TL494CN: Functions, working principles and typical applications


The TL494CN is a pulse width modulation (PWM) controller chip manufactured by Texas Instruments. It is widely used in power supply and motor control applications. Here's an overview of its functions, working principles, and typical applications:


Functions: The TL494CN offers the following key functions:

  1. PWM Generation: It generates pulse width modulated signals with adjustable duty cycle. The TL494CN provides precise control over the width of the output pulses, allowing efficient power conversion and motor control.

  2. Error Amplifier: It includes an error amplifier that compares a feedback voltage with a reference voltage to regulate the output. This allows for feedback control and regulation of the output voltage or current in power supply applications.

  3. Oscillator: The TL494CN incorporates an internal oscillator that sets the frequency of the PWM waveform. The frequency can be adjusted using external components to suit the specific application requirements.

  4. Dead-Time Control: It provides dead-time control between complementary PWM output signals. The dead-time ensures that both high-side and low-side switch transistors in power circuits do not conduct simultaneously, preventing shoot-through current and improving overall system efficiency.

Working Principles: The TL494CN operates based on the principle of pulse width modulation. It compares the feedback signal of the output voltage or current (from a power supply or motor) with a reference voltage. The error amplifier generates an error voltage that is then fed into a comparator. This comparator compares the error voltage with the voltage obtained from the internal oscillator. The result is a series of variable-width pulses proportional to the error voltage.

These variable-width pulses are then passed through the dead-time control logic to create complementary PWM signals. The outputs of the controller are typically used to drive power MOSFETs or other switching devices in power supply or motor control circuits. By adjusting the duty cycle of the pulses, the TL494CN can control the average output voltage or current.

Typical Applications: The TL494CN is commonly used in the following applications:

  1. Switched-Mode Power Supplies (SMPS): It is extensively employed as a PWM controller in AC-DC and DC-DC power supply designs, including offline flyback converters, forward converters, buck converters, boost converters, and half-bridge converters.

  2. Motor Control: The TL494CN can be utilized for motor control applications such as brushless DC (BLDC) motor drivers or stepper motor drivers, where precise PWM signals are required to regulate motor speed or torque.

  3. Uninterruptible Power Supplies (UPS): It finds application in UPS systems, where it controls the inverter to convert DC power into AC power during power failures.

  4. Battery Chargers: The TL494CN can be employed for designing battery charging circuits, such as lead-acid battery chargers or lithium-ion battery chargers, providing accurate control of charging currents and voltages.

  5. Audio Amplifiers: It can be utilized in class D audio amplifiers, where it generates the PWM signals that control the switching of power MOSFETs to amplify audio signals efficiently.


When using the TL494CN, it is important to refer to the datasheet and application notes provided by Texas Instruments for detailed information on its operation, recommended external components, and circuit design guidelines specific to your application needs.