use of a mechanical relay. All I want is something that can be switched on/off at 1kHz. Energy efficiency is important also as it will be running on AA NiMHs. * Currently the microcontroller is 5V, but soon will be moving to 3v device. The power circuit consists of one or more (in parallel) 1W LEDs each running at 0.35A and ~3.6v (3xNiMH AA). A max current of 1A would be fine. Is the answer obvious? Mario and sonic at the olympic games. Any specific devices spring to mind? As always, your help is greatly appreciated. Here's what I've being toying with. MOSFET: More complicated operation than I expected, since efficacy depends on gate-source and drain-source voltages. In my case these are very/too small (both. Oh dear, the dreaded line. Sorry, I hoped my threads were of acceptable quality. Yes I searched widely, although I may not have a talent or it. My opening line alluded to thoughtful readings of Paul Scherz's book and posts such as these, None of which equates to experience. I posted schematics for 3 possible approaches. What I was hoping for is something incisive, such as 'Sir, a low Vgs MOSFET such as ZXMN6A07F is perfect, albeit surface mount only. However, for a range of power voltages, a BJT may be a better guarantee of versatility - at the cost of energy wastage. A solid-state relay is best is you need isolation and large power transmission, but is generally more expensive and therefore overkill for your project.' Or a link to a previous hashing that is pertinent to my scenario. Thanks, truly - I don't take for granted the infinite patience of people like Nigel Goodwin, Eric Gibbs et. Sorry, I forgot to add that the driver's actually just a single component (ignoring the protection diode) - the AMC7135 - the rest is just empty PCB. I don't know its history but it's a brilliant little thing, Datasheet doesn't mention AC at all. While the subject is discussed on flashlight forums, I don't know if it's okay with 1kHz PWM. Even if I don't use the AMC7135 the basic switching issue still remains. EDIT: I found that I have some ULN2003A Darlington arrays. Presumably this would be a usable solution along the BJT line - in case no MOSFET solution is forthcoming. I've never used a MOSFET in a circuit, and it would be nice to try them as they sound potentially ideal. I was wondering if anyone could clarify whether this AQV2121 solid-state relay would be suitable for switching my 3.6V LED (+ v. Low-dropout constant current driver) from 3.6 or 4.8volt supply. It says it can switch 500mA DC loads, has Ron~1 Ohm, and has an '.extremely low closed-circuit offset voltage to enable control of low-level analog signals.' , which presumably includes my case ( it doesn't seem to state the lowest voltage it can switch). Right now I'm not concerned with switching speed - just want a basic switch. Perhaps even better, though not providing isolation, is this N-MOSFET which explicitly states that it is good for interfacing directly with microcontrollers. A typical pic can output 20ma on an given pin so it should have no problem directly driving a 500ma load through a bjt (of reasonable beta) or a mosfet. The advantage with bjt for this application is their low Vbe so you can saturate those devices even if you go to a 3v device. The disadvantage of a bjt is that it has to have big enough of current out of the PIC - not a problem here, and they do suffer from 2ndary breakdown so be careful reading the datasheet for SoA. The advantage of using a mosfet is that a) they are very easy to drive so even if you move to a 2ma / 4ma device later, your driver section remains intact; b) they are ohmic device once they are on; and c) they are cheap and robust. However, you have to use a logic level mosfet to be sure that it operates on 3v rails. I would go with a bjt here because I have lots of them.
0 Comments
Leave a Reply. |