JPS6055856A - Power source - Google Patents

Abstract

PURPOSE:To reduce the quantity of heat of a stabilized resistor by connecting a switch in series with the resistor, and controlling ON or OFF of the switch in response to the operating state of a load. CONSTITUTION:When a machine of a load side is at a standby time, an external control signal becomes ''0'', a switch 56 is turned OFF, and a stabilized resistor 55 is released. On the other hand, while the machine of the load side is operating, the external control signal becomes ''1'', the switch 56 becomes ON, and the resistor 55 is connected. Thus, since the resistor 55 is released even at the machine standby time, the resistor 55 does not generate heat, thereby preventing the thermal deterioration of circuit component parts such as semiconductors and the like in a power source.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a stabilized power supply device that outputs a predetermined DC voltage, and more particularly, to a stabilized power supply device that outputs a predetermined DC voltage. The present invention relates to a power supply device that improves device reliability and reduces power consumption by controlling the value of and reducing the amount of heat generated by the stabilizing resistor.

(Background Art) As a conventional stabilized power supply device used in facsimiles and the like, there is one shown in FIG. 1, for example. This power supply device includes a rectifying section 2 that rectifies and smoothes an AC power supply to obtain a DC voltage, and a rectifying section 2 that is connected to the rectifying section 2. A drive unit 3 that converts into current, a primary winding and 2
A force applied to the primary winding that has a secondary winding.

a pulse transformer 4 that steps up or steps down the pulse current and outputs it from the secondary winding; and 2 that rectifies and smoothes the pulse current given from the secondary winding to obtain a DC voltage.
a secondary output section 5; a control section 6 that controls the conduction angle of the switching element of the drive section 3 to control the pulse current flowing to the primary winding; and a DC output voltage at the secondary output section 5. A feedback section 7 feeds back the fluctuations in the control section 6 to the control section 6.

Here, the secondary output section 5 includes diodes 51 and 52 connected in series in opposite directions to both ends of the secondary winding, a coil 53 and a capacitor 54 connected in series to both ends of the diode 52, It consists of a fixed stabilizing resistor 55 connected in parallel to the capacitor 54 and having a resistance value greater than the impedance of the machine during standby on the load side, and a diode 5.
After the pulse current is half-wave rectified in step 1, it is smoothed by a coil 53 and a capacitor 54, and a secondary DC voltage VDC-for example +
Outputs DC24V.

In the above configuration, for example, if a facsimile machine equipped with a thermal printer, station, archiver, magnet, etc. is connected as a load to the output terminals T and TB, this load will be placed in the standby state when the machine is not in use. Fluctuations in impedance occur during transmission and when the machine is operating during transmission and reception. Therefore, if the output voltage of the secondary output section 5 changes from the rated value, for example 10024 V, due to load fluctuations,
This change in output voltage is fed back to the control unit 6 via the feedback unit 7, and the control unit 6 changes the conduction angle of the switching element in the drive unit 3 to change the Varne width of the pulse current on the primary side. By controlling the output voltage to always keep it at the rated value, it is possible to output constant voltage at full output. In addition, a stabilizing resistor 55 is provided on the output side of the secondary output section 5, and the output current is shunted through the stabilizing resistor 55 to reduce changes in the current supplied to the load side, and the capacitor 54 is charged when no load is applied. Since the charge is discharged through the stabilizing resistor 55 to suppress an excessive rise in the output voltage, the fluctuation rate of the output voltage can be reduced and a stable DC voltage can be output.

However, in the conventional power supply device, a stabilizing resistor 55 is provided in the secondary output section 5 to suppress the voltage fluctuation rate.
Therefore, the fluctuation rate of the output voltage should be kept below a specified value, for example, the rated voltage 24V ± 4, over the entire range from no load to full load.
If you try to keep it below v, you will have to reduce the resistance value of the stabilizing resistor 55 and increase the shunt of the output current, which may increase the amount of heat generated by the stabilizing resistor 55. be. Especially in the case of a standby power supply that supplies a predetermined voltage even when the machine is on standby, such as a load such as a facsimile machine, this heat generation is a problem in terms of the reliability and power consumption of circuit components such as semiconductors used inside the power supply. It was an unpleasant thing.

However, depending on the type of load, there are some that do not require the rate of fluctuation of the output voltage to be kept below a certain value over the entire range from no-load power to full load.

For example, when supplying a predetermined voltage to a facsimile machine, etc., or when operating a thermal printer, motor, etc., it is preferable to suppress the voltage fluctuation rate to a predetermined value while the machine is operating, but when the machine is on standby, the output voltage However, it is often a hindrance. This is a drive for a transistor etc. that drives a motor etc.

This is because the circuit often has a withstand voltage higher than the rated value, for example +34V or higher. With such a load IC, for example, when the machine is on standby, even if the output voltage rises to +32V, there is no problem, but when the machine is operating, it is often necessary to keep the voltage fluctuation within +24±4V. Therefore, for this type of load, trying to keep the output voltage within +24V+4V-+24V even during standby will result in an increase in the amount of heat generated during standby by reducing the resistance value of the stabilizing resistor 55. cause problems.

(Objects and Structure of the Invention) The present invention has been made in view of the above, and has the object of reducing the heat generation amount of the stabilizing resistor provided in the secondary output section and improving the reliability of circuit components provided in the power supply device. In order to improve power consumption and reduce power consumption, a switch is connected in series with the stabilizing resistor, and the value of the stabilizing resistor is controlled by turning this switch on and off depending on the operating status of the load. The present invention provides a power supply device with the following features.

(Example) The power supply device according to the present invention will be explained in detail below.

FIG. 2 shows an embodiment of the present invention, and the same parts as in FIG. Stabilizing resistor 5 having a resistance value larger than the impedance during standby
In a configuration in which a switch 56 is connected in series with the first
It is different from the one in the illustration. Here, the switch 56 is composed of a transistor, a relay, etc., and this switch 56 is turned on or off based on an external control signal given from a machine control section (not shown) depending on the operating state of the load, and is stabilized. Turn on or release the resistor 55. The external control signal is, for example, 10 when the machine as a load is in a standby state, and Nl when the machine is in operation.

Turn on 56tl-.

In the above configuration, the operation shown in FIG. 2 will be explained with reference to FIG. First, when the load-side machine is on standby, the external control signal KO1*□AI is activated, which turns off the switch 56 and releases the stabilizing resistor 55. When the machine is on standby, the load impedance increases, so the output voltage vDc rises, but the feedback signal from the feedback section 7 causes the control section 6 to operate, reducing the conduction angle of the switch element in the drive section 3. The output voltage v
The rise in Dc is suppressed, and the output voltage vDc is reduced to a in Fig. 3.
(V). In this way, even if the output voltage VDC increases when the machine is on standby, the drive circuits such as transistors that drive the machine generally have a high withstand voltage, so it does not pose a performance problem, or the stabilizing resistor 55 is released. Since the stabilizing resistor 55 does not generate heat, thermal deterioration of circuit components such as semiconductors in the power supply device can be prevented.

On the other hand, when the machine on the load side is in operation, the external control signal becomes "1", and this nK turns on the switch 56 and turns on the stabilizing resistor 55. Then stabilizing resistor 5
5 and the load impedance constitute a parallel composite impedance when viewed from the pulse transformer 4.

Here, when there is no load, the combined impedance is small υ, the output current is large, and the output voltage VDC is
However, as mentioned above, the feedback signal from the feedback section 7 causes the control section 6 to operate, increasing the conduction angle of the switch element in the drive section 3, suppressing the decrease in the output voltage vDC, and the output current. is X(4), and the output voltage vDo is B
(V). Furthermore, when the load is full, the combined impedance becomes even smaller9, and as the output current increases, the output voltage vnc decreases, but as described above, the control unit 6 suppresses the decrease in the output voltage vnc. , the output current is Z(A), and the output voltage is D(b). In this way, even though the output voltage VDC is a (V) when the machine is on standby, it only fluctuates between D (To) and B (B) when the machine is operating, even if there is a load change. Practically less pressure can be achieved.

In the above embodiment, as shown by the two-dot chain line in FIG.
Another stabilizing resistor 57 may be connected in parallel with 6. Here, the resistance value of the other stabilizing resistor 57 is selected to be much larger than the impedance of the machine on the load side during standby. With this configuration, even if one stabilizing resistor 55 is in an open state when the machine is on standby, the other stabilizing resistor 57 is connected, so that a part of the output current is transferred to this stabilizing resistor 57. Sorry, but this stabilizing resistor 57
Since the resistance value is large, the amount of heat generated is small, and there is no adverse thermal effect on other circuit components. Moreover, when there is no load when the machine is running, the parallel combined resistance of stabilizing resistors 55 and 57 decreases by /J%, so the output current flowing through this parallel combined resistance is Corresponding to a larger Y(A), the output voltage VDC also becomes B(
b) It becomes a very small C (V).

Therefore, the output voltage vn during actual operation of the machine on the load side
The variation range of c is from D(V) to C(to), and the voltage variation rate can be suppressed much smaller. Here stabilizing resistor 5
The number of 5.57s, the thickness of the awns, and the number of switches 56 can be variously selected depending on the type and size of the load.

Further, in FIG. 2, the switch 56 is turned on when the machine is operating and turned off when the machine is on standby, but conversely, it may be turned off when the machine is operating and turned on when it is on standby. Such control is effective in the following cases. In other words, if the load on the power supply device is too light (that is, the load impedance is large), it is easy to generate a firing sound, and in order to stop the noise, it may be necessary to reduce the current flowing to the stabilizing resistor 55. . Since it is a problem for the machine on the load side to generate oscillation noise during standby with a light load, a current is passed through the stabilizing resistor 55, and on the other hand, when the machine is operating, the output current is sent to the platform and load side. Since the current flows, no oscillating noise is generated, so the stabilizing resistor 55 is unnecessary. Therefore, in this case, by controlling the switch 56 on and off as described above, it is possible to prevent the generation of oscillation noise when the machine is on standby, while at the same time, when the machine is operating, the load current flowing to the total stabilizing resistor is There is an advantage to taking a larger value.

Furthermore, although the power supply device in the above embodiment is configured with a switching regulator, other stabilized power supply devices having a constant voltage function, such as a series control type stabilized power supply device (
It goes without saying that the present invention can also be applied to series regulators, etc. (Effects of the Invention) As explained above, in the power supply device of the present invention, a switch is connected in series with a stabilizing resistor, and a switch is connected in series with the stabilizing resistor. Since the switch is controlled on and off according to the operating status of the load,
It is possible to reduce the amount of heat generated by the stabilizing resistor installed in the secondary output section, prevent thermal deterioration of the circuit components installed in the power supply, and improve its reliability. power consumption can be reduced.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional power supply device, Fig. 2 is a circuit diagram showing the main parts of a power supply device according to an embodiment of the present invention, and Fig. 3 is a load characteristic of the power supply output in Fig. 2. This is a diagram showing Ruru. Explanation of symbols 2... Rectifier section, 3... Drive section, 4... Pulse transformer, 5... Secondary output section, 6... Control section, 7
°・°feedback section, 51.52...diode)
", 53... Coil, 54... Capacitor, 54.
55...Stabilizing resistance.

Claims (1)

[Claims] In a power supply device configured to output a predetermined DC voltage by suppressing the change in output voltage by feeding the change in output voltage, a series circuit of a stabilizing resistor and a switch is connected in parallel to the output side of the power supply device. A power supply device characterized in that the switch is controlled on and off according to the operating state of the load.