Dual mode input signal conditioner
First Claim
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1. For a blower motor which requires a predetermined type of control signal, an interface comprising:
- a) a first system for receiving a steady voltage, and producing the predetermined type of signal in response; and
b) a second system for receiving a PWM signal, and producing the predetermined type of signal in response.
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Abstract
An interface for a blower in an automotive vehicle. The interface allows a blower requiring a DC control voltage to be controlled by either (1) a DC control voltage or (2) a Pulse Width Modulated (PWM) signal. The interface converts the PWM signal to a DC voltage.
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Citations
10 Claims
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1. For a blower motor which requires a predetermined type of control signal, an interface comprising:
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a) a first system for receiving a steady voltage, and producing the predetermined type of signal in response; and b) a second system for receiving a PWM signal, and producing the predetermined type of signal in response. - View Dependent Claims (2, 3)
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4. An interface for providing a control signal for a blower in an automotive vehicle, comprising:
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a) input means for receiving either i) a voltage under control of a driver of the vehicle;
orii) a PWM signal produced by a digital control; and b) output means for i) producing a DC voltage in response to the control voltage; and ii) producing a digital signal stream for receipt by a smoothing capacitor, in response to the PWM signal.
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5. A circuit for providing a control voltage for a blower in an automotive vehicle, comprising:
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a) a first circuit for receiving a DC input voltage and producing said control voltage in response; b) a second circuit for receiving a PWM input signal, and producing said control voltage in response; and c) a mode selector for selectively actuating either the first or second circuit. - View Dependent Claims (6, 7, 8)
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9. An interface for a blower in an automotive vehicle, comprising:
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a) a differential amplifier, having i) two inputs, connecting to respective terminals A and B; and ii) a connection to a first output terminal; b) reference means for generating a reference voltage; c) a digital comparator, having i) two inputs, one connected to terminal A, and the other connected to the reference voltage; and ii) a connection to a second output terminal; and d) a constant current source for drawing current from terminal B; whereby two operating modes are possible, including 1) a first mode, wherein A) a variable resistor is connected between terminals A and B, B) a DC power supply is connected to terminal B, and C) the first output is connected to a blower speed control and wherein the differential amplifier produces a replica of the voltage between terminals A and B at the first output; and 2) a second mode, wherein A) an input PWM signal is applied to terminal B; B) a capacitor is connected between the second output and ground; and C) a resistor is connected between the first and second outputs; and
wherein the digital comparator produces an output PWM signal in response to the input PWM signal, and the resistor and capacitor smooth the PWM signal into a signal having an average DC voltage with a ripple.
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10. A system for providing a demand signal which demands a blower speed in a vehicle, comprising:
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a) a resistor having a resistance which is variable by an operator of the vehicle; b) means for driving a substantially constant current through the resistor to produce a substantially constant voltage; and c) means for i) producing the demand signal from the substantially constant voltage, and ii) and holding the demand signal substantially constant, when battery voltage of the vehicle changes.
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Specification