JP4729330B2 - Switching power supply - Google Patents

Description

The present invention relates to a switching power supply device including an input capacitor circuit in which a plurality of electrolytic capacitors are connected in series between positive and negative power supply lines.

  Conventionally, as a switching power supply device including an input capacitor circuit in which a plurality of electrolytic capacitors are connected in series between positive and negative power supply lines, for example, one shown in FIG.

  The switching power supply device of FIG. 4 is provided with a boost chopper circuit with an inverter switch 3 using a boost choke coil L1, a rectifier diode D1, a MOSFET, and the like on positive and negative power supply lines from input terminals 1a and 1b to output terminals 7a and 7b. ing.

  An input capacitor circuit in which electrolytic capacitors C1 and C2 are connected in series is provided on the output side of the boost chopper circuit. When the input capacitor circuit handles a high voltage that cannot be handled by the electrolytic capacitor alone, the electrolytic capacitors C1, C2 are connected in series, and the divided voltage of the resistance voltage dividing circuit in which the resistors R1, R2 are connected in series is used as the electrolytic capacitors C1, C2. The voltage of the electrolytic capacitors C1 and C2 is made uniform.

In addition, an inrush current prevention resistor RT using a fuse resistor is inserted and connected to the positive power line following the input terminal 1a, and the switch element 2 is connected in parallel with the inrush current prevention resistor RT. When a DC voltage is applied to the input terminals 1a and 1b, the switch element 2 is in an off state, and an excessive current flows to the step-up chopper circuit due to an input current flowing through the inrush current prevention resistor RT at the time of startup. It prevents that. When the step-up chopper circuit is activated, the switch element 2 is switched to the on state, bypassing the inrush current prevention resistor RT.
Japanese Patent Laid-Open No. 11-299230 JP 2000-134919 A JP 2001-268901 A

  However, in such a conventional switching power supply device including an input capacitor circuit in which a plurality of electrolytic capacitors are connected in series between positive and negative power supply lines, one of the electrolytic capacitors C1 and C2 connected in series is short-circuited. In such a case, a high voltage is applied to the remaining electrolytic capacitor, and in the worst case, there is a risk of destruction accompanied by ignition.

  In order to solve this problem, if either of the electrolytic capacitors C1 and C2 is short-circuited, use an electrolytic capacitor with a withstand voltage so that it does not smoke or ignite even if a high voltage is applied to the remaining electrolytic capacitor. There is a need to. However, there is a problem that an increase in cost due to an increase in the size of the electrolytic capacitor is inevitable due to the allowance for withstand voltage.

An object of the present invention is to provide a switching power supply device that safely stops operation without causing smoke or ignition of the remaining electrolytic capacitor when a series-connected electrolytic capacitor is short-circuit broken.

In order to achieve this object, the present invention is configured as follows. The switching power supply device of the present invention is
An input capacitor circuit in which a plurality of electrolytic capacitors are connected in series between positive and negative power supply lines;
By connecting a plurality of resistors provided for each electrolytic capacitor in the input capacitor circuit in series between the power supply lines and connecting the connection points of the resistors to the connection points of the electrolytic capacitors, the voltage across the electrolytic capacitors is equalized. A resistance voltage dividing circuit for applying a divided voltage so that
A resistance located on the negative side of the resistance voltage dividing circuit is configured by connecting two resistors in series, and a monitoring voltage detection circuit that outputs a divided voltage of the series connection resistance as a monitoring voltage of the input capacitor circuit;
A reference voltage output circuit that outputs a reference voltage that matches a monitoring voltage output from the monitoring voltage detection circuit when the electrolytic capacitor is in a normal state, as a divided voltage generated by connecting two resistors in series between the power supply lines;
A potential difference detection circuit that detects a potential difference between the monitoring voltage of the monitoring voltage detection circuit and the reference voltage of the reference voltage output circuit, and outputs an abnormality detection signal indicating an abnormality of a plurality of electrolytic capacitors when the potential difference exceeds a predetermined threshold; ,
A switch element connected in parallel to an inrush current prevention resistor using a fuse resistor inserted in series on the input side of the power line;
A switching element connected between the power supply lines and a drive circuit for driving the switching element on and off;
When an abnormality detection signal is output from the potential difference detection circuit, the switch element is turned off, and a signal is output to the drive circuit to prevent the switching element from being turned off and fixed to the on state. A switch driving circuit to be disconnected;
It is provided with.

As a specific example of the switching power supply device of the present invention, the input capacitor circuit has two electrolytic capacitors C1 and C2 connected in series, and the monitoring voltage detection circuit has two resistors R2 and R3 connected in series. The voltage dividing circuit connects the resistor R1 and the resistors R2 and R3 in series, and the reference voltage output circuit connects the resistor R4 and the resistor R5 in series, and between the resistors R1, R2, R3, R4, and R5,
(R1 + R2): R3 = R4: R5
It is characterized by setting the relationship.

As another specific example of the switching power supply device of the present invention, the input capacitor circuit includes three capacitors, ie, an electrolytic capacitor C1, an electrolytic capacitor C2, and an electrolytic capacitor C3, and the monitoring voltage detection circuit includes two resistors R31 and R32. Are connected in series, the resistor voltage divider circuit is a resistor R1, resistor R2, and four resistors R31 and R32 are connected in series, and the reference voltage output circuit is a resistor R4 and a resistor R5 connected in series, and resistors R1, R2, and R31 are connected. , R32, R4, R5,
(R1 + R2 + R31): R32 = R4: R5
It is characterized by setting the relationship.

  According to the present invention, when any one of the plurality of electrolytic capacitors directly connected to the input capacitor circuit is short-circuited due to a component defect or external foreign matter, the monitoring voltage of the input capacitor circuit fluctuates and changes from the reference voltage. In the meantime, a potential difference exceeding a predetermined threshold occurs, and this detects an abnormality and switches the switch element connected in parallel to the inrush current prevention resistor from the ON state during operation to the OFF state. The power supply device can be safely stopped before a high voltage is applied to the remaining normal electrolytic capacitor to cause smoke or fire by cutting it in a fixed manner.

Furthermore, the divided voltage of the resistance voltage divider circuit for equalizing the voltage of the electrolytic capacitors connected in series and the resistor voltage divider circuit for generating the monitoring voltage and the reference voltage is input to the drive circuit as an output voltage to turn on the switching element. In the case of off control (control to keep the output voltage constant), for example, switching control is performed to increase the output voltage when the resistor is disconnected or short-circuited. A potential difference exceeding a predetermined threshold occurs between the reference voltage and the power supply can be safely stopped.

  FIG. 1 is a circuit diagram of an embodiment of a step-up chopper type switching power supply device according to the present invention in which two electrolytic capacitors are connected in series.

  In FIG. 1, the switching power supply device has input terminals 1a, 1b and output terminals 7a, 7b. After a predetermined DC voltage is input to the input terminals 1a, 1b and stabilized by switching control, the output terminals 7a, 1b, The specified DC voltage is output to the load from 7b.

  An inrush current prevention resistor RT is inserted and connected to the positive side input terminal 1a, and a fuse resistor is used as the inrush current prevention resistor RT. The switch element 2 is connected in parallel with the inrush current prevention resistor RT. The switch element 2 is off while the charging current flows through the electrolytic capacitor when the DC power supply to the input terminals 1a and 1b is turned on. When the capacitor is charged, the switch element 2 is turned on to bypass the inrush current prevention resistor RT. .

  Subsequent to the inrush current prevention resistor RT, a boost chopper circuit including a boost choke coil L1, a rectifier diode D1, a switching element 3 using a MOSFET, and a drive circuit 4 is provided. The drive circuit 4 controls the switching element 3 to be turned on and off. When the switching element 3 is turned on, current is passed through the boosting choke coil L1 to accumulate energy, and the switching element 3 is stored in the boosting choke coil L1 when the switching element 3 is turned off. The energy conversion is performed by flowing the obtained energy to the output side through the rectifier diode D1. The drive circuit 4 receives an output voltage and controls the switching element 3 on and off so as to keep the output voltage constant.

  Subsequent to the boost chopper circuit, an input capacitor circuit 11 is provided. Capacitors C1 and C2 are connected to the input capacitor circuit 11 in series. Since this input capacitor circuit 11 handles an output voltage of a high step-up chopper circuit that cannot be handled by a single electrolytic capacitor, electrolytic capacitors C1 and C2 are connected in series.

  A resistance voltage dividing circuit 12 is provided for the input capacitor circuit 11 so that a voltage is evenly applied to each of the electrolytic capacitors C1 and C2. The resistor voltage dividing circuit 12 has resistors R1, R2, and R3 connected in series, and applies a divided voltage by connecting between the resistors R1 and R2 between the electrolytic capacitors C1 and C2.

  The negative-side resistors R2 and R3 in the resistance voltage dividing circuit 12 constitute a monitoring voltage detection circuit 13 by their series connection. The monitoring voltage detection circuit 13 determines the voltage dividing resistor so that the voltage V1 at the point A that gives the divided voltage of the resistors R2 and R3 becomes a voltage that can be input to an IC circuit or the like.

Here, the resistance voltage dividing circuit 12 needs to apply a voltage evenly to the capacitors C1 and C2 by voltage division by the plus-side resistor R1 and the minus-side series resistor (R2 + R3).
R1 = (R2 + R3)
The resistance value is set so that

  Subsequent to the resistor voltage dividing circuit 12, a reference voltage output circuit 14 is provided. The reference voltage output circuit 14 connects a resistor R4 and a resistor R5 in series between positive and negative power supply lines, and outputs a reference voltage V2 from point B.

Here, between the resistors R1, R2, and R3 constituting the resistor voltage dividing circuit 12 and the resistors R4 and R5 constituting the reference voltage output circuit 14, the monitoring voltage V1 at the point A of the resistor voltage dividing circuit 12 and the reference voltage are provided. When the reference voltage V2 at point B of the output circuit 14 and the electrolytic capacitors C1 and C2 are normal
V1 = V2
Therefore, the following relationship is set between the resistors R1, R2, R3, R4, and R5.

(R1 + R2): R3 = R4: R5
The monitoring voltage of the input capacitor circuit 11 by the monitoring voltage detection circuit 13, that is, the monitoring voltage V 1 at the point A and the reference voltage from the reference voltage output circuit 14, that is, the reference voltage V 2 from the point B are input to the potential difference detection circuit 5. ing. The potential difference detection circuit 5 has a potential difference ΔV between the monitoring voltage V1 and the reference voltage V2.
ΔV = V1-V2
When the absolute value exceeds a predetermined threshold value, it is determined that one of the series-connected electrolytic capacitors C1 and C2 provided in the input capacitor circuit 11 has caused an abnormality such as a short-circuit breakdown. The abnormality detection signal E1 is output to the switch drive circuit 6. When the switch drive circuit 6 receives the abnormality detection signal E1 from the potential difference detection circuit 5, the switch drive circuit 6 outputs the switch drive signal E2 to the switch element 2, turns off the switch element 2 due to the ON state, and adds the inrush current prevention resistor RT. To the power line on the side.

  At the same time, the switch drive circuit 6 outputs a switch drive signal E3 to the drive circuit 4, and in response to this, the drive circuit 4 stops the on / off control of the switching element 3 and fixes it to the on state.

  In the drive circuit 4, the divided voltage in the monitoring voltage detection circuit 13 provided in the resistance voltage dividing circuit 12, that is, the voltage at the point A is input as the output voltage of the output terminals 7 a and 7 b. Switching control is performed so that the output voltage is maintained at a constant voltage with the output voltage as the output voltage.

  As for the input of the output voltage to the drive circuit 4, the voltage at the point B of the reference voltage output circuit 14 may be input in addition to the voltage at the point A of the resistance voltage dividing circuit 12. Of course, the divided voltage of the resistance voltage dividing circuit 12 and the reference voltage output circuit 14 may not be used, but may be directly taken in from the output line for the output terminal 7a.

  Next, the operation of the embodiment of FIG. 1 will be described. When a DC voltage is applied to the input terminals 1a and 1b, the switch element 2 is in an OFF state, so that a charging current flows through the inrush current prevention resistor RT to the electrolytic capacitors C1 and C2 of the input capacitor circuit 11, and charging is performed. When completed, the drive circuit 4 is started, and switching control for setting the output voltage to a constant voltage is started by the operation of the step-up chopper circuit when the switching element 3 is turned on / off.

  When the charging of the electrolytic capacitors C1 and C2 is completed, the switch element 2 is turned on, and the inrush current prevention resistor RT is disconnected from the positive power line.

  During the operation of the switching power supply device, the voltages across the electrolytic capacitors C1 and C2 of the input capacitor circuit 11 are equalized by the voltage dividing by the resistance voltage dividing circuit 12, and in this state, from the point A of the monitoring voltage detection circuit 13 The monitoring voltage V1 coincides with the reference voltage V2 from the point B of the reference voltage output circuit 14, the potential difference ΔV by the potential difference detection circuit 5 is ΔV = 0, and the switch drive signals E2 and E3 from the switch circuit 6 are Output is stopped.

  On the other hand, if the electrolytic capacitor C1 is short-circuited during the operation of the switching power supply device due to, for example, defective parts of the electrolytic capacitor C1 or insertion of foreign matter from the outside, both ends of the electrolytic capacitor C2 remaining due to the short-circuit of the electrolytic capacitor C1. As a result, the voltage at point A of the monitoring voltage detection circuit 13 rises, and the potential difference ΔV2 with respect to the reference voltage V2 exceeds the threshold in the potential difference detection circuit 5, and the abnormality detection signal E1 is output. Is done.

  Upon receiving this abnormality detection signal E1, the switch drive circuit 6 outputs the switch drive signal E2 to the switch element 2, forcibly turns off the switch element 2 in the on state, and the positive power line from the input terminal 1a. The inrush current prevention resistor RT is inserted into the state. At the same time, the switch drive circuit 6 outputs a switch drive signal E3 to the drive circuit 4, and in response to this, the drive circuit 4 stops the on / off drive of the switching element 3 and fixes it to the on state.

  As a result, current continuously flows from the input terminal a to the inrush current preventing resistor RT and the switching element 3 and further to the negative input terminal 1b, and the fuse element is used as the inrush current preventing resistor RT. When is fixed to the on state, the fuse resistance is cut in a millisecond order, and a cut state is entered.

  On the other hand, a normal electrolytic capacitor C2 receiving a high voltage between the power supply lines requires a time of several seconds until smoke or ignition occurs, so that the inrush current prevention resistor RT is cut before that. Thus, the operation of the switching power supply device is stopped, and the switching power supply device can be safely stopped without causing the remaining electrolytic capacitor C2 to be damaged by the application of a high voltage.

  On the other hand, any of the resistors R1, R2, and R3 provided in the resistor voltage dividing circuit 12 and the resistors R4 and R5 provided in the reference voltage output circuit 14 during the operation of the switching power supply device has an abnormality such as a short circuit or disconnection. Even if it occurs, the potential difference ΔV by the potential difference detection circuit 5 increases and exceeds the threshold value, and the abnormality detection signal E1 is output, so that the switch drive circuit 6 turns off the switch element 2 and the switching element 3 by the drive circuit 4 Is fixed to the on-state, and the inrush current prevention resistor RT using the fuse resistor is disconnected to safely stop the circuit operation of the switching power supply device.

  In the embodiment of FIG. 1, the drive circuit 4 inputs the divided voltage at the point A of the resistance voltage dividing circuit 12 as an output voltage. For example, if the resistor R3 is short-circuited, the output voltage decreases. The drive circuit 4 controls the switching element 3 on and off so as to increase the output voltage. In such a case, it is detected that the threshold value of the potential difference ΔV is exceeded by the potential difference detection circuit 5 and an abnormality detection signal E1 is output, and the inrush current prevention resistor RT using the fuse resistor is disconnected to stop the switching operation. Thus, it is possible to prevent abnormal operation in which the output voltage becomes abnormally high and to stop it safely.

  The monitoring voltage detection circuit 13 shown in FIG. 1 can also be used as an output voltage overvoltage protection circuit. Further, the monitoring voltage detection circuit 13 can be used interchangeably with the reference voltage output circuit 14.

  FIG. 2 is a circuit diagram of an embodiment of a step-up chopper type switching power supply device according to the present invention in which three electrolytic capacitors are connected in series. In FIG. 2, three electrolytic capacitors C1, C2, and C3 are connected in series to the input capacitor circuit 11, and the high voltage between the power supply lines is equally divided into three electrolytic capacitors C1, C2, and C3. Capacitors C1, C2, and C3 having a low withstand voltage can be used.

  Resistor voltage dividing circuit 12 is provided with resistors R1, R2, and (R31 + R32) corresponding to electrolytic capacitors C1, C2, and C3. The divided voltage is applied so that the voltage between the terminals of the electrolytic capacitors C1, C2, and C3 is equalized.

  The resistance corresponding to the negative side capacitor C3 in the resistance voltage dividing circuit 12 is a series circuit of resistors R31 and R32. This series circuit constitutes a monitoring voltage detection circuit 13, and the input capacitor circuit 11 is monitored from the point A. The voltage V1 is output. The reference voltage output circuit 14 connects resistors R4 and R5 in series between positive and negative power supply lines, and outputs a reference voltage V2 from point B.

When the electrolytic capacitors C1, C2, and C3 of the input capacitor circuit 12 are normal, the voltage V1 at the point A of the resistance voltage dividing circuit 12 and the reference voltage V2 of the reference voltage output circuit 14 need to have a matching relationship, that is, V1 = V2. Therefore, the following relationship is set between the resistors R1, R2, R31, R32, R4, and R5.
(R1 + R2 + R31): R32 = R4: R5
It has become.

Of course, R1 = R2 = R31 + R32 between the resistors R1, R2, R31, R32 in order to equalize the voltages of the electrolytic capacitors C1, C2, C3.
The relationship is set. Other configurations and operations are the same as those in the embodiment of FIG.

  In the embodiment of FIG. 2 also, if any of the three electrolytic capacitors C1, C2, C3 provided in the input capacitor circuit 11 is short-circuited due to a component failure or entry of foreign matter from the outside, the potential difference detection circuit 5 The potential difference ΔV due to the output exceeds the threshold value, and the abnormality detection signal E1 is output. Upon receipt of this, the switch drive circuit 6 outputs the switch drive signals E2 and E3, and the switch element 2 is turned off. At the same time as inserting into the positive power supply line, the drive circuit 4 stops the on / off operation of the switching element 3 and fixes it to the on state so that a current flows continuously to the inrush current prevention resistor RT using a fuse resistor. The switching power supply is safely stopped before the remaining electrolytic capacitor is damaged by high voltage.

  FIG. 3 is a circuit diagram of an embodiment of an inverter type switching power supply device according to the present invention. In FIG. 3, an inrush current prevention resistor RT using a fuse resistor and a switch element 2 are provided following the input terminals 1a and 1b, and subsequently, an input capacitor circuit 11, a resistance voltage dividing circuit 12, and a monitoring voltage detection circuit. 13 and a reference voltage output circuit 14 are provided, and a potential difference detection circuit 5 and a switch drive circuit 6 are further provided.

  These configurations are the same as those in the embodiment of FIG. Subsequently, an inverter circuit is provided. The inverter circuit has a transformer 8, a positive power line from the input terminal 1a is connected to one of the primary windings 8a of the transformer 8, and the switching element 10 is connected to the other of the primary windings 8a. Is connected to the negative side of the input terminal 1b.

  The switching element 10 is ON / OFF controlled by the drive circuit 9. Following the secondary winding 8b of the transformer 8, a rectifier circuit including diodes D2 and D3 is provided, followed by a choke coil L2, and a smoothing capacitor C3. An output voltage is input to the drive circuit 9 from the plus line on the output terminal 9a side. The drive circuit 9 controls on and off of the switching element 10 so as to keep the output voltage at a constant voltage.

  Even in the embodiment of FIG. 3, when either one of the electrolytic capacitors C1 and C2 provided in the input capacitor circuit 11 is short-circuited during operation due to defective components or entry of foreign matter from the outside, the potential difference detection circuit 5 When the potential difference ΔV exceeds the threshold value, the abnormality detection signal E1 is output, and in response to this, the switch drive circuit 6 outputs the switch drive signals E2 and E3.

  The switch drive signal E2 switches the switch element 2 from the on state to the off state, and inserts an inrush current prevention resistor RT using a fuse resistor into the positive power line from the input terminal 1a. At the same time, the switch drive signal E2 stops the on / off drive of the switching element 10 by the drive circuit 9, and is fixed to the on state.

  For this reason, current continuously flows from the input terminal 1a to the input terminal 1b on the negative side through the inrush current prevention resistor RT, the primary winding 8a of the transformer 8, and the switching element 10 in the ON state, The inrush current prevention resistor RT using the fuse resistor is cut in a short time, and the switching power supply can safely stop the operation before the remaining normal electrolytic capacitor is damaged by receiving a high voltage.

  In the above embodiment, the case where two or three electrolytic capacitors are connected in series to the input capacitor circuit is taken as an example. However, the number of electrolytic capacitors connected in series can be determined as appropriate. .

  In the above embodiment, when an abnormality due to a short circuit of the electrolytic capacitor in the input capacitor circuit is detected, the switching element is fixed to ON and a continuous current is passed through the inrush current prevention resistor using the fuse resistor. Although the switching power supply device is stopped by disconnecting, the switching power supply device may be stopped based on the abnormality detection signal by other methods.

The present invention includes appropriate modifications that do not impair the object and advantages thereof, and is not limited by the numerical values shown in the above embodiments.

Circuit diagram of an embodiment of a step-up chopper type switching power supply device according to the present invention in which two electrolytic capacitors are connected in series Circuit diagram of an embodiment of a step-up chopper type switching power supply device according to the present invention in which three electrolytic capacitors are connected in series 1 is a circuit diagram of an embodiment of an inverter type switching power supply device according to the present invention. Circuit diagram of conventional switching power supply

Explanation of symbols

1a, 1b: input terminal 2: switch element 3, 10: switching element 4, 9: drive circuit 5: potential difference detection circuit 6: switch drive circuit 7a, 7b: output terminal 8: transformer 11: input capacitor circuit 12: resistance component Voltage circuit 13: Monitoring voltage detection circuit 14: Reference voltage output circuit

Claims (3)

An input capacitor circuit in which a plurality of electrolytic capacitors are connected in series between positive and negative power supply lines;
A plurality of resistors provided corresponding to each electrolytic capacitor of the input capacitor circuit are connected in series between the power supply lines, and a connection point between the resistors is connected to a connection point between the electrolytic capacitors. A resistance voltage dividing circuit that applies a divided voltage so as to equalize both-end voltage;
A resistor located on the negative side of the resistor voltage dividing circuit is configured by connecting two resistors in series, and a monitoring voltage detection circuit that outputs a divided voltage of the series connection resistor as a monitoring voltage of the input capacitor circuit;
A reference voltage output circuit that outputs a reference voltage that matches a monitoring voltage output from the monitoring voltage detection circuit when the electrolytic capacitor is in a normal state as a divided voltage generated by connecting two resistors in series between the power supply lines When,
A potential difference between a monitoring voltage of the monitoring voltage detection circuit and a reference voltage of the reference voltage output circuit is detected, and when the potential difference exceeds a predetermined threshold, an abnormality detection signal indicating an abnormality of the plurality of electrolytic capacitors is output. A potential difference detection circuit;
A switch element connected in parallel to an inrush current preventing resistor using a fuse resistor inserted in series on the input side of the power line;
A switching element connected between the power lines and a drive circuit for driving the switching element on and off;
When an abnormality detection signal is output from the potential difference detection circuit, the switch element is turned off, and a signal is output to the drive circuit to prevent the switching element from being turned off and fixed to the on state. A switch drive circuit for cutting off the inrush current prevention resistor;
A switching power supply device comprising:
In the switching power supply device according to claim 1,
In the input capacitor circuit, an electrolytic capacitor C1 and an electrolytic capacitor C2 are connected in series,
The monitoring voltage detection circuit connects two resistors R2 and R3 in series,
The resistor voltage dividing circuit connects a resistor R1 and three resistors R2 and R3 in series,
The reference voltage output circuit includes a resistor R4 and a resistor R5 connected in series,
Between the resistors R1, R2, R3, R4, R5,
(R1 + R2): R3 = R4: R5
The switching power supply device characterized by setting the relationship.
In the switching power supply device according to claim 1,
In the input capacitor circuit, an electrolytic capacitor C1, an electrolytic capacitor C2, and an electrolytic capacitor C3 are connected in series.
The monitoring voltage detection circuit connects two resistors R31 and R32 in series,
The resistor voltage divider circuit is composed of a resistor R1, a resistor R2, and four resistors R31 and R32 connected in series.
The reference voltage output circuit includes a resistor R4 and a resistor R5 connected in series,
Between the resistors R1, R2, R31, R32, R4, R5,
(R1 + R2 + R31): R32 = R4: R5
The switching power supply device characterized by setting the relationship.

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