JPH01294963A - Temperature compensating system for current limiting circuit - Google Patents

Abstract

PURPOSE:To obtain a temperature compensating system excellent in cost performance by supplying emitter voltage of an output power transistor to the base of a current limiting transistor through a positive characteristic resistor element and correcting a current amplification factor for its fluctuation due to a temperature. CONSTITUTION:A negative characteristic resistor element and a positive characteristic resistor element are used in combination serving as a temperature compensating element for a current limiting circuit in an ignition device. That is, the positive characteristic resistor element 12 of large temperature coefficient is connected in series between the base of a transistor 3 and a connection point connecting an output current detecting resistor 6 to the emitter of an output power transistor 2, and a fluctuation of a current amplification factor is corrected. While between the base and the earth, a series-parallel circuit, in which an ordinary resistor 5 is connected in series to a parallel circuit of the negative characteristic resistor element 11 and an ordinary resistor 4, is connected, and a fluctuation of between base-emitter voltage is corrected. In this way, a temperature compensating system for a current limiting circuit excellent in cost performance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to a temperature compensation system for a current control circuit in an ignition device for an internal combustion engine.

[Prior art]

Conventionally, as a technology in this kind of field, Japanese Patent Application Laid-Open No. 51-92
There are some methods disclosed in JP-A-933, JP-A-52-114833, JP-A-53-11242, JP-A-54-25336 and JP-A-54-30328. When the primary current exceeds a certain value, it is limited to that certain value to protect the output power transistor and to keep the energy stored in the ignition coil constant.

FIG. 6 is a circuit diagram showing an example of a circuit configuration of an internal combustion engine equipped with a conventional current limiting circuit, and FIG. 3 shows input/output 1! in FIG. Shows the flow waveform.

In Figure 6, 1 is a resistor, 2 is an output power transistor, 3 is a transistor, 4, 5.6 is a resistor, 7 is an ignition driver, 8 is a battery, 9 is a spark plug, and 10 is a current limiting circuit. .

In FIG. 6, when a base current I is applied to the input terminal IT as an input of the output power transistor 2 for a time TON, the collector current Ic gradually increases to a -constant value ■. When reaching L, transistor 3, resistor 4, resistor 5 and resistor 6
The current limiting circuit 10 configured by the above operates, and thereafter the collector current of the output power transistor 2 becomes {circle over (2)}. is limited to the certain limit value ICL.

This fixed limit value rct is mainly determined by the base-emitter voltage V□ of the transistor 3 and the current amplification factor. As shown in FIG. 7, it varies depending on the temperature. In other words, the collector current limit value I (L is 2.6 at a temperature range of 150°C)
It fluctuates by about A.

As a method of correcting the temperature characteristics of the base-emitter voltage V□, a measure is taken in which a thermistor, which is a negative characteristic resistance element, is connected between the base of the transistor 3 and ground to correct the voltage applied to the base. These circuits and the above constant value I. An example of the temperature characteristics of L (limit value) is shown in Figure 8(a).
(b) and 0 shown in FIGS. 9(a) and (b),
Reference numeral 11 indicates a thermistor which is the negative characteristic resistance element. The base-emitter voltage vllllL of the transistor has a negative characteristic, and its value decreases at high temperatures. Therefore, the voltage detected by the resistor 6, which is a resistor for detecting the output current, is divided by the resistor 5, which is a resistor with a small temperature coefficient, and the thermistor 11, which is a negative characteristic resistance element, and is supplied to the base of the transistor 30. It performs temperature compensation for voltage (2).

[Problem to be solved by the invention]

In the current-limited ignition device configured as described above, it is desirable that the fluctuation range of the current limit value ICL be smaller in order to keep the stored energy of the ignition coil substantially constant. However, in any of the above conventional methods, the resistance value of the thermistor 11 changes logarithmically with respect to the base-emitter voltage VO whose temperature characteristics change linearly, so the current limit value ICL is kept constant. There was a problem in that the fluctuation range was about 0.8 to 1.3 A in a temperature range of 150°C.

Furthermore, since the base current is not corrected, there is a problem that the current amplification factor h□ varies with temperature.

The present invention has been made in view of the above points, and is a temperature compensation method for a current limiting circuit that eliminates the drawback that the temperature fluctuation range of the current limiting value of the current limiting circuit using the thermistor is large and has excellent cost performance. Our goal is to provide the following.

[Means to solve the problem]

In order to solve the above problems, the present invention uses a combination of a negative characteristic resistance element and a positive characteristic resistance element as a temperature compensation element of a current limiting circuit in an ignition device, and compensates for the temperature characteristic of the base-emitter voltage V□ of the transistor 3 and Amplification factor hF
! As shown in Fig. 1, a positive characteristic resistance element 12 with a large temperature coefficient is connected to the connection point of the base of the transistor 3, the resistor 6 for output current detection, and the emitter of the output power transistor 2. A normal resistor 5 is connected in series between the base and ground to compensate for fluctuations in the current amplification factor, and a normal resistor 5 is connected in series between the base and the ground in a parallel circuit of the negative characteristic resistance element 11 and the normal resistor 4. Connect the connected series-parallel circuits to obtain the base-emitter voltage vll! This is to correct for fluctuations in .

[Effect]

With the above configuration, since the emitter voltage of the output power transistor 2 is supplied to the base of the transistor 3 via the positive characteristic resistance element, it is possible to correct the current amplification factor for temperature, and also to connect the base to the ground. A series-parallel circuit consisting of a resistor 5, a negative characteristic resistance element 11, and a resistor 4 is connected, and the emitter voltage is divided by the positive characteristic resistance element 12 and the series-parallel circuit and supplied to the base of the transistor 3. - Fluctuations in the emitter voltage vIlK with respect to temperature can also be corrected.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing a circuit configuration of an ignition device to which a temperature compensation method of a current limiting circuit according to the present invention is applied. In the same figure, 1 is a resistor, 2 is an output power transistor, and 3 is a resistor.
is a transistor that shunts the base current d of the output power transistor 2, 4.5.6 is a resistor, 7 is an ignition plug, 8 is a battery, 9 is a spark plug, 10 is a current limiting circuit, and 11 is a negative characteristic resistor. Element 12 is a positive characteristic resistance element.

The collector of the output power transistor 2 is connected to one terminal of the ignition coil 7 via the output terminal OT, and the child terminal of the ignition coil 7 is connected to the child terminal of the battery 8. The secondary winding output terminal HV of the ignition filter 7 is connected to the ignition plug 9, and when the input signal is cut off again after the input signal has been applied, the ignition plug 9 discharges and generates a spark.

The resistor 6 is connected to the collector current of the output power transistor 2 (
This is a resistor for detecting the output (M, current) and is connected between the emitter and ground. A positive characteristic resistance element 12 is connected in series between the emitter of output power transistor 2 and the base of transistor 3. Further, a negative characteristic resistance element 11 and a resistor 4 are connected between the base of the transistor 3 and the ground.
A parallel circuit of resistor 5 and a series circuit of resistor 5 are connected.

The operation of the current limiting circuit 10 having the above configuration will be explained using FIG. 2. In the figure, Q represents the output power transistor, Ql represents the transistor 3, R3 represents the resistance of the resistor 6, RP represents the resistance of the positive characteristic resistance element 12, and R8 represents the resistance of the resistor 6.
is the resistance of the negative characteristic resistance element 11, RA is the resistance of the resistor 5,
R3 indicates the resistance of the resistor 4, respectively.

Input terminal I? When an input current I having a current waveform shown in FIG. 3(b) is applied to the output terminal OT, a current Ic flows through the collector which gradually increases as shown in FIG. 3(a). On the other hand, the emitter voltage vSI of the output power transistor Q1 is the product of the resistance value R5 and the collector current Ic, and its waveform is shown in FIG. 3(a).
The waveform becomes a gradually increasing waveform similar to the waveform of the collector current Ic.

The emitter voltage VS+ is divided by resistors Rp, RA, R1, and RN and applied to the base of the transistor Q. Letting this applied voltage be vsl, the following equation is obtained. Here, the resistance value R5 is about 0.1 to 0.2 [Ω], and the value of the composite voltage dividing resistor connected in parallel to this resistance value R3 is 104.
RS CΩ], the resistance value R3 can be omitted from the following equation.

vst"'vs+・[(RA+〈RN-R-/(RN+
RIl))/(Rp"RA"(Rs-Ri)/(RN"
Re) ) :] ...(1) In formula (1), RA+RN-R3/(RN+R11)=Ro...(
2), equation (1) can be rearranged into equation (3).

Vs*=Vs+ −Rc/ (RP”RC)
...(3) Vsx is the base-emitter voltage vll of transistor Q! , the transistor Q, becomes conductive and the base current rs+ flowing through the output power transistor Q, decreases by the current II+1 which is shunted into the transistor Q,. When the base current 1111 decreases, the collector-emitter voltage VCt of the output power transistor Q1 increases, and the collector current becomes ■. is constant. That is, it operates so that the emitter voltage vSl remains constant.

This constant current region is the collector current I in FIG. 3(a). This is the time t3 portion of the waveform. In this way, the current limiting circuit 1
0 is configured as a closed loop between the base and emitter of the output power transistor Q, and if the temperature characteristics of the transistor Q can be easily compensated for, the circuit can have a small number of parts and have excellent cost performance.

In general, the base-emitter voltage of a transistor is V! lt
is approximately 0.78V (25°C)-C"-2~2.2m
It is well known that the temperature characteristic is V/'C. −
On the other hand, the maximum temperature coefficient of positive characteristic resistance elements is currently 5000pp.
m types have been manufactured, and the change in resistance value with temperature is approximately linear as shown in FIG. 4(b). Further, the temperature change of the negative characteristic resistance element is a logarithmic value as shown in FIG. 4(a).

Next, to show an example of setting each constant of the present invention, in FIG. 2, the emitter voltage V S of the output power transistor Q1
I is about IV, collector current ■. To set the limit value ■cL to 7A, RS = V s+/I CLΦ0.1
It may be set to 5 [Ω].

Assuming that the value of the combined resistance connected in parallel with the resistor R3 is about 10@4 ·R3 as described above, it is tentatively set in the range of 800 to 1500 Ω. Since the resistance R8 of the negative characteristic resistance element 11 has a large resistance value at low temperatures, the reference resistance value at 25° C. is set as low as possible. However, the resistance value at high temperatures should not suddenly drop to 0 [Ω]. In this example, 200
[Ω] (25°C). By specifying the resistance RN of the negative characteristic resistance element 11, the resistance value within the compensation temperature range can be calculated or estimated from a graph. As shown in FIG. 4(a), the resistance R of this negative characteristic resistance element 11 is 1200 [Ω].
(-30°C) to 12 [Ω) (120°C), so the high temperature side correction resistance RA (resistance of resistor 5) is connected in series with the low temperature side correction resistance R, (resistance of resistor 4). Connect in parallel.

Next, the resistor R4 of the positive characteristic resistance element 12 is set to the emitter voltage V
51, collector current I. The limit value I. , the current amplification factor of the output power transistor Q, and the transistor Q,
Calculate and set the current amplification factor h□ and other characteristics. In this example, 240 [Ω] (25°C), temperature coefficient +45
By selecting 00ppm, the resistance RP of the positive characteristic resistance element 12 is
By specifying , the resistance value within the compensation temperature range can be calculated.

Here, the following equation is obtained from the above equation (3).

Rc= (Vsz/ (Vst-Vst)) ・Rp
・= 44) Furthermore, Vs*=Vst(Qt)
and obtain the following expression.

RC= (Vllt(Qt)/(Vst-Vllt(Q
z) ) -RP - (s) In equation (5), the base-emitter voltage V of the transistor Q. (Q, ) and the value at each temperature within the temperature compensation range of the resistance R2 of the positive characteristic resistance element 12, the resistance value of the combined resistance R6
This means that it is possible to calculate After calculating the resistance value R6, (2)
Calculate and set RA and R from the formula. Output power transistor Q and transistor Q selected for Kira! Each constant is corrected according to the characteristics of

An example of each resistance value set and calculated as described above is shown below.

Rs: 0.15, R: 240Ω (+4500p
pm), R: 200Ω, RA: 430Ω, RB near 50Ω.

FIG. 5 shows the collector current I in the circuit of FIG. 1 having each resistance value set and calculated as described above. It is a diagram showing the fluctuation state of the limit value IcL, and as is clear from the figure, the limit value ■. It can be seen that the fluctuation width of L is about 0.3 A in a temperature range of 150°C, which is a significant improvement compared to the conventional temperature compensation method.

As described above, according to this embodiment, the transistor 3 (Q
The emitter voltage (VS, ) of the power transistor 2 is output as the voltage supplied to the base of the positive characteristic resistance element 12 (
RP) and the negative characteristic resistance element 11 (RN) are combined to divide the voltage and supply it, and to compensate for the temperature of the base-emitter voltage v0, the temperature change of the base-emitter voltage VB1 is more closely approximated than in the conventional example. It becomes possible to do so.

As a result, when this embodiment is applied to a current-limiting type ignition device, the current limit value becomes substantially constant over substantially the entire temperature range, and it is expected that the ignition energy will be stabilized. This is shown in Figure 7 (without compensation element), Figures 8 and 9 (with negative characteristic resistance element), and Figure 5 (in this example).
Each collector N, flow■. This is also clear from the fluctuation state of the limit value IcL.

Further, in the above embodiment, the current limiting circuit of an ignition device for an internal combustion engine was explained as an example, but the temperature compensation method of the current limiting circuit according to the present invention is not limited to this, and the inductive load such as a solenoid is It can also be applied to a drive circuit driven by an output power transistor.

〔Effect of the invention〕

As explained above, according to the present invention, the following excellent effects can be obtained.

■Since the emitter voltage of the output power transistor detected by the output current detection resistor is supplied to the base of the current limiting transistor via the positive characteristic resistance element, it is possible to correct temperature-related fluctuations in the current amplification factor. Fluctuations in the limited current due to fluctuations in the current amplification factor are reduced.

■A resistor circuit equipped with a negative characteristic resistance element is connected between the base and ground, and the emitter voltage is divided by the positive characteristic resistance element and the resistor circuit and supplied to the base of the current limiting transistor, so the temperature of the base-emitter voltage This makes it possible to correct fluctuations in the limit i current due to fluctuations in the base-emitter voltage.

(2) Furthermore, since the temperature compensation described above can be realized by a combination of a positive characteristic resistance element, a negative characteristic resistance element, and a normal resistor, the cost is extremely low.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the circuit configuration of an ignition device to which the temperature compensation method of the current limiting circuit according to the present invention is applied, and FIG.
Circuit diagram for explaining the operation of the current limiting circuit shown in Figure 3.
Figure 4 (a) shows the collector current waveform of the output power transistor, Figure 4 (b) shows the input current waveform, and Figure 4 (a) shows the temperature characteristics of the negative characteristic resistance element. (b) is a diagram showing the temperature characteristics of the positive characteristic resistance element, and FIG. 5 is the limit value I of the collector current of this embodiment. , FIG. 6 is a circuit diagram showing an example of a circuit configuration in an ignition system for an internal combustion engine equipped with a conventional current control circuit, and FIG. Limit value I. A diagram showing the fluctuation state of L, FIG. 8(a) shows the conventional 1! a circuit diagram showing another circuit configuration example of an ignition device for an internal combustion engine including a flow control circuit;
9(b) is a diagram showing the fluctuation state of the collector current limit value ICL by this current limiting circuit, and FIG. 9(a) is an example of the circuit configuration of an ignition system required for an internal combustion engine equipped with a conventional current control circuit. FIG. 2B is a circuit diagram showing the fluctuation state of the collector current limit value ICL by this current limiting circuit. In the figure, 1...Resistor, 2...Output power transistor, 3...Transistor, 4...Resistor,
5...Resistor, 6...Resistor, 7...Ignition coil, 8...Battery, 9...Ignition plug, 10...
...Current limiting circuit, 11...Negative characteristic resistance element, 1
2...Positive characteristic resistance element. , 1. v: η 訃f 嶽 dissection cycle L intestine 7 zo human long summer 1 figure 2 figure 2 night shift 1 power ax i tool plow, zo, NJ(λ) ra r'(: ) (b) Figure 8

Claims (3)

[Claims] (1) An output current detection resistor is connected between the emitter of the output power transistor and ground, and the collector is connected to the base of the output power transistor, and when the voltage detected by the output current detection resistor exceeds a predetermined value, In a current limiting circuit comprising a current limiting transistor that operates to shunt the base current of the output power transistor to limit the output current of the output power transistor to a certain value or less, the output current is detected by the output current detection resistor. A temperature compensation method for a current limiting circuit, characterized in that the emitter voltage of the output power transistor is supplied to the base of the current limiting transistor via a positive characteristic resistance element to correct temperature-induced fluctuations in current amplification factor. (2) Claim (1) characterized in that a resistance circuit including a negative characteristic resistance element is connected between the base of the current limiting transistor and the ground to correct variations in the base-emitter voltage due to temperature. Temperature compensation scheme for the current limiting circuit described. (3) The current limiting circuit according to claim (2), wherein the resistance circuit comprises a series-parallel circuit in which a normal resistance is connected in series to a parallel circuit of a negative characteristic resistance element and a normal resistance. Temperature compensation method.