Control device for battery charging AC generator used in motor vehicle
First Claim
1. A control device for a battery charging AC generator system for a motor vehicle, which system includes an AC generator, a rectifier device connected between output terminals of the AC generator, a battery to be charged by the AC generator and a flywheel diode connected in parallel with the field winding, said control device comprising:
- a semiconductor power switching element connected in series with the field winding of the AC generator for performing switching control of a current flowing through the field winding;
a voltage detection resistor connected in parallel with the battery for detecting a voltage of the battery;
means coupled to said voltage detection resistor for determining a voltage proportional to a deviation of the detected voltage of the battery from a reference voltage and for producing a voltage deviation signal representing said voltage proportional to said deviation;
means for generating a PWM signal based on said voltage deviation signal from said voltage deviation determining means for causing on and off operation of said semiconductor power switching element;
means for limiting the switching frequency of operation of said semiconductor power switching element to below a predetermined frequency;
a current detection resistor connected in series with said semiconductor power switching element for detecting a current flowing through the field winding of said AC generator; and
current determining means for determining whether the current detected by, said current detection resistor exceeds a constant reference current and for generating a turn off signal for said semiconductor power switching element when the detected current is determined to have exceeded the constant reference current;
wherein said switching frequently limiting means is a latch circuit which operates in response to a clock signal from said PWM signal generating means.
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Accused Products
Abstract
A control device for a battery charging AC generator for a motor vehicle including a power transistor connected in series with a field winding of the AC generator for performing switching control of a current flowing through the field winding. A voltage deviation circuit detects a deviation of the battery voltage from a reference voltage; and a PWM signal generating circuit is responsive to a voltage deviation signal from the voltage deviation circuit for turning the power transister on and off a resistor connected in series with the power transistor detects a current flowing through the field winding; and a current limiting circuit generates a turn off signal for the power transistor when the detected current is determined to have exceeded a reference current. A latch circuit operates in response to a clock signal from the PWM signal generating circuit to limit the frequency of turning on and off of the power transistor to below 1 KHz.
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Citations
13 Claims
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1. A control device for a battery charging AC generator system for a motor vehicle, which system includes an AC generator, a rectifier device connected between output terminals of the AC generator, a battery to be charged by the AC generator and a flywheel diode connected in parallel with the field winding, said control device comprising:
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a semiconductor power switching element connected in series with the field winding of the AC generator for performing switching control of a current flowing through the field winding; a voltage detection resistor connected in parallel with the battery for detecting a voltage of the battery; means coupled to said voltage detection resistor for determining a voltage proportional to a deviation of the detected voltage of the battery from a reference voltage and for producing a voltage deviation signal representing said voltage proportional to said deviation; means for generating a PWM signal based on said voltage deviation signal from said voltage deviation determining means for causing on and off operation of said semiconductor power switching element; means for limiting the switching frequency of operation of said semiconductor power switching element to below a predetermined frequency; a current detection resistor connected in series with said semiconductor power switching element for detecting a current flowing through the field winding of said AC generator; and current determining means for determining whether the current detected by, said current detection resistor exceeds a constant reference current and for generating a turn off signal for said semiconductor power switching element when the detected current is determined to have exceeded the constant reference current; wherein said switching frequently limiting means is a latch circuit which operates in response to a clock signal from said PWM signal generating means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10)
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9. A control device for a battery charging AC generator system for a motor vehicle, which system includes an AC generator, a rectifier device connected between output terminals of the AC generator, a battery to be charged by the AC generator and a flywheel diode connected in parallel with the field winding, said control device comprising:
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a semiconductor power switching element connected in series with the field winding of the AC generator for performing switching control of a current flowing through the field winding; a voltage detection resistor connected in parallel with the battery for detecting a voltage of the battery; means coupled to said voltage detection resistor for determining a voltage proportional to a deviation of the detected voltage of the battery from a reference voltage and for producing a voltage deviation signal representing said voltage proportional to said deviation; means for generating a PWM signal based on said voltage deviation signal from said voltage deviation determining means for causing on and off operation of said semiconductor power switching element; means for limiting the switching frequency of operation of said semiconductor power switching element to below a predetermined frequency; a current detection resistor connected in series with said semiconductor power switching element for detecting a current flowing through the field winding of said AC generator; and current determining means for determining whether the current detected by said current detection resistor exceeds a constant reference current and for generating a turn off signal for said semiconductor power switching element when the detected current is determined to have exceeded the constant reference current; wherein said voltage deviation determining means, said PWM signal generating means, said frequency limiting means, and said current determining means are formed into a digital processing means which includes an A/D converter for converting the detected voltage from said voltage detection resistor and the detected current from said current detection resistor into respective digital signals, a ROM for storing PWM patterns, a processing circuit for determining an optimum duty of a PWM pulse for said semiconductor power switching element based on the converted digital signals from said A/D converter and a PWM pattern inputted from said ROM, and a clock circuit for controlling input timing of the converted digital signals from said A/D converter and the PWM pattern from said ROM to said processing circuit. - View Dependent Claims (11)
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12. A control device for a battery charging AC generator system for a motor vehicle, which system includes an AC generator, a rectifier device connected between output terminals of the AC generator, a battery to be charged by the AC generator and a flywheel diode connected in parallel with the field winding, said control device comprising:
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a semiconductor power switching element connected in series with the field winding of the AC generator for performing switching control of a current flowing through the field winding; a voltage detection resistor connected in parallel with the battery for detecting a voltage of the battery; means coupled to said voltage detection resistor for determining a voltage proportional to a deviation of the detected voltage of the battery from a reference voltage and for producing a voltage deviation signal representing said voltage proportional to said deviation; means for generating a PWM signal based on said voltage deviation signal from said voltage deviation determining means for causing on and off operation of said semiconductor power switching element; and means for limiting the switching frequency of operation of said semiconductor power switching element to below a predetermined frequency; wherein said switching limiting means is a latch circuit which operates in response to a clock signal from said PWM signal generating means. - View Dependent Claims (13)
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Specification