The emergence of Internet Protocol Voice over IP (VoIP) telephones has brought a demand for generating multiple high-voltage negative outputs. CC-TDIL01 51308386-175 voltage rails are used to drive telephone lines. When the line is in call mode, there is usually one -24V output to provide loop current, while there is usually another negative output or two to drive the phone to ring. It is interesting that for each telephone line, these loads are mutually exclusive, which means you cannot make the phone ring and call simultaneously. However, there may be multiple telephone lines in a system, resulting in many load situations. These systems are usually powered by a 12V power supply, which is already isolated from the input power, so secondary isolation is generally no longer required. The power level is generally below 25W, and the adjustment requirements are usually within the range of 3% to 10%.

Reverse topology appears to be the best choice for this application. The power level is consistent with the reverse topology structure. CC-TDIL01 51308386-175 can easily generate multiple high-voltage outputs using a reverse topology structure, which has been well known. However, the reverse topology also has many shortcomings: this topology includes non clamped power supply switch voltages that will excessively ring; It usually requires a secondary output filter; The cross adjustment from zero to full load cannot be 3%.