Date: 04/08/2011

Effecient dual switch flyback based DC/DC power supply solution from Fairchild

Fairchild Semiconductor is offering a dual switch flyback solution for all-in-one type switching power supply designers. Fairchild says its new solution is better than the LLC (Inductor-Inductor- Capacitor) and single switch Quasi-resonant (QR) flyback topologies used in designing switching power supplies. LLC is efficient but its transformer is difficult to design, where as single switch QR flyback transformer is simple to design but this mode is not energy efficient. Fairchild claims its dual switch QR flyback topology and secondary synchronous rectification manages low power loss at light load, while providing ease of design.

Fairchild's solution is suggested for designing dc/dc power supplies in the range of 75W~230W. The power semiconductor devices consists of the FAN6920MR integrated critical mode PFC and Quasi-resonant Current Mode PWM controller, the FAN7382 gate driver, in tandem with the FAN6204 secondary synchronous rectifier controller for flyback topology and forward freewheeling rectification. Fairchild says these devices provide best-in-class power consumption at no/light load, enabling designs to meet 2013 ErP standard without the additional circuitry LLC solutions require.

Fairchild used a tech what it named as mWSaver to offer the lowest standby power input for AIO solutions. Quasi-resonant control reduces snubber and leakage inductance losses, while improving thermal issues. It also lowers the Vds of the SR MOSFET to provide improved efficiency, and allows for smaller board size. Built-in two-level PFC output improves low line efficiency, these are other advantages mentioned by Fairchild.

FAN7382, a high and low side gate drive IC provides the ability to drive Fairchild's High Voltage MOSFETs up to 600V. This device is designed to provide stable operation of the high-side driver under high-dv/dt noise circumstances.

The FAN6920MR combines a power factor correction (PFC) controller and a quasi-resonant PWM controller. For PFC, the device uses a controlled on-time technique to provide a regulated DC output voltage and to perform natural power factor correction. With an innovative total harmonic distortion (THD) optimizer, the FAN6920MR can reduce input current distortion at zero-crossing duration in order to improve THD performance. For PWM control, the FAN6920MR provides functions such as extended valley detect up to the 12th valley cycle for reduced switching frequency, improved light load efficiency, green-mode operation, an internal 10ms soft start, and high/low line over-power compensation.

Using a proprietary linear prediction timing-control technique, not limited to the RDS(ON) of the external Fairchild power-trench SR MOSFET, the FAN6204 is suitable for fixed frequency or quasi-resonant (QR) flyback converters operating in discontinuous or continuous conduction mode (DCM and CCM) control, suggests Fairchild. This technique includes a simple control method without current-sense circuitry, which provides better noise immunity. With PWM frequency tracking and secondary-side winding voltage detection, the device can operate in both fixed-and variable-frequency systems, making it adaptable to flyback and forward freewheeling topologies. The FAN6204 also features an ultra-low green mode operating current (1.1mA typical). This internal green mode provides lower no-load power consumption and higher light-load efficiency.

The FAN7382 can drive Fairchild's super-junction SupreMOS and SuperFET MOSFETs. Fairchild's high-voltage (up to 600V) process and common-mode noise canceling technique provides stable operation under high dv/dt noise circumstances. An advanced level shift circuit allows high-side gate driver operation up to VS = -9.8 V (typ.) for VBS = 15V. The input logic level is compatible with standard TTL-series logic gates. UVLO circuits for both channels prevent malfunction when VCC and VBS are lower than the specified threshold voltage.

Price: in 1,000 quantity pieces

FAN6920MR US $1.20

FAN6204 US $0.57

FAN7382 US $0.83

Availability: Samples available now

Delivery: 8-10 weeks ARO