JP5130835B2 - Differential amplifier circuit and current control device using the same - Google Patents

Description

  The present invention relates to a differential amplifier circuit used in the field of semiconductor industrial equipment including automobile electrical equipment, a current control device using the same, and a semiconductor integrated circuit device. In particular, the present invention relates to a differential amplifier circuit including an operational amplifier composed of a p-channel MOSFET that operates normally even when the common-mode input voltage is higher than the vicinity of the power supply voltage, and a current control device using the same.

In electric power steering devices for automobiles, speed converters for automatic vehicles, etc., current that flows through an inductance load such as a motor or solenoid is detected with high accuracy, and the current is fed back to control the current with high accuracy. A control device is used.
The current control device mainly consists of PWM circuit, differential amplifier circuit and current detector. As the current detector, current can be converted into voltage, high-precision measurement is possible, it can be used in a wide temperature range, and it is inexpensive. This shunt resistance is often used in automotive applications.
FIG. 5 is a main part circuit diagram of an in-vehicle current control device for controlling the solenoid current. Here, as an example in which the common-mode input voltage rises to near Vcc, a current control device 115 constituting an on-vehicle ECU (Electronic Control Unit) will be taken up. As described above, the circuit of the current control device 115 is mainly configured by the differential amplifier circuit 104 including an operational amplifier using the PWM circuit 102 and a p-channel MOSFET (hereinafter referred to as PchMOS). Here, the common-mode input voltage (Vcommon) is a voltage on the low potential side of the shunt resistor 58.
5 is a PWM (Pulse width modulation) circuit 102 including switching devices 52 and 55 (HSP, LSP), a solenoid 57, a shunt resistor 58 (whose resistance value is Rshunt), and a diode 54.

The shunt resistor 58 is a current detector that can convert a minute current into a voltage. HSP is a high-side power switching element (for example, n-channel power MOSFET), and LSP is a low-side power switching element (for example, n-channel power MOSFET).
The circuit on the right side of FIG. 5 is an operational amplifier using a PchMOS that amplifies the differential voltage (Vs = Is × Rshunt) generated by the current Is flowing through the shunt resistor 58 to a fixed value (for example, 5 times) and inputs it to the microcomputer 59. This is a conventional differential amplifier circuit 104 including:
In the differential amplifier circuit 104, for example, Vs is amplified five times by setting an arbitrary resistance satisfying R2 = Rf = 5R1 = 5Rs, and output from the output point 28 as the output voltage Vout.
6A and 6B show operation waveforms of each part of the PWM circuit 102. FIG. 6A shows a voltage waveform of LSP-IN, FIG. 6B shows a voltage waveform of VINN1, FIG. 6C shows a voltage waveform of VINP1, FIG. 4D is a voltage waveform of Is × Rshunt, and FIG. 4E is a voltage waveform of Vout. The horizontal axis is time and is an arbitrary scale.
HSP-IN is a gate voltage signal of the switching device 52, and LSP-IN is a gate voltage signal of the switching device 55. VINN1 is a voltage at the second input point 27 and is a voltage on the low potential side of the shunt resistor 58. VINP1 is a voltage at the first input point 26 and is a voltage on the high potential side of the shunt resistor 58. Is × Rshunt is a voltage (VINP1−VINN1) which is a difference between the voltage (VINP1) on the high potential side of the shunt resistor 58 and the voltage (VINN1) on the low potential side, and is a differential voltage Vs. Vout is the voltage at the output point 28 and the output voltage of the operational amplifier 15.

In FIG. 6, a malfunction occurs in the Vout waveform obtained by amplifying Vs = Is × Rshunt five times at the falling portion of LSP-IN, and the Vout waveform jumps up.
This is because VINN2 was raised to near 4.3 V simultaneously with the fall of LSP-IN, and VINP2 was further raised to around 4.7 V. That is, the voltages (VINN2 and VINP2) input to the −input terminal and the + input terminal of the operational amplifier 15 exceed the upper limit value of the common-mode input voltage range of the operational amplifier.
When the upper limit value of the common-mode input voltage range of the operational amplifier is exceeded, the operational amplifier 15 operates abnormally. When the operational amplifier 15 operates abnormally, an abnormal Vout waveform is output to the output point 28 of the operational amplifier 15. When this abnormal Vout waveform is input to the microcomputer 59, the feedback signal becomes abnormal and the PWM control circuit 56 of the PWM circuit 102 cannot operate normally. If it does so, it will become impossible to control the electric current sent through the solenoid 57 which is an inductance load with high precision.
The operational amplifier 15 used here is a Pch input type (a MOSFET into which an input signal enters is a PchMOS). In the differential amplifier circuit 104 including the operational amplifier 15 used for controlling the solenoid current and the like, the operational amplifier 15 needs to output with high accuracy from the lower limit (0 V) of the common-mode input voltage. An operational amplifier cannot be used.

In addition, the rail-to-rail input type that can output from ground potential to power supply voltage causes gm (mutual conductance) distortion during the period when the input voltage is turned on simultaneously with NMOS and PMOS. The challenges are big.
Therefore, a Pch input type operational amplifier must be used in the differential amplifier circuit 104 including the operational amplifier 15 used for controlling the solenoid current and the like. In order for the Pch input type operational amplifier to operate normally, it is necessary to operate the PchMOS in the saturation region, that is, the input voltage of the operational amplifier is the sum of the gate threshold voltage of the PchMOS and the overdrive voltage with respect to the power supply voltage Vcc ( About 1V) or less.
That is, the limit value of the input voltage at the − input terminal and the + input terminal of the operational amplifier 15 is Vcc−1V. The common-mode input voltages (VINN2 and VINP2) have a value that is lower than the voltage at the second input point 27 and the first input point 26 by the voltage borne by the resistor 4 and the resistor 3 from VINN1 and VINP1.
Therefore, the upper limit value of the common-mode input voltage level of VINN1 and VINP1 depends on the input resistances of the resistors 4 and 3. Further, when the power supply voltage Vcc increases, the value of ((Vcc-1V) / Vcc) increases, so that the values of the common-mode input voltage levels of VINN1 and VINP1 also increase. Therefore, the upper limit value of the common-mode input voltage level of VINN1 and VINP1 also depends on Vcc.

Patent Document 1 discloses a first reference voltage source based on a potential of a battery anode of a motor, a second reference voltage source based on a ground potential, an upper arm switching element, and a lower arm switching element. A shunt resistor provided between the connection point and the motor, a switching means for outputting a voltage from one of the first and second reference voltage sources based on the potential of the shunt resistance, and an output of the switching means Voltage dividing means for dividing the potential difference between both ends of the shunt resistor to generate two voltage signals, and input of the two voltage signals generated by the voltage dividing means, and a current value flowing through the shunt resistor, There is disclosed a current detection circuit having amplification means for outputting a voltage that increases or decreases at a predetermined amplification rate based on a current direction.
Patent Document 2 discloses a switching means that is provided between a DC power supply and an inductive load, and that opens and closes a circuit by a control signal, and a free-wheeling diode for returning a current flowing through the inductive load when the switching means opens the circuit. A current detecting resistor for detecting the current flowing through the inductive load, a differential amplifier having the voltage across the current detecting resistor as an input, and a reference voltage and a differential corresponding to the current to be passed through the inductive load An error amplifier that amplifies the difference between the output voltages of the amplifier and outputs it as a control signal, and a compensation voltage that generates a compensation voltage corresponding to the in-phase voltage of the voltage input to the differential amplifier when the switching means opens the circuit A current control circuit comprising a source is disclosed.

In FIG. 5, when VINP1 = Vcommon + Is · Rshunt and VINN1 = Vcommon, the voltage levels of VINP1 and VINN1 are referred to as common-mode input voltage levels input to the differential amplifier.
When VINP2 = (R2 / R1 + R2) · (Vcommon + Is · Rshunt), VINN2 = ((1 / (Rf + Rs)) · (Vf · Vcommon + Rs · Vout) = ((Rf / (Rf + Rs)) · Vcommon) And the voltage range of VINN2 is referred to as an in-phase input range that is input in the immediate vicinity of the + input terminal and the −input terminal of the operational amplifier.
JP 2006-64596 A Japanese Patent No. 3330022

FIG. 7 is a diagram showing the power supply voltage dependency of the upper limit value of the common-mode input voltage level in the conventional differential amplifier circuit. The circles in column c are the upper limit values of the common-mode input voltage level when the differential voltage amplification factor is 5 times (in the case of 5 times amplification). When Vcc = 5V, the upper limit value of the common-mode input voltage level is 4V, which is lower than Vcc. On the other hand, from FIG. Since this upper limit value (4V) is exceeded, the operational amplifier 15 malfunctions, and the Vout waveform becomes an abnormal waveform as shown in FIG.
One of the measures for increasing the upper limit of the common-mode input voltage level in the differential amplifier circuit is R2 (resistance value of resistor 5) = Rf (resistance value of resistor 14) = 2.5R1 (resistance value of resistor 3) = 2. 5Rs (resistance value of resistor 4), such as a resistance ratio change (Δ mark in row b), the upper limit value of the common-mode input voltage level rises to be higher than Vcc, but the differential voltage gain is Decrease by a factor of 2.5.
That is, in the differential amplifier circuit 104 of FIG. 5, when the upper limit value of the common-mode input voltage level is increased, the differential voltage amplification factor is decreased. Thus, in the conventional differential amplifier circuit 104, there is a trade-off relationship that the differential voltage amplification factor decreases when the upper limit value of the in-phase input level is increased.
In Patent Document 1, the switching means for switching the first and second reference voltage sources, the potential difference between the output of the switching means and the voltage at both ends of the shunt resistor are respectively divided to generate two voltage signals. Pressure means are required and the circuit is complex. Further, there is no description that the voltage on the high voltage side and the voltage on the low voltage side of the shunt resistor related to the present invention are divided and input to the amplifying means to increase the upper limit value of the common-mode input voltage level.

Patent Document 2 describes that the voltage on the high voltage side and the voltage on the low potential side of the shunt resistor related to the present invention are divided and input to the differential amplifier to increase the upper limit value of the common-mode input voltage level. Absent.
The object of the present invention is to solve the above-mentioned problems and increase the differential voltage gain while increasing the upper limit of the common-mode input voltage level (expanding the common-mode input voltage range as a differential amplifier circuit). It is an object to provide a dynamic amplifier circuit and a current control device using the same.

In order to achieve the above object, in a differential amplifier circuit including a Pch input type operational amplifier (an operational amplifier using a p-channel MOSFET as an input element), a voltage dividing resistor for dividing an input voltage is connected to an input terminal of the operational amplifier. A differential amplifier circuit having a configuration installed in front of the input resistor to be connected is used.
And in the current control device using the differential amplifier circuit,
A high-side switching element connected between the power supply and the inductance load;
And a diode connected between the low-side switching element connected, and the high-side switching element and the low-side switching element between the shunt resistor and the ground connected in series with the inductive load The voltage dividing resistors are connected to both ends of the shunt resistor, the output signal of the differential amplifier circuit is input to the PWM control circuit as a feedback signal, and the gate signal of the low-side switching element is output from the PWM control circuit The current control device is configured as follows.

According to the present invention, in addition to the resistors (R1, R2, Rs, Rf) that form the front stage of the differential amplifier circuit including the operational amplifier, the voltage dividing resistors (R1.1, R1.2, Rs1, and Rs2) are provided further upstream. ) Can be used to lower the voltage input to the input terminal of the operational amplifier composed of PchMOS, so that the common-mode input voltage level can be increased to near the power supply voltage and the common-mode input as a differential amplifier circuit. The voltage range can be expanded.
Further, the differential voltage amplification factor can be increased by setting this voltage dividing resistor as a part of the input resistance of the differential amplifier circuit and setting it to a suitable resistance value.
By producing a current control device using this differential amplifier circuit and controlling the current flowing through the inductance load, the current flowing through the inductance load can be controlled with high accuracy.
By forming this current control device on a semiconductor substrate to form a semiconductor integrated circuit device, the current control device can be reduced in size and weight.

  Embodiments of the invention will be described in the following examples. In the following description of the drawings, the same parts as those in the prior art are denoted by the same reference numerals.

FIG. 1 is a circuit diagram of a differential amplifier circuit according to a first embodiment of the present invention. The differential amplifier circuit 101 includes an operational amplifier 15, a resistor 9 and a resistor 13 connected to the + input terminal (non-inverting input terminal) of the operational amplifier 15, a resistor 7 and a resistor 8 connected to the resistor 9, The resistor 12 and the resistor 14 are connected to the input terminal (inverted input terminal), and the resistor 10 and the resistor 11 are connected to the resistor 12.
The resistors 13, 11, and 8 are connected to the ground GND, and the resistor 14 is connected to the output point 28 of the operational amplifier 15. The resistor 7 is connected to the first input point 26 (its voltage is VINP1), and the resistor 10 is connected to the second input point 27 (its voltage is VINN1). Resistors 9 and 12 are input resistors connected to the + input terminal and the −input terminal of the operational amplifier 15 via the third connection point 23 (its voltage is VINP2) and the fourth connection point 24 (its voltage is VINN2), respectively. is there.
The resistors 7 and 8 are voltage dividing resistors that divide VINP1, and the resistors 10 and 11 are voltage dividing resistors that divide VINN1. The resistors 9 and 13 are voltage dividing resistors that divide the voltage at the first connection point 21, and the resistors 9 and 12 are input resistors of the operational amplifier. VINP1 is a voltage on the high potential side of the shunt resistor (the voltage at the first input point 26), and VINN1 is a voltage on the low potential side of the shunt resistor (the voltage at the second input point 27). The output point 28 of the operational amplifier 15 (its voltage is the output voltage Vout) is connected to the microcomputer.

In the figure, 21 is a first connection point for connecting the resistors 7, 8 and 9, 22 is a second connection point for connecting the resistors 10, 11 and 12, and 23 is a resistor 9, 13 and an operational amplifier. 15 is a third connection point for connecting the + input terminal, 24 is a fourth connection point for connecting the resistor 12 and the resistor 14, and 25 is a fifth connection point for connecting the resistor 14 and the output point 28 of the operational amplifier. Reference numerals 26 and 27 denote first and second input points of the differential amplifier circuit.
R1.1 is the resistance value of the first resistor 7, R1.2 is the resistance value of the second resistor 8, RS1 is the resistance value of the third resistor 10, RS2 is the resistance value of the fourth resistor 11, and R1.3 is the fifth value. The resistance value of the resistor 9, R 2 is the resistance value of the sixth resistor 13, RS 3 is the resistance value of the seventh resistor 12, and Rf is the resistance value of the eighth resistor 14.
VINP1 and VINN1 are voltages input to the differential amplifier circuit, VINP2 is a voltage input to the positive input terminal of the operational amplifier 15, and VINN2 is a voltage input to the negative input terminal of the operational amplifier.
The difference from the conventional differential amplifier circuit 104 is that, in the differential amplifier circuit 101 of the present invention, in addition to the resistor 9 corresponding to the resistor 3, the resistor 12 corresponding to the resistor 4, the resistor 13, and the resistor 14, a voltage dividing role is provided. This is the point that resistance 7, resistance 8, resistance 10, and resistance 11 are added.

Here, the resistance 7 (R1.1) and the resistance 10 (Rs), the resistance 8 (R1.1) and the resistance 11 (Rs2), the resistance 9 (R1.3) and the resistance 12 (Rs3) have the same resistance value, respectively. It is necessary to use something. VINP1 is divided by resistors 7 and 8 at a resistance ratio (R1.2 / (R1.1 + R1.2)), and becomes VINP2 by dividing voltage with resistor 13 through resistor 9, and this voltage is the + input terminal of operational amplifier 15 Applied to
On the other hand, VINN1 is divided by resistors 10 and 11 at a resistance ratio (Rs2 / (Rs1 + Rs2)) and becomes VINN2 through resistor 12, and this voltage is applied to the negative input terminal of operational amplifier 15.
The overall amplification factor by this circuit is the level shift rate by the resistor 7 (or resistor 10) and the resistor 8 (or resistor 11), the resistor 7, 8, 9 (or the resistor 10, 11, 12) and the resistor 13 (or It can be expressed as follows by the product of the amplification factors by the resistance ratio of the resistor 14).

または、

Or

但し、Ｒ１．１＝Ｒｓ１、Ｒ１．２＝Ｒｓ２、Ｒ１．３＝Ｒｓ３、Ｒ２＝Ｒｆ
今、電位が低い方の電圧（ここではＶＩＮＮ１）をＶｃｏｍｍｏｎ、差動電圧をＶｓとして、ＶＩＮＮ１にＶｃｏｍｍｏｎ、ＶＩＮＰ１にＶｃｏｍｍｏｎ＋Ｖｓを印加したときのＯＵＴ出力（＝Ｖｏｕｔ）は以下の（１）式〜（３）式の関係式から導き出される。

However, R1.1 = Rs1, R1.2 = Rs2, R1.3 = Rs3, R2 = Rf
Now, when the voltage having the lower potential (here VINN1) is Vcommon, the differential voltage is Vs, and Vcommon is applied to VINN1, and Vcommon + Vs is applied to VINP1, the OUT output (= Vout) is expressed by the following equations (1) to (1): 3) It is derived from the relational expression.

[Equation 3]
VINP2 = [R2 / {(R1.2 / (R1.1 + R1.2)) + R1.3 + R2)}]. (Vcommon + Vs) (1)

[Equation 4]
VINN2 = [Rf / {(Rs2 / (Rs1 + Rs2)) + Rs3 + Rf}] · Vcommon (2)

[Equation 5]
VINP2 = VINN2 (virtual short of operational amplifier) (3)

例えば、Ｒ１．１＝Ｒ１．２＝Ｒｓ１＝Ｒｓ２＝２Ｒ、Ｒ１．３＝Ｒｓ３＝Ｒ、Ｒ２＝Ｒｆ＝２０Ｒという任意のＲによりＶｃｏｍｍｏｎの係数は相殺され、Ｖｏｕｔ＝５Ｖｓという５倍増幅の出力が可能となる。
図２は、図１の本発明の差動増幅回路の同相入力電圧レベルの上限値の電源電圧依存性を示す図である。ａが本発明の場合であり、ｂ、ｃ、ｄは従来の場合である。ａ列のデータ（黒四角）は差動電圧増幅率が５倍の場合である。図で示すように、同相入力電圧レベルの上限値はＶｃｃ＝５Ｖで、９Ｖとなり、Ｖｃｃ＝１５Ｖでは３０Ｖとなる。つまり、Ｖｃｃの１．８倍〜２倍にすることができる。また、抵抗比を変更することにより、さらに広い同相入力電圧範囲での差動増幅動作が可能となる。
この差動増幅回路１０１では、分圧抵抗回路１０３を構成する分圧抵抗（抵抗７と抵抗８、抵抗１０と抵抗１１）により差動電圧Ｖｓも分圧されてしまうことから、使用するオペアンプ１５は低い同相入力電圧領域ではオフセットが小さいことが望まれる。
本発明の差動増幅回路１０１とシャント抵抗５８を組み合わせ、さらにスイッチングデバイスを加えて電流制御装置を製作し、この電流制御装置で自動車用のソレノイド電流を制御することで、ソレノイド電流を高精度に制御することができる。つぎに、この電流制御装置について説明する。

For example, the coefficient of Vcommon is canceled by an arbitrary R of R1.1 = R1.2 = Rs1 = Rs2 = 2R, R1.3 = Rs3 = R, R2 = Rf = 20R, and an output of 5 times amplification of Vout = 5Vs Is possible.
FIG. 2 is a diagram showing the power supply voltage dependency of the upper limit value of the common-mode input voltage level of the differential amplifier circuit of the present invention shown in FIG. a is the case of the present invention, and b, c, and d are conventional cases. The data in the a column (black square) is when the differential voltage amplification factor is 5 times. As shown in the figure, the upper limit value of the common-mode input voltage level is 9V when Vcc = 5V, and 30V when Vcc = 15V. That is, it can be 1.8 to 2 times Vcc. Further, by changing the resistance ratio, a differential amplification operation in a wider common-mode input voltage range becomes possible.
In this differential amplifier circuit 101, the differential voltage Vs is also divided by the voltage dividing resistors (resistor 7 and resistor 8, resistor 10 and resistor 11) constituting the voltage dividing resistor circuit 103. It is desirable that the offset is small in the low common-mode input voltage region.
By combining the differential amplifier circuit 101 of the present invention and the shunt resistor 58 and further adding a switching device, a current control device is manufactured, and by controlling the solenoid current for automobiles with this current control device, the solenoid current is highly accurate. Can be controlled. Next, the current control device will be described.

FIG. 3 is a circuit diagram of a current control apparatus according to the second embodiment of the present invention. The difference from the conventional current control device 115 shown in FIG. 5 is that a differential amplifier circuit 101 to which a voltage dividing resistor is added is used as the differential amplifier circuit. The current control device 110 of the present invention mainly includes a PWM circuit 102 and a differential amplifier circuit 101. The PWM circuit 102 includes a power supply 51, a high-side switching device 52, a gate power supply 53, a diode 54, a shunt resistor 58, The low-side switching device 55 is composed of a PWM control circuit 56 that drives the low-side switching device 55.
The output voltage OUT of the operational amplifier 15 becomes a feedback signal via the microcomputer 59, and this feedback signal is input to the PWM control circuit 56, and the gate voltage LSP-IN of the low-side switching device 55 is output from the PWM control circuit 56.
By using the current control device 110 of the present invention, the solenoid current can be controlled with higher accuracy than the conventional current control device 115.

FIG. 4 is a layout of the main part of the semiconductor integrated circuit device according to the third embodiment of the present invention. FIG. 4 is a main part arrangement diagram when the circuit of the current control device 110 shown in FIG. 3 is formed on a semiconductor substrate 111. By integrating each component on the semiconductor substrate 111 to form the semiconductor integrated circuit device 112, the current control device 110 can be reduced in size and weight. Of the components, the shunt resistor 58 is shown as being externally attached, but it can also be formed in the semiconductor substrate.
In the figure, reference numerals 61, 62, and 63 denote electrode pads for connection to the solenoid 57 and the shunt resistor 58, which correspond to the terminal 29, the first input point 26, and the second input point 27 in FIG.

1 is a circuit diagram of a differential amplifier circuit according to a first embodiment of the present invention. The figure which shows the power supply voltage dependence of the upper limit of the common mode input voltage range of the differential amplifier circuit of this invention of FIG. Circuit diagram of current controller of second embodiment of this invention Arrangement of principal part of semiconductor integrated circuit device according to third embodiment of this invention. Main part circuit diagram of in-vehicle current control device for controlling solenoid current The operation waveform of each part of the PWM circuit 102 is shown, (a) is a voltage waveform of LSP-IN, (b) is a voltage waveform of VINN1, (c) is a voltage waveform of VINP1, and (d) is a voltage waveform of Is × Rshunt. (E) is a figure which shows the voltage waveform of Vout. The figure which shows the power supply voltage dependence of the upper limit of the common mode input voltage range in the conventional differential amplifier circuit

Explanation of symbols

7-14 resistor 15 operational amplifier 21-25 first to fifth connection point 26, 27 first and second input point 28 output point 29 terminal 51 power supply 52 switching device (HSP)
53 Gate power supply 54 Diode 55 Switching device (LSP)
56 PWM control circuit 57 Solenoid 58 Shunt resistor 59 Microcomputer 61-63 Electrode pad 101 Differential amplifier circuit 102 PWM circuit 103 Voltage dividing resistor circuit 110 Current controller 111 Semiconductor substrate 112 Semiconductor integrated circuit device VINP1 First input point voltage VINN1 First Voltage at two input points VINP2 Voltage at third connection point VINN2 Voltage at fourth connection point Vout Voltage at output point (output voltage)
HSP-IN HSP gate voltage signal LSP-IN LSP gate voltage signal Vs Differential voltage Vcommon In-phase input voltage

Claims (1)

A voltage dividing resistor that divides the input voltage of the differential amplifier circuit including the Pch input type operational amplifier is installed in front of the input resistor connected to the input terminal of the operational amplifier .
A high-side switching element connected between the power supply and the inductance load;
A low-side switching element connected between a shunt resistor connected in series to the inductance load and a ground;
A diode connected between the high-side switching element and the low-side switching element,
The voltage dividing resistors are connected to both ends of the shunt resistor, the output signal of the differential amplifier circuit is input as a feedback signal to the PWM control circuit, and the gate signal of the low-side switching element is output from the PWM control circuit. A current control device.

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