TL494 PWM (Pulse Width Modulation) IC Tutorial : How to use in Power Supplies & Inverters

TL494 IC PWM (Pulse Width Modulation) Circuit Overview

TL494 IC PWM Pulse Width Modulation Circuit electrobuff.blogspot.com

TL494 is a PWM controller integrated circuit that you can use for devices with power electronic circuits. It features two on-chip error amplifiers alongside an oscillator for adjusting frequencies, an output control circuit with feedback, and a flip-flop output with pulse steering control.
The error amplifiers are responsible for compensating voltage between -0.3 to VCC -2V in a standard voltage configuration. Also, the comparator dishes out almost a 5% range by controlling the dead-time with a fixed offset.
Further, the external oscillator provides a reference frequency signal for the PWM integrated circuit, while the Internal Regulator delivers a stable 5 V Reference Supply. However, you can always bypass the on-chip oscillator by attaching an RT to the output pin of the reference.
Interestingly, the TL494 is a complete PWM power-control circuitry that you can use for single-end operations. Also, the TL494 is useful for push & pull configurations.

Watch my YouTube Video Tutorial

https://youtu.be/dBlKm6VGC5M?si=ibzQCZUBkU4YzZwu

TL494 Specifications

The supply voltage ( Vcc) is up to 41 volts
The maximum output current for both PWMs is 250mA
Output voltage at collector pins is 41 volts
It has a temperature range of -65 to 150 degrees

TL494 Features

It has an in-built PWM control channel
200mA sink or source current
It has dual output selectable operations, which include Single-ended and push-pull operation
The TL494 has a variable range deadtime control feature
You can easily synchronize the TL494 with other circuits
It has two PWM outputs
It comes with a fixed frequency oscillator

TL494 Pinout & Pin Configuration

TL494 pinout electrobuff.blogspot.com

TL494 internal block diagram electrobuff.blogspot.com

TL494 block diagram guide electrobuff.blogspot.com

Pin Name	Pin NO.	Pin Description
1IN+	1	Noninverting input to error amplifier 1
1IN	2	Inverting input to error amplifier 1
2IN+	16	Noninverting input to error amplifier 2
2IN-	15	Inverting input to error amplifier 2
C1	8	The collector terminal of BJT output 1
C2	11	The collector terminal of BJT output 2
CT	5	The capacitor terminal used to set the oscillator frequency
DTC	4	Dead-time control comparator input
E1	9	The emitter terminal of BJT output 1
E2	10	The emitter terminal of BJT output 2
FEEDBACK	3	Input pin for feedback
GND	7	Ground
OUTPUT CTRL	13	Selects single-ended/parallel output or push-pull operation
REF	14	The 5-V reference regulator output
RT	6	The resistor terminal used to set the oscillator frequency
VCC	12	Positive Supply

How does the TL494 PWM controller work?

As mentioned earlier, it is a fixed frequency and variable duty cycle dual PWM control circuit. It does not require any external components to operate except a few resistors and capacitors for an oscillator. This oscillator is responsible for generating a sawtooth waveform according to timing capacitor CT. This TL494 IC generates signals by comparing a sawtooth waveform with two control signals of the error amplifiers. The output signal will be on during the time when sawtooth voltage is greater than the voltage at error amplifiers outputs. You can see a block diagram given above.

Output signal low: if sawtooth voltage less than the control signal voltage
Output signal High: if sawtooth voltage greater than the control signal voltage

Pulse-Steering Flip-Flop transfers the PWM output signal to output transistors.

How to select TL494 Oscillator Frequency?

In the last section, we see that the oscillator is mainly responsible for generating sawtooth waveform. This sawtooth waveform used for deadtime control and PWM comparator amplifiers. Therefore, the frequency of the oscillator determines the frequency of output signals. Now, we will see how to choose the frequency of an oscillator.

We can select frequency by selecting suitable values of RT resistor and CT capacitor. We can select the capacitor and resistor values according to this formula:

Frequency= 1/ RT X CT

TL494 Frequency calculation Formula electrobuff.blogspot.com

TL494 Applications

Switch Mode Power Supplies
High Power Inverters
Power Electronics Applications
Power factor correction meters
Desktop and Portable applications

TL494 Packages

This IC is available in four different 16 pin packages such as SOIC, PDIP, SOP, TSSOP. You can check the datasheet for the 2D physical dimension diagram of these packages.