Forward Converter Calculator

Omni Calculator's forward converter calculator helps you find the output voltage and ripple current of your forward converter circuit.

Keep with us in this article to explore:

• What is a forward converter​?

• Forward converter design​ and the forward converter circuit.

• Flyback vs. forward converter​.

• What are the applications of a forward converter?

• Can a forward converter boost voltage?

• What are the advantages of a single-switch converter?

• How do you calculate the windings ratio for a forward converter?

With our forward converter calculator, you can choose freely whether to step up or down your voltage.

A forward converter is another example of a DC/DC converter that uses a transform to step up or down an output voltage. Like a flyback converter, the forward converter comprises two galvanically isolated electronic circuits.

A circuit is sad to be galvanically isolated if a transformer is added to the converter, providing electrical isolation between the input and output circuits. This design transfers energy between the two sides of the converter despite no direct current flowing between these circuits. The forward converter transformer​ has an ungapped core, and it transfers energy directly from the input to the output circuit during the switch-on period.

We can see in the diagram below a standard example of a forward converter where:

• $Q_1$ — Switching transistor, typically a MOSFET;
• $C_\mathrm{in}$ and $C_\mathrm{out}$ — Capacitors on the input and output circuits, respectively;
• $N_p$ and $N_s$ — Primary and secondary windings of a transformer​;
• $D_1$, $D_2$, and $D_3$ — Diodes for a proper current flow;
• $L_1$ — Inductor to control the output current and reduce the ripple in the output voltage;
• $N_d$ — Reset winding to make sure that the transformer's magnetic core is reset during the switch-off period;
• $V_\mathrm{in}$ and $V_\mathrm{out}$ — Input and the output voltages; and
• $I_\mathrm{ripple}$ — Ripple current to the output inductor $L_1$.

Moreover, in our forward converter calculator, we will consider a relation $1:1$ between $N_d$ and $N_p$. This is often used to simplify the forward converter design and improve efficiency.

Now that we know about the forward converter design​, we can approach the equations behind it. The key parameters that we can compute are the output voltage and the ripple current.

The output voltage can be computed using the following equations:

where:

• $V_{\mathrm{in}}$ — Input voltage;
• $V_{\mathrm{out}}$ — Output voltage;
• $D$ — Duty cycle;
• $N_p$ — Primary winding;
• $N_s$ — Secondary winding; and
• $N$ — Windings ratio.

Moreover, we can use the duty cycle and the windings ratio to find the ripple current over the $L_1$ inductor. The ripple current is determined through the formula:

where:

• $L$ — Inductance of $L_1$; and
• $f_s$ — Switching frequency.

We know that it was a lot to understand. However, our forward converter calculator is here to make all the hard work for you instantaneously.

The flyback and forward converters are variations of a DC/DC converter. They have some similarities, like the possibility to set up or step down an output voltage and the fact that they are galvanically isolated. However, their main differences are the process of energy transfer, the sizes of the transformers, and the frequencies of operation.

The flyback converter stores energy in the magnetic core of the transformer during the "on" period of the switch and releases it in the "off" period. As we saw, the forward converter transfers energy directly from the input to the output circuit during the "on" period of the switch. The forward converter transformer​ is larger and works at higher power than the flyback converter.

Moreover, the flyback converter is efficient at lower to moderate switching frequencies, while the forward converter operates better at higher frequencies.

In this example, we will show how easy and intuitive using our calculator is. Thus, let us consider the following set of parameters for our forward converter:

• $V_{\mathrm{in}} = 15\, \mathrm{V}$;
• $D = 30\%$;
• $N_p = 20$;
• $N_s = 40$;
• $f_s = 150\,\mathrm{kHz}$; and
• $L = 180\,\mu\mathrm{H}$.

By substituting them in our tool, we can determine the respective values for the output voltage and the ripple current: $V_{\mathrm{out}} = 9\, \mathrm{V}$, and $I_{\mathrm{ripple}} = 233.33\,\mathrm{mA}$.

You should always remember that our calculator works backward and forward. Thus, you can use the output voltage and the ripple current to determine other parameters, such as the duty cycle or the input voltage.