Power Electronics

Offline Switching Chip Extends Power Ratings, Adds Features

From Power Integrations, TinySwitch-III is the third generation of the company’s family of highly integrated, offline switching power supply ICs. This latest generation is designed to implement universal-input power supplies ranging from 3 W to 28 W, which is nearly double the output power capability of previous TinySwitch chips. Other enhancements include a selectable current limit, reduced no-load power consumption, and on-time extension (see the table). TinySwitch-III devices are suited for use in an array of power supply applications such as DVD players and LCD TVs.

TinySwitch-III features a 700-V MOSFET alongside low-voltage control circuitry on a monolithic IC. Other features include integrated auto-restart, input undervoltage and output overvoltage protection, hysteretic thermal shutdown, and frequency jittering to minimize EMI.

A key improvement from previous generations allows designers to optimize their power supplies for either maximum efficiency or greatest power output. Also, adjacent family members have matching available current limits, permitting the substitution of one TinySwitch-III family member for another without redesigning the transformer.

Feature Benefit
Selectable current limit Increased design flexibility-three current limits available for each IC, allowing tradeoffs between power output and efficiency/thermal rise
Extended power range Addresses universal-input power supplies with up to 28 W of output, compared to 15 W for TinySwitch-II
Even lower no-load consumption <150 mW at 265 Vac input without use of a bias winding; <50 mW achievable with bias winding
On-time extension Typically reduces size of bulk capacitor required for low-line power delivery/hold-up time

TinySwitch-III is available in 8-pin DIPs and SMDs. Pricing in 1000-piece quantities for the TNY274PN, a 6-W part in an 8-pin DIP, is $0.79 each. The TNY280PN, a 28-W part, is priced at $1.45 each.

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