circuit included four micro-LEDs arranged averagely in four
rectifying branches and one micro-LED in the output branch.
Fig. 1 shows the photographs and circuit diagrams of the WB
AC-LED-A and B, and micro-LEDs in rectifying and output
branches were labeled with gray and white triangles, respectively.
Dimensions of both WB AC-LEDs were m
m, and there were 28 and 27 micro-LEDs, about 1.05
and 1 m in area, of the WB AC-LED-A and B illuminated
in each bias direction, respectively. The AC electrical characteristics
of WB AC-LED chips were measured by the Xitron 2802
analyzer, and the AC signal was generated by a 60-Hz AC sine
wave power generator. The light output power characteristics
of WB AC-LED chips were measured with the calibrated integrating
sphere, and the integrating duration was 50 ms. The AC
root-mean-square (rms) voltages applied to the WB AC-LED-A
and B chips in the lifetime tests were 100 and 90 V, respectively,
so that the initial input powers (real power) of all WB AC-LED
chips could be 1 W. The ambient temperature and humidity in
WB AC-LED lifetime time tests were controlled at 28 C and
60%, respectively.