JPS58197694A - Dimming strobe device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor type light control strobe device with improved light control characteristics.

An example of a conventional transistor type dimming flash device is shown in FIG. In the figure, (700) is a high voltage power supply (10
0) A flash discharge circuit consisting of a series circuit consisting of a flash energy storage capacitor (200) charged by 4, a flash discharge tube (300), and a connection between the collector and emitter terminals of the main transistor (400). It is. In addition, (500) is a trigger circuit that receives the flash start signal "8YNO" and gives a trigger signal ■1 to the flash discharge tube (300), and a base xi bias drive signal (500m) to the main transistor (400), that is, a base forward bias current. A drive circuit (600) also serves as a base forward bias circuit that supplies IB for a predetermined energization time;
These circuits (700), (500), and (600) constitute the present dimming strobe device.

Next, the operation of this device will be explained based on FIG. 1 and FIG. 2 showing its operation waveforms. First, a flash energy storage capacitor (200) is charged to a voltage of several hundred volts by a high voltage power supply (100). Next, when the flash start signal V8YNO is given from a camera etc., the drive circuit (500
) gives a trigger signal 1 to the flash discharge tube (300) and starts supplying a base forward bias current 1B to the main transistor (400). From this one flashlight discharge tube (
300) and the collector-emitter of the main transistor (4(a)) are electrically connected, and the power of the flash energy storage capacitor (200) is applied to the flash discharge tube (300).
Generates a flash of light. When it is detected that the civilian light cover has reached a predetermined value, the energization time setting circuit (600) generates a flash stop signal (3). As a result, the drive circuit (500) cuts off the base forward bias current 19 that was being supplied to the main transistor (400), and as a result, the main transistor (400)
) is turned off. At this time, the main transistor (40
Due to the turn-off characteristics of 0), the collector current continues to flow even after the base forward bias current 1B is cut off during the accumulation time and fall time, so the flash time of the flash discharge tube (300) is determined by the energization time setting circuit. The energization time td set in step (600) may be longer than the energization time td, and the number of flash lids may be too large. This phenomenon is especially noticeable when using a small flash amount.
The dimming accuracy in this area is often impaired. This is the previous 2
The turn-off characteristics of the g-transistor (400) tend to become longer as the accumulation time or the driving conditions of the main transistor (400) (i.e., the ratio of the base forward bias current value to the collector current value) increases. This is because the turn-off time becomes long when the collector current is small during the several tens of microseconds when the discharge current IXe of the discharge tube (300) starts to rise.

Thereafter, when the main transistor (400) is completely turned off, the flash discharge tube (300) stops flashing, and the impedance increases after an ion extinction period of about several tens of milliseconds.

At this time, the collector-emitter voltage ■c of the main transistor (400) is determined by impedance division with the flash discharge tube (300) as shown in Figure 1s2, and the impedance at steady state is the same as that of the flash discharge tube (300). If the phase is larger than that between the collector and emitter of the main transistor (400), the waveform will be as shown in ■, and in the opposite case, the waveform will be as shown in [phase].

Conventional transistor type dimming strobe devices are configured and operated as described above, so if the turn-off time of the main transistor is long, the accuracy of the flash t will be poor, and especially when operating with a small amount of light, overflow may occur, making it difficult to take photographs. This had the disadvantage that close-up photography was difficult.

The present invention has been made to eliminate the drawbacks of the conventional ones as described above, and by providing a circuit that actively flows a base reverse bias current when cutting off the base forward bias current of the main transistor, the main transistor It is an object of the present invention to provide a dimming strobe device that can shorten the turn-off time of a transistor and can accurately set the flash time even when operating a weak light II1wJ.

Embodiments of the present invention will be described below with reference to the drawings.

3, 5, and 7 show the first part of the dimming type strobe device according to the present invention. This shows the second and third embodiments, and the structures of these will be explained below.

In FIG. 3, (801) is the main transistor (400
) is an OFF transistor constituting a base reverse bias circuit (900) that causes a base reverse current to flow out from the OFF transistor (801), and the collector of the OFF transistor (801) is connected to the base terminal of the main transistor (400). ) is connected to the emitter terminal of the main transistor (400) via a diode (802), and the base terminal of the off transistor (801) is connected to the base reverse bias drive signal (500) from the drive circuit (500).
b) is configured to be driven complementary to the base terminal of the main transistor (400).

The diode (802) is inserted to increase the effect of the present invention, and basically may be omitted.

Next, in FIG. 5, a P type transistor is used as the off transistor (801), a diode (804) is connected between its base and emitter, and the main transistor (
When the diode (804) is generating a forward voltage drop due to the base forward bias current IB of the transistor (400), the base and emitter of the off transistor (801) are reverse biased. Also, the off transistor (
A resistor (803) is connected between the collector and base of the transistor (801), and the off transistor (801), the diode (804), and the resistor (803) constitute a base reverse bias circuit (900). Note that the diode (802) may basically be omitted as in the case of FIG.

Next, in FIG. 7, a base reverse bias power source (805) is inserted between the collector and emitter of the off transistor (801) and between the base and emitter of the main transistor (400). In addition, the main transistor 2
A resistor (806) is connected between the base and emitter of 00), and a base reverse bias circuit (900) is constituted by the off transistor (801), reverse bias current (805), and resistor (806). . Note that this reverse bias power source (805) can also be replaced by a charged capacitor.

The operations of the embodiments shown in FIGS. 3, 5, and 's7 will be explained below with reference to FIGS. 4, 6, and 8, which are operational waveform diagrams.

When the drive circuit (500) receives the flash start signal V8YNO, the drive circuit (500) generates a base forward bias current lB.
is output, the main transistor (400) is forward biased, the flash discharge tube (300) emits a flash in response to a trigger from the drive circuit (500), and when a predetermined amount of flash is reached, the energization time is stopped. The setting circuit (600) generates the flash stop signal ■3 and the base forward bias current IB that the drive circuit (500) supplies to the main transistor (400).
The operation up to the point of shutting off is the same as the conventional one in any of the embodiments shown in FIGS. 3, 5, and 7.

Now, when this base forward bias current IBL is disconnected, the base reverse bias drive signal (500
b) turns on the off transistor (801),
When the collector and emitter are short-circuited, the accumulated charge that has not been accumulated in the base layer of the main transistor (400) flows out from the base terminal, and a base reverse current IBoff flows. this is! As shown in Figure 3 and Figure 5, especially the base reverse bias power supply (805) in Figure 7.
), and the effect becomes greater when a base reverse bias power supply (805) is used as shown in FIG.

From this base reverse current IBof, the main transistor (
Since the excess carriers in the base layer of the main transistor (400) are rapidly reduced, the turn-off time of the main transistor (400), especially the storage time, is shortened, and the collector current of the raw transistor (400) is reduced quickly after the base current IBL or turn-off. It will be held in Therefore, the flash of the flash discharge tube (300) can also be quickly stopped, thereby preventing an unnecessary increase in the amount of flash.

In particular, the effect is large when the discharge current Ix of the flash discharge tube (300) is still starting to rise and is small, for several tens of microseconds, and the turn-off time can be reduced to less than 1/2 of the conventional one, so the amount of flash can now be reduced to less than 1/4 of the conventional one.

Here, the diode (802) is the main transistor (400
) while the collector current is not yet cut off, the emitter potential is increased and acts as a power supply for the off transistor (801), so the base reverse bias current I
This has the effect of further shortening the turn-off time of the main transistor (400) by increasing Boff.

In addition, the base reverse bias power supply (805
) can be expected to have the same effect, and since the voltage drop caused by the diode (802) is not used, the power loss in the flash discharge circuit (W00) can be reduced, and a reduction in the amount of flash can be prevented. There is.

In this case as well, the operation after the main transistor (400) is turned off is similar to the conventional one.

In addition, in the circuit of FIG. 5, when the main transistor (400) is base-forward biased, the forward voltage drop generated in the diode (804) is transferred to the OFF pnp T-transistor (
When the base and emitter of the main transistor (801) are reverse biased to keep the off transistor (801) in the off state, and the base forward bias current lB of the main transistor (400) is removed, the off transistor (801) becomes the resistor (801). 80
3) The base of the 4 beam is forward biased and turns on, causing the base reverse bias current IBo of the main transistor (400)
Play ff.

In this circuit, the transistor drive output of the drive circuit (500) is used as one signal, namely the base forward bias drive signal (500).
00λ), which not only simplifies the circuit but also eliminates the need to separately provide a drive power source for the base reverse bias current circuit (900). In addition, the diode (80
4) can be replaced with a resistor of an appropriate resistance value.

In the present invention, the main transistor has been described as an npn type single transistor, but it may be a Darlington type transistor or a PnP type transistor.

As described above, according to the present invention, since a circuit is provided that actively flows the base reverse bias current when cutting off the base forward bias current of the main transistor, the turn-off characteristics of the main transistor can be improved and the dimming accuracy can be improved. It is possible to provide a device that has good brightness and can control light down to minute amounts of light, and can be expected to have practical effects such as enabling extremely close-up photography in photography.

[Brief explanation of the drawing]

Figure g741 is a circuit diagram showing an example of a conventional transistor type dimming strobe device, and Figures 3, 5, and 7 are first, second, and third embodiments of the dimming type strobe device according to the present invention. 2, FIG. 4, FIG. 6, and FIG. 8 are diagrams showing operating waveforms of the circuits of FIG. 1, FIG. 3, FIG. 5, and FIG. 7, respectively. (700) is a flash discharge circuit, (200) is a flash energy storage capacitor, (300) is a flash discharge tube, (400)
) is the main transistor, (801) is the off transistor (base reverse bias circuit), (500) is the drive circuit (trigger circuit, base forward bias circuit), (600) is the energization time setting circuit, (802), (804) is a diode, (SOa) is a resistor, and (805) is a base bias current terminal. In the figure, the same reference numerals indicate the same or equivalent gls. Agent Makoto Kuzuno - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendment (voluntary) Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent application No. 1981-81863 No. 2 Akira Zuko Name of dimming stolibo device, 37 mountains 11
Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent address Marunouchi, Chiyoda-ku, Tokyo 2-2-3 No. 5, Detailed explanation of the invention in the specification subject to amendment 6, The description of contents of the amendment is amended as follows.

Claims (5)

[Claims] (1) A flash discharge circuit in which a flash energy single product capacitor, a flash discharger, and the collector-emitter of the main transistor are all connected in series to form a closed circuit; a trigger circuit that provides a trigger signal to the discharge tube; a base forward bias circuit that receives the flash start signal and supplies the main transistor with a base forward current having a time width corresponding to a predetermined flash device; A dimming strobe device comprising: a base reverse bias circuit that causes a base reverse current to flow out from the main transistor after being cut off. (2) The base reverse bias circuit is an off transistor whose collector and emitter are connected to the base and emitter of the main transistor, respectively, and which is turned on by a base reverse bias drive signal. The dimming strobe device according to item 1. (3) The base reverse bias circuit includes a diode inserted in the forward direction between the output of the base forward bias circuit and the base of the main transistor, and a base of J at the anode terminal and cathode terminal of the diode, respectively. 2. The dimming strobe device according to claim 1, further comprising: an off transistor whose emitter is connected; and a resistor connected between the base and collector of the off transistor. (4) The base reverse bias circuit has a power supply whose positive terminal is connected to the emitter of the main transistor, and a base reverse bias circuit whose positive terminal is connected to the emitter of the main transistor and whose emitter is connected to the negative terminal of the power supply and whose collector is connected to the base of the MiJ main transistor. The dimming strobe device according to claim 1, further comprising an off transistor that is turned on by a bias drive signal. (5) Any one of claims 1 to 4, wherein the flash discharge circuit has a diode toward the emitter of the main transistor and the negative terminal of the flash energy storage capacitor. The dimming strobe device described in .