The TL494 is a legendary integrated circuit. Introduced in the late 1970s by Texas Instruments, it has become the backbone of countless switch-mode power supplies (SMPS), from simple boost converters to sophisticated offline flyback designs. Its longevity is a testament to its robustness and flexibility: it features pulse-width modulation (PWM) control, two error amplifiers, a dead-time control comparator, and an internal oscillator—all packed into a 16-pin DIP or SOIC package.
Available on GitHub's sunnyiisc Spice Collections or via customized fixes on MK Dynamics .
Comprehensive Guide to Simulating the TL494 in LTspice The TL494 is a industry-standard pulse-width modulation (PWM) control circuit. It is widely used in switch-mode power supplies (SMPS), DC-DC converters, and inverter designs. Simulating this controller in LTspice allows you to test loop stability, duty cycle limits, and dead-time control before building physical hardware.
: Start your simulation with a long enough time (e.g., 10ms-20ms) to allow the internal tl494 ltspice
To use the TL494 in LTspice, you must download two files—the subcircuit (.sub) symbol (.asy)
The biggest challenge is that LTSpice does not include a native TL494 model in its standard library. You have three options:
The simulation results are shown below:
Run the simulation. Probe the collector output pins. You should see a PWM signal at ~11 kHz. Vary the voltage at the non-inverting input of error amplifier 1 (pin 2) to see duty cycle modulation.
power_inverter/ltspice/logic/tl494/tl494. sub at master · texane/power_inverter · GitHub.
: If you did not place the .sub file into the system directory, add the following text command anywhere on your schematic: .include TL494.sub Use code with caution. Running the Analysis The TL494 is a legendary integrated circuit
The is a match made for power electronics engineers. While finding a reliable model requires a bit of searching, the payoff is immense: you can iterate on compensation networks, observe startup behavior, and catch shoot-through currents without risking hardware.
+--------------------------------------------+ | TL494 | | | | [1] 1IN+ (V_FB) VCC [12] <--+--- VDC (+12V) | [2] 1IN- (V_REF) GND [11] <--+--- GND | [3] FEEDBACK C1 [8] ----> Output Switch 1 | [4] DTC (GND) E1 [9] | [5] CT (To C_ext) C2 [11] ----> Output Switch 2 | [6] RT (To R_ext) E2 [10] | [14] REF (5V Out) OUT_CTRL [13] ----> V_REF (Push-Pull) +--------------------------------------------+ Essential Pin Connections for the Simulation: : Connect Pin 12 ( VCC ) to a DC source. Connect Pin 7 ( GND ) to the SPICE ground ( G ). Oscillator Setup : Connect Pin 5 ( CT ) to a capacitor to ground. Connect Pin 6 ( RT ) to a resistor to ground.
The TL494 is a popular PWM (Pulse Width Modulation) controller IC used in a wide range of power supply applications, including switching power supplies, DC-DC converters, and motor control circuits. LTSpice, on the other hand, is a powerful and widely-used SPICE-based circuit simulator that allows designers to simulate and analyze complex electronic circuits. In this article, we will explore how to use LTSpice to simulate and analyze TL494-based power supply circuits. Available on GitHub's sunnyiisc Spice Collections or via
Better: use oscillator half-cycle detection (simplified for stability)
The TL494 model typically includes several functional blocks that must be correctly biased for simulation: Error Amplifiers (Pins 1, 2 and 15, 16)