Motor drive control circuit

• US 4,933,614 A
• Filed: 01/11/1989
• Issued: 06/12/1990
• Est. Priority Date: 04/02/1986
• Status: Expired due to Term

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Kawata, Toshihiko
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Martin, David
• Application Number:
  US07/295,953
• Time in Patent Office: 517 Days
• Field of Search: 318/432, 318/139, 318/433, 388/800, 388/821, 388/833, 388/815, 388/847, 388/929, 388/930, 62/133, 236/35, 236/DIG. 9
• US Class Current: 318/432
• CPC Class Codes: B60H 1/00828 Ventilators, e.g. speed control B60H1/00864 takes precedence
• CPC Class Codes: F04D 27/00 Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
• CPC Class Codes: F24F 11/0001 for ventilation F24F11/30 takes precedence
• CPC Class Codes: G05D 7/0676 by action on flow sources G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: H02P 7/288 using variable impedance
• CPC Class Codes: Y10S 388/929 Fluid/granular material flow rate, pressure, or level
• CPC Class Codes: Y10S 388/93 Load or torque

Abstract

A blower motor drive control circuit is configured to maintain a fixed value of motor driving current to maintain a constant amount of air supply from an air conditioner regardless of changes in the amount of intake air.

Claims

1. A motor drive circuit for a DC motor on which the mechanical load is varied and which is powered by a supply supplying an electric current to the DC motor, comprising:

a drive transistor for controlling the electric current supplied from the power supply to the DC motor;

a current sensing resistor for detecting the electric current supplied to the DC motor and providing an analog voltage, current value signal indicative thereof;

amplifier means connected to both ends of said current sensing resistor for amplifying the current value signal of said current sensing resistor and providing an amplified current value signal, said amplifier means having a characteristic of producing an offset voltage signal below an offset level of said amplifier means due to an inter-terminal potential difference of said amplifier means;

comparison means responsive to the current value signal obtained from said amplifier means for comparing the current value signal to a reference current value signal and providing a desired current value signal to said drive transistor for controlling the electric current supplied to the DC motor so as to compensate for mechanical load variations;

setting means for providing a reference current value signal to said comparison means; and

a voltage divider connected between said amplifier means and said comparison means for dividing the amplified current value signal of said amplifier means and providing a divided current value signal as an output to said comparison means which is a predetermined fractional amount of the amplified current value signal, wherein the range of the current value signal detected by said current sensing resistor which is affected by the offset voltage level of said amplifier means is decreased by said fractional amount.

2. The motor drive circuit of claim 1 further comprising an integrator connected between said comparison means and said drive transistor.