JPH022369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overvoltage suppression device that suppresses transient overvoltage generated in a constant voltage power supply to prevent damage to load equipment due to overvoltage.

In general, many electronic devices made of electronic components have extremely important duties. However, as a power source for ensuring the reliability of such electronic equipment, a constant voltage power supply device using a power conversion device such as a generator or an inverter is used. Although these constant voltage power supply devices normally generate a constant output voltage, transient output voltage fluctuations usually occur in response to a sudden change in the load or a sudden change in the input power supply voltage. On the other hand, for load equipment, fluctuations in the power supply voltage can hinder normal operation and stable operation, and overvoltage is particularly important. , resulting in damage or serious consequences. Therefore, it is important to pay more attention to voltage fluctuations in the direction of overvoltage than to voltage fluctuations in the direction of low voltage, and consideration must be given to suppressing overvoltage.

The amount of transient voltage fluctuation in the constant voltage power supply output when the load suddenly changes is determined by the amount of load fluctuation and the internal impedance of the constant voltage power supply. Therefore, by reducing the internal impedance, the transient voltage fluctuation can be reduced. can be made smaller. However, there is an optimum value for the internal impedance of this constant voltage power supply, and if the internal impedance is reduced beyond that value, the constant voltage power supply becomes bulky and expensive, making it impractical. . Furthermore, even if it were possible to reduce fluctuations in output voltage due to sudden changes in load by reducing internal impedance, it would be completely powerless against transient fluctuations in output voltage due to sudden changes in input power supply voltage of a power converter or the like.

The present invention is intended to alleviate these shortcomings of the conventional devices, and is capable of handling electronic equipment regardless of the internal impedance of the constant voltage power supply, and regardless of sudden changes in load or input power supply voltage. The present invention provides an overvoltage suppression device that can suppress transient overvoltages that are important for load equipment. The present invention will be explained below based on the drawings.

FIG. 1 shows a conventional constant voltage power supply device, in which 1 is a constant voltage power supply device, 2 is a constant voltage power supply device 1
This is a load device that is powered by a In the figure, a constant voltage power supply device 1 is composed of a power supply device 11 and a constant voltage control circuit 12, and the power supply device 11 is shown divided into an ideal power source 11a and an internal impedance 11b for convenience. Further, the constant voltage control circuit 12 is a circuit of a so-called negative feedback control system, and includes a voltage detection circuit 12a that detects the output voltage of the power supply device 11, a voltage setter 12b that sets the output voltage of the power supply device 11, and a voltage detection circuit 12a. An adder 12c that compares and calculates the detected voltage and the voltage set by the voltage setter 12b to generate a deviation signal.
and an integral amplifier 12a that amplifies the deviation signal and generates a voltage control signal to the ideal power source 11a. The integral element of the integral type amplifier 12a serves as a control delay element necessary to maintain the stability of the control element in negative feedback control.

In such a conventional device, the output voltage of the constant voltage power supply device 1 is constantly controlled so as to match the set voltage, so that the value of the output voltage of the constant voltage power supply device 1 is constant. However, if the load suddenly changes or the input power of the constant voltage power supply device 1 (not shown)
When a disturbance such as a sudden voltage change occurs, it is essentially impossible to avoid transient output voltage fluctuations occurring in the constant voltage power supply 1 due to the integral element of the integral type amplifier 12a, that is, the control delay element. It was becoming.

Figures 2a, b, and c show the temporal transition of voltage waveforms at various parts during sudden load changes in the configuration shown in Figure 1, where A1 is the output of the ideal power supply 11a, and B1 is the output of the power supply 11, that is, the constant voltage. The output of the power supply device 1, C1 is the deviation signal, that is, the output of the adder 12c, and D1 is the voltage control signal, that is, the integral type amplifier 1.
2d output, t is time. In other words, in a constant load state before time T1, the integral amplifier 1
As a result of amplifying the deviation signal by 2dd and applying a voltage control signal to the ideal power supply 11a to control its output voltage, the deviation signal becomes approximately zero and the constant voltage power supply 1
The output voltage is a constant value approximately equal to the set voltage. In this state, as shown by outputs A1 and B1, the output voltage of the ideal power supply 11a is higher than the output voltage of the power supply 11 by the voltage due to the internal impedance 11b. When the load suddenly decreases at time T1, the voltage drop caused by the internal impedance 11b also decreases rapidly, so that the output voltage of the power supply 11 increases rapidly by the amount of the sudden decrease in voltage drop, as shown by the output B1. At the same time, the adder 12c has an output C1.
deviation signal is generated. This deviation signal is integrally amplified by the integral type amplifier 12d, and as a result, the voltage control signal that is its output changes gradually from the value before time T1, as shown by the output D1, and accordingly. Therefore, the output voltage of the ideal power supply 11a is also output A.
It starts to slowly descend as shown in 1. Therefore, the output voltage of the power supply device 11 also decreases as shown by the output B1 and approaches a steady constant value.

In this way, in negative feedback control as shown in the constant voltage control circuit 12, the essential factor is that corrective control is started only after a change in the output voltage is detected, and the control has a control delay. Due to the essential factor of the necessity of an integral element as an element, it is fundamentally impossible to avoid transient voltage fluctuations after sudden load changes. Further, a constant voltage power supply device 1 configured with a power conversion device etc.
The same applies to sudden changes in the voltage of the input power source. As described above, for the electronic device serving as the load device 2, transient voltage fluctuations in the overvoltage direction are extremely important.

In view of the above-mentioned points, the present invention realizes a device capable of suppressing transient overvoltage occurring in a constant voltage power supply device and shortening the transient time by overcoming the time constant restriction due to the control delay element in feedback control. This is what I did.

FIG. 3 is a configuration diagram of a constant voltage power supply device in which the overvoltage suppression device shown for explaining the present invention is used, and 3 is the overvoltage suppression device. In the figure, the same reference numerals as in FIG. 1 indicate the same components.

That is, the overvoltage suppression device 3 includes a rectifier circuit 31 whose input is connected to the output of the constant voltage power supply device 1, a capacitor 32 connected to the output of the rectifier circuit 31, and a discharge resistor 33 for the capacitor 32. For practical purposes, an electrolytic type capacitor 32 may be adopted as the capacitor 32. It should be noted that the discharge resistor 33 may be extremely small as long as it can discharge the voltage of the capacitor 32, which has increased due to the rise in transient voltage described later, back to its original state by an appropriate time in the steady state. , will be omitted to simplify the explanation.

In FIG. 3, when both the constant voltage power supply 1 and the load device 2 are in a steady state, the capacitor 32 is charged to a value corresponding to the output voltage value of the constant voltage power supply 1 via the rectifier circuit 31. The overvoltage suppressor 3 is in an extremely high impedance state. If an increase factor occurs in the output voltage of the constant voltage power supply 1 due to some disturbance such as a sudden load change, this increase factor causes the rectifier circuit 31 to
A charging current is generated to the capacitor 32 via the capacitor 32 . That is, the overvoltage suppressing device 3 provides a circuit with extremely low impedance in response to a factor that increases the output voltage of the constant voltage power supply device 1. Therefore, the output voltage of the constant voltage power supply device 1 cannot rise rapidly, but rises very slowly as the voltage of the capacitor 32 rises due to the charging current. During this time, the constant voltage control circuit 12 detects this voltage increase and acts to lower the output voltage of the ideal power supply 11a, so the output voltage of the constant voltage power supply 1 is suppressed to a low value. This is shown in FIG.

In Figures 4a, b, and c, the solid lines indicate the temporal transition of voltage waveforms at various parts during sudden load changes in the configuration shown in Figure 3, and for comparison, the dotted lines are shown in Figure 2. It represents the output characteristics.

That is, when the load suddenly decreases at time _T1 , the output voltage of the power supply 11 tries to increase, but as mentioned above, it cannot increase due to the overvoltage suppressor 3, and the sudden decrease in the load is transferred to the capacitor 32 as a charging current. Inflow. As a result, the voltage of the capacitor 32 gradually increases, and along with this, the voltage of the power supply device 11 increases.
The output voltage of will gradually rise as shown in output _B2 . The constant voltage control circuit 12 detects this voltage increase and controls the ideal power source 11a to reduce its output voltage. During this time, power supply 1
As the output voltage of the ideal power supply 11a increases and the output voltage of the ideal power supply 11a decreases, the charging current to the capacitor 32 also decreases.
At the time when the output voltage with 1a is balanced, that is, at time _T2 , the charging current to the capacitor 32 also becomes zero, and the output voltage of the power supply device 11 reaches its peak. After this, the overvoltage suppression device 3 is electrically disconnected, and the output voltage of the power supply device 11 is reduced by the detection control of the constant voltage control circuit 12 alone, and reaches a steady state.

In this way, according to the configuration shown in FIG. 3, it is possible to extremely effectively suppress transient overvoltages that occur in the constant voltage power supply device 1 due to sudden changes in load. However, as compared with the dotted line and solid line in FIG. 4, the configuration of FIG. 3 requires a longer settling time than the conventional device. This is because the overvoltage suppression device 3 causes the output voltage of the power supply device 11 to rise more slowly than in the conventional device, and as a result, the deviation signal also changes small and gradually as shown in the output _C2 .
This is because changes in the voltage control signal, which is the integral value, and in the output voltage of the ideal power supply 11a controlled thereby are also delayed compared to the conventional device, as shown by the outputs C ₂ and B ₂ , respectively. This delay appears as an increase in the period from time _T1 to time _T2 . This period is a charging period for the capacitor 32, and therefore, a longer period means that a capacitor with a larger capacity is required. In order to suppress the transient voltage rise even further, the above-mentioned period becomes longer, and the change in the voltage of the capacitor 32 must be suppressed even smaller for this longer charging period. It becomes necessary to increase the capacitance of the capacitor 32 by a factor that is the square of the factor
Therefore, the capacitor 32 may require an extremely large capacity depending on the amount of load fluctuation, the output voltage suppression value, or the response speed of the device.

FIG. 5 shows one embodiment of the present invention.
The same reference numerals as those in the figures and FIG. 3 indicate the same functions. That is, the difference between FIG. 5 and FIG. 3 shown in this way is that the overvoltage suppressor 3' is provided with a current transformer 34 and a current detection circuit 35 for detecting the charging current to the capacitor 32, and its output is is added to the adder 12c. The current transformer 34 may be of any type as long as it can detect the charging current, and may be replaced by another method such as a method of detecting the output current of the rectifier circuit 31 or a method of detecting the current of the capacitor 32. It may be something like that. Next, the operation of this embodiment will be explained using FIG. 6.

Figures 6a, b, and c show the temporal transition of voltage waveforms at various parts when the load suddenly decreases in the embodiment shown in Figure 5, and are expressed in a manner similar to the displays in Figures 2 and 4. There is. In FIG. 6b, the dotted line indicated by _E1 indicates the voltage component of the difference between the voltage detected by the voltage detection circuit 12a and the voltage set by the voltage setter 12b, and the dotted line indicated by _E2 indicates the voltage component of the difference between the voltage detected by the voltage detection circuit 12a and the voltage set by the voltage setter 12b.
The output component of the adder 12C, which is a composite value of these components, is shown as a deviation voltage at _E3 .

In FIG. 6, when the load suddenly decreases at time T ₁ , the sudden decrease in load flows into the capacitor 32 as a charging current, similar to what is shown in FIG. It shows a gradual increase with the On the other hand, current transformer 34
The charging current to the capacitor 32 is detected by the current detection circuit 35, and a current detection signal as shown in the output component _E2 is applied to the adder 12c. As a result, the output of the adder 12c is the voltage detection circuit 12.
C ₃ as illustrated in which the current detection signal having a large voltage is added to the voltage component E ₁ of the difference between the voltage detected by a and the voltage set by the voltage setter 12b.
A deviation signal shown in is generated, and the integral type amplifier 12d integrates this deviation signal, so the voltage control signal that is its output and the output voltage of the ideal power supply 11a controlled by this signal are also output. _D3 , _A3
It is quickly lowered as shown in respectively. Therefore, the charging current to the capacitor 32 is also rapidly reduced, and the time after an extremely short period of time.
It disappears at T ₂ ′ and the current detection signal also disappears,
Thereafter, normal negative feedback control is performed. As a result, the rise in the output voltage of the power supply device 11 and the charging period from time T ₁ to time T ₂ ' are suppressed to an extremely small level, making it possible to significantly reduce the capacitance of the capacitor 32.

Although the current detection circuit 35 has been described as one that generates a constant voltage output while the charging current is flowing, it is easily understood that it may also generate a voltage output corresponding to the charging current. be. Furthermore, it is clear that even when the voltage of the input power source (not shown) suddenly changes, the rise in the output voltage is suppressed by the same mechanism. The overvoltage suppression device 3' constructed in this way does not detect and control the output voltage as a mere element in feedback control, but detects and controls the charging current in a state where the rectifier circuit 31 and the capacitor 32 are added. Therefore, the output voltage of the ideal power supply 11a, that is, the internal electromotive voltage of the power supply device 11, is equivalently detected and controlled, and the control is automatically disconnected as the internal electromotive voltage decreases. Although this method enables extremely high-speed control, it also has the advantage of not causing any concerns about stability in negative feedback control.

As is clear from the above description, the present invention is extremely effective without impeding control stability, regardless of the internal impedance of the constant voltage power supply, or sudden changes in the load or input power supply voltage. Moreover, it is possible to provide a device that suppresses transient overvoltage at high speed, and its practical effects are exceptional.

In addition, although this explanation shows the case of a three-phase AC power supply, it is not necessarily limited to this.
It may be a single-phase AC power source or another multi-phase AC power source, and may also be applied to a DC power source in some cases.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing a conventional constant voltage power supply device, Fig. 2 is a voltage waveform diagram of various parts when the load suddenly changes in the configuration of Fig. 1, and Fig. 3 is an overvoltage suppression diagram shown to explain the present invention. FIG. 4 is a diagram of voltage waveforms at various parts when the load suddenly changes in the configuration of FIG. 3, FIG. 5 is a configuration diagram showing an embodiment of the present invention, and FIG. It is a voltage waveform diagram of each part when the load suddenly changes. 1... Constant voltage power supply device, 3, 3'... Overvoltage suppression device.

Claims (1)

[Claims] 1. A constant voltage power supply device comprising a power supply device and a constant voltage control circuit that detects the output voltage of the power supply device and performs negative feedback so that the output voltage becomes a set value, the input side of which is connected to the output of the constant voltage power supply device. It comprises a rectifier, a capacitor connected to the output of the rectifier, and current detection means for detecting a charging current to the capacitor, and the output voltage of the constant voltage power supply is reduced by the output of the current detection means. An overvoltage suppressing device characterized in that it corrects to increase the voltage.