Pulse width modulator with pulse width limiting

Claim 2

A circuit for producing a periodic generally rectangular pulse having its leading and trailing edges at independently selected points in each cycle comprising: means for producing a periodic timing signal; means connected to receive said timing signal and to switch to a predetermined state after an adjustable interval to form a first pulse of one polarity; means for producing a pulse width limiting signal; means responsive to said pulse width limit signal to switch to a state to form a second pulse of the opposite polarity; means connected to receive said first and second pulses and to produce a pulse having its leading edge corresponding to the leading edge of said first pulse and having its trailing edge corresponding to the leading edge of said second pulse; and means connected to be responsive to said timing pulse producing means to reset said pulse width limiting means.

Claim 3

A control for periodically turning a power switch on and off at independently selected points in each period, comprising: means providing a periodic timing pulse and a simultaneous reset pulse; circuit means connected to receive said timing pulse and to produce a signal to turn on the power switch at a selected delay in the period from said timIng pulse; means connected to receive a pulse width limiting signal and to turn off the power switch in response to said signal, said limiting means remaining in a state to turn off the power switch until reset; and means connecting said pulse width limiting means to receive said reset pulse at the end of each period.

Claim 4

A control for periodically turning a power switch on and off at independently selected points in each period, comprising: means providing a periodic timing pulse and a simultaneous reset pulse; circuit means connected to receive said timing pulse and to produce a signal to turn on the power switch at a selected delay in the period from said timIng pulse; means connected to receive a pulse width limiting signal and to turn off the power switch in response to said signal, said limiting means remaining in a state to turn off the power switch until reset; and means connecting said pulse width limiting means to receive said reset pulse at the end of each period.

Claim 5

A control for periodically turning a power switch on and off at independently selected points in each period comprising: means providing a timing pulse and a simultaneous reset pulse; means connected to receive said timing pulse and to produce a signal to turn on the power switch at a selected delay from said timing pulse; means responsive to an electrical condition in the circuit of the power switch to produce a pulse width limit signal; pulse width limiting means connected to receive said pulse width limiting signal to turn off the power switch, said limiting means remaining in a state to turn off the power switch until reset; and means connecting said pulse width limiting means to receive said reset pulse at the end of each period.

Claim 6

A control for periodically turning a power switch on and off at independently selected points in each period comprising: means providing a timing pulse and a simultaneous reset pulse; means connected to receive said timing pulse and to produce a signal to turn on the power switch at a selected delay from said timing pulse; means responsive to an electrical condition in the circuit of the power switch to produce a pulse width limit signal; pulse width limiting means connected to receive said pulse width limiting signal to turn off the power switch, said limiting means remaining in a state to turn off the power switch until reset; and means connecting said pulse width limiting means to receive said reset pulse at the end of each period.

Claim 7

A control for periodically turning a power switch on and off at independently selected points in each period comprising: means providing a periodic timing pulse and a simultaneous reset pulse; means connected to receive said timing pulse and to produce a signal to turn on the power switch at a selected point during the period; means comparing an electrical characteristic of the circuit of the power switch with a reference and producing a pulse width limiting signal when said characteristic has a predetermined value; and pulse width limiting means connected to receive said pulse width limiting signal and said reset pulse and to turn off the power switch in response to the limiting signal and to maintain the power switch turned off until said limiting means is reset.

Claim 8

A control for periodically turning a power switch on and off at independently selected points in each period comprising: means providing a periodic timing pulse and a simultaneous reset pulse; means connected to receive said timing pulse and to produce a signal to turn on the power switch at a selected point during the period; means comparing an electrical characteristic of the circuit of the power switch with a reference and producing a pulse width limiting signal when said characteristic has a predetermined value; and pulse width limiting means connected to receive said pulse width limiting signal and said reset pulse and to turn off the power switch in response to the limiting signal and to maintain the power switch turned off until said limiting means is reset.

Claim 9

A circuit for periodically turning on and off a semiconductor power switch at selected points in the period, comprising: means providing a periodic timing signal, a monostable circuit responsive to said timing signal to switch to its unstable mode for a selected part of each period, said monostable circuit producing an output when it switches to its stable mode; means connected to produce a limit signal indicating that an electrical characteristic of the power switch has reached an undesirable instantaneous value after the switch is turned on; and means connected to respond to said monostable circuit output and the absence of said timing signal to turn on the switch and responsive to said limit signal to turn off the switch.

Claim 10

A circuit for periodically turning on and off a semiconductor power switch at selected points in the period, comprising: means providing a periodic timing signal, a monostable circuit responsive to said timing signal to switch to its unstable mode for a selected part of each period, said monostable circuit producing an output when it switches to its stable mode; means connected to produce a limit signal indicating that an electrical characteristic of the power switch has reached an undesirable instantaneous value after the switch is turned on; and means connected to respond to said monostable circuit output and the absence of said timing signal to turn on the switch and responsive to said limit signal to turn off the switch.

Claim 11

A circuit for periodically turning on and off a transistor switch at selected points in the period, comprising: means providing a periodic timing signal, a monostable circuit responsive to said timing signal to switch to its unstable mode for a selected part of each period, said monostable circuit producing an output while in its stable mode; means connected to produce a first signal indicating instantaneous undervoltage in the base drive power supply for the transistor switch; means connected to produce a second signal indicating instantaneous overcurrent in the circuit of the switch, a pulse width limit circuit having a set state and a reset state and connected to switch to its set state and produce a limit signal in response to said first or second signals; means connected to respond to the absence of said timing signal, the presence of said monostable circuit output, and the absence of said limit signal to turn on the transistor switch; and means connected to said timing signal means to reset said pulse width limit circuit at the beginning of each period.

Claim 12

A circuit for periodically turning on and off a transistor switch at selected points in the period, comprising: means providing a periodic timing signal, a monostable circuit responsive to said timing signal to switch to its unstable mode for a selected part of each period, said monostable circuit producing an output while in its stable mode; means connected to produce a first signal indicating instantaneous undervoltage in the base drive power supply for the transistor switch; means connected to produce a second signal indicating instantaneous overcurrent in the circuit of the switch, a pulse width limit circuit having a set state and a reset state and connected to switch to its set state and produce a limit signal in response to said first or second signals; means connected to respond to the absence of said timing signal, the presence of said monostable circuit output, and the absence of said limit signal to turn on the transistor switch; and means connected to said timing signal means to reset said pulse width limit circuit at the beginning of each period.

Claim 13

A power control system comprising: means providing a periodic reference signal, pulse forming means connected to receive said reference signal and to form a pulse having its leading edge at a selected point in the period; an electroresponsive load device having A time constant that is long relative to said period; power switch means for connecting said electroresponsive device to a source of power in response to the leading edge of said pulse; pulse width limit means connected to turn off said power switch in response to a pulse width limit signal; and means responsive to a characteristic of said electroresponsive device that changes measurably in each period to signal said pulse width limit means to turn off the power switch when said characteristic reaches a predetermined value.

Claim 14

A power control system comprising: means providing a periodic reference signal, pulse forming means connected to receive said reference signal and to form a pulse having its leading edge at a selected point in the period; an electroresponsive load device having A time constant that is long relative to said period; power switch means for connecting said electroresponsive device to a source of power in response to the leading edge of said pulse; pulse width limit means connected to turn off said power switch in response to a pulse width limit signal; and means responsive to a characteristic of said electroresponsive device that changes measurably in each period to signal said pulse width limit means to turn off the power switch when said characteristic reaches a predetermined value.

Claim 15

A power control system comprising: means providing a periodic reference, pulse forming means connected to receive said reference and to form a pulse having its leading edge at a selected point in the period; an electroresponsive device having a time constant that is long relative to said period; power switch means connecting said device in circuit with an electrical source in response to the leading edge of said pulse; means responsive to a characteristic of said circuit of said electroresponsive device and said switch means that varies measurably in each period to produce a pulse width limiting signal when said electrical characteristic reaches a predetermined value; and means responsive to said pulse width limiting signal to turn off said switch means for the rest of a period.

Claim 16

A power control system comprising: means providing a periodic reference, pulse forming means connected to receive said reference and to form a pulse having its leading edge at a selected point in the period; an electroresponsive device having a time constant that is long relative to said period; power switch means connecting said device in circuit with an electrical source in response to the leading edge of said pulse; means responsive to a characteristic of said circuit of said electroresponsive device and said switch means that varies measurably in each period to produce a pulse width limiting signal when said electrical characteristic reaches a predetermined value; and means responsive to said pulse width limiting signal to turn off said switch means for the rest of a period.

Claim 17

A power control system comprising, means providing a periodic reference, pulse forming means connected to receive said reference and to form the pulse having its leading edge at a selected point in the period, means for varying the duty cycle of the pulses applied by said motor switching means from said DC source to energize said motor; and means for monitoring the motor current and producing signals to operate said duty cycle varying means to reduce the duty cycle of said power switching means when the motor current reaches a predetermined level.

Claim 18

A power control system comprising, means providing a periodic reference, pulse forming means connected to receive said reference and to form the pulse having its leading edge at a selected point in the period, means for varying the duty cycle of the pulses applied by said motor switching means from said DC source to energize said motor; and means for monitoring the motor current and producing signals to operate said duty cycle varying means to reduce the duty cycle of said power switching means when the motor current reaches a predetermined level.

Claim 19

A pulse width modulation system for controlling the speed of DC traction motors comprising: a. a battery; b. transistor pulse generating means operated from said battery, having a time constant element and capable of having the pulse duration of the output pulses controlled both by varying said time constant element and by input pulses; c. transistor amplifying means operated from said battery for raising the output level of pulses supplied by said pulse generating means to a sufficient power level to drive the traction motor; d. means for controlling the time constant of said pulse generating means so as to control the speed of the motor; d. means for controlling the time constant of said pulse generating means so as to control the speed of the motor; e. a unidirectional element connected across said traction motor to provide a current path between pulses; and f. means for monitoring the motor current and operated from said battery for producing pulses to prematurely terminate the pulse duration of the output pulses from said pulse generating means when the traction motor current reaches a predetermined level.

Claim 20

A pulse width modulation system for controlling the speed of DC traction motors comprising: a. a battery; b. transistor pulse generating means operated from said battery, having a time constant element and capable of having the pulse duration of the output pulses controlled both by varying said time constant element and by input pulses; c. transistor amplifying means operated from said battery for raising the output level of pulses supplied by said pulse generating means to a sufficient power level to drive the traction motor; d. means for controlling the time constant of said pulse generating means so as to control the speed of the motor; d. means for controlling the time constant of said pulse generating means so as to control the speed of the motor; e. a unidirectional element connected across said traction motor to provide a current path between pulses; and f. means for monitoring the motor current and operated from said battery for producing pulses to prematurely terminate the pulse duration of the output pulses from said pulse generating means when the traction motor current reaches a predetermined level.

Claim 21

In a speed control system for an industrial truck having a power storage battery: a. a DC traction motor; b. switch means for applying variable duty cycle drive impulses to said motor from said battery, said switch means comprising; c. an oscillator; d. a control pulse producing circuit triggered by the cycles of said oscillator for producing control pulses of adjustable time duration; e. a switching circuit energized by said control pulses for applying said drive impulses from said battery to said motor during the time interval of said control pulses; and f. an adjustable feedback pulse generator circuit triggered by the amplitude of current through said motor during said drive impulses exceeding a preset amplitude for triggering said control circuit to terminate the control pulse then being produced prior to its normal termination.

Claim 22

In a speed control system for an industrial truck having a power storage battery: a. a DC traction motor; b. switch means for applying variable duty cycle drive impulses to said motor from said battery, said switch means comprising; c. an oscillator; d. a control pulse producing circuit triggered by the cycles of said oscillator for producing control pulses of adjustable time duration; e. a switching circuit energized by said control pulses for applying said drive impulses from said battery to said motor during the time interval of said control pulses; and f. an adjustable feedback pulse generator circuit triggered by the amplitude of current through said motor during said drive impulses exceeding a preset amplitude for triggering said control circuit to terminate the control pulse then being produced prior to its normal termination.

Claim 23

In the speed control system of claim 11, manually controlled means for said control circuit for adjusting the duration of the control pulses thereby to control the duration of the drive pulses applied to the motor.

Claim 24

In the speed control system of claim 12, additional manually controlled means for said feedback pulse generator circuit for preselecting the amplitude of motor current required to trigger said feedback pulse generator circuit.

Claim 25

A control system for energizing a DC traction motor from a power storage battery by variable duty cycle impulses comprising: a. a traction motor; b. a storage battery; c. cyclically operating transistor switch means for applying DC drive pulses from the battery to energize said motor; d. manual control means for adjusting the time duration of said drive pulses; and e. feedback pulse producing means responsive to the amplitude of current through said motor exceeding a preset amplitude during any one of said drive pulses for producing a feedback pulse to said transistor switch means for prematurely terminating the operation of said transistor switch means in advance of its normal time duration.

Claim 26

A control system for energizing a DC traction motor from a power storage battery by variable duty cycle impulses comprising: a. a traction motor; b. a storage battery; c. cyclically operating transistor switch means for applying DC drive pulses from the battery to energize said motor; d. manual control means for adjusting the time duration of said drive pulses; and e. feedback pulse producing means responsive to the amplitude of current through said motor exceeding a preset amplitude during any one of said drive pulses for producing a feedback pulse to said transistor switch means for prematurely terminating the operation of said transistor switch means in advance of its normal time duration.

Claim 27

In the motor control system of claim 14, the addition of manual control means for adjusting said feedback pulse producing means to respond to different preset amplitudes of current through said motor.

Claim 28

In a system for controlling a DC motor from a DC source, means for producing a succession of pulses; power switching means controlled by said pulses for connecting said DC motor to said DC source, means for varying the duty cycle of the pulses applied by said power switching means from said DC source to energize said motor; and means for sensing an undesirable operating condition of said power switching means and means responsive to said sensing means for operating said duty cycle varying means to reduce the duty cycle of said pulses.

Claim 29

In a system for controlling a DC motor from a DC source, means for producing a succession of pulses; power switching means controlled by said pulses for connecting said DC motor to said DC source, means for varying the duty cycle of the pulses applied by said power switching means from said DC source to energize said motor; and means for sensing an undesirable operating condition of said power switching means and means responsive to said sensing means for operating said duty cycle varying means to reduce the duty cycle of said pulses.

Claim 30

In a system for controlling a DC motor from a DC source, means for producing a succession of pulses, power switching means controlled by said pulses for connecting said DC motor to said DC source, manually controlled means having a variable time constant element for varying the duty cycle of the pulses applied by said power switching means from said DC source to energize said motor, means to generate a limit signal when an electrical condition of said power switch means reaches an undesirable instantaneous magnitude after said power switching means is turned on, and means responsive to said limit signal to reduce the duty cycle by terminating said pulses prior to their normal termination.

Claim 31

In a system for controlling a DC motor from a DC source, means for producing a succession of pulses, power switching means controlled by said pulses for connecting said DC motor to said DC source, manually controlled means having a variable time constant element for varying the duty cycle of the pulses applied by said power switching means from said DC source to energize said motor, means to generate a limit signal when an electrical condition of said power switch means reaches an undesirable instantaneous magnitude after said power switching means is turned on, and means responsive to said limit signal to reduce the duty cycle by terminating said pulses prior to their normal termination.

Claim 32

A power system for an industrial truck, comprising: a battery; a DC motor; means to produce a train of unidirectional pulses; transistor monostable circuit means having adjustable time constant elements driven by said train of unidirectional pulses to produce output pulses for controlling the motor; amplifying means for raising the power level of the pulses from said monostable circuit means to drive said motor; means for varying said time constant elements of the monostable circuit means to control the time duration of said unidirectional pulses and thereby vary the truck speed; and means for monitoring the current supplied to the motor and producing signals to control said monostable circuit means so as to decrease the time duration of said output pulses when the motor current exceeds predetermined level.

Claim 33

A power system for an industrial truck, comprising: a battery; a DC motor; means to produce a train of unidirectional pulses; transistor monostable circuit means having adjustable time constant elements driven by said train of unidirectional pulses to produce output pulses for controlling the motor; amplifying means for raising the power level of the pulses from said monostable circuit means to drive said motor; means for varying said time constant elements of the monostable circuit means to control the time duration of said unidirectional pulses and thereby vary the truck speed; and means for monitoring the current supplied to the motor and producing signals to control said monostable circuit means so as to decrease the time duration of said output pulses when the motor current exceeds predetermined level.

Claim 34

In a system for controlling a DC motor from a DC source, means for producing a succession of pulses; power switching means controlled by said pulses for connecting said DC motor to said DC source; means for varying the duty cycle of the pulses applied by said motor switching means from said DC source to energize said motor; and means for monitoring the motor current and producing signals to operate said duty cycle varying means to reduce the duty cycle varying means to reduCe the duty cycle of said power switching means when the motor current reaches a predetermined level.

Claim 35

In a system for controlling a DC motor from a DC source, means for producing a succession of pulses; power switching means controlled by said pulses for connecting said DC motor to said DC source; means for varying the duty cycle of the pulses applied by said motor switching means from said DC source to energize said motor; and means for monitoring the motor current and producing signals to operate said duty cycle varying means to reduce the duty cycle varying means to reduCe the duty cycle of said power switching means when the motor current reaches a predetermined level.