Understanding the TL494 IC: A Versatile PWM Controller

The TL494 is a highly popular pulse-width modulation (PWM) controller IC developed by Texas Instruments. It's widely used in switch-mode power supplies (SMPS), inverters, DC-DC converters, and motor control circuits due to its flexibility and reliability. Let's break down its key features, pinout, and applications.

Key Features of the TL494

Adjustable PWM Control – Allows precise duty cycle adjustment (0% to nearly 100%).
Push-Pull or Single-Ended Output – Can drive two transistors (for push-pull or half-bridge topologies).
On-Board Oscillator – Frequency set by external RT (resistor) and CT (capacitor).
Error Amplifiers – Two built-in op-amps for feedback control (voltage/current regulation).
Dead-Time Control – Prevents shoot-through in half/full-bridge circuits.
5V Reference Output – Provides a stable voltage for feedback networks.
Operating Voltage: 7V to 40V (wide range for different applications).

TL494 Pinout & Functions

Here’s a quick rundown of the 16-pin IC:

Pin	Function
1	Non-inverting input (Error Amp 1)
2	Inverting input (Error Amp 1)
3	Feedback/Error Amplifier Output
4	Dead-Time Control (0-3V adjusts duty)
5	CT (Oscillator Timing Capacitor)
6	RT (Oscillator Timing Resistor)
7	Ground (GND)
8	Collector of Output Transistor 1
9	Emitter of Output Transistor 1
10	Emitter of Output Transistor 2
11	Collector of Output Transistor 2
12	VCC (Power Supply, 7V-40V)
13	Output Control (Push-Pull/Single)
14	5V Reference Output
15	Inverting input (Error Amp 2)
16	Non-inverting input (Error Amp 2)

How the TL494 Works

Oscillator Setup – The frequency is set by RT & CT (Formula: f ≈ 1.1 / (RT × CT)).
PWM Generation – Compares the sawtooth waveform with error amp output to control duty cycle.
Output Stage – Can be configured in single-ended or push-pull mode (Pin 13 selects mode).
Feedback Control – Error amplifiers adjust PWM based on voltage/current feedback.

Common Applications

✅Switch-Mode Power Supplies (SMPS) – Used in PC PSUs, battery chargers.

✅ DC-DC Converters – Boost/buck converters for voltage regulation.

✅ Inverters – Converts DC to AC (modified sine wave).

✅ Motor Speed Control – PWM-based speed regulation.

✅ LED Drivers – Constant current/voltage control.

Example Circuit (Basic Inverter Setup)

A classic 12V to 220V inverter uses the TL494 to generate a 50Hz/60Hz signal driving MOSFETs in a push-pull configuration.

Key Steps:

Set oscillator frequency (e.g., 100Hz for 50Hz output after division).
Use error amp for feedback (over-voltage/current protection).
Drive MOSFETs via a gate driver transformer.

Pros & Cons

✔ Highly configurable for different topologies.

✔ Built-in protections (dead-time control, error amps).

✔ Widely available & cost-effective.

❌ Requires external components (MOSFETs, drivers).

❌ Not ideal for high-frequency designs (max ~300kHz).

Final Thoughts

The TL494 remains a go-to choice for PWM control in power electronics due to its simplicity, robustness, and versatility. Whether you're building an SMPS, inverter, or motor controller, this IC offers great performance with minimal complexity.