Hybrid pulse width-pulse rate digital-to-analog converter method and apparatus

In a digital-to-analog converter in which multi bit digital representations of instantaneously measured analog wave form voltages are received as inputs and from which it is desired to produce analog voltage outputs by controlling the total energy content of the output spectrum produced by an output voltage from a switched supply means, which waveform spectrum is applied to an integrator to reconstruct the desired analog waveform, the method of operating said converter comprising steps of:

• allocating the total duration of a voltage output from said switched voltage supply into n discontinuous periods of time, each of said periods having at least a minimum duration;
• and
• controlling the duration of each of said allocated discontinuous periods of time independently and in correspondence with the digital value of said received inputs, said periods being increased in duration over said minimum period by a number of said minimum sized increments the total number of said increments of increase being equal to the binary value of the totality of the high order bits contained in said multi bit digital input, said total incremental increase in duration being divided equally among said n discontinuous periods;
• and also increasing certain of said n discontinuous periods of time by one said minimum increment each, the number of said periods so increased being in correspondence with the binary value of the individual low order bits of said multi bit digital input.