US3911341A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Switching type motor speed control
Assignee: Prestolite Electric Inc
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Filing: 1974-09-20
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Granted: 1975-10-07
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Expires: 1994-09-20
Abstract
Abstract Current from a battery is supplied to a DC motor in a series of pulses by a circuit having a plurality of transistor switches which are alternately rendered conductive and nonconductive by control signals from a free-running multivibrator, and the speed of the motor is controlled by varying the duty cycle of the multivibrator so as to vary the duration of the current pulses being supplied to the motor. To avoid the destruction of any of the transistor switches the circuit has overcurrent protection means which is responsive to excessive current through any of the transistor switches for resetting the multivibrator to bias the transistor switches nonconductive and causing the current pulses to be supplied to the motor at a higher frequency resulting in an increased motor impedance which limits the current through the transistor switches. To prevent a declining battery potential from reducing the effectiveness of the control signals alternately biasing the transistor switches fully conductive or nonconductive the circuit is provided with low voltage protection means which is responsive to a first low battery voltage for resetting the multivibrator to bias the transistor switches nonconductive and continuing that condition until the battery potential rises to a second voltage level.
Inventors
- 👤 Daniel P Carlson
- 👤 James T Hardin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 06:28
CPC Classifications
H; H03; H03K; H03K3/00; H03K3/02; H03K3/26; H03K3/28; H03K3/281; H03K3/282; H03K3/2823; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/29; Y; Y10; Y10S; Y10S388/00; Y10S388/90; Y10S388/903; Y10S388/907; Y10S388/916
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
213 words
A circuit for controlling the speed of a DC motor, comprising: a free running multivibrator alternately providing first and second control signals at a substantially constant predetermined frequency and with a time ratio determined by the duty cycle of the multivibrator, switch means for connecting the motor to a source of direct current and being electrically conductive in response to said first control signal and electrically nonconductive in response to said second control signal for supplying current to said motor in a succession of pulses corresponding to the predetermined frequency of said multivibrator and having a duration determined by the duty cycle of said multivibrator, manual control means for selectively varying the duty cycle of said multivibrator to control the average voltage being supplied to the motor, current sensing means providing a current signal indicative of the current being supplied to the motor by said switch means, overcurrent protection means operable in response to the current signal exceeding a predetermined value for resetting said multivibrator to provide said switch means with a second control signal whereby voltage is supplied to said motor in a succession of pulses at a frequency greater than the predetermined frequency of the multivibrator and with a duration different from the duty cycle determined by the manual control means.
Claim 2
Dependent Claim
213 words
A circuit for controlling the speed of a DC motor, comprising: a free running multivibrator alternately providing first and second control signals at a substantially constant predetermined frequency and with a time ratio determined by the duty cycle of the multivibrator, switch means for connecting the motor to a source of direct current and being electrically conductive in response to said first control signal and electrically nonconductive in response to said second control signal for supplying current to said motor in a succession of pulses corresponding to the predetermined frequency of said multivibrator and having a duration determined by the duty cycle of said multivibrator, manual control means for selectively varying the duty cycle of said multivibrator to control the average voltage being supplied to the motor, current sensing means providing a current signal indicative of the current being supplied to the motor by said switch means, overcurrent protection means operable in response to the current signal exceeding a predetermined value for resetting said multivibrator to provide said switch means with a second control signal whereby voltage is supplied to said motor in a succession of pulses at a frequency greater than the predetermined frequency of the multivibrator and with a duration different from the duty cycle determined by the manual control means.
Claim 3
Dependent Claim
99 words
In a circuit according to claim 1: said switch mEans including a plurality of semiconductor switch means each adapted to conduct a portion of the current supplied to the motor, said current sensing means including a plurality of current sensing resistors each connected in series with a different semiconductor switch means to provide a current signal indicative of the current being conducted by the corresponding semiconductor switch means, and said overcurrent protection means being responsive to any of the current signals exceeding said predetermined value for resetting said multivibrator to provide a second control signal to said switch means.
Claim 4
Dependent Claim
65 words
In a circuit according to claim 1, the combination further comprising: voltage sensing means providing a voltage signal indicative of the potential of the power source from which current is supplied to the motor, and low voltage protection means operable in response to the voltage signal declining to a predetermined value for resetting said multivibrator to provide a second control signal to said switch means.
Claim 5
Dependent Claim
72 words
In a circuit to claim 3, the combination further comprising: hysteresis means responsive to the operation of said low voltage protection means for reducing the value of the voltage signal provided by said voltage sensing means, and said low voltage protection means being operable in response to the voltage signal increasing to said predetermined value for enabling said multivibrator to alternately provide said first and second control signals to said switch means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-06 | 1979-04-07 | 1979-10-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-06 | 1983-04-07 | 1983-10-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-06 | 1987-04-07 | 1987-10-07 | $7700.00 | Window Closed / Lapsed |