JPH08116670A - Stabilized dc power supply - Google Patents

Abstract

PURPOSE: To obtain a stabilized DC power supply in which the reliability is enhanced by eliminating the difference among powers being fed to a load from a plurality of power supplies. CONSTITUTION: The stabilized DC power supply comprises a plurality of power supplies PS1, PS2, each comprising a converter transformer T1 delivering an output voltage to a load from the secondary thereof and control circuits 16, 18 generating a signal for controlling the output voltage from the converter transformer, and impedances 19 connected between the output terminals of the control circuits for the plurality of power supplies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilized DC power supply used in a communication device or the like which uses a telephone line.

[0002]

2. Description of the Related Art In a conventional DC stabilized power supply, as a method of increasing an output voltage, there is, for example, a master / slave control system using a plurality of identical power supplies. Here, the conventional DC stabilized power supply of the master / slave control system is shown in FIG.
Will be described with reference to.

Reference numeral 51 is a DC voltage source. DC voltage source 51
Supplies a DC voltage to the master power supply M and the slave power supply S. In this case, the master power supply M is connected to the primary side of the converter transformer Tm through the current detection circuit 52, and the slave power supply S is directly connected to the primary side of the converter transformer Ts.

A current switch circuit 53 is connected to the primary side of the converter transformer Tm which constitutes the master power supply M. The current flowing to the primary side is interrupted by opening / closing the current switch circuit 53.

The current detection circuit 52 detects the pulse current Ip flowing through the primary side of the converter transformer Tm,
The pulse current Ip is converted into a detection signal I corresponding to its magnitude.
It is converted to s and added to the comparator 54.

Further, in response to the interruption of the current on the primary side, a current flows to the secondary side of the converter transformer Tm, and a voltage is output to the secondary side. The voltage output to the secondary side is smoothed by the rectifying / smoothing unit 55 and output to the load terminal OUT as the output voltage V0.

In the above structure, the output voltage V0 is taken out and applied to the output voltage control circuit 56 in order to stabilize the output voltage V0. A reference voltage Vref from a reference voltage source 57 is applied to the output voltage control circuit 56, the output voltage V0 and the reference voltage Vref are compared, and a control voltage Vb corresponding to the difference between them is generated.
This control voltage Vb is input to the insulation circuit 58 that insulates the primary side and the secondary side, and is converted into the control voltage Vc on the secondary side.
It is added to the comparator 54.

The comparator 54 compares the detection signal Is applied from the current detection circuit 52 with the control voltage Vc to generate a control pulse Sp having a width corresponding to the difference between the two.
The control pulse Sp is applied to the current switch circuit 53 to control the opening / closing time of the current switch circuit 53. By this control, the opening / closing time of the current switch circuit 53 changes, and the time during which the pulse current Ip flows to the primary side of the converter transformer Tm is adjusted. As a result, the output voltage V of the secondary side is adjusted.
0 is controlled. In this way, the output voltage V0 is controlled to a constant value. The timing for generating the control pulse Sp is the pulse Cp supplied from the clock circuit 59.
Is determined.

By the way, in the case of the master / slave control method described above, the control pulse S generated by the master power source M is generated.
p is the current switch circuit 53 of the slave power supply S as it is.
It is supplied to p and is used for controlling the output voltage V0p of the slave power supply S. The rest of the configuration of the slave power source S is the same as that of the master power source M, and thus the description thereof is omitted.

Next, as another example of the conventional DC stabilized power supply, a method using the output voltage drooping characteristic due to overcurrent will be described with reference to FIG. This example also has multiple power sources P
This is a configuration in which the outputs of S1 and PS2 are combined and supplied to the load. The power sources PS1 and PS2 have the same configuration, and the power sources PS1 and PS2 each independently control the output voltage. Therefore,
One power source PS1 will be mainly described, and the other power source PS2 will be described.
The overlapping description will be omitted.

The DC voltage source 61 is connected to the primary side of the converter transformer T1 through a current detection circuit 62. A current switch circuit 63 is connected to the primary side of the converter transformer T1, and the current is switched on and off by opening and closing the current switch circuit 63. The current detection circuit 62 detects the pulse current Ip flowing through the primary side of the converter transformer T1, converts the pulse current Ip into a detection signal Is corresponding to the magnitude thereof, and outputs the current mode P.
It is added to the WM circuit 64.

Further, due to the interruption of the current on the primary side, a current flows to the secondary side of the converter transformer T1 and a predetermined voltage is output to the secondary side. The voltage output to the secondary side is smoothed by the rectifying / smoothing unit 65, passes through the diode CR, and is output from the terminal OUT as the output voltage V0.

Then, in order to stabilize the output voltage V0, the output voltage V0 is taken out and applied to the output voltage control circuit 66. A reference voltage Vref is applied from the reference voltage source 67 to the output voltage control circuit 66, and the output voltage V0 and the reference voltage Vref are compared,
The control signal Vb is generated according to the difference between the two voltages. The control signal Vb is input to the insulating circuit 68, converted into the control signal Vc on the primary side, and added to the current mode PWM circuit 64.

In the current mode PWM circuit 64, the detection signal Is applied from the current detection circuit 62 is compared with the control signal Vc to generate the control pulse Sp having a width corresponding to the difference between the two. The control pulse Sp is applied to the current switch circuit 63 to control the opening / closing time of the current switch circuit 63. As a result, the time during which the pulse current Ip flows through the primary side of the converter transformer T1 is controlled, and the output voltage V0 is adjusted to have a constant value. The above-described operation is the same for the power supply PS2, and thus the description thereof is omitted.

[0015]

In the former master / slave control method, a control signal for controlling the output voltage is generated by the master power supply, and this control signal is supplied to another slave power supply. Therefore, if there are variations in the characteristics of the switching elements of the current switch circuit that make up each power supply, there will be a difference between the power supplied from the master power supply to the load and the power supplied from the slave power supply to the load. When the difference in the supplied power occurs between the power sources in this way, the heat generation status of each power source becomes different, and the reliability of each power source varies. Further, if the output voltage control system of the master power supply fails, the voltage control for other slave power supplies cannot be performed.

In the latter method utilizing the output voltage drooping characteristic due to overcurrent, the output voltage V0 is controlled independently for each power supply. Therefore, the output voltage V0 depends on the power supply.
May be different. For example, when the output voltage V01 of PS1 is higher than the output voltage V02 of PS2 (V01> V02),
Pulse current Ip detected by the current detection circuit 62 of PS1
However, the power supply PS1 supplies electric power to the load until the current exceeds the threshold value set in the current mode PWM circuit 64 and becomes an overcurrent. Then, when the power supply PS1 becomes overcurrent and V01 <V02, the power supply PS2 then supplies power to the load. Therefore, the maximum power is supplied from the power source having a high output voltage, and the power sources PS1 and P1 are supplied.
There is a difference in power supply between S2. In this configuration, the output terminals of the respective power supplies PS1 and PS2 are connected to the load terminal through the diodes CR1 and CR2, and each can operate independently. Therefore, even if one of the power supplies PS1 and PS2 becomes inoperable, the output can be supplied from another power supply.

The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide a stabilized direct current power supply which eliminates the difference in power supplied from a plurality of power supplies to a load and improves reliability.

[0018]

A stabilized direct current power supply of the present invention generates a converter transformer in which an output voltage supplied to a load is output to a secondary side, and a control signal for controlling the output voltage of the converter transformer. And a plurality of power sources each having a control circuit for controlling the impedance, and an impedance connected between the output terminals of the control circuit of each of the plurality of power sources. The control circuit is composed of an output voltage control circuit for comparing the output voltage of the converter transformer with a reference voltage, and an insulating circuit for converting the control signal generated by the output voltage control circuit into a control signal on the primary side. ing.

[0019]

According to the above construction, the impedance is connected between the output terminals of the control circuits of the respective power sources. Therefore, if there is a difference in the control signal generated by comparing the output voltage of each power supply and the reference voltage, a current flows through the impedance connected between the output terminals of the control circuit according to the difference, and the control signal Are equal in size. Therefore, the pulse currents flowing on the primary side of each power supply are compared with control signals of equal value. As a result, the outputs of the respective power supplies become equal and the secondary side current is evenly distributed. Also,
Further, since there is no difference in power supply, reliability is improved.

The ratio of the load current between the power supplies can be adjusted by making the values of the impedances connected between the output sides of the output voltage control circuits of the power supplies different among the predetermined power supplies.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

Reference numeral 11 is a DC voltage source for generating a DC voltage,
A DC voltage is supplied from the DC voltage source 11 to the terminals IN of the power supplies PS1 and PS2. Since the power supplies PS1 and PS2 have the same configuration, first one power supply PS1 will be described.

The current detection circuit 12 is connected to the terminal IN to which the DC voltage is supplied, and the current detection circuit 12 is connected to the primary side of the converter transformer T1. A current switch circuit 13 is connected to the primary side of the converter transformer T1. The current flowing to the primary side is interrupted by opening / closing the current switch circuit 13. The current detection circuit 12 is a converter transformer T
1 detects the pulse current Ip flowing through the primary side, and detects the detected pulse current Ip as a detection signal Is corresponding to its magnitude.
And is added to the current mode PWM circuit 14.

A predetermined voltage is output to the secondary side of the converter transformer T1 due to the interruption of the current flowing to the primary side. This output voltage is smoothed by the rectifying / smoothing unit 15, and is supplied from the diode CR1 to the terminal OUT as the output voltage V0.

In order to stabilize the output voltage V0,
Output voltage V0 is taken out and output voltage control circuit 1
Added to 6. A reference voltage Vref from a reference voltage source 17 is applied to the output voltage control circuit 16, the output voltage V0 and the reference voltage Vref are compared, and a control signal Vb corresponding to the difference between the two voltages is generated. Control signal V
b is input to the isolation circuit 18 that insulates the primary side from the secondary side, is converted into the control signal Vc on the primary side, and is converted into the current mode PW.
It is added to the M circuit 14.

Then, in the current mode PWM circuit 14,
The detection signal Is applied from the current detection circuit 12 is compared with the control signal Vc, and the control pulse Sp having a width corresponding to the difference between the both is generated. The control pulse Sp is applied to the current switch circuit 13 to control the opening / closing time of the current switch circuit 13. As a result, the time during which the pulse current Ip flows through the primary side of the converter transformer T1 is controlled, and the output voltage V0 is adjusted to a predetermined value.

The configuration and operation of the power supply PS2 is also the power supply PS2.
Similar to 1, the output voltage of the power supply PS2 is also supplied to the terminal OUT via the diode CR2. An impedance 19, for example, a resistor is connected to the output side of the insulation circuit 18 of each of the power supplies PS1 and PS2, and each impedance 19 is connected to the common point a.

According to the above configuration, the power sources PS1 and P1
The output terminal of S2 is connected to a terminal OUT and a load (not shown) through diodes CR1 and CR2, respectively. Therefore, even if either of the power supplies PS1 and PS2 becomes inoperable, the output can be supplied from the other power supply and the backup function is provided.

The output terminals of the insulating circuit 18 are connected to a common point a via an impedance 19. Therefore, even if the control signal Vc applied from the insulating circuit 18 to the current mode PWM circuit 14 varies between the power supplies PS1 and PS2, current flows through the impedance 19 from the higher control voltage Vc to the lower control voltage Vc, and The control signals Vc have the same magnitude, for example, the same voltage. For this reason,
In the current mode PWM circuit 14, the magnitude of the control signal Vc compared with the pulse current Ip flowing through the primary side of the converter transformer T1 is equal in all the power supplies PS1 and PS2.

Therefore, when the power supplies PS1 and PS2 are operated in parallel, even if there is a difference in the control voltage of the power supplies, they act on each other via the impedance 19 and have stable and equal values. As a result, the peak value and pulse width of the pulse current Ip flowing through the primary side of the converter transformer (determined by the current gradient due to the inductance of the converter transformer and the inductance of the smoothing choke) are substantially equal between the power supplies PS1 and PS2. Controlled to be.
In this case, the pulse current Ip is determined by the load current Io on the secondary side and the exciting current ΔI. In this case, Io >> Δ
Since it is I, it is almost equal to the load current Io.

According to the above configuration, the output voltage Vo is controlled so as to be stabilized, and the load current Io is also distributed from each power source substantially evenly. Therefore, the heat generation of each power source is equalized, and the reliability is improved. In addition, the current on the secondary side is evenly distributed, and there is no difference in the supplied power, which also improves reliability.

In the above embodiment, each power source PS
Impedances 19 are connected to the output sides of the insulating circuits 18 of 1 and PS2, and the impedances 19 are connected to a common point a. However, the insulation circuit 1 of the power supply PS1
1 between the output side of 8 and the output side of the insulation circuit 18 of the power supply PS2
The same effect can be obtained by connecting the two impedances in common.

Here, a specific circuit of the insulating circuit 18 (FIG. 1) will be described with reference to FIG. Insulation circuit 18
Is a circuit that insulates the primary side and the secondary side of the converter transformer T1 and converts the control signal Vb generated by the output voltage control circuit 16 on the secondary side into the control signal Vc on the primary side. It is composed of a resistor R. Then, the control signal Vb obtained by comparing the output voltage V0 and the reference voltage Vref is applied to the terminal A. At this time, the photodiode 21a emits light and the phototransistor 21b
To conduct. When the phototransistor 21b is conducting, the control signal Vc having a magnitude corresponding to the input control signal Vb
Is output to the terminal B, and the control signal Vc is simultaneously output to the terminal C.
Is output to The terminal C is connected to the impedance circuit 19, and the impedance circuit 19 is connected to the common point a.

Next, the current mode PWM circuit 14 (FIG. 1)
A specific circuit of the above will be described with reference to FIG. The current mode PWM circuit 14 includes a comparator 31, a clock circuit 32, and a logic circuit 33. Then, the control signal Vc sent from the insulating circuit 17 is input to the comparator 31 from the terminal D. Further, the detection signal Is from the current detection circuit 12 is input to the comparator 31 through the terminal E. Then, the control signal Vc and the detection signal Is are compared, and the difference is sent to the logic circuit 33. A clock signal CL is added to the logic circuit 33 from the clock circuit 32, and a pulse S having a time width corresponding to the difference between the control signal Vc and the detection signal Is at the timing of the clock signal CL.
generate p. The pulse Sp is sent from the terminal F to the current switch circuit 13 (FIG. 1) to control the opening / closing of the current switch circuit 13.

FIG. 4 shows an example of the signal waveform of each circuit. (A) is a clock signal CL generated by the clock circuit, which is generated at a certain fixed period. (B) is the control signal Vc generated by the insulation circuit 17, (c) is the detection signal Is sent from the current detection circuit, and (d) is the control pulse Sp generated by the current mode PWM circuit 14. . The control pulse Sp rises at the clock signal CL and falls at the point when the detection signal Is becomes equal to the control signal Vc. (E) is a current Ip flowing through the primary side of the converter transformer T1 and has the same waveform as the detection signal Is. Further, (f) shows the current Ia output to the secondary side of the converter transformer T1 and the rectified load current Ib.

In the above embodiment, the case where two power supplies are operated in parallel has been described, but the same applies to the case where three or more power supplies are operated in parallel.

Although the above-mentioned structure is a forward structure, it can be applied to other systems such as flyback. Also,
Although a photocoupler is used as the insulating circuit, another transformer transmission method can be used. It can also be applied to a system that does not use an insulation circuit. Although the impedance circuit is described as a resistor, other impedances can be used.

[0038]

According to the present invention, there is no difference in the electric power supplied from each power source to the load, and a stabilized DC power source with improved reliability can be realized.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an insulating circuit of the present invention.

FIG. 3 is a diagram illustrating a current mode PWM circuit of the present invention.

FIG. 4 is a diagram illustrating a waveform of each part of the present invention.

FIG. 5 is a circuit configuration diagram showing a conventional example.

FIG. 6 is a circuit configuration diagram showing a conventional example.

[Explanation of symbols]

 11 ... DC voltage source 12 ... Current detection circuit 13 ... Current switch circuit 14 ... Current mode PWM circuit 15 ... Rectification smoothing section 16 ... Output voltage control section 17 ... Reference voltage source 18 ... Insulation circuit 19 ... Impedance circuit T1 ... Converter transformer PS1 , PS2 ... Power supply

Claims (2)

[Claims] 1. A plurality of power supplies each having a converter transformer that outputs an output voltage supplied to a load to a secondary side and a control circuit that generates a control signal for controlling an output voltage of the converter transformer, and A stabilized direct current power supply comprising: an impedance connected between the output terminals of the control circuit of each of a plurality of power supplies. 2. An output voltage control circuit, wherein the control circuit compares an output voltage of a converter transformer with a reference voltage, and an insulation circuit for converting a control signal generated by the output voltage control circuit into a primary side control signal. 2. The stabilized DC power supply according to claim 1, wherein