JPS5947616A - Controller of inductive load - Google Patents

Abstract

PURPOSE:To keep a relation between the driving signal duty which controls a switching element and the control state of an inductive load in a linear form, by controlling directly the inductive energy which is generated at the inductive load when the switching element is turned off. CONSTITUTION:A coil 11 serving as an inductive load is connected in series to a transistor TR13 serving as a switching element. A driving circuit 14 which controls the TR13 controls the time width of a driving signal by a command given from an arithmetic control part 17. At the same time, a control circuit 18 which processes the induction energy is connected to the joint between the coil 11 and the TR13. The circuit 18 is controlled by the part 17 in response to the time width of the driving signal. In such a way, the current flowing to the coil 11, i.e., the inductive load can be set constant in the induction energy. Thus a relation is ensured in a linear form between the driving signal duty and the control state of the inductive load.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention applies to coils that convert electrical signals into force, such as linear control solenoid valves that linearly control valve circuits, or fuel supply solenoid valves that control on and off positions. It is a control device for driving a device equipped with an inductive load, and is particularly suitable for controlling the load such as the former.
] Regarding the device. When converting an electrical signal into force, it is common practice to drive an inductive load such as a coil. For example, the coil, which is a load, is configured to be supplied with power through a switching element such as a transistor, and the switching element is configured to be turned on and off in response to a load drive command. However, when controlling such an inductive load on and off, inductive energy is generated especially when switching from an on state to an off state, and this inductive energy acts on switching elements etc. as a flyback voltage. .

FIG. 1 shows the basic configuration for controlling the excitation coil 1, which is an inductive load.
The drive is turned on and off by the previous #514. In such a circuit, transistor 1
With respect to point a, which is the base of
When a drive signal as shown in FIG.
The transistor 13 is turned off as the drive signal falls. However, when the transistor 13 is controlled to be off, a flyback voltage VF as shown in FIG. 2(B) is generated at a point 6b, which is the connection point between the coil 1 and the transistor 13.

Generally, this flyback voltage 2 is higher than the withstand voltage of the drive transistor 13, but if left as it is, there is a possibility that the transistor 137:)ZR may be damaged.

For this reason, conventionally, a Zener diode 15 is inserted between point b and the ground point, as shown in FIG. 3, so that the flyback voltage flows through the ground circuit. However, in the case of such a circuit, if a drive signal as shown in FIG. 4 (A) is supplied to point a, the potential at point b becomes K as shown in FIG. The cut energy E1 becomes a current flowing through coil 1, and iH+'5 due to coil IIVC! 5i<It becomes a factor that hinders the linearity of load control. However, the residual energy El in the part that is not cut becomes a factor that obstructs the current flowing through the coil 11, which is an inductive load. ni stylen
As a result, the current changes, and inductive load control corresponding to the command from the drive circuit 14 cannot be executed.

Also, drive time T is T. The cut size when enlarged is 1
E3. If the residual energy energy is E4, then rEa+E4J will be larger than E10B2J.As a result, the ratio of energies E3 and E4 will also fluctuate, causing an additional nonlinear factor to be added to the control using drive time T. .

Here, the induction energy is determined by "-!-L-1" n
It is a function of one driving time T. However, l is the current flowing through the inductive load and is a function of the drive time T, and L is the inductance of the inductive load.

In addition, as shown in Fig. 5, the flywheel diode 1
It is also possible to configure the flyback voltage to be returned to the power supply line 12 at 6. When configured in this way, the potential at point b for the drive signal shown in Figure 6 (A) becomes as shown in Figure 6 (l), and all of the induced energy E shown in the shaded area is generated by the power supply line. It will return to 12.

Therefore, all the current corresponding to this induced energy becomes the current flowing through the coil 11. That is, the current actually flowing through the coil 11 becomes larger than the drive current corresponding to the drive time T. As the drive time T increases, the induced energy E also increases, making linear control of the inductive load difficult.

That is, in the friend circuits shown in FIGS. 3 and 5,
In the case where the transistor IJve is controlled to turn on and off by a signal whose time width is controlled from the drive circuit 14, and the coil 1) which is an inductive load is controlled by nity, the following will occur.

First, if no induced energy flows through the coil 11, the relationship between the duty time and the control position r& is linear. However, in reality, as mentioned above, part of the inductive energy flows into the first coil, so the relationship between the duty time and the control position is nonlinear, and the accuracy cannot be determined by the electric signal of the inductive load. This makes it difficult to maintain control.

This invention takes into account the above points, and provides a relationship between the drive signal duty for controlling the switching element that opens and closes the drive current for the inductive load and the control state of the inductive load, for example, the control position by the tθ inductive load. It is an object of the present invention to provide a control device for an inductive load which ensures that the linearity of the inductive load is maintained linearly.

That is, in a control circuit according to the present invention, in a circuit including an inductive load and a switching element that controls a drive current flowing through the load, a control circuit that directly controls inductive energy is provided, and this control circuit controls the switching element. The configuration is such that control is performed by shifting the drive signal to the OFF state.

In the circuit shown in Fig. 3, point b has a voltage as shown in Fig. 4 (B) in response to the drive signal shown in Fig. 4, and ■8 is the Zener voltage, VB. is the drive #I power supply voltage. Then, the n4 energy El cut by the Zener voltage vx is transferred to the Zener diode 15
? A current flows through the coil II, and the induced energy E2 acts to prevent the current flowing through the coil II. Therefore, by directly controlling the ratio of the induced energies E1 and E2, it is possible to control the current flowing through the coil 11 when the drive signal is turned off.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 7 shows its configuration. The transistor 13 is grounded through an inductor 13, and a drive signal from a drive circuit 14 turns on the transistor 13, thereby causing a drive current to flow through the coil 11. Here, the drive circuit 14 controls the drive signal time width T based on a command from the arithmetic control section 17. Further, at the connection point between the coil 1 and the transistor 13, a control circuit 18 for processing the induction energy is provided.
is connected to the control circuit 18, which is connected to the arithmetic control section 1.
7, the control is performed in accordance with the drive signal time width T.

The control circuit 18 is configured as shown in FIG. 8, for example. That is, the connection point between the transistor 13 and the coil 11 is connected to a plurality of Zener diodes DZI, DZ2 .
.・
Each connection point of... is a transistor Tri
It should be grounded via pTry, . That is, transistors 'l' r 1 , T r 2
By selectively turning on the Zener diodes DZ1. DZ2.・
. . , the Zener voltage v2 at point b can be variably set.

And these switching transistors Tri,
Tr2. . . . are selectively controlled by a decoder 20 supplied with a signal corresponding to the drive time width T from the arithmetic control unit 17.

That is, the Zener voltage V2 shown in FIG. 4(B) changes in response to the drive signal width T, and the ratio relationship between the induced energies E1 and E2 changes in response to the time width T. Can change. Therefore, the calculation control section 17
If the Zener voltage V2 is controlled in accordance with the drive time T for the drive circuit 14, the coil 1 is
In other words, it becomes possible to keep the current flowing through the inductive load constant. As a result, the linearity of the control state such as the control position with respect to the drive signal duty is effectively maintained.

In the above example, the Zener voltage was changed, but
As shown in FIG. 9, the control circuit 18 can also be configured to control the current flowing through the Zener diode. That is, the wide connection point between the coil 1 and the transistor 13 is grounded through the Zener diode DZ, the control transistor Tr, and the resistor R in series, and the transistor Illr is controlled by the output of the operational amplifier OP. so that The operational n amplifier OP receives a signal VD obtained by converting a signal corresponding to the drive time T from the calculation control unit 17 into an analog voltage signal by the D/A converter 21 as an addition element, and a resistor R as a subtraction element. A terminal voltage signal v3 is supplied.

That is, in the operational amplifier OP, the Zener diode DZ
Compare the voltage 8 corresponding to the current flowing through the drive time T with the voltage VD corresponding to the drive time T, and control the transistor Tr so that V5 matches VD to control the current flowing through the Zener diode DZ. do. However, even if the drive time T changes, the current flowing through the coil 1 in the inductive energy is controlled to remain constant, and linearity of control of the inductive load, that is, the coil 11, is achieved. It is something that will make you feel better.

The operation of the control circuit 1H shown in the ninth factor will be further explained. Now, assuming that the drive signal from the drive circuit 14 supplied to the transistor 130 is in the state shown in FIG. 10(A), this drive signal is turned off.
Ru. The arithmetic control unit 17 recognizes the drive time T at M points before the first point. Therefore, at this point, the 11th
The analog voltage VD75K corresponding to the drive time T shown in the figure
An operational amplifier 0FIC obtained from the D/A converter 21 is added. In this case, as shown in FIG. 11, the longer the drive time T, the more the induced energy increases, so the VD corresponding to T is set small and the drive signal is turned off. After that, the transistor Tr is controlled to reduce the inductive energy flowing into the coil 1 which is an inductive load, thereby compensating for linearity. FIG. 10(B) shows the voltage waveform at the connection point between the coil 1 and the transistor 13.

The control circuit 18 shown in FIG. 12 is connected between the D/A converter 2 and the operational amplifier OP of the control circuit shown in FIG.
An analog switch 22fA' is inserted, and the command from the 7-channel switch 2zr-s', rRif2 control unit 17 controls the conduction state at one point in Figure 1O, that is, when the drive signal is turned off. , the cut-off control is performed at the rising edge of the drive signal. Therefore, in this way, it becomes possible to reduce the control error caused by the stray capacitance between the base and collector of the transistor Tr.

As described above, according to the present invention, the fly/? that occurs when the driving current to the &I inductive load is cut off. Directly controls the induced energy by the load voltage, and even when the induced energy increases in accordance with the driving time, it flows into the inductive load6.
It is possible to specify the conductive energy,
It is possible to effectively set the operating characteristics for the drive r needy with linearity, and the g' load control can be executed with high precision.

[Brief explanation of drawings]

Figures 1-, 3, and 5 are diagrams showing conventional inductive load control circuits, and Figures 2, 4L, and 6 are diagrams showing conventional inductive load control circuits, respectively.
A waveform diagram illustrating the operation of the upper circuit, FIG. 7 is a configuration diagram illustrating a control device according to an embodiment of the present invention, and FIG. 8 is a circuit diagram showing the control circuit section of the above embodiment σ). - FIG. 9 is a block diagram 410 illustrating another embodiment of the present invention.
Figure 1 is a waveform diagram explaining this embodiment, Figure 1 is a diagram showing the relationship between driving time and control magnetic pressure VD, and Figure 1 is a diagram showing the relationship between driving time and control magnetic pressure VD.
FIG. 2 is a block diagram showing an embodiment of the pond according to the present invention. 11...Coil (inductive load), 12...R source line, 13...Transistor (switching element), I
4... Drive circuit, 17... Arithmetic control unit, 18...
control circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] A switching element connected in series with an inductive load, a drive circuit for controlling the switching element 4, and a mechanism for measuring the inductive energy generated in the inductive load at the end of the driving state. a circuit, the arithmetic and control unit sets the time width of the drive signal from the drive circuit, controls the control circuit in accordance with this time width, and specifies the inductive energy flowing into the inductive load. An inductive load control device characterized by: