Electronic rheostat method and apparatus
First Claim
1. A power control circuit for regulating energizing power coupled to a device in a motor vehicle comprising:
- (a) a d.c. voltage source for energizing the device;
(b) oscillator means for generating an oscillating voltage waveform that varies between a maximum and a minimum voltage;
(c) comparator means for comparing the oscillating voltage waveform from the oscillator means with a reference voltage to produce a pulse width modulated output whose duty cycle varies as a function of the reference voltage; and
(d) drive means coupled to the pulse width modulated output of the comparator means for coupling the device to the d.c. voltage source in synchronism with the pulse width modulated output;
(e) said comparator means including a reference voltage divider circuit connected to the d.c. voltage source including adjustment means to allow a user to adjust the reference voltage and control the average voltage applied to the device by the drive means.
1 Assignment
0 Petitions
Accused Products
Abstract
An electronic reostat circuit having a pulse width modulated output for controlling energization of a device such as a vehicle dashboard illumination lamp. A comparator circuit compares a reference signal adjusted by a user with an alternating signal, preferably a saw tooth waveform, and generates a pulse width modulated output whose duty cycle varies directly with the size of the reference signal. The reference signal is generated by a tapped resistor array wherein contacts on the array are coupled to ground by a rotary switch contact which can be adjusted by the user. By raising and lowering the reference signal, the duty cycle can be changed from a minimum to maximum and thereby produce a minimum and maximum lamp illumination signal.
14 Citations
15 Claims
-
1. A power control circuit for regulating energizing power coupled to a device in a motor vehicle comprising:
-
(a) a d.c. voltage source for energizing the device; (b) oscillator means for generating an oscillating voltage waveform that varies between a maximum and a minimum voltage; (c) comparator means for comparing the oscillating voltage waveform from the oscillator means with a reference voltage to produce a pulse width modulated output whose duty cycle varies as a function of the reference voltage; and (d) drive means coupled to the pulse width modulated output of the comparator means for coupling the device to the d.c. voltage source in synchronism with the pulse width modulated output; (e) said comparator means including a reference voltage divider circuit connected to the d.c. voltage source including adjustment means to allow a user to adjust the reference voltage and control the average voltage applied to the device by the drive means. - View Dependent Claims (2)
-
-
3. A method of controlling power delivered to a motor vehicle device by pulse width modulating a direct current energizing signal that is coupled to the device, said method comprising the steps of:
-
(a) providing an oscillating signal that repeatedly varies from a maximum to a minimum value; (b) comparing the repeatedly varying oscillating signal with a reference signal and generating a pulse width modulated output signal whose duty cycle depends on how long the oscillating signal is less than the reference signal; (c) adjusting the reference signal to control the duty cycle of the pulse width modulated output signal; and (d) coupling the direct current energizing signal to the device in synchronism with the pulse width modulated output signal. - View Dependent Claims (4)
-
-
5. An electronic rheostat comprising:
-
(a) a modulating circuit for generating a pulse width modulated output;
said modulating circuit including;(i) a comparator; (ii) an oscillator having an output coupled to one comparator input; and (iii) an adjustable voltage divider for coupling an adjustable reference signal to a second input of said comparator; (iv) said comparator producing a pulse width modulated output with a duty cycle controlled by the reference signal; (b) a switching element electrically connected to the comparator output and responsive to the pulse width modulated output of said comparator to selectively couple an energizing signal through the electronic rheostat to a rheostat output at the duty cycle of said comparator output; (c) a rheostat housing defining an enclosure for housing the modulating circuit and the switching means and including mounting tabs for mounting said rheostat housing to a panel; (d) a rheostat actuator movably mounted to said rheostat housing for adjusting the setting of the adjustable voltage divider and thereby control the duty cycle of said comparator output; and (e) three electric contacts supported by said housing, one contact for routing a reference or ground signal into said housing to said modulating circuit, a second contact for routing the energizing signal into the housing, and the third contact for routing a modulating output from said rheostat from the housing. - View Dependent Claims (6)
-
-
7. A power control circuit for regulating energizing power coupled to a device, said control circuit comprising:
-
(a) a d.c. voltage source for energizing the device; (b) oscillator means for generating an oscillating voltage waveform that varies between a maximum and a minimum voltage; (c) comparator means for comparing the oscillating voltage waveform from the oscillator means with a reference voltage to produce a pulse width modulated output whose duty cycle varies as a function of the reference voltage; (d) drive means coupled to the pulse width modulated output of the comparator means for energizing the device in synchronism with the pulse width modulated output by coupling the d.c. voltage source to said device; (e) said comparator means including a reference voltage divider circuit connected to the d.c. voltage source including adjustment means to allow a user to adjust the reference voltage and control the average voltage applied to the component by the drive means; and (f) an analog output amplifier coupled to the voltage divider circuit to provide an analog output in addition to the output from the drive means.
-
-
8. A power control circuit for regulating energizing power coupled to a component, said control circuit comprising:
-
(a) a d.c. voltage source for energizing the device; (b) oscillator means for generating an oscillating voltage waveform that varies between a maximum and a minimum voltage; (c) comparator means for comparing the oscillating voltage waveform from the oscillator means with a reference voltage to produce a pulse width modulated output whose duty cycle varies as a function of the reference voltage; and (d) drive means coupled to the pulse width modulated output of the comparator means for energizing the device in synchronism with the pulse width modulated output by coupling the d.c. voltage source to said device; (e) said comparator means including a reference voltage divider circuit connected to the d.c. voltage source including adjustment means to allow a user to adjust the reference voltage and control the average voltage applied to the device by the drive means; and (f) said drive means including (i) a field effect transistor having a drain coupled to the d.c. voltage source and a source coupled to the device and wherein the output of the comparator means is coupled to the gate of said field effect transistor to bias said transistor into conduction in synchronism with said pulse width modulated output; and (ii) a voltage doubler coupled to an output from the comparator means to assure a sufficient bias voltage is coupled to the gate of said field effect transistor to bias the transistor into conduction.
-
-
9. A module for detachably mounting to a display panel and controlling a device of a motor vehicle:
-
(a) a monitoring circuit including ignition and ground inputs and powered by a voltage difference between said inputs, said monitoring circuit having an interface for generating an output signal in response to a sensed condition that varies during the operation of the motor vehicle; (b) a driving circuit coupled to the output signal for driving such device; and (c) a support for mounting the monitoring circuit to the panel so that a portion of the module is accessible to an information conveying side of said display panel. - View Dependent Claims (10, 11, 12, 13, 14, 15)
-
Specification