The TEA1938T is a member of the GreenChip family of controller ICs for switched-mode 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 secondary side 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 brown in/brown out sensing at the input).
The TEA1938T enables low-cost, highly efficient and reliable supplies for power requirements up to 75 W using a minimum number of external components.
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