Zener diode on the input of DC DC boost

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Hello,

 

I have a DC DC energy harvester - boost IC. For this IC the VIN should not go beyond 5.5V. So I hooked up a 5.1V zener on its inputs. I do not know if I am doing this right. As per the zener connection

diagram the zener's cathode indicated by the black line should go to VIN + and the anode should go to VIN-. I did this but when I apply the voltage at VIN to the DC DC boost I do not get the output but when I disconnect the zener I get voltage on VOUT of the DC-DC boost. Am I supposed to use the zener in the reverse? Why is this happening when I connected the zener the right way as many circuit diagrams showed in google search results.Please let me know.

Last Edited: Mon. Feb 12, 2018 - 05:01 PM
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Pictures (schematics) are worth a 1k words, please post the circuit in question showing your zener in place.

 

Jim

 

Mission: Improving the readiness of hams world wide : flinthillsradioinc.com

Interests: Ham Radio, Solar power, futures & currency trading - whats yours?

 

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@ki0bk wrote:

Pictures (schematics) are worth a 1k words

+1 yes      Post that schematic.

 

If I understand you correctly, this is not the way to use a zener diode.  A zener is not meant for over-voltage protection, at least not directly.  Without a current limiting resistor, the zener most likely failed the first time you applied >5V1.

 

Greg Muth

Portland, OR, US

Xplained/Pro/Mini Boards mostly

 

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Without a current limiting resistor, the zener most likely failed the first time you applied >5V1.

Tis true in general, an energy harvester picking up a breeze with a butterfly wing, or poaching some excess field energy from the nearby power lines or radio station, probably is self limiting, in that the few microwatts aren't enough to burn out anything.  If you're harvesting energy from a tidal wave, then that's a different story.     

 

============

 

It would be very easy to apply too much voltage and overload the source, or wire the diode backwards & clamp at a few hundred mv. What is the typical source voltage from the harvester(??) without the zener?

When in the dark remember-the future looks brighter than ever.

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I have done exactly this on an energy converter driven by a small solar cell. 5V1 zener in shunt across the input that has a Vmax of 5.5V. 

 

In that setting, the source is very current limited, and everything is OK. The big question in my mind is: What kind of power source did you use for the test?

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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I am using RF power.

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Try reversing the diode, in case you got it backwards...if backwards it will clamp to one diode drop (few hundred mv) & your circuit will probably do nothing.  The diodes in either case have leakage current (they are never 100% off in either direction), which could be as much as a very weak rf signal...check your diode specs.  Schottky diodes have higher leakage. Leakage also varies greatly with temperature.  Glass diodes can pick up light too, which could skew circuit operation: (or perhaps harvest more energy).

 

https://www.eevblog.com/forum/projects/glass-diode-photoelectric-effect/

When in the dark remember-the future looks brighter than ever.

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Are you rectifying the RF first? What chip are you using? What did you use for your test?

 

If the RF is going directly into the converter chip, a zener is not the best choice because of its high capacitance.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Zener diodes are more like regular diode's than you think.

In forward direction they conduct with a voltage drop of around 600mV just like a regular diode.

If you connect it in "Reverse" it starts conducting at the the specified voltage.

 

(For zender diodes above about 6V this is the "avalanche" effect, and not "Zener" although all such diodes are called "zener" diodes).

P.S: Look up some tutorial. Maybe wikipedia or some more specialized electronics tutorials website.

 

Or just measure it witha a power supply (9V battery?) and a series diode. Use a breadboard or whatever.

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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Don't forget the series resistor!

 

Zeners have a current and a power limit just like other components.

 

JC

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Don't forget the series resistor!

 

Zeners have a current and a power limit just like other components.

But:

I am using RF power.

So unless he's parked in front of a ATC radar dome, he can probably skip the resistor ;-)

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