JPS634318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention can be used as a power source for a flash discharge lamp, a spot welding machine, a magnetizer, etc., where a large amount of direct current is required in an extremely short period of time. The present invention relates to a DC power supply device that supplies a load with accumulated charges stored in a capacitor group formed by connecting several capacitors in series.

Conventionally, this type of DC power supply basically
It is configured as shown in the figure. First, when the switch 1 is open, the output current from the rectifier circuit 2 flows through the resistor 3 as a charging current for the capacitor group 8 consisting of a series connection circuit of capacitors 4, 5, 6, and 7. While charging the capacitors 5, 6, and 7, the current also flows to the resistors 9, 10, 11, and 12 that are individually connected in parallel to each of the capacitors 4, 5, 6, and 7. Then, when switch 1 is closed, the charges accumulated in capacitor group 8 are discharged through switch 1 and load 13, and DC current is supplied to load 13, but at the same time, resistors 9, 10, 11, and 12 are also A discharge current flows due to the accumulated charges in the capacitors 4, 5, 6, and 7.

As shown in FIG. 1, each capacitor 4, 5, 6, 7 is connected to a resistor 9, 10, 11, 1
There have also been proposals that take measures to eliminate unnecessary power consumption by connecting the capacitors 4, 5, 6, and 7 in parallel, and to eliminate charging of the capacitors 4, 5, 6, and 7 with opposite polarity. In any case, it is possible to connect DC capacitors in series.

However, if the leakage current increases due to deterioration of the capacitor over time, the terminal voltage will decrease due to the loss even if the same charging current is passed through the capacitor. In this case, since charging is performed until a predetermined voltage is reached, an overvoltage is applied to the series-connected capacitors whose leakage voltage does not increase. When overvoltage is applied in this way, dielectric breakdown occurs, loss increases, and heat is generated, leading to destruction of the capacitor case and activation of the explosion-proof valve. As a result, the deterioration of one capacitor in a capacitor group may lead to the destruction of many capacitors connected in series, and the ejection of the filling may stain the device, making repair difficult.

The present invention has been made in view of the above points, and provides a DC power supply device that can prevent the adverse effects that occur when the capacitors forming a capacitor group deteriorate and leak current increases. The purpose is to obtain.

The present invention connects individual diodes in parallel with series-connected capacitors constituting a capacitor group with a predetermined polarity, detects the forward current flowing through the diodes with a detection means, and prohibits charging based on this detection output. The structure is such that it is possible to prevent harmful effects such as destruction of the capacitor case by prohibiting charging.

A first embodiment of the present invention will be described based on FIGS. 2 to 4. This embodiment is used as a DC power source for a flash discharge lamp in a flash fixing device of a copying machine, and first a power supply source 14 is provided. This power supply source 14 includes an AC power supply 15, a solid state relay 16, and a leakage transformer 1.
7 and a full-wave rectifier circuit 18. Here, the solid state relay 16 becomes conductive when the control input to it is at L level, connecting the AC power supply 15 and leakage transformer 17, and becomes disabled when the control input is at H level. The AC power source 15 and the leakage transformer 17 are cut off by becoming conductive. A capacitor group 19 is connected between the DC output terminals of the full-wave rectifier circuit 18. This capacitor group 1
9 is a capacitor 19a, 19b, 19c, 19d
are connected in series. Further, a flash discharge lamp 20 is provided in which the terminal voltage of this capacitor group 19 is applied to the discharge electrode inclination. This flash discharge lamp 20 emits light by discharging the charges accumulated in the capacitor group 19 when a trigger pulse St is supplied to its trigger electrode 21 from a trigger pulse generator (not shown).

Furthermore, charging control means/recharging control means 22 for controlling the solid state relay 16 is provided. That is, the resistor 2 is connected in parallel to the capacitor group 19 and is generated at the midpoint of the connection as a comparison voltage obtained by dividing the terminal voltage of the capacitor group 19.
3 and 24 are provided. And this resistance 2
A differential amplifier 26 is provided, in which a comparison voltage from 3 and 24 is input to an inverting input terminal via a resistor 25. The non-inverting input terminal of this differential amplifier 26 is connected via a resistor 27 to resistors 28, 29 and the power supply Vcc.
It is connected to the midpoint between the resistor 28 and the resistor 29 in the reference voltage generating circuit. Here, the differential amplifier 26 does not produce the output signal Se when the comparison voltage is higher than the reference voltage, and outputs the output signal Se when it is lower than the reference voltage. and,
Flip-flops 30 and 31 each constituted by two NAND gates are provided.
That is, when the output signal Se from the differential amplifier 26 is at the L level, the flip-flop 30 is set and its output signal Sf goes to the L level, and this L level output signal Sf resets the flip-flop 31 so that its output signal Sg becomes the L level. This is the H level. This output signal Sg is input to the solid state relay 16 as a control input.

Therefore, each of the capacitors 19a, 19b,
Diodes 32a and 3 are individually connected to 19c and 19d.
2b, 32c, and 32d are connected in parallel.
Here, these diodes 32a, 32b, 3
The connection polarity of 2c and 32d is such that it shows a non-conducting state with respect to the charging current for the capacitor group 19. And each diode 32a, 32
A light emitting diode 33 is connected in series to b, 32c, and 32d.
a, 33b, 33c, 33d are connected, and these light emitting diodes 33a, 33b, 33c, 33
d have resistors 34a, 34b, 34c, and 3, respectively.
4d are connected in parallel. Further, the light emitting diodes 33a, 33b, 33c, and 33d operate to cause the diodes 32a, 32b, and 3
Phototransistors 35a, 35b, 35c, and 35d are provided for detecting currents 2c and 32d. These phototransistors 35a, 35b,
35c and 35d are light emitting diodes 33a and 33
b, 33c, and 33d constitute a detection means, each emitter is commonly connected to the OV terminal, and each collector is commonly connected to the output terminal 36.

The detection output from this output terminal 36 is input to the charging inhibiting means 37. That is, a memory element 38 that receives the detection output as an input, and a driver 39 that is controlled by the output of this memory element 38.
, a relay 40 driven by this driver 39 , and a relay contact 41 that is opened and closed by this relay 40 to cut off the AC power supply 15 .

In such a configuration, the capacitor group 19 is connected so that the flash discharge lamp 20 is repeatedly emitted six times.
A case where the charging operation for the capacitor group 19 and the discharging operation from the capacitor group 19 are controlled will be described with reference to FIG.

First, when the charging set signal Sa output from the sequence controller of the copying machine goes to L level,
Flip-flop 31 is set and its output signal Sg goes to L level, making solid state relay 16 conductive. As a result, the AC power supply 15 and the leakage transformer 17 are connected, and the capacitor group 19 is charged by the output current from the full-wave rectifier circuit 18. Then, when the terminal voltage of the capacitor group 19 reaches a predetermined first voltage, the output signal Se of the differential amplifier 26 becomes L level and the flip-flop 30 is set. Therefore, the output signal Sf goes to L level and resets the flip-flop 31, and the output signal Sg goes to H level.
level, the solid state relay 16 becomes non-conductive and the charging operation for the capacitor group 19 is stopped. This means that the terminal voltage of the capacitor group 19 is always maintained at a predetermined voltage value due to the charging operation, so that light is emitted by the discharge current of the capacitor group 19 after the charging operation is stopped. The amount of light emitted by the operating flash discharge lamp 20 is stabilized. specifically,
During this charging operation, the change in the terminal voltage Vc of the capacitor group 19 increases along the charging curve, as shown in FIG. 4d, and when the first voltage is reached, the charging operation is stopped. The change mode is such that the voltage value stops increasing.

When the trigger pulse St is applied to the trigger electrode 21, the flash discharge lamp 20 enters a discharge state, discharges the accumulated charge in the capacitor group 19, and emits light for a period of several tenths of milliseconds to several milliseconds. do. Here, for example, the light emission output of the flash discharge lamp 20 is converted into an electric signal by a photoelectric conversion element, or the magnetic field is obtained by detecting a discharge current, or a magnetic field generated by the discharge current is detected. A light emission signal Sc, which can be obtained by has been entered. Therefore,
As described above, when the flash discharge lamp 20 emits light and the light emission signal Sc is generated, the flip-flop 30 is reset by the inverted light emission signal and its output signal Sf is changed to H level.

In this way, the flip-flop 30 maintains the L level state until it is reset by the inverted light emission signal, so even if the charge set signal Sa is input during this L level period, the charge set signal Sa Capacitor group 19 by Sa
The charging operation for the battery will not be restarted. Therefore, after the capacitor group 19 is once charged by the charging operation for the capacitor group 19 and reaches a predetermined first voltage, the flip-flop 30 is activated by an inverted light emission signal indicating that the capacitor group 19 has been discharged. is reset and its output signal Sf
The recharging operation for the capacitor group 19 is inhibited until the voltage reaches the H level.

In this way, after the capacitor group 19 is charged once until the terminal voltage of the capacitor group 19 reaches a predetermined first voltage, the accumulated charge of the capacitor group 19 is discharged to the load, and the terminal voltage is lower than the first voltage. Since recharging of the capacitor group 19 is prevented until the voltage falls below the predetermined second voltage, the capacitor 19 in the capacitor group 19
Each terminal voltage of a, 19b, 19c, and 19d has a voltage value that is inversely proportional to the respective capacitance value. That is, in the operation for the capacitor group 19, each capacitor 1 connected in series is charged using the output current of the full-wave rectifier circuit 18 as a charging current.
Since charging currents of the same current value flow through capacitors 9a, 19b, 19c, and 19d, each capacitor 19a,
The amount of charge (time integral value of charging current) accumulated in each capacitor 19b, 19c, and 19d is
9a, 19b, 19c, and 19d are all equal. Therefore, each capacitor 19a, 19
The terminal voltages at capacitors 19a, 19c, 19d are inversely proportional to their respective capacitance values, and as a result, each capacitor 19a, 19b, 19c, 1
If the variation in capacitance value of capacitance 9d is kept within a predetermined range, each capacitor 19a, 19b, 19
Variations in the terminal voltages of terminals c and 19d can also be suppressed within a predetermined range.

Note that the signal Sr is sent to the flip-flops 30 and 31.
This is a reset signal used to determine the initial state of the device, or to return the device to its initial state when the device is in an abnormal operating state. Also, the fourth
In the figure, the period is the operating period of the flash fixing device, but the period is the period when the flash fixing device is not functioning, and this period is when the reset signal Sr is applied or the operating period of the flash fixing device. arises from the termination of

By the way, as mentioned above, each capacitor 19
The charges stored in a, 19b, 19c, and 19d are all equal. Then, charge it to the specified voltage,
Even when the flash discharge lamp 20 is made to emit light after charging has stopped, the discharge current is generated by each capacitor 19a, 19b, 19
c, 19d, so each capacitor 1
The charges of 9a, 19b, 19c, and 19d decrease by an equal amount, and when the voltage of the flash discharge lamp 20 reaches its discharge stop voltage, the discharge stops. At this time, the charges on the capacitors 19a, 19b, 19c, and 19d are also equal. Such capacitors 19a, 19
b, 19c, and 19d, diodes 32a, 32b, and 32b are connected in parallel to each other.
32c, 32d and light emitting diodes 33a, 3
No forward current flows through 3b, 33c, and 33d. Therefore, the light emitting diodes 33a, 33
Since none of the transistors b, 33c, and 33d emit light and the phototransistors 35a, 35b, 35c, and 35d are not conductive, the output terminal 36 is always at the L level, and the charging inhibiting means 37 does not operate.

However, the capacitors 19a, 19b, 19
When either of the leakage currents c and 19d increases, the energy lost as leakage current increases within the time from the start of charging to light emission. Therefore, at the start of light emission, the amount of charge stored in the capacitor with a large leakage current is small. and,
When the flash discharge lamp 20 emits light, the capacitors 19a, 1
Since the discharge currents of 9b, 19c, and 19d flow as a common current, each capacitor 19a, 19b,
The electric charges of capacitors 19c and 19d decrease by the same amount, and the one with the least electric charge among the capacitors 19a, 19b, 19c, and 19d reaches zero first (and therefore, its terminal voltage also becomes zero). becomes. At this time, capacitors 19a, 19b, 19c, 19
Other parts of d still have charges, so
As the discharge continues, this current becomes a current that charges the capacitor that has lost its charge first to the opposite polarity. However, each capacitor 19a, 19b, 19c, and 19d has diodes 32a, 32b, 32c, and
32d is connected, the discharge current from other capacitors is bypassed, and the capacitors are not charged to the opposite polarity. In this way, any of the diodes 32a, 32b, 32c, 3
When current flows through 2d, current also flows through the corresponding light emitting diodes 33a, 33b, 33c, and 33d, causing them to emit light. Then, phototransistors 35a, 35b, 35c, 3 corresponding to the light emitting diodes 33a, 33b, 33c, 33d emitted light.
5d becomes conductive and the output terminal 36 becomes L level.
The L level detection output from the output terminal 36 is input to the memory element 38, and the memory result is transmitted to the relay contact 41 via the driver 39 and the relay 40.
is opened, and the input of the AC power supply 15 is cut off. In this way, any of the capacitors 19a, 19b,
19c and 19d are detected as currents flowing through diodes 32a, 32b, 32c, and 32d parallel to them, and the input of AC power supply 15 is cut off to prohibit charging operation to capacitor group 19, so it is possible to detect deteriorated capacitors. This will not lead to insulation breakdown, destruction of the capacitor case, or activation of the explosion-proof valve. Therefore, it is possible to take measures such as replacing the capacitor before the capacitor breaks down and the filling material spews out, contaminating the device.

Next, a second embodiment of the present invention will be described based on FIG. The same parts as those shown in the previous embodiment are given the same reference numerals, and the explanation will be omitted. In this embodiment, a battery 42 is used as the power supply source, and the capacitor group 19 is connected via a switch 43 and a resistor 44 controlled by the charge control means/recharge control means 22. Furthermore, only one phototransistor 35 is provided for each of the light emitting diodes 33a, 33b, and 33c, and the light guides 45 are optically connected to each other. Note that the charging control means/recharging control means 22 is omitted in the figure.

In this way, even when the battery 42 is used, the operation can be controlled in the same manner as in the previous embodiment.

By the way, in these embodiments, the input of the AC power supply 15 and battery 42 is cut off by the detection output of the output terminal 36, but the detection output may be used to display the occurrence of an abnormality or to signal system downtime as a signal foretelling the deterioration of the capacitor. It is also possible to perform maintenance without any maintenance. Also, diode 3
As means for detecting the current flowing through 2a, 32b, 32c, and 32d, in addition to those shown in the examples, methods for detecting the change when the current starts flowing in a current transformer, a method for detecting with an alarm fuse, a Hall element or a magnetoresistive element are available. Various methods can be used, such as a method of detecting a magnetic field generated by an electric current. In any case, it is preferable to use an insulated type of detection means since the potentials of the detection parts are different. Furthermore, each light emitting diode 33a, 33b, 33c,
Although the light emission result of 33d is outputted as a logical sum to the output terminal 36, it is outputted individually to the memory element 3.
8, which capacitors 19a, 19b,
It may also be possible to indicate whether the leakage currents of 19c and 19d have increased so that subsequent measures can be easily taken.

Further, by providing a circuit configuration including flip-flops 30 and 31 as the charging control means/recharging control means 22, a recharging prevention function is provided. flash discharge lamp 20
If the time interval from the start of discharging to the capacitor group 19 is short and the terminal voltage of the capacitor group 19 does not decrease due to discharge of accumulated charges due to various factors during that time, the charging set signal Sa and the trigger pulse St For example, the hysteresis characteristic of the detection level of the differential amplifier 26 may be used to prevent the capacitor group 19 from being recharged between the two.

Furthermore, it goes without saying that the number of capacitors 19a, 19b, 19c, 19d, . . . constituting the capacitor group 19 is arbitrary.
Each capacitor 19a, 19b, 19 constituting
A resistor may be connected in parallel to each of c and 19d. In addition, individual capacitors 19a, 19b, 1
A plurality of element capacitors may be connected in series or in parallel so that 9c and 19d have a predetermined withstand voltage and capacitance.

In addition, in the embodiment, a case where the DC power source is used as a DC power source for the flash discharge lamp 20 of the flash fixing unit of a copying machine is explained, but it can also be used as a DC power source for the exposure lamp of a copying machine, a DC power source for a facsimile fixing unit, a welding machine, etc. It can also be effectively used as a DC power source for magnetizing machines, etc. For example, when applied to a DC power supply for a facsimile, the DC power supply of the present invention, which can be configured by simply connecting a plurality of capacitors in series as a capacitor group, can be effectively utilized. That is, in general, the feeding speed of recording paper in a facsimile machine varies depending on the state of image signal transmission on the time axis, so the light emitting cycle of the flash discharge lamp used in the fixing device in a facsimile machine is not constant. Therefore, the time from when the capacitor group in the DC power supply device finishes charging until the flash discharge lamp starts emitting light is also not constant.
Therefore, even if the time from the end of charging until the flashlight discharge lamp emits light is not constant, in order to keep the amount of light emitted from the flashlight discharge lamp approximately constant, it is necessary to discharge the capacitor during the irregular time. However, in the DC power supply device of the present invention, a capacitor group in which capacitors are simply connected in series can be used without requiring a resistor to connect each capacitor in parallel. This is because the amount of charge lost during non-constant time is extremely small.

In the present invention, diodes are individually connected in parallel to a group of capacitors connected in series as described above, and charging control means, recharging control means, detection means for detecting the current of the diode, and charging prohibition means are provided. Therefore, when the leakage current increases due to deterioration of the capacitor, the charging operation is reliably prohibited, and it has the effect of preventing harmful effects such as destruction of the capacitor case and spouting of the filling material. .

[Brief explanation of the drawing]

1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram showing a first embodiment of the present invention, FIG. 3 is a block diagram, FIGS. 4 a to 4 g are waveform diagrams for explanation, and FIG. The figure is a circuit diagram showing a second embodiment of the present invention. 14... Power supply source, 19... Capacitor group,
19a-19d...Capacitor, 22...Charging control means/recharging control means, 32a-32d...Diode, 35a-35d...Phototransistor (detection means), 37...Charging inhibiting means.

Claims (1)

[Claims] 1. A capacitor group consisting of a plurality of capacitors connected in series so that a charging current flows in common is connected to a power supply source, and each capacitor is individually connected with a diode with a connection polarity that shows a non-conducting state with respect to the charging current. Charging control means is provided which connects the capacitors in parallel and charges the capacitors until their terminal voltage reaches a predetermined first voltage, and stops charging when the terminal voltage reaches the first voltage, and after charging is stopped, the capacitors are charged. Recharging control means is provided to prevent recharging of the capacitor group until the terminal voltage of the group falls below a predetermined second voltage set lower than the first voltage, and a forward current flows through the diode. A detection means for detecting this current is provided,
A direct current power supply device comprising charging inhibiting means for inhibiting charging of the capacitor group based on the detection output of the detecting means.