LinkSwich-PH Questions
I have came across the new LinkSwitch-PH product and thought it will be wonderful for my application. I have downloaded the datasheet and have some questions that will need some experts advice.
1) Since this is a LED driver, it should be CC. How do we determine the current output. On top of that, How do we determine the maximum open load output voltage. I do not seems to find any direct formula in the datasheet to calculate the resistor value for V pin and BP pin. I understand that PI Xls Designer is able to help with the design. However, there is no formula or clear indication on how to calculate the output current. Maybe I overlook. Pls advice
2) Am I able to generate extra CV 5V as auxiliary voltage on top of the CC output for my LED.
Thanks
John
Comments
Thanks for your reply. At the moment I would only have to rely on the spreadsheet. However I have another question unanswered from the previous posting
2) Am I able to generate extra CV 5V as auxiliary voltage on top of the CC output for my LED.
On top of that, I have some enquiries on the PI Xls Designer generated parameters. Below is the spreadsheet generated for my design. May I know what is
RV1, RV2, RFB1 and RFB2. Attached is the reference design from PI. May I know which resistor in the schematics correspond to RV1, RV2, RFB1 and RFB2
FINE TUNING (Enter measured values from prototype)
V pin Resistor Fine Tuning
RV1 3.91 M-ohms
RV2 1.40 M-ohms
VAC1 115.0 V
VAC2 230.0 V
IO_VAC1 0.24 A
IO_VAC2 0.24 A
RV1 (new) 3.91 M-ohms
RV2 (new) 1.40 M-ohms
V_OV 318.3 V
V_UV 70.8 V
FB pin resistor Fine Tuning
RFB1 127 k-ohms
RFB2 1E+012k-ohms
VB1 18.0 V
VB2 22.0 V
IO1 0.24 A
IO2 0.24 A
RFB1 (new) 126.9 k-ohms
RFB2(new) 1.00E+12k-ohms
Thanks
John
Hi Experts,
Is there anyone out there who could reply my question on the last posting. TQ very much
John
Hi
2) Am I able to generate extra CV 5V as auxiliary voltage on top of the CC output for my LED.
Thanks
John
The open cicrcuit voltage is controled by an external OVP cicrcuit. See figure 6 in datasheetand OVP operation description in Feedback section on page 6 of datasheet.
Determining CC is complex and involves the bias current established into Vpin and also bias current into feedback pin. The weighting of these two paths is programmed by the Feedback pin resistor to ground. The choice of value this resistor depends on application -- 115VAC only, 230VAC only, Universal, dimming mode. The turns ratio of transformer also has influence on output CC. All of these parameters are part of the spreadsheet calculation for output CC. There is an application note in the process that will more fully describe the formula that determines output CC. Until then you will have to rely on spreadseet.