Isolated Input Boost Controller with HCPL3120 and GT30F124

Function of the Boost converter is to convert DC voltage to higher DC voltage levels. Boost converts are used in various application in modern electronics from inverters to almost every mobile equipment. Minimal boost converters consist mainly of an inductor and a switching transistor. Today we are going to see how to make a minimal boost converter with isolated input for controlling the voltage levels. For this we are going to use GT30F124 IGBT as the switching transistor and the HCPL3120 optocoupler as the input signal isolator.

What is HCPL3120?

HCPL3120 is an optical isolator with inbuilt gate driving capabilities. You can see the physical appearance of the HCPL3120 IC in below image.

Figure 1. — Physical Appearance of HCPL3120

Pinout of HCPL3120:

HCPL3120 is made with 8Pin DIP package and it is available in both SMD and THT mounting types. You can see the pinout of the HCPL3120 optocoupler IC and pin description of the HCPL3120 IC in below.

Figure 2. — Pinout of HCPL3120

Let’s see more details the pins of HCPL3120 optical isolator IC

· Pin 1 — N/C — Not connected to anything.

· Pin 2 — Anode– Anode or the positive pin of the input signal LED.

· Pin 3 — Cathode — Cathode or the negative pin of the input signal LED.

· Pin 4 — N/C — Not connected to anything.

· Pin 5 — VEE– Negative or the ground level

· Pin 6 — VO — Gate Drive pin

· Pin 7 — VO — Gate Drive pin

· Pin 8 — Vcc — Gate positive voltage

Features of HCPL3120:

Lets discuss the main features of the HCPL3120 IC.

· Wide operation voltage of 15V to 30V.

· 2.5A gate current

· 500ns Switching time

· Under voltage lock out protection

What is GT30F124?

GT30F124 is a N channel IGBT suitable for general purpose switching applications. You can see the symbol of the GT30F124 in below given image.

Figure 3. — Symbol of GT30F124

Pinout of GT30F124:

GT30F124 comes in TO220SIS package with 3 pins. Pinout of the GT30F124 IGBT is given in below image.

Figure 4. — Pinout of GT30F124

Let’s see more details the pins of TCA785 phase angle control IC

· Pin 1 — G (Gate) — Gate pin of the GT30F124 IGBT

· Pin 2 — C (Collector) — Collector pin of the IGBT.

· Pin 3 — E (Emitter) — Emitter pin of the GT30F124.

Features of GT30F124:

We can identify fallowing features of the GT30F124 IGBT by studying it’s datasheet

· Maximum output current of 50A

· 500V maximum CE voltage

· 4kV isolation between input and output.

Basic Circuit Diagram:

You can find the circuit diagram of the boost controller in following image.

Figure 5. — Boost Converter Circuit Diagram

Key Components :

We will need the fallowing components to build the boost converter circuit.

1. UTSOURCE FGPF4633 N channel IGBT

2. UTSOURCE HCPL3120 Optocoupler IC

3. 3.9mH inductor

4. 1N4001 diode

5. 220Ω resistor

6. 3.9mH inductor

Tools Needed:

1. Soldering Iron

2. Iron Stand

3. Flux

4. Nose pliers

Step By Step Guide:

Step 1: Arrange the components.

Step 2: Connect the components as shown in the circuit diagram using a proof board

Step 3: Supply the Input DC voltage and connect the controller output to the input pins.

Step 4: you can set the output voltage by varying the pulse width of the input signal

How It Works:

When the transistor is switched on it will connect the inductor to the input voltage. When the IGBT is switched off the stored energy will flow to the capacitor and by doing this process in high speed it will increase the output voltage.

Conclusion:

We can use this circuit to drive higher voltage devices using low voltage sources using this circuit. We can improve this by adding a close loop feedback to the signal generator