Searching for a modern "TL494 circuit diagram" yields millions of results because the chip is cheap ($0.50), robust, and incredibly forgiving. While specialized chips like the UC3843 or digital controllers exist for specific tasks, the TL494's dual error amplifiers make it unique for battery charging and LED driving where constant current is required.
Whether you are building a 500W inverter for a camping trip, a laboratory power supply, or a solar charge controller, the TL494 remains a reliable, well-documented workhorse. Bookmark this guide, buy a few ICs, and build the circuits above—starting with the simple oscillator test, then moving to the buck converter. Once you see that clean PWM waveform on your oscilloscope, you will understand why this 1970s IC refuses to retire.
For further study, download the official Texas Instruments TL494 datasheet (SLVS074G). It contains 20+ reference designs that directly match the circuit diagrams discussed here.
The TL494 is a versatile, fixed-frequency Pulse Width Modulation (PWM) control circuit designed primarily for Switch Mode Power Supplies (SMPS)
. It is highly popular due to its ability to manage push-pull, bridge, or single-ended output configurations.
Below is a comprehensive overview of the TL494, including its pinout, functional blocks, and a typical circuit design. 1. TL494 Pin Configuration The TL494 comes in a 16-pin package (SOP-16/DIP-16). iFuture Technology 1-IN+ (Pin 1): Non-inverting input of Error Amplifier 1. 1-IN- (Pin 2): Inverting input of Error Amplifier 1. 2-IN- (Pin 15): Inverting input of Error Amplifier 2. 2-IN+ (Pin 16): Non-inverting input of Error Amplifier 2. Feedback (Pin 3): Common feedback output of error amplifiers. DTC (Pin 4): Dead Time Control comparator input (sets minimum off-time). CT (Pin 5): External capacitor for oscillator frequency set. RT (Pin 6): External resistor for oscillator frequency set. GND (Pin 7): Ground reference. C1/E1 & C2/E2 (Pins 8, 9, 10, 11): Collectors and Emitters for Output Transistors 1 & 2. VCC (Pin 12): Supply voltage (7V to 40V). VREF (Pin 14): 5V Reference output (±5% precision). OUTPUT CTRL (Pin 13): Selects parallel (0V) or push-pull (VREF) operation. 2. Functional Block Diagram tl494 circuit diagram
The TL494 integrates several components to manage PWM, as shown in the TI TL494 datasheet Oscillator: Adjustable from 1 kHz to 300 kHz. Error Amplifiers: Two amplifiers to control output voltage and current. PWM Comparator: Compares control signals against a saw-tooth waveform. Dead-Time Controller: Prevents overlap of the two output transistors. 5V Reference Regulator: Provides a stable voltage to external components. 3. Basic TL494 Circuit Diagram (Buck Converter Example) A typical application is a step-down buck converter. Input Pin 12 (VCC): Connected to the unregulated input voltage. Pin 5 (CT) & Pin 6 (RT):
Resistor and capacitor are connected to determine frequency ( Pin 13 (Output Ctrl):
Tied to VREF (pin 14) for push-pull, or Ground for single-ended. Feedback (Pin 3):
Connected through a compensation network to the output voltage for regulation. Outputs (Pins 8-11): Connected to external switching MOSFETs. 4. Key Features & Advantages Versatility: Supports single-ended or push-pull switching. Dead-Time Control: Reduces switching losses by preventing shoot-through. Stability: High-precision, on-chip 5V reference. Alternatives: is a commonly used, functionally equivalent alternative. 5. Common Applications Switch Mode Power Supplies (SMPS). DC-DC Converters (Buck, Boost, Flyback). Inverters and UPS systems. Battery Chargers. For detailed circuit schematics, refer to the TI TL494 datasheet or specialized engineering resources for smps applications
TL494 Pulse-Width-Modulation Control Circuits datasheet (Rev. I) Searching for a modern "TL494 circuit diagram" yields
Before diving into schematics, understanding why you would choose the TL494 over a simpler chip like the SG3525 or a microcontroller is crucial.
This is the most common TL494 circuit diagram for converting a higher voltage (e.g., 24V battery) to a lower voltage (e.g., 12V at 10A).
How it works: Error Amp 1 compares the output voltage to the 5V reference. Error Amp 2 monitors voltage across a current shunt (R_shunt) for over-current protection.
Key Connections:
Schematic Specs:
Critical Component Value:
Even with a perfect TL494 circuit diagram, beginners fail for these reasons:
If you need 24V from a 12V battery, use this TL494 boost circuit diagram.
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.