The TEA1938T is a member of the GreenChip family of controller ICs for switchedmode
power supplies. It is intended for flyback topologies to be used either standalone
or together with USB PD or smart charging controllers (like the TEA190x series) at the
secondary side. The built-in green functions provide high efficiency at all power levels.
The TEA1938T is compatible with multiple output voltage applications with a wide output
range from 5 V to 20 V in Constant Voltage (CV) mode. When used with a secondaryside
controller IC, like the TEA190x series, it supports Constant Current (CC) mode down
to 3 V output voltage.
At high power levels, the flyback converter operates in Quasi-Resonant (QR) mode. At
lower power levels, the controller switches to Frequency Reduction (FR) in Discontinuous
Conduction Mode (DCM) operation. The peak current is limited to a minimum level.
Valley switching is used in all operating modes.
At very low power levels, the controller uses a minimum-ripple burst mode to regulate
the output power. A special optocoupler current reduction regulation has been integrated
which reduces the average optocoupler current in all modes to a minimum level. This
reduction ensures high efficiency at low power and excellent no-load power performance.
As the number of pulses per burst is kept at a minimum in this mode, the output ripple is
minimized. For further efficiency optimization, the internal IC supply current is minimized
during the non-switching phase of the burst mode.
The TEA1938T includes a wide set of protections that are safe-restart protections. One
of these protections is an accurate OverPower Protection (OPP). If the output is shorted,
the system stops switching and restarts. The output power is then limited to a lower level.
The TEA1938T is manufactured in a high-voltage Silicon-On-Insulator (SOI) process.
The SOI process combines the advantages of a low-voltage process (accuracy, highspeed
protection, functions, and control). However, it also maintains the high-voltage
capabilities (high-voltage start-up, low standby power, and brownin/brownout sensing at
The TEA1938T enables low-cost, highly efficient and reliable supplies for power
requirements up to 75 W using a minimum number of external components.