This application note presents practical step-by-step design considerations for a power supply system employing Fairchild’s FAN6920 PFC / PWM combination CONTROLLER, an integrated Boundary Conduction MODE (BCM) Power Factor Correction (PFC) CONTROLLER and Quasi-Resonant (QR) PWM CONTROLLER. Figure 1 shows the typical application circuit, where the BCM PFC converter is in the
front end and the dual-switch quasi-resonant flyback converter is in the back end.
This application note presents practical step-by-step design considerations for power supply system employing Fairchild’s FAN6921 PFC/PWM combination CONTROLLER, which combines a Boundary Conduction MODE (BCM) Power Factor Correction (PFC) CONTROLLER and QuasiResonant (QR) PWM CONTROLLER. Figure 1 shows the typical application circuit, where the BCM PFC converter is in the
front end and the Quasi-Resonant flyback converter is in the back end.
The KA3882/3/4/5 are flxed PWM CONTROLLER for Off-Line and DC to DC converter applications. The internal circuits include UVLO, low start up CURRENT circuit, temperature compensated reference, high gain error amplifier, CURRENT sensing comparator, and high CURRENT totempole output for driving a POWER MOSFET. Also KA3882/3/4/5 provide low start up CURRENT below 0.3mA and short shutdown delay time type. 100ns.
The highly integrated FAN6921ML combines a Power Factor Correction (PFC) CONTROLLER and a QuasiResonant PWM CONTROLLER. Integration provides cost effect design and allows for fewer external components. For PFC, FAN6921ML uses a controlled on-time technique to provide a regulated DC output voltage and to perform natural power factor correction. With an innovative THD optimizer, FAN6921ML can reduce input CURRENT distortion at zero-crossing duration to
improve THD performance.
Integrated PFC and Flyback CONTROLLER
Critical MODE PFC CONTROLLER
Zero-CURRENT Detection for PFC Stage
Quasi-Resonant Operation for PWM Stage
Internal Minimum toff 8µs for QR PWM Stage
Internal 10ms Soft-Start for PWM
H/L Line Over-Power Compensation (OPC)
Latched Protection (FB Pin)
− Over-Power/ Overload Protection
− Short-Circuit Protection
− Open-Loop Protection
Externally Latch Triggering (RT Pin)
Adjustable Over-Temperature Latched (RT Pin)
VDD Pin & Output Voltage OVP (Latched)
Internal Temperature Shutdown (140°C)
The FAN7602C is a green CURRENT-MODE PWM CONTROLLER. It is specially designed for off-line adapter applications; DVDP, VCR, LCD monitor applications; and auxiliary power supplies.
The internal high-voltage startup switch and the burst MODE operation reduce the power loss in standby MODE. As a result, the input power is lower than 1W when the input line voltage is 265VACand the load is 0.5W. At no load condition, input power is under 0.15W. The maximum power can be limited constantly, regardless of the line voltage change, using the power limit function. The switching frequency is not fixed and it has random frequency fluctuation.
The FAN7602C includes various protections for the system reliability and the internal soft-start prevents the output voltage over-shoot at startup.
Green CURRENT MODE PWM CONTROLLER
Random Frequency Fluctuation for Low EMI
Internal High-Voltage Startup Switch
Burst MODE Operation
Line Voltage Feedforward to Limit Maximum Power
Line Under-Voltage Protection
Latch Protection & Internal Soft-Start (10ms) Function
Low Operation CURRENT: 1mA Typical