JP2000241565A - Timer circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a timer circuit for measuring time accurately even if measurement time is long. SOLUTION: A timer circuit is provided with a constant current output part 11 for outputting a constant current, a charge part C1 that is charged by the constant current output part 11, a first signal comparison part 14 for outputting a first timer signal to an external circuit to be controlled when the potential of the charge part C1 is higher than a first reference voltage by comparing the first reference voltage with the potential of the charge part C1, and a second signal comparison part 14 for outputting a second timer signal to an external circuit to be controlled when the potential of the charge part C1 is higher than a second reference voltage by comparing the second reference voltage that is higher than the first reference voltage with the potential of the charge part C1. In the timer circuit, a current-switching part 16 for switching current that is outputted from the constant current output part is connected to the constant current output part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a timer circuit, and more particularly to a timer circuit capable of measuring a plurality of times.

[0002]

2. Description of the Related Art A conventional timer circuit is shown in FIGS.
Explanation will be made using 0. FIG. 6 is a circuit diagram of the timer circuit. FIG. 7 is an operation explanatory diagram showing the relationship between the time measured by the timer circuit, the reference voltage, and the potential of the capacitor. FIG. 8 is an explanatory diagram of the chattering operation of the timer circuit. FIG. 9 is a circuit diagram of another timer circuit. FIG. 10 is an operation explanatory diagram showing the relationship between the time measured by the timer circuit and the reference voltage.

Conventionally, there is a timer circuit that outputs a timer signal when the amount of charge charged to a capacitor increases to a certain level or more due to an increase in the amount of charge. As shown in FIG. 6, for example, this type of timer circuit includes a constant current circuit 1, reference voltage generation circuits 2 and 3, signal comparators 4 and 5, and a capacitor C.

In this case, the signal comparators 4, 5
Are the potential charged in the capacitor C and the reference voltages Vref1, Vref2 set by the reference voltage generation circuits 2 and 3.
Are compared, the timer signals S1 and S2 are output when the potential charged in the capacitor C exceeds the reference voltages Vref1 and Vref2, thereby measuring two times.

[0005] Such a timer circuit is used for a high-pressure discharge lamp such as an HID lamp, for example, and has a function of giving two timings immediately after lighting and several seconds after lighting. In the high-pressure discharge lamp, lighting abnormality is detected at the two timings.

[0006]

In the above-described timer circuit shown in FIG. 6, when a timer circuit having a long measurement time is to be constructed, the capacity of the capacitor must be increased or the constant value must be increased. It is necessary to reduce the current value of the current circuit. However, since increasing the capacity of the capacitor increases the cost, a method of reducing the current value is often used.

That is, as shown in FIG. 7, a measurement time T1 for measuring from time t0 to time t1 is used as the measurement time.
And a measurement time T2 for measuring from time t0 to time t2.
When the time from time t0 to time t2 is long, the current value is reduced and the capacitor C is gradually charged. In this case, a straight line L representing a rise in potential
Becomes smaller. By the way, a little noise or the like is often superimposed on the current, and when the noise is superimposed on the current, as shown in FIG. Meanwhile, the potential increases as a whole. In this case, the potential of the capacitor C changes up and down even near the reference voltage, and may temporarily exceed or fall below the reference voltage Vref1 or Vref2 several times. Then, as shown in FIG. 8, so-called chattering in which high and low are repeated several times occurs as an output of the signal comparator.

Therefore, there is a problem that it is difficult to accurately determine the times t1 and t2 due to the chattering. And this chattering is a straight line L
Is more likely to occur as the slope of the measurement is smaller, that is, as the measurement time is longer.

Further, as shown in FIG.
And the capacitor C, for example, in FIG.
As shown at 0, chattering occurs at time t2 and the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a timer circuit capable of accurately measuring time even when the measurement time is long. Is to do.

[0011]

In order to solve the above-mentioned problems, the present invention provides a constant current output section for outputting a constant current, a charging section charged by the constant current output section, and a first reference voltage. And a first signal comparison unit that compares the potential of the charging unit and outputs a first timer signal to an external control target circuit when the potential of the charging unit is higher than a first reference voltage; Comparing a second reference voltage higher than a reference voltage with the potential of the charging unit and outputting a second timer signal to an external control target circuit when the potential of the charging unit is higher than the second reference voltage; And a signal switching unit for switching a current output from the constant current output unit, the current switching unit being connected to the constant current output unit.

The constant current output section is capable of outputting a constant high current and a constant low current and outputs a constant high current in an initial operation state. The current switching section detects the first timer signal. By outputting a constant low current to the constant current output unit, the measurement time corresponding to the first reference voltage can be accurately measured, and the measurement time corresponding to the second reference voltage can be measured even if the measurement time is long. Becomes

Further, a third reference voltage, which is a value between the first reference voltage and the second reference voltage, is compared with the potential of the charging unit, and the potential of the charging unit is set to a third reference voltage. By providing a current re-switching unit connected to the constant current output unit to output a high current to the constant current output unit when the voltage is higher than the voltage, the measurement time corresponding to the second reference voltage can be accurately measured. preferable.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a timer circuit according to the present invention will be described with reference to FIGS. 1 to 3, and a second embodiment will be described with reference to FIGS.

FIG. 1 is a block diagram of a timer circuit according to the present invention. FIG. 2 is an explanatory diagram of the operation of the timer circuit of the present invention. FIG. 3 is an explanatory diagram of the operation of the timer circuit of the present invention, showing a state where chattering does not occur.

In FIG. 1, a timer circuit includes a constant current circuit 11 corresponding to a constant current output section, and reference voltage generation circuits 12 and 1.
3, a comparator 14 corresponding to a first signal comparing unit, a comparator 15 corresponding to a second signal comparing unit, a current switching circuit 16 corresponding to a current switching unit, and a capacitor C1 corresponding to a charging unit. I have.

The constant current circuit 11 includes transistors T1, T
, T3 and resistors R1, R2, R4, and a resistance value r of the resistors R1, R2.
By adjusting 1, r2, an output current I1 having a constant current value is determined. Specifically, the resistance R
1 and R2 are connected to a power supply 17 and a resistor R
1 is connected to the emitter of the transistor T1 and the resistor R2
Is connected to the emitter of the transistor T2. The base of the transistor T1 and the transistor T2
Are connected, and the connection point and the transistor T
3 emitters are connected. And the transistor T
3 is the collector of the transistor T1 and the resistor R4
The collector of the transistor T3 is connected to the other end of the resistor R4 and grounded.
The collector of the transistor T2 is connected to one end of the capacitor C1 and the inverting input terminals of the comparators 14 and 15. When the resistance value r1 of the resistor R1 is equal to the resistance value r2 of the resistor R2, the constant current circuit 11
2 is equal to the current value, but the resistance value r2 is equal to the resistance value r1.
When the current value becomes smaller, the current value of the current I1 becomes larger than the current value of the current I2.

The reference voltage generation circuit 12 generates a reference voltage Vref1 corresponding to a first reference voltage and inputs the reference voltage Vref1 to a non-inverting input terminal of a comparator 14. The reference voltage generation circuit 13 generates a second reference voltage. The reference voltage Vref2 corresponding to the voltage is generated and input to the non-inverting input terminal of the comparator 15.

The capacitor C1 inputs the potential charged by the constant current circuit 11 to the inverting input terminals of the comparators 14 and 15.

The comparator 14 compares the reference voltage Vref1 with the potential of the capacitor C1, and outputs Low when the potential of the capacitor C1 is lower than the reference voltage Vref1, and outputs Low when the potential of the capacitor C1 is higher than the reference voltage Vref1. Outputs High. The High signal is output to an external circuit such as the lighting main circuit 18 as a first timer signal S3. The output of the comparator 14 is also input to the current switching circuit 16.

The comparator 15 compares the reference voltage Vref2 with the potential of the capacitor C1, and outputs Low when the potential of the capacitor C1 is lower than the reference voltage Vref2, and outputs Low when the potential of the capacitor C1 is higher than the reference voltage Vref2. Outputs High. The High signal is output to an external circuit such as the lighting main circuit 18 as a second timer signal S4. The reference voltage Vref2 is equal to the reference voltage Vre
It is higher than f1.

The current switching circuit 16 includes an inverter INV1 and
It is composed of a switch SW1 and a resistor R3.
The series circuit of the resistor R3 and the switch SW1 is connected in parallel to the resistor R2. The switch SW1 is a normally closed contact,
It is closed when the operation of the constant current circuit 11 starts. The switch SW1 opens the contact when a Low signal is input from the inverter INV1, and closes the contact when a High signal is input from the inverter INV1.

Next, the operation of the timer circuit configured as described above will be described. First, at the start of the operation of the timer circuit, since the contact of the switch SW1 is closed, it is the combined resistance value of the resistors R2 and R3 (r2 *
The current value of the current I1 is determined by the ratio of (r3) / (r2 + r3) to the resistance value r1 of the resistor R1. Capacitor C
1 is charged by the current I1 and has a potential of the reference voltage Vref.
If it exceeds 1, the comparator 14 outputs the first timer signal S3
Is output to the lighting main circuit 18 and also to the inverter INV1. The inverter INV1 inverts the signal and outputs a Low signal to the switch SW1.

Then, the switch SW1 receives the Low signal and opens the contact, and the resistor R2 becomes a resistor independent of the resistor R3. Therefore, the constant current circuit 11 has a resistance value r1 of the resistor R1.
The current value of the current I1 is determined by the ratio between the current I1 and the resistance value r2 of the resistor R2.

Here, the resistance value r2 of the resistor R2 and the resistance R
2 and resistance R3 (r2 * r3) / (r2 +
r3), the combined resistance value (r2 * r3) /
(R2 + r3) has a smaller resistance value. Therefore, the current value of the current I1 output from the constant current circuit 11 is the switch SW1
At the start of the timer circuit operation when the switch SW1 is opened when the potential of the capacitor C1 exceeds the reference voltage Vref1 and the switch SW1 is opened (hereinafter referred to as the switch SW1).
Current is high when switch is closed, switch S
The current I1 when W1 is open is a low current).

That is, as shown in FIG.
Until time t1 when the potential of the capacitor C1 exceeds the reference voltage Vref1, the capacitor C1 is charged by the high current I and the capacitor C
After time t1 when the potential of 1 exceeds the reference voltage Vref1, the capacitor C1 is charged by the low current I1. Therefore, the capacitor C1 is charged relatively quickly until the time t1, and is gradually charged after the time t1.
Then, as shown in FIG. 3, when the capacitor C1 is charged relatively quickly, the potential rise due to the charging is large, so that even if the noise is superimposed on the current I1, it is hardly affected by the noise. Therefore, although the potential of the capacitor C1 is above and below the potential near the reference voltage Vref1, chattering hardly occurs.

As described above, in the timer circuit of the present embodiment, the charging is performed relatively quickly during the measurement of the first measurement time T1, so that chattering at the time t1 is hardly generated, and the timer signal is accurately measured. Can be generated, and after the time t1, the current switching circuit 16 slowly charges the capacitor C1 with the current I1 as a low current value, so that the measurement can be performed even if the measurement time T2 is long.

[Second Embodiment] FIG. 4 is a block diagram of a timer circuit according to the present invention. FIG. 5 is an explanatory diagram of the operation of the timer circuit of the present invention. In FIG. 5, the same reference numerals are given to the same portions as those of the timer circuit described in the first embodiment, and the detailed description of the same portions will be omitted.

The timer circuit of the present embodiment shown in FIG.
The following configuration is different from the timer circuit described in the first embodiment in features.

That is, as the current re-switching circuit 22 corresponding to the current re-switching unit, the current value switching comparator 19
In this configuration, a gate 20 and a reference voltage generation circuit 21 are provided. Specifically, the reference voltage generation circuit 21 outputs the reference voltage Vre
f3 is generated and input to the non-inverting input terminal of the comparator 19, and the potential of the capacitor C1 is input to the inverting input terminal of the comparator 19. The reference voltage Vref3 is equal to the reference voltage Vref1 and the reference voltage Vref.
2.

The comparator 19 compares the reference voltage Vref3 with the potential of the capacitor C1, and outputs Low when the potential of the capacitor C1 is lower than the reference voltage Vref3, and outputs Low when the potential of the capacitor C1 is higher than the reference voltage Vref3. Outputs High.

The OR gate 20 receives a high signal from one of the comparator 19 and the inverter INV1.
A high signal is input to the switch SW1 and the comparator 1
When a low signal is input from both the inverter 9 and the inverter INV1, a low signal is input to the switch SW1.

Next, the operation of the timer circuit having the above configuration will be described. First, at the start of the operation of the timer circuit, since the contact point of the switch SW1 is closed, the combined resistance value of the resistors R2 and R3 is (r2 * r3) / (r2 +
The constant current circuit 11 outputs a high current I1 according to the ratio between r3) and the resistance value R1 of the resistor R1. When the capacitor C1 is charged by the high current I1 and the potential exceeds the reference voltage Vref1, the comparator 14 outputs a High signal, which is the first timer signal S3, to the lighting main circuit 18 and also to the inverter INV1. The inverter INV1 inverts the signal and outputs a Low signal to the OR gate 20. At this time, since the potential of the capacitor C1 has not yet exceeded the reference voltage Vref3, the comparator 19 outputs Low. Accordingly, since Low and Low are input to the OR gate 20, the OR gate 20 inputs Low to the switch SW1.

Then, the switch SW1 receives the Low signal and opens the contact, and the resistor R2 is independent of the resistor R3. Therefore, the constant current circuit 11 has a resistance value r1 of the resistor R1.
And the resistance R2 of the resistor R2 to output a low current I1. Then, the charging of the capacitor C1 is performed slowly (period t1 to t3 in FIG. 5).

When the charging of the capacitor C1 further proceeds after a lapse of time, the potential of the capacitor C1 becomes equal to the reference potential Vref3.
(Time t3 in FIG. 5). Then, the comparator 19 outputs High, and the OR gate 20 becomes High by the High of the comparator 19 and the Low of the inverter INV1.
Will be output. And the switch SW1 is High
Since the signal is received and the contact is closed again, the constant current circuit 1
1 again charges the capacitor C1 with the high current I1 (period t3 to t2 in FIG. 5). The reference voltage Vr
ef3 is (Vref1 / t1) = (Vref2-Vre
f3) / (t2-t3)> (Vref3-Vref1)
What is necessary is just to satisfy the relationship of / (t3−t1), and it may be appropriately set according to the output current value of the constant current circuit 11.

After a further time has passed, the capacitor C
1 advances, the potential of the capacitor C1 becomes the reference potential V
ref2 (time t2 in FIG. 5). Then, the comparator 15 outputs Hi as the second timer signal S4.
The gh signal is output to the lighting main circuit 18.

With the above configuration, when the potential of the capacitor C1 exceeds the reference voltages Vref1 and Vref2, the constant current circuit 11 outputs the high current I1 and chattering occurs because the capacitor C1 is rapidly charged. And the potential of the capacitor C1 is lower than the reference voltage Vref.
1 to the reference voltage Vref3, the low current I1
This allows the capacitor C1 to be charged, thereby enabling long-time measurement.

Further, since a plurality of capacitors are not used, errors due to individual variations of the capacitors do not occur, and the circuit configuration is simplified.

In the present embodiment, the description has been made on the assumption that two measurement times, ie, the measurement time T1 and the measurement time T2, are measured. However, the present invention is not limited to this. It may be time. In this case, the constant current circuit 11 outputs a high current I1 when the potential of the capacitor C1 rises near each reference voltage, and outputs a low current again when the potential of the capacitor C1 exceeds the reference voltage. Thus, a plurality of current switching circuits and current re-switching circuits may be provided.

In the present embodiment, the resistor R3 and the switch are used as the current switching section and the resistor R3 of the current mirror circuit is used.
2 are provided in parallel, but the present invention is not limited to this configuration, and the current value may be switched outside the constant current output unit. For example, a configuration may be employed in which a circuit that varies the current is interposed between the constant current output unit and the capacitor.

In the present embodiment, the reference voltage generating circuit is connected to the non-inverting input terminal of the comparator and the capacitor is connected to the inverting input terminal. However, the present invention is not limited to this. When the reference voltage generation circuit is connected to the inverting input terminal of the comparator and the capacitor is connected to the non-inverting input terminal, the high and low outputs are inverted with respect to the description of the embodiment. What is necessary is just to make the structure of a re-switching part correspond to what inverted the signal.

[0042]

Since the timer circuit according to the present invention is constructed as described above, according to the first aspect of the present invention, the current switching section for switching the current output from the constant current output section is replaced with the constant current output section. Because the charging section is charged with a high current when the potential of the charging section is near the reference voltage, and charged with a low current otherwise, the charging section is charged even with a long measurement time. This has the effect that the time can be accurately measured.

According to the present invention, the constant current output section can output a constant high current and a constant low current and outputs a constant high current in an initial operation state. The unit causes the constant current output unit to output a constant low current when detecting the first timer signal,
The measurement time corresponding to the first reference voltage can be accurately measured, and the measurement can be performed even if the measurement time corresponding to the second reference voltage is long.

According to the present invention, a third reference voltage which is a value between the first reference voltage and the second reference voltage is compared with a potential of the charging section. When the potential of the charging unit is higher than the third reference voltage, a current re-switching unit that outputs a high current to the constant current output unit is provided connected to the constant current output unit. This has the effect that the measurement time can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an example of a timer circuit according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of the timer circuit according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the timer circuit according to the first embodiment of the present invention, showing a state where chattering does not occur.

FIG. 4 is a configuration diagram of an example of a timer circuit according to a second embodiment of the present invention;

FIG. 5 is an operation explanatory diagram of the timer circuit of the present invention.

FIG. 6 is a circuit diagram of a conventional timer circuit.

FIG. 7 is an operation explanatory diagram showing a relationship between a time measured by a conventional timer circuit, a reference voltage, and a potential of a capacitor.

FIG. 8 is an explanatory diagram of chattering operation of a timer circuit according to a conventional technique.

FIG. 9 is a circuit diagram of another timer circuit of the related art.

FIG. 10 is an operation explanatory diagram showing a relationship between a time measured by a conventional timer circuit and a reference voltage.

[Explanation of symbols]

 Reference Signs List 11 constant current output section 14 first signal comparison section 15 second signal comparison section 16 current switching section 22 current re-switching section C1 charging section

Claims (3)

[Claims] 1. A constant current output section for outputting a constant current, a charging section charged by the constant current output section, and comparing a first reference voltage with a potential of the charging section to determine a potential of the charging section. A first signal comparison unit that outputs a first timer signal to an external control target circuit when the first reference voltage is higher than the first reference voltage, a second reference voltage higher than the first reference voltage, and a potential of the charging unit. A second signal comparison unit that outputs a second timer signal to an external control target circuit when the potential of the charging unit is higher than a second reference voltage by comparing the constant current output unit A timer circuit, wherein a current switching unit for switching a current output from the current circuit is connected to a constant current output unit. 2. The constant current output section is capable of outputting a constant high current and a constant low current, and outputs a constant high current in an initial operation state. The current switching section outputs the first timer signal. 2. The timer circuit according to claim 1, wherein upon detection, the constant current output section outputs a constant low current. 3. A third reference voltage, which is a value between the first reference voltage and the second reference voltage, is compared with a potential of the charging unit, and a potential of the charging unit is set to a third reference voltage. 3. The timer circuit according to claim 2, wherein a current re-switching unit for outputting a high current to the constant current output unit when the voltage is higher than the voltage is connected to the constant current output unit.