FAN7602 is a green current mode PWM controller. It is designed for off-line adapter applications, DVDP, VCR, LCD monitor applications and auxiliary power supplies. Internal high voltage start switch and burst mode operation reduce power loss in standby mode. Due to the internal start switch and burst mode, 0.5W loads can be provided, limiting input power to less than 1W at 265VAC input line voltage.
Typical application diagram
In no-load state, input power is less than 0.3W. With the power limit function, the maximum power can be continuously limited regardless of the line voltage changes. Switching frequency is fixed internally at 65kHz, and frequency modulation technology reduces EMI. FAN7602 includes various protection for system reliability, internal soft starting prevents output voltage overshoot during startup.
Internal block diagram
The FAN7602 contains a start switch to reduce power loss from the external start circuit of conventional PWM converters. If an AC line is connected, the internal starting circuit charges the VCC capacitor with a 0.9mA current source. As shown in Figure 19, after the IC is started, the start switch is off for 15ms. The soft start function starts when the VCC voltage reaches the startup threshold of 12V and ends when the internal soft start voltage reaches 1V. If the VCC voltage is reduced to the minimum operating voltage of 8V, the internal starting circuit restarts charging the VCC capacitor.
The UVLO block closes the output driver circuit and some blocks to reduce the IC operating current and the internal soft start voltage to zero. If the VCC voltage reaches the start threshold voltage, the IC restarts the switch and the soft boot block works normally. During soft start, the pulse width modulation comparator compares the CS/FB pin voltage with the soft start voltage. The soft start voltage starts at 0.5V and ends at 1V. The soft start time is 10ms. When the soft start voltage reaches 1.5V, the start switch is closed.
Pin Assignments
