Take a Flier on the Flyback for Your High-Voltage Circuit Design (.PDF Download)

Applications ranging from consumer electronics to high-power energy-conversion systems leverage the benefits of dc-dc power converters in their designs. Among these, flyback converters are popular for low-power applications such as backlighting for LCD monitors and TVs, micropumps (i.e., microbiological experiments), piezoelectronics, and Geiger counter tubes. This kind of flyback converter is highly scalable and reusable for applications ranging from 30 V to 450 V by simply varying configuration parameters of a Silego GreenPAK programmable device, a configurable mixed-signal IC (CMIC).

For instance, high-voltage LEDs offer the optimum solution for indoor retrofit lamps. High-voltage LEDs usually have a higher turn-on voltage, greater than 20 V, than conventional LEDs (white LEDs), which is typically 3 V. This low-current, high-voltage architecture enables simpler, smaller, cheaper, and higher-efficiency driver topologies. A high-voltage, low-current LED string matches the LED output voltage more closely to its ac input voltage versus that of a low-voltage, high-current string using the same number of LEDs and lumen output.

For LCD backlight lamps, the LEDs are on the edge of the display, and a light-guide plate helps achieve uniform backlighting (Fig. 1). White LEDs usually employ a constant-current drive using pulse-width modulation (PWM) for dimming control. You can drive the LEDs in series through the flyback converter in order to produce enough voltage to illuminate a large LED string. Along with easy control, series connections also simplify pc-board routing and enable optimum current matching between LEDs. Therefore, series connection is the preferred approach.