AP3105

Application Note 1062 High Voltage Green Mode PWM Controller AP3105 Prepared by Wu Qikun System Engineering Dept. 1. Introduction The AP3105 is a low start-up current, current mode PWM controller with green-mode power-saving operation. Different from AP3103, AP3105 PWM switching frequency at normal operation is fixed at 65kHz dithering with a narrow range. The difference between AP3103/AP3105 is shown in Table 1. The dithering of frequency will improve EMI feature. When the load decreases, the frequency will reduce and when at a very low load, the IC will enter the “burst mode” to minimize switching loss. A minimum 20kHz frequency switching is to avoid the audible noise as well as reducing the standby loss. A so-called VCC Maintain Mode is applied under light load to realize a stable output and to reduce the loss on the start-up resistor. The standby power of the system using AP3105 can be reduced to 60mW at 230V input. AP3103 Frequency VFB Resistor Standby Performance External Protection VCC OVP Adjustable 4.5kΩ Better NA Auto-recoverable Auto-recoverable AP3105 Fixed at 65kHz 10kΩ Best By “CTRL” pin Latch /Auto-recoverable Latch /Auto-recoverable the PCB layout, and methods for reducing the standby power loss, and finally presents a demo design of a 12V 1A adaptor. 2. Function Description 2.1 CTRL Pin For some applications, the system requires external programmable protection function. The CTRL pin has two kinds of modes to trigger the protection: high level trigger and...