JP6241306B2 - Circuit board, image forming apparatus including the board, and circuit board error detection method - Google Patents

Description

  The present invention relates to a circuit board, an image forming apparatus including the board, and a circuit board error detection method, and more particularly, to a technique related to ensuring the safety of a circuit board in a circuit board including a fuse.

  Conventionally, for example, a technique described in Patent Document 1 is known as a technique related to ensuring safety of a circuit board including a fuse. In Patent Document 1, when soldering the terminal of the thermal fuse to the land, in order to prevent the solder from flowing out of the land and generating solder balls or the like, a wall for preventing the solder from flowing out is provided on the outer periphery of the land. The providing technique is disclosed. Thereby, it is possible to prevent a short circuit between the terminals of the switching element due to the solder balls or the like.

JP 2011-023556 A

  However, although it is possible to prevent the generation of solder balls and the like according to Patent Document 1, it is necessary to form a wall that prevents the outflow of solder around the land (input / output terminal portion of the fuse). The land formation may become complicated. Further, in recent years, when a fuse such as a micro fuse is miniaturized, when soldering the fuse to the input / output terminal portion, as a soldering abnormality related to the input / output terminal portion of the fuse, for example, between the input / output terminal portions. The occurrence of a short circuit, that is, the occurrence of a solder bridge cannot be ignored. If a solder bridge occurs between the input and output terminals, even if an overcurrent is generated in the circuit and the fuse is blown, energization is continued through the solder bridge, and the overcurrent protection function by the fuse is In other words, the safety of the circuit board is reduced.

  Therefore, the present invention provides a technique capable of maintaining the safety of a circuit board including a fuse by a simple circuit design.

The circuit board disclosed in the present specification includes a fuse, a first power supply line having an input terminal connected to the fuse, a second power supply line having an output terminal connected to the fuse, and the first power supply line. A wiring pattern provided between one power supply line and the second power supply line, the wiring pattern having a conductive portion provided at a position intersecting with a virtual straight line connecting the input terminal portion and the output terminal portion; Is provided.
According to this configuration, for example, when a solder bridge occurs between the input terminal portion and the output terminal portion as a soldering abnormality, the conductive portion of the wiring pattern and the solder bridge are in a conductive state. Therefore, for example, a solder bridge can be detected by detecting a voltage (amount of electricity) from a power supply line supplied via the solder bridge and the wiring pattern. Thereby, the safety of the circuit board including the fuse can be maintained by a simple circuit design.

In the circuit board, a detection circuit connected to the wiring pattern, wherein the amount of electricity differs depending on whether or not at least one of the input terminal portion and the output terminal portion and the conductive portion are in a conductive state. May be further provided with a detection circuit for detecting the above via the wiring pattern.
According to this configuration, since the detection circuit is provided in the circuit board, a soldering abnormality can be detected by the circuit board itself. At this time, it can be determined whether or not at least one of the input terminal portion and the output terminal portion and the conductive portion are in a conductive state based on a difference in the amount of electricity detected through the wiring pattern, for example, a voltage.

In the circuit board, the wiring pattern may be covered with a solder resist at a portion other than the conductive portion.
According to this configuration, when the circuit board is a resist board covered with a solder resist, a solder abnormality that occurs between the input and output terminals of the fuse, for example, a solder bridge, is maintained while maintaining the protection of the circuit board by the solder resist. It can be detected reliably.

In the circuit board, the wiring pattern may include lands for chip parts that constitute the conductive portion.
According to this configuration, for example, when a solder bridge is generated between the input / output terminal portions of the fuse, the wiring pattern becomes conductive with the solder bridge via the land for chip components, and the solder bridge can be detected via the wiring pattern. .

In the above circuit board, the wiring pattern may include a land portion of a through hole that constitutes the conductive portion. Usually, a land portion of a through hole (including a through hole for mounting a component, including no plating on a hole wall). Is not coated with a resist for soldering lead pins or the like of electronic components. Therefore, for example, when a solder bridge occurs between the input / output terminal portions of the fuse, the wiring pattern becomes conductive with the solder bridge by the land portion of the through hole, and the solder bridge can be detected via the wiring pattern.

In the circuit board, provided on the primary side of the transformer, the control unit for controlling the secondary side voltage of the transformer to a predetermined voltage, the first power supply line provided on the secondary side of the transformer, Connected to the second power supply line to which the secondary voltage is supplied from the first power supply line via a fuse and to the first power supply line, and supplies information corresponding to the secondary voltage to the control unit The feedback circuit includes two voltage dividing resistors provided between the first power supply line and the ground, and a connection line connecting the two voltage dividing resistors, A voltage dividing circuit that generates a divided voltage of a secondary side voltage; and a photocoupler that supplies information corresponding to the divided voltage generated by the voltage dividing circuit to the control unit, wherein the connection line includes the wiring pattern Configure down, the detection circuit may be constituted by the feedback circuit and the control unit.
According to this configuration, if the circuit board is originally provided with a feedback circuit and a control unit, they can also be used as a detection circuit.

Further, in the circuit board, provided on the primary side of the transformer and the transformer, the control for stopping the generation of the secondary side voltage when detecting an overvoltage in which the secondary side voltage of the transformer is a predetermined value or more. A first power line provided on a secondary side of the transformer, the second power line supplied with the secondary voltage from the first power line via the fuse, and the first power source An overvoltage protection circuit connected to a line, detecting the overvoltage of the secondary side voltage, and supplying information of the detected overvoltage to the control unit, the overvoltage protection circuit including the first power supply line and a ground The series circuit includes a Zener diode connected to the first power supply line, a resistor connected to the Zener diode, and the Zener diode. A connection line connecting between the resistor and the resistor, and a photocoupler connected between the resistor and the ground and supplying the overvoltage information to the control unit, and the connection line constitutes the wiring pattern The detection circuit may be constituted by the overvoltage protection circuit and the control unit.
According to this configuration, if the circuit board originally has an overvoltage protection circuit and a control unit, they can also be used as a detection circuit.

The circuit board includes a main power supply circuit and a sub power supply circuit having a power supply capacity smaller than that of the main power supply circuit. The main power supply circuit includes a transformer and the first power supply provided on the secondary side of the transformer. The sub power circuit includes a capacitor and a diode connected to an AC power source, a capacitor input type rectifier, a sub power line connected to the rectifier, and a sub power line. A rectangular wave detection circuit that generates a detection signal corresponding to the waveform of the AC power supply via the rectifier, and a rectangular wave included in the AC power supply is detected based on the detection signal from the rectangular wave detection circuit When the rectangular wave is detected, a main power supply control unit that generates a control signal for stopping the operation of the main power supply circuit, a resistor connected to the sub power supply line, and one end connected to the resistor And an open circuit including an open line that is open at the other end, wherein the open line constitutes the wiring pattern, and the detection circuit includes the open circuit, the rectangular wave detection circuit, and the control You may make it comprise by a part.
According to this configuration, as long as the power supply board originally has a rectangular wave detection circuit and a control unit, they can also be used as a part of the detection circuit.

In the circuit board, the wiring pattern may be covered with a solder resist at a portion other than the conductive portion.
According to this configuration, for example, when a solder bridge occurs as a soldering abnormality, a portion of the connection line that is not covered with the solder resist becomes conductive with the solder bridge, and the partial pressure (electrical quantity) supplied through the solder bridge ) To detect a solder bridge.

Further, in the circuit board, the circuit board includes a chip component provided such that an electrode is positioned at a position intersecting with the virtual straight line, and the wiring pattern is for the chip component constituting the conductive portion. The land may be included.
According to this configuration, for example, when a solder bridge occurs as a soldering abnormality, the electrode of the voltage dividing resistor becomes conductive with the solder bridge, and the solder bridge is based on the divided voltage (amount of electricity) supplied through the solder bridge. Can be detected.

In the circuit board, the wiring pattern may include a land portion of a through hole that constitutes the conductive portion.
According to this configuration, for example, when a solder bridge occurs as a soldering abnormality, the through-hole electrode becomes conductive with the solder bridge, and the solder bridge is detected based on a partial pressure (amount of electricity) supplied through the solder bridge. it can.

The circuit board may further include a notification unit that notifies a warning related to an error of the circuit board.
According to this configuration, for example, when a soldering abnormality such as a solder bridge occurs between the input / output terminal portions of the fuse, the user or the like can notice it. Here, “circuit board errors” include feedback control errors, overvoltage errors, overcurrent errors, AC (alternating current) power supply errors (rectangular wave detection errors, etc.), soldering errors, and the like.

In addition, an image forming apparatus disclosed in this specification uses the voltage supplied from the second power supply line via the circuit board according to any one of the above, the first power supply line, and the fuse. An image forming unit to be formed.
According to this configuration, the safety of the circuit board including the fuse included in the image forming apparatus can be maintained by a simple circuit design. Thereby, the reliability of the image forming apparatus is improved.

  Further, the circuit board error detection method disclosed in the present specification includes a fuse, an input terminal connected to the fuse, a first power supply line to which a power supply voltage is applied, and the fuse connected to the fuse. A second power line having an output terminal portion, and a wiring pattern provided between the first power line and the second power line, wherein the wiring pattern is provided between the first power line and the second power line. Forming a wiring pattern having a conductive portion provided at a position intersecting with a virtual straight line connecting the input terminal portion and the output terminal portion; and at least one of the input terminal portion and the output terminal portion; A detection step of detecting, via the wiring pattern, different amounts of electricity depending on whether or not the conductive portion is in a conductive state, and the amount of electricity in the conductive state in the detection step is detected. If it is, an error occurs in the circuit board, including, a stopping step of stopping the application of the power supply voltage to the first power supply line.

  In the circuit board error detection method, in the forming step, the wiring pattern may be formed using a connection line connected to a circuit component provided on the circuit board.

  The circuit board error detection method may further include a notification step of notifying a warning related to a circuit board error.

  According to the present invention, the safety of a circuit board including a fuse can be maintained by a simple circuit design.

1 is a block diagram illustrating an electrical configuration of a printer according to a first embodiment of the present invention. Circuit diagram of switching power supply in embodiment 1 Sectional view showing the installation state of the fuse on the power supply board Plan view of power supply board showing positional relationship between fuse and wiring pattern Circuit diagram showing another example using existing circuit for detection of soldering abnormality Circuit diagram showing another example using existing circuit for detection of soldering abnormality Circuit diagram showing another example using existing circuit for detection of soldering abnormality Circuit diagram showing another example using existing circuit for detection of soldering abnormality Circuit diagram showing another example using existing circuit for detection of soldering abnormality The circuit diagram which shows roughly the switching power supply of Embodiment 2. The circuit diagram which shows roughly the switching power supply of Embodiment 3. The top view which shows another example of the electroconductive part of a wiring pattern The top view which shows another example of the electroconductive part of a wiring pattern

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
1. Description of Printer FIG. 1 is a block diagram showing an electrical configuration of a printer (an example of an “image forming apparatus” of the present invention) 1. The printer 1 includes a printing unit (an example of the “image forming unit” in the present invention) 2, a communication unit 3a, an image memory 3b, and a power supply system PS. The power supply system PS includes a power supply board 10 and a control device 80. The power supply substrate 10 includes a switching power supply 20. The switching power supply 20 is a power supply for the printer 1 and supplies power to the printing unit 2, the communication unit 3 a, the image memory 3 b, and the control device 80. The control device 80 is provided with an internal memory (not shown) for storing various data and a timer 85.

  The printing unit 2 includes a photosensitive drum 2a, a charger 2b that executes a charging process for charging the surface of the photosensitive drum 2a, an exposure device 2c that executes an exposure process for forming an electrostatic latent image on the surface of the photosensitive drum 2a, and a photosensitive drum. A developer 2d that executes a development process for forming a developer image by attaching a developer to the electrostatic latent image formed on the surface of 2a, and a transfer device 2e that executes a transfer process for transferring the developer image to a recording medium. And a fixing device 2f for executing a fixing process for fixing the developer image transferred onto the recording medium.

  The printing unit 2 executes a charging process, an exposure process, a development process, a transfer process, and a fixing process by using a voltage supplied from the switching power supply 20 to perform a printing process for printing print data on a recording medium. . The communication unit 3a performs communication with an information terminal device such as a PC, and has a function of receiving a print instruction and print data from the information terminal device. The image memory 3b temporarily stores print data received from the information terminal device.

  When the communication unit 3a receives a print instruction from the information terminal device and receives print data, the control device 80 causes the printing unit 2 to execute print processing. The operating voltage of the printing unit 2 is 24V, whereas the operating voltages of the communication unit 3a, the image memory 3b, and the control device 80 are 3.3V. The power supply board 10 is an example of the “circuit board” in the present invention.

2. Next, the configuration of the switching power supply 20 provided on the power supply substrate 10 will be described with reference to FIG. The switching power supply 20 includes a full-wave rectifying / smoothing circuit 21, a control IC 22, a FET (field effect transistor) 23, a voltage generating circuit 24, a transformer 25, a rectifying / smoothing circuit 26, a feedback circuit 27, an overvoltage detection circuit 28, and a DC-DC converter. 29.

  The full-wave rectifying and smoothing circuit 21 is a so-called capacitor input type, and includes a diode bridge DB that full-wave rectifies an AC voltage (for example, 220 V) of the AC power supply AC, and a capacitor C1 that smoothes the rectified voltage. A transformer 25 is provided on the output side of the full-wave rectifying / smoothing circuit 21, and an input voltage Vin (for example, about DC322V) obtained by rectifying and smoothing an AC voltage is applied to the primary coil N1 of the transformer 25 through the input line Lin. Is done.

  The FET 23 is an N-channel MOSFET having a drain D connected to the primary coil N1 and a source S connected to the ground line Lg. The gate G of the FET 25 is connected to the output port OUT of the control IC 22. When the control IC 22 outputs an on / off signal, that is, a PWM signal to the gate G through the output port OUT, the FET 25 performs an on / off operation. As a result, the primary side of the transformer 25 oscillates, and a voltage is induced in the secondary coil N2 of the transformer 25.

  A voltage generation circuit 24 is provided on the primary side of the transformer 25. The voltage generation circuit 24 smoothes the voltage induced in the auxiliary coil N3 provided on the primary side of the transformer 25 by the diode D1 and the capacitor C2. The voltage generation circuit 24 generates a voltage of 20 V, for example, and serves as a power source for the control IC 22.

  As shown in FIG. 2, the control IC 22 includes a power supply port VCC connected to the voltage generation circuit 24, a high voltage input port VH connected to the input line Lin via the resistor R20, etc., and an output voltage from the feedback circuit 27. (Secondary side voltage) This includes five ports of a feedback port FB to which information corresponding to Vo1 is input, an output port OUT, and an overvoltage detection port ERROR.

  The control IC 22 controls the output voltage Vo1 of the transformer 25 (an example of “secondary side voltage”) Vo1 to a predetermined voltage based on information (signal) input to the feedback port FB. When the control IC 22 detects an overvoltage (an example of “error”) in which the output voltage Vo1 of the transformer 25 is equal to or higher than a predetermined value based on information (signal) input to the overvoltage detection port ERROR, the FET 25 The on / off operation is stopped, and the generation of the output voltage Vo1 is stopped (an example of a “stop process”). The control IC 22 is an example of a “control unit”.

  On the secondary side of the transformer 25, as shown in FIG. 2, a rectifying / smoothing circuit 26, a feedback circuit 27, an overvoltage detection circuit 28, a fuse 40, a first output line Lo1, a second output line Lo2, and a DC-DC converter. 29 is provided.

  The rectifying / smoothing circuit 26 includes a diode D2 and a capacitor C3. The rectifying / smoothing circuit 26 rectifies and smoothes the voltage induced in the secondary coil N2 of the transformer 25 to generate, for example, an output voltage Vo1 of 24V. A feedback circuit 27 and an overvoltage detection circuit 28 are provided on the output side of the rectifying / smoothing circuit 26.

  The feedback circuit 27 (an example of a “feedback circuit”) is connected to the first output line Lo1, and corresponds to the output voltage Vo1 in order to maintain the output voltage (an example of a “secondary voltage”) Vo1 at a target value. Information is supplied to the control IC 22. The feedback circuit 27 includes a voltage dividing circuit (an example of a “voltage dividing circuit”), a first photocoupler (an example of a “photocoupler”) PC1, and a shunt regulator RE1.

  The voltage dividing circuit (R2, R3) includes two voltage dividing resistors R2, R3 provided between the first output line Lo1 and the ground line Lg, and generates a divided voltage Vdv of the output voltage Vo1. The first photocoupler PC1 includes a light emitting diode LED1 and a phototransistor PT1. As shown in FIG. 2, the light emitting diode LED1 is connected in series with the resistor R1 and the shunt regulator RE1 between the first output line Lo1 and the ground line Lg. The photocoupler PC1 supplies information corresponding to the divided voltage Vdv generated by the voltage dividing circuit to the control IC 22.

  That is, the shunt regulator RE1 passes a current corresponding to the level difference between the predetermined reference voltage and the divided voltage Vdv. Therefore, a current corresponding to the level difference flows through the light emitting diode LED1, and the light emitting diode LED1 outputs an optical signal having a light amount corresponding to the level difference between the reference voltage and the divided voltage Vdv. The optical signal of the light emitting diode LED1 is returned to an electrical signal by the phototransistor PT1. Thereby, a signal indicating the level difference of the divided voltage Vdv with respect to the reference voltage (hereinafter referred to as a feedback signal) is fed back to the feedback port FB of the control IC 22. Therefore, the feedback signal includes information corresponding to the divided voltage Vdv of the output voltage Vo1. Here, the feedback signal is an example of “information according to the secondary side voltage”.

  An overvoltage detection circuit (an example of an overvoltage protection circuit) 28 is provided on the rear stage side of the feedback circuit 27, is connected to the first output line Lo1, detects an overvoltage of the output voltage Vo1, and controls information related to the detected overvoltage. Supply to IC22. The overvoltage detection circuit 28 includes an example of a series circuit (“series circuit”) provided between the first output line Lo1 and the ground line Vg.

  The series circuit includes a Zener diode ZD1, a resistor R4, and a second photocoupler (an example of a “photocoupler”) PC2. As shown in FIG. 2, the Zener diode ZD1 is connected to the first output line Lo1, and the resistor R4 is connected to the Zener diode ZD1. The second photocoupler (an example of a “photocoupler”) PC2 includes a light emitting diode LED2 and a phototransistor PT2, and the light emitting diode LED2 is connected between the resistor R4 and the ground line Vg, and information on overvoltage of the output voltage Vo1. Is supplied to the control IC 22.

  Here, the Zener voltage of the Zener diode ZD1 is 27 V, for example. Therefore, when the output voltage Vo1 exceeds 27V, a current flows through the light emitting diode LED2, and the phototransistor PT2 connected to the overvoltage detection port ERROR of the control IC 22 is turned on. Thereby, the control IC 22 detects an overvoltage of the output voltage Vo1. When detecting the overvoltage, the control IC 22 turns off the FET 25 and stops the generation of the output voltage Vo1. Here, the overvoltage detection circuit 28 and the control IC 22 are examples of a “detection circuit”.

  As shown in FIG. 2, a fuse 40 is provided between the first output line Lo1 and the second output line Lo2. The first output line Lo1 has an input terminal portion 31 connected to the input terminal 41 of the fuse 40. The second output line Lo <b> 2 has an output terminal portion 32 that is connected to the output terminal 42 of the fuse 40.

  The DC-DC converter 29 is connected to the second output line Lo2, converts the voltage of 24V of the second output line Lo2 into 3.3V, and outputs it from the third output line Lo3. The first output line Lo1 is an example of a first power supply line, and the second output line Lo2 is an example of a second power supply line.

3. Arrangement of Fuse and Wiring Pattern Next, the positional relationship between the fuse 40 and the wiring pattern 50 will be described with reference to FIGS. In the present embodiment, an electrical component having terminal pins is mainly provided on the component surface 10A which is the surface of the power supply substrate 10, and an electrical component is mainly disposed on the solder surface 10B which is the back surface of the power supply substrate 10. Lands for soldering and electrical wiring such as power supply lines are provided. A chip component is provided on the solder surface 10B.

  FIG. 3 shows a cross section of the power supply substrate 10 in the vicinity where the fuse 40 is provided, and FIG. 4 shows the solder surface 10B of the power supply substrate 10 in the vicinity where the fuse 40 is provided. As shown in FIGS. 3 and 4, the fuse 40 has an input terminal 41 and an output terminal 42, and is mounted on the component surface 10 </ b> A of the power supply substrate 10. As shown in FIG. 3, the input terminal 41 and the output terminal 42 of the fuse 40 pass through the terminal holes provided in the power supply substrate 10, and are provided on the solder surface 10 </ b> B that is the back surface of the power supply substrate 10. The terminal portion 31 and the output terminal portion 32 are soldered with solder (HD).

  The input terminal portion 31 is provided on the first output line Lo1, and the input terminal 41 of the fuse 40 is soldered to the input terminal portion 31. The output terminal portion 32 is provided on the second output line Lo2, and the output terminal 42 of the fuse 40 is soldered to the output terminal 42. In the present embodiment, the input terminal portion 31 and the input terminal portion 31 are formed by circular lands in plan view (see FIG. 4).

  As shown in FIGS. 3 and 4, the wiring pattern 50 is provided between the first output line Lo1 and the second output line Lo2 on the solder surface 10B. In addition, the wiring pattern is formed to include a conductive portion 51 provided at a position intersecting with a virtual straight line connecting the input terminal portion 31 and the output terminal portion 32 (an example of “forming step”). In the present embodiment, as shown in FIG. 2, the connection line connecting the anode of the Zener diode ZD1 and one end of the resistor R4 included in the overvoltage detection circuit 28 constitutes the wiring pattern 50. Therefore, hereinafter, the wiring pattern 50 is referred to as a “connection line 50”. In addition, when the wiring pattern is collectively shown, it is described as “wiring pattern 50”.

  Further, as shown in FIGS. 3 and 4, the connection line 50 is connected to the first output line Lo1 at a substantially central portion between the end portion of the first output line Lo1 and the end portion of the second output line Lo2. The second output line Lo2 is formed to extend in a vertical direction. The line width of the connection line 50 is narrower than the line widths of the first output line Lo1 and the second output line Lo2.

  Here, the conductive portion 51 is shown in black in FIG. That is, in this case, in the connection line 50, a portion that does not overlap with the straight region TE connecting the input terminal portion 31 and the output terminal portion 32 on the substrate 10 (the portion other than the black portion in FIG. 4) is covered with the solder resist. ing. On the other hand, a portion overlapping with the straight region TE (a black portion in FIG. 4) is not covered with the solder resist, and constitutes the conductive portion 51. Note that the straight line area TE is indicated by an area filled with dots in FIG. The straight line region TE is an example of “a virtual straight line connecting the input terminal unit 31 and the output terminal unit 32”.

  Here, as shown in FIG. 4, the width of the straight line region TE (the width of the virtual straight line) has at least the diameter dimensions of the input terminal portion 31 and the output terminal portion 32, in other words, the input terminal portion 31. It is preferable that the diameter is equal to or larger than the diameter of the output terminal portion 32. Moreover, it is preferable that the length of the conductive part 51 has at least the width dimension of the linear region TE, in other words, not less than the width of the linear region TE. By forming the conductive portion 51 having such dimensions, a solder bridge generated between the input terminal portion 31 and the conductive portion 51 or a solder bridge generated between the conductive portion 51 and the output terminal portion 32, Alternatively, it is possible to reliably detect a solder bridge generated between the input terminal portion 31 and the output terminal portion 32.

  For example, when a solder bridge is generated between the input terminal 41 and the output terminal 42 of the fuse 40, that is, between the input terminal portion 31 and the output terminal portion 32, the conductive portion 51 is connected to the solder bridge. Accordingly, when a voltage of 24V from the first output line Lo1 is applied from the input terminal portion 31 to the connection line 50 of the overvoltage detection circuit 28 via solder, a current flows through the LED 2 via the resistor R4. In other words, the overvoltage detection circuit 28 (detection circuit) has a different amount of electricity (in this case, a voltage depending on whether or not at least one of the input terminal portion 31 and the output terminal portion 32 and the conductive portion 51 are in a conductive state). ) Is detected via the connection line 50 (wiring pattern) (an example of a “detection step”).

  Then, the phototransistor PT2 connected to the overvoltage detection port ERROR of the control IC 22 is turned on, and the control IC 22 detects the overvoltage of the output voltage Vo1 and stops generating the output voltage Vo1. Accordingly, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design in which the arrangement of the connection lines 50 is changed.

  At this time, in the present embodiment, the generation of the output voltage Vo1 can be stopped using the existing overvoltage detection circuit 28 and the control IC 22. In other words, if the power supply substrate 10 originally has the overvoltage detection circuit 28 and the control IC 22, they can be used as the detection circuit.

  Further, only the conductive portion 51 of the connection line 50 is not covered with the solder resist. Therefore, when the power supply substrate 10 is a resist substrate covered with a solder resist, a soldering abnormality that occurs between the input / output terminal portions of the fuse 40, for example, a solder bridge, is maintained while maintaining the protection of the power supply substrate 10 with the solder resist. It can be detected reliably.

  The soldering abnormality that occurs between the input / output terminal portions of the fuse 40 is not limited to the solder bridge. For example, when the input terminal portion 31 and the conductive portion 51 of the wiring pattern 50 are connected due to poor soldering of the input terminal portion 31, or when the output terminal portion 32 is poorly soldered, connected to the output terminal portion 32. Even when the conductive part 51 of the line 50 is connected, the generation of the output voltage Vo1 can be stopped by the same configuration as that of the solder bridge.

  Note that the control IC 22 (an example of the “notification unit”) may notify a warning related to an error of the power supply substrate 10 when the phototransistor PT2 is turned on (an example of the “notification step”). As a result, for example, when a soldering abnormality such as a solder bridge occurs between the input and output terminals of the fuse 40, it can be noticed by the user or the like. That is, the control IC 22 stops the generation of the output voltage Vo1 in which the phototransistor PT2 is turned on even when an overvoltage of the output voltage Vo1 occurs. For example, the control IC 22 stops the output voltage Vo1 due to the overvoltage or the output voltage due to a soldering abnormality. By notifying the warning for confirming whether Vo1 is stopped, when a soldering abnormality occurs, it is possible to make the user aware of it.

4). Examples of Other Power Supply Boards Next, an example in which the configuration originally provided as the switching power supply 20 can be used as a soldering abnormality detection circuit will be described with reference to FIGS. In addition, the same member number is attached | subjected to the same structure as the structure shown by FIG. 2, and the description is abbreviate | omitted.

4-1. When using a feedback circuit (1)
First, an example in which the feedback circuit 27 is used will be described with reference to FIG. In the circuit shown in FIG. 5, a transistor Q1 whose collector is connected to the connection point of the voltage dividing resistors R2 and R3 of the feedback circuit 27, a resistor R5 whose one end is connected to the base of the transistor Q1, and a wiring pattern 50A (“wiring” An example of “pattern” is further provided for detecting a soldering abnormality between the input / output terminal portions of the fuse 40. As shown in FIG. 5, one end of the wiring pattern 50 is connected to the other end of the resistor R <b> 5, and the other end is opened via the input / output terminal portion of the fuse 40.

  In this case, if, for example, a solder bridge occurs between the input / output terminal portions of the fuse 40 as a soldering abnormality, the conductive portion 51 is connected to the solder bridge. Thereby, when a voltage of 24V is applied to the wiring pattern 50 from the output line Lo1, the transistor Q1 is turned on via the resistor R5. Then, since the divided voltage Vdv becomes zero, the current flowing through the light-emitting diode LED1 is greatly increased. As a result, the feedback control of the control IC 22 exceeds the control range, and the control IC 22 stops generating the output voltage Vo1. Let Therefore, even in this case, the safety of the power supply substrate 10 including the fuse 40 can be maintained by the simple circuit design by adding the transistor Q1, the resistor R5, and the wiring pattern 50A.

4-2. Case of Using Overcurrent Detection Circuit Next, an example of using the overcurrent detection circuit 30 instead of the overvoltage detection circuit 28 in FIG. 2 will be described with reference to FIG. As shown in FIG. 6, the overvoltage detection circuit 28 includes a reference voltage source Vth, a comparator IC1, resistors R6 and R7, and a light emitting diode LED2. When the potential difference generated in the resistor R6 exceeds a predetermined value set by the reference voltage Vth due to the current flowing through the resistor R6, the comparator IC1 causes the light-emitting diode LED2 to emit light because an overcurrent has occurred.

  In this embodiment, the resistor R8 connected to the connection point between the resistor R7 and the light emitting diode LED2 and the wiring pattern 50B (an example of “wiring pattern”) detect a soldering abnormality between the input / output terminal portions of the fuse 40. In order to do that, it is further provided. As shown in FIG. 6, one end of the wiring pattern 50 </ b> B is connected to the other end of the resistor R <b> 8, and the other end is opened via the input / output terminal portion of the fuse 40.

  In this case, if, for example, a solder bridge occurs between the input / output terminal portions of the fuse 40 as a soldering abnormality, the conductive portion 51 is connected to the solder bridge. Accordingly, when a voltage of 24 V is applied to the wiring pattern 50B from the first output line Lo1, a current flows through the light emitting diode LED2 via the resistor R8, and the light emitting diode LED2 emits light. Then, the phototransistor PT2 connected to the overvoltage detection port ERROR of the control IC 22 is turned on, and the control IC 22 stops generating the output voltage Vo1, assuming that the overcurrent of the output voltage Vo1 is detected. Therefore, even in this case, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design by adding the resistor R8 and the wiring pattern 50B.

4-3. When using a feedback circuit (2)
Next, another example using the feedback circuit 27 will be described with reference to FIG. The switching power supply 20 shown in FIG. 7 does not include the overvoltage detection circuit 28 and the photocoupler PC2 shown in FIG. The connection line 50C that connects the voltage dividing resistor R2 and the voltage dividing resistor R3 of the feedback circuit 27 constitutes a “wiring pattern”. That is, the connection line 50C is connected between the input / output terminal portions of the fuse 40, one end of the connection line 50C is connected to the voltage dividing resistor R2, and the other end is connected to the voltage dividing resistor R3.

  In this case, if, for example, a solder bridge occurs between the input / output terminal portions of the fuse 40 as a soldering abnormality, the conductive portion 51 is connected to the solder bridge. Thereby, when a voltage of 24V is applied to the connection line 50C from the output line Lo1, the transistor Q1 is turned on via the resistor R5. Then, since the divided voltage Vdv becomes 24V, the current flowing through the light emitting diode LED1 is greatly increased. Accordingly, since the feedback control of the control IC 22 exceeds the control range, the control IC 22 stops generating the output voltage Vo1. Therefore, even in this case, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design by simply changing the arrangement of the connection lines 50C.

4-4. Case of Using DC-DC Converter Next, an example of using the DC-DC converter 29 in place of the overcurrent detection circuit 30 in FIG. 7 will be described with reference to FIG. As shown in FIG. 8, the fuse 40 is provided on the output line Lo <b> 1 to the DC-DC converter 29. Further, a transistor Q2, a resistor R9, and a wiring pattern 50D (an example of a “wiring pattern”) are further provided to detect a soldering abnormality between the input / output terminal portions of the fuse 40.

  The collector of the transistor Q2 is connected to the enable signal output terminal of the control device 80 and the enable signal input terminal EN of the DC-DC converter 29, and one end of the resistor R9 is connected to the base of the transistor Q2. One end of the wiring pattern 50 </ b> D is connected to the other end of the resistor R <b> 9 as shown in FIG. 8, and the other end is opened via the input / output terminal portion of the fuse 40.

  In this case, if, for example, a solder bridge occurs between the input / output terminal portions of the fuse 40 as a soldering abnormality, the conductive portion 51 is connected to the solder bridge. Accordingly, when a voltage of 24V is applied to the wiring pattern 50D from the output line Lo1, the transistor Q2 is turned on via the resistor R9. Then, the enable signal input terminal EN is invalidated, and the output of the 3.3V output voltage Vo2 from the DC-DC converter 29 is stopped. By detecting this by input from the 3.3V output detection terminal, the control device 80 can detect the occurrence of soldering abnormality between the input / output terminal portions of the fuse 40. Therefore, even in this case, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design in which the transistor Q2, the resistor R9, and the wiring pattern 50D are added.

  In this case, the power supply (3, 3 V) for operating the control device 80 is supplied from a power supply different from the DC-DC converter 29, for example, from another DC-DC converter.

4-5. Case of Using AC Square Wave Detection Circuit Next, another example of using the AC square wave detection circuit 62 will be described with reference to FIG. A power supply substrate 10 shown in FIG. 9 includes a switching power supply (an example of a main power supply circuit) 20 shown in FIG. 7 and a sub power supply circuit 60 having a power supply capacity smaller than that of the switching power supply 20.

  The sub power supply circuit 60 includes a rectifying unit 61, a sub power supply line Ls1, a rectangular wave detection circuit 62, a main power control IC (an example of a main power control unit) 65, a light emitting diode LED2, a diode drive circuit 63, and an open circuit 64. .

  The rectification unit 61 is a capacitor input type rectification unit including capacitors C5 and C6 and a diode bridge DB2 connected to an AC power supply. The sub power line Ls1 is connected to the rectifying unit 61.

  The rectangular wave detection circuit 62 is connected to the sub power supply line Ls1, generates a detection signal Sdt according to the waveform of the AC power supply via the rectifier 61, and supplies the detection signal Sdt to the main power supply control IC 65. As shown in FIG. 9, the rectangular wave detection circuit 62 includes a Zener diode ZD2, a capacitor C7, and a transistor Q3.

  The main power supply control IC 65 detects a rectangular wave included in the AC power supply based on the detection signal Sdt from the rectangular wave detection circuit. When the main power supply control IC 65 detects the rectangular wave, the main power supply control IC 65 outputs a control signal PScon that stops the operation of the main power supply circuit 20. The control signal PScon is generated and supplied to the diode drive circuit 63.

  The diode drive circuit 63 causes the light emitting diode LED2 to emit light in accordance with the control signal PScon. Thereby, the control IC 22 stops the generation of the output voltage Vo1, assuming that a rectangular wave is detected as the AC power supply.

  The open circuit 64 includes a resistor R10 connected to the sub power supply line Ls1, and an open line 50E (an example of a “connection line”) having one end connected to the resistor R10 and the other end open. In this embodiment, the open line 50E constitutes a “wiring pattern”.

  In this case, if, for example, a solder bridge occurs between the input / output terminal portions of the fuse 40 as a soldering abnormality, the conductive portion 51 is connected to the solder bridge. Thereby, when a voltage of 24V is applied to the open line 50E from the output line Lo1, the output voltage Vo1 (24V) is supplied to the sub power supply line Ls1 via the resistor R10. Then, the transistor Q3 is turned on, and the detection signal Sdt becomes constant at the ground voltage. Therefore, the main power supply control IC 65 generates a control signal PScon for stopping the operation of the main power supply circuit 20 and supplies the control signal PScon to the diode drive circuit 63, assuming that a rectangular wave is detected. Then, the diode drive circuit 63 causes the light emitting diode LED2 to emit light according to the control signal PScon. At this time, the control IC 22 stops generating the output voltage Vo1, assuming that a rectangular wave is detected as the AC power supply.

  Therefore, even in this case, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design in which the resistor R10 and the wiring pattern 50 are added.

  In this case, the soldering abnormality detection circuit includes the open circuit 64, the rectangular wave detection circuit 62, and the main power supply control IC 65.

5. Effects of First Embodiment As a soldering abnormality, for example, when a solder bridge occurs between the input terminal portion 31 and the output terminal 32, the conductive portion 51 of the wiring pattern 50 and the solder bridge are in a conductive state. Therefore, for example, the solder bridge can be detected based on the voltage (electric amount) from the first output line Lo1 supplied via the solder bridge and the wiring pattern 50. Thereby, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design.

  In addition, since a detection circuit is provided in the power supply board (circuit board) 20, it is possible to detect a soldering abnormality by the power supply board 20 itself or based on a detection result by the power supply board 20.

  In addition, when the power supply substrate 20 is a resist substrate covered with a solder resist, solder abnormality that occurs between the input / output terminal portions of the fuse 40, for example, a solder bridge, is reliably maintained while maintaining the protection of the circuit substrate by the solder resist. It can be detected.

<Embodiment 2>
In the first embodiment, the switching power supply 20 has been described as an example of a soldering abnormality detection circuit. However, the present invention is not limited to this. The detection circuit may be provided separately from the existing circuit. For example, as shown in FIG. 10, voltage dividing resistors of resistors R11 and R12 and a wiring pattern 50F (an example of “wiring pattern”) are provided as the detection circuit. One end of the resistor R11 is connected to the wiring pattern 50F, the wiring pattern 50F is provided between the input / output terminal portions of the fuse 40, and the other end is opened. One end of the resistor R12 is connected to the resistor R11, and the other end of the resistor R12 is connected to the ground line Vg. A connection point between the resistor R11 and the resistor R12 is connected to the control device 80, for example.

  In this case, if, for example, a solder bridge occurs between the input / output terminal portions of the fuse 40 as a soldering abnormality, the conductive portion 51 is connected to the solder bridge. Thereby, for example, when a voltage of 24 V is applied to the wiring pattern 50 from the first output line Lo1, the divided voltage by the resistors R11 and R12 is supplied to the control device 80. Thereby, the control device 80 can detect the occurrence of soldering abnormality between the input / output terminal portions of the fuse 40. Therefore, even in this case, the safety of the power supply substrate 10 including the fuse 40 can be maintained by a simple circuit design in which the resistors R11 and R12 and the wiring pattern 50F are added.

  Further, it is possible to detect the occurrence of a soldering abnormality in distinction from other abnormal states, for example, the occurrence of an overvoltage.

<Embodiment 3>
In the first and second embodiments, the example in which the detection circuit for the soldering abnormality is provided on the power supply substrate 10 is shown, but the present invention is not limited to this. As shown in FIG. 11, only a wiring pattern 50G (an example of “wiring pattern”) for detecting a soldering abnormality may be provided on the power supply substrate 10. In FIG. 11, the wiring pattern 50 is provided between the input / output terminal portions of the fuse 40, one end thereof is connected to the ground Vg, and the other end is opened. An inspection terminal T1 is provided at the other end. Even in this case, for example, during product inspection, a soldering abnormality can be detected using the wiring pattern 50 by an inspection jig.

  For example, the impedance (resistance value) between the input terminal portion 31 and the inspection terminal T1 and the impedance (resistance value) between the output terminal portion 32 and the inspection terminal T1 are measured, and the resistance value is more than a predetermined value. If it is smaller, it may be determined that the soldering is abnormal.

  Alternatively, one end of the wiring pattern 50G is opened without being connected to the ground line Vg, and one end of the wiring pattern 50G is connected to the ground via a predetermined resistance on the inspection jig side. A predetermined voltage is applied from the inspection jig between the input terminal portion 31 and the inspection terminal T1, and between the output terminal portion 32 and the inspection terminal T1, and at that time, the input terminal portion 31 and the inspection terminal T1 are inspected. The current flowing between the terminal T1 and the current flowing between the output terminal portion 32 and the inspection terminal T1 are measured, and when the measured current is larger than a predetermined value, it may be determined that the soldering is abnormal. Good. The predetermined resistance may be provided on the power supply substrate 10 side.

  Alternatively, a predetermined voltage is applied from the inspection jig between the input terminal portion 31 and the inspection terminal T1 and between the output terminal portion 32 and the inspection terminal T1, and at that time, the input terminal portion 31 and the inspection terminal T1 are inspected. The potential difference between the output terminal T1 and the potential difference between the output terminal portion 32 and the inspection terminal T1 may be measured, and if the measured potential difference is smaller than a predetermined value, it may be determined that the soldering is abnormal.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

(1) In the first to third embodiments, a portion (blacked portion in FIG. 4) 51 of the wiring pattern 50 that is not covered with the solder resist is configured as a conductive portion for detecting a soldering abnormality. Although an example was shown, a conductive part is not restricted to this. For example, resistor R4 in FIG. 2, resistor R5 in FIG. 5, resistor R8 in FIG. 6, resistor R2 in FIG. 7, resistor R9 in FIG. 8, resistor R10 in FIG. 9, and resistor R11 in FIG. In the case of being configured by an example of a component, as shown in FIG. 12, the end portion of the wiring pattern 50 is located at a portion overlapping the linear region TE connecting the input terminal portion 31 and the output terminal portion 32 on the substrate 10. Thus, the land 52 or 53 for chip parts may be provided, and the land 52 or 53 for chip parts may be configured as a conductive portion.
Even in this case, when a soldering abnormality occurs, for example, when a solder bridge occurs, the chip component land 52 or 53 is connected to the output line Lo1, so that the soldering abnormality is reliably ensured via the wiring pattern 50. It can be detected.

Alternatively, as shown in FIG. 13, the land portion of the through hole is located at the end portion of the wiring pattern 50 so as to be located in a portion overlapping the linear region TE connecting the input terminal portion 31 and the output terminal portion 32 on the substrate 10. 54 or 55 may be provided, and the land portion 54 or 55 of the through hole may be configured as a conductive portion.
Even in this case, when a soldering abnormality occurs, for example, when a solder bridge occurs, the land part 54 or 55 of the through hole is connected to the output line Lo1, so that the soldering abnormality is reliably ensured via the wiring pattern 50. It can be detected.

  (2) In the first to third embodiments, the circuit board according to the present invention is shown as an example applied to the power supply board 10 of the printer 1, but the present invention is not limited to this. The circuit board according to the present invention can be applied to any circuit board having a fuse provided in a power supply line.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 10 ... Power supply board, 20 ... Switching power supply, 22 ... Control IC, 27 ... Feedback circuit, 28 ... Overvoltage detection circuit, 29 ... DC-DC converter, 30 ... Overcurrent detection circuit, 31 ... Input terminal part, 32 ... Output terminal part, 40 ... Fuse, 50 ... Wiring pattern, 51 ... Conducting part, 60 ... Sub power supply circuit, 62 ... Rectangle wave detection circuit, 65 ... Main power supply control IC, Lo1 ... First output line, Lo2 ... First 2 output lines

Claims (16)

A fuse,
A first power supply line having an input terminal connected to the fuse;
A second power line having an output terminal connected to the fuse;
A wiring pattern provided between the first power supply line and the second power supply line, the wiring having a conductive portion provided at a position intersecting with a virtual straight line connecting the input terminal portion and the output terminal portion With patterns,
With a circuit board. The circuit board according to claim 1,
A detection circuit connected to the wiring pattern, wherein the amount of electricity varies depending on whether or not at least one of the input terminal portion and the output terminal portion and the conductive portion are in a conductive state. A circuit board further comprising a detection circuit for detecting via the circuit board. In the circuit board according to claim 1 or 2,
The wiring pattern is a circuit board in which a portion other than the conductive portion is covered with a solder resist. In the circuit board according to claim 1 or 2,
The wiring pattern is a circuit board including a land for chip parts that constitutes the conductive portion. In the circuit board according to claim 1 or 2,
The wiring pattern includes a land portion of a through hole that constitutes the conductive portion. The circuit board according to claim 2,
With a transformer,
A control unit provided on a primary side of the transformer and controlling a secondary side voltage of the transformer to a predetermined voltage;
The first power supply line provided on the secondary side of the transformer;
The second power supply line supplied with the secondary voltage from the first power supply line via the fuse;
A feedback circuit connected to the first power supply line and supplying information according to the secondary side voltage to the control unit;
The feedback circuit includes:
A voltage divider that includes two voltage dividing resistors provided between the first power supply line and the ground, and a connection line that connects the two voltage dividing resistors, and generates a divided voltage of the secondary side voltage; Circuit,
A photocoupler that supplies information corresponding to the divided voltage generated by the voltage dividing circuit to the control unit,
The connection line constitutes the wiring pattern,
The detection circuit is a circuit board configured by the feedback circuit and the control unit. The circuit board according to claim 2,
With a transformer,
A controller that is provided on the primary side of the transformer and that stops generation of the secondary side voltage when detecting an overvoltage in which the secondary side voltage of the transformer is equal to or higher than a predetermined value;
The first power supply line provided on the secondary side of the transformer;
The second power supply line supplied with the secondary voltage from the first power supply line via the fuse;
An overvoltage protection circuit connected to the first power supply line, detecting the overvoltage of the secondary side voltage, and supplying information of the detected overvoltage to the control unit;
The overvoltage protection circuit includes a series circuit provided between the first power supply line and the ground,
The series circuit is
A Zener diode connected to the first power line;
A resistor connected to the zener diode;
A connection line connecting the Zener diode and the resistor;
A photocoupler connected between the resistor and the ground and supplying information on the overvoltage to the control unit;
The connection line constitutes the wiring pattern,
The detection circuit is a circuit board configured by the overvoltage protection circuit and the control unit. The circuit board according to claim 2,
A main power circuit;
A sub power supply circuit having a smaller power supply capacity than the main power supply circuit,
The main power circuit is
With a transformer,
Including the first power supply line provided on the secondary side of the transformer,
The sub power circuit is
A capacitor input type rectifier including a capacitor and a diode connected to an AC power supply; and
A sub power supply line connected to the rectifying unit;
A rectangular wave detection circuit that is connected to the sub power supply line and generates a detection signal corresponding to the waveform of the AC power supply via the rectifying unit;
A main power supply that detects a rectangular wave included in the AC power supply based on the detection signal from the rectangular wave detection circuit and generates a control signal for stopping the operation of the main power supply circuit when the rectangular wave is detected A control unit;
An open circuit including a resistor connected to the sub power line, and an open line having one end connected to the resistor and the other end open;
Including
The open line constitutes the wiring pattern,
The detection circuit is a circuit board configured by the open circuit, the rectangular wave detection circuit, and the main power supply control unit. In the circuit board according to any one of claims 6 to 8,
The wiring pattern is a circuit board in which a portion other than the conductive portion is covered with a solder resist. In the circuit board according to any one of claims 6 to 8,
The circuit board includes a chip component provided such that an electrode is positioned at a position intersecting with the virtual straight line,
The circuit pattern, wherein the wiring pattern includes a land for the chip component that constitutes the conductive portion. In the circuit board according to any one of claims 6 to 8,
The wiring pattern includes a land portion of a through hole that constitutes the conductive portion. In the circuit board according to any one of claims 6 to 11,
A circuit board further comprising a notification unit that notifies a warning related to an error of the circuit board. The circuit board according to any one of claims 1 to 12,
An image forming unit that forms an image using a voltage supplied from the second power line through the first power line and the fuse;
An image forming apparatus. A circuit board having a fuse, a first power supply line having an input terminal connected to the fuse, to which a power supply voltage is applied, and a second power supply line having an output terminal connected to the fuse A method of detecting errors in
A wiring pattern provided between the first power supply line and the second power supply line, the wiring having a conductive portion provided at a position intersecting with a virtual straight line connecting the input terminal portion and the output terminal portion A forming step of forming a pattern;
A detection step of detecting, via the wiring pattern, different amounts of electricity depending on whether or not at least one of the input terminal portion and the output terminal portion and the conductive portion are in a conductive state; and A stop step of stopping application of the power supply voltage to the first power supply line, assuming that an error has occurred in the circuit board when an electrical quantity in a conductive state is detected;
A circuit board error detection method comprising: The circuit board error detection method according to claim 14,
The circuit board error detection method, wherein, in the forming step, the wiring pattern is formed also as a connection line connected to a circuit component provided on the circuit board. The circuit board error detection method according to claim 14 or 15,
A circuit board error detection method further comprising a notification step of notifying a warning related to an error of the circuit board.

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