PT6909_10 Datasheet, PDF (5/8 Pages) Princeton Technology Corp – Power Factor Correction LED Driver

PT6909
PWM DIMMING AND TRAIC DIMMING
PWM dimming scheme can be implemented by external low frequency PWM signal to the PWMD pin. When the PWMD
pin is pulled high, the gate driver is enabled and the circuit operates normally. When the PWMD pin is left open or
connected to GND, the gate driver is disabled and the external MOSFET turns off. By using the duty cycle of the PWM
control method that can change the working and the closing time, and the light output can be adjusted between zero and
the internal set. In addition, the PWM dimming method is limited because the output current cannot be exceeded the
internal set.
The power topology does not require filter capacitance at the output side of rectifier bridge. Therefore, sampling the
phase-controlled voltage waveform of TRAIC connects PT6909’s PWMD pin can realize TRAIC dimming.
OSCILLATOR
Connecting an external resistor from RF pin to GND programs switching frequency:
Fosc
=
2.6 x 10¹⁰
R_RF
V1.1
5
April 2010