JPS6311853B2 - - 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, so that the voltage across the capacitor group 8 as a whole becomes a predetermined value. However, even if the leakage current increases or the capacitance decreases in each capacitor 4, 5, 6, 7,
Since the charging operation is performed until a predetermined voltage value is reached, excessive voltage may be applied to other capacitors or to a capacitor whose capacitance has decreased. When excessive voltage 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, one capacitor in the capacitor group failed or deteriorated, causing other capacitors to be destroyed as well, and the equipment was contaminated by the spewing of the filling.
Repair may be difficult.

The present invention has been made in view of the above points, and is designed to prevent capacitors constituting a capacitor group from failing.
It is an object of the present invention to provide a DC power supply device that can prevent the adverse effects that occur when excessive voltage is applied due to deterioration.

The present invention detects an overvoltage occurring in each capacitor connected in series constituting a capacitor group using an overvoltage detection means, operates a voltage control means based on the detected output, controls the charging voltage of the capacitor group, and destroys the capacitor case. In addition, when charging is completed, charging to the capacitor group is stopped by the charging stop means, so that the amount of charge of all capacitors becomes constant.
In addition, since recharging is prohibited by the recharging inhibiting means from the time charging is stopped until the discharge operation to the load, the amount of charge in each capacitor is equal when discharging a group of capacitors, which prevents repeated charging and discharging of each capacitor. The structure is such that charging and discharging is performed with a constant amount of charge even when the battery is charged, so that no local unbalance occurs.

A first embodiment of the present invention will be described based on FIGS. 2 and 3. 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 is composed of an AC power supply 15, a solid state relay 16, a leakage transformer 17, 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 as a load in which the terminal voltage of the capacitor group 19 is applied to the discharge electrode. This flash discharge lamp 20 emits light by discharging the charges accumulated in the capacitor group 19 when a trigger pulse S _t is supplied to its trigger electrode 21 from a trigger pulse generator (not shown).

Further, a charge control means/recharge control means 22 is provided as a charge stop means and a recharging prohibition means for controlling the solid state relay 16. That is, resistors 23 and 24 are connected in parallel to the capacitor group 19 and are generated at the midpoint of the connection as a comparison voltage obtained by dividing the terminal voltage of the capacitor group 19.
is provided. And this resistance 23, 24
A differential amplifier 26 is provided, in which a comparison voltage obtained by the voltage is inputted to an inverting input terminal via a resistor 25.
The non-inverting input terminal of this differential amplifier 26 is connected to a resistor 27.
It is connected between the resistors 28 and 29 in the reference voltage generation circuit using the resistors 28 and 29 and the power supply V _CC through the resistors 28 and 29 . Here, this differential amplifier 26 outputs its output signal Se when (comparison voltage)≧(reference voltage).
becomes an L level, and when (comparison voltage)<(reference voltage), the output signal Se becomes an H level.
Flip-flops 30 and 31 each constituted by two NAND gates are provided. That is, the flip-flop 30 is set when the output signal Se from the differential amplifier 26 is at the L level, and its output signal S _f becomes the L level, and the flip-flop 31 is reset by this L level output signal S _f and its output becomes low. The signal Sg becomes H level. This output signal Sg is applied to the solid state relay 16 as a control input.
has been entered.

Resistors 32a and 33a are connected in parallel to the capacitor 19a to divide the terminal voltage thereof. A series circuit of a light emitting diode 34a and a Zener diode 35a is connected in parallel to this resistor 33a. Here, when the voltage of the resistor 33a exceeds the conduction start voltage of the series circuit of the light emitting diode 34a and the Zener diode 35a, a current flows to the light emitting diode 34a and it emits light. It is set so that current flows through the light emitting diode 34a when an overvoltage is applied to the light emitting diode 19a. In this case, either of the resistors 32a and 33a may be used as a variable resistor to adjust the overvoltage detection level. A phototransistor 36a is provided which receives the light from the light emitting diode 34a and becomes conductive. These constitute overvoltage detection means for the capacitor 19a. Other capacitors 19b, 19c, 1
Similarly, overvoltage detection means are provided for each of the voltages 9d and 9d. The emitters of the phototransistors 36a, 36b, 36c, and 36d are commonly connected to the OV terminal, and the collectors are also commonly connected to the output terminal 37 and to the power supply V _CC through a resistor. That is, the configuration is such that the logical sum of the overvoltage signals for each capacitor 19a, 19b, 19c, and 19d is output from the output terminal 37. In this case, since the signal sources of the overvoltage signals of the capacitors 19a, 19b, 19c, and 19d have different potentials, the electrically isolated phototransistors 36a, 3
By transmitting signals through 6b, 36c, and 36d, their logical sum can be easily calculated. Further, a voltage control means 38 is provided which cuts off input to the capacitor group 19 based on an L level detection output from the output terminal 37.

In such a configuration, the third example describes a case where the charging operation for the capacitor group 19 and the discharging operation from the capacitor group 19 are controlled so that the flash discharge lamp 20 repeatedly emits light six times.
This will be explained with reference to the figures.

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 S _f 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 at the predetermined first level due to the charging operation.
Because it means that it is made with voltage,
After the charging operation is stopped, the amount of light emitted by the flash discharge lamp 20, which performs the light emitting operation by the discharge current of the capacitor group 19, is stabilized. Specifically, the terminal voltage of the capacitor group 19 during this charging operation
As shown in Figure 3d, the change in V _C rises along the charging curve, and when the charging operation stops when the first voltage is reached, the voltage value stops increasing. This will show the following.

When the trigger pulse St is applied to the trigger electrode 21 under the control of the sequence controller, the flash discharge lamp 20 enters a discharge state and discharges the accumulated charge in the capacitor group 19 for several tenths of a millisecond to a second millisecond. It emits light over a period of . 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. (However, since the light emitting operation is caused by the application of the trigger pulse St, the trigger pulse St may be used in place of the light emitting signal Sc.)
It is input to the 0 reset terminal. Therefore, as described above, the flash discharge lamp 20 emits light and sends a light emission signal.
When Sc occurs, the flip-flop 30 is reset by the inverted light emission signal and its output signal is
Sf changes 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 is input. The charging operation for the capacitor group 19 is not restarted by the signal Sa. Therefore, after the capacitor group 19 is once charged by the charging operation to the capacitor group 19 and reaches a predetermined first voltage, the capacitor group 19
The recharging operation of the capacitor group 19 is inhibited until the flip-flop 30 is reset by the inverted light emission signal indicating that the capacitor group 19 is discharged and its output signal Sf becomes H level.

In this way, the capacitor group 19 continues until the terminal voltage of the capacitor group 19 reaches the predetermined first voltage.
After the capacitor group 19 has been charged once, the capacitor group 19 is prevented from being recharged until the accumulated charge in the capacitor group 19 is discharged to the load and the terminal voltage becomes equal to or less than a predetermined second voltage lower than the first voltage. , capacitor 19 in 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 charging operation for the capacitor group 19, charging currents of the same current value flow through the series-connected capacitors 19a, 19b, 19c, and 19d, which are charged using the output current of the full-wave rectifier circuit 18 as the charging current. , 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, 19
If the variation in capacitance value of d 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 input to the flip-flop 30
Sr is a reset signal for determining the initial state of the flip-flops 30, 31, or for returning the device to its initial state when the device is in an abnormal operating state. Further, in FIG. 3, 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 when the flash fixing device is not functioning. Occurs due to the end of the fuser operating period.

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, no overvoltage is applied to each, and the resistors 33a, 33b,
The voltages at 33c and 33d do not exceed the Zener voltage, and no current flows through the light emitting diodes 34a, 34b, 34c, and 34d. Therefore, light emitting diode 3
4a, 34b, 34c, 34d do not emit light, and phototransistors 36a, 36b, 36
Since the terminals c and 36d are not conductive, the output terminal 37 is always at the H level due to the power supply V _CC and the voltage control means 38 does not operate.

However, the capacitors 19a, 19b, 19
If either capacitors c or 19d deteriorates or the capacitance decreases, the charging operation is performed until the voltage of the entire capacitor group 19 reaches a predetermined voltage, so the other capacitors or capacitance decreases. Overvoltage will be applied to the capacitor. now,
Assuming that an overvoltage is applied to the capacitor 19a,
The terminal voltage of the resistor 33a is the Zener diode 35a.
A current flows beyond the conduction start voltage of , and the light emitting diode 34a emits light. Then, upon receiving the light from the light emitting diode 34a, the phototransistor 3
6a becomes conductive, and an L level detection output is output from the output terminal 37. The voltage control means 38 is operated by this L level detection output, and the capacitor group 1
Input to 9 is cut off. Therefore, it is possible to protect the capacitor 19a by prohibiting the charging operation before an excessive voltage is applied to the capacitor 19a and causes dielectric breakdown or increases loss and generates heat. As a result, the capacitor case will not be destroyed or the explosion-proof valve will be activated, and measures such as replacing the capacitor 19a can be taken before the capacitor is destroyed and the filling material is ejected and the equipment becomes dirty. . Such operation is caused by the other capacitors 19b, 1
The same applies to 9c and 19d.

Next, a second embodiment of the present invention will be described with reference to 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 example,
The overvoltage detection means for the capacitor 19a is used as the overvoltage detection means for the capacitor group 19, and the capacitor 19a itself is omitted. That is, in the embodiment described above, overvoltage is detected for all capacitors 19a, 19b, 19c, and 19d, but the sum of the voltages of each capacitor 19a, 19b, 19c, and 19d becomes the voltage of the capacitor group 19 as a whole. Therefore, the resistors 32a, 33a, the light emitting diode 34
When the Zener diode 35a and the phototransistor 36a provide a protection function by overvoltage detection for the entire capacitor group 19, overvoltage detection for the capacitor 19a itself can be omitted.

According to such a configuration, it is possible to effectively prevent the voltage of the entire capacitor group 19 from becoming an overvoltage due to accumulation of setting errors in the detection levels of the respective capacitors 19a, 19b, 19c, and 19d.

In this case, capacitors 19a, 19b, 19c, and 19d are used to omit overvoltage detection.
It may be any of the following, and the capacitor 1
This embodiment may be applied by dividing the blocks 9a, 19b, 19c, and 19d into a plurality of blocks.

Incidentally, in these embodiments, the voltage control means 38 is operated by the detection output from the output terminal 37 to cut off the input to the capacitor group 19, but the detection output generates the trigger pulse St to activate the flash discharge lamp 20. A device that lowers the voltage by discharging, or a device that lowers the voltage by discharging the power source 14,
The capacitor may be discharged by connecting a circuit including a resistor and a switch in series between the pole and controlling the switch. Also, regarding the power supply source 14, the AC power supply 1
5. Although the full-wave rectifier circuit 18 is included, a direct current battery may be used instead.

In addition, capacitors 19a, 19b, 19c, 1
As a means for detecting overvoltage applied to 9d, as shown in FIG. 5, which takes the capacitor 19a as an example,
A series circuit of a constant voltage element 39a, a resistor 40a, and a light emitting diode 34a may be connected in parallel to the capacitor 19a. In this case, constant voltage element 39
A value that allows current to flow when an overvoltage is applied to the capacitor 19a is used as a. According to this, in the normal usage state in which no overvoltage is applied to the capacitor 19a, no current flows, so energy loss as a power source is reduced, and a low-power overvoltage detection element can be used. And light emitting diodes 34a, 34b, 3
Only one phototransistor is used for light emission detection of 4c and 34d, and each light emitting diode 34
The light from a, 34b, 34c, and 34d may be guided to this phototransistor by a light guide.

Further, the detection output from the output terminal 37 may be used to operate the voltage control means 38 and may also be output to the display section to display a trouble. In this case, each light emitting diode 34a, 34b, 34c,
34d may be output individually to display which capacitor 19a, 19b, 19c, 19d has a problem, 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 decreases little due to discharge of accumulated charges due to various causes during that time, the charge 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 recharging of the capacitor group 19 between the capacitors 19 and 19.

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 9
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 breakdown voltage and capacitance. Then, a diode is connected to each capacitor 1 with a connection polarity that indicates a non-conducting state with respect to the charging current for the capacitor group 19.
9a, 19b, 19c, 19d in parallel, and capacitors 19a, 19b, 19c, 19 when discharging.
It is also possible to prevent d from being charged to the opposite polarity, thereby eliminating the risk of heat generation, loss problems, damage, and the like. In this case, if a resistor is connected in series with each of these diodes, a relatively small capacitance diode can be used, and there is an advantage that the degree of freedom in selecting the diode can be increased.

In addition, in the embodiment, the case where the DC power supply is used as a DC power supply for the flash discharge lamp 20 of the flash fixing device of a copying machine is explained. It can also be effectively used as a DC power source for magnetizing machines, etc.

As described above, the present invention includes overvoltage detection means for detecting overvoltage occurring in each of the series-connected capacitors constituting the capacitor group, and voltage control means that operates based on the detection output to reduce the charging voltage of the capacitor group. Because of this, if the capacitor breaks down or deteriorates and overvoltage is applied, the charging voltage is lowered, thereby preventing damage such as destruction of the capacitor case or spouting of the filling material, and making it easier to replace the capacitor. This has the effect of allowing measures to be taken.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram showing a first embodiment of the present invention, FIGS. 3 a to 3 are waveform diagrams for explaining the same, and FIG. FIG. 5 is a circuit diagram showing a modification of the overvoltage detection means. 14... Power supply source, 19... Capacitor group,
19a to 19d...capacitor, 38...voltage control means.

Claims (1)

[Claims] 1. A power supply source, a group of capacitors made up of a plurality of capacitors connected in series so that a charging current flows in common, and supplying the sum voltage of the capacitors to a load; overvoltage detection means for detecting overvoltage occurring in each of the capacitors; Voltage control means for controlling the charging voltage of the capacitor group based on the detection output of the overvoltage detection means; Charging stop means for detecting the terminal voltage of the capacitor group and stopping charging the capacitor group when the charging is completed. , a DC power supply comprising a recharging prohibition means for prohibiting recharging of the capacitor group from the time when the charge is stopped by the charge stop means until the capacitor group discharges to the load. Device.