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Topic: How to use boost converters in sleep mode (Read 308 times) previous topic - next topic

JCSB

Hi,
I use my uCs in sleep mode in my projects, going down to a few uA consumption. Sometimes I want to add a boost converter so I can power it with a single cell, or use it with an application that requires constant voltage. But a boost converter wastes power, i can go up to 2-3 mA in sleep mode, depending on Vin and Vout (I normally want to boost a lipo to 5v or 1 AA to 3.3 or 5v). I have been using 34063. How do professional designers conveniently boost their circuit so that sleep mode remains in the uA range?? I want to make ultra lowpower with regulated voltage yet I cant find a way to minimize power losses! Thanks a lot!

jremington

Quote
How do professional designers conveniently boost their circuit so that sleep mode remains in the uA range?
What makes you think this is the case?

Most likely, your application does not require a boost converter. If it does, please supply the details so that people can make informed comments.

srnet

How do professional designers conveniently boost their circuit so that sleep mode remains in the uA range??#
Can you point to some examples;

Where a device uses a 1.2V Alkaline battery with boost converter, and has a sleep current of a few uA ?
http://www.50dollarsat.info/
http://www.loratracker.uk/

JCSB

What makes you think this is the case?
Maybe laptops in sleep mode? I guess there are regulators in sleep mode (but maybe the circuit responsible for wake ups during sleep is not boosted. I do not know). I didnt have anything in mind but I was convinced it was possible. Looks like not!
Quote
Most likely, your application does not require a boost converter. If it does, please supply the details so that people can make informed comments.
I could have a voltage divider reading different voltages for a few buttons (tact switches). Theoretically, the voltage divider keeps the same voltage ratios for all the buttons, but the final voltage my microcontroller is reading is not the same as the voltage drops, right? And end up lower than the expected Voltage range with very low voltages.
Also, can the voltage affect frequency and therefore affect internal clock speed of your uC? (Im sorry I didnt find any nice answer to this online)
Thanks a lot for your time!

jremington

#4
Mar 24, 2019, 01:37 am Last Edit: Mar 24, 2019, 01:42 am by jremington
The ADC is ratiometric, which means that the representation that it outputs is the ratio of the input voltage to the ADC reference voltage. So, if you power a voltage divider with Vcc, and also use it as the ADC reference voltage the result does not depend on Vcc.

Quote
Also, can the voltage affect frequency and therefore affect internal clock speed of your uC?
Usually not significantly, especially if you use a crystal. These data are available in the processor data sheet -- see graph below for data on the internal, calibrated RC 8 MHz oscillator.

The ATmega used in the standard Arduino works down to 1.8V, but the clock speed needs to be lowered to 8 MHz if the voltage is less than about 4V.

Most people use about 3V (2xAA, 2xAAA, CR2032, 1xLiPo) for low power operation, sometimes for years without battery change. This is covered in Nick Gammon's excellent tutorial on low power operation.


6v6gt

If you require a constant voltage for a low power application which spends time sleeping, you can power the MCU with a 3 volt source (batteries) and get the MCU to switch on the boost converter when it wakes up or as needed.
If it a low power application, you do not want a voltage divider between Vcc and ground (even one with high value resistances). Maybe post a schematic so it is clear what you are doing.

JCSB

Can you point to some examples;

Where a device uses a 1.2V Alkaline battery with boost converter, and has a sleep current of a few uA ?

I believe the Attiny43u has an internal boost reg and can have a vvery low output current. I thought it could be possible to do the same outside of a single IC someway?

The ADC is ratiometric, which means that the representation that it outputs is the ratio of the input voltage to the ADC reference voltage. So, if you power a voltage divider with Vcc, and also use it as the ADC reference voltage the result does not depend on Vcc.

Do you have any link to explainations/tutorial on how to do this (use it as the adc ref voltage)? I do not power the v divider with vcc though, i use an interrupt digital pin to do it so i can wake the uC when pressing any button. Thank you for your answers. They are always very helpful and complete

surveyranger

#7
Mar 24, 2019, 05:49 am Last Edit: Mar 24, 2019, 05:50 am by surveyranger
They are always very helpful and complete
Your thread is not complete.  It's lacking a diagram of the setup (real or imagined), the type of uC(s), and code.  

Even something crude like a pencil drawing is helpful.


JCSB

I believe the Attiny43u has an internal boost reg and can have a vvery low output current. I thought it could be possible to do the same outside of a single IC someway?

Do you have any link to explainations/tutorial on how to do this (use it as the adc ref voltage)? I do not power the v divider with vcc though, i use an interrupt digital pin to do it so i can wake the uC when pressing any button. Thank you for your answers. They are always very helpful and complete
Your thread is not complete.  It's lacking a diagram of the setup (real or imagined), the type of uC(s), and code. 

Even something crude like a pencil drawing is helpful.


Thanks! I am often using attiny85. I do not have any particular code or schematic, im looking for one that can help me have a low consumption while boosting the voltage (the regulator is undefined too, but I have some 34063s)

surveyranger

Most people use about 3V (2xAA, 2xAAA, CR2032, 1xLiPo) for low power operation, sometimes for years without battery change. This is covered in Nick Gammon's excellent tutorial on low power operation.
jremington linked to a great tutorial by Nick Gammon on reducing power consumption for ATMega328P & the ATTiny85.

I usually use the Digispark ATTiny85s (or clones) in my simple projects...that I seem to make ultra complicated.  A couple other articles I have saved for low power operations are:

Technoblogy ATTiny Low Power

Sleep Modes on ATTiny85


Definitely read up on using a transistor as a switch controlled by the ATTiny or Arduino.

Lastly, please DON'T use my drawing for anything other than a general layout.  It is filled with errors and probably wouldn't work, but it does depict using transistors as a switch.

JCSB

jremington linked to a great tutorial by Nick Gammon on reducing power consumption for ATMega328P & the ATTiny85.

I usually use the Digispark ATTiny85s (or clones) in my simple projects...that I seem to make ultra complicated.  A couple other articles I have saved for low power operations are:

Technoblogy ATTiny Low Power

Sleep Modes on ATTiny85


Definitely read up on using a transistor as a switch controlled by the ATTiny or Arduino.

Lastly, please DON'T use my drawing for anything other than a general layout.  It is filled with errors and probably wouldn't work, but it does depict using transistors as a switch.
Thanks! However I am pretty at ease with sleep functions. I am rather looking for a way to build a boost circuit that minimally increases the consumption while sleeping, similar to the internal attiny43u boost circuit

Southpark

#11
Mar 25, 2019, 04:42 am Last Edit: Mar 25, 2019, 04:46 am by Southpark
Sometimes I want to add a boost converter so I can power it with a single cell, or use it with an application that requires constant voltage.
A boost converter is a step-up-voltage switching power supply (converter), right? So does this mean you want to use a step-up switching power supply for powering your sleeping device?

edmcguirk

Sorry if this is a noob stupid answer but what is the voltage requirement for a sleeping processor? Can you turn off the boost and run the sleeping processor at reduced voltage and turn the boost back on when the processor wakes up?

srnet

Sorry if this is a noob stupid answer but what is the voltage requirement for a sleeping processor?
See post #4
http://www.50dollarsat.info/
http://www.loratracker.uk/

srnet

I believe the Attiny43u has an internal boost reg and can have a vvery low output current. I thought it could be possible to do the same outside of a single IC someway?
Yes, that is a possible mechanism for doing it.

I cant recall a microcontroller based product using a single Alakaline cell, which makes me think there must be a good reason why designers choose not to use a single cell setup.

A great products use 2 Alkaline cells of course.
http://www.50dollarsat.info/
http://www.loratracker.uk/

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