JP6300845B2 - Switching power supply circuit - Google Patents

Description

  The present invention relates to a switching power supply circuit having a DC / DC converter or the like, and more particularly to a switching power supply circuit that can reduce power loss and increase the efficiency of power conversion.

  2. Description of the Related Art Conventionally, a switching power supply circuit that converts a DC power supply to an AC power supply by a DC / DC converter, rectifies the converted AC power supply by a rectifier circuit, and converts it into DC power is known. FIG. 8 is a circuit diagram showing a configuration of a conventional switching power supply circuit, and FIG. 9 is a block diagram showing a configuration in which three power supplies of the conventional switching power supply circuit are used and the outputs of a diode bridge are connected in series. is there. FIG. 10 is a diagram showing a path of current flowing through the diode bridge shown in FIG.

  As shown in FIG. 8, the switching power supply circuit 50 includes a switching circuit 52 that switches the DC power supply 40 and outputs a current to the primary winding of the transformer 60, a primary winding, and a secondary winding, and is magnetic. A transformer 60 that performs power conversion by coupling, a diode bridge 65 that rectifies alternating current from the secondary winding of the transformer 60 into direct current, and a control circuit 75 that controls switching of the switching circuit 52 are included.

  As shown in FIG. 8, the switching circuit 52 of the switching power supply circuit 50 includes switching elements such as MOSFETs, and two sets of switching elements connected in series are connected to the output terminal of the DC power supply 40.

  The connection point of the two switching elements 53 and 54 connected in series is connected to one end of the primary winding 61 of the transformer 60, and the connection point of the other two switching elements 55 and 56 connected in series is the transformer. 60 is connected to the other end of the primary winding 61. Further, the current input to the primary winding 61 of the transformer 60 is converted into AC power and output from the secondary winding 62 of the transformer 60.

  The control circuit 75 controls the switching of the switching circuit 52 so that the switching elements 53 and 56 and the switching elements 54 and 55 are alternately turned on. Thereby, currents in different directions alternately flow in the primary winding 61 of the transformer 60.

  The secondary winding 62 of the transformer 60 is connected to the input end of a diode bridge 65 composed of diodes D1, D2, D3, and D4. The secondary bridge 62 is rectified by the diode bridge 65, and current is output from the output end to the load 48 and the like. Is output. The output terminal of the diode bridge 65 is connected to an electrolytic capacitor or the like as the smoothing circuit 80 that suppresses the ripple current. If necessary, an inductor is also connected.

  FIG. 9 is a block diagram showing a configuration in which n (n = 3) power supply units of a conventional switching power supply circuit are used and the outputs of the diode bridge are connected in series.

  As shown in FIG. 9, the conventional switching power supply circuit 50 has n (n is an integer of 2 or more) power supply units 51 in which a switching circuit 52, a transformer 60, and a diode bridge 65 are integrally formed. The outputs of the power supply unit 51 are connected in series, and power is supplied to the load 48 from the output terminals a and b connected in series.

  The switching power supply circuit 50 shown in FIG. 9 has a configuration in which the power supply unit 51 has n = 3, the power supply unit with n = 1 is 51a, the switching circuit of the power supply unit 51a is 52a, the transformer is 60a, and the diode bridge is. Described as 65a. The power supply unit with n = 2 is 51b, the switching circuit of the power supply unit 51b is 52b, the transformer is 60b, the diode bridge is 65b, the power supply unit with n = 3 is 51c, and the switching circuit of the power supply unit 51c is 52c. The transformer is denoted as 60c and the diode bridge as 65c.

  FIG. 10 is a diagram showing a path of current flowing through the diode bridge shown in FIG. As shown in FIG. 10, the current flowing through the diode bridges 65a, 65b, and 65c flows from the output terminal b and flows to the transformer 60c through the diode D11. The current from the transformer 60c flows to the transformer 60b through the diode D10 and the diode D7. The current from the transformer 60b flows to the transformer 60a through the diode D6 and the diode D3. The current from the transformer 60a flows out of the output terminal a through the diode D2.

  As shown in FIG. 10, the total number of diodes through which current passes when n diode bridges are connected in series during rectification is 2 × n.

  Further, Patent Document 1 discloses a DC power supply device that reduces switching loss and diode loss for high-frequency operation of a semiconductor switch, particularly in a DC power supply device in which input and output are electrically isolated by a transformer. Yes.

  The DC power supply device disclosed in Patent Document 1 has a low impedance on the input side of the rectifier diode bridge circuit of the DC power supply device with respect to the current direction until the recovery of the rectifier diode occurs, and a high impedance in the opposite direction. By providing a circuit element having impedance, generation of a surge voltage accompanying recovery is effectively suppressed to reduce power loss, and destruction of a rectifier diode and generation of electromagnetic noise are prevented.

JP2013-27162A

  When a diode bridge is used for the rectifier circuit and n diode bridges are connected in series, the output voltage of the diode bridge is a voltage value obtained by adding the voltages output from the diode bridges. At this time, a current flows when a load is connected to the output terminal. The total number of diodes through which current flows in the rectification operation is n (the number of diode bridges connected in series) × 2. For example, in a rectifier circuit in which three diode bridges are connected in series, the total number of diodes through which current in the rectification operation passes is six.

  When current flows through the diode of the diode bridge, loss due to the diode occurs. When the current flowing through the diode is I (A), the forward voltage of the diode is Vf (V), and the number of diode bridges n is 3, the loss Pd is Pd = Vf × I × 2 × 3.

  For this reason, the loss which generate | occur | produces in a diode will increase according to the number of diode bridges. Since the loss generated in the rectifier circuit is large, for example, even if the loss is reduced other than the rectifier circuit as in Patent Document 1, the effect may not be improved. For this reason, it is required to reduce the loss generated in the diode bridge connected in series.

  Therefore, the present invention uses a plurality of transformers, uses a diode as a rectifier circuit between the transformers, and can reduce the loss generated from the diodes and increase the power conversion efficiency even when the outputs are connected in series. An object is to provide a switching power supply circuit.

To achieve the above object, the switching power supply circuit of the present invention comprises n (n is an integer of 2 or more) transformers,
Provided on the primary side of the transformer, provided on the secondary side of the transformer, and a switching circuit provided on each of the transformers for switching a DC power source and alternately flowing currents of different directions to the primary winding of the transformer , a switching power supply circuit and a (n-1) of the rectifier circuit consisting of diodes for converting the voltage into a DC output from the secondary winding of the transformer, each of said rectifying circuit, while the fit Ri next One of two diodes having the same polarity is connected to each of both ends of the secondary winding of one of the transformers, and one of the transformers The other terminals of the two diodes connected to one end of the secondary winding of the other are connected to both ends of the secondary winding of the other transformer, respectively, The other terminal of the two diodes other other connected to an end of the secondary winding of the transformer, which is connected to both ends of the other of said transformer secondary winding, the switching power supply circuit , the connected said two diodes and the other between the ends of the n number of ends and the other of the secondary winding of the neighboring Ri meet one of the transformer in the transformer of the transformer secondary winding The secondary windings of the n transformers are connected in series by the rectifier circuit including a total of four diodes of the two diodes, and two of the first transformers in the n transformers are connected. One terminal of one backflow preventing diode is opposite to each of the two diodes of the rectifier circuit connected to both ends of the secondary winding of the first transformer at each end of the secondary winding. The other two backflow prevention diodes are connected to each other, and a connection point between the other terminals is connected to one of output terminals to which a load is connected, One terminal of one other backflow prevention diode is connected to each of both ends of the secondary winding of the nth transformer at each of both ends of the secondary winding of the nth transformer in each of the n transformers. The other rectifier circuit connected to the two rectifier circuits are connected to have opposite polarity, and the other two backflow prevention diodes in total are connected to each other, and between the other terminals. The connection point is connected to the other output terminal to which a load is connected, and the current flowing through the rectifier circuit passes through n + 1 diodes.

The switching power supply circuit of the present invention is connected to said rectifier circuit between one of the transformer and the other of said transformer, during rectification operation, one of both ends of one of the transformer secondary winding and the end of which is the one end of both ends of the other of said transformer secondary winding is electrically connected via one of the diodes, is characterized in that the flow a current.

Also, the rectifier circuit of the switching power supply circuit of the present invention, between opposite ends of said n ends and the other of the secondary winding of the neighboring Ri meet one of the transformer in the transformer of the transformer secondary winding The switching frequency of the switching circuit for switching the DC power source provided on the primary side of one of the transformers connected to the rectifier circuit is provided on the primary side of the other transformer connected to the rectifier circuit. The switching frequency of the switching circuit for switching the direct-current power supply is twice the switching frequency.

In the switching power supply circuit of the present invention, the total of the four diodes of the rectifier circuit switches 1 / of the switching frequency period of the switching circuit that switches the DC power supply provided on the primary side of the other transformer. It is characterized in that it becomes conductive in order of four.

The switching power supply circuit of the present invention, the DC power source provided to the DC power source provided on the primary side of the neighboring Ri meet one of the transformer to the primary side of said switching circuit and the other of said transformer for switching switching frequency of said switching circuit for switching, the same is the frequency, by switching the switching circuit and one of the transformer and the other of said transformer phase with each Ri next switching frequency shifted 90 degrees, the rectifier circuit The total of four diodes are made conductive in order of 1/4 of the period of the switching frequency.

  Further, the rectifier circuit in the switching power supply circuit according to the present invention rectifies the output from the secondary winding of the transformer by using a rectifier element having an action of flowing a current only in one direction instead of the diode. The voltage and current in only one direction can be obtained.

  In addition, the rectifier circuit in the switching power supply circuit of the present invention uses a switching element capable of flowing an electric current only in one direction by inputting a control signal, instead of the diode, and uses two switching elements. The output from the next winding is rectified to obtain a voltage and current in only one direction.

  In the conventional diode bridge, the total number of diodes through which current passes when n diode bridges are connected in series during rectification is 2 × n. According to the present invention, the total number of diodes through which current passes when n diode bridges are connected in series is n + 1. Thereby, the loss which generate | occur | produces with the diode which is a rectifier can be reduced.

  Further, according to the present invention, it is possible to reduce the amount of decrease in the output voltage after rectification. That is, the decrease in output voltage after rectification depends on the total number of diodes through which current flows when n diode bridges are connected in series. The present invention can reduce the total number of diodes through which current passes, as compared with the prior art. For this reason, the fall amount of the output voltage after rectification can be reduced.

  Further, according to the present invention, the rectifier circuit connected between the transformers has one end of the secondary winding of one transformer and the other end of the secondary winding of the other transformer in a rectifying operation. Connected by one diode. Conventionally, two diodes are connected between the transformers during the rectifying operation. For this reason, the voltage drop due to the current flowing through the diode between the transformers is reduced, and the efficiency of power conversion can be increased.

  According to the present invention, in the rectifier circuit connected between the transformers, the switching frequency of one transformer is set to be twice the switching frequency of the other transformer, so that the current flowing through the diode of the bridge circuit is changed to the switching frequency. The four diodes are turned on one by one in order of 1/4 of the period.

  For this reason, four diodes share in one cycle of the switching frequency and become conductive. Since the current flowing through the diodes connected between the transformers flows through the four diodes sequentially in one cycle of the switching frequency, it is possible to reduce the heat generation of the diodes. As a result, a rectifying element having a small maximum rated current can be used.

It is a block diagram which shows the structure of the switching power supply circuit by this invention. It is a figure which shows the circuit structure of the pressure | voltage rise part in a switching power supply circuit. It is a block diagram which shows the structure of the switching power supply circuit provided with three transformers. (A)-(d) is a figure which shows the path | route of the electric current which flows through the diode of a rectifier circuit based on the polarity of a transformer output. (A) And (b) is a figure which shows the path | route of the electric current which flows through the diode of a rectifier circuit based on the polarity of a transformer output. It is a block diagram which shows the structure of the switching power supply circuit provided with two transformers. It is a figure which shows the timing of the control signal input into the switching circuit shown in FIG. 6, and the figure which shows the diode through which an electric current flows in 1 period of the switching frequency in a rectifier circuit. It is a circuit diagram which shows the structure of the conventional switching power supply circuit. It is a block diagram which shows the structure which used the power supply part of the conventional switching power supply circuit, and connected the output of the diode bridge in series. FIG. 10 is a diagram illustrating a path of current flowing through the diode bridge illustrated in FIG. 9.

  Hereinafter, an embodiment for implementing a switching power supply circuit according to the present invention will be described with reference to the drawings. In the present invention, even when a plurality of transformers are used and a rectifier circuit composed of diodes is connected between the transformers and the outputs of the rectifier circuits are connected in series, the loss of the rectifier circuit generated from the diodes is reduced. This is to reduce the power conversion efficiency of the switching power supply circuit.

  FIG. 1 is a block diagram showing a configuration of a switching power supply circuit of a switching power supply apparatus according to the present invention, and FIG. 2 is a diagram showing a circuit configuration of a booster in the switching power supply circuit according to the present invention.

[Configuration of switching power supply circuit]
As shown in FIG. 1, the switching power supply circuit 1 switches the DC power input from the DC power supply 40, converts it to DC power having a predetermined voltage, and supplies it to the load 48, etc. (N is an integer greater than or equal to 2) voltage boosters 3, a rectifier circuit 20 that rectifies the AC power from the voltage booster 3, and a control circuit 30 that controls each voltage booster 3.

  As shown in FIGS. 1 and 2, the boosting unit 3 of the switching power supply circuit 1 switches the DC power input from the DC power supply 40 and converts it into AC power, and the switching circuit 7 A transformer 16 is provided that inputs AC power to the primary winding 17 and transmits power to the secondary winding 18 by magnetic coupling.

  In the following description, the first booster, which is the first of the n boosters 3, is referred to as 3a, the switching circuit of the first booster 3a is referred to as the first switching circuit 7a, and the transformer is the first The transformers 16a are respectively described. Also, the second boosting unit, which is the second of the n boosting units 3, is 3b, the switching circuit of the second boosting unit 3b is the second switching circuit 7b, and the transformer is the second transformer 16b. I write.

  Similarly, the nth boosting unit, which is the nth boosting unit 3, is 3n, the switching circuit of the nth boosting unit 3n is the nth switching circuit 7n, and the transformer is the nth transformer 16n. Each is described.

  The rectifier circuit located between the first transformer 16a and the second transformer 16b is referred to as a first rectifier circuit 20ab, and the rectifier circuit located between the second transformer 16b and the third transformer 16c is used. The second rectifier circuit 20bc and the rectifier circuit positioned between the (n-1) th transformer 16n-1 and the nth transformer 16n are referred to as the (n-1) th rectifier circuit 20 (n-1) n. Moreover, when naming a name generically, it describes as the step-up part 3, the switching circuit 7, the transformer 16, and the rectifier circuit 20.

  As shown in FIG. 1, the switching power supply circuit 1 has n boosting units 3, and each boosting unit 3 has a switching circuit 7 connected corresponding to a transformer 16.

  The output from the secondary winding 18 of the transformer 16 that is the output unit of the booster unit 3 is connected to the rectifier circuit 20. (N-1) rectifier circuits 20 are provided between the transformers 16, and the transformers 16 and the rectifier circuits 20 are connected in series to prevent backflow prevention diodes D1, D2 and D11, D12 (see FIG. 3). (When n = 3 shown), power is supplied to the load 48 and the like from both ends of the output.

  FIG. 2 is a diagram illustrating a circuit configuration of one boosting unit in the switching power supply circuit. As shown in FIG. 2, the switching circuit 7 includes switching elements 11, 12, 13, and 14 made of MOSFETs. The switching element 11 and the switching element 12 are connected in series to the DC power supply 40, and switching is performed. The element 13 and the switching element 14 are connected in series. The diode connected to the MOSFET indicates a parasitic diode.

  A connection point between the switching element 11 and the switching element 12 is connected to one end of the primary winding 17 of the transformer 16, and a connection point between the switching element 13 and the switching element 14 is the other end of the primary winding 17 of the transformer 16. It is connected to the.

  As a result, the switching element 11 and the switching element 14 are turned on, and the switching element 13 and the switching element 12 are turned off, whereby a current flows in the direction indicated by ia (shown in FIG. 2) through the transformer 16. When the switching element 12 is turned on and the switching element 11 and the switching element 14 are turned off, a current flows through the transformer 16 in the direction indicated by ib (shown in FIG. 2).

  Note that the switching element is not limited to a MOSFET, and may be any electronic component that can turn on and off a circuit current with a control signal. For example, the switching element may be a transistor or an IGBT.

  The control circuit 30 shown in FIGS. 1 and 2 applies a control signal (voltage) to the input of the switching element, for example, the gate of the MOSFET, and controls ON (conducting) and OFF (non-conducting) of the switching element. The control circuit 30 shown in FIG. 2 turns on the switching element 11 and the switching element 14 and controls the switching element 13 and the switching element 12 to be turned off at this time. When the switch is turned on, the switching element 11 and the switching element 14 are controlled to be turned off.

  A period T from the start of ON of the control signal to the end of OFF at this time is defined as a period T. The switching frequency f is 1 / T.

  The control circuit 30 inputs a control signal having a switching frequency having a period T for each switching circuit 7, and the switching circuit 7 repeats ON / OFF of the switching element according to the control signal.

  The switching circuit 7 switches the DC power supply according to a control signal from the control circuit 30 and converts it into AC power, and inputs the converted AC power to the primary winding 17 of the transformer 16. The transformer 16 transmits AC power to the secondary winding 18 by magnetic coupling.

  The AC power output from the secondary winding 18 of the transformer 16 is input to a rectifier circuit (diode bridge) 20 that converts AC power into DC power.

  The rectifier circuit 20 includes a diode bridge, and a DC voltage is output from the output end of the diode bridge.

[Current path of rectifier circuit]
Next, the configuration of the rectifier circuit in the switching power supply circuit 1 and the path of the current flowing through the diode of the rectifier circuit based on the output voltage polarity of the transformer will be described with reference to FIGS.

  FIG. 3 is a block diagram showing a configuration of a switching power supply circuit including three transformers, and FIGS. 4A to 4D are diagrams showing paths of currents flowing through the diodes of the rectifier circuit based on the polarity of the transformer output. FIGS. 5A to 5B are diagrams showing a path of current flowing through the diode of the rectifier circuit based on the polarity of the transformer output.

  As shown in FIG. 3, the rectifier circuit 20ab is formed of a diode bridge and is connected between the transformers 16a and 16b. The rectifier circuit 20bc is formed of a diode bridge and is connected between the transformers 16b and 16c. ing.

  The rectifier circuit 20ab connects one terminal of two diodes D3, D4, D5, and D6 having the same polarity to both ends c and d of the secondary winding of one transformer 16b, and one transformer 16b. The other terminals of the two diodes D3 and D4 connected to one end c of the secondary winding are connected to both ends a and b of the secondary winding of the other transformer 16a. Further, the other terminals of the two diodes D5 and D6 connected to the other end d of the secondary winding of one transformer 16b are connected to both ends a and b of the secondary winding of the other transformer 16a, respectively. doing.

  In the rectifier circuit 20ab connected between the transformers 16a and 16b, one of the four diodes becomes conductive so that a current flows from one transformer 16b to the other transformer 16a. For example, when the d terminal of the transformer 16b shown in FIG. 4A is a positive pole and the c terminal is a negative pole, the b terminal of the transformer 16a is a positive pole, and the a terminal is a negative pole, the diode D5 of the rectifier circuit 20 is The conduction state is established, and a current flows through the a terminal of the transformer 16a. As described above, the diode that becomes conductive in the rectifier circuit connected between the transformers is determined by the polarity of the terminal of one transformer 16 and the polarity of the other transformer 16.

[Current path by polarity of transformer]
A current path according to a voltage direction generated in the transformer in the rectifier circuit will be described with reference to FIG. As shown in FIG. 4A, when the voltage generated at the terminals a and b of the secondary winding of the transformer 16a is in the direction indicated by the arrow, the polarity of the output voltage is set to + polarity, and FIG. As shown, when the voltage generated at the terminals a and b of the transformer 16a is in the direction indicated by the arrow, the polarity of the output voltage is negative.

  The current flowing through the rectifier circuit 20 and the transformer 16 is indicated by a thick dotted line, and the direction in which the current flows is indicated by an arrow.

  As shown in FIG. 4A, when the polarity of the transformer 16a is + polarity, the polarity of the transformer 16b is + polarity, and the polarity of the transformer 16c is + polarity, current flows from the terminal o2, flows to the diode D11, and e terminal To the transformer 16c. The current from the transformer 16c flows from the terminal f through the diode D9 to the transformer 16b from the c terminal.

  The current from the transformer 16b flows from the terminal d through the diode D5 to the transformer 16a from the terminal a. Furthermore, the current from the transformer 16a flows from the terminal b through the diode D2 to the load or the like from the terminal o1.

  4B, when the polarity of the transformer 16a is -polarity, the polarity of the transformer 16b is -polarity, and the polarity of the transformer 16c is -polarity, current flows from the terminal o2 and flows to the diode D12. It flows from the f terminal to the transformer 16c. The current from the transformer 16c flows from the terminal e through the diode D8 to the transformer 16b from the d terminal.

  The current from the transformer 16b flows from the terminal c through the diode D4 to the transformer 16a from the b terminal. Furthermore, the current from the transformer 16a flows from the terminal a through the diode D1 to the load or the like from the terminal o1.

  As shown in FIGS. 4A and 4B, when the transformers 16a, 16b, and 16c change with the same polarity, no current flows through the diodes D7, D10, D3, and D6. For this reason, in the switching power supply circuit 1, when the transformers 16a, 16b, and 16c change with the same polarity, the diodes D7, D10, D3, and D6 may not be provided.

  However, as will be described below, diodes D7, D10, D3, and D6 are provided when the transformers 16a, 16b, and 16c have different switching frequencies and different phases, and the transformers have different polarities.

[Current path when the polarity of each transformer is different]
The current path when the polarities of the transformers are different will be described below. As shown in FIG. 4C, when the polarity of the transformer 16a is -polarity, the polarity of the transformer 16b is + polarity, and the polarity of the transformer 16c is + polarity, current flows from the terminal o2, flows to the diode D11, and flows to the e terminal. To the transformer 16c. The current from the transformer 16c flows from the terminal f through the diode D9 to the transformer 16b from the c terminal.

  The current from the transformer 16b flows from the terminal d through the diode D6 to the transformer 16a from the b terminal. Further, the current from the transformer 16a flows from the terminal a through the diode D1 to the load or the like from the terminal o1.

  As shown in FIG. 4D, when the polarity of the transformer 16a is + polarity, the polarity of the transformer 16b is -polarity, and the polarity of the transformer 16c is -polarity, current flows from the terminal o2 and flows to the diode D12. It flows from the f terminal to the transformer 16c. The current from the transformer 16c flows from the terminal e through the diode D8 to the transformer 16b from the d terminal.

  The current from the transformer 16b flows from the terminal c through the diode D3 to the transformer 16a from the terminal a. Furthermore, the current from the transformer 16a flows from the terminal b through the diode D2 to the load or the like from the terminal o1.

  As described above, when the transformer 16b and the transformer 16a have different polarities, current flows through D6 and D3.

  Next, a current path when the polarities of the transformers are alternately different will be described with reference to FIG. As shown in FIG. 5A, when the polarity of the transformer 16a is + polarity, the polarity of the transformer 16b is -polarity, and the polarity of the transformer 16c is + polarity, current flows from the terminal o2, flows to the diode D11, and flows to the e terminal. To the transformer 16c. The current from the transformer 16c flows from the terminal f through the diode D10 to the transformer 16b from the d terminal.

  The current from the transformer 16b flows from the terminal c through the diode D3 to the transformer 16a from the terminal a. Furthermore, the current from the transformer 16a flows from the terminal b through the diode D2 to the load or the like from the terminal o1.

  Further, as shown in FIG. 5B, when the polarity of the transformer 16a is -polarity, the polarity of the transformer 16b is + polarity, and the polarity of the transformer 16c is -polarity, current flows from the terminal o2 and flows to the diode D12. It flows from the f terminal to the transformer 16c. The current from the transformer 16c flows from the terminal e through the diode D7 to the transformer 16b from the c terminal.

  The current from the transformer 16b flows from the terminal d through the diode D6 to the transformer 16a from the b terminal. Furthermore, the current from the transformer 16a flows from the terminal a through the diode D1 to the load or the like from the terminal o1.

  As described above, when the polarities of the transformer 16a, the transformer 16b, and the transformer 16c change alternately, a current flows through the diodes D3 and D10 or the diodes D7 and D6.

  Further, as in the current paths shown in FIGS. 4A, 4B, 4C, and 5D and FIGS. 5A and 5B, one diode is provided between the transformer 16c and the transformer 16b. Are connected in series. The transformer 16b and the transformer 16a are connected in series with one diode. In the conventional diode bridge, two diodes are connected in series between the transformers. Thus, the present invention can reduce the decrease in output voltage due to the diode. Further, loss due to the diode can be reduced.

  The output terminal of the rectifier circuit 20 is composed of two sets of backflow prevention diodes D1, D2 and D11, D12 (when n = 3) connected in series to both poles of the transformer located on the output terminals o1, o2. Output from each connection point.

  As shown in FIGS. 4C and 4D and FIGS. 5A and 5B, by providing the diodes D7, D10, D3, and D6, the voltage output from the transformer is set in the same direction at the same timing. There is no need to control it to occur.

  As shown in FIGS. 4A and 4B, currents do not flow through the diodes D7, D10, D3, and D6 by generating the voltage output from the transformer in the same direction at the same timing. Therefore, the number of diodes connected between the transformers can be reduced.

  Although the embodiment using a diode for the rectifier circuit has been described, instead of the diode, a rectifier having an action of flowing a current only in one direction, for example, a mercury rectifier, a cuprous oxide rectifier, a thyratron, a selenium rectifier, a bipolar vacuum tube May be used to rectify the output from the secondary winding of the transformer so as to obtain voltage and current in only one direction.

  In addition, the rectifier circuit uses a switching element, such as a MOSFET, a transistor, an IGBT, or a thyristor, that can operate to flow a current only in one direction by inputting a control signal instead of a diode. The output from the next winding may be rectified to obtain voltage and current in only one direction.

[Current sharing of each diode in the rectifier circuit]
Next, a switching power supply circuit capable of sharing the current flowing through the rectifier circuit connected between the transformers to each diode to shorten the conduction period of the diode will be described with reference to FIGS.

  FIG. 6 is a block diagram showing a configuration of a switching power supply circuit including two transformers, FIG. 7 is a diagram showing timings of control signals input to the switching circuit shown in FIG. 6, and during one cycle of the switching frequency in the rectifier circuit It is a figure which shows the diode through which an electric current flows.

  As shown in FIG. 6, a rectifier circuit 20ab including diodes D3, D4, D5, and D6 is connected between the two transformers 16a and 16b.

  As described above, the rectifier circuit 20ab connects one terminal of two diodes D3, D4 and D5, D6 having the same polarity to both ends c, d of the secondary winding of one transformer 16b. The other terminals of the two diodes D3 and D4 connected to one end c of the secondary winding of one transformer 16b are connected to both ends a and b of the secondary winding of the other transformer 16a, respectively. ing.

  Further, the other terminals of the two diodes D5 and D6 connected to the other end d of the secondary winding of one transformer 16b are connected to both ends a and b of the secondary winding of the other transformer 16a, respectively. doing.

[Switching frequency of switching circuit]
As shown in FIG. 7, the switching frequency fa of the first switching circuit 7a that switches the first transformer 16a is twice the switching frequency fb of the second switching circuit 16b that switches the second transformer 16b. Like that.

  For example, if the switching frequency fa of the first switching circuit 7a that switches the first transformer 16a is 100 kHz, the switching frequency fb of the second switching circuit 7b that switches the second transformer 16b is 50 kHz.

  Next, rectification when the switching frequency fa of the first switching circuit 7a that switches the first transformer 16a is twice the switching frequency fb of the second switching circuit 7b that switches the second transformer 16b. The diode through which the current in the circuit 20ab passes and its conduction time will be described.

  As shown in FIG. 7, the switching elements 11a and 14a of the first switching circuit 7a are turned on during the time t1 to t2 corresponding to ¼ of the cycle Tb of the switching frequency fb of the second switching circuit, and the switching elements 13a, When 12a is OFF, current ia1 flows, and voltage Va2 (-polarity) indicated by an arrow is generated at the terminals a and b on the secondary side of the transformer 16a.

  Further, when the switching elements 11b and 14b of the second switching circuit 7b are turned off and the switching elements 13b and 12b are turned on, the current ib2 flows, and the voltage of Vb1 (+ polarity) indicated by an arrow is applied to the transformer 16b. As shown by the current passing diode in FIG. 7, the diode D6 becomes conductive.

  Next, as shown in FIG. 7, the switching elements 11a and 14a of the first switching circuit 7a are turned off and the switching element 13a from time t2 to t3 corresponding to the period ¼ of the switching frequency fb of the second switching circuit. , 12a is ON, current ia2 flows, and Va1 voltage (+ polarity) indicated by an arrow is generated at the secondary side terminals a, b of the transformer 16a.

  Further, when the switching elements 11b and 14b of the second switching circuit 7b are turned off and the switching elements 13b and 12b are turned on, the current ib2 flows, and the voltage of Vb1 (+ polarity) indicated by an arrow is applied to the transformer 16b. As shown by the current passing diode in FIG. 7, the diode D5 becomes conductive.

  Next, as shown in FIG. 7, the switching elements 11a and 14a of the first switching circuit 7a are turned on from time t3 to t4 corresponding to the period ¼ of the switching frequency fb of the second switching circuit, and the switching element 13a. , 12a is OFF, the current ia1 flows, and a voltage Va2 (-polarity) indicated by an arrow is generated at the terminals a and b on the secondary side of the transformer 16a.

  In addition, when the switching elements 11b and 14b of the second switching circuit 7b are turned on and the switching elements 13b and 12b are turned off, the current ib1 flows, and the voltage of Vb2 (−polarity) indicated by an arrow is applied to the transformer 16b. As shown by the current passing diode in FIG. 7, the diode D4 becomes conductive.

  Next, as shown in FIG. 7, the switching elements 11a and 14a of the first switching circuit 7a are turned off and the switching element 13a from time t4 to t5 corresponding to the period ¼ of the switching frequency fb of the second switching circuit. , 12a is ON, current ia2 flows, and Va1 voltage (+ polarity) indicated by an arrow is generated at the secondary side terminals a, b of the transformer 16a.

  In addition, when the switching elements 11b and 14b of the second switching circuit 7b are turned on and the switching elements 13b and 12b are turned off, the current ib1 flows, and the voltage of Vb2 (−polarity) indicated by an arrow is applied to the transformer 16b. As shown by the current passing diode in FIG. 7, the diode D3 becomes conductive.

  As described above, the four diodes of the rectifier circuit connected between the (n−1) th transformer and the nth transformer are turned on by a quarter of the period of the switching frequency f (n−1). .

  When three or more transformers are used, for example, when n = 3, the switching frequency of the third transformer 16c is set to be twice the switching frequency of the second transformer 16b. Further, the switching frequency of the first transformer 16a is set to be twice the switching frequency of the second transformer 16b.

  In the above description, the embodiment using two transformers and one rectifier circuit has been described. However, the switching frequency of the switching circuit that uses n transformers and switches the transformers at both ends connected to the rectifier circuit is described. The ratio should be 1: 2 (or 2: 1). The current flowing through the rectifier circuit during one cycle of a low frequency can be shared by each diode. In addition, one diode is connected between the transformers at this time.

  In addition, even when n transformers are used and the switching frequency of the switching circuit that switches the transformers at both ends connected to the rectifier circuit is the same, and the phase of the switching frequency is shifted by 90 degrees, one cycle of the switching frequency A current flowing through the rectifier circuit can be shared between the diodes. In addition, one diode is connected between the transformers at this time.

  Thus, when n transformers are used, the number of rectifier circuits can be reduced to n-1. As a result, the number of diodes through which current passes is reduced, and loss can be reduced.

  Moreover, although the switching power supply circuit provided with the two transformers shown in FIG. 6 has been described, a plurality of switching power supply circuits provided with the two transformers shown in FIG. 6 are provided, and the outputs of the rectifier circuits are connected in parallel. It is also possible to supply power to a load or the like.

  As described above, in the conventional diode bridge, the total number of diodes through which current passes when n diode bridges are connected in series during rectification is 2 × n. According to the present invention, the total number of diodes through which current passes when n diode bridges are connected in series is n + 1. Thereby, the loss which generate | occur | produces with the diode which is a rectifier can be reduced.

  Further, according to the present invention, it is possible to reduce the amount of decrease in the output voltage after rectification. That is, the decrease in output voltage after rectification depends on the total number of diodes through which current flows when n diode bridges are connected in series. The present invention can reduce the total number of diodes through which current passes, as compared with the prior art.

  Further, according to the present invention, the rectifier circuit connected between the transformers has one end of the secondary winding of one transformer and the other end of the secondary winding of the other transformer in a rectifying operation. Connected by one diode. Conventionally, two diodes are connected between the transformers during the rectifying operation. For this reason, the voltage drop due to the current flowing through the diode between the transformers is reduced, and the efficiency of power conversion can be increased.

  According to the present invention, in the rectifier circuit connected between the transformers, the switching frequency of one transformer is set to be twice the switching frequency of the other transformer, so that the current flowing through the diode of the bridge circuit is changed to the switching frequency. The four diodes are turned on one by one in order of 1/4 of the period.

  For this reason, four diodes share in one cycle of the switching frequency and become conductive. Since the current flowing through the diodes connected between the transformers flows through the four diodes sequentially in one cycle of the switching frequency, it is possible to reduce the heat generation of the diodes. As a result, a rectifying element having a small maximum rated current can be used.

  Hereinafter, a comparison between the prior art document discovered in the prior art search by the applicant and the present invention will be described. In Patent Document 1 (Japanese Patent Laid-Open No. 2013-27162), in a DC power supply device in which input and output are electrically insulated by a transformer, switching loss and diode loss are reduced especially for high-frequency operation of a semiconductor switch. A DC power supply is disclosed.

  The DC power supply device disclosed in Patent Document 1 has a low impedance on the input side of the rectifier diode bridge circuit of the DC power supply device with respect to the current direction until the recovery of the rectifier diode occurs, and a high impedance in the opposite direction. By providing a circuit element having impedance, generation of a surge voltage accompanying recovery is effectively suppressed to reduce power loss, and destruction of a rectifier diode and generation of electromagnetic noise are prevented.

  The present invention includes n (n is an integer of 2 or more) transformers 16, a switching circuit 7 provided in each of the transformers 16, and a rectifier circuit 20 including a diode that converts a voltage output from the transformer 16 into a direct current. The rectifier circuit 20 is connected between one transformer and the other transformer, two diodes having the same polarity are connected to both ends of the secondary winding of the one transformer, and connected. The other terminals of the two diodes connected to both ends of the secondary winding of the other transformer, the transformer 16 and the rectifier circuit 20 are connected in series, and the current flowing through the rectifier circuit 20 is It passes through n + 1 diodes. The total number of diodes through which current passes when n diode bridges are connected in series during conventional rectification is 2 × n.

  Further, according to the present invention, in the rectifier circuit connected between the transformers, the switching frequency of one transformer is set to be twice the switching frequency of the other transformer, so that the current flowing through the diode of the bridge circuit is The four diodes are turned on one by one in turn. For this reason, since four diodes flow in order during one cycle of the switching frequency, it is possible to reduce the heat generation of the diodes. As a result, a rectifying element having a small maximum rated current can be used.

  As described above, according to the present invention, even when a diode is used as a rectifier circuit between transformers, it is possible to reduce loss generated from the diode and increase power conversion efficiency. Conventionally, since the loss generated in the rectifier circuit is large, for example, even if the loss is reduced other than the rectifier circuit as in Patent Document 1, the effect may not be improved. For this reason, this invention has the characteristic which a prior art document does not have.

  The present invention can be embodied in many forms without departing from its essential characteristics. Therefore, it is needless to say that the above-described embodiment is exclusively for description and does not limit the present invention.

1, 50 Switching power supply circuit
3 Boosting Units 7, 52 Switching Circuit 7a First Switching Circuit 7b Second Switching Circuits 11, 12, 13, 14 Switching Elements (MOSFETs)
16, 60 Transformer 17, 61 Primary winding 18, 62 Secondary winding 20 Rectifier circuit 30, 75 Control circuit 40 DC power supply 51 Power supply unit 65 Diode bridge 80 Smoothing circuit (electrolytic capacitor)

Claims (7)

n transformers (n is an integer of 2 or more),
A switching circuit provided on the primary side of the transformer, provided on each of the transformers for switching a DC power supply and alternately flowing currents of different directions to the primary winding of the transformer;
A switching power supply circuit comprising: n-1 rectifier circuits that are provided on the secondary side of the transformer and configured by a diode that converts a voltage output from the secondary winding of the transformer into a direct current;
Each of the rectifier circuit, is connected between one of the transformer and the other of the transformer to suit Ri next to the respective ends of one of the transformer secondary winding, the two diodes having the same polarity One terminal is connected, and the other terminal of the two diodes connected to one end of the secondary winding of one of the transformers is connected to both ends of the secondary winding of the other transformer. The other terminal of the other two diodes connected to the other end of the secondary winding of one of the transformers is connected to both ends of the secondary winding of the other transformer ,
The switching power supply circuit, the n of said one of said transformer secondary winding to fit Ri next in transfected both ends and the other connected the two between opposite ends of the transformer secondary winding The secondary windings of the n number of transformers are connected in series by the rectifier circuit including a total of four diodes including a diode and the other two diodes.
One terminal of one backflow prevention diode is connected to each of both ends of the secondary winding of the first transformer at each of both ends of the secondary winding of the first transformer of the n transformers. The two diodes of the connected rectifier circuit are connected so as to have a reverse polarity, and the other two terminals of the backflow prevention diodes are connected to each other,
The connection point between the other terminals is connected to one of the output ends to which the load is connected,
One end of one other backflow prevention diode is connected to both ends of the secondary winding of the nth transformer at each end of the secondary winding of the nth transformer of the n transformers. Each of the two diodes of the rectifier circuit connected to each other is connected so as to have a reverse polarity, and the other two backflow prevention diodes in total are connected to each other.
The connection point between the other terminals is connected to the other of the output ends connected to the load,
A switching power supply circuit characterized in that a current flowing through the rectifier circuit passes through n + 1 diodes.   The rectifier circuit connected between one of the transformers and the other of the transformers, during rectification operation, either end of the secondary winding of one of the transformer and the secondary of the other of the transformer 2. The switching power supply circuit according to claim 1, wherein any one of both ends of the winding is electrically connected through one diode so that a current flows. The rectifier circuit is connected between both ends of n ends and the other of the secondary winding of the neighboring Ri meet one of the transformer in the transformer of the transformer secondary winding, connected to the rectifier circuit The switching frequency of the switching circuit that switches the DC power source provided on the primary side of the one of the transformers is the switching frequency of the DC power source provided on the primary side of the other transformer connected to the rectifier circuit. The switching power supply circuit according to claim 1, wherein the switching power supply circuit is twice the switching frequency of the switching circuit.   The total of four diodes of the rectifier circuit are made conductive in order of 1/4 of the cycle of the switching frequency of the switching circuit that switches the DC power source provided on the primary side of the other transformer. The switching power supply circuit according to claim 3. Switching frequency of said switching circuit for switching the DC power source provided on the primary side of said switching circuit and the other of said transformer for switching the DC power source provided on the primary side of the neighboring Ri fit one of said transformer , the same is the frequency, by switching the switching circuit and one of the transformer and the other of said transformer phase with each Ri next switching frequency shifted 90 degrees,
2. The switching power supply circuit according to claim 1, wherein the total of the four diodes of the rectifier circuit are sequentially turned on by a quarter of the period of the switching frequency.   The rectifier circuit rectifies the output from the secondary winding of the transformer by using a rectifying element having an action of flowing a current only in one direction instead of the diode, so that a voltage and a current in only one direction are The switching power supply circuit according to claim 1, wherein the switching power supply circuit is obtained.   In place of the diode, the rectifier circuit rectifies the output from the secondary winding of the transformer by using a switching element capable of flowing a current only in one direction by inputting a control signal. 2. The switching power supply circuit according to claim 1, wherein voltage and current in only one direction are obtained.

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