Buck Converter Disadvantages

One of the main disadvantages of the buck converter and the interleaved buck converter is the narrow duty cycle which limits the application of the converters for high step-down applications. The interleaved buck converter with high conversion ratio overcomes this drawback. This converter provides continuous input current and also reduces the voltage stress of the semi-conductor devices to below the input voltage. This is possible due to the presence of two input capacitors. Also, compared to the conventional interleaved buck converter the converter provides much lower output current ripple. The simulation of the circuit with 200 V input, 24V/10A output is done using MATLAB. One-cycle control is used to generate the gate pulses.

The step-down

Thus, the regulation period is very short and becomes very difficult in high frequency applications. In applications where non-isolated, high step-down conversion ratio and high output current with low ripple are required, interleaved buck converters (IBC) have received a lot of attention. Fig. 1. shows the conventional interleaved buck topology. However the semiconductor devices in the conventional IBC suffers from input voltage stress and hence various topologies have been introduced to reduce the voltage stress. In [2] an IBC having low switching losses has been implemented by carrying out zero current transition. [3] describes a topology in which the switches are connected in series rather than parallel. The voltage stress of the semiconductor devices is half of the input voltage after turn-on and before turn-off. However, the input rms current is high in spite of the interleaved structure. [4] introduces a two phase transformer-less interleaved structure with an improved step-down conversion ratio and lower switch voltage stress. It can be noted that in [4] for a 2 phase converter 4 switches are used and the number of components are higher. Thus, the topology becomes more complicated as the number of phases

The relationship between the number of phases and the passive element design is given. PWM generated pulses are provided as gate signals to the interleaved converters. [18] discusses a hysteretic controller which provides the required pulses for the interleaved converter. The control circuit for N number of phases is described. Fig. 2 shows the control pulse generation, proposed in [18], for two and four interleaved phases. It must be noted that the current shared among the phases of the interleaved converter are balanced. Imbalance in the duty ratio causes one phase to operate at continuous conduction mode and the other phase to operate at discontinuous conduction mode. In [19], a comparison of the current sharing in non-isolated and isolated converters with interleaved structure is