JPS63121547A - Lamp burnout detector - Google Patents

Abstract

PURPOSE:To make a switchover performable without increasing terminal numbers of an integrated circuit, by making an internal circuit so as to be switched over to concentrating delay of separating delay by only connecting a concentrating or separating condenser to a capacitor connecting terminal. CONSTITUTION:A delay circuit 31 has two types of constant current sources 61 and 71, and this constant current source 71 feeds a current larger than a current I of the source 61. A constant current I flows in a transistor T1 or a terminal 51, while a constant current 1.5I flows in a diode D1 or a comparator output A side. A delay circuit 32 is also in the same constitution, having constant current sources 62 and 72 of these currents I and 1.5I, transistor T2 and a diode D2. And, an internal circuit is made so as to be switched over to concentrating delay or separating delay by only connecting concentrating or separating capacitor C, C1 and C2 to capacitor connecting terminals 51 and 52. Therefore, a switchover can be done without increasing terminal number of an integrated circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lamp breakage detection device that provides a delay time between detection of a breakage and output in order to prevent malfunctions due to noise, and particularly relates to a lamp breakage detection device that provides a delay time between detection of a breakage and output. This is intended to facilitate switching between separate delay and concentrated delay for detection items.

[Conventional technology]

Automobile lamp breakage detection devices usually detect two items, stop lamps and tail lights, but to prevent malfunctions due to noise, a predetermined delay time is set between detection of a breakage and output for each item. Since this delay time is used to check that the disconnection detection state continues for a certain period of time, a type that charges the capacitor with a constant current is usually used. However, (all detection item 2
There is a specification with one output system and a specification with two output systems under the same conditions, so the former uses a concentrated delay method that requires only one capacitor, and the latter uses a separated delay method. .

FIG. 3 shows the basic configurations of separate delay type and concentrated delay type lamp burnout detection devices. In the figure, 11.12 is a reference voltage generation unit that generates a reference voltage vR that approximates the lamp current, and 21.22 is an input voltage that is generated when the reference voltage vR and lamp current are passed through a reference resistor (Rs to be described later). and 31.32 is its output signal A.
, B, 41.42 is an inverter that inverts the output of the delay circuit, and 51.52 is an external terminal for connecting a capacitor.

In the separated delay method in (a), the two systems are independent, so the detection output 1.2 is generated by the two delay circuits 31 and 32.
are obtained as individual outputs of On the other hand, in the concentrated delay method b), one delay circuit 31 is shared, so that the output is unified. In both circuit systems, the parts other than capacitors C1, C2, and C are integrated into ICs, but since both circuits have many common parts, when actually integrated into ICs, the fourth
As shown in the figure, a configuration that can be shared by both types is often used.

In FIG. 4, Gl and G2 are switching gates, SW is a changeover switch, and 53 is an external terminal for connecting the switch. Switch SW sets terminal 53 to 0 (ground) when it is on, and sets terminal 53 to 1 (open) when it is off.
When turned on, it becomes a separate delay method, and when it is turned off, it becomes a concentrated delay method. External capacitors C1 and C2
are selectively connected according to these methods. L is a lamp to be detected, and the lamp current is passed through a reference resistor Rs to be used as an input voltage of the comparator 21. The same applies to the comparator 22 side.

The delay circuit 31 (and 32 as well) is constructed as shown in FIG. 5, and when the output A of the comparator 21 is 0, the transistor T is turned off and the capacitor C is charged with a constant current . Further, when the output A of the comparator 21 is 1, the transistor T is turned on, so that the charge in the capacitor C is discharged. Comparator CMP is the voltage A of capacitor C
' is compared with the reference voltage E, and the output is shown depending on the magnitude.

The delay time of this delay circuit 31 is determined by the capacitance of the capacitor C, the value of the constant current I, and the value of the reference voltage E.

[Problem that the invention seeks to solve]

By the way, the configuration shown in FIG. 4 requires a switching terminal 53, and also requires logic games G1 and G2, which is disadvantageous when integrated into an IC. According to the present invention, the internal circuit can be switched to a concentrated delay or a separated delay simply by connecting a concentrated or isolated capacitor to a terminal for connecting a capacitor.

[Means for solving problems]

FIG. 1 is a basic configuration diagram showing essential parts of the present invention, and the overall configuration is based on FIG. 3(a). FIG. 1 is a circuit diagram centered on delay circuits 31 and 32 (comparator CMP is not shown).

The delay circuit 31 has two types of constant current sources 61 and 71, and the constant current source 71 supplies a current larger than the current I of the constant current source 61. Here, the current is 1.51, which is 1.5 times the current. The constant current (2) flows to the transistor T+ or the terminal 51, and the constant current 1.5I flows to the diode D1 or the comparator output A side. The delay circuit 32 also has a similar configuration,
62 is a constant current source of ■, 72 is a constant current source of 1.5I, T2
is a transistor, and D2 is a diode. However, when the diodes DI and D2 are integrated into an IC, they are formed by connecting the collectors and bases of transistors, and the bases are connected to the bases of the transistors TI and T2 to form a current mirror.

[Effect]

In the configuration of FIG. 1, the terminal 51.5 is shown as a solid line.
Assume that a single capacitor C is connected thereto. In this case, comparator output A is H (high) and B
is L (low), transistor T+ is on, T2
is off, the sum of the currents of constant current sources 61 and 62 2I
A part of flows into capacitor C, and the rest flows into transistor T1.
flows to The current flowing through the transistor T1 is 1°5I, which flows through the diode D+ due to the current mirror effect.
is equal to 21-1. Therefore, the current flowing through capacitor C is 21-1.
5 I=0.51...■. When the comparator output A is high and B is H, 1.5 µ flows through the transistor T2, and 0.5 I flows through the capacitor C.

The above is a case where one of the detection units detects a wire breakage (a wire breakage is detected when the comparator output is L).

Next, both detection parts detect a disconnection, and the comparator outputs A,
When both B become L, both transistors TI+T2 are turned off, so the current flowing through the capacitor C becomes 1+I=21...■.

On the other hand, when neither detection unit detects disconnection, comparator outputs A and B are both H, so transistors TI and T2 are both turned on, and capacitor C has 21-2X1.5 I=-I.・・・・・・
■A current flows. This is a discharge state, contrary to ■■.

In case ■■, capacitor C is charged (charging time is longer in case ■), so capacitor voltage A' (= B')
A comparator (CMP in FIG. 5) that monitors outputs a detection output at a level opposite to ■ after a delay time. This is a concentrated delay method.

On the other hand, if capacitors CI and C2 are individually connected to terminals 51 and 52 as shown by broken lines in FIG. 1, a separate delay system is obtained. In this case, when the comparator output A becomes H, 1.5I flows through the transistor T1, so the capacitor C+
is 1-1.51 = -0,5I...
・■Flow (discharge), and when output A becomes L, all I flows to capacitor C+ (charge). Therefore, this capacitor voltage A' can also be distinguished by a comparator. The same applies to capacitor C2. The currents of the constant current sources 71 and 72 are selected from a range (greater than I and smaller than 2) that makes the equation 00 negative and the equation (2) positive. Examples 1 and 5
I is this intermediate value and has the largest margin.

〔Example〕

FIG. 2 is a circuit diagram showing an embodiment of the present invention, and corresponds to FIG. 1. The constant voltage diode ZD creates a stable reference voltage, which is connected to the series resistor R+.

A reference value of constant current I is created by applying it to R2. At this time, the resistance RJ is equal to R2, and the resistance R4 is 1/1 of R2.
．． When set to 5, a current I flows through the transistor T3, and a current 1.5I flows through the transistor T4. As a result, a constant current I flows from each collector of the multi-collector transistor T5, and a constant current 1.5I flows from each collector of the multi-collector transistor T6. Diode D3 is connected to transistor T3. This is for canceling out the voltage between the base and emitter of Ta.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to switch between concentrated delay and separated delay without increasing the number of IC terminals. Furthermore, since there is no need to implement logic within the IC, there is no need for an increase in the number of elements, and there is an advantage that the IC design does not become complicated.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram showing the main parts of the present invention, Fig. 2 is a main part circuit diagram showing an embodiment of the invention, Fig. 3 is a basic configuration diagram of a lamp breakage detection device, and Fig. 4 is a conventional configuration diagram. FIG. 5 is a block diagram of a delay method switching type lamp burnout detection device, and FIG. 5 is a block diagram of a conventional delay circuit. In the figure, 11.12 is a reference voltage generator, 21 and 22 are comparators, 31.32 is a delay circuit, 51.52 is an external terminal, 61.62 is a first constant current source, and 71.72 is a second Constant current source, TI, T2 are transistors, DI, D2
is a diode, L is a lamp, Rs is a reference resistance, C, CI
, C2 is a capacitor.

Claims (1)

[Claims] In a lamp breakage detection device that includes the same number of rechargeable delay circuits that delay the output of a plurality of lamp breakage detection sections, and an external terminal to which a capacitor used in each delay circuit is externally connected, each delay circuit is configured to A transistor that is turned on and off by the output of the disconnection detection section, a first constant current source that causes current to flow through the transistor or the capacitor, and a diode and a second constant current source that configure a current mirror circuit together with the transistor. A lamp breakage detection device characterized in that when capacitors are individually connected to the plurality of external terminals, a separate delay method is used, and when a common capacitor is connected to the plurality of external terminals, a concentrated delay method is used.