KR20060053876A - Power source protecting device - Google Patents

Abstract

When a voltage higher than the input guarantee range is supplied to the power source, the operation of the power supply is reliably stopped at low cost, thereby reliably protecting internal components such as the switching element. In the flyback switching power supply, an excessive voltage which continuously stops the control unit 2 when the control unit 2 for controlling switching and the output voltage of the auxiliary winding 4a of the switching transformer 4 are detected to reach a predetermined level or more. A detection section 6 and a feedback section 5 for feeding back the secondary output of the switching transformer 4 to the control section 2, wherein the switching transformer 4 has an excess voltage detecting winding 4b wound in the forward direction. ), And when an excessive voltage is applied, the control power supply is continuously stopped to protect the switching element 3 and the like.

Description

Power protection device {POWER SOURCE PROTECTING DEVICE}

1 is a configuration diagram of a power supply protection device in a first embodiment of the present invention.

2 is a representative waveform diagram of a forward operation of the configuration of FIG. 1;

3 is a waveform diagram of an applied voltage to an excess voltage detector of the configuration of FIG. 1;

4 is a configuration diagram of a power supply protection device in a second embodiment of the present invention.

5 is a configuration diagram of a power supply protection device in a third embodiment of the present invention.

6 is a configuration diagram of a conventional power protection device.

7 is a representative waveform diagram of a flyback operation in the configuration of FIG. 6; FIG.

* Explanation of symbols for main parts of the drawings

1: rectifier

2: control unit

3: switching element

4: switching transformer

4a: auxiliary winding

4b: overvoltage detection winding

4c: output winding

5: feedback

6: excess voltage detector

7: microcomputer

8: display

9: input section

10: By-pass section

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for a switching power supply (hereinafter also referred to as a "power supply protection circuit") that draws out power by high frequency switching.

The breakdown voltage protection of the conventional main switching element is carried out assuming a country such as Japan having a commercial power supply of 100 V and 200 V as a power source. The structure of the withstand voltage protection of such a main switching element is a 1st structure example, The surge absorption element which becomes a short circuit mode by the application of a fixed voltage or more, and the electric current which interrupts a circuit by the electric current at the time of short circuit mode. As the second configuration example, a wide input standard having a wide input voltage range was set. As a third configuration example, an excessive voltage application was detected to cut off the circuit by a switch element. See, for example, Patent Documents 1 to 3). In the following description, it is assumed that a certain voltage or overvoltage means a voltage higher than the input guarantee range of the power supply.

FIG. 6 is a circuit configuration diagram of a conventional protection device for a conventional flyback switching power supply. FIG. 7 is a typical operation waveform diagram, and FIG. 7A illustrates an input switching operation of the switching transformer to the primary winding. b) shows the timing of power supply to the flyback winding on the secondary side.

A representative example of a conventional protection device for a flyback type switching power supply will be described with reference to FIGS. 6 and 7. In the structure shown in the same figure, the switching element 3 is controlled by high frequency switching by the control part 2 using the DC voltage rectified by the rectifier 1 as a power supply, Power the flyback winding on the side.

To start the power supply, a constant current is supplied from the starter circuit. That is, the switching element 3 is configured to start the switching operation because the primary DC input exceeds a certain value. After the power supply is started, the switching operation is continued using the voltage Vds obtained by the output current Id from the auxiliary winding of the switching transformer 4 as the control power supply. In the flyback type DC converter, energy is accumulated in the switching transformer 4 in the ON period of the main switching element 3 shown as Ton1 in FIG. 7, and in FIG. 7B in the OFF period. The power release is performed by repeating the operation of supplying power to the secondary side as shown by the output current Id shown by high frequency switching. Moreover, the secondary output voltage is fed back to the control part 2 of the primary side by the feedback 5, and the secondary output is stabilized.

Here, when AC 200V is applied to the switching power supply designed for AC 100V due to construction problems or the like, the DC voltage after rectification is applied twice the normal voltage and exceeds the breakdown voltage of the switching element. In the case of a device such as an inverter type separate air conditioner, AC 200V is applied to an outdoor unit for AC 100V, and the internal pressure of the outdoor component becomes a problem.

(Patent Document 1)

Japanese Patent Application Laid-Open No. 62-225165

(Patent Document 2)

Japanese Patent Application Laid-Open No. 11-83116

(Patent Document 3)

Japanese Patent Application Laid-Open No. 2000-346427

In the first configuration example of the prior art, parts breakdown is involved, and replacement of parts is required to recover the device. In the second configuration example, high breakdown voltage of the main switching element is required, and winding standards such as switching transformers are complicated in order to satisfy the regulation standard over a wide range, and both contribute to the component cost.

In Patent Document 1 of the third configuration example, when the overvoltage detection winding and the overvoltage detection circuit are constituted, and when a voltage is input at a predetermined level or more, the overvoltage detection dedicated circuit operates by the corresponding detection voltage. It is disclosed to stop the main switching element. In addition, in the structural examples of Patent Literature 2 and Patent Literature 3, by the action of the excess voltage detection circuit configured on the secondary side of the power supply, a part of the secondary side circuit is cut off when a certain voltage or more is applied, thereby preventing the influence of the excessive voltage. Is described. The structural example of these patent documents 1-3 protects a switching element by stopping a power supply by detecting an excessive voltage application. In such a configuration, the output of the secondary side and the excessive voltage detection winding is reduced by stopping the operation of the switching element. For this reason, the result of the excessive voltage detection is reset, and the switching power supply is a repetitive operation in which the operation starts again. Therefore, the power supply to the load due to the excessive voltage continues continuously.

In addition, the structural example of patent documents 2 and 3 is a technique which tries to prevent the destruction of the secondary side circuit by an excessive voltage application by interrupting the power supply secondary side circuit after an excess voltage detection circuit. However, in such a configuration, the application of the excessive voltage to the primary side input remains a state. Moreover, in the structure of patent documents 1-3, operation | movement as an apparatus is stopped, without specifying the cause of a stop, in order to complete protection to an excess voltage only in the power supply periphery. For this reason, there existed a subject that it was hard to know on the user side that the cause of stopping was an abnormality of excessive voltage application.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. When an excessive voltage is applied to the power supply, the operation of the power supply is stopped at a low cost, and the breakdown of components such as switching elements is prevented, An object of the present invention is to provide a power supply protection circuit that also prevents the influence. It is also an object of the present invention to provide a power supply protection circuit which indicates that an excessive voltage application is abnormal and makes it easy for the user to understand the cause of the stop.

In order to solve the above-mentioned problems, the present invention provides a high-precision detection of an excessive voltage by adding the forward winding sensitive to the change of the primary input voltage and the output of the flyback winding sensitive to the change of the secondary output voltage. It is characterized by. Specifically, the power supply protection device according to the first aspect of the present invention is a protection device for a flyback switching power supply for supplying power to a load, the switching element performing a high frequency switching operation using DC power as the power supply, and the switching. A control unit for controlling the high frequency switching operation of the element, a switching transformer for obtaining supply power to the secondary winding by using the power obtained by the high frequency switching operation of the switching element as the input to the primary winding, and a secondary output of the switching transformer. A switching power supply having a feedback section for feeding an output of a winding to the control unit to stabilize the secondary output, wherein the secondary winding of the switching transformer comprises at least one output winding for outputting a low voltage for supplying power to the load. And a flyback auxiliary winding for supplying power for the controller, and for detecting an excessive voltage. It has the over-voltage detection winding, and the over-voltage detection winding is a winding wound in the forward direction to the input in parallel with the flyback secondary winding.

And an overvoltage detector for detecting a combined value of the output voltage of the overvoltage detecting winding and the output voltage of the flyback auxiliary winding and determining whether the combined value is at a level higher than or equal to a certain level. The high frequency switching control of the switching element using the output voltage of the flyback auxiliary winding as a power source, and when the excess voltage detection unit determines that the combined value of the output voltage is a certain level or more, latches the state of the control unit. It is characterized by continuing to stop the operation.

It is good also as a structure which provided the excess voltage detection part in the control part in the said 1st characteristic.

In the power supply protection device according to the second aspect of the present invention, in the first aspect of the present invention, the excess voltage detection unit is provided on the secondary side of the switching transformer independently of the control unit, and is disposed on the output side of the excess voltage detection unit. When the computer is connected and the microcomputer detects an abnormality of excessive voltage application, the operation of the control unit is stopped and the standby state is set.

In the second aspect, the display portion may be connected to the output side of the microcomputer, and the display portion may be configured to display an abnormality of the excessive voltage application detected by the microcomputer.

In the second aspect of the present invention, a power supply protection device according to a third aspect of the present invention includes a bypass portion having a switching function connected in parallel to an input portion having a constant DC resistance value and connected in parallel to the input portion, The bypass portion is controlled by a microcomputer.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described with reference to an accompanying drawing. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted for simplicity.

(First embodiment)

1 is a configuration diagram of a power supply protection device according to a first embodiment of the present invention, FIG. 2 is a representative operation waveform diagram, and FIG. 3 is a waveform diagram showing an example of a change in the applied voltage to the excess voltage detection unit. to be. Below, the structure and operation | movement of the power supply protection apparatus of 1st Embodiment are demonstrated with reference to FIGS.

As shown in Fig. 1, the basic configuration of the power supply protection device according to the first embodiment is activated by the rise of the DC voltage of the primary input, and after the startup of the switching transformer 4 fed back from the secondary side. And a flyback switching power supply for continuing the switching operation by the voltage Vds generated by the output current Idl of the auxiliary winding 4a.

In the first embodiment, in the flyback type switching power supply, an excess voltage detecting winding 4b wound in the forward direction is connected in parallel to the auxiliary winding 4a wound on the flyback, which is a control power supply supplied to the control unit. It features.

In this flyback type switching power supply, the control unit 2 includes the excess voltage detecting unit 6 and uses the output Idl of the auxiliary winding 4a as a power source to make the main switching element 3 such as a FET high frequency. Switching control. The excessive voltage detection unit 6 detects the output voltage of the auxiliary winding 4a, and when the output voltage reaches a predetermined level or more, latches the state to stop the control unit 2 continuously.

That is, the excess voltage detection unit 6 determines the output state when the voltage level determination unit 6a that determines whether the detected output voltage value is at or above a predetermined level and the voltage detection value are at or above a predetermined level. A latch circuit 6b held until there is another input and a blocking means 6c such as a relay forcibly interrupting the operation of the control unit 2 by forcibly cutting off the switching power supply are possible. As described above, in the present first embodiment, when an excessive voltage is applied, the excessive voltage detection unit 6 forcibly stops the switching power supply and, in order to continue the stop, the apparatus is in a state of not operating at all. The voltage level determination, latching and blocking means can also be performed by control by a microcomputer.

The switching transformer 4 has at least one output winding 4c which outputs a low voltage, and outputs the low voltage corresponding to the winding specification to the secondary by the high frequency switching of the main switching element 3, and supplies it to the load. In addition, the switching transformer 4 has an auxiliary winding 4a for generating a power supply for the controller, and an excessive voltage detection winding 4b wound in the forward direction so as to be inputted in parallel to the auxiliary winding. The feedback part 5 feeds the output voltage of the secondary side output winding 4c of the switching transformer 4 back to the control part 2 of a primary side, and stabilizes a secondary side output.

In the above configuration, after starting the switching power supply, switching is continued using the voltage Vds obtained by the output current Idl from the auxiliary winding 4a of the switching transformer 4 as the control power supply. That is, the operation of accumulating energy in the switching transformer 4 in the ON period of the main switching element 3 represented by Ton1 in FIG. 2 and performing power supply to the secondary side in the OFF period is performed at a high frequency. Power dissipation is performed by repeating the switching. In addition, as shown in FIG. 2, in the ON period Ton1 of the main switching element 3 which is the timing of supplying power to the secondary side of the overvoltage detecting winding 4b which is the forward winding, the excess voltage detecting winding 4b Output current Id2 is generated.

In addition, the specification of the excessive voltage detection winding 4b is that in the input guarantee range (for example, less than 150 V AC) of the power supply designed for AC 100V, the output voltage (Vd2 of FIG. 3) is the auxiliary winding output for power supply (FIG. 3). Vdl) or less, and the minimum value of the AC 200V (175V in consideration of -15%) is used as the standard for reaching an excessive voltage detection level.

3 shows an example of the change in the voltage applied to the excess voltage detection unit 6. As shown in the figure, normally, the flyback winding output Vdl of the auxiliary winding 4a for power supply is retained as a magnetic energy in a switching transformer at the time when the main switching element 3 is ON. In the off time, the output Vd2 of the forward winding (excessive voltage detection winding 4b) becomes the opposite operation to Vdl. By the above operation, the flyback winding 4a and the forward winding 4b are connected in parallel, and their synthesized output is used as the secondary power source to control the power supply. By inputting this secondary power supply output to the excess voltage detection part 6, it is comprised so that it may respond sensitively to the change of a primary side input voltage.

When the excessive voltage is detected by the voltage level determining unit 6a, the excessive voltage detector 6 maintains the result of the excessive voltage detection in the latch circuit 6b, and forcibly cuts off the switching power supply to control the controller. The operation of (2) is stopped continuously. As a result, for example, when a commercial power supply of AC 200V is applied in the AC 100V standard, the switching power supply can be stopped quickly and reliably, and the main switching element and the circuits after the switching power supply are doubled. It can protect against component breakdown by applying excessive voltage such as electromagnetism. In addition, in this embodiment, although it demonstrated in the structural example using the rectifier circuit of the AC power which incorporated the DC power as a power supply, the structural example which used DC power supply, such as a separate DC power supply device or a battery, may be sufficient.

(2nd Embodiment)

4 is a configuration diagram of a power supply protection device according to a second embodiment of the present invention. Below, the structure and operation | movement of the power supply protection apparatus of 2nd Embodiment are demonstrated with reference to FIG.

In FIG. 4, the power protection device of the second embodiment includes an overvoltage detection unit 6 independent of the control unit 2, and executes control of the device based on the detection result of the output voltage. When monitoring at (7) and detecting an excessive voltage, such as the voltage at the time of application of a double voltage, for example, all control is stopped and it is made into the standby state. Moreover, the display part 8 connected to the microcomputer 7 is set as the structure which performs abnormal display like flashing of a specific monitor LED.

In the first embodiment, when an excessive voltage is applied, the excessive voltage detection unit 6 forcibly stops the switching power supply and, in order to continue the stop, the apparatus is in a state of not operating at all. Therefore, even if the user of a device is a construction problem, for example, applying 200V to a 100V standard device, the user does not know the cause of stopping the device.

In the second embodiment, the apparatus is placed in a standby state, whereby an abnormal output is applied to the secondary side circuit of the power supply, a system for supplying commercial power to the next stage, such as an inverter type separate air conditioner, and the like. It is possible to prevent the damage from expanding by applying an excessive voltage.

In addition, by displaying the abnormality, the user can immediately determine that the device is in a stopped state by applying the double voltage, and can quickly cope with a construction problem or the like.

In addition, since excessive voltage detection always operates even during normal input, in the configuration of detecting excessive voltage on the primary side, power loss is large and standby power increases, but detection of excess voltage is performed in the circuit on the secondary side. In this configuration, power consumption by the detection circuit can be reduced.

(Third Embodiment)

5 is a configuration diagram of a power protection device according to a third embodiment of the present invention. Below, the structure and operation | movement of the power supply protection apparatus of 3rd Embodiment are demonstrated with reference to FIG.

In FIG. 5, the power supply protection device of 3rd Embodiment is connected to the input part 9 which has a constant DC resistance value R in the rectification circuit 1 which is a DC voltage generation circuit, and is connected in parallel with the said input part 9. In FIG. A bypass section 10 having a switching function is provided, and the bypass section 10 is controlled by the microcomputer 7. With such a configuration, when an excessive voltage such as a double voltage is applied, a voltage drop occurs due to the DC resistance portion R of the input unit 9, and the input to the rectifier circuit 1 decreases due to the voltage drop. Therefore, the voltage applied to the switching power supply becomes equal to or less than the maximum value of the input guarantee.

Thus, in the structure of 3rd Embodiment, it is not necessary to make a component breakdown voltage into the specification which considered the excessive voltage of the double voltage application state, and can lower a component cost.

In addition, when the normal input voltage (AC 100V) is applied, the switching unit 10 can be short-circuited by operating the bypass unit 10 to operate the switching power supply as a normal input.

The power supply protection device according to the first aspect of the present invention can stop the switching operation of the power supply when an excessive voltage is applied, thereby protecting the main switching element and eliminating the influence on the circuits after the secondary side.

The power supply protection device according to the second aspect of the present invention transmits an excessive voltage detection to a microcomputer that is a main control device of the device, thereby preventing damage to the device such as application of an excessive voltage to an outdoor unit of an air conditioner. Prevent magnification. In addition, by displaying the result, it is possible to inform the user of the device what problem is occurring.

The power supply protection device according to the third aspect of the present invention provides an input portion having a constant DC resistance or more and a bypass portion for bypassing the input portion, so that when an excessive voltage is applied, the input lowered due to the voltage drop of the DC resistance. Since the voltage is applied to the power supply, the breakdown voltage protection of the switching power supply primary part including the rectifier circuit part can be performed.

The power supply protection device according to the present invention can be applied to a switching power supply that generates a circuit voltage by high frequency switching, and can also be applied to an application device using the power supply as a control power supply.

Claims (5)

A protective device for a flyback switching power supply for supplying power to a load, A switching element that performs a high frequency switching operation using DC power as a power source, A control unit for controlling a high frequency switching operation of the switching element; A switching transformer which obtains supply power to the secondary winding by using the power obtained by the high frequency switching operation of the switching element as an input to the primary winding; In the switching power supply having a feedback part which feeds the output of the secondary side output winding of the said switching transformer to the said control part, and stabilizes the secondary side output, The secondary output winding of the switching transformer includes at least one output winding for outputting a low voltage for power supply to the load, a flyback auxiliary winding for supplying power for the controller, and an excess voltage for detecting an excessive voltage. Has a voltage sensing winding, the excess voltage detecting winding being a winding wound forward to input in parallel to the flyback auxiliary winding, An excess voltage detector for detecting a combined value of an output voltage of the excess voltage detecting winding and an output voltage of the flyback auxiliary winding, and determining whether the combined value is at a certain level or more; The control unit controls high-frequency switching of the switching element using the output voltage of the flyback auxiliary winding as a power source, and the excess voltage detection unit latches the state when it determines that the combined value of the output voltage is a predetermined level or more. (latch) to continuously stop the control operation. The power protection device of claim 1, wherein the excess voltage detection unit is installed in the control unit. The overvoltage detector is provided on the secondary side of the switching transformer independently of the control unit, and a microcomputer is connected to an output side of the overvoltage detector, and the microcomputer has an abnormal voltage application. When detecting (iii), the operation of the control unit is stopped, and the power supply protection device characterized by the above-mentioned. The power supply protection device according to claim 3, wherein a display portion is connected to an output side of the microcomputer, and the display portion displays an abnormality of an excessive voltage application detected by the microcomputer. 4. The power supply according to claim 3, wherein an input section having a constant DC resistance value is connected, and a bypass section having a switching function connected in parallel to the input section, wherein the bypass section is controlled by the microcomputer. Protection device.

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