JP2012196080A - Switching power supply apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply apparatus that reduces conduction loss in windings and is downsized in its entirety.SOLUTION: A rectifying device 13 that smooths an output voltage Vout into a direct current is connected in reverse bias to a direct-current power supply 11 via a switching element 12. The switching element 12 is connected between a positive terminal of the direct-current power supply 11 and a cathode terminal of the rectifying device 13 and interrupts a current from the direct-current power supply 11. One end of an induction element 16a is connected to the connection of the switching element 12 and the rectifying device 13. A capacitative element 17 is connected between the other end of the induction element 16a and a negative terminal of the direct-current power supply 11. The output voltage Vout between both ends of the capacitative elements 17 is provided to a load not shown. An auxiliary winding 16b is magnetically coupled to the induction element 16a, and a clamp element 15 is connected in series to the auxiliary winding 16b. A current according to a surge voltage generating at the rectifying device 13 is passed from the clamp element 15 to the direct-current power supply 11 via the auxiliary winding 16b.

Description

  The present invention relates to a switching power supply device that is used in a DC-DC converter or the like and can be downsized by suppressing a surge voltage of a diode and a conduction loss of a coil.

  Conventionally, for example, there is a DC-DC converter described in Patent Document 1 as a switching power supply device. The DC-DC converter includes a switching element Q1, a choke coil L1, an output capacitor C5, a flywheel diode D3, a first winding (primary winding) T2A, and a second winding (secondary winding) T2B. An auxiliary transformer T2 is provided. One end of the first winding T2A is connected to the drain of the switching element Q1, and the first winding T2A and the switching element Q1 constitute a series circuit. The other end of the first winding T2A is connected to the anode end of the diode D3, and the load R1 is connected to the cathode terminal of the diode D3 and the negative terminal of the DC power source Vi. The capacitor C5 is connected in parallel with the load R1. In addition, the cathode terminal of the diode D2 is connected to one end of the second winding T2B, and a series circuit is configured by the second winding T2B and the diode D2, and other than the second winding T2B. The end is connected to the positive terminal of the DC power source Vi, and the anode terminal of the diode D2 is connected to the negative terminal of the DC power source Vi.

  As described above, the switching power supply device includes the switching element Q1 and the diode D3, the primary winding T2A of the auxiliary transformer T2 is connected in series to the diode D3, and the diode D2 is connected in series to the secondary winding T2B. The input terminal of the primary winding T2A and the anode terminal of the diode D2 are connected to the DC power source Vi. In this circuit configuration, the voltage applied to the diode D3 is clamped by the diode D2 with the total value of the output voltage applied to the load R1 and the flyback voltage of the auxiliary transformer T2. This clamping can reduce the loss due to the recovery current of the diode D3.

JP 2007-185072 A

  However, in the device disclosed in Patent Document 1, since the primary winding T2A of the auxiliary transformer T2 is connected in series to the diode D3, if the load R1 is a device that consumes a large current, the current flowing through the diode D3 is large. Therefore, there arises a problem that the conduction loss of the primary winding T2A of the transformer T2 increases.

  Further, the magnetic core of the transformer T2 has to have a cross-sectional area that increases as the current increases so as not to cause magnetic saturation. Assuming that the load R1 through which a large current flows is connected as described above, There is a problem that the cross-sectional area has to be increased, and the overall size of the transformer T2 is increased accordingly, resulting in an increase in the size of the switching power supply device.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a switching power supply device capable of reducing the conduction loss of the windings and reducing the size of the entire device.

  In order to achieve the above object, the invention according to claim 1 is directed to a DC power supply, a switching element for interrupting current from the DC power supply, and a reverse bias state connected to the DC power supply via the switching element. A rectifying element, an inductive element that is an inductor having one end connected to an input end of the rectifying element and a connection portion of the switching element, and the other end of the inductive element and the DC power source, A switching power supply that includes a capacitive element that forms a smoothing circuit together with the inductive element, and smoothes the output voltage across the capacitive element by the rectifying element or the smoothing circuit; Provided with a surge reduction circuit that allows a current corresponding to a surge voltage of a predetermined level generated in the rectifier element to flow so that the output voltage is kept constant at the time of ON. It is characterized in.

  According to this configuration, when a surge voltage is generated in the rectifier element, a current corresponding to the surge voltage is caused to flow in the surge reduction circuit so that the output voltage of the switching power supply device is kept constant. Only the current corresponding to the surge energy generated in the rectifying element flows. Therefore, the conduction loss of the winding can be reduced, and the required rating of the surge reduction circuit does not depend on the magnitude of the output current, so that the surge reduction circuit can be made small. Therefore, the switching power supply device can be reduced in size. In addition, even when the switching power supply outputs a large current, the surge voltage can be suppressed by the surge reduction circuit. Thus, when the surge voltage is low, a low withstand voltage rectifier, in other words, a rectifier with a low on-voltage is generated. This can reduce the conduction loss of the rectifying element.

  According to a second aspect of the present invention, there is provided a DC power supply, an inductive element that is an inductor having one end connected to the DC power supply, a rectifier having an input end connected to the other end of the inductive element, A capacitive element connected between the output terminal and the DC power supply, and connected between the capacitive element and the DC power supply, and between the inductive element and the rectifying element, and interrupts current from the DC power supply. In a switching power supply device having a switching element that suppresses a surge, a surge is reduced so that a current corresponding to a surge voltage of a predetermined level generated in the rectifier element when the switching element is turned on is turned on so that the output voltage is held constant A circuit is provided.

  According to this configuration, when the switching element is switched from OFF to ON, the current of the DC power source flows through a loop that returns to the DC power source through the inductive element and the switching element. Since a voltage is applied, the rectifying element transitions to a non-conducting state. In this case, since a surge voltage is generated in the rectifying element due to the reverse recovery operation, a current corresponding to the surge voltage is supplied by the surge reduction circuit so that the output voltage of the switching power supply device is kept constant. Thus, the same effect as that of the first aspect can be obtained.

  According to a third aspect of the present invention, there is provided a direct current power source, a switching element for intermittently supplying a current from the direct current power source, an inductive element that is an inductor connected in series to the direct current power source via the switching element, and the inductive element In a switching power supply device comprising: a rectifying element having an output terminal connected to a connection portion between an element and the switching element; and a capacitive element connected between the input terminal of the rectifying element and the DC power supply. A surge reduction circuit is provided that flows a current corresponding to a surge voltage of a predetermined level generated in the rectifier element from OFF to ON so that the output voltage is kept constant.

  According to this configuration, when the switching element is turned on from off, the voltage of the DC power supply is applied to the output terminal of the rectifying element via the switching element, that is, the reverse voltage is applied to the rectifying element, so that the rectifying element is non-conductive. Transition to the state. In this case, since a surge voltage is generated in the rectifying element due to the reverse recovery operation, a current corresponding to the surge voltage is supplied by the surge reduction circuit so that the output voltage of the switching power supply device is kept constant. Thus, the same effect as that of the first aspect can be obtained.

  According to a fourth aspect of the present invention, the surge reduction circuit includes an auxiliary winding by an inductor magnetically coupled to the inductive element, and a clamp element by a diode connected in series to the auxiliary winding, The end of the auxiliary winding facing the connection end to the clamp element is connected to the positive terminal of the DC power supply, and the end of the clamp element facing the connection end to the auxiliary winding is the negative electrode of the DC power supply. It is characterized by being connected to a side terminal.

  According to this configuration, when a predetermined level of surge voltage is generated in the rectifying element, the clamp element is made conductive, and a current corresponding to the surge voltage is regenerated from the clamp element to the DC power source via the auxiliary winding. it can.

  According to a fifth aspect of the present invention, the surge reduction circuit includes an auxiliary winding made of an inductor magnetically coupled to the inductive element, and a clamp element made of a diode connected in series to the auxiliary winding, An end of the auxiliary winding facing the connection end to the clamp element is connected to a connection portion between the induction element and the capacitive element, and an end of the clamp element facing the connection end to the auxiliary winding is the end. It is connected to the negative terminal of the DC power supply.

  According to this configuration, when a predetermined level of surge voltage is generated in the rectifying element, the clamp element is turned on, and a current corresponding to the surge voltage is output from the clamp element to the output side of the switching power supply device via the auxiliary winding. It can flow.

  According to a sixth aspect of the present invention, there is provided a DC power source, a transformer, and the DC power source so that a current flows in the primary winding in the forward direction or the reverse direction between the DC power source and the primary winding of the transformer. A switching circuit that switches current from the center tap, a center tap type full-wave rectifier circuit having a plurality of rectifier elements connected to the secondary winding of the transformer, and a cathode terminal of the plurality of rectifier elements of the full-wave rectifier circuit In a switching power supply device having an inductive element that is a connected inductor, and a capacitive element connected between the inductive element and a center tap of the full-wave rectifier circuit, the forward or backward direction by the switching circuit Current corresponding to a predetermined level of surge voltage generated in one of the rectifying elements of the full-wave rectifier circuit when switching the output voltage so that the output voltage is kept constant. Characterized in that it comprises a surge reduction circuit.

  According to this configuration, when the switching circuit switches the current flowing through the primary winding in the forward direction or the reverse direction, a surge voltage is generated by reverse recovery operation in any rectifier element of the full-wave rectifier circuit. A current corresponding to the surge voltage is passed through the surge reduction circuit so that the output voltage of the switching power supply device is kept constant. Thus, the same effect as that of the first aspect can be obtained.

  According to a seventh aspect of the present invention, there is provided a direct current power source, a transformer, and the direct current power source so that a current flows through the primary winding in a forward direction or a reverse direction between the direct current power source and the primary winding of the transformer. Switching circuit for switching the current from the bridge, a bridge-type full-wave rectifier circuit having a plurality of rectifier elements connected to the secondary winding of the transformer, and connected to the anode ends of the plurality of rectifier elements of the full-wave rectifier circuit In a switching power supply device comprising: an inductive element that is an inductive inductor; and a capacitive element connected between the inductive element and cathode ends of a plurality of other rectifying elements of the full-wave rectifying circuit. The output voltage is held constant at a current corresponding to a predetermined level of surge voltage generated in one of the rectifying elements of the full-wave rectifier circuit when switching to the forward or reverse direction. Characterized in that it comprises a surge reduction circuit for supplying way.

  According to this configuration, when the switching circuit switches the current flowing through the primary winding in the forward direction or the reverse direction, a surge voltage is generated by reverse recovery operation in any rectifier element of the full-wave rectifier circuit. A current corresponding to the surge voltage is passed through the surge reduction circuit so that the output voltage of the switching power supply device is kept constant. Thus, the same effect as that of the first aspect can be obtained.

  The invention according to claim 8 is characterized in that the surge reduction circuit includes an auxiliary winding by an inductor magnetically coupled to the inductive element, and a clamp element by a diode connected in series to the auxiliary winding, The end of the auxiliary winding facing the connection end to the clamp element is connected to the positive terminal of the DC power supply, and the end of the clamp element facing the connection end to the auxiliary winding is the negative electrode of the DC power supply. It is characterized by being connected to a side terminal.

  According to this configuration, when a predetermined level of surge voltage is generated in the rectifying element, the clamp element is made conductive, and a current corresponding to the surge voltage is regenerated from the clamp element to the DC power source via the auxiliary winding. it can.

  The invention according to claim 9 is characterized in that the surge reduction circuit includes an auxiliary winding by an inductor magnetically coupled to the inductive element, and a clamp element by a diode connected in series to the auxiliary winding, An end of the auxiliary winding facing the connection end to the clamp element is connected to a connection portion between the induction element and the capacitive element, and an end of the clamp element facing the connection end to the auxiliary winding is the end. It is connected to the negative electrode side terminal of the DC power supply or the center tap.

  According to this configuration, when a predetermined level of surge voltage is generated in the rectifying element, the clamp element is turned on, and a current corresponding to the surge voltage is output from the clamp element to the output side of the switching power supply device via the auxiliary winding. It can flow.

  According to a tenth aspect of the present invention, the surge reduction circuit includes: an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core; and a second induction connected to the primary winding of the auxiliary transformer. And a clamp element by a diode connected in series to the secondary winding of the auxiliary transformer, and one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifying elements of the full-wave rectifier circuit The other end is connected to the center tap of the full-wave rectifier circuit via the second induction element, and the end of the secondary winding of the auxiliary transformer opposite to the connection end to the clamp element is the DC power supply. An end connected to the positive terminal and opposite to the connection end to the secondary winding in the clamp element is connected to the negative terminal of the DC power supply.

  According to this configuration, when a predetermined level of surge voltage is generated in any of the plurality of rectifying elements, the clamp element is turned on, and a current corresponding to the surge voltage is passed from the clamp element to the secondary winding of the auxiliary transformer. It can be regenerated to a direct current power source.

  According to an eleventh aspect of the present invention, the surge reducing circuit includes an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core, and a second induction connected to the primary winding of the auxiliary transformer. And a clamp element by a diode connected in series to the secondary winding of the auxiliary transformer, and one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifying elements of the full-wave rectifier circuit The other end is connected to the center tap of the full-wave rectifier circuit via a second inductive element, and the end opposite to the connection end to the clamp element in the secondary winding of the auxiliary transformer is connected to the inductive element It is connected to a connection portion with the capacitive element, and an end facing the connection end to the secondary winding in the clamp element is connected to a negative side terminal of the DC power supply or the center tap. .

  According to this configuration, when a predetermined level of surge voltage is generated in any of the plurality of rectifying elements, the clamp element is turned on, and a current corresponding to the surge voltage is passed from the clamp element to the secondary winding of the auxiliary transformer. Through the output side of the switching power supply.

  According to a twelfth aspect of the present invention, the surge reduction circuit includes: an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core; and a second induction connected to the primary winding of the auxiliary transformer. And a clamp element by a diode connected in series to the secondary winding of the auxiliary transformer, and one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifying elements of the full-wave rectifier circuit The other end is connected to the anode ends of the other rectifier elements of the full-wave rectifier circuit via the second inductive element, and faces the connection end to the clamp element in the secondary winding of the auxiliary transformer. An end of the DC power supply is connected to a positive terminal of the DC power source, and an end of the clamp element opposite to the connection terminal to the secondary winding is connected to a negative terminal of the DC power source.

  According to this configuration, when a predetermined level of surge voltage is generated in any of the plurality of rectifying elements, the clamp element is turned on, and a current corresponding to the surge voltage is passed from the clamp element to the secondary winding of the auxiliary transformer. It can be regenerated to a direct current power source.

  According to a thirteenth aspect of the present invention, the surge reducing circuit includes an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core, and a second induction connected to the primary winding of the auxiliary transformer. And a clamp element by a diode connected in series to the secondary winding of the auxiliary transformer, and one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifying elements of the full-wave rectifier circuit The other end is connected to the anode ends of the other rectifier elements of the full-wave rectifier circuit via the second inductive element, and faces the connection end to the clamp element in the secondary winding of the auxiliary transformer. And an end opposite to the connection end to the secondary winding in the clamp element is connected to the negative electrode side terminal of the DC power source. Features.

  According to this configuration, when a predetermined level of surge voltage is generated in any of the plurality of rectifying elements, the clamp element is turned on, and a current corresponding to the surge voltage is passed from the clamp element to the secondary winding of the auxiliary transformer. Through the output side of the switching power supply.

It is a circuit diagram which shows the structure of the conventional switching power supply apparatus. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 1st Embodiment of this invention. It is a timing chart for demonstrating operation | movement of the switching power supply device of 1st Embodiment. It is a figure which shows the relationship between the turns ratio N2 / N1 in the maximum voltage characteristic Vm of the rectifier in the switching power supply device of 1st Embodiment, and the voltage V of the rectifier. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 3rd Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 3rd Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 4th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 4th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 5th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 5th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 6th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 6th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on 7th Embodiment of this invention. It is a circuit diagram which shows the structure of the switching power supply device which concerns on the modification of 7th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. However, parts corresponding to each other in all the drawings in this specification are denoted by the same reference numerals, and description of the overlapping parts will be omitted as appropriate.
(First embodiment)
FIG. 2 is a circuit diagram showing a configuration of the switching power supply device according to the first embodiment of the present invention. The switching power supply device 10 includes a DC power supply 11, a switching element 12, a rectifying element 13 made of a diode, a smoothing circuit 14 having an inductive element 16a made of an inductor and a capacitive element 17 made of a capacitor, a clamp element 15 made of a diode, and an inductor. The surge reduction circuit 18 includes an auxiliary winding 16b.

  In the circuit configuration of the switching power supply device 10, a rectifying element 13 that smoothes the output voltage Vout to DC is connected to a DC power supply 11 via a switching element 12 in a reverse bias state. The switching element 12 is connected between the positive terminal of the DC power supply 11 and the cathode end side of the rectifying element 13, and interrupts current from the DC power supply 11. One end of the inductive element 16 a is connected to the connection portion between the switching element 12 and the rectifying element 13, and the capacitive element 17 is connected between the other end of the inductive element 16 a and the negative terminal of the DC power supply 11. . The output voltage Vout across the capacitor element 17 is supplied to a load (not shown). Further, the auxiliary winding 16 b is wound around the same magnetic core as the induction element 16 a, one end of the auxiliary winding 16 b is connected to the cathode end of the clamp element 15, and the other end is the positive terminal of the DC power source 11. It is connected to the. The anode end of the clamp element 15 is connected to the negative terminal of the DC power supply 11.

  The switching power supply 10 is characterized in that the auxiliary winding 16b is magnetically coupled to the induction element 16a, the clamp element 15 is connected in series to the auxiliary winding 16b, and a surge voltage of a predetermined level is generated in the rectifying element 13. In this case, the clamp element 15 is turned on, and a current corresponding to the surge voltage is regenerated from the clamp element 15 to the DC power source 11 through the auxiliary winding 16b, thereby suppressing the surge voltage and keeping the output voltage Vout constant. The point is that the voltage is maintained.

  The operation of the switching power supply apparatus 10 when the surge voltage is suppressed and the output voltage Vout is kept constant will be described with reference to FIG.

  When the switching element 12 is off (OFF) as shown in (a) between times t1 and t2 in FIG. 3, the forward voltage from the inductive element 16a causes the rectifying element 13 to pass through the capacitive element 17. As a result, the rectifying element 13 becomes conductive as shown in FIG. Therefore, as shown in (c), the voltage of the rectifying element 13 is 0V. At this time, since the reverse voltage from the DC power supply 11 is applied to the clamp element 15 via the auxiliary winding 16b, the clamp element 15 remains in a non-conductive state, and a current flows as shown in (d). Absent.

  Further, when the switching element 12 is off, a current corresponding to the stored energy of the inductive element 16a flows through a loop that returns to the inductive element 16a through the capacitive element 17 and the rectifying element 13, and at this time, as shown in FIG. Thus, the voltage on the primary side that is the DC power supply 11 side of the induction element 16a is held constant at the potential of the output voltage Vout by the capacitive element 42. Therefore, the primary current of the inductive element 16a flows in a substantially constant state as shown in (f). That is, the energy accumulated in the induction element 16 a is supplied via the rectifying element 13 to a load (not shown) connected to both ends of the output side capacitive element 17.

  Next, at time t2, when the switching element 12 is turned on as shown in (a), a reverse voltage is applied to the rectifying element 13 from the DC power supply 11, and as shown in (b), the rectifying element 13 is turned on. Transitions to a non-conducting state and no current flows. In this way, when a reverse bias is applied to the rectifying element 13, a current (recovery current) flows in the reverse direction through the rectifying element 13 by a reverse recovery operation that allows energization by the carriers accumulated in the rectifying element 13. . Due to this reverse recovery operation, a high reverse voltage exceeding the input voltage Vin of the DC power supply 11 is applied to the rectifying element 13.

  Here, the applied voltage of the rectifying element 13 = the output voltage Vout + the primary voltage of the induction element 16a. Since the time change of the output voltage Vout is sufficiently small with respect to the time change of the current, and the output voltage Vout can be regarded as constant, if the voltage fluctuation of the induction element 16a is reduced, the fluctuation of the voltage applied to the rectifying element 13 is reduced. be able to.

  In the present embodiment, when the number of turns of the induction element 16a (primary side number of turns) is N1 and the number of turns of the auxiliary winding 16b (secondary side number of turns) is N2, the number of turns N2 of the auxiliary winding 16b and the auxiliary winding 16b are fixed. The voltage Vc (= Vin) is set so as to satisfy the condition of the following expression (1).

Vc / (Vp−Vout) <N2 / N1 <Vc / (Vin−Vout) (1)
However, Vp is the maximum surge voltage of the rectifier 13 when the surge reduction circuit 18 is not provided.

  The clamp element 15 has an auxiliary winding when the potential difference between the input and output sides (primary side and secondary side) of the induction element 16a exceeds (Vin−Vout) shown between times t2 and t3 in FIG. When a voltage exceeding Vin = Vc is generated in 16b, a conductive state is established and current flows. Therefore, when the applied voltage of the rectifying element 13 exceeds the input voltage Vin, that is, when the primary side voltage of the inductive element 16a shown between time t2 and time t3 in FIG. It is set to conduct. The turn ratio N2 / N1 at this time is Vc / (Vin−Vout).

  Here, FIG. 4 shows the relationship between the turn ratio N2 / N1 in the maximum voltage characteristic Vm of the rectifier 13 and the voltage V of the rectifier 13. As shown in FIG. 4, the turn ratio N2 / N1 may be larger than the turn ratio in the case of Vc / (Vp−Vout) when the maximum surge voltage Vp is generated, and Vc / (Vin when the input voltage Vin is applied. It is sufficient that the turn ratio is smaller than that in the case of -Vout). That is, as shown by the effective range e, the turn ratio N2 / N1 is the turn ratio between Vc / (Vp−Vout) and Vc / (Vin−Vout), and the applied voltage of the rectifying element 13 is input. When the voltage Vin is exceeded, the primary side voltage of the inductive element 16a exceeds Vin−Vout, and the clamp element 15 becomes conductive.

  Therefore, when the applied voltage of the rectifying element 13 exceeds the input voltage Vin, that is, when the primary side voltage of the inductive element 16a shown in FIG. 3E at time t2> Vin−Vout, as shown in FIG. The clamp element 15 becomes conductive and current flows. Since this current is a current due to a surge voltage caused by the reverse recovery operation of the rectifying element 13, it gradually decreases toward zero at time t3.

  As described above, when the applied voltage of the rectifying element 13 exceeds the input voltage Vin, the clamp element 15 becomes conductive through the auxiliary winding 16b, whereby the voltage of the auxiliary winding 16b is Vc, that is, the voltage of the DC power supply 11. Fixed to Vin. At this time, the primary voltage of the inductive element 16a is fixed to Vin−Vout, and no voltage exceeding the input voltage Vin is applied to the rectifying element 13. At this time, the surge energy exceeding the input voltage Vin accompanying the reverse recovery operation of the rectifying element 13 is regenerated to the DC power supply 11 that supplies the fixed voltage Vc of the auxiliary winding 16b via the clamp element 15. Energy is supplied to the load from the DC power supply 11 via the switching element 12.

  As described above, according to the switching power supply 10 of the first embodiment, only the current corresponding to the surge energy generated in the rectifying element 13 flows through the auxiliary winding 16b of the surge reduction circuit 18 and the clamp element 15 using the diode, and the auxiliary power Since the required ratings of the winding 16b and the clamp element 15 do not depend on the magnitude of the output current, the auxiliary winding 16b and the clamp element 15 can be made small. Accordingly, such a small auxiliary winding 16b is magnetically coupled to the existing inductive element 16a, and the small clamp element 15 is connected in series to the auxiliary winding 16b to form the surge reduction circuit 18. The switching power supply device 10 can be reduced in size.

Further, even when the switching power supply 10 outputs a large current, the surge voltage can be suppressed by the surge reduction circuit 18. Here, the on-voltage of the rectifying element 13 is determined by the breakdown voltage, and the higher the breakdown voltage, the higher the on-voltage of the element. Therefore, the higher the surge voltage, the higher the withstand voltage rectifier element 13 is required. On the contrary, when the surge voltage is low, the rectifying element 13 having a low withstand voltage can be used. That is, in this embodiment, the surge reduction circuit 18 prevents a surge voltage of a predetermined level or higher from being generated, so that the rectifier element 13 having a low on-voltage can be used, thereby reducing the conduction loss of the rectifier element 13.
(Modification of the first embodiment)
FIG. 5 is a circuit diagram showing a configuration of a switching power supply device according to a modification of the first embodiment of the present invention. The switching power supply device 10A of this modification is different from the above-described switching power supply device 10 in that the other end of the auxiliary winding 16b in which the clamp element 15 is connected in series with one end is connected to the induction element 16a and the capacitive element 17. This is because it is configured by connecting to the connection part.

That is, according to the switching power supply device 10A, when a predetermined level of surge voltage is generated in the rectifying element 13, the clamp element 15 is turned on and current corresponding to the surge voltage is supplied from the clamp element 15 to the auxiliary winding 16b. To the output side (the output side of the switching power supply device 10A) at both ends of the capacitive element 17, thereby suppressing the surge voltage and holding the output voltage Vout at a constant voltage. Therefore, the switching power supply device 10A can obtain the same effects as those of the switching power supply device 10 described above.
(Second Embodiment)
FIG. 6 is a circuit diagram showing a configuration of a switching power supply device according to the second embodiment of the present invention. The switching power supply device 20 includes a DC power supply 11, an inductive element 16a, a switching element 12, a rectifying element 13, a capacitive element 17, a surge reducing circuit 18 including a clamp element 15 and an auxiliary winding 16b. ing.

  The circuit configuration of the switching power supply device 20 is such that the anode terminal of the rectifying element 13 is connected to the positive terminal of the DC power supply 11 via the induction element 16 a, and between the cathode terminal of the rectifying element 13 and the negative terminal of the DC power supply 11. A capacitive element 17 is connected to the. The switching element 12 is connected between the capacitive element 17 and the negative electrode side terminal of the DC power source 11 and between the induction element 16 a and the rectifying element 13. An auxiliary winding 16b is wound around the same magnetic core as the induction element 16a. One end of the auxiliary winding 16b is connected to the cathode end of the clamp element 15 and the other end is connected to the positive terminal of the DC power source 11. It is connected. The anode end of the clamp element 15 is connected to the negative terminal of the DC power supply 11.

  In this switching power supply device 20, when the switching element 12 is off, a current corresponding to the voltage Vin of the DC power supply 11 is supplied to the negative side terminal of the DC power supply 11 via the induction element 16 a, the rectifying element 13, and the capacitive element 17. Flow through the loop back. That is, since the forward voltage from the inductive element 16a is applied to the rectifying element 13, the rectifying element 13 becomes conductive and current flows. At this time, the clamp element 15 is connected to the clamping element 15 via the auxiliary winding 16b. Since the reverse voltage from the DC power supply 11 is applied, the clamp element 15 remains in a non-conductive state.

  On the other hand, when the switching element 12 is turned on, a current corresponding to the voltage Vin of the DC power supply 11 flows through a loop that returns to the negative terminal of the DC power supply 11 via the induction element 16 a and the switching element 12. At this time, a reverse voltage due to the energy stored in the capacitive element 17 is applied to the rectifying element 13, and the rectifying element 13 transitions to a non-conductive state. Thus, when a reverse bias is applied, a surge voltage is generated in the rectifying element 13 by a reverse recovery operation. When the applied voltage of the rectifying element 13 due to the surge voltage exceeds the input voltage Vin, the clamp element 15 becomes conductive. Due to this conduction, surge energy exceeding the input voltage Vin accompanying the reverse recovery operation of the rectifying element 13 is regenerated to the DC power supply 11 that supplies the voltage Vin (= Vc) to the auxiliary winding 16b via the clamp element 15. Since this regenerative current is a current due to a surge voltage caused by the reverse recovery operation of the rectifying element 13, it gradually decreases and reaches zero.

As described above, also in the switching power supply device 20 of the second embodiment, when a surge voltage of a predetermined level is generated in the rectifying element 13, the clamp element 15 is turned on and a current corresponding to the surge voltage is assisted from the clamp element 15. The current flows to the positive terminal of the DC power supply 11 via the winding 16b, thereby suppressing the surge voltage and maintaining the output voltage Vout at a constant voltage. Therefore, the same effect as that of the first embodiment described above can be obtained.
(Modification of the second embodiment)
FIG. 7 is a circuit diagram showing a configuration of a switching power supply device according to a modification of the second embodiment of the present invention. The switching power supply device 20A of this modification is different from the above-described switching power supply device 20 in that the other end of the auxiliary winding 16b in which the clamp element 15 is connected in series with one end is connected to the cathode end of the rectifying element 13 and the capacitive element. 17 in that it is connected to the connecting portion with the 17.

That is, according to the switching power supply device 20A, when a surge voltage of a predetermined level is generated in the rectifying element 13, the clamp element 15 is turned on and a current corresponding to the surge voltage is passed from the clamp element 15 via the auxiliary winding 16b. Thus, it flows to the output side (the output side of the switching power supply device 20A) at both ends of the capacitive element 17, thereby suppressing the surge voltage and holding the output voltage Vout at a constant voltage. Therefore, the switching power supply device 20A can obtain the same effects as those of the switching power supply device 20 described above.
(Third embodiment)
FIG. 8 is a circuit diagram showing a configuration of a switching power supply device according to the third embodiment of the present invention. The switching power supply device 30 includes a DC power supply 11, a switching element 12, an inductive element 16a, a rectifying element 13, a capacitive element 17, and a surge reduction circuit 18 including a clamp element 15 and an auxiliary winding 16b. Yes.

  The circuit configuration of the switching power supply 30 is such that the inductive element 16a is connected in series to the DC power source 11 via the switching element 12, and the cathode end of the rectifying element 13 is connected to the connection portion between the switching element 12 and the inductive element 16a. A capacitive element 17 is connected between the anode end of the rectifying element 13 and the negative terminal of the DC power supply 11. An auxiliary winding 16b is wound around the same magnetic core as the induction element 16a. One end of the auxiliary winding 16b is connected to the cathode end of the clamp element 15 and the other end is connected to the positive terminal of the DC power source 11. It is connected. The anode end of the clamp element 15 is connected to the negative terminal of the DC power supply 11.

  In this switching power supply device 30, when the switching element 12 is off, the current due to the stored energy of the inductive element 16 a is supplied to the anode end of the rectifying element 13 via the capacitive element 17, thereby becoming conductive. It flows through a loop returning from the rectifying element 13 to the inductive element 16a. At this time, since the reverse voltage from the DC power supply 11 is applied to the clamp element 15 via the auxiliary winding 16b, the clamp element 15 remains in a non-conductive state.

  On the other hand, when the switching element 12 is turned on, a current corresponding to the voltage Vin of the DC power supply 11 is applied to the cathode terminal of the rectifying element 13, that is, a reverse voltage is applied, so that the rectifying element 13 transitions to a non-conductive state. A surge voltage is generated by the reverse recovery operation at this time. When the applied voltage of the rectifying element 13 due to the surge voltage exceeds the input voltage Vin, the clamp element 15 becomes conductive. Due to this conduction, surge energy exceeding the input voltage Vin of the rectifying element 13 is regenerated to the DC power supply 11 that supplies the voltage Vin (= Vc) to the auxiliary winding 16b via the clamp element 15. Since this regenerative current is a current due to a surge voltage caused by the reverse recovery operation of the rectifying element 13, it gradually decreases and reaches zero.

As described above, also in the switching power supply device 30 of the third embodiment, when a surge voltage of a predetermined level is generated in the rectifying element 13, the clamp element 15 is made conductive and current corresponding to the surge voltage is assisted from the clamp element 15. The current flows to the positive terminal of the DC power supply 11 via the winding 16b, thereby suppressing the surge voltage and maintaining the output voltage Vout at a constant voltage. Therefore, the same effect as that of the first embodiment described above can be obtained.
(Modification of the third embodiment)
FIG. 9 is a circuit diagram showing a configuration of a switching power supply device according to a modification of the third embodiment of the present invention. The switching power supply 30A of this modification is different from the above-described switching power supply 30 in that the other end of the auxiliary winding 16b in which the clamp element 15 is connected in series to one end is connected to the anode end of the rectifying element 13 and the capacitive element. 17 in that it is connected to the connecting portion with the 17.

That is, according to the switching power supply device 30A, when a surge voltage of a predetermined level is generated in the rectifying element 13, the clamp element 15 is turned on and a current corresponding to the surge voltage is passed from the clamp element 15 via the auxiliary winding 16b. Thus, it flows to the output side (the output side of the switching power supply device 30A) at both ends of the capacitive element 17, thereby suppressing the surge voltage and maintaining the output voltage Vout at a constant voltage. Therefore, the switching power supply device 30A can achieve the same effect as the switching power supply device 30 described above.
(Fourth embodiment)
FIG. 10 is a circuit diagram showing a configuration of a switching power supply apparatus according to the fourth embodiment of the present invention. The switching power supply device 40 includes a DC power supply 11, a switching circuit 12-1 having four switching elements 12 a to 12 d, and secondary windings 42 b and 42 c connected to a magnetic core in series with a primary winding 42 a. Insulation transformer 42, center tap type full-wave rectifier circuit 13-1 having rectifier elements 13a and 13b connected to both ends of serially connected secondary windings 42b and 42c, an induction element 16a, a capacitor An element 17 and a surge reduction circuit 18 including a clamp element 15 and an auxiliary winding 16b are provided.

  The circuit configuration of the switching power supply 40 is such that switching elements 12a and 12b connected in series to both ends of the DC power supply 11 and two switching elements 12c and 12d connected in series are connected in parallel. The primary winding 42a of the insulating transformer 42 is connected between the one series switching elements 12a and 12b and the other series switching elements 12c and 12d, and one end of the series connected secondary windings 42b and 42c. The anode end of the rectifying element 13a is connected to the other end, the anode end of the rectifying element 13b is connected to the other end, and the cathode ends of the rectifying elements 13a and 13b are connected to one end of the induction element 16a. Furthermore, the capacitive element 17 is connected between the neutral wire (or neutral point) that is the center tap of each of the secondary windings 42b and 42c and the other end of the induction element 16a.

  An auxiliary winding 16b is wound around the same magnetic core as the induction element 16a. One end of the auxiliary winding 16b is connected to the cathode end of the clamp element 15 and the other end is connected to the positive terminal of the DC power source 11. It is connected. The anode end of the clamp element 15 is connected to the negative terminal of the DC power supply 11.

  In the switching circuit 12-1, the switching elements 12a and 12d at one diagonal position are used as the first set of switching elements 12a and 12d, and the switching elements 12c and 12b at the other diagonal position are used as the second set of switching elements 12c. , 12b. Of the secondary windings 42b and 42c connected in series, the upper side from the neutral point toward the drawing is referred to as the first secondary winding 42b, and the lower side is referred to as the second secondary winding 42c.

  In this switching power supply device 40, when each of the switching elements 12a to 12d is turned off and the first set of switching elements 12a and 12d is turned on, a current is primary from the positive terminal of the DC power supply 11 via the switching element 12a. The current flows through the winding 42a and further returns to the negative terminal of the DC power supply 11 through the switching element 12d. In this case, the direction of the current flowing through the primary winding 42a is assumed to be the forward direction. In response to the forward current, on the secondary side of the insulating transformer 42, forward current flows from the neutral point to the rectifying element 13a via the first secondary winding 42b. Further, the inductive element 16a and the capacitive element 17 A current flows through the loop to return to the neutral point.

  When the first set of switching elements 12a and 12d are turned off and the second set of switching elements 12c and 12b are turned on, the current from the positive terminal of the DC power supply 11 to the primary winding 42a via the switching element 12c is as described above. It flows in the reverse direction and further flows in the direction of returning to the negative terminal of the DC power supply 11 through the switching element 12b. In this case, the direction of the current flowing through the primary winding 42a is the reverse direction. In response to the current flowing in the reverse direction, a forward current flows from the neutral point to the rectifying element 13b through the second secondary winding 42c on the secondary side of the insulating transformer 42. Further, the inductive element 16a and the capacitive element It flows in the loop which returns to a neutral point via 17.

  Here, it is assumed that the second set of switching elements 12c and 12b is turned off from on, and the first set of switching elements 12a and 12d is turned on from off. In this case, the rectifying element 13a connected to the first secondary winding 42b becomes conductive, and forward current flows. At this time, since a reverse bias is applied to the rectifying element 13b connected to the second secondary winding 42c, the rectifying element 13b transitions to a non-conductive state, and a surge voltage is generated by the reverse recovery operation at this time. When the voltage of the rectifying element 13b due to the surge voltage exceeds 2 × Vin / n (n: the turn ratio of the transformer 42), the clamp element 15 becomes conductive through the auxiliary winding 16b. Due to this conduction, surge energy exceeding 2 × Vin / n of the rectifying element 13 b is regenerated to the DC power supply 11 that supplies the voltage Vin (= Vc) to the auxiliary winding 16 b via the clamp element 15. Since this regenerative current is a current due to a surge voltage caused by the reverse recovery operation of the rectifying element 13b, it gradually decreases and reaches zero.

  On the contrary, it is assumed that the first set of switching elements 12a and 12d are turned off and the second set of switching elements 12c and 12b are turned on. In this case, the rectifying element 13b connected to the second secondary winding 42c becomes conductive and forward current flows. At this time, since a reverse bias is applied to the rectifying element 13a connected to the first secondary winding 42b, a surge voltage is generated by the reverse recovery operation. When the voltage of the rectifying element 13a due to the surge voltage exceeds 2 × Vin / n, the clamp element 15 becomes conductive through the auxiliary winding 16b and current is regenerated to the DC power supply 11 through the auxiliary winding 16b. The Since this regenerative current is a current due to a surge voltage caused by the reverse recovery operation of the rectifying element 13a, it gradually decreases and reaches zero.

As described above, also in the switching power supply device 40 of the fourth embodiment, when a surge voltage of a predetermined level is generated in the rectifying element 13a or 13b, the clamp element 15 is turned on and a current corresponding to the surge voltage is supplied to the clamp element 15. To the positive terminal of the DC power supply 11 through the auxiliary winding 16b, thereby suppressing the surge voltage and maintaining the output voltage Vout at a constant voltage. Therefore, the same effect as that of the first embodiment described above can be obtained.
(Modification of the fourth embodiment)
FIG. 11 is a circuit diagram showing a configuration of a switching power supply device according to a modification of the fourth embodiment of the present invention. The switching power supply device 40A of this modification is different from the above-described switching power supply device 40 in that the other end of the auxiliary winding 16b in which the clamp element 15 is connected in series with one end is connected to the inductive element 16a and the capacitive element 17. This is because the anode end of the clamp element 15 is connected to the neutral line on the secondary side of the insulating transformer 42.

  That is, according to the switching power supply device 40A, when a predetermined level of surge voltage is generated in the rectifying element 13a or 13b, the clamp element 15 is turned on and a current corresponding to the surge voltage is supplied from the clamp element 15 to the auxiliary winding 16b. To the output side (the output side of the switching power supply device 40A) at both ends of the capacitive element 17, whereby the surge voltage can be suppressed and the output voltage Vout can be held at a constant voltage. Therefore, the switching power supply device 40A can obtain the same effects as those of the switching power supply device 40 described above.

In the switching power supply device 40A, the anode end of the clamp element 15 is connected to the neutral line of the insulating transformer 42, but the anode end is connected to the negative terminal of the DC power supply 11. Also good.
(Fifth embodiment)
FIG. 12 is a circuit diagram showing a configuration of a switching power supply apparatus according to the fifth embodiment of the present invention. This switching power supply device 50 is different from the above-described switching power supply device 40 in that the full-wave rectifier circuit 13-1 is a bridge-type full-wave rectifier circuit 13-2, and the insulating transformer 42 is centered on the secondary side. The type of insulation transformer 51 does not include

  In such a configuration, when the second set of switching elements 12c and 12b is turned off and the first set of switching elements 12a and 12d is turned on, a current flows from the positive terminal of the DC power supply 11 via the switching element 12a. And flows in the forward direction to the primary winding 51a. In response to this, a current flows through the secondary winding 51b in the opposite direction, this current flows forward through the rectifier element 13a, and further forward current flows through the rectifier element 13d via the inductive element 16a and the capacitive element 17. And flows in a loop returning to the secondary winding 51b. The rectifying elements 13a and 13d at this time are set as a first set.

  On the other hand, when the first set of switching elements 12a and 12d are turned off and the second set of switching elements 12c and 12b are turned on, current is supplied from the positive terminal of the DC power source 11 via the switching element 12c to the primary winding 51a. It flows in the opposite direction to the above. In response to this, a current flows through the secondary winding 51b in the opposite direction, this current flows in the forward direction through the rectifying element 13c, and further, a forward current flows through the rectifying element 13b via the inductive element 16a and the capacitive element 17. It flows in a loop that flows back to the secondary winding 51b. The rectifying elements 13c and 13b at this time are set as a second set.

  By the way, when the second set of switching elements 12c and 12b are turned off and the first set of switching elements 12a and 12d are turned on, the first set of rectifying elements 13a and 13d connected to the secondary winding 51b are in order. Although a directional current flows, at this time, a reverse bias is applied to the second set of rectifier elements 13c and 13b connected to the secondary winding 51b, so that a surge voltage is generated by the reverse recovery operation. When the voltage of the second set of rectifying elements 13c and 13b due to this surge voltage exceeds Vin / n, the clamp element 15 becomes conductive via the auxiliary winding 16b, and Vin / of the second set of rectifying elements 13c and 13b The surge energy exceeding n is regenerated to the DC power supply 11 that supplies the voltage Vin (= Vc) to the auxiliary winding 16b via the clamp element 15.

  Conversely, when the first set of switching elements 12a and 12d are turned off and the second set of switching elements 12c and 12b are turned on, the second set of rectifying elements 13c and 13b connected to the secondary winding 51b. A forward current flows through the first rectifier element, but a reverse bias is applied to the first set of rectifying elements 13a and 13d, so that a surge voltage is generated by the reverse recovery operation. When the voltage of the first set of rectifying elements 13a and 13d due to this surge voltage exceeds Vin / n, the clamp element 15 becomes conductive via the auxiliary winding 16b, and Vin / of the first set of rectifying elements 13a and 13d Surge energy exceeding n is regenerated to the DC power supply 11 via the clamp element 15.

That is, according to the switching power supply device 50, when a predetermined level of surge voltage is generated in the first set of rectifying elements 13a and 13b or the second set of rectifying elements 13c and 13b, the clamp element 15 is turned on and the surge A current corresponding to the voltage is supplied from the clamp element 15 to the output side (the output side of the switching power supply device 50) at both ends of the capacitive element 17 via the auxiliary winding 16b, thereby suppressing the surge voltage and keeping the output voltage Vout constant. The voltage can be held. Therefore, the switching power supply device 50 can achieve the same effect as the switching power supply device 40 described above.
(Modification of the fifth embodiment)
FIG. 13 is a circuit diagram showing a configuration of a switching power supply apparatus according to a modification of the fifth embodiment of the present invention. The switching power supply device 50A of this modification is different from the above-described switching power supply device 50 in that the other end of the auxiliary winding 16b in which the clamp element 15 is connected in series with one end is connected to the inductive element 16a and the capacitive element 17. It is in connecting to the part.

That is, according to the switching power supply device 50A, when a predetermined level of surge voltage is generated in the first set of rectifying elements 13a and 13b or the second set of rectifying elements 13c and 13b, A current corresponding to the voltage is supplied from the clamp element 15 to the output side (the output side of the switching power supply device 50A) at both ends of the capacitive element 17 via the auxiliary winding 16b, thereby suppressing the surge voltage and keeping the output voltage Vout constant. The voltage can be held. Therefore, the switching power supply device 50A can achieve the same effect as the switching power supply device 50 described above.
(Sixth embodiment)
FIG. 14 is a circuit diagram showing a configuration of a switching power supply according to the sixth embodiment of the present invention. The switching power supply 60 is different from the switching power supply 40 shown in FIG. 10 described above in that the switching power supply 60 includes a surge reduction circuit 18-1 instead of the surge reduction circuit 18 of the switching power supply 40.

  The surge reduction circuit 18-1 includes an auxiliary transformer 62 in which a primary winding 62a and a secondary winding 62b are wound around a magnetic core, a capacitive element 63, and a clamp element 15. One end of the primary winding 62a of the auxiliary transformer 62 is connected between the connection portion between the cathode ends of the rectifying elements 13a and 13b and the induction element 16a, and the other end is a capacitor for preventing a short circuit of the primary winding 62a of the transformer 62. The element 63 is connected between the neutral point on the secondary side of the insulating transformer 42 and the other end of the capacitive element 17 via the element 63. Furthermore, one end of the secondary winding 62 b of the auxiliary transformer 62 is connected to the positive terminal of the DC power supply 11, the other end is connected to the cathode terminal of the clamp element 15, and the anode terminal of the clamp element 15 is the negative electrode of the DC power supply 11. Connected to the side terminal.

  In the switching power supply 60 having such a configuration, when a reverse bias is applied to the rectifying element 13a or the rectifying element 13b and a surge voltage is generated by the reverse recovery operation, the clamping is performed via the secondary winding 62b of the auxiliary transformer 62. The element 15 becomes conductive. Due to this conduction, surge energy is regenerated to the DC power supply 11 that supplies the voltage Vin (= Vc) to the secondary winding 62b through the clamp element 15. Since this regenerative current is a current caused by a surge voltage caused by the reverse recovery operation of the rectifying element 13a or 13b, it gradually decreases and reaches zero.

  As described above, also in the switching power supply device 60 of the sixth embodiment, when a surge voltage of a predetermined level is generated in the rectifying element 13a or 13b, the clamp element 15 is in a conductive state via the secondary winding 62b of the auxiliary transformer 62. As a result, a current corresponding to the surge voltage is allowed to flow from the clamp element 15 to the positive terminal of the DC power supply 11 via the secondary winding 62b, thereby suppressing the surge voltage and maintaining the output voltage Vout at a constant voltage. I can do it. Therefore, the same effect as that of the first embodiment described above can be obtained.

Even when the smoothing circuit 14 is multistaged and a plurality of inductive elements 16a are provided, only one auxiliary transformer 62 is required. This is because the primary winding 62a of the auxiliary transformer 62 is connected between the inductive element 16a and the cathode end connection portion of the rectifying elements 13a and 13b, and the clamp element 15 is connected to the secondary winding 62b. This is because even when there are a plurality of inductive elements 16a, it is only necessary to connect the inductive elements 16a to one auxiliary transformer 62.
(Modification of the sixth embodiment)
FIG. 15 is a circuit diagram showing a configuration of a switching power supply device according to a modification of the sixth embodiment of the present invention. The switching power supply device 60A of this modification is different from the above-described switching power supply device 60 in that the other end of the secondary winding 62b of the auxiliary transformer 62 to which the clamp element 15 is connected in series is connected to the inductive element 16a. This is because the anode end of the clamp element 15 is connected to the neutral line on the secondary side of the insulating transformer 42 and connected to the connection portion with the element 17.

  That is, according to the switching power supply device 60A, when a predetermined level of surge voltage is generated in the rectifying element 13a or 13b, the clamp element 15 is turned on and a current corresponding to the surge voltage is supplied from the clamp element 15 to the auxiliary transformer 62. The current flows to the output side (the output side of the switching power supply device 60A) at both ends of the capacitive element 17 through the secondary winding 62b, thereby suppressing the surge voltage and maintaining the output voltage Vout at a constant voltage. Therefore, the same effect as that of the switching power supply 60 described above can be obtained in the switching power supply 60A.

In the switching power supply 60A, the anode end of the clamp element 15 is connected to the neutral line of the insulating transformer 42, but the anode end is connected to the negative terminal of the DC power supply 11. Also good.
(Seventh embodiment)
FIG. 16 is a circuit diagram showing a configuration of a switching power supply according to the seventh embodiment of the present invention. The switching power supply device 70 is different from the switching power supply device 50 shown in FIG. 12 described above in that it includes a surge reduction circuit 18-1 instead of the surge reduction circuit 18 of the switching power supply device 50.

  The surge reduction circuit 18-1 includes an auxiliary transformer 62 in which a primary winding 62a and a secondary winding 62b are wound around a magnetic core, a capacitive element 63, and a clamp element 15. One end of the primary winding 62a of the auxiliary transformer 62 is connected between the connection portion between the cathode ends of the rectifying elements 13a and 13c and the induction element 16a, and the other end is a capacitor for preventing a short circuit of the primary winding 62a of the transformer 62. The element 63 is connected between the anode ends of the rectifying elements 13 b and 13 d and the capacitive element 17 via the element 63. Furthermore, one end of the secondary winding 62 b of the auxiliary transformer 62 is connected to the positive terminal of the DC power supply 11, the other end is connected to the cathode terminal of the clamp element 15, and the anode terminal of the clamp element 15 is the negative electrode of the DC power supply 11. Connected to the side terminal.

  In the switching power supply 70 having such a configuration, when the first set of rectifying elements 13a and 13d or the second set of rectifying elements 13c and 13b are reverse-biased and a surge voltage is generated by the reverse recovery operation, the auxiliary power supply 70 The clamp element 15 becomes conductive through the secondary winding 62b of the transformer 62. Due to this conduction, surge energy is regenerated to the DC power supply 11 that supplies the voltage Vin (= Vc) to the secondary winding 62b through the clamp element 15. Since this regenerative current is a current caused by a surge voltage caused by the reverse recovery operation of the first set of rectifying elements 13a, 13d or the second set of rectifying elements 13c, 13b, it gradually decreases and reaches zero.

Thus, also in the switching power supply 70 of the seventh embodiment, when a predetermined level of surge voltage is generated in the first set of rectifying elements 13a and 13d or the second set of rectifying elements 13c and 13b, the clamp element 15 is The secondary transformer 62b of the auxiliary transformer 62 is rendered conductive, and a current corresponding to the surge voltage is passed from the clamp element 15 to the positive terminal of the DC power source 11 via the secondary winding 62b. The output voltage Vout can be held at a constant voltage by being suppressed. Therefore, the same effect as that of the first embodiment described above can be obtained. Even when the smoothing circuit 14 is multistaged and a plurality of inductive elements 16a are provided, the number of the auxiliary transformers 62 is only one as described in the sixth embodiment.
(Modification of the seventh embodiment)
FIG. 17 is a circuit diagram showing a configuration of a switching power supply device according to a modification of the seventh embodiment of the present invention. The switching power supply device 70A of this modification is different from the above-described switching power supply device 70 in that the other end of the secondary winding 62b of the auxiliary transformer 62 to which the clamp element 15 is connected in series is connected to the inductive element 16a and the capacitance. This is because it is connected to a connection portion with the element 17.

  That is, according to the switching power supply device 70A, when a predetermined level of surge voltage is generated in the first set of rectifying elements 13a and 13d or the second set of rectifying elements 13c and 13b, A current corresponding to the voltage is supplied from the clamp element 15 to the output side (the output side of the switching power supply device 70A) at both ends of the capacitive element 17 through the secondary winding 62b of the auxiliary transformer 62, thereby suppressing the surge voltage. The output voltage Vout can be held at a constant voltage. Therefore, the switching power supply device 70A can achieve the same effect as the switching power supply device 70 described above.

10, 10A, 20, 10A, 30, 30A, 40, 40A, 50, 50A, 60, 60A, 70, 70A Switching power supply device 11 DC power supply 12 Switching element 13, 13a, 13b, 13c, 13d Rectifier element 13-1 , 13-2 Full-wave rectifier circuit 14 Smoothing circuit 16a Inductive element 16b Auxiliary winding 17, 63 Capacitor element 18, 18-1 Surge reduction circuit 42, 51 Insulating transformer 42a, 51a, 62a Primary winding 42b, 42c, 51b 62b Secondary winding 62 Auxiliary transformer

Claims (13)

DC power supply, switching element for interrupting current from the DC power supply, rectifying element connected to the DC power supply through the switching element in a reverse bias state, input terminal of the rectifying element and connection of the switching element An inductive element that is an inductor having one end connected to the part, and a capacitive element that is connected between the other end of the inductive element and the DC power source and forms a smoothing circuit together with the inductive element, In the switching power supply device that smoothes the output voltage across the capacitor element by the rectifier element or the smoothing circuit,
A switching power supply device comprising: a surge reduction circuit that allows a current corresponding to a surge voltage of a predetermined level generated in the rectifying element when the switching element is turned on to flow so that the output voltage is kept constant. . A direct current power supply, an inductive element that is an inductor having one end connected to the direct current power supply, a rectifying element having an input end connected to the other end of the inductive element, and an output end of the rectifying element and the direct current power source. And a switching element connected between the capacitive element and the DC power supply, and between the induction element and the rectifying element, and for intermittently supplying a current from the DC power supply. In
A switching power supply device comprising: a surge reduction circuit that allows a current corresponding to a surge voltage of a predetermined level generated in the rectifying element when the switching element is turned on to flow so that the output voltage is kept constant. . DC power supply, switching element for interrupting current from the DC power supply, inductive element that is an inductor connected in series to the DC power supply via the switching element, and a connecting portion between the inductive element and the switching element In a switching power supply device having a rectifying element having an output terminal connected to the capacitor, and a capacitive element connected between the input terminal of the rectifying element and the DC power supply,
A switching power supply device comprising: a surge reduction circuit that allows a current corresponding to a surge voltage of a predetermined level generated in the rectifying element when the switching element is turned on to flow so that the output voltage is kept constant. .   The surge reduction circuit includes an auxiliary winding made of an inductor magnetically coupled to the inductive element, and a clamp element made of a diode connected in series to the auxiliary winding, to the clamp element in the auxiliary winding. The end opposite to the connection end of the DC power supply is connected to the positive electrode side terminal of the DC power supply, and the end of the clamp element opposite to the connection end to the auxiliary winding is connected to the negative electrode side terminal of the DC power supply. The switching power supply device according to any one of claims 1 to 3.   The surge reduction circuit includes an auxiliary winding made of an inductor magnetically coupled to the inductive element, and a clamp element made of a diode connected in series to the auxiliary winding, to the clamp element in the auxiliary winding. An end opposite to the connection end is connected to a connection portion between the inductive element and the capacitive element, and an end opposite to the connection end to the auxiliary winding in the clamp element is connected to a negative terminal of the DC power source. The switching power supply device according to any one of claims 1 to 3, wherein A switching circuit that switches a current from the DC power source between the DC power source, the transformer, and a primary winding of the DC power source and the transformer so that a current flows in the primary winding in a forward direction or a reverse direction; A center tap type full-wave rectifier circuit having a plurality of rectifier elements connected to the secondary winding of the transformer, and an inductive element that is an inductor connected to the cathode ends of the plurality of rectifier elements of the full-wave rectifier circuit; In the switching power supply device having the capacitive element connected between the inductive element and the center tap of the full-wave rectifier circuit,
A current corresponding to a surge voltage of a predetermined level generated in any rectifier element of the full-wave rectifier circuit when the switching circuit switches to the forward direction or the reverse direction so that the output voltage is kept constant. A switching power supply comprising a surge reducing circuit. A switching circuit that switches a current from the DC power source between the DC power source, the transformer, and a primary winding of the DC power source and the transformer so that a current flows in the primary winding in a forward direction or a reverse direction; A bridge-type full-wave rectifier circuit having a plurality of rectifier elements connected to the secondary winding of the transformer, and an inductive element that is an inductor connected to the anode ends of the plurality of rectifier elements of the full-wave rectifier circuit; In the switching power supply device having the inductive element and a capacitive element connected between the cathode ends of the other rectifier elements of the full-wave rectifier circuit,
A current corresponding to a surge voltage of a predetermined level generated in any rectifier element of the full-wave rectifier circuit when the switching circuit switches to the forward direction or the reverse direction so that the output voltage is kept constant. A switching power supply comprising a surge reducing circuit.   The surge reduction circuit includes an auxiliary winding made of an inductor magnetically coupled to the inductive element, and a clamp element made of a diode connected in series to the auxiliary winding, to the clamp element in the auxiliary winding. The end opposite to the connection end of the DC power supply is connected to the positive electrode side terminal of the DC power supply, and the end of the clamp element opposite to the connection end to the auxiliary winding is connected to the negative electrode side terminal of the DC power supply. The switching power supply device according to claim 6 or 7, characterized in that   The surge reduction circuit includes an auxiliary winding made of an inductor magnetically coupled to the inductive element, and a clamp element made of a diode connected in series to the auxiliary winding, to the clamp element in the auxiliary winding. An end opposite to the connection end of the DC power source is connected to a connection portion between the inductive element and the capacitive element, and an end opposite to the connection end to the auxiliary winding in the clamp element is the negative terminal of the DC power source or the center The switching power supply device according to claim 6, wherein the switching power supply device is connected to a tap.   The surge reduction circuit includes an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core, a second induction element connected to the primary winding of the auxiliary transformer, and a secondary of the auxiliary transformer A clamp element formed of a diode connected in series with the winding, wherein one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifier elements of the full-wave rectifier circuit, and the other end is a second induction. Connected to the center tap of the full-wave rectifier circuit through an element, the end of the secondary winding of the auxiliary transformer facing the connection end to the clamp element is connected to the positive terminal of the DC power supply, and the clamp The switching power supply device according to claim 6, wherein an end of the element facing the connection end to the secondary winding is connected to a negative electrode side terminal of the DC power supply.   The surge reduction circuit includes an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core, a second induction element connected to the primary winding of the auxiliary transformer, and a secondary of the auxiliary transformer A clamp element formed of a diode connected in series with the winding, wherein one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifier elements of the full-wave rectifier circuit, and the other end is a second induction. Connected to the center tap of the full-wave rectifier circuit through the element, and the end facing the connection end to the clamp element in the secondary winding of the auxiliary transformer is connected to the connection part of the induction element and the capacitive element The switch according to claim 6, wherein an end of the clamp element opposite to a connection end to the secondary winding is connected to a negative electrode side terminal or the center tap of the DC power supply. Grayed power supply.   The surge reduction circuit includes an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core, a second induction element connected to the primary winding of the auxiliary transformer, and a secondary of the auxiliary transformer A clamp element formed of a diode connected in series with the winding, wherein one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifier elements of the full-wave rectifier circuit, and the other end is a second induction. The terminal connected to the anode ends of the other rectifier elements of the full-wave rectifier circuit through the element, the end facing the connection end to the clamp element in the secondary winding of the auxiliary transformer is the positive side of the DC power supply 8. The switching power supply device according to claim 7, wherein an end connected to a terminal and facing a connection end to the secondary winding in the clamp element is connected to a negative terminal of the DC power supply.   The surge reduction circuit includes an auxiliary transformer in which a primary winding and a secondary winding are wound around a magnetic core, a second induction element connected to the primary winding of the auxiliary transformer, and a secondary of the auxiliary transformer A clamp element formed of a diode connected in series with the winding, wherein one end of the primary winding of the auxiliary transformer is connected to the cathode ends of the plurality of rectifier elements of the full-wave rectifier circuit, and the other end is a second induction. An end of the secondary winding of the auxiliary transformer facing the connection end to the clamp element is connected to the anode end of the plurality of rectifier elements of the full-wave rectifier circuit through an element. 8. The device according to claim 7, wherein an end connected to a connection portion with an element and facing a connection end to the secondary winding in the clamp element is connected to a negative electrode side terminal of the DC power supply. Switching power Apparatus.

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