Circuit Diagram: Tl494

The TL494 is a versatile fixed-frequency Pulse-Width Modulation (PWM) control circuit that integrates all the essential building blocks for switching power supply designs on a single chip. It is widely used for DC-DC converters, inverters, and motor control applications. Core Internal Architecture

Since PWM effectively controls the average power delivered to a load, the TL494 is an excellent choice for high-power LED dimmers or DC motor speed controllers. Tips for Building Your Circuit tl494 circuit diagram

6. Typical Waveforms (Oscilloscope)

  1. The error amplifier compares the feedback voltage with the reference voltage and produces an error signal.
  2. The error signal is amplified and used to control the PWM section.
  3. The PWM section generates a high-frequency pulse train that is used to control the output voltage.
  4. The pulse train is sent to the output section, where it is converted into a DC output voltage.
  5. The output voltage is regulated by the error amplifier, which continuously monitors the output voltage and adjusts the PWM pulse train accordingly.

5. Output Mode Selection (Pin 13)

| Connection | Mode | Max Duty Cycle | |---------------|---------------|----------------| | Ground | Push-pull | < 48% per output | | Vref (5V) | Single-ended | < 96% (both outputs parallel) | Pin5 (CT) : Sawtooth, 0V to ~3V, f = f_osc

TL494 Circuit Diagram

How the TL494 Circuit Diagram Works

7. Troubleshooting Common Issues

| Problem | Likely Cause | |------------------------|--------------------------------------------| | No switching | Pin12 VCC < 7V; Pin13 floating; CT/RT wrong; no power to outputs | | Full duty cycle always | Pin4 too low; feedback loop open (Pin3 stuck low) | | Output voltage too low | Divider resistors wrong; inductor saturating; load too high | | IC hot | Output transistors shorted; excessive drive current; VCC > 40V | | Instability / noise | Poor compensation; missing bypass caps; ground loops | The error amplifier compares the feedback voltage with