Tl494 Circuit Diagram May 2026

Understanding the TL494: A Deep Dive into the Classic PWM Control Circuit

If you’ve ever cracked open a PC power supply or a car audio amplifier, there is a very high chance you’ve seen a 16-pin chip labeled TL494. Released decades ago, this integrated circuit remains the "old reliable" of the power electronics world.

In this guide, we’ll break down the TL494 circuit diagram, how it works, and how you can use it in your own DIY power projects. What is the TL494?

The TL494 is a fixed-frequency, Pulse Width Modulation (PWM) control circuit. Its primary job is to monitor an output voltage and adjust the "on-time" of its switching transistors to keep that voltage rock-steady. Key Features:

Dual Error Amplifiers: Allows you to monitor both voltage and current simultaneously.

Adjustable Dead-Time Control: Prevents "shoot-through" (where both output transistors are on at once, causing a short).

Uncommitted Output Transistors: Can provide 200mA of current, enough to drive MOSFETs or power transistors directly.

Push-Pull or Single-Ended Options: Versatile enough for many topologies. The Basic TL494 Circuit Diagram

While the internal architecture is complex, a standard application circuit (like a Buck Converter or Inverter) usually follows a specific layout. 1. The Oscillator Section (Pins 5 & 6)

To get the chip running, you need to set its internal frequency. This is done with a resistor ( RTcap R sub cap T ) on Pin 6 and a capacitor ( CTcap C sub cap T ) on Pin 5. Formula:

Common values for a 50kHz frequency are a 10k resistor and a 2.2nF capacitor. 2. The Power Supply (Pins 12 & 7)

Pin 12 (VCC): Accepts a wide range of DC voltage, typically between 7V and 40V. Pin 7 (Ground): Connects to the common negative rail. 3. The Feedback Loop (Pins 1, 2, 15, & 16) This is the "brain" of the circuit.

Voltage Control: Pin 1 (Non-inverting input) usually samples the output voltage via a voltage divider. Pin 2 (Inverting input) receives a reference voltage (usually 5V from Pin 14).

If the output drops, the TL494 increases the PWM duty cycle to compensate. 4. Output Configuration (Pins 8, 9, 10, & 11) The TL494 has two internal transistors.

In Parallel: Used for single-ended designs (like a basic buck converter).

In Push-Pull: Used for inverters or bridge circuits where two sides need to alternate. Common Applications DC-to-DC Buck Converters

By using the TL494 to drive a high-side MOSFET, you can create a highly efficient step-down converter. The chip ensures that even as your battery drains, the output voltage remains exactly where you set it. Pure Sine Wave Inverters

Because of its precision, the TL494 is often the first stage in an inverter circuit, converting 12V DC into a high-frequency AC signal that can then be stepped up by a transformer. LED Dimming and Motor Control tl494 circuit diagram

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

Use the Reference Voltage: Pin 14 provides a very stable 5.0V output. Use this for your feedback dividers rather than the raw VCC to ensure accuracy.

Mind the Heat: If you are driving large MOSFETs at high frequencies, the TL494 might get warm. Consider using a dedicated gate driver IC between the TL494 and your MOSFETs.

Breadboard Caution: High-frequency PWM circuits can be "noisy." For best results, move from a breadboard to a soldered PCB as soon as your design is finalized to minimize interference.

The TL494 might be an "old" chip, but its flexibility and low cost make it a staple for anyone serious about power electronics. Whether you're building a laboratory power supply or a solar inverter, mastering this circuit is a rite of passage.

Are you planning to use the TL494 for a voltage regulator or a power inverter project?

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 |

1. Introduction

The TL494 is a fixed-frequency, pulse-width modulation (PWM) control IC, widely used in switching power supplies, DC-DC converters, battery chargers, and inverters. Understanding its circuit diagram is essential for designing efficient power electronics.

4.3 Battery Charger with Current Limit

Conclusion

The TL494 is a powerful and affordable IC for learning and building PWM-based power electronics. Its two error amplifiers, adjustable dead-time control, and flexible output stage make it suitable for almost any DC-DC conversion or inversion task.

Whether you are building a simple PWM dimmer or a 500W push-pull inverter, the TL494’s circuit diagram follows the same fundamental architecture shown above. Start with the simple PWM generator on a breadboard, then move to a buck or boost converter.

Have you built a circuit using the TL494? Share your experience or questions in the comments below.

The TL494 is a versatile fixed-frequency Pulse Width Modulation (PWM) controller that has served as the backbone of switch-mode power supplies (SMPS) for decades. Its circuit architecture is designed to handle every stage of power regulation—from frequency generation to error correction—on a single chip. Core Functional Blocks

The "deep" logic of the TL494 lies in how its eight internal functional blocks interact to create a stable output:

Designing Switching Voltage Regulators With the TL494 (Rev. E)

is a versatile fixed-frequency Pulse Width Modulation (PWM) controller IC designed to handle all necessary functions for power-supply control on a single chip. It is widely used in applications like switch-mode power supplies (SMPS) , DC-DC converters, and inverters. Core Features and Specifications Dual Error Amplifiers

: On-chip amplifiers allow for feedback control and output regulation by comparing the output voltage to a reference. Adjustable Oscillator

: The internal oscillator's frequency can be set between 1 kHz and 300 kHz using an external resistor ( cap R sub cap T ) and capacitor ( cap C sub cap T Precision 5V Reference Understanding the TL494: A Deep Dive into the

: Provides a stable internal 5V reference supply with a 5% tolerance to simplify external circuitry. Selectable Output Mode

: Supports both push-pull and single-ended operation via the Output Control pin (Pin 13). Variable Dead-Time Control

: Allows users to set a specific "dead time" to prevent switching overlap and protect power transistors. Uncommitted Output Transistors

: Features two transistors capable of sinking or sourcing up to 200 mA (or 500 mA in some variants), offering flexibility for driving external loads. Wide Operating Voltage : Functions reliably with a supply voltage range of Pinout Configuration (16-Pin DIP/SOIC) The following pinout is standard for the TL494 controller Description 1IN+, 1IN- Inputs for the first error amplifier. Input for feedback control. Dead-time control comparator input. External capacitor/resistor to set oscillator frequency. Ground terminal. Collector and Emitter for transistor 1. Emitter and Collector for transistor 2. Positive supply voltage. OUTPUT CTRL Selects single-ended (GND) or push-pull (REF) mode. 5V reference output. 2IN-, 2IN+ Inputs for the second error amplifier. Typical Applications

The TL494 is a staple in various power management solutions, including: Desktop PCs and Servers : Providing regulated power to internal components. Solar Inverters

: Managing power conversion from solar panels to AC or battery storage. Electric Bikes : Controlling motor speed and battery management. Consumer Electronics : Used in microwave ovens and washing machines. circuit diagram for a buck converter or an inverter application? TL494 Pulse-Width-Modulation Control Circuits

• Complete PWM Power-Control Circuitry. • Uncommitted Outputs for 200-mA Sink or. Source Current. • Output Control Selects Single- TL494 - Switch mode Pulse Width Modulation Control Circuit

The TL494 is a versatile and cost-effective pulse-width-modulation (PWM) control IC that has been a staple in power electronics for decades. Designed primarily for switch-mode power supply (SMPS) control, it offers a complete set of functions—including an adjustable oscillator, two error amplifiers, and dead-time control—on a single chip. TL494 Pinout and Functional Diagram

The TL494 is typically housed in a 16-pin DIP or SOIC package. Understanding its pin configuration is essential for designing any TL494 circuit diagram:

The TL494 is a popular fixed-frequency, current-mode Pulse Width Modulation (PWM) controller IC designed primarily for power supply control, such as step-down switching regulators, buck/boost converters, and inverters. It provides all necessary functionality on a single chip, including an oscillator, error amplifiers, dead-time control, and a 5V reference regulator. Typical TL494 Circuit Components

A standard TL494 circuit consists of the following key functional blocks: Oscillator (Pins 5 & 6): An external capacitor ( CTcap C sub cap T ) and resistor ( RTcap R sub cap T ) set the operating frequency.

Error Amplifiers (Pins 1-3, 15, 16): Compare feedback voltage to the reference to adjust PWM.

Dead-time Control (Pin 4): Sets the maximum duty cycle to prevent both output transistors from being on simultaneously.

Output Control (Pin 13): If high, enables alternate output; if low, single-ended output.

Reference Output (Pin 14): Provides a precise 5V regulator output. Basic TL494 Circuit Functionality

Operation: The IC uses an error amplifier to adjust the output voltage relative to the load, providing consistent output current, say, in a buck converter scenario.

Output Driving: The TL494 has two output transistors, which can sink or source up to 200mA, generally requiring an external totem pole gate drive for controlling power MOSFETs effectively. two error amplifiers

Dead Time Control: The DTC pin ensures efficient switching by managing dead time to prevent shoot-through in push-pull topologies. Common Applications

SMPS (Switch Mode Power Supplies): Both buck and boost topologies. Battery Chargers: Such as 36V Li-ion chargers.

Inverters: PC power supplies, solar inverters, and lamp ballasts. If you can tell me: What input and output voltage you need? What is your maximum load current? Are you aiming for a buck, boost, or push-pull circuit?

I can provide a more specific circuit diagram and component values.

TL494 resistors of output signals - Power management forum - TI E2E

is a classic fixed-frequency Pulse Width Modulation (PWM) control integrated circuit (IC) that has served as the backbone for switch-mode power supplies (SMPS) for decades. Its enduring popularity stems from its comprehensive architecture, which integrates all the essential functions for PWM control—oscillator, error amplifiers, dead-time control, and output steering—into a single 16-pin package. The Core Architecture

The TL494 circuit works by comparing a linear sawtooth waveform against two control signals to determine the output pulse width. Microcontrollers Lab The Internal Oscillator

: The timing of the circuit is determined by an external resistor ( cap R sub cap T ) and capacitor ( cap C sub cap T

) connected to pins 6 and 5, respectively. This creates a sawtooth waveform that defines the fixed switching frequency. Dual Error Amplifiers

: These allow the IC to monitor both voltage and current simultaneously. One amplifier typically regulates the output voltage, while the second acts as a current limit for protection. Dead-Time Control (DTC)

: Connected to pin 4, this comparator provides a fixed or adjustable minimum "off" period. This is critical in push-pull configurations to prevent "shoot-through," where both switching transistors are on at the same time, causing a short circuit. Output Steering Flip-Flop

: This internal logic ensures that in push-pull mode, the two output transistors (pins 8–11) alternate correctly, preventing the same output from being pulsed twice in a row. Pin Configuration and Functionality

The 16-pin layout is designed for maximum flexibility in various power topologies: 电子工程世界（EEWorld） Pins 1, 2 & 15, 16 : Inputs for the two error amplifiers. Pin 3 (Feedback)

: Used to compensate the control loop, allowing for stable regulation under varying loads. Pin 13 (Output Control)

: This determines the operation mode. Grounding this pin sets it to "single-ended" mode (both transistors pulse together), while connecting it to the internal 5V reference (Pin 14) enables "push-pull" mode (alternating pulses). Pin 14 (REF)

: Provides a stable 5V reference voltage used for biasing the error amplifiers and setting control thresholds. Diverse Applications

Because the TL494 can operate from 7V up to 40V, it is found in a wide variety of electronics: TL494 Pulse-Width-Modulation Control Circuits

Tl494 Circuit Diagram May 2026