JP2011192724A - Composite transformer module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and inexpensively constitute a high-function switching power supply that includes a high-speed response control circuit, a synchronous rectifier drive circuit, and a protecting circuit by enhancing efficiency and heat dissipation of a switching power supply and suppressing high-frequency EMI noise. <P>SOLUTION: A composite transformer module 12 includes a pair of cores 18T and 18B, a bobbin 20, a power transmission transformer section 14 provided in the bobbin 20, and a multilayer substrate 13. The multilayer substrate 13 has signal transmission transformer sections 15L and 15R, a primary signal processing circuit 17, and a secondary signal processing circuit 22. The multilayer substrate 13 has core leg insertion holes into which core legs of the cores 18T and 18B are inserted. The multilayer substrate 13 further has a plurality of connection terminal insertion holes 21 for mounting a plurality of connection terminals 23 of the bobbin 20 on the multilayer substrate 13. The connection terminals 23 of the bobbin 20 which protrude from a reverse surface of the multilayer substrate 13 serve as connection terminals for mounting the composite transformer module 12 on a mother board. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a composite transformer module in which a transformer including a power transmission transformer unit and a signal transmission transformer unit and a signal processing circuit unit are integrally formed as a module.

  A switching power supply module in which a transformer having a conductor pattern formed on a multilayer substrate as a coil and a switching power supply circuit are integrated is disclosed in Patent Document 1.

  FIG. 1A is a diagram illustrating an example of a switching power supply module related to Patent Document 1. FIG. In the switching power supply module 1, a switching power supply circuit 3 is configured on the circuit board 2. The switching power supply circuit 3 includes a transformer 4, a plurality of circuit components 5, and a wiring pattern (not shown) formed on the circuit board 2. The circuit component 5 is an IC chip, a capacitor element, a switching element, a rectifying element, or the like. In addition, a connection terminal 6 for connecting the switching power supply module 1 to the motherboard is provided.

  The transformer 4 includes a coil pattern 7 formed on the circuit board 2 and a pair of cores 8. The circuit board 2 is a laminated body in which a plurality of conductor layers are laminated. A coil pattern to be a primary coil and a coil pattern to be a secondary coil are formed on the circuit board 2, and the plurality of coil patterns are substantially coaxially related. Are stacked.

  A core leg insertion hole 9 is formed in the formation area of the coil pattern 7 on the circuit board 2. The core leg of the core 8 is inserted into the core leg insertion hole 9, and the pair of cores 8 are combined and attached to the coil pattern 7. As shown in FIG. 1, the pair of cores 8 are mounted such that a part of the coil pattern 7 is sandwiched from both the front and back sides of the circuit board 2.

Japanese Patent No. 3414386

  The switching power supply module 1 in which the transformer having the conductor pattern formed on the multilayer substrate as a coil and the switching power supply circuit are integrated has the following problems.

  (A) In order to reduce the direct current resistance and alternating current resistance in the coil pattern 7 of the transformer 4 and reduce the conduction loss of the coil, it is necessary to increase the number of laminated circuit boards. In order to increase the degree of coupling between the primary and secondary sides of the transformer, it is effective to increase the number of multilayer substrates to form a sandwich structure. On the other hand, when the number of multilayer substrates is increased, the cost of the substrate increases in proportion to it. The inner layer of the coil pattern 7 is used to form the coil pattern, but the inner layer directly below the circuit component 5 is not necessarily effectively used. In particular, in a switching power supply circuit that requires many large circuit components, mounting the entire switching power supply circuit on an expensive multilayer board is inefficient from the viewpoint of cost reduction.

  (B) Since the thermal resistance of the circuit component 5 mounted on the integrated switching power supply module 1 to the motherboard is large, there may be a problem in the heat dissipation of the circuit component 5. In the case where the integrated switching power supply module 1 has a structure in which the heat generated from the components is mainly dissipated to the mother board, the heat dissipating path is predominantly a path from the circuit board 2 to the mother board via the connection terminals 6. However, since the base material of the circuit board 2 constituting the integrated switching power supply module 1 has a relatively large thermal resistance and the distance of the heat transfer path between the circuit component 5 and the motherboard is long, the heat dissipation of the circuit component 5 The nature is bad. In particular, when the power handled by the integrated switching power supply module 1 is large, the heat generation of the circuit component 5 such as the transformer coil pattern 7 and the switching element becomes very large, and the efficiency of the integrated switching power supply module 1 is reduced. Or the operating temperature range of the integrated switching power supply module 1 is narrowed.

  (C) In the multilayer board constituting the circuit board 2 of the integrated switching power supply module 1, if the prepreg having a thickness of a certain value or more is not sandwiched between the insulating parts between the double-sided boards, voids are generated in the insulating parts. Reliability cannot be secured. Therefore, it is necessary to increase the ratio of the thickness of the insulating layer to the thickness of the conductor layer forming the coil pattern 7. In order to reduce the DC resistance of the transformer coil, it is necessary to increase the ratio (space factor) of the coil conductor part in the core window frame. However, the printed coil formed of a multilayer substrate has a thin structure. However, the effect of the skin effect is small, and there is an advantage that conduction loss can be reduced in high-frequency switching operations. There is a problem that it cannot be lowered.

  (D) Further, in a transformer composed of a laminated coil formed with a conductor pattern on a multilayer board, a minimum pattern width and a minimum pattern interval for ensuring the reliability of the board are specified, and the number of layers is reduced to the cost of the multilayer board. Since it greatly affects, it is difficult to form a coil having an extremely large number of turns (for example, 100 turns or more). For this reason, in a switching power supply with an extremely large step-up ratio or step-down ratio, it is difficult to form a transformer with a printed coil that forms a coil with a conductor pattern on a substrate.

  (E) Regarding the characteristics of the transformer, there are the following problems. FIG. 1B is a cross-sectional view showing an example of a winding structure of a transformer. In general, in a transformer having a structure in which a primary coil winding 10 and a secondary coil winding 11 are repeatedly stacked as shown in FIG. 1B, a parasitic capacitance Cs shown in FIG. 1B is generated between the windings. . The combined capacitance of the parasitic capacitance Cs between the windings becomes equal to that connected between the primary coil and the secondary coil. For this reason, the parasitic capacitance Cs between the windings increases the noise current flowing between the primary and secondary sides of the transformer in a high-frequency / high-speed switching operation, causing a short-circuit loss of the parasitic capacitance and generation of high-frequency EMI noise. As in the transformer 4 shown in FIG. 1A, a coil in which a plurality of coil patterns 7 are arranged in parallel has a problem that the parasitic capacitance Cs between windings is larger than a winding type coil wound around a coil bobbin. There is. For example, it has a parasitic capacitance of about 10 times that of a winding type coil.

  (F) As another problem, when it is cheaper to form the switching power supply circuit on the motherboard than to purchase the conventional integrated switching power supply module 1, the switching power supply circuit is configured on the motherboard. In such a case, an engineer who does not specialize in switching power supply may design. In addition to the power conversion circuit and control circuit, switching power supply design requires technologies such as protection circuits, thermal design, noise countermeasures, etc.Insulated switching power supplies require further transformer design, which is optimal for synchronous rectifiers. Driving at timing is also difficult. Therefore, a problem arises that it is difficult for a non-specialist engineer to design a high-performance switching power supply having high efficiency and high-speed response.

  An object of the present invention is to provide a composite transformer module that solves the various problems described above.

The composite transformer module of the present invention is configured as follows to determine the various problems described above.
(1) A set of fitted cores, a power transmission transformer unit that transmits power between the primary and secondary, and a signal between the primary and secondary that is substantially independent of the power transmission transformer unit. A signal transmission transformer section for transmitting,
The signal transmission transformer unit is composed of a multilayer substrate that penetrates the magnetic legs of the core and a coil pattern formed on the multilayer substrate, and a signal processing circuit unit that processes input / output signals of the signal transmission transformer unit The composite transformer and the signal processing circuit unit are mounted on a substrate, and are integrally formed as a module.

(2) For example, the signal processing circuit unit includes a primary signal processing circuit provided on the primary side of the transformer and a secondary signal processing circuit provided on the secondary side of the transformer.

(3) For example, the core has at least four or more magnetic legs including a middle leg portion and an outer leg portion.

(4) For example, the primary coil and the secondary coil of the power transmission transformer are wound around the outer periphery of the middle leg of the core, and at least three or more outer legs are formed outside the power transmission transformer. Yes.

(5) For example, the primary coil and the secondary coil of the power transmission transformer unit are configured by copper wires wound around a bobbin through which the middle leg passes, and the multilayer substrate is joined to the bobbin.

(6) For example, the primary coil and the secondary coil of the power transmission transformer unit are formed of a coil pattern formed around the middle leg and formed on the multilayer substrate.

(7) For example, a coil pattern for a signal processing circuit power source that is wound around the middle leg is formed on the multilayer substrate, and a voltage induced in the coil pattern for the signal processing circuit power source is rectified and smoothed to A rectifying and smoothing circuit for supplying a power supply voltage to the signal processing circuit is provided.

(8) For example, a circuit for controlling a primary power switch for switching a voltage applied to a primary coil of the power transmission transformer unit is provided, and the composite transformer module constitutes a part of an insulated switching power supply.

(9) For example, the secondary signal processing circuit has a function of transmitting a signal correlated with an output voltage or an output current of the isolated switching power supply from the secondary side to the primary side, and the primary signal processing A circuit that receives a signal correlated with the output voltage or output current, and a pulse width control function that controls a drive signal width of the primary power switch so that the output voltage or output current approaches a target value; And means for outputting a drive signal for the primary power switch.

(10) For example, the insulated switching power supply circuit includes a high-side power switch having a drive signal reference potential different from that of the primary power switch on the primary side, and the primary signal processing circuit includes the primary power switch. Means for outputting a drive signal of the high-side power switch related to the drive timing of the module from the module.

(11) For example, the primary signal processing circuit has a function of transmitting a signal related to the driving timing of the synchronous rectifier from the primary side to the secondary side, and the secondary signal processing circuit is a signal related to the driving timing of the synchronous rectifier. Is received, a synchronous rectifier drive signal is formed and output from the module.

(12) For example, the signal processing circuit includes an overcurrent state of the primary coil or the secondary coil of the power transmission transformer unit, an overheat state of the power transmission transformer unit, a low voltage state of an input voltage of the insulating switching power supply, A detection circuit for detecting an abnormal state of at least one of an overvoltage state of the input voltage of the isolated switching power supply, an undervoltage state of the output voltage of the isolated switching power supply, and an overvoltage state of the output voltage of the isolated switching power supply;
When the detection circuit detects an abnormal operation, the abnormal power protection unit protects the isolated switching power supply by performing any one of a duty reduction of the primary power switch, a switching operation stop, or a hiccup operation. .

According to the present invention, the following effects can be obtained.
By using a wound coil for the transformer, the space factor can be increased compared to the laminated coil, so it is easy to reduce DC resistance and coil conduction loss, and the associated transformer cost. You can also suppress the up. In applications where conduction loss due to direct current resistance is the main component, it is advantageous to reduce the loss by forming the coil portion with a winding.

  Since there are no restrictions on the pattern of a wound coil like a laminated coil, the number of turns can be made extremely large or small, and a large step-up ratio or step-down ratio can be realized. High degree.

  In the wound coil, the parasitic capacitance between the windings is smaller than in the laminated coil, so that the noise current flowing between the primary and secondary of the transformer and the parasitic capacitance short-circuit loss are reduced in the high-frequency / high-speed switching operation. Therefore, the characteristics of the switching power supply module such as high frequency EMI noise suppression and efficiency can be improved.

  The composite transformer module and the mother board can be composed of different circuit boards. Therefore, for example, if a low-cost paper phenol substrate or a glass epoxy substrate with a small number of layers is used as the motherboard on which circuit components are mounted, the substrate cost is reduced, and the manufacturing cost of the entire switching power supply can be reduced. Further, when importance is attached to the heat dissipation of the power conversion circuit component, a heat dissipation method can be adopted in which the power conversion circuit component is mounted on a motherboard using a high heat dissipation substrate such as an aluminum substrate and the motherboard is in close contact with the heat sink.

  Even if it is cheaper to form the switching power supply circuit on the motherboard than to purchase the conventional integrated switching power supply module, the composite transformer module is purchased from a power supply vendor instead of the transformer and mounted on the motherboard. If a power conversion circuit component or an input / output filter component is mounted around the composite transformer module, a high-function switching power supply with high efficiency and high-speed response can be configured easily and inexpensively. Motherboard designers can omit high-speed response control circuits, synchronous rectifier drive circuits, protection circuit designs, and transformer designs that require advanced expertise, and power conversion circuit components and smoothing circuits are mounted on the motherboard. And just do the thermal design.

FIG. 1A is a diagram illustrating an example of a switching power supply module disclosed in Patent Document 1. FIG. 1 is an exploded perspective view of a composite transformer module 12 according to a first embodiment. FIGS. 3A and 3B are plan views of two different surfaces (layers) of the multilayer substrate 13. 4A shows a magnetic path of the signal transmission transformer unit, and FIG. 4B shows a magnetic path of the power transmission transformer unit. It is an equivalent circuit diagram of the transformer part of the composite transformer module according to the first embodiment. It is a disassembled perspective view of the composite transformer module 24 which concerns on 2nd Embodiment. FIGS. 7A and 7B are plan views of two different surfaces (layers) of the multilayer substrate 13. FIG. 8A is a diagram showing a magnetic path of the signal transmission transformer unit, and FIG. 8B is a diagram showing a magnetic path of the power transmission transformer unit. It is a perspective view of the switching power supply module provided with the compound transformer module 24 concerning a 2nd embodiment. 3 is a circuit diagram of a switching power supply module 301. FIG. It is a wave form diagram of each part of switching power supply module. It is a circuit diagram of the switching power supply module 302 provided with the compound transformer module based on 3rd Embodiment.

<< First Embodiment >>
The composite transformer module according to the first embodiment will be described with reference to FIGS.
FIG. 2 is an exploded perspective view of the composite transformer module 12 according to the first embodiment. The composite transformer module 12 includes a set of E-type cores 18T and 18B, a bobbin 20, a power transmission transformer unit 14 provided on the bobbin 20, and a multilayer substrate 13.

  The multilayer substrate 13 includes signal transmission transformer units 15L and 15R that transmit signals between the primary and secondary, a primary signal processing circuit 17, and a secondary signal processing circuit 22. The multilayer board 13 is formed with core leg insertion holes 19C, 19La, 19Lb, 19Ra, 19Rb through which the core legs of the cores 18T, 18B are inserted. Furthermore, a plurality of connection terminal insertion holes 21 for mounting the plurality of connection terminals 23 of the bobbin 20 on the multilayer substrate 13 are formed in the multilayer substrate 13. In a state where the bobbin 20 is mounted on the multilayer substrate 13, the connection terminal 23 of the bobbin 20 protruding from the lower surface of the multilayer substrate 13 is also a connection terminal for mounting the composite transformer module 12 on the motherboard.

  The primary coil and the secondary coil of the power transmission transformer unit 14 are copper wire windings and are wound around the bobbin 20 in an insulated state. The middle legs 18TC and 18BC of the cores 18T and 18B are inserted into the holes H of the bobbin 20.

  The signal transmission transformer section 15L is formed around core leg insertion holes 19La and 19Lb through which the outer legs 18BLa and 18BLb of the core 18B are inserted. Similarly, the signal transmission transformer 15R is formed around core leg insertion holes 19Ra and 19Rb through which the outer legs 18BRa and 18BRb of the core 18B are inserted.

  The primary signal processing circuit 17 is provided on the primary side of the transformer, and the secondary signal processing circuit 22 is provided on the secondary side of the transformer. A coil pattern for a signal processing circuit power supply is formed on the multilayer substrate 13 so as to wind around the core leg insertion hole 19C through which the middle leg 18BC of the core 18B is inserted. The multilayer substrate 13 is provided with a rectifying / smoothing circuit that drives the signal processing circuits 17 and 22 with power obtained by rectifying and smoothing the output of the coil pattern for the signal processing circuit power supply.

  In the composite transformer module 12, the bobbin 20 provided with the power transmission transformer unit 14 is mounted on the multilayer board 13, the middle leg 18TC of the core 18T is inserted into the hole H of the bobbin 20, and the core leg insertion hole 19C of the multilayer board 13 is inserted. , 19La, 19Lb, 19Ra, 19Rb, the core 18B is inserted, and further, a core fixing frame (not shown) for fixing the cores 18T and 18B in a joined state is attached.

  FIGS. 3A and 3B are plan views of two different surfaces (layers) of the multilayer substrate 13. 4A shows a magnetic path of the signal transmission transformer unit, and FIG. 4B shows a magnetic path of the power transmission transformer unit. 3A and 3B show cross sections of the outer legs 18BLa, 18BLb, 18BRa, and 18BRb of the core 18B.

  On the surface (layer) of the multilayer substrate 13 shown in FIG. 3A, coils 102a and 102c wound around the outer leg 18BLb and the outer leg 18BLa in opposite directions one by one through the via electrode 102b. Are connected in series. Since the outer leg 18BLb and the outer leg 18BLa have the same distance from the middle leg of the core and the same cross-sectional area, the outer legs 18BLb and the outer legs 18BLa are induced in the coils 102a and 102c by the change of the magnetic flux passing through the outer legs 18BLb and 18BLa by the power transmission transformer. Since the voltages have opposite polarities and the same voltage value, they are canceled out. As a result, the voltage due to the power transmission transformer does not appear at the output ends ab of the coils 102a and 102c.

  Further, on the surface (layer) of the multilayer substrate 13 shown in FIG. 3B, coils 104a and 104c wound around the outer leg 18BLb and the outer leg 18BLa in opposite directions one by one are provided on the via electrode 104b. Are connected in series. Since the outer leg 18BLb and the outer leg 18BLa have the same distance from the middle leg of the core and the same cross-sectional area, the outer legs 18BLb and the outer legs 18BLa are induced in the coils 104a and 104c by the change of magnetic flux that passes through the outer legs 18BLb and 18BLa by the power transmission transformer. Since the voltages have opposite polarities and the same voltage value, they are canceled out. As a result, the voltage due to the power transmission transformer does not appear at the output ends cd of the coils 104a and 104c.

  On the other hand, since the coils 102a and 102c and the coils 104a and 104c are magnetically coupled via the outer legs 18BLb and 18BLa, the coils 102a and 102c are, for example, primary coils and the coils 104a and 104c are secondary coils. Acts as a signal transmission transformer.

  What has been described above also applies to the other outer legs 18BRb and 18BRa. That is, on the surface (layer) of the multilayer substrate 13 shown in FIG. 3A, coils 105a and 105c wound around the outer leg 18BRb and the outer leg 18BRa in opposite directions by one turn are provided on the via electrode 105b. Are connected in series. Since the outer leg 18BRb and the outer leg 18BRa have the same distance from the middle leg of the core and the same cross-sectional area, the outer legs 18BRb and the outer leg 18BRa are induced in the coils 105a and 105c by the change of magnetic flux that passes through the outer legs 18BRb and 18BRa by the power transmission transformer. Since the voltages have opposite polarities and the same voltage value, they are canceled out. As a result, the voltage due to the power transmission transformer does not appear at the output terminals km of the coils 105a and 105c.

  Further, on the surface (layer) of the multilayer substrate 13 shown in FIG. 3B, coils 106a and 106c wound around the outer leg 18BRb and the outer leg 18BRa in opposite directions by one turn are provided on the via electrode 106b. Are connected in series. Since the outer leg 18BRb and the outer leg 18BRa have the same distance from the middle leg of the core and the same cross-sectional area, the outer legs 18BRb and the outer leg 18BRa are induced in the coils 106a and 106c by the change of magnetic flux that passes through the outer legs 18BRb and 18BRa by the power transmission transformer. Since the voltages have opposite polarities and the same voltage value, they are canceled out. As a result, the voltage due to the power transmission transformer does not appear at the output ends ij of the coils 106a and 106c.

  On the other hand, the coils 105a and 105c and the coils 106a and 106c are magnetically coupled via the outer legs 18BRb and 18BRa, so that the coils 105a and 105c are, for example, primary coils and the coils 106a and 106c are secondary coils. Acts as a signal transmission transformer.

  FIG. 5 is an equivalent circuit diagram of the transformer part of the composite transformer module according to the first embodiment. As described above, the first embodiment can be used as a composite transformer module including one power transmission transformer unit 14 and two signal transmission transformers 15L and 15R.

  The secondary signal processing circuit 22 configured on the multilayer substrate 13 uses, for example, an output voltage detection circuit that detects an output voltage on the secondary side of the power transmission transformer unit 14 and a signal transmission transformer unit 15 to transmit power. And a control circuit for controlling the primary side or the secondary side of the transformer unit. This makes it possible to achieve output voltage stabilization control that responds quickly to transient fluctuations in the input voltage and output current.

  Also, the composite transformer module 12 is provided with a function of instructing the optimum synchronous rectifier drive timing via the signal transmission transformer unit 15, and the gate drive signal of the primary power switch element and the gate drive of the synchronous rectifier from the composite transformer module 12. If the signal is output, the synchronous rectifier can be driven at an optimum timing simply by mounting the power conversion circuit components around the composite transformer module 12, and a highly efficient switching power supply device can be easily obtained. Can be configured.

  Also, the signal processing circuits 17 and 22 are instructed to stop the switching operation of the primary power switch element when detecting the abnormal operation such as an overcurrent state or an overheat state of the power transmission transformer unit 14 and the abnormal operation. A protective function may be provided by providing a function to output.

  In the first embodiment, if the space factor of the power transmission transformer 14 that is a component of the composite transformer module 12 is increased, the DC resistance and the AC resistance can be reduced, and the conduction loss of the coil can be reduced. The heat dissipation of the coil can be improved.

  In the first embodiment, since the winding coil is used for the power transmission transformer, the parasitic capacitance between the windings is small, and noise flowing between the primary and secondary of the transformer during high-frequency / high-speed switching operation. Short circuit loss of current and parasitic capacitance can be reduced, and switching power supply characteristics such as high-frequency EMI noise suppression and efficiency can be improved. Also, since it is easy to change the number of turns of the winding, it is easy to purchase a composite transformer module and mount it on the motherboard to create the step-up ratio or step-down ratio intended by the designer who designs the switching power supply. Yes, it is possible to omit the design of a high-speed response control circuit, a synchronous rectifier drive circuit, a protection circuit, and a transformer. Therefore, the man-hours and cost required for designing the switching power supply can be reduced.

<< Second Embodiment >>
A composite transformer module according to the second embodiment will be described with reference to FIGS.
FIG. 6 is an exploded perspective view of the composite transformer module 24 according to the second embodiment. The composite transformer module 24 includes an I-type core 18T, an E-type core 18B, the multilayer substrate 13, and a heat dissipation sheet 25.

  In the second embodiment, the power transmission transformer 14 is not a winding transformer in which a copper wire is wound around a bobbin, but a multilayer transformer in which a primary coil and a secondary coil are formed in a conductor pattern on a multilayer substrate 13. ing. In the second embodiment, the same reference numerals are assigned to the same name portions as those in the first embodiment, and duplicate descriptions of common portions are omitted.

  The heat dissipation effect of the composite transformer module 24 is enhanced by sandwiching the heat dissipation sheet 25 between the back surface of the multilayer substrate 13 and the core 18B. In addition, the multilayer substrate 13 includes a connection terminal 26 for mounting the composite transformer module 24 on the motherboard.

  FIGS. 7A and 7B are plan views of two different surfaces (layers) of the multilayer substrate 13. 8A shows a magnetic path of the signal transmission transformer unit, and FIG. 8B shows a magnetic path of the power transmission transformer unit. 7A and 7B show the cross sections of the middle leg 18BC and the outer legs 18BLa, 18BLb, 18BRa, and 18BRb of the core 18B.

  On the surface (layer) of the multilayer substrate 13 shown in FIG. 7A, a coil 101a is formed around the core insertion hole through which the middle leg 18BC is inserted. Both ends of the coil 101a are drawn out to output terminals ef.

  On the surface (layer) of the multilayer substrate 13 shown in FIG. 7B, a coil 103a is formed around the core insertion hole through which the middle leg 18BC is inserted. Both ends of the coil 103a are drawn to the output end g-h.

  Since the coil 101a and the coil 103a are magnetically coupled via the middle leg 18BC, the coil 101a functions as a power transmission transformer having, for example, a primary coil and the coil 103a as a secondary coil.

  FIG. 9 is a perspective view of a switching power supply module including the composite transformer module 24 according to the second embodiment. The composite transformer module 24 shown in FIG. 8 is mounted on the high heat dissipation substrate 27 to constitute a switching power supply module 301. Circuit components such as a switch element 28 and an input / output filter 29 necessary for configuring a switching power supply circuit are mounted on the high heat dissipation substrate 27. The composite transformer module 24 is mounted on the surface of the high heat dissipation substrate 27 by the connection terminal 26. Further, the high heat dissipation substrate 27 includes a plurality of connection terminals 31 for connecting the switching power supply module 301 to the mother board.

FIG. 10 is a circuit diagram of the switching power supply module 301, and FIG. 11 is a waveform diagram of each part thereof.
The switching power supply module 301 includes a first signal transmission transformer unit 15L, a second signal transmission transformer unit 15R, and a power transmission transformer unit illustrated in FIG. 10 by the composite transformer module 24 having the structure shown in the second embodiment. 14 is constituted. The first signal transmission transformer unit 15L includes a primary coil 15Lp and a secondary coil 15Ls, the second signal transmission transformer unit 15R includes a primary coil 15Rp and a secondary coil 15Rs, and the power transmission transformer unit 14 includes a primary coil 15Lp. A coil 14p, a secondary coil 14s, and an auxiliary coil 14t are included.

  Here, the + input terminal 115 of the DC input power supply, the −input terminal 116 of the DC input power supply, the smoothing capacitors 117 and 122, the power switch 118, the synchronous rectifiers 119 and 120, the choke coil 121, and the + output terminal 123 of the insulated switching power supply. The power conversion circuit is configured by the -output terminal 124 of the insulated switching power supply.

  Also, the multivibrator 125, resistors 126, 128, 135, 142, 146, 148, 149, diodes 127, 133, 134, 139, 144, inverters 129, 130, capacitors 131, 138, 143, 145, AND gate 132, The MOS-FETs 136 and 137, the NOR gate 140, the comparator 141, and the reference voltage source 147 constitute a control circuit.

  This insulated switching power supply is a one-stone resonant reset forward converter. The DC input voltage applied between the + input terminal 115 and the − input terminal 116 is smoothed by the smoothing capacitor 117 and then switched by the power switch 118 connected via the primary coil 14p of the power transmission transformer unit 14 to be AC. Convert.

  Although not shown in FIG. 10, a coil pattern for power supply for the signal processing circuit is formed at a position wound around the middle leg portion of the multilayer substrate, and a voltage induced in the coil pattern for power supply is A rectifying / smoothing circuit that rectifies and smoothes and supplies a power supply voltage to the signal processing circuit is provided.

  A configuration for controlling the synchronous rectifier 120 for commutation (auxiliary coil 14t, MOS-FET 137, first signal transmission transformer unit 15L, diode 133) is known as disclosed in Japanese Patent Laid-Open No. 2000-262051. This uses one pulse transformer to transmit a signal for controlling the MOS-FET 137 for turning off the synchronous rectifier 120 for commutation. Here, the first signal transmission transformer unit 15L is used as a pulse transformer. .

  The power transmission transformer unit 14 includes an auxiliary coil 14t in addition to the primary coil 14p and the secondary coil 14s. The auxiliary coil 14t is the same as those other than the coils 101a and 103a shown in FIG. Thus, another coil wiring is provided.

  By the way, on / off control of the power switch 118 which is a primary side switching element is performed by a control circuit provided on the primary side. In this case, the output voltage is detected and controlled by an indirect control type using the voltage of the auxiliary winding provided in the transformer or by providing an output voltage detection circuit on the secondary side and feeding back to the primary side via a photocoupler. There is a direct control type. The indirect control type has a problem that the output voltage detection accuracy is not good. Since the direct control type uses a photocoupler, there is a problem that the operating temperature condition is limited. In addition, both have a problem of poor response to output voltage fluctuations.

On the other hand, there is a hysteresis-controlled switching power supply as a switching power supply with good response.
Hysteresis control uses a comparator to compare the output voltage and the reference voltage, so it is necessary to provide a control circuit on the secondary side, but a separate power supply is required to operate the control circuit at startup when no voltage is generated on the secondary side. There is a problem of becoming.

  As a solution to each of the above problems, at the time of soft start at start-up, the primary side gradually defines the on / off timing of the switching element while gradually widening the pulse width, and when the output voltage reaches the target value, the switching element off timing signal is A control method in which the switching element is turned off by transmitting from the secondary side to the primary side via a pulse transformer, and the on-timing of the switching element is defined by the primary-side control circuit in a fixed cycle (the signal of the on-timing is secondary The primary side control circuit may define the off timing from the primary side to the primary side), and the present applicant has filed an application in International Publication WO2007 / 018227. Since this is a converter that applies hysteresis control to an insulation type, it has good responsiveness, and it operates even when there is no signal from the secondary side at startup, so there is a power supply for startup of the control circuit on the secondary side. It becomes unnecessary.

  In the example shown in FIG. 10, the off-timing signal of the power switch 118 based on the comparison between the output voltage and the reference voltage is transmitted from the secondary side to the primary side via the second signal transmission transformer unit 15R. is doing.

  11, (a) is the drain voltage of the power switch 118, (b) is the drain current of the power switch 118, (c) is the gate voltage of the power switch 118, (d) is the output voltage of the multivibrator 125, (e ) Is the voltage of the primary coil 15Rp of the second signal transmission transformer unit 15R, (f) is the output voltage of the AND gate 132, (g) is the voltage of the secondary coil 15Ls of the first signal transmission transformer unit 15L, (h) Is the gate voltage of the synchronous rectifier 120, (i) is one input voltage of the comparator 141, and (j) is the other input voltage of the comparator 141.

The circuit operation will be described below with reference to FIG.
While the power switch 118 is on, the power transmission transformer unit 14 transmits the alternating current from the primary coil 14p to the secondary coil 14s and rectifies it by the rectification side synchronous rectifier 119 and the commutation side synchronous rectifier 120, and then choke. By smoothing with an output filter composed of the coil 121 and the smoothing capacitor 122, alternating current is converted into direct current, and a direct current voltage is output from the positive output 123 and negative output 124.

  After the power switch 118 is turned off, the exciting inductance of the power transmission transformer unit 14 and the equivalent parallel parasitic capacitance of the power switch 118 undergo LC resonance to reset the transformer (see FIGS. 11A and 11B).

In the off period of the power switch 118 after the reset of the transformer is completed, the transformer excitation current flows back through the parasitic diode loop of the secondary coil 14 s → the synchronous rectifier 120 → the synchronous rectifier 119 of the power transmission transformer unit 14. The voltage across section 14 is clamped to zero volts, and the drain voltage of power switch 118 is clamped to the input voltage.
The above cycle is repeated to perform power conversion.

  The multivibrator 125 in the control circuit oscillates at a fixed frequency (see FIG. 11D). Since the drain voltage of the MOS-FET 136 is also at the high level at the on timing of the multivibrator 125, the output of the AND gate 132 is also at the high level simultaneously with the turning on of the multivibrator 125 (see FIG. 11F).

  When the AND gate 132 is turned on, the gate of the power switch 118 is charged through the primary coil 15Lp of the first signal transmission transformer unit 15L (see FIG. 11C). The pulse signal generated at this time is transmitted from the primary coil 15Lp of the first signal transmission transformer unit 15L to the secondary coil 15Ls, and the MOS-FET 137 is turned on (see FIG. 11G). When the MOS-FET 137 is turned on, the gate accumulated charge of the commutation side synchronous rectifier 120 is discharged and turned off (see FIG. 11 (h)).

  The power switch 118 is turned on with a certain time delay because the primary coil 15Lp of the first signal transmission transformer unit 15L is present in the gate charging path. By this operation, the commutation side synchronous rectifier 120 is turned off immediately before the power switch 118 is turned on, so that a short-circuit current due to the turn-off delay of the commutation side synchronous rectifier 120 does not occur and a highly efficient power conversion operation is possible. become.

  The control circuit performs hysteresis control by a comparator instead of PID control in order to make high-speed response to transient changes in input voltage and output current.

  A voltage obtained by dividing the output voltage by resistors 148 and 149 is input to the inverting input of the comparator 141, and the voltage of the reference voltage source 147 is input to the non-inverting input via the resistor 146. The comparator 141 compares the two.

  A ripple voltage is superimposed on the output voltage, and a ramp voltage having a slope opposite to that of the ripple voltage is superimposed on the voltage input to the non-inverting input of the comparator 141 by the resistors 142 and 146 and the capacitor 145 ( (Refer FIG.11 (i)).

  When the inverting input voltage of the comparator 141 exceeds the non-inverting input voltage during the ON period of the power switch 118, the output voltage of the comparator 141 becomes low level and is input to the NOR gate 140 (see FIG. 11 (j)). .

  Since the other input of the NOR gate 140 becomes low level during the ON period of the power switch 118, the output of the NOR gate 140 changes from low level to high level, and the second signal transmission transformer unit 15R of the second signal transmission transformer unit 15R passes through the capacitor 138. A current flows through the primary coil 15Rp to generate a pulse signal. This pulse signal is transmitted from the primary coil 15Rp of the second signal transmission transformer unit 15R to the secondary coil 15Rs, and the MOS-FET 136 is turned on (see FIG. 11E).

  In the drain of the MOS-FET 136, charges are accumulated through the diode 134 and the resistor 135 during the ON period of the inverter 129 (the OFF period of the multivibrator 125), but when the MOS-FET 136 is turned on, the drain of the MOS-FET 136 is high. From level to low level. When the drain of the MOS-FET 136 goes to a low level, the output of the AND gate 132 also goes to a low level, the gate accumulated charge of the power switch 118 is discharged via the diode 133, and the power switch 118 is turned off.

  In this way, the ON period of the power switch 118 is controlled by controlling the timing of the pulse signal that turns off the power switch 118. Since the length of the off period of the power switch 118 is a value obtained by subtracting the on period of the power switch 118 from the oscillation period of the multivibrator 125, the secondary side circuit is substantially led and PWM control is performed. The output voltage is stabilized. This control method has no phase lag caused by error amplifiers or photocouplers like PID control, and responds immediately to the cycle in which fluctuations occur for output voltage fluctuations caused by transient fluctuations in input voltage and output current. Bi-pulse operation is possible.

  Thus, the switching power supply can be thinned by configuring the composite transformer module 24 with a laminated transformer formed of a conductor pattern. The design of the high-speed response control circuit, the synchronous rectifier drive circuit, the protection circuit, and the design of the transformer can be omitted, and the man-hour and cost required for designing the switching power supply can be reduced as in the first embodiment. .

  In the switching power supply module 301 in which the composite transformer module 24 is mounted on the high heat dissipation board 27, particularly when the heat dissipation of the circuit components of the power conversion circuit that generates a large amount of heat is important, the high heat dissipation board 27 can be made of a high aluminum board or the like. Using a heat dissipating substrate, the power conversion circuit component is mounted on the high heat dissipating substrate 27, and the high heat dissipating substrate 27 is adhered to the heat sink. According to this structure, high heat dissipation is obtained.

  In addition, it has a function of transmitting a signal having a correlation with the output current instead of the output voltage of the switching power supply from the secondary side to the primary side, and the primary signal processing circuit outputs a signal having a correlation with the output current. A pulse width control function for receiving and controlling the drive signal width of the primary power switch so that the output current gradually approaches the target value may be provided.

  Moreover, the overcurrent state of the primary coil or the secondary coil of the power transmission transformer unit 14, the overheat state of the power transmission transformer unit 14, the low voltage state / overvoltage state of the input voltage of the switching power supply, the low voltage of the output voltage of the switching power supply It is equipped with a detection circuit that detects at least one of the abnormal states of the state and overvoltage, and when abnormal operation is detected, the duty of the primary power switch is reduced, the switching operation is stopped, or the hiccup operation is performed. An abnormal operation protection means for protecting the switching power supply may be provided.

<< Third Embodiment >>
FIG. 12 is a circuit diagram of the switching power supply module 302 according to the third embodiment.
The switching power supply module 302 includes a first signal transmission transformer unit 209 and a second signal transmission transformer shown in FIG. 12 with basically the same configuration as the composite transformer module 24 having the structure shown in the second embodiment. The unit 210 and the power transmission transformer unit 208 are configured. The first signal transmission transformer unit 209 includes a primary coil 209A and a secondary coil 209B, the second signal transmission transformer unit 210 includes a primary coil 210A and a secondary coil 210B, and the power transmission transformer unit 208 includes a primary coil. A coil 208A, a secondary coil 208B, and an auxiliary coil 208C are included.

  This switching power supply module 302 constitutes a so-called double-end insulated DC-DC converter (half-bridge converter). A power transmission transformer unit 208 having a primary coil 208A and a secondary coil 208B, a first power switch 204 and a second power switch (high side power switch) 205 connected to the primary side of the power transmission transformer 208, A primary-side control circuit 280 that performs switching control of the first and second power switches 204 and 205, a first synchronous rectifier 211, a second synchronous rectifier 212 connected to the secondary side of the power transmission transformer unit 208, A choke coil 213 is provided.

  Also, a first edge that generates a first turn-off edge signal and a first turn-on edge signal that substantially correspond to the turn-on and turn-off timings of the first power switch 204 based on a signal from the primary side control circuit 280. Based on signals from the signal generation circuit 271 and the primary side control circuit 270, a second turn-off edge signal and a second turn-on edge signal substantially corresponding to the turn-on and turn-off timings of the second power switch 205 are generated. A second edge signal generation circuit 272 is provided.

  Also, a first signal transmission transformer 209 that transmits the first turn-off edge signal and the first turn-on edge signal to the secondary side, and the second turn-off edge signal and the second turn-on edge signal to the secondary side. The first synchronous rectifier 211 is turned off by the first signal transmission transformer unit 209 and the first turn-off edge signal transmitted by the first signal transmission transformer unit 209, and the first signal transmission transformer unit 209 A first synchronous rectifier control circuit 273 is provided to turn on the first synchronous rectifier 211 with the transmitted first turn-on edge signal. Further, the second synchronous rectifier 212 is turned off by the second turn-off edge signal transmitted by the second signal transmission transformer unit 210, and the second turn-on edge signal transmitted by the second signal transmission transformer unit 210 is turned on. A second synchronous rectifier control circuit 274 that turns on the second synchronous rectifier 212 is provided.

  A series circuit of first and second power switches 204 and 205 and capacitors 206 and 207 is connected between the lines of the input DC power supply 201, respectively, and a connection point between the first and second power switches 204 and 205 is connected. The primary coil 208A of the power transmission transformer unit 208 is connected between the connection points of the capacitors 206 and 207.

  One end of the choke coil 213 is connected to the connection point of the secondary coils 208B and 208C of the power transmission transformer unit 208, and the output smoothing capacitor 214 is connected between the other end of the choke coil 213 and the secondary side ground. .

  A first synchronous rectifier 211 is connected between one end of the secondary coil 208 </ b> B of the power transmission transformer 208 and the secondary side ground. Further, a second synchronous rectifier 212 is connected between one end of the secondary coil 208C of the power transmission transformer unit 208 and the secondary side ground.

  An input DC power supply 201 is connected to the input of the switching power supply module 302, and a load 215 is connected to the output. A control power supply voltage is applied to the primary side control circuit power supply input unit 216.

  The first edge signal generation circuit 271 includes Schottky barrier diodes (hereinafter “SBD”) 219 and 220, and a capacitor 222, and includes a primary side control circuit power input unit 216, a primary side ground, Connected between. Similarly, the second edge signal generation circuit 272 includes SBDs 217 and 218 and a capacitor 221 and is connected between the primary side control circuit power supply input unit 216 and the primary side ground.

  A primary coil 209A of the first signal transmission transformer unit 209 is connected between the first PWM signal output terminal 2A of the PWM control circuit 202 and the first edge signal generation circuit 271. Similarly, the primary coil 210 </ b> A of the second signal transmission transformer unit 210 is connected between the second PWM signal output terminal 2 </ b> B of the PWM control circuit 202 and the second edge signal generation circuit 272.

  The first synchronous rectifier control circuit 273 includes an N-channel MOSFET 224, a P-channel MOSFET 225, diodes (PN diodes) 226 and 227, a Zener diode 229, and a resistor 228. Similarly, the second synchronous rectifier control circuit 274 includes an N-channel MOSFET 235, a P-channel MOSFET 236, diodes (PN diodes) 232 and 233, a Zener diode 230, and a resistor 231.

  The series circuit of the FET 224, the FET 225, and the resistor 223 is connected between the secondary side control circuit power supply input unit 237 and the secondary side ground, and the connection point between the FET 224 and the FET 225 is the N-channel MOSFET of the first synchronous rectifier 211. Connected to the gate. Similarly, a series circuit of the FET 235, the FET 236, and the resistor 234 is connected between the secondary side control circuit power supply input unit 237 and the secondary side ground, and a connection point between the FET 235 and the FET 236 is an N-channel MOSFET. 212 is connected to the gate.

  Further, the secondary coil 209B of the first signal transmission transformer unit 209 is connected between the connection point of the diodes 226 and 227 and the connection point of the FETs 224 and 225 of the first synchronous rectifier control circuit 273. Similarly, the secondary coil 210B of the second signal transmission transformer unit 210 is connected between the connection point of the diodes 232 and 233 of the second synchronous rectifier control circuit 274 and the connection point of the FETs 235 and 236.

  The primary side control circuit 280 uses the second signal transmission transformer unit 210 to drive the second power switch 205 whose reference potential (source) is not connected to the ground without using the high side driver IC. It is configured.

  In order to secure driving power for the second power switch 205, a bootstrap circuit 254 including a capacitor 256 and a diode 255 is provided. A series circuit of FET 258, FET 259, and resistor 257 is connected between the output part of the bootstrap circuit 254 and the primary side ground, and the connection point of FET 258 and FET 259 is connected to the gate of the second power switch 205. Yes. A circuit composed of diodes 260 and 261, a Zener diode 263, and a resistor 262 is connected to the gates of the FET 258 and the FET 259. A tertiary coil 210 </ b> C of the second signal transmission transformer unit 210 is connected between the connection point of the diodes 260 and 261 and the connection point of the FETs 258 and 259.

  A first power switch side delay circuit 278 including a resistor 264 and SBD 265 is provided between the first PWM signal output terminal 202 A of the PWM control circuit 202 and the gate of the first power switch 204.

  In FIG. 12, components other than the power switches 204 and 205, capacitors 206 and 207, synchronous rectifiers 211 and 212, choke coil 213, output smoothing capacitor 214, input DC power supply 201, and load 215 are configured by a composite transformer module.

  The operation of this switching power supply module 302 is as follows. First, the second turn-off edge signal output from the tertiary coil of the second signal transmission transformer unit 210 is applied to the gate of the FET 258 through the diode 260, the FET 258 is turned on, and the gate of the second power switch 205 is charged. Is charged and the second power switch 205 is turned on. Thereafter, the second turn-on edge signal is applied to the gate of the FET 259 through the diode 261, the FET 259 is turned on, the charge of the gate of the second power switch 205 is discharged, and the second power switch 205 is turned off.

  In accordance with the polarity of the second signal transmission transformer 210, the power switch 205 is driven at the same timing as the second PWM signal output from the PWM control circuit 202, and the second synchronous rectifier 212 is driven at the inverted timing. Therefore, the second power switch 205 and the second synchronous rectifier 212 are driven with substantially complementary timing. Similarly, the first power switch 204 and the first synchronous rectifier 211 are driven with substantially complementary timing. Note that the charging current of the gate of the second power switch 205 is limited by the resistor 257. As a result, the second delay time is secured. Further, the gate charge current of the power switch 204 is limited by the first power switch side delay circuit 278. As a result, the first delay time is secured.

<< Other embodiments >>
This invention can take not only the embodiment shown above but various embodiments. For example, the core shape of the composite transformer has various applications, and the cross section of the middle leg and the outer leg of the core 18 may be other shapes such as a circle and an ellipse. A plurality of transformers may be configured concentrically as disclosed in JP-A-11-340058.

  In addition, this invention can take not only the embodiment shown above but various embodiment. For example, in each embodiment, the cross section of the middle leg and the outer leg may be other shapes such as an ellipse in addition to a rectangle or a circle.

The core is not limited to a five-leg core, and a single leg transmission transformer section may be provided using a four-leg core.
In addition, a magnetic gap may be provided at the joint portion of the middle leg of the core to improve the DC superposition characteristics of the power transmission transformer unit.

  Moreover, the method of fitting the cores 18 may use metal fittings for core fastening, or may form parts for core fastening with other materials such as plastic. You may adhere | attach cores by an adhesive agent, without using the component for core fastening.

  In addition, the coil forming the power transmission transformer part may be formed by forming a conductor pattern on a printed circuit board, or by winding a wire rod around a bobbin, and winding a copper foil around the bobbin via an insulating sheet. Other well-known coil forming methods can be applied without any problem.

  Further, in the switching power supply module of the present invention, the signal transmission transformer 15 is configured to drive the synchronous rectifier, control the output voltage and output current, or reduce the overcurrent state, overheat state, and input voltage of the switching power source. In addition to the use in various protection circuits that protect the switching power supply by detecting abnormal operation such as voltage state, overvoltage state, undervoltage state of switching power supply output voltage, or overvoltage state, it can be applied to other uses . For example, it may be used for transmission of a digital signal.

DESCRIPTION OF SYMBOLS 12 ... Composite transformer module 13 ... Multilayer board 14 ... Power transmission transformer part 14t ... Auxiliary coil 14p ... Primary coil 15L, 15R ... Signal transmission transformer part 14s ... Secondary coil 15Lp ... Primary coil 15Rp ... Primary coil 16 ... Composite Transformer 15Ls ... Secondary coil 15Rs ... Secondary coil 17 ... Primary signal processing circuit 18BLa, 18BLb, 18BRa, 18BRb ... Outer leg 18T, 18B ... Core 18TC, 18BC ... Middle leg 19C, 19La, 19Lb, 19Ra, 19Rb ... Core Leg insertion hole 20 ... Bobbin 21 ... Connection terminal insertion hole 23 ... Connection terminal 22 ... Secondary signal processing circuit 24 ... Composite transformer module 25 ... Heat radiation sheet 26 ... Connection terminal 27 ... High heat dissipation board 28 ... Switch element 29 ... Input / output Filter 31... Connection terminals 101a and 103a... Coils 102a and 10 c ... Coil 102b ... Via electrode 103a ... Coils 104a, 104c ... Coil 104b ... Via electrode 115 ... Input terminals 117, 122 ... Smoothing capacitor 118 ... Power switch 119 ... Commutation side synchronous rectifier 120 ... Commutation side synchronous rectifier 121 ... Choke coil 105a, 105c ... coil 105b ... via electrode 123 ... output terminal 106a, 106c ... coil 106b ... via electrode 124 ... output terminal 125 ... multivibrators 129, 130 ... inverter 132 ... AND gates 136, 137 ... MOS-FET
301, 302 ... switching power supply module

Claims (12)

One set of cores, a power transmission transformer unit for transmitting power between the primary and secondary, and a signal transmission transformer for transmitting a signal between the primary and secondary substantially independently of the power transmission transformer unit A composite transformer having
The signal transmission transformer unit is composed of a multilayer substrate that penetrates the magnetic legs of the core and a coil pattern formed on the multilayer substrate,
A signal processing circuit for processing input / output signals of the signal transmission transformer is mounted on the multilayer substrate,
A composite transformer module, wherein the composite transformer and the signal processing circuit are integrally formed as a module.   2. The composite transformer according to claim 1, wherein the signal processing circuit includes a primary signal processing circuit provided on a primary side of the transformer and a secondary signal processing circuit provided on a secondary side of the transformer. module.   The composite transformer module according to claim 1, wherein the core has at least four or more magnetic legs including a middle leg portion and an outer leg portion.   The primary coil and the secondary coil of the power transmission transformer unit are wound around the outer periphery of the middle leg part of the core, and at least three or more outer leg units are formed outside the power transmission transformer unit. The composite transformer module described in 1.   The primary coil and the secondary coil of the power transmission transformer unit are configured by copper wires wound around a bobbin through which the middle leg portion passes, and the multilayer substrate is bonded to the bobbin. Composite transformer module.   5. The composite transformer module according to claim 4, wherein the primary coil and the secondary coil of the power transmission transformer unit are configured by a coil pattern formed around the middle leg portion and formed on the multilayer substrate. A coil pattern for a power source for the signal processing circuit is formed at a position wound around the middle leg portion of the multilayer substrate,
7. The composite transformer module according to claim 5, further comprising a rectifying / smoothing circuit that rectifies and smoothes a voltage induced in the coil pattern for power supply and supplies a power supply voltage to the signal processing circuit.   8. The circuit according to claim 1, further comprising a circuit that controls a primary power switch that switches a voltage applied to a primary coil of the power transmission transformer unit, wherein the composite transformer module constitutes a part of an insulated switching power supply. A composite transformer module according to any one of the above. The secondary signal processing circuit has a function of transmitting a signal having a correlation with an output voltage or an output current of the isolated switching power supply from the secondary side to the primary side,
The primary signal processing circuit receives a signal having a correlation with the output voltage or output current, and controls the drive signal width of the primary power switch so that the output voltage or output current approaches a target value. 9. The composite transformer module according to claim 8, comprising a pulse width control function and means for outputting a drive signal for the primary power switch. The isolated switching power supply includes a high-side power switch having a drive signal reference potential different from that of the primary power switch on the primary side,
The composite transformer module according to claim 9, wherein the primary signal processing circuit includes means for outputting a drive signal of the high-side power switch related to the drive timing of the primary power switch from the module. The primary signal processing circuit includes a circuit for transmitting a signal related to the driving timing of the synchronous rectifier from the primary side to the secondary side,
The said secondary signal processing circuit is provided with the circuit which receives the signal relevant to the drive timing of the said synchronous rectifier, forms the drive signal of a synchronous rectifier, and outputs it from a module. Composite transformer module. The signal processing circuit includes: an overcurrent state of a primary coil or a secondary coil of the power transmission transformer unit; an overheat state of the power transmission transformer unit; a low voltage state of an input voltage of the insulated switching power supply; A detection circuit for detecting an abnormal state of at least one of an overvoltage state of the input voltage, an undervoltage state of the output voltage of the isolated switching power supply, and an overvoltage state of the output voltage of the isolated switching power supply;
When the detection circuit detects an abnormal operation, the abnormal power protection means protects the isolated switching power supply by performing any one of a duty reduction of the primary power switch, a switching operation stop, or a hiccup operation. The composite transformer module according to any one of claims 8 to 11.

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