Power Integrations introduces the LinkSwitch™-TNZ, a new power supply switching IC that combines offline power conversion, lossless Zero-Cross detection, and optional X-capacitor discharge functions in a compact SO-8C package. The highly efficient LinkSwitch-TNZ IC can be used for non-isolated buck and buck-boost power supplies with up to 575 mA output current and provides up to 12 W output for universal-input isolated flyback designs.

Adnaan Lokhandwala, product marketing manager at Power Integrations, states: “The new LinkSwitch-TNZ ICs provide a precise signal indicating that the sinusoidal AC line is at zero volts. This signal is used by smart home and building automation products and devices to control the switching of relays, IGBTs, and TRIACs to minimize switching voltage and system input current. LinkSwitch-TNZ Zero-Cross point detection consumes less than 5 mW, enabling systems to reduce quiescent power losses compared to alternative approaches that require ten or more discrete components and consume 50 to 100 mW of continuous power.”.

Devices such as light switches, dimmers, sensors, and outlets periodically connect and disconnect the AC line using a relay or TRIAC. A discrete circuit is typically implemented to detect the zero-crossing of the AC line and control the power transition of the main power device, while simultaneously reducing switching losses and inrush current. This approach is component-intensive and has significant losses, consuming nearly half of the standby power budget in some cases. Similarly, household appliances often use a discrete zero-crossing detection circuit to control motor timing and the microcontroller unit (MCU). These applications also require an auxiliary power supply for functions such as wireless connectivity, door controllers, sensors, and displays.

LinkSwitch-TNZ ICs offer best-in-class light-load efficiency, enabling more system functions to be powered and meeting stringent standby regulations, such as the European Commission (EC) regulation for household appliances (1275), which requires equipment to consume no more than 0.5 W in standby or off mode; ENERGY STAR version 1.1 for Smart Home Energy Management Systems (SHEMS), which limits standby power consumption for smart lighting control devices to 0.5 W; and the Chinese standard GB24849, which limits microwave oven power consumption in off mode to 0.5 W. LinkSwitch-TNZ ICs also reduce the number of components by 40% or more compared to discrete designs.

Optionally, a capacitor discharge function X can be included in the package for high-power applications, allowing for reduced printed circuit board space, reduced bill of materials number, and increased reliability (LNK331x).

LinkSwitch-TNZ power supply switching ICs enable ±3% line and load regulation, no-load consumption of less than 30 mW with external bias, and IC standby current of less than 100 µA. The components are easy to design, feature integrated soft start, and operate with both isolated and non-isolated topologies.

Availability and Resources:
LinkSwitch-TNZ power supply switching ICs are priced at $0.84 in volume for 1,000 units. Four reference design examples are available for download. DER-874 and RDR-866 are non-isolated buck designs providing 6V/80mA and 5V/500mA outputs, respectively. RDR-877 describes an isolated 12V/0.5A output flyback with a ZCD signal on the secondary side, while DER-879 describes an isolated 12V/0.75A and 5V/0.2A flyback with ZCD and an integrated capacitor discharge circuit. For more information, contact a Power Integrations sales representative or one of the company's authorized worldwide distributors: Digi-Key, Farnell, Mouser, and RS Components.

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