I came across this TL494 PWM controller IC while studying the ATX power supply. It is a PWM controller IC designed to control the power mosfet switches used in various types of power supplies. It is used in DC to DC converters like boost converter, buck converter, flyback, or forward converters. In short, TL494 is a general-purpose PWM controller IC, so it shows up anywhere you need regulated, high-efficiency DC power or controlled switching.
The TL494 can operate in different modes, mainly depending on how you configure its two output transistors.
These modes affect how the PWM pulses are delivered to your power stage.
Single-Ended Mode
* Each output transistor drives its load independently.
* You use only one output (pin 9 or pin 10) to feed your MOSFET driver.
* The output frequency is the same as the oscillator frequency \(f_{OUT} \approx f_{OSC}\).
Use case: Simple buck, boost, or flyback converters.
Push-Pull Mode(Alternating Outputs)
* The TL494 alternates between the two outputs, each driving on opposite half-cycles.
* Output frequency, \(f_c = \frac{f_{OSC}}{2}\) per output, but together they form a full cycle.
Use case: Push-pull converters, full-bridge inverters, center-tapped transformer drives.
Parallel (Paralleled Outputs)
* The two outputs are connected together to increase drive current.
* Both transistors turn on simultaneously for higher load capability.
Use case: Driving a single heavy gate load or external driver stage.
The output mode (single-ended, push-pull, parallel) is set by wiring the outputs (pins 8, 9, 10, 11).
The following shows circuit diagram of TL494 in push pull output mode.
Here are the common TL494 applications:
1. Switch-Mode Power Supplies (SMPS)
* ATX computer power supplies(very common in older designs)
* TV and monitor SMPS boards
* Industrial SMPS units for control electronics
Reason: TL494 integrates PWM generation, error amplifiers, and reference voltage, making it ideal for regulating output voltage in buck converter, boost converter, flyback converter, or forward converters.
2. DC–DC Converters
* Boost converters for battery-powered devices
* Car power adapters (e.g., 12 V → 5 V USB chargers)
* Solar charge controllers
Reason: Can operate in both single-ended and push-pull mode, covering many DC–DC topologies.
3. DC–AC Inverters
* Low-cost sine wave or modified sine wave inverters
* UPS systems (often as the front-end PWM stage)
4. Battery Chargers
* Lead-acid battery chargers with constant-voltage/current control
* NiMH/Li-ion chargers in older or industrial designs
5. Motor Speed Controllers
* PWM-based DC motor controllers
* Servo motor power stages
6. Lighting Control
* LED drivers (especially high-power LEDs)
* Fluorescent lamp ballasts
Why it’s popular?
* Wide supply voltage range (7–40 V)
* Adjustable frequency (up to \~300 kHz)
* Built-in error amplifiers, dead-time control, and reference voltage
* Can directly drive bipolar transistors or MOSFET gate driver stages
