JP2002067791A - Head lamp load line short detection device - Google Patents

Abstract

(57) [Summary] (With correction) [PROBLEMS] To enable ON / OFF control of a driving element without erroneous detection of a load short even if a battery power supply voltage drops. SOLUTION: When a voltage at a connection point between a driving element 2 and a headlamp 1 becomes lower than a preset short detection voltage by a CPU 4, a short circuit of a load line is detected, and a driving circuit 3 is controlled to control the driving circuit 3. 2 off,
A drive element output circuit section configured to stop the supply of power from a battery to the headlamp 1; and a drive element output circuit section when the battery power supply voltage VB is higher than a preset battery voltage value. And a drive stop signal for stopping the short-circuit detection control of the drive element output circuit unit when the battery power supply voltage VB is lower than the preset battery voltage value. Output to control the driving of the driving element output circuit section 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a short circuit in a load line when a headlamp is turned on when a battery power supply voltage fluctuates.

[0002]

2. Description of the Related Art When a load line is short-circuited while a headlamp is lit, a large current flows to the ground, the battery voltage drops sharply, and various control devices driven by power supply from the battery do not operate normally. There is. Therefore, if the load line is shorted while the headlamp is on,
The load line short circuit is detected as soon as possible, and the load line connected to the headlamp is immediately turned off (open).
It is important to do. As a method for the short circuit of the load line during the headlamp lighting, a drive element for turning on / off the power supply to the headlamp is inserted and connected between the battery power supply of the load line and the headlamp,
A voltage at a connection point between the driving element and the headlamp is detected, and when this voltage becomes lower than a predetermined voltage, it is determined that a load short-circuit has occurred (an overcurrent has flown), and the driving element is turned on.
There is a method of protecting the circuit by stopping power supply to the headlamp by FF.

[0003]

However, in the method of monitoring the voltage of the headlamp on the battery power supply side and detecting a load short-circuit based on whether or not the voltage has become lower than a predetermined voltage, When the battery power supply voltage decreases, the driving capability of the drive circuit that controls ON / OFF of the drive element decreases, and the drive element cannot be driven (lamp drive). An erroneous detection that the CPU makes a short-circuit determination may be performed.

An object of the present invention is to provide a headlamp load line short-circuit detecting device capable of performing ON / OFF control of a driving element without erroneous detection of a load short-circuit even when a battery power supply voltage drops. It is in.

[0005]

According to a first aspect of the present invention, there is provided a headlamp load line short-circuit detecting apparatus, comprising: a load line for supplying power from a battery to the headlamp; A driving element inserted and connected between a battery power supply, for turning on and off the headlamp, a driving circuit for turning on and off the driving element, and a CPU for controlling the driving circuit;
PU detects a short circuit in the load line when the voltage at the connection point between the driving element and the headlamp drops below a preset short detection voltage, controls the driving circuit to turn off the driving element, A drive element output circuit for stopping supply of power from a battery to the headlamp, and detecting a short circuit of the drive element output circuit when the battery power supply voltage is higher than a preset battery voltage value. Outputs a drive signal for control,
When the battery power supply voltage is lower than the preset battery voltage value, a control stop signal for stopping the short-circuit detection control of the drive element output circuit is output to control the drive of the drive element output circuit. And an output circuit control unit. With this configuration, according to the headlamp load line short-circuit detecting device according to the first aspect, even if the battery power supply voltage is reduced, the ON / OFF control of the driving element can be performed without erroneous detection of a load short-circuit. It can be performed.

In order to achieve the above object, a short-circuit detection device for a headlamp load line according to claim 2 is provided.
The output circuit control unit includes a Zener diode having a cathode connected to a battery power source, a grounded NPN transistor having a base connected to the anode of the Zener diode, and a predetermined voltage applied to a collector of the NPN transistor. , The CPU of the drive element output circuit section is connected to the collector of the NPN transistor, and a Hi / Low signal is output from the collector of the NPN transistor to the CPU to control the drive of the drive element output circuit section. . With this configuration, according to the headlamp load line short-circuit detecting device according to the second aspect, erroneous detection of a load short-circuit when the battery power supply voltage is reduced is prevented with a simple configuration, and the drive element is turned on.
-OFF control can be performed.

According to a third aspect of the present invention, there is provided an apparatus for detecting a short circuit in a headlamp load line.
The voltage at the connection point between the drive element and the headlamp, which is taken into the drive element output circuit section, is passed through a low-pass filter. With this configuration, it is possible to prevent a malfunction due to a disturbance from occurring in the headlamp load line short-circuit detecting device according to the third aspect.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a headlamp load line short detection device according to the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of a headlamp load line short detection device according to the present invention.

In FIG. 1, a power supply to the headlamp 1 is provided between the headlamp 1 having one end grounded and the other end connected to a battery power supply VB and the battery power supply VB of the load line. A drive element (for example, N-channel FET) 2 to be turned ON / OFF is inserted and connected in series (the battery power supply VB is connected to the drain terminal, and the headlamp 1 is connected to the source terminal). The drive element 2 is connected to a drive circuit 3 for driving the drive element 2 ON / OFF. That is, the driving circuit 3 includes the driving element 2
Is turned ON / OFF, and when a Hi output from the drive circuit 3 occurs, the gate of the drive element 2 opens and the drive element 2 is turned ON
Then, power is supplied to the headlamp 1 from the battery power supply VB. Then, the driving element 2 receives Hi from the driving circuit 3.
The ON state is continued as long as the output is continued.

From the state where the output of the driving circuit 3 is Hi,
When it changes to Low, the gate voltage of the driving element 2 becomes Low.
, The gate is closed and the driving element 2 is turned off,
Power supply from the battery power supply VB to the headlamp 1 is stopped. The drive element 2 keeps the OFF state as long as the output of the drive circuit 3 is low. When the output of the drive circuit 3 changes from a low state to a high state, the gate of the drive element 2 opens again, the drive element 2 turns on, and the operation of supplying power from the battery power supply VB to the headlamp 1 is repeated.

A CPU 4 is connected to the drive circuit 3, and ON / OFF control of the drive element 2 by the drive circuit 3 is performed by a control signal from the CPU 4. That is, when there is an output of Hi for driving the drive circuit 3 from the CPU 4, the drive circuit 3 is driven, and the drive circuit 3 outputs a Hi output signal to the drive element 2. When the drive circuit 3 outputs Low from the CPU 4, the drive circuit 3 stops driving, and the drive circuit 3 outputs a Low output signal to the drive element 2. The CPU 4 is connected to the connection point a through a low-pass filter 5 including a resistor R4 and a capacitor C1. The voltage at the point a is input to the CPU 4 and the voltage between the point a and GND is monitored.
When the voltage at the point is lower than a preset voltage (for example, 2.5 V), it is determined that a load short circuit has occurred, and the load short circuit is detected.

A load drive signal (from drive circuit 3 to drive element 2)
Is turned on (becomes Hi), the driving element 2 is turned on and the headlamp 1 is turned on. When the headlamp 1 is turned on in this way, the voltage at the point a in the normal state immediately rises to almost the power supply voltage (for example, 12 V) in response to the load drive signal. Therefore, the voltage at the point a is almost the power supply voltage (for example, 12 V) and is higher than a preset voltage (for example, 2.5 V).
It is determined that the drive circuit 3 is normal (there is no load short-circuit), the output of Hi for driving the drive circuit 3 is continued, the drive element 2 is maintained in the ON state, and the lighting of the headlamp 1 is continued.

Now, the load drive signal (the signal output from the drive circuit 3 to the drive element 2) is turned on, and the drive element 2 is turned on.
Then, the headlamp 1 is turned on, the voltage at point a also rises to the power supply voltage (for example, 12 V), and after this ON state continues,
When a load short-circuit occurs, the voltage at point a immediately drops to a value lower than a preset voltage (for example, 2.5 V) (the head lamp 1 is driven in a load short-circuit state, or the head lamp 1 is being driven. When a load short occurs,
The voltage at point a hardly rises). Immediately after the voltage at the point a has dropped to a value lower than the preset voltage (for example, 2.5 V), the load drive signal is in the ON state. The CPU 4 detects that the voltage at the point a has become lower than a preset voltage, determines that the voltage is abnormal (load short-circuit), outputs Low to the drive circuit 3, and outputs Lo to the drive circuit 3.
The w signal is output to the driving element 2, and the driving element 2 is turned off. As a result, power is not supplied to the load line,
The circuit (element) is protected from excessive current. The low-pass filter 5 composed of the resistor R4 and the capacitor C1 is for preventing the CPU 4 from malfunctioning due to disturbance.

The driving element 2, the driving circuit 3, and the CPU
4 and the low-pass filter 5 constitute a drive element output circuit unit 6.

On the other hand, the drain terminal of the driving element 2 is connected to the cathode of a Zener diode ZD, and the anode of the Zener diode ZD is connected to the base of an NPN transistor Tr via a resistor R1. The emitter of the NPN transistor Tr is grounded, and a predetermined voltage V0 is applied to the collector via the resistor R3. The base and emitter of the NPN transistor Tr are connected via a resistor R2. The Zener diode ZD, the resistor R1, the resistor R2,
The output circuit control unit 7 includes the resistor R3 and the NPN transistor Tr.

Next, the operation of the output circuit control section 7 will be described. First, the battery power supply voltage VB (12 V)
Is larger than the drive voltage determined by the Zener voltage of the Zener diode ZD and the base drive voltage of the NPN transistor Tr, a current flows through the base of the NPN transistor Tr, the NPN transistor Tr turns on, and the NPN transistor Tr turns on.
The output signal output from the collector of the transistor Tr to the CPU 4 is Low. This NPN transistor T
When the output signal output from the collector of r is Low,
The CPU 4 normally performs short-circuit detection control. That is, the CPU 4 detects the voltage at the point a, and when the voltage at the point a falls to a value lower than a preset voltage (for example, 2.5 V), determines that the drive circuit 3 is abnormal (load short).
, A low signal is output from the drive circuit 3 to the drive element 2, and the drive element 2 is turned off.

The battery power supply voltage VB (12 V)
Falls to a value smaller than the drive voltage determined by the Zener diode ZD and the base drive voltage of the NPN transistor Tr, the current does not flow through the base of the NPN transistor Tr, so that the NPN transistor Tr is in the OFF state and the NPN transistor Tr is turned off. From collector to CP
The output signal output to U4 is a Hi signal. This N
When the output signal output from the collector of the PN transistor Tr is Hi, the CPU 4 does not perform the short-circuit detection control because the battery power supply voltage VB has dropped. As described above, the NPN transistor Tr does not turn on due to the decrease in the battery power supply voltage VB (12 V), and a Hi signal is output to the CPU 4 from the collector of the NPN transistor Tr.
The CPU 4 of the driving element output circuit unit 6 receives the Hi signal
Stop the short-circuit detection control function. That is, CPU
4 detects the voltage at the point a, and when the detected voltage at the point a falls below a preset voltage (for example, 2.5 V), it is determined that an abnormality (load short-circuit) has occurred, and the drive circuit 3 determines Lo.
The signal w is output, the driving circuit 3 outputs a low signal to the driving element 2, and short-circuit detection control such as turning off the driving element 2 is not performed. As described above, when the Hi signal is output to the CPU 4 and the Hi output signal is output from the terminal connected to the collector of the NPN transistor Tr of the output circuit control unit 7, it is determined that the battery power supply voltage VB has dropped and short-circuiting occurs. You will ignore the detection.

The preset battery voltage value in the output circuit control section 7 is a drive voltage for driving the NPN transistor Tr, and is determined by the Zener voltage VZ of the Zener diode ZD and the base drive voltage of the NPN transistor Tr. It is determined. That is, the set battery voltage value is determined by adding NP to the Zener voltage VZ of the Zener diode ZD.
It is determined by a voltage value obtained by adding the base drive voltage of the N transistor Tr. The set battery voltage value obtained by adding the base drive voltage of the NPN transistor Tr to the Zener voltage VZ of the Zener diode ZD is within the range of the battery power supply voltage at which the drive circuit 3 can drive the drive element 2 (lights the headlamp 1). In this case, the NPN transistor Tr is turned on and the driving element (FET) 2 cannot be driven (the headlamp 1
Cannot be turned on) NP in the range of battery power supply voltage
The N transistor Tr is set to be turned off.

FIG. 2 is a flowchart showing the operation of the load line short-circuit detecting device shown in FIG.

First, in step 101, when the switch of the headlamp 1 is turned on, in step 102, the CPU 4 outputs an ON signal (Hi signal) to the drive circuit 3. When an ON signal is output to the drive circuit 3 in step 102, the drive circuit 3 is turned on in step 103, and an ON signal (Hi signal) is output from the drive circuit 3 to the drive element 2. When an ON signal is output to the driving element 2 in step 103, the driving element 2 is turned on by the ON signal from the driving circuit 3 in step 103, and in step 104, the battery power supply VB passes through the driving element 2. The power is supplied to the headlamp 1 and the headlamp 1 is turned on.

When the headlamp 1 is turned on in step 104, it is determined in step 105 whether or not the battery power supply voltage VB is higher than a preset battery voltage. If it is determined in step 105 that the battery power supply voltage VB is not higher than the preset battery voltage, that is, that the battery power supply voltage VB is lower than the preset battery voltage, step 1 is executed.
At 06, since no current flows to the base of the NPN transistor Tr and the NPN transistor Tr is turned off, a Hi signal is output from the collector of the NPN transistor Tr to the CPU 4 indicating that the battery power supply voltage VB is lower than the set battery voltage. Then, the CPU 4 stops driving the normal load short detection function.

If it is determined in step 105 that the battery power supply voltage VB is higher than a preset battery voltage, in step 107, the CPU 4
It is determined whether the voltage at point a is higher than a predetermined voltage (a preset voltage). If it is determined in step 107 that the voltage at point a is higher than the predetermined voltage, in step 108, the CPU 4 continuously outputs an ON signal to the drive circuit 3. The drive circuit 3 keeps the ON state by the ON signal from the CPU 4, and the drive circuit 3
The N signal is continuously output, and the ON state of the driving element 2 is continued. Due to the continuation of the ON state of the driving element 2, the battery power VB is supplied to the headlamp 1 through the driving element 2.

If it is determined in step 107 that the voltage at point a is not higher than the predetermined voltage, that is, if the voltage at point a is lower than the predetermined voltage, it is detected in step 107 that the voltage at point a is lower than the predetermined voltage. It is determined whether or not the number of times (continuous number) has reached a predetermined number (here, five times). The number of times that the voltage at the point a is detected to be lower than the predetermined voltage (continuous number) is counted in order to prevent erroneous detection. If it is determined in step 109 that the number of times of detection of the low voltage has reached five, step 1
At 10, the CPU 4 detects a short circuit of the load line, outputs an OFF signal (Low signal) to the drive circuit 3, and outputs an O signal to the drive circuit 3 when the detection of a low voltage continues.
Output of the FF signal is continuously performed. When an OFF signal (Low signal) is output to the drive circuit 3 in step 110, the drive element 2 is turned off in step 111, so that the power supply from the battery power supply VB to the headlamp 1 is stopped.

If it is determined in step 109 that the number of times of detection of the low voltage has not reached five, it is determined in step 112 whether or not a set time (in this case, 20 ms) has elapsed after the detection of the low voltage. I do. This 20 ms is an optimal time for preventing erroneous detection. If it is determined in Step 112 that the set time has not elapsed, the process waits until the set time has elapsed. If it is determined that the set time has elapsed in Step 112, the process returns to Step 107, and the voltage at the point a becomes higher than the predetermined voltage. It is determined whether it is high (or low).

Therefore, according to the present embodiment, the ON / OFF control of the driving element can be performed with a simple configuration by preventing erroneous detection of a load short circuit when the battery power supply voltage drops.

[0026]

Since the present invention is configured as described above, it has the following effects. According to the headlamp load line short-circuit detecting device according to the first aspect, even if the battery power supply voltage drops, the ON / OFF control of the drive element can be performed without erroneous detection of a load short-circuit. According to the headlamp load line short-circuit detecting device according to the second aspect, the ON / OFF control of the driving element can be performed with a simple configuration by preventing erroneous detection of a load short-circuit when the battery power supply voltage drops. it can. According to the headlamp load line short-circuit detecting device according to the third aspect, it is possible to prevent malfunction due to disturbance.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an apparatus for detecting a short circuit of a headlamp load line according to the present invention.

FIG. 2 is an operation flowchart of the headlamp load line short-circuit detecting device shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Head lamp 2 ... Driving element 3 ... Driving circuit 4 ... CPU 5 ... Low-pass filter 6 ... Driving element output circuit part 7. Output circuit control unit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masayuki Nakayama 206-1 Nunobikihara, Haibara-cho, Haibara-gun, Shizuoka Prefecture Inside (72) Inventor Yoshio Ito 206-1 Nunobikihara, Haibara-cho, Haibara-gun, Shizuoka Prefecture Yazaki Parts (72) Inventor Shigeru Uehara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 2G014 AA03 AB24 AB25 AB38 AC18

Claims (3)

[Claims] 1. A drive element inserted and connected between a headlight and a battery power supply in a load line for supplying power to a headlight from a battery, and turning the headlight on and off, and turning the drive element on and off. A drive circuit;
A CPU for controlling the drive circuit, wherein the CPU
When the voltage at the connection point between the drive element and the headlamp is lower than a preset short detection voltage, a short circuit in the load line is detected, the drive circuit is controlled to turn off the drive element, A driving element output circuit for stopping supply of power from a battery to a headlamp; and a short detection control for the driving element output circuit when the battery power supply voltage is higher than a preset battery voltage value. And outputting a control stop signal for stopping short-circuit detection control of the driving element output circuit section when the battery power supply voltage is lower than the preset battery voltage value, and outputting the driving signal. A headlamp load line short-circuit detecting device, comprising: an output circuit control unit for controlling driving of the output circuit unit. Place. 2. An output circuit control unit comprising: a Zener diode having a cathode connected to a battery power source; a grounded NPN transistor having a base connected to the anode of the Zener diode; and a predetermined voltage applied to a collector of the NPN transistor. Is applied, and the collector of the NPN transistor is connected to the CPU of the drive element output circuit section.
From the collector of the NPN transistor to the C
2. The headlamp load line short-circuit detecting device according to claim 1, wherein a Hi-Low signal is output to the PU to control the driving of the driving element output circuit. 3. The headlamp according to claim 1, wherein a voltage at a connection point between the driving element and the headlamp, which is taken into the driving element output circuit unit, is taken through a low-pass filter. Load line short detection device.