When you are working with battery depending low power-consuming circuits, then you may need this innovative power switch. The concept is to save energy while the device is not operating but the battery is connected.
Why we need to save energy
We use electricity almost all the time. In some cases, it comes from the common home power line or from a battery, or from any other sources. But when you are using some kind of device only on a battery, then you may try to save energy to run that device longer time.
But, when you are making some kind of device that needs to last a couple of days even weeks, or even months on only on a battery and also, the battery power is not so much, then you must think about low energy consuming circuits that can save energy while the device is in standby mode.
For an example, you want to make a GPS tracking device that has a small battery, and you give this device to a customer who can use it after several months. Then, you must think about saving the battery energy while the device is off.
In those cases, the circuit I’m presenting here will help you a lot. Although there are ultra-low energy-consuming ICs, this works as a master of those.
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| Figure 1. | This is a common block based diagram, you should select the right components for the blocks according to your requirement. |
The circuit diagram of the power switch is shown in Figure 1.
Explanation
At first, when the circuit is connected to the battery, nothing will happen. Why? due to the R4 discharge resistor, the Q1 (P-Channel MOSFET) is off. Because the Q2 is not active. So the gate of Q1 will remain high. That is why Q1 will remain off. So? no current flow to the DC to DC converter block and so does the MCU.
Now, when you press the on/off switch, the N-Channel MOSFET Q2 will be turned on and so does the Q1. And whenever the Q1 is on, DC to DC converter (or regulator) will be on.
Now, you are getting your required power to start the microcontroller. And in the code, just set a pin high through which, you can turn on the MOSFET Q2.
If you can put this code on the starting, the MCU will hold the power line. So, if you release the on/off switch now, your circuit will be still on. And at any moment, you need to turn it off, simply push that button again and sense it with another pin of your MCU.
Then, set your code for shutting down. Do all the necessary tasks before shutdown and then simply set Low to that pin which was triggering Q2 through D1.
Advantage
There are some advantages of this configuration.
- Ultra Energy-saving is possible
- Smart power on/off algorithm
- MCU can shut itself down if required
- Integration of other controls that can activate the system is possible.
Conclusion
The circuit can be different for your purpose. But you can use the concept. So, you should calculate and set the values according to your requirement.
