Pulse width modulator

Claim 2

Pulse width modulation apparatus for providing an output signal whose duration depends upon the deviation of an input signal from a predetermined value, said modulation apparatus comprising: means means for producing a pair of output pulse signals and for cyclically varying each signal between first and second voltage values, one of said output signals normally having the first value when the other output signal has the second value and vice versa; means responsive to the input signal for varying the time period that one of said output signals is at its first and second values; an output terminal for applying said output signals to a load; and a logic circuit connected between said output terminal and said output signal-producing means, said logic circuit including means for coupling said output terminal to said output signalproducing means only when each of said output signals is at its first voltage value.

Claim 3

Pulse width modulation apparatus as defined in claim 1 wherein said logic circuiT comprises and AND-gate having: a first input for receiving one of said output signals; a second input for receiving the other of said output signals; and an output coupled to said output terminal.

Claim 4

Pulse width modulation apparatus as defined in claim 1 wherein said means for producing said output signals and for varying the duration of said one output signal comprises: a monostable multivibrator for producing said one output signal; an astable multivibrator for producing the other of said output signals; and means for modulating said monostable multivibrator for changing the time period that said one output signal signal is at its first and second values.

Claim 5

Pulse width modulation apparatus as defined in any one of claims 1- 3 wherein the frequency of said output signals are approximately double the highest frequency of said input signal. 5, Pulse width modulation apparatus as defined in any one of claims 1-4 wherein the frequency of said output signals is approximately 25kHz.

Claim 6

Pulse width modulation apparatus for providing a pair of output signals whose respective durations are dependent upon the direction and amount of deviation of an input signal from a predetermined value, said modulation apparatus comprising: carrier-generating means for generating first and second output pulse signals and for cyclically varying each signal between first and second voltage values; carrier-modulating means for producing third and fourth output pulse signals and for cyclically varying each signal between first and second voltage values, said first output pulse signal normally having the first voltage value when said third output pulse signal has the second voltage value and vice versa second output pulse signal normally having the first voltage value when said fourth output signal has the second voltage value and vice versa; means responsive to the direction and amount of deviation of the input signal from the predetermined value for varying the time period that said third and fourth output signals are at their first and second values; output terminals for applying said output signals to a load; and a logic circuit connected between said output terminals and said carrier-generating and modulating means, said logic circuit including means for coupling said output terminals to said carrier-generating and modulating means only if each of said first and third output signals is at its first value or if each of said second and fourth output signals is at its first value.

Claim 7

Pulse width modulation apparatus for providing a pair of output signals whose respective durations are dependent upon the direction and amount of deviation of an input signal from a predetermined value, said modulation apparatus comprising: carrier-generating means for generating first and second output pulse signals and for cyclically varying each signal between first and second voltage values; carrier-modulating means for producing third and fourth output pulse signals and for cyclically varying each signal between first and second voltage values, said first output pulse signal normally having the first voltage value when said third output pulse signal has the second voltage value and vice versa second output pulse signal normally having the first voltage value when said fourth output signal has the second voltage value and vice versa; means responsive to the direction and amount of deviation of the input signal from the predetermined value for varying the time period that said third and fourth output signals are at their first and second values; output terminals for applying said output signals to a load; and a logic circuit connected between said output terminals and said carrier-generating and modulating means, said logic circuit including means for coupling said output terminals to said carrier-generating and modulating means only if each of said first and third output signals is at its first value or if each of said second and fourth output signals is at its first value.

Claim 8

Pulse width modulation apparatus as defined in claim 6 wherein said logic circuit comprises: a first AND-gate having first and second inputs for receiving said first and third output signals, respectively, said first AND-gate further having an output coupled to one of said output terminals; and a second AND-gate having first and second inputs for receiving said second and fourth output signals, respectively, said second AND-gate further having an output coupled to the other of said output terminals.