LCD-LED DisplayPower Supplies

Discrete Low-drop Regulator Schematic Circuit Diagram

Maintaining Safe Voltage Levels for TDA1516Q Amplifier

This circuit was specifically devised to prevent an amplifier circuit incorporating a TDA1516Q from surpassing its maximum supply voltage, especially when the load is minimal. This amplifier finds its application in personal computers, enhancing the audio power output. However, the power supply originating from the PC generated excessive interference, necessitating the incorporation of an additional power supply.

This supplementary power supply operates with its own power transformer (for US users: with a 115 V primary winding) producing a secondary voltage of 12 V AC. Following rectification and filtering, this yields a direct current (DC) voltage of approximately 16 V. The voltage regulator in this setup comprises a P-channel MOSFET SJ117, whose gate is controlled through a voltage divider linked to T2. The base of T2 is stabilized at a constant voltage by LED D2, ensuring that the voltage across the emitter resistor R2 remains consistent, thereby maintaining a steady current flow.

Discrete Low-drop Regulator Schematic Circuit Diagram

Maintaining Output Voltage Stability

In this circuit, once the output voltage exceeds approximately 13.5 V, Zener diode D1 starts conducting, diverting some current through R2. Consequently, the MOSFET experiences a slight reduction in its activation. This creates a balance where the output voltage stabilizes a little above 13.5 V (1.5 V across R2 plus the 12 V Zener voltage). The regulator can deliver a maximum of about 2 A; however, it’s advisable to equip the MOSFET with a heatsink to manage heat dissipation effectively.

Adjusting Output Voltage and Power Supply Activation

An optional potentiometer can be added in series with the 12-V Zener diode, enabling minor adjustments to the output voltage. Additionally, a relay located at the AC power line input ensures that the power supply activates only when the PC is turned on. This relay is operated through a 4-way power supply connector originating from the PC, enhancing control over the power supply’s operation.

Role of Regulators in Various Fields

A regulator, whether an individual or an organization designated by the government, oversees specific areas of activity like banking or industry. An independent regulator ensures equitable competition, comparing the output voltage against a precise reference voltage. It then adjusts the pass device to maintain a consistent output voltage. Meanwhile, a switching regulator transforms the DC input voltage into a switched voltage applied to a power MOSFET or BJT switch, enabling efficient regulation of the electrical supply.


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