TNY278 Off-Line Switcher IC

TinySwitch-III TNY278 combines a high voltage power MOSFET switch with a power supply controller in one device. Unlike conventional PWM (pulse width modulator) controllers, it uses a simple ON/OFF control to regulate the output voltage. The controller consists of an oscillator, enable circuit (sense and logic), current limit state machine, 5.85 V regulator, Undervoltage, overvoltage circuit, and current limit selection circuitry, over-temperature protection, current limit circuit, leading-edge blanking, and a 700 V power MOSFET. This makes it suitable for many applications.

 

TNY278 Pinout Configuration

Pin Number	Pin Name	Pin Description
1	EN/UV	enable input and line Undervoltage sense.
2	BP/M	It is the connection point for an external bypass capacitor for the internally generated 5.85 V supply.
3	-	Pin is Removed.
4	D	This pin is the power MOSFET drain connection.
5	S	This pin is internally connected to the output MOSFET source for high voltage power return and control circuit common.
6	S	This pin is internally connected to the output MOSFET source for high voltage power return and control circuit common.
7	S	This pin is internally connected to the output MOSFET source for high voltage power return and control circuit common.
8	S	This pin is internally connected to the output MOSFET source for high voltage power return and control circuit common.

 

Features & Specifications

• Simple ON/OFF control, no loop compensation needed
• Selectable current limit through BP/M capacitor value
• Higher current limit extends peak power or, in open frame applications, maximum continuous power
• Lower current limit improves efficiency in enclosed adapters/chargers
• Allows optimum TinySwitch-III choice by swapping devices with no other circuit redesign
• Maximizes MOSFET and magnetics power delivery
• Minimizes max overload power, reducing the cost of the transformer, primary clamp & secondary components
• ON-time extension – extends low line regulation range/hold-up time to reduce input bulk capacitance
• Self-biased: no bias winding or bias components
• Frequency jittering reduces EMI filter costs
• SOURCE pins are electrically quiet for low EMI
• Accurate hysteretic thermal shutdown protection with automatic recovery eliminates the need for manual reset
• Improved auto-restart delivers <3% of maximum power in short circuit and open loop fault conditions
• Output overvoltage shutdown with optional Zener
• Line Undervoltage detect threshold set using a single optional resistor
• Very low component count enhances reliability and enables single-sided printed circuit board layout.

 

Note: Complete technical details can be found in the TNY278 Datasheet linked at the bottom of this page.

 

TNY278 Equivalents

TNY274P, TNY275P, TNY276P, TNY277P, TNY279

 

Available Packages for TNY278

DIP-8C, SMD-8C

 

How to use TNY278 Switching Converter IC

The reason behind Power Integration and their ICs popularity is that they are easy-to-use, have enormous availability of support documents, low external parts count, and reduced cost.

The example circuit above shows you how a low cost, high efficiency, flyback power supply designed for 12 V, 1 A output from universal input using the TNY278. The supply features Undervoltage lockout, primary sensed output overvoltage latching shutdown protection, high efficiency (>80%), and very low no-load consumption (<50 mW at 265 VAC). Output regulation is accomplished using a simple Zener reference and optocoupler feedback. As the TinySwitch-III devices are completely self-powered, there is no requirement for an auxiliary or bias winding on the transformer. However, by adding a bias winding, the output overvoltage protection feature can be configured, protecting the load against open feedback loop faults.

 

Applications

• Chargers/adapters for cell/cordless phones, digital cameras, portable audio, shavers
• PC Standby and other auxiliary supplies
• DVD/PVR and other low power set-top decoders
• Supplies for appliances, industrial systems, metering, etc.
• General Power Adapters
• High-Quality Audio Grade Power Supplies

 

2D Model and Dimensions

If you are designing a PCB or Perf board with this component then the following picture from the Datasheet will be useful to know its package type and dimensions.