0 to 25V 5A TL494 Adjustable DC DC Supply

 TL494 PWM control IC is the heart of the Switch Mode DC DC Adjustable Power Supply circuit. Elements C13 1.5NF, R14-10K set the internal oscillator frequency to approximately 77kHz. First, the comparator, together with the elements R7, R8, R9, R15, R16 and C14, is the output voltage stabilization circuit, the value of which is regulated by the potentiometer P2.

The second comparator with the elements R10, R11, R12, R21 and R22 forms the current regulator circuit, the value of which is adjusted by potentiometer P1. The POW connector enables the power supply of the control block and the power block with the same block (short circuit 1-2) or activates the power supply control block from an external source, connecting them to pins 2-3
Elements T1 BDW84C, D1 F16C20 (or BYW29), L1 and C5 form a typical impulse “cascade” converter. Other elements filter the input and output voltages.

Feature

• 0…25V output voltage
• current limitation 0… 5A (0.5A… 5A)
• smooth adjustment of voltage and current
• power supply: 24VAC or 2x24VAC

The system is fed directly from the transformer. It must have 2×24 VAC 150 W power. The single-winding transformer is included according to the scheme. After the first start-up, we need to set the maximum voltage of 25 V with potentiometer R7 and the maximum current with potentiometer R10.
Potentiometer R22 is adjusted so that the current is adjusted equally throughout the entire rotation range of the potentiometer P1. If we expect a high load on the circuit for a long time, we must use a fan.

DC DC Adjustable Power Supply Circuit Diagram

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