JP4501051B2 - Voltage control device for vehicle alternator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage control device for an AC generator for a vehicle that controls energization of an exciting coil of a generator using a semiconductor element.
[0002]
[Prior art]
Japanese Patent No. 2529237 and Japanese Patent No. 3019377, filed by the present applicant, change the control voltage (current driving force) at a constant rate of change when the semiconductor element for feeding control to the exciting coil is cut off. A technique for slowing down the current reduction rate of the semiconductor element and reducing electromagnetic noise caused by inductance of wiring connecting the semiconductor element and the battery (hereinafter also referred to as a turn-off slowing technique). ) Is disclosed.
[0003]
[Problems to be solved by the invention]
However, the turn-off slowing technique disclosed in the above-mentioned publication causes a significant increase in internal loss in the transition period when the semiconductor element is cut off (transition period when the semiconductor element is cut off) due to a decrease in the current reduction rate. There is a drawback that derives the problem of increasing and requiring a new device for the cooling structure, and it is difficult to put it to practical use.
[0004]
In particular, there is a problem that a large amount of heat is generated in the early stage of the transitional period during interruption due to the large inductance of the exciting coil.
[0005]
The present invention has been made in view of the problems of the prior art, and provides a voltage control apparatus for an AC generator for a current vehicle that realizes noise reduction while suppressing an increase in heat generation of a semiconductor element for interrupting exciting coil feeding current. That is the purpose.
[0006]
[Means for Solving the Problems]
  The voltage control device for a vehicle alternator according to claim 1 is provided in parallel with a semiconductor element for intermittently supplying power to the excitation coil of the vehicle alternator having a rectifier for rectifying the generated AC output, and in parallel with the excitation coil. A connected reflux element, and a power generation voltage control means for commanding on / off of the semiconductor element to converge the output voltage to a predetermined adjustment voltage value according to a signal correlated with the output voltage of the rectifier, In a voltage control device for a vehicle alternator comprising a driving means for controlling the semiconductor element based on the command,Comparing means for comparing a predetermined value with a signal voltage having a correlation with a voltage drop between the main electrodes of the semiconductor element, and the driving means has the signal voltage reach the predetermined value in the transition period during the shut-off. Immediately after, the current driving force reduction rate of the control electrode of the semiconductor element is made smaller than immediately beforeIt is characterized by that.
[0007]
  According to this configuration, the rate of change of current between the main electrodes of the semiconductor element is reduced (the turn-on of the semiconductor element is smaller than that of a normal turn-off operation in which the current driving force is greatly reduced stepwise at the beginning of the transition period at the time of shutoff. By increasing the time required from the current value to 0, the surge voltage and electromagnetic wave noise proportional to the current change rate di / dt can be reduced.In addition, it is possible to reliably determine the initial period of the above-described transition period at the time of interruption that should increase the current decrease rate and the remaining period of the above-described transition period at the time of interruption that should decrease the current decrease rate. The signal voltage includes a voltage at a connection point between the semiconductor element and the exciting coil, a voltage drop between the main electrodes of the semiconductor element, a voltage drop of the exciting coil, a current between the main electrodes of the semiconductor element, and the reflux. It consists of either the current of the element or the current of the exciting coil. In particular, in the source follower or emitter follower circuit, the detection of the circulating current immediately means the start of a decrease in the current decrease of the semiconductor element, and is particularly suitable as a signal voltage.
[0008]
Compared to the conventional turn-off slowing technique described above that keeps the current driving force decrease rate (approximately equal to the current decrease rate of the semiconductor element) from the beginning to the end of the transition period at the time of interruption, the necessary transition at the time of interruption is required. Since the period can be shortened, heat generation can be reduced, and the frequency component of the electromagnetic noise that is inversely proportional to the transition period at the time of interruption can be changed so that it does not overlap with the band component of the electromagnetic noise that should be suppressed by the in-vehicle electronic device. Can be.
[0009]
Further explanation will be given.
[0010]
When the current of the semiconductor element is changed to an ideal step shape from the turn-on current value to 0, the surge voltage of the battery power supply line is determined by multiplying the differential value of the current change by the wiring inductance of the battery power supply line. The magnitude of this surge voltage increases as the frequency increases. On the other hand, for each frequency component of the surge voltage, the AC impedance (1 / jωc) in the space around the battery power supply line becomes smaller as the frequency becomes higher. It can be seen that the magnitude of the electromagnetic noise radiated to the outside increases in proportion to the square of the frequency, and becomes extremely large when the current of the semiconductor element is turned off with an ideal step waveform. However, since the transition period at the time of interruption is extremely short, the heat generation of the semiconductor element during the transition period at the time of interruption can be made extremely small.
[0011]
Next, when the current driving force of the semiconductor element represented by, for example, a control voltage applied to the control electrode of the semiconductor element is turned off at a constant reduction rate by the turn-off slowing technique, the current change rate di / Since the magnitude of dt decreases in inverse proportion to the extension of the transition period at the time of interruption, electromagnetic wave noise can be significantly reduced, but the amount of heat generated by the semiconductor element during the transition period at the time of interruption increases accordingly.
[0012]
On the other hand, according to the present configuration, it is possible to realize intermediate characteristics between the two turn-off methods, and to reduce electromagnetic noise without increasing heat generation.
That is, while reducing the electromagnetic wave noise of the semiconductor element in the transition period at the time of interruption significantly compared to the case of step change, the average current reduction in the transition period at the time of interruption compared to the turn-off slowing technique and It can be reduced by shortening the transition period at the time of interruption.
[0013]
Furthermore, in this configuration, as will be described later, the current is hardly reduced due to the influence of the energy of the accumulation time of the exciting coil in spite of the decrease in the current driving force at the beginning of the transition period at the time of interruption, but between the main electrodes of the semiconductor element. The voltage drop is very large, and the generation of large heat generation can be reduced satisfactorily while suppressing the increase in electromagnetic noise.
[0014]
  According to the configuration of claim 2, in the voltage control apparatus for an AC generator for vehicle according to claim 1, the drive means further supplies the control voltage or control current of the semiconductor element to the transition period during shut-off.Before and after the signal voltage reaches the predetermined value,Each is changed at a substantially constant rate of change,Before the signal voltage reaches the predetermined valueThe rate of change ofThe signal voltage has reached the predetermined valueIt is characterized in that it is set to be larger than the rate of change of the remaining period thereafter.
[0015]
According to this configuration, switching of the current driving force reduction rate according to the first aspect can be realized with a simple circuit configuration. Note that the control voltage or control current here refers to the potential or current of the control electrode of the semiconductor element.
[0016]
According to a third aspect of the present invention, in the voltage control apparatus for an automotive alternator according to the second aspect, the semiconductor element further performs a follower operation. The follower operation here refers to an operation in a circuit configuration in which an excitation coil and a flywheel diode are connected to a source electrode or an emitter electrode.
[0017]
In this way, the following effects can be achieved.
[0018]
That is, if an N-channel MOSFET is described as an example, in this source follower circuit, since the inductance of the exciting coil is extremely large, if the gate electrode voltage of the semiconductor element decreases at the beginning of the transition period at the time of interruption,
The exciting coil emits magnetic energy, and an operation for sustaining the energization of the exciting coil occurs, and the source electrode potential is lowered.
[0019]
This decrease in the source potential is such that the channel current of the N-channel MOSFET is in the saturation region and is approximately proportional to the square of the gate-source voltage Vgs, so that the decrease in the source electrode suppresses a change in the current of the semiconductor element. On the other hand, the decrease in the source electrode potential increases the voltage effect of the N-channel MOSFET, that is, the semiconductor element, and increases heat generation.
[0020]
In other words, at the beginning of the transition period at the time of shut-off, the current due to the release of magnetic energy is applied to the semiconductor element in order to suppress the current change despite the decrease in the current drive capability of the semiconductor element due to the decrease in the gate electrode potential. The current change of the semiconductor element is suppressed. This means that at the initial stage of the transition period at the time of interruption, a situation occurs in which the channel current is large and the voltage drop of the semiconductor element is large, so that the heat generation is large.
[0021]
That is, in the first period of the transition period when the source electrode potential of the semiconductor element is lowered from the high power supply voltage to the low power supply voltage, magnetic energy is released from the exciting coil, so that the actual channel current change is small. As described above, since the absolute amount of current is large and the heat generation is large, the current decrease rate is small and the electromagnetic noise is small. Therefore, the gate electrode voltage, that is, the control voltage is decreased as quickly as possible. It is preferable to shift to the current reduction process.
[0022]
Even if the transition is performed rapidly, the current change in this initial period is small as described above, and therefore the electromagnetic wave noise does not increase so much even if the gate electrode potential of the source follower N-channel MOSFET is rapidly decreased.
[0023]
Next, when the source electrode potential of the semiconductor element is lowered to about −0.7 V from the lower power supply potential (ground potential), a freewheeling current is supplied from the flywheel diode to the source electrode of the N-channel MOSFET (semiconductor element). The decrease in the channel current of the N-channel MOSFET starts following the decrease in the control voltage by the amount of the reflux current and the consumption of the magnetic energy, and this decrease in the channel current causes electromagnetic noise. Therefore, at this stage, it is preferable to reduce the electromagnetic wave noise by regulating the reduction rate of the control voltage, that is, the reduction rate of the current drive capability of the N-channel MOSFET. As a result, it is possible to reduce heat generation while suppressing an increase in electromagnetic wave noise. Although the above description has described the source follower operation, the same is true for the emitter follower operation.
[0024]
A similar phenomenon occurs in the grounded source operation.
[0025]
That is, in a circuit configuration in which the drain electrode or the collector electrode is connected to the excitation coil and the flywheel diode, when the gate electrode potential is lowered to reduce the current drive capability of the transistor, the excitation coil attempts to maintain the current state, This causes the drain electrode potential to rise rapidly.
[0026]
This increase in the drain electrode means a significant increase in the voltage drop between the main electrodes of the semiconductor element when the channel current is large, so that the heat generation of the semiconductor element, that is, the channel current / voltage drop is greatly increased. Further, the increase in the drain electrode potential increases the channel current due to the expansion of the drain depletion layer in the channel region.
[0027]
After all, even in the source grounded circuit configuration, in the initial period of the cut-off transition period in which the current change is small, it is necessary to quickly reduce the control voltage (gate electrode voltage), that is, the current driving capability, and quickly end this large heat generation state. is there.
[0028]
Next, when the drain electrode potential exceeds the high power supply potential by about 0.7 V or more, a reflux current flows to the flywheel diode, preventing further increase of the drain electrode, and at the same time, only the amount of the reflux current and the attenuation of magnetic energy. Since the channel current of the semiconductor element is reduced and electromagnetic noise is generated according to the current reduction rate, the current driving force reduction rate is reduced to regulate the electromagnetic noise.
[0032]
  Claim4Claims according to the arrangement describedAny one of 1 to 3Further, in the voltage control device for a vehicle alternator according to the present invention, the comparison means immediately after the signal voltage reaches the predetermined value during the transition period when the semiconductor element comprising the transistor having a gate electrode is on. Increase the charging current of the gate electrode of the semiconductor element than immediately before,When shut offThe predetermined value for switching the discharge current in the transition period is set higher than the predetermined value for switching the charging current in the transition period during conduction.
[0033]
As a result, even if a signal voltage detection delay occurs, the control voltage input to the semiconductor element does not drop rapidly and the semiconductor element is not completely turned off. Therefore, spike voltage and radio noise can be surely reduced.
[0037]
  Claim5The voltage control device for a vehicle alternator described above is connected in parallel to a semiconductor element that intermittently feeds power to the excitation coil of the vehicle alternator having a rectifier that rectifies the generated AC output, and the excitation coil. A return voltage element, and a generated voltage control means for commanding on / off of the semiconductor element to converge the output voltage to a predetermined adjustment voltage value in accordance with a signal correlated with the output voltage of the rectifier. A voltage control device for a vehicle alternator comprising a driving means for controlling the semiconductor element based on a command, wherein the rectifier device is constituted by a reverse recovery time shortening type diode, and the Zener diode at the time of reverse recovery The maximum value (%) of the current change rate is set to be not more than twice the maximum value (%) of the current change rate in the transition period when the semiconductor element is cut off or the conduction period. To.
[0038]
According to this configuration, when the semiconductor element changes from ON to OFF and from OFF to ON, the return current flows through the return element, that is, when the AC output voltage is rectified by the diode by the rectifier, the diode Since the recovery current flowing in the diode when the bias of the switching from the forward direction to the reverse bias can be suppressed, spike noise generated in the charging line can be reduced, radio noise can be suppressed, and further, when switching the semiconductor element Since the time rate of change of the energization current is less than twice the time rate of change of the recovery current of the rectifier diode, the spike noise level generated in the charging line due to switching can be suppressed to the commutation noise level of the diode. As a generator, spike voltage and radio noise can be reliably reduced.
[0039]
In addition, the reverse recovery time shortening diode has a feature that the breakdown voltage is lower, and since the breakdown voltage of the return element can be set relatively low, the recovery voltage of the return element can also be reduced. The effect is achieved by reduction.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the invention are illustrated by the following examples.
[0041]
[Example 1]
A voltage control apparatus for an automotive alternator of this embodiment will be described with reference to FIGS. FIG. 1 shows a circuit diagram of a voltage control device for a vehicle alternator.
(overall structure)
The in-vehicle electric load 1 is fed by a battery 2, and the battery 2 is charged by a generator 3 driven by an engine (not shown).
[0042]
The generator 3 includes an excitation coil 4 that is energized to form a magnetic field, and an armature coil 5 that generates an electromotive force due to a time change of a magnetic field generated by the linkage excitation coil 4. The coil 5 is rotationally driven by an engine (not shown). The AC output of the armature coil 5 is converted into a DC output by the rectifier circuit 6 and then output to the electric load 1 and the battery 2.
[0043]
The power generation amount of the generator 3, that is, the power generation amount of the armature coil 5 is determined by the driving speed of the generator 3 and the energization state of the excitation coil 4, and the energization state of the excitation coil 4 is controlled by the control circuit 7.
[0044]
(Configuration of control circuit 7)
The control circuit 7 includes a semiconductor element 8 for interrupting excitation current to the excitation coil 4, a flywheel diode 9,
The battery state determination circuit 10, the inter-terminal voltage determination circuit 50 of the semiconductor element 8, the charge pump circuit 11, the gate discharge circuit 12, and the pre-transistor 32 are included.
[0045]
The semiconductor element 8 is composed of an N-channel MOSFET, and a flywheel diode 9 is connected in antiparallel with the exciting coil 4. The gate electrode of the semiconductor element 8 is discharged by the pre-transistor 32 and charged and controlled by the charge pump circuit 11. The pre-transistor 32 is controlled by the gate discharge circuit 12, and the gate discharge circuit 12 and the charge pump circuit 11 are controlled by the inter-terminal voltage determination circuit 50 and the battery state determination circuit 10.
[0046]
The battery state determination circuit 10 is a circuit that determines whether to increase or decrease the power generation amount of the generator 3 based on the voltage of the battery 2, that is, whether to turn on or off the semiconductor element 8, and is a constant voltage circuit 13, a comparator 14, and resistors 15 and 16 connected in series to divide the battery voltage. The battery state determination circuit 10 compares the divided voltage of the battery voltage with the adjustment voltage output from the constant voltage circuit 13, and when the battery voltage is higher than the adjustment voltage, the comparator 14 turns off the semiconductor element 8. A Hi signal is output as much as possible. Conversely, when the battery voltage is lower than the adjustment voltage, the comparator 14 outputs a Lo signal so that the semiconductor element 8 is turned on.
[0047]
The inter-terminal voltage determination circuit 50 detects the voltage of the connection terminal 400 of the semiconductor element 8 and the exciting coil 4 in order to determine the state of the drain-source voltage of the semiconductor element 8, and based on the determination result, the gate of the semiconductor element 8 It is a circuit that outputs a switching signal for switching the charge / discharge current value of the electrode. The inter-terminal voltage determination circuit 50 compares the divided voltage value of the voltage at the terminal 400 and the adjustment voltage output from the constant voltage circuit 13 by the comparator 51, and when the divided voltage at the terminal 400 is higher than the switching reference voltage. The comparator 51 outputs a Hi signal, and when the divided voltage of the voltage at the terminal 400 is lower than the switching reference voltage, the comparator 51 outputs a Lo signal. The voltage division of the voltage at the terminal 400 is output from a voltage dividing ratio switching type resistance voltage dividing circuit including resistors 52 to 54, a transistor 55, a base current limiting resistor 56, and an inverter 57.
[0048]
The operation of the voltage dividing ratio switching type resistance voltage dividing circuit will be described. When the transistor 55 is turned on, the resistor 54 is connected in parallel to the resistor 53, and the voltage dividing ratio is changed. That is, the transistor 55 is turned on when Hi is input from the buffer 57 that has received the output of the comparator 14 when the battery voltage is higher than the adjustment voltage, and receives the output of the comparator 14 when the battery voltage is lower than the adjustment voltage. The Lo is input from the buffer 57 and turned off. Therefore, the voltage division ratio increases when the transistor 55 is turned on and decreases when the transistor 55 is turned off.
[0049]
Therefore, the switching determination voltage of the inter-terminal voltage determination circuit 50 is such that the battery voltage is lower than the adjustment voltage as compared with the case where the battery voltage is lower than the adjustment voltage and the semiconductor element 8 is on and the voltage at the terminal 400 is high. It is set to be lower when the semiconductor element 8 is higher and the voltage at the terminal 400 is lower.
[0050]
The charge pump circuit 11 is a circuit that controls the gate voltage of the semiconductor element 8 according to the output of the battery state determination circuit 10 and the output of the inter-terminal voltage determination circuit 50, and includes a constant current supply unit 18 and a pump unit 19. Become. The constant current supply unit 18 includes transistors 20, 21, and 22 constituting a current mirror circuit. This current mirror circuit is controlled by the transistor 23.
[0051]
The transistor 23 is further controlled by a transistor 24 and a transistor 241. The transistor 24 is ON / OFF controlled by a signal obtained by inverting the output of the comparator 14 of the battery state determination circuit 10 by the inverter 25. The transistor 241 is ON / OFF controlled by an AND circuit 243 that receives the signal inverted by the inverter 25 and the output of the inter-terminal voltage determination circuit 50 as inputs.
[0052]
That is, when the output of the comparator 14 of the battery state determination circuit 10 is Lo and the output of the comparator 51 of the inter-terminal voltage determination circuit 50 is Hi, the transistor 241 is turned on. The transistor 24 and the transistor 241 draw current from the collector electrode of the transistor 22 through the constant current circuit 26 and the constant current circuit 261 connected in series, respectively. The magnitude of the charging current to be fed to is controlled by the output state of the circuits 10 and 50.
[0053]
Reference numeral 19 denotes a current pump unit 19, which includes an oscillation circuit 27 that outputs a periodic pulse voltage, a transistor 28 that is turned on and off by the oscillation circuit 27, and a charge that is supplied to the gate electrode of the semiconductor element 8 when the transistor 28 is turned on and off. It consists of the capacitor | condenser 29 which accumulates. The diodes 30 and 31 are elements for preventing a reverse current flow.
[0054]
(Operation)
An operation when the semiconductor element 8 is turned on will be described.
[0055]
When the semiconductor element 8 is turned off and the exciting current flowing back through the exciting coil 4 decreases, the battery voltage decreases. At this time, when the battery voltage becomes lower than the adjustment voltage, the comparator 14 of the battery state determination circuit 10 outputs Lo. Then, the transistor 24 is turned on by the Hi signal inverted by the inverter 25, and the gate charging current determined by the constant current circuit 26 is supplied to the gate electrode of the semiconductor element 8 through the diodes 30 and 31. This gate charging current gradually charges the gate capacitance and increases the gate voltage. From the time when the gate voltage exceeds the threshold value of the semiconductor element 8, the drain current of the semiconductor element 8 increases.
[0056]
Since the gate voltage gradually increases, the time change of the drain current becomes gentle (the time change di / dt of the current drain current is small), which contributes to suppression of spike voltage and radio noise.
[0057]
As the gate voltage further increases, the drain-source voltage of the semiconductor element 8 decreases, and the voltage at the terminal 400 begins to rise. Eventually, when the voltage division of the voltage at the terminal 400 becomes higher than the switching voltage (adjustment voltage), the comparator 51 of the inter-terminal voltage determination circuit 50 outputs Hi, the AND circuit 243 turns on the transistor 241, and the current mirror circuit is fixed. The current value becomes a composite value of the constant current circuits 26 and 261 and increases the gate charging current supplied to the gate of the semiconductor element 8. As a result, the gate voltage of the semiconductor element 8 increases rapidly, and the drain-source voltage of the semiconductor element decreases rapidly.
[0058]
In this state, the drain current is large and the drain-source voltage is high, so the heat generation is large (used in the active region). However, since the gate voltage rises quickly, the change time is short and the heat generation amount (Voltage × current × time) can be suppressed. Thus, when switching the gate charging current, it is preferable to make a difference of about 20 times as the charging current ratio.
[0059]
Further, when the voltage at the terminal 400 becomes close to the battery voltage, the charge pump current (C × Vc × f) that is determined by the capacitance C of the capacitor 29 of the pump unit 19, the oscillation period f of the oscillation circuit 27, and the applied voltage Vc of the capacitor 29. ) To charge the gate.
[0060]
Next, the gate discharge circuit 12 will be described.
[0061]
When the battery voltage is higher than the adjustment voltage, the comparator 14 of the battery state determination circuit 10 inputs Hi to the inverter 25, and the gate electrode charging operation of the semiconductor element 8 by the circuit 11 is stopped.
[0062]
The Hi output of the comparator 14 is inverted by the inverter 43 to turn off the transistor 35. As a result, the current of the constant current circuit 37 is input to the base electrodes of the transistors 32 and 33 constituting the current mirror circuit, and the transistor 32 has a discharge current equal to the current value of the constant current circuit 37 and the gate of the semiconductor element 8. The electrode is discharged and the semiconductor element is turned off.
[0063]
Since the drain-source voltage of the semiconductor element 8 is low at the beginning of the off-operation transition period (transition period when cut off), the voltage of the connection terminal 400 is high, and the comparator 51 of the terminal voltage determination circuit 50 outputs a Hi signal. To do. Therefore, the Hi signal is input from the comparator 14 of the battery state determination circuit 10 and the Hi signal is input from the comparator 51 of the inter-terminal voltage determination circuit 50 to the NAND circuit 44 of the circuit 12. The NAND circuit 44 turns off the transistor 34. . Therefore, the current of the constant current circuit 36 is input to the bases of the transistors 32 and 33 constituting the current mirror circuit together with the current of the constant current circuit 37 via the diode 38. The transistor 32 is connected to the constant current circuits 37 and 36. The gate electrode of the semiconductor element 8 is rapidly discharged with a discharge current determined by the combined current value. As a result, the gate voltage of the semiconductor element 8 quickly decreases, and the drain-source voltage of the semiconductor element 8 increases rapidly. This process is a region where heat generation is large, but since the gate voltage decreases rapidly, the change time is short and the amount of heat generation can be suppressed.
[0064]
Further, when the drain-source voltage of the semiconductor element 8 increases, the voltage at the terminal 400 starts to decrease. When the voltage at the terminal 400 eventually becomes lower than the switching voltage, the comparator 51 of the inter-terminal voltage determination circuit 50 outputs Lo, The NAND circuit 44 turns on the transistor 34, and the current of the constant current circuit 36 flows through the transistor 34. Only the current of the constant current circuit 37 flows through the base electrodes of the transistors 32 and 33 constituting the current mirror circuit. become. As a result, the discharge current for discharging the charge of the gate electrode of the semiconductor element 8 decreases, the gate voltage gradually decreases, and the drain current of the semiconductor element 8 decreases gradually. In this process, the time change di / dt of the drain current is reduced, which contributes to suppression of spike voltage and radio noise. Thus, when switching the gate discharge current, it is preferable to make a difference of about 20 times as the charge current ratio.
[0065]
In this embodiment, the threshold voltage of the terminal 400 for switching the discharge current at the time of turn-off is set higher than that at the time of turn-on (provided as a hysteresis in the comparator 51 of the inter-terminal voltage determination circuit 50). The operation is accelerated and the semiconductor element 8 is prevented from being cut off at a stage where the discharge current (constant current circuit 36 + 37) is large. Preferably, a more stable operation can be obtained by making a difference of about 1 V in the voltage of the terminal 400 as this hysteresis.
[0066]
As described above, when the semiconductor element 8 is turned on and off, noise is suppressed by suppressing the time change of the current flowing through the semiconductor element 8, and the voltage across the terminals of the semiconductor element 8 at a stage where the current change is small. The switching loss can be reduced.
[0067]
[Example 2]
Another embodiment of the present invention will be described with reference to FIG.
[0068]
In the first embodiment, the voltage at the connection terminal 400 of the exciting coil 4 is determined by the inter-terminal voltage determination circuit 50 in order to determine the energization state of the semiconductor element. In this embodiment, the current flowing through the semiconductor element 8 is detected, and the charge / discharge current of the gate of the semiconductor element 8 is controlled by the magnitude of the current.
[0069]
The operation of this energization current detection circuit will be described.
[0070]
The semiconductor element 800 is a transistor that forms a mirror circuit with the semiconductor element 8, and supplies a current that is substantially proportional to the current flowing through the semiconductor element 8. As a result, when the semiconductor element 8 is turned on, a current substantially proportional to the energization current of the semiconductor element 8 flows to the detection resistor 801, and a voltage drop corresponding to the energization current is generated at both ends of the detection resistor 801. Thus, compared with the reference voltage Vr1, it is possible to suppress the time change of the current when the semiconductor element 8 is turned on and turned off by the magnitude of the energization current.
[0071]
Here, if a MOSFET is used as the semiconductor element 800, it is advantageous because a mirror ratio can be set with a relatively high accuracy to configure a mirror circuit and detect the current flowing through the transistor 8.
[0072]
[Example 3]
Another embodiment of the present invention will be described with reference to FIG.
[0073]
In the present invention, as in the second embodiment, instead of the inter-terminal voltage determination circuit 50, the current flowing through the return element that circulates the current flowing through the exciting coil 4 when the semiconductor element 8 is off is detected, and the semiconductor element is determined by the magnitude of the current 8 is used to control the charge / discharge current of the gate.
[0074]
The operation of this circulating current detection circuit will be described.
[0075]
The detection resistor 900 detects the circulating current flowing through the return element 9, and a voltage drop corresponding to the circulating current is generated at both ends of the detection resistor 900. Comparing this voltage drop with the reference voltage Vr2 by the comparator 901, it is possible to suppress the time change of the current when the semiconductor element 8 is turned on and when it is turned off. Here, the recirculation element 9 may be configured by the same MOSFET as the semiconductor element 8, and the mirror circuit may be configured by detecting the current by controlling the on / off operation of the semiconductor element 8 in a complementary manner.
[0076]
More specifically, when the semiconductor element 8 is turned on, the amount of the circulating current flowing through the circulating element 9 decreases and the current flowing through the semiconductor element 8 increases. Therefore, while the circulating current flows and it is determined that the circulating current detection circuit is circulating, it is possible to suppress the time change of the current flowing through the semiconductor element 8 by suppressing the charging current of the semiconductor element 8. it can.
[0077]
In turn-off, since the current flowing through the semiconductor element 8 decreases and the amount of the circulating current flowing through the circulating element 9 increases, noise can be suppressed by suppressing the discharge current of the semiconductor element 8 during the circulating flow.
[0078]
In this embodiment for detecting the circulating current, it is possible to reliably detect the state in which the current changes in the transient state associated with the on / off of the semiconductor element 8, and the accuracy is high.
[0079]
[Example 4]
Another embodiment of the present invention will be described with reference to FIG.
[0080]
The present invention is to reduce current pulsation due to a charge pump current by stopping oscillation of the charge pump circuit when the voltage across the semiconductor element 8 is sufficiently low in the first embodiment in the first embodiment.
[0081]
The operation of this charge pump operation limiting circuit will be described.
[0082]
The resistors 62 and 63 constituting the resistance voltage dividing circuit divide the voltage at the connection point between the semiconductor element 8 and the exciting coil 4 and input it to the negative input terminal of the comparator 61. The resistors 64 and 65 constituting the resistance voltage dividing circuit divide the connection terminal voltage between the semiconductor element 8 and the battery 2 and input the voltage to the positive input terminal of the comparator 61. The comparator 61 determines the state of the voltage across the semiconductor element 8 by comparing both input voltages. When the inverter 25 inputs the Hi voltage to the NAND circuit 66, the voltage across the semiconductor element 8 is high while the gate-source voltage of the semiconductor element 8 has not yet increased sufficiently, so the comparator 61 outputs the Hi output. Input to the NAND circuit 66. At this time, since Lo is input from the NAND circuit 66 to the transistor 67, the transistor 67 is turned off, and the output of the oscillation circuit 27 is input to the transistor 28. Therefore, the gate voltage of the semiconductor element 8 is boosted by the charge pump operation. The
[0083]
When the gate voltage of the semiconductor element 8 increases sufficiently, the ON voltage (voltage drop) of the semiconductor element 8 decreases, the output of the comparator 61 is inverted, Lo is input to the NAND circuit 66, and the NAND 66 circuit is connected to the transistor 67. Hi is input, the transistor 67 is turned on, the signal of the transmitter 27 is not input to the base of the transistor 28, and the charge pump operation is stopped. The same applies when the output of the inverter 25 becomes Lo and the semiconductor element 8 is turned off.
[0084]
[Example 5]
Another embodiment of the present invention will be described with reference to FIG.
[0085]
In the present invention, by changing the rectifier 6 from a junction diode to a Zener diode having a small recovery current, the time change rate of the energization current when the semiconductor element 8 is turned on and off with respect to the magnitude of the time change rate of the recovery current. The effect of switching of the semiconductor element 8 is reduced to the commutation noise level of the rectifier 6 (difference of about 3 dB, see FIG. 8). According to the present invention, the switching operation can be further stabilized without suppressing the turn-on and turn-off of the semiconductor element 8 during the switching transient period more than necessary.
[0086]
(Modification)
In the above-described embodiment, the circuit configuration using the semiconductor element 8 as the high-side element has been described as an example. However, it goes without saying that the same effect is exhibited even in the case of the low-side element configuration.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a voltage control device for a vehicular AC generator according to a first embodiment;
2 is a characteristic diagram showing switching characteristics of the semiconductor element 8 in Example 1. FIG.
3A and 3B are timing charts showing switching characteristics of the semiconductor element 8 according to the first embodiment. FIG. 3A is a timing chart at the time of turn-on, and FIG. 3B is a timing chart at the time of turn-off.
4 is a circuit diagram of a voltage control device for a vehicle AC generator according to Embodiment 2. FIG.
FIG. 5 is a circuit diagram of a voltage control device for a vehicle AC generator according to a third embodiment.
FIG. 6 is a circuit diagram of a voltage control apparatus for an automotive alternator according to a fourth embodiment.
7A is a timing chart showing a change in current of a Zener diode used in the voltage control device for a vehicle alternator of Example 5, and FIG. 7B is a turn-on time when a Zener diode is used as a circulating element. FIG. 7C is a timing chart showing a change in drain current of the semiconductor element 8 at turn-off when a Zener diode is used as a circulating element.
8 is a characteristic diagram showing the relationship between the ratio of the current change rate at turn-on / current change rate at turn-off of the Zener diode used in FIG. 7 and noise.
[Explanation of symbols]
3 …… Generator
4 ... Excitation coil
5 ... Armature coil
7. Control circuit
8 …… Semiconductor element

Claims (5)

A semiconductor element that intermittently feeds power to the exciting coil of an AC generator for vehicles having a rectifier that rectifies the generated AC output;
A reflux element connected in parallel to the exciting coil;
A generated voltage control means for commanding on / off of the semiconductor element to converge the output voltage to a predetermined adjustment voltage value in accordance with a signal correlated with the output voltage of the rectifier;
Drive means for controlling the semiconductor element based on the command;
In a voltage control device for a vehicle alternator comprising:
Comparing means for comparing a predetermined value with a signal voltage having a correlation with a voltage drop between the main electrodes of the semiconductor element,
The vehicle is characterized in that immediately after the signal voltage reaches the predetermined value in the transition period at the time of the cutoff, the current driving force reduction rate of the control electrode of the semiconductor element is made smaller than immediately before the signal voltage. AC generator voltage control device. In the voltage control apparatus of the alternating current generator for vehicles of Claim 1,
The driving means changes the control voltage or control current of the semiconductor element at a substantially constant rate of change after the signal voltage reaches before the predetermined value in the transition period at the time of interruption,
The voltage control of an AC generator for a vehicle, wherein the rate of change before the signal voltage reaches the predetermined value is set larger than the rate of change after the signal voltage reaches the predetermined value. apparatus. In the voltage control apparatus of the alternating current generator for vehicles of Claim 2,
The voltage control apparatus for an AC generator for a vehicle, wherein the semiconductor element performs a follower operation. In the voltage control apparatus of the alternating current generator for vehicles in any one of Claims 1 thru | or 3 ,
The comparison means increases the charging current of the gate electrode of the semiconductor element immediately before the signal voltage reaches a predetermined value in the transition period when the semiconductor element including the transistor having the gate electrode is in a conduction state. ,
The voltage control device according to claim 1, wherein the predetermined value for switching the discharge current in the transition period at the time of interruption is set higher than the predetermined value for switching the charging current in the transition period at the time of conduction. A semiconductor element that intermittently feeds power to the exciting coil of an AC generator for vehicles having a rectifier that rectifies the generated AC output;
A reflux element connected in parallel to the exciting coil;
A generated voltage control means for commanding on / off of the semiconductor element to converge the output voltage to a predetermined adjustment voltage value in accordance with a signal correlated with the output voltage of the rectifier;
Drive means for controlling the semiconductor element based on the command;
In a voltage control device for a vehicle alternator comprising:
The rectifier is
Consists of diodes with reduced reverse recovery time,
The maximum value (%) of the current change rate at the time of reverse recovery of the Zener diode is set to be not more than twice the maximum value (%) of the current change rate during the transition period when the semiconductor element is cut off or when the semiconductor element is turned on. A voltage control apparatus for an AC generator for a vehicle.

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