AP1601 datasheet(13/22 Pages) AKM

13 / 22 page

［AP1601］

MS 1454-E-01

2012/08

110

130

150

170

Number of LEDs vs Switching frequency

(Example)

Number of LEDs connected in series

102

106

110

85 105 125 145 165 185 205 225 245 265

Input voltage (VAC)

(kHz)

AC input voltage vs Switching frequency

(Example)

Figure 9. Examples of frequency changes as in input voltage changes or number of LEDs change

Switching frequency

F is approximately given by the following formula,





bottom

peak











ILp_bottom is the bottom current on the transformer primary side after the off-time tOFF period.

2-2-3) Analog dimming

LED analog dimming is available using the LD pin. Analog dimming is achieved by decreasing the peak current on

the transformer primary side. Analog diming is controlled by applying an external voltage to the LD pin. The

allowable voltage range on the LD pin is from 0 to VREF(5V (typ)). The peak detection voltage on the CS pin is

changed when the LD voltage is less than 2.65V(typ) as shown in Figure 10. Switching will not stop even if the LD

pin connects to GND.

100

LD (V)

Figure 10. Relationship between LD pin voltage and transformer primary side current (ILp_peak)

2-2-4) PWM dimming

AP1601 Datasheet(PDF) 13 Page - Asahi Kasei Microsystems