JP2010258146A - Solenoid current control device, and solenoid current control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solenoid current control device that detects a fed current value of a solenoid with high precision with a simple circuit configuration. <P>SOLUTION: The fed current value of the solenoid is input to a V/F converter through a sense resistance, and output pulses from the V/F converter are counted by a counter circuit to obtain a pulse counted value. The pulse counted value corresponds to an integrated value of a solenoid current, and feedback control over a duty ratio of a PWM signal is performed using the pulse counted value to improve precision of average current value detection of the solenoid under current control over the solenoid. Further, the current value is converted into the pulse counted value and controlled, so that the solenoid current control device with the simple circuit configuration is actualized. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solenoid current control device and a solenoid current control method, and more particularly, to a current control device and a current control method for controlling a current flowing through a linear solenoid used for driving control of an opening of a solenoid valve and a hydraulic circuit of a vehicle transmission. Therefore, it is suitable.

Current control devices for linear solenoids used in automobile transmissions, etc., detect the current value that flows through the solenoid and use a pulse width modulation signal (hereinafter referred to as PWM (Pulse Width Modulation)) to match the desired current value. Feedback control using signal).
FIG. 4 is a block diagram showing an example of a conventional solenoid current control device (see, for example, Patent Document 1).
The solenoid current control device of FIG. 4 controls the duty ratio of the PWM signal applied to the MOS transistor M0 so that the average energization current value of the solenoid L0 becomes the specified current value _ID . The control circuit 30 instructs the duty ratio of the PWM signal to the PWM signal output circuit 40, and the PWM signal output circuit 40 generates a PWM signal according to the instruction and outputs it to the MOS transistor M0. The MOS transistor M0 is connected between the solenoid L0 and the DC power supply Vbat, and is turned on / off according to the PWM signal to connect / disconnect the solenoid L0 and the DC power supply Vbat. During the off period of the MOS transistor M0, the flywheel current of the solenoid L0 flows to the GND via the diode D0. A sense resistor R0 for current detection is inserted in the energization path of the solenoid L0, and a voltage proportional to the energization current is generated at both ends of the sense resistor R0. The voltage across the sense resistor R0 is amplified by the amplifier 50 and input to the A / D converter 60 via the filter circuit 90 for noise removal, whereby the energization current value of the solenoid L0 is converted into a digital value. This converted value is stored in a RAM (storage device) 70. The control circuit 30 reads an energization current value (conversion value) stored in the RAM 70 at any time via the A / D converter 60. The control circuit 30 corrects the command value related to the duty ratio of the PWM signal by performing a comparison calculation process on the read energization current value and the specified current value _ID, and instructs the PWM signal output circuit 40 of the corrected duty ratio. .

FIG. 5 is a timing chart for explaining the detection operation of the energization current value of the solenoid L0 in FIG. In FIG. 5, (A) shows the waveform of the PWM signal, and (B) shows the current waveform of the solenoid.
In FIG. 5A, the MOS transistor M0 is turned on while the PWM signal is at the H level, and the MOS transistor M0 is turned off during the L level. The ratio of the ON period of the MOS transistor M0 in the period T of the PWM signal is referred to as the duty ratio of the PWM signal. The duty period adjusts the ON period of the MOS transistor M0 to control the energization current amount of the solenoid L0.
In FIG. 5 (B), when the MOS transistor M0 is turned on at time t1, the solenoid L0 is connected to the DC power source Vbat, the current increases from the minimum current value I _L. On the other hand, when the MOS transistor M0 is turned off at time t2, the solenoid L0 is disconnected from the DC power supply Vbat, the current decreases from the maximum current value I _H.

As a method for calculating the average current value of the solenoid L0, Patent Document 1 discloses the following.
The average energization current value I is calculated by the following equation, where I _L is the minimum current value at time t1 when the PWM signal rises and I _H is the maximum current value at time t2 when the PWM signal falls.

Here, Kduty is a value based on the following equation.

Since Kduty is a numerical value between “0” and “1.0” and changes based on the duty ratio of the PWM signal, the DC power supply voltage Vbat, and the resistance value of the solenoid L0, the numerical value is tabulated. The search method is used at the time of calculation.
The deviation between the calculated energization current value I of the solenoid L0 and the designated current value _ID input from the outside is obtained, and multiplied by the feedback gain K _{FB according} to the PID control law to calculate a correction value I _C to perform feedback control. Do.
However, this method has the following problems.
The actual energization current I of the solenoid L0 increases / decreases as follows according to the ON / OFF operation of the MOS transistor M0.
First, when the MOS transistor M0 is on, the solenoid current I increases according to the following equation.

However, t is time, Vbat is the voltage value of the DC power supply Vbat (for the sake of simplicity, the power supply name and voltage value are given the same sign), R ₀₁ is the ON resistance value of the MOS transistor M0 and the solenoid L0. The sum of the resistance value and the resistance value of the sense resistor R0, L is the inductance of the solenoid L0. Also, I _L is the solenoid current at t = t1.
When the MOS transistor M0 is off, the solenoid current I decreases according to the following equation.

Here, R ₀₂ is the sum of the resistance value of the diode D0, the resistance value of the solenoid L0, and the resistance value of the sense resistor R0. I _H is the solenoid current at t = t2.
When performing numerical calculation, the on-resistance of the diode D0 may be ignored for simplicity.
As shown in the above formulas (3), (4) and FIG. 5, the solenoid current I increases and decreases while changing exponentially rather than linearly, so sampling such as the minimum value I _L and the maximum value I _{H is performed.} In the method of calculating the average current value using the detected current values at the two locations (the method of approximating the curve of the solenoid current I shown by the solid line in FIG. 5B with the straight line shown by the one-point difference line), the actual current value There is a problem that a large difference occurs.
Further, the solenoid current I is a function such as the DC voltage Vbat and the solenoid L0 as shown in the equations (3) and (4). The resistance value of the solenoid L0 is known to change depending on the ambient temperature, and the management of constants (Kduty) of arithmetic expressions including fluctuations in the power supply voltage and fluctuations in the duty ratio of the PWM signal becomes very complicated. There is a point. Furthermore, when the number of solenoids to be controlled increases, constant (Kduty) management becomes larger and more complicated, and problems such as the inability to perform arithmetic processing in time occur.

FIG. 6 is a block diagram showing an example of another conventional solenoid current control device (for example, see Patent Document 2) that can improve such a problem.
6 is different from FIG. 4 only in that the RAM 70 for data transfer of the A / D converter 60 and the RAM 80 for data transfer of the PWM signal are provided independently. Functional parts are denoted by the same reference numerals, and detailed description thereof is omitted.
The difference between FIG. 6 and FIG. 4 regarding the control method is the calculation method of the average current value. That is, the current value of the solenoid L0 is converted into a digital value every A / D conversion period tm (where T / tm is an integer) shorter than the period T of the PWM signal (2 ⁿ conversion values per period T). Is stored in the data transfer RAM 70. The digital value stored for each period tm is taken for the period T of the PWM signal and is arithmetically averaged to calculate the average current value Iave of the solenoid L0. A deviation EV between the average current value Iave and the designated current value _ID is calculated, and the deviation one time before is defined as EVold. Then, a correction value (corrected duty ratio) Dduty of the duty ratio of the PWM signal is obtained based on the following equation using a preset control gain (proportional gain: KP, integral gain: KI) as a parameter.

  The duty ratio correction value Dduty is output to the PWM signal output circuit 40 via the transfer RAM 80. It is disclosed that the calculation from the average current value Iave to the correction value Dduty of the duty ratio and the feedback control process are continuously executed every cycle tm so that the average current value matches the specified current value.

Japanese Patent No. 3085132 Japanese Patent No. 4091163

In the conventional solenoid current control device shown in FIG. 4, since the average current value is calculated using the sampled detected current value at a specific location, there is a problem that an accurate average current value flowing through the solenoid cannot be detected. . In addition, there is a problem in that the constant (Kduty) management of the arithmetic expression applied when calculating the average current value becomes very complicated.
In addition, in another conventional solenoid current control device shown in FIG. 6, the accuracy of the detected average current value is improved, but in order to bring the average current value closer to the actual current value, the A / D conversion cycle tm is shorter. It is necessary to set the period. However, on the contrary, the digital value of A / D conversion has a huge amount of data, and there is a problem that the RAM capacity to be stored and the control circuit become large. Further, when the number of solenoids to be controlled increases, the load on the CPU increases, and there is a problem that a high-speed processing CPU is required.

  The present invention has been made in view of such points, and the object of the present invention is to solve the above problems, detect the average current value flowing through the solenoid with high accuracy, and realize with a simple circuit configuration. A solenoid current control device and a solenoid current control method that can be used.

  In order to solve the above-described problem, according to the solenoid current control device of claim 1, a series circuit in which a solenoid, a DC power supply, a switch element, and a sense resistor for detecting a current flowing through the solenoid are connected in series. A reflux element for securing a current path of the series circuit when the switch element is turned off, and a PWM signal which is a pulse signal having a constant cycle is supplied to the switch element to control on / off of the switch element. PWM signal output circuit, a V / F converter that outputs a pulse signal whose frequency changes in accordance with the voltage across the sense resistor, and the number of output pulses of the V / F converter counted in a predetermined period And a counter circuit that performs pulse count value of the counter circuit so that an average current value of the solenoid matches a specified current value. A control circuit for controlling the Yuti ratio, characterized by comprising a.

According to the solenoid current control device of the second aspect, the return element is a diode.
According to the solenoid current control apparatus of the third aspect, the return element is a switch element that performs synchronous rectification.
According to the solenoid current control device of the fourth aspect, the pulse counting period of the counter circuit is set to one cycle of the PWM signal or an integral multiple thereof.
The solenoid current control method according to claim 5 is a solenoid current control method for controlling the current flowing to the solenoid by turning on and off the switch element by a PWM signal which is a pulse signal having a constant period. Converting the current value of the solenoid into a pulse signal having a frequency corresponding to the current value, counting the pulse signal in a predetermined period, and using the pulse count value, the average current of the solenoid And a step of controlling the duty ratio of the PWM signal so that the value matches the specified current value.

  According to the present invention, the energization current value of the solenoid is converted into a pulse count value by the V / F converter and the counter circuit via the sense resistor, and the duty of the PWM signal is set so as to match the specified current value by this pulse count value. By feedback control of the correction of the ratio, the current value can be controlled by detecting the average current value of the solenoid with high accuracy. Further, since the current value is converted into a pulse count value and controlled, a highly accurate solenoid current control device can be realized with a simple circuit configuration.

It is a block diagram which shows the circuit structure of the solenoid current control apparatus which concerns on embodiment of this invention. It is a timing chart for demonstrating operation | movement of embodiment shown in FIG. It is a circuit which shows the case where a synchronous rectification type is applied to a switch circuit with the circuit composition of the solenoid current control device concerning an embodiment of this invention. It is a block diagram which shows an example of the circuit structure of the conventional solenoid current control apparatus. It is a timing chart for demonstrating operation | movement of the conventional Example shown in FIG. It is a block diagram which shows another example of the circuit structure of the conventional solenoid current control apparatus.

Hereinafter, a solenoid current control device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a circuit configuration example of a solenoid current control device according to the present invention. The same parts as those in the conventional circuit example shown in FIG.
A MOS transistor M0 and a diode D0 are connected in series between a DC power supply Vbat for energizing the solenoid L0 and a GND power supply, thereby forming a switch circuit. The switch circuit functions so that the on / off operation of the switch circuit is controlled by the PWM signal output circuit 40, and the average value of the current flowing through the solenoid L0 becomes the specified current value _ID . A sense resistor R0 for current detection is inserted in the current path of the solenoid L0, and a voltage value proportional to the current value is generated at both ends of the resistor R0. The voltage across the sense resistor R0 is input to the V / F converter 10 and outputs a pulse signal having a frequency corresponding to the input voltage, that is, the current flowing through the solenoid L0. This pulse signal is input to the counter circuit 20 and counts the number of pulses in one period T of the PWM signal. The pulse count value Nc is input to the control circuit 30, and the control circuit 30 performs a comparison operation between the input value and the specified current value _ID to calculate a correction value (corrected duty ratio) of the duty ratio of the PWM signal. . This correction value is fed back to the switch circuit via the PWM signal output circuit 40 and controlled so that the average energization current value of the solenoid L0 matches the specified current value _ID . Further, the control circuit 30 outputs a reset signal Reset synchronized with the period T of the PWM signal to the counter circuit 20 to control the counting operation of the pulse signal.

FIG. 2 is a timing chart for explaining the operation of the embodiment shown in FIG. 2, (A) is the waveform of the PWM signal, (B) is the current waveform of the solenoid, (C) is the pulse signal output waveform of the V / F converter, (D) is an overview of the pulse counting operation of the counter circuit, (E) is a reset signal waveform of the counter circuit. With reference to FIG. 2, the current control method of the present invention will be described.
2 (A) and 2 (B) are the same as FIGS. 5 (A) and 5 (B) described in the prior art, and detailed description thereof is omitted.
In FIG. 2B, the current waveform of the solenoid is the same as the waveform of the voltage across the sense resistor R0. The voltage across the sense resistor R0 is input to the V / F converter 10, and the V / F converter 10 outputs a pulse signal having a frequency corresponding to the input voltage.

As shown in FIG. 2C, when the MOS transistor M0 is turned on at time t1, the input voltage of the V / F converter 10 rises from the minimum voltage V _L and the frequency of the output pulse signal gradually increases from the minimum frequency f _L. Become. On the other hand, when the MOS transistor M0 is turned off at time t2, the input voltage of the V / F converter 10 decreases from the maximum voltage V _H, and the frequency of the output pulse signal gradually decreases from the maximum frequency f _H. The output frequency characteristic of the V / F converter 10 is set so as to increase or decrease in proportion to the solenoid current, as shown by the following equation (6).
Variables and constants are set as follows.
Solenoid current: I [A], V / F converter output frequency: fout [Hz], counter circuit output: Nc, PWM signal cycle: T [sec], solenoid current maximum value: Imax [A], Number of bits of counter circuit: N [bit].

  As shown in FIGS. 2D and 2E, the counter circuit 20 counts the number of output pulse signals of the V / F converter 10 for each period of one cycle T of the PWM signal. The pulse counting operation of the counter circuit 20 is reset in synchronization with the period T of the PWM signal. The counter output Nc, which is the pulse count value of the counter circuit 20, is expressed by the following equation.

That is, the counter output Nc is a numerical value proportional to a value obtained by integrating the energization current I of the solenoid L0 over one period of the PWM signal. For example, when the solenoid current I is DC at Imax (maximum current), the counter output Nc becomes full as follows.

  As described above, the counter output Nc of the counter circuit 20 that counts the output pulse signal of the V / F converter 10 is a numerical value proportional to the value obtained by integrating the energization current I of the solenoid L0 for the T period of one cycle of the PWM signal. Become. As a result, the average current value Iave of the solenoid L0 can be calculated as shown in the following equation.

The control circuit 30 calculates the average current value Iave from the counter output value Nc according to the above equation (9), appropriately calculates the deviation between the specified current value _ID and the average current value Iave according to the PID rule, and outputs the result to the PWM The correction value of the signal duty ratio is fed back to the MOS transistor M0 via the PWM signal output circuit 40, and control is performed so that the average energization current value of the solenoid L0 matches the specified current value _ID .
As described above, according to the present invention, it is impossible to accurately detect the average current value of the solenoid, which has been a problem in the prior art, and a large-scale circuit configuration is required to increase the detection accuracy, or the average It is possible to realize a solenoid current detection device that solves the very complicated calculation method of the current value. That is, according to the present invention, by providing the V / F converter 10 and the counter circuit 20, the integral amount of the energization current of the solenoid L0 during one cycle of the PWM signal is converted into a pulse count value and detected. Accordingly, the present invention can detect an accurate average current value with a very simple circuit configuration, and can realize highly accurate feedback control.

Next, as an example of such a solenoid current control device, an embodiment in which a synchronous rectification method is applied to a switching element and its operation will be described.
FIG. 3 is a block diagram showing the configuration of the solenoid current control device of this embodiment.
A MOS transistor M0 and a MOS transistor M1 are connected in series between a DC power supply Vbat for energizing the solenoid L0 and a GND power supply, thereby forming a switch circuit. The switch circuit is controlled by the PWM signal output circuit 40, and the MOS transistors M0 and M1 are complementarily turned on and off (when one is on, the other is off), and the average current value of the solenoid L0 is the specified current. The energization of the solenoid L0 is controlled so as to be a value. The MOS transistor M1 of this embodiment is provided in place of the diode D0 in order to take measures against power loss due to the forward voltage drop of the diode D0 of the first embodiment. The MOS transistor M1 performs the same function as the diode D0 by turning on and off complementarily with the MOS transistor M0. Hereinafter, the detection and control method of the energization current of the solenoid L0 is the same as that of the first embodiment and will not be described.

  Further, in FIG. 1 to FIG. 3 shown as circuit configuration examples of the solenoid current control device according to the embodiment, the pulse counting operation is set to one period T period of the PWM signal, but a period that is an integral multiple of the PWM signal period T. May be set.

10 V / F converter (voltage frequency converter)
20 Counter circuit 30 Control circuit (CPU)
40 PWM signal output circuit (frequency modulation signal output circuit)
50 Amplifier (Op Amp)
60 A / D converter (analog / digital converter)
70, 80 RAM (storage device)
90 filter circuits D0 diode GND ground power supply terminal _{I, Iave, I D, I} L, the current value L0 solenoid M0 of I _H solenoid, M1 switching element (MOS transistor)
Nc Output signal of counter circuit Reset Reset signal of counter circuit R0 Resistance T PWM signal cycle Vbat DC power supply or its voltage

Claims (5)

A series circuit in which a solenoid, a DC power supply, a switch element, and a sense resistor for detecting a current flowing through the solenoid are connected in series;
A reflux element for securing a current path of the series circuit when the switch element is turned off;
A PWM signal output circuit that applies a PWM signal, which is a pulse signal of a constant period, to the switch element to control on / off of the switch element;
A V / F converter that outputs a pulse signal whose frequency changes in accordance with the voltage across the sense resistor;
A counter circuit for counting the number of output pulses of the V / F converter in a predetermined period;
A control circuit for controlling the duty ratio of the PWM signal so that an average current value of the solenoid matches a specified current value using a pulse count value of the counter circuit;
A solenoid current control device comprising:   The current control device according to claim 1, wherein the return element is a diode.   The solenoid current control device according to claim 1, wherein the return element is a switch element that performs synchronous rectification.   4. The solenoid current control device according to claim 1, wherein a pulse counting period of the counter circuit is set to one cycle of the PWM signal or an integral multiple thereof. A solenoid current control method for controlling the current flowing through the solenoid by turning on and off the switch element by a PWM signal that is a pulse signal having a constant period for the current flowing through the solenoid,
Converting the current value of the solenoid into a pulse signal having a frequency corresponding to the current value;
Counting the pulse signal in a predetermined period;
Controlling the duty ratio of the PWM signal so that an average current value of the solenoid matches a specified current value using the pulse count value;
A solenoid current control method comprising:

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