JPS5816312A - Dc power supply device - Google Patents

Abstract

PURPOSE:To avoid an abnormal increase of the DC output voltage and to increase the efficiency of a DC power supply device, by flowing a dummy current only in a nonload mode when a connector containing a load is not connected. CONSTITUTION:In the case of a nonload state with no connection of a connector 6, an open state is secured between the terminals B and C of the connector 6. Thus a transistor TR7 is turned on. As a result, a dummy resistance 5 is connected between the output terminals A and B of the connector 6 through the area between the emitter and the collector of the TR7. Then a prescribed dummy current flows, and as a result the voltage of an abnormally high level never occurs across a capacitor 3. While in the case of a load state with connection of the connector 6, the TR7 is turned off. Therefore no dummy current flows to the resistance 5. In such way, an abnormal increase is avoided for the DC output voltage. At the same time the efficiency is increased for a DC power supply device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply device that prevents an increase in rectified and smoothed output voltage during no-load and light-load conditions.

First, a conventional example will be explained according to the drawings.

FIG. 1 is a block diagram of an example of a conventional DC power supply device, and FIG. 2 is a diagram showing its operating characteristics.

Here, 1 is a transformer that transforms the AC input voltage VAC to a desired value, 2 is a diode bridge that rectifies the AC transformed by the transformer 1, 3 is a smoothing capacitor related to the smoothing circuit, and 4 is: A series control circuit for stabilizing the DC output voltage, 5A is a dummy resistor, and 6A is a connector for connecting the DC output to the load Rt.

The AC input is rectified by the diode bridge 2 and the DC output voltage v, (rectified/smoothed output voltage) smoothed by the smoothing capacitor 3, changes depending on the load current IL flowing through the load R1, but as is known, series control Due to the stabilizing effect of the circuit 4, the DC output voltage vt applied to the load Rs is increased by the output current (including the current flowing through the dummy resistor 5A).

)K becomes a constant value almost regardless of

In this case, if the dummy resistor 5A is not connected, the output current ■ will be smaller than the predetermined value I0 depending on the load RL, or there will be no load (a contact failure between the output terminals A and B of the connector 6A). (including) when the state becomes 0,
As shown by the broken line in FIG. 2, the rectified/smoothed output voltage v1 suddenly becomes a high voltage, which causes the smoothing capacitor 3. This may cause deterioration and damage to the parts of the series control circuit 4.

Therefore, due to the dummy effect of this dummy resistor 5A, even if there is no load, the minimum output current IO is caused to flow, thereby preventing the generation of the above-mentioned high voltage.

However, this minimum output current. is constantly flowing even when the normal load current It is supplied, which reduces the efficiency of this DC power supply and increases its implementation scale due to its ineffective heat generation.

An object of the present invention is to eliminate the drawbacks of the prior art described above, to prevent the rectified/smoothed output voltage from increasing during no-load and light-load conditions, and to do so without increasing the packaging scale.
Our objective is to provide an efficient DC power supply.

The present invention is characterized by providing a switch circuit in a DC power supply device that has the function of rectifying and smoothing an AC input, stabilizing its output voltage to a desired value through series control, and applying this to a load via a connector. In the DC power supply device, the dummy resistor is connected between the output terminals of the connector by turning on the connector when the connector is not connected.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of an embodiment of the DC power supply device according to the present invention, in which 5 is a dummy resistor, 6 is a connector, 7 is a transistor related to a switch circuit, and 8 is a
The resistors for supplying the control current and other symbols are equivalent to those of the same symbols in FIG.

Since the general functions and operations of the DC power supply device are the same as those of the conventional example shown in FIG. 1, only the method of passing the dummy current will be described below.

First, when the connector 6 is not connected and under no load (including poor contact between the terminals of the connector 6), the terminals B and C of the connector 6 are open, so the output DC voltage causes a resistance The pace current of transistor 7 flows through device 8, and transistor 7 is turned on.

Therefore, the dummy resistor 5 is connected between the output terminals A and B of the connector 6 through the emitter and collector of the transistor 7, and a predetermined dummy current (for example, the current value shown in FIG. Therefore, no abnormal high voltage is generated across the capacitor 3.

Next, when the connector 6 is connected and in a load state, terminals B and C of the connector 6 are connected on the load RL side, so a corresponding current flows through the resistor 8, but the transistor 7 No pace current flows, and transistor 7 remains off.

Therefore, the dummy resistor 5 is connected to the output terminal A of the connector 6.
, B, and the output current of the present DC power supply is only the sum of the load current of the load Rt and the current flowing through the resistor 8.

That is, in a loaded state, a relatively large dummy current by the dummy resistor 5 does not flow, but since the load current is flowing, the above-mentioned abnormal high voltage across the capacitor 3 naturally does not occur.

Note that when the connector 6 is connected and in a loaded state, the load current of the load Rt is very small (for example, the second
In the figure, the output current is the current value.

Since a predetermined current flows through the resistor 8 even when the voltage is around (approximately the following), this becomes a dummy current and can suppress the occurrence of the abnormally high voltage.

For example, in order to obtain a dummy effect, the sum of the small load current and the current of the resistor 8 is used as the current value. The resistance value of resistor 8 should be selected so that the
This current may be smaller than the normal dummy current by υ, so the efficiency will not decrease significantly.

As explained in detail above, according to the present invention, it is only necessary to flow a dummy current in a no-load state, which improves the efficiency of the DC power supply and further reduces the size of the device by reducing its reactive heat generation. , a remarkable effect on economicization can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of a conventional DC power supply device, FIG. 2 is a diagram of its operating characteristics, and FIG. 3 is a block diagram of an embodiment of the DC power supply device according to the present invention. 1...Transformer, 2...Diode bridge, 3...
・Capacitor, 4...Series control circuit, 5...Dummy resistor, Figure 1 $2 B$3 Eye!

Claims (1)

[Claims] 1. In a DC power supply device that has the function of rectifying and smoothing an AC input, stabilizing its output voltage to a desired value through series control, and applying this to a load via a connector, a switch circuit is provided. . A DC power supply device characterized in that the dummy resistor is connected between the output terminals of the connector by turning it on when the connector is not connected. 2. In the switch circuit according to claim 1, when the connector is connected, the resistor for supplying the control current is connected between the output terminals of the connector, and when the connector is connected, A DC power supply device configured to supply a pace current to a transistor through the control current supply resistor when the control current supply is not available.