JP3726732B2 - Power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply apparatus that uses a rectification method using a bridge rectifier circuit to supply DC power to an apparatus, a system, or the like.
[0002]
[Prior art]
Various rectification methods using diodes have been known.
[0003]
4 to 7 show a conventional power supply configuration. The power supply device shown in each figure includes a bridge rectifier circuit 6 formed of four diodes 2 to 5 and an AC power supply 1. A reactor 8 is connected between the AC power source 1 and the AC input terminal of the bridge rectifier circuit 6, and a capacitor 10 is connected between the AC input terminal and the DC output terminal of the bridge rectifier circuit.
[0004]
4 and 5, the capacitor 10 is connected between the AC input terminal 6a or 6b of the bridge rectifier circuit 6 and the negative DC output terminal 6c via a bidirectional switch 9. 6 and 7, the capacitor 10 is connected between the AC input terminal 6a or 6b of the bridge rectifier circuit 6 and the positive DC output terminal 6d.
[0005]
A smoothing capacitor 7 is connected between the positive DC output terminal 6d and the negative DC output terminal 6c of the bridge rectifier circuit 6. The smoothing capacitor 7 can make the direct current of drastic change obtained by the bridge rectifier circuit 6 a smooth direct current.
[0006]
Further, a zero-cross detection unit 12 that detects a zero-cross point of the voltage of the AC power supply 1, a bidirectional switch drive signal generation unit 13 that generates a drive signal for the bidirectional switch 9 based on the output of the zero-cross detection unit 12, Bidirectional switch drive means 14 for driving the bidirectional switch 9 based on the output of the bidirectional switch drive signal generation means 13, DC output voltage detection means 15 for detecting the DC output voltage across the smoothing capacitor 7, Overvoltage protection first means 17 for turning off the bidirectional switch 9 until the DC output voltage exceeds the output voltage over-rise prevention level OV1 and falls below the output voltage over-rise prevention release level set lower than OV1. .
[0007]
4 to 7, the description of the zero cross detection means 12, the bidirectional switch drive signal generation means 13, the bidirectional switch drive means 14, the DC output voltage detection means 15, and the overvoltage protection first means 17 is omitted.
[0008]
Hereinafter, the operation of the power supply apparatus shown in FIG. 4 will be described with reference to FIGS. 8 and 9 show the AC input voltage Vi during the positive half cycle, and FIGS. 10 and 11 show the negative half cycle.
[0009]
The full-wave rectifier circuit shown in FIG. 8 includes a bridge rectifier circuit 6 composed of four diodes 2 to 5. Reference numeral 11 denotes a load.
[0010]
FIG. 9 shows the flow of current during the period in which the AC from the AC power source 1 is positive. Since the current flows in the order of the diode 2, the smoothing capacitor 7, and the diode 5, as indicated by the arrows, the positive voltage Vo can be taken out.
[0011]
FIG. 10 shows a current flow during a half cycle in which the AC from the AC power source 1 is negative. Since the current flows in the order of the diode 4, the smoothing capacitor 7, and the diode 3 as indicated by the arrows, the positive voltage Vo can be taken out. That is, the AC input from the AC power source 1 is full-wave rectified to obtain a positive DC voltage.
[0012]
FIGS. 12 and 13 show the waveforms of the embodiment when Vi is 200 V, L is 10 mH, C is 300 μF, and Co is 1800 μF for the power supply device shown in FIG.
[0013]
12 shows the waveforms of the AC input voltage Vi, the current flowing through the reactor 8 (AC input current) IL, the DC output voltage Vo, and the drive signal Vg of the bidirectional switch 9, and FIG. 13 shows the AC input voltage Vi, the capacitor 10 shows waveforms of a current Ic flowing through the capacitor 10 and a voltage Vc across the capacitor 10.
[0014]
In the above configuration, immediately after the zero crossing of the positive AC half cycle of the AC input voltage Vi, the bidirectional switch 9 is turned off, the DC output voltage Vo is higher than the AC input voltage Vi, and the diodes 2 and 5 are reverse biased. Input current does not flow. At this time, as a result of charging the capacitor 10 in the previous cycle, the capacitor 10 has the voltage Vc1 with the polarity shown in the figure. The bidirectional switch drive signal generation means 13 generates an ON signal of the bidirectional switch 9 after a time Δd from the zero crossing point of the AC input voltage Vi from negative to positive, and the bidirectional switch drive means 14 turns on the bidirectional switch 9. Then, a current flows as shown by an arrow in FIG.
[0015]
That is, in order from the AC power source 1, a current flows through the reactor 8, the diode 2, the smoothing capacitor 7, and the capacitor 10, and the capacitor 10 is discharged and its voltage drops below Vc 1. Note that Δd is selected so that the sum of the AC input voltage Vi and the voltage Vc1 of the capacitor 10 becomes larger than the voltage Vo of the smoothing capacitor 7 when the bidirectional switch 9 is turned on.
[0016]
Then, the bidirectional switch drive signal generation means 13 generates an OFF signal of the bidirectional switch 9 after a time Δt from the ON time of the bidirectional switch 9, and when the bidirectional switch 9 is turned off by the bidirectional switch drive means 14, While the capacitor 10 maintains the voltage Vc2 at that time, the current flows from the AC power source 1 to the reactor 8, the diode 2, the smoothing capacitor 7, and the diode 5 in this order as shown in FIG. 6, and eventually becomes zero due to the decrease in the AC input voltage Vi. It becomes.
[0017]
Immediately after the zero crossing of the negative AC half cycle of the AC input voltage Vi, the bidirectional switch 9 is turned off, the DC output voltage Vo is higher than the AC input voltage Vi, and the diodes 3 and 4 are reverse-biased. No current flows. After Δd from the zero crossing point of the AC input voltage Vi from positive to negative, the bidirectional switch drive signal generation means 13 generates an ON signal for the bidirectional switch 9, and the bidirectional switch drive means 14 turns on the bidirectional switch 9. Then, a current flows as shown by an arrow in FIG.
[0018]
That is, in order from the AC power source 1, current flows through the capacitor 10, the diode 3, and the reactor 8, and the capacitor 10 is charged. Then, the bidirectional switch drive signal generating means 13 generates an OFF signal of the bidirectional switch 9 after Δt from the on-time of the bidirectional switch 9, and when the bidirectional switch 9 is turned off by the bidirectional switch drive means 14, the capacitor 10 holds the voltage in a state of being charged up to the voltage Vc1, and the current flows from the AC power source 1 in the order of the diode 4, the smoothing capacitor 7, the diode 3, and the reactor 8 as shown in FIG. It will eventually become zero due to the decrease.
[0019]
By charging / discharging the capacitor 10 as described above, an input current can flow from a position close to the zero cross of the input voltage, so that a high power factor has been achieved.
[0020]
Further, by increasing Δt, the amount of magnetic energy stored in the reactor 8 and the amount of charge in the capacitor 10 can be increased, and the DC output voltage Vo can be increased. Similarly, the output voltage Vo can be decreased by decreasing Δt, and the DC output voltage Vo can be varied by increasing / decreasing Δt. The variable range of Δt is limited to be less than or equal to the conduction width Δto of the bidirectional switch that generates the DC output voltage required at the maximum load.
[0021]
As shown in FIG. 10, the conventional power supply device accumulates energy in the reactor 8 and the capacitor 10 during the conduction period Δt of the bidirectional switch 9 in the negative half cycle of the AC input voltage Vi, and the AC input voltage Vi becomes positive. It has a so-called boosting action that releases the energy to the smoothing capacitor 7 in a half cycle.
[0022]
As shown in FIG. 15, the relationship between Δt and the DC output voltage Vo increases as the Δt increases, the DC output voltage Vo increases. The value depends on the load, and the DC output for the same Δt decreases as the load decreases. The voltage Vo increases. Therefore, if Δt is excessively increased at light load, the DC output voltage Vo becomes abnormally high, and the withstand voltage of the smoothing capacitor 7 may be exceeded.
[0023]
In order to avoid the above phenomenon, the maximum value of Δt is limited to a conduction width Δto that generates the DC output voltage Vo required at the maximum load as described above. The width is limited to Δto or less, and the DC output voltage Vo can be prevented from rising abnormally.
[0024]
Furthermore, since the current becomes a series resonance current between the reactor 8 and the capacitor 10 or the smoothing capacitor 7, the rapid increase of the current can be suppressed as compared with the reactor power supply short circuit method generally used in the booster circuit. Can be suppressed. Furthermore, since the current becomes a series resonance current between the reactor 8 and the capacitor 10 or the smoothing capacitor 7 and does not include a high-frequency ringing component, the inductance L of the reactor 8 and the capacitances C, Δd, and Δt of the capacitor 10 are appropriately selected. , Harmonics can be appropriately suppressed. FIG. 14 shows an example of comparison between the harmonic component of the input current and the harmonic regulation domestic guidelines 15. In this figure, the horizontal axis indicates the harmonic order, and the vertical axis indicates the current value.
[0025]
Although the operation of the power supply device shown in FIG. 4 has been described, the operation is the same for any of the power supply devices shown in FIGS.
[0026]
However, in the conventional power supply apparatus as described above, there is a problem that the power factor is low and the power supply harmonics are large because the input current flows only during a period in which the voltage of the AC power supply 1 is higher than the DC output voltage.
[0027]
Usually, a method of connecting a reactor between the AC power source 1 and the bridge rectifier circuit 6 is used as an improvement measure. However, even if harmonics can be suppressed by this method, the power factor is only about 70%. However, as a medium-capacity to large-capacity power source, there is a problem that an element used for the medium-capacity power source is increased, an apparatus size is increased, and a load is imposed on the power supply system.
[0028]
In order to solve such conventional problems, as a power supply device that can achieve both high power factor and harmonic suppression and can protect against overvoltage and overcurrent, the AC power supply and the AC input of the bridge rectifier circuit There is a power supply device provided with a reactor connected between the two ends and a capacitor connected via a bidirectional switch between the AC input end and the DC output end of the bridge rectifier circuit.
[0029]
[Problems to be solved by the invention]
However, such a power supply device has a problem that the components of the power supply device are destroyed due to overcurrent when the bidirectional switch is broken and short-circuited.
The power supply device of the present invention solves such a problem, and it is an object of the present invention to protect the components of the power supply device even if the bidirectional switch of the component is broken and short-circuited.
[0030]
[Means for Solving the Problems]
When the bidirectional switch breaks and is short-circuited, the overcurrent flowing through the connection path connecting the bidirectional switch and the bridge rectifier circuit is detected, and the open / close switch provided in this connection path is opened to perform protective operation in the event of an overcurrent. Provide overcurrent protection means to perform.
[0031]
By providing the above-described overcurrent protection means, the current flowing through the communication path is interrupted to prevent the components of the power supply apparatus from being overcurrent.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to the claim for solving the above-mentioned problems includes an AC power source, a bridge rectifier circuit formed by four diodes for full-wave rectification of AC from the AC power source, and a DC output terminal of the bridge rectifier circuit. A smoothing capacitor connected to the AC power source and a reactor connected between the AC input terminal of the bridge rectifier circuit, and a bidirectional switch between the AC input terminal and the DC output terminal of the bridge rectifier circuit. A capacitor connected through the zero-crossing means, zero-cross detection means for detecting a zero point of the voltage of the AC power supply, and bidirectional switch drive signal generation means for generating a drive signal for the bidirectional switch based on the output of the zero-cross detection means And bi-directional switch driving means for driving the bi-directional switch based on a signal from the bi-directional switch driving signal generating means.
[0033]
By making the bidirectional switch conductive with an appropriate phase and conduction width with such a configuration, it is possible to achieve both suppression of harmonics of the input current and high power factor, and a DC output voltage equal to or higher than the voltage peak value of the AC power supply. Is obtained.
[0034]
In the power supply apparatus according to the present invention described above, when an overcurrent is detected by the overcurrent detection means in order to prevent destruction of the circuit of the power supply apparatus when a failure occurs due to a short circuit of the bidirectional switch, the open / close switch is turned on by the overcurrent protection means. Provide overcurrent protection control to open.
[0035]
Embodiments of the present invention will be described below with reference to the drawings. Components having the same configurations as those of the conventional example will be described with the same numbers.
[0036]
(Embodiment 1)
FIG. 1 shows the operation of overcurrent protection control of a power supply apparatus according to the present invention. When the bidirectional switch 9 is broken and short-circuited, the overcurrent detection means 16 outputs an overcurrent detection signal to the overcurrent protection first means 17. In response to the overcurrent detection signal, a signal for opening the open / close switch 15 is output.
[0037]
Therefore, since the communication path connecting the bidirectional switch 9 and the bridge rectifier circuit 6 is cut off and no current flows, the components of the power supply device are prevented from being destroyed.
[0038]
Even when the overcurrent state is settled, the open / close switch 15 continues to open, so that safety can be ensured.
(Embodiment 2)
FIG. 2 shows an overcurrent protection circuit of a power supply device according to the present invention. In addition, the same number is attached | subjected to the location of the same structure as FIG.
[0039]
As shown in FIG. 2, when the bidirectional switch 9 is broken and short-circuited as the overcurrent protection means 2, the overcurrent determination unit 20 determines the overcurrent reference value 19 and the current value output from the overcurrent detection means 16. Compare.
[0040]
The overcurrent determination unit 20 sends an overcurrent detection signal, and the open / close switch control unit 21 opens the open / close switch 15 to prevent the circuit of the power supply device from being destroyed by interrupting the current.
(Embodiment 3)
FIG. 3 shows an overcurrent protection circuit of a power supply device according to the present invention. Note that parts having the same configuration as in FIG.
[0041]
As shown in FIG. 3, when the bidirectional switch 9 is broken and short-circuited, the output of the overcurrent detection means 16 exceeds the overcurrent reference value (OC1) 19 that sets the overcurrent level and When the three means 22 are reversed, the open / close switch control means 23 opens the open / close switch 15 connected in series with the bidirectional switch 9 to prevent the circuit of the power supply device from being destroyed by interrupting the current.
[0042]
【The invention's effect】
As described above, according to the power supply device of the present invention, even if an overcurrent is generated in the connection path connecting the bidirectional switch and the bridge rectifier circuit, the overcurrent protection that opens the open / close switch that opens and closes the connection path is provided. By providing the means, it is possible to prevent destruction of the components of the power supply device due to overcurrent.
[Brief description of the drawings]
1 is a configuration diagram of a power supply apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram of a power supply apparatus according to Embodiment 2 of the present invention. FIG. 3 is a power supply according to Embodiment 3 of the present invention. FIG. 4 is a block diagram of a conventional power supply apparatus. FIG. 5 is a block diagram of a conventional power supply apparatus. FIG. 7 is a block diagram of a conventional power supply apparatus. 8 is a diagram for explaining the operation of the conventional power supply device. FIG. 9 is a diagram for explaining the operation of the conventional power supply device. FIG. 10 is a diagram for explaining the operation of the conventional power supply device. FIG. 13 is a waveform diagram of a conventional power supply device. FIG. 14 is a waveform diagram of a conventional power supply device. FIG. 15 is a waveform diagram of a conventional power supply device.
DESCRIPTION OF SYMBOLS 1 AC power supply 2, 3, 4, 5 Diode 6 Bridge rectifier circuit 7 Smoothing capacitor 8 Reactor 9 Bidirectional switch 10 Capacitor 11 Load 12 Zero cross detection means 13 Bidirectional switch drive signal generation means 14 Bidirectional switch drive means 15 Open / close switch 16 Overcurrent detection means 17 Overcurrent protection first means 18 Overcurrent protection second means 19 Overcurrent reference value 20 Overcurrent determination section 21 Open / close switch control section 22 Overcurrent protection third means 23 Open / close switch control means 24 OC1

Claims (3)

A power supply device comprising: an AC power supply; a bridge rectification circuit for full-wave rectification of alternating current from the AC power supply; and a smoothing capacitor connected to a DC output terminal of the bridge rectification circuit, the AC power supply and the bridge rectification A reactor connected between the AC input terminal of the circuit, a capacitor connected via a bidirectional switch between the AC input terminal and the DC output terminal of the bridge rectifier circuit, and zero voltage of the AC power supply Zero-cross detection means for detecting a point, bidirectional switch drive signal generation means for generating a drive signal for the bidirectional switch based on the output of the zero-cross detection means, and both based on a signal from the bidirectional switch drive signal generation means A bidirectional switch driving means for driving a bidirectional switch, and a current flowing through a communication path connecting the bidirectional switch and the bridge rectifier circuit. Overcurrent detection means for outputting and an open / close switch for opening and closing the communication path, and overcurrent protection means for opening the open / close switch when the overcurrent detection means detects a current value greater than or equal to a predetermined value. A power supply device comprising: As an overcurrent protection means, an overcurrent reference value for determining an overcurrent is compared with a signal from the overcurrent reference value and the overcurrent detection means, and the signal from the overcurrent detection means exceeds the overcurrent reference value. And an on / off switch control unit that performs control to open the on / off switch when the overcurrent determination unit determines that the overcurrent is detected. Item 1. The power supply device according to Item 1. As the overcurrent protection means, the first input value determined as overcurrent and the current value detected by the overcurrent detection means are set as the second input value, and the first input value is compared with the second input. 2. A power supply apparatus according to claim 1, further comprising an open / close switch control means for opening the open / close switch when the output is inverted when an overcurrent occurs.

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