JPH0829465A - Capacitor capacity variation detecting circuit and power source life detecting circuit - Google Patents

Abstract

PURPOSE:To eliminate the necessity of using an accumulator and/or a memory by eliminating the need to accumulate the operation time of equipment at ambient temperature and to eliminate the necessity of using an expensive sensor for measuring the ambient temperature. CONSTITUTION:A detecting capacitor C2 is installed at substantially the same ambient temperature as a temperature at which a capacitor C1 for a power supply is used, and the capacitor C2 is charged and discharged by the turning-on and -off of a transistor Tr1 by charge and discharge pulses S1 from a microcomputer CPU, and the time at which charging of the capacitor C2 is started, and the time required to attain a reference voltage from the starting time according to the ascending speed of a charging curve corresponding to the degree of decrease in capacity of the capacitor C2 are calculated from outputs of a comparator AMP, and the microcomputer CPU judges decrease in capacity of the capacitor C2, i.e., decrease in capacity of the capacitor C1, thereby judging the functional deterioration of equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor capacitance change detecting circuit and a power source life detecting circuit.

[0002]

2. Description of the Related Art In recent years, the temperature of the inside of the temperature controller tends to remarkably increase due to the free power source and miniaturization. If not only the temperature controller but also the device is continuously used in a state of being placed under a high environmental temperature, the internal parts will be worn out and the function thereof will deteriorate. It is necessary for the temperature controller and other devices to be used safely and constantly in an optimal state by estimating that the ambient temperature has reached the end of its service life and being able to report this to the outside. Often.

[0003]

A smoothing aluminum electrolytic capacitor, which is often used for a power source, is one of the devices which are driven by a power source and whose lifetime is affected by an increase in the internal environmental temperature. This electrolytic capacitor causes capacity loss depending on the ambient temperature and the usage time under the ambient temperature. Therefore, in addition to installing an environmental temperature sensor inside the equipment, we will add a measuring means to measure the operating time of the equipment and accumulate the operating time related to the environmental temperature in memory under the control of the microcomputer. ,
It is conceivable that the remaining life of the capacitor can be calculated from the accumulated data when necessary using a predetermined formula, for example, a formula called Arrhenius, so that the life of the device can be output to the outside. .

However, in the estimation of such a life, it is necessary to accumulate the calculation result in the memory, but when the memory is destroyed due to a runaway of the microcomputer or there is a garbled memory. There is a problem that the accumulated data is damaged and accurate life estimation cannot be performed at all.

In addition, in estimating such a life, it is necessary to dispose an expensive sensor in order to directly measure the environmental temperature inside the equipment, which causes a problem in cost.

Therefore, in the present invention, the need for a memory for accumulating and storing data is eliminated by completely eliminating the need for accumulative calculation of the operating time of the equipment under ambient temperature, which results in the destruction of the memory or the memory. It is an object of the present invention to solve the above-mentioned inconveniences caused by garbles, and to substantially eliminate the need for a sensor for measuring the environmental temperature, and to eliminate the cost inconveniences caused by using expensive sensors.

[0007]

In order to achieve such an object, in the capacitor capacitance change detection circuit of the present invention, a detected capacitor whose capacitance change is to be detected is substantially the same. A detection capacitor provided under ambient temperature conditions, a charging / discharging means for charging / discharging the detection capacitor, and a voltage across the detection capacitor that is being charged / discharged by the charging / discharging means are input, and the voltage across the detection capacitor is input. Output means for outputting a predetermined output when the reference voltage is reached from the predetermined voltage, and monitoring the time until the voltage across the detection capacitor reaches the reference voltage from the predetermined voltage by the output from the output means The calculation means for calculating the capacitance change of the detected capacitor from the monitoring data is provided.

The charging / discharging means has a switching transistor having a collector and an emitter connected between both ends of the detection capacitor, and the switching transistor is turned on when the capacitance change of the detected capacitor is not measured to turn on the collector and the emitter. It may be constituted by means for discharging the charged electric charge of the detection capacitor through the means, and controlling so that the detection capacitor is charged by being turned off during the measurement.

The output means is composed of a comparator having one input portion connected to the detection capacitor and the other input portion connected to a reference voltage generating portion, and the comparator is input to the one input portion. The predetermined output may be output when the voltage across the detected capacitor exceeds a reference voltage applied to the other input section.

The power supply life detecting circuit of the present invention comprises a detection capacitor arranged under substantially the same environmental temperature condition as that in which the power supply capacitor is used, charging / discharging means for charging / discharging the detection capacitor, From the output means, inputting the voltage across the detection capacitor that is being charged / discharged by the charging / discharging means, outputting a predetermined output when the voltage across the detection capacitor reaches a reference voltage from the predetermined voltage, and the output means. The time taken for the voltage across the detection capacitor to reach the reference voltage from a predetermined voltage is monitored by the output of the output of the capacitor, the capacity loss of the power supply capacitor is measured from the monitoring data, and the power supply capacitor is built in from the measurement. It is characterized in that it is provided with a calculation means for calculating the life of the power supply.

The power supply life detection circuit may further include a warning device for warning the life of the power supply by turning on in response to a predetermined calculation output of the calculation means.

The calculating means is composed of a microcomputer, and the microcomputer controls the charging / discharging means so as to discharge the detection capacitor when the capacity loss of the power supply capacitor is not detected, and the detection means when the capacity loss is detected. Charging of the capacitor is started at a first time, and the capacity of the power supply capacitor is removed from the first time and a second time until the voltage across the detection capacitor reaches a reference voltage from a predetermined voltage. May be calculated.

The detection capacitor may be electrically connected in parallel to the power supply capacitor, and a charging voltage may be supplied from the power supply in common with the power supply capacitor.

The detection capacitor may be supplied with a charging voltage from the power supply via a resistor, and the charging time constant for the detection capacitor may be substantially determined by the detection capacitor and the resistor.

[0015]

In the capacitor capacitance change detection circuit of the present invention, the detection capacitor is arranged under substantially the same environmental temperature condition as that of the detected capacitor whose capacitance change is to be detected. When the capacitance changes under the ambient temperature, the detection capacitor also changes in capacitance almost in the same manner. Therefore, it is not necessary to provide a sensor that directly measures the ambient temperature in order to obtain data on how the capacitance of the detected capacitor changes with the ambient temperature.

Further, the rate of change of the voltage across the detection capacitor as it is charged and discharged, calculated by the calculation means, is
Corresponds to the capacitance change of the detection capacitor itself,
This capacitance change corresponds to the capacitance change of the detected capacitor because the detection capacitor is under the same environmental temperature as the detected capacitor.Therefore, in order to estimate the life of the detected capacitor, Does not need to be cumulatively stored, and a memory for the cumulative storage becomes unnecessary. As a result, there is no possibility that the life estimation cannot be determined due to memory destruction or memory corruption.

The charging / discharging means is a switching transistor having a collector and an emitter connected between both ends of the detection capacitor, and the switching transistor is turned on when the capacitance change of the detected capacitor is not measured. By discharging the charged electric charge of the detection capacitor through the emitter, and controlling it so that it is turned off at the time of measurement to charge the detection capacitor, the charged electric charge of the detection capacitor is changed to the capacitance of the detected capacitor. It can be reliably discharged for accurate measurement of changes.

The output means is composed of a comparator having one input portion connected to the detection capacitor and the other input portion connected to a reference voltage generating portion, and the comparator has the one input portion. In the case where the predetermined output is output when the voltage across the detection capacitor input to the input voltage exceeds the reference voltage applied to the other input section, the detection capacitor has a simplified configuration. When the voltage across both ends exceeds a predetermined value, that fact can be reliably output.

According to the power supply life detecting circuit of the present invention, the detection capacitor is arranged under substantially the same environmental temperature condition as that of the power supply capacitor whose capacitance change is to be detected. When the capacitance changes under the ambient temperature, the detection capacitor also changes in capacitance almost in the same manner. Therefore, it is not necessary to provide a sensor that directly measures the ambient temperature in order to obtain data on how the capacitance of the power supply capacitor changes with ambient temperature. Further, the rate of change of the voltage across the detection capacitor, which is calculated by the calculation means, according to the charging / discharging of the detection capacitor corresponds to the change in the capacitance of the detection capacitor itself. Since it is under temperature, it corresponds to the change in the capacity of the power supply capacitor. Therefore, it is not necessary to cumulatively store the operating time in order to estimate the life of the power source. Is unnecessary, and as a result, it is possible to prevent the life estimation from being determined due to memory destruction or memory corruption.

Further, when a warning device is provided to warn the life of the power source by lighting in response to a predetermined calculation output of the calculation means, it is convenient because the life of the device can be known.

The calculating means is constituted by a microcomputer, and the microcomputer controls the charging / discharging means so as to discharge the detection capacitor when the capacity loss of the power supply capacitor is not detected, and the capacity detecting means detects the capacity loss. The charging of the detection capacitor is started at a first time, and the power supply is started from the first time and a second time until the voltage across the detection capacitor from the output means reaches a reference voltage from a predetermined voltage. When the degree of capacity loss of the power supply capacitor is calculated, the life of the power supply can be accurately determined from the capacity loss of the power supply capacitor.

In the case where the detection capacitor is electrically connected in parallel to the power source capacitor and the charging voltage is supplied from the power source in common with the power source capacitor, the power source capacitor is further connected. Since it can be placed in the same usage environment, it is possible to accurately calculate the capacity omission of the power supply capacitor and thus to accurately determine the life of the power supply.

In the case where the detection capacitor is supplied with the charging voltage from the power source through the resistor and the detection capacitor and the resistor substantially determine the charging time constant for the detection capacitor, It is convenient to supply the charging voltage to the detection capacitor, and the charging / discharging time constant can be easily set.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a power supply including a power supply capacitor,
A capacitor capacitance change detection circuit according to an embodiment of the present invention for detecting a capacitance change (capacity loss) of the power supply capacitor is shown. With reference to the figure, this embodiment is applied to, for example, a power supply of a temperature controller.

The power supply P / S is for converting an AC input into a DC, and the main body PM including a transformer and a bridge rectification circuit is shown in a block diagram for easy understanding in the drawing, Separately from this, a smoothing capacitor for smoothing the output of the rectifier circuit is shown outside the main body PM. This smoothing capacitor is a power supply capacitor C1 composed of an aluminum electrolytic capacitor or the like. A resistor R1 and a detection capacitor C are connected in parallel to the power supply capacitor C1.
A series connection circuit with 2 is provided. The detection capacitor C2 is in close contact with the power supply capacitor C1 on, for example, a circuit board inside the temperature controller and is adhered by, for example, hot melt resin, so that this power supply is a detected capacitor for which a capacitance change such as capacitance loss should be detected. Capacitor C
1 is deployed under substantially the same environmental temperature conditions as used. The collector / emitter of the switching transistor Tr1 as a charging / discharging means for charging / discharging the detection capacitor is connected in parallel to the detection capacitor C2. The base of the switching transistor Tr1 is connected via a resistor to the microcomputer CPU which constitutes the charging / discharging means together with the switching transistor. One input part of the comparator AMP is connected to the common connection part of the resistor R1 and the detection capacitor C2. The comparator AMP inputs the voltage across the detection capacitor C2, which is being charged / discharged by the on / off operation of the switching transistor Tr1 serving as the charging / discharging means, to one input portion thereof, while the resistor R3 is input to the other input portion thereof. And a Zener diode D1 are connected to the reference voltage section. The comparator AMP also serves as an output means.
The voltage across the detection capacitor C2 applied to one input portion is compared with the reference voltage set in the reference voltage portion, and when the voltage across the detection capacitor reaches the reference voltage, a predetermined output is output to the microcomputer CPU. The microcomputer CPU, as the charging / discharging means, outputs a charging / discharging pulse for turning the switching transistor Tr1 on and off at regular intervals, and keeps the charging / discharging pulse at a high level when the capacity loss of the power supply capacitor C1 is not detected. At the time of detection, the voltage of both ends of the detection capacitor C2 reaches the reference voltage from the predetermined voltage by the output from the comparator AMP from the first time when it falls to the low level, with the function of causing the voltage to fall to the low level for a predetermined period. It also has a function as a calculation means for monitoring the second time until the time of the operation and using the difference between the two times as the monitoring data to calculate the capacity omission of the power supply capacitor C1.

To the output section of the microcomputer CPU is connected a warning means for executing the function as the arithmetic means and responding to the arithmetic output from the arithmetic means. This warning means is composed of a transistor Tr2 which is turned on and off by this operation output, and a warning display light emitting diode D2 which is turned on by a current given through a current limiting resistor R4 when the transistor Tr2 is turned on. Is turned on to warn the outside that the capacity of the power supply capacitor C1 has fallen below a predetermined value and the life of the device has reached the end.

First, the operation when there is no capacity omission in the detection capacitor C2 will be described with reference to FIG. 2. The microcomputer CPU periodically applies the charging / discharging pulse S1 to the base of the switching transistor Tr1 via a resistor. There is. When the charging / discharging pulse S1 is at the high level, it means that the capacity loss of the power supply capacitor C1 is not detected. At this high level, the switching transistor Tr1 is on. Therefore, the power supply capacitor C1 functions as a smoothing capacitor for the power supply, while both ends of the detection capacitor C2 are connected to the switching transistor Tr.
It is short-circuited at the collector-emitter of 1 and has no charge. Then, when the capacitance loss is detected, the switching transistor Tr1 is turned off when the high level is lowered to the low level, that is, when the charging / discharging pulse S1 is dropped at the first time or at O, the detection capacitor C2 is charged with no electric charge. It is charged with the voltage from the power supply from the zero state.
The voltage across the detection capacitor C2 rises as indicated by S2. This rising curve corresponds to the degree of capacity omission of the detection capacitor C2. That is, FIG. 2 corresponds to the case where there is no capacity omission of the detection capacitor C2, so the voltage S2 across the voltage reaches the reference voltage Vref of the reference voltage section at the second time t1. When the voltage S2 across the detection capacitor C2 reaches the reference voltage Vref,
The output S3 of the comparator AMP rises from a low level to a high level, whereby the microcomputer CP
The first time t0 when the charging / discharging pulse S1 falls in U
And the monitoring data which is the time T1 which is the difference from the second time t1 at which the voltage across the detection capacitor C2 reaches the predetermined value is given, and the microcomputer CPU of the detection capacitor C2 based on this monitoring data. There is no capacity omission, and therefore, it is determined that the power supply capacitor C1 under the same environmental temperature as the detection capacitor C2 also has no capacity omission.

On the other hand, the case where the detection capacitor C2 has a missing capacity will be described with reference to FIG. 3. As described above, the charging / discharging pulse S1 from the microcomputer CPU will be described.
Falls at the first time t0, the switching transistor Tr1 is thereby turned off, and the detection capacitor C2
Will be charged. When the detection capacitor C2 has a missing capacity, the time constant formed by the resistor R1 and the detection capacitor C2 becomes small, so this charging curve is S2 in FIG.
Ascends rapidly. Therefore, the second time t1 ′ when the voltage S2 across the detection capacitor C2 reaches the reference voltage Vref of the comparator AMP from the first time t0.
The time T2 up to is shorter than the time T1 in the case of FIG. The microcomputer CPU can determine the degree of capacity loss of the detection capacitor C2 from the monitoring data at this time T2, and can determine the capacity loss of the power supply capacitor C1 under the same environmental temperature as the detection capacitor C2. Further, when the time T2 becomes equal to or less than the value stored in advance, the above-described operation is repeated several times, and a program is configured to prevent malfunction due to the influence of noise or power supply fluctuation, thereby increasing the detection accuracy. Is configured.

[0030]

As described above, according to the capacitor capacitance change detection circuit of the present invention, the detection capacitor is arranged under substantially the same environmental temperature condition as that of the detected capacitor whose capacitance change is to be detected. Therefore, when the capacitance of the detected capacitor changes at the ambient temperature, the detection capacitor also changes in substantially the same capacity. Therefore, it is not necessary to provide a sensor that directly measures the ambient temperature in order to obtain data on how the capacitance of the detected capacitor changes with the ambient temperature. Further, the rate of change of the voltage across the detection capacitor, which is calculated by the calculation means, according to the charging / discharging of the detection capacitor corresponds to the change in the capacity of the detection capacitor itself. Since it is under temperature, it corresponds to the capacitance change of the detected capacitor.Therefore, it is not necessary to cumulatively store the operating time in order to estimate the life of the detected capacitor. There is no need for a memory for cumulative storage, and as a result, there is no disadvantage that the life estimation cannot be determined due to memory destruction or memory corruption.

Further, according to the power supply life detecting circuit of the present invention, the detection capacitor is arranged under substantially the same environmental temperature condition as that of the power supply capacitor whose capacitance change is to be detected. When the capacitor for use changes its capacitance under the ambient temperature, the capacitance of the detection capacitor also changes in a similar manner. Therefore, it is not necessary to provide a sensor that directly measures the ambient temperature in order to obtain data on how the capacitance of the power supply capacitor changes with ambient temperature. Also, calculated by the calculation means,
The rate of change of the voltage across the detection capacitor due to charging / discharging corresponds to the change in the capacitance of the detection capacitor itself.However, because this change in capacitance is at the same environmental temperature as the power supply capacitor, the power supply capacitor Therefore, it is no longer necessary to store the operating time in order to estimate the life of the power supply, which eliminates the need for the accumulator and the memory for the accumulative storage. In addition, it is advantageous in terms of cost, and the problem that the life estimation cannot be determined due to memory destruction or memory corruption is eliminated.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a capacitor capacity change detection circuit according to an embodiment of the present invention for detecting capacity loss of a power supply and a power supply capacitor as a smoothing capacitor thereof.

FIG. 2 is a timing chart for explaining the operation when there is no capacity omission in the power supply capacitor.

FIG. 3 is a timing chart for explaining the operation when the power supply capacitor has a missing capacity.

[Explanation of symbols]

 C1 Power supply capacitor C2 Detection capacitor R1 Charging resistance Tr1 Switching transistor AMP Comparator CPU Microcomputer

Claims (8)

[Claims] 1. A detection capacitor arranged under substantially the same environmental temperature condition as that of a capacitor to be detected whose capacitance change is to be detected; a charging / discharging means for charging / discharging the detection capacitor; Outputting means for inputting the voltage across the detection capacitor that is being charged and discharged by the charging and discharging means and outputting a predetermined output when the voltage across the detection capacitor reaches a reference voltage from the predetermined voltage; and the output means And a calculation means for calculating the capacitance change of the detected capacitor from the monitoring data of the time taken for the voltage across the detection capacitor to reach a reference voltage from a predetermined voltage by the output of Capacitor capacitance change detection circuit. 2. The charging / discharging means includes a switching transistor having a collector and an emitter connected between both ends of the detection capacitor, and the switching transistor is turned on when a capacitance change of the detected capacitor is not measured. 2. The capacitor capacitance change detection circuit according to claim 1, further comprising means for discharging the charged electric charge of the detection capacitor through the emitter and controlling the charging operation so that the detection capacitor is charged by being turned off during the measurement. 3. The output means comprises a comparator having one input portion connected to the detection capacitor and the other input portion connected to a reference voltage generating portion, the comparator having the one input portion. 3. The capacitor according to claim 1, wherein the predetermined output is output when the voltage across the detection capacitor input to the input voltage exceeds a reference voltage applied to the other input portion. Capacitance change detection circuit. 4. A detection capacitor arranged under substantially the same environmental temperature condition as that of a power supply capacitor, a charging / discharging means for charging / discharging the detection capacitor, and a charging / discharging operation by the charging / discharging means. The voltage across the detection capacitor is being input, and output means outputs a predetermined output when the voltage across the detection capacitor reaches a reference voltage from a predetermined voltage; Calculation to monitor the time required for the voltage across both ends to reach a reference voltage from a predetermined voltage, measure the capacity loss of the power supply capacitor from the monitoring data, and calculate the life of the power supply incorporating the power supply capacitor from the measurement. A power supply life detection circuit comprising: 5. The power supply life detection circuit according to claim 4, further comprising a warning device which lights up in response to a predetermined calculation output of the calculation means to warn the life of the power supply. 6. The calculating means is composed of a microcomputer, and the microcomputer controls the charging / discharging means so as to discharge the detection capacitor when the capacity drop of the power supply capacitor is not detected, and when the capacity drop is detected. Charging of the detection capacitor is started at a first time, and at the first time and a second time until the voltage across the detection capacitor reaches a reference voltage from a predetermined voltage, the charging of the power supply capacitor is started. The power supply life detection circuit according to claim 4 or 5, wherein the degree of capacity omission is calculated. 7. The detection capacitor is electrically connected in parallel to the power supply capacitor, and a charging voltage is supplied from the power supply in common with the power supply capacitor. The power supply life detection circuit according to any one of 1. 8. The detection capacitor is supplied with a charging voltage from the power source via a resistor, and the detection capacitor and the resistor substantially determine a charging time constant for the detection capacitor. The power supply life detection circuit according to claim 7, which is characterized in that.