Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Reexamination Certificate
2003-01-06
2003-12-09
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
C341S157000
Reexamination Certificate
active
06661364
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device including an AD converter for inverter controlling.
A conventional microcomputer for inverter controlling includes, as shown in
FIG. 12
, a CPU
1
a
, a ROM
1
b
, a RAM
1
c
, a timer
1
d
, a serial communication circuit
1
e
, an I/O port
1
f
, two AD converters
1
g
and
1
b
, a PWM signal generation circuit
1
i
and the like.
In general, the PWM signal generation circuit
1
i
used for inverter controlling generates a three-phase PWM (Pulse Width Modulation) signal as shown in FIG.
13
. This signal is composed of a PWM signal of three phases, that is, a U-phase, a V-phase and a W-phase respectively having different duties, and an inverted signal of three phases, that is, a /U-phase, a N-phase and a /W-phase. Between the two corresponding phases (namely, between the U-phase and the /U-phase, the V-phase and the N-phase or the W-phase and the /W-phase), a predetermined time at which neither of these two phases are ON (i.e., a dead time) is provided.
A variety of configurations of the PWM signal generation circuit
1
i
are known, and the circuit generally includes a counter, a comparator and the like. An exemplified configuration is shown in FIG.
14
. In the configuration shown in
FIG. 14
, the PWM signal generation circuit includes a counter
3
, a carrier set resistor
4
for storing the maximum count value (carrier set value) of the counter
3
, and a comparator
5
for comparing a current count value of the counter
3
with the carrier set value. As shown in
FIG. 13
, when the current count value of the counter
3
accords with the carrier set value or 0 (zero), the comparator
5
inverts the operation of the counter
3
from an up-counting operation to a down-counting operation or vice versa.
The PWM signal generation circuit
1
i
of
FIG. 14
further includes a phase circuit
6
u
. Although merely the phase circuit
6
u
for the U-phase is shown in
FIG. 14
, phase circuits having the same configuration are provided with respect to the V-phase and the W-phase. The phase circuit
6
u
includes a duty set resistor
7
u
for storing a duty set value U shown in
FIG. 13
, a comparator
8
u
for comparing the count value of the counter
3
with the duty set value U stored in the duty set resistor
7
u
, a flip-flop circuit
9
u
for inverting the PWM signal between the U-phase and the /U-phase in response to a signal supplied from the comparator
8
u
when the count value of the counter
3
accords with the duty set value U, and a dead time inserting circuit
10
u
for inserting the dead time between the U-phase and the /U-phase of the PWM signal.
The microcomputer
1
for inverter controlling including this PWM signal generation circuit
1
i
is used for controlling an inverter device for driving a motor M, for example, as shown in FIG.
15
. Specifically in
FIG. 15
, the microcomputer
1
for inverter controlling outputs the six phases of the PWM signal generated by the PWM signal generation circuit
1
i
included therein to corresponding driving transistors
15
u
,
15
/
u
,
15
v
,
15
/
v
,
15
w
and
15
/
w
via the I/O port if of
FIG. 12
, so as to control the rotating rate and the like of the motor M. For this control, the various states of the motor M, such as the position of a rotor, the value of a current supplied to the motor M and the voltage value of the current, are measured with sensors
16
and
17
for successively changing the duty set value stored in the duty set resistor (
7
u
for the U-phase) of each phase in accordance with the measured values, so as to finely determine the pulse width of each phase of the PWM signal.
Accordingly, it is indispensable for fine control of the motor M to precisely measure the current value and the like with the sensors
16
and
17
. In the case where the current supplied to the motor M is measured by using the sensor
16
or
17
, timing for starting AD conversion with the AD converter
1
g
or
1
h
included in the microcomputer
1
for inverter controlling of the value measured by using the sensor
16
or
17
is significant. Conventionally, in order to subject the output value of the sensor
16
or
17
resulting from measuring the supplied current value of the motor M to the AD conversion, a microcomputer for inverter controlling having a function to automatically start the AD conversion in synchronization with the count value of the counter
3
periodically at given intervals as shown in
FIG. 16
is also generally used. The configuration of an AD converter included in the microcomputer having such a function is shown in FIG.
17
.
FIG. 17
is a block diagram for showing the internal configuration of, for example, the AD converter
1
g
shown in FIG.
12
. In
FIG. 17
, a register ADCTR
1
ga is an AD conversion control register for controlling the AD conversion. In this register ADCTR
1
ga, a bit ADST (i.e., the 7th bit) controls the start of the AD conversion, and when this bit value is changed from “0” to “1”, an analog-digital conversion circuit
1
gb is operated for starting the AD conversion. Other bits for controlling the AD conversion are allocated to the other bits 0 through 6 of the register ADCTR
1
ga. In this configuration, either a write signal from the CPU or a signal corresponding detection of underflow or overflow of the counter
3
is selected as a signal for setting the value of the bit ADST in FIG.
17
. In the case where the detection signal for the underflow or overflow of the counter
3
is selected, the AD conversion is started at the timing of the underflow or overflow of
FIG. 13
in synchronization with the underflow or overflow.
The present inventors have examined at what timing the current value of the motor should be measured. In the case where the six-phase PWM signal is used, current flow to the motor M is different among time periods A, B, C and D of
FIG. 13
because the ON/OFF combinations of the three phases, i.e., the U-phase, the V-phase and the W-phase, of the PWM signal are different among these three periods. For example, in the time period B, the U-phase and the W-phase of the PWM signal are OFF and the V-phase of the PWM signal is ON, and hence, a current from the V-phase to the U-phase and W-phase flows to the motor M. On the other hand, in the time period C, the U-phase and the V-phase of the PWM signal are ON and the W-phase of the PWM signal is OFF, and hence, a current from the U-phase and V-phase to the W-phase flows to the motor M. Accordingly, in order to finely measure the current value of the motor M, it is desired to measure it in one or a plurality of the time periods A, B, C and D at which a current flows to the motor M differently.
In the conventional microcomputer for inverter controlling, when the measured current value of the motor M is to be subjected to the AD conversion in at least one of the time periods A, B, C and D, it is necessary to control the start of the AD conversion by using the CPU
1
a
. For this control by using the CPU
1
a
, the following three software interruption processing are necessary: Processing for measuring start timing of the AD conversion (which is specifically processing for starting the timer at the underflow of the counter
3
); AD conversion start processing (namely, processing for setting the bit ADST of the AD conversion control register ADCTR
1
ga to “1”); and processing for obtaining an AD conversion value. There recently is a trend in using merely one microcomputer for simultaneously performing not only the motor control but also other control such as power control and system control. Therefore, any of the three interruption processing may be delayed due to the priority level in the control. In such a case, the start timing for the AD conversion can be shifted, so that a precise current value cannot be obtained. On the other hand, when the three interruption processing are priorly performed, there arises a problem that other control such as the system control may be delayed.
SUMMARY OF THE INVENTION
An object of the invent
Kawamichi Koji
Kohara Masaru
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