JPS603162B2 - Electric shutter device for cameras, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized by an electric shutter circuit used in a camera or the like, particularly a turtle current conversion circuit.

An example of the current conversion circuit in this type of electric shutter circuit is shown in FIG. 1, which outputs an electric signal from the adjustment output section 1 according to the film sensitivity value and the certified aperture value, and outputs an electric signal from the photodiode SBC. The electric signal output corresponding to the brightness of the subject sensed by the neck 9 optical calculation circuit A is calculated, and the total output is used as control information to be sent to the transistor T2.
, and the transistor T2 is given a fin flow l according to the information.
The collector current lo of the transistor T2 is converted into a current lc by a current conversion circuit consisting of PNP transistors T3 and T4, and the integrating capacitor C is charged with the current lc. , when the voltage between the terminals due to the charging of the capacitor CT rises to a certain value from the start of the timing operation by opening the timing switch S, this is sensed and the switching circuit A2 operates to determine the timing for determining the timing value. It is arranged to drive a magnet M which is converted into a mechanical signal. Therefore, when attempting to integrate such an electric shatter circuit, particularly the turtle current conversion circuit, in such a conventional electric shatter circuit,
The following drawbacks arise due to the PNP transistor due to lq.

That is, first of all, the current amplification factor (grounded emitter) hfe of the PNP transistor is low (characteristic curve 1 in Figure 3, shown).
.

For that, the current is 1. The conversion current lc of transistor T4
This is likely to be affected by the base current. Now, lo=183
10lc3 184...[1}IC=hfe401
84......'21 Then, if the characteristics of transistors T3 and L are equal, lc3=lc, IB3; IB4,
hfe3 ni h to 4......Since it is a glue, the above formula {11 is 1.

i Agriculture + 1C Ten Beard. ．． ．． ．． ．． ．． ．． ．． ．． '41 and lo
h to IC = 10h word e = h seat house 32-10...
...{5}.

Therefore, in order for the converted current lc to be proportional to the current lo,
It is necessary that the height of the conversion element in the current conversion circuit is as high as possible.

This means that, for example, the timing value can be changed from 1/2000 sec to S
If you want to change the current to about ec, it is necessary to change the current lc from lmA to about 10A, and in the PNP transistor shown in the characteristic curve 1 in Figure 3, hfe = 10 when lc is 10A. , h The previous proof 5' formula is lc = h
Persimmon: 32・lo=0.89o.

In lc = 100 mountains A, hfe = spots, so the above [5
} From the formula, lc=0.97, etc., and the converted current lc does not change in proportion to the current lo. Next, when the collector current outside the PNP transistor becomes large, the linearity of the lc-VBE characteristic becomes sharper (the part shown by the dotted line in FIG. 34). As shown in the figure, for example, when lc=30 peaks A, the linearity deteriorates, so if the characteristics of transistors T3 and T4 are slightly different, as the current increases, the currents lo and lc will no longer be proportional. In reality, when lc=lmA, there is a lot of error and it is practically used.
As a result, it becomes impossible to integrate a circuit using this type of transistor into an IC. SUMMARY OF THE INVENTION An object of the present invention is to provide an electric shutter device for a camera or the like that can solve the above-mentioned problems.

In order to achieve the above purpose,
The electric shutter device in a camera or the like according to the present invention has N
a bias circuit T31 of the Darlington connection circuit consisting of a first Darlington connection circuit in which the collector of a PNP transistor T32 is connected to the base of the PN transistor T42; and a diode connection transistor connected between the base and emitter of the PNP transistor T32; and,
The spotlight calculation circuit [S8CA,] and the bias circuit T3
1 and whose cathode is connected in series with the transistor T42.
The diode T41 connected to the emitter and the output voltage of the side light calculation circuit [to SBC] are connected to the base, and the collector current l is connected to the bias circuit T31 and the Darlington connection circuit according to the brightness of the subject.
o, and a PNP transistor T34 in a circuit equivalent to the Darlington connection circuit.
a second Darlington connection circuit in which the base and emitter of the NPN transistor T44 are connected to the bias circuit T31 and the base of the NPN transistor T44 is connected to the collector of the PNP transistor T34;
and an integrating capacitor CT connected between the emitter of the NPN transistor T2 and the emitter of the NPN transistor T2, and is configured to supply a charging current lc proportional to the current lo to the integrating capacitor CT. According to the above configuration, the current according to the brightness of the subject is N with good linearity.
Supplied to the PN transistor. The linearity is then improved by connecting the collector of the NPN transistor to the base of the NPN transistor. When a current corresponding to the brightness of the subject is passed through a PNP transistor, P
Since the NP transistor has a low h-value, the problem of loss of linearity can be completely solved.

The illustrated embodiment will be described in detail below.

In the implementation circuit of the device of the present invention shown in the second figure, the conventional first
Circuit elements and functional parts common to the illustrated circuit are given the same symbols, and other currents 1 according to control information.

The circuit that allows the flow of
32 and a Darlington connection circuit consisting of an NPN transistor T42, which receives control input from the midpoint of the direct connection circuit, and a Darlington connection circuit consisting of a PNP transistor T33 and an NPN transistor T43 through which a conversion current lc flows. The circuit is connected in parallel to a Darlington connection circuit consisting of a PNP transistor T34 and an NPN transistor T44, both of which are configured to receive control input from the midpoint.
In the device of the present invention having such a configuration, during operation, the current lo according to the control information is 10=1C42+1C3
21,832, IC31, 1,831...・．． ... [6
1. Also, the converted current lc is 1C 2 1C44 1C34 1C43 1C33 .
．． ．． ．． ．． ．． ．． ．． ．． ■If the characteristics of the PNP transistors are equal to each other and the characteristics of the NPN transistors are also equal to each other, then hfe42=hfe43=h44hihfe4 Equivalent lc3・=lc32=lc33kolc3
4...equivalent to lc8...[1 leg = 1832; IB33:
IB34 three 1B3 equivalent = Kenno 1C42 = 1C43:1C
443 IC4 equivalent number Also, , C3 = Constitution... side, so [6', '7', '8', ■From the formula, lc
=2(lc30lc4)=21.

・[(lc4×lc3)/kuIC4×21C3×21
&)]=2L・[(h-ship 11)/(hfe4-12-2/
hfe3)] ......OU, h
If fe4>>2, lc is proportional to lo. For example, when lc=10A, hfe=
70 (Characteristic curve 12 shown in Figure 3), the above (
11) Equation is lc = 0.972 x lolc = 100 μA, hfe4 = 170, so from equation (11) above, 1
.

=0. Pollination×2L, which indicates that the proportional relationship between the mother flow lo and lc in the device of the present invention is greatly improved compared to the relationship between the fin flow lo and lc in the conventional device.

Moreover, PNP transistors T13, T32 . T33 and T
Since the current flowing through 34 is equivalent to a poisonous enemy in the conventional device, the current flowing outside the PNP transistor even when IC = 1M is the same as the current flowing through the PNP transistor is hfe4 = 200 (atlc4 = 500 mountain A), and lc3 = 2.5 μA. As a result, a relatively small current flows through the PNP transistor outer coil of the present invention, so that in this small current range, the linearity of the VB8-LC characteristic is maintained as shown in Fig. 4. Therefore, the device of the present invention can improve the disturbance in the proportional relationship between the currents lo and lc due to the non-linear characteristics of the PNP transistor in the slave device.

In this way, the present device is capable of extremely improving the conversion characteristics of the current conversion circuit in conventional mounting, and is fully applicable to the conversion of this circuit into an IC. By inserting the converter, the converted current can be easily detected, and it also has the secondary effect of being easily attached to the current limiting section.

Brief Description of the Drawings Fig. 1 is a circuit diagram showing an example of a current conversion circuit in a conventional electric shirtter circuit, Fig. 2 is a circuit diagram showing an embodiment of the present invention Fukurotaka, and Fig. 3 is a circuit diagram showing an example of a current conversion circuit in a conventional electric shirtter circuit.
Transistor h-sasa characteristic diagram, Figure 4 is PNP and NPN
FIG. 3 is a characteristic diagram of the VB terminal 1c of a transistor.

T, ~44...transistor or diode,
SBC...Photodiode, CT...
・Capacitor for time setting, R...Load resistance, N...Leakage light calculation circuit, A2...Switching circuit, M...Magnet, 1...Current according to control information, lc・
...Conversion current. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A first Darlington connection circuit in which the collector of the PNP transistor T32 is connected to the base of the NPN transistor T42;
Bias circuit T3 of the Darlington connection circuit consisting of a diode-connected transistor connected between emitters
1, a photometric calculation circuit [SBCA_1], and a diode T41 which is connected in series with the bias circuit T31 and whose cathode is connected to the emitter of the transistor T42.
and an NPN transistor T_2 whose base is connected to the output voltage of the photometric calculation circuit [SBCA_1], and whose collector supplies a collector current I_o according to the brightness of the subject to the bias circuit T31 and the Darlington connection circuit.
and a second Darlington connection circuit, which is a circuit equivalent to the Darlington connection circuit, in which the base and emitter of the PNP transistor T34 are connected to the bias circuit T31, and the base of the NPN transistor T44 is connected to the collector of the PNP transistor T34. and an integrating capacitor C connected between the emitter of the NPN transistor T44 and the emitter of the NPN transistor T_2.
T, and the current I_ to the integrating capacitor CT.
An electric shutter device for a camera or the like configured to supply a charging current I_c proportional to o.