Deep dive into the space of Electronics -Part 4

Are you aware of what are electronic gadgets and how are they powered up?

Adhish Velingkar
12 min readFeb 27, 2022
Retro Gadgets

Supposed, if I would split the terms separately then ‘electronic’ would be defined as — a combination of circuits, transistors, microchips, and the behaviour and flow of electrons covered by an area of science and technology. It uses basic approaches to handle electric circuits with active and passive elements. And ‘gadgets’ in simpler terms can be defined as an item or a product that can make one’s life easier and less stressful. For example, before the invention of the telephone or email, sending letters or messages to reach its place would take so many days. (PS: For those who have watched the anime ‘Doraemon’ can relate to this term more closely).

In short, all gadgets are electronically streamlined as applications that make our work so easy.

In earlier days, there were telephones, where one needed to sit in one place and talk, but now with smartphones, one can travel around and talk wherever. Moreover, with the innovations of electronic devices such as cameras or webcams, living away from family or friends is no more unpleasant.

These mobile-video calling devices have made human accessibility so relaxed to make far-off things easily available to us. Today, we are using various types of electronic gadgets extending from the washing machine, electric chimney, simply the television, to the instruments that have invaded every part of our regular life, have proved to be so useful and indispensable.

I got my first ever mobile phone(Sony Xperia M) in 2014, almost 8 years back and growing up as a 90s kid, I never thought that these devices one day will become an eternal part of my life. For example, nowadays I cannot imagine myself in a gym without portable music players or a smartwatch.

Statistical View

Back in time when I was studying in high school, there were not many portable devices available in the market and it was said that by 2020 — electronic devices will be more than an individual person and I can see that happening at the current stage where I personally own 4–5 devices!!

Well, here is an article from ‘The Indian Express’ dated in 2012 which discusses the mobile market for your reference.

It is obvious that since these devices are portable so they need to be given power in terms of electronic measures on a periodic basis as per the application. Be it a mobile phone, tablet, wireless earphones or laptop.

There are many times when we decide to go out for travelling and at that time such devices are very helpful when there is no electricity available around. But these devices are useful only till they last long for a sufficient amount of time, otherwise, if the battery drains away or you have left the home without charging the device then the device won’t be of any use.

Owing to this let’s discuss the topic for today which is based on the power supply to the electronic devices in our daily life.

Portable USB Chargers — Rechargeable

In order to know about portable chargers, I believe it is necessary to know at least some basic concepts of non-rechargeable batteries and their application usage.

For that let's rewind to high school science!!!

Schematic of Disposable Battery

Non-Rechargeable/Disposable Batteries:

It consists of two electrodes called the cathode and the anode, which are placed in electrolytes. When the electrodes are connected, chemical reactions take place at the cathode and anode.

At the anode, zinc reacts with the hydroxide ions released from the cathode, producing zinc oxide and water, and releasing electrons in the process:

Anode Reaction

At the cathode, the released electrons are combined with manganese (IV) oxide and water to produce manganese (III) oxide and hydroxide ions:

Cathode Reaction

These chemical reactions result in a flow of electrons from the anode to the cathode. The ions are continuously travelling through the electrolyte while the electrons are travelling outside the electrolyte through the wires that connect the anode and the cathode. This creates an electric current in the wire. These electrons have electrical energy, and if we connect an electric component between the electrons’ paths, the electrons can lose their energy as they go through the component.

The electrical energy that the electrons lose can be then converted into a form that is useful to us. For instance, a light bulb converts electrical energy into light energy (and thermal energy).

These batteries are called non-rechargeable because these reactions can only take place as mentioned above. Once all of the manganese (IV) oxide has been converted into manganese (III) oxide, the reactions come to a halt and the battery can no longer produce an electric current.

Manual Video Game


  • Non-rechargeable batteries are a prime choice for low drain applications such as alarm clocks or radios, remote controls, electronic keys and kid’s toys.
  • Non-rechargeable batteries can only be fully discharged once. After that, the battery cannot be charged and it cannot be used to produce an electric current. Thus, it follows an irreversible process.
  • Non-Rechargeable types: Zinc-Carbon/ZnCl /LiMnO2 /Alkaline (For more reference refer to this Wikipedia page).
  • Non-rechargeable batteries are also known as primary batteries.

Rechargeable Batteries:

Is there anything more terrible than a battery that isn’t charging? — Well, that’s what a portable charger or power bank is for!

Portable Battery with multiple USB’s

There are various types of portable charges available but according to my usage, I would like to categorise those into two types as follows:

  • Car USB charger
  • Power Bank

Let's take an example of a simple Lithium-Ion Battery that is used to power most mobile phones and laptops and understand how it works!

Li-ion Battery working

When the batteries are being used to power up devices, we say the battery is ‘discharging’. While this is happening, the -ve terminal releases lithium ions, which travel through the electrolyte to the +ve terminal. At the same time, electrons flow outside the circuit from the -ve terminal towards the +ve terminal. During ‘charging’, the battery takes energy from an external source to reverse these flows: lithium ions flow from the “positive terminal” towards the “negative terminal”, replenishing the battery’s ability to conduct current again.

Thus making it a reversible process.

The main difference between rechargeable and non-rechargeable batteries is that rechargeable batteries can be put to use again after have been fully discharged once, while non-rechargeable batteries cannot be charged again once they discharge fully.

I guess now you must be aware of the basic concepts of rechargeable batteries now let's explore the electronics associated with it as per the types mentioned above!

Inside a Charger!

1. Car USB Charger


A car USB charger is a compact adaptor that connects to the cigarette lighter/accessory port on almost all cars and delivers one or more USB outputs.

The automotive USB charger converts the nominal 12-volt output from the cigarette lighter/accessory port to the 5 volts required for the USB supply.

As a result of the various automotive electrical systems, the car 12 volt supply can vary significantly and have spikes and surges on it.

Note: The car’s cigarette lighter port is only operational when the engine is running. This is done to prevent the car battery from being unintentionally depleted by leaving high-current equipment plugged in. If you think your car cigar lighter port will deliver a clean and steady 12 VDC from the car battery, you are sadly mistaken. What you actually get is a noisy DC supply output, often with severe fluctuations, especially when the car is running. An additional input protection mechanism is very crucial inside the charger.

The car USB charger must be protected against these in order for everything attached to the USB port to be unharmed. In general, Universal Serial Bus (USB), is a common type of computer port that makes it easy to charge a device or transfer data between two devices. For more history you can refer to the below link:

There are really only four things that matter when choosing a USB:

a. Form factor — USB-A, USB-B, Mini-USB, Micro-USB, and USB-C

b. Transfer speed — USB cables are data transfer only, and others are power delivery only, but also that there are options that can handle both tasks.

c. Power delivery — PD (power delivery) standards fall into one of three main categories: power only, slow charge, and fast charge. PD also provides the necessary charge to your device but won’t overcharge it. For example10W is enough to slow charge your phone, and 18W is enough to fast charge your smartphone or power a Notebook or similar bare-bones laptops.

d. Video delivery — Instead of using a hefty HDMI or VGA connection, you may utilise USB-C to connect to monitors. For an instance, 4K video distribution to a screen is also supported by USB-C and Thunderbolt 4 connections are capable of simultaneously displaying 4K content on two monitors.

It consists of two capacitors, an inductor, an LED, a USB port, a diode and the main IC seems to be an MC34063 switching regulator.

I won’t get into describing the working of this circuitry as it is somewhat similar to the one which I demonstrated in my first article on Electric Flyswatter.

2. Power Bank


Smartphones and batteries go together like bread and jam, one depends on the other for its functions. Powerbanks are portable batteries with circuitry that regulates the amount of power coming in and going out.

A wireless battery that can both receive and provide charge is known as a power bank. A power bank must be charged in order to store energy. To charge the power bank with a wall outlet, first, use the adapter cable that came with it. The power bank can be used to charge electronic devices once the indicator light on the power bank indicates that the accessory is fully charged. The energy stored in a power bank is then transmitted to the device via a charging wire from a USB port.

The term “power bank” refers to a financial institution where money can be deposited, stored, and withdrawn as needed. These items are sometimes known as portable chargers since they can charge items such as mobile phones without needing to be connected to the mains during charging.


A mobile phone’s battery needs 5 V at 1 A or 2 A but cells inside the power bank have a maximum output voltage of 3.7 volts. Thus a boost converter boosts up the level to 5Volts which is required to charge a phone.

PCB-plus-five-battery assembly

18650 cells - which have a charge capacity of around 3000 mAh each. As a result, they’re most likely connected in parallel to match the battery pack’s total capacity of 12,000 mAh. Because 18650 cells have a 3.7V standard, voltage boost circuitry must be used elsewhere in the system architecture to meet the USB outputs’ 5V requirement.

Our mobile phone’s battery needs 5 V at 1 A or 2 A but cells inside the power bank have a maximum output voltage of 3.7 volts. Thus a boost converter boosts up the level to 5Volts which is required to charge a phone.

A Hotchip HT4906 power management IC (IC U1) is seen on the right.

U2, a Sino IC Technology SE9926 N-Channel 20V MOSFET, is to its left.

The power switch is located in the centre of the PCB. The four charge active-and-level LEDs are to their left. Two discrete transistors are located above them.

On another side of the PCB, you’ll see the micro-USB input (charging) connector, three USB output connectors, and the “flashlight” LED, among other things. Below the middle USB connector are two ON Semiconductor SS34 3A Schottky barrier rectifiers, and on the right is an ON Semiconductor SS24 Schottky rectifier diode.

Battery Type:

The two technologies that are currently used have slightly different properties:

  • Lithium-ion: Lithium-ion batteries have a higher energy density, i.e. they can store more electrical charge in a given size or volume, and are cheaper to manufacture, but they can have issues with ageing.
  • Lithium-polymer: Lithium-polymer power banks do not suffer from ageing to the same extent so are a better choice. However they are more costly to manufacture and as a result, they may not suit all budgets.

Power bank lifetime:

There are two main forms of a lifetime that are associated with power banks —

Charge-discharge cycle — Typically, a battery’s lifetime is expressed in terms of the number of charge-discharge cycles it can withstand before its performance degrades to a certain extent. Some of the less expensive power banks may only last 500 or so charge-discharge cycles, while the more expensive ones will last many more.

Self-discharge time — All battery cells, whether rechargeable has some self-discharge time. A small amount of electricity is required to keep rechargeable batteries with their own control circuitry alive these days. As a result, a battery can only be charged for a limited amount of time.

Power bank types:

The main types of USB power banks include the following:

a) Universal or standard Power Banks: These power banks are usually charged using a regular USB charger, and the state of charge is indicated on the power bank. This might be a row of miniature LED LEDs or a basic alphanumeric display that shows the percentage of full charge.

b) Solar Power Bank: As the name implies, these solar power banks can be charged using sunlight. Photovoltaic panels are used to do this. Because the solar cells are small, they can only trickle-charge the internal battery when put in sunlight. Nonetheless, this can be a highly helpful capability, but only in extremely sunny or bright settings. They can also be charged using a USB charger because solar charging is slow. Solar charging is a good backup, especially if you’re going somewhere without access to electricity.

c) Wireless Power Bank: Many gadgets, such as phones, ear-pods, and other similar devices, now have the potential to be charged wirelessly. These power banks support the Qi wireless charging standard, which is used by almost all electronic devices that can be charged wirelessly. The to-be-replaced electronic gadget is placed on the power bank; alignment is often critical.


As we studied the different battery types and their respective application area…

I would like to end this article by adding some of the references which discusses some of the factors that one should consider while buying a car USB charger and Portable charger.

Until then….

Thank You!!!



Adhish Velingkar

A novice blogger who talks about Power-Analog Electronics, EV's, Low Voltage devices, Embedded interface, Hardware-Simulation, Renewables, Electrical Designs