Dual 35V 300 Watt SMPS Circuit

Designing a high power dual 35V 300 Watt SMPS circuit demands careful consideration of parameters such as power, resistance and voltage to achieve optimal performance.

What is a Dual 35V 300 Watt SMPS Circuit:

A high power dual of 35V 300 Watt SMPS circuit needs to be designed correctly in terms of power, resistance and voltage in order to function at the highest level.

The circuit for a Dual 35V 300W SMPS Switched Mode Power Supply can give a total power output of 300 watts and two output voltages of ±35 volts.

Audio amplifiers and other electrical devices that need a constant high power DC voltage frequently use this kind of power source.

Circuit Working:

Parts List:

• Printed Circuit Board
• MOSFETs SPB17N80C3
• IC UC3844
• Heat sinks
• Resistors, capacitors and diodes
• Power supply components (transformer, rectifier)
• Voltage regulators
• Wiring and connectors
• Multimeter and oscilloscope
• Soldering iron and solder
• Insulating materials

It is necessary to choose MOSFETs with a low on state resistance Rds on so as to reduce conductive losses.

The standard resistance in the conductive state (Rds on typ) for a 300W power supply should not be greater than 0.8 R.

This can be achieved by significantly reducing the total resistance by connecting MOSFETs in parallel.

A key component is the voltage across the UDSs source and drain terminals.

UDS should ideally be between 900 and 1000V with 800V as a backup in the worst circumstances.

Keeping a safe margin within the specified voltage range requires extreme caution.

The decision between MOSFETs and IGBTs comes up when thinking about power semiconductor devices for this dual 35V 300 Watt SMPS circuit.

It is crucial to keep in mind that 600V IGBTs may not be suitable for the use.

IGBTs with a 1200V rating however, may react more slowly.

In practical tests the MOSFET SPP17N80C3 which have an extremely low resistance of 0.25 R, is compared against an IGBT such as the BUP213 which proved larger losses.

Formulas:

Below are the formulas for Dual 35V 300 Watt SMPS Circuit:

R_total = R_dson / N

The above formulas are used to calculate the total equivalent resistance Rtotal of N MOSFETs linked in parallel when they are in the conducting mode or on state.

Below is an explanation of the terminology and the idea:

R_dson is the drain to source on resistance of a single MOSFET is represented as R_dson.

When a MOSFET is turned on the conducting current, it is the resistance between the drain and source terminals of the MOSFET.

A MOSFET with a lower R_dson is more efficient and loses less power as a result of internal resistance.

N is the number of MOSFETs linked in parallel is indicated by this.

Parallel Connection is the voltage across the terminals of components connected in parallel is the same.

When parallel connections are made the overall resistance is less than the resistance of each individual component.

The Formulas Operation:

Imagine that each MOSFET has a resistance Rdson.

By connecting them in parallel you are only creating multiple paths for current to flow.

According to formulas the total resistance Rtotal is equal to the number of parallel MOSFETs N divided by the initial on resistance of a single MOSFET Rdson.

Transformer and Inductor Details:

Tr1 is transformer with a ferrite core, EE type, without a gap, cross sectional area 90 to 140 mm²

Tr2 is the Inductor with 80 turns wound with two wires of diameter 0.8 to 1 mm simultaneously.

The core is a large iron powder toroid (yellow-white or green-blue for example, from a PC power supply internal diameter 14 mm, external diameter 27 mm and height 11 mm)

L1 is 2x inductor 20 turns of 0.8 mm on a ferrite cylinder from a PC power supply.

Warning:

It is not advised for newbies to design dual 35V 300 Watt SMPS circuits since they involve circuits that are paired to potentially lethal mains voltage.

Circuits with poor design may allow mains voltage to reach the output.

Also, even after being disconnected from the mains capacitors may continue to hold hazardous voltage.

Involve yourself in this project at your own risk as no accountability is taken for any property or health damage.

There are various processes and factors to take into account when building a high power switching supply.

Here is an important technique for building a 300W power switching supply with MOSFETs in parallel while the details can change depending on the design and parts selected.

How to Build:

• Select MOSFETs such as SPP17N80C3 that have low on state resistance and work well for high power applications.
• Based on the desired power rating calculate the required number of MOSFETs.
• To lower on state resistance connect MOSFETs in parallel.
• To provide equal load sharing use the proper resistors for gate source voltage balancing.
• Choose a transformer that provides the voltage and power requirements.
• Add a circuit for a rectifier to change AC to DC.
• Use voltage regulators to keep the output voltage constant.
• Feedback circuits can be used to control and modify the output.
• To disperse heat released during operation connect heat sinks to the MOSFETs.
• To avoid overheating make sure there is sufficient thermal coupling.
• When designing a PCB layout take signal integrity, heat dissipation and component placement into account.
• To construct the PCB layout use design services or software tools.
• Using the layout as a guide assemble the parts on the PCB.
• Correctly soldering connections provides a strong electrical connection.
• To confirm voltage levels and waveforms test the circuit with an oscilloscope and multimeter.
• Look for any bad connections or short circuits.

Safety Measures:

• Place precautions into action to guard against overheating, overvoltage and overcurrent.
• To avoid accidental contact enclose the circuit in a suitable protection

Note:

The article give us a general idea but some aspects may change depending on the circuit parts and layout requirements selected.

It is important to check the datasheets by thorough testing and follow safety measures through out the circuit building process.

Seek help from an expert or educated person if you lack experience with high voltage circuits.

References

Switch−Mode Power Supply