JP5043889B2 - Device mounting manufacturing method and power supply device - Google Patents

Description

  The present invention relates to an element mounting manufacturing method for keeping a final product within a target value, and a power supply device including an assembly obtained by the element mounting manufacturing method.

  FIG. 7 shows a conventional example of a separately excited switching power supply device on which a plurality of elements, that is, electronic components are mounted. In the figure, reference numeral 1 denotes a power transmission transformer that insulates the primary side from the secondary side. A primary circuit 1A of the transformer 1 and an FET 2 as a switching element form a series circuit, and between both ends of the series circuit. A DC input voltage Vin is applied to. A control IC 3 that controls switching of the FET 2 is disposed on the primary side of the transformer 1. Here, a pulse drive signal is output from the output terminal OUT of the control IC 3 to the gate of the FET 2, and the ground terminal GND is grounded together with the source of the FET 2.

  Connected to the secondary winding 1B of the transformer 1 is a diode 4 as a rectifier, a diode 5 as a commutator, a choke coil 6 and a smoothing capacitor 7 as an output circuit. The transformer 1, FET 2 and rectifying / smoothing circuit 8 constitute a converter unit 9 that converts the DC input voltage Vin from the input voltage source E into an appropriate DC output voltage VOUT. The output voltage VOUT is detected by the output voltage detection circuit 10, and the detection signal is output to the feedback terminal FB of the control IC 3, so that an error signal obtained by comparing the voltage level of the detection signal with the reference voltage is obtained. It is generated as a control signal by the control IC 3.

  In addition to the output terminal OUT, the ground terminal GND, and the like, the control IC 3 switches a reference voltage terminal REF that outputs a high-precision reference voltage VREF generated in the control IC 3 and the frequency of the pulse drive signal, that is, switching of the FET 2. A timing resistor terminal RT for setting the frequency is provided. The terminal RT is connected to a frequency setting circuit 11 composed of a resistor Rt. The frequency setting circuit 11 determines the amount of current flowing through the terminal RT and sets the switching frequency of the pulse drive signal to the FET 2 generated by the control IC 3 accordingly. Since the internal configuration of the control IC 3 is disclosed in detail in, for example, Patent Document 1, only necessary portions will be described here.

  In the above circuit configuration, when the FET 2 is switched by a pulse drive signal from the control IC 3, the input voltage Vin is intermittently applied to the primary winding 1A of the transformer 1, and the primary winding 1A and the secondary winding 1B are connected to each other. The voltage induced in the secondary winding 1B according to the turns ratio is rectified and smoothed by the rectifying and smoothing circuit 8, and the output voltage VOUT is supplied to the load LD. The output voltage detection circuit 10 generates a detection signal corresponding to the output voltage VOUT and outputs the detection signal to the control IC 3, and the control IC 3 generates a control signal obtained by comparing the voltage level of the detection signal with the reference voltage. The frequency of the pulse drive signal generated at the output terminal OUT of the control IC 3 is set to a fixed value by the frequency setting circuit 11 in advance, and a pulse drive signal (PWM signal: whose conduction width changes according to the control signal). A pulse width modulation signal) is applied to the gate of FET2. As a result, the output voltage VOUT supplied from the converter unit 9 to the load LD can be stabilized.

JP 2001-112251 A

  In the power supply device described above, the switching frequency of the FET 2 in the converter unit 9 is set by the resistance value of the resistor Rt connected to the terminal RT. FIG. 8 shows the relationship between the resistance value of the resistor Rt connected between the terminal RT and the ground line and the switching frequency fosc set thereby.

  However, in the method of setting the switching frequency by attaching the resistor Rt having the same resistance value to any power supply device, a large frequency variation (about ± 20%) occurs due to the circuit variation inside the control IC 3. Therefore, for example, in a power supply device using a forward converter unit 9 as shown in FIG. 7, there is a problem that circuit design using LC resonance in the power supply device such as resonance reset in the converter unit 9 becomes difficult. It was happening.

  Such a problem is not limited to the variation of the switching frequency in the power supply device, but extends to all electronic devices.

  The present invention has been made paying attention to the above-mentioned problems, and a first object thereof is to provide an element mounting manufacturing method capable of easily and reliably suppressing the operation variation of the operation section.

  A second object of the present invention is to provide a power supply device that can effectively suppress a large variation in switching frequency of the switching element from the assembly obtained by such a manufacturing method.

  In order to achieve the first object, the element mounting manufacturing method of the present invention attaches all the elements to the mounting body in order to connect all the elements that determine the operation of the operation part to the operation part. A first step is to connect all of the elements and measure the operating state of the operating unit, and when the measurement result deviates from a target value, remove any of the elements from the mounting body. Steps.

  In the element mounting manufacturing method, in a state where the element is mounted on the mounting body, a region where no component is mounted is formed around the element, and in the second step, a removal tool is positioned in the region, It is preferable to remove any of the elements from the mounting body.

  Furthermore, the present invention is a power supply device according to the above-described element mounting manufacturing method, wherein the mounting body is a circuit board, and the operation unit is a control unit that receives a detection signal and outputs a pulse drive signal corresponding to the detection signal. The all elements determine the frequency of the pulse drive signal, the assembly obtained by the element mounting manufacturing method according to claim 1 or 2, and a switching element switched by the pulse drive signal. And a converter unit that converts an input voltage to a desired output voltage, and the control unit stabilizes the output voltage according to the detection signal obtained from the converter unit. A configuration for controlling the element is adopted.

The power supply device of the present invention is connected to the circuit board, a control unit that is provided on the circuit board, receives a detection signal as an input, and outputs a pulse drive signal corresponding to the detection signal, and the control unit. A frequency setting circuit including a plurality of elements for determining the frequency of the pulse drive signal; and a converter unit that includes a switching element that is switched by the pulse drive signal and converts an input voltage to a desired output voltage. The conductive pattern of the circuit board connected to the terminals of the plurality of elements is formed in a shape that is less heat radiating than the conductive pattern connected to a component other than the plurality of elements, and around at least a part of the plurality of elements It said component forming a region that does not implement the constructed by forming the region on the circuit board edge surface vicinity.

  According to the present invention, before measuring the operating state of the operating unit, all elements related to the operation are mounted on the mounting body and connected to the operating unit in advance, and the subsequent measurement result is determined from the design value. Only when it is detached, it is possible to easily and reliably suppress the operation variation of the operation unit by simply removing one of the elements from the mounting body.

  In addition, the removal tool can be inserted directly from the area where no parts are mounted toward the periphery of the element to be removed, so that the influence on other parts is minimized and the element is mounted. Can be easily removed.

  Furthermore, by incorporating the assembly obtained by such an element mounting manufacturing method as a power supply device, it is possible to effectively suppress the switching frequency of the switching element from greatly varying, and the circuit design of the converter unit is facilitated.

Furthermore, as a power supply device, before measuring the operating state of the control unit, all the elements related to the operation are connected to the control unit, and only when the subsequent measurement result is out of the design value, By simply removing any one from the mounting body, it is possible to easily and reliably suppress the operation variation of the control unit. At that time, the removal tool can be inserted directly from the area where the component is not mounted to the periphery of the element to be removed, so that the influence on other parts is minimized and the element is circuitized. It can be easily removed from the substrate. Furthermore, by providing such a region in the vicinity of the end face of the circuit board, it is possible to easily insert the removal tool from the end face of the circuit board. Moreover, if the conductive pattern of the circuit board connected to the terminals of the plurality of elements is formed in a shape that is less heat radiating than the conductive pattern connected to the components other than the plurality of elements, heat concentrates on the attached solder, A plurality of elements can be removed from the circuit board more easily.

It is a circuit diagram of a power supply device showing a configuration before shipping inspection in the present invention. It is a top view of the power supply device which shows the structure before the shipment inspection in this invention. It is a graph which shows the example by which frequency dispersion | variation is improved by this invention. It is a schematic circuit diagram of the example of an internal circuit related to the frequency setting of control IC, and the element connected to the internal circuit. In this invention, it is a circuit diagram which shows the modification of a frequency setting circuit. In this invention, it is a circuit diagram which shows the modification of a frequency setting circuit. It is a circuit diagram of the power supply device in a prior art example. It is a graph which shows the relationship between timing resistance and an oscillation frequency.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings. In addition, although the power supply device provided with the forward type converter unit 9 described above will be described as an example here, there are other types of converter units 9 such as a flyback type, a half bridge type, a full bridge type, etc. Alternatively, it may be a non-insulating converter unit 9 in which the transformer 1 is not interposed. Furthermore, the concept of the present invention can be applied to various electronic devices other than the power supply device as long as they have an operation unit corresponding to the control IC 3 and various elements that determine the operation of the operation unit.

  The circuit in FIG. 1 is an example of a power supply device proposed in the present invention. In the description of the detailed configuration and operation, portions common to the conventional example are omitted here to avoid duplication. However, the circuit shown in FIG. 1 is not the final form of all shipped power supply apparatuses, but has a configuration common to all power supply apparatuses before the shipment inspection. Hereinafter, the manufacturing method will be described in detail as to how to suppress the variation of the switching frequency.

  The control IC 3 described above sets the switching frequency of the FET 2 according to the magnitude of the current flowing through the terminal RT. Particularly, in the circuit example of FIG. 1, resistors R1 to R4 are connected to the terminal RT, and the control IC 3 sets the switching frequency of the FET 2 according to the magnitude of the current flowing from the terminal RT to the resistor R1. That is, the frequency setting circuit 11 includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4. One end of the resistor R1 is connected to the terminal RT, and one end of the resistor R4 is a terminal. The other ends of these resistors R1 and R4 are connected to one end of resistors R2 and R3 connected in parallel, and the other ends of the resistors R2 and R3 are both grounded. . That is, the resistors R2 and R3 connected in parallel pull down the other end of the resistor R1 with the ground, and the resistor R4 connected to the terminal REF pulls up the other end of the resistor R1 with the reference voltage VREF.

  When the power supply device of FIG. 1 is manufactured, first, an all component mounting process for connecting all electronic components including the resistors R1 to R4 to the control IC 3 is performed. As shown in FIG. 2, this step is achieved by mounting a control IC 3 and resistors R1 to R4 on the surface of a circuit board 13 formed by forming a desired conductive pattern (not shown) on the base material 12. All other components constituting the power supply device are also mounted on the circuit board 13. Specifically, the transformer 1, the FET 2, and the choke coil 6 are mounted on the circuit board 13, and the transformer 1 has the above-described primary winding 1 </ b> A and secondary winding 1 </ b> B spirally in the conductive pattern of the circuit board 13. A core 1 </ b> C that is formed and electromagnetically coupled to the primary winding 1 </ b> A and the secondary winding 1 </ b> B is disposed on the circuit board 13. Similarly, the choke coil 6 has its winding 6 </ b> A formed in a spiral shape with the conductive pattern of the circuit board 13, and a core 6 </ b> B electromagnetically coupled to the winding 6 </ b> A is disposed on the circuit board 13.

  Here, the control IC 3 and the resistors R1 to R4 are each composed of a surface mounting component in which a terminal is brought into contact with a conductive pad formed on the surface of the circuit board 13 and soldered and connected to the portion. It may be a component for insertion mounting in which a terminal is inserted into a conductive through hole formed in the circuit board 13 and soldered between the through hole and the terminal.

  Next, a shipping inspection process as a power supply device is performed in a state where all electronic components including the resistors R1 to R4 are mounted on the circuit board 13. In this inspection process, the switching frequency of the FET 2 is measured and inspected. As a method of measuring the frequency, for example, a check terminal connected to the drain of the FET 2 is provided on the circuit board 13 and the frequency of the voltage generated at the check terminal is measured with a frequency counter as an inspection tool (not shown). Alternatively, the ripple included in the output voltage Vout may be similarly measured with a frequency counter. In any case, when the measured frequency value varies beyond the range of ± 10% of the target design value, the resistor R3 or the resistor R4 is removed from the circuit board 13 in the inspection process, and the A frequency adjustment process is performed to place the frequency within a range of ± 10% of the design value. If the measured frequency value is within ± 10% of the design value, the frequency adjustment step is not performed, and the resistors R3 and R4 are all mounted on the circuit board 13.

  In this additional frequency adjustment step, as shown in FIG. 2, resistors R3 and R4 are arranged at the end of the circuit board 13 so that the resistor R3 or the resistor R4 can be easily removed from the circuit board 13 before shipping. In addition, around the terminals located on both sides of the resistors R3 and R4, a component prohibited area 14 is formed as a non-mounting portion where no component is mounted on the circuit board 13. The component prohibited region 14 is formed larger than the tip of the soldering iron used when the resistor R3 or the resistor R4 is removed from the circuit board 13. Therefore, by inserting a soldering iron as a removal tool from the end of the circuit board 13 into the component prohibited area 14 and melting the solder adhered between the resistor R3 or the resistor R4 and the conductive pad on the circuit board 13. The resistor R3 or the resistor R4 can be easily removed from the circuit board 13 while minimizing the influence of heat on other components. Therefore, it is preferable that the component prohibited area 14 is provided in the vicinity of the end face of the circuit board 13 so that the removal tool can be easily inserted. Further, if the conductive pattern of the circuit board 13 connected to the terminals of the resistors R3 and R4 is formed in a shape having a heat dissipation property inferior to that of the conductive pattern connected to other power supply device components, heat is concentrated on the attached solder. Thus, the resistor R3 or the resistor R4 can be removed from the circuit board 13 more easily.

  After measuring the frequency and adjusting the frequency as necessary, the case is attached and a safety test is performed, and the product is shipped as a product after this measurement.

Next, how the resistance values of the resistors R1 to R4 are set will be described. In FIG. 8, the relationship between the timing resistor Rt and the switching frequency fosc is fosc · Rt = 4 × 10 ⁹ depending on the specifications of the control IC 3. Therefore, for example, when the voltage V _RT terminal RT is 1V, when the current flowing through the terminal RT and I _RT, the relationship between the current I _RT flowing through the switching frequency fosc and the terminal RT is, fosc = 4 × 10 ⁹ · I _RT .

When all the resistors R1 to R4 are connected as shown in FIG. 1 before the frequency is measured, the current IRT flowing through the terminal _RT is expressed by the following equation.

Here, the current I _{RT — H} flowing through the terminal RT when the resistor R4 is removed is expressed as the following formula.

Further, the current I _{RT — L} flowing through the terminal RT when the resistor R3 is removed can be expressed as the following formula.

Therefore, the constant of each of the resistors R1 to R4, that is, the resistance value, is selected so that the current _{IRT and} thus the switching frequency fosc obtained thereby becomes a desired value and satisfies the following formula. The value of a is, for example, 15% (= 0.15).

  FIG. 3 shows an example in which frequency variation is improved by the present invention. In each figure in the upper stage, the normal distribution curve C shown here is a statistical (probability) value of the predicted frequency distribution, and F_max and F_min are the maximum value and the minimum value of the switching frequency fosc predicted as the power supply device, respectively. It is. Also, let Co be the most expected center value of the switching frequency fosc that varies between the maximum value F_max and the minimum value F_min, and the difference between the maximum value F_max and the center value Co, that is, the difference between the minimum value F_min and the center value Co. Let Δ.

  FIG. 3A shows an example in which the frequency variation b is b = Δ / 3 compared to before the improvement. Here, when the variation of each of the resistors R1 to R4 itself is not taken into account, the variation of the switching frequency fosc is most improved. FIG. 3B shows an example in which the frequency variation b becomes b = Δ / 2 compared to before the improvement, and the variation of the switching frequency fosc is larger than that shown in FIG. However, it is possible to reduce the ratio of products that perform the removal process of the resistor R3 or the resistor R4.

  In order to determine the constants of the resistors R1 to R4, it is necessary to determine the value of the constant a described above. In FIG. 3A, a = (Δ + b) / 2 = Δ · 2/3 is obtained. In (b) of 3, a = (Δ + b) / 2 = Δ · 3/4.

  As described above, the element mounting manufacturing method proposed in the present embodiment includes all the resistors R1 to R4 that determine the operation of the control IC 3 that is the operation unit, that is, the switching frequency fosc for driving the FET 2, in the control IC 3. In order to connect, all the component mounting process as the first step of mounting all the resistors R1 to R4 on the circuit board 13 which is a mounting body, and the operation of the control IC 3 by connecting all the element resistors R1 to R4 This is realized by a frequency adjustment process as a second step of measuring the state and removing the resistor R3 or the resistor R4 from the circuit board 13 when the measurement result deviates from the design value as the target value.

  In this case, before measuring the operation state of the control IC 3, all the resistors R1 to R4 related to the operation are mounted on the circuit board 13 and connected to the control IC 3 in advance, and the subsequent measurement result is Only when the resistor R3 or the resistor R4 is removed from the circuit board 13 only when it is outside the design value, the operation variation of the control IC 3 can be easily and reliably suppressed.

  In order to suppress such variations, it may be possible to use, for example, a variable resistor or a trimming resistor that can variably adjust the resistance value from the outside, instead of the general-purpose resistors R1 to R4 as shown in this embodiment. . However, the cost of trimming resistors and variable resistors alone is high, and in the case of trimming resistors in particular, trimming equipment for adjusting the resistance value is required, and the trimming resistor cut portion after adjusting the resistance value is exposed. In addition to the concern that the reliability is lowered, there is a concern that the size (especially the height dimension) is large in the case of the variable resistor, and the reliability is lowered due to the movable part. In this regard, the method of removing either the resistor R3 or the resistor R4 from the circuit board 13 as in this embodiment can reduce the cost of a single element compared to a variable resistor or a trimming resistor, and expensive equipment is also available. It is not necessary and can be handled with an inexpensive removal tool such as a soldering iron, and since it is only an operation of attaching / detaching the resistor R3 or the resistor R4, the reliability is high. Furthermore, if the measurement result does not deviate from the target value, it is not necessary to make adjustments, so there is no need to adjust the total number, and man-hours can be reduced.

  Furthermore, the element mounting manufacturing method proposed here is an area in which no components are mounted around the resistors R3 and R4 in a state where the resistors R3 and R4 to be removed are mounted on the circuit board 13. If the measurement result is out of the design value in the frequency adjustment step, for example, a soldering iron is positioned in the component prohibition area 14 and either of the resistors R3 and R4 is connected to the circuit. It is removed from the substrate 13.

  In this way, the soldering iron can be inserted directly from the component prohibited area 14 where no component is mounted toward the periphery of the resistor R3 or the resistor R4, so that the influence on other components is minimized. The resistor R3 or the resistor R4 can be easily removed from the circuit board 13.

  In the present embodiment, the circuit board 13 is provided as a mounting body, and a control IC 3 as a control unit that outputs a pulse drive signal corresponding to the detection signal as an input is provided as an operation unit. Resistors R1 to R4, which are elements, are provided to determine the frequency of the pulse drive signal, and the control IC 3 and the frequency setting circuit 11 that are the assemblies after measurement and adjustment obtained by the element mounting manufacturing method are provided. And a converter unit 9 that includes an FET 2 as a switching element that is switched by a pulse drive signal and converts the input voltage Vin to a desired output voltage Vout, and configures a power supply device, for example, an output voltage obtained from the converter unit 9 The control IC 3 is configured to control the FET 2 so that the output voltage Vout is stabilized by the detection signal of Vout. It is.

  By incorporating an assembly obtained by such an element mounting manufacturing method as a power supply device, the switching frequency fosc of the FET 2 can be effectively prevented from greatly varying, and the circuit design of the converter unit 9 is facilitated.

Furthermore, here, as a power supply device, a frequency setting circuit 11 having a plurality of elements R1 to R4 is connected to the control IC 3, and a conductive pattern of the circuit board 13 connected to the terminals of the plurality of elements R1 to R4 has a plurality of elements. Formed in a shape that is inferior in heat dissipation than the conductive pattern connected to the components other than the elements R1 to R4, and forms a component prohibited region 14 in which no components are mounted around at least a part to be removed of the plurality of resistors R1 to R4. The component prohibited area 14 is formed in the vicinity of the end face of the circuit board 13.

In this case, in addition to the advantages of the present embodiment described above, the soldering iron can be easily inserted from the end face of the circuit board 13 by providing the component prohibited area 14 in the vicinity of the end face of the circuit board 13. Furthermore, if the conductive pattern of the circuit board 13 connected to the terminals of the resistors R3 and R4 is formed in a shape that is less heat radiating than the conductive pattern connected to the components of other power supply devices, heat concentrates on the attached solder. Thus, the resistor R3 or the resistor R4 can be more easily removed from the circuit board 13.

Next, a modification of the present invention will be described with reference to FIGS. FIG. 4 is a schematic circuit diagram of an example of an internal circuit related to the frequency setting of the control IC 3 and elements connected to the internal circuit. FIG. 4A shows an example of the same internal circuit of the control IC 3 as shown in FIG. 1, in which the switching frequency fosc is set in proportion to the current I _RT flowing through the terminal RT. V _RT is a voltage at the terminal RT, which is generated inside the control IC 3 based on the reference voltage VREF generated at the terminal REF. Reference numeral 21 denotes a current limiting resistor connected between the terminal RT and a ground line connected to the ground terminal GND.

  FIG. 4B shows another example of the control IC 3. The control IC 3 here has a current source 22 inside, and this current source 22 is connected between the timing capacitor terminal CT and the terminal REF. Reference numeral 23 denotes a charging / discharging capacitor connected between the terminal CT and a ground line connected to the ground terminal GND. The switching frequency fosc is set according to the time until the capacitor 23 is charged to a constant voltage. The

  FIG. 5 shows an embodiment of the frequency setting circuit 11 incorporated in the control IC 3 of FIG. FIG. 5A shows the same circuit configuration as that shown in FIG. 1, and this suppresses variations in the switching frequency fosc by removing the resistor R3 or the resistor R4 from the frequency setting circuit 11 as necessary. The circuit shown in FIG. 5B is obtained by omitting the resistor R1 from the frequency setting circuit 11 in FIG. 5A. In this case, the resistor R3 or the resistor R4 is also removed from the frequency setting circuit 11, thereby switching frequency. Variation in fosc can be suppressed.

  FIG. 6 shows an embodiment of the frequency setting circuit 11 incorporated in the control IC 3 of FIG. The frequency setting circuit 11 in FIG. 6A is configured by connecting a parallel circuit of a capacitor C1 and a resistor R3 between a terminal CT and a ground line, and connecting a resistor R4 between the terminal REF and the terminal CT. The Here, the switching frequency fosc is set according to the time until the capacitor C1 connected to the terminal CT is charged to a constant voltage. However, by removing the resistor R3 or the resistor R4 from the frequency setting circuit 11, the switching frequency fosc is removed. Variation in fosc can be suppressed. Further, the circuit shown in FIG. 6B is obtained by changing the resistor R3 to the capacitor C3 in the frequency setting circuit 11 of FIG. 6A, and switching the capacitor C3 or the resistor R4 by removing the capacitor C3 or the resistor R4 from the frequency setting circuit 11. Variations in the frequency fosc can be suppressed.

  The present invention is not limited to the present embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in order to automate and realize the element mounting manufacturing method of the present invention, the measured value of the switching frequency obtained by the inspection tool is input, and if this measured value deviates from the preset target value, the removal tool is operated. The automatic adjustment tool which outputs the signal to make and removes resistance R3 or resistance R4 from the circuit board 13 may be provided. As the switching element, various semiconductor elements such as transistors can be used in addition to the MOS type FET.

2 FET (switching element)
3 Control IC (operation part, assembly, control part)
R1-R4 resistance (element)
9 Converter 11 Frequency setting circuit (assembly)
13 Wearing body (circuit board)
14 Parts prohibited area (area)

Claims (4)

A first step of mounting all the elements on a mounting body in order to connect all the elements that determine the operation of the operating section to the operating section;
A second step of connecting all of the elements and measuring the operating state of the operating section, and removing any of the elements from the mounting body when the measurement result deviates from a target value; An element mounting manufacturing method characterized by the above. In a state where the element is mounted on the mounting body, a region where no component is mounted is formed around the element,
The element mounting manufacturing method according to claim 1, wherein in the second step, a removal tool is positioned in the region to remove any of the elements from the mounting body. The mounting body is a circuit board;
The operation unit is a control unit that receives a detection signal and outputs a pulse drive signal corresponding to the detection signal;
All the elements determine the frequency of the pulse drive signal,
An assembly obtained by the device mounting manufacturing method according to claim 1,
Including a switching element that is switched by the pulse drive signal, and a converter unit that converts an input voltage into a desired output voltage, and
The control unit controls the switching element so that the output voltage is stabilized by the detection signal obtained from the converter unit. A circuit board;
A control unit provided on the circuit board, which receives a detection signal as an input and outputs a pulse drive signal corresponding to the detection signal;
A frequency setting circuit connected to the control unit and comprising a plurality of elements for determining the frequency of the pulse drive signal;
Including a switching element that is switched by the pulse drive signal, and a converter unit that converts an input voltage into a desired output voltage, and
The conductive pattern of the circuit board that is connected to the terminals of the plurality of elements is formed in a shape that is inferior in heat dissipation than the conductive pattern that is connected to components other than the plurality of elements,
At least a portion of the surrounding part forming a region that does not implement, the power supply apparatus characterized by forming the region in the vicinity of the circuit substrate end face of said plurality of elements.

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