Hi. From the diagram shown here, I am trying to provide an alternative power supply for my esp-12E using lipo 3.7V battery. But i noticed that after adding the 3.3V regulator to the design my voltage comes down to 2.8 which is not enough supply for my esp12. again i know that the circuit is not a good practice for the lipo battery. Can anyone help me out with a standard way of doing this so that i van use my esp8266 while charging the lipo battery as it is in the mobile phone. Thank you.

 

Hi. From the diagram shown here, I am trying to provide an alternative power supply for my esp-12E using lipo 3.7V battery. But i noticed that after adding the 3.3V regulator to the design my voltage comes down to 2.8 which is not enough supply for my esp12. again i know that the circuit is not a good practice for the lipo battery. Can anyone help me out with a standard way of doing this so that i van use my esp8266 while charging the lipo battery as it is in the mobile phone. Thank you.

Which 3.3V regulator are you using ?

Have you tried Microchip MCP1802T-33 ? It is specifically made for battery power devices.

What is your current requirement ? If less than 300 mA then use the regulator which I mentioned.

 

ok. Thank you so much

 

If your battery is 3.7V, you can not charge it with 3.3V.

 

If your battery is 3.7V, you can not charge it with 3.3V.

He wants a good 3.3V regulator to get 3.3V from 3.7V Li-Po Battery for ESP8266 (3.3V device).

 

Aha ok, I thought he wants to charge it and use at the same time with 3.3V. Its not the best option to use a regulator. There are much easier ways. Even with 1 resistor it will work.

 

Aha ok, I thought he wants to charge it and use at the same time with 3.3V. Its not the best option to use a regulator. There are much easier ways. Even with 1 resistor it will work.

Yes, He also wants to charge the battery but that is a different circuit and not the question of this thread.

 

The easiest way with a regulator is to regulate the voltage with a maximum current that can change based on the load. The regulator will be before the battery to charge it with a stable voltage and varying current and after the batter you put 1 resistor and 1 zener in order to limit the current further and stabilize the voltage. That way there will always be charging current for the battery and working current for the rest of the circuit. Or you could just put a zenere after the battery and use the rest of the circuit as the resistor, but the current will be limited only by the regulator and when the circuit after the zener is off, the whole current will go to the battery.

 

The easiest way with a regulator is to regulate the voltage with a maximum current that can change based on the load. The regulator will be before the battery to charge it with a stable voltage and varying current and after the batter you put 1 resistor and 1 zener in order to limit the current further and stabilize the voltage. That way there will always be charging current for the battery and working current for the rest of the circuit. Or you could just put a zenere after the battery and use the rest of the circuit as the resistor, but the current will be limited only by the regulator and when the circuit after the zener is off, the whole current will go to the battery.

If you use 3.3V zener then when 3.7V Li-Po battery is charging the battery terminal voltage will be 4.3V and this will make the zener to conduct in breakdown region and battery will not charge.

 

Why would it be 4.3V? The zener will stabilize the voltage after it at 3.3V, the voltage on the line under the zener will be 2.7V.

 

Here is a quick circuit, not the full device, but you get the idea.

 

Here is a quick circuit, not the full device, but you get the idea.

Why battery is connected in reverse ?

 

Sorry, I just put the elements for a quick example, I didnt mean to connect it in reverse . This is what happens when you do 50 times at the same time (in modern day world called "multitasking").

 

Sorry, I just put the elements for a quick example, I didnt mean to connect it in reverse . This is what happens when you do 50 times at the same time (in modern day world called "multitasking").

According to my understanding of zener diode working if you take 3.3V zener diode as example and then apply 4.3V or even 3.7V accross it then the breakdown occurs at 3.3V and zener starts conducting heavily. All the current flows through zener but voltage across zener is maintained at 3.3V. So, no current will be available for ESP8266.

Am I correct ? Maybe I have forgotten the basics.

 

According to my understanding of zener diode working if you take 3.3V zener diode as example and then apply 4.3V or even 3.7V accross it then the breakdown occurs at 3.3V and zener starts conducting heavily. All the current flows through zener but voltage across zener is maintained at 3.3V. So, no current will be available for ESP8266.

Am I correct ? Maybe I have forgotten the basics.

See this video which I made but zener model is not working. Proteus bug. Anything above 3.3V should be clamped at 3.3V and load current will be zero.

 

The current will be divided according to Kirhov's law of currents. In 1 node all currents summed equal zero. To limit the current flowing through the diode you can put a resistor after it. The diode will consume "0.6V", so the resistor should be "(3.3V-0.6V)/diode current". The current depends on the diode. The rest of the current should go towards the load. I will simulate it on proteus and show you a graph.

 

The current will be divided according to Kirhov's law of currents. In 1 node all currents summed equal zero. To limit the current flowing through the diode you can put a resistor after it. The diode will consume "0.6V", so the resistor should be "(3.3V-0.6V)/diode current". The current depends on the diode. The rest of the current should go towards the load. I will simulate it on proteus and show you a graph.

Ok.

I know I have to put a series resistor in zener circuit to limit the zener current. I was just testing the zener diode working in Proteus but using a 3.3V model it doesn't clamp the o/p voltage at 3.3V if i/p is > 3.3V.

 

Put ground if you forgot and put a resistor to take the "0.3V" drop and limit the current. After this you will need a transistor.

 

Put ground if you forgot and put a resistor to take the "0.3V" drop and limit the current. After this you will need a transistor.

Ok. I tried and it works but have to confirm this on hardware. I used 60R resistor in series with zener.

 

This is not the whole circuit. After you add the transistor then you will get what you need. Plus it might be good to do the following circuit.