JPH05344717A - Power supply - Google Patents

Abstract

PURPOSE:To control respective small-sized and two or more loads accurately in a power supply for supplying the loads with power. CONSTITUTION:A voltage not higher than the load voltage of loads 21 and 22 is generated in a capacitor 37 at the output end of a DC conversion circuit 33 by a first control circuit 48. Also, one end of a capacitor 42 at the output end of a first power supply circuit 38 is connected with the capacitor 37, the additional value of voltages of the capacitors 37 and 42 is added to the load 21, and the consumed power of the load 21 is controlled by a second control circuit 49 so as to be always constant. Further, one end of a capacitor 47 at the output end of a second power circuit 43 is connected with the capacitor 37, the additional value of voltages of the capacitors 37 and 47 is added to the load 22, and the consumed power of the load 22 is controlled by a third control circuit 53 so as to be always constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type power supply device.

[0002]

2. Description of the Related Art In recent years, power supplies have been required to be small, lightweight, highly efficient, and inexpensive, and switching type power supplies have been widely adopted.

A conventional power supply device will be described below.
FIG. 3 shows the configuration of a conventional power supply device. In FIG. 3, 6
0 and 61 are loads. 62 is a detection circuit, and resistors 63 and 6
The load voltage of the load 61 is detected by the resistors 63 and 64, the load current of the load 61 is detected by the resistor 65, and the detected load current is input to the multiplier circuit 66. Output a signal proportional to. 67 is a DC power supply. 68 is 2
It is a power supply circuit based on a general flyback converter method of output, and is composed of a transformer 69, a transistor 70 that is a switching element, diodes 71 and 72, and capacitors 73 and 74. By turning on and off the transistor 70, Supplies power to loads 60 and 61. 75 is a control circuit, which is a switching control IC such as TL494
PWM control section 76 and error amplifier 77 of its input section
The output signal of the detection circuit 62 proportional to the power consumption of the load 61 is used as the negative input of the error amplifier 77, the reference voltage 78 is used as the positive input, and the transistor 70 is used as the load 61.
Outputs a signal for on / off control so that the load power of is constant. Also, the two secondary windings 69b, 69 of the transformer 69
Since c is magnetically coupled, a voltage proportional to the secondary winding 69b is output from 69c, and the power consumption of the load 60 is also substantially constant.

With such a configuration, a current intermittently flows from the DC power source 67 to the primary winding 69a of the transformer 69 and the transistor 70, and when the transistor 70 is off, the transformer 69 is turned on.
The energy stored in the secondary winding 69a is output from the secondary windings 69b and 69c of the transformer 69, and smoothed and stored in the capacitors 73 and 74 via the diodes 71 and 72. At this time, the control circuit
The transistor 70 is turned on / off by 75 so that the power supplied to the load 61 is constant. At the same time, the power supplied to the load 60 is controlled to be almost constant,
Even if the output voltage of the DC power supply 67 changes, the power supplied to the loads 60 and 61 is always controlled to be constant.

[0005]

In such a conventional power supply device, all the electric power to be supplied to the loads 60 and 61 is supplied through the transformer 69, the transistor 70 and the diodes 71 and 72. Therefore, the iron loss / copper loss of the transformer 69 and the transistor 70
And the losses of diodes 71 and 72 were major factors that reduced circuit efficiency. Also diode 7
1 and 72 and capacitors 73 and 74 require elements rated above the load voltage, especially when the load voltage is high.
74 needed a high withstand voltage. From the above points, there is a problem in that the size of the heat dissipation plate becomes large, and the device becomes large due to the necessity of high withstand voltage parts.

When controlling the two loads 60 and 61,
Generally, as shown in FIG. 3, the output winding of the transformer 69 has two windings, and a load is connected to each output. At this time, the detection circuit 62 detects the load electrical characteristic of the load 61, and from the result, the control circuit 75 outputs a predetermined signal to the transistor 70,
Controls one load 60, 61. Therefore two loads 60, 61
Will be controlled by one load 61.
Variation, secular change, load fluctuation, etc.
There was a problem that the power consumption of 60 could not be controlled at a constant level. Therefore, in order to accurately control the two loads, two power supply devices are required, which causes a problem that the device becomes large.

The present invention solves the above-mentioned conventional problems, and is a small-sized power supply device for supplying electric power to a load.
Further, it is an object of the present invention to provide a power supply device capable of accurately controlling each of two or more loads.

[0008]

In order to solve the above problems, a power supply device of the present invention has a load, a detection circuit for detecting the load characteristics of the load, a DC power supply, and a switching element. A power supply circuit connected between the output end of the DC power supply and the load so as to add a predetermined voltage to the output voltage of the DC power supply, and an output signal of the detection circuit, and load electrical characteristics of the load. And a control circuit for outputting a drive signal to the switching element so that the predetermined characteristic is obtained.

Further, it has two or more loads, two or more detection circuits for individually detecting at least the load power of the loads, a DC power supply, and a switching element, and is connected to the output end of the DC power supply. A direct current conversion circuit that outputs a voltage equal to or lower than the lowest load voltage among the loads, and a switching element, and an output end of the direct current conversion circuit and a load other than at least the lowest load voltage among the loads. And at least one power supply circuit connected so as to add a predetermined voltage to the output voltage of the DC conversion circuit, and the output signal of the detection circuit are input, and predetermined power is supplied to the load. As described above, a control circuit that outputs a drive signal to at least two or more switching elements is provided.

[0010]

According to the present invention, since the output obtained by adding the output of the power supply circuit to the output of the DC power supply is supplied to the load and the power can be directly supplied from the DC power supply to the load, the power supply circuit can be supplied to the load. The power supply circuit may have a capacity smaller than the power supplied by the power supply, and the loss may be reduced by reducing the power supplied through the power supply circuit.

Further, most of the power supply to two or more loads can be supplied from the DC conversion circuit, and the part for correcting load variations, aging changes, load fluctuations, etc. can be supplied from the power supply circuit. It is possible to accurately control the loads individually, and a power supply circuit with a small capacity is sufficient for the power supply circuit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention. In FIG. 1, 1 is a DC power supply and 2 is a load. A detection circuit 3 is composed of resistors 4 and 5 and outputs a signal proportional to the voltage of the load 2. Reference numeral 6 is a power supply circuit of a general flyback converter system, which is composed of a transformer 7, a transistor 8 which is a switching element, a diode 9 and a capacitor 10. One end of the capacitor 10 which is an output end of the power supply circuit 6 is a direct current. It is connected to the positive output terminal of the power supply 1 and is configured to apply the added value of the voltage of the DC power supply 1 and the capacitor 10 to the load. By turning the transistor 8 on and off, the DC power supply 1 and the capacitor are connected across the load 2. The sum of the 10 voltages is added. Reference numeral 11 denotes a control circuit, which is composed of a PWM control unit 12 including a switching control IC such as TL494, an error amplifier 13 at its input unit, and a reference power supply 14, and outputs an output signal of the detection circuit 3 proportional to the voltage of the load 2. The error amplifier 13 has a negative input, the reference voltage 14 has a positive input, and the transistor 8 is on / off controlled so as to keep the load voltage of the load 2 constant.

With such a configuration, the output from the DC power supply 1 has a current intermittently flowing through the primary winding 7a of the transformer 7 and the transistor 8, and when the transistor 8 is off, the primary winding 7a of the transformer 7 is turned off. The energy stored in is output from the secondary winding 7b of the transformer 7 and is smoothed and stored in the capacitor 10 via the diode 9. Since one end of the capacitor 10 is connected to the positive output terminal of the DC power supply 1, the added value of the voltage of the DC power supply 1 and the capacitor 10 is added to the load 2.
The electric power supplied to the load 2 is the sum of the electric power supplied directly from the DC power supply 1 and the electric power supplied via the power supply circuit 6.

As described above, by adding the power supplied to the load 2 directly from the DC power supply 1 and the power supplied via the power supply circuit 6, the power supply circuit 6 is set to the load 2
The power supply circuit having a capacity smaller than the power supplied to the power supply circuit is sufficient, and the output voltage of the power supply circuit 6 can be reduced. Further, since the electric power through the power supply circuit 6 becomes small, the loss in each element is reduced and the circuit efficiency can be improved. Therefore, as the element used for the power supply circuit 6, a small rated element can be used, the circuit efficiency can be improved, and the device can be downsized.

FIG. 2 is a circuit diagram of a power supply device according to a second embodiment of the present invention. In FIG. 2, 20 is a DC power supply, and 21 and 22 are loads. Reference numeral 23 is a first detection circuit, which includes resistors 24, 25,
26 and a multiplication circuit 27. A load 21 is formed by resistors 24 and 25.
Of the load 21, the load current of the load 21 is detected by the resistor 26, the load current is input to the multiplication circuit 27, and a signal proportional to the power consumption of the load 21 is output. 28 is a second detection circuit,
It is composed of resistors 29, 30, 31 and a multiplication circuit 32,
The load voltage of load 22 is detected by
The load current is detected and input to the multiplication circuit 32, and a signal proportional to the power consumption of the load 22 is output.

Reference numeral 33 is a direct current conversion circuit by a general flyback converter system, which is composed of a transformer 34, a transistor 35 which is a switching element, a diode 36 and a capacitor 37, and is turned on / off by operating the transistor 35. A DC voltage is generated across the capacitor 37. Further, 38 is a first power supply circuit by a general flyback converter method, which is composed of a transformer 39, a transistor 40 which is a switching element, a diode 41 and a capacitor 42, and is turned on / off by the transistor 40. A DC voltage is generated across both ends of the capacitor 42, and one end of the capacitor 42 is connected to the positive output terminal of the capacitor 37, which is the output end of the DC conversion circuit 33.
And the added value of the voltage of the capacitor 42 is added to the load 21. Reference numeral 43 is a second power supply circuit based on a general flyback converter method, which is composed of a transformer 44, a transistor 45 that is a switching element, a diode 46 and a capacitor 47, and turns on and off the transistor 45 to turn the capacitor on and off. DC voltage is generated across both ends of the capacitor 47, and one end of the capacitor 47 is connected to the positive output terminal of the capacitor 37, which is the output end of the DC conversion circuit 33.
And the added value of the voltage of the capacitor 47 is added to the load 22.

Reference numeral 48 is a first control circuit, which is a DC conversion circuit.
A signal for turning on / off the transistor 35 is output to the capacitor 37 at the output end of 33 so that a voltage equal to or lower than a voltage required to operate the loads 21 and 22 with a predetermined characteristic is generated. Reference numeral 49 is a second control circuit, which is composed of a PWM control unit 50 including a switching control IC such as TL494, an error amplifier 51 of its input unit, and a reference power supply 52, and which is proportional to the power consumption of the load 21. The output signal of the detection circuit 23 is used as the negative input of the error amplifier 51, the reference voltage 52 is used as the positive input, and a signal for on / off controlling the transistor 40 so as to keep the load power of the load 21 constant is output. 53 is the third
Of the second detection circuit 28 proportional to the power consumption of the load 22. The control circuit is composed of a PWM control unit 54 including a switching control IC such as TL494, an error amplifier 55 of its input unit, and a reference power supply 56. The output signal is used as the negative input of the error amplifier 55, the reference voltage 56 is used as the positive input, and a signal for on / off controlling the transistor 45 so as to keep the load power of the load 22 constant is output.

With such a configuration, the output from the DC power source 20 outputs the primary windings of the transformers 34, 39 and 44 and the transistor 3 to each other.
Current flows intermittently in 5, 40, 45, and transistors 35, 4
When 0 and 45 are off, the energy stored in the primary windings of the transformers 34, 39 and 44 is output from the secondary windings of the transformers 34, 39 and 44, and is passed through the diodes 36, 41 and 46. The capacitors 37, 42, and 47 store the data smoothly. At this time, the output signal of the first control circuit 48 causes the capacitor 37 at the output end of the DC conversion circuit 33 to generate a voltage equal to or lower than the voltage required to operate the loads 21 and 22 with predetermined characteristics. Also, connect one end of the capacitor 42 to the positive output terminal of the capacitor 37,
The added value of the voltages of 37 and the capacitor 42 is added to the load 21, and the power consumption of the load 21 is constantly controlled. Further, one end of the capacitor 47 is connected to the positive output terminal of the capacitor 37, the added value of the voltages of the capacitor 37 and the capacitor 47 is added to the load 22, and the power consumption of the load 22 is constantly controlled.

As described above, the power supply to the load 21 is supplied from the DC conversion circuit 33 and the first power supply circuit 38, and the load 22 is supplied.
The power supply to the first DC power supply circuit 38 and the second power supply circuit 43 is controlled by the DC power conversion circuit 33 and the second power supply circuit 43. Can be made variable, and the others can be output by the DC conversion circuit 33. Therefore, the two loads 21 and 22 can be individually and accurately controlled, and the first power supply circuit 38 and the second power supply circuit 43 have a small capacity. The power supply circuit is improved and the power supply device can be downsized.

In FIG. 2, one power supply circuit is provided, a load other than the lowest load voltage among the loads is connected to this power supply circuit, and the load with the lowest load voltage among the loads is connected to the DC conversion circuit. By connecting, the circuit efficiency can be similarly improved, and the device can be downsized.

In the above embodiments, the flyback converter system is used as the DC conversion circuit and the power supply circuit, but other systems such as a forward converter system having a switching element may be used. Further, the DC power supply may be a power supply obtained by rectifying and smoothing AC, or a power supply having another configuration. Further, the control circuit may be of a PWM control system or a frequency control system. Further, the self-excited method may be used instead of the separately excited method. further,
It goes without saying that the transistors may be FETs, IGBTs or thyristors. Further, although the load is controlled with a constant voltage or constant power as compared with the reference power source, it may be variable or not constant.

[0022]

As described above, according to the present invention, the output obtained by adding the output of the power supply circuit to the output of the DC power supply is supplied to the load,
Since the power can be directly supplied to the load from the DC power supply, the power supply circuit may be a power supply circuit having a capacity smaller than the power supplied to the load, and the power through the power supply circuit is small, so that the loss is reduced. Therefore, the circuit efficiency can be improved with a simple configuration, and the element used in the power supply circuit can be a small rated element, so that a compact and highly efficient power supply device can be realized.

Further, most of the power supply to two or more loads is supplied from the DC conversion circuit, and the power supply circuit supplies a part for correcting load variations, secular changes, load fluctuations, etc. The above loads can be individually and accurately controlled, and a power supply circuit with a small capacity is sufficient for the power supply circuit, and a small power supply device can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional power supply device.

[Explanation of symbols]

 1,20 DC power supply 2,21,22 Load 3,23,28 Detection circuit 6,38,43 Power supply circuit 11,48,49,53 Control circuit 33 DC conversion circuit

Claims (3)

[Claims] 1. A load, a detection circuit for detecting load characteristics of the load, a DC power supply, and a switching element,
A power supply circuit connected between the output end of the DC power supply and the load so as to add a predetermined voltage to the output voltage of the DC power supply, and an output signal of the detection circuit, and load electrical characteristics of the load. And a control circuit that outputs a drive signal to the switching element so that the predetermined characteristic is obtained. 2. A load having two or more loads, two or more detection circuits individually detecting at least load power of the loads, a DC power supply, and a switching element, and connected to an output end of the DC power supply. A direct current conversion circuit that outputs a voltage equal to or lower than the lowest load voltage among the loads, and a switching element, and an output end of the direct current conversion circuit and a load other than at least the lowest load voltage among the loads. And at least one power supply circuit connected so as to add a predetermined voltage to the output voltage of the DC conversion circuit, and the output signal of the detection circuit are input, and predetermined power is supplied to the load. And a control circuit that outputs a drive signal to at least two of the switching elements. 3. The power supply device according to claim 2, wherein the control circuit includes a maximum voltage setting circuit or a maximum current setting circuit and sets an upper limit value of the load voltage or the load current.