Part Number: TNY286DG

Manufacturer: Power Integrations


Shipped from: Shenzhen/HK Warehouse

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TNY286DG-TL Introduction

The TNY286DG plays a crucial role in power conversion applications, specifically as an offline flyback topology converter. This device is capable of operating within a frequency range of 124 kHz to 140 kHz, which makes it highly suitable for efficient power conversion systems. The SO-8C package is designed to be compact, with eight pins that allow for efficient use of space and seamless integration into various systems.

TNY286DG-TL Operating Principle

The flyback topology is a commonly employed method in offline power conversion applications due to its benefits, including isolation and simplicity. The TNY286DG efficiently converts the input voltage to the desired output voltage using this topology.

During the “on” time of the switching transistor in a flyback converter, energy is stored in the transformer. Once the transistor turns off, the energy that is stored in the transformer gets transferred to the output by means of a diode. The transfer of energy takes place during the flyback period, which is why it is referred to as the “flyback” topology.

The TNY286DG functions as a flyback converter by regulating the switching transistor according to the feedback obtained from the output voltage. The output voltage is regulated by adjusting the duty cycle of the switching transistor. This controls the transfer of energy from the input to the output.

The TNY286DG has a frequency range of 124 kHz to 140 kHz and is designed to optimize power conversion efficiency while minimizing the need for external components. Higher operating frequencies enable the use of smaller transformers and output capacitors, leading to a decrease in the overall size and cost of the system. Moreover, the broad frequency range offers versatility in designing the converter to fulfill particular application needs.

The TNY286DG is designed to provide efficient energy conversion, a compact design, and cost-effective power solutions for offline applications. It utilizes the flyback topology and operates within the frequency range of 124 kHz to 140 kHz. Electronic systems.

TinySwitch-4 Design Considerations

Overvoltage protection is a safety feature that prevents electrical devices from being damaged by excessive voltage. TinySwitch-4 incorporates an internal latch to trigger the output overvoltage protection. This latch is activated by a threshold current of around 5.5 mA into the BYPASS/MULTI-FUNCTIONAL pin. The BYPASS/MULTI-FUNCTIONAL pin capacitor serves as an external filter in addition to the internal filter to provide noise immunity and prevent inadvertent triggering. In order for the bypass capacitor to function effectively as a high-frequency filter, it is recommended that the capacitor be positioned in close proximity to both the SOURCE and BYPASS/MULTI-FUNCTIONAL pins of the device.

A winding voltage with a relatively high bias is utilized, typically ranging from 15 V to 30 V. By minimizing the error voltage on the bias winding caused by leakage inductance, this approach guarantees sufficient voltage during no-load operation to power the BYPASS/MULTI-FUNCTIONAL pin, resulting in reduced no-load consumption.

For most designs, it is recommended to choose a Zener diode voltage that is around 6 V higher than the bias winding voltage (which is 28 V for a 22 V bias winding) to achieve optimal OVP performance. However, it is possible to make adjustments to this voltage to account for any variations in leakage inductance. You can improve the filtering process by putting a low-value resistor in series with the bias winding diode and the OVP Zener. The value of this resistor should be between 10 W and 47 W.

This is demonstrated in Figure 16 by R7 and R3. The resistor that is connected in series with the OVP Zener serves the purpose of limiting the maximum current that flows into the BYPASS/MULTI-FUNCTIONAL pin.

● Audible Noise

TinySwitch-4 utilizes a cycle-skipping mode of operation that has the potential to produce audio frequency components in the transformer. In order to minimize the amount of audible noise produced, it is recommended that the transformer be designed with a peak core flux density of no more than 3000 Gauss (300 mT). By following this guideline and utilizing the standard transformer production technique of dip varnishing, it is possible to effectively eliminate audible noise. It is not recommended to use vacuum impregnation for transformers because it can lead to high primary capacitance and increased losses.

Although higher flux densities can be achieved, it is important to thoroughly assess the audible noise performance by utilizing production transformer samples prior to approving the design. When utilized in clamp circuits, ceramic capacitors that employ dielectrics like Z5U may produce audio noise. If you encounter this issue, consider replacing the capacitors with ones that have a different dielectric or construction, such as a film-type capacitor.

● Primary Clamp Circuit

A clamp is utilized to restrict the peak voltage on the DRAIN pin during turn-off. One way to achieve this is by using either an RCD clamp or a Zener (200 V) and diode clamp across the primary winding. In order to reduce electromagnetic interference (EMI), it is recommended to minimize the loop between the clamp components and the transformer and TinySwitch-4.

● Thermal Considerations

The SOURCE pins of the IC are internally connected to the lead frame and serve as the primary pathway for dissipating heat from the device. It is recommended to connect all the SOURCE pins to a copper area beneath the TinySwitch-4. This will serve as both a single-point ground and a heat sink. Since this area is linked to the quiet source node, it is important to optimize it for effective heat dissipation. To maximize the PCB area connected to the cathode, follow the same approach for axial output diodes.

● Y Capacitor

The Y capacitor should be placed directly from the positive terminal of the primary input filter capacitor to the common or return terminal of the secondary transformer. This placement will divert common-mode surge currents of high magnitude away from the TinySwitch-4 device. Note: When using an input π (C, L, C) EMI filter, it is recommended to place the inductor in the filter between the negative terminals of the input filter capacitors.

● Optocoupler

Place the optocoupler close to the TinySwitch-4 so that the primary-side trace lengths are as short as possible. Keep the high-voltage drain and clamp lines away from the optocoupler to keep it from picking up noise.

● Output Diode

To achieve optimal performance, it is recommended to minimize the area of the loop that connects the secondary winding, output diode, and output filter capacitor. Also, there should be enough copper at the anode and cathode ends of the diode to get rid of heat. At the quiet cathode port, it’s better to have a bigger space. EMI at high frequencies can be made worse by a large anode area.


The TNY286DG is an affordable and versatile solution for power conversion needs. It features an integrated offline flyback topology, a wide frequency range, a compact package, and input voltage flexibility, making it an attractive option for achieving optimal performance while minimizing system costs. By utilizing the TNY286DG, designers can create efficient and cost-effective power supply solutions for a variety of applications.

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