JP3456787B2 - Electrolytic capacitor deterioration determination circuit and DC power supply equipped with the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deterioration determining circuit for an electrolytic capacitor, which detects a deterioration state of an electrolytic capacitor and compares it with a preset reference signal to determine the deterioration state.

[0002]

2. Description of the Related Art Conventionally, a method of detecting a ripple voltage applied to a capacitor has been used as a means for discriminating aging deterioration of an electrolytic capacitor of a power supply device in which chemical deterioration is caused and aging deterioration cannot be avoided. That is, when the electrolytic capacitor deteriorates with time, the internal electrolytic solution decreases and the equivalent series resistance (ES
R) increases. In this method, deterioration is determined by detecting the increase in ESR in the form of increase in ripple component (ripple voltage or current) and comparing it with the initial ripple component. FIG. 9 is a result of experimentally determining ESR (results are internal resistance and impedance) that increase during this deterioration. It can be seen that both internal resistance and impedance increase when the capacitor capacity deteriorates (capacity decreases). (Figure 9 x) (3)

[0003]

2. Description of the Related Art Heretofore, as a ripple detecting means, a low-pass filter (LP) or a band-pass filter (BP) has been known, but the former (LP) is The ripple voltage applied to the electrolytic capacitor contains various frequency components and noise, and the ripple voltage waveform applied changes depending on the power on the load side to be supplied, so it is possible to judge deterioration with high reliability and stability. It is difficult to obtain a detection signal to do. Further, in the latter method (BL), even if the center frequency of the filter is set to be synchronized with the operating frequency of the power supply device, it is expected that the respective frequencies will be deviated in the actual operation, and stable detection is possible. It is difficult to get a signal.
Further, it cannot be applied to a power supply device of a frequency modulation type or a power supply device of different operating frequency, and thus lacks versatility.

[0004]

SUMMARY OF THE INVENTION The first object of the present invention is to provide a highly accurate electrolytic capacitor deterioration establishment circuit by adopting a novel ripple voltage detection method. A second object of the present invention is to provide a power supply device which is equipped with this deterioration determination circuit and constantly monitors the deterioration state of the electrolytic capacitor to improve the added value of the device.

[0005]

In order to achieve this object, an electrolytic capacitor deterioration judging circuit of the present invention uses a DC voltage composed of a capacitor and a transformer, with a DC voltage superimposed with a ripple voltage applied to the electrolytic capacitor as an input. By extracting the ripple voltage (AC) isolated by the voltage cut circuit and inputting it to the LC tuning circuit, only the sinusoidal ripple voltage component that tunes to the operating frequency set by the LC is output, and this is converted to DC. The signal and the reference signal are compared, and this is used as a detection signal for deterioration determination.

[0006]

[Action]

(4) LC for detecting ripple voltage of electrolytic capacitor deterioration judgment circuit
By using a tuning circuit, it is possible to detect a sinusoidal signal of only the arbitrary frequency component of the ripple voltage applied to the electrolytic capacitor. Noise characteristics are improved. Also LC
By adopting a variable capacitance diode in the capacitance portion of the tuning circuit, it becomes possible to correct the tuning frequency by applying an external DC voltage and adapt to the corresponding frequency of various power supply devices, and in addition to the above, versatility is improved. In addition, the power supply device equipped with the deterioration determination circuit using the electrolytic capacitor deterioration determination circuit can constantly monitor the deterioration state of the electrolytic capacitor, so that the added value of the power supply device can be further improved. Further, the DC voltage applied to the variable capacitance diode for varying the capacitance is, for example, a required DC level F synchronized with the operating frequency of the power supply device, F
If it is configured to be supplied from the / V conversion circuit, the accuracy of tuning frequency detection is improved and automatic adjustment is possible.

[0007]

1 and 2 are diagrams showing an embodiment of a deterioration judging circuit of the present invention and operation waveform diagrams of respective parts thereof, in which 1 is an electrolytic capacitor deterioration judging circuit, 3-1 and -2 are voltage inputs across electrolytic capacitors. Reference numeral 4 is a DC cut capacitor, 5 is an insulating transformer, 6 is an inductance, 7 is a capacitance, 8 is a DC conversion circuit, 9 is a deterioration determination comparison circuit, 10 is a reference signal circuit, A and L are alarms, etc. The display unit, 13 is a variable capacitance diode, and 13-1 is an external DC input terminal.

The operation of this circuit will be described with reference to FIG. In FIG. 2, (a) to (d) are parts a to e of FIG.
, The dotted line a shows the initial waveform, and the broken line shows the degraded waveform. C is a reference signal. First, a DC voltage on which ripple voltage is superimposed is input to the voltage inputs 3-1 and -2 across the electrolytic capacitor. 2 (a) and converted into an AC signal by the DC cutting capacitor 4 and the insulating transformer 5,
2 (b) The frequency components input to the LC tuning circuit composed of the inductance 6 and the capacitance 7 and tuned to the arbitrarily set tuning frequency. 2D, the deterioration discrimination comparison circuit 9 compares the reference signal with the reference signal shown in FIG. L (for example, LED lighting, buzzer ringing, etc.)
Is output to the outside. Further, in FIG. 1, the capacitance C of the LC tuning circuit is composed of a variable capacitance diode 13 and a capacitor 7 which make it possible to vary the capacitance by applying a DC voltage by an external signal 13-1.

As shown in FIG. 3, the variable capacitance diode has a characteristic that its CD capacitance decreases when the applied DC voltage VDC is increased, and conversely increases when it is decreased. However, since it is basically a diode, care must be taken when using it in a low voltage application region where the applied voltage falls below the oscillation output. In this embodiment, two variable capacitance diodes are connected in series in opposite directions and a DC voltage (13-1) is applied to the connecting portion. With this configuration, the diode characteristics in the low voltage application region can be canceled, and stable operation is possible up to this region. Incidentally, in the case of LC tuning, the tuning frequency fr is fr = 1 / 2π
√ Determine by LC. At this time, if either L or C can be changed, fr changes. By adopting a variable capacitance diode for this C, fr can be made variable by the L of this embodiment.
It is a C tuning method. For example, suppose that until now it has been synchronized with the ripple of 200 KHZ. Next, in order to deal with a ripple of 100 KHZ, the voltage applied to C may be lowered and the capacitance may be increased so that fr = 100 KHZ.

FIG. 4 shows an AC-DC deterioration determination circuit according to the present invention.
In the block diagram when mounted on a DC power supply device such as a converter, REC is a rectifier circuit that rectifies an AC voltage AC,
L. C is an input smoothing choke coil and capacitor, T
Is an output transformer, S is a switching element such as MOSFET provided in the primary winding n1 of the output transformer T, D is a rectifying diode, C1 is an input electrolytic capacitor, C2 is an output electrolytic capacitor, and RL is a load. is there. The deterioration establishing circuit 1 may be provided in either the input or output electrolytic capacitor C1 or C2, or in both. FIG. 5 shows an example in which the electrolytic capacitor 17 for output is used. (6)

In the operation of this circuit, the switching element S alternately repeats ON-OFF by the control signal of the set operating frequency output from the control circuit COT. By this operation, a DC voltage on which a ripple voltage synchronized with the operating frequency is superimposed is applied to the output electrolytic capacitor C2 of the power supply device. Then, this DC voltage is input to the deterioration determination circuit 1 to perform deterioration determination. Also, the variable capacitance diode 13
Although a DC voltage is applied to correct the tuning frequency, the operating frequency is input from the control circuit COT to the F / V conversion circuit 14 and the required DC voltage 13-1 is supplied to the variable capacitance diode 13.

FIG. 6 is a circuit diagram of a deterioration establishing circuit 1 applied to the above DC power supply device (FIG. 5). The circuit configuration is a DC converting circuit 8 for converting a detection voltage into a DC to obtain a DC detection value for deterioration determination,
LC tuning circuit, tuning frequency control 13-1 for applying DC voltage to variable capacitance diode 13 used in LC tuning circuit, detection electrolytic capacitor voltage input 3-1, 3-2 for inputting ripple voltage It is composed of As the operation, the ripple voltage superimposed on the direct current is input to the detection electrolytic capacitor voltage input. Then, only the ripple voltage component is applied to the LC tuning circuit, and when a DC voltage that tunes to the frequency of the ripple voltage component is applied from the tuning frequency control, a sine wave with the maximum voltage amplitude is output to the output VPO. . This is a circuit for inputting the DC conversion circuit to obtain the deterioration determination DC detection value DC.

FIG. 7 is a characteristic diagram showing the relationship between the output voltage detection VQDC (mv), the ripple voltage Vp (mv) and the capacitance Cr (μF) when a deteriorated capacitor is used as the output electrolytic capacitor C2 and applied to a DC power supply. In the figure, (a) is ripple voltage (Vp) (b) is detection voltage VQDC (mv)
Shows the respective changes. The deteriorated capacitor used was one in which a hole of about 1φ was made in advance in the capacitor head, and accelerated deterioration was carried out by reducing the electrolytic solution by heating at high temperature on a hot plate. See also L. The tuning frequency of the C tuning circuit was the operating frequency of the switching element S of the power supply device. The power supply used was 5V, 10A, the operating frequency was 200KHz, and the capacitor (7) used was LXF10V2200μF. As is clear from FIG. 7, when the deteriorated capacitor is used, both the ripple voltage and the detected voltage increase in the same tendency as the deterioration progresses. Therefore, it can be said that the LC tuning circuit can determine deterioration. For example, if it is attempted to judge the deterioration with 1300 μF of the capacitor capacity of 65%, the detected value voltage is 250 mV, so the circuit in the latter stage may be configured to send the alarm when the voltage exceeds this value. Although not shown, the load (RL) current (± 0) under the above conditions was measured under the conditions of I0 = 0A and 10A. As a result, the relationship between the ripple voltage and the detection voltage VPO due to the difference in the load current of the power supply device It is shown that the detected waveform does not change even if the ripple voltage waveform changes depending on the load. Furthermore, when the ripple voltage increases due to the load, the detected voltage also increases and it is confirmed that the increase change of the ripple voltage can be detected by the LC tuning circuit. .

FIG. 8 is a block diagram showing an embodiment of the present invention and shows an example in which a deterioration determining circuit with a correction circuit added to a power supply device is mounted. An example of one circuit configuration in the case is shown. The component circuit is
Reference signal (RE
It is composed of a REF circuit for correcting F), a circuit for detecting an operating frequency, correcting a deviation of a tuning frequency, and correcting a detected value in the case of a frequency modulation system, and using the detection input of a deterioration determination circuit.

[0015]

Since the present invention is constructed as described above, it has the following effects. (1) Since the electrolytic capacitor deterioration determination circuit employs an LC tuning circuit as a signal detection circuit that detects the ripple voltage of the electrolytic capacitor, the detection signal is a component that is tuned to an arbitrary frequency, for example, the operating frequency of the power supply device. Only a sine wave signal is obtained, and a DC signal obtained by converting this into a DC signal has high reliability and stability. Furthermore, by making the capacitance C portion of the LC tuning circuit a variable capacitance diode whose capacitance can be changed by applying a DC voltage (8), it becomes possible to correct the tuning frequency and adapt to various power supply devices. The reliability, stability, and versatility of the circuit can be selected and improved. Further, since it is possible to compare and judge the reference signal corrected by the electrolytic capacitor deterioration determination circuit by detecting the temperature of the electrolytic capacitor and the load current of the power supply device and the DC detection signal, it is possible to propose a highly accurate deterioration determination circuit. Further, if the DC voltage applied to the variable capacitance diode is configured to be supplied by using a variable resistor that can be externally adjusted, an inexpensive deterioration determination circuit at a tester level can be proposed. (2) A power supply device equipped with a deterioration determination circuit that uses an electrolytic capacitor deterioration determination circuit has a variable capacitance diode in the LC tuning circuit.
Since the DC voltage to be applied is input from the F / V conversion circuit that receives the operating frequency of the control circuit of the power supply device as input, the ripple voltage component that is always tuned to the operating frequency of the power supply device can be detected, Further, since the state of the electrolytic capacitor of the power supply device can be constantly monitored, it is possible to judge deterioration with high reliability and stability.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention (deterioration determination circuit).

FIG. 2 is an operation waveform diagram of each part of the embodiment (FIG. 1) of the present invention.

[Fig.3] Characteristic diagram of capacitance CD (μF) -DC applied voltage VDC (V) of variable capacitance diode

FIG. 4 is a block diagram of a DC power supply device to which the present invention is applied.

FIG. 5 is a circuit diagram of an embodiment of the present invention (DC power supply device)

FIG. 6 is a circuit diagram of an embodiment of the present invention (deterioration determination circuit).

FIG. 7 shows the ripple voltage VP− of the embodiment of the present invention (FIG. 5).
Detection voltage VQDC characteristic diagram (9)

FIG. 8 is a circuit diagram of an embodiment of the present invention (DC power supply device)

FIG. 9 is a characteristic diagram of internal resistance R / internal impedance when the electrolytic capacitor is deteriorated.

[Explanation of symbols]

1 Electrolytic capacitor deterioration judgment circuit 3-1, 3-2 Electrolytic capacitor input terminal 4 DC cut capacitor 5 isolation transformer 6 Inductance (L) 7 Capacitance (C) 8 DC conversion circuit 9 Degradation establishment department 10 Reference signal AL display 13 Variable capacitance diode 13-1 External DC input terminal S switching element REC rectifier circuit C1, C2 electrolytic capacitors T output transformer 14 F / V conversion circuit COT control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01R 31/00 H02H 7/12 H02M 3/28 H02M 7/06

Claims (7)

(57) [Claims] 1. A ripple voltage detection circuit for an electrolytic capacitor is constituted by a DC cut capacitor and an insulating transformer, and is constituted by an inductance and a capacitance for detecting the ripple voltage detection signal as a sine waveform.
The LC tuning circuit, a DC converting circuit for converting the sine wave detection signal into a DC signal, and a deterioration determining section for comparing the DC converting signal with a reference signal .
The electrolytic capacitor deterioration judgment circuit is characterized by being tuned to an arbitrary frequency . 2. The electrolytic capacitor deterioration determining circuit according to claim 1, characterized in that a display means of the alarm such as the output of said deterioration determining unit. 3. Connect the variable capacitance diode to the LC tuning circuit, according to claim 1 or 2 SL, characterized in that as allowed to apply an external DC voltage to variable capacitance diodes
Electrolytic capacitor deterioration determination circuit mounting. 4. A rectifier circuit for rectifying an AC voltage, an electrolytic capacitor for smoothing the rectified output, an output transformer,
In a DC power supply device provided with a switching element connected to the primary winding side of the output transformer and a rectifying diode connected to the secondary winding side of the output transformer, a deterioration determination circuit for the electrolytic capacitor is provided. And a deterioration determination circuit for the electrolytic capacitor, a ripple voltage detection circuit for the electrolytic capacitor using a DC cut capacitor and an insulating transformer, an LC tuning circuit for detecting the ripple voltage detection signal as a sine waveform, and the sine wave detection signal. A DC conversion circuit for converting to DC and a deterioration determination unit for comparing the DC conversion signal with a reference signal, and the LC tuning circuit is connected to an external DC signal.
DC power supply device characterized in that it can be tuned to an arbitrary frequency by . 5. A DC power supply device comprising a switching element provided on the primary winding side of an output transformer, a rectifying diode for rectifying and smoothing an output on the secondary winding side of the output transformer, and an electrolytic capacitor for output, An LC capacitor deterioration judgment circuit is provided, and the electrolytic capacitor deterioration judgment circuit is a ripple voltage detection circuit for the electrolytic capacitor using a DC cut capacitor and an insulating transformer, and LC tuning for detecting the ripple voltage detection signal as a sine waveform. A circuit, and a direct current circuit for converting the sine wave detection signal into a direct current,
The LC tuning circuit is configured by a deterioration determining unit that compares the DC signal and a reference signal, and the LC tuning circuit is arbitrarily rotated by an external DC signal.
A DC power supply device characterized in that it can be tuned to the wave number . 6. A DC power supply device according to claim 4, wherein a switching operation frequency detection signal of a switching element is used as the external DC signal. Characterized by using the temperature detection signal or the load current detection signal of the electrolytic capacitor as the determination signal correction element with 7. adds a determination signal correction element to the deterioration determination of the deterioration determination circuit of the electrolytic capacitor Claim
The DC power supply device according to 4, 5, or 6 .