Control apparatus for automotive generator
View Patent ↗An A/D conversion device includes a counter for counting a clock signal fed from a clock signal generator, a D/A converter for converting a digital output of the counter into an analog value, a comparator for comparing an analog output of the D/A converter and an analog field current detection value fed from a current detecting resistor and outputting a result of comparison, an AND circuit for calculating a logical product of an output signal of the comparator and the clock signal fed from the clock signal generator and outputting the logical product to the counter, and a memory for storing the output of the counter according to a transfer signal. The output of the counter is reset when a reset signal is input thereinto.
1. A control apparatus for controlling an automotive generator, said control apparatus comprising:
a field coil to which a DC output voltage of the automotive generator is supplied;
a switching device connected in series with said field coil, whereby switching on/off operation of said switching device controls a field current flowing through said field coil;
a diode connected in parallel with said field coil for recirculating the field current flowing through said field coil when said switching device is in an OFF state;
a field current detector for outputting a voltage generated by a detecting device which is connected in series with said switching device as an analog field current detection value;
an A/D conversion device for converting the analog field current detection value detected by said field current detector into a digital value and outputting said digital value to an external control unit; and
a voltage control circuit for outputting an ON/OFF drive signal to said switching device such that the DC output voltage of the automotive generator follows a specific reference voltage by PWM control operation performed at recurring cycles;
wherein said A/D conversion device includes:
a counter;
a D/A converter for converting a digital output of said counter into an analog value;
a comparator for comparing an output of said D/A converter and the analog field current detection value;
a counter control circuit for controlling said counter according to an output of said comparator such that said counter counts up when the output of said D/A converter is less than the analog field current detection value;
reset means for resetting the output of said counter at a point in time immediately following a rising edge of said ON/OFF drive signal at intervals of a specific number of PWM control operation cycles; and
transfer means for transferring the output value of said counter to said external control unit at a point in time immediately preceding the rising edge of said ON/OFF drive signal at intervals of a specific number of PWM control operation cycles.
2. A control apparatus for controlling an automotive generator, said control apparatus comprising:
a field coil to which a DC output voltage of the automotive generator is supplied;
a switching device connected in series with said field coil, whereby switching on/off operation of said switching device controls a field current flowing through said field coil;
a diode connected in parallel with said field coil for recirculating the field current flowing through said field coil when said switching device is in an OFF state;
a field current detector for outputting a voltage generated by a detecting device which is connected in series with said switching device as an analog field current detection value;
an A/D conversion device for converting the analog field current detection value detected by said field current detector into a digital value;
a current limit value memory for storing a specific current limit value in digital form;
a voltage control circuit for outputting an ON/OFF drive signal to said switching device such that the DC output voltage of the automotive generator follows a specific reference voltage by PWM control operation performed at recurring cycles; and
a current limiter to which an output of said A/D conversion device and the current limit value are input, whereby said current limiter turns off said switching device when the output value of said A/D conversion device exceeds the current limit value regardless of the ON/OFF drive signal;
wherein said A/D conversion device includes:
a counter;
a D/A converter for converting a digital output of said counter into an analog value;
a comparator for comparing an output of said D/A converter and the analog field current detection value;
a counter control circuit for controlling said counter according to an output of said comparator such that said counter counts up when the output of said D/A converter is less than the analog field current detection value;
reset means for resetting the output of said counter at a point in time immediately following a rising edge of said ON/OFF drive signal at intervals of a specific number of PWM control operation cycles; and
transfer means for transferring the output value of said counter to said current limiter at a point in time immediately preceding the rising edge of said ON/OFF drive signal at intervals of a specific number of PWM control operation cycles.
3. The control apparatus according to claim 2 , wherein the output of said transfer means is transmitted to an external control unit via a communication link, and the current limit value stored in said current limit value memory can be overwritten from said external control unit via the communication link.
4. The control apparatus according to claim 1 , wherein said reset means resets the output of said counter every cycle of the PWM control operation and said transfer means transfers the output value of said counter at intervals of a specific plural number of PWM control operation cycles.
5. The control apparatus according to claim 4 , wherein said specific plural number of PWM control operation cycles is set based on a conducting time constant of said field coil such that the waveform of an output of said transfer means of said A/D conversion device resembles the waveform of the field current flowing through said field coil.
6. The control apparatus according to claim 2 , wherein said reset means resets the output of said counter every cycle of the PWM control operation and said transfer means transfers the output value of said counter at intervals of a specific plural number of PWM control operation cycles.
7. The control apparatus according to claim 6 , wherein said specific plural number of PWM control operation cycles is set based on a conducting time constant of said field coil such that the waveform of an output of said transfer means of said A/D conversion device resembles the waveform of the field current flowing through said field coil.