An alternative-circuit arrangement of a two-quadrant converter, operating from a single-phase supply, is a fully controlled bridge-circuit as shown in Fig.1. The operation of this circuit is in principle similar to that of the two -pulse midpoint circuit. In the bridge circuit, diagonally opposite pair of thyristors are made to conduct, and are commutated, simultaneously.

During the first positive half-cycle, SCRs $T_{1}$ and $T_{2}$ and $T_{2}$ are forward biased and if they are triggered simultaneously, then current flows through the path $L-T_{1}-R-T_{2}-N .$ Hence, in the positive half cycle, thyristors $T_{1}$ and $T_{2}$ are conducting.

During the negative half-cycle of the a.c. input, SCRs $T_{3}$ and $T_{4}$ are forward biased and if they are triggered simultaneously, current flows through the path $N-T_{3}-R-T_{4}-L .$ Thyristors $T_{1}, T_{2}$ and $T_{3}, T_{4}$ are triggered at the same firing angle $\alpha$ in each positive and negative half-cycles of the supply voltage, respectively.

When the supply voltage falls to zero, the current also goes to zero. Hence thyristors $T_{1}, T_{2}$ in positive half-cycle and $T_{3}, T_{4}$ in negative half cycle turn-off by natural commutation. The related voltage and current waveforms for this circuit are shown in Fig.2. The relations for $E_{\mathrm{dc}}, I_{\mathrm{dc}}$ and $E_{\text { rms }}$ for this bridge configuration is similar to the equations in mid-point configuration.