TNY268G

TNY268G is an integrated power management and optimization IC by Power Integrations designed to provide effective power supply solutions for electronic applications. It is available in SOP-8, TSSOP-14, and SO-14 package options. The TNY268G is a part of one of Power Integrations’ popular Tiny Switch family and represents the 4th generation of secondary side switchers. It has many features like output voltage adjustment and constant on time regulation, making it suitable in various switching power supply applications.

Application fields

The most popular application of the TNY268G is as an AC/DC offline switcher. It is typically used in AC/DC power supply designs with output DC voltages ranging from 8V to 50V. As this IC can meet the requirements of many off line AC/DC applications and provides superior performance compared to conventional switchers, it is widely used in many commercial and industrial applications,such as video devices for security surveillance, LED drivers for TV, notebook computers, desktop computers, exhaust fans, low voltage power adapter, three-phase UPS system, medium and low voltage industrial equipment, washing machines and charge controllers, to name a few.

Working Principle

The TNY268G is generally used to regulate an AC/DC power supply. Its basic function is to take the line AC voltage and convert it into regulated DC voltage. This is achieved by first the rectifying the line AC voltage through an internal Bridge rectifier and then regulating and controlling the output voltage with the help of Pulse Width Modulation (PWM) control.The IC has various internal circuits like the oscillator, current sense amplifier and driver stage, which are used to control the switching behavior of the power MOSFET.

The internal oscillator is used to generate the main switching frequency which can be programmed from 35khz to 135khz. As the frequency increases, the size of the external components can be reduced for more efficient and compact system designs. The current sense amplifier monitors the power delivered to the output and protects against over current conditions by generating an internal shut down signal. The driver stage charges the external MOSFET to turn it on and off, thus controlling the output voltage.

The voltage at the output is regulated by controlling the duty cycle of the PWM signal. As demand for current increases, the duty cycle is increased automatically and when the demand is reduced, the duty cycle is decreased. This process results in a constant output voltage despite varying load conditions.

The output voltage can be adjusted with the help of a simple, low cost external voltage divider. By connecting a zener diode and resistor between VDD pin and DF pin. The DF pin is used to set the voltage level at the output. The voltage range adjustment range of the TNY268G is 2.3V to VDD.

Apart from these features, the TNY268G also has an in-line power multiplexer for increased system reliability and an internal Under Voltage Lockout (UVLO) circuit for start up control.