FORWARD CONVERTER

Forwar Converter With PI Controller

9-36V Input Voltage, 28 Output Voltage, All Ripple: %2, 50KHz, 50 Watt DC-DC Forward Converter Design And Production

The aim of the project is to design and produce a dc-dc forward converter according to following requirements: Vin: 36-9 V, Vout: 28 V, Power: 50 Watt, Ripple Ratings: 2%, Fsw : 50 KHz, Control System: PI with a STM32F4 MCU. In addition to this, this paper shows formulas, calculations, experimental and simulation results of dc-dc forward converter.

Forward Converter

A forward converter is a switched-mode power supply (SMPS) circuit that transfers energy to secondary side from primary side and ensures to decrease secondary side input voltage. Forward converter circuit is similar to the fly-back converter circuit but it is more efficient than fly-back converter circuit. Forward converter is mainly used for the application which requires higher power output. Secondary side of forward converter basicly derives from buck converter. But forward converter can increase or decrease the input voltage thanks to transformer. Forward converter is an isolated circuit as it has transformer.

As per the above block diagram, when the switch is turned ON, the input is applied to the primary winding of the transformer and a voltage is appeared at the secondary winding of transformer. Therefore, the dot polarity of the windings of transformer is positive, due to this the diode D1 gets forward biased. Then the output voltage of the transformer is fed to the low pass filter circuit which is connected to the load. When switch is turned OFF, the current in the windings of transformer comes down to zero (assuming the transformer to be ideal). A typical forward converter consists of a:  Transformer which is either a step-up or step-down with a single or multiple secondary windings. The type used depends on the available input voltage and desired output voltage. It also provides isolation of the load from the input voltage.

• Switching components
• Diodes
• Capacitors
• Inductor

Circuit Design For Simulation On Simulink

The all calculations, values and simulations result in the report.

Circuit Schematic

PCB Design

About Software

As it is known, this designed circuit is designed as a close loop system and will be controlled by PI. The software of this circuit works as follows: voltage is read with ADC and required ratio calculation is made. This calculated value enters the PI algorithm and is compared with the setpoint. If this value is not the same as the setpoint, the PI calculates a new value close to or the same as the setpoint. This value is again proportioned and the PWM signal driving the mosfet is updated again.

The closed loop system of Forward Converter is as above diagram. It is PID system. But Kd equals 0 as seting PI. The software generally consists of two or three main modules:

1. main.c : It is the file where all the configurations are found, the main algorithm and PWM are set.
2. ADC_READ.c : It is an analog reading value module that I developed specially for the STM32F4 discovery board.
3. PID.c : It is the module where I wrote the PID algorithm. Other folders belong to the HAL Library used and the processor's drivers.

All necessary explanations are in the software modules in the software folder in the project file.

Product:

If you have any question, you can contact me.

Omer Karslioglu omerkarsliogluu@gmail.com