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In this article, we will present a boost converter circuit to step up 12-24 volts DC using a transformer, and another circuit using the UC3843 chip. Both circuits rely on entirely different operating principles. Let’s start with the transformer circuit.
12 VDC to 24 VDC
The purpose of this circuit is to obtain a voltage of 24 volts from a 12-volt source. It is used in many electronic devices such as phones, computers, and power bank circuits (which typically step up voltage from 1.2 volts to 5 volts, etc.).
The circuit is designed straightforwardly, and with some simple modifications, it can boost any voltage values.
Transistors Q1 and Q2 of type (D1616) primarily drive the primary winding of the transformer. The diodes rectify the output from the transformer to obtain a 24-volt DC output under load (which is the fan in our example). Meanwhile, capacitors play an important role in filtering noise and ripples in the output signal.
12V to 24V Boost Circuit
Notes on the Circuit:
- The component values are not precisely defined here. Any NPN transistor such as D1616, 2N3055, C2236, SL100, etc., can be used for transistors Q1 and Q2.
- Any center-tapped transformer with a turns ratio of 7:1 can be used.
- Diodes 1N914 can be utilized.
- All the mentioned components can be easily found if you search in your magical toolbox as an electrical engineer.
- By experimenting with the transformer winding, different voltage boosting values can be achieved.
- To achieve high current values (around 5 amps), you can use a 2N3055 transistor or Darlington pairs for transistors Q1 and Q2.
You can learn about the simplest 12-volt 70 amp battery charging circuit through this article.
Voltage Boosting Circuit Using UC3843
The size of the transformer can be somewhat confusing. Most voltage boosting circuits use a different method than transformers that boost voltage through two coils with different thicknesses, wire types, and number of turns. Electronic boost circuits that contain a chip or IC rely on switching current through an inductor in the circuit. The inductor generates a high voltage during discharge that exceeds the source voltage. This principle is entirely different from that of a conventional transformer for boosting voltage and yields a much higher efficiency.
This is the principle in simplified terms, but there are additional complexities that the UC3843 chip handles.
Let’s get to know the UC3843 electronic chip, which is a PWM pulse generator with a fixed frequency (50 kHz). It was primarily designed for DC to DC conversions. It mainly requires some auxiliary electronic components connected to its terminals. It is a fantastic circuit with many features and can drive an external MOSFET transistor.
As we can see, the chip has 8 pins. By referring to the DATASHEET for this circuit, we can assemble a voltage boosting circuit, leading us to the following final circuit:
Electronic Components for the Voltage Boosting Circuit:
- UC3843 Chip
- IRFZ44 MOSFET Transistor
- R2060CT Diode
- 100uH Inductor
- 3 Capacitors (1nF)
- 4 Capacitors (1000uF, 50V)
- 10k Trimpot Variable Resistor
- 1 Resistor (0.1R, 5W)
- 1 Resistor (22R)
- 1 Resistor (470R)
- 1 Resistor (2K2)
- 3 Resistors (10k Ohm)
- 1 Resistor (100k)
- 2 Pin Terminal Block Power Connectors
- Connecting Wires
It is essential to place a heat sink for the IRFZ44 transistor.
The MBR2060CT diode is of the Schottky type. It is widely used in voltage converters because it has a low forward voltage drop. This is very important for reducing power losses and achieving higher efficiency in the circuit. The diode can handle a forward current of up to 20 Amperes.
The reason for using this diode is for protection. We used it as a freewheel diode to allow current to flow in one direction when the MOSFET is turned off, protecting the transistor from back current.
The 10k Ohm variable resistor is necessary for precisely adjusting the output voltage, as it allows us to set the reference voltage applied to pin number 2 of the IC. The chip uses this voltage to regulate the output voltage.
Have you tried this circuit? Or do you have another preferred voltage boosting circuit? Share your thoughts in the comments.
