US3617845A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Energy-conserving control circuit using power transistors
Assignee: Pacific Scientific Co
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Filing: 1970-04-27
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Granted: 1971-11-02
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Expires: 1990-04-27
Abstract
Abstract A control circuit for supplying pulses of current, with a variable duty cycle, from a voltage source through a load which may vary in its effective impedance and wherein a power transistor is in series with the load to turn the current on and off. The transistor is driven always to collector current saturation when it is turned on so that power loss in the transistor and excessive heating are substantially minimized. But when the effective load impedance is high, the base-emitter current required to saturate the transistor is considerably less than that required when the effective load impedance is low. To avoid energy dissipation and loss due to unnecessarily high emitter-base current, the base-emitter circuit includes a control transistor which acts as a controllable impedance, the control transistor receiving emitter-base current proportional to the voltage drop across the power transistor so that emitter-base current of the power transistor is always just sufficiently great to keep the power transistor saturated. The average current through the load, e.g., a DC motor, is varied by employing a multivibrator adjustable in its duty cycle to produce a control signal which alternately enables or disables the control transistor. And to avoid energy loss due to slow turnoff of the power transistor, the emitter-base junction of the power transistor is shunted by a transistor automatically switched to its conductive, low-impedance state or its nonconductive, highimpedance state by a signal from the multivibrator when the power transistor is turned on or off. These energy-conserving features are of particular benefit in applications such as speed control of a DC motor in golf carts, fork lift trucks and the like where the voltage source is a battery and maximum usage between recharges is important.
Inventors
- 👤 William F Mckenna
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 07:27
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/29
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
95 words
In a system fOr energizing a variable impedance load from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a controllable impedance in series with the emitter-base path of said transistor across said voltage source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive, and means responsive to changes in the voltage drop between said emitter and collector for causing an inverse change in the value of said controllable impedance.
Claim 2
Dependent Claim
95 words
In a system fOr energizing a variable impedance load from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a controllable impedance in series with the emitter-base path of said transistor across said voltage source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive, and means responsive to changes in the voltage drop between said emitter and collector for causing an inverse change in the value of said controllable impedance.
Claim 3
Dependent Claim
157 words
In a system for energizing a DC motor with current from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, a control transistor having an emitter, base and collector with its emitter-collector path connected in series with the emitter-base path of said power transistor across said voltage source, and means for supplying current, which varies according to the variations of the voltage drop across the emitter-collector path of said power transistor, through the emitter-base path of said control transistor, whereby the emitter-base current through said power transistor is increased or decreased in response to decreases or increases in the effective impedance of said motor and said power transistor is maintained substantially in a state of saturated conduction with substantially the least amount of emitter-base current through the power transistor as the effective impedance of the motor changes.
Claim 4
Dependent Claim
157 words
In a system for energizing a DC motor with current from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, a control transistor having an emitter, base and collector with its emitter-collector path connected in series with the emitter-base path of said power transistor across said voltage source, and means for supplying current, which varies according to the variations of the voltage drop across the emitter-collector path of said power transistor, through the emitter-base path of said control transistor, whereby the emitter-base current through said power transistor is increased or decreased in response to decreases or increases in the effective impedance of said motor and said power transistor is maintained substantially in a state of saturated conduction with substantially the least amount of emitter-base current through the power transistor as the effective impedance of the motor changes.
Claim 5
Dependent Claim
102 words
The combination set forth in claim 2 further characterized in that said means for supplying current includes a third transistor having an emitter, base and collector, means connecting the emitter-base path of said third transistor across the emitter-collector path of said power transistor, and means connecting the emitter-collector path of said third transistor in series with the emitter-base path of said control transistor across said voltage source, whereby the emitter-collector impedance of said control transistor varies according to the current through the emitter-collector path of said third transistor and varies according to changes in the emitter-collector voltage drop of the power transistor.
Claim 6
Dependent Claim
202 words
In a system for controlling the average current drawn from a voltage source through a variable impedance load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series and said load across said voltage source, a controllable impedance connected in series with the emitter-base path of said transistor across said source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive to energize said load, means for producing a recurring control signal having successive ''''on'''' and ''''off'''' values adjustable in their respective time durations, means responsive to said control signal having an ''''off'''' value for causing said controllable impedance to have a predetermined high value, and means responsive to said control signal having an ''''on'''' value for causing said controllable impedance to have a value which varies inversely according to the value of the voltage drop across the emitter-collector path of said transistor, whereby the on-off duty cycle of energization of said load is adjustable to vary the average voltage applied to the load, and during the ''''on'''' intervals the emitter-base current through said transistor varies in an inverse fashion with changes in the effective impedance of the load.
Claim 7
Dependent Claim
202 words
In a system for controlling the average current drawn from a voltage source through a variable impedance load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series and said load across said voltage source, a controllable impedance connected in series with the emitter-base path of said transistor across said source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive to energize said load, means for producing a recurring control signal having successive ''''on'''' and ''''off'''' values adjustable in their respective time durations, means responsive to said control signal having an ''''off'''' value for causing said controllable impedance to have a predetermined high value, and means responsive to said control signal having an ''''on'''' value for causing said controllable impedance to have a value which varies inversely according to the value of the voltage drop across the emitter-collector path of said transistor, whereby the on-off duty cycle of energization of said load is adjustable to vary the average voltage applied to the load, and during the ''''on'''' intervals the emitter-base current through said transistor varies in an inverse fashion with changes in the effective impedance of the load.
Claim 8
Dependent Claim
218 words
In a system for controlling the average current supplied from a voltage source to energize a variable impedance load, the combination comprising a power transistor having an emitter, base and cOllector with its emitter-collector path connected in series with said load across said voltage source, a controllable impedance in series with the emitter-base path of said transistor across said voltage source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive, means for producing a recurring square wave control voltage adjustable in the ratio of the duration of its ''''on'''' to ''''off'''' values, means responsive to said control voltage for causing said controllable impedance to have a predetermined high value during those time intervals when the control voltage has its ''''off'''' value, and means responsive to said control voltage and to the voltage drop across the emitter-collector path of said transistor for causing said controllable impedance to vary according to changes in the last-named voltage drop during those time intervals when said control voltage has its ''''on'''' value, whereby said load is energized by successive pulses of current through the emitter-collector path of said transistor to vary the average energization current, and during each pulse of current the emitter-base current through said transistor is generally inversely proportional to the impedance presented by said load.
Claim 9
Dependent Claim
218 words
In a system for controlling the average current supplied from a voltage source to energize a variable impedance load, the combination comprising a power transistor having an emitter, base and cOllector with its emitter-collector path connected in series with said load across said voltage source, a controllable impedance in series with the emitter-base path of said transistor across said voltage source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive, means for producing a recurring square wave control voltage adjustable in the ratio of the duration of its ''''on'''' to ''''off'''' values, means responsive to said control voltage for causing said controllable impedance to have a predetermined high value during those time intervals when the control voltage has its ''''off'''' value, and means responsive to said control voltage and to the voltage drop across the emitter-collector path of said transistor for causing said controllable impedance to vary according to changes in the last-named voltage drop during those time intervals when said control voltage has its ''''on'''' value, whereby said load is energized by successive pulses of current through the emitter-collector path of said transistor to vary the average energization current, and during each pulse of current the emitter-base current through said transistor is generally inversely proportional to the impedance presented by said load.
Claim 10
Dependent Claim
167 words
In a system for controlling the current excitation of a DC motor from a DC voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, a control transistor having an emitter, base and collector; means connecting the emitter-collector path of said control transistor in series with the emitter-base path of said power transistor across said voltage source; means for producing a recurring square wave signal including means to adjust the ratio of the durations of the ''''on'''' and ''''off'''' values of such signal; and means responsive to said control signal for (a) substantially interrupting current through the emitter-base path of said control transistor when the control signal has its ''''off'''' value, and (b) supplying current, which in magnitude is generally proportional to the voltage drop across the emitter-collector junction of said power transistor, through the emitter-base path of said control transistor when the control signal has its ''''on'''' value.
Claim 11
Dependent Claim
167 words
In a system for controlling the current excitation of a DC motor from a DC voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, a control transistor having an emitter, base and collector; means connecting the emitter-collector path of said control transistor in series with the emitter-base path of said power transistor across said voltage source; means for producing a recurring square wave signal including means to adjust the ratio of the durations of the ''''on'''' and ''''off'''' values of such signal; and means responsive to said control signal for (a) substantially interrupting current through the emitter-base path of said control transistor when the control signal has its ''''off'''' value, and (b) supplying current, which in magnitude is generally proportional to the voltage drop across the emitter-collector junction of said power transistor, through the emitter-base path of said control transistor when the control signal has its ''''on'''' value.
Claim 12
Dependent Claim
198 words
In a system for controlling the current excitation of a DC motor from a DC voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, a control transistor having an emitter, base and collector, first means connecting the emitter-collector path of said control transistor in series with the emitter-base path of said power transistor across said voltage source, a third transistor having an emitter, base and collector, second means connecting the emitter-collector path of said third transistor in series with the emitter-base path of said control transistor across said voltage source, third means connecting the emitter-base path of said third transistor across the emitter-collector path of said power transistor, said second means including a switching device adapted to be turned on or off to complete or interrupt the series connection, a free-running multivibrator having means to adjust the ratio of the durations of the ''''on'''' and ''''off'''' periods of its output signal, and means coupling said output signal to said switching device to turn the latter on or off respectively during the ''''on'''' and ''''off'''' periods of such output signal.
Claim 13
Dependent Claim
198 words
In a system for controlling the current excitation of a DC motor from a DC voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, a control transistor having an emitter, base and collector, first means connecting the emitter-collector path of said control transistor in series with the emitter-base path of said power transistor across said voltage source, a third transistor having an emitter, base and collector, second means connecting the emitter-collector path of said third transistor in series with the emitter-base path of said control transistor across said voltage source, third means connecting the emitter-base path of said third transistor across the emitter-collector path of said power transistor, said second means including a switching device adapted to be turned on or off to complete or interrupt the series connection, a free-running multivibrator having means to adjust the ratio of the durations of the ''''on'''' and ''''off'''' periods of its output signal, and means coupling said output signal to said switching device to turn the latter on or off respectively during the ''''on'''' and ''''off'''' periods of such output signal.
Claim 14
Dependent Claim
118 words
In a system for turning a transistor on and off to supply or terminate current from a voltage source through a load, the combination comprising a transistor having a emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, first means for supplying or interrupting current through the emitter-base path of said transistor to render the emitter-collector path respectively conductive or nonconductive, a controllable impedance device connected in shunt across the emitter-base path of said transistor, and means for making the impedance of said device high or low in timed synchronism with the operation of said first means respectively supplying or interrupting current through the emitter-base path of said transistor.
Claim 15
Dependent Claim
118 words
In a system for turning a transistor on and off to supply or terminate current from a voltage source through a load, the combination comprising a transistor having a emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, first means for supplying or interrupting current through the emitter-base path of said transistor to render the emitter-collector path respectively conductive or nonconductive, a controllable impedance device connected in shunt across the emitter-base path of said transistor, and means for making the impedance of said device high or low in timed synchronism with the operation of said first means respectively supplying or interrupting current through the emitter-base path of said transistor.
Claim 16
Dependent Claim
166 words
In a system for supplying current pulses from a voltage source through a load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, means for generating a recurring square wave signal having alternate ''''on'''' and ''''off'''' values, means responsive to said signal having an ''''on'''' or ''''off'''' value for respectively supplying or terminating current flow through the emitter-base junction of said power transistor to render the emitter-collector path respectively conductive or nonconductive, a controllable switching device connected across the emitter-base path of said transistor, and means responsive to said signal having an ''''on'''' or ''''off'''' value for respectively rendering said switching device nonconductive or conductive, whereby said switching device forms a shunt for discharge of accumulated charge carriers in the emitter-base path of said transistor whenever said signal reverts to its ''''off'''' value so that the emitter-collector path of said transistor is more quickly placed in its nonconductive state.
Claim 17
Dependent Claim
166 words
In a system for supplying current pulses from a voltage source through a load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, means for generating a recurring square wave signal having alternate ''''on'''' and ''''off'''' values, means responsive to said signal having an ''''on'''' or ''''off'''' value for respectively supplying or terminating current flow through the emitter-base junction of said power transistor to render the emitter-collector path respectively conductive or nonconductive, a controllable switching device connected across the emitter-base path of said transistor, and means responsive to said signal having an ''''on'''' or ''''off'''' value for respectively rendering said switching device nonconductive or conductive, whereby said switching device forms a shunt for discharge of accumulated charge carriers in the emitter-base path of said transistor whenever said signal reverts to its ''''off'''' value so that the emitter-collector path of said transistor is more quickly placed in its nonconductive state.
Claim 18
Dependent Claim
207 words
In a system for supplying pulses from a voltage source through a load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a free-running multivibrator producing a first output signal having alternately first and second values and producing a second output signal complemental to the first and having alternately second and first values, means responsive to said first signal for respectively supplying or interrupting current through the emitter-base path of said power transistor when such signal has its first or second values to render the emitter-collector path of said power transistor respectively conductive or nonconductive, a shunt transistor having an emitter, base and collector with its emitter-collector path connected in parallel with the emitter-base path of said power transistor, and means responsive to said second signal for respectively supplying or interrupting current through the emitter-base path of said shunt transistor when the second signal has its first or second values to render the emitter-collector path of said shunt transistor respectively conductive or nonconductive, whereby accumulated charge carriers in the emitter-base junction of said power transistor are quickly discharged through said shunt transistor each time the power transistor is turned off.
Claim 19
Dependent Claim
207 words
In a system for supplying pulses from a voltage source through a load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a free-running multivibrator producing a first output signal having alternately first and second values and producing a second output signal complemental to the first and having alternately second and first values, means responsive to said first signal for respectively supplying or interrupting current through the emitter-base path of said power transistor when such signal has its first or second values to render the emitter-collector path of said power transistor respectively conductive or nonconductive, a shunt transistor having an emitter, base and collector with its emitter-collector path connected in parallel with the emitter-base path of said power transistor, and means responsive to said second signal for respectively supplying or interrupting current through the emitter-base path of said shunt transistor when the second signal has its first or second values to render the emitter-collector path of said shunt transistor respectively conductive or nonconductive, whereby accumulated charge carriers in the emitter-base junction of said power transistor are quickly discharged through said shunt transistor each time the power transistor is turned off.
Claim 20
Dependent Claim
33 words
The combination set forth in claim 10, further characterized in that said multivibrator includes means for adjusting the ratios of the durations of the first and second values of the two output signals.
Claim 21
Dependent Claim
165 words
In a system for applying energizing pulses to a variable impedance load from a voltage source, the combination comprising a transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a controllable impedance in series with the emitter-base path of said transistor across said voltage source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive, means for making said controllable impedance very high during first time periods and relatively low dUring second time periods, whereby voltage pulses and applied to said load during the second time periods, means responsive to changes in the voltage drop between said emitter and collector for causing an inverse change in the relatively low value of said controllable impedance during said second time periods, a controllable switching device connected across the emitter-base path of said transistor, and means for rendering said switching device conductive or nonconductive respectively during said first or second time periods.
Claim 22
Dependent Claim
165 words
In a system for applying energizing pulses to a variable impedance load from a voltage source, the combination comprising a transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a controllable impedance in series with the emitter-base path of said transistor across said voltage source to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive, means for making said controllable impedance very high during first time periods and relatively low dUring second time periods, whereby voltage pulses and applied to said load during the second time periods, means responsive to changes in the voltage drop between said emitter and collector for causing an inverse change in the relatively low value of said controllable impedance during said second time periods, a controllable switching device connected across the emitter-base path of said transistor, and means for rendering said switching device conductive or nonconductive respectively during said first or second time periods.
Claim 23
Dependent Claim
194 words
In a system for energizing a variable impedance load with current pulses from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a first controllable impedance connected in series with the emitter-base path of said transistor across said voltage source to draw emitter base current and thereby render the emitter-collector path of said transistor conductive to energize said load, means for causing said first controllable impedance during alternate ones of successive time intervals to have relatively high and low range values to respectively render said power transistor cut off and conductive, means for varying the value of said first controllable impedance in the same sense as and according to changes in the value of the load impedance during those intervals when the controllable impedance has low range values, a second controllable impedance connected in shunt across the emitter-base path of said power transistor, and mans for causing said second impedance to have relatively low and high range values during those time intervals in which the first impedance respectively has high and low range values.
Claim 24
Dependent Claim
194 words
In a system for energizing a variable impedance load with current pulses from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a first controllable impedance connected in series with the emitter-base path of said transistor across said voltage source to draw emitter base current and thereby render the emitter-collector path of said transistor conductive to energize said load, means for causing said first controllable impedance during alternate ones of successive time intervals to have relatively high and low range values to respectively render said power transistor cut off and conductive, means for varying the value of said first controllable impedance in the same sense as and according to changes in the value of the load impedance during those intervals when the controllable impedance has low range values, a second controllable impedance connected in shunt across the emitter-base path of said power transistor, and mans for causing said second impedance to have relatively low and high range values during those time intervals in which the first impedance respectively has high and low range values.
Claim 25
Dependent Claim
185 words
In a system for energizing a DC motor with current from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, means for generating a recurring square wave signal having alternate ''''on'''' and ''''off'''' values, a control transistor having an emitter, base and collector with its emitter-collector path connected in series with the emitter-base path of said power transistor across said voltage source, means responsive to said signal for rendering said control transistor nonconductive when said signal has ''''off'''' values, means responsive to said control signal when it has ''''on'''' values for supplying current, which varies according to the variations of the voltage drop across the emitter-collector path of said power transistor, through the emitter-base path of said control transistor, a further transistor having an emitter, base and collector with its collector-emitter path connected in parallel across the emitter-base path of said power transistor, and means for rendering said further transistor conductive or nonconductive during those times when said signal respectively has ''''off'''' or ''''on'''' values.
Claim 26
Dependent Claim
185 words
In a system for energizing a DC motor with current from a voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source, means for generating a recurring square wave signal having alternate ''''on'''' and ''''off'''' values, a control transistor having an emitter, base and collector with its emitter-collector path connected in series with the emitter-base path of said power transistor across said voltage source, means responsive to said signal for rendering said control transistor nonconductive when said signal has ''''off'''' values, means responsive to said control signal when it has ''''on'''' values for supplying current, which varies according to the variations of the voltage drop across the emitter-collector path of said power transistor, through the emitter-base path of said control transistor, a further transistor having an emitter, base and collector with its collector-emitter path connected in parallel across the emitter-base path of said power transistor, and means for rendering said further transistor conductive or nonconductive during those times when said signal respectively has ''''off'''' or ''''on'''' values.
Claim 27
Dependent Claim
195 words
In a system for controlling the average current drawn from a voltage source through a variable impedance load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a first controllable impedance connected in series with the emitter base path of said transistor to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive to energize said load, means for producing a recurring control signal having successive ''''on'''' and ''''off'''' values adjustable in their respective time durations, means responsive to said control signal having an ''''off'''' value for causing said first impedance to have a predetermined high value, means responsive to said control signal having an ''''on'''' value for causing said first impedance to have a value which varies inversely according to the value of the voltage drop across the emitter-collector path of said transistor, a second controllable impedance connected across the emitter-base path of said transistor, and means responsive to said control signal for making said second impedance have a high or a low value whenever said signal respectively has its ''''on'''' or ''''off'''' values.
Claim 28
Dependent Claim
195 words
In a system for controlling the average current drawn from a voltage source through a variable impedance load, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said load across said voltage source, a first controllable impedance connected in series with the emitter base path of said transistor to draw emitter-base current and thereby render the emitter-collector path of said transistor conductive to energize said load, means for producing a recurring control signal having successive ''''on'''' and ''''off'''' values adjustable in their respective time durations, means responsive to said control signal having an ''''off'''' value for causing said first impedance to have a predetermined high value, means responsive to said control signal having an ''''on'''' value for causing said first impedance to have a value which varies inversely according to the value of the voltage drop across the emitter-collector path of said transistor, a second controllable impedance connected across the emitter-base path of said transistor, and means responsive to said control signal for making said second impedance have a high or a low value whenever said signal respectively has its ''''on'''' or ''''off'''' values.
Claim 29
Dependent Claim
258 words
In a system for controlling the current excitation of a DC motor from a DC voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source; a control transistor having an emitter, base and collector; means connecting the emitter-collector path of said control transistor in series with the emitter-base path of said power transistor across said voltage source; means for producing a recurring square wave signal including means to adjust the ratio of the durations of the ''''on'''' and ''''off'''' values of such signal; means responsive to said control signal for (a) substantially interrupting current through the emitter-base path of said control transistor when the control signal has its ''''off'''' value, and (b) supplying current, which in magnitude is generally proportional to the voltage drop across the emitter-collector junction of said power transistor, through the emitter-base path of said control transistor when the control signal has its ''''on'''' value; a further transistor having an emitter, base and collector with its emitter-collector path connected across the collector-base path of said power transistor; and means responsive to said control signal for (a) supplying current to the base-emitter path of said further transistor when said control signal has its ''''off'''' value to thereby enable the emitter-collector path of the further transistor for saturated conduction, and (b) terminating current through the base-emitter path of said further transistor when said control signal has its ''''on'''' value to render the emitter-collector path of said further transistor nonconductive.
Claim 30
Dependent Claim
258 words
In a system for controlling the current excitation of a DC motor from a DC voltage source, the combination comprising a power transistor having an emitter, base and collector with its emitter-collector path connected in series with said motor across said voltage source; a control transistor having an emitter, base and collector; means connecting the emitter-collector path of said control transistor in series with the emitter-base path of said power transistor across said voltage source; means for producing a recurring square wave signal including means to adjust the ratio of the durations of the ''''on'''' and ''''off'''' values of such signal; means responsive to said control signal for (a) substantially interrupting current through the emitter-base path of said control transistor when the control signal has its ''''off'''' value, and (b) supplying current, which in magnitude is generally proportional to the voltage drop across the emitter-collector junction of said power transistor, through the emitter-base path of said control transistor when the control signal has its ''''on'''' value; a further transistor having an emitter, base and collector with its emitter-collector path connected across the collector-base path of said power transistor; and means responsive to said control signal for (a) supplying current to the base-emitter path of said further transistor when said control signal has its ''''off'''' value to thereby enable the emitter-collector path of the further transistor for saturated conduction, and (b) terminating current through the base-emitter path of said further transistor when said control signal has its ''''on'''' value to render the emitter-collector path of said further transistor nonconductive.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |