JP4158487B2 - Safety power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply device that uses a switching element to control an output voltage to be constant, and more particularly to a safety power supply device that can safely cut a power supply circuit when a hybrid IC is short-circuited.
[0002]
[Prior art]
As a conventional power supply circuit in a power supply device, for example, as shown in FIG. 2, a hybrid IC including a switch b, a control unit c for controlling the switch b, and a power device d, and a current detection resistor e between AC voltage input terminals. And fuses a and the like are known.
[0003]
However, in such a conventional device, when a short circuit failure occurs between the high voltage part and the terminal of the hybrid IC, an excessive current flows into the current detection resistor e, causing the current detection resistor e to be broken open and causing a fuse. Since a does not melt safely, there is a risk that the voltage applied to the power device d suddenly increases and the power device bursts.
[0004]
Therefore, a switching power supply is proposed in which a protective diode connected in reverse polarity is connected in parallel with the current detection resistor to cut a large current through the fuse by receiving a voltage exceeding the reverse breakdown voltage when the switching element is short-circuited and breaking. (For example, refer to Patent Document 1).
[0005]
[Patent Document 1]
JP-A-2001-145339
[Problems to be solved by the invention]
However, in Patent Document 1, when the voltage applied to the switching element that is a power device is smaller than the voltage that destroys the diode, the current detection resistor is opened and the surge current does not flow into the fuse. Since the overvoltage is applied to the control unit that controls the voltage, it is impossible to prevent the control unit from being destroyed.In other words, it is difficult to adjust the voltage at which the diode breaks and the voltage at which the switching element breaks down. It is left.
[0007]
In addition, a protective diode has to be newly added, and an increase in cost due to an increase in the number of parts is inevitable.
[0008]
Conventionally, in order to ensure safety, safety is reflected in the design so that it does not become a dangerous state as a device (circuit) even in an abnormal state. A third party organization, UL (USA), CSA (Canada), VDE (Germany), etc., is requested to be evaluated and certified as conforming to each standard, and must be a safety standard compliant product. To users as product value. That is, when supplying power products as global products, compliance with safety standards cannot be avoided.
[0009]
However, it is becoming more important to ensure safety against the background of the recent increase in safety requirements and the importance of responsibility regarding PL / PS as a manufacturer.
[0010]
On the other hand, along with demands for downsizing of devices, power devices used in power supply devices have been actively integrated with components (hybrid ICs), and single failure of components has become complicated.
[0011]
In order to ensure the safety as a device by fusing fuses safely in all of the complicated failure modes, it is difficult to select fuse characteristics. This is because, when trying to maintain safety as a fusing characteristic of the fuse, there is a trade-off in which the fuse life during normal use is shortened.
[0012]
When the fuse does not blow safely, if an abnormality (short between terminals) occurs in the integrated power device part, it becomes a large electric energy, which leads to a blast and disperses sparks.
[0013]
The blasting mechanism at this time has been elucidated as follows. (1) Abnormality caused by short circuit between terminals, (2) Excessive current flows into the current detection resistor, (3) Current detection resistance increases and open breakdown, (4) Increase in applied voltage of power device, 5 ▼ The power device bursts and sparks are generated.
[0014]
The present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide an inexpensive safety power supply apparatus that can safely turn off a power supply circuit even if an abnormality occurs in a hybrid IC.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a safety power supply apparatus in which a fuse, a switching element, and a current detection resistor are connected in series between voltage input terminals, and a hybrid IC is provided. By providing in series a power device provided in the hybrid IC and a ground line with a surge-resistant high current element that cannot be blown by a surge current caused by a short-circuit failure occurring between terminals, a surge current is supplied to the fuse. It is configured to be meltable by flowing.
[0016]
Accordingly, in the present invention, since a high surge current resistant element that cannot be blown by a surge current is provided in series between the power device and the ground line, a short circuit failure occurs between the hybrid IC and the terminal, resulting in a high surge current resistant element. Even if an excessive current flows, a high surge current resistant element will not blow regardless of the voltage applied to the power device such as a switching element, so the fuse will always be blown. Can be secured. Further, since the high surge current-resistant element has a function as a current detection resistor, the number of parts is not increased even though safety is ensured, and thus the cost can be reduced. Furthermore, since the high surge current resistant elements are simply provided in series, the power supply circuit can be configured simply.
[0017]
Further, the present invention is a safety power supply apparatus in which a fuse, a switching element, and a current detection resistor are connected in series between voltage input terminals and a hybrid IC is provided, and is generated between a high voltage portion of the hybrid IC and a terminal. By providing a low surge current element that can be blown by a surge current caused by a short circuit failure in the high voltage portion of the hybrid IC, either the low surge current element or the fuse is configured to be blown.
[0018]
Therefore, in the present invention, since the low surge current element that can be blown by surge current is provided in the high voltage portion of the hybrid IC, when a short circuit failure occurs in the hybrid IC between the terminals on the fuse side, the surge current Flows into the control section, which is a low voltage section, so that either the low surge current element or the fuse can be surely blown, thereby ensuring stable safety.
[0019]
Furthermore, the present invention is a safety power supply apparatus in which a fuse, a switching element, and a current detection resistor are connected in series between voltage input terminals and a hybrid IC is provided, and is generated between a high voltage portion and the terminal of the hybrid IC. A high surge current-resistant element that cannot be blown by a surge current caused by a short-circuit failure is provided between the switching element and the ground line so that a surge current flows through the fuse so that the fuse can be blown. By providing a low surge current resistant element that can be melted by a surge current caused by a short circuit fault occurring between the high voltage portion and the terminal in the high voltage portion of the hybrid IC, either the low surge current resistant element or the fuse It is configured to be capable of fusing.
[0020]
Therefore, according to the present invention, even if a short circuit failure occurs in the hybrid IC on either the primary side or the fuse side of the power device, it is possible to prevent destruction of the power device at low cost and stably.
[0021]
Furthermore, in the present invention, the high surge current resistant element may be selected from metal resistance, surge resistance or metal, and the low surge current resistant element may be composed of a square chip resistance, a carbon film resistance or a fuse resistance. Conceivable.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a safety power supply apparatus according to the present invention will be described with reference to the drawings.
[0023]
A fuse F, a thermistor resistor 1, a noise filter 2 and a rectifier bridge 3 are DC-connected between the input terminals of the AC voltage, and further, a first winding L1 composed of a transformer primary winding L1 and a MOSFET following the rectifier bridge 3. The switching element 4 and the current detection resistor 5 are DC-connected.
[0024]
Furthermore, a hybrid IC connected to the ground line is provided between the boost inductor 9 and the primary winding L1 of the transformer. The hybrid IC is for adjusting the input current into a sine wave shape that is similar to an AC voltage and suppressing a harmonic current that is normally generated. The hybrid IC includes a second switching element 6, a rectifying element 7 and a MOSFET. The first control unit 8 that controls on / off of the second switching element 6 is provided, and the present invention further includes a low surge current resistant element 15 in addition to these.
[0025]
The low surge current element 15 is connected in series between the rectifier bridge 3 and the terminal 103 of the hybrid IC. The low surge current element 15 has a resistance that is easily blown by a surge current, for example, a surge withstand capability, and a value obtained by multiplying the square of the current I by time t is in the range of about 20 to 60 [square of A / SEC]. Use square chip resistor, carbon film resistor or fuse resistor.
[0026]
The second switching element 6 is connected between the step-up inductor 9 and the rectifying element 7 and a terminal 104 of a hybrid IC, which will be described later, and a high surge current resistance between the second switching element 6 and the ground line. Element 10 is connected. The high surge withstand current element 10 has a resistance with a sufficiently large surge resistance, for example, a surge withstand value of a value obtained by multiplying the square of the current I by time t within a range of about 400 to 800 [square of A / SEC]. It is selected from a certain metal plate resistance, surge resistance or metal. Furthermore, the voltage at both ends of the low surge current resistant element 15 and the rectifying element 7 is input to the first control unit 8.
[0027]
The hybrid IC is composed of a package element, and includes a first terminal 101 between the boost inductor 9 and the rectifier element 7, a second terminal 102 between the rectifier element 7 and the primary winding L1 of the transformer, and a low surge current resistance. A third terminal 103 is connected between the element 15 and the first control unit 8, a fourth terminal 104 is connected between the second switching element 6 and the high surge current resistant element 10, and the first control unit 8 is connected to the ground line. A fifth contact 105 is provided between the capacitor C1 and a sixth terminal 106 which is located on the ground line side and directly connected to the ground line.
[0028]
On the other hand, a rectifying / smoothing circuit including a diode 11 and a capacitor 12 is connected to the secondary winding L2 of the transformer, and an output voltage is supplied from the output terminal to the load. This output voltage is detected by the voltage detection unit 13 and compared with a reference voltage, and the error is fed back to the second control unit 14 via a photocoupler as a control amount. The second control unit 14 matches the output current with the required value by changing the ON / OFF interval of the first switching element 4 according to the control amount.
[0029]
When the output voltage becomes an overvoltage that is equal to or higher than a predetermined voltage value, the overvoltage detection unit 13a detects the output voltage, and the detection signal is fed back to the second control unit 14. Then, the second control unit 14 turns off the first switching element 4 and controls the output voltage to zero.
[0030]
On the other hand, when an overcurrent is detected on the primary side of the transformer by the current detection resistor 5, the detection signal is fed back to the second control unit 14. Accordingly, the second control unit 14 limits the output current by changing the ON / OFF interval of the first switching element 4.
[0031]
Next, how the safety is ensured when the hybrid IC is short-circuited will be described. The region including the low surge current resistant element 15 and the rectifying element 7 is at a high voltage. For example, between this high voltage portion and the fourth terminal 104, that is, between the second terminal 102 and the fourth terminal 104. If a short-circuit failure occurs, assuming that the surge resistance of the high surge current-resistant element 10 is small, the hybrid IC will rupture following the course shown in the flowchart in FIG. That is, when an excessive current flows into the high surge current resistant element 10, if the fuse F is blown, the circuit is disconnected and safety is maintained, but when the surge resistance of the high surge current resistant element 10 is small, Since the high surge current-resistant element 10 is blown and the fuse is not blown, the hybrid IC is applied to a high voltage, resulting in a rupture.
[0032]
However, in the present invention, the high surge current-resistant element 10 is composed of a resistor having a sufficient surge resistance, so that the fuse F is blown without being blown. Therefore, as shown in the flowchart in FIG. 3, a high voltage is not applied to the second switching element 6, and thus the destruction of the rectifying element 7 as a power device is prevented.
[0033]
On the other hand, if a short circuit failure occurs between the high voltage portion and the other terminals, for example, between the first terminal 103 and the fifth terminal 105, if the low surge current element 15 is not provided, The hybrid IC bursts following the process shown in the flowchart in FIG. In other words, when an excessive current flows into the first control unit 8 which is a low voltage part, safety is maintained if the fuse F is blown, but if the fuse F is not blown, the hybrid IC will burst. It reaches.
[0034]
However, in the present invention, since the low surge-resistant element 15 is provided, when a high voltage is applied to the first control unit 8 and an excessive current flows, as shown in the flowchart of FIG. Safety is ensured because the low surge current resistant element 15 is melted even if it does not melt.
[0035]
FIG. 6 shows an explosion-proof cover that accommodates the hybrid IC package. The peripheral wall 51 is erected from the outer peripheral portion of the bottom plate 50 on which the hybrid IC substrate on which the power device 7 and the first control unit 8 are mounted, A part of the peripheral wall 51 is formed into a fragile portion that can be broken by the bursting of the power device.
[0036]
If the fragile part is not provided, the cover will be blown off in all directions due to the rupture of the power device, but it is dangerous, but by providing the fragile part, the blast will flow out toward the fragile part. Can be directed in a safe direction.
[0037]
Note that an opening may be formed instead of the fragile portion, or the fragile portion may be formed so as to be deformable by a blast. This is because the energy of bursting can be absorbed by deformation.
[0038]
【The invention's effect】
According to the first aspect of the present invention, since a high surge current element that cannot be melted by a surge current is provided in series between the switching element and the ground line, a short circuit failure occurs between the hybrid IC and the terminal, resulting in a high surge current resistance. Even if an excessive current flows into the element, the high surge current-resistant element does not blow regardless of the voltage applied to the power device such as a switching element, so the fuse is surely blown and thus stable. Safety can be ensured. Further, since the high surge current-resistant element has a function as a current detection resistor, the number of points is not increased despite the safety being ensured, and thus the cost can be reduced. Furthermore, since the high surge current resistant elements are simply provided in series, the power supply circuit can be configured simply.
[0039]
In the invention according to claim 2, since the low surge current element that can be melted by a surge current is provided in the high voltage portion of the hybrid IC, when a short circuit failure occurs in the hybrid IC between the terminals on the fuse side, Since the surge current flows into the control unit, which is a low voltage unit, either the low surge current resistant element or the fuse can be surely blown, and thus stable safety can be ensured.
[0040]
According to the third aspect of the present invention, even if a short circuit failure occurs in the hybrid IC on either the primary side or the fuse side of the power device, it is possible to prevent destruction of the power device at low cost and stably.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a safety power supply apparatus according to the present invention.
FIG. 2 is a flowchart according to a conventional configuration when a short-circuit failure occurs between a high voltage portion of a hybrid IC and a terminal 104;
FIG. 3 is a flowchart according to the configuration of the present invention when a short-circuit failure occurs between the high voltage portion of the hybrid IC and the terminal 104;
FIG. 4 is a flowchart according to a conventional configuration when a short-circuit failure occurs between a high voltage portion of a hybrid IC and a terminal 105;
FIG. 5 is a flowchart according to the configuration of the present invention in the case where a short-circuit failure occurs between the high voltage portion of the hybrid IC and the terminal 105.
FIG. 6 is a perspective view showing an explosion-proof cover of a hybrid IC in the safety power supply device according to the present invention.
FIG. 7 is a circuit diagram showing an outline of a circuit in a conventional power supply device.
[Explanation of symbols]
4 First switching element 5 Current detection resistor 6 Second switching element 8 First control unit 9 Step-up inductor 10 High surge withstand current element 14 Second control unit 15 Low surge withstand current element

Claims (5)

A safety power supply device in which a fuse, a switching element, and a current detection resistor are connected in series between voltage input terminals and a hybrid IC is provided,
A high surge current element that cannot be blown by a surge current caused by a short-circuit failure occurring between a high voltage portion and a terminal of the hybrid IC is provided in series between a power device provided in the hybrid IC and a ground line. Thus, a safety power supply device is constructed so that a surge current is allowed to flow through the fuse and can be blown. A safety power supply device in which a fuse, a switching element, and a current detection resistor are connected in series between voltage input terminals and a hybrid IC is provided,
By providing a low surge current element that can be melted by a surge current caused by a short-circuit failure occurring between the high voltage part and the terminal of the hybrid IC in the high voltage part of the hybrid IC, the low surge current element or A safety power supply device, wherein any one of the fuses is configured to be blown. A safety power supply device in which a fuse, a switching element, and a current detection resistor are connected in series between voltage input terminals and a hybrid IC is provided,
By providing, between the switching element and the ground line, a surge current that cannot be blown by a surge current caused by a short-circuit failure occurring between the high-voltage portion and the terminal of the hybrid IC, the surge current is supplied to the fuse. A low surge resistant current element that can be blown by a surge current caused by a short-circuit failure occurring between the high voltage portion of the hybrid IC and a terminal is provided in the high voltage portion of the hybrid IC. Thus, either the low surge current element or the fuse can be blown. 4. The safety power supply device according to claim 1, wherein the high surge current resistant element is selected from metal plate resistance, surge resistance or metal. 4. The safety power supply device according to claim 2, wherein the low surge current-resistant element is composed of a square chip resistor, a carbon film resistor, or a fuse resistor.

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