JP3267427B2 - Power supply device having start-up circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply having a starting current limiting resistor between an AC power supply and an AC / DC converter.

[0002]

2. Description of the Related Art As shown in FIG. 1, an uninterruptible power supply is constructed by sequentially connecting a converter (AC / DC converter) 2, a capacitor 3 and an inverter 4 to a 200 V three-phase AC power supply 1. There is. The converter 2 includes the input AC lines 5a, 5b, 5c and a pair of DC output lines 6a,
6b, a well-known three-phase bridge circuit composed of switching elements Q1 to Q6 composed of IGBTs (insulated gate bipolar transistors) and diodes D1 to D6 connected in parallel to these elements. Have been. Although not shown, converter 2 has a well-known control circuit for turning on / off switching elements Q1 to Q6. The capacitor 3 is connected between the pair of DC lines 6a and 6b and has a smoothing function and a standby power function. The inverter 4 converts a DC voltage of the converter 2 and the capacitor 3 into an AC voltage.

In order to prevent an inrush current of the capacitor 3 at the time of starting the converter 2, the power supply 1 and the converter 2
The power switch 7 is connected between the start switch 9 and the start switch 9 via the current limiting start resistors 8a, 8b, 8c.
Is connected. The power switch 7 is formed of a three-phase electromagnetic contactor, and includes switches (contact points) 7a, 7b, 7c of each phase and an electromagnetic drive device 7d. The start switch 9 is formed of a three-phase electromagnetic contactor, and switches (contacts) 9a, 9 of each phase.
b, 9c and an electromagnetic drive device 9d. Starting resistance 8a
Since relatively large currents flow through .about.8c, which may lead to overheating and smoking, thermostats 10a, 10b, and 10c are provided to detect this.

A control circuit 11 comprising a DSP (digital signal processor) forms a start-up switch-on control signal in response to a drive command signal supplied from a line 12, and controls the start-up switch 9 to an on state. The start-up switch-on control signal maintains a high-level voltage state for a predetermined time (approximately 6 seconds) corresponding to the initial charging time of the capacitor 3 from the start of the start-up, and then goes low. The power switch 7 is turned on instead of turning off the start switch 9.

[0005]

Incidentally, the pair of DC output lines 6a and 6b may be short-circuited via the switching element due to the destruction of the switching element of the converter 2 or the like. If this kind of state occurs during the ON period (initial charge period) of the start switch 9, the short-circuit current continues to flow for a predetermined time (initial charge period) through the start resistors 8a, 8b, 8c, and the start resistors 8a to 8c Overheating and fuming may occur. Note that the thermostats 10a to 10c provided in FIG. 1 notify the control circuit 11 when overheating occurs, but do not notify that the overheating may occur. Further, since the thermostats 10a to 10c have a low response speed, it is impossible to detect an overheated state during the initial charging period.

An object of the present invention is to provide a power supply device capable of reliably and easily protecting a starting resistor.

In order to achieve the above object, the present invention provides an AC / DC converter for converting AC to DC, a capacitor or a storage battery connected between a pair of DC output terminals of the converter, an AC power supply and the converter. A power switch connected between the AC input terminal of the converter, a start switch connected between the AC power supply and the AC input terminal of the converter via a start current limiting resistor, and a pair of the converter. Voltage detection means for detecting the voltage between the DC output terminals of the converter, drive command signal supply means for supplying a drive command signal for the converter, the power switch, the start switch, the voltage detection means, and the drive command signal supply Means, and turns on the start switch in response to the drive command signal, and the voltage detected by the voltage detecting means increases at a speed equal to or higher than a predetermined speed. And determining whether the voltage is increasing at a speed equal to or higher than the predetermined speed, maintaining the ON state of the start switch for a predetermined time, and turning the power switch ON after the predetermined time has elapsed. And a control means for controlling the start switch to an off state without waiting for the end of the predetermined time when the voltage detected by the voltage detection means is not increasing at a speed higher than the predetermined speed. It concerns the device. Instead of judging a change in the increase in the voltage, the start switch can be controlled by detecting a change in the decrease in the start-up current.

[0008]

When the AC / DC converter is normal, the voltage of the capacitor or the storage battery gradually increases after the start of the startup, and conversely, the current gradually decreases. On the other hand, if the converter is short-circuited due to abnormality of the converter, the output voltage does not increase and the current does not decrease after the start of the startup. Claim 1 of the present application
In the invention of the above, the output voltage of the converter does not increase at a predetermined speed
Sometimes, it is determined that an excessive current is flowing through the starting resistor,
According to the second aspect of the present invention, the input current of the converter is set at a predetermined speed.
Excessive current is flowing through the startup resistance
The start switch is controlled to be in the OFF state even during the start period. Therefore, it is possible to reliably prevent the starting resistor from being overheated or smoking.

[0009]

First Embodiment Next, a power supply device according to an embodiment of the present invention will be described with reference to FIGS. However, in FIG. 2 and FIG. 5, which will be described later, portions common to FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

The circuit of FIG. 2 differs from that of FIG. 1 in that it has a DC voltage detection line 13 and a control circuit 11a for controlling the start switch 9 based on this voltage detection. It is configured similarly.

The control circuit 11a is constituted by a DSP, but in FIG. 2, the control circuit 11a is shown by an equivalent circuit of the DSP for easy understanding. Note that it is of course possible to configure the control circuit 11a with the individual circuits shown in FIG. The control circuit 11a includes a counter 14, an A / D converter 15, a delay memory 16, a subtractor 17, a reference value generator 18, a comparator 19, a power switch control circuit 20, and a start switch control circuit 21. The counter 14 is connected to the start command signal line 12 and counts an initial charging period, that is, a predetermined time (about 6 seconds) in response thereto. The two switch control circuits 20 and 21 control the driving devices 7d and 9d based on the output of the counter 14. The switch control circuits 20 and 21 are substantially irrelevant to the output of the comparator 19 when normal, but are controlled by the output of the comparator 19 when abnormal. The A / D converter 15 converts the voltage of the output voltage detection line 13 of the converter 2 from an analog detection voltage to a digital signal at a predetermined sampling period sufficiently shorter than the initial charging period. The memory 16 holds the data obtained from the A / D converter 15 at the first time point t1 until the second time point t2. The subtracter 17 obtains a difference between the data at the time t2 obtained from the A / D converter 15 and the data at t1 obtained from the memory 16 and sends the difference to the comparator 19. The comparator 19 is a subtractor 17
Is compared with the reference value of the reference value generator 18 to generate an output indicating whether the difference data is equal to or greater than the reference value. The reference value is set so as to prevent erroneous determination due to noise.

[0012]

[Operation] The control steps in the control circuit 11a comprising a DSP are as follows. (1) It is determined whether the drive command signal supplied from the line 12 is at a high level or a low level. If this is a low level, the same operation is repeated until it becomes a high level. (2) If the drive command is at a high level in Step 1, the initial charging time T3 from t0 to t3 shown in FIGS. 3 (B) and 4 (B) is measured by a counter, and the start switch 9 is turned on. , T0 as shown in FIGS. 3 (D) and 4 (D).
The first time T1 is measured by a counter (timer) from t1 to t1, and the data of the DC output voltage (capacitor voltage) at the time t1 after the elapse of the first time T1 is extracted and held. (3) Next, a second time T2 from t1 to t2 is measured by a counter (timer), and at the time t2 after the elapse of the second time T2, the second data of the DC output voltage (capacitor voltage) is obtained. Extract and keep this. (4) Next, a difference between the first data at time t1 and the second data at time t2 is determined. (5) Next, it is determined whether or not the value of the difference in step 4 is equal to or greater than a reference value. When the value is equal to or more than the reference value, it is in a normal state, so that the start switch 9 is kept on until the time point t3 at which the predetermined time T3 ends, and then the power switch 7 is turned off.
Turn on. On the other hand, when the reference value is not reached, an abnormal state such as a short-circuit of the converter 2 occurs.
Is turned off at time t2 to cut off the current flowing through the starting resistors 8a to 8c, thereby preventing this overheating or smoking. It is also prohibited to turn on the power switch 7 after the end of the predetermined time T3. However, when a protection means such as a breaker is provided, the power switch can be turned on after the lapse of the predetermined time T3.

Next, an equivalent control circuit 11a shown in FIG.
The operation at the time of startup will be described with reference to FIG. When the converter 2 is in a normal state, each part in FIG. 2 changes as shown in FIG. That is, as shown in FIG. 3A, when the drive command signal goes high at time t0, the counter 14 counts a predetermined time T3 (about 6 seconds) corresponding to the initial charging time shown in FIG. 3B. , A pulse having this time width is generated. The start switch control circuit 21 gives the start switch driving device 9d an ON control signal shown in FIG. 3C having the same time width as the predetermined time T3 in FIG. 3B, and the start switch 9 is turned on. t
When the predetermined time T3 ends at the time point 3, the start switch 9 is turned off, and in response to this, the power switch control circuit 20 sends an ON control signal (not shown) to the power switch driving device 7d, and the power switch 7 Turns on. Even in the normal state as described above, the determination of the abnormality during the startup period is performed. This determination operation will be described next. When the starting switch 9 is turned on at time t0 in FIG. 3, the charging current limited by the starting resistors 8a to 8c flows through the capacitor 3. Thus, the voltage between the pair of DC output lines 6a and 6b gradually increases as shown in FIG. A / D
The converter 15 performs A / D conversion based on the clock of the sampling clock signal generation means incorporated therein, and performs output sampling shown in FIG. 3E by means of first and second timers incorporated therein. A pulse is formed, and voltage data at times t1 and t2 is output. The data at the time t1 is held in the memory 16. When the voltage data at the time t2 is obtained, the data at the time t1 in the memory 16 is subtracted therefrom by the subtractor 17, and the comparator 19 determines whether or not the difference data is equal to or more than the reference value of the reference value generator 18. You. When the difference data is equal to or larger than the reference value, the transmission of the activation switch-on control signal from the activation switch control circuit 21 is continued until time t3 as shown in FIG.

When converter 2 is short-circuited, the operation shown in FIG. 4 is performed. That is, since the capacitor 3 is not charged when the converter 2 is in a short-circuit state, the voltage between the pair of DC lines 6a and 6b, that is, the capacitor voltage Vc is kept substantially zero. Therefore, t1 and t2 shown in FIG.
The output of the A / D converter 15 is zero at the timing of .times .. The output of the subtractor 17 at time t2 is also zero, and the signal from the comparator 19 indicates that the difference data is smaller than the reference value. That is, an abnormal signal is output. The activation switch control circuit 21 terminates the transmission of the activation switch on control signal at time t2 as shown in FIG. 4C in response to the abnormality signal of the comparator 19. As a result, the start switch 9 is turned off at t2 without waiting for the end of the predetermined time T3 to protect the start resistors 8a to 8c. In addition, t of the power switch 7
Prohibit turning on at 3 points. However, if necessary t3
To turn on the power switch 7.

By setting T1 + T2 to be shorter than T3 as described above, it is possible to determine an abnormality of the converter 2 before the predetermined time T3 ends, and to protect the starting resistors 8a to 8c from damage.

[0016]

Second Embodiment In the circuit of FIG. 5, instead of the voltage detection in the circuit of FIG. 2, current detectors 31, 32 for a U-phase line 5a and a W-phase line 5c are provided, and these are A / D-converted. And a peak detection circuit 15a. The A / D conversion and peak detection circuit 15a has a U-phase A / D converter and a W-phase A / D converter, and detects U-phase and W-phase currents at a sampling frequency sufficiently higher than the frequency of the AC power supply voltage. It is converted into a digital signal, the V-phase current is calculated from the U-phase current and the W-phase current, and the average peak of the peak values of the three phase currents is calculated. This peak value is obtained at two time points t1 and t2 in FIG. It is configured to sample and output. Therefore,
In the second embodiment, the abnormality is determined based on the magnitude of the change in the current, instead of determining the abnormality based on the magnitude of the change in the voltage in the first embodiment.

FIG. 6 shows the current of each part when the converter 2 of FIG. 5 is normal. In a normal case, the charging current of the capacitor 3 gradually decreases after the start of the startup. Therefore, U, V, W
The currents of the phase lines 5a, 5b, 5c are shown in FIGS.
It decreases with time as shown in FIG. The peak values of the currents of the three phases also decrease with time as illustrated in FIG. 6 (G). A / D conversion and peak detection circuit 15a
Calculates the current peak values shown in FIG.
Obtain a sample of the time point. The sample at time t1 is in memory 1.
6 and is subtracted by the subtractor 17 from the sample at the time t2. The first sample (current data) at t1 and t
The comparator 19 determines whether the difference from the second sample (current data) at the time 2 is equal to or greater than the reference value of the reference value generator 18,
Determine if it is abnormal. In a normal state, the difference between the current values t1 and t2 is larger than the reference value. During this normal time,
The start switch ON control signal is not interrupted by the output of the comparator 19, and the start switch 9 is turned ON for a predetermined time T3.

FIG. 7 shows the state of each part when the converter 2 of FIG. 5 is in a short-circuit state, similarly to FIG. When the converter 2 is short-circuited, the capacitor 3 is not charged, and the peak of the current of each phase does not decrease during the start-up period as shown in FIGS. Although the period of the current is longer than the actual period in FIG. 7 for the sake of illustration, there are many peaks during the period T1 or T2. When the current peak is obtained by the A / D conversion and peak detection circuit 15a, a substantially constant peak value is obtained as illustrated in FIG. 7G. Therefore, there is substantially no difference between the sample (current data) at time t1 and the sample (current data) at time t2.
An output indicating that the value of this difference is smaller than the reference value, that is, an output indicating an abnormality is obtained from the comparator 19, and the start switch does not wait for the end of the predetermined time (initial charging time) T3 as in the first embodiment. 9 is turned off at time t2 and the starting resistors 8a to 8
c protection is achieved.

The step of the processing by the DSP of the control circuit 11b in FIG. 5 corresponds to the step in which the voltage in the step of the processing by the DSP of the control circuit 11a of FIG. 2 is replaced with a current. In short, the power supply device of the second embodiment is substantially the same as the power supply device of the first embodiment except for the difference in voltage and current.

[0020]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) A / D conversion and peak detection circuit 1 in FIG.
In 5a, a peak detection circuit can be provided before the A / D converter. (2) It is also possible to determine the abnormality by detecting the currents of all three phases, or to determine the abnormality only by the current of one phase. (3) The converter 2 may be any circuit as long as it can perform AC / DC conversion. For example, a control rectifier circuit using a thyristor can be used. Also, FIG.
A full-wave rectifier circuit in which the switching elements Q1 to Q6 are omitted from the circuit of FIG. (4) The switches 7 and 9 can be electronic switches. (5) The control circuit 11b in FIG. 5 can be configured by an individual circuit or an analog circuit. (6) In the embodiment of FIG. 2, A /
Although D conversion is performed, A / D conversion may be performed only at the time points t1 and t2. Further, the abnormality determination may be performed based on the voltage or current data at a time point greater than the two time points t1 and t2.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a conventional power supply device.

FIG. 2 is a circuit diagram showing a power supply device according to a first embodiment of the present invention.

3 is a waveform diagram of each part when the converter of FIG. 2 is normal.

4 is a waveform diagram of each part when the converter of FIG. 2 is in a short-circuit state.

FIG. 5 is a circuit diagram showing a power supply device according to a second embodiment.

6 is a waveform chart of each part when the converter of FIG. 5 is normal.

7 is a waveform chart of each part when the converter of FIG. 6 is in a short-circuit state.

[Explanation of symbols]

 2 Converter 3 Capacitor 8a to 8c Starting resistor 9 Starting switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/219 G05F 1/10 H02H 3/20 H02J 9/06 H02M 7/155

Claims (2)

(57) [Claims] 1. An AC / DC converter for converting AC to DC, a capacitor or a storage battery connected between a pair of DC output terminals of the converter, and an AC power supply and an AC input terminal of the converter. A power switch connected thereto; a start switch connected between the AC power supply and an AC input terminal of the converter via a start current limiting resistor; and detecting a voltage between a pair of DC output terminals of the converter. Voltage detecting means, a driving command signal supplying means for supplying a driving command signal for the converter, connected to the power switch, the starting switch, the voltage detecting means and the driving command signal supplying means, and The start switch is turned on in response to the drive command signal, and it is determined whether or not the voltage detected by the voltage detection means is increasing at a speed equal to or higher than a predetermined speed, and When increasing at a speed equal to or higher than the predetermined speed, the ON state of the start switch is maintained for a predetermined time, and after the predetermined time has elapsed, the power switch is controlled to the ON state, and the power switch is detected by the voltage detecting means. A power supply device comprising: control means for controlling the start switch to an off state without waiting for the end of the predetermined time when the voltage is not increasing at a speed higher than the predetermined speed. 2. An AC / DC converter for converting AC to DC, a capacitor or a storage battery connected between a pair of DC output terminals of the converter, and an AC power supply and an AC input terminal of the converter. A power switch connected thereto, a start switch connected between the AC power supply and an AC input terminal of the converter via a start current limiting resistor, and a current detection means for detecting a current on an input side of the converter. A drive command signal supply unit that supplies a drive command signal for the converter; a power switch, the start switch, the current detection unit, and the drive command signal supply unit, and the drive command signal And controls whether the current detected by the current detecting means is decreasing at a speed equal to or lower than a predetermined speed, and determines whether the current is equal to or lower than the predetermined speed. When decreasing at a lower speed, the on state of the start switch is maintained for a predetermined time, and after the predetermined time has elapsed, the power switch is controlled to the on state. A power supply device comprising: control means for controlling the start switch to an off state without waiting for the end of the predetermined time when the speed is not reduced at a speed lower than a predetermined speed.