The problem of the complex control switching algorithm is effectively tackled in [17] by introducing the simple control scheme in which only two switching signals govern the overall circuit operation. Here the variable frequency at the output is insured by alternatively inverting and non-inverting the input voltage for both half cycles of the input voltage. This converter uses eight controlled switches and eight diodes, as can be seen in Figure 1. The emitter of each switching IGBT is connected to the anode of a diode. This connection arrangement of a transistor and diode simplifies the switching or control scheme. For example, four IGETs \(Q_{1}\), \(Q_{4}\), \(Q_{6}\), and \(Q_{7}\), are turned on simultaneously with one control input. During positive input voltage, the turned-on IGETs \(Q_{4}\) and \(Q_{7}\) cannot conduct as their series-connected diodes are reverse biased. In the same way, the turned-on IGETs \(Q_{1}\) and \(Q_{6}\) remain off because their series-connected diodes maintain their reverse bias state once the input polarity is negative. The switching signal generated by a PWM controller is connected to an IGBT via a gate driving circuit. As there are eight IGETs that are to be turned on and turned off, so the realization of this topology requires eight gate driving circuits. This overall impact increases the circuit size, cost, and complication. The reduction of two controlled switches (IGBTs or MOSFETs) and two diodes is ensured in [18] to simplify the circuit in terms of size and cost. Its realization only requires six diodes and six MOSFETs, as shown in Figure 2. This converter operates in a similar fashion as in [17] but with fewer solid-state devices. A center tap transformer-based direct ac-ac topology, as depicted in Figure 3, is introduced in [19]. Here a single-phase full-wave diode rectifier is connected at the output of the center tap transformer. Two fully controlled switching transistors are employed to realize the variable frequency at the output. There is a problem with the current shoot-through during the high-frequency operation. In addition, the use of the low-frequency center tap transformer has many power quality concerns that are reported in [20]. The large component count and solid-state devices are a big challenge in these converters. The use of large component count and solid-state devices is reduced in the proposed research. Here variable frequency at the output is ensured by cascading a single-phase  
Figure 1: Dual bridge direct ac-ac converter. Figure 3: Direct frequency converter topology based on center tap transformer. Figure 2: Direct frequency controller with reduced solid-state devices. full-bridge diode rectifier and high-frequency full-bridge inverter by eliminating the dc-link capacitor at the intermediate stage. This elimination solves the problem of low reliability and reduces the size and cost. The output of the first stage is now a pulsating dc, meaning that the output is the absolute value of the input voltage. Then this output is converted to high-frequency ac with the help of a second-stage high-frequency inverter just by non-inverting and inverting it. Therefore, with this circuit arrangement, only four diodes and four switching transistors ensure conversion of low input frequency to the high frequency at the output. There is no need to align the gating signal required for controlling the switching transistors with the input voltage, as the rectified voltage at the output of the first converting stage is a pulsating voltage, as there is no need to use a dc-link capacitor to smooth it. This feature enables the employment of any low-cost PWM generator like Arduino. The switching action of the transistors alternatively non-inverts and inverts the input at the output continuously to get variable output frequency. This characteristic improves the power quality and power factor of the input current.