Power Integrations TinySwitch-4 off-line switcher IC family

Steve Taranovich - October 14, 2012

The TinySwitch families of products combine a high voltage power MOSFET switch with a power supply controller in one device, offering a design flexible solution with low system cost and extended power capability. Unlike conventional PWM (Pulse Width Modulator) controllers, TinySwitch uses a simple ON/OFF control to regulate the output voltage.

The TinySwitch-4 family is an energy-efficient, off-line switcher with line-compensated overload power

With line-compensated overload power protection, TinySwitch-4 devices reduce the maximum overload variation over the universal input voltage range. It is particularly helpful in applications such as PC standby and CV adapters to limit the maximum output power during the overload fault condition. TinySwitch-4 also incorporates a 725 V MOSFET that easily allows 80% de-rating for high reflected voltage and high bus voltage designs.

The BP/M pin permits the MOSFET current limit to be adjusted up or down, allowing designers to optimize power delivery and efficiency in a variety of physical implementations. An on-time extension function extends the low-line regulation range, enabling hold-up time to be met with lower values of input capacitance.

The TinySwitch-4 family has Low System Cost with Enhanced Flexibility

725 V rated MOSFET
- Increases BV de-rating margin
Line compensated overload power – no additional components
- Dramatically reduces max overload variation over universal input voltage range
±5% turn on UV threshold: line voltage sense with single external resistor
Simple ON/OFF control, no loop compensation needed
Selectable current limit through BP/M capacitor value
- Allows optimum TinySwitch-4 choice by swapping devices with no other circuit redesign
Tight I₂f parameter tolerance reduces system cost
- Maximizes MOSFET and magnetics utilization
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

Enhanced Safety and Reliability Features

Accurate hysteretic thermal shutdown protection with auto¬matic recovery eliminates need for manual reset
Auto-restart delivers <3% of maximum power in short-circuit and open loop fault conditions
Output overvoltage shutdown with optional Zener
- Fast AC reset with optional UV external resistor
Very low component count enhances reliability and enables single-sided printed circuit board layout
High bandwidth provides fast turn-on with no overshoot and excellent transient load response

EcoSmart™ – Energy Efficient

Easily meets all global energy efficiency regulations
No-load <30 mW with bias winding, <150 mW at 265 VAC without bias winding
ON/OFF control provides constant efficiency down to very light loads – ideal for mandatory CEC regulations and EuP standby requirements

Applications

PC Standby and other auxiliary supplies
DVD/PVR and other low power set top decoders
Supplies for appliances, industrial systems, metering, etc
Chargers/adapters for cell/cordless phones, PDAs, digital cameras, MP3/portable audio, shavers, etc.

Reference design

Here is a typical standby application from Power Integrations website.

The reference design is a universal input 5 V, 4 A power supply designed around a TNY290PG device from the TinySwitch-4 family of ICs. Although designed as an auxiliary or bias supply for a personal computer (PC) power supply, this design can also be used as a general-purpose evaluation platform for TinySwitch-4 devices.

This report is incredibly detailed with:

Power supply specification table
PCB layout
BOM
Transformer spec and build diagram with construction details and figures
Complete performance data curves
Average efficiency measurement chart
Thermal imaging
Waveforms
Output ripple measurements and instructions how to properly measure it
Full EMI test and chart results with graphs

Typically, PC power supplies have a power factor corrected (PFC) input stage. However, since the bias supply must operate before the PFC stage is active, this supply has been designed for universal input operation.

In this design input rectification and input storage capacitance have been included, for evaluation purposes. This stage and the EMI filter components would normally be part of the main PC supply, in an actual application.

This converter is configured as a flyback. The output provides 4 A at 5 V. The converter will operate over an input voltage range of 90 VAC to 295 VAC or 100 VDC – 420 VDC. The output is regulated using a TL431 regulator IC located on the secondary side. An optocoupler is used to isolate the feedback signal in this circuit.