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.

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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.

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 - 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.

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

You can download the files for free from a direct link in the Download option below.

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

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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.

Component List

Files to download, Direct Link:

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• 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.

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• VP = VAC * √(2)

• VP = 110 *1.414
• VP = 155.54VAC

• VP = 220V * 1.414
• VP = 311,08VAC
  
  

• V = R * I

• R = (VS - VL) / I 

• R = (155,54 - 3.2) / 0.02
• R = 152,34 / 0.02
• R = 7.617R

• 7.617Ω + 40% = 3.047Ω
• 7.617Ω + 3.047Ω = 10.6638Ω or 10.66KΩ
• That is, the value of the closest commercial resistor, knowing that we always take the closest one with the highest value is 12KΩ.

Project Finished - Circuit 1

• It is a Simple and easy circuit to assemble
• Only 2 components

• Voltage dissipation will be on the resistor (Joule effect)
• Consumption higher than necessary
• Circuit operating in half wave, LED half off 
• Short LED lifetime, reverse voltage on LED
• Low Efficiency

This model is still quite simple, it is a circuit widely used also in cheaper electrical extensions of those Chinese products... 

The circuit presented has a resistor R1, which limits the current that passes through the LED, and a Diode, which polarizes the AC voltage coming from the power grid, which is connected in series with the LED, as we can see in Circuit 2.1 in Figure 4 below. .

We also have Circuit 2.2, which is the same circuit, but we have added a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit. 

Fig. 4 - Wire LED in 110v or 220V Circuit 2 - ELC

We need to determine the capacitive reactance to be used, for this we will use the Ohms' Law formula, it is exactly the formula used to figure out the resistance of R1 in the previous circuits.

Remember: The V and I values are effective, so we will use the RMS voltage, not the VPP voltage. 

Applying the formula to our circuit:

• C = 1 / (2 π  * F * XC) 

This model is a more complete and improved circuit, because it brings with it a diode bridge, improving efficiency even more, since the LED will no longer work for half a wave period, but for a full wave period.

This circuit is widely used in small luminaires, even in LED lamps, rechargeable flashlights, or in commercial products. 

This circuit is the junction of circuits 3 and 4, thus forming an efficient circuit, with good LED brightness, with full wave, it is almost the perfect circuit. 

The circuit presented has a diode bridge, which polarizes the AC voltage coming from the mains, which is connected in series with the LED, as we can see in Circuit 5.1 in Figure 7 below.

We also have Circuit 5.2, which is the same circuit, but we add a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit.

Fig. 7 - Wire LED in 110v or 220V Circuit 5 - ELC

This model is more complete and, like the previous circuit, is more efficient. This circuit is widely used in small light fixtures, some LED lamps, rechargeable flashlights, and in some commercial products. 

The circuit presented is identical to circuit 5, with the only difference that we put a resistor R1, that serve to limit the capacitor inrush current. A diode bridge, which polarizes the AC voltage coming from the mains, which is connected in series with the LED, as we can see in Circuit 6.1 in Figure 8 below.

We also have Circuit 6.2, which is the same circuit, but we have added a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit.

Fig. 8 - Wire LED in 110v or 220V Circuit 6 - ELC

• V = R * I

• R = (VS - VL) / I 
• VS = Mains voltage, which is 110Vac
• VL = Voltage of the LED, which is 3.2V
• IL = Inrush current, which is 0.1A or 100mA

• R = (110 - 3.2) / 0.100
• R = 106 / 0.100
• R = 1,068Ω or ~1KΩ

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

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The circuit operation is quite simple, and its operation is applied with an artifice that we did to join two adjustable power sources into one.

Since we don't have "as far as I know", a regulator of the same negative line, like what happens with the regulators LM317, LM7812 and etc.

The bridges of diodes KBPC5010 D1 and D4, are responsible for rectifying the circuit, this diode bridge is able to support currents up to 50A. 

I know it's an exaggeration, but it was what I had here, you can be putting with lower current, as the KBPC1510, for 15A, or the KBPC1010 for 10A.

The capacitors C1 and C3, are electrolytic capacitors responsible for filtering the circuit, we use them of 10,000uF, but if you don't have one you can put one of 8,000uF. Remembering that they have to be able to avoid Ripple in the power supply.

The resistors R1 and R3 are the limiters for LED1 and LED2, which are used as voltage signaling for the two sources.

The voltage that comes already rectified and filtered enters the Positive Voltage Regulators, as we can see in the circuit, they are identical circuits, and through the double potentiometer the output voltage regulation is done, ranging from 1.5V to 28V.

The diodes D2, D3, D5, and D6, are for reverse voltage protection that can arise from the circuit and damage the Regulators, and the diodes protect these voltages in the regulators.

The resistors R2 and R4, are responsible for the Feedback voltage, or feedback, they keep the output voltage stable, they are resistors that if you have conditions, put the ones with low error percentage, such as precision resistors with 1%.

And finally, the capacitors C2 and C4, are for spurious filter, if you can afford it, it is preferable tantalum capacitors. 

The Power Transformer

The transformer must be symmetrical with center tape open, this means that it will to have two independent winding: "2 Wire + 2 Wire", as illustrated in Figure 4 below. 

Fig. 4 - Symmetrical Transformer with Independent secondary winding

The transformer must be able to supply 8A at the symmetrical output. The primary voltage, “input voltage”, must correspond to the voltage in your area; 110V or 220Vac. 

The secondary voltage, “output voltage”, should be 21Vac in each coil, because after rectification it will supply the circuit with 30Vdc.

Component List

• Semiconductors
• U1, U2 .................. LT1083 Voltage Regulator  
• D1, D4 .................. KBPC5010 - 50A Rectifier Bridge *See Text
• D2, D3, D5, D6 .... 1N4007 Diode Rectifier 
• LED1, LED2 ........ Light Emitter Diode (General Use)
  
  
• Resistors
• R1, R3 ....... 2K7Ω 1/8w Resistor (red, violet, red, gold) 
• R2, R4 ....... 120Ω 1/8w Resistor (brown, red, brown, gold) 
• RP1 ........... 5KΩ Double Potentiometer 
  
  
• Capacitors
• C1, C3 ........ 10.000uF - 45V Electrolytic capacitor 
• C2, C4 ........ 10uF - 45V Electrolytic capacitor 
  
  
• Miscellanies
• P1, P2 ........ Connector 2 screw terminal 5mm 2 Pins
• P3 .............. Connector 3 screw terminal 5mm 3 Pins
• Others ....... Wires, Power Transformer, Solders, pcb, heat sink, etc.

Printed Circuit Board - Download

We provide the files with the PCB, the schematic, the PDF, GERBER and JPG, PNG and provide a direct link for free download and a direct link, "MEGA".

Fig. 5 - PCB - 1.5V to 28V, 7.5 Amps Adjustable Symmetric Power Supply using IC LT1083

Click on the direct link to download the files: Layout PCB, PDF, GERBER, JPG

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.

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My Best Regards!!!