Transformers operate on the principle of electromagnetic induction, which relies on a changing magnetic field to induce a voltage in a coil. In AC (alternating current) transformers, the primary coil is connected to an AC source, causing the magnetic field around it to continuously change direction. This changing magnetic field induces a varying voltage in the secondary coil, resulting in AC output. However, DC (direct current) does not cause a varying magnetic field because it flows steadily in one direction. As a result, a transformer cannot induce a voltage in a secondary coil from DC alone.
A traditional transformer cannot operate directly on DC current because it requires a varying magnetic field to induce voltage in the secondary coil. In a DC circuit, the current flows in one direction without alternating, thus maintaining a constant magnetic field around the primary coil. Without changes in magnetic flux, there is no induction of voltage in the secondary coil, rendering the transformer ineffective in converting or transforming DC voltage levels.
A DC to DC transformer, often referred to as a DC-DC converter, operates by first converting the DC input voltage to AC using electronic switching devices such as transistors or switches. This switching action alternately connects and disconnects the DC input to an inductor or transformer primary winding. By rapidly switching the input DC on and off, an alternating current (AC) is effectively generated within the transformer, allowing it to induce a voltage in the secondary winding. Subsequent rectification and filtering steps then convert this AC voltage back to DC at the desired output voltage level.
Transformers cannot operate directly on DC because their fundamental principle of operation relies on electromagnetic induction, which requires a varying magnetic field. AC (alternating current) continuously changes direction, causing the magnetic flux in the transformer core to alternate as well. This changing magnetic flux induces a voltage in the secondary coil. In contrast, DC (direct current) flows steadily in one direction, creating a constant magnetic flux around the transformer core. Without a changing magnetic flux, there is no induction of voltage in the secondary coil, which means a transformer cannot step up or step down DC voltages like it can with AC. Therefore, transformers are specifically designed to work with AC current, where their ability to induce voltage through electromagnetic induction is effectively utilized.