JP2817183B2 - Power generation control device for vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power generation control device for a vehicle, and more particularly to a power generation control device for a vehicle, in which a differential amplifier circuit in the device includes a capacitor provided on a monolithic IC substrate. The present invention relates to an improvement in a vehicle power generation control device.

(Prior Art) Conventionally, a vehicle power generation control device has a function of inputting a battery voltage, smoothing the battery voltage with a smoothing circuit using a chip capacitor, comparing the battery voltage with a reference voltage, and controlling the battery voltage to a desired set voltage. Have. Therefore, from demands such as cost reduction,
By using a differential amplifier circuit using a capacitor of several tens of PF formed in a monolithic IC without using a chip capacitor, a configuration has been proposed to have a function equivalent to that when the above-described chip capacitor is used. ing. One example is JP-A-54-46313.

(Problems to be Solved by the Invention) However, in the differential amplifier circuit having the configuration proposed above, when the temperature becomes high, the leak in the reverse direction of the directional separation layer of the capacitor in the monolithic IC (here, the isolation There is a problem that the balance of the normal comparison operation is lost due to the increase of the leakage, and the normal operation is not performed.

The present invention has been made in view of such a problem, and has as its object to provide a vehicular power generation control device that enables a stable comparison operation of a differential amplifier circuit with a simple configuration. is there.

(Means for Solving the Problems) According to the present invention, a vehicle power generation control device having the following configuration is provided.

A differential amplifier circuit having an input stage for inputting a vehicle-mounted battery voltage detection value and a comparison reference voltage to be compared with the input stage, and an output stage for generating a comparison output voltage based on a result of the mutual comparison of the input voltages. In a power generation control device for a vehicle including a voltage control circuit, the output stage of the differential amplifier circuit includes two current supply circuits for supplying two currents respectively increasing and decreasing simultaneously according to a result of the mutual comparison of the two input voltages; Two current decay circuits connected by a PNP transistor whose collectors are grounded and connected so that the currents of the two current supply circuits are input from the emitters and the decay current is output from the base, and are connected across both the current decay circuits By including a charge / discharge capacitor, both of the capacitor currents due to the charge / discharge of the capacitor caused by the increase / decrease of the respective decay currents of the currents. Based on the change between the voltage, the comparator output voltage is configured to generate, further the capacitor is provided in the substrate in a monolithic IC,
The electrodes consist of a set of anti-parallel thin film capacitors connected in parallel in opposite directions, and the ground leakage currents occurring on the respective electrode sides of the set of thin film capacitors are made substantially equal to each other. A power generation control device for a vehicle.

(Operation) As described above, if a pair of thin film capacitors provided in a monolithic IC substrate and connected in antiparallel to each other are used as charge / discharge capacitors, ground leakage occurring on each electrode side of the antiparallel connected thin film capacitors The effect of the current on the potential difference across the anti-parallel connected thin film capacitor cancels out each other.

In addition, since both current attenuating circuits attenuate the current of each current supply circuit to charge and discharge the capacitor, a sufficient comparison output voltage can be obtained even with the same capacitor provided in the monolithic IC substrate.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

Referring to FIG. 1, the structure of the device of the present invention will be described.
Is a flywheel diode connected in parallel with the field coil 2, and 3 is a rectifier. 4 is a battery and 5 is a power MOS for driving the field coil. Reference numeral 7 enclosed by a dashed line indicates a voltage control circuit. The voltage control circuit 7 includes a block 13 representing a constant current circuit, a differential amplifier circuit indicated by a dashed line box 41, a comparator 38, and a constant voltage circuit (not shown). IG terminal 8
The positive voltage of the battery 4 is applied via a key switch 40, and the IG terminal 8 is further connected via a resistor 12 to a constant current supply section described below. The differential amplifying circuit 41 has a constant current supply unit including current adjusting transistors 17, 18, 19 and 20 having a common base and resistors 14, 15 and 16 for adjusting current; Transistors 25, 26 forming an input stage for inputting a value and a comparison reference _Vref1 to be compared with: two current supplies supplying two currents respectively increasing and decreasing simultaneously according to the result of the mutual comparison of the two comparison input voltages Transistors 23, 24, resistors 21,
22; two current attenuating circuits formed by transistors 27 and 28 whose collectors are grounded, each of two current supply circuits being input from an emitter and outputting an attenuated current from a base; and a thin film capacitor provided in a monolithic IC substrate And an output stage including a smoothing circuit composed of charge / discharge capacitors 29 and 30 connected across the outputs of both attenuation circuits.
The output stage is a transistor 3 for controlling the charge and discharge of the capacitor.
Including 1,32.

Differential to one input 42 of the amplifier circuit 41 includes an input terminal 36 than the first comparison reference V _ref1 is applied to the other input terminal 43, the resistance voltage of the S terminal 9 for Batsuteri voltage sensing 3
A divided voltage divided at 4,35 is applied. The output terminal 44 of the differential amplifier circuit 41 is connected to the negative input terminal of the comparator 38. A second comparison reference voltage _Vref2 is applied to the positive input terminal 37 of the comparator, and the output of the comparator is supplied to the gate of the power MOS 5 via the gate input terminal 10 via the resistor 39.

Next, the operation of the device of the present invention having the above configuration will be described.

When the key switch 40 is turned on, the three-phase alternator 1
Of when the rotational speed is low, the partial voltage of the positive voltage Batsuteri 4 applied to the input terminal 43 is lower than the reference voltage V _ref1 applied to the other input terminal 42, current flows through the resistor 21 I
_R21 is larger than the current I _R22 flowing through the resistor 22. Accordingly, the collector current I _{C (} Tr 31 ₎ of the transistor 31 becomes larger than the collector current I _{C (} Tr 32 ₎ of the transistor 32, so that the potential of one terminal 45 of the capacitors 29 and 30 is higher than the potential of the other terminal 46. As a result, the capacitors 29 and 30 are charged positively on the terminal 45 side and negatively charged on the terminal 46 side. At this time, the output terminal 44 of the differential amplifier circuit 41 has a low potential (about 0.7 V).
The output of the comparator 38 becomes high potential. As a result, the power MOS 5 is turned on, the current flowing through the field coil 2 increases, and the power output of the three-phase AC generator 1 increases. Thus, when the divided voltage becomes equal to or higher than the reference voltage V _ref1 applied to the input terminal 42 applied to the input terminal 43 becomes high Batsuteri voltage, I _R22 is larger than I _R21, slave connexion I _{C (Tr32)
Becomes} larger than I _{C (Tr 31)} , the capacitors 29 and 30 are discharged, and the voltage on the terminal 46 side of the capacitors 29 and 30 rises. Therefore, the output of the output terminal 44 of the differential amplifier circuit 41 has a high potential,
The output of the comparator 38 goes low. Thereby,
The power MOS 5 is turned off, and the current of the field coil 2 disappears, so that the output of the generator 1 decreases and the battery voltage decreases. By repeating the above operation, I _{C (Tr31)}
The battery voltage is controlled so as to maintain the relationship of = _{IC (Tr32)} .

Here, as in the configuration of the prior art device, the first
It is assumed that only a single capacitor 29 is used as the capacitor in the configuration shown in the drawing. In this case, the ground leakage current I _LEAK29 flows from the terminal 46 due to the isolation leakage, so that I _{C (Tr31)} and I _{C
Even if C (Tr32)} is equal, the collector current I _{C (Tr28)} of the transistor 28 is equal to the collector current I _C of the transistor 27.
_{It is} larger than _{C (Tr27)} by h _FE × I _LEAK29, and is represented by the following equation (1).

I _{C (Tr28)} = I _{C (Tr27)} + h _FE × I _LEAK29 (1) where h _FE is the emitter ground current amplification factor of the transistor, and those of the transistors 27 and 28 are equal.
_{Assume that} h _FE = h _{FE (T27)} = h _{FE (T28)} .

On the other hand, the target adjustment voltage of the battery voltage at the terminal 9 is
If V _S , it is expressed by the following equation.

Here, V _R21 = I _R21 × R ₂₁ ≒ I _{C (Tr27)} × R ₂₁ V _R22 = I _R22 × R ₂₂ ≒ I _{C (Tr28)} × R ₂₂ × I _{C (Tr28)} × R ₂₁ (∵R ₂₁ = R ₂₂ ) Therefore, equation (2) is Becomes From (1) and (2) ' Is obtained.

Accordance connexion, adjustment voltage V _S is the ground leakage current, than desired value Just rise. This ground leakage current is not a problem because it is very small at room temperature, but it rises rapidly at high temperatures,
The fluctuation range of the adjustment voltage cannot be ignored.

If you give one numerical example, _{Assuming that} R ₂₁ = _10KΩ , h _FE = 100, and I _LEAK29 = 300nA, the fluctuation width is ΔV _S = 8 × 10 ⁴ × 100 × 300 × 10 ^-9 = 2.4V, which is the value of V _S in the normal case. , It is known that the fluctuation range becomes considerably large. Note that, by interposing the transistors 27 and 28 form a current attenuation circuit, h _FE acts noted from the above equation be the amount of current for charging and discharging the capacitor is small.

As described above, when the thin-film capacitor as shown in FIG. 2 is used in the differential amplifier circuit 11 shown in FIG.
By grounding leakage current increases due to a parasitic diode when has decreased to a high temperature, a problem that the adjustment voltage V _S is varied occurs.

Therefore, in the present invention, in order to solve the above-mentioned problem, when a thin-film capacitor as shown in FIG. 2 is used as the capacitor of the differential amplifier circuit 41, as shown in FIG. Two thin-film capacitors having a value and their electrodes connected in anti-parallel are used as capacitors 29 and 30 shown in FIG.

The upper part in FIG. 2 illustrates the configuration of a thin-film capacitor provided on the substrate of the monolithic IC. In FIG. 2, reference numeral 51 denotes an Al electrode piece, 52 denotes an electrode a, 53 denotes an electrode b, and 54 denotes an SiO ₂ insulating layer on the substrate surface. Five
Reference numerals 5, 56 and 57 denote N ⁺ , N and P ⁻ -type layers formed by the respective pn junction isolation systems. The lower part of FIG. 2 shows an equivalent circuit for the above-mentioned thin film capacitor and a diode junction causing a ground leakage current.

On the left side of FIG. 3, two thin film capacitors having the configuration shown in FIG. 2 and having substantially the same ground leakage current as shown in FIG. The figure shows a configuration in which the electrodes are connected in parallel between the two terminals 45 and 46 so that the electrodes are opposite to each other. On the right side, an equivalent circuit showing the connection state of the two thin-film capacitors is shown. Shown therein are ground leakage currents I _LEAK30 and I _LEAK29 having substantially the same magnitude and occurring on each side of both terminals 45 and 46.

The size of the fluctuation width due to ground leakage current of the adjustment voltage V _S in this case, However, since I _LEAK29 ≒ I _LEAK30 , Δ
The _E-S ≒ 0.

Thus, by using the configuration shown in FIG.
It is possible to prevent the fluctuation of the adjustment voltage V _S caused by the isolation leak.

(Effects of the Invention) As described above, according to the present invention, by using an extremely simple configuration, grounding which occurs on one electrode side of a thin film capacitor in a monolithic IC substrate, which is a problem in the prior art device, is achieved. It is possible to prevent adverse effects caused by leakage current, and to minimize the charge / discharge control current of the capacitor by providing a current attenuating circuit to obtain a stable control output voltage of the vehicle power generation control device. Is possible.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an overall configuration of a vehicle power generation control device according to the present invention. FIG. 2 is a monolithic IC used as charge / discharge capacitors 29, 30 included in the output stage of the differential amplifier circuit in the voltage control circuit of the vehicle power generation control device shown in FIG.
FIG. 2 is a configuration diagram showing a configuration of one thin-film capacitor provided in a substrate and an equivalent circuit thereof. FIG. 3 shows a configuration of two thin film capacitors 29 and 30 in which two thin film capacitors shown in FIG. 2 are used and their electrodes are connected in parallel with their directions being opposite to each other and an equivalent circuit thereof. FIG. (Explanation of reference numerals) 1 ... three-phase AC generator, 2 ... field coil, 3 ... rectifier, 4 ... battery, 5 ... power MOS for driving field coil, 6 ... flywheel diode, 7 ... … Voltage control circuit, 8 IG terminal, 9… S terminal, 10… Gate input terminal, 11… Ground terminal, 12… Resistance, 13… Constant current circuit, 14-16… For current adjustment Resistance, 17-20: Current adjustment transistor, 21,22: Resistance, 23-28: Transistor, 29,30: Capacitor, 31-33: Transistor, 34,35: Voltage division resistance, V _ref1 , V _ref2 …… Reference voltage, 38 …… Comparator, 39 …… Output resistance, 40 …… Key switch, 41 …… Differential amplifier circuit, 42 …… Differential amplifier circuit reference voltage input terminal, 43 …… Difference Battery detection voltage input terminal of dynamic amplifier circuit, 44 …… Output terminal of differential amplifier circuit, 45, 46 …… Both terminals of the capacitors 29 and 30.

Claims (1)

(57) [Claims] An input stage for inputting an on-vehicle battery voltage detection value and a comparison reference voltage to be compared with the input stage, and an output stage for generating a comparison output voltage based on a result of the mutual comparison of the input voltages. In a power generation control device for a vehicle including a voltage control circuit including a differential amplifier circuit, an output stage of the differential amplifier circuit supplies two currents that respectively increase and decrease at the same time according to a result of the mutual comparison between the two input voltages. A current supply circuit and a PNP transistor whose collectors are grounded are connected so that the currents of the two current supply circuits are input from the emitters and the attenuation current is output from the base.
Two current attenuating circuits and a charging / discharging capacitor connected across the two current attenuating circuits. Based on the change in the voltage between both ends of the capacitor due to the charging / discharging of the capacitor caused by the increase / decrease of the respective decay currents of the two currents. A pair of anti-parallel thin film capacitors, wherein the capacitors are provided in a substrate in a monolithic IC, and the electrodes are connected in parallel in opposite directions to each other. And said 1
A power generation control device for a vehicle, wherein ground leakage currents generated on respective electrode sides of a set of thin film capacitors are made substantially equal to each other.