AiT Semiconductor Inc.

www.ait-ic.com

AP8366

AC-DC PWM CONTROLLER

LOW STANDBY-POWER QUASI-RESONANT

PRIMARY-SIDE CONVERTER

REV1.2

- SEP 2017 RELEASED, SEP 2018 UPDATED -

- 11 -

Current Sensing and Leading Edge Blanking

Cycle-by-Cycle current limiting is offered in AP8366. The switch current is detected by a sense resistor at CS

pin. The CC set-point and maximum output power can be externally adjusted by external current sense

resistor at CS pin. An internal leading edge blanking circuit chops off the sensed voltage spike at initial power

MOSFET on-state so that the external RC filtering on sense input is no longer needed.

Programmable Cable Drop Compensation

In AP8366, an offset voltage is generated at FB pin by an internal current flowing into the divider resister, as

shown in Figure 3. The Cable Drop Compensation block compensates the voltage drop across the cable. As

the load current decreases from full load to no load, the voltage drop across the cable decreases. It can be

programmed by adjusting the external resistor R2 or R1 at FB pin. The maximum compensation is

2.5V

(R2//R1)

x

I

V

V

cable

o

(4)

Because of the influence of the chip’s sampling position and devices of the system, the actual maximum

compensation is less than theoretical value.

Figure 3. Icable

Reference Negative Temperature Compensation

As shown in Figure 3, the voltage of FB pin is

Ns

x

R2)

(R1

N

x

R2

K

AUX





(5)

Where ΔV has a negative temperature coefficient, K is a constant.

In AP8366, the voltage reference uses the negative temperature compensation technology. At room

of chip increases. The reference negative temperature compensation block compensates the ΔV, thus the

output voltage keeps constant at full range of temperature. The reference negative temperature

compensation improves output precision.