Reference design for PAR38 LED spotlight

Technology News |
By eeNews Europe

Fig. 1: The populated DER-350 circuit board assembled

Fig. 2: The populated DER-350 board is placed inside the CREE PAR38 lamp

The 20W reference design includes an isolated, high-power-factor, TRIAC-dimmable LED driver optimized to deliver an LED current of 550 mA at 36 V (nominal) from an input voltage range of 90 VAC to 132 VAC. The combined PFC (>0.98) and CC single-stage, isolated topology of the LYTSwitchTM-4 IC delivers excellent efficiency, and low component count. Over-voltage, overcurrent and over-temperature protection features are built-in.

The following brief outline of this extensive reference design will give a taste of how complete and robust this design is:


Fig. 3: Schematic of DER-350. For better resolution click here.

DER-350 also showcases the LYTSwitchTM-4 IC’s excellent TRIAC dimming with very fast sub-200 ms start-up, reduced pop-on and no dead-travel, easily satisfying NEMA dimming curve requirements, for both leading-edge and trailing-edge dimmers.

Fig. 4: Transformer build diagram

Transformer spec

The reference design outlines the electrical specs and materials for the transformer. In addition, a transformer build diagram is included with construction details. Finally, a detailed transformer design spreadsheet is shown.

L1 Inductor spec

Fig. 5: L1 inductor electrical diagram

An electrical diagram is shown for the L1 inductor along with electrical specs and materials. A build diagram and inductor construction details are also included.

U1 Heat sink

Fig. 6: U1 heat sink

Performance data

A full work-up of actual performance test data including efficiency graph, line/load regulation graph, power factor graph, A-THD graph, harmonic currents bar graph with 11, 12 and 13 LED loads. Test charts include data for 11, 12 and 13 LED loads; Current harmonics limits for IEC61000-3-2 for 11, 12 and 13 LED loads—all passing.

Dimming performance data is shown graphically.

Fast Start-up of less than 200 ms with TRIAC-based dimmer is shown in graphs.

Pop-on point with TRIAC-based dimmer is graphically shown.

Output and input current waveforms with dimmer are shown as well.

Dimmer compatibility

A full US list of 71 Lutron, Cooper and Leviton dimmer part numbers are outlined

Thermal Performance

Fig. 7: Thermal test set-up

Full sets of thermal measurements were done and recorded with a PAR38 lamp

Conducted EMI

Conducted EMI tests proved well below the maximum limits in EN55015 B

Fig. 8: EMI Test Set-up with the unit and LED load placed inside a conical metal housing as described in CISPR 15 / IEC: 2005 standard.

The unit was subjected to ±2500 V 100 kHz ring wave and ±500 V differential surge at

120 VAC using 10 strikes at each condition. A test failure was defined as a non-recoverable

interruption of output requiring supply repair or recycling of input voltage.

The unit tested passed both ±2500 V 100 kHz ring wave and ±500 V differential surge with and without MOV.

For more information please go the Power Integrations website.

This article originally appeared on EDN


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