US 5,471,122 A · DC-motor bridge driver with end-of-braking detector

Abstract

A full-bridge driver, and especially an entirely integrated bridge driver, for driving DC motors in either direction is capable of automatically braking the motor when the motor direction is to be reversed. The bridge circuit is of "H" configuration and has four transistor switches connected in bridge configuration and has two bridge output terminals to which a motor may be connected. A differential window comparator has the input connected to the two bridge output terminals, producing a high level binary signal only when the voltage across the two output terminals is within a small voltage range centered at about zero volts. A pulse-width filter circuit having an input connected to the window comparator produces a high binary output signal only when the comparator-produced binary signal remains high for greater than a predetermined time. The effect of the pulse-width filter in combination with the window comparator is to ignore the first occurrence during braking of zero motor voltage, and to recognize the second occurrence of zero motor voltage which indicates the end of the braking period at which time the motor has stopped, after which the motor can be operated in the reverse direction without creating large transient transistor and motor currents during such a transition of motor running direction.

Claims7

Dependent claims

A full-bridge permanent magnet DC-motor driver circuit of the kind having four transistor switches connected in bridge configuration and having two bridge output terminals to which a motor may be connected, wherein the improvement comprises:

an end-of-braking detector including:
a) a differential window comparator having a differential input connected to said bridge output terminals and having a comparator output, for producing a binary signal of a first level at said comparator output only when the voltage across said two bridge output terminals is within a small voltage range centered at about zero volts;
and
b) a pulse-width filter circuit means having an input connected to said window comparator output and having a filter circuit output, for producing an end-of-braking signal of a particular binary level at said filter circuit output only when said comparator-produced binary signal remains at the first level for greater than a predetermined time.

1 more element

A full-bridge permanent-magnet-DC-motor driver comprising:

a) a full-bridge including a pair of DC voltage supply terminals, an upper pair of transistor switches connected to one of said DC supply terminals and a lower pair of transistor switches connected to the other of said DC supply terminals, a first of said upper pair transistors and a first of said lower pair transistors connected in series between said DC supply terminals, a second of said upper pair transistors and a second of said lower pair transistors connected in series between said DC supply terminals, two bridge output terminals connected respectively to the junctions between said series-connected first transistors and said series-connected second transistors;
and
b) an end-of-braking detector comprising a differential window comparator having a differential input connected to said bridge output terminals and having a comparator output, for producing a binary signal of a first level at said comparator output only when the voltage across said two bridge output terminals is within a small voltage range centered at about zero volts;
and a pulse-width filter circuit means having a filter circuit output and having an input connected to said window comparator output, for producing an end-of-braking signal of a particular binary level at said filter circuit output only when said comparator-produced binary signal remains at the first level for greater than a predetermined time.

1 more element

Dependencies are inferred from the claim text.

DC-motor bridge driver with end-of-braking detector

Life of this patent

DC-motor bridge driver with end-of-braking detector

Life of this patent

Abstract

Claims7