*3.2.2. Series resonant converter with inductive output filter*

The converter topology shown in Figure 15 is an LCL type SRC with inductive output filter. This uses an LCL resonant tank for soft switching of high frequency switches and an inductive output filter. Its main characteristics can be summarized as follows:


Note: This configuration can also be modified to a series resonant converter (SRC), which uses an (L-C)||C resonant tank for soft switching of high frequency switches, which, in this case is also called series-parallel resonant converter (SPRC).

*3.2.4. Full-bridge converter with controlled at secondary side*

which represents a drawback of the converter.

and input line voltage variations.

**1.** Control is easy and simple.

input voltage conditions.

**Figure 17.** PWM full-bridge converter.

*3.2.5. Current-fed two-inductor boost converter*

voltage.

The configuration shown in Figure 17 corresponds to a secondary side controlled converter with a full-bridge inverter on primary side and phase-controlled rectifier on secondary side. The switches on primary side are operated by complementary gating scheme with fixed duty ratio. The switches on secondary side are controlled to produce phase difference between primary and secondary side voltages of HF transformer to control the output voltage with load

Methodology of Designing Power Converters for Fuel Cell Based Systems: A Resonant Approach

http://dx.doi.org/10.5772/54674

345

**2.** The switches on secondary side show ZVS or ZCS depending upon the line and load,

**3.** The switches on secondary side show ZVS for lower input voltage and ZCS for higher

**4.** The efficiency of this converter is near to 92%, obtained at full load and varying line

Figure 18 shows the current-fed two-inductor boost converter, which is a dual of voltage-fed half-bridge converter configuration. This topology requires a very small turns ratio trans‐ former with only two switches used on the primary side. The turn off of the primary switches is smooth since voltage across the switches is sinusoidal. Also the same for turn on and turn off of rectifier diodes. However, the peak and average current through rectifier diodes is high and this is very difficult to achieve ZVS at variable line input and load condition. This topology

is a good selection for constant-input and constant-output voltage applications.

The main characteristics of this configuration can be summarized as follows:

**Figure 15.** Series Resonant converter with inductive output filter.

#### *3.2.3. PWM full-bridge converter with inductive output filter*

The configuration shown in Figure 16 is Phase-shifted full bridge converter with inductive output filter. This is most widely used soft-switched configuration for high power applications. This constant frequency converter features ZVS of the primary switches with relatively small circulating circuit. The ZVS is achieved by filter inductance, transformer leakage inductance, snubber capacitance and parasitic junction capacitances of switches. The control of the output voltage at constant frequency is achieved by phase shift technique. Its main characteristics can be summarized as follows:


**Figure 16.** PWM full-bridge converter.
