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A pulse-width modulated circuit applies a voltage across a load in accordance with a command signal. The command signal is converted into first and second trains of pulses, by electronically comparing the command signal, and its inverse, with a triangular dither signal. These two pulse trains, and t

A pulse-width modulated circuit applies a voltage across a load in accordance with a command signal. The command signal is converted into first and second trains of pulses, by electronically comparing the command signal, and its inverse, with a triangular dither signal. These two pulse trains, and two pulse trains obtained by taking the complements of the original pulse trains, are applied to a pair of bridge circuits. The load is connected to both bridge circuits. Both bridge circuits include electronic switching devices actuated by the pulses. The bridge circuits are configured such that when a pulse is present, from either the first or the second pulse train, no net voltage appears across the load. At all other times, substantially the entire power supply voltage is applied across the load. Compared to pulse-width modulated circuits of the prior art, having similar pulse frequencies and power supplies, the present circuit reduces the undesirable effects of current ripple through the load by a factor of four. This reduction is due to the use of two alternating pulse trains, which doubles the effective frequency of pulses, and to the fact that the maximum voltage excursion of the signal across the load is no greater than the absolute value of the maximum power supply voltage available. As a result, the present circuit has a much higher bandwidth than circuits of the prior art having comparable voltage and frequency parameters.

대표청구항 ▼

A circuit for providing a current through a load, the current being generated by a power supply having a predetermined maximum voltage, the current through the load being determined by a command signal, the circuit comprising: (a) means for converting the command signal into a first train of pulses,

A circuit for providing a current through a load, the current being generated by a power supply having a predetermined maximum voltage, the current through the load being determined by a command signal, the circuit comprising: (a) means for converting the command signal into a first train of pulses, the pulses of the first train having a width which is representative of the value of the command signal, the first train of pulses being called signal x, (b) means for inverting the command signal, and for converting the inverted command signal into a second train of pulses, the pulses of the second train having a width which is representative of the value of the command signal, the second train of pulses being called signal x′, (c) means for providing a signal which is the complement of signal x, the latter being called signal y, (d) means for providing a signal which is the complement of signal x′, the latter being called the signal y′, (e) a pair of bridge circuits, the first bridge circuit including four switching means, two of the switching means being controlled by signal x and two of the switching means being controlled by signal y, the second bridge circuit also including four switching means, two of the switching means of the second bridge circuit being controlled by signal x′and two of the switching means of the second bridge circuit being controlled by signal y′, (f) the load being connected to both bridge circuits such that the load receives pulses of voltage applied through electrical paths formed in the bridges, wherein the first bridge is connected across two terminals extending from the load, and wherein the second bridge is connected across the same two terminals, wherein both the first and second bridges are connected to each other at the same terminals which extend from the load, wherein the pulses of voltage are of a frequency which is substantially double the frequency of pulses of signal x, and wherein the magnitude of the peak-to-peak voltage across the load is no greater than the magnitude of the maximum voltage of the power supply.