Power Integrations report details power design

Power Integrations has published a Design Engineering Report (DER-229) that details the design of a 27W power supply for LCD monitors and similar applications.

Based on Power Integrations' TNY380PN, a member of the Tinyswitch PK product family, the design is more than 80 per cent efficient at full load under worst-case conditions.

The 15V main output, 5V auxiliary output power supply draws less than 80mW input power when delivering 30mW to the system in standby mode.

This ensures that there is ample power available to incorporate remote on/off functionality without exceeding the limits of OEM PC system integrators, and exceeds the 1W specification of Energy Star and the 500mW requirement of the European Union Tier 2 Ecodesign Directive for Energy-Using Products (EuP).

Tinyswitch-PK includes control and regulation functions that minimise power consumption at no-load.

The IC also uses frequency jittering to reduce the size of the EMI (electromagnetic interference) filter, eliminating the need for X capacitors and their associated bleed resistors (required for safety compliance), which can themselves dissipate more than 30mW.

The transformer used in DER-229 was designed using Power Integrations' PI Expertp power supply design software to reduce parasitic losses between windings.

High switching frequency at full load suppresses acoustic noise from the power supply and enables the use of small magnetic components, making the design suited to slim form-factor LCD monitors and similar space-constrained applications.

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