JPH0261047B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parallel operation system for stabilized power supplies generally used for industrial purposes, for example, for control microcomputers.

Generally, the purpose of connecting multiple power supplies in parallel and using them as a power supply system is to
There are two ways to improve the reliability of the power supply, and second, to increase the power supply capacity.

FIG. 1 is a block diagram showing an example of a conventional power supply system called a diode matching system.

In the figure, power supply 1 and power supply 2 are power supply devices that are intended to operate in parallel. D1 and D2 are
This is an output matching diode that prevents the output current from flowing from the power supply with a higher output voltage to the power supply with a lower output voltage due to an error in the output voltage between the two power supplies during power supply operation. It is something.

When two power supplies are operated in parallel like this, the power supply with the higher output voltage will supply almost 100% of the load current. If the power supply with the lower output voltage goes down in this state, the power supply with the higher output voltage continues to supply power to the load, and there is no effect on the load destination side. On the other hand, if the power supply with a higher output voltage goes down, the power supply with a lower output voltage starts supplying power to the load again, so the load side is likely to go down in this case as well.

In this way, the parallel operation of power supplies using the diode matching method requires fewer parts and is simple, but it has the following drawbacks.

(1) In practice, it is impossible for the output voltage error between power supplies operating in parallel to become zero, so
It is difficult to balance the load between the two power supplies, and the load current concentrates on one power supply.
Therefore, the temperature of the power supply on the side where the load current is concentrated increases, and the reliability of the power supply alone and as a result of the power supply system decreases. Since reliability as a power supply system is dominated by the power supply on the side where the load current is concentrated, increasing the number of power supplies operating in parallel does not lead to improvement in reliability.

(2) When performing parallel operation for the purpose of increasing output capacity, the load balance is poor, and the load current is concentrated on one power supply, so the capacity of the transistors that make up the power supply must also be increased.
Even if an attempt is made to reduce the transistor capacitance by adopting an overcurrent protection method in which the relationship between output voltage and load current has a fold-back characteristic, it is not possible.

(3) Due to poor load bounce, when the power supply with the higher output voltage goes down and switches to the other power supply, a large dip may occur in the output voltage.

(4) Due to the characteristics of the matching diodes D1 and D2, the output voltage fluctuates depending on the load current, ambient temperature, etc., and it is difficult to keep the output voltage constant with high precision.

(5) When the load current is large, the power loss in the matching diodes D1 and D2 becomes large, and the efficiency decreases.

FIG. 2 is a circuit diagram showing a conventional power supply system called a master-slave system.

In the figure, M is a master type power supply device, S is a slave type power supply device, Tr ₁ and Tr ₂ are output voltage control transistors, A1 and A2 are error amplifiers,
ZD1 is a Zener diode for reference voltage, R14,
R24 is an output current detection resistor.

The master power supply M is a normal stabilized power supply, and the - input side voltage (Vc = R13・EO/R12+R13) and the + input side voltage (Zener voltage, which is the reference voltage) of the error amplifier A1.
The conduction of the transistor Tr ₁ is controlled by the output of the error amplifier A1 so that the output voltage EO becomes equal to V _ZD1 ), and the output voltage EO is maintained constant.

On the other hand, in the slave power supply S, the transistor Tr ₂ is turned on by the output of the error amplifier A2 so that the positive input voltage (voltage at point b) of the error dynamic amplifier A2 becomes equal to the input voltage on one side (voltage at point a). is controlled to keep the output voltage EO constant. Therefore, if the current supplied from the master power supply M to the load is i1, and the current supplied from the slave power supply S to the load is i2, then the following equation holds true under the condition that the voltage at point a and the voltage at point b are equal.

i2·R24=i1·R14 Here, if R24=R14, i2=i1 That is, the currents supplied to the load from the master power supply M and the slave power supply S are equal. Therefore, the disadvantages of the diode matching method explained with reference to FIG. 1 and the master-slave method,
Most of the problems have been resolved except for a few. but,
The master-slave system has the following new drawbacks.

(1) If the slave power supply goes down, it will be backed up by the power supplies of other slaves and the master, but if the master power supply goes down,
The slave power supply also goes down. Therefore, the reliability of the entire power supplies operating in parallel is dominated by the master power supply. Therefore, in this method, although it is possible to increase the output capacity by increasing the number of slave power supplies, it is not possible to expect an improvement in reliability.

(2) Since the master power supply and the slave power supply have different circuit configurations, it is difficult to achieve mass production, the associated cost reduction, and ease of maintenance management, compared to when both circuit configurations are the same.

This invention eliminates all of the above-mentioned drawbacks, and increases the total output capacity of the power supply system while distributing the output current proportional to the output capacity even when power supplies with different output capacities are combined. The object of the present invention is to provide a parallel operation method for stabilized power supplies that can achieve improved reliability.

The first main point of the configuration of the present invention is that it includes an error voltage detection means that compares a certain reference voltage and the output voltage of a power supply circuit, detects an error voltage between the two, and outputs it as a current setting value; voltage dividing means for dividing the current set value and outputting it as an output current set value so that the distribution ratio is equal to the distribution ratio of the output capacity of the stabilized power source; and detecting the output current of the stabilized power source. A plurality of stabilized power supplies are connected in parallel, each comprising an output current detection means and a current adjustment means for adjusting the output current of the power supply circuit so that the detected voltage in the output current detection means becomes equal to the output current setting value. The output side of the error voltage detection means in each stabilized power supply is connected by a common bus line, and the output current is distributed to each stabilized power supply in proportion to the output capacity. The second point is that instead of dividing the current setting value according to the output capacity of the stabilized power supply, the detection voltage of the output current detection means for each stabilized current is made equal at the output current corresponding to the output capacity. It is in the point that I made it.

Next, the present invention will be explained with reference to the drawings.

FIG. 3 is a circuit diagram showing the basic principle of the present invention and other embodiments to be described later. First, a case in which the output capacities of the power supplies are equal will be explained. In the figure, power supply 1, power supply 2, . . . power supply N are all stabilized power supplies having the same configuration, and in this case, a parallel operation system of N power supplies is shown. And each power supply is
The respective + and - outputs are commonly connected and coupled by a common bus line B as shown. Tr ₁ in the power supply 1 is an output voltage control transistor that operates the output current i1 and controls the output voltage EO, 11 is a current adjustment amplifier, and A12 is
A voltage follower (a type of impedance converter), A13 is a voltage error amplifier, R11 is a current setting value mixing resistor, R15 is a resistor for output current detection, and _ZD1 is a Zener diode for reference voltage.

Note that the power supplies 2 to N have the same configuration as the power supply 1, and therefore will not be particularly described. However, if the input impedance of the current adjustment amplifier A11 is sufficiently large compared to the current setting value mixing resistor R11, the voltage follower A12 is unnecessary.

First, considering the operation when the power supply used in this method is operated alone (power supply 1 only), its output voltage EO can be calculated using the following formula in the same way as explained earlier with reference to Figure 2. Express.

EO=R13+R14/R14・V _ZD1 (However, V _ZD1 is the Zener voltage of diode ZD ₁ ) If the output voltage deviates from this value, the output voltage from the voltage error amplifier A13 is adjusted to match the voltage error.
Vi ₁ is the current setting value at the output point, and resistance R1
1. It is input as the current setting value Vis ₁ at the input point to the current adjustment amplifier A11 via the voltage follower A12. The current adjustment amplifier A11 changes the current setting value Vis ₁ , which is the setting value of the output current, by a value commensurate with the output voltage error, so the output current of the power supply
The transistor Tr ₁ is controlled so as to make the detected voltage i 1 ·R 15 at the output current detection resistor R 15 coincide with the current setting value Vis ₁ , thereby adjusting the output voltage EO. Therefore, the error, which is the deviation of the output voltage from the reference voltage, is canceled. In this case, the voltage drop at the output current detection resistor R15, that is, the detection voltage i
The magnitude of 1.R15 is about several tens to 100 mV,
Sufficiently small compared to the output voltage EO and output voltage error,
This can be considered by ignoring the influence of the output voltage EO on the detected value.

Next, consider a case where N power supplies are connected in parallel in a configuration as shown in FIG. Each power supply controls the transistors Tr ₁ , Tr ₂ , Tr _N so that the same value of current as the current setting value inputted to the + input side of the current adjustment amplifiers A11, A21, AN1 is outputted. Adjust the output voltage. However, in the case of parallel operation of N power supplies, the current setting value input to the current adjustment amplifier in each power supply is different from the case of individual operation. R21...This is the value obtained by mixing and averaging by RN1. The parallel bus line B is a line that serves to mix the current setting values of each power source and average them.

Here, the current setting value of the output point of each power supply is
V _i1 , V _i2 ...V _iNIf the input impedance of each voltage follower is Zi ₁ , Zi ₂ , ...Zi _N , power supply 1
The current setting value of the input point input to the current error amplifier _A11 is expressed by the following equation.

Vis ₁ = R21R31……R _N1 Zi／R21R31……R _N1
Zi＋R11・Vi ₁ +R11R31……R _N1 Zi／R11R31……R _N1
Zi＋R21・Vi ₂ ＋……＋R11R21……R _(N-1)1 Zi／R11R21……
R _(N-1)1 AZi+R _N1・Vi _N (however, Zi=Zi ₁ Zi...Zi _N ).

In general, when R1R2 is written, it means (1/1/R1+1/R2). Furthermore, although the above formula can be calculated using the superposition principle, the calculation process will be complicated, so it will not be described.

Here, R11=R21=...R _N1 =R. Also, voltage follower 12, A22...A _N2
If the input impedance of R is sufficiently larger than the resistance R, the above equation can be transformed as follows.

Vis ₁ = 1/N (Vi ₁ +Vi ₂ B+...+Vi _N ) Therefore, the current setting value at the input point of power supply 1 is the average value of the current setting values at the output points of each power supply. Further, since the current set value of the power source 2 to the current N is also the same value as the current set value Vis ₁ at the input point of the power source 1, the load of each power source can be balanced. Therefore, the temperature rise of each power source is equally small compared to the case of the diode combination method, which is advantageous in terms of reliability.

Now, when N power supplies are operating in parallel, if the total output current is I, then the output of each power supply is I/N. Here, if one of the power supplies running in parallel goes down,
The remaining (N-1) power supplies each have an I/N
The output current is increased by (N-1) to cover the output of the downed power supply. Therefore, the output capacity of each power supply is 1/N+I/N(N-1)=N(N-1)+1
/N(N-1)I, it can cope with the power failure of one unit. Furthermore, by increasing the number N of parallel operating units, even if multiple units are powered down at the same time, a highly reliable power source that can be backed up using the remaining power source can be constructed.

In addition, if N power supplies are operated in parallel and backup is not required when the power goes down, it is possible to take out the output up to (N x i) (where i is the power supply 1).
output capacity per unit). Therefore, if it is necessary to increase the output capacity, it is sufficient to add an appropriate number of power supplies. Of course, it is also possible to increase the output capacity while maintaining the backup function during power down.

Next, a method of parallel operation of power supplies with different output capacities, which is the main focus of the present invention, will be explained. FIG. 4 shows an embodiment of the present invention, and the difference from FIG. The point is that the output current set values Vjs to Vjs _N, which are the current set values, are input to the current adjustment amplifiers A11 to AN1.
With such a configuration, the average current setting value Vis ₁ described above can be divided and the output current setting values Vjs ₁ to Vjs _N according to the output capacity of each power source can be given again by proportional distribution. In other words, when N power supplies are operated in parallel using this method, if the output current corresponding to the output capacity of each power supply is I1, I2, ..., IN, then the voltage dividing resistors RKa and RKb in each power supply (number K) are Efficient parallel operation is possible if the settings are made to satisfy the following equation.

I1:I2:…:N=Vji ₁ :Vjs ₂ :…:Vjs _N =R1b/R1a+R1b:R2b/R2a+R2b:…:RNb/RNa+RNb In this case, each current adjustment amplifier (A11 to AN
1) Assuming that the output current of each power supply at any given time is il~iN, the output currents i1~iN are adjusted as described above so that Vjs ₁ = i1·R15 : Vjs _N = iN·RN5. Therefore, if the output current detection resistances of each power supply are equal, that is, R15=...=RN5, then I1:I2:...:IN=i1:...:N, and each power supply always has an output current proportional to its output capacity. can be shared.

Note that if the output current detection resistors R15 to RN5 are all equal in configuration as in the above embodiment, the voltage dividing resistors RKa and RKb may be of small capacity.
Therefore, by using a small semi-solid resistor or the like instead of these, it becomes easy to make the setting of the output current variable in accordance with the output capacity of the power supply. That is, there is an advantage that it can be standardized as having the same component configuration.

However, although the capacitance is relatively large, it is also possible to distribute the output current by changing the output current detection resistors R15 to RN5, and this is also included in the present invention. The circuit configuration in this case is visually the same as that shown in Fig. 3, and the voltage dividing resistor RKa,
RKb becomes unnecessary. In this case, for the output currents I1 to IN corresponding to the output capacity of each power supply and the output current detection resistors R15 to RN5, 1・R15=…=IN・RN5, that is, I1:II2:…:IN=1/R15: It can be easily inferred from the above explanation that the output current detection resistor should be selected so as to satisfy the relationship 1/R25:...:1/RN5.

According to this invention, a diode matching method,
All the drawbacks of the master-slave system are eliminated, and multiple power supplies with different output capacities can be efficiently operated in parallel without requiring any common parts or with almost the same circuit configuration.

This invention can be applied to switching regulators as well as the series regulators already described.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing an example of a conventional power supply system, FIG. 3 is a circuit diagram showing the basic principle of the present invention and another embodiment, and FIG. 4 is a circuit diagram showing an embodiment of the present invention. FIG. Description of symbols, 1, 2, N...Power supply, B...Parallel bus, A11, A21, AN1...Current adjustment amplifier, A13, A23, AN3...Voltage error amplifier, R15, R25, RN5...Output current Detection resistor, R1a, R2a, RNa, R1b, R2b,
RNb...Resistance.

Claims (1)

[Claims] 1. Error voltage detection means that compares a certain reference voltage and the output voltage of a power supply circuit, detects an error voltage between the two, and outputs it as a current setting value; voltage dividing means for dividing the current set value and outputting it as an output current set value so as to be equal to the distribution ratio of the output capacity of the stabilized power supply; and output current detection means for detecting the output current of the stabilized power supply. and current adjustment means for adjusting the output current of the power supply circuit so that the detected voltage in the output current detection means becomes equal to the output current setting value, a plurality of stabilized power supplies are connected in parallel, and each stabilized power supply is connected in parallel. Connect the output side of the error voltage detection means in the stabilized power supply with a common bus,
A parallel operation method for stabilized power supplies characterized by distributing output current to each stabilized power supply in proportion to its output capacity. 2 Error voltage detection means that compares a certain reference voltage and the output voltage of a power supply circuit, detects the error voltage between the two, and outputs it as a current setting value; output current detection means for outputting an equal detection voltage at an output current corresponding to the output capacity of the stabilized power supply; and adjusting the output current of the power supply circuit so that the detection voltage in the output current detection means becomes equal to the current setting value. A plurality of stabilized power supplies each having a current adjustment means are connected in parallel, and the output side of the error voltage detection means in the stabilized power supplies is connected through a common bus, and a voltage proportional to the output capacity of each stabilized power supply is connected in parallel. A parallel operation method for stabilized power supplies characterized by distribution of output current.