Tl494 Ltspice [2021] -

The TL494 is a fixed-frequency PWM controller widely used in switch-mode power supplies (SMPS). Its robustness stems from its flexibility: it contains two error amplifiers, an adjustable oscillator, a precise 5V reference, and output steering logic. While LTspice does not include a built-in TL494 model by default, its functionality can be replicated using behavioral sources, or by utilizing the specific vendor models provided by manufacturers like Texas Instruments or ON Semiconductor. This paper focuses on the behavioral modeling approach for educational clarity and simulation speed.

* TL494 Behavioral Model for LTspice .SUBCKT TL494 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 * Pins: 1(IN1+) 2(IN1-) 3(FB) 4(DT) 5(CT) 6(RT) 7(GND) 8(C1) 9(E1) 10(C2) 11(E2) 12(VCC) 13(OUT_CTRL) 14(VREF) 15(IN2+) 16(IN2-)

Let's construct a basic open-loop test to verify the TL494's core functions. tl494 ltspice

At 100kHz, the sawtooth waveform on CT (pin 5) should ramp from approximately 0.5V to 2.8V, then discharge quickly. The output on the collectors should be a PWM signal varying with the voltage on pin 3.

Simulating a buck converter with the TL494 can be a good starting point. A typical schematic includes the TL494, its timing components (R, C), an output stage consisting of a MOSFET and a gate driver, an inductor, a capacitor, and a feedback network from the output voltage to the TL494's error amplifier. The TL494 is a fixed-frequency PWM controller widely

Click Simulate -> Edit Simulation Cmd .

Move the subcircuit file ( tl494.sub or .lib ) to the subcircuit directory: C:\Users\[YourUsername]\Documents\LTspiceXVII\lib\sub\ This paper focuses on the behavioral modeling approach

Connect to GND for minimum dead time, or to a small voltage to set a specific dead time.

The schematic diagram of the circuit is shown below:

Schematic summary:

Connect OUTPUT CTRL to GND . Both output transistors toggle simultaneously, allowing up to a 90% duty cycle. 5. Running the Simulation