An apparatus (508,510; 802,803) for providing switching signals to at least first and second converter switches (503,504; 841,842) of a closed loop converter for directly converting an input alternating current signal to an output AC signal of the same frequency using synchronous pulse width modulation, the apparatus comprising: a pulse width modulator (508; 801,802) adapted to receive a duty cycle control signal and first ramp signal and to provide substantially complementary first and second switching signals, wherein the duty cycle control signal, in an alternating pattern, changes from an intermediate value to a large positive or negative value before a zero crossing of the input AC signal or the output AC signal, remains at the large positive or negative value respectively, and changes back from the large positive or negative value to the intermediate value after the zero crossing of the input AC signal or the output AC signal; and a selectable crossover module (510; 803) adapted to receive the first and second switching signals produced by the pulse width modulator (508; 801,802) and to provide switching at first and second outputs to the first and second converter switches (503,504; 841,842), the crossover module (510; 803) having first and second modes; wherein in the first mode, the first output of the crossover module (510; 803) is connected to provide the first switching signal, and the second output is connected to provide the second switching signal, and in the second mode, the first output of the crossover module (510; 803) is connected to provide the second switching signal, and the second output is connected to provide the first switching signal; and wherein the selectable crossover module (510; 803) is adapted to change modes based on polarity of the input AC signal and/or on polarity of the output AC signal. a pulse width modulator (508; 801,802) adapted to receive a duty cycle control signal and first ramp signal and to provide substantially complementary first and second switching signals, wherein the duty cycle control signal, in an alternating pattern, changes from an intermediate value to a large positive or negative value before a zero crossing of the input AC signal or the output AC signal, remains at the large positive or negative value respectively, and changes back from the large positive or negative value to the intermediate value after the zero crossing of the input AC signal or the output AC signal; and a selectable crossover module (510; 803) adapted to receive the first and second switching signals produced by the pulse width modulator (508; 801,802) and to provide switching at first and second outputs to the first and second converter switches (503,504; 841,842), the crossover module (510; 803) having first and second modes; wherein in the first mode, the first output of the crossover module (510; 803) is connected to provide the first switching signal, and the second output is connected to provide the second switching signal, and in the second mode, the first output of the crossover module (510; 803) is connected to provide the second switching signal, and the second output is connected to provide the first switching signal; and wherein the selectable crossover module (510; 803) is adapted to change modes based on polarity of the input AC signal and/or on polarity of the output AC signal.