It does not need auxiliary windings, which makes it a complete IC, with DIP8 encapsulation, with a PWM working frequency of 132kHz and a voltage of up to 700V.

We will dive into the technical specifications, design, and features of this power supply and how it compares to other similar products in the market.

⚠️ Caution!⚠️

"This circuit works directly connected to the electrical network, this is extremely dangerous, any carelessness, or wrong connections, design error, or any other occasion, can lead to irreversible damage.

We are not responsible for any type of occurrence. If you don't have enough experience, don't build this circuit, and if you build it, when testing it, be sure to have the proper protections and be accompanied by someone else."

🧷 TNY268 - Pinout and Description

The TNY268 is packaged in a DIP-8B structure for perforated pinouts and an SMD-8B package for SMD.

The package is similar to the well-known IC LM555, with the exception of pin 6 hidden in the TNY268, as we can see in the pinout of Figure 2, below.

Fig. 2 - Pinout - Pinout TNY268

🧮 We leave below the description of each pin of the TNY268 Integrated Circuit to facilitate our understanding.

The Mini Switched Power Supply Circuit with TNY268 for 5V - 24V, 3A output is a simple yet powerful design, as shown in Figure 3 below.

However, due to the involvement of electricity, it requires careful handling and at least intermediate knowledge of electronics to assemble the circuit.

Fig. 3 - Schematic Diagram Mini Switching Power Supply 5V - 25V, 3A with TNY268

The schematic diagram of the Mini Switched Power Supply Circuit is well laid out and easy to understand. It includes a TNY268 controller that regulates the output voltage and current of the power supply.

The circuit has a few essential components such as capacitors, resistors, diodes, and an inductor, which work together to provide stable and efficient power.

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🔧 Regulate The Output Voltage

The output voltage is adjusted through two parameters in the circuit:

📌 The Zener Diode

The zener diode D4, is the diode that will adjust the output voltage, we must configure it as follows,
when the desired voltage is Xv, the zener diode must have a voltage Xv - 1.

The diode should be 1V lower than the nominal voltage of the power supply, this lower voltage is due to the photocoupler being connected in series with the zener diode, and since it is an “LED” diode, we have the voltage drop on it.

💡 For example:

🌀 The Transformer

The transformer used in this circuit was a high frequency transformer, often found in PC power supplies, as illustrated in Figure 4 below, a model EE-25 Ferrite transformer.

• N = Number of Turns
• V = Desired Voltage
• C = Constant = 1.4

• V = 5V
• C = 1.4
• N = ?

• N = 5 * 1.4
• N = 7 laps

• V = 9V
• F = 1.4
• N = ?
  
  
• N = 9 * 1.4
• N = 12.6 = ~13 Rounds

• V = 12V
• F = 1.4
• N = ?
  
  
• N = 12 * 1.4
• N = 16.8 = ~17 Rounds

• V = 25V
• F = 1.4
• N = ?
  
  
• N = 25 * 1.4
• N = 35 Turns

🧮 Components list

Semiconductor

Resistor

Capacitors

Several

🖨️ Printed Circuit Board (PCB) - Download

In Figure 5 below, we are making the PCI available in GERBER, PDF and JPEG files, for those who want to create a more optimized assembly, either at home, or if you prefer, at a company that prints the board.

Fig. 5 - PCB-Mini Switching Power Supply 5V - 25V, 3A with TNY268

📥 Files to Download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

You can see the official post by clicking here! fvml.com.br

1. Protection Circuit: It comprises a 5A/250V fuse, which operates if there is a current greater than the fuse's breaking current.
   At the same time we also have an NTC (Negative Temperature Coefficient), it is a surge current limiter, this same topology can be found in most SMPS power supplies, such as notebook power supplies, PC power supplies, computer AT / ATX power supplies, etc.
   
   
2. Transient Filter: This step consists of an initial capacitive filter that inhibits high frequencies from returning to the network, or vice versa, and soon after, the EMI filter coil, which serves to attenuate high frequency noise.
   
   
3. Primary Rectification: Made up of the D1 rectifier bridge.
   
   
4. Primary Filter: Composed of capacitors C4 and C5.
   
   
5. Switching: Composed of a PWM generator, and the IRF840 power MOSFETS transistors.
   
   
6. Transformer: The transformer is a high-frequency Chopper Trafo, and it performs the isolation and high-frequency transformation of the signal generated by the PWM set and switching transistors.
   
   
7. Fast Rectification: Formed by diode D3, this is a fast and double diode, since the oscillated frequency in the circuit is quite high.
   
   
8. Output filter: Composed of inductor L2 and capacitor C9.
   

🛠️ The PWM Circuit

The power supply for the IR2153 IC comes through a 27K 5W power-limiting resistor together with the C5 capacitor. In the internal package of this IC, there is already a 15.6V Zener diode, which stabilizes this voltage, but the current is low.

So, be careful not to put the resistor R3 with a smaller resistance, as it would increase the current at the input of the IC, and the Zener could break and consequently burn the IC.

An improved solution would be to put a 15V Zener diode to ensure voltage stabilization and IC protection, which you can be doing if you wish.

If you are using the IR2153D, there is no need to use the D2 diode which is the FR107 or BA159, as this IC already has this diode internally, if it is the IR2153 “without the letter D”, leave it as it is in the schematic, “ with diode D2”.

The complete schematic diagram is displayed just below in Figure 2, both the diagram and the materials are available for download at the link below.

🧷 The Transformer

The TR1 transformer was taken from a scrap ATX power supply, the model is the IE-35A, but you can be using practically any model of ATX power supply Trafo.

There is no need to rewind the transformer, just pay attention to the Pinout that we will use for the Trafo, as shown in Figure 3 below.

The L1 inductor is the same used in the ATX power supply, we removed it and didn't make any changes, and the L2 inductor, from the output EMI filter.

You can also use the AT/ATX power supply scrap, but if you want to wind your own filter, you can wind it on a Ferrite Toroidal core.

The winding must be carried out using a Toroidal core winding, with the coil using 0.6 mm super-enamelled copper wire with 25 turns.

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🧮 Component List

📥 Files to download, Direct Link:

It is worth remembering that even with changes to the set of pairs, when the same standards are used at both ends of the cable, the results will be the same, with direct connections at their ends.

In Table 1 below, we have the configuration of the pins and their corresponding colors, following the two standards side by side for comparison.

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📌 Sequential Table of Colors and Pinning Standard T-568A and T-568B

ℹ️ Crossover Cable

Crossover cables, use the T-568A and T-568B standards at each end as illustrated in Figure 2 below. These categories of cables are used when we need to, for example, connect two computers or laptops without using a router or switch.

Fig. 2 - Connection of Crossover Cable Standards T-568A and T-568B

It is worth remembering that if you are still using older equipment, you should not connect crossover cables between the computer and a switch or router, as in some cases it can damage the equipment.

Now if you work with newer, more modern equipment, they use AUTO MDI/MDIX technology, which automatically identifies the connected interface and even if it is of the crossover type, there is no problem, as it automatically configures itself.

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• Programmable charging current up to 500mA
• No need for external MOSFET, sensing resistor, reverse diode
• Constant current or constant voltage mode operation, with thermal protection function Preset charging voltage
• Standby current is 20uA
• 2.9V slow charge voltage
• Soft start limits the inrush current
• Adopt SOT23-5 package, application line
  

🖥️ External programming of the load current:

🔌 The Circuit Schematic

In Figure 3, below, we can see the schematic diagram of the Automatic Programmable 4.2V Battery Charge, Current up to 500mA using LTH7R IC.

All circuit components are SMD, the power supply input is done by soldering on the PCB. This type of miniaturized SMD circuit is great to be implemented in circuits with small spaces.

The capacitors are SMD electrolytic, but if you have tantalum capacitors, you can put them on, it will help with the plate height, but if you can't find them, you can use electrolytic.

The charger circuit supports voltage between 4.4V to 7V, the recommended is 5V, which is great news for us to be able to charge our battery in a PC USB port or even with cell phone chargers.

Fig. 3 - Automatic Programmable 4.2V Battery Charge, Current up to 500mA using TH7R IC

🖨️ Printed Circuit Board

In Figure 4, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass.

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 4 - PCB Automatic Programmable 4.2V Battery Charge, Current up to 500mA using TH7R IC

📥 Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

👋 I hope you enjoyed it!!!

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

🙏 Subscribe to our blog!!! Click here - elcircuits.com!!!

My Best Regards!!!

You may be interested in: 

• High Output Current up to 5A
• Internal Soft-Start
• 100mΩ Internal Power MOSFET Switch 
• Internal  Compensation  Minimizes  External  Parts Count
• High Efficiency up to 90%
• 25μA Shutdown Current
• Fixed 500kHz Frequency
• Thermal Shutdown Protection
• Cycle-by-Cycle Over Current Protection
• Wide 5.5V to 32V Operating Input Range
• Adjustable Output  Voltage from 1.222V to 26V
• Available in an SOP-8 (Exposed Pad) Package
• RoHS Compliant and Halogen Free
  

⚡ Output Voltage Setting

Fig. 2 - Schematic 5A, 1.22V to 26V, 500kHz Step-Down Converter Using RT8289 IC

🖨️ Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass.

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

The PCB tracks are doubled, the main ones have their tracks on the bottom and top of the PCB as the current is 5 amps.

Fig. 3 - PCB 5A, 1.22V to 26V, 500kHz Step-Down Converter Using RT8289 IC

📥 Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

👋 I hope you enjoyed it!!!

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

🙏 Subscribe to our blog!!! Click here - elcircuits.com!!!

My Best Regards!!!