JPS63234166A - Current detector - Google Patents

Abstract

PURPOSE:To accurately detect current by forming one of a couple of resistances by using a material which has negative resistance temperature characteristics, varying the resistance value of one resistance according to negative resistance characteristics even if the temperature of the other varies, and maintaining a detected voltage at a proper value. CONSTITUTION:This detector consists of flash lamps 10a-10f, an oscillation control circuit 20, a changeover switch 30, and a semiconductor chip E. Further, the device is formed of the chip E, a longitudinal power MOSFET 40, and a voltage dividing circuit 50, and boron, etc., is implanted in polycrystalline silicon to give one resistance 51 of the circuit 50 the negative resistance temperature characteristics. Consequently, even if the breaking of a wire occurs to the lamp 10a, etc. when the temperature of the CHIP E is high, variations in resistance values of the resistances 51 and 52 cancel each other and a detection voltage from the circuit 50 has no error. Therefore, the state of a load current is accurately detected from the detection voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a current detection device, and particularly to a current detection device employing an MO8 type field effect transistor (hereinafter referred to as MOSFET).

(Prior Art) Conventionally, in this type of current detection device, U.S. Pat.
As shown in Japanese Patent No. 553084, a sub MO8FET having a single cell and a plurality of MO8FETs connected in parallel to each other (
For example, a main MO8FET with 2,000 cells and a detection resistor with an extremely small resistance value are adopted, and both MO3F
When ET conducts, most of the load current flows into the main MO8FET and the remaining part of the load current flows into ljMO8
There is a system in which it is detected whether the load current is below a permissible value by allowing the current to flow into a detection resistor via a FET and comparing the terminal voltage of the detection resistor with a reference voltage using a comparator.

(Problems to be solved by the invention) By the way, in such a configuration, as mentioned above,
Since the resistance value of the detection resistor is extremely small, even if the ambient temperature changes, the influence of a change in internal resistance when the rMMO3FET is turned on as an error on the terminal voltage of the detection resistor can be suppressed to a very small level. However, since the terminal voltage of the detection resistor is also small by itself, comparison using a comparator requires an extra amplifier to amplify the terminal voltage of the detection resistor, as well as a highly accurate amplifier and comparator. There is a problem with being requested.

In order to deal with this, it is conceivable to increase the resistance value of the detection resistor, but in such a case, the change in internal resistance when the sub MO8FET becomes conductive in accordance with the change in ambient temperature, and the Both MO8FETs respond to temperature changes
Each M of the load current due to the change in the difference of each internal resistance when conducting
A problem arises in that a change in the shunt ratio to the OSFET has a large adverse effect as an error on the terminal voltage of the detection resistor.

Therefore, in order to deal with the above-mentioned problems, the present invention attempts to accurately detect current in response to temperature changes in a current detection device without using unnecessary elements such as an amplifier. It is something to do.

(Means for solving the problem) In solving the problem, the structural features of the present invention are as follows:
A pair of resistors (51, 52), a control terminal (43), an input terminal (41) connected to one end of the resistor (51), and an output terminal (42) connected to the other end of the resistor (52). This MOSFET (40) is equipped with a MOSFET (40) having
40) has a control signal generating means (
A part of the load current that flows into the load when it receives a series of control signals from the MOSFET (40) flows into the MOSFET (40) from its input terminal (41) and flows out from its output terminal (42), The remaining part of the current flows through the pair of resistors (51, 52) and these resistors (
In the current detection device, one of the resistors 51 and 52) detects the inflow current, generates a detection voltage from a common terminal with the other resistor, and further detects the state of the load current based on this detection voltage, One of the pair of resistors (51°52),
The reason is that it is made of a material having negative resistance-temperature characteristics.

(Operation and Effect) By configuring the present invention in this way, M
Even if the temperatures of the OSFET (40) and one of the pair of resistors (51°52) change in the same way, the MOSFET (40)
Since the resistance value of one of the pair of resistors (51, 52) changes according to its negative resistance temperature characteristic so as to cancel the change according to the temperature in the internal resistance value of the pair of resistors (51, 52)
) can be maintained at the same appropriate value regardless of the temperature change, and as a result,
without adopting unnecessary circuit elements such as amplifiers.
The state of the load current can always be detected accurately based on the detected voltage.

Furthermore, when one of the pair of resistors (51, 52) is formed by ion-implanting boron or phosphorus into a polycrystalline silicon resistance material, one of the pair of resistors (51, 52) is formed by MOSFET. (40) It can be easily realized as a P-type or N-type semiconductor resistance element having a negative resistance temperature characteristic necessary to cancel the temperature change in the internal resistance value. In such a case, since boron has the property of having a larger negative temperature coefficient of resistance than phosphorus, when boron is used, the resistance of the pair of resistors (51, 52>
The resistance value and volume of one of the two can be reduced.

Furthermore, when the boron or phosphorus ion implantation concentration is determined so that the ratio of the resistance values of the pair of resistors (51, 52) is approximately constant, one of the pair of resistors (51, 52) The current sensitivity will vary from production rod to production rod, more precisely from product to product, but in order for the current sensitivity of a product to not fluctuate due to temperature, the negative resistance of one of the pair of resistors (<51.52) must be Since it is possible to make the characteristics substantially the same for all products, the boron or phosphorus implantation concentration can be made substantially the same, and as a result, this type of device can be provided with high mass productivity. A pair of resistors (5
By trimming and adjusting the other resistance value of 1 and 52) so that the ratio approaches the constant value, the error in the detected voltage due to temperature changes in the internal resistance value of the MOSFET (40) can be reduced for each product. It can be easily canceled out with high accuracy.

(Example) Hereinafter, one example of the present invention will be described with reference to the drawings.
The figure shows an example in which the present invention is applied to a direction indicating device for a vehicle. The direction indicating device includes a set of 7 rough shear lamps 10a connected in parallel so as to blink when the vehicle turns left;
10b, 10e, and a set of 7 lash lamps 10d connected in parallel so as to blink when the vehicle turns right.
10e, 10f, a known oscillation control circuit 20 connected to the DC power supply BI via the ignition switch IG of the M vehicle, and a changeover switch 3 connected between this oscillation control circuit 20 and each of the seven rough shear lamps 10a to 10f.
0 (turn signal switch), this changeover switch 30 is grounded via each of the seven lash lamps 10a to 10c at its fixed contact 31, and connected to each of the seven lash lamps 10d to 10f at its fixed contact 32. It is grounded through. In addition, the changeover contact 3 of the changeover switch 30
3 is cut off from both rotating contacts 31 and 32 in its neutral position, and is closed to the fixed contact 31 (or 32) when switching to the left or right turn direction. It should be noted that since the left and right sets of lamps have the same wattage, the internal resistance values of the seven lash lamps 10a to 10F are the same.

The oscillation control circuit 20 is activated by being supplied with power from the DC power supply B via the ignition switch IG, and the starting terminal 21 of the oscillation control circuit 20 is connected to the changeover switch 30
It is connected to the switching contact 33 of. Thus, the oscillation control circuit 20 starts its oscillation control action in response to the switching contact 33 of the changeover switch 30 being connected to the fixed contact 31 (or 32), and generates a series of control pulses having a predetermined level and a predetermined frequency. A signal is generated from output terminal 22. Also,
The oscillation control circuit 20 receives a detected voltage generated from the semiconductor tube E constituting the main part of the present invention (as described later) at an input terminal 23.
The detected voltage is compared with a reference voltage to notify the presence or absence of an abnormality in each of the seven rough shear lamps 10a to 10''.

The semiconductor chip E is formed by forming a vertical power MO8FET 40 and a voltage dividing circuit 50 in an MO8I structure.
The 8FET 40 has its source 41 connected to a DC power supply B via an ignition switch IG. In addition, the drain 42 of this MO3FET 40 is connected to the selector switch 30.
It is connected to the switching contact 33 of the same MO3FET40.
The gate 43 of is connected to the output terminal 22 of the oscillation control circuit 20. Thus, on date 43, this MO8FET 40 receives a series of control pulse signals from the output terminal 22 of the oscillation control circuit 20 and becomes intermittently conductive.

The voltage divider circuit 50 includes a pair of resistors 51 .
52, and the resistor 51 has a puff at one end.
It is connected to the source 41 of the MO8FET 40, while the other end is connected to the drain 42 of the power MO8FET 40 via a resistor 52. Therefore, the voltage dividing circuit 50
are the source 41 and drain 4 of the power MO3FET 40
The voltage generated between the resistors 51. It is applied to the input terminal 23. However, resistance 5
1 is formed as a P-type semiconductor resistor by uniformly ion-implanting (doping) boron into polycrystalline silicon at a predetermined concentration. In such a case, the predetermined concentration of boron is -
0,148C%/'C) to give the resistor 51 a negative resistance temperature characteristic (,1,0X10"~1,3X10"
The concentration is within the range of g (numbers/cff+').

By the way, how to determine the implantation concentration of boron in the resistor 51 of the semiconductor chip E will be explained below. Let I be the direct current flowing into the semiconductor chip E, Io be the shunt current flowing into the voltage dividing circuit 50, Rs be the resistance value of the resistor 51, and R be the resistance value of the resistor 52 (assumed to be unchangeable with respect to temperature).
Further, if the internal resistance value of the power MO8FET 40 when conducting (hereinafter referred to as ON resistance value) is Ron, then l
o(R8+R)=(I-Io)Ron Therefore, the following holds true. However, Rs+R>>Ron.

Further, if the terminal voltage of the resistor 51 is Vs, the ON resistance Ran of the power MO3FET 40 changes as shown in FIG. It is known that it changes with a positive temperature coefficient, such as the secondary ItIl#iX, which changes at a constant rate of change.

Therefore, in order to keep the coefficient of ■ in equation (2), that is, the current sensitivity a, constant despite changes in the chip temperature t, in other words, when ■ is constant, the terminal voltage Vs must be kept constant. It is understood that in order to maintain the value Rs in equation (2), the resistance value Rs must have at least a negative resistance temperature characteristic (temperature coefficient). In other words, Ro
It is understood that the change due to the positive temperature coefficient of n needs to be canceled out by the negative temperature coefficient of Rs.

However, even if the chip temperature t is the same, the resistance value of the ON resistance value Ron at a certain temperature depends on delicate production conditions.
Since there are variations from production rod to production rod due to differences, the quadratic curve X moves from production rod to production rod in the direction of the arrow shown in FIG. However, a lot means a bundle of products manufactured under substantially the same conditions, and variations between individual products within the same lot can be ignored. Therefore, under a constant current sensitivity a, the range of change in the resistance value R8 of the resistor 51 necessary to maintain the terminal voltage Vs at the same value regardless of the change in the chip temperature t is determined by the change in the chip temperature t. When investigated in relation to
As shown in FIG. 3, both curves Yu.

YI! It was found that the resistance value Rs must be changed within the dark region. *9, Yu and Y in Figure 3! If the value of Rs in the region surrounded by can be arbitrarily set in relation to the chip temperature, the value of α can be made constant between rods even if Ron changes from rod to rod and depending on the temperature. This means that a=However, as can be understood from FIG.
In determining s, the reference value Rs of the resistance value Rs at the reference chip temperature (certain predetermined temperature, for example 25°C)
o and the negative resistance temperature characteristic of the resistance value Rs must be made different for each production rod.In other words, the above-mentioned boron implantation concentration may be changed for each production rod, and the reference value Rso may be trimmed, etc. have to change,
It can be said that such a situation is not suitable for mass production of semiconductor chips E.

Therefore, based on the above study results, we discovered something important.

(1) It goes without saying that the reference value Rso can be easily adjusted by trimming. In addition, such adjustments are
This can also be done by adjusting the resistance value R of the resistor 52 by shimming.

(2) The current sensitivity a does not need to be constant between rods, and even if it differs between rods, such as 'It'2t..., these al, α2... themselves vary depending on the temperature. In other words, as long as it does not have temperature characteristics, by setting the current judgment level in the oscillation control circuit 20 to 11!i! for each rod (for each product), it can be determined whether a predetermined current is flowing or not. It does not interfere with the judgment.

(3) If it is allowed that the current sensitivity a varies from production rod to production rod, the ON resistance value Ron of the power MO8FET40
No matter how it changes in accordance with the change in chip temperature t, the division ratio of the resistor 51 to the resistor 52 with respect to the drain-source voltage of the power MO8FET 40, that is, (Rs/
If R)=1/(N-1) is kept constant, the concentration of boron implanted into the resistor 51, that is, the negative resistance temperature characteristic of the resistor 51, can be made almost the same for all production ports γ, and the terminal voltage Vs can be kept constant. It was discovered that it is possible to maintain the same value. If the boron implantation concentration can be made constant between 071 and 071 in this way, manufacturing becomes extremely easy.

Incidentally, if we substitute Rs/R= 1/(N-1) into equation (2), we get Vs= RonI=ffI...=-
(3) is obtained. Here, in order to keep a constant,
Just change sNs or QRs as Ron changes. Therefore, in order to prevent the a of the rod from changing due to temperature and eliminate the detection error of the terminal voltage Vs,
ON resistance value R at standard chip temperature (e.g. 25°C)
If the value of on is Rono, the sensitivity atS at 25° C. is expressed by the following equation (4), and Rs may be changed so that aSS does not change depending on the temperature.

1 1RonRs RonoI = =a2. ■
・−・−・・(4)NRs+
R In other words, RRon.

R11=...
...(5)NRon-Ron.

All you have to do is make sure that it holds true. Therefore, based on this equation (5), by setting N as a parameter, that is, by changing N, Rs
When we investigated the relationship between and t, we found that (, N
When = 3, the ■ line Zu is obtained, and when N = 2, the song Il
! ZII was obtained. What this figure 4 means is:
As the chip temperature changes and N changes, the value of Rs changes to the fourth value.
If we choose from the figure, the current sensitivity a of the rod can be made constant regardless of the temperature. Also, the curve Z u @ Z
g has the same negative temperature characteristics, and it was found that the boron implantation concentration can be kept constant. Note that the larger N is, the higher the accuracy is, but the sensitivity is lower. Therefore, N should be made as small as possible within the allowable range of the required accuracy.

In addition, in FIG. 4, each straight line Za, Zb is
1Zus Zs is linearly approximated to the same negative resistance temperature coefficient, and the temperature characteristics of the resistance Rs due to actual boron implantation are this linear characteristic, and there is an error by the diagonal line, but it can be ignored. be.

As can be understood from the above explanation, when implanting boron into the resistor 51 of the semiconductor chip E, by allowing the current sensitivity a to vary from production rod to production rod and keeping Rs/R constant, The boron implantation concentration can be made almost the same in all production rods, and mass productivity can be achieved. In addition, the reference value Rso and the resistance value R of the resistance value Rs are:
Trimming can be easily adjusted so that the division ratio with respect to Ron, that is, N=constant.

As a result, the current sensitivity of the product itself varies depending on the produced rod, but this does not pose any problem by adjusting the judgment level on the user side.
Since the current sensitivity of this product does not change due to temperature changes, accurate current detection and current judgment are possible.

In this embodiment configured as described above, if the vehicle is running straight with the ignition switch IQ set to rR, the oscillation control circuit 20 is supplied with power from the DC power source B and is in an operating state, and the q exchange switch is activated. 30 is a switching contact 33
is maintained in a neutral position, and the semiconductor chip E is maintained in a state of being cut off from each of the seven rough shear lamps 10a to 10r. Therefore, even if power is supplied from the DC power supply B to the semiconductor chip E via the ignition switch IG,
Since T40 and the voltage divider circuit 50 are maintained in an ungrounded state, unnecessary current does not flow through the power MO3FET 40 and the voltage divider circuit 50.

In this state, when the vehicle turns left, the changeover switch 30
When the switching contact 33 of
~10c is grounded to start the oscillation control action and generate a series of control pulse signals from the output terminal 22.
It is sequentially applied to the gates of FET40. When the power MO8FET 40 is intermittently turned on in response to each control pulse signal, part of the DC current from the DC power source B flows into the power MO3FET 40 as an intermittent current, and the remaining DC current flows into the power MO3FET 40 as an intermittent current. portion sequentially flows into each resistor 51 and 52 of the voltage dividing circuit 50, and the power MO3FET4
The intermittent current flowing out from the resistor 52 and the intermittent current flowing out from the resistor 52 are combined and flow through the changeover switch 30 into each of the seven lash lamps 10a to 10c.

Thus, each of the seven rough shear lamps 10a to 10e blinks in response to the intermittent merging current, instructing the vehicle to turn left. At this time, the voltage dividing circuit 50 converts the inflow current into a detection voltage V
s from the output terminal 53, but since none of the seven latsier lamps 10a to 10c are disconnected, the oscillation control circuit 20 generates each of the seven latsier lamps 10a to 10c based on the detected voltage from the voltage dividing circuit 50 and the reference voltage. 10c is normal. Note that the reference voltage is applied to the resistor 52.
and the sum of the parallel combined internal resistance values of each of the seven rough shear lamps 10a to 10a.

In such a state, each of the seven lash lamps 10a to 10
When any one of e is disconnected, the parallel combined internal resistance value increases, the detected voltage from the voltage divider circuit 50 increases by m yuan above the reference voltage, and the oscillation control circuit 2 which detected this abnormal voltage
As is well known, abnormality in each of the seven lash lamps 10a to 10c is notified by a change in the number of blinks. Furthermore, even if the breakage of any one of the seven lash lamps 10a to 10c as described above occurs when the chip temperature of the semiconductor chip E is high or low, the concentration of boron implanted into the resistor 51 will be reduced as described above. The setting and trimming adjustment of each resistance value of both resistors 51 and 52 are based on the chip temperature t of power MO8FET40.
Since the change in the ON resistance value is canceled out accurately, the detected voltage from the voltage dividing circuit 50 does not produce an error due to a change in the chip temperature t.

In addition, in the explanation of the operation, the case where the vehicle turns left is explained, but the present invention is not limited to this, and substantially the same operation and effect as when turning left can be achieved also when the vehicle turns right.

Furthermore, in carrying out the present invention, the division ratio, that is, N(>
1) may be modified and implemented as necessary, and
The implantation concentration of boron is 1.0×10”-1.3×1
The implantation may be carried out with appropriate changes within 0.011 (pieces/C-co), and the lower the implantation concentration, the more negative the resistance-temperature characteristic tends to be.

Further, in the above embodiment, an example was explained in which boron was used as the implantation material for the resistor 51, but instead of this, phosphorus could be used as the implantation material and the resistor 51 could be formed as a P-type semiconductor resistance element. Good too.

Furthermore, in implementing the present invention, instead of the resistor 51,
The resistor 52 may be provided with a negative resistance temperature characteristic.

In addition, in the embodiment, each of the 7 rough shear lamps 10
An example in which the present invention is applied to abnormality detection of a to 10f has been described, but the present invention is not limited to this, and the present invention can be applied to current detection in intermittent control of various electrical loads such as intermittent drive control of a motor. It may be applied and implemented.

[Brief explanation of drawings]

Figure 1 is an electric circuit diagram of a vehicle direction indicator to which the present invention is applied, Figure 2 is a graph showing the relationship between ON resistance value Ron and chip temperature t, and Figure ttS3 is a graph showing the current sensitivity of all rods, which is constant. The graph showing the relationship between the resistance value Rs and the chip temperature t for the purpose of
2 is a graph showing the relationship between the resistance value Rs and the chip temperature t when R) is kept constant. Explanation of symbols 10゛a~10f...7 Ratsunya lamp, 20...
Oscillation control circuit (control signal generation means), 40...power MO8FET. 41... Source (input terminal), 42... Drain (output terminal), 43... Date (control terminal), 50... Voltage divider circuit, 51.52... Resistor, E... semiconductor chip.

Claims (3)

[Claims] (1) A pair of resistors (51, 52) and a control terminal (43)
, an input terminal (41) connected to one end of the resistor (51),
and an output terminal (42) connected to the other end of the resistor (52).
MOSFET (40) having
When the ET (40) receives a series of control signals from the control signal generating means (20) at its control terminal (43) and becomes conductive, a portion of the load current flowing into the load flows through the MOSFET (40).
flows from its input terminal (41) into its output terminal (42).
), the remaining part of said load current flows through a pair of resistors (51, 52), and one of these resistors (51, 52) detects the incoming current and connects it to a common terminal with the other resistor. In the current detection device, one of the pair of resistors (51, 52) is made of a material having negative resistance temperature characteristics. A current detection device characterized in that the current detection device is configured to have a shape. (2) The current according to claim 1, characterized in that one of the pair of resistors (51, 52) is formed by ion-implanting boron or phosphorus into a polycrystalline silicon resistance material. Detection device. (3) The boron or phosphorus ion implantation concentration is determined and the trimming is adjusted so that the ratio of the resistance values of the pair of resistors (51, 52) is approximately constant for each product rod. A current detection device according to claim 2.