JP3254667B2 - Switching power supply controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply control device and, more particularly, to load sharing control between switching power supplies when a plurality of switching power supplies supply power to a common load.

[0002]

2. Description of the Related Art When power is supplied from a switching power supply to a DC load, if the load is larger than the output capacity of a single switching power supply, the power is supplied in parallel from a plurality of switching power supplies as shown in FIG. That is being done. In the example of FIG. 5, the first switching power supply 1 has two output systems of 24V / 1A and 5V / 15A, and the second switching power supply 2 has only an output system of 5V / 20A. The first switching power supply 1 supplies power to the load 3 of 24V / 1A from the 24V / 1A system, and supplies 5V / 2 from the 5V / 15A system.
Power is supplied to the 4 A load 4, and the second switching power supply 2 supplies power to the 5 V / 24 A load 4 in parallel with the 5 V / 15 A system of the first switching power supply 1. The switching power supplies 1 and 2 are supplied with power from a common input power supply 5.

When power is supplied in parallel from a plurality of switching power supplies to a common load in this way, in order to prevent the load from being biased to a specific switching power supply,
It is necessary to control so that the load is equally shared among a plurality of switching power supplies. FIG. 6 is a block diagram showing an example of such a conventional load sharing control circuit configuration. In each of the switching power supplies 1 and 2, 11 and 21 are transformers, and a DC voltage is commonly input to one end of a primary winding from an input power supply (not shown), and switch elements 12 and 22 are connected to the other end. Have been. Switch element 1
The pulse widths of the driving pulses of the switching control circuits 13 and 23 are controlled by the switching control circuits 13 and 23, respectively. Rectifier smoothing circuits 14 and 24 are connected to the secondary windings, respectively, and the output is supplied in parallel to a load (not shown). The rectifying / smoothing circuit 14 of the switching power supply 1 has a voltage of 5 V / 1.
The output system is 5 A, and the output system of 24 V / 1 A is not shown. Further, current detection circuits 15 and 25 for detecting an output current are provided on each secondary side. The detection signal of the current detection circuit 15 of the first switching power supply 1 is applied to a control signal generation circuit 26 provided in the second switching power supply 2 together with the detection signal of the current detection circuit 25 of the second switching power supply 2. I have. The output voltage on the secondary side of the first switching power supply 1 is
The control signal output from the control signal generating circuit 26 is fed back to the switching control circuit 23 via the photocoupler 27.

With this configuration, the switching control circuit 13 adjusts the drive pulse width of the switch element 12 based on the output voltage of the secondary side input via the photocoupler 16 so that the voltage error becomes zero. The switching control circuit 23 controls the drive pulse width of the switch element 22 according to the output signal of the control signal generation circuit 26 input via the photocoupler 27 so that the current error becomes zero.

As a result, 5 V / 1 of the switching power supply 1
The load sharing of the output current of the output system of 5A and the output current of the output system of the switching power supply 2 becomes equal. By the way, the total rated output power of the first switching power supply 1 in the case of FIG. 5 is 99 W by the sum of 24 V × 1 A = 24 W and 5 V × 15 A = 75 W, and the output power of the second switching power supply 2 is 5 V × 20 A = 100 W, and the rated output powers of both are almost equal.

[0006]

However, switching power supplies 1 and 2 having different output power specifications as shown in FIG.
When the load sharing control circuits are operated in parallel as described above, the output power of each switching power supply is balanced in different states. That is, the switching power supply 1 is in an output state of 84% of the rated output power, but the switching power supply 2 is in an output state of 60%.

In such a state, stress is applied to the switching power supply 1, which is not preferable in terms of life and reliability. In the configuration in which the load sharing control circuit is provided on the secondary side as shown in FIG. 6, an auxiliary power supply for supplying power to the load sharing control circuit must be prepared before the output voltage of the secondary side rises. In addition, there is a problem that the entire circuit configuration including such an auxiliary power supply circuit becomes complicated.

Further, when the switching power supply is provided with a plurality of output systems, a load sharing control circuit function must be provided for each output system, which increases the circuit cost. The present invention is to solve such a conventional problem, and an object of the present invention is to share the load among the switching power supplies when a plurality of switching power supplies supply power to a common load. An object of the present invention is to realize a switching power supply control device capable of controlling circuit currents to be equal to each other.

[0009]

According to the present invention, in a configuration in which power is supplied from a plurality of switching power supplies to a common load, each switching power supply has a current detection circuit for detecting a circuit current flowing to the primary side; A maximum current selection circuit for selecting a maximum current from the detection results of these current detection circuits,
A control signal generating circuit for outputting a control signal for driving in a voltage control state or a current control state according to the selection output of these maximum current selection circuits and the magnitude of the detection output of each current detection circuit ; Circuit of the current detection circuit
Switching power supply whose detection result is selected as the maximum current
Is driven in voltage control state and the other switching power supplies
By driving in a controlled state, load sharing control is performed so that the currents on the primary side of each switching power supply become equal.

[0010]

The load sharing between the switching power supplies in the present invention is realized by controlling the current flowing through the primary side of each transformer to be equal. Thereby, even when current is supplied in parallel to a common load from some output systems of a plurality of switching power supplies provided with a plurality of output systems, the current flowing on the primary side of each switching power supply is Since they are controlled to be equal, stress on a specific switching power supply can be reduced and reliability can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG.
FIG. 7 is a block diagram showing an example of an apparatus in the process of realizing the present invention, and portions common to FIGS. 5 and 6 are denoted by the same reference numerals. In each of the switching power supplies 1 and 2,
Reference numeral 41 denotes a current transformer for measuring a current flowing to the primary side, and a current detection circuit 3
2, 42 are connected. The switching power supply 1
The rectifying / smoothing circuit 33 is of a 24 V / 1 A output system. The detection current of the current detection circuit 32 of the switching power supply 1 is connected to the signal line 50. The control signal generation circuit 43 of the second switching power supply 2 includes a current detection circuit 32,
The detection signal 42 is input, and the output signal of the control signal generation circuit 43 is applied to the switching control circuit 23.

The operation of such a circuit configuration will be described. First, the switching control circuit 13 of the first switching power supply 1 controls the drive pulse width of the switch element 12 based on the secondary output voltage input via the photocoupler 16 so that the voltage error becomes zero. I do. In contrast, the second
The switching control circuit 23 of the switching power supply 2 of
The switching element 22 is driven such that an error between the detection current of the current detection circuit 32 flowing through the signal line 50 according to the output signal of the control signal generation circuit 43 and the detection current of the current detection circuit 42 of the second switching power supply 2 becomes zero. Control the pulse width.

As a result, the current flowing through the primary side of the transformer 11 of the first switching power supply 1 and the switching power supply 2
The current flowing on the primary side of the transformer 21 becomes equal. That is, when switching power supplies 1 and 2 having different output power specifications are operated in parallel by a load sharing control circuit as shown in FIG. 1 as shown in FIG. 5, each of the switching power supplies 1 and 2 has an output of 72% of the rated output power. State. Compared with the configuration of FIG. 6, the output state of 84% of the rated output power of the first switching power supply 1 is reduced by 12% of the rated output power, and the rated output power of the second switching power supply 2 is reduced. Of the rated output power is 60%
%, But does not enter an extreme stress state, and can improve the life and reliability as a whole.

The configuration of an auxiliary power supply for supplying power to the load sharing control circuit is such that a load sharing control circuit is provided on the primary side and a load sharing control circuit is provided on the secondary side as shown in FIG. And the entire circuit configuration including such an auxiliary power supply circuit can be simplified.
In the embodiment shown in FIG. 1, the switching power supply 1 operates only in the voltage control state and the switching power supply 2 operates only in the current control state. Thus, the voltage control state and the current control state can be realized as a whole. On the other hand, the switching power supplies 1 and 2 alone cannot switch and drive between the voltage control state and the current control state.

FIG. 2 is a block diagram of one embodiment of the present invention, which enables switching drive between the voltage control state and the current control state of each of the switching power supplies 1 and 2 alone.
1 are given the same reference numerals. In the configuration of FIG. 2, a circuit function for controlling the output voltage of each of the switching power supplies 1 and 2 (photocouplers 16 and 27 and control signal generation circuits 35 and 43) and a circuit function for controlling the current on the primary side (current detection Circuits 32 and 42 and a maximum current selection circuit 34,
44 and control signal generation circuits 35 and 43).

FIG. 3 is a circuit diagram showing a specific example of a main part of FIG. 2,
FIG. 4 is a waveform diagram illustrating the operation of the switching power supply 1 of FIG. 1 corresponding to the load power of switching power supply 1
The current on the next side is detected by the current transformer 31 and is converted by the current detection circuit 32 into the DC voltage CS1. The maximum current selection circuit 34 composed of the operational amplifier A1 compares the DC voltage CS1 of the switching power supply 1 with the DC voltage CS2 of the switching power supply 2, and outputs CS1 to the signal line 50 as LS when CS1> CS2. When <CS2, CS2 is output to the signal line 50 as LS. The operational amplifier A2 forming the control signal generation circuit 35 has a reference voltage V
_r , DC voltage CS1 and LS applied to the signal line 50, and outputs an error signal FB 'to the operational amplifier A3. This error signal FB 'is given by the following equation.

[0017] _{FB' = [{(R 2 V} r + R 1 V CS1) (R 3 + R 4) / (R 1 + R 2)} -R 4 V LS] / R 3 wherein, R ₁ / R ₂ = If R ₃ / R ₄ , then FB ′ = V _r + R ₁ / R ₂ (V _CS1 −V _LS ). In addition, the V _r> V _S.

In such a circuit, CS1 and CS2
It operates as follows according to the magnitude relation of. _{[CS1> CS2] V CS1 =} V LS becomes, the FB' = V _r. Further, the lower one of FB ′ and V _S is selected by the operational amplifier A3, and FB =
It becomes V _S, the switching power supply 1 operates in a voltage control state. _{[CS1 <CS2] V CS2 =} V LS becomes, V _CS1> FB' from V _CS2 is R ₁ / R
₂ (V _CS2 −V _CS1 ). Then, FB ′ <V _S
FB = FB ', and the switching power supply 1 switches from the voltage control state to the current control state. As a result,
The level of FB ′, that is, FB according to the difference of V _CS −V _LS
Is changed to change the pulse width of the pulse for driving the switch element 12, thereby increasing the output current _IO .

That is, the two switching power supplies 1 and 2 operating in parallel in this way operate in the following state. CS1> CS2 CS1 <CS2 Switching power supply 1 Voltage control state Current control state Switching power supply 2 Current control state Voltage control state According to the switching power supply as shown in FIG. 3, any control of voltage and current can be performed independently of each other. Is possible,
It is also effective as a redundant power supply.

Although the above embodiment has been described with respect to an example in which two switching power supplies are driven in parallel, even when three or more switching power supplies are connected in parallel, the operating state of each switching power supply is the same as the level of the common signal line 50 and each switching power supply. It is determined by the level of the detection current of the switching power supply, and operates similarly to the case of two switches.

[0021]

As described above, according to the present invention,
In supplying power to a common load from a plurality of switching power supplies in parallel, load sharing control is performed so that the currents on the primary side of each switching power supply become equal. Therefore, a plurality of output systems are provided in the switching power supply. In this case, it is only necessary to provide a circuit function for controlling the primary side so that the currents are equal, and the configuration can be simplified.

As shown in FIG. 5, even when switching power supplies are combined and driven in parallel with substantially different rated output capacities, the currents on the primary side are controlled to be equal. Strong stress is not applied to a specific switching power supply, and the reliability of the whole combination can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an apparatus in a process of establishing the present invention.

FIG. 2 is a block diagram showing one embodiment of the present invention.

FIG. 3 is a circuit diagram showing a specific example of a main part of FIG. 2;

FIG. 4 is a waveform diagram illustrating an operation of the switching power supply 1 of FIG.

FIG. 5 is an explanatory diagram of an example of parallel power supply.

FIG. 6 is a block diagram showing an example of a conventional load sharing control circuit configuration.

[Explanation of symbols]

 1,2 switching power supply 11,21 transformer 12,22 switch element 13,23 switching control circuit 14,24,33 rectification smoothing circuit 16,27 photocoupler 31,41 current transformer 32,42 current detection circuit 34,44 maximum current Selection circuit 35, 43 Control signal generation circuit

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 3/28

Claims (1)

(57) [Claims] In a configuration in which power is supplied from a plurality of switching power supplies to a common load, each switching power supply has a current detection circuit for detecting a circuit current flowing to a primary side, and a detection result of the current detection circuit. A maximum current selection circuit for selecting the maximum current from among them, and a control signal for driving in the voltage control state or the current control state according to the selection output of these maximum current selection circuits and the magnitude of the detection output of each current detection circuit. A control signal generation circuit for output is provided, and the detection result of the current detection circuit is maximized by the maximum current selection circuit.
Set the switching power supply selected as current to voltage control state
And other switching power supplies are driven in current control state
A switching power supply control device that performs load sharing control so that the primary-side current of each switching power supply becomes equal.