JPH08111978A - Switching power supply - Google Patents

Abstract

PURPOSE: To obtain a switching power unit the production of which can be easily controlled and the cost of which can be reduced for obtaining such a switching power unit that the power unit must be constituted in at least two types, with one type being made to improve the power factor of the power unit and the other type being made to not improve the power factor. CONSTITUTION: A switching power unit which is made to improve the power factor of the unit and to not improve the power factor is constituted by only mounting a changing circuit board K1 mounted with changing parts required for improving the power factor or another circuit board K2 mounted with changing parts required for not improving the power factor on the power unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device, and is suitable for application to, for example, a switching power supply device in which the presence or absence of a power factor correction circuit is selectively configured.

[0002]

2. Description of the Related Art In recent years, by developing a switching element capable of withstanding a relatively large current and voltage of high frequency, most of the power supplies of a switching system are used as a power supply device for rectifying a commercial power supply to obtain a desired DC voltage. It is a device. The switching power supply is used as a power supply for various electronic devices as a high-power DC-DC converter, while increasing the switching frequency to downsize transformers and other devices.

By the way, in general, when a commercial power supply is rectified, the current flowing through the smoothing circuit has a distorted waveform, which causes a problem that the power factor indicating the utilization efficiency of the power supply is impaired. In addition, there is a need for measures to suppress harmonics generated by the distorted current waveform. In order to improve the power factor of the power supply, it is known to use, for example, a choke input type rectifier circuit, and in this case, it is the simplest method and is preferable in terms of measures against electromagnetic noise (EMI). Further, by utilizing the intermittent voltage of the switching power supply, the average charging voltage of the smoothing capacitor is lowered, the conduction angle of the rectifying element is widened, and the power factor is improved.
The Agnet-Switch method (hereinafter referred to as MS method) is considered.

[0006] The present applicant previously applied a magnetic coupling transformer in which a voltage according to a switching output is excited in a choke coil from a primary side or a secondary side of an insulating converter transformer (hereinafter referred to as an insulating transformer). A switching power supply circuit has been proposed, which is designed to improve the power factor by superposing the voltage of the switching cycle on the rectified output of the bridge rectifier circuit.
(Japanese Patent Application No. 6-192737). According to this, the normal M
Fluctuations in the rectified and smoothed voltage Vi can be suppressed more easily than in a switching power supply circuit in which the power factor is improved by the S method.

FIG. 5 is a circuit diagram showing an example of a switching power supply circuit including the magnetic coupling transformer. In this figure, AC indicates a commercial AC power source, CMC provided for this AC power source AC is a common mode choke coil, and a capacitor C _L inserted between both pole lines in the preceding stage thereof indicates an across capacitor. Also,
For this AC power supply AC, an LC low-pass filter composed of an impedance element of a filter choke coil L _N and a filter capacitor C _N is provided at the subsequent stage of the common mode choke coil CMC, which has a high switching frequency. It is intended to prevent noise from flowing into the AC line. D ₁ is a bridge rectification circuit composed of four diodes, and performs full-wave rectification on the input AC power supply AC. A so-called fast recovery type (shown as D _FR ) is used for the two rectifier diodes indicated by broken lines, because a high-frequency current of a switching cycle flows in the full-wave rectified output line as described later. Correspondingly, at least any two of the diodes forming the bridge rectification circuit are required to be of the high speed recovery type. This full-wave rectified output is the inrush current limiting resistor R
i, the smoothing capacitor Ci is charged via a magnetic coupling transformer MCT described later. Where inrush current limiting resistor R
i is inserted to suppress a surge current when the power is turned on to protect the circuit, and may be provided for the line of the AC power supply AC.

Q ₁ and Q ₂ are switching elements that form a half-bridge type switching circuit. These switching elements Q ₁ and Q ₂ are collectors of the smoothing capacitor Ci between the connection point on the positive electrode side and the ground. , Connected via the emitter. The resistors R ₆ and R ₆ are starting resistors, and the bases of the switching elements Q ₁ and Q ₂ are
D _D1 and D _D2 inserted between the emitters are damper diodes, respectively. The resistors R ₅ and R ₅ are
The resistors for adjusting the base current (drive current) of the switching elements Q ₁ and Q ₂ are shown. Then, C _5, C ₅ is a capacitor for resonance, drive winding N _B of drive transformer PRT described below, together with the N _B, to form a resonant circuit of a self-mutabilis.

In this case, the PRT is a switching element Q.
A drive transformer for variably controlling the switching frequency of ₁ and Q ₂ is shown. In the case of this figure, the drive windings N _B and N _B are shown.
Further, the resonance current detecting winding N _D is wound, and the control winding N _C is wound in a direction orthogonal to each of these windings to form an orthogonal saturable reactor. The drive winding N on the switching element Q ₁ side of this drive transformer PRT
One end of _B is connected to the capacitor C ₅ , and the other end is connected to the emitter of the switching element Q ₁ . One end of the drive winding N _B of the switching element Q ₂ side is grounded to the earth, the other end is connected to the capacitor C _5, the switching element Q ₁
A voltage having a polarity opposite to that of the drive winding N _B is output. The current detection winding N _D is connected one end to the primary winding N ₃ magnetic coupling transformer MCT, the other end is connected to the primary winding N ₁ of the insulating transformer PIT via the resonance capacitor C ₁ It

PIT is an insulating transformer for transmitting the switching outputs of the switching elements Q ₁ and Q _{2 to} the secondary side, and one end of the primary winding N ₁ of this insulating transformer PIT detects a current through a resonance capacitor C _1. The winding N _D is connected in series, and the other end is grounded with respect to the ground. A resonant circuit is formed by the inductance component of the insulating transformer PIT including the resonant capacitor C ₁ and the primary winding N ₁ . On the secondary side, the induced voltage induced in the secondary winding N ₂ by the switching output flowing in the primary winding N ₁ causes the bridge rectifier circuit D ₄ and the smoothing capacitor C
_It is converted into a DC voltage by ₃ and output as an output voltage E ₀ . The control circuit 1 uses, for example, a DC voltage output E on the secondary side.
_O is compared with the reference voltage, and a direct current corresponding to the error is supplied as the control current I _{C to} the control winding N _C of the drive transformer PRT.

In this figure, the MCT is a magnetic coupling transformer. This magnetic coupling transformer MCT is a standard M
In the S method, a winding Ni (Li indicates self-inductance) corresponding to a choke coil inserted in a charging line to the smoothing capacitor Ci is used as a secondary winding for transmitting a switching voltage. Further, in the normal MS method, the winding N ₃ corresponding to the tertiary winding of the insulation transformer PIT is used.
The (inductance L ₃ ) is the primary winding, and both windings are tightly coupled by a ferrite core at a winding ratio of, for example, 1: 1. Here, the magnetic coupling transformer MCT
One end of the primary winding N ₃ of the switching element Q ₁ ,
It is connected to the emitter-collector connection point of Q ₂ , and the other end is connected in series to the primary winding N ₁ of the insulating transformer PIT via the current detection winding N _D and the resonance capacitor C ₁ .

In the switching operation of the switching power supply having the above structure, when a commercial AC power supply is first turned on, for example, the switching element Q is started via the starting resistors R ₆ and R _{6.
Although the} base current is supplied to the bases of ₁ and Q ₂ , if the switching element Q ₁ is turned on _first , the switching element Q ₂ is controlled to be turned off. Then, as the output of the switching element Q _1, the secondary winding N ₃ of the magnetic coupling transformer MCT → the current detection winding N
_A resonance current flows through _D → capacitor C ₁ → primary winding N ₁ , but in the vicinity where the resonance current becomes 0, switching element Q
₂ is turned on and the switching element Q ₁ is turned off. Then, a resonance current in the opposite direction to the above flows through the switching element Q ₂ . After that, the self-excited switching operation in which the switching elements Q ₁ and Q ₂ are alternately turned on is started. In this way, the switching elements Q ₁ and Q ₂ are alternately opened and closed by using the terminal voltage of the smoothing capacitor C _i as the operating power supply, thereby supplying the drive current close to the resonance current waveform to the primary winding N ₁ of the insulation transformer. Then, an alternating output is obtained from the secondary winding N ₂ .

When the DC output voltage (E _O ) on the secondary side decreases, the control circuit 1 controls the current flowing through the control winding N _C so that the switching frequency becomes low (close to the resonance frequency. In order to make a constant voltage, the drive current flowing through the primary winding N ₁ is controlled to increase.

As the power factor improving operation, the magnetic coupling transformer MCT causes the switching voltage corresponding to the resonance current flowing in the insulating transformer PIT to be supplied to the secondary winding Ni of the secondary winding Ni by the magnetic coupling transformer MCT primary winding N _3. The inductance Li is excited. Therefore, the full-wave rectified voltage rectified by the bridge rectification circuit is charged with the switching voltage by the winding Ni of the self-inductance Li and is charged in the smoothing capacitor Ci. The terminal voltage of the capacitor Ci is lowered in the switching cycle. Then, the charging current starts to flow during the period when the terminal voltage of the capacitor Ci is lower than the rectified voltage level of the bridge rectifier circuit, and the number of turns or the number of turns of the magnetic coupling transformer MCT is set so that this period extends to around zero volt. The power factor is set to 1 by setting the line ratio etc.
Will show a value close to. That is, the average AC input current is similar to the AC voltage waveform, and the power factor is improved.

In the power supply circuit using the magnetic coupling transformer, the drive current of the insulating transformer PIT becomes small when the load is light, so that the switching signal induced on the secondary side of the magnetic coupling transformer MCT by this drive current is also small. become. Therefore, since the level of the charging current becomes small when the load is light and the charging current becomes large when the load is heavy, the phenomenon that the terminal voltage of the smoothing capacitor Ci abnormally rises is solved especially when the load is light, and it is difficult for the normal MS method. The regulation can be improved. Therefore, for example, the fluctuation of the rectified and smoothed voltage Vi is suppressed even when the fluctuation of the _AC input voltage V _AC ± 20%,
Switching elements Q ₁ and Q ₂ and smoothing capacitor Ci
It is not necessary to improve the withstand voltage.

An invention in which the MS power factor improving means is applied to a switching power supply circuit using a current resonance type converter has been previously proposed by the present applicant (Japanese Patent Application No. 6-
210740). The circuit diagram of FIG. 6 shows an example of a switching power supply circuit constructed according to the present invention.

In this case, the current resonance type converter is a self-excited type using a half bridge, and a voltage doubler rectifier circuit is provided so as to obtain a rectified and smoothed voltage which is about twice the AC input voltage. For example, it can be used even under heavy load. The same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted.

In the MS method, an insulation transformer PRT is used.
To the tertiary winding N ₃ provided, performs the power factor correction as described later with the choke coil CH connected to the the tertiary winding N ₃ series, in the circuit of this figure, these choke coils CH and the tertiary winding N ₃ are provided on the AC line. In this case, the inrush current limiting resistor Ri is also inserted in the AC line.

D _A and D _B are rectifying diodes, both of which are of the fast recovery type as shown by the dashed line D _FR . The connection point between the anode of the diode D _{A and} the cathode of the diode D _B is the choke coil C.
It is connected to one end of H, the cathode of the diode D _A is connected to the positive electrode of the smoothing capacitor Ci ₁ , and the anode of the diode D _B is grounded. Further, as shown in the figure, the smoothing capacitor has Ci ₁ and Ci ₂ connected in series, and is connected to the positive side of the AC line via the diode D _B. In addition, the smoothing capacitor Ci
It is connected to the negative side of the AC line with respect to the connection point of ₁ and Ci ₂ .

Further, in this circuit, the switching element Q
₁ and Q ₂ are drive transformers CDT (Converter Drive)
Driven by a transformer), the switching frequency is fixed. By providing the control winding N _C so as to be orthogonal to the other winding with respect to the insulating transformer, the insulating transformer is provided with a PRT (Power Regulation Transforme).
r). Therefore, in the constant voltage control of this circuit, the control circuit 2 controls the leakage magnetic flux of the insulation transformer PRT by causing the control winding N _C to flow a current having a level according to the fluctuation of the DC output voltage E _O. It is a series resonance frequency control method.

As the voltage doubler operation in this circuit, the charging path during the period when the AC power source AC is positive is AC → CMC (positive side) → filter choke coil L _N → inrush current limiting resistance Ri → tertiary winding N ₃ → Choke coil CH → diode D _A → smoothing capacitor Ci ₁ → CMC (negative electrode side) → A
C, and the smoothing capacitor Ci _{1 is} charged. In addition, the charging path when the AC power supply AC is negative is AC
→ CMC (negative electrode side) → smoothing capacitor Ci ₂ → diode D _B → choke coil CH → tertiary winding N ₃ → inrush current limiting resistance Ri → filter choke coil L _N → CMC
(Positive electrode side) → AC, and the smoothing capacitor Ci ₂ is charged. By such a charging operation, a rectified and smoothed voltage corresponding to approximately twice the AC input voltage is obtained across the smoothing capacitors Ci ₁ and Ci ₂ connected in series.

Further, the insulating transformer PRT as described above in this circuit is tertiary winding N ₃ are wound, the switching voltage V ₃ is the choke coil CH and a smoothing capacitor C which is induced in the tertiary winding N ₃ Supplied between _i . That is, the switching voltage is supplied to the charging path of the smoothing capacitor C _i . Therefore, the rectified full-wave rectified voltage passes through the choke coil CH, and then the switching voltage is superimposed on the smoothed capacitor C.
_Charged to _i . Therefore, also in this case, the action of lowering the terminal voltage of the smoothing capacitor Ci in the switching cycle is obtained, the distribution angle of the current flowing out from the rectifier circuit side is expanded, and the average value becomes a charging current close to a sine wave. Then, the harmonic distortion of the alternating current is reduced and the power factor is improved.

Similar to the circuit diagram of FIG. 5, FIG. 7 shows an example of a switching power supply circuit having a magnetic coupling transformer to improve the power factor. The same parts as those in FIG. To do. In this circuit, a secondary winding N _2A is further provided on the secondary side of the isolation transformer PIT, and rectifying diodes D provided at both ends of the secondary winding N _2A , respectively.
DC output voltage E by ₅ , D ₆ and smoothing capacitor C _4
Trying to get _one . And, in this case, is connected across the two ends of the primary winding N ₃ magnetic coupling transformer MCT secondary winding N _2A, the switching voltage of the magnetic coupling transformer MCT induced in the secondary winding N _2A The primary winding N ₃ is provided.

Further, in the circuit shown in this figure, the control winding N _C of the magnetic coupling transformer MCT is the windings Ni, N ₃
It is configured as a saturable reactor provided so as to be orthogonal to. One end of the control winding N _C is grounded, and the other end of the control winding N _C has a transistor Q ₃ described next.
Connected to the collector. Q ₃ is a transistor for supplying the control current I _C to the control winding N _C , and forms a class A amplifier together with the resistor R ₃ connected to the emitter. The base supplies the rectified and smoothed voltage Vi to the resistors R ₁ and R
It is connected to the dividing point divided by ₂ . The emitter is a rectifier diode D ₇ via a resistor R _3.
And the smoothing capacitor C ₂ are connected. Rectifying and smoothing circuit consisting of the rectifying diode D ₇ and the smoothing capacitor C ₂ converts an AC voltage appearing on the windings N ₄ formed by winding a primary winding N ₄ insulating transformer PIT in DC resistance Supply to the emitter of the transistor Q ₃ via R ₃ .

In the case of such a circuit configuration, the resistance R
_The rectified and smoothed voltage Vi is detected by ₁ and R ₂ , and the base current of the transistor Q ₃ according to the level of the rectified and smoothed voltage Vi is made to flow. For example, when the rectified and smoothed voltage Vi increases, the base current of the transistor Q ₃ increases and the collector current, that is, the control current I _C decreases. As a result, the inductances L ₃ and Li of the windings Ni and N ₃ of the magnetic coupling transformer MCT increase, but this increases the transmission efficiency from the primary winding N _{3 of the} magnetic coupling transformer MCT to the secondary winding Ni. . For example, magnetic coupling transformer MCT
If is not configured as an orthogonal saturable reactor, it has the property that the power factor decreases as the AC input voltage rises if the load power is constant. Can keep the power factor constant regardless of changes in the AC input voltage. Therefore, the circuit configuration of this figure is effective as a so-called wide range switching power supply device corresponding to the AC input voltage of 100 V system to 200 V system. As described above, various types of switching power supplies are provided with power factor improving means to form a switching power supply device.

[0024]

By the way, when a switching power supply device is mounted on a certain model, for example, even if the power supply circuit is of the same type in the converter type, the constant voltage control system, and the rectification system, There are cases where the switching power supply device needs to be provided with a power factor improving means and cases where it is not particularly necessary to improve the power factor. If it is not necessary to improve the power factor, it is preferable to omit the circuit components for improving the power factor as shown in FIGS. 5 to 7 from the viewpoint of weight and cost.

Therefore, as a measure to cope with the above situation, for example, in a power supply circuit of the same type, a circuit component configured to cope with the power factor improvement is mounted, and a power factor improvement is supported. Prepare at least two different types of mounting boards, one with a circuit configuration not mounted,
Depending on whether it is necessary to improve the power factor, one of these mounting boards is selected and mounted on the device to avoid unnecessary cost, but in reality it differs for the same model. Since there are a plurality of types of mounting boards, the management becomes complicated, which causes a problem in the process of commercialization, which may not be particularly advantageous in terms of cost.

[0026]

Therefore, in consideration of the above-mentioned problems, the present invention is applied to a switching power supply device which needs to be divided into at least two types, that is, a power factor correction type and a non-power factor type. The objective is to obtain one that is easy to manage and cost effective.

Therefore, in the switching power supply device having the switching circuit unit which intermittently supplies the rectified and smoothed voltage obtained by rectifying and smoothing the AC input voltage by the rectifying circuit and the smoothing circuit to the primary side of the converter transformer, A fixed circuit unit including a group of components that can be fixed regardless of power factor improvement support, and a first change circuit including some or all of the component groups for a power supply circuit supporting power factor correction Section and a second change circuit section including a group of parts for making a power supply circuit that does not support power factor improvement, and only the first change circuit section and the second change circuit section with respect to the fixed circuit section. It was decided that the power supply circuit compatible with and not compatible with power factor improvement can be formed by replacing the above.

The fixed circuit section and the first and second modified circuit sections are constructed as separate mounting boards, and the mounting boards of the first and second modified circuit sections are respectively mounted on the fixed circuit section. It was decided to replace the substrate. Further, the mounting boards of the first and second modified circuit parts are
It is decided to use a common substrate section.

Further, the switching circuit section is constituted by a self-excited or separately excited current resonance type converter.

Further, in the power factor correction circuit configured by combining the fixed circuit unit with the second change circuit unit, the choke coil provided in the charging path to the smoothing capacitor is based on the switching operation of the switching circuit unit. It is magnetically coupled with the coil to which the alternating current obtained is supplied, and a normal mode low-pass filter is provided on the AC input voltage line or the output side of the rectifier circuit. It was decided to connect them in series.

Further, the power factor correction circuit constructed by combining the fixed circuit unit with the second modification circuit unit is a normal mode low-pass filter provided for the AC input voltage line or the output side of the rectifier circuit. A choke coil and a tertiary winding provided in the converter transformer are provided, and the filter choke coil, the choke coil, and the tertiary winding of the low pass filter are configured to be connected in series to the charging path for the smoothing capacitor, and It was decided to provide a high-speed recovery type diode connected in series with the filter choke coil. Further, the filter capacitor of the low pass filter is connected between one end of the filter choke coil and the positive electrode of the smoothing capacitor.

Further, as the constant voltage control, in the case of a self-excited current resonance type, the switching frequency of the switching circuit section is changed based on the DC output voltage obtained on the secondary side of the converter transformer. Or the magnetic flux of the insulating transformer is changed based on the DC output voltage obtained on the secondary side of the insulating transformer. Further, in the case of the separately excited type, the driving is performed by a control circuit that generates a driving signal that changes according to the output voltage. The switching power supply device having the above configuration is configured to include a voltage doubler rectifier circuit.

[0033]

According to the above configuration, for example, it is not compatible with power factor improvement only by replacing the change parts required for power factor improvement support and non-power factor improvement support on the same power supply circuit board. The switching power supply device can be configured. Alternatively, for the board on which the components of the fixed circuit section are mounted, prepare a modified circuit board on which modified components compatible with power factor correction and a modified circuit board on which non-compatible modified components are mounted, and make these modifications. By replacing the board with respect to the fixed circuit board and attaching it, it is possible to configure a switching power supply device compatible with and not compatible with power factor correction. At this time, if a common substrate is used for the change circuit that is compatible with and does not support the power factor improvement, only one type of board is required to mount the change circuit on a plurality of types.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of a switching power supply device according to the present invention, in which a circuit configuration for improving power factor is shown. The switching power supply circuit of this embodiment includes a self-excited current resonance type converter and a magnetic coupling transformer to improve the power factor. Also, the drive transformer is an orthogonal transformer PRT having a control winding, and constant voltage control is performed by a switching frequency control method. It should be noted that the same components as those in FIG.

In this circuit, the diodes forming the bridge rectifier circuit D ₁ are all of the low speed recovery type. Therefore, the bridge rectifier circuit D ₁ is 1
It is possible to reduce the circuit size and cost by using package components. Further, an LC including a filter choke coil L _N and a filter capacitor C _N
A low-pass filter circuit is provided on the rectification output side of the bridge rectification circuit D ₁ . That is, the diode between the rectification output terminal of the bridge rectification circuit and the secondary winding Ni of the magnetic coupling transformer MCT via the pin terminal T ₁ (the pin terminals T _{1 to} T ₄ will be described later). Filter choke coil L _N connected in series with D ₂
Is inserted, one end of the filter capacitor C _N is connected to the connection point of the filter choke coil L _N and the diode D ₂ , and the other end (via the pin terminal T ₂ ) of the positive electrode of the smoothing capacitor Ci. Inserted in between.

Here, a diode D ₂ shown by being enclosed by a broken line
Is a high-speed recovery type diode and prevents high frequency of the switching period from flowing into the AC line side. Here, a so-called high-speed recovery type diode element formed by connecting two diode elements in parallel is used. It is a recovery type twin diode (hereinafter, this type of diode is referred to as a high speed twin diode), and is configured as, for example, a component of one package. Where diode D ₂
The twin type is for improving the surge current resistance characteristic described later, and for example, the surge current resistance characteristic I _FSM = 6 of one diode element of the twin diodes is used.
If it is 0 A, the high speed twin diode D ₂ is 12
It has a surge current resistance of 0A.

According to such a circuit configuration, the positive side output terminal of the bridge rectifying diode and the smoothing capacitor Ci
The filter choke coil L _N , the high-speed twin diode D ₂ , and the secondary winding Ni of the magnetic coupling transformer MCT are connected in series and inserted in the line between them.
The value obtained by combining the resistance components of these elements is set so that the inrush current when the power is turned on can be suppressed to the required level, and this destroys elements such as diodes in the current path. With such a configuration, the inrush current limiting resistor Ri can be omitted as shown in this figure. For example, as described above, the high speed twin diode D
_If the surge current resistance characteristic of No. ₂ is 120 A, the above elements may be selected so that the surge current is suppressed within 120 A by the combined resistance of the above elements. Further, since the power consumption is dispersed by the resistance component of each element, heat generation can be suppressed.

Further, one end of the filter capacitor C _N is not directly grounded to the ground, but the smoothing capacitor Ci as shown in FIG.
, But the voltage across the filter capacitor C _N can be much lower than when it is inserted on the AC line side.
For example, it is not necessary to use a product that has acquired safety standards, and if ordinary parts are used, it is possible to cope with them sufficiently, which is advantageous in terms of size and cost.

In this circuit configuration, the power factor is improved by the same operation as described with reference to FIG. 5, but in the present embodiment, for example, the magnetic coupling transformer M which is related to the power factor improvement.
The CT, LC low-pass filter (filter choke coil L _N and filter capacitor C _N ) and high-speed twin diode D ₂ are used as a change circuit section for power factor improvement, and the remaining circuit section is a fixed circuit section. Further, in this figure, K _{1 which} is obtained by enclosing the above-mentioned modified circuit portion by a one-dot chain line is a modified circuit board for power factor improvement, and actually, for example, as shown in the perspective view of FIG. It is configured by mounting the modified circuit component corresponding to the above power factor improvement on the phenol printed circuit board S ₁ . Then, T _{1 to} T ₄ provided on the lower side of the printed circuit board S ₁ are used as pin terminals, and these pin terminals T _{1 to} T ₄ are connected and fixed to, for example, terminals provided on the fixed circuit board side. By doing so, the switching power supply device corresponding to the power factor improvement equivalent to that shown in FIG. 1 is configured.

In order to make the switching power supply device of this embodiment non-compliant with power factor correction, instead of the modified circuit board K ₁ , the modified circuit board K not compatible with power factor correction shown on the upper right side of FIG. ₂ should be attached to the fixed circuit side. This modified circuit board K _{2 that} does not support power factor correction is shown in Figure 1 (upper right side).
And a printed circuit board S as shown in the perspective view of FIG.
Inrush current limiting resistor R across pin terminals T _1, T ₂ against ₂
i (which is a cement resistor) is connected, and the pin terminals T ₃ and T ₄ are short-circuited by a jumper wire J. As for the printed boards S ₁ and S ₂ shown in FIGS. 2A and 2B, if the same printed boards S ₁ and S ₂ are used and their sizes and wiring patterns are made common, the printed boards for the modified circuit section Since only one type is required, the cost can be reduced and the production management can be simplified.

When the modified circuit board K ₂ that does not support the power factor correction is mounted on the fixed circuit section of FIG. 1, the output line on the positive side of the bridge rectifier circuit D ₁ has the inrush current limiting resistance Ri. Is connected to the positive electrode of the smoothing capacitor Ci via the series resonance circuit on the primary side of the insulating transformer PIT (the primary winding N _{1 of the} insulating transformer PIT and the resonant capacitor C ₁ are provided only via the current detection winding N _D). Since the switching elements Q ₁ and Q ₂ are connected to the emitter-collector connection point, a switching power supply device of the self-excited current resonance type without power factor correction is configured.

As described above, in the present embodiment, the modified circuit board K for improving the power factor is provided for the board on which the fixed circuit portion is mounted.
₁ or, only by mounting the non-corresponding change circuit board K ₂ , a switching power supply device compatible or non-corresponding to the power factor can be obtained, so that the production management becomes easy. Also,
Even after the product is manufactured, it is possible to easily replace the changed circuit board as an option and newly work to improve the power factor, for example. As for the printed boards S ₁ and S ₂ shown in FIGS. 2A and 2B, if the same printed boards S ₁ and S ₂ are used and their sizes and wiring patterns are made common, the printed boards for the modified circuit section Since only one type is required, cost can be reduced and production management can be further simplified.

In the above embodiment, the modified circuit board is provided separately from the fixed circuit board, but the fixed circuit section and the modified circuit board are formed on the same board. When the power factor correction is applied to this substrate, the magnetic coupling transformer MCT, the LC low-pass filter, and the high-speed twin diode D ₂ are mounted at the required positions, and when not compatible, the inrush current limiting resistor Ri and When the jumper wire J is loaded at a required position, a power circuit board compatible with or not compatible with power factor improvement may be formed.

FIG. 3 is a circuit diagram of a switching power supply device according to another embodiment of the present invention, which is of a self-excited current resonance type and is provided with a voltage doubler rectifying and smoothing circuit.
Orthogonal transformer P with control winding N _C provided in the insulation transformer
By adopting RT, a constant voltage control method by series resonance frequency control is adopted. In this figure, the same parts as those shown in FIGS. 1 and 6 are designated by the same reference numerals and the description thereof will be omitted.

Change times for power factor improvement in this circuit diagram
Road board K₁ First, the five pin terminals T₁ ~ T_Five Is provided
Can be And this modified circuit board K₁ Above,
Terminal T₁ For filter choke coil L_N Is connected
And the other end has the forward direction opposite to each other as shown in the figure.
Two high-speed twin diodes installed in parallel in this way
Do D₂ , D_2AOne of the connection points is connected. And high
Fast twin diode D ₂ , D_2AThe other connection point of is the pin end
Child T₃ Connected with. Also, the choke coil CH is a pin
Terminal T₂ And pin terminal T_Four Connected in between. And a pin
Terminal T_Five Is a filter capacitor C_N One end of is connected
Filter capacitor C_N The other end of the filter choke
Coil L_N And high-speed twin diode D₂ , D_2AConnection point
Connected to. This high speed twin diode D₂ ,
D_2AIs the switching period superimposed on the AC input current.
It is provided according to the current, and it also conducts in both directions.
As much as possible, the opposite voltage directions are used to adjust the voltage doubler.
This is because it corresponds to the charging path formed for the flow.

When the modified circuit board K ₁ is mounted on the fixed circuit section side, the pin terminal T ₁ is connected to the positive end of the common mode choke coil CMC, and the pin terminal T ₂ will be described later. It is connected to the connection terminals T _B and T _{D of the} rectifying diode D ₃ . The pin terminals T ₃ and T ₄ are respectively connected to both ends of the tertiary winding N ₃ of the insulating transformer PRT.
The pin terminal T ₅ is a common mode choke coil CMC.
Is connected to the negative electrode side end of the.

Further, in this embodiment, the rectifier circuit D ₃ is composed of four low speed recovery type diodes (D _A1 , D _A2 , D _B1 , D).
The bridge rectification element of one package by _B2 ) is diverted, the connection terminal T _A is grounded, the connection terminal T _C is connected to the positive electrode of the smoothing capacitor Ci ₁ , that is, the rectification smoothing line, and the connection terminal T _B , T _D are connected to one end of the choke coil CH, and an AC power source is input. Here, the reason why the rectifier circuit D ₃ is such a bridge rectifier is that, for example, in the present embodiment, the high speed twin diode D ₂ ,
Since D _2A is provided in the AC line, it is not particularly necessary to configure the rectifier circuit D ₃ with a high-speed recovery type.
This is because it is more cost effective to use two bridge rectifying elements.

Then, for example, in the power supply circuit according to the configuration of the present embodiment, when the modified circuit board K ₁ for power factor improvement is mounted and the circuit configuration is as shown in the figure, charging as a voltage doubler rectification operation is performed. In the path, when the AC power source AC is positive, the bridge rectifier circuit D ₃ simultaneously outputs 2
The charging current flows through the diodes D _A1 and D _A2 of the book, and the charging current flows through the diodes D _B1 and D _B2 at the same time while the AC power supply AC is negative.

As the power factor improving operation, LC by the filter choke coil L _N and the filter capacitor C _N is used.
Since the low-pass filter, the choke coil CH, the tertiary winding N _3, and the high speed twin diodes D ₂ and D _2A are provided in the AC line, the power factor improving operation is performed by the same operation as described with reference to FIG. Further, in this case, by combining the filter choke coil L _N , the choke coil CH, the tertiary winding N ₃ and the resistance component of the high speed twin diode D ₂ or D _2A , the high speed twin diode D ₂ ,
The inrush current limiting resistor Ri is controlled so that the inrush current at the time of power-on is suppressed to a required level such that D _2A does not break.
Is omitted.

Further, K ₂ shown in the upper right of FIG. 3 is a modified circuit board which is incompatible with the power factor correction in this embodiment. The modified circuit board K _{2 that} does not support power factor correction is configured to be replaceable by using, for example, the same printed circuit board as the modified circuit board K ₁ that supports power factor correction, as in the previous embodiment. To be taken. Alternatively, the fixed circuit unit and the both changing circuit units may be formed on the same substrate and the parts may be replaced.

In the modified circuit board K ₂ that does not support the power factor correction in this embodiment, the inrush current limiting resistor Ri is provided between the pin terminals T ₁ and T ₂ . When the modified circuit board K ₂ that does not support power factor correction is mounted on the board on the fixed circuit side instead of the modified circuit board K ₁ that supports power factor improvement, the filter choke coil L is connected in the AC line. _N, choke coil CH, tertiary winding N ₃ is deleted, instead, a common mode choke coil CMC and the input terminal of the rectifier circuit D ₃ on the positive electrode side (T
Only the resistor Ri is inserted between _D and T _B ). Further, since both ends of the insulation transformer PRT tertiary winding N ₃ are opened, this is equivalent to the removal of this tertiary winding N _{3 as} well. As a result, a circuit for power factor improvement is omitted, and a voltage doubler rectification type switching power supply device that does not support power factor improvement is configured.

Next, FIG. 4 is a circuit diagram showing still another embodiment of the present invention. The same parts as those of the circuits shown in FIG. 7, FIG. 1 and FIG. Omit it.

In this power supply circuit, a separately excited current resonance type converter using MOS-FET transistors is used for the two switching elements Q ₁ and Q ₂ . Therefore, the constant voltage control is performed by controlling the switching frequency, for example, based on the level of the DC voltage E _O obtained by the control circuit 1 via the photocoupler 3. Also,
In this case, the voltage obtained by converting the alternating voltage excited in the winding N ₄ into a direct current by the capacitor C ₂ and the rectifying diode D ₅ is supplied to the emitter of the transistor Q _{3 which} will be described later, and the control circuit 1 and the starting circuit. It is also supplied as a driving power source to the drive unit 2. It should be noted that D _CL and D _CL provided in parallel with the switching elements Q ₁ and Q ₂ , respectively, are clamp diodes for flowing a reverse current when the switch is off.

The modified circuit board K ₁ for power factor correction of this embodiment is provided with an LC low-pass filter, a high-speed twin diode D ₂ , and a control winding N _C, and is formed as a saturable reactor. A coupling transformer MCT, a class A amplifier including a transistor Q ₃ and a resistor R ₃ for controlling a control current flowing through the control winding N _C , and resistors R ₁ and R ₂ are mounted. Such a modified circuit board K
_When the fixed circuit unit side and the modified circuit board K ₁ are connected via the pin terminals T _{1 to} T ₆ provided in FIG. 1, the configuration of the circuit unit for power factor improvement is shown in FIG. A switching power supply device for power factor improvement is constructed in the same manner as the configuration shown. However, as in the embodiment described with reference to FIG. 1, the bridge rectifier circuit D together with the fast recovery diode D _{2 is used.}
By providing the LC low-pass filter on the positive electrode output line side of ₁ , it is possible to omit the inrush current limiting resistor Ri and use a normal product for the filter capacitor C _N.

Then, in the modified circuit board K ₂ that does not support the power factor correction in this embodiment, as shown in the upper right part of FIG. 4, it is mounted so that the resistor Ri is inserted between the pin terminals T ₁ and T _2. And connect pin terminals T ₃ and T ₄ to jumper wire J
It is configured by short-circuiting with. When the change circuit board K ₂ that does not support power factor correction is replaced with the fixed circuit section side, only the resistor Ri is inserted and connected to the positive electrode output terminal of the bridge rectifier circuit D ₁ and the positive electrode side of the smoothing capacitor Ci, Isolation transformer P
The IT primary winding N ₁ is connected to the source-drain connection point of the switching elements Q ₁ and Q ₂ via only the resonance capacitor C ₁ . As a result, the power supply circuit of this embodiment is configured as a switching power supply device including the separately excited current resonance type converter that does not support power factor correction.

The power factor correction method of the present invention described so far in each of the above-described embodiments uses the converter type as the switching power supply circuit, the switching frequency control method (the drive transformer is an orthogonal PRT) / series. Resonant frequency control method (isolation transformer orthogonal type PRT
Can be applied to a power supply circuit configured by various combination patterns such as a half-bridge coupling type / full-bridge coupling type of switching element, and a voltage doubler rectifier circuit. It goes without saying that the pattern is not limited to the combination pattern.

[0057]

As described above, the present invention does not support power factor improvement only by replacing and mounting a board on which modified components required for power factor improvement support and non-power factor correction are mounted. Since the switching power supply device can be configured, the production management is facilitated and the cost can be reduced. Moreover, if a common one is used for the modified circuit board that is compatible with and does not support power factor improvement, only one board is required to mount it for multiple types of modified circuits. Will be advantageous.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching power supply device as an embodiment of the present invention.

FIG. 2 is a perspective view showing a structure of a modified circuit board according to an embodiment.

FIG. 3 is a circuit diagram showing a switching power supply device as another embodiment.

FIG. 4 is a waveform diagram showing an operation of a switching power supply device of still another embodiment.

FIG. 5 is a circuit diagram showing a switching power supply device as a conventional example.

FIG. 6 is a circuit diagram showing a switching power supply device as a conventional example.

FIG. 7 is a circuit diagram showing a switching power supply device as a conventional example.

[Explanation of symbols]

1 Control circuit 2 Start circuit 3 Photo coupler L _N Filter choke coil C _N filter capacitor D ₁ Bridge rectifier circuit D ₂ Fast recovery type twin diode D ₃ Rectifier circuit CH Choke coil PIT Isolation transformer PRT Control transformer CDT Drive transformer MCT Magnetic coupling transformer Q _1, Q ₂ switching elements Ci, Ci _1, Ci ₂ smoothing capacitor C ₁ resonance capacitor N ₁ primary winding

Claims (12)

[Claims] 1. A switching power supply device comprising switching means for intermittently supplying a rectified smoothed voltage obtained by rectifying and smoothing an AC input voltage by a rectifying circuit and a smoothing circuit to a primary side of a converter transformer, wherein the power supply circuit is a power factor. A fixed circuit unit including a group of components that can be fixed regardless of improvement / non-correspondence, and a first change circuit unit including a part or all of the components for forming a power supply circuit compatible with power factor improvement. , A second change circuit section including a group of components for a power supply circuit that does not support power factor improvement, and the first change circuit section and the second change circuit section with respect to the fixed circuit section. A switching power supply device capable of forming a power supply circuit compatible with and not compatible with power factor improvement by replacing only the power supply circuit. 2. The fixed circuit section and the first and second modified circuit sections are separate mounting boards, and the mounting boards of the first and second modified circuit section are the fixed circuits, respectively. The switching power supply device according to claim 1, wherein the switching power supply device is configured to be replaceable with respect to a mounting board of the unit. 3. The switching power supply device according to claim 1, wherein a common board portion is used as a mounting board for the first and second change circuit portions. 4. The switching power supply device according to claim 1, wherein the switching means is a self-excited or separately-excited current resonance type converter. 5. In the power factor correction circuit configured by combining the fixed circuit unit with the second change circuit unit, a choke coil provided in a charging path to the smoothing capacitor is provided in the switching unit. It is magnetically coupled to a coil to which an alternating current obtained based on a switching operation is supplied, and a normal mode low-pass filter is provided on the AC input voltage line or the output side of the rectifier circuit, and the filter choke of the low-pass filter is provided. The switching power supply device according to claim 1, wherein a coil and the choke coil are connected in series. 6. The power factor correction circuit configured by combining the fixed circuit unit with the second change circuit unit is a normal mode provided for an AC input voltage line or an output side of the rectifier circuit. Of the low pass filter, the choke coil and the tertiary winding are connected in series to the charging path for the smoothing capacitor. The switching power supply device according to claim 1, wherein the switching power supply device is configured as follows. 7. The switching power supply device according to claim 5, further comprising a high-speed recovery type diode connected in series with the filter choke coil. 8. The filter capacitor of the low-pass filter is connected between one end of the filter choke coil and the positive electrode of the smoothing capacitor, according to claim 5, 6 or 7. The switching power supply described. 9. A constant voltage control is performed by varying a switching frequency of the switching means based on a DC output voltage obtained on the secondary side of the converter transformer. The switching power supply device according to claim 1. 10. A constant voltage control is performed by varying the magnetic flux of the insulation transformer based on a DC output voltage obtained on the secondary side of the insulation transformer. 9. The switching power supply device according to claim 8. 11. The switching device according to claim 1, wherein the switching device is configured as a separately excited type, and is driven by a control circuit that generates a driving signal that changes according to an output voltage. Switching power supply. 12. The switching power supply device according to claim 1, comprising a voltage doubler rectifier circuit.