JP2020141487A - Power supply device - Google Patents

Abstract

To surely perform zero voltage switching when a mechanical relay is closed used in a rush current prevention circuit for suppressing a rush current flowing in a smoothing capacitor in a power supply device for rectifying an AC power supply.SOLUTION: A rush current prevention circuit 20 includes a mechanical sub relay 25, a diode 24, a resistor 26 connected in series between an input terminal 1a and a rectifier 2, and a voltage polarity detector 21 for detecting polarity of an AC voltage applied to the input terminal 1a to output it as a polarity signal. When a sub relay signal for supplying a current to a smoothing capacitor 7 is input, the rush current preventing circuit 20 outputs a drive signal that closes the sub relay by delaying a predetermined time from a zero cross point detected by the polarity signal so that a timing when a contact point of the sub relay 25 becomes closed within a period of polarity of an AC voltage during which the diode 24 is reversely biased.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power supply device, and more particularly to an inrush current prevention circuit that suppresses an inrush current to a smoothing capacitor.

Conventionally, a power supply device provided with an inrush current prevention circuit is provided in the inverter device 100 and the like shown in FIG. 3 (see, for example, Patent Document 1). In the inverter device 100, the voltage output from the fuel cell 102 is input to the booster circuit 104, the booster circuit 104 boosts the input voltage and supplies it to the inverter 105, and the inverter 105 receives the input voltage. After converting to a three-phase power supply, it is output to the motor 109.

Further, the inverter device 100 includes a main relay 103 in series between the fuel cell 102 and the booster circuit 104, and an inrush current prevention circuit 110 is connected in parallel with the main relay 103, and further, the booster circuit 104-2 A smoothing capacitor 101 is connected in parallel with the booster circuit 104 between the two output ends. Further, in the inrush current prevention circuit 110, the resistor 107 and the sub-relay 106 are connected in series.

The control circuit 108 opens both the main relay 103 and the sub relay 106 when the motor 109 is stopped. Then, the control circuit 108 closes the sub-relay 106 before rotating the motor 109, causes a current (inrush current) to flow through the smoothing capacitor 101 via the resistor 107, and raises the voltage of the smoothing capacitor 101 to a predetermined voltage. .. Next, the control circuit 108 closes the main relay 103 and then opens the sub relay 106.

Then, the control circuit 108 operates the booster circuit 104 to boost the input voltage and supplies it to the inverter device 100. Next, the control circuit 108 operates the inverter 105 to rotate the motor 109.

By the way, in mechanical relays, the contact current is specified in the specifications, and by limiting this current to within the specified contact current, it is necessary to prevent contact welding due to the inrush current that flows when the relay is closed. It has become. Therefore, when the capacitance of the smoothing capacitor 101 is fixed and an inexpensive sub-relay 106 having a small contact current is used, the value of the resistor 107 must be increased to make the inrush current equal to or less than the contact current. Naturally, in this case, there is a problem that the time for the voltage of the smoothing capacitor 101 to rise to a predetermined voltage becomes long, and the time until the rotation of the motor 109 starts becomes long.

On the other hand, in order to shorten the time for the voltage of the smoothing capacitor 101 to rise to a predetermined voltage, it is necessary to adopt an expensive sub-relay 106 having a large contact current, which causes a problem of cost increase. Further, in this case, since the inrush current becomes large, it is necessary to select the parts in the booster circuit 104 and the smoothing capacitor 101 having the performance to withstand the large inrush current, which further increases the cost.

In order to solve this problem, the sub-relay 106 can be closed when the current flowing through the sub-relay 106 is the minimum. For example, in the case of an AC power supply device in which a voltage obtained by rectifying the AC voltage is applied to the inrush current prevention circuit 110 instead of the fuel cell 102 in FIG. 3, the contact of the sub-relay 106 is closed at the zero crossing point of the AC voltage. It is sufficient to prevent a large current from suddenly flowing when the sub-relay 106 is closed. That is, this problem can be solved by performing so-called zero voltage switching.

However, mechanical relays have a mechanical delay time from the input of a control signal to the closing of contacts, but this delay time varies depending on the characteristics of each relay, aging, drive voltage, ambient temperature, etc. To do. Therefore, even if a relay with a small contact current standard is used to close the contact of the sub-relay 106 at the zero crossing point of the AC voltage, the contact cannot be closed at the target timing due to the fluctuation of the delay time. Inrush current larger than the contact current standard of the relay may flow.

Japanese Unexamined Patent Publication No. 2005-261040 (paragraph numbers 0014 to 0021)

The present invention solves the above-mentioned problems, and in a power supply device that rectifies an AC power supply, zero voltage switching is performed when the mechanical relay used in the inrush current prevention circuit that suppresses the inrush current flowing through the smoothing capacitor is closed. The purpose is to ensure that.

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention
A pair of input ends to which an AC power supply is connected, a rectifier that rectifies the AC voltage applied to the input ends, and a smoothing capacitor that smoothes the rectified voltage.
An inrush current preventing means connected in series between one of the pair of input ends and the rectifier to suppress an inrush current flowing through the smoothing capacitor.
A power supply device including a control unit that outputs a control signal for opening and closing the relay to the inrush current prevention means.
The inrush current prevention means
A mechanical relay, a diode, and a resistor connected in series between one of the pair of input ends and the rectifier, and the polarity of the AC voltage applied to the pair of input ends are detected and used as a polarity signal. Equipped with a voltage polarity detector to output
The inrush current prevention means
When the control signal for closing the relay is input,
The relay is delayed by a predetermined time from the zero crossing point detected by the polarity signal so that the timing at which the contacts of the relay are closed is within the period of the polarity of the AC voltage which is the reverse voltage in the diode. It is characterized in that a drive signal for closing is output to the relay.

By using the above means, according to the power supply device according to the present invention, the inrush current preventing means closes the relay during the period when no current flows through the diode connected in series with the relay, so that the smoothing capacitor is used. The inrush current can be reduced. Therefore, a relay having a smaller contact current than the relay used in the conventional inrush current prevention circuit system can be adopted.

It is a block diagram which shows the Example of the power supply device by this invention. It is explanatory drawing explaining the operation of the power supply apparatus by this invention. It is a block diagram which shows the conventional power supply device.

Hereinafter, embodiments of the present invention will be described in detail as examples based on the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the power supply device 30 according to the present invention. The power supply device 30 includes an input end 1a and an input end 1b, which are a pair of input ends to which an AC power supply of 50 hertz (not shown) is connected, an output end 6a and an output end 6b from which a DC voltage is output, and an input end 1a. A rectifier 2 that rectifies the output voltage of the AC power supply connected between the input ends 1b, a smoothing capacitor 7 that is connected between the output ends 6a and the output end 6b and smoothes the output voltage of the rectifier 2, and an input end 3e. A switching unit 3 having an input end 3h, an output end 3f, and a common end 3g, and a control unit 5 for outputting a switching pulse signal for driving the switching unit 3 to the input end 3h are provided.

The input end 3e of the switching unit 3 is connected to the output side positive electrode of the rectifier 2, and the common end 3g of the switching unit 3 and the negative electrode end of the smoothing capacitor 7 are connected to the output side negative electrode of the rectifier 2. Further, a main relay 4 is connected in series between the input end 1a and one end on the input side of the rectifier 2, and the contacts of the main relay 4 are opened and closed by the main relay signal output by the control unit 5. The control unit 5 also opens and closes the contacts of the sub-relay, which will be described later.

On the other hand, the switching unit 3 includes an inductor 3a having one end connected to the input terminal 3e, a diode 3b having the other end of the inductor 3a connected to the anode terminal and a cathode terminal connected to the output terminal 3f, and the inductor 3a. It is provided with an IGBT 3c, which is a switching element connected between the end and the common end 3g and turned on / off by an input switching pulse signal. The collector terminal of the IGBT 3c is connected to the other end of the inductor 3a, the emitter terminal is connected to the common end 3g, and the gate terminal is connected to the input end 3h.

In this switching unit 3, the IGBT 3c is connected between the output side positive electrode and the output side negative electrode of the rectifier 2 via an inductor 3a. In the switching unit 3, when the IGBT 3c is in a short-circuited state, a current flows through the inductor 3a and is stored as energy, and then when the IGBT 3c is opened, the stored energy becomes a current and flows from the inductor 3a into the smoothing capacitor 7, resulting in It has a boosting function that raises the voltage of the smoothing capacitor 7.

On the other hand, an inrush current prevention circuit (inrush current prevention means) 20 for suppressing the inrush current to the smoothing capacitor 7 is provided between the input end 1a and the input end 1b and the rectifier 2. The inrush current prevention circuit 20 includes an auxiliary relay (mechanical relay) 25, a diode 24, a resistor 26, and an input terminal 1a connected in series between the input terminal 1a and one input side of the rectifier 2. Output from the voltage polarity detection unit 21 that detects the polarity of the AC voltage applied between the input terminals 1b and outputs it as a polarity signal, the sub-relay signal (control signal) output by the control unit 5, and the voltage polarity detection unit 21. The AND circuit 23, which inputs the polarity signal to be input and outputs the trigger signal which is the logical product of these, and the input trigger signal are delayed by 5 milliseconds for a predetermined time to open and close the sub-relay 25. A delay circuit 22 for outputting a drive signal to be performed is provided. The diode 24 is connected in a direction in which a current flows when a positive half cycle of the AC voltage is applied to the input terminal 1a.

Next, the operation of the power supply device 30 will be described.
Before the power supply device 30 outputs the DC voltage, both the main relay 4 and the sub relay 25 are open, and the IGBT 3c is also off. Then, after the AC power supply is connected to the input terminal 1a and the input terminal 1b, the control unit 5 first raises the sub-relay signal to a high level in order to charge the smoothing capacitor 7. The power supply device 30 includes a DC power supply for control (not shown), and AC power is input to the DC power supply for control from the input terminal 1a and the input terminal 1b. When the AC power supply is input, the control unit 5 And the inrush current prevention circuit 20 is supplied with DC control power such as +5 volt and +12 volt.
Further, in this embodiment, since the power supply device is described as a single unit, the trigger for closing each relay is described as when the AC power supply is turned on, but the present invention is not limited to this, and this power supply device is incorporated. It may be given by an instruction from the device, for example, an instruction to start rotation of the compressor in the air conditioner.

The high-level sub-relay signal is input to one input end of the AND circuit 23 of the inrush current prevention circuit 20. On the other hand, the voltage polarity detection unit 21 outputs a high level polarity signal when the AC voltage has a positive half cycle, and outputs a low level polarity signal when the AC voltage has a negative half cycle. The AND circuit 23 outputs the trigger signal from the low level to the high level to the delay circuit 22 when the AC voltage first becomes a positive half cycle after the sub-relay signal reaches the high level. The delay circuit 22 delays the input signal by 5 milliseconds and then outputs it as a drive signal to the sub-relay 25.

The sub-relay 25 has a mechanical delay time from the input of the control signal to the closing of the contacts, and even if the drive signal changes from the low level (open) state to the high level (closed) state, The contacts of the sub-relay 25 are not actually connected until this mechanical delay time elapses. Further, since this mechanical delay time fluctuates due to various factors as explained in the background art, the sub-relay 25 of this embodiment has a specification of this mechanical delay time of 10 msecond ± 1.5 msecond. However, the fluctuation range may increase further depending on aging and the surrounding environment.

In this embodiment, since the frequency of the AC power supply is 50 hertz, the low-level sub-relay signal becomes high-level, and the predetermined time: 5 milliseconds and the sub-relay from the time when the AC voltage first becomes a positive half cycle. After 15 ms, which is the sum of the 25 mechanical delay times, the contacts of the sub-relay 25 are actually connected. This timing is 5 milliseconds after the AC voltage becomes a negative half cycle, and is the center of the negative half cycle.

Since the period of the reverse voltage in which no current flows through the diode 24 is within this negative half cycle, no current flows through the contacts when the contacts of the sub-relay 25 are actually connected. In addition, since no current flows from the center of this negative half cycle to the front and back for a period of 5 milliseconds, even if the mechanical delay time of the sub-relay 25 fluctuates, it will be a contact within the period of this negative half cycle. No current flows. Further, within this negative half-cycle period, even if chattering occurs at the contact, no current actually flows, so noise generated by intermittent current due to chattering does not occur.

FIG. 2 is an explanatory diagram illustrating the operation of the power supply device 30 including the inrush current prevention circuit 20 according to the present embodiment.
The horizontal axis of FIG. 2 is time, and with respect to the vertical axis, FIG. 2 (1) shows an AC voltage of 50 hertz, FIG. 2 (2) shows an output voltage of a diode 24, and FIG. 2 (3) shows a polarity signal. 2 (4) shows the sub-relay signal, FIG. 2 (5) shows the drive signal, FIG. 2 (6) shows the contact state of the sub-relay 25, and FIG. 2 (7) shows the current flowing through the rectifier 2 (rush according to the present invention). (In the case of a circuit using the current prevention circuit 20), FIG. 2 (8) shows the current flowing through the rectifier (in the case of using the conventional circuit). Note that t0 to t9 are times.

As shown in FIG. 2 (1), the AC voltage has one cycle, for example, a positive half cycle of 10 milliseconds represented by t2 to t4 and a negative half cycle of 10 milliseconds represented by t4 to t7. .. Further, as shown in FIG. 2 (2), when the sub-relay 25, which will be described later, is closed and when the AC voltage is in a positive half cycle, for example, only during the period from t7 to t9, the cathode terminal of the diode 24 The output voltage appears in. Further, as shown in FIG. 2 (3), the polar signal changed from the low level to the high level when the negative half cycle of the AC voltage was switched to the positive half cycle, and switched from the positive half cycle to the negative half cycle. Sometimes it goes from high level to low level. Therefore, this switching timing, for example, t2, t4, t7, t9 becomes the zero crossing point.

As shown in FIG. 2 (4), when the control unit 5 sets the sub-relay signal from low level to high level (instruction to close) at t1, the AND circuit 23 of the inrush current prevention circuit 20 changes the polarity signal from low level at t2. The trigger signal is changed from low level to high level when it changes to high level, that is, at the zero crossing point and at the start of a positive half cycle. The delay circuit 22 to which the trigger signal is input changes the drive signal from low level to high level as shown in FIG. 2 (5) at t3 which is delayed by 5 milliseconds from t2.

The sub-relay 25 to which this drive signal is input starts a mechanical operation so as to connect the contacts, but as described above, the contacts are closed at t5 when the mechanical delay time (10 milliseconds) has elapsed. However, this contact is completely closed at t6 after the chattering period has elapsed. Then, a current (inrush current) starts to flow in the rectifier 2 from t7, which is the next positive half cycle, as shown in FIG. 2 (7). However, the current flowing after t7 increases gently according to the sine waveform in which the AC voltage rises from zero volt. The peak current at this time is 15 amperes at t8. After that, the peak current becomes 15 amperes every positive half cycle.

The charge accumulated in the smoothing capacitor 7 at a certain voltage is fixed. Therefore, in order to accumulate this charge in a short time, it is accumulated at once with a large current. Therefore, the peak current becomes large. However, the magnitude of the current that can be passed is defined by the characteristics of the capacitor. On the other hand, when accumulating for a long time, it may be accumulated gradually with a small current. In the case of this embodiment, the current flowing into the smoothing capacitor 7 gradually increases as the instantaneous value of the AC voltage increases from the time when the AC voltage is zero volt. That is, since the current flowing through the smoothing capacitor 7 is dispersed in time, the peak current can be suppressed.

On the other hand, when a conventional circuit (diode 24 is not installed) is used as shown in FIG. 2 (8), the contact of the sub-relay 25 is closed first at t5 when the peak voltage is reached in a negative half cycle. In the case, the inrush current is 20 amperes at the peak current. Further, the contact current will flow a plurality of times due to the contact chattering. Therefore, it is necessary to adopt a relay having a larger contact current than the relay used in this embodiment.

As described above, the inrush current prevention circuit 20 closes the sub-relay 25 while the current does not flow through the diode 24 connected in series with the sub-relay 25, so that the inrush current to the smoothing capacitor 7 is reduced. can do. Therefore, a relay having a smaller contact current than the relay used in the conventional inrush current prevention circuit can be adopted.

1a Input end 1b Input end 2 Rectifier 3 Switching part 3a Inductor 3b Diode 3c IGBT
3e Input end 3f Output end 3g Common end 3h Input end 4 Main relay 5 Control unit 6a Output end 6b Output end 7 Smoothing capacitor 20 Inrush current prevention circuit (Inrush current prevention means)
21 Voltage polarity detector 22 Delay circuit 23 AND circuit 24 Diode 25 Secondary relay 26 Resistor 30 Power supply

Claims (1)

A pair of input ends to which an AC power supply is connected, a rectifier that rectifies the AC voltage applied to the input ends, and a smoothing capacitor that smoothes the rectified voltage.
An inrush current preventing means connected in series between one of the pair of input ends and the rectifier to suppress an inrush current flowing through the smoothing capacitor.
A power supply device including a control unit that outputs a control signal for opening and closing the relay to the inrush current prevention means.
The inrush current prevention means
A mechanical relay, a diode, and a resistor connected in series between one of the pair of input ends and the rectifier, and the polarity of the AC voltage applied to the pair of input ends are detected and used as a polarity signal. Equipped with a voltage polarity detector to output
The inrush current prevention means
When the control signal for closing the relay is input,
The relay is delayed by a predetermined time from the zero crossing point detected by the polarity signal so that the timing at which the contacts of the relay are closed is within the period of the polarity of the AC voltage which is the reverse voltage in the diode. A power supply device characterized in that a drive signal for closing is output to the relay.

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