I am looking for a single ic that will provide a 5v dc output at zero crossing. This would have the rectifier diode bridge on the ic. All the circuits for zero crossing seem to have a separate diode bridge.
Does anybody know of a zero crossing detector ic which has the bridge on the ic? Ideally also the dropping resistors would also be on the ic. Then you would only have the mains inputs to the ic.
I need a low parts circuit. I had a look at a circuit with the diode bridge connected to a transistor opto coupler. The 5v spike was not sharp enough and broadened a lot going to zero as shown in LTspice.

 

What you didn't mention was the width of the +5 VDC pulse at the zero crossing.
IMHO a single chip solution does not exist.

 

There are optocouplers with two, back-to-back LEDs in them, eliminating the need for an external bridge. This plus a capacitor could do what you want.

https://www.mouser.com/datasheet/2/308/MID400-D-1811614.pdf

ak

 

Based on experiments years ago, along with that capacitor it is a very good practice to put a bleeder resistor across it with the RC time constant render the capacitor "painless" in the event to the circuit being disconnected from the mains at exactly the wrong instant, leaving the capacitor charged to a dangerous voltage. A resistor in series with the parallel RC circuit would limit the current to a value low enough so that components are not damaged by the initial charging of the capacitor.

The output transistor in the optoisolator that @AnalogKid i mentioned is isolated from the primary and can be used with a grounded circuit.

 

There are optocouplers with two, back-to-back LEDs in them, eliminating the need for an external bridge. This plus a capacitor could do what you want.

https://www.mouser.com/datasheet/2/308/MID400-D-1811614.pdf

ak

Not a full bridge and no specification on zero crossing pulse width. Three external resistors and a capacitor is not too bad.

 

MicroChip

 

For the part in #3, the datasheet recommends a 22K input resistor. This works out to approx 8 mA peak LED current at 120 V and 16 mA at 240 V. Both are well below the 30 mA rating. Power dissipation will be above 1/2 W, and you always should have at least two resistors in series (with values that total up to 22K) so that a single-resistor failure does not expose the circuit to a direct powerline connection.

ak

 

I have a patent on low-power zero-cross detection off of the mains AC for relay actuation. I did it by charging a capacitor off of the mains line (DRC), as the voltage collapses, a j-FET discharges the capacitor through an optocoupler, providing a short pulse on the output that a micro controller senses... it was very low power (a few mW) compared to all of the other options I found. Had a few small parts + an opto.

I am not aware of an IC that does this sort of thing. Meeting UL requirements requires a fair bit of PCB real estate... which might be why.




or...

 

Not a full bridge and no specification on zero crossing pulse width. Three external resistors and a capacitor is not too bad.

Looks good Papabravo. I will try the mid 400. Must find supplier now. I agree with tindel that there appears to be no dedicated IC for zero crossing.

 

Here's an excellent zero crossing detector candidate circuit for your consideration.

 

I have a patent on low-power zero-cross detection off of the mains AC for relay actuation.

Do you have an expanded view that shows the exact timing between the pulse edges and the zero-crossing?

ak

 

I agree with tindel that there appears to be no dedicated IC for zero crossing.

1 external resistor (not counting the output pullup) seems pretty dedicated to me.

ak

 

Do you have an expanded view that shows the exact timing between the pulse edges and the zero-crossing?

I don't... that was a couple companies back... and they kept my lab book. There may be more information in the patent... but a quick skim didn't reveal much. PM me if you'd like the patent number.