TNY278GN Product Overview & Efficiency

The TNY278GN is a high-performance offline switcher IC from the TinySwitch-III family by Power Integrations. It integrates a 700V power MOSFET, oscillator, high-voltage switched current source, and thermal shutdown into a single monolithic device. Designed for AC-DC conversion, it is widely used in DVD/PVRs, standby power supplies, and industrial controls due to its ON/OFF control scheme, which offers constant efficiency down to very light loads.

Technical Specifications & Pinout Configuration

The TNY278GN is typically available in the SMD-8C (GN package), which is surface-mount compatible.

• Drain Voltage Rating ($V_{DSS}$): 700V

• Output Power (Adapter/Open Frame): 15W / 28W (at 230VAC)

• Frequency: 132 kHz (Jittered to reduce EMI)

• Operating Temperature: -40°C to 150°C

• Package: SMD-8C (G-Package)

Key Features & Protection

• EcoSmart Technology: Extremely energy efficient, easily meeting global energy standards like Energy Star.

• Enhanced Flexibility: Selectable current limit allows designers to optimize for efficiency or power delivery.

• Comprehensive Protection: Includes auto-restart for short-circuits, open-loop protection, and hysteretic thermal shutdown.

FAQ

Q1: What is the TNY278GN used for in power supply design? 

A: The TNY278GN is an off-line switcher used to design high-efficiency AC-DC flyback power supplies. It is ideal for applications requiring up to 28W of power, such as chargers, standby supplies for PCs/TVs, and industrial appliances.

Q2: What are the differences between TNY278GN and TNY278PN? 

A: The main difference is the package type. TNY278GN is in a surface-mount (SMD-8C) package, while TNY278PN is in a through-hole (DIP-8C) package. Electrically, their performance is identical.

Q3: Does the TNY278GN require a bias winding on the transformer? 

A: No. One of the major advantages of the TinySwitch-III family is that it is self-biased, which eliminates the need for a bias winding on the transformer, simplifying the design and reducing cost.

Q4: What is the maximum output power of the TNY278GN? 

A: In an open-frame design with a 230VAC input, the TNY278GN can deliver up to 28W. For a universal input (85-265VAC), the peak power is typically around 15W in an adapter configuration.

Q5: How does the TNY278GN reduce EMI? 

A: The TNY278GN uses a frequency jittering feature. By slightly modulating the 132 kHz switching frequency, it spreads the energy of the harmonic peaks, significantly reducing the cost and complexity of EMI filtering.

Q6: What is a suitable TNY278GN equivalent or replacement? 

A: The TNY278 is part of a scalable family. You can often use the TNY279 or TNY280 as a higher-power replacement. For cross-brand equivalents, designers sometimes look at the Fairchild (Onsemi) FSL series, but layout changes are usually required.

Q7: What does the "-TL" suffix in TNY278GN-TL mean? 

A: The -TL suffix indicates that the product is supplied in "Tape and Reel" packaging, which is standard for automated SMT (Surface Mount Technology) assembly lines.

Q8: How does the ON/OFF control in TinySwitch-III work? 

A: Unlike traditional PWM controllers, the TNY278GN uses ON/OFF control to regulate the output voltage. It skips switching cycles based on the feedback pin, which maintains high efficiency even at very light loads.

Q9: What causes the TNY278GN to enter Auto-Restart mode? 

A: The IC enters auto-restart if the feedback loop is broken or if a short-circuit occurs at the output. It will periodically attempt to restart until the fault is cleared, protecting the device and the load.

Q10: Is the TNY278GN compliant with Energy Star standards? 

A: Yes. Its EcoSmart technology ensures that standby power consumption is well below the 150mW or 300mW limits required by international energy efficiency standards.

Q11: What is the function of the BP/M pin on the TNY278GN? 

A: The BP/M (Bypass/Multi-function) pin is used for the connection of an external bypass capacitor. The value of this capacitor (0.1µF to 10µF) also determines the current limit of the internal MOSFET.