Dual mode input signal conditioner

• US 5,875,966 A
• Filed: 03/07/1997
• Issued: 03/02/1999
• Est. Priority Date: 03/07/1997
• Status: Expired due to Fees

• Current Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Original Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Inventors: Barnhart, Brian J.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US08/813,170
• Time in Patent Office: 725 Days
• Field of Search: 236/49.3, 236/74 R, 236/74 A, 236/DIG. 9, 327/100, 327/102, 327/104, 417/14, 417/32, 165/202, 165/203, 165/204, 62/180, 62/186
• US Class Current: 236/49.3
• CPC Class Codes: B60H 1/00828 Ventilators, e.g. speed control B60H1/00864 takes precedence
• CPC Class Codes: F04D 27/004 by varying driving speed
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
• CPC Class Codes: Y10S 236/09 Fan control

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.

Claims

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.

2. Interface according to claim 1, and further comprising a detector for detecting whether the steady voltage is being received and, if so,

i) activating the first system, and

ii) de-activating the second system.

3. Interface according to claim 2, in which the detector de-activates the first system, and activates the second system, when the steady voltage is not being received.

4. An interface for providing a control signal for a blower in an automotive vehicle, comprising:

a) input means for receiving either

i) a voltage under control of a driver of the vehicle;

or

ii) 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.

5. A circuit for providing a control voltage for a blower in an automotive vehicle, comprising:

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.

6. Circuit according to claim 5, wherein the first circuit comprises a constant current source, a variable resistor, and a differential amplifier, and wherein the constant current source produces a voltage in the variable resistor, which voltage acts as input to the differential amplifier, which produces the control voltage.

7. Circuit according to claim 5, wherein the second circuit comprises a digital comparator which receives the PWM signal and delivers an output signal to a smoothing capacitor, thereby producing the control signal.

8. Circuit according to claim 5, and further comprising a detector for determining whether the DC input voltage is being received.

9. An interface for a blower in an automotive vehicle, comprising:

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.

10. A system for providing a demand signal which demands a blower speed in a vehicle, comprising:

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.