JPH0122717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strobe device protection circuit for preventing heat damage to a strobe tube or the like in a strobe device used in, for example, an endoscope.

For example, an endoscope is used to inspect the inside of a human organ such as the stomach and intestines, and the situation is photographed. This endoscope is equipped with a strobe device for photographing. This strobe device controls light emission based on a discharge voltage from a main capacitor that is set to be charged, and includes a charging resistor for controlling charging of the main capacitor, a step-up transformer for triggering light emission, and the like.

The strobe tube, etc. installed in this strobe device can be damaged due to heat generation, for example, when taking frequent photographs.To prevent this thermal damage, a temperature fuse is installed in the charging resistor. When this charging resistor generates abnormal heat, the temperature fuse is blown, stopping charging for the next light emission and protecting the strobe tube, etc.

However, the quality of the temperature fuse itself, which is installed to protect the strobe tube from damage caused by heat, deteriorates significantly, and it is difficult to set the fuse cutting temperature, so it is difficult to set the charging stop temperature to a constant value. cannot be determined. Furthermore, unless a cut fuse is manually replaced, it cannot be charged for the next light emission.

This invention was made to solve the above-mentioned problems. For example, when stopping charging for light emission to protect a strobe tube from thermal damage, the charging stop temperature is set to a constant value. An object of the present invention is to provide a flash device protection circuit that can restore the charging state without any manual operation.

In other words, the strobe device protection circuit according to the present invention includes a device that integrates a value proportional to the charging operation and continuously subtracts the integrated value at a constant rate. Charging will stop if the

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

Figure 1 shows its configuration.
1, charging section 12, light emitting section 13, and control detection section 1
Consists of 4. The power supply unit 11 includes a transformer 16 to which AC voltage is supplied from an AC commercial power supply 15. Two secondary windings A and B of this transformer 16 are used as a high voltage power source for driving light emission and for circuit control. Take out the low voltage power supply.

The high voltage AC power from the secondary winding A of the transformer 16 is supplied to a full-wave rectifier circuit 18 via a triax 17 serving as a switching element in series.
It is converted into a DC voltage, and the main capacitor C1 is charged and controlled using this converted voltage. The terminal voltage of this main capacitor C1 is supplied to the strobe tube 19 of the light emitting section 13 via an inductance 20. At the gate of the strobe tube 19,
The switching thyristor 22 is turned on via the trigger coil 21 to apply a discharge signal to the capacitor C2, thereby driving the light emission.

Further, the output AC voltage from the secondary winding B of the transformer 16 is full-wave rectified by a rectifier circuit 23, stabilized by a capacitor C3 and a series regulator 24, and converted into a DC voltage signal of, for example, 8V.
Set charging to 4. The terminal voltage of this capacitor C4 is divided by resistors R1 and R2 to the charging section 12.
The signal is supplied to the negative terminal of a comparator 25 that constitutes the control section of the circuit. The negative terminal of this comparator 25 has
It supplies a voltage signal from the connection point of resistors R3 and R4 connected in series between both ends of the main capacitor C1, and when the charging voltage of the main capacitor C1 is below a specified value, the output terminal level of the comparator 25 is It is set to a low level (“L” level). In this case, the output level of the comparator 25 is set to the "L" level when the charging voltage of the capacitor C1 is in a low voltage state that makes it impossible to drive the strobe tube 19 to emit light.This setting control is performed by variable adjustment of the resistor R1. It is done as follows.

Two light emitting diodes 26a and 27a are connected to the output terminal of the comparator 25, which are driven to emit light when the output is at the "L" level. The light emitting diode 27a constitutes a photocoupler, and the light emitting diode 27a constitutes a phototransistor 27b of the control detection section 14, which will be described later. A phototransistor 28b is connected in parallel to the series-connected light-emitting diodes 26a and 27a, and the phototransistor 28b forms a photocoupler with the light-emitting diode 28a of the control detection section 14.

Next, the control detection unit 14 performs calculation control.
CPU 29, memory 30 and input/output device I/O
31, and the terminal of the input/output device I/O 31 when the phototransistor 27b is turned on in the light receiving state.
PC is set to “L” level. While this terminal PC is at the "L" level, the CPU 29 performs addition control of a specific number, and the integration result is stored in the memory 30.

In this case, the CPU 29 performs a subtraction operation corresponding to the passage of time using a specific clock signal to subtract the integrated value stored in the memory 30. When the result of this subtraction is less than or equal to the specified value, the output signals of the terminals PA and PB of the input/output device I/O31 are set to high level (“H” level).
When the output signals of the terminals PA and PB go to the "L" level, the warning light emitting diode 32 and the light emitting diode 28a begin to emit light.
In the figure, reference numeral 33 denotes a normally closed light emitting start switch, and this switch 33 always causes the light emitting diode 34a to emit light, and turns off when it is open. This light emitting diode 34a is a phototransistor 34b of the light emitting section 13.
constitutes a photocoupler, applies a gate voltage to the switching thyristor 22 in the off state, and
This is turned on and a gate trigger signal is applied to the strobe tube 19 to drive it to emit light.

That is, in the above device, the strobe tube 19
The terminal voltage of the main capacitor C1 that drives the light emission is constantly monitored by a comparator 25. When this terminal voltage is not in a sufficient state to drive the strobe tube 19 to emit light, the output level of the comparator 25 becomes "L" level, and the triac 17 is gate-controlled by the photocoupler, and the main capacitor C1
A charging operation is performed for. Then, the charging voltage of the main capacitor C1 is a sufficiently high voltage, e.g.
When the voltage reaches 330V, the output level of the comparator 25 is inverted to "H" level, and the triac 17 is inverted.
Close the gate and stop charging operation.

At the same time, the terminal PC for the input/output circuit I/O 31 is connected in accordance with the output level of the comparator 25.
The input signal is controlled, and addition control is performed on the accumulated value stored in the memory 30 in the charging operation state.

That is, an addition operation is performed by the charging operation of the main capacitor C1, and a subtraction operation is performed in response to the passage of time.When the charging and discharging operation of the main capacitor C1, that is, the light emission operation of the strobe tube 19 is repeated, , when the addition element increases and the addition/subtraction integrated value in the memory 30 exceeds a certain value, the terminals PA and PB become "L" level, the light emitting diode 32 issues a warning, and the light emitting diode 28
At step a, the light emitting diodes 26a and 27a connected in series are turned off to cut off the charging circuit, and the input level to the input/output circuit 31 is set to "H" level to stop all charging operations for the main capacitor C1, thereby performing a protective operation. It will be done.

Then, as time passes, when the addition/subtraction integrated value in the memory 30 becomes less than a certain value, the output level of the terminals PA and PB of the input/output circuit I/O 31 becomes "H" level again, and the charging operation for strobe light emission resumes. will be done.

In the above embodiment, all of the voltage charged in the main capacitor C1 is supplied to the strobe tube 19 for full emission, but as shown in FIG. Good too. In other words, this automatic light control section 40 receives light reflected back from an object (not shown) with a photodiode 41, and turns on the thyristor 42 when the integrating capacitor C5 reaches a certain voltage value, thereby turning on the commutating capacitor. The charge accumulated in C6 gives a reverse bias signal to the main thyristor 43, and stops the light emitting operation of the strobe tube 19.

In other words, when the subject is very close to the subject, the reflected light will be strongly reflected back, and the charging voltage of the main capacitor C1 of the charging section 12 will stop emitting light before it is completely discharged.
Therefore, the charging time for the next light emission can be shortened.

As described above, according to the present invention, the charging operation in the charging section is constantly monitored according to the integration and subtraction values corresponding to the strobe light emission driving state, and when a protective condition for stopping the charging operation is reached, the charging operation is automatically performed. Charging stop control can be executed, and the strobe light emission operation can be automatically stopped in accordance with the temperature at which the strobe tube or the like is damaged. Then, this charging stop state is automatically canceled and the charging possible state can be restored again. Therefore, it is possible to reliably protect the strobe tube and the like from damage caused by heat generation without the need to use parts for which it is difficult to set the charging stop timing.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating a strobe device protection circuit according to one embodiment of the present invention, and FIG. 2 is a block diagram illustrating another embodiment of the protection circuit. 11... Power supply section, 12... Charging section, 13... Light emitting section,
14... Control detection unit, 19... Strobe tube, 25... Comparator, 29... CPU, 30... Memory, 31
...Input/output device I/O, 32...Warning light emitting diode.

Claims (1)

[Scope of Claims] 1. A strobe device that emits light using a discharge voltage of a main capacitor, comprising a detection means for detecting a charging operation following the discharging operation of the main capacitor, and a value corresponding to the charging operation detected by the detection means. an integrating means for integrating, a means for counting a value specified in response to the passage of time, a means for comparing and subtracting the value integrated by the integrating means and the counted value, and a means corresponding to the comparing and subtracting means. 1. A strobe device protection circuit, comprising: a protection means that is activated. 2. The strobe device protection circuit according to claim 1, wherein the protection means includes a warning device that is activated when the value subtracted by the comparison and subtraction means exceeds a preset value. 3. The strobe device protection circuit according to claim 1, wherein the protection means includes circuit means for stopping charging of the main capacitor when the value subtracted by the comparison subtraction means exceeds a preset value. .