JP2000217348A - Switching power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate useless expenses by specifying the cause of an overvoltage and not exchanging a switching power source itself, but only the parts related to the cause. SOLUTION: A switching power source is provided with a converter section 6 which converts an input voltage into a prescribed output voltage, an output rectifying and smoothing section 8 which rectifies and smoothes the output of the section 6, and an output voltage detecting section 10 which detects the output voltage of the section 8. The power source is also provided with a comparing and feeding-back section 12 which compares the detected voltage inputted from the detecting section 10 with a reference value and feeds back the compared result, a control section 14 which controls the converting operations of the converter section 6 based on the output of the section 12 and, when the output voltage is an overcurrent, performs necessary controlling operations, and an output voltage fluctuating width detecting section 18 which detects the fluctuating width of the output voltage. In addition, the power source is also provided with a displaying section which displays the output of the section 18, a memory 22 storing the mode of the fluctuating width of the output voltage when the output voltage shifts to an overvoltage mode, and a collating section 24 which collates the mode of the fluctuating width of the output voltage detected by means of the detecting section 18 with the made stored in the memory 22.

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 which performs a required protection operation when an output voltage exceeds an overvoltage rating.

[0002]

2. Description of the Related Art In a conventional switching power supply, when an output voltage is overvoltage exceeding a rating, a protection operation is performed so as to prevent an abnormally high voltage from being applied to a load by, for example, stopping output. There is.

[0003]

When the output voltage becomes excessive, it is generally considered that the internal power supply parts are damaged or the performance is deteriorated. Therefore, when the output voltage becomes overvoltage, it is necessary to investigate the cause and repair or replace the power supply component. Causes of the occurrence of the overvoltage include, for example, loss of capacity of the smoothing capacitor on the primary side or the secondary side of the transformer, control response delay due to performance degradation of the photocoupler in the comparison feedback unit that feeds back the output voltage detection to the control unit, and the like. However, conventional overvoltage detection is performed, for example, only by detecting whether or not the average value of the output voltage exceeds the rating. Therefore, even if any power supply component is damaged or deteriorates in performance, a similar or similar overvoltage state is detected. In addition, it was difficult to identify the cause of the overvoltage.
Therefore, if the cause of the overvoltage is, for example, the loss of capacity of the smoothing capacitor or the performance degradation of the photocoupler,
Although the repair should be completed only by replacing the smoothing capacitor or the photocoupler, the switching power supply itself had to be completely replaced, which wasted a great deal of money. In addition, if the power supply is abandoned one after another due to such a full replacement, there is a high possibility that the environment will be adversely affected, and it is a great resource to abandon the power supply that only requires replacement of parts such as smoothing capacitors. It was a waste of money.

Accordingly, in the present invention, the cause of the occurrence of overvoltage can be specified, so that it is not necessary to replace the switching power supply itself, but only to replace or repair a power supply component related to the cause, thereby wasting money. The main issue to be solved is to be able to eliminate as much as possible.

The present invention also enables the cause of overvoltage to be identified, so that the switching power supply itself is not replaced, but only the power supply parts related to the cause or replacement is repaired. Another problem to be solved is to make it possible to eliminate the adverse effects of waste and waste of resources.

[0006]

According to the present invention, in order to solve the above-mentioned problems, a converter section for converting an input voltage to a predetermined output voltage, an output rectification smoothing section for rectifying and smoothing the output of the converter section, An output voltage detection unit that detects an output voltage from the output rectification smoothing unit, a comparison feedback unit that compares a detection input from the output voltage detection unit with a reference value and feeds back the reference input, and based on the output of the comparison feedback unit. Control the conversion operation of the converter section,
And, when the output voltage is overvoltage, the control unit performs a required control operation, and a fluctuation width detection unit that detects a fluctuation width of the output voltage, and when the output voltage is in the overvoltage mode, the output Since the voltage fluctuation range corresponds to the cause of the overvoltage, the above-mentioned problem can be solved by making it possible to specify the power supply component related to the cause of the overvoltage by the output voltage fluctuation range obtained from the output voltage fluctuation range detection unit. Solved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a switching power supply according to an embodiment of the present invention will be described in detail with reference to the drawings. The type of the switching power supply to which the present invention is applied is not limited. The driving method of the switching element in the converter section described later includes both the PWM and the PFM.

FIG. 1 is a circuit diagram of a switching power supply according to the present embodiment. In FIG. 1, 2 is an AC power supply, 4 is an input rectifying and smoothing section, and 6 is a transformer T1 and a switching element T.
R1, an output rectifying / smoothing unit including a smoothing capacitor, 10 an output voltage detecting unit,
2 is a comparison feedback unit including a photocoupler, 14 is a control unit, and 16 is a load. The operation of the switching power supply having such a basic configuration is such that the output of the AC power supply 2 is rectified and smoothed by the input rectifying and smoothing unit 4 to obtain a DC input voltage.
This input voltage is converted into a predetermined output by the converter unit 6,
The converted output is rectified and smoothed by an output rectifying / smoothing unit 8 to obtain a DC output voltage, and the output voltage detected by the output voltage detecting unit 10 is compared with a reference value by a comparison feedback unit 12, and the comparison result is controlled. Input to the control unit 14
Controls the operation of the converter unit 6 based on the comparison input to supply a constant output voltage to the load 16. Since the details of these operations are well known, their description will be omitted. In this case, the control unit 14 stops the operation of the converter unit 6 and performs the shutdown control of the output when the output voltage exceeds the rating from the detection input of the output voltage input via the comparison feedback unit 12. .

In the embodiment, in order to easily and accurately find the cause of the occurrence of such an overvoltage, in addition to the above-described configuration, a variation width of the output voltage within a predetermined time T is detected. Output voltage fluctuation width detector 1
8 and a display unit 20 for displaying the output of the output voltage fluctuation range detecting unit 18 or the output of the collating unit 24 described later in real time.
And a memory 22 storing an output voltage variation width when the output voltage shifts to the overvoltage mode, and a memory 22 storing the output voltage variation width detected by the output voltage variation detection unit 18. Collating unit 2 for collating with the present mode
4 is provided. In this case, when there are a plurality of causes of overvoltage occurrence, the memory 22 stores the variation width of the output voltage corresponding to each cause. There are a plurality of power supply components that cause overvoltage, and therefore, there are also a plurality of modes of the fluctuation width of the output voltage.In the present embodiment, a mode by a capacitance change of a smoothing capacitor described later and a mode by a performance change of a photocoupler are described. This will be described with reference to FIG.

The output voltage fluctuation width detecting section 18 calculates the maximum value MA of the output voltage from the output voltage from the output voltage detecting section 10.
X and the minimum value MIN are detected, and the maximum value MAX is detected.
And the minimum value MIN, the fluctuation range of the output voltage is detected. As a specific example of the output voltage fluctuation width detecting unit 18, a DC voltage component is removed from a detection input from the output voltage detecting unit 10 by a capacitor, and a capacity of a smoothing capacitor (not shown) of the output rectifying / smoothing unit 8 or a photocoupler is used. In this case, only the ripple component corresponding to the above-mentioned performance is set, and the amplitude of the ripple component is detected, whereby the fluctuation width of the output voltage can be detected. In this case, the output voltage fluctuation width detection unit 18 detects the fluctuation width of the output voltage within the fixed time T.

The operation of the output voltage fluctuation detecting section 18 will be described with reference to FIG.

As the causes of the fluctuation of the output voltage, loss of the capacity of the smoothing capacitor of the output rectifying and smoothing section 8 and deterioration of the performance of the photocoupler of the comparison feedback section 12 will be described. FIGS. 2A and 2B relate to the description of the loss of capacity of the smoothing capacitor, and FIG. 2C relates to the description of the performance degradation of the photocoupler.

First, the loss of capacity of the smoothing capacitor will be described. Fig. 2 when the capacity of the smoothing capacitor is normal
The output voltage fluctuates according to the waveform shown in FIG. The voltage width of this output voltage, that is, the fluctuation width, is defined as Vd1. If the smoothing capacitor has a capacity loss, the output voltage fluctuates in a waveform as shown in FIG. The variation range in this case is V
d2. As apparent from a comparison between FIG. 2A and FIG. 2B, when the smoothing capacitor loses capacity, the charge / discharge time constant decreases, and the fluctuation range of the output voltage increases (Vd2> Vd1). . Here, the loss of the capacity of the smoothing capacitor does not occur suddenly, but rather from FIG.
The state to (b) gradually progresses.

Next, the performance degradation of the photocoupler will be described. When the performance of the photocoupler deteriorates, the detection input of the output voltage detection unit 10 is input to the control unit 14 with a delay,
The output voltage rises as shown in FIG.
The fluctuation range Vd3 within the range becomes larger. When the performance of the photocoupler is not deteriorated, there is no fluctuation width Vd3 as described above. Here, comparing the loss of capacity of the smoothing capacitor shown in FIGS. 2A and 2B with the deterioration of the performance of the photocoupler of FIG. 2C, the loss of capacity of the smoothing capacitor progresses gradually. Is small, but in the case of performance degradation of the photocoupler, the response of the control is delayed. Therefore, the fluctuation of the voltage width within the fixed time T is large. As described above, the two have different modes of fluctuation of the voltage width within the fixed time T.

Therefore, comparing the loss of capacity of the smoothing capacitor with the deterioration of the performance of the photocoupler, (a) the output voltage width when the capacity of the smoothing capacitor has loss of capacity is shown in FIG.
Fluctuates as shown by. (B) The output voltage width when the performance of the photocoupler is degraded fluctuates as shown in FIG.

Accordingly, the cause of the overvoltage is caused by the loss of the capacity of the smoothing capacitor in the case of FIG.
In the case of FIG. 2C, it can be specified that the performance of the photocoupler is deteriorated.

The output voltage fluctuation width detecting section 18 is provided with a display section 20.
The detection result of the output voltage fluctuation width is input in real time. As a result, the display unit 20 displays a waveform change of the output voltage fluctuation width with respect to time in real time. With this display content, the smoothing capacitor can be changed from the change mode of the output voltage fluctuation width when the power supply shifts to the overvoltage mode. It is possible to determine whether an overvoltage has occurred due to the loss of capacity of the photocoupler or an overvoltage has occurred due to deterioration in the performance of the photocoupler.

Since the memory 22 stores the variation of the variation range of the output voltage when the overvoltage mode is set, the collation unit 24 compares the variation variation detected by the output voltage variation detection unit 18 with the memory. The control unit 20 compares the variation range stored in the storage unit 22 with the storage variation range, and outputs to the display unit 20 a comparison output corresponding to the power supply component that caused the overvoltage mode.
The display unit 20 may display the voltage fluctuation waveform shown in FIG. 2 graphically based on the output from the output voltage fluctuation width detecting unit 18. A display element, such as a light-emitting diode, which is illuminated, and a display element, which is illuminated when the performance of the photocoupler is deteriorated. These display elements are driven and displayed in accordance with the variation of the output voltage fluctuation width. No problem. Note that the voltage or current output itself from the output voltage fluctuation range detection unit 18 or the comparison unit 24 may be output.

In the above, even if the output voltage does not enter the overvoltage mode, the progress of the loss of the capacity of the smoothing capacitor and the performance deterioration of the photocoupler can be grasped from the display contents on the display unit 20. Since the replacement time of the power supply component can be grasped before shifting to the overvoltage mode, it is possible to prevent the power supply from shifting to the overvoltage mode in advance. In addition, when the overvoltage mode is set, it is easy to determine whether the cause of the overvoltage is the loss of the capacity of the smoothing capacitor or the performance degradation of the photocoupler. Causes can be eliminated.

[0020]

As described above, according to the present invention, it is possible to identify the cause of overvoltage occurrence from the fluctuation range of the output voltage. It is only necessary to replace the replaced parts, and as a result, waste of cost can be eliminated.

According to the present invention, the cause of the occurrence of overvoltage can be specified.
It is only necessary to replace or repair the power supply components related to the cause, and it is possible to eliminate the above-mentioned adverse effects on the environment and waste of resources due to the abandonment of the power supply.

In the above case, if the detection of the output voltage fluctuation width is performed within a predetermined time, the temporal variation of the output voltage fluctuation width when the power supply component shifts to the overvoltage mode within the predetermined time is considered. It becomes easier and more accurate to identify the component that caused the overvoltage from the change.

In the above case, when the output voltage fluctuation range is displayed, the component that caused the overvoltage is visually identified, and the component that caused the overvoltage is more easily identified. Be accurate.

In this case, if the display is made in real time, it is not necessary to store data for displaying the output voltage fluctuation width, and the components are simplified. As a result, the circuit for specifying the cause of the overvoltage is connected to the power supply. It is possible to reduce the cost of adding.

In the above case, the memory for storing the mode of the output voltage fluctuation when the output voltage shifts to the overvoltage mode, and the mode of the output voltage fluctuation detected by the fluctuation detector are described as follows. In the case where the apparatus further includes a collation unit for collating with the mode stored in the memory, when there are a plurality of causes of overvoltage, the plurality of modes of output voltage fluctuation are stored in the memory, and collation can be performed for each mode. Therefore, even if there are a plurality of overvoltage occurrences, it is possible to specify the component that caused the overvoltage occurrence.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention.

2A and 2B are output voltage waveform diagrams for explaining an overvoltage mode of the switching power supply in FIG. 1, wherein FIG. 2A shows a case where the capacity of a smoothing capacitor is normal, FIG. (C) shows a case where the feedback control system has a response delay.

[Explanation of symbols]

 2 AC power supply 4 Input rectification smoothing unit 6 Converter unit 8 Output rectification smoothing unit 10 Output voltage detection unit 12 Comparison feedback unit 14 Control unit 18 Output voltage fluctuation width detection unit 20 Display unit 22 Memory 24 Collation unit

Claims (5)

[Claims] A converter for converting an input voltage into a predetermined output voltage; an output rectifying and smoothing unit for rectifying and smoothing the output of the converter; and an output voltage detecting unit for detecting an output voltage from the output rectifying and smoothing unit. A comparison feedback unit that compares a detection input from the output voltage detection unit with a reference value and feeds back the control signal, and controls a conversion operation of the converter unit based on the comparison feedback unit output, and when an output voltage is an overvoltage. A switching power supply comprising: a control unit that performs a required control operation; and an output voltage fluctuation width detection unit that detects a fluctuation width of the output voltage. 2. The switching power supply according to claim 1, wherein the output voltage fluctuation range detection unit detects a fluctuation range of the output voltage within a predetermined time. 3. The switching power supply according to claim 1, further comprising a display unit for displaying an output of said output voltage fluctuation range detection unit. 4. The switching power supply according to claim 3, wherein the display is performed in real time. 5. The switching power supply according to claim 1, wherein a mode of the output voltage fluctuation width detected by said output voltage fluctuation width detecting section is an output when said output voltage shifts to an overvoltage mode. A switching power supply having a configuration capable of checking each of a plurality of variations of a voltage fluctuation width.