JP3033721B2 - Output current monitor method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an output current monitoring method, and more particularly, to an output current monitoring method in a power supply system for supplying current to a load from a plurality of power supply modules connected in parallel.

[0002]

2. Description of the Related Art Conventionally, monitoring of an output current in a power supply system for supplying current to a load from a plurality of switching power supplies connected in parallel has been performed by a method as shown in FIG. In FIG. 3, the PWM control circuit 131
The control circuit 13 except for the unit load (U)
NITRODE, Inc., "Products and Applications Handbook (Product)
& Applicationations Handbook) 1
Control I described on pages 6-424 of 999-96 "
C is used.

The operation of the conventional technique will be described below with reference to FIG.

Conventionally, the output current monitoring system of this type of power supply system employs a plurality of switching power supplies (1) to (n).
, A DC power supply 2 and a load 3. Outputs of the switching power supply (1) 1 are connected in parallel by an output bus 4 and supplied to a load 3. Each switching power supply (1)
The control circuits 13 to (n) are connected via the maximum current monitor line 5. Since the configurations of the switching power supplies (1) to (n) are the same, the following description will be made using the switching power supply (1) 1.

[0005] The switching power supply (1) 1 comprises a primary side main circuit 11, a secondary side rectifying and smoothing circuit 12, and a control circuit 13.

The primary side main circuit 11 is connected from the positive side of the DC power supply 2 to one terminal of the switching element SW1 via the current transformer T2 and the primary side winding of the main transformer T1. The other terminal of the switching element SW1 is connected to the negative side of the DC power supply 2. The switching element SW1 is turned on by the ON-OFF signal S1 of the switching element.

The secondary-side rectifying / smoothing circuit 12 supplies a rectifying forward diode D from the secondary-side winding of the main transformer T1.
1, flywheel diode D2, choke coil C
L, connected to the capacitor C, and outputs an output voltage Vo (1) via the OR diode D3.

The control circuit 13 includes a PWM control circuit 131
, A current detection circuit 132, and a current detection value output circuit 133
And a current feedback circuit 134.

[0009] The PWM control circuit 131 outputs the output voltage Vo.
The input signal S4 of the PWM control circuit obtained by multiplying the output signal S2 of (1) by the output signal S3 of the current feedback circuit 134 is used as an input signal, and the ON / OFF signal S1 of the switching element SW1 is changed so that the signal S4 becomes constant. Supplying.

The current detection circuit 132 includes a current transformer T proportional to the DC output current of the switching power supply (1) 1.
The peak value of the pulse current obtained from the secondary winding No. 2 is detected and supplied to the current detection value output circuit 133 and the current feedback circuit 134 as a voltage signal S5.

The current detection value output circuit 133 composed of an operational amplifier OA1 and a diode D4 outputs a voltage signal S5.
At the same time as the voltage monitor signal S6 to the maximum current monitor line 5, and to the current feedback circuit 134. The current feedback circuit 134 outputs the voltage signal S5 and the voltage monitor signal S
6 is subtracted by the operational amplifier OA2 and the current feedback signal S
3 are supplied.

As described above, the voltage signal S 5 proportional to the output current of the switching power supply (1) 1 is output from the current detection circuit 132 to the maximum current monitor line 5, and is output via the current detection value output circuit 133. It is transmitted to the other switching power supplies (2) to (n).

Accordingly, the voltage monitor signal S6 output to the maximum current monitor line 5 is such that the DC power supply to the load 3 becomes maximum among the switching power supplies (1) to (n) connected in parallel. The output voltage value Vm (Max) of the current detection circuit 132 of the switching power supply is monitored.

For example, assuming that the voltage value of the DC voltage signal S5 output from the current detection circuit 132 is Vm (1), the output voltage Vo (1) of the switching power supply (1) 1 is Vo (1) = Vs + α ( Vm (Max) -Vm (1)) where Vs: output set voltage value α: current feedback coefficient.

As represented by the equation, the output voltage value V of the current detection circuit of the switching power supply having the largest output current among the switching power supplies (1) to (n) connected in parallel.
The current balance is controlled by controlling the output voltage Vo (1 to n) of each switching power supply by adding an error to the output voltage value Vm (1 to n) of the current detection circuit of the own switching power supply based on m (Max) as a reference. I am taking.

[0016]

However, the above-mentioned prior art has the following problems.

When the switching element SW1 of the primary side main circuit 11 of the switching power supply connected in parallel is damaged in the short mode, or when the capacitor C of the secondary side rectifying and smoothing circuit 12 is damaged in the short mode, a steady state is established. The impossible current is the primary side main circuit 1.
It flows inside 1.

This abnormal current is detected by the current detection circuit 132 via the current transformer T2, and the voltage signal S
The value 5 is transmitted to the maximum current monitor line 5 via the current detection value output circuit 133, and controls the maximum current monitor line 5.

Assuming that the output voltage value of the current detection circuit 132 at this time is Vm (Over), the switching power supply (1)
From the equation, the output voltage (1) is as follows: Vo (1) = Vs + α (Vm (Over) −Vm (1))...

(Vm (Over) −Vm (1))> (Vm (Max) −Vm (01)) Therefore, the output voltage Vo of each normally operating switching power supply is a power supply in a steady state. Will be output higher than when the is operating, and the overvoltages will be overvoltage in ascending order of the overvoltage value. As a result, the redundant configuration cannot be maintained and the power supply system will be down. To avoid this problem, the amount of current feedback must be reduced, but the current balance between the switching power supplies connected in parallel is lost.

According to the present invention, when an abnormal short circuit occurs in a switching power supply connected in parallel and redundant connection, the output voltage of another normally operating switching power supply is prevented from rising and becoming overvoltage, The purpose is to improve reliability.

[0022]

A first output current monitoring method according to the present invention is an output current monitoring method in a power supply system for supplying current to a load from a plurality of power supply modules connected in parallel. If the output current value is less than the reference value, a voltage proportional to the output current value is output to the other power supply module connected in parallel, and if the output current value is equal to or more than the reference value, the other power supply modules connected in parallel No voltage proportional to the output current value is output to the power supply module.

According to a second output current monitoring method of the present invention, in the first output current monitoring method of the present invention, when there is a power supply module whose output current value is equal to or more than a reference value, the output current value is equal to the reference value. Control the output current value of each power supply module based on the difference between the voltage proportional to the output current value of the power supply module with the largest output current and the voltage proportional to the output current value of each power supply module among the power supply modules of It is characterized by.

A third output current monitoring method according to the present invention is an output current monitoring method in a power supply system for supplying current to a load from a plurality of power supply modules connected in parallel, and detects an output current of each power supply module. After that, it includes a current detection circuit that converts a voltage to generate a voltage signal, an operational amplifier and a diode, and outputs the voltage signal to the other power supply module connected in parallel via the operational amplifier and the diode connected in series. A current detection value output circuit; and a comparator having an output connected to an output of an operational amplifier of the current detection value output circuit, wherein the comparator compares the voltage signal with a reference value, and the voltage signal is higher than the reference value. If the voltage signal is smaller than the reference value, the voltage signal is output to the other power supply module connected in parallel. It is characterized by having a current monitor shutdown circuit for controlling the current detection value output circuit so as not to output the voltage signal to the other power supply modules the parallel connected to each power module.

According to a fourth output current monitoring method of the present invention, in the third output current monitoring method of the present invention, a switch is provided between an operational amplifier and a diode of the current detection value output circuit, and the current monitor shutdown circuit is If the voltage signal is less than the reference value,
N, and when the voltage signal is equal to or higher than the reference value, the switch is controlled to be turned off.

According to a fifth output current monitoring method of the present invention, in the first to fourth output current monitoring methods of the present invention, the reference value is variable.

According to a sixth output current monitoring method of the present invention, in the first to fifth output current monitoring methods of the present invention, the power supply module is a switching power supply.

[0028]

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

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which a plurality of switching power supplies (1) to (n);
It comprises a DC power supply 2 and a load 3. Outputs of the switching power supply (1) 1 are connected in parallel by an output bus 4 and supplied to a load 3. Each switching power supply (1) ~
The control circuit 13 in (n) is connected via the maximum current monitor line 5. Here, a feature of the present invention is that the control circuit 13 includes the current monitor shutdown circuit 135. Since the configurations of the switching power supplies (1) to (n) are the same, the following description will be made using the switching power supply (1) 1.

The switching power supply (1) 1 comprises a primary side main circuit 11, a secondary side rectifying and smoothing circuit 12, and a control circuit 13.

The primary side main circuit 11 is connected from the positive side of the DC power supply 2 to one terminal of the switching element SW1 via the current transformer T2 and the primary side winding of the main transformer T1. The other terminal of the switching element SW1 is connected to the negative side of the DC power supply 2. The switching element SW1 is turned on by the ON / OFF signal S1 of the switching element.

The secondary rectifying / smoothing circuit 12 supplies a rectifying forward diode D from the secondary winding of the main transformer T1.
1, flywheel diode D2, choke coil C
L, connected to the capacitor C, and outputs an output voltage Vo (1) via the OR diode D3.

The control circuit 13 includes a PWM control circuit 131
, A current detection circuit 132, and a current detection value output circuit 133
, A current feedback circuit 134, and a current monitor shutdown circuit 135.

The PWM control circuit 131 outputs the output voltage Vo
The input signal S4 of the PWM control circuit obtained by multiplying the output signal S2 of (1) by the output signal S3 of the current feedback circuit is used as an input signal, and the ON / OFF signal S1 of the switching element SW1 is supplied so that the signal S4 becomes constant. doing.

The current detection circuit 132 includes a current transformer T proportional to the DC output current of the switching power supply (1) 1.
The peak value of the pulse current obtained from the secondary winding No. 2 is detected and supplied as a voltage signal S5 to the current detection value output circuit 133, the current feedback circuit 134, and the current monitor shutdown circuit 135.

The current detection value output circuit 133 composed of the operational amplifier OA1 and the diode D4 outputs the voltage signal S5
At the same time as the voltage monitor signal S6 to the maximum current monitor line 5, and to the current feedback circuit 134. The current feedback circuit 134 outputs the voltage signal S5 and the voltage monitor signal S
6 is subtracted by the operational amplifier OA2 and the current feedback signal S
3 are supplied.

The current monitor shutdown circuit 135
Comparator CMP is provided.
Has a voltage signal S5 and a reference voltage Vref as inputs, and has an output connected to the output of the operational amplifier OA1 of the current detection value output circuit 133.

As described above, the maximum current monitor line 5
, A voltage signal S5 proportional to the output current of the switching power supply (1) 1 is output from the current detection circuit 132 and transmitted to the other switching power supplies (2) to (n) via the current detection value output circuit 133. You.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIG.

As shown in FIG. 1, switching power supplies (1) to (n) are connected in parallel, and supply electric power to the load 3 by performing parallel redundant operation. A voltage signal S5 proportional to the output current of the switching power supply 1 is output from the current detection circuit 132 of each switching power supply 1 to the maximum current monitor line 5, and is connected via a current detection value output circuit 133 by a diode OR. I have.

Accordingly, the voltage monitor signal S6 output to the maximum current monitor line 5 is such that the DC power supply to the load 3 becomes maximum among the switching power supplies (1) to (n) connected in parallel. The output voltage value Vm (Max) of the current detection circuit 132 of the switching power supply is monitored.

For example, assuming that the voltage value of the DC voltage signal S5 output from the current detection circuit 132 is Vm (1), the output voltage Vo (1) of the switching power supply (1) 1 is Vo (1) = Vs + α ( Vm (Max) -Vm (1)) where Vs: output set voltage value α: current feedback coefficient.

As represented by the above equation, the output voltage value V of the current detection circuit of the switching power supply having the largest output current among the switching power supplies (1) to (n) connected in parallel.
The current balance is controlled by controlling the output voltage Vo (1 to n) of each switching power supply by adding an error to the output voltage value Vm (1 to n) of the current detection circuit of the own switching power supply based on m (Max) as a reference. I am taking.

Now, in one of the n switching power supply modules connected in parallel, if the switching element SW1 of the primary side main circuit 11 is broken in the short mode, the current corresponding to the impedance of the primary side main circuit 11 is obtained. Until the current transformer T2 causes magnetic saturation, the abnormal current value is transmitted to the current detection circuit 132 by the current transformer T2.

If the voltage value whose peak value is rectified and detected is V132 (SW1 short), this voltage value is reported as a signal S5 to the current detection value output circuit 133 and the current feedback circuit 134, and at the same time, It is also reported to the shutdown circuit 135.

In the current monitor shutdown circuit 135, the reference voltage Vref is Vref = V132 (100%) × 1.1 where V102 (100%): the primary side main circuit 11 when the rated output current is supplied. Current detection circuit 1
Value converted by voltage at 32. Is set. This is because, with respect to the signal S5 of the current detection value V132 (SW1 short) transmitted at this time, the relationship shown as Vref <V132 (SW1 short) holds, so that the output of the comparator CMP becomes low (0V) level, Current detection value output circuit 13
3 is also low (0 V), the reference voltage Vref is applied to the maximum current monitor line 5.
Abnormal voltage V132 (SW1 short) exceeding the value is not transmitted.

Accordingly, for the maximum current monitor line 5, the supply of the DC output current to the load 3 among the n-1 switching power supplies 1 other than the switching power supply 1 that failed in the short-circuit mode is the largest. The output voltage value Vm (Ma) of the current detection circuit 132 of the switching power supply 1
Since x) is monitored, the output voltage fluctuation of the normally operating switching power supply 1 is within a steady value, and redundancy is possible without lowering the current feedback amount without overvoltage.

When the capacitor C of the secondary rectifying / smoothing circuit 12 is damaged in the short mode, a current exceeding the rated value flows in the secondary rectifying / smoothing circuit 12, and the primary main circuit 11 A current proportional to the current flows therein, and is transmitted to the current detection circuit 132 by the current transformer T2.

At this time, assuming that the voltage value at which the peak value is current detected by the current detection circuit 132 is V132 (C short), the relationship of Vref <V132 (C short) holds for this voltage value.

The subsequent operation is the same as when the above-described switching element SW1 is damaged in the short-circuit mode. Even in this failure mode, the output voltage fluctuation of each switched-on power supply 1 can be achieved without reducing the amount of current feedback. Is within the steady-state value, and redundancy is possible without overvoltage.

Next, another embodiment of the present invention will be described with reference to FIG.

In another embodiment of the present invention, the switching element SW2 is provided between the operational amplifier OA1 and the diode D4 in the current detection value output circuit 133 of the embodiment of the present invention described above. . FIG. 2 is a circuit diagram showing another embodiment of the present invention, and the same reference numerals as those in FIG. 1 indicate the same components. Note that the following description is made for portions different from the embodiment of the present invention.

In one embodiment of the present invention, the voltage signal S5 is supplied to the current detection value output circuit 133, the current feedback circuit 1
34 and a current monitor shutdown circuit 135, and is supplied to the maximum current monitor line 5 via a current detection value output circuit 133 constituted by a series circuit of an operational amplifier OA 1 and a diode D 4.

In this embodiment, a switching element SW2 is provided between the operational amplifier OA1 of the current detection value output circuit 133 and the diode D4, and the switching of the switching element SW2 is performed by the current monitor shutdown circuit 135.
Is controlled by The current monitor shutdown circuit 135 includes a comparator CMP. The comparator CMP receives the voltage signal S5 and the reference voltage Vref.

The comparator CMP compares the voltage signal S5 with the reference voltage Vref, and determines that the voltage signal S5 <the reference voltage Vref.
When ref, the switching element SW2 is closed. When the voltage signal S5> the reference voltage Vref, the switching element SW2 is closed.
2 open, 0N / OFF of the switching element
It is controlled by a signal S7.

In the above-described embodiment and other embodiments of the present invention, the output current monitoring method of the switching power supplies connected in parallel and redundantly has been described. It is clear that the present invention is applicable.

[0057]

As described above, according to the present invention, when an abnormal short circuit occurs in a switching power supply connected in parallel and redundant manner, normal operation can be performed without lowering the amount of current feedback and deteriorating current balance. By preventing the output voltage of another switching power supply from becoming excessive, the reliability of the power supply system is improved.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 switching power supplies (1) to (n) 11 primary side main circuit 12 secondary side rectification smoothing circuit 13 control circuit 131 PWM control circuit 132 current detection circuit 133 current detection value output circuit 134 current feedback circuit 135 current monitor shutdown circuit 2 DC Power supply 3 Load 4 Output bus 5 Maximum current monitor line C Capacitor CL Choke coil CMP Comparator D1 Rectifier forward diode D2 Flywheel diode D3 OR diode D4 Diode OA1, OA2 Operational amplifier S1, S7 Switching element ON / OFF signal S2 Output voltage Vo S3 Output signal of current feedback circuit S4 Input signal of PWM control circuit S5 Voltage signal S6 Voltage monitor signal SW1, SW2 Switching element T1 Main transformer T2 Current Nsu

Claims (6)

(57) [Claims] An output current monitoring method in a power supply system for supplying current to a load from a plurality of power supply modules connected in parallel, wherein when an output current value of each power supply module is less than a reference value, the power supply module is connected in parallel. A voltage proportional to the output current value is output to another power supply module, and a voltage proportional to the output current value is not output to the other power supply modules connected in parallel when the output current value is equal to or more than a reference value. An output current monitoring method characterized by the following. 2. When there is a power supply module whose output current value is equal to or greater than a reference value, a voltage proportional to the output current value of the power supply module having the largest output current among the power supply modules whose output current value is less than the reference value. 2. The output current monitoring method according to claim 1, wherein an output current value of each power supply module is controlled based on a difference from a voltage proportional to an output current value of each power supply module. 3. An output current monitoring method in a power supply system for supplying current to a load from a plurality of power supply modules connected in parallel, wherein after detecting an output current of each power supply module, voltage conversion is performed to generate a voltage signal. A current detection value output circuit for outputting the voltage signal to the other power supply module connected in parallel via the operational amplifier and the diode connected in series; and A comparator connected to an output of an operational amplifier of the current detection value output circuit, wherein the comparator compares the voltage signal with a reference value, and connects the voltage signal in parallel when the voltage signal is smaller than the reference value. Output to another power supply module, and when the voltage signal is equal to or greater than the reference value, the voltage signal is connected in parallel to the power supply module. And a current monitor shutdown circuit for controlling the current detection value output circuit so as not to output to another power supply module. 4. A switch is provided between an operational amplifier and a diode of the current detection value output circuit, and the current monitor shutdown circuit turns on the switch when the voltage signal is smaller than the reference value, and the voltage signal is 4. The output current monitoring method according to claim 3, wherein the control is performed such that the switch is turned off when the output current is equal to or larger than the reference value. 5. The output current monitoring method according to claim 1, wherein the reference value is variable. 6. The output current monitoring method according to claim 1, wherein said power supply module is a switching power supply.