JPH0116108B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device that supplies stable power to a load, and relates to one used, for example, as a high voltage generator for a copying machine.

Generally, there are three types of power supplies of this type: those that utilize fero-resonance, those that utilize piezoelectric transformers, and those that utilize inverter circuits. Of these, the latter two types are rapidly becoming more popular because they allow devices to be made smaller and lighter. especially,
A transformer using an inverter circuit has the advantage of being able to easily vary the output voltage and output current, and further reducing the size of the transformer by increasing the oscillation frequency, and is currently the most anticipated. However, the power supply used as a high-voltage generator in the copying machine requires constant current output and constant voltage output, whereas conventional power supplies using inverter circuits are miniaturized, so the transformer winding width It was difficult to take out multiple taps, and it was difficult to take out two or more taps from the same winding at the same time. Also, even if two or more outputs can be taken out from the same winding at the same time, some of these outputs may have constant current characteristics,
Some of them, such as constant voltage characteristics, could not be independently controlled and extracted. As described above, although the conventional power supply device using an inverter circuit can be made smaller and lighter, it has the disadvantage that it cannot output a plurality of outputs with different characteristics.

The present invention has been made in view of the above-mentioned drawbacks, and includes first and second rectifying diodes connected in series to one output end of the alternating current generating section, and between each of these diodes and the other output end of the alternating current generating section. A current detection circuit for controlling the output of the AC generator is connected in series with the smoothing capacitor connected to the AC generator side, and a current detection circuit for controlling the output of the AC generator is connected in series to the smoothing capacitor connected to the AC generator side. By making the capacitance of the smoothing capacitor at least 20% smaller than the capacitance of other smoothing capacitors, and using the cathode of each of the diodes as the output terminal, it is possible to make the high-voltage power supply smaller and lighter, and to connect multiple wires with different properties from the same winding. The present invention provides a power supply device that can output an output of .

Next, the configuration of an embodiment of the present invention will be explained with reference to FIG.

Reference numeral 1 denotes an alternating current generating section, which includes an inverter 2 and an inverter transformer 3, converts a direct current voltage applied between input terminals 4a and 4b into an alternating current high voltage, and outputs it from output terminals 5a and 5b. First and second rectifying diodes 6 and 7 are connected in series to one output terminal 5a. Between the connection point between the cathode of the first diode 6 and the anode of the second diode 7 and the other output end 5b of the AC generator 1, a smoothing capacitor 8 and a primary current transformer 9 as a current detection circuit are connected. A series circuit with the winding is connected. The secondary winding of this current transformer 9 is connected to the inverter 2 via a rectifier bridge 10, so that the charging and discharging current of the smoothing capacitor 8 is fed back to the inverter 2. A parallel circuit including a smoothing capacitor 11 and a discharge resistor 12 is connected between the cathode of the second diode 7 and the other output end 5b of the AC generator 1. Output terminals A and B are provided at the cathodes of the first and second diodes 6 and 7, respectively.

In this circuit configuration, in order to obtain constant current characteristics from output terminal A and constant voltage characteristics from output terminal B, the capacitances C ₁ and C ₂ of smoothing capacitors 8 and 11 are changed,
In each case, tests were conducted by varying the load connected to output terminal A. The results are shown in FIG. In addition, in this test, the capacitance of capacitor 11
C ₂ is constant at 1000 [PF], and the capacitance of capacitor 8 is C ₁
The capacitance ratio (C ₂ /C ₁ ) is a
is 10, b is 5, c is 2, d is 1.2, and e is 1.

As is clear from the test results shown in Figure 2, the capacitance ratio (C ₂ /C ₁ ) of smoothing capacitors 8 and 11 is
1.2 or more, i.e. smoothing capacitor 8
When the capacitance C ₁ of the smoothing capacitor 11 is at least 20% smaller than the capacitance C ₂ of the smoothing capacitor 11, the output characteristics of the output terminal A are constant current characteristics. In this case, the output characteristics of the output terminal B were constant voltage characteristics.

The reason for making the capacitance C ₁ of the smoothing capacitor 8 20% or more smaller than the capacitance C ₂ of the smoothing capacitor 11 is to increase the current detection ability of the current transformer 9 by making the output ripple rate larger than other outputs. In addition, the capacitance C ₁ of the smoothing capacitors 8 and 11,
If the difference in C ₂ is less than 20%, it becomes impossible to suppress the short-circuit current when output terminal A is short-circuited, as shown in Figure 2e, and it is no different from a constant voltage power supply.

Note that the output characteristics of output terminals A and B when the capacitance ratio (C ₂ /C ₁ ) of smoothing capacitors 8 and 11 is approximately 10 and the load connected to output terminal A is varied are shown in Figure 3. The output characteristics of output terminals A and B when the load connected to output terminal B is varied are shown in the fourth section.
As shown in the figure.

In addition, in the above description, the smoothing capacitor 11
The explanation was given assuming that the capacity C ₂ is 1000 [PF], but the capacity C ₂
If the capacitance C ₁ of the smoothing capacitor 8 is within the range of 100 [PF] to 300 [PF], outputs similar to those explained above can be obtained from output terminals A and B. It will be done.

In the embodiment shown in FIG. 1, a current transformer is used as the current detection circuit in order to separate the secondary side of the inverter transformer 3 that generates high voltage from the primary side that generates low voltage. can also be used, but with a photocoupler,
The current transformer 9, which does not have such restrictions, is used because it can only be used for small currents. Note that if there is no need to separate the primary side and the secondary side, a resistor may be used.

According to the present invention, the high voltage power supply device can be made smaller and lighter, and outputs with different properties such as constant current characteristics and constant voltage characteristics can be obtained simultaneously from the same winding. Since the input is smoothed by the capacitor, the smoothing capacitor at the final stage can be made small and a discharge resistor can be made unnecessary.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the power supply device of the present invention, Fig. 2 is an output characteristic diagram from output terminal A when the ratio of the capacitance of the smoothing capacitor is changed, and Fig. 3
The figure shows the output characteristics of output terminals A and B when the load connected to output terminal A is varied, and Figure 4 shows the output characteristics of output terminal A and B when the load connected to output terminal B is varied.
It is an output characteristic diagram of B. 1... AC generator, 6... First diode,
7... Second diode, 8, 11... Smoothing capacitor, 9... Current transformer as a current detection circuit.

Claims (1)

[Claims] 1. An alternating current generating section, first and second diodes connected in series to one output terminal of the alternating current generating section, and a smoothing capacitor connected between each of these diodes and the other output terminal of the alternating current generating section. , a current detection circuit that detects the charging/discharging current of the smoothing capacitor connected to the AC generating section side closest to the AC generating section and controlling the output of the AC generating section; Make the capacitance at least 20% smaller than that of other smoothing capacitors,
A power supply device characterized in that an output is obtained from the cathode of each of the diodes.