US 5,309,087 AGranted

Air core gauge, multi-frequency pulse width modulator system therefor

AssigneeChrysler Corporation

InventorsPaul A. Markow, Kevin R. Hammond, Donald E. Hutchings

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Abstract

A pulse-width modulation system provides means for controlling dual-coil, air-core gauges at a various rates over 360 degrees. The system moves a dial needle from one octant of the gauge to the next in response to coded data representing measurands by holding one coil at 100% duty cycle while applying a PWM of a varying duty signal to the other coil. When the magnitude of the measurand dictates that the needle should move into another octant of the dial, the PWM signal and the 100% duty cycle signal are interchanged between the coils in a manner permitting the needle to move to other octants of the dial. The system includes a variable PWM count clock that permits selecting at least PWM rates and periods for forming PWM duty cycles ranging from 0% to 100%.

Claims17

Dependent claims

A variable drive apparatus for an air core gauge, comprising:

(a) variable PWM counter with an input terminal for receiving a chosen fixed clock oscillator signal and having at least a pair of multiplexer circuits for digitally selecting a plurality of PWM clock signals scaled down from the clock oscillator signal and after the selection of one of the plurality of scaled down PWM clock signals which matches the frequency required for operating a chosen air core gauge, producing at one output terminal pulse signals at a selected PWM clock signal, and producing at another output terminal a quotient latch signal each time after counting a chosen number of pulses of the selected PWM clock signal,
(b) a ROM-BASE current controller having one input terminal for receiving input data related to a measurand to be displayed, a second input terminal for receiving the quotient latch signal for initiating converting the input data into current direction control signals and into address bytes for addressing a ROM having selected time period data stored therein used by a down counter that decrements at the rate of the selected PWM clock signal from a selected time period provided from the addressed time period data down to a zero count and while the down counter is decrementing toward the zero count, producing at a set of output terminals, the current direction control signals and at an independent output terminal an enabling PWM signal which changes to a disabling PWM signal when the down counter decrementations reach zero;
(c) a half-bridge driver current control circuit having logic circuits for receiving the PWM signal and the control signals, and producing at a first output port modulated current for exciting an X-axis oriented gauge coil and at a second output port modulated current for exciting a Y-axis oriented gauge coil, the modulation current for exciting one of the gauge coils being held at 100% modulation while the other gauge coil receives current modulated at the selected PWM clock signal and flowing in the direction dictated by the current direction control signals, the modulation currents developing current signals in the X- and Y- axes oriented gauge coils, having a vectorial relationship which causes a rotor with a dial needle connected thereto to rotate to dial positions indicative of the magnitude and direction of the measurand.

A gauge driver system for driving a variety of air core gauges in response to digitally coded data representing magnitudes and polarities of varying measurands from a measurand sensing device, the driver system comprising:

(a) clock means arranged to receive a fixed clock oscillator signal and for dividing the oscillator signal into a selected number of different PWM clock signals of selected frequencies relative to the oscillator signal, each of the different PWM clock signals having an accompanying quotient latch signal that develops after the occurrence of a chosen multiple of the number of pulses in the selected PWM clock signal;
(b) PWM current controller means connected to the clock means and to the measurand sensing device for receiving the varying measurands as bytes of coded data and then using one of the different PWM clock signals and the coded data to form PWM and polarity signals of durations and polarity proportional to the varying magnitudes and polarities of the varying measurand sensed by the measurand sensing device, the quotient latch signal being used to control receipt of each byte of coded data into the PWM current controller means;
and
(c) driver means for driving one stator coil of the gauge with PWM and polarity signals for durations and polarities in proportion to the magnitudes and polarities of the measurand while driving another stator coil with a fixed voltage of a chosen polarity to position a needle connected to a rotor to a dial position proportional to the magnitude of the measurand.

1 more element

Dependencies are inferred from the claim text.