Offline flyback controller for auxiliary and bias supplies
The BD7672BG-GTR is an offline PWM controller designed for flyback topologies, targeting auxiliary power supplies, bias rails in motor drives, and isolated DC-DC stages in industrial and consumer equipment. It operates at a fixed 65 kHz switching frequency — a common choice that avoids AM radio band interference while keeping the transformer core size manageable for designs up to around 30 W output. The 75% maximum duty cycle supports a wide input range without pulse skipping at low line, typical for universal AC input (85-265 VAC) flyback stages.
Supply range and protection set
The Vcc supply range of 8.5 V to 25 V covers the output of a standard bias winding or auxiliary regulator, with a 13.5 V start-up threshold that ensures clean turn-on above the UVLO threshold. Built-in fault protection includes current limiting and over-voltage detection — the controller latches off or auto-restarts depending on the fault condition, eliminating the need for discrete sense circuits. Output isolation is configurable as either — the same footprint supports primary-side-regulated (PSR) designs with an auxiliary winding or secondary-side regulation via an optocoupler and TL431.
Package and thermal integration
Housed in a SOT-23-6 (6-SSOP) package, the controller requires minimal PCB area — the 0.95 mm pin pitch and 2.9×1.6 mm body fit dense single-sided layouts common in USB charger and appliance PSU boards. Supplied on tape and reel (3,000 units per reel) for automated pick-and-place; cut-tape samples also available for prototyping.
Lifecycle and sourcing posture
ROHS3 compliant — no exemptions for lead, cadmium, or phthalates — and compatible with standard lead-free reflow profiles (260°C peak).