AN2811

Test results and waveforms

Doc ID 14904 Rev 1

17/25

The current sense circuit (R9 and R12 in Figure 5) is one portion of output voltage. The

additional voltage drop is 300 mV. The following figures show the output voltage and current

waveforms for the load (one LED vs. two LEDs). In Figure 22 and Figure 23 the waveform is

captured at 176 VAC. In Figure 24 and Figure 25 the waveform is captured at 264 VAC. We

can observe that the output ripple current always less than 30 mA. Independent of the load

condition, the output current is regulated at precisely 500 mA.

Figure 22.

Vo and Io at 176 VAC, one LED

Figure 23.

Vo and Io at 176 VAC, two LEDs

Top trace: Io (200 mA/div)

Bottom trace: Vo (2 V/div)

Time: 2 ms/div

Top trace: Io (200 mA/div)

Bottom trace: Vo (2 V/div)

Time: 2 ms/div

Figure 24.

Vo and Io at 264 VAC, one LED

Figure 25.

Vo and Io at 264 VAC, two LEDs

Top trace: Io (200 mA/div)

Bottom trace: Vo (2 V/div)

Time: 2 ms/div

Top trace: Io (200 mA/div)

Bottom trace: Vo (2 V/div)

Time: 2 ms/div