JP5148614B2 - Automotive power signal input circuit - Google Patents

Description

  The present invention relates to an in-vehicle power supply signal input circuit suitable for use in, for example, a discharge lamp lighting device, an electric power steering control device, or the like that requires relatively large power to drive a load.

  FIG. 7 is a block diagram showing a configuration of a conventional in-vehicle power supply signal input circuit used in a discharge lamp lighting device mounted on a vehicle. As shown in FIG. 7, a conventional vehicle power signal input circuit used for a discharge lamp lighting device having a self-diagnosis function lights a discharge lamp (hereinafter referred to as a HID (High Intensity Discharge) bulb 71) as a load. Power supply path L including a lighting switch 72 that supplies a large amount of power to the power supply, and a power supply path IG connected to the ignition switch 73 so that the self-diagnosis function operates even when the HID bulb 71 is not lit. And a control circuit CTL (a broken line portion in FIG. 7) to which current is supplied from both sides.

  Thus, one power source (supplied to the HID valve 71) is supplied from the power supply path L including the lighting switch 72, and the other power source (supplied to the control unit 75) is supplied to the power source including the ignition switch 73. The circuit configuration is such that both are connected with a logical sum (OR) of the diodes D1 and D2 so as to be supplied from the path IG. In addition, in the power supply path L including the lighting switch 72 described above, it is essential to connect a large-capacitance capacitor C for filtering to alleviate ripples generated in the circuit in the path.

  For this reason, in the discharge lighting device having the self-diagnosis function, even if the lighting switch 72 is turned off when the HID bulb 71 is turned off due to fail-safe due to an abnormal situation of the HID bulb 71, the power supply path L including the lighting switch 72 is included. If the voltage of the power supply path IG including the ignition switch 73 is higher than the charging voltage of the large-capacitance capacitor C disposed in the filter, all the power to the control unit 75 is supplied from the power supply path IG including the ignition switch 73. . For this reason, the discharge of charge from the large-capacitance capacitor C for filtering is reduced, and the voltage drop is delayed. Therefore, in a discharge lamp lighting device having a self-diagnosis function, it takes a relatively long time to determine that the lighting switch 72 is OFF when the voltage reaches a predetermined level (threshold voltage) or less. .

In addition, although said description illustrated the discharge lamp lighting device, it is not restricted to a discharge lamp lighting device, The electric power which uses two power supplies isolate | separated by each switch, and puts a big load on one power supply. The same applies to control devices such as a steering control device and an engine control device.
FIG. 8 shows a configuration of a conventional in-vehicle power supply signal input circuit used in the electric power steering control device. In the control device, switching of the power supply path L through which a large current is passed is performed via a relay contact 82. Therefore, as in the above-described discharge lamp lighting device, the power supply path L through which a large load current flows includes the filter large-capacitance capacitor C for reducing ripple, and the capacity is inevitably increased. In this case as well, the situation where it is difficult to detect and determine OFF of the power supply path L with a voltage in a short time is the same. In FIG. 8, M81 is a motor for electric steering control which is a load.

A number of patent applications have been filed for the on-vehicle power supply signal input circuit used in the above-described electric power steering control device. For example, abnormal output of the steering wheel torque sensor is prohibited when the power supply voltage drops. An electric power steering control device is known (see, for example, Patent Document 1). In this case, one power supply is input from the output side L of the power supply relay (relay contact 82), the other power supply is input from the power supply path IG connected to the ignition switch 73, and both are OR-connected to the diodes D1 and D2. Thus, the power is led to the power supply unit 80 in the control circuit CTL.
There is also known an electric power steering control device that uses a step-up power supply for driving a motor as a backup power supply for a control circuit CTL (see, for example, Patent Document 2). In this case, one power source (supplied to M81) is input from the power source boosted by the DC / DC converter 86 via the relay contact 82, and the other power source (supplied to the control unit 74) is input to the ignition switch 73. Input from the connected power supply path IG is led to the power supply unit 80 in the control circuit CTL by OR connection of the diodes D1 and D2.

JP 2001-122143 A JP 2004-276841 A

According to the techniques disclosed in Patent Document 1 and Patent Document 2 described above, when the relay contact 82 is turned OFF in a state where M81 is not driven, the presence of the large-capacitance capacitor C for the filter connected to the power supply path L As a result, the voltage drop rate of the power supply path L is reduced. Therefore, when detecting the OFF of the relay contact 82, the voltage on the relay contact 82 side included in the power supply path L reaches a predetermined voltage or less, so that it is difficult to make an immediate determination to determine that the relay contact 82 is OFF.
For this reason, a diode for preventing the reverse flow of the charge of the large-capacitance capacitor C is inserted in series in the power supply path L including the relay contact 82 described above or in the power supply path L including the lighting switch 72 in the discharge lamp lighting device. Can be considered.

According to the above configuration, the voltage changes in response to the operation of the lighting switch 72 or the relay contact 82 without being affected by the electric charge of the filter large-capacitance capacitor C, and the lighting switch 72 and the relay contact 82 depend on the input voltage. It is possible to determine OFF.
However, according to the discharge lamp lighting device or the electric power steering control device having the diode or the like in the power supply path L for preventing the reverse flow of the charge of the large capacity capacitor C for the filter, the power supply path including the lighting switch 72 or the relay contact 82 is a load. The loss due to the voltage drop of the diode is large because the power supplied to the device is a large path, so the adoption of the diode is not practical. In addition, a FET (field effect transistor) with a small ON resistance is used as an alternative to the diode, and the FET is turned on when supplying current, and the FET is turned off as necessary to detect the voltage on the power supply path L side. However, in an electric power steering control device or the like that requires a larger power supply current, it is not practical to use an FET because the loss is large even if it is replaced with an FET. For this reason, in-vehicle power supply signal input circuits are often designed without using diodes or FETs, and thus the above-described problems are potentially present.

  In particular, as shown in FIG. 7, a power supply path L including a lighting switch 72 that does not have a circuit such as a diode for preventing a reverse flow of charge of a large capacity capacitor C for a filter, and a power supply path including an ignition switch 73. In the discharge lamp lighting device provided with the control unit 75 to which current is supplied from both the IG and the HID 71 is turned off by fail-safe due to an abnormal situation of the HID bulb 71, the control is performed even if the lighting switch 72 is turned off. Since the current of the unit 75 is supplied from the power supply path IG including the ignition switch 73, there is no path for discharging the charge of the power supply path L including the lighting switch 72 having the large-capacitance capacitor C for filtering. When capacitor is turned off, the voltage drop of capacitor C is slower Ri, immediately detects the OFF state of the lighting switch 72 by measuring the voltage of the power supply path L including lighting switch 72, it is difficult to determine.

  Not only the discharge lamp lighting device but also two power sources separated by respective switches are used, and one power source is subjected to a large load. For example, an electric power steering control device and an engine control device shown in FIG. This also applies to control devices such as this, and in this case as well, a configuration having a power supply path in which a series diode is not inserted is present. The same.

  The present invention has been made to solve the above-described problems, and includes a power switch (lighting switch 72 and relay contact 82) included in a power supply path for supplying power to a load and a large-capacitance capacitor C for filtering. For automotive use, which can quickly determine the OFF state of the power switch without interposing a backflow prevention element such as a diode in between, and can quickly escape from the extinguishing state of the discharge lamp due to a fail-safe due to a transient abnormal situation, for example It is an object to provide a power signal input circuit.

In order to solve the above-described problems, an in-vehicle power supply signal input circuit according to the present invention includes a first power supply path including a first switch that mainly supplies power to a load, and a first power supply that mainly supplies control power. The second power supply path including two switches, the first power supply path and the second power supply path as power supply sources, and the time constant at the time of no load for relaxing ripples in the first power supply path is 0. A capacitor having a filter of 1 second or longer, and acquiring a voltage of the capacitor as a voltage applied to the first power supply path and a voltage applied to the second power supply path, and applying the voltage to the first power supply path When the voltage drops and the voltage applied to the second power supply path is held, the controller has a control unit that detects the cutoff of the first switch.

In order to solve the above-described problems, an in-vehicle power supply signal input circuit according to the present invention includes a first power supply path including a first switch that mainly supplies power to a load, and a first power supply that mainly supplies control power. A second power path including two switches, the first power path and the second power path as a power supply source, the first power path including a filter with a large-capacitance capacitor for relaxing ripples, Obtaining the voltage of the capacitor as the voltage applied to the first power supply path and the voltage applied to the second power supply path, the voltage applied to the first power supply path decreases, and the second power supply When the voltage applied to the path is held, a control unit that detects interruption of the first switch, and a first internal circuit that generates a control power supply voltage from a capacitor terminal voltage provided in the first power supply path A power source and the second power source A second internal power supply for generating an internal control power supply voltage using the path as a power supply source, and setting an output set voltage of the first internal power supply higher than an output set voltage of the second internal power supply Among the first internal power supply and the second internal power supply, the power supply having the higher control power supply voltage is preferentially used .

It is a block diagram which shows the internal structure of the vehicle-mounted power signal input circuit which concerns on Embodiment 1 of this invention. It is a timing diagram which shows operation | movement of the vehicle-mounted power signal input circuit which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the vehicle-mounted power signal input circuit which concerns on Embodiment 1 of this invention. It is the discharge characteristic graph shown in order to demonstrate operation | movement of the vehicle-mounted power signal input circuit which concerns on Embodiment 1 of this invention. It is a block diagram which shows the internal structure of the vehicle-mounted power signal input circuit which concerns on Embodiment 2 of this invention. FIG. 7 is a circuit diagram illustrating an example of a circuit configuration of a power supply unit illustrated in FIG. 6. It is a block diagram which shows an example of the conventional vehicle-mounted power signal input circuit used for a discharge lamp lighting device. It is a block diagram which shows an example of the conventional vehicle-mounted power signal input circuit used for an electric power steering control apparatus.

Hereinafter, in order to describe the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
1 is a block diagram showing an internal configuration of an in-vehicle power supply signal input circuit according to Embodiment 1 of the present invention. As shown in FIG. 1, the in-vehicle power signal input circuit according to the first embodiment of the present invention is mainly a lighting switch 2 as a first switch for supplying power to an HID valve 1 used as a load. And a second power supply path (hereinafter referred to as control) including an ignition switch 3 as a second switch that mainly supplies control power to the control unit 5. Power line IG), power line L and control power line IG as power supply sources, obtain voltage V _L applied to power line L and voltage V _IG applied to control power line IG, and V _L The voltage interface unit 4 and the control unit 5 detect that the lighting switch 2 is turned off when it is lowered and V _IG is held.

The power line L is connected to a filter large-capacitance capacitor C that alleviates ripples generated in the power supply path. The DC / DC converter unit 6 steps up and down the voltage of the in-vehicle DC power supply 9, the DC / AC converter unit 7 converts the output of the DC / DC converter unit 6 into AC, and the igniter unit 8 is connected to the HID valve 1. The control unit 5 is a well-known circuit that controls the power supplied to the HID valve 1 by applying a high-pressure pulse.
In addition, the communication interface unit 11 serves as a communication path with another on-vehicle control device (ECU) (not shown) and has a function of exchanging data with the control unit 5.

FIG. 2 is a waveform diagram shown for explaining the operation of the in-vehicle power supply signal input circuit according to the first embodiment of the present invention, where (a) shows the lighting switch 2 and (b) shows the power line L. Voltages V _L and (c) indicate the voltages V _IG applied to the control power line IG, respectively.

As shown in FIG. 2, when the lighting switch 2 is turned off while the lighting switch 2 is on and the ignition switch 3 is on, the voltage V _IG applied to the control power line IG becomes equal to the battery voltage E. At this time, due to the presence of the large-capacitance capacitor C for filtering, the voltage V _L applied to the power line L gradually falls while discharging the electric charge of the capacitor C. For this reason, it takes a relatively long time to discharge the capacitor C in order to determine whether or not the lighting switch 2 is turned off in accordance with whether or not a preset threshold voltage has been exceeded (in FIG. 2, as a delay due to C). Notation).

In the first embodiment of the present invention, when the voltage V _L of the power line L decreases (V _L → V _SL ) in order to quickly detect the voltage drop of the power line L described above, the control power line IG If the voltage V _IG is held at a constant value, it is determined that the lighting switch 2 is turned off. Therefore, when the lighting switch 2 is turned on after the lighting switch 2 is turned on and the ignition switch 3 is turned on, the voltage interface unit 4 turns off the lighting switch 2 after stopping the DC / DC converter unit 6. The voltage V _L applied to _L and the voltage V _IG applied to the control power line IG are measured (acquired), and after the control unit 5 performs AD conversion, the lighting switch 2 is determined to be OFF by comparing both voltages. did.

FIG. 3 is a flowchart showing the operation of the in-vehicle power supply signal input circuit according to the first embodiment of the present invention. Here, in particular, the flow of processing when the HID valve 1 is turned on by the control unit 5 is shown. Yes.
As shown in the flowchart of FIG. 3, after the lighting of the HID bulb 1 is started, the control unit 5 determines whether there is a power line L voltage drop (step ST301). (Step ST302), and if there is a voltage drop, it is determined whether there is a voltage drop in the control power line 1G (step ST306).
After determining in steps ST302 and ST306, the control unit 5 determines ON / OFF of the lighting switch 2. When the lighting switch is ON (step ST302 "predetermined voltage" or more), it is determined whether there is an abnormality flag (step ST303). If there is no abnormality flag, the HID valve 1 is turned on (step ST304), and it is determined whether there is an abnormality (step ST305).
On the other hand, when the lighting switch is OFF, after the abnormality flag is cleared (step ST307), the HID valve 1 is turned off when it is determined at step ST303 that there is an abnormality flag (step ST308). An abnormality flag is set (step ST309), and the process returns to step ST301.
The output of the HID bulb 1 is controlled so as to be constant at 35 W, for example, when the stable output is 35 W, and when the luminous flux is rapidly raised immediately after startup, for example, when the maximum output is 75 W. If so, the operation is determined by determining the state from the specified value based on the specification, or the detected value of the measured voltage or current. For this reason, whether or not the HID valve 1 operates according to the specifications is appropriately subjected to self-diagnosis by the control unit 5 and the diagnosis result is stored in a flag.

Or the control part 5 acquires the voltage _VL concerning the power line L via the voltage interface part 4, and determines the presence or absence of the voltage fall (step ST301). Here, when the observed voltage drop V _L (step ST 305 "There lowered voltage"), the control unit 5 further voltage V _IG applied to the control line IG, obtained through voltage interface unit 4, the It is determined whether or not the voltage value V _IG has a change (step ST306).
If a constant voltage value is held as the voltage value V _IG (step ST306 “No voltage drop”), the control unit 5 determines that the lighting switch 2 is turned off and turns off the HID valve 1.

  When the lighting switch 2 is turned off, the flag is returned to the normal state (step ST307). As a result, when the HID valve 1 is turned off by fail-safe based on a transient abnormal situation, the lighting switch 2 can be released from the turned-off state by the temporary fail-safe by a short-time OFF operation. The lighting operation can be performed again by turning on the lighting switch 2 again, and the HID bulb 1 can be re-lighted quickly.

According to the first embodiment described above, the voltage V _L applied to the power line _L is increased by the lighting OFF determination (steps ST302 and ST306) by the control unit 5 using the software for comparing and determining both the voltages V _L and V _IG. There is no need to wait until the lighting switch is turned off (step ST302) by the descending hardware, and the lighting switch 2 can be quickly turned off. Therefore, it is possible to provide an in-vehicle power supply signal input circuit that can quickly escape from a fail-safe extinguished state based on a transient abnormal situation of the HID valve 1.

In the first embodiment described above, the control unit 5 performs the OFF determination of the power switch 2 by comparing and determining both the voltages V _L and V _IG , but the voltage per unit time of V _L When the decrease is larger than the voltage decrease per unit time of V _IG , the power switch 2 may be turned off.
Specifically, the voltage V _IG applied to the control line IG connected to the in-vehicle DC power supply E includes voltage fluctuations, but the voltage value is basically constant, whereas the lighting switch 2 side turned off The voltage V _L applied to (power line L) decreases uniformly. Therefore, the voltage interface unit 4 acquires both voltages, and the control unit 5 calculates a voltage drop (slope: ΔV _L and ΔV _{IG in} FIG. 2) per unit time (for example, 0.1 second) and compares them. Then, if the voltage drop on the power line L side to which the power source E is not supplied is large, and the voltage drop is a predetermined voltage value (for example, 1 V) or more, it is immediately confirmed that the lighting switch 2 is turned off. Can be determined.

According to the application example of the first embodiment described above, the lighting switch 2 is determined to be OFF by comparison based on a voltage drop per predetermined time, but the control line IG connected to the in-vehicle DC power supply E is applied. The voltage V _IG is simply compared with the voltage V _L applied to the turned-off lighting switch 2 side (power line L). If the potential difference is not less than a predetermined value such as 1 V, the lighting switch 2 is turned off. It may be determined that

  According to the application example of the first embodiment described above, the power line L is determined by performing the OFF switch determination of the lighting switch 2 when the potential difference is greater than or equal to a predetermined value by comparison based on a voltage drop per predetermined time or by simple comparison. Therefore, it is not necessary to wait until the voltage applied to the voltage drops greatly, and the lighting switch 2 can be quickly turned off.

FIG. 4 is a graph showing the discharge characteristics (curve) of the filter capacitor C. As shown in FIG. As shown in FIG. 4, it is known that the capacitor voltage V _{C with} respect to the elapsed time changes with a constant relationship of V _C exp ^{1 / RC} between the time constant.
That is, the voltage V _IG applied to the control line IG connected to the in-vehicle DC power supply E includes voltage fluctuations, but basically the voltage value is substantially constant, whereas the lighting switch 2 side turned off ( The voltage V _L applied to the power line L) decreases uniformly along a discharge curve determined by the capacitance of the filter large-capacitance capacitor C connected to the lighting switch 2 and the impedance R of the discharge path. For this reason, when the voltage drop per unit time of the voltage _VL applied to the power line L is reduced along a predetermined discharge curve as shown in FIG. May be. In this case, the control unit 5 stores a discharge curve as shown in FIG. 4 in a built-in memory in advance, and the voltage V _L applied to the power line L acquired via the discharge curve and the voltage interface unit 4. By comparing with, it is recognized that the power switch 2 is turned off when it is determined that the voltage decreases along the stored discharge curve.

  According to the further application example of the first embodiment described above, it is not necessary to wait until the voltage applied to the power line L is greatly reduced by the comparison based on the discharge curve of the large-capacitance capacitor C for filtering. Can be determined to be OFF.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing an internal configuration of an in-vehicle power supply signal input circuit according to Embodiment 2 of the present invention. A difference in configuration from the first embodiment shown in FIG. 1 resides in the power supply unit 10, and a switching regulator 100 as a first internal power supply that generates an internal control power supply voltage using the power line L as a power supply source, And a series regulator 110 as a second internal power source that generates an internal control power supply voltage using the control power line IG as a power supply source. Other configurations are the same as those of the first embodiment shown in FIG.

  FIG. 6 shows an example of a circuit diagram of the power supply unit 10. The switching regulator 100 is a voltage conversion device that obtains a desired output voltage from an in-vehicle DC power supply E supplied via a power line L, and is a DC / DC converter that includes a switching control unit 101 that converts and adjusts the voltage. Here, it is assumed that the switching regulator 100 capable of step-up (step-up) and step-down (step-down) is used. According to the switching regulator 100, it is a well-known matter that the output voltage is determined by the ratio (duty ratio) of the ON / OFF time by the control signal. The series regulator 110 is a constant voltage DC power supply circuit capable of only stepping down, in which a current control element Tr2 is connected in series with a load (control unit 5).

Here, the output set voltage of the switching regulator 100 is designed to be higher than the output set voltage of the series regulator 110. That is, even if the voltage of the large-capacitance capacitor C for filtering included in the power line L becomes equal to or lower than the output set voltage of the switching regulator 100, the relationship of the output set voltage of the switching regulator 100> the output set voltage of the series regulator 110 described above. Trying to maintain.
As shown in FIG. 6, for example, when the output setting voltage of the switching regulator 100 is 8.5 V, for example, and the output setting voltage of the series regulator 110 is 8.4 V, for example, the switching regulator 100 first outputs 8.5 V. Attempts are made to discharge the electric charge of the filter capacitor C connected to the lighting switch 2, and the voltage of the filter capacitor C eventually decreases, and 8.5 V cannot be output. As described above, when the output of the switching regulator 100 becomes 8.4 V or less by using the charge of the filter capacitor C, the series regulator 110 serves as a control power source and supplies power.

As described above, the switching regulator 100 is preferentially operated over the series regulator 110, so that the charge of the filter large-capacitance capacitor C connected to the lighting switch 2 is quickly discharged, and the voltage of the capacitor C is quickly increased. Can be reduced. In this way, if the voltage on the lighting switch 2 side decreases quickly, it is possible to reliably detect OFF of the lighting switch 2 at an early timing compared to a predetermined voltage.
If the lighting switch 2 is turned off by setting the internal power supply of the power supply unit 10 to the step-up / step-down type switching regulator 100, the charge accumulated in the large-capacitance capacitor C for filtering connected to the lighting switch 2 is Since it is discharged by the boosting action of the switching regulator 100, the electric charge accumulated in the capacitor C is quickly discharged, and the voltage drop rate is increased as indicated by a broken line (forced discharge of C) in FIG. Therefore, it becomes easy to quickly detect that the lighting switch 2 is turned off due to the voltage drop.

  According to the second embodiment described above, the internal power supply of the power supply unit 10 is separately supplied from the two systems of the lighting switch 2 side and the ignition switch 3 side, and the switching regulator 100 connected to the lighting switch 2 side is configured. Since the output setting voltage is made higher than the output setting voltage of the series regulator 110 connected to the ignition switch 3 side, the voltage on the lighting switch 2 side quickly decreases. 2 can be reliably detected at an early timing.

That is, when measuring the voltage of the power supply path without interposing a backflow prevention element such as a diode between the lighting switch 2 and the large-capacitance capacitor C for the filter in the circuit, the electric charge of the capacitor C is quickly discharged. The voltage of the power supply path is made to follow the OFF of the lighting switch 2 and input as a signal, and the voltage of the power supply path is determined to quickly determine the OFF of the lighting switch 2.
By quickly determining whether the lighting switch 2 is OFF, for example, when the discharge lamp is extinguished due to a fail-safe due to a transient abnormal situation of the discharge lamp, The HID bulb 1 can be quickly restored and lighted by turning off the lighting switch again after turning off the light-off state due to the temporary fail-safe.

Some lighting devices that turn on the HID bulb 1 used as a vehicle headlamp have a fail-safe function that stops the lighting operation when an abnormal operation of the HID bulb 1 occurs. Typical abnormal operation of the HID valve 1 is “flickering” that repeatedly turns off and off at a short cycle, “flashing” that repeatedly turns on and off at a slow cycle, and sudden “disappearance” caused by vibration and the like. In either case, “disappear” for a moment is the beginning of abnormal operation. In addition, it is not without the possibility that the extinction caused by the external factor of the HID valve 1 is erroneously determined as the above abnormality. There is no abnormality in either the HID bulb 1 or the lighting device, and if the lighting operation is performed again, it can be normally lit.
It is preferable that the lighting operation is performed again when there is no abnormality in both of them by re-operating the lighting switch 2 that allows the driver of the vehicle to perform a functionally natural operation. However, since the large-capacitance capacitor C for filtering is provided in the power supply circuit, it is difficult for the discharge lamp lighting device to recognize the operation quickly even when the lighting switch 2 is turned off. As described in the first and second embodiments, by adopting a means that can quickly determine whether the lighting switch 2 is turned off, even if the HID valve 1 is turned off due to an external factor, it is possible to revive the lamp quickly. An electric lamp lighting device can be realized.

  The present invention is not limited to the above-described discharge lamp lighting device, but uses two power sources that are disconnected by each switch and places a large load on one of the power sources, an electric power steering control device, an engine control device, etc. In-vehicle control equipment has a power supply path that does not insert a series diode, so it can detect a short-time OFF of the power switch that supplies power to the connected load, and use the power supply path as a control signal be able to.

  As described above, the in-vehicle power supply signal input circuit according to the present invention includes the first power supply path including the first switch that mainly supplies power to the load, and the second power supply that mainly supplies control power. Using the second power supply path including the switch, the first power supply path and the second power supply path as a power supply source, the voltage applied to the first power supply path and the voltage applied to the second power supply path are obtained. And a control unit that detects the cutoff of the first switch when the voltage applied to the first power supply path decreases and the voltage applied to the second power supply path is maintained. Therefore, the power switch OFF state can be quickly determined without interposing a backflow prevention element such as a diode between the power switch and the capacitor included in the power supply path for supplying power to the load. Faye due to sexual abnormalities It is possible to provide a vehicle power supply signal input circuit capable departure prematurely from off state of the discharge lamp by safe.

Claims (3)

A first power path including a first switch that primarily supplies power to the load;
A second power supply path including a second switch that mainly supplies power for control;
The first power supply path and the second power supply path are used as power supply sources, and the first power supply path includes a filter with a large-capacitance capacitor that relaxes ripples,
Obtaining the voltage of the capacitor as the voltage applied to the first power supply path and the voltage applied to the second power supply path, the voltage applied to the first power supply path decreases, and the second power supply A control unit for detecting the cutoff of the first switch when the voltage applied to the path is held ;
A first internal power supply for generating a control power supply voltage from a capacitor terminal voltage provided in the first power supply path;
A second internal power supply for generating an internal control power supply voltage using the second power supply path as a power supply source;
Setting an output set voltage of the first internal power supply higher than an output set voltage of the second internal power supply;
An in-vehicle power supply signal input circuit that preferentially uses a power supply having a higher control power supply voltage generated from the first internal power supply and the second internal power supply . The first internal power supply is constituted by a step-up / step-down type switching regulator, and the first internal power supply even if the voltage of the capacitor included in the first power supply path is equal to or lower than the output set voltage of the first internal power supply. output settings voltage> automotive power signal input circuit according to claim 1, wherein maintaining the relationship of the second output set voltage of the internal power supply. The in-vehicle power supply signal input circuit according to claim 1 or 2, wherein the load is a discharge lamp, the first switch is a lighting switch, and the second switch is an ignition switch.

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