Connect Pin 4 directly to GND.
By following these guidelines, you can effectively use the TL494 in LTspice for a wide range of power electronics simulation tasks.
Dead Time Control (Pin 4)
Feedback input (pin 5) overrides if lower D_FB 5 6 DCLAMP .MODEL DCLAMP D(Vfwd=0.7)
Vin (120V AC) --> Bridge Rectifier --> Vcc (170V DC) Vcc --> R1 --> TL494 (Pin 1) TL494 (Pin 2) --> R2 --> Q1 (MOSFET) TL494 (Pin 3) --> R3 --> Q2 (MOSFET) Q1 --> L1 --> Vout (12V DC) Q2 --> Vout tl494 ltspice
Verify FB pin is not pulled above ~3.5V, and COMP pin voltage is below sawtooth peak.
| Error | Likely cause | Fix | |-------|--------------|-----| | Unknown subcircuit | Missing .lib directive or wrong filename | Add .lib TL494.sub | | Floating node | Unconnected input pins | Tie unused inputs to GND or VREF via 10k | | No oscillation | CT/RT missing or DTC > 3V | Set DTC ≤ 0.5V, check CT/RT values | | Output always high/low | Feedback pin (3) not driven | Connect to error amp output or voltage source | | Convergence error | Steep edges, missing cap | Add 1nF from outputs to GND, use uic or startup | Connect Pin 4 directly to GND
Simulating the TL494 in LTspice allows you to test power converter topologies—such as push-pull, half-bridge, and buck regulators—before building physical hardware. This article provides a comprehensive guide to sourcing the model, installing it, and configuring a functional simulation. Sourcing and Installing the TL494 Model Files