FAN6300A: Green-Mode QR PWM Controller for Flyback Converter

The highly integrated FAN6300A/H of PWM controller provides several features to enhance the performance of flyback converters. FAN6300A is applied on quasiresonant flyback converters where maximum operating frequency is below 100kHz. FAN6300H is suitable for high-frequency operation (up to 190kHz). A built-in HV startup circuit can provide more startup current to reduce the startup time of the controller. Once the VDD voltage exceeds the turn-on threshold voltage, the HV startup function is disabled immediately to reduce power consumption. An internal valley voltage detector ensures power system operates at quasi-resonant operation over a wide-range of line voltage and any load conditions, as well as reducing switching loss to minimize switching voltage on drain of power MOSFET.

To minimize standby power consumption and light-load efficiency, a proprietary green-mode function provides off-time modulation to decrease switching frequency and perform extended valley voltage switching to keep to a minimum switching voltage. The operating frequency is limited by minimum tOFF time, which is 38µs to 8µs in FAN6300A and 13µs to 3µs in FAN6300H, so FAN6300H can operate at higher switching frequency than FAN6300A.

FAN6300A/H controller also provides many protection functions. Pulse-by-pulse current limiting ensures the fixed-peak current limit level, even when a short circuit occurs. Once an open-circuit failure occurs in the feedback loop, the internal protection circuit disables PWM output immediately. As long as VDD drops below the turn-off threshold voltage, the controller also disables PWM output. The gate output is clamped at 18V to protect the power MOS from high gate-source voltage conditions. The minimum tOFF time limit prevents the system frequency from being too high. If the DET pin triggers OVP, internal OTP is triggered and the power system enters latch-mode until AC power is removed. The FAN6300A/H controller is available in an 8-pin Small Outline Package (SOP).

Features

• High-Voltage Startup
• Quasi-Resonant Operation
• Cycle-by-Cycle Current Limiting
• Peak-Current-Mode Control
• Leading-Edge Blanking (LEB)
• Internal Minimum t_OFF
• Internal 5ms Soft-Start
• Over Power Compensation
• GATE Output Maximum Voltage
• Auto-Recovery Over-Current Protection (FB Pin)
• Auto-Recovery Open-Loop Protection (FB Pin)
• VDD Pin and Output Voltage (DET Pin) OVP Latched
• Low Frequency Operation (below 100kHz) for FAN6300A
• High Frequency Operation (up to 190kHz) for FAN6300H

Application Notes