JPS646635B2 - - Google Patents

Description

[Detailed Description of the Invention] A capacitor group formed by connecting a plurality of capacitors in series is charged so that the output current of the rectifier circuit becomes a common charging current, and the charging causes the capacitor group to be charged. A DC power supply device that supplies the accumulated charge to the load for use.
For example, it has been widely used as a DC power supply device in cases where a large DC current is required within an extremely short period of time, such as in flash discharge lamps, spot welding machines, and magnetizing machines.

Fig. 1 is a block diagram for explaining the problems of the above-mentioned type of DC power supply. In Fig. 1, RA is a rectifier circuit, SW is a switch,
L is a load, C ₁₁ to _{C 14} are capacitors, and R ₁₁ to _{R 15} are resistors. When the switch SW is open, the output current from the rectifier circuit RA passes through the resistor R ₁₅ to the capacitors C ₁₁ to C. The current flows as a charging current of a capacitor group consisting of ₁₄ series connected circuits, and the capacitor C ₁₁ ~
While C ₁₄ is charged, it also flows into the circuit of resistors R ₁₁ to _{R 14} .

Next, when the switch SW is closed, the charges accumulated in the capacitor group are discharged through the switch SW and the load L, and a DC current is supplied to the load L. At the same time, however, the charges accumulated in the capacitor group are discharged through the switch SW _and the load L, and a DC current is supplied to the _{load L.} A discharge current due to the accumulated charge of each capacitor C ₁₁ to C ₁₄ also flows through the resistors R ₁₁ to R 14 connected to the capacitors C 11 to _{C 14} .
By the way, the above-mentioned resistors R ₁₁ to _{R 14} are designed so that the discharge current flowing through them is several times to several tens of times larger than the leakage current value in the capacitors C ₁₁ to _{C 14} , and the applied voltage of the capacitors C ₁₁ to _{C 14} is Since each resistance value is selected to prevent excessive non-uniformity, in conventional DC power supplies, the resistance
Wasteful power consumption due to R ₁₁ to R ₁₄ was unavoidable.

For each of the multiple capacitors C ₁₁ to _{C 14} connected in series as described above, set a separate resistance.
The reason why one of each of _R11 to _R14 must be connected in parallel is that the equivalent parallel resistance value (usually the leakage current value) of each capacitor connected in series to form a capacitor group is The capacitors used to form a group of capacitors have a large variation among each capacitor, and this has a large temperature dependence and also varies greatly depending on the usage time. If a resistor is not connected in parallel to each capacitor, as charging is repeated, the voltage applied to each capacitor will gradually become uneven ( A capacitor with a small leakage current value has a higher terminal voltage (non-uniformity), and in extreme cases, a voltage higher than the allowable withstand voltage is applied to a capacitor with a small leakage current value. This is because the capacitor may be destroyed.

To this end, the plurality of series-connected capacitors C ₁₁ to _{C 14} that make up the capacitor group each have a discharge current with a current value several times to several tens of times the leakage current value. By connecting resistors R ₁₁ to _{R 14} with a resistance value that allows current to flow, uniform voltage is applied to each capacitor during charging, but by using resistors R ₁₁ to _{R 14} , As mentioned above, a large amount of wasteful power consumption will occur.

In addition, in a DC power supply device that supplies a load with a discharge current of a capacitor group consisting of a plurality of capacitors connected in series, there are variations in the voltage value V and the capacitance value C applied to the plurality of capacitors. , there will be a difference in the amount of charge (VxC) stored in each capacitor, but since the discharge current supplied to the load flows through each capacitor in series, the amount of charge that decreases in each capacitor during discharge is All capacitors are the same. Therefore, if there is a difference in the amount of charge stored in each capacitor during charging, the capacitor with a smaller amount of charge will lose its charge faster, and the other capacitors will continue discharging. Then, the capacitor that has lost its charge is charged to the opposite polarity by the current of discharge from the other capacitor.

If the capacitor used is polarized, such as an aluminum electrolytic capacitor, charging with the reverse polarity described above may cause significant internal heat generation and may significantly reduce performance. Furthermore, as mentioned above, the fact that there is a current that charges other capacitors with the opposite polarity means that the stored energy in the capacitor group is used for something other than the load. This means that the usage efficiency is poor. Therefore, it has also been desired that the DC power supply device be prevented from reducing the utilization efficiency of stored energy in the sense described above.

The present invention has been made for the purpose of providing a DC power supply device that can satisfactorily solve the problems that have arisen in the conventional DC power supply device described above. The specific contents of the DC power supply device will be explained in detail.

Figure 2 is a connection diagram showing an embodiment of the DC power supply of the present invention when a flash discharge lamp is used as the load. In Figure 2, AC is a power supply, SSR is a solid state relay, and T is a leakage Transformer, _Rec is a full-wave bridge rectifier circuit, L is a flash discharge lamp, TPG is a trigger pulse generation circuit, C is a capacitor group consisting of multiple capacitors C ₁ to C ₅ connected in series, and is a solid state relay
When the SSR is in the conductive state (in the following explanation, the solid state relay SSR is in the conductive state when the control input to it is low level, connects the AC power supply AC to the leakage transformer T, and also connects the control input to it) When the input is at a high level, it becomes non-conducting and cuts off the connection between the AC power supply AC and the leakage transformer T), while the AC power supply AC is connected to the leakage transformer T. , the AC voltage boosted by the leakage transformer T is applied to the full-wave bridge rectifier circuit _Rec , and the rectified output current from the full-wave bridge rectifier circuit _Rec is applied to the plurality of capacitors in the capacitor group C.
Charge to _C1 ~ _C5 .

Since the terminal voltage of the capacitor group generated by the above-mentioned charging is applied to the discharge electrode of the flash discharge lamp L, the flash discharge lamp L receives a trigger pulse from the trigger pulse generator TPG to its trigger electrode _te . When supplied, the accumulated charges in the capacitor group C described above are discharged and light is emitted. trigger pulse generator
The TPG is started by applying a lamp trigger signal supplied from a circuit (not shown) (when the flash discharge lamp is used for flash fixing in a copy machine, the sequence controller of the copy machine), and the flash discharge lamp is activated. It operates to give a trigger pulse to the L trigger electrode _te .

In the DC power supply device shown in the second figure, the charging operation for the capacitor group C described above is performed when the solid state relay SSR is brought into conduction.
Control of the non-conducting state is performed by a circuit composed of a comparator COMP, flip-flops FF ₁ and FF ₂ , and the like.

In the illustrated example, the comparator COMP is composed of a differential amplifier DA and resistors R ₅ to R ₇ , and the non-inverting input terminal of the differential amplifier DA is connected to the resistor R through the resistor R ₅ . It is connected to the connection point between resistor R ₃ and resistor R ₄ in the reference voltage generation circuit consisting of R ₃ , R ₄ and power supply V _cc , and is also connected to the connection point between resistor R 3 and resistor R 4.
The inverting input terminal of is connected to resistors R ₁ and R ₂ through resistor R ₆ .
It is connected to the connection point between resistor R ₁ and resistor R ₂ in the comparison voltage generation circuit consisting of the following.

Since the series connection circuit of resistors R ₁ and R ₂ that constitutes the comparison voltage generation circuit is connected to the terminal of capacitor group C, the terminal voltage of capacitor group C is connected to the connection point of resistor R ₁ and resistor R ₂ . A comparison voltage appears which is divided by the resistor _R1 and the resistor _R2 .

A comparator to which the reference voltage generated at the connection point between resistor R ₃ and resistor R ₄ in the reference voltage generation circuit and the comparison voltage generated at the connection point between resistor R ₁ and resistor R ₂ in the comparison voltage generation circuit are applied. COMP provides a low level (high level) output S _e to flip-flop _FF1 when the comparison voltage becomes higher (lower) than the reference voltage.

Flip-flops FF ₁ and FF ₂ may be of a well-known construction consisting of two NAND circuits. When the comparison voltage becomes higher than the reference voltage, the comparator
When the output of COMP is set to low level, the input to solid state relay SSR is set to high level through flip-flops FF ₁ and FF ₂ , and solid state relay SSR becomes non-conducting.
The charging operation for capacitor group C is stopped.
This means that the terminal voltage of capacitor group C is always set to a predetermined voltage value due to the charging operation, so after the charging operation is stopped, the terminal voltage of capacitor group C is Thus, the amount of light emitted by the flash discharge lamp L which performs the light emitting operation is stabilized.

Next, the operation of the DC power supply device shown in the second figure will be explained with reference to FIGS. 3a to 3g. FIG. 3 is an example waveform diagram when the charging operation for the capacitor group C and the discharging operation from the capacitor group C are controlled so that the flash discharge lamp L repeatedly emits light six times.

Fig. 3a shows the charging set signal S _a , and Fig. _3b shows the lamp trigger _signal S _b . When used as a discharge lamp for flash fixing, it is output from a sequence controller of a copying machine (not shown).

When the charge set signal S _a shown in FIG. 3A goes low level, the flip-flop FF ₂ is set and its output S _g goes low level, making the solid state relay SSR conductive and leaking the AC power source AC. Connected to the transformer T, the capacitor group C is charged by the output current from the full-wave bridge rectifier circuit _Rec . When the terminal voltage of the capacitor group C reaches a predetermined voltage value, the output S _e of the comparator COMP (Fig. 3 e) becomes a low level, thereby setting the flip-flop FF ₁ and changing the output of the flip-flop FF _1. S _f {Fig. 3 f} becomes low level, resets the flip-flop FF ₂ and makes its output S _g {Fig. 3 g} high level, solid state relay SSR becomes non-conductive and the capacitor The charging operation for group C is stopped. The change in the terminal voltage S _d of the capacitor group C during the charging operation is as follows:
The voltage rises along the charging curve in Figure d, and when a predetermined voltage value is reached, the charging operation is stopped and the voltage value stops increasing.

When the trigger pulse generated by the trigger pulse generator TPG by the lamp trigger signal S _b shown in FIG. 3b is applied to the trigger electrode t _e of the flash discharge lamp L, the flash discharge lamp L enters the discharge state. The accumulated charge in the capacitor group C is discharged, and light is emitted over a period of several tenths of a millisecond to several milliseconds. The signal S _c shown in FIG. may be obtained by detecting the flow, or
It may also be obtained by detecting the magnetic field generated by the discharge stream. The symbol S _c shown in Fig. 2
is the inverted signal S _c of the light emission signal S _c obtained as the output of the inverter by applying the above-mentioned light emission signal S _c to the inverter, and the symbol S _r shown in FIG. 2 is the flip-flop FF ₁ , This is a reset signal for determining the initial state of FF ₂ , or for returning the device to its initial state when the device is in an abnormal operating state. In addition, the above-mentioned light emission signal
S _c can be obtained by detecting a drop in the terminal voltage of the capacitor that accompanies the light emitting operation, or because the light emitting operation occurs by applying a trigger signal, the light emitting signal S _c can be substituted with the lamp trigger signal S _b . You may.

In Fig. 3, in the periods , , , the period is the operating period of the flash fixing device, and the period is the period in which the flash fixing device is not functioning, and during this period, the reset signal S _r is applied. Occurs either by time or by the end of a flash fuser operating period.

Now, when the flash discharge lamp L emits light and a light emission signal S _c is generated, the flip-flop FF ₁ is reset by the inverted signal S _c and its output S _f changes to a high level.

As mentioned above, flip-flop FF ₁ maintains the low level state until it is reset by the inverted signal S _c , so even if the charging set signal S _a is generated during the low level period, ,
The charging operation for the capacitor group C is not started by the charging set signal, and therefore, after the capacitor group C is once charged by the charging operation for the capacitor group C and reaches a predetermined terminal voltage. The recharging operation for the capacitor group C is prevented until the flip-flop FF ₁ is reset by the inverted signal S _c indicating that the capacitor group C is discharged and its output S _f becomes high level. It is.

In this way, in the DC power supply device of the present invention, the capacitor group C is charged once until the terminal voltage of the capacitor group C reaches the first predetermined voltage value, and then the accumulated charge of the capacitor group C is discharged to the load. Since the capacitor group C is prevented from being charged again until the terminal voltage reaches the second predetermined voltage value lower than the first predetermined voltage value,
The terminal voltage of each individual of the plurality of series-connected capacitors C ₁ to C ₅ in the capacitor group C is:
The voltage value is inversely proportional to the capacitance value of each capacitor C ₁ to C ₅ .

That is, in the charging operation for capacitor group C, a charging current with the same current value flows through C ₁ to _{C 5} of multiple capacitors connected in series, which are charged using the output current of the rectifier circuit as a charging current. Therefore, the amount of charge accumulated in each individual capacitor C ₁ to C ₅ (time integral value of charging current) is equal for each individual capacitor C ₁ to _{C 5} ,
Therefore, the terminal voltage at each individual capacitor is set to a voltage value that is inversely proportional to the capacitance value of each capacitor C ₁ to C ₅ , and therefore,
If the variation in the capacitance values of C ₁ to _{C 5} is kept within a predetermined range, the variation in the terminal voltage of each capacitor C ₁ to _{C 5} can also be suppressed within a predetermined range.

In the above case, even if there are variations in leakage current among the capacitors C ₁ to _{C 5} that make up capacitor group C, this is because the terminal voltage of each capacitor C ₁ to _{C 5} varies according to the variation in leakage current. However, the DC power supply device of the present invention has the problem as explained with reference to FIG. 1, that is, when recharging is performed, a capacitor with a small leakage current may have an excessive terminal voltage. The fact that this does not occur in the DC power supply device of the present invention is that there is no recurrent charge applied to the capacitor group C until the accumulated charge in the capacitor group C is discharged to the load L and the terminal voltage of the capacitor group C reaches the second predetermined voltage value. This can be easily understood since the charging operation is blocked.

The terminal voltage of the capacitor group C is determined by the charge accumulated in the capacitor group C being discharged through the resistors R ₁ and R ₂ in the comparison voltage generation circuit, or by each individual capacitor C ₁ making up the capacitor group C. Even if the accumulated charge in ~ _C5 decreases due to discharge due to the respective leakage currents, the accumulated charge in capacitor group C decreases due to the load L.
Because it can only be recharged after it has been discharged,
The terminal voltage of each individual capacitor in the plurality of series-connected capacitors constituting the capacitor group C in the DC power supply device of the present invention does not become excessive as in the conventional example. It is.

Therefore, in the DC power supply device of the present invention, the capacitors used to form the capacitor group C are not only capacitors with relatively low leakage current such as paper capacitors and film capacitors, but also aluminum electrolytic capacitors. Even if the capacitors have a large leakage current, it is possible to configure the capacitor group C by connecting the capacitors in series without connecting a resistor in parallel with them.

The DC power supply device of the present invention shown in FIG. 2 has a circuit configuration including flip-flops FF ₁ and FF ₂ to provide a recharging prevention function. If the time interval between the point in time and the point in time when discharge starts from capacitor group C to the load is short, and the drop in the terminal voltage of capacitor group C due to discharge of accumulated charges due to various causes during that time is small, It is also possible to prevent recharging of the capacitor group C between the charge set signal S _a and the lamp trigger signal S _b by using, for example, the hysteresis characteristic of the detection level of the comparator COMP.

In carrying out the present invention, it goes without saying that the number of capacitors forming the capacitor group C is arbitrary, and a parallel resistor may be connected to each of the plurality of capacitors forming the capacitor group C. . Further, a plurality of element capacitors may be connected in series or in parallel so that each capacitor constituting the capacitor group C has a predetermined withstand voltage and capacitance. In the example circuit shown in the second figure, a leakage transformer T, a solid state relay SSR, etc. are used, but for example, a high frequency inverter, a choke coil, etc. are used, and the oscillation state of the high frequency inverter is controlled by the solid state relay SSR. It may be configured as follows.

4 to 6 illustrate other embodiment circuits of the DC power supply device of the present invention, and each of FIGS. 4 and 5 shows the capacitor group C in the device shown in FIG. and corresponding parts of the flash discharge lamp L, and FIG. 6 shows the leakage transformer T, the full-wave bridge rectifier circuit R _ec , the capacitor group C, and the flash discharge lamp L in the device shown in FIG. Only the parts corresponding to each part are shown, and illustrations and descriptions of other constituent parts are omitted.

First, in FIG. 4, a capacitor group C includes a plurality of capacitors C ₁ to C ₅ connected in series, and diodes D ₁ to D ₅ are individually connected in parallel to each capacitor C ₁ to C ₅ . ing. The connection polarities of the diodes D ₁ to _{D 5} described above are set so that they exhibit a non-conducting state with respect to the charging current to the capacitor group C. In this way, diodes D ₁ - _{D 5} are individually paralleled to each capacitor C ₁ - C ₅ .
When using capacitor group C connected to
Even if the amount of accumulated charge in each capacitor C ₁ to _{C 5} varies when supplying a discharge current to the load due to variations in leakage current in each capacitor C ₁ to _{C 5} , capacitors with a small amount of accumulated charge By using capacitor group C having the configuration shown in Figure 4, the accumulated charge in capacitor group C can be completely prevented. In addition, even if a polar capacitor is used as a capacitor, it will not be charged to the opposite polarity, which reduces the heat generation and loss that occur when it is charged to the opposite polarity. , there is no risk of damage.

That is, in the capacitor group C shown in Figure 4, each of the capacitors C ₁ to _{C 5} has a small amount of accumulated charge, and even after the accumulated charge of that capacitor has been completely discharged, the other capacitors are still discharging. , the capacitor will not be charged with the opposite polarity because the discharge current from the other capacitor will be bypassed by the diode connected in parallel with that capacitor. be.

In addition, in implementation, a configuration may be adopted in which the diodes D _{1 to D 5 are connected to the capacitors C 1 to C 5} , and then resistors are connected individually to the diodes D ₁ to _{D 5 in} parallel.

In the capacitor group C shown in the configuration example shown in Figure 5, a series connection circuit of a diode and a resistor is individually connected in parallel to each capacitor C ₁ to C ₅ making up the capacitor group C. . The connection polarity of the diodes D ₁ to D ₅ in FIG. 5 is the same as in the case of the configuration example shown in FIG. 4, and the resistors 1 to 5 are connected in series with the diodes D ₁ to D ₅ because This is because by connecting a resistor in series, a relatively small capacitance diode can be used, which has the advantage of increasing the degree of freedom in selecting the diode. In addition, as the resistors 1 to 5 used in this case, when the discharge current of another capacitor flows through the series connection circuit of a diode and a resistor, the voltage value generated across the series connection circuit is the same as that of the series connection circuit. A capacitor having a resistance value that is smaller than the reverse voltage value allowed by the capacitor to which it is connected is used.

In the embodiment shown in FIG. 6, a voltage doubler rectifier circuit is constructed by diodes D ₆ and D ₇ and capacitors C ₁ to C ₆ forming a capacitor group C. This is an example of the configuration when used, and in FIG. 6, 6 is a transformer. Even in the configuration example shown in FIG. 6, the configuration of the capacitor group C as described with reference to FIGS. 4 and 5 may be adopted.

The embodiments so far have concerned the case where the DC power supply device of the present invention is used as a DC power supply for a flash discharge lamp of a flash fixing device of a copying machine. It can also be effectively used as a power supply for an exposure lamp, a facsimile fixing device, a welding machine, a magnetizing machine, etc.

When the DC power supply device of the present invention is applied to a DC power supply device for a facsimile fixing device, the DC power supply device of the present invention may have a configuration in which a plurality of capacitors are simply connected in series as the capacitor group C. can be used effectively. 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 C 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 to the time when the flash discharge lamp emits light is not constant, in order to keep the amount of light emitted from the flash discharge lamp approximately constant, it is necessary to However, in the DC power supply device of the present invention, each capacitor in capacitor group C is connected in series with no resistor connected in parallel. This is because the capacitor group C having a configuration connected to the capacitor group C can be used, so that the amount of charge lost during the above-mentioned irregular time is extremely small.

Furthermore, as mentioned above, the DC power supply device of the present invention allows the use of aluminum electrolytic capacitors, making it possible to downsize the device and reduce costs. In particular, in a flash fixing device, the length of the flash discharge lamp must correspond to the size of the paper to be fixed.
In the case of a long flash discharge lamp, a high discharge start voltage is inevitable, but in the past, an excessive voltage was sometimes applied during recharging due to the reasons mentioned above, so a low withstand voltage aluminum electrolytic capacitor was connected in series. However, in the DC power supply device of the present invention, aluminum electrolytic capacitors can be simply connected in series until the required withstand voltage is obtained, which reduces the size and cost of the device. This makes it easier to reduce.

As is clear from the above description, according to the present invention, all of the conventional problems mentioned above have been satisfactorily resolved, and it is possible to easily and inexpensively produce a high-performance DC power supply device that can be applied to various types of equipment. can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a conventional DC power supply device, FIG. 2 is a circuit diagram of an embodiment of the DC power supply device of the present invention, FIGS. 3A to 3G are explanatory waveform diagrams, 4 to 6 are partial circuit diagrams of the DC power supply device of the present invention. RA... Rectifier circuit, SW... Switch, L...
Load, R _ec ...Full wave bridge rectifier circuit, SSR...
Solid state relay, COMP... comparator,
TPG...Trigger pulse generator, C...Capacitor group, _FF1 , _FF2 ...Flip-flop, C1 _~
C ₆ , C ₁₁ ~ C ₁₄ ... Capacitor, R ₁ ~ R ₆ , R ₁₁ ~
_R14 , 1 to 5...Resistance, _D1 to _D7 ...Diode,
T...Leakage transformer, 6...Trance.

Claims (1)

[Scope of Claims] 1. A rectifier circuit, and a capacitor group formed by connecting a plurality of capacitors in series so that the output current from the rectifier circuit flows in common as a charging current;
Control that charges the capacitor group until the terminal voltage thereof reaches a first predetermined voltage, and stops charging when the terminal voltage of the capacitor group reaches the first predetermined voltage. and means for preventing recharging of the capacitor group after charging is stopped until the terminal voltage of the capacitor group falls below a second predetermined voltage that is lower than the first predetermined voltage. DC power supply comprising means for preventing recharging. 2. a rectifier circuit, and a capacitor group formed by connecting a plurality of capacitors in series so that the output current from the rectifier circuit flows in common as a charging current;
A diode connected in parallel with each individual capacitor in the capacitor group with a connection polarity that can prevent the discharge of the charge in each capacitor, and a diode connected in parallel with each individual capacitor in the capacitor group, control means capable of charging the capacitor group until the voltage reaches the first predetermined voltage and stopping the charging when the terminal voltage of the capacitor group reaches the first predetermined voltage; A DC power supply device comprising recharging prevention means for inhibiting recharging of the capacitor group until the voltage falls below a second predetermined voltage that is lower than the first predetermined voltage.