UDG-12169

Time

ASNS

Rectified AC

Controlled Reference

V

Internal

Time

Controlled Reference

UDG-12168

TPS92075

www.ti.com

SLUSB88B – DECEMBER 2012 – REVISED JANUARY 2014

Figure 9. Line Synchronization

Non-Dimming Ramp Mode

When the conduction angle is greater than 70%, the controller begins to create a triangular ramp that is

synchronized to the line and is centered between rising and falling edges of the ASNS signal as shown in

Figure 10. The triangular shape is much easier to generate than a sine wave while maintaining a high power

factor and low THD. The edges of the ramp do not decrease completely to zero to ensure compatibility with

TRIAC dimmers that can provide conduction angles approaching 100%.

Figure 10. Controlled Reference Output, Non-dimming

When changing between dimming mode and non-dimming mode, the ramp is created over 127 line cycles (see

is very similar and the change very gradual, it is impossible for the user to perceive a change in output level. The

ramp morphs from a DC level to a ramp using a method that further ensures transparency to the user. Ramp

transition occurs during construction and deconstruction of the ramp and is reversed if the conduction angle

changes sufficiently during the change process. A hysteresis in angle length is also built in to the change-to-

ramp-mode and change-from-ramp-mode transition.

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