JP2001128355A - Control method for lamp for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method, for a lamp load for a vehicle, in which a semiconductor relay system constituted of a MOSFET with a built-in heat shutoff circuit or the like is used and in which the core cutoff stated of the lamp load such as a tail lamp for the vehicle, a stop lamp or the like can be controlled properly without an errors in judgment. SOLUTION: A rated load current, which flows to a lamp load such as a tail lamp 4, a stop lamp 5 or the like, is sampled four times, e.g. at every 5 ms, and their mean value is stored in a microcomputer 6 as a 'reference current value'. By supposing the reset initial state of the microcomputer 6, also a 'current threshold' is store. For example, when the core of any one lamp of the load lamp is cut off, the reference current value is reduced by a load current value by nearly one lamp portion. When its state exceeds the reference detecting time, the microcomputer 6 judges the state to be as the core cutoff of the lamp load. A case, in which the current value by one lamp portion of the lamp load is actually reduced, can be discriminated clearly from a case in which the current value is less than the reference current value, when a usage environment is changed due to a noise or when an actually flowing electrification current is changed with reference to a rated current by using the lamp load in a time-dependent manner, and it is possible to prevent errors in judgment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MOSFET (Metal Oxide Semiconductor-Field Effe
The present invention relates to a method of controlling a lamp load for a vehicle, which uses a semiconductor relay system including a ct transistor and the like to accurately determine the disconnection of a lamp load such as an automobile tail lamp or a stop lamp without erroneous detection.

[0002]

2. Description of the Related Art In recent years, in the case of a relay used for electronic control of an engine control system or a safety control system of an automobile,
Semiconductor relay systems with built-in thermal shutdown circuits and IPS (intelligent power switches), which have excellent high-speed switching characteristics, no contacts, and high reliability due to self-protection functions, have been widely used in place of the mechanical relays up to that time. .

A power supply voltage from a vehicle-mounted battery is supplied to a lamp load or the like through a power supply line arranged on a vehicle body. If the wire insulation film of the power supply line is worn out due to body vibration during use over time, excessive current flows continuously due to dead shorts, and excessive current flows intermittently due to so-called chattering shorts due to poor insulation. Overcurrent flows through the line and lamp load. In the above-mentioned MOSFET with a built-in thermal cutoff circuit, in order to protect the semiconductor switch when the semiconductor switch is overheated due to the occurrence of such a short circuit, an overcurrent exceeding the rated current flows through the semiconductor switch and the temperature rises to a temperature exceeding the specified level. The switching function can be forcibly turned off.

FIG. 2 is a circuit diagram showing an example of a lamp control circuit using such a semiconductor relay system. A power supply voltage Vb from a vehicle-mounted battery is supplied to a lamp load such as a tail lamp 4 and a stop lamp 5 through a shunt resistor 2 serving as a current detection resistor connected to the power supply line 1 and a MOSFET 3 with a built-in heat cutoff circuit. Further, a multiplex communication microcomputer (microcomputer) 6 including a CPU or the like which operates based on a control program is provided. The microcomputer 6 has a plurality of switches SW for selectively turning on / off the various lamp loads. signal _{s 1} is sent. Further, a current detection circuit 8 including the shunt resistor 2 and the differential amplifier 7 is provided. In the current detection circuit 8, the current value I flowing through the shunt resistor 2 is
s, that is, the load current flowing through the lamp load is calculated and obtained from the voltage drop due to the potential difference between both ends. Both ends of the shunt resistor 2 are connected to a non-inverting input terminal and an inverting input terminal of the differential amplifier 7, and a detection load current I
and is output as a voltage signal s ₄ corresponding to s.

[0005] Voltage signals s ₄ corresponding to the way the load current Is output from the current detection circuit 8 the microcomputer 6
Is sent to an A / D conversion port 9 where it is digitally converted and captured. In this way, the microcomputer 6 constantly monitors the load current Is of the lamp load. With respect to that monitor by the microcomputer 6, the microcomputer 6 is monitored constantly monitors the potential s ₆ of the source S of the heat cutoff circuit built-in MOSFET 3.

This lamp control circuit comprises a drive circuit 1 for turning on / off a MOSFET 3 with a built-in heat cutoff circuit.
It has 0. The drive circuit 10 includes a charge pump circuit 11, a semiconductor switch circuit 12 including transistors Tr1 and Tr2, and the like. When using the MOSFET 3 with a built-in thermal shutdown circuit on the high side of the lamp load such as the tail lamp 4 and the stop lamp 5,
To increase the voltage applied to the gate G, the power supply voltage V
It is necessary to increase b. The charge pump circuit 11
Run only when receiving a command signal s ₂ based on the positive logic from the microcomputer 6, the power semiconductor switch circuit 12 voltage is raised to Vb making a driving voltage required to turn on the operation of the thermal shutdown circuit built-MOSFET3 Supply. Thereby, one of the transistors Tr1 is turned on of the semiconductor switching circuit 12, when the other transistor Tr2 is turned off, the thermal shutdown circuit a signal s ₃ of the drive voltage from the charge pump circuit 11 boosts the power supply voltage Vb It is applied to the gate G of the built-in MOSFET 3 to turn on.
Conversely, when one transistor Tr1 is turned off and the other transistor Tr2 is turned on, the gate G is turned off.

In the lamp control circuit shown in FIG. 2, even if any kind of lamp load such as the tail lamp 4 or the stop lamp 5 is not actually burned out and is not in a core-cut state. Regardless, there is a possibility that the lamp may be erroneously determined to be disconnected by taking the following control procedure.

That is, the load current I flowing through the lamp load
The microcomputer 6 monitoring s compares the load current value calculated by fetching it from the A / D conversion port 9 with a current threshold value stored in advance based on the control program. At this time, if the calculated load current value is smaller than the current threshold value and lower than the current threshold value, and if the state exceeds the set time, it is determined that the lamp is disconnected due to the burnout of the ball.

[0009]

However, the fact that the load current value calculated by the detection falls below the current threshold value is not necessarily limited to the time when the lamp load is cut off due to a burnout of the bulb, and the use environment such as noise changes. In some cases, when the lamp load is used for a long time, the current flowing therethrough changes with respect to the rated current.

In other words, according to the above-described conventional method for determining the lamp centering, although the lamp is not in the centered state,
When the detected load current value falls below the current threshold value, the microcomputer 6 may erroneously determine that the lamp is broken, and issue a light-out instruction from the microcomputer 6 in many cases.

Accordingly, an object of the present invention is to use a semiconductor relay system including a MOSFET with a built-in thermal cutoff circuit and the like to properly determine the disconnection state of a lamp load such as a vehicle tail lamp or a stop lamp without erroneous judgment. An object of the present invention is to provide a method of controlling a vehicle lamp load to be controlled.

[0012]

According to a first aspect of the present invention, there is provided a method of controlling a lamp load for a vehicle, comprising the steps of: Times, the average value is stored as a reference current value in the microcomputer, and the load current value for one lamp is reduced by approximately one lamp with respect to the reference current value due to disconnection of one lamp of the lamp load. When the detection time exceeds the detection time, the microcomputer determines that it is the disconnection of the lamp load.

From the above, data for several times when the load current is detected is stored and the average value is stored as a reference current value. If the current value for one lamp of the lamp load actually decreases, the first By detecting and counting that the current of the lamp has decreased from the reference current value, it is possible to reliably determine that one lamp of the lamp load has been broken due to a burnout. In other words, when the operating environment changes due to noise, etc., and when the lamp load is used over time, the actual flowing current changes with respect to the rated current. Phenomena can be clearly distinguished, and erroneous judgment can be avoided.

According to a second aspect of the present invention, there is provided a vehicle lamp load control method assuming that the reference current value cannot be obtained when the microcomputer is in an initial reset state.
A current threshold value when the lamp load is disconnected is set and stored in the microcomputer, and in a reset initial state, the load current flowing through the lamp load becomes equal to or less than the current threshold value, and the state determines a reference detection time. When exceeding, the microcomputer determines that it is the disconnection of the lamp load.

As described above, when the microcomputer is reset and in the initial state, the load current of the lamp load is detected several times, an averaged reference current value is obtained, and it cannot be stored. Assuming that a reference current value cannot be obtained in such a reset initial state of the microcomputer, a current threshold value at the time of disconnection of the lamp load is set and stored in advance. Thereby, when the reset initial state of the microcomputer is actually reached, the load current value of the currently detected lamp load is compared with the current threshold value. As a result, as in the case of the above-mentioned claim 1, the current threshold value is set when the use environment such as noise changes, or when the actual current flowing with respect to the rated current changes due to the use of the lamp load over time. The under phenomenon and the under phenomenon of the current threshold value due to a broken ball can be clearly distinguished, and erroneous determination can be avoided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for controlling a vehicle lamp load according to the present invention will be described below with reference to a vehicle light control circuit shown in FIG.

FIG. 1 is a flowchart showing a lamp load control method according to this embodiment. Power supply voltage V from vehicle battery
When the switch SW corresponding to any one of the lamp loads of the tail lamp 4 and the stop lamp 5 is turned on in step S1 in a state where b is supplied through the power supply line 1, a Hi (high) level switch is turned on. signal s ₁ is outputted, the drive command signals s ₂ toward the driving circuit 10 is output from the microcomputer 6 to receive it. Based on the drive command signal s ₂ from the microcomputer 6, boosts the charge pump circuit 11 in the power supply voltage Vb to the driving voltage. The signal of this drive voltage is applied to the semiconductor switch circuit 1
0, for example, is supplied to the collector of an NPN transistor Tr1 to be turned on.
By off operation of r2, and applies outputs a drive voltage signal _{s 3} to the gate G of the thermal shutdown circuit built-in MOSFET 3.

When the operation of the MOSFET 3 with a built-in thermal cutoff circuit is turned on, a current of a lighting output flows to a target lamp load, and a current flowing through the load is detected by a current detection circuit 8. That is, the load current Is flowing through the shunt resistor 2 is calculated by the differential amplifier 7. The differential amplifier 7 has a load current Is
And outputs a voltage signal s ₄ corresponding to A / D of the microcomputer 6
Send to conversion port 9. Here, the microcomputer 6 constantly monitors the load current Is flowing through the lamp load by taking in the voltage output from the differential amplifier 7 by digital conversion.

Here, the microcomputer 6 determines that the lamp load is 1
The rated load current Is flowing through the lamp is stored as a reference current value. This reference current value is average data of several times of the load current Is detected by sampling at regular intervals. In the case of this example, detection is performed four times at intervals of, for example, 5 ms (seconds), and the average of the four load currents Is stored as a reference current value.

If one lamp load is broken, the detected current value is reduced by the load current value Is for one lamp. In step S3, the microcomputer 6 monitors such a decrease in the detected current value. If the microcomputer 6 determines that the detected current value has decreased by one lamp (Yes), the detection time is counted up (step S4). Step S
At 6, the microcomputer 6 monitors whether or not the time for detecting the state in which the detected current value has decreased has exceeded the reference. If the detection time has exceeded the reference (Yes), the microcomputer 6 determines that the lamp load has failed based on the detection. It is determined that the ball has been cut due to a broken ball (step S7).

On the other hand, if the detected current value does not fluctuate in step S3 due to a decrease in current for one lamp load (No), the detection time count is cleared and sampling is performed four times every 5 ms. The average data of the obtained load current Is is stored as a reference current value (step S5). At this time, the process proceeds to step S6 to continue monitoring whether or not the time for detecting the state of decrease in the detected current value exceeds the reference. In this step S6,
If the decreasing state of the detected current value does not exceed the reference detection time, the process proceeds to the waiting time process of step S7, and returns to step S1 to repeat the control routine.

On the other hand, in this series of control routines, if the microcomputer 6 is in the reset initial state in step S2 (Yes), the stored reference current value cannot be compared with the detected current value.

At this time, in step S9, the microcomputer 6 compares the load current value of the lamp load detected at the present stage with a current threshold value set in advance assuming lamp disconnection. It monitors whether the value has exceeded the current threshold. If exceeding (Yes), step S
At 10, the detection time is counted up. If it has not exceeded (No), in step S11, the data of the load current Is detected from time to time is accumulated and stored, and the number of times of sampling by the detection is counted. The data of the obtained load current values are averaged, obtained, updated and stored as reference current values. At this point, the initial state due to the reset of the microcomputer 6 is released.

Therefore, in step S10, counting up of the detection time is started, and in step S12, it is monitored whether the detection count-up has exceeded a reference detection time. If the detection count exceeds the reference detection time (Yes), the microcomputer 6 determines that the lamp load is "disconnection" (step S13). If the detection count does not exceed the reference detection time (No), the process proceeds to the waiting time process of step S8.

[0025]

As described above, the method for controlling a vehicle lamp load according to the first aspect of the present invention accumulates data for several times when the load current is detected and averages the data for the reference current. When the current value of one lamp of the lamp load actually decreases, the count of the decrease of the current of one lamp from the reference current value is detected and counted. Can be determined to have been broken due to a broken ball. That is, when the use environment changes due to noise, etc., and when the lamp load is used over time, the actual current flowing through the lamp changes with respect to the rated current. Phenomena can be clearly distinguished, and erroneous judgment can be avoided.

According to a second aspect of the present invention, when the microcomputer is reset and in the initial state, the load current of the lamp load is detected several times and an averaged reference current value is obtained. , Will not be able to store it. Assuming that a reference current value cannot be obtained in such a reset initial state of the microcomputer, a current threshold value at the time of disconnection of the lamp load is set and stored in advance. Thereby,
When the reset initial state of the microcomputer is actually reached, the load current value of the currently detected lamp load is compared with the current threshold value. As a result, as in the case of the above-mentioned claim 1, the current threshold value is determined when the use environment such as noise changes, or when the current that actually flows with respect to the rated current changes due to the use of the lamp load over time. The under phenomenon and the under phenomenon of the current threshold value due to a broken ball can be clearly distinguished, and erroneous determination can be avoided.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of a method for controlling a vehicle lamp load according to the present invention.

FIG. 2 is a circuit diagram illustrating an example of a vehicle light control circuit that executes a control method according to the present embodiment.

[Explanation of symbols]

 Reference Signs List 1 power supply line 2 shunt resistor 3 MOSFET with built-in thermal cutoff circuit 4 tail lamp (lamp load) 5 stop lamp (lamp load) 6 microcomputer 7 differential amplifier 8 current detection circuit 9 A / D conversion port 10 drive circuit 11 charge pump circuit 12 Semiconductor switch circuit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H05B 37/02 H05B 37/02 GF term (reference) 2G014 AA02 AB24 AB47 AC19 3K073 AA12 AA21 AA93 BA09 CA01 CF10 CF14 CF16 CG02 CG06 CJ19 CJ21 5G004 AA04 AB03 BA05 CA06 DA02 DC01 DC06 DC14 EA01 5G053 AA07 BA01 BA04 CA08 DA01 EA01 EC03 FA05

Claims (2)

[Claims] 1. A rated load current flowing through a lamp load is sampled several times at fixed time intervals, and an average value thereof is stored in a microcomputer as a reference current value. When the load current value for one lamp is reduced by about one lamp and the state exceeds a reference detection time, the microcomputer determines that the lamp load is disconnected. Control method. 2. When the microcomputer is in a reset initial state, assuming that the reference current value cannot be obtained, a current threshold value when the lamp load is disconnected is set and stored in the microcomputer. When the load current flowing in the lamp load in the reset initial state is lower than the current threshold value and the state exceeds a reference detection time, the microcomputer determines that the lamp load is disconnected. The method for controlling a vehicle lamp load according to claim 1.