JP2005210819A - Fault-detecting method for pulse-width-modulation dc power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to detect a fault of a control power supply which is used in a power converting device and the like, quickly on the occurrence of the fault. <P>SOLUTION: Periods of time are detected from a rise point of a pulse to that of the next pulse, from a fall point of a pulse to that of the next pulse, or from a rise point of a pulse to its fall point that appear at the secondary side of a transformer 2023 with the ON-OFF operations of a switching element 2024. It is judged to be a fault if these detected periods of time deviate from the time ranges determined for each period of time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an abnormality detection method for a pulse width modulation type DC power source that detects an abnormality by monitoring the time of each part of a pulse waveform that appears in a secondary winding of a transformer.

In power converters composed of semiconductor switch elements such as transistors and thyristors, AC power can be converted to DC power, or DC power can be converted into AC power by appropriately controlling on / off of each semiconductor switch element. It is well known that conversion to can be done freely. However, in this power conversion, it is necessary to supply control power necessary for controlling the semiconductor switch element. Therefore, the details of the present invention will be described below by taking a control power source used for an uninterruptible power supply as a power converter as an example.
A commercial power supply may cause a power outage for a very short time due to a lightning strike or a ground fault, but some of the loads that receive AC power from this commercial power supply are very similar to computers. There are devices that can cause problems even during a short blackout. Therefore, an uninterruptible power supply is installed in such a load so that the power supply to the load is not cut off. This uninterruptible power supply is largely divided into a constant inverter power supply type and a constant commercial power supply type depending on the power supply method when the commercial power supply is not interrupted (hereinafter, this state is referred to as normal time or always). Can be separated.

FIG. 9 is a block circuit diagram schematically showing a conventional example of a single-phase AC always-inverter-fed uninterruptible power supply. In the following, the single-phase AC constant inverter power supply type uninterruptible power supply is abbreviated as a constant inverter power supply type UPS.
In FIG. 9, a CVCF inverter device 20 for supplying AC power having a constant voltage and a constant frequency includes an AC / DC converter 201 that converts AC power from a single-phase AC power source 10 as commercial power into DC power, A smoothing capacitor 206 that smoothes the pulsation component contained in the DC component by smoothing, and a DC / AC converter 203 that converts the smoothed DC power into a single-phase AC power having a desired constant voltage and frequency. ing. In the DC intermediate circuit between the AC / DC converter 201 and the AC / AC converter 203, there are a battery and a charger for charging the battery. Omitted. Further, a bypass power feeding circuit 31 is laid between the single-phase AC power supply 10 and the load 40 via a changeover switch 30. In a normal inverter-fed UPS, the AC / DC converter 203 supplies AC power to the load 40 in both normal and power outages, so the changeover switch 30 is always on the DC / AC converter 203 side. When the DC / AC converter 203 is maintained and inspected, when a battery (not shown) is replaced, or when a failure described later is performed, the changeover switch 30 is switched so that the bypass power supply circuit 31 supplies AC power to the load 40. To do. The change-over switch 30 is shown as having a configuration in which the circuit is switched at the contact point.

  The AC / DC converter 201 and DC / AC converter 203 perform a power conversion operation based on a control signal from the control device 205, but the power supply voltage required by the control device 205 is generally different from the DC intermediate circuit voltage. . Therefore, a control power having a desired voltage is generated by the control power source 202 connected to the DC intermediate circuit, and this control power is supplied to the control device 205 via the power supply line 210. By the way, this always-inverter-fed UPS must continue to operate without stopping during normal times and must continue to supply AC power to the load 40 without stopping for a time corresponding to the battery capacity during a power failure. However, if the control power supply 202 fails, the normal operation of the control device 205 is hindered even during normal operation, and stable AC power cannot be supplied to the load 40 by the AC / DC converter 201 and DC / AC converter 203. The trouble that cannot always fulfill the mission of the inverter power supply type UPS occurs. Therefore, a control power supply monitoring device 220 for monitoring the output of the control power supply 202 is provided, and when an abnormality occurs in the output of the control power supply 202, a switching signal 301 is sent to the changeover switch 30 via the OR circuit 207. At the same time, an abnormality notification signal 208 is output to the load 40, for example. Therefore, the supply source of AC power to the load 40 is switched from the DC / AC converter 203 to the bypass power supply circuit 31 without a power failure.

In a single-phase AC constant commercial power supply uninterruptible power supply (hereinafter abbreviated as a constant commercial power supply UPS), the changeover switch 30 is normally connected to the bypass power supply circuit 31, and the load 40 is supplied with an AC single-phase power supply. Therefore, even if the control power supply 202 fails and the DC / AC converter 203 cannot be operated in this state, it is not necessary to switch the power supply circuit as in the case of the constant inverter power supply type UPS described above. No. However, if the AC single-phase power supply 10 fails, AC power cannot be supplied from the battery to the load 40 via the DC / AC converter 203. Therefore, when the control power supply 202 fails, an abnormality notification signal is also sent to the outside. It is necessary to output 208.
FIG. 10 is a block circuit diagram showing a conventional example of a control power supply and a control power supply monitoring circuit. FIG. 10 shows a switching power supply of the pulse width modulation (hereinafter abbreviated as PWM) system shown in FIG. The most widely used as the control power source 202 of.

In FIG. 10, the control power source 202 obtains a differential voltage by inputting a target voltage (not shown) and a voltage detected from the smoothing capacitor 2026 connected to the secondary side of the transformer 2023 to the error amplifying circuit 2027. . This is fed back to the PWM switching control circuit 2022, and the switching element 2024 connected in series to the primary winding of the transformer 2023 is turned on / off and its pulse width is controlled. At this time, the conventional control power supply monitoring device 220 monitors the voltage VCC of the smoothing capacitor 2026, and outputs an abnormality notification signal 208 when this value exceeds a predetermined voltage range (for example, non-patent) Reference 1).
Morio Sato, “Partial Digital Control Power Supply with Dedicated IC”, Transistor Technology SPECIAL, CQ Publishing Co., Ltd., April 1, 2001, No. 74, p. 95-105

  The DC power for controlling the desired voltage is obtained by controlling on / off of the switching element 2024 constituting the control power source 202, but a large pulsating current is generated when the switching element 2024 is turned on / off. In order to smooth the pulsating flow, a large-capacity smoothing capacitor 2026 is mounted on the control power source 202. By the way, the conventional control power supply monitoring device 204 monitors the voltage VCC of the smoothing capacitor 2026 as shown in FIG. 10. Therefore, when a failure occurs in the control power supply 202, the smoothing capacitor is caused by the failure. There is a problem that it takes time until a change in voltage VCC of 2026 appears. Further, it is general that the power for switching operation of the changeover switch 30 is also supplied from the control power supply 202 (see FIG. 9). However, in the always-inverter power supply type UPS, the power supply for switching to the bypass power supply circuit 31 is used. However, it takes time to detect the failure of the control power source 202 as described above, even though there is a request to detect the failure of the control power source 202 at an early stage.

The failure of the control power source 202 may include a power failure of the original AC power source in a broad sense, but the present invention is limited to the failure of the control power source 202 itself.
SUMMARY OF THE INVENTION An object of the present invention is to make it possible to quickly detect an abnormality in a control power source used for a power conversion device or the like simultaneously with the occurrence of the abnormality.

In order to solve the above-described problems, the abnormality detection method for a pulse width modulation type DC power supply according to the present invention includes connecting a primary winding of a transformer and a switching element in series, and applying DC power to the series circuit. The pulse width modulation type DC which maintains the DC voltage obtained through the rectifier connected to the secondary winding of the transformer and the smoothing capacitor at a predetermined value by controlling the pulse for turning on and off the switching element. In the power supply control method,
The time from the rise of the pulse appearing in the secondary winding of the transformer to the rise of the next pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined that there is an abnormality.
Alternatively, the time from the fall of the pulse appearing in the secondary winding of the transformer to the fall of the next pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined as abnormal.

Alternatively, the time from the rise of the pulse appearing in the secondary winding of the transformer to the fall of the pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined as abnormal.
Alternatively, the time from the fall of the pulse appearing in the secondary winding of the transformer to the rise of the next pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined that there is an abnormality.

  A switching power supply is often used as a conventional control power supply for a power converter, and a large-capacity smoothing capacitor is used to smooth the output DC power of the switching power supply. Conventionally, since the voltage of the smoothing capacitor is detected and an abnormality of the control power supply is detected from the change, there is a disadvantage that a time delay occurs in the abnormality detection. On the other hand, in the present invention, the pulse width and pulse interval of the pulse waveform appearing at the output terminal of the transformer, which is the previous stage of the smoothing capacitor, are detected, and if this value exceeds the predetermined time range, it is determined that there is an abnormality. Therefore, an effect that abnormality detection can be greatly accelerated as compared with the prior art can be obtained.

  The time from the rise time of the pulse appearing in the secondary winding of the transformer to the rise time of the next pulse, the time from the fall time of the pulse to the fall time of the next pulse, or the rise time of the pulse From the falling time of the pulse to the falling time of the pulse or each time from the falling time of the pulse to the rising time of the next pulse.

FIG. 1 is a block circuit diagram showing a first embodiment of the present invention. The configuration of the control power supply monitoring device 204 is the same as that of the conventional circuit described in FIG. Is different. The control power supply monitoring device 204 shown in FIG. 1 inputs the voltage extracted from the secondary winding of the transformer 2023 to the pulse interval monitoring circuit 2043 via the rectifier diode 2042. An abnormality occurs in the output voltage of the control power supply 202 due to an abnormality in the PWM switching circuit 2022 or the switching element 2024. An abnormality occurring in a pulse interval or the like prior to the change of the output voltage is detected by the rectifier diode 2042 and the pulse interval monitoring This can be detected by the circuit 2043.
FIG. 2 is a PWM pulse waveform diagram for explaining which part of the PWM pulse detection signal is detected when an abnormality occurs, wherein A represents the time from the rising edge of the pulse to the rising edge of the next pulse, B represents the time from the falling edge of the pulse to the falling edge of the next pulse, C represents the time from the rising edge of the pulse to the falling edge of the pulse (that is, the pulse width), and D represents the rising edge of the pulse. It represents the time from the falling edge to the rising edge of the next pulse.

3 is a block circuit diagram showing the configuration of the pulse interval monitoring circuit according to the first embodiment of the present invention shown in FIG. 1. FIG. 3 shows A (shown from the rising edge of the pulse to the next pulse). This represents a case where it is detected whether or not an abnormality has occurred in the time until the rising edge).
In FIG. 3, the pulse interval monitoring circuit 2043 includes a timer 20431, an abnormality determination circuit 20432, and three setting devices 20433 to 20435, and the PWM pulse detection signal obtained from the rectifier diode 20423 (see FIG. 1) is constant. Input to the timer 20431 that counts at an interval is repeated, but every time the rising edge of the PWM pulse detection signal is input to the timer 20431, the operation is cleared. Note that the count interval of the timer 20431 is sufficiently shorter than the pulse interval of the PWM pulse detection signal input thereto. A set value C _T1 set by the setter 20433, a set value C _T2 set by the setter 20434, and a set value C _T3 set by the setter 20435 are input to the abnormality determination circuit 20432, and the output signal of the timer 20431 is output. And the PWM pulse detection signal are input, and the rising edge interval of the PWM pulse detection signal is shorter than the set value _CT1, and the rising edge interval of the PWM pulse detection signal is longer than the set value _CT2. And when the pulse width becomes longer than the set value C _T3 , the abnormality notification signal 208 is issued.

FIG. 4 is an operation waveform diagram showing the operation when the rising edge interval of the PWM pulse detection signal is shorter than the set value. FIG. 4 (1) shows the operation of the timer 20432, and FIG. Represents the waveform of the PWM pulse detection signal. Since the pulse interval is long at the rising times t _{1 to} t _{4 of} each pulse, the timer value exceeds the set value C _T1 of the setter 20433. Therefore, the timer 20431 is reset at each time point t _{1 to} t ₄ , but when the pulse interval is shortened, the timer value at the reset time point does not reach the set value C _T1 (see time points t ₅ and t ₆ ). 20432 outputs an abnormality notification signal 208.
FIG. 5 is an operation waveform diagram showing the operation when the rising edge interval of the PWM pulse detection signal is longer than the set value. FIG. 5 (1) shows the operation of the timer 20432, and FIG. Represents the waveform of the PWM pulse detection signal. Since the pulse interval is short at the rising times t _{11 to} t _{13 of} each pulse, the timer value does not reach the set value C _T2 of the setting device 20434, so the timer 20431 is reset at each time t _{11 to} t ₁₃ If the interval is long, the timer value will be exceeded the set value C _T2 (see point t _14), the abnormality judging circuit 20432 outputs an abnormality notification signal 208.

FIG. 6 is an operation waveform diagram showing the operation when the pulse width of the PWM pulse detection signal is longer than the set value. FIG. 6 (1) shows the operation of the timer 20432, and FIG. The PWM pulse detection signal waveform is represented. Since the pulse interval at the rise time t ₂₁ ~t ₂₃ of each pulse is short, because the timer value does not reach the set value C _T3 setter 20435, timer 20431 is being reset at each time point t ₂₁ ~t _23, pulse If the width becomes long rise of the next pulse does not arrive, the timer value will be exceeded the set value C _T3 (see point t _24), the abnormality judging circuit 20432 outputs an abnormality notification signal 208.

The most common failure of the control power supply 204 is a failure in which the on / off operation is interrupted or the pulse is missing due to the failure of the PWM switching control circuit 2022 or the switching element 2024. Therefore, the circuit of the second embodiment described below easily detects this specific failure.
FIG. 7 is a block circuit diagram showing a pulse interval monitoring circuit according to the second embodiment of the present invention. The pulse interval monitoring circuit 2044 shown in FIG. 7 includes a retriggerable circuit 20441 and an adjustment circuit 20442. When the interval between the rising edges of the PWM pulse detection signal input to the retriggerable circuit 20441 becomes longer than the time T _A set by the adjustment circuit 20442, the retriggerable circuit 20441 issues an abnormality notification signal 208.
FIG. 8 is an operation waveform diagram showing the operation of the retriggerable circuit shown in FIG. 7. FIG. 8 (1) is a PWM pulse detection signal input to the input terminal TRGIN of the retriggerable circuit 20441. FIG. is abnormality notification signal output from the output terminal ^* Q of the retriggerable circuit 20441, the time point t ₃₁ ~t ₃₄ is an input point of the rising edge of the PWM pulse detection signal.

Retriggerable circuit 20441 is triggered by the input of a rising edge of the PWM pulse detection signal (t ₃₁ time), ^* the output signal from the Q terminal is changed to a logic 0 signal from the logic 1 signal at this time. In this state, if the time T ₃₁ until the time t ₃₂ when the rising edge of the next pulse is input is shorter than the time T _A set by the adjustment circuit 20442, ^* the output from the Q terminal changes with the logic 0 signal unchanged. Although not, for example, the time from t ₃₄ time longer than the set time T _a, the output from the ^* Q terminal at t ₃₅ the time is changed to a logic 1 signal, the abnormality notification signal 208 is issued. The setting time T _A of the adjustment circuit 20442 is of course can be set to any value.

1 is a block circuit diagram showing a first embodiment of the present invention. PWM pulse waveform diagram explaining which part of the PWM pulse detection signal is detected when an abnormality occurs 1 is a block circuit diagram showing the configuration of a pulse interval monitoring circuit according to the first embodiment of the present invention shown in FIG. Operation waveform diagram showing the operation when the rising edge interval of the PWM pulse detection signal is shorter than the set value Operation waveform diagram showing the operation when the rising edge interval of the PWM pulse detection signal is longer than the set value Operation waveform diagram showing the operation when the pulse width of the PWM pulse detection signal is longer than the set value Block circuit diagram showing a pulse interval monitoring circuit of the second embodiment of the present invention Operation waveform diagram showing operation of retriggerable circuit shown in FIG. A block circuit diagram showing a simplified example of a conventional single-phase AC continuous inverter-fed uninterruptible power supply Block circuit diagram showing conventional example of control power supply and control power supply monitoring circuit

Explanation of symbols

10 Single-phase AC power supply
20 CVCF inverter device
30 selector switch
31 Bypass power supply circuit
40 Load
201 AC / DC converter
202 Control power supply
203 DC / AC converter
204, 220 Control power supply monitoring device
205 Control unit
206 Smoothing capacitor
207 OR circuit
208 Error notification signal
210 Power supply line
2022 PWM switching circuit
2023 transformer
2024 Switching element
2025, 2042 Rectifier diode
2026 Smoothing capacitor
2027 Error amplification circuit
2043 Pulse interval monitoring circuit
20431 timer
20432 Abnormality judgment circuit
20433 to 20435 Setting device
20441 Retriggerable circuit
20442 Adjustment circuit

Claims (4)

A transformer primary winding and a switching element are connected in series, DC power is applied to the series circuit, and a pulse for turning on and off the switching element is controlled, whereby a secondary winding of the transformer is controlled. In a control method of a pulse width modulation type DC power supply for maintaining a DC voltage obtained through a rectifier connected to a line and a smoothing capacitor at a predetermined value,
The time from the rise of the pulse appearing in the secondary winding of the transformer to the rise of the next pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined that there is an abnormality. An abnormality detection method for a pulse width modulation type DC power supply. A transformer primary winding and a switching element are connected in series, DC power is applied to the series circuit, and a pulse for turning on and off the switching element is controlled, whereby a secondary winding of the transformer is controlled. In a control method of a pulse width modulation type DC power supply for maintaining a DC voltage obtained through a rectifier connected to a line and a smoothing capacitor at a predetermined value,
The time from the fall of the pulse appearing in the secondary winding of the transformer to the fall of the next pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined as abnormal. An abnormality detection method for a pulse width modulation type DC power supply. A transformer primary winding and a switching element are connected in series, DC power is applied to the series circuit, and a pulse for turning on and off the switching element is controlled, whereby a secondary winding of the transformer is controlled. In a control method of a pulse width modulation type DC power supply for maintaining a DC voltage obtained through a rectifier connected to a line and a smoothing capacitor at a predetermined value,
The time from the rising edge of the pulse appearing in the secondary winding of the transformer to the falling edge of the pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined that there is an abnormality. An abnormality detection method for a pulse width modulation type DC power supply. A transformer primary winding and a switching element are connected in series, DC power is applied to the series circuit, and a pulse for turning on and off the switching element is controlled, whereby a secondary winding of the transformer is controlled. In a control method of a pulse width modulation type DC power supply for maintaining a DC voltage obtained through a rectifier connected to a line and a smoothing capacitor at a predetermined value,
The time from the fall of the pulse appearing on the secondary winding of the transformer to the rise of the next pulse is monitored, and if it is detected that this value is out of the predetermined range, it is determined that there is an abnormality. An abnormality detection method for a pulse width modulation type DC power supply.

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