Before diving into circuits, it is crucial to understand the pins. The TL494 is available in DIP-16, SOIC-16, and TSSOP-16 packages.
| Pin No. | Name | Function | |---------|------|----------| | 1 | 1IN+ | Non-inverting input of Error Amplifier 1 | | 2 | 1IN- | Inverting input of Error Amplifier 1 | | 3 | FEEDBACK | PWM comparator input (usually for output voltage control) | | 4 | DTC | Dead-Time Control (sets minimum off-time) | | 5 | CT | Timing Capacitor (sets oscillator frequency) | | 6 | RT | Timing Resistor (sets oscillator frequency) | | 7 | GND | Ground | | 8 | C1 | Collector of Output Transistor 1 | | 9 | E1 | Emitter of Output Transistor 1 | | 10 | E2 | Emitter of Output Transistor 2 | | 11 | C2 | Collector of Output Transistor 2 | | 12 | VCC | Positive supply voltage (7V to 40V) | | 13 | OUT CTRL | Output control (High = Push-Pull mode, Low = Single-ended) | | 14 | REF | 5V Precision Reference Output | | 15 | 2IN- | Inverting input of Error Amplifier 2 | | 16 | 2IN+ | Non-inverting input of Error Amplifier 2 |
The TL494 is arguably one of the most successful and iconic integrated circuits (ICs) in the history of power electronics. Introduced by Texas Instruments in the late 1970s, this fixed-frequency, pulse-width modulation (PWM) control IC has stood the test of time. From inexpensive computer power supplies (PSUs) in the 1990s to modern inverter circuits, battery chargers, and DC-DC converters, the TL494 remains a favorite among hobbyists and professional engineers.
Searching for a TL494 circuit diagram often leads to confusing schematics or incomplete theory. This article aims to be the definitive guide. We will break down the internal architecture, explain the pinout, and provide practical, tested circuit diagrams for several key applications: a basic PWM generator, a buck converter (step-down), a boost converter (step-up), and a full-bridge inverter. tl494 circuit diagram
| Application | Configuration | |-------------|---------------| | Boost converter | Single-ended, external MOSFET | | Push-pull inverter | Pin 13 to REF, external transformers | | Battery charger | Use second error amp for current limiting | | Solar MPPT controller | Dual-loop control using both error amps | | ATX power supply modification | Replace original PWM controller |
Before building a power supply, build this simple test circuit to verify your TL494 works. It outputs complementary square waves without feedback.
Specifications:
Component List:
Operating Notes:
If you need 24V from a 12V battery, use this TL494 boost circuit diagram. Before diving into circuits, it is crucial to
Principle: When the MOSFET turns on, current flows through L1 to ground. When it turns off, the magnetic field collapses, forcing current through D1 into the output capacitor at a higher voltage than the input.
Design Notes for Boost Topology:
Warning: Boost converters are dangerous to prototype. If the MOSFET fails shorted, input voltage appears directly at the output, destroying your load. Always add a fuse. Component List: