JPH0442075Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser beam control circuit for a laser trimming device, and in particular, the invention relates to a laser beam control circuit for a laser trimming device, and in particular, to stop the laser beam by an output from a comparison circuit that compares a trimming target value and a measured value. This invention relates to a laser light control circuit.

[Conventional technology]

Conventionally, in this type of laser light control circuit, the CPU reads and judges the state of the output from the comparison circuit between the trimming target value and the measured value, and either stops laser oscillation via software or controls the output of the comparison circuit. Laser oscillation was directly stopped depending on the situation.

[Problem that the invention attempts to solve]

In conventional laser beam control circuits, the comparison between the trimming target value and the measured value is performed asynchronously with the laser beam pulse, or even if it is synchronous, it does not take into account the stabilization time of the measured value immediately after the laser beam is emitted. Therefore, high trimming accuracy was often not achieved. In particular, when trimming a measured quantity such as voltage, if there is an active element such as a transistor in the vicinity of the element to be trimmed, the photoelectric effect caused by the laser light will turn on the PN junction, for example, and the measured value will fluctuate greatly. This often makes normal trimming impossible.

Therefore, an object of the present invention is to provide a laser light control circuit that has a simple configuration and enables highly accurate trimming.

[Means for solving problems]

The control circuit according to the present invention includes an oscillator that generates a sampling pulse, a flip-flop that maintains the output state of a comparator circuit that compares a trimming target value and a measured value in synchronization with the leading edge of the sampling pulse, and an output of this flip-flop. It includes an AND circuit which receives the sampling pulse as an input, and a monostable multivibrator for generating a pulse synchronized with the trailing edge of the pulsed output from the AND circuit.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Comparison circuit 1
The trimming target value and the measured value are compared, and the comparison circuit output becomes "1" or "0" depending on the magnitude relationship. The output state of the comparator circuit 1 is held in a flip-flop 2 in synchronization with the leading edge of a sampling pulse periodically generated by a square wave oscillator 3. The sampling pulse is logically ANDed with the inverted output of the flip-flop 2 by an AND circuit 4 and inputted to a monostable multivibrator 5. This monostable multivibrator 5 is triggered at the trailing edge of the sampling pulse and produces a pulse of appropriate width that is synchronized with the trailing edge of the sampling pulse. Laser light is emitted in synchronization with this pulse.

FIG. 2 is a signal waveform diagram illustrating the above operation. Periodically generated sampling pulse 10
Output 11 of comparator circuit 1, which is the comparison result between trimming target value 16 and measured value 15, is synchronized with the leading edge of
is stored in flip-flop 2. At this time, the laser beam has not yet been emitted, so there is no change in the measured value 15. If it is smaller than the trimming target value 16, the output 11 of the comparator circuit 1 is in the "0" state, and the output 12 of the flip-flop 2 is in the state of "0". also becomes “0”. At this time, the inverted output of flip-flop 2 becomes "1". Therefore, sampling pulse 1 ANDed with the inverted output of flip-flop 2
0 is input to the monostable multivibrator 5.
The monostable multivibrator 5 generates a pulse 13 synchronized with the trailing edge of the sampling pulse, and a laser beam 14 is emitted in synchronization with this. Measured values fluctuate greatly due to effects such as photoelectric effects due to laser light irradiation. As a result, if the trimming target value 16 is exceeded, the output 1 of the comparator circuit 1
1 becomes "1". However, at this point, the next sampling pulse 10 has not yet appeared, so
The output 12 of the flip-flop 2 remains at "0" and remains unchanged, maintaining its original state.

Here, if the period of the sampling pulse 10 is sufficiently longer than the time constant of the fluctuation of the measured value due to the laser beam, the measured value will have reached a steady state and will show a constant value when the next sampling pulse arrives. Become. If the measured value is below the target value at this time, the inverted output of flip-flop 2 remains "1" and does not change, and therefore the next laser beam is emitted in synchronization with the trailing edge of the sampling pulse. become. Conversely, if the target value is exceeded, the output 11 of the comparison circuit 1 becomes "1", the output of the flip-flop 2 also changes to "1", and the inverted output becomes "0". Therefore, the sampling pulse is passed through the AND circuit 4
, the trigger input to the monostable multivibrator 5 is also stopped, and the laser beam is no longer emitted.
Therefore, if the period of the sampling pulse is sufficiently longer than the time constant of the fluctuation of the measured value due to the laser beam, the measured value can always be compared with the target value when it becomes stable, making it possible to perform highly accurate trimming.

FIG. 3 shows a second embodiment of the present invention, in which a delay circuit 6 is inserted in the line from the oscillator 3 to the AND circuit 4. The trimming target value and the measured value are compared in the comparison circuit 1, and when the measured value becomes larger than the trimming target value, its output becomes "1". This state is held in the flip-flop 2 in synchronization with the leading edge of the sampling pulse 10 generated by the oscillator 3. The sampling pulse 10 is delayed by a suitable amount of time by the delay circuit 6 and then enters the AND circuit 4. The other input of the AND circuit 4 receives the inverted output of the flip-flop 2, and the sampling pulse to the monostable multivibrator 5 is regulated by the state of the inverted output of the flip-flop 2. That is, when the measured value becomes larger than the trimming target value and the output of the flip-flop 2 becomes "1", its inverted output becomes "0" and the sampling pulse is blocked by the AND circuit 4.

Incidentally, although the output state of the comparator circuit 1 is held in the flip-flop 2 in synchronization with the leading edge of the sampling pulse 10 and appears at its output, there is always a delay from the leading edge of the sampling pulse. Therefore, even if the output of the comparator circuit 1 becomes "1" and the inverted output of the flip-flop 2 becomes the state "0", a pulse with a width comparable to this delay will appear at the output of the AND circuit 4. . In order to compensate for this delay, the sampling pulse is also input to the AND circuit 4 with a delay equal to or more than the delay caused by the flip-flop 2 by the delay circuit 6.
The output of the AND circuit 4 is input to the monostable multivibrator 5, and this monostable multivibrator 5
generates a pulse synchronized with the trailing edge of the sampling pulse delayed by an appropriate time, and laser light is emitted in synchronization with this pulse.

FIG. 4 is a signal waveform diagram illustrating the above operation. The state of the output 11 of the comparison circuit 1 is held in the flip-flop 2 in synchronization with the leading edge of the sampling pulse 10. At this time, the laser beam has not yet been emitted, so there is no change in the measured value 15, and if it is smaller than the trimming target value 16, the output 11 of the comparator circuit 1 is "0", and the inverted output of the flip-flop 2 is "1". It is. Therefore, comparison circuit 1
When the output of is "0", the sampling pulse 10' passes through the AND circuit 4 and enters the monostable multivibrator 5. The monostable multivibrator 5 pulses 1 in synchronization with the trailing edge of the sampling pulse 10'.
3 is generated, and a laser beam 14 is emitted in synchronization with this. If the measured value 15 changes due to the laser beam as shown in the figure and exceeds the trimming target value 16, the output 11 of the comparator circuit 1 becomes "1", but at this point the next sampling pulse 10 has not yet arrived. Therefore, the inverted output of flip-flop 2 does not change and maintains its original state.

Here, if the period of the sampling pulse 10 is sufficiently longer than the time constant of the fluctuation of the measured value due to the laser beam, the measured value will be in a steady state when the next sampling pulse 10 comes, and the measured value 15 will be the trimming target. If the value is smaller than 16, the inverted output of flip-flop 2 remains at "1" and the next laser beam is emitted. If the measured value 15 exceeds the trimming target value 16 when the leading edge of the sampling pulse 10 arrives, the output of the flip-flop 2 becomes "1" and the inverted output becomes "0".
become. At this time, the sampling pulse 10' is blocked by the AND circuit 4, but there is a delay 19 when the inverted output of the flip-flop 2 changes to "0" in synchronization with the leading edge of the sampling pulse 10. This delay 19 is, as mentioned above,
This causes a pulse with a delayed time width to be output from the AND circuit 4, and based on this pulse, an extra pulse 20 is output from the monostable multivibrator 5, and an extra laser beam 21 is output.
In order to compensate for this delay 19, the sampling pulse 10' delayed by an appropriate amount of time in the delay circuit 6 is inputted to the AND circuit 4, thereby preventing the generation of extra pulses and preventing the output of extra laser light 21. I can do it.

From FIG. 4, it can be seen that the sampling pulse always samples the change in the measured value due to the laser beam emitted one cycle before. Therefore, by making the period of the sampling pulse sufficiently longer than the time constant of the fluctuation of the measured value and the pulse width narrower than the difference between the period and the time constant of the fluctuation, the steady-state measured value and the trimming target value can always be matched. It can be seen from the comparison results that the laser beam can be controlled.

[Effect of idea]

As explained above, the present invention stores the comparison result between the trimming target value and the measured value in a flip-flop in synchronization with the leading edge of the sampling pulse, thereby causing the laser to emit in synchronization with the trailing edge of the sampling pulse. By stopping the light, the trimming target value and the measured value can be compared at any time when the measured value is stable, enabling highly accurate trimming.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the first embodiment of the present invention;
The figure is a waveform diagram of each signal in the operating state of Figure 1,
FIG. 3 is a configuration diagram of a second embodiment of the present invention, and FIG. 4 is a signal waveform diagram of each part in FIG. 3. 1...Comparison circuit, 2...Flip-flop, 3
...oscillator, 5...monostable multivibrator,
6...Delay circuit.

Claims (1)

[Scope of utility model registration request] In a laser light control circuit that stops laser light using the output of a comparison circuit that compares a trimming target value and a measured value of a laser trimming device, the laser beam control circuit includes an oscillator for generating a sampling pulse, and the comparison circuit in synchronization with the leading edge of the sampling pulse. a flip-flop for holding the output of the flip-flop, an AND circuit receiving the output of the flip-flop and the sampling pulse as inputs, and a monostable multivibrator triggered by the trailing edge of the pulsed output from the AND circuit. A laser light control circuit for a laser trimming device characterized by: