JPS62203554A - Power unit - Google Patents

Abstract

PURPOSE:To obtain the high power factor of a power source while using a filter of small capacity by sufficiently increasing the switching frequency of a switching unit by the frequency of an AC power source. CONSTITUTION:High power factor is obtained by sufficiently increasing the switching frequency of a switching unit 3 than the frequency of an AC power source 2 while employing a filter 8 of small capacity. Since the current of an inductor 5 is set to become a discontinuous mode, only power stored when the unit 3 is ON is supplied to a load 4, and since the ON duty of the unit 3 does not alter by the state of the load 4, a constant power can be supplied to the load 4 even if the load 4 is varied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device which rectifies an AC power supply voltage and then switches it to supply power to a load.

(Prior Art) Conventionally, in this type of power supply device, in order to supply constant power to the load, one or both of the load current and load voltage is detected, and the on/off duty ratio of the switching device is determined based on this detection signal. Negative feedback control was used.

In addition, in this type of power supply device, it is desirable to have a high power factor of the AC power output, but as a solution to this problem, for example, as shown in Japanese Patent Application Laid-Open No. 50-129923, a non-smooth pulsating current voltage is used for resistant current. It has been proposed that the power is supplied to a push-pull type inverter through an inductor.
ing.

(Problems to be Solved by the Invention) However, a device that detects the load current and performs negative feedback control to make the power constant has a complicated configuration. For example, a device that detects the load current and load voltage and multiplies them to obtain the load power requires a special multiplier, and also supplies power to the load via a 9-way separate transformer. In this case, it is necessary to use an insulated type as a load current and load voltage detection device, which is complicated and expensive.

Therefore, even when converting the device disclosed in JP-A-50-129923 to constant power, the above-mentioned problem still exists.
Figure 1. Constant power and high power factor at the same time. Moreover, a power supply device with a simple configuration has been desired.

The present invention meets these demands, and the following 9 power supplies of the present invention provide constant power and high power factor with a simple configuration.
&6 configuration will be explained with reference to FIG. 1 and 1j'. (1) is a rectifier that rectifies the voltage of an AC power source (2), for example, a commercial power source, and outputs a pulsating current. (3) is a switching device, which is provided between the output side terminal of the rectifier (1) and the load (4), and switches the pulsating voltage. (5) is an inductor and the switching device (
3) provided on the output side of the switching device (3);
When the rectifier (1) is turned on, power is supplied from the rectifier (1) and power is stored.

The stored power is supplied to the load (4) when the switching device (3) is off. (6) is a diode which prevents the output of the rectifier (1) from being applied to the load (4) when the switching device (3) is on, and prevents the inductor (5) from being applied to the load (4) when the switching device (3) is off. ) is used to form a path for supplying the accumulated power of the load (4). (7) The switching device (
In the control device of 3), the switching device (3) operates at a frequency higher than the frequency of the AC power source (2) and does not change depending on the state of the load (4).

Further, the inductor (5) should be turned on and off at a duty ratio that causes the current flowing through the inductor (5) to be in a discontinuous mode. Here, when the current flowing through the inductor (5) is in a discontinuous mode, the electric power accumulated when the switching device (3) is turned on is completely discharged when the switching device (3) is turned off, (3) The discharge current of the stored Wt power continues to flow 1 (meaning no current) until the state is turned on.

A filter (8) is provided on the input side of the switching device (3) marked # and has a smoothing effect on the switching frequency of the switching device (3). therefore.

The filter (8) causes a sinusoidal current to be output from the rectifier (3).

(Function) A voltage as shown in Figure 2 (al) is generated between the output terminals of the rectifier (1), and an output current of the switching device (3) is as shown in Figure 2 (bl). The output of the device (1) flows through the filter (8) as shown in Figure 2 (C). Therefore, by making the switching frequency of the switching device (3) sufficiently higher than the frequency of the AC power supply (2), the filter As (8), a high power factor can be obtained while using a small capacity one.Also.

This is because the current flowing through the inductor (5) is set to be in a discontinuous mode as shown in FIG.

Only the power accumulated when the switching device (3) is turned on is supplied to the load (4), and the switching device (3)
) does not change depending on the state of the load (4), so even if the load (4) fluctuates, constant power can be supplied to the load (4). In FIG. 3, (a) shows the on and off periods of the switching device (3), (b) shows the input current of the inductor, and (C) shows the emission current. As is clear from Figure 3, the discontinuous mode requires that the emission current be zero at the next turn on, but the power emission time of the inductor (5) depends on the capacity of the load (4). Since it is different, the load (4
) The on/off duty ratio may be determined by taking into account the capacity of the capacitor. Note that in this case, constant power cannot be supplied if the AC power source (2) fluctuates.

In order to supply constant power even in such a case, the switching device (
It is only necessary to change the on-duty ratio so that the output voltage value of 3) becomes constant. In this case, since no special multipliers, current transformers, etc. are required, the configuration can be relatively simple.

(Example) Yo 5, 4,, Aox physical -5, example 1 customer. ga.

I will refer to and explain. The same parts as in FIG. 1 are given the same reference numerals. In this example, the load (4) is the discharge lamp 01)
This discharge lamp (4I), for example, consists of a current limiting device (4 units) mainly composed of an inverter and a smoothing capacitor (43) provided on the input side of this current limiting device (42). In order to compensate for voltage fluctuations in the AC power supply (2), the average value of the output voltages of the rectifier It, (11) is detected, and the control device (7) is activated according to this detected value.
A detection device a (9) is provided that changes the tutey ratio of the switching device (3) so that the output voltage value of the switching device (3) is constant.

The operation of this embodiment is almost the same as that in FIG.
) is supplied with a current limiting device (4Z output (for example, 20 kHz to 50 kHz) with no rest period), resulting in a high luminous efficiency.

Note that the present invention is limited to the above-mentioned embodiment, and various modifications are possible. For example, the inductor may be a separate transformer and power may be supplied to the load from the secondary side. Also,
The load may include not only a discharge lamp but also a charging and neutralizing device for a copying machine. Furthermore, the switching device may be other than a transistor.

(Effect of the invention) As described above, the present invention rectifies the AC power supply voltage
A switching device is provided between a rectifying device that outputs a pulsating voltage and a load, and further, when the switching device is turned on, the output of the rectifying device is supplied to store electric power.t2 When the switching device is turned off, the stored power is stored in the an inductor that supplies power to a load, which blocks the output of the rectifier from being applied to the load when the switching device is on, and forms a path that supplies the power stored in the inductor to the load when the switching device is off. A diode is provided, and the switching device is turned on and off at a duty ratio that is higher than the frequency of the alternating current power source and does not change depending on the load condition, and the current flowing through the inductor is in a discontinuous mode. Furthermore, since a filter for the switching frequency is provided on the input side of the switching device, a power supply device that can obtain a high power factor and constant power with a simple configuration is provided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a single bowl configuration of the present invention. Figures 2 and 3 are waveform diagrams showing the effect of Figure 1;
The figure is a circuit diagram showing a specific embodiment of the present invention. (1)... Rectifier (3)... Switching device 6)... Inductor (6)... Diode (
7)...control device (8)...filter.

Claims (3)

[Claims] (1) A rectifier that rectifies AC power supply voltage and outputs a non-smooth pulsating voltage; A switching device installed between the output side terminal of this rectifier and the load; and A switching device installed on the output side of this switching device. an inductor that is supplied with the output of the rectifier when the switching device is turned on, stores power, and supplies the stored power to the load when the switching device is turned off; a diode that prevents power from being applied to the power supply and forms a path for supplying the stored power of the inductor to the load when the switching device is turned off; and a control device that turns on and off at a duty ratio such that the current flowing through the inductor is in a discontinuous mode; and a filter provided on the input side of the switching device for the switching frequency of the switching device. Features a power supply device. (2) The power supply device according to claim (1), wherein the load includes a discharge lamp. (3) A patent characterized in that the control device changes the on/off duty ratio of the switching device so that the accumulated power of the inductor is constant with respect to fluctuations in the AC power supply voltage value. A power supply device according to claim (1) or (2).