Method of Regulating an AC Signal

1 . A method of regulating an ac input signal to provide an ac output signal, comprising:

receiving the ac input signal;

generating a reference signal;

detecting the points when the ac input signal is zero and synchronising the reference signal to these points;

performing a subtraction between the reference and ac input signals to obtain an error signal;

dividing the error signal by the reference signal to obtain a fractional error; and

producing a regulated ac output signal by modulating the ac input signal to correct for the fractional error.

2 . The method of claim 1 , further comprising ensuring the error signal is of a single polarity.

3 . The method of claim 2 , comprising adding an offset to the error signal to ensure that it is of a single polarity.

4 . The method of claim 1 , further comprising scaling the fractional error and then modulating the ac signal to correct for the scaled fractional error.

5 . The method of claim 1 , further comprising performing a scaling to adjust the relative magnitudes of the ac input signal and the reference signal and then performing a subtraction between the scaled reference and ac input signals to obtain an error signal.

6 . The method of claim 4 , comprising scaling relative to the voltage of an electrical grid.

7 . The method of claim 6 , comprising scaling relative to a rms voltage of 230 volts.

8 . The method of claim 4 , comprising scaling the ac input signal.

9 . The method of claim 1 , comprising subtracting the scaled ac input signal from the reference signal .

10 . The method of claim 1 , comprising generating a reference signal corresponding to a full wave rectified sinusoid, and full wave rectifying the ac input signal.

11 . The method of claim 1 , comprising pulse width modulating the ac input signal to correct for the fractional error.

12 . The method of claim 11 , comprising pulse width modulating by using a comparator to compare the fractional error to a ramp signal.

13 . The method of claim 12 , comprising pulse width modulating to remove portions of the ac input signal when the fractional error indicates that the voltage of the ac input signal exceeds the reference signal.

14 . The method of claim 1 , comprising feeding back the ac output signal, and using the feedback signal during the regulation to compensate for inaccuracies in the ac output signal.

15 . The method of claim 14 , comprising modifying the ac input signal according to the feedback signal to compensate for inaccuracies in the ac output signal.

16 . The method of claim 1 , comprising allowing the voltage of the regulated ac output signal to drop when a connected load requires a large current.

17 . The method of claim 16 , further comprising scaling the fractional error and then modulating the ac signal to correct for the scaled functional error, and allowing the voltage to drop by adjusting the scaling.

18 . The method of claim 1 , further comprising regulating the ac input signal using a switching regulator comprising:

input terminals for receiving the ac input signal; output terminals for providing the regulated ac output signal;

an inductor and/or a capacitor arranged to smooth the regulated ac output signal appearing at the output terminals;

a positive half-cycle part and a negative half-cycle part arranged to regulate the positive and negative half-cycles respectively of the input ac signal; each of the positive and negative half-cycle parts comprising:

a modulating transistor operable to modulate the respective half-cycle of the ac input signal and having an associated modulator diode arranged to allow current flow through the modulating transistor during that modulating transistor's respective half-cycle and to resist current flow through the modulating transistor during the other half-cycle; and

a clamping diode arranged to protect the modulating transistor from reverse-bias voltages and having an associated clamp switch operable to connect the clamping diode into the regulator during that modulating transistor's respective half-cycle and to disconnect the clamping diode from the regulator during the other half-cycle; the method further comprising using the modulating transistors to produce the regulated ac output signal by modulating the ac input signal to correct for the fractional error.

19 . A switching regulator for regulating an ac signal, the regulator comprising:

input terminals for receiving an ac input signal;

output terminals for providing an output signal;

an inductor and/or a capacitor arranged to smooth the output signal appearing at the output terminals;

a positive half-cycle part and a negative half-cycle part arranged to regulate the positive and negative half-cycles respectively of the input ac signal;

each of the positive and negative half-cycle parts comprising:

a modulating transistor operable to modulate the respective half-cycle of the ac input signal and having an associated modulator diode arranged to allow current flow through the modulating transistor during that modulating transistor's respective half-cycle and to resist current flow through the modulating transistor during the other half-cycle; and

a clamping diode arranged to protect the modulating transistor from reverse-bias voltages and having an associated clamp switch operable to connect the clamping diode into the regulator during that modulating transistor's respective half-cycle and to disconnect the clamping diode from the regulator during the other half-cycle; the regulator further comprising:

a signal generator arranged to generate a reference signal; and

an arithmetic unit arranged to perform a subtraction between the reference and ac input signals to obtain an error signal, and to divide the error signal by the reference signal to obtain a fractional error; and wherein the modulating transistors are arranged to produce a regulated ac output signal by modulating the ac input signal to correct for the fractional error.

20 . The switching regulator of claim 19 , further comprising a first switching controller operable to cause the modulating transistors to switch, and a second, separate switching controller operable to cause the clamp switches to switch.

21 . A computer programmed to cause a switching regulator to operate in accordance with the method of claim 1 .

22 . A computer program that, when loaded into a computer, causes a switching regulator to operate in accordance with the method of claim 1 .

23 . A computer readable medium carrying a computer program according to claim 22 .