TL494 - UC3710T High Current Driver for Half-Bridge Inverter/SMPS High V...

High Voltage Power Supply with TL494

Complete Circuit Diagram

TL494 - UC3710T High Current Driver for Half-Bridge Inverter/SMPS High Voltage Power Supply

Overview:

Power inverters play a crucial role in converting direct current (DC) electricity into alternating current (AC) electricity, enabling the use of electronic devices and appliances that operate on AC power. The process involves several key components, including a gate driver, a low DC voltage to high voltage DC converter, and a high voltage DC to modified square wave DC to AC inverter.

1. Gate Driver: At the heart of a power inverter is the gate driver, which is responsible for controlling the switching of power transistors. Power transistors are semiconductor devices that allow or block the flow of electrical current. The gate driver ensures precise and synchronized switching of these transistors, enabling the conversion of DC to AC.

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3. Low DC Voltage to High Voltage DC Converter: The power source for the inverter is typically a low DC voltage, often sourced from batteries or solar panels. To make this power suitable for the inverter's operation, a low DC voltage to high voltage DC converter is employed. This converter boosts the input DC voltage to a higher level, usually in the range of a few hundred volts. This high voltage DC serves as the intermediate stage before being converted to AC.

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5. High Voltage DC to Modified Square Wave DC to AC Inverter: The main component responsible for converting the high voltage DC into AC is the inverter itself. This process involves the creation of a modified square wave or a modified sine wave, depending on the type of inverter. The modified square wave is a stepped approximation of a sine wave and is often sufficient for powering many household and electronic devices.

   The inverter utilizes power transistors that are switched on and off in a specific sequence, creating an alternating current waveform. This waveform is then shaped to mimic a sine wave through various techniques, such as pulse-width modulation (PWM). Pulse-width modulation involves adjusting the width of the pulses in the square wave to approximate the sinusoidal waveform more closely.

   The resulting AC output is then available for powering a variety of devices, making it compatible with standard household appliances and electronics.

It's important to note that some high-quality inverters produce a pure sine wave output, which closely resembles the waveform of electricity supplied by utility companies. Pure sine wave inverters are generally more efficient and compatible with a wider range of electronic devices, but they are often more expensive.

In summary, a power inverter transforms low DC voltage into high voltage DC, and then the high voltage DC is converted into a modified square wave or modified sine wave AC output through precise switching of power transistors and waveform shaping techniques. This process enables the use of a variety of electrical devices that require alternating current power sources.

Video Tutorial

TL494 Pinout and Pin Functions

TL494 Pinout and internal block diagram

The TL494 is a popular pulse-width modulation (PWM) controller integrated circuit (IC) that is commonly used in power supply and voltage regulation applications. It's widely used in switch-mode power supplies and inverters. The TL494 comes in a standard 16-pin dual-in-line (DIP) package, and each pin serves a specific function. Below is an overview of the TL494 pinout and its corresponding pin functions:

1. Pin 1 (Comp):

   • Function: Compensation pin.
   • Purpose: Connects to an external resistor and capacitor to adjust the error amplifier's response and compensate for any variations in the power supply.

2. Pin 2 (FB):

   • Function: Feedback input.
   • Purpose: Connects to an external voltage divider that samples the output voltage. The feedback voltage is compared to the internal reference voltage to regulate the output.

3. Pin 3 (RT/CT):

   • Function: Oscillator timing resistor and capacitor connection.
   • Purpose: Connects to an external resistor (RT) and capacitor (CT) to set the frequency of the internal oscillator, determining the PWM switching frequency.

4. Pin 4 (GND):

   • Function: Ground.
   • Purpose: Connects to the ground reference of the circuit.

5. Pin 5 (Vcc):

   • Function: Supply voltage input.
   • Purpose: Connects to the positive supply voltage, typically between 7V and 40V, to power the IC.

6. Pin 6 (Out):

   • Function: Output.
   • Purpose: The PWM output signal is present on this pin. It is used to drive an external power transistor or MOSFET that controls the power delivered to the load.

7. Pin 7 (Discharge):

   • Function: Discharge transistor collector.
   • Purpose: Connects to an external resistor to discharge the timing capacitor during the discharge portion of the oscillator cycle.

8. Pin 8 (Vref):

   • Function: Reference voltage output.
   • Purpose: Provides a stable reference voltage of approximately 5V. This pin can be used as a reference for other components in the circuit.

9. Pin 9 (Deadtime):

   • Function: Deadtime control.
   • Purpose: Connects to an external resistor to set the dead time between the complementary PWM outputs to prevent shoot-through in the power switches.

10. Pin 10 (Control Voltage):

    • Function: Control voltage input.
    • Purpose: Connects to an external resistor to set the internal reference voltage and regulate the output voltage.

11. Pin 11 (Sync):

    • Function: Synchronization input.
    • Purpose: Allows external synchronization of the PWM oscillator to an external clock source.

12. Pin 12 (Reset):

    • Function: Reset input.
    • Purpose: When pulled low, this pin resets the latch in the error amplifier, disabling the output.

13. Pin 13 (Vfb):

    • Function: Voltage feedback.
    • Purpose: Connects to an external resistor divider to sample the output voltage and provide feedback to the error amplifier.

14. Pin 14 (S/S):

    • Function: Soft start.
    • Purpose: Connects to an external capacitor to control the soft-start time, gradually ramping up the PWM duty cycle during startup.

15. Pin 15 (Error Amplifier Inverting Input):

    • Function: Error amplifier inverting input.
    • Purpose: Connects to the inverting input of the error amplifier, which compares the feedback voltage to the reference voltage to regulate the output.

16. Pin 16 (Error Amplifier Non-Inverting Input):

• Function: Error amplifier non-inverting input.
• Purpose: Connects to the non-inverting input of the error amplifier, which compares the feedback voltage to the reference voltage to regulate the output.

TL494 Current-Mode PWM Controller IC Explained: Pinout, Equivalent, Sample Circuits, Applications, Features 

TL494 PWM IC Pinout DIP Package electrobuff.blogspot.com

 

TL494 Current-Mode PWM Controller
TL494 Pinout

The TL494 IC is a fixed frequency current-mode PWM controller IC with all the functions that are required in the construction of the pulse-width modulation (PWM) control circuit on a single chip.

 

TL3843 Pinout Configuration

Pin Number	Pin Name	Description
1	1IN+	Noninverting input to error amplifier 1
2	1IN-	Inverting input to error amplifier 1
3	FEEDBACK	Input pin for feedback
4	DTC	Dead-time control comparator input
5	CT	Capacitor terminal used to set the oscillator frequency
6	RT	Resistor terminal used to set the oscillator frequency
7	GND	Ground Pin
8	C1	The collector terminal of BJT output 1
9	E1	The emitter terminal of BJT output 1
10	E2	The emitter terminal of BJT output 2
11	C2	The collector terminal of BJT output 2
12	VCC	Positive Supply
13	OUTPUT CTRL	Selects single-ended/parallel output or push-pull operation
14	REF	The 5-V reference regulator output
15	2IN-	Inverting input to error amplifier 2
16	2IN+	Noninverting input to error amplifier 2

TL494 Specifications & Features

• Supply Voltage: 7V to 40V
• Number of Outputs: 2 Output
• Switching Frequency: 300 kHz
• Duty Cycle - Max: 45 %
• Output Voltage: 40 V
• Output Current: 200 mA
• Fall Time: 40 ns
• Rise Time: 100 ns
• Available in 16-pin PDIP, TSSOP, SOIC and SOP Packages

 

Equivalent/Substitute for TL494: UC3843, TL3842

Alternatives PWM controller IC:  UC2842, SG2524

 

Where to use the TL494 PWM Controller IC

The TL494 fixed frequency PWM Controller can be used for DC to DC conversion regardless of buck or boost topology. TL494 can be used to provide a constant current by varying the output voltage to the load. This IC feature an output control circuit, a flip flop, a dead time comparator, two different error amplifiers, a 5V reference voltage, an oscillator, and a PWM comparator.

So if you are looking for an IC to produce PWM signals for controlling a power switch based on the current flowing through the circuit, then this IC might be the right choice for you.

 

How to use TL494 IC

A test circuit from the TL494 datasheet is shown below.

TL494 PWM IC Circuit Application and Pinout electrobuff.blogspot.com

Non inverting pins are connected to the Ref pin while inverting pins are connected to the ground. Test inputs are given to DTC and FEEDBACK pins. External capacitor and resistor are connected to pin 5 & 6 to control the oscillator frequency. The error amplifier compares a sample of the 5-V output to the reference and adjusts the PWM to maintain a constant output current

 

Applications of TL494

• Desktop PCs
• Microwave Ovens
• Server PSUs
• Solar Micro-Inverters
• Washing Machines: Low-End and High-End
• E-Bikes
• Power: Telecom/Server AC/DC Supplies:
• Smoke Detectors
• Solar Power Inverters

 

2D-Model of TL494

Dimensions for TL3494 IC is given below. These dimensions are for the PDSO package. If you are using a different package IC, please refer to the TL494 datasheet.

TL494-Dimensions 2D PCB Footprint  electrobuff.blogspot.com

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