JPH11141721A - Solenoid valve driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely operate a solenoid valve with a high efficiency when battery voltage is reduced, in the case where it is controlled to apply high voltage outputted form a booster circuit on the solenoid valve using a N-type semiconductor switching element. SOLUTION: In a solenoid valve driving device which is provided with a N-channel FET 22A for on/off-controlling to apply a high voltage output HV outputted from a booster circuit 11 on a high side of a coil for the solenoid valve, and which is arranged to operate the solenoid valve with high speed by applying the high voltage output HV on the coil through the N-channel FET 22A in a driving initial step of the solenoid valve; a high side driving circuit 21 is arranged so as to drive the N-channel FET 22A, a capacitor 211 for supplying voltage used to drive the N-channel FET 22A is arranged in the high side driving circuit 21, and the capacitor 211 is charged by at least one of battery voltage VB and reverse electromotive voltage VR generated on a low side end of the coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a high voltage from a booster circuit to a solenoid valve coil through a high-side switch in an initial stage of driving the solenoid valve, thereby supplying a large current to the solenoid valve coil. The present invention relates to an electromagnetic valve driving device that operates an electromagnetic valve at high speed.

[0002]

2. Description of the Related Art For example, when controlling the operation of a solenoid valve used as a fuel injection control valve in a vehicle fuel injection system, the solenoid valve can be operated at high speed, and seizure of the solenoid coil of the solenoid valve is prevented. Japanese Patent Laid-Open No. 6-2658 discloses a solenoid valve driving device capable of
The configuration disclosed in Japanese Patent Application Laid-Open No. 9-99 is known. The solenoid valve driving device disclosed herein generates a voltage higher than a battery voltage by a step-up chopper circuit, stores the voltage in a capacitor, and stores the high voltage stored in the capacitor in a solenoid of the solenoid valve in an early stage of driving the solenoid valve. It is configured to apply a voltage to the coil to operate the solenoid valve at high speed. The solenoid valve operation holding current after high-speed operation is passed from the battery to the solenoid coil via the current limiting resistor.

When driving this type of solenoid valve as described above, it is desirable to control the energization of the solenoid valve by a high-side switch. This is the case where the wiring for driving the solenoid valve is short-circuited to the body when the solenoid valve is used for the fuel injection control system of the internal combustion engine vehicle because the body of the automobile or the like is connected to the negative terminal of the battery. However, if the solenoid valve is configured to be driven and controlled by the high-side switch, the solenoid valve is not turned on and is safe.

In the case of employing a configuration in which the solenoid valve is driven and controlled by a high-side switch, a switch element provided on the high side is replaced by a PNP transistor or a P-channel field-effect transistor (Si) because the configuration of the control circuit is simplified. FET). However, these have a problem that the breakdown voltage is lower than the NPN transistor and the N-channel FET, and if a high breakdown voltage transistor is used, the cost increases. As seen in the electromagnetic valve driving device described in the publication, a circuit using an NPN transistor as a high-side switch is widely used. In this conventional circuit, as shown in FIG. 3B of the publication, an NPN transistor for controlling a drive current to an electromagnetic valve is driven by a PNP transistor.

[0005]

However, according to the above circuit configuration, the collector-emitter voltage VCE of the NPN transistor is equal to the collector-emitter voltage VCE of the PNP transistor and the base-emitter voltage VBE of the NPN transistor. Since it is a sum, it becomes about 2.3V. Here, if the current of the solenoid valve is, for example, 2 A, the power consumption of the NPN transistor is 4.6 W, and this value is wastefully consumed, which is not only unfavorable for the battery but also preferable in terms of wasteful heat generation. is not.

Further, the minimum operating voltage of the solenoid valve also increases by 2.3 V, which is not preferable from the viewpoint of effective use of the battery voltage. That is, since the voltage applied to the solenoid valve becomes lower than the battery voltage by about 2.3 V, when the battery voltage drops for some reason, the operation of the booster circuit becomes insufficient and the solenoid valve may not operate. Because there is.

As described above, an NPN transistor or an N-channel FET serving as a high-side switch is
According to the conventional circuit configuration driven by a transistor, not only is power consumption wasted, but it is not preferable in terms of heat generation, and the minimum operating voltage of the solenoid valve is increased. When the voltage decreases, various problems occur such that the solenoid valve may not operate.

An object of the present invention is to control the application of a high voltage from a booster circuit to a solenoid valve by using an NPN transistor or an N-channel FET provided on the high side of the solenoid valve to switch a high side switch. The above-mentioned problem in the case of configuring can be solved,
An object of the present invention is to provide a solenoid valve driving device.

[0009]

A feature of the present invention for solving the above-mentioned problems is that a booster circuit for boosting a battery voltage and an N-channel FET or an NPN transistor are used as switching elements, A high-side switch unit for controlling on / off of applying a high voltage to the high side of the coil of the solenoid valve, and in the initial stage of driving the solenoid valve, the high voltage is applied via the high-side switch unit. Is applied to the coil of the solenoid valve to operate the solenoid valve at a high speed, comprising a drive circuit for driving the high-side switch unit, wherein the drive circuit includes the switching element A capacitor for supplying a voltage used to drive the battery, the capacitor being connected to the battery voltage and the coil. In that is adapted to be charged by at least one of the counter-electromotive voltage generated in the low-side end.

According to this configuration, when the capacitor is charged by the battery voltage, the charged voltage is used for driving the switching element on and off.
The capacitor is also charged by a back electromotive voltage which is sufficiently higher than the battery voltage generated at the low side end of the coil when current is cut off to the solenoid valve. Therefore, the battery voltage drops for some reason and the capacitor cannot be charged with a sufficient level of voltage.
Even if a situation occurs in which the high-side switch cannot be driven as it is, the capacitor is separately charged by the back electromotive voltage, and the high-side switch is reliably turned on.
It can be driven off.

The capacitor can be charged by using a high voltage generated in the booster circuit in addition to the battery voltage and the back electromotive voltage. In this case, in order to prevent the terminal voltage of the capacitor from excessively rising, a configuration may be adopted in which a resistor having an appropriate value is inserted in the charging path, or a configuration in which a constant voltage diode is connected in parallel with the capacitor. Good.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the solenoid valve driving device of the present invention. The electromagnetic valve driving device 1 shown in FIG. 1 drives an electromagnetic valve for fuel injection control of a vehicle fuel injection system (not shown), and includes a power supply unit 10 and a high-side energization control unit 2.
0, low-side conduction control unit 30, drive current detection unit 40,
A timing control unit 50 is provided.

The power supply unit 10 includes a booster circuit 11 that boosts a battery voltage VB of a battery 12 of, for example, 12V connected to the terminal 10A to, for example, 160V and outputs a high voltage output HV.

The booster circuit 11, as shown in FIG.
It has a known configuration in which high-voltage energy accumulated from the battery 12 in the boosting coil 11B with the on / off operation of the boosting switching FET element 11A is accumulated in the boosting capacitor 11D through the diode 11C.

Referring back to FIG. 1, the high-side power supply control unit 20
Includes a high-side drive circuit 21 and a high-side drive circuit 2
A high-side switch unit 22 for turning on / off the application of the high-voltage output HV to the coil 2 of the solenoid valve in response to
A hold drive drive circuit 23 and a hold drive switch unit 24 for turning on / off applying the battery voltage VB to the coil 2 in response to the hold drive drive circuit 23 are provided.

The high-side drive circuit 21 controls the on / off operation of the high-side switch 22 composed of an N-channel FET in response to a timing signal PEAK from the high-side timing generator 51 of the timing controller 50. Is what you do. Here, the high-side switch section 22 is formed of an N-channel FET having an excellent high withstand voltage characteristic, and a high-side drive circuit 21 is provided to drive the N-channel FET constituting the high-side switch section 22 on and off. Is provided. The high-side drive circuit 21, as will be described later in detail with reference to FIG.
A capacitor for supplying a voltage used to drive the N-channel FET on and off;
This capacitor is charged by at least one of the battery voltage VB and the back electromotive voltage generated at the low side end of the coil 2, so that the high side switch unit 22 can be driven reliably.

The hold drive driving circuit 23 applies a high-voltage output HV to the coil 2 by the high side switch unit 22 to drive the coil 2 at a high speed, and after a large current is passed through the coil 2 for a predetermined period, 2 to supply a required current smaller than the large current for maintaining the operation of the solenoid valve, after the high-side switch 22 is turned off, the hold is performed only for a required period during which the solenoid valve needs to be held and driven. This is a circuit for turning on the drive switch unit 24 and applying the battery voltage VB to the coil 2. The hold drive drive circuit 23 turns on a P-channel FET 24A, which is a switching element of the hold drive switch 24, in response to a timing signal HOLD output from the hold drive timing generator 52 of the timing controller 50 as described later. To control off.

Diodes 3 and 4 are connected between the drain of the P-channel FET 24A and the ground as shown. The diode 4 is a flywheel diode, and when the P-channel FET 24A is turned off as described later, a flywheel current can be supplied to the coil 2 immediately thereafter by the back electromotive voltage generated in the coil 2. This is a known circuit configuration.

Here, the hold drive switch section 24
Uses a P-channel FET to ensure operation even when the battery voltage VB is low.
An N-channel type FET element can also be used.

The low-side energization control section 30 includes a low-side drive circuit 31, a low-side switch section 32, and a back electromotive voltage detection section 33. The low-side drive circuit 31 responds to the fact that the level of the timing signal LOW from the low-side timing generation section 53 of the timing control section 50 has changed to the high level state. (Not shown) is turned on. The drive current detector 40 is provided to detect the level of the solenoid valve drive current IV flowing through the coil 2.

The back electromotive voltage generated in the coil 2 when the current flowing through the coil 2 is suddenly cut off is detected by the back electromotive voltage detection unit 33, and the value of the back electromotive voltage is set to a predetermined value (for example, 60 V) or more. The low-side switch unit 32
Is turned on, thereby preventing the value of the back electromotive voltage from rising above a predetermined value.

The timing controller 50 comprises a high side timing generator 51, a hold drive timing generator 52, and a low side timing generator 53. Each of the timing generators 51, 52, and 53 is provided with a high-side drive circuit 21, a hold drive drive circuit 23, and a low-side drive circuit 31 based on a solenoid valve drive signal DRV input from outside to indicate the valve opening period of the solenoid valve. , A timing signal PEAK, a timing signal HOLD, and a timing signal LOW.

Here, the timing signal PEAK is a signal for defining a peak period (see FIG. 4) for supplying a large current for high-speed driving to the coil 2. The timing signal HOLD is supplied with a relatively small current sufficient to maintain the operating state of the solenoid valve after the solenoid valve is quickly opened by supplying a large current to the coil 2 as described above.
Is a signal for controlling the supply to The timing signal LOW is a signal for performing control for stopping supply of the drive current to the coil 2. Each timing signal PEA in response to the solenoid valve drive signal DRV
Since a circuit configuration for generating K, HOLD, and LOW is known per se, a detailed description of the circuit configuration of the timing control unit 50 will be omitted here.

Next, a more specific configuration of the high side drive circuit 21 and the high side switch section 22 will be described with reference to FIG.

As described above, the high-side drive circuit 21 is an N-channel FE that functions as a switching element.
T22A, whose drain has a high voltage output HV
And its source is connected to the high side end of the coil 2. The high-side drive circuit 21 is provided at the gate of the N-channel FET 22A.

The high-side drive circuit 21 is a circuit for controlling ON / OFF of the N-channel FET 22A in response to the timing signal PEAK.
It has a capacitor 211 for storing a voltage for driving T22A. One end of the capacitor 211 is connected to the high side end of the coil 2 via a common line 212, and the other end of the capacitor 211 is commonly connected to each cathode of the diodes 214 and 215 via a resistor 213. The anode of the diode 214 is connected to the terminal 10A to which the battery voltage VB is supplied via the terminal 21A, and the anode of the diode 215 is connected to the low side terminal of the coil 2 via the terminal 21B (FIG. 1).
reference). The constant voltage diode 216 connected in parallel with the capacitor 211 is for preventing an excessive charging voltage from being applied to both ends of the capacitor 211. For example, a diode having a Zener voltage of about 180 V is used. .

217 is a PNP transistor, 218 to
Reference numeral 220 denotes resistors, which are connected as shown in FIG. The timing signal PEAK is connected to the base of the PNP transistor 217 via a resistor 219.
Is applied.

Since the high-side drive circuit 21 is configured as described above, the capacitor 211 is charged via the diode 214 and the resistor 213 by the battery voltage VB applied to the terminal 21A. Through this path, the level of the voltage charged in the capacitor 211 is up to the battery voltage VB.

Further, a back electromotive voltage (approximately 60 V) generated in the coil 2 is taken into the terminal 21B from its low side, and the capacitor 211 is charged by the back electromotive voltage via the diode 215 and the resistor 213. . For this reason, for example, even when the battery voltage VB drops (it may drop to at least about 6 V) and the level of the charging voltage of the capacitor 211 at that time is insufficient to turn on the N-channel FET 22A, V
By charging with a back electromotive voltage sufficiently higher than B, the capacitor 211 can be charged to a level sufficient to turn on the N-channel FET 22A. As a result, even when the battery voltage has dropped, the N-channel FET 22A can be reliably operated.

The constant voltage diode 216 limits the charging voltage of the capacitor 211 so that the gate-source voltage of the N-channel FET 22A of the high-side switch section 22 does not exceed its absolute maximum rating.

Then, the timing signal PEAK is output from the high side timing generator 51 of the timing controller 50.
Is applied to the base of the transistor 217 via the resistor 219, the transistor 217 is turned on, and the charging voltage of the capacitor 211 is applied to the gate of the N-channel FET 22A. Regardless, it is surely turned on.

According to the circuit configuration in which the high-side drive circuit 21 is configured as described above to control ON / OFF of the N-channel FET, when the gate-source voltage Vgs of the N-channel FET 22A is about 5 V, the ON resistance Is 0.1 Ω due to the operating characteristics of the N-channel FET 22A, and the loss is reduced. At this time, with a potential difference of about 5 V, N
When the channel FET 22A is driven, the on-resistance is about 0.1Ω, so that the loss is about 0.4W even at a current of 2A. In the case of an NPN type switching transistor, the voltage Vbe between the collector and the emitter is set by setting the voltage Vbe between the base and the emitter to about 2 V.
ce becomes about 0.3 V, and the loss decreases.

Therefore, according to the configuration shown in FIG.
Since an N-channel FET or an NPN-type transistor is used for the high-side switch section 22, the power loss is small in any case, which is advantageous in terms of heat generation due to the flowing current, and the battery voltage VB and / or the back electromotive voltage generated in the coil 2. And the high-side switch unit 22 is driven by using the charging voltage, so that the N-channel FET or the NPN transistor can be reliably turned on and off regardless of the decrease in the battery voltage VB.

Next, the operation of the solenoid valve driving device 1 configured as described above will be described. First, as shown in FIG. 4, when the solenoid valve drive signal DRV falls at the timing of t = t1, the high-side drive section 51 and the low-side timing generator 53 shown in FIG. The respective levels of the timing signal PEAK and the timing signal LOW applied to the circuit 21 and the low-side drive circuit 31 rise ((B) in FIG.
(D)).

That is, the levels of the timing signal PEAK and the timing signal LOW rise in synchronization with the fall of the level of the solenoid valve drive signal DRV (the solenoid valve is turned on). As a result, at t = t1, the timing signal P
In response to the EAK, the high-side drive circuit 21 turns on the high-side switch unit 22, and in response to the timing signal LOW, the low-side drive circuit 31 turns on the low-side switch unit 32. Voltage VA applied to both ends of coil 2 by high voltage output HV from booster circuit 11
As shown in FIG. 4 (F), the voltage waveform becomes a voltage waveform that rapidly increases and then gradually decreases until the timing signal PEAK is turned off. This is because the voltage from the booster circuit 11 at t = t1 (about 160 V in this example)
Is applied to the coil 2, a large current flows through the coil 2, and electric energy is released from the booster circuit 11, so that the level of the high-voltage output HV from the booster circuit 11 decreases over time. . The solenoid valve drive current IV flowing through the coil 2 once increases, as shown in FIG. 3E, and then reaches the timing signal PEA at t = t2.
When the timing signal LOW falls in accordance with the fall of K, the current waveform sharply falls and becomes a current waveform smaller than the second threshold value Lb.

At this time, due to the eddy current generated in the solenoid valve in accordance with the fall of the timing signal LOW, the solenoid valve drive current IV becomes the second threshold value L as shown by the dotted line a.
Try to rise after dropping below b. However, coil 2
The magnitude of the back electromotive force is detected by the back electromotive voltage detection unit 33, and when the magnitude of the back electromotive force generated in the solenoid valve coil 2 exceeds a predetermined value, the low side switch unit 32 is turned off, Solenoid valve drive current I flowing through coil 2
V is cut off. Immediately after t2, the low-side switch unit 32 of FIG. 1 repeats the on / off operation at the second threshold Lb as a boundary, thereby suppressing an increase in the solenoid valve driving current IV due to the back electromotive force of the coil 2, The drive current of the coil 2 is maintained at a substantially constant value. This constant value is smaller than the high current to the coil 2 provided for quickly operating the solenoid valve from t1 to t2. FIG. 4D shows a waveform of the timing signal LOW.

At this time, the back electromotive voltage VR ((G) in FIG. 4) generated in the coil 2 corresponds to the high-side drive circuit 2 in FIG.
1 and is charged in the capacitor 211 shown in FIG. As a result, the battery voltage VB decreases for some reason, the charging voltage of the capacitor 211 by the battery voltage VB is low, and the voltage drop in the transistor 217 is insufficient to turn on the N-channel FET 22A of the high-side switch unit 22. Even
The charging by the back electromotive force generated in the coil 2 increases the charging voltage of the capacitor 211 to a level sufficient to drive the high-side drive circuit 21 and the high-side switch unit 22, so that the N-channel FET 22A operates normally. This can be performed as described above.

Next, the operation of charging the capacitor 211 will be described in detail with reference to FIG. At the timing T1, the capacitor 211 is charged to the battery voltage VB (12 V in this example), and the transistor 217 is turned on by the input of the timing signal PEAK.
When the high-side switch unit 22 is turned on, the level of the solenoid valve drive current IV sharply increases as shown in FIG.

Since the electric charge stored in the capacitor 211 is discharged for the ON operation of the high-side switch section 22, the capacitor 211 is turned off as shown in FIG.
The charging voltage level gradually decreases. However, when the large current driving of the coil 2 of the solenoid valve ends at the timing T2, the back electromotive voltage VR1 is generated at the low side end of the coil 2, and the capacitor 211 is charged. As a result, the charging voltage level of the capacitor 211 returns to a value larger than 12V. Further, another counter electromotive voltage V generated when the driving of the solenoid valve ends at timing T3.
The capacitor 211 is charged again by R2, and the charged voltage of the capacitor 211 further increases.

As can be seen from the above description, the capacitor 2
11 is charged using not only the battery voltage VB but also the back electromotive voltage generated by the driving of the coil 2, so that the high-side switch unit 2 is charged by a decrease in the battery voltage VB.
Thus, the high-side switch unit 22 can be reliably driven without making the on / off control of the second unit impossible.

Since the charging by the back electromotive voltage regenerates the energy given to the solenoid valve, the energy that would otherwise have been consumed as heat of the flywheel element is effectively used. Another advantage is that the heat load is reduced.

Further, since an N-channel FET or an NPN transistor is used as an element of the high-side switch section 22, less power loss and less heat are generated as compared with the use of a P-type element. Further, the voltage drop in the high-side switch section 22 can be reduced, and the minimum operating voltage of the solenoid valve can be reduced.

Returning to FIG. 4, the back electromotive force generated in the coil 2 decreases with the lapse of time, and the solenoid valve driving current IV falls below the first threshold value La as shown in FIG. When,
The ON / OFF timing signal HOLD keeps the solenoid valve drive current IV substantially at the level of the first threshold value La. This is because the value of the solenoid valve drive current IV detected by the drive current detection unit 40 at that time is input to the hold drive timing generation unit 52, and the solenoid valve drive current I
This is realized by setting the level of the timing signal HOLD to “H” when V becomes smaller than the first threshold value La.

As described above, at the timing t = t5 when the drive period of the solenoid valve ends, the solenoid valve drive signal D
The level of RV rises (the solenoid valve is turned off), and the level of the timing signal LOW falls. As a result, coil 2
The current supply to the solenoid valve is cut off, and the solenoid valve drive current IV rapidly decreases to zero. In this case, as shown in FIG. 4G, at t = t5 when the solenoid valve is driven, a counter electromotive force is generated in the coil 2. However, the high-side switch unit 22 and the low-side switch Both parts 32 are off, and the capacitor 211 of the high-side drive circuit 21 is charged by the back electromotive force.

In this embodiment, the case where a field effect transistor (FET) is used as the N-type switching element has been described. However, the present invention is not limited to this example, and other N-type semiconductor switching elements such as NPN transistors may be used. Can also.

Further, in this embodiment, the back electromotive voltage of the coil 2 is
Although the description has been given of the case where the voltage is used as the charging voltage, the high voltage output of the booster circuit 11 or the like may be used as the charging voltage of the capacitor 211. In this case, it is desirable to charge the capacitor 211 via a resistor so as to suppress the charging voltage of the capacitor 211 from excessively increasing.

[0047]

According to the present invention, there is provided a high-side switching device for controlling the on / off of a high voltage applied to a coil on the high side of a coil of an electromagnetic valve by using an N-channel FET or an NPN transistor as a switching element. Since the voltage stored in the capacitor using the battery voltage or the back electromotive voltage of the coil is used as the voltage for turning on and off the elements, for example, even if the battery voltage drops, the high side voltage is applied. The operation of the switching element is reliably performed, and the solenoid valve can be reliably operated.

In addition, since the energy is regenerated by charging a part of the energy given to the solenoid valve to the capacitor, the energy which has been conventionally released as heat energy can be effectively used, and the heat load can be reduced. Help.

As described above, the N-channel FET or the NP
Since the high-side switching operation is favorably performed using the N-transistor, the loss in the high-side switching element is small, and the problem of heat generation can be solved.

The use of the N-channel FET has the advantage that the voltage drop in high-side switching can be reduced and the minimum operating voltage of the solenoid valve can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a solenoid valve driving device according to the present invention.

FIG. 2 is a circuit diagram illustrating details of a booster circuit in FIG. 1;

FIG. 3 is a circuit diagram showing details of a high-side drive circuit and a high-side switch unit of FIG. 1;

FIG. 4 is a waveform chart for explaining the operation of the solenoid valve driving device of FIG. 1;

FIG. 5 is a waveform chart for explaining the operation of the high-side drive circuit of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 solenoid valve driving device 2 coil 10 power supply unit 11 step-up circuit 12 battery 20 high-side conduction control unit 21 high-side drive circuit 22 high-side switch unit 22A N-channel FET 50 timing control unit 211 capacitor 213 resistor 214, 215 diode 217 PNP Type transistor DRV Solenoid valve drive signal HV High voltage output IV Solenoid valve drive current PEAK Timing signal VB Battery voltage VR, VR1, VR2 Back electromotive force

Claims (3)

[Claims] A booster circuit for boosting a battery voltage;
A channel FET or an NPN transistor is used as a switching element, and a high-side switch unit for on / off control of applying a high voltage from the booster circuit to a high side of a coil of the solenoid valve; and An electromagnetic valve driving device in which the high voltage is applied to the coil of the electromagnetic valve through the high-side switch unit at an initial stage of driving the electromagnetic valve to operate the electromagnetic valve at high speed, wherein the high-side switch unit is A drive circuit for driving, the drive circuit being provided with a capacitor for supplying a voltage used to drive the switching element, the capacitor being connected to the battery voltage and a low side end of the coil. Characterized by being charged by at least one of a back electromotive voltage generated in Drive. 2. The switching device according to claim 1, wherein the switching element is an N-channel F.
The electromagnetic valve driving device according to claim 1, which is an ET. 3. The solenoid valve driving device according to claim 1, wherein the capacitor is charged also by a high voltage generated in the booster circuit.