JPH0250713B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a value obtained by amplifying the difference between a reference value and an output control value as a current reference signal, and uses the current reference signal and each conduction of a switching element as a current reference signal. The present invention relates to a DC-DC converter device in which a plurality of DC-DC converter units are operated in parallel to control the current integral value at the same time as the current integral value.

[Conventional technology]

The power supplies of systems that would be significantly affected by a power outage are operated in parallel and redundantly, but if one unit operating in parallel fails, it is necessary to promptly detect the faulty unit, disconnect it from parallel operation, and repair it.

Conventionally, there are methods for determining the faulty aircraft when DC-DC converters that convert DC voltage are operated in parallel, such as comparing the sharing ratio of output current and comparing the input and output voltage difference of output rectifier diodes.

[Problem that the invention seeks to solve]

However, the method of comparing the sharing ratio of output current requires a current transformer for current detection, and also requires a circuit to follow changes in the number of parallel operating units, and is complicated.

In addition, the method of comparing the input and output voltage difference of the output rectifier diode is based on the fact that as long as current flows through the output rectifier diode, the voltage drop across the diode is almost the same, so even if there is a large imbalance in the load sharing ratio, the output will not change. The disadvantage is that it cannot be detected if it is supplied.

[Means and actions to solve the problem]

In order to eliminate the above drawbacks, the present invention uses a value obtained by amplifying the difference between a reference value and an output control value as a current reference signal, and uses the current reference signal and a current integral value at each conduction of a switching element. In a DC-DC converter device in which multiple DC-DC converter units are operated redundantly in parallel, the average value of the sum of the currents of the switching elements and the current reference signal are determined for each DC-DC converter unit. compared, and a difference above a certain level persisted for a certain period of time.
The present invention provides a DC-DC converter device characterized by being equipped with a selective cutoff circuit that determines that a DC-DC converter unit is in failure and disconnects it from parallel operation.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, transistors 1 and 1', which are switching elements, are driven and switched by drive circuits 2 and 2' to convert voltage E _i of a DC power source 3 into an AC voltage,
The transformer 4 insulates and transforms the voltage, the rectifier circuit 5 rectifies, the capacitor _C1 smoothes, and the diode 6 supplies power to the load 7. If transistors 1 and 1' have simultaneous on periods, the output voltage will be higher than the input voltage when the turns ratio of transformer 4 is 1, so it is called boost mode. Conversely, if simultaneous off periods are provided, the output voltage will be lower than the input voltage. Therefore, it is called step-down mode. FIG. 2 is an operating waveform diagram in the step-up mode shown in FIG. First, at time _t1, when transistors 1 and 1' are turned on simultaneously, transformer 4 is short-circuited and all input voltage is borne by reactor L. The current in the reactor L increases with a slope of E _i /L and is divided into each transistor. Next, when the transistor 1' is turned off at time _t2 , all the current in the reactor L flows to the transistor 1, and the transformer 4 is disconnected from the short circuit and supplies power to the secondary side. At this time, the current in the reactor decreases at a slope of (E _p −E _i )/L, where E _p is the output voltage. When they turn on simultaneously again at time t ₃ , the time
The current in the reactor L increases in the same way as at _t1 . When transistor 1 turns off at time t ₄ , time t ₂
As in the case of , all of the current of the reactor L flows through the transistor 1' and supplies power to the load 7. Note that the secondary side of the reactor L is blocked by the diode 8 and is equivalent to being opened. This buck-boost converter control method involves stepping down the output voltage using resistors R ₁ and R ₂ , amplifying the error voltage with respect to the voltage of the reference power supply 9 using an error amplifier 10 , and using a signal isolation transmission circuit 11 such as a photocoupler on the converter side. as a current reference signal. The reason why it is sent as a current reference signal is that the current can be shared evenly and is not affected by the number of parallel operating units. On the other hand, the current of the transistors 1 and 1' is detected by the current transformers 12 and 12', and the converted current is converted to the current sources 14 and 14' by the conversion circuits 13 and 13'.
C ₂ and C ₂ ' are charged and compared with a current reference signal by comparators 24 and 24', and when they match the current reference signal, transistors 1 and 1' are controlled to be turned off. Therefore, the current of the transistor is i(t), the current transformation ratio for converting the transistor current into a current source is N, the voltage of the current reference signal is E _r , the on period is τ, and the period is T
Then, the voltage e _C2 of capacitor C ₂ is as follows.

e _C2 = 1/C ₂ ∫〓 _p i(t)/Ndt=E _r Also, the average value I _a of the transistor current is I _a = 1/T∫ ^T _p i( t) dt=1/T∫〓 _p i(t) dt, and the following equation is derived.

E _r = I _a /NT1/C ₂ ... (1) On the other hand, the current e _C3 of the capacitor C ₃ is converted by detecting the currents i ₁ and i 1 ' of the transistors 1 _{and 1} ' by the current transformers 12 and 12'. If the current converted by circuits 13 and 13' into current sources 15 and 15' flows through resistors R ₃ and R ₄ , and the average values of currents i ₁ and i ₂ are equal, and capacitor C ₃ is sufficiently large, e _C3 = 1/T∫ ^T _p i ₁ + i ₂ /N (R ₃ + R ₄ )dt=
2×I _a /N(R ₃ +R ₄ ) (2), and an abnormality can be detected by the relationship between equations (1) and (2).

When the average value of the current that should flow through transistors 1 and 1' during normal operation is I _r , when the current of the transistor becomes smaller than (1 - r) I _r , there is an undercurrent, (1
+r) When it becomes larger than I _r , it is considered an overcurrent, and when detected by the comparators 16 and 17, the following equation holds true.

2(1-r)I _r /N (R ₃ + R ₄ ) = E _r =I _r /N・T/C ₃ ...
…(3) 2(1+r)I _r /N・R ₄ = E _r =I _r /N・T/C ₃ …(4) From equations (3) and (4), R ₃ = r/1−r ²・T/C ₃ ...(5) R ₄ =T/2(1+r)C ₃ ...(6) is found. Therefore, by appropriately selecting R ₃ and R ₄ from equations (5) and (6), the unbalanced current r can be changed arbitrarily, and an abnormality can be detected at any unbalance. Furthermore
Since _Ir is not included in equations (5) and (6), it can be seen that it is not affected by the load current and can be detected at any load current.

On the other hand, when converters are operated in parallel using the error value between the aforementioned reference value and output control value as the current reference and are controlled to match the current integral value at each conduction of the transistor, the reference value follows the number of units operated in parallel. and change. For example, when N converters are operated in parallel with the reference value as the output voltage reference and the output control value as the output voltage and power is supplied to the load, if one converter is disconnected, if the current before disconnection is supplied to the load as it is, the load The current becomes N-1/N and decreases. Then, the output voltage decreases to N-1/N, the difference from the output voltage reference increases, and the error value (current reference) increases. Since this error value is controlled to match the current integral value of the transistor of each converter at each conduction, the current integral value of the transistor of each converter increases until the output voltage reference and the output voltage become equal. Conversely, when the number of operating units increases, the load current increases, the output voltage increases, the current reference decreases, and the current integral value of the transistor of each converter decreases, so that the output current reference and the output voltage match. In this way, since the current reference signal follows the number of parallel operating units, unbalance can be detected without operating an unbalance detection circuit according to the number of parallel operating units. After detecting an abnormality, a time limit circuit 19 sets a time limit via an OR logic circuit 18, and sends an abnormality signal to a control circuit 20 to stop the converter and at the same time drive a trip coil 21 to shut off an input breaker 22. After converter 23 is stopped, diode 6 prevents inflow from other normal converters 23'. still,
The reason for setting a time limit after detecting an abnormality is to prevent operation when transient imbalances in load sharing occur, such as during startup or sudden changes in load.

On the other hand, since the proportion of unbalance does not change even under light load or no load, it is considered abnormal even if the absolute amount of unbalance is small. For example, if r = 0.2 and the standard is 100A at full load, an excess or deficiency of 20A will cause a failure at full load, but a failure will occur at 10A at 50A, 2A at 10A, and 0.2A at 1A. This is fine if the load variable is small and the load will not become no-load or light-load, but if this is not the case, a certain degree of unbalance will occur due to variations in parts, etc., so if the load becomes light, the circuit may shut off even though it is not abnormal. There is. In order to prevent this, it is sufficient to add or subtract a current equal to the absolute value J to the detected value as shown in FIG. The insufficient current can be solved by passing a current J through the resistor R ₅ R ₅ = T/
2C ₂ (1-r), when the transistor current is less than normal by rI _r +J, the comparator 16
transitions. Conversely, if the overcurrent is reduced by J, then R ₄ =T/2C ₂ (1+r), the comparator 17 transitions when the transistor current becomes rI _r +J higher than the normal state.

FIG. 4 shows an embodiment applied to a one-stone forward converter, and FIG. 5 shows operating waveforms. In Fig. 5A, the current of transistor 1 (L) is the current of reactor L' (C) is the primary winding voltage of transformer 4.When transistor 1 is turned on at time _t1 , the turns ratio of transformer 4 is 1.
Then, the initial value I _p rises at a slope of (E _i -E _p )/L', and the same current flows through the reactor L' on the secondary side.
When transistor 1 is turned off at time _t2 , the current in the transistor is cut off, and the current in reactor L' flows through diode 25 and decreases with a slope of E _p /L'.
The excitation current of the transformer 4 is fed back to the DC power supply 3 via the diode 8, and the excitation is reset at time _t3 . At time _t4 , transistor 1 is turned on again and this operation is repeated. A forward type converter that operates in this manner can also be selectively shut off using a circuit configuration similar to that of the push-pull type. The potential of capacitor C ₂ is the same as described in the embodiment of Fig. 1, and the potential of capacitor C ₃ is (2) since there is only one transistor.
The formula can be reduced to 1/2, so R ₃ = 2r/(1-r) ²・T/C ₂ ……(7) R ₄ =T/(1+r)C ₂ ……(8) So 2 stones pushupuru Just double the resistance value compared to the shape. Therefore, it can be seen that the forward type can also be selectively shut off.

FIG. 6 shows an embodiment in which the present invention is applied to a flyback converter, and FIG. 7 shows its operating waveforms. In FIG. 7, A shows the current waveform of the transistor 1, B shows the current waveform of the secondary winding of the transformer 4, and C shows the voltage of the primary winding of the transformer 4. When the excitation inductance of transformer 4 is L'' and transistor 1 is turned on at time t ₁ , the current of transistor 1 becomes smaller than the initial value I _p .
It rises with a slope of E _i /L, and at time t ₂ transistor 1
When transistor 1 is turned off, the primary current of transformer 4 moves to the secondary side and decreases with a slope of E _p /L''.When transistor 1 is turned on again at time _t3 , the secondary current of transformer 4 moves to the primary side and decreases at time t3. As in the case of t ₁ , it rises at a slope of E _i /L''. Repeat the above operations. The flyback type converter that operates in this way is exactly the same as the forward type, and the resistors R ₃ and R ₄ are the same as in equations (7) and (8).

FIG. 8 shows an example in which the output current is applied to a current output type push-pull converter. The output current is converted to voltage by a current detection resistor _R6 , compared with the voltage of a reference power supply 9, and amplified by an error amplifier 10. and sends it to each unit converter as a current reference signal. The operation is similar to that of a voltage output type push-pull capacitor, so the explanation will be omitted.

〔Effect of the invention〕

As described above, the present invention amplifies the difference between the reference value and the output control value, uses the obtained value as the current reference signal, and matches the current reference signal with the current integral value at each conduction of the switching element. DC to control like
In a DC-DC converter device that operates multiple DC converter units in parallel and redundantly, the DC-
For each DC converter unit, compare the average value of the sum of the currents of the switching elements with the current reference signal, and if the DC-
This DC-DC converter device is characterized by being equipped with a selective cutoff circuit that determines that a DC converter unit has failed and disconnects it from parallel operation. Since the present invention has such features, it is possible to detect abnormalities in converters operating in parallel using a simple circuit without using a new current transformer, and at any setting value, and it is also possible to detect abnormalities in converters operating in parallel with any change in the number of converters operating in parallel. On the other hand, an abnormality in the shared current can be detected by using the same settings for each unit converter without adding any switching circuit or the like.

[Brief explanation of the drawing]

FIGS. 1 to 8 are diagrams for explaining embodiments of the present invention. 1, 1'... Transistor, 2, 2'... Drive circuit, 3... DC power supply, 4... Transformer, 5... Rectifier circuit, 6, 8, 25... Diode, 7... Load, 9... ... Reference power supply, 10 ... Error amplifier, 11
... Signal insulation transmission circuit, 12, 12' ... Current transformer,
13, 13'... Conversion circuit, 14, 14', 15,
15'... Current source, 16, 17, 24, 24'...
Comparator, 18...OR logic circuit, 19...
Time limit circuit, 20... Control circuit, 21... Trip coil, 22... Input breaker, 23, 23'...
...Converter, L, L'...Reactor, R ₁ to _{R 6}
...Resistor, C ₁ , C ₂ , C ₂ ', C ₃ ... Capacitor.

Claims (1)

[Claims] 1. A DC-DC converter that uses a value obtained by amplifying the difference between a reference value and an output control value as a current reference signal, and controls the current reference signal and the current integral value at each conduction of a switching element to match. In a DC-DC converter device in which multiple units are operated redundantly in parallel, the average value of the sum of the currents of the switching elements for each DC-DC converter unit is compared with the current reference signal, and if a difference of more than a certain value is detected for a certain period of time. A DC-DC converter device characterized by being equipped with a selective cutoff circuit that determines that a sustained DC-DC converter unit has failed and disconnects it from parallel operation.