JPS60189520A - Power supply device - Google Patents

Abstract

PURPOSE:To obtain a simple and inexpensive power supply device for a camera, etc. without using an expensive FET by connecting a bipolar transistor in parallel to a resistance with a voltage stabilized circuit consisting of a resistance and a capacitor. CONSTITUTION:When a switch S1 is turned on before a capacitor 102 is charged, a current flows to the base of a bipolar transistor TR104 via a resistance 103. Thus the TR104 is turned on and the current given from a battery 91 is applied to the capcitor 102 through the TR104. Then the capacitor 102 is charged quickly. When the charging voltage of the capacitor 102 reaches a prescribed level, the base-emitter voltage of the TR104 is dropped. Then the TR104 is turned off and the stable voltage is applied to a part 94a where the voltage stabilization is needed from the capacitor 102. Furthermore no external pin is needed unlike a circuit using an FET. This facilitate the easy conversion of this power supply device into an IC.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a stabilized power supply device using a capacitor. Conventional technology For example, as a distance measuring device for a camera system, a pulsed light is emitted from a projector at the target tree, and its reciprocal beam is used to measure the distance between the target tree, the bulge, and the armpit. 1. There is a known method that determines in which zone the distance of the subject from the camera is located based on the ratio of the tatami pot output. In this type of distance measuring device, there is a part in the distance measuring circuit that requires a voltage stabilized power supply, and a stable voltage must be supplied to this part even against fluctuations in the power supply voltage when the above-mentioned projector emits light. Must be. FIG. 1 shows an example of a conventional power supply device for this type of purpose, in which 91 is a power source, 92 is a light emitting diode that is lit in pulses during distance measurement, 93 is a transistor that turns on and off the light emitting diode 92, and 94 is a distance measuring circuit, 94a is a part that requires voltage stabilization, and 94b is a part that does not particularly require voltage stabilization. 95 is a switch for instructing the start of distance measurement; 96 is a FET (field effect transistor); 9
7 is a capacitor for voltage stabilization. transistor 9
3 is applied to the date of FET 96, which is turned on when switch 95 is turned on, charging capacitor 97 and providing a regulated voltage to section 94a, while transistor 93 When the light emission start signal is applied to the light emitting diode 92, the FET 96 is turned off, so that the voltage drop of the battery 91 due to the current flowing through the light emitting diode 92 does not affect the portion 94a. However, since the above-mentioned circuit uses an expensive FET, there is a problem in that the cost of the distance measuring device increases. Also, when converting this type of distance measuring device into an IC, F
Since the ET is an external circuit, it requires pins on the IC board for external use of the FET, which causes various problems such as an increase in the cost of the board, an increase in the space required, and an increase in the defective rate. Purpose of the Invention The present invention was made to solve the various problems mentioned above, and its object is to provide a power supply device that is inexpensive, has a simple configuration, and can rapidly output a stabilized voltage. It is. In FIG. 2 of the embodiment, 91 is a power supply, and 94 is a distance measuring circuit. The capacitor 102 for voltage stabilization is connected to the battery 91 via the resistor 101 and a switch S1 that is turned on at the start of distance measurement, and the connection point between the resistor 101 and the capacitor 102 is a part 94a where a stabilizing voltage is required. It is connected to the. The collector and emitter of a transistor 104 are connected in parallel to the resistor 101, and the base of the transistor 104 is connected to the connection point between the switch S1 and the resistor 101 via a resistor 103. In the above configuration, when the switch S1, in which the capacitor 102 is not charged, is turned on, the transistor 1
Current flows into the base of 04 through resistor 103, turning on transistor 104 (1), current from battery 91 is applied to capacitor 102 through transistor 104, and capacitor 102 is rapidly charged. . When the charging voltage of the capacitor 102 reaches a predetermined value, the voltage between the base and emitter of the transistor 104 drops, and the transistor 104 is turned off. As a result, a stabilized voltage is supplied from the capacitor 102 to the portion 94a. When converting this circuit into an IC, the transistor 104 is also integrated into an IC, so there is no need to provide external pins as in conventional circuits using FETs.
Since no ET is used, the stabilized power supply can be constructed at low cost. Hereinafter, the case where the present invention is used in the distance measuring device will be explained in more detail. First, the principle of distance measurement will be explained with reference to FIGS. 3 and 4. Light emitted from the distance measuring light emitting element 1 passes through a projection lens 3 and is projected onto a subject 6. The light reflected on the subject 6 is focused by the light receiving lens 4, passes through a filter 5 for cutting harmful light, and is imaged onto two light receiving elements 2a and 2b arranged in parallel. FIG. 4 shows an image of the light emitting element 1 on the light receiving elements 2a, 21+. FIG. 4 shows reflected light from a distance R2. In this case, the same amount of light enters the light receiving elements 2a and 2b. The reflected light from the distance R, which is closer than R2, enters the light receiving element 2b in a larger amount than the light receiving element 2a, and the reflected light from the distance R3, which is farther than R2, enters the light receiving element 2a.
More light enters than b. As can be seen from FIGS. 5 and 6, the light receiving elements 2a and 2b enter the light receiving elements 2a and 2b.
The outputs of the light-receiving element 2b and 2b become equal at the distance R2, and at a distance closer than R2, the output of the light-receiving element 2b is P2a>light-receiving power, 8° 8°, 2. -78 Map P2a/P2b 1 becomes smaller as the object approaches distance R2, and at distances farther than R2, P2b < P2a, and the ratio P2a/P2b becomes larger as the distance becomes farther from R2. Therefore, by detecting the ratio P2a/P2b of the outputs of the light receiving elements 2a and 2b, the distance Rx of the subject 6 can be known. FIG. 7 shows the output ratio of the light receiving elements 2a and 2b. As can be seen in Fig. 7, the output ratio P of the light receiving elements 2a and 2b
2a/P2b monotonically decreases nearer than distance R2, R2
It increases monotonically on the far side. Therefore, the subject distance is divided into zones based on the depth of field determined by the camera's photographic lens, and the distance at the dividing point is calculated based on the value of the output ratio of the corresponding light receiving elements 2a and 2b and the actual distance measurement. The ratio of the resulting light receiving elements 2a and 2b can be obtained using the body distance as a zone output. For example, suppose that the subject 6 is located at a distance Rx between R2 and R3 in FIG. In this case, a little more of the reflected light from the subject 6 is incident on the light receiving element 2a than on the light receiving element 2b. Therefore, the tjSV diagram shows the output ratio between the distances R2 and R1, and it can be seen that the subject 6 exists in the comparison zone III as described above. Next, the distance measuring circuit will be explained. In Fig. 8, switch S1 is activated in conjunction with pressing the shutter button of the camera.
is turned on. When the switch 5ION is turned on, the first quick charging circuit 11 that rapidly charges the capacitor 102 of the stabilized power supply 10 operates, and the stabilized voltage Veal rises. Timer 24 is started with switch 5ION, and switch 5I is started.
Rapid charging from timer 24 after time t1 has passed since ON
The signal 51 becomes H", the second quick charging circuit 12 is activated, and the first photometric circuit 13 and second photometric circuit 14 are rapidly stabilized. This continues until time t2, and after t2, the quick charging circuit 12 is activated.
The K times signal 1 becomes "L" and the second quick charging circuit 12 is turned off. Next, after t3 has passed since the switch 5ION is turned on, the distance measurement enable signal 52 is sent from the timer 24 to the light emission control circuit 25.
The light emitting pulse 53 is output, and the light emitting element 1 is pulse-lit. This light pulse is projected onto the subject 6,
The reflected light from the subject 6 enters the light receiving elements 2b and 2a. The light receiving elements 2b and 2a output photocurrent according to the subject distance according to the above-mentioned principle to the first photometry circuit 1.
3. It is input to the second photometric circuit 14. Each of the photometric circuits 13 and 14 outputs the photocurrent input from the light receiving elements 2b and 2a as a logarithmically compressed value. The output 61 of the first photometric circuit 13 and the output 62 of the second photometric circuit 14 are input to the difference amplification circuit 15, and one is subtracted from the other. This means that the difference in the logarithmically compressed outputs, that is, the ratio P2a/P2b of the outputs of the light receiving elements 2b and 2a, is calculated. Therefore, the output 63 of the difference amplification circuit 15 is the fourth
The output corresponds to the ratio of the light receiving element output shown in the figure. The output 61 of the first photometering circuit 13 is also used for infinity determination when the distance to the subject is far and there is little reflected light, and distance measurement is not possible. It is also used to control light emission below. The output 63 of the difference increasing circuit 15, that is, the light receiving element 2b. The output ratio of 2a is input to the zone discrimination circuit 18, and according to the magnitude of the output ratio, it is discriminated in which zone the subject 6 is located, and stored in the zone memory circuit 20. This storage is performed under timing control by a distance measurement memory signal 54 synchronized with the light emission pulse 53. The memorized zone signal 59 is sent to the decoder 21, where it is decoded into first and second zone signals 64 and 65 that are sent to the camera control unit, and a third zone signal 66 for stopping the camera lens in a predetermined position. Ru. On the other hand, after the distance measurement is completed, by further pressing the camera's shutter button, the camera's photographing lens (not shown)
starts running, and as the lens moves, a lens position signal 56 indicating the lens position is input to the lens position input circuit 19. This output 60 and the zone signal 66 are compared by the lens stop circuit 22, and if they match, the IN brick/mage 1. turn off and stop the lens. Next, a specific example of the above-mentioned circuit will be explained. FIG. 10 shows the bias circuit 27 and the first quick charging circuit 11 in the block diagram of FIG. Second quick charging circuit 12゜First photometry circuit 13
．． Second photometric circuit 14. The ω determination circuit 16 is shown. Further, FIG. 11 shows each waveform and time chart. First, the switch S1 is turned on in conjunction with pressing the shutter button. Vcc2 is a power supply that immediately reaches the power supply voltage at 5 ION. Vcc is resistance 1
01 and a capacitor 102, the power supply is stabilized against power fluctuations. Vcc is a circuit that must not be affected by power supply fluctuations, especially power supply fluctuations during pulse lighting of the light projecting means during distance measurement;
In other words, the bias circuit 27. First and second photometric circuit 13.1
It is used as a power source for 4. The first quick charging circuit 11 is a circuit for accelerating the rise of Vcc+. Its configuration consists of an NPN (NPN) transistor 104 whose collector is connected to Vcc2 and whose emitter is connected to Vcc, the base of the transistor 1α4, and the
c2 and a resistor 103 connected between them. When switch S1 is turned on, Vcc. = OV Considering the case where there is no charge in the main capacitor 102, the transistor 10 is connected from Vcc2 through the resistor 103.
The base current IB flows through the transistor 104, and the base current IB flows through the transistor 104.
FE is doubled and the collector current IC of the transistor 104 flows. The capacitor 102 is charged with this IB+Ic, and Vcc+ rises rapidly as shown in Figure 11. When Vcc rises and approaches Vcc2, the base current IB of the transistor 104 decreases, and therefore the collector current IC also decreases. From now on, capacitor 102 will be charged primarily through resistor 101. Therefore, the rise of Vcc takes the form of a polygonal line, as shown in FIG. In the absence of the first quick charging circuit 11, Vccl rises with the time constant of the resistor 101 and capacitor 102. The situation is shown in Figure 11 with the dashed line Vc.
Indicated by c. Eventually, Vccl becomes stable at a voltage lower than Vcc2 by the voltage drop caused by the resistor 101, but at this time, almost no current flows through the transistor 104, and it is as if the first quick charging circuit 11 does not exist. become. Therefore, there is no negative impact on others. In this way, the first quick charging circuit 11 causes a large current to flow into the capacitor 102 when Vccl rises, causing Vcc to rise rapidly. Next, the second quick charging circuit 12 will be explained. As shown in FIG. 11, the first quick charge circuit 11 starts up the power supply Vccl, waits for the time until the bias starts up, and then outputs the quick charge OK signal 1 at time t. At this time, the capacitor 12 of the first photometric circuit 13
Assuming that no charge is stored in transistor 9, transistor 1
25, or the bias current flowing from the legal current source 123 becomes the base current of the transistor 127, and this base current is multiplied by II FE and becomes the collector current of the transistor 127. This collector current is determined by the area ratio of transistors 130 and 132 (for example, 1:
10), it is further amplified and becomes the collector current of the transistor 132. This collector current is sufficiently thicker than the current of the constant current source 135.The output 61 of the first photometric circuit 13 is sufficiently higher than the reference voltage V ref of the photometric circuit. Therefore, no current flows through the transistor 138, and the transistors 139, 140, 141, 142, 143, 1
Current no longer flows to 44,128 as well. On the other hand, a current flows through the transistor 145 in proportion to the area ratio (for example, 2:1) to the transistor 130, and this current is proportional to the area ratio between the transistors 146 and 147 (for example, 1:10) and the area ratio between the transistors 148 and 149. (for example, 1:10) and charges the capacitor 129, for example. Therefore, as shown in FIG. 11, the potential of the capacitor 129 rapidly increases from time LI. Then, when the potential of capacitor 129 rises and exceeds the original stable level of the charging voltage of this capacitor,
Since the base potential of the transistor 125 has risen above the stable level, the collector current of the transistor 125 becomes larger than the stable state, and the bias current from the constant current source 123 and the IS pin 21. If you want to know more about this, please enter F)t Yunaru. Then, since the base current of the transistor 127 disappears, the collector current also disappears, and the transistors 130 and 13
Since the collector current 2 also disappears, the photometric output 61 becomes sufficiently lower than the reference voltage Vref. Then the constant current source 136
All the currents flow as collector current of transistor 138, so transistors 139, 140, 141,
142.143.144, 128 also has a constant current source 136
The same current flows. On the other hand, since no current flows through transistor 130, no current flows through transistor 145 either. Therefore, transistor 146 r 147 + circuit 12 becomes inoperative. No current flows through the transistors 148 and 149, and the capacitor 129 is discharged by the collector current of the transistor 128 during the second quick charge. Next, when the capacitor 129 is discharged and reaches a level slightly lower than the stable state, the collector current of the transistor 125 becomes lower than the stable state, and the bias current from the constant current source 123 and the light receiving element 2b
The difference between the photocurrent and the sum of the photocurrents flows as the base current of the transistor 127, which doubles IIFE and becomes the collector current. The rest is the same as the charging process described above. As described above, the charging process and discharging process of the capacitor 129 are repeated. If the switching speed of the transistor was ideal, the level of the capacitor 129 would remain completely stable once it rose from Ov to a stable state, but in reality, due to the delay in switching,
By repeating charging and discharging as described above, each signal becomes saw-toothed as shown in FIG. This charging and discharging is repeated until time [2. At time L2, the quick charge OK double signal 1 becomes “L”.
”, which forcibly pulls down the base of the transistor 147 and makes the second quick charging circuit 12 inoperable. At time t2, the potential of the capacitor 129 is very close to the stable level, so the first photometric circuit stabilizes in a short time after t2.The second photometric circuit 14 is also equipped with a similar circuit.Next, an embodiment of the first photometric circuit 13 shown in FIG. 10 will be described. The output 61 is the reference voltage V ref
Let us consider a time when the first photometric circuit 13 is in a stable state. Give specific numbers and apply them to make it easier to understand. Assuming that the current I of the constant current source 135 = 10 μA, and the current I of the constant current source 136 = 2 μA, the first photometry circuit 13
In order for the output 61 to be the reference voltage Vref, the collector current of the transistor 137 = the collector current of the transistor 138 = 1 μA. At this time, transistor 139
．． ) transistor 140. ) transistor 142. ) The collector current of each transistor 128 is 1 μA. Therefore, the collector current of the transistor 130 (transistor 127t) is 1 μA, and if the area ratio of the transistor 130 and the transistor 132 is 1:10, the collector current of the transistor 132 is 10 μA, and the constant current source 1
35 current and balance. The first photometric circuit 13 is thus in a stable state, and at this time the transistor 125
Ignoring the base current of the transistor 127, if the subject 6 is in the dark, the bias current 123 will flow through the resistor 126 and the subject will be exposed to light that does not change over time, such as sunlight (abbreviated as constant light). When the light receiving element 2b is illuminated with light, the sum of the output current of the light receiving element 2b and the bias current of the constant current source 123 flows to the transistor 125. In other words, the transistor 125 is a bypass circuit for constant light. Now, suppose that the brightness of the illumination light on the subject changes from a stable state to brighter, such as when pointing the camera at a bright wall instead of pointing it at a dark wall under constant light. At this time, since the base of the transistor 125 is regulated by the voltage of the capacitor 129, the collector current of the transistor 125 does not flow more than the current flowing in the stable state. Therefore, the increase iL in the photocurrent of the light receiving element 2b due to the brightness becomes the base current of the transistor 127. Therefore transistor 1
The collector current of transistor 27 increases by IIFE times iL, and is further amplified by the area ratio of transistors 130 and 132 of 1:10 to become the collector current of transistor 132. This current flows into the logarithmic compression diodes 133 and 134, and the photometric output 61 increases. Then transistors 137 and 1
38 becomes unbalanced, the collector current of the transistor 138 decreases, and the transistor 139, 140.1
42 collector current is small I), transistor 12
8 collector current decreases. Therefore transistor 1
The collector current of 27 becomes a current that charges the capacitor 129, and the potential of the capacitor 129, that is, the transistor 1
The potential at the base of 25 rises. Therefore, the collector current of transistor 125 increases,
It works to bypass the increased photocurrent iL caused by the brightness of the object. Then, the collector current of transistor 127 decreases,
The photometric circuit returns to a stable state. In other words, transistors 127 → 130 → 132 → 137 → 138 → 139 → 1
40→142→128→125 form a negative feedback circuit. If there is no capacitor 129, the feedback will be instantaneous, but if the capacitor 129 is large, the feedback will take a long time. During distance measurement, the light emitting element 1 is lit in pulses, and the increase in photocurrent Δ'+L of the light receiving element due to the reflected light from the object is increased by the transistor 127.
IFE is doubled, and the area ratio of transistors 130 and 132 is further increased. If the current flowing through the logarithmic compression diodes 133 and 134 in a stable state is iD, the increase in photometric output due to ΔiL is T 2 X Tpn(10X IIF EXΔii, /iD
). Since distance measurement is performed in a pulsed manner, the potential of the capacitor 129 hardly increases during the pulse, and therefore, negative feedback does not occur. Rather, in terms of design, the capacitance of the capacitor 129 is determined to be such that negative feedback is strong enough for steady light, but negative feedback is not strong during the pulse-like time of distance measurement. It is something. Second photometric circuit 14
The same applies to Finally, the infinity judgment level V■ at high brightness will be described. As described above, in the stable state of the first photometry circuit 13, a part of the photocurrent IL of the light receiving element 2b and the bias current of the power supply 123 flows as the base current of the transistor 127, and most of it flows as the collector current of the transistor 125. There is. The transistor 124 has a common base and emitter with the transistor 125. Therefore, the collector current of transistor 124 is
It is the same as the collector current of 5. That is, the collector current of the transistor 124 is approximately equal to the photocurrent output iL of the light receiving element 2b when the subject is illuminated with high-intensity light, and approximately equal to the bias current of the power supply 123 in darkness. Further, the collector of the transistor 124 is connected to the collector of a transistor (not shown) that has the same function as the transistor 124 in the second photometric circuit 14, and is also connected to the base and collector of the transistor 114. Therefore, the collector current of the transistor 114 is approximately equal to the sum of the optical output currents of the light receiving elements 2a and 2b during high brightness, and is approximately twice the via input current of the constant current source 123 during darkness. Transistors 114 and 113 constitute a mirror circuit, and a collector current equal to the collector current of transistor 114 flows through transistor 113. The collector of transistor 113 is transistor 1 of the constant current circuit.
10 and the contact point of resistor 111. The resistor 111 creates an infinity determination level V(X) by the sum of the constant current created by the transistor 110 and the collector current of the transistor 113. resistance 11
The other end of transistor 112 is coupled to the emitter of transistor 112 . Transistor 112 together with diode-connected transistor 108 connects the first and tjS2 photometric circuit 13.1
4 reference voltage Vref is created. In other words, ■ω created by the resistor 111 is the reference voltage Vr
This is the level raised by the resistor 111 to ef. As mentioned above, the collector current of the transistor 113 is large when the brightness is high and small when it is dark, so that when the brightness is high, v
oo becomes large, and when it's dark it becomes Mr. I. This state is shown in Fig. 121, 8, which shows that when it is dark, the noise is small, so there is little variation in the photometric output during distance measurement due to noise, and therefore there is little variation in distance measurement. - When the blade brightness is high, the noise is large, so the noise-induced fluctuations in the photometry output during distance measurement are large, and the distance measurement variation is also large. For this reason, when light that is strong enough to not be affected by noise is reflected from the subject, the distance measurement is set to finite, and when there is a large fluctuation, V(Xl is raised to infinity).In this way, Naturally, it will be determined that the distance is infinity even if the distance is closer than when it is dark.However, if the subject is illuminated with high-brightness light, the photographic lens is stopped down, so the subject will be photographed as shown in Figure 42. The depth of field becomes deeper.Therefore, even if the distance is measured at infinity at a closer distance than when it is dark, there is no problem from a photographic point of view.Rather, it is caused by the fact that the distance is determined to be close due to the distance measurement variation even though the distance is far away. Since this poses many problems for photography, it is better to raise ■(1) when the brightness is high and set the distance to infinity even if the distance is relatively short compared to when the brightness is low. The invention relates to a voltage stabilizing circuit consisting of a resistor and a capacitor, in which a bipolar transistor is connected in parallel to the resistor, and when power is applied to the stabilizing circuit, the transistor is turned on to supply a charging current to the capacitor. By using an inexpensive bipolar transistor, the stabilizing circuit can be made inexpensive and can be easily integrated into a circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional voltage stabilizing circuit, FIG. 2 is a circuit diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing the principle of distance measurement, and FIG. A plan view showing a light receiving element in the device shown in the figure and a reflected light image of the light emitting element from the subject;
FIG. 5 is a graph showing the output of the light receiving element in FIG.
6 to 8 are graphs showing the relationship between the subject distance and the amount of light reflected from the subject, FIG. 8 is a block diagram showing a distance measuring device using the present invention, and FIG. 9 is a circuit diagram of the circuit shown in FIG. 8. The output waveform diagram of the main part, Figure 10 is a detailed circuit diagram of the main part of Figure 9, @11 is the waveform diagram of the main part of the circuit in Figure 10, and Figures 12 and 13 are the diagram of Figure 10. FIG. 2 is an explanatory diagram of the operation of the circuit. 91...Battery, 94...Distance measuring circuit, 101...
・Resistance (first resistance), 102...Capacitor, 10
3...Resistor (second resistor), 104...Transistor, Sl...Switch. Patent applicant Minolta Camera Co., Ltd. Representative Patent Attorney Aoyama Hogai (2)

Claims (1)

[Claims] (1) A first resistor and a capacitor connected in series to each other to form a stabilized power supply by being connected to a power supply via a switch, a transistor whose collector and emitter are connected in parallel to the first resistor, and a transistor whose collector and emitter are connected in parallel to the first resistor. A power supply device comprising a second resistor connected between a base and a voltage output side of the switch, and turning on the transistor when the switch is turned on.