JPH0330887B2 - - Google Patents

Description

[Detailed Description of the Invention] When an inductive load or a capacitive load is connected to an AC power source, a problem arises in that reactive current flows through the AC power source and reduces the effective power capacity of the AC power source. Become. As is well known, it has been a common practice to connect a capacitor or inductor for power factor correction in parallel with the load to avoid using an AC power source with a larger capacity than necessary. It is.

By the way, a capacitor or an inductor conventionally used for power factor improvement is used to flow a leading phase current or a slow phase current to cancel a slow phase current or a leading phase current flowing due to a load. Therefore, from the load side, a capacitor or inductor for power factor correction is useless for load operation, but in order to have the required current capacity, a capacitor or inductor must be prepared for power factor correction. This has resulted in imposing a large economic burden on the users of the devices.

Now, in a rectifier for converting AC power to DC power, if the overcurrent limiting impedance element used in the rectifier is a capacitor or inductor, it can be used as a load that flows reactive current to the AC power source. The same applies to capacitors or inductors used as overcurrent limiting impedance elements used in rectifiers for flash lamp power supplies of copying machines.

In other words, in a rectifier configured to rectify and smooth AC power to supply DC power to a load, when the power switch is turned on, the smoothing capacitor ( In order to prevent the rectifier from being damaged by a large charging current flowing into the energy storage capacitor (energy storage capacitor), an impedance element is installed between the AC power source and the rectifier circuit to limit excessive current when the power is turned on. It is well known that a resistor, an inductor, or a capacitor is used as the impedance element.

When a resistor is used as an impedance element for overcurrent limiting, problems arise such as large power loss and heat generation, so if an inductor or capacitor is used as an impedance element for overcurrent limiting, AC It operates as a load that causes a large reactive current to flow through the power supply. In the case where the rectifying device for the flash lamp power supply of the copying machine repeatedly charges and discharges the smoothing capacitor (4 energy storage capacitors) within a short period of time, the rectifying device for the flash lamp power supply of the copying machine Improving the power factor is a particularly important issue.

The present invention provides an impedance element for overcurrent limiting used as a component of a rectifying device for a flash lamp power supply of a copying machine, which is a capacitor for power factor correction;
Alternatively, the present invention provides a rectifying device for a flash lamp power source of a copying machine, which can be effectively used as an inductor and solve various conventional problems. The specific contents will be explained in detail.

1 to 5 are block diagrams of a rectifier for a flash lamp power source of a copying machine according to different embodiments of the present invention, and FIGS. 1 and 2 are block diagrams of a case in which a power transformer is not used, FIGS. 3 to 5 each show an example of a configuration using a power transformer.

In each figure, 1 is an AC power supply, L is an inductor for overcurrent limiting, C is a capacitor for overcurrent limiting, 2 is a flash lamp of a copying machine connected as a load of a rectifier for the flash lamp power supply, 3 is a trigger electrode, and SW is a switch.

First, in the rectifying device for a flash lamp power supply of a copying machine shown in the embodiment shown in FIG. and a full-wave bridge rectifier circuit AR2 are connected via a switch SW, and the DC outputs from the full-wave bridge rectifier circuits AR1 and AR2 are connected to a common smoothing capacitor (energy storage capacitor) Cf with matching polarity. The voltage across the smoothing capacitor (energy storage capacitor) Cf is applied to the flash lamp 2 of the copying machine.

In the rectifier for the flash lamp power supply of the copying machine shown in the first diagram, when the switch SW is turned on, the DC output full-wave rectified by the two rectifier circuits AR1 and AR2 is transferred to the capacitor (energy storage capacitor) Cf. When a trigger pulse is applied to a trigger electrode 3, a flash lamp 2 of the copying machine discharges and emits light by the accumulated charge of a smoothing capacitor (energy storage capacitor) Cf.
The switch SW performs opening and closing operations under the control of a control circuit (not shown), and supplies AC power to the full-wave rectifier circuits AR1 and AR2 every time the accumulated charge of the smoothing capacitor (energy storage capacitor) Cf is discharged. , the smoothing capacitor (energy storage capacitor) Cf is charged with a predetermined amount of charge.

In the above-mentioned rectifier for flash lamp power supply of a copying machine according to the present invention shown in FIG. When the rectifier circuit AR11 supplies DC current to the smoothing capacitor (energy storage capacitor) Cf, it operates to supply a delayed current to the full-wave bridge rectifier circuit AR1, and also supplies a delayed current to the full-wave bridge rectifier circuit AR2. An overcurrent limiting capacitor C connected between the AC power supply 1 prevents all of the lead current from flowing when the full-wave bridge rectifier circuit AR2 supplies DC current to the smoothing capacitor (energy storage capacitor) Cf. Wave bridge rectifier circuit AR2
Therefore, by making the above-mentioned overcurrent limiting inductor L and overcurrent limiting capacitor C have the same reactance value at the power supply frequency,
The rectifier for the flash lamp power supply of the copying machine connected to the AC power supply 1 has a power factor of 1 with respect to the AC power supply 1.
It will operate as a load.

As mentioned above, when the reactance value of the inductor L for overcurrent limitation at the power supply frequency is equal to the reactance value of the capacitor C for overcurrent limitation at the power supply frequency, the The rectifier for a flash lamp power source of a copying machine that operates as a load with a power factor of 1 with respect to the AC power source 1 has an impedance shown by the above-mentioned overcurrent limiting inductor L, A large capacitor with an impedance negligible compared to the impedance of capacitor C for overcurrent limiting is used as an energy storage capacitor charged by the combined output current of each full-wave bridge rectifier circuit. The fact that it is
The rectifier for the flash lamp power supply of the copying machine connected to the AC power supply 1 has a power factor of 1 with respect to the AC power supply 1.
Draw a vector diagram of the voltage and current during operation of the rectifier for the flash lamp power supply of a copying machine that operates as a load, and calculate the reactance value at the power frequency of the inductor L for overcurrent limiting and the capacitor C for overcurrent limiting. The condition that the reactance value at the power supply frequency of It is quite easy to understand based on the considerations that have been put into it.

As described above, in the rectifier for the flash lamp power supply of a copying machine according to the present invention, the reactance element for overcurrent limiting is also operated as a reactance element for power factor improvement, so that a special This makes it unnecessary to use a reactance element, and the reactance element used for overcurrent limiting may have half the power supply capacity of the reactance element used for normal power factor correction. Therefore, the device can be manufactured at low cost.

In addition, unless the conduction period of the output of the full-wave bridge rectifier circuit to the smoothing capacitor (energy storage capacitor) Cf corresponds to the rising part of the input AC, the overcurrent limiting inductor L and the overcurrent Limiting capacitor C
It is preferable to set the reactance value and the capacitance value to be shifted from the values determined by the above-mentioned conditions so that a good power factor improvement effect can be obtained.

That is, depending on the length of the conduction period for the smoothing capacitor (energy storage capacitor) Cf,
The content of high frequencies in the alternating current flowing through the overcurrent limiting inductor L and overcurrent limiting capacitor C changes, and the reactance value of the overcurrent limiting inductor L and overcurrent limiting capacitor C changes accordingly. This is because it changes depending on the length of the conduction period for the smoothing capacitor (energy storage capacitor) Cf.

The circuit shown in FIG. 2 is an example of a case where the rectifier for a flash lamp power supply of a copying machine according to the present invention is constructed using a voltage doubler rectifier circuit. In the figure, D1 to D4 are rectifier diodes; C1, C2
is a smoothing capacitor (energy storage capacitor).

3 to 5 are block diagrams in which a power transformer T is used in a rectifier for a flash lamp power supply of a copying machine to obtain a DC output of a desired DC voltage value. Since the power transformer T used in each of the circuit arrangements shown in Figures 3 to 5 has a load power factor of approximately 1, a small power transformer can be used as the power transformer T. .

In the rectifier for the flash lamp power supply of the copying machine shown in Figure 3, an inductor L for overcurrent limiting, a capacitor C for overcurrent limiting, and a full-wave bridge rectifier circuit are connected to the secondary winding N2 of the power transformer T. The circuit section consisting of AR1, AR2, smoothing capacitor (energy storage capacitor) Cf, flash lamp 2 of the copying machine, etc. is the same as shown in Fig. 1, and resistors R1 and R2 are used for detecting DC voltage. It is resistance.

In Figure 3, a bidirectional thyristor is used as the switch SW.
SW is controlled to open and close by a gate pulse given from pulse transformer PT. CC is for control, including error detection amplifier circuit EDA and pulse generation PG.
It consists of an error detection amplifier circuit and
In the EDA, the error signal obtained by comparing the DC voltage Ec detected from the connection point of the resistors R1 and R2 with the reference voltage Es from the reference voltage source 5 is amplified and applied to the pulse generator PG to generate pulses. The output signal from the error detection amplifier circuit EDA described above in the device PG,
The output pulse is applied to the 11th winding of the pulse transformer PT only during the period when both the operation command signal and the operation command signal applied to terminal 4 are present.
Ensure that a gate pulse is given to the switch SW from the secondary side of the PT. Note that N1 in the figure is the primary winding of the power transformer T. Figure 4 shows a combination of the power transformer T and the circuit arrangement shown in Figure 2, which has already been described.
The figure shows that the secondary winding N2 of the power transformer T is provided with a tap so that it can be selectively changed to the connection position of an inductor L for overcurrent limiting or a capacitor C for overcurrent limiting, thereby limiting overcurrent. This is an example in which the effect of canceling the reactive current by the inductor L for overcurrent limiting and the capacitor C for overcurrent limiting can be easily adjusted by switching the taps.

When implementing the present invention, settings may be made such that the power factor improvement by the inductor L for overcurrent limiting and the capacitor C for overcurrent limiting is achieved satisfactorily at any part of the charging curve. .

As described above, in the rectifying device for a flash lamp power source of a copying machine according to the present invention, an inductor for overcurrent limiting and a capacitor for overcurrent limiting connected to an AC power source are connected to a rectifier for power factor correction. Since the rectifier for the flash lamp power supply of the copying machine is configured so as to be used also as a reactance element, the apparatus of the present invention does not require a reactance element with a large current capacity for power factor correction. Therefore, it is possible to easily provide a rectifying device for a flash lamp power source of a copying machine that does not cause power loss due to an impedance element for overcurrent limiting.

[Brief explanation of drawings]

1 to 5 are circuit diagrams of different embodiments of a rectifying device for a flash lamp power source of a copying machine according to the present invention. 1...AC power supply, L...Inductor for overcurrent limiting, C...Capacitor for overcurrent limiting, SW...
...Switch, AR1, AR2...Full-wave bridge rectifier circuit, Cf, C1, C2...Smoothing capacitor (energy storage capacitor), D1-D4...Rectifier diode, 2...Flash lamp of copying machine, 3... ...Trigger electrode, PT...Pulse transformer,
T...Power transformer, CC...Control circuit, EDA...
...Error detection amplifier circuit, PG...Pulse generator.

Claims (1)

[Claims] 1. A first circuit network consisting of a cascade connection of an inductive reactance and a rectifier circuit for overcurrent limitation, and a second circuit network consisting of a cascade connection of a capacitive reactance and a rectification circuit for overcurrent limitation, The first mentioned above,
The input side of the second circuit network is connected to the same AC power supply, and the output sides of the rectifier circuits in the first and second circuit networks are connected in parallel with the same polarity, and the rectifier circuit as described above is connected in parallel. An inductive reactance for overcurrent limiting provided in the first circuit network is installed on the output side of the first circuit as an energy storage capacitor to be charged by the combined output current of the flash lamp of the copier and the rectifier circuits described above. A copying machine's flash drive is constructed by connecting in parallel a capacitor having an impedance that is negligible compared to the impedance shown by the capacitive reactance for overcurrent limiting provided in the second circuit network. Rectifier for power supply of lamps.