The STACF01A and STACF01B ICs drive and control active clamp flyback converters with non-complementary driving of the active clamp (high-side, HS) switch. It is specifically intended for high performance AC-DC adapters with GaN HEMTS rated up to 100 W and beyond, which are aimed at high efficiency as well as high power density.

The ICs seamlessly change operating mode with loading conditions to optimize efficiency under an extremely wide range of loads: variable frequency with frequency foldback at heavy-medium load, bottom-clamped, load-proportional frequency at light load, burst mode at very light, and no-load.

An automatic adjustment mechanism ensures that the reverse primary current needed to achieve ZVS is properly set for any input/output voltage combination.

This ICs can achieve output voltage regulation from the secondary side via an optocoupler-based feedback.

The ICs are provided with an embedded high-voltage startup circuit that also implements the line voltage monitoring system. The STACF01A also discharges the X capacitors when the converter gets disconnected from the AC power line. The STACF01B is intended for use with DC input, like SMPS with PFC in front or supplied by a DC bus.

The ICs incorporate two low-side low-power drivers intended to drive the inputs of an external high-voltage half-bridge driver ICs or an SiP such as one of the MasterGaN families.

It also provides an extensive set of protection features against primary and secondary side faults (two-level overcurrent, overpower, overload, short circuit, brownout, output overvoltage). A general protection input (active low latch type and active high autorestart) helps implement an external OTP, an external input OVP, or a general-purpose protection.

• Non-complementary control of active clamp flyback converter
• Multimode operation optimizes efficiency over a very wide load range
• Up to 500 kHz operating frequency with programmable deadtime
• Automatic reverse current control for ZVS of low-side switch
• ZCD circuit for demagnetization instant detection and OVP setting
• Embedded high-voltage startup and active x-cap discharge circuit
• Integrated buck-boost regulator for wide output voltage range
• Very low quiescent current enables ultra-low no-load input power
• Full set of protection features
• Interface with PFC controller
• Dual low-side driver and enable for easy pairing with MasterGaN family, other types of GaN power IC, or half-bridge driver IC