Everything You Need to Know About TL494 Current-Mode PWM Controller

The TL494 device incorporates all the functions required in the construction of a pulse-width-modulation (PWM) control circuit on a single chip. Designed primarily for power-supply control, this device offers the flexibility to tailor the power-supply control circuitry to a specific application.

The TL494 device contains two error amplifiers, an on-chip adjustable oscillator, a dead-time control (DTC) comparator, a pulse-steering control flip-flop, a 5-V, 5%-precision regulator, and output-control circuits.

The error amplifiers exhibit a common-mode voltage range from –0.3 V to VCC – 2 V. The dead-time control comparator has a fixed offset that provides approximately 5% dead time. The on-chip oscillator can be bypassed by terminating RT to the reference output and providing a sawtooth input to CT, or it can drive the common circuits in synchronous multiple-rail power supplies.

The uncommitted output transistors provide either common-emitter or emitter-follower output capability. The TL494 device provides for push-pull or single-ended output operation, which can be selected through the output-control function. The architecture of this device prohibits the possibility of either output being pulsed twice during push-pull operation.

The TL494C device is characterized for operation from 0°C to 70°C. The TL494I device is characterized for operation from –40°C to 85°C.

• Complete PWM Power-Control Circuitry

• Uncommitted Outputs for 200-mA Sink or Source Current

• Output Control Selects Single-Ended or Push-Pull Operation

• Internal Circuitry Prohibits Double Pulse at Either Output

• Variable Dead Time Provides Control Over Total Range

• Internal Regulator Provides a Stable 5-V Reference Supply With 5% Tolerance

• Circuit Architecture Allows Easy Synchronization

• Desktop PCs

• Microwave Ovens

• Power Supplies: AC/DC, Isolated, With PFC, > 90 W

• Server PSUs

• Solar Micro-Inverters

• Washing Machines: Low-End and High-End

• E-Bikes

• Power Supplies: AC/DC, Isolated, No PFC, < 90 W

• Power: Telecom/Server AC/DC Supplies: Dual Controller: Analog

• Smoke Detectors

• Solar Power Inverters

  
  

As we mentioned earlier, the TL494 is a PWM controller circuit. Hence, most of its applications are PWM-based circuits. Here are a few examples:

TL494 Solar Charger

You can easily configure this design by building a 5v/10A switching power supply buck. For this configuration, you can get your output in parallel modes. While you’re at it, connect the output-control pin 13 to the ground.

This application also uses two error amps efficiently (one controls voltage feedback and maintains a constant output while the other controls the maximum current).

TL494 Classic Inverter Circuit

In this application, you can configure the output to work in the push-pull mode. Hence, it would help connect the out-put control pin with the +5 V reference to pin 14. The other nails have the same configuration as the pinout datasheet above.

Equivalent/Substitute for TL494: UC3843, TL3842

Alternatives PWM controller IC:  UC2842, SG2524

A test circuit from the TL494 datasheet is shown below.

Non-inverting pins are connected to the Ref pin while inverting pins are connected to the ground. Test inputs are given to DTC and FEEDBACK pins. The external capacitor and resistor are connected to pins 5 & 6 to control the oscillator frequency. The error amplifier compares a sample of the 5-V output to the reference and adjusts the PWM to maintain a constant output current

The TL494 fixed frequency PWM Controller can be used for DC to DC conversion regardless of buck or boost topology. TL494 can be used to provide a constant current by varying the output voltage to the load. This IC feature an output control circuit, a flip flop, a dead time comparator, two different error amplifiers, a 5V reference voltage, an oscillator, and a PWM comparator.

So if you are looking for an IC to produce PWM signals for controlling a power switch based on the current flowing through the circuit, then this IC might be the right choice for you.