Introduction to Linear Power Supplies
The topology of a conventional linear power supply, as shown in figure 1.1, uses a low frequency transformer comprosing of a core made of silicon steel sheet to convert AC mains to a desired voltage, and rectifies and filters the voltage to a DC level. Since general equipment requires stable DC voltage, the rectified and filtered DC level should be regulated through a power regulator. The power regulator clamps excessive viltage at the predetermined lecel and dissipates unwanted voltage in the form of heat.
In order not to greatly reduce the efficiency, linear power supplies should put a limit to the variable range of the AC input voltage. The concept of linear power supplies is to clamp the unwanted voltage along with ripple voltage and dissipate them in the form of heat, which results in quite small ripple voltage. Due to linear topology, there will be no problems of ripple noise and EMI in linear power supplies.
Figure 1.2 shows a typical linear power supply with the main features indicated: (A) transformer comprising a core made of silicon steel sheet, (B) the big input capacitor, and (C) the big transistor with its heat sink.
Last Amendment: 11/08/2006 17:10:29