JP2009273280A - Dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC-DC converter which prevents breakage of a switching element and a DC power supply when the output terminal of a booster circuit is short-circuited. <P>SOLUTION: This DC-DC converter comprises: a breaker for opening an input power supply, two IGBT elements connected in parallel, a reactor for suppressing a current changing rate, a reactor magnetically coupled in the reverse direction to the reactor for suppressing the current changing rate at a voltage ratio of substantially 1:1, a current sensor for detecting the current flowing in the winding wire of the magnetically coupled reactor, and a breaker opening means for suppressing the IGBT elements and outputting an open signal to the breaker for opening the breaker when the output of the current sensor exceeds a prescribed value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a DC-DC converter that boosts a voltage of a DC power source with a boost chopper and supplies power to a load.

  [Patent Document 1] discloses a DC-DC converter that boosts an input DC voltage and supplies a voltage approximately twice the input voltage to a load. FIG. 5 shows a circuit configuration described in a representative diagram of [Patent Document 1]. In this circuit, a terminal DC input + and a terminal GND are input terminals, a DC power source is connected to the terminal DC input + and the terminal GND, and the switching elements SW1 and SW2 are alternately turned on to boost the input voltage. Specifically, when SW1 is turned on and SW2 is turned off, a voltage between the terminal DC input + and the terminal GND (hereinafter referred to as input voltage) is applied to the reactor L1, and the reactor L2 magnetically coupled in the opposite direction is applied to the reactor L2. Causes an input voltage to be induced in a direction opposite to reactor L1. Therefore, a voltage twice as large as the input voltage is generated between the terminal B and the terminal GND, and a voltage twice as large as the input voltage can be supplied to the terminal DC output + and the terminal DC output − via the diode D2. The same applies when SW1 is turned off and SW2 is turned on.

  The feature of this circuit system is that the step-up reactor is magnetically coupled in the reverse direction, and the switching elements SW1 and SW2 of the chopper circuit connected in parallel are alternately turned on. In this system, the magnetic fluxes generated in the cores of reactors L1 and L2 are offset by the currents I1 and I2 flowing through the reactors L1 and L2, and the booster circuit can be downsized.

Japanese Patent No. 3751306

  In the circuit system of FIG. 5, when the terminal DC output + and the terminal DC output − are short-circuited with the switching element SW1 turned on, a short-circuit current flows from the DC power source through the diode D2. At this time, the voltage appearing between the terminals of the reactor L2 is a voltage obtained by dividing the input voltage by the winding resistance of the reactor L2 and the forward voltage of the diode D2. Since reactors L1 and L2 are magnetically coupled, the voltage across reactor L1 is also equal to or lower than the input voltage. Therefore, a large current equivalent to the short-circuit current flowing through the reactor L2 also flows through the switching element SW1, and there is a problem that the switching element SW1 may be damaged.

  In addition, since the short circuit current at the output end and the current flowing through the switching element SW1 are supplied from the DC power supply, there is a possibility that the DC power supply is damaged when an excessive current flows.

  The above-described problems include a circuit breaker connected between the terminal DC input + and the reactors L1 and L2, a current change rate suppressing reactor connected between the circuit breaker and the reactors L1 and L2, and the reactors L1 and L2, respectively. And a circuit breaker opening means for outputting an opening command to the circuit breaker when the current value detected by the current sensor exceeds a predetermined value that is equal to or less than the maximum breaking current of the switching element. Can be solved.

  It can also be solved by providing a suppress circuit that turns off the switching element when the current value detected by the current sensor exceeds a predetermined value that is equal to or less than the maximum cutoff current of the switching element.

  The DC-DC converter of the present invention is characterized by including a current change rate suppression reactor having a novel structure of the present invention between a terminal DC input + and the reactors L1 and L2, and according to this characteristic, the terminal DC output + When the terminal DC output − is short-circuited, the rate of change of increase in short-circuit current flowing through the diode or semiconductor switching element can be suppressed. The current flowing through the reactors L1 and L2 is detected by a current sensor, and when the current value detected by the current sensor becomes equal to or greater than a predetermined value that is less than or equal to the maximum breaking current of the switching element, an opening command is output to the breaker. By opening the circuit breaker, it is possible to avoid continuing to supply a short-circuit current from the DC power source connected to the input terminal, thereby avoiding damage to the switching element and the DC power source.

  Also in this configuration, the DUTY ratio of switching elements SW1 and SW2 (the percentage of the on-time of the switching element in one carrier wave of the switching element) is set to 50%, so that the terminal DC output + and the terminal DC output-are between Can output a voltage approximately twice the input voltage.

  The DC-DC converter according to the present invention further includes a circuit that turns off the switching element when a current value detected by the current sensor is equal to or greater than a predetermined value that is equal to or less than a maximum cutoff current of the switching element. . With this feature, the switching element can be turned off before an excessive short-circuit current exceeding the maximum cutoff current of the switching element flows through the switching element, and the switching element is prevented from being damaged by interrupting the excessive current. can do.

  In addition, the DC-DC converter of the present invention is characterized by including a current change rate suppressing reactor having a novel structure of the present invention between the terminal DC input + and the reactors L1 and L2, and the switching element according to the present feature. Even when a period for simultaneously turning on is provided, it is possible to avoid an excessive current flowing through the switching element, and to output a voltage more than twice the input voltage to the output terminal.

  And a switching element connected in reverse parallel to a diode provided between the switching element and the terminal DC output +, and a controller that complementarily PWMs the switching element connected to the switching element and the terminal DC output +. This feature enables regenerative operation in which the direction of power flow is from the output terminal to the input terminal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings for explaining the embodiments, elements having the same function are given the same reference numerals. In addition, the parallel bodies 1a to 1n including the IGBT and the diode connected in antiparallel with the IGBT shown in FIG. 1 and the like are referred to as IGBT elements 1a to 1n.

  In this embodiment, the input voltage can be boosted and a voltage twice the input voltage can be output to the output terminal, and when the output terminal is short-circuited, the switching element is prevented from being damaged due to overcurrent, and the short-circuit current continues to flow from the input power supply. This is a DC-DC converter that can avoid the above.

  FIG. 2 shows a main part of the DC-DC converter of the present embodiment, a DC power source connected to the DC-DC converter, and a load connected to the DC-DC converter. The configuration of this embodiment will be described with reference to FIG.

  The DC-DC converter 1 of the present invention is connected to a DC power supply 80 and a load 90. Input terminals 50 and 51 of the DC-DC converter 1 are connected to a DC power supply 80, and the other terminals 52 and 53 of the DC-DC converter 1 are connected to a load 90.

  The configuration of the main part of the DC-DC converter 1 is shown in FIG.

  The DC-DC converter 1 includes a main circuit unit 300, a control unit 100, and a suppress circuit 200.

  The main circuit unit 300 includes a circuit breaker 4 for disconnecting the DC power supply 80, an input smoothing capacitor 5, a reactor 3 for suppressing a current change rate, 3 wound around a common iron core, and has a turns ratio of 1: 1, and is magnetized in the reverse direction. Reactors 2a and 2b to be coupled, IGBT elements 1a and 1b, diodes 1p and 1q, an output smoothing capacitor 6, and current sensors 10 and 11 for detecting a current flowing through the reactors 2a and 2b.

  The circuit breaker 4 is connected between the input terminal 50 and the current change rate suppressing reactor 3.

  The input smoothing capacitor 5 is provided to reduce the amount of ripple current caused by switching of the IGBT elements 1a and 1b flowing into the DC power supply 80. The smoothing capacitor 5 may be omitted when the DC power source 80 connected to the DC-DC converter 1 does not overheat even when the ripple current flows and can maintain the output voltage of the DC power source.

  The other end of the current change rate suppressing reactor 3 is connected to the reactors 2 a and 2 b at a connection point 56.

  Current sensors 10 and 11 detect currents Ia and Ib flowing from reactor 56 to output side in reactors 2a and 2b, and output voltages proportional to the current values of currents Ia and Ib to suppress circuit 200.

  The other end of the reactor 2a is connected to the IGBT element 1a and the anode of the diode 1p through a connection point 54.

  The other end of the reactor 2b is connected to the IGBT element 1b and the anode of the diode 1q through the connection point 55.

  The cathodes of the diodes 1 p and 1 q are connected at the connection point 57, and the connection point 57 is connected to the output terminal 52.

  The other ends of the IGBT elements 1 a and 1 b are connected to an input terminal 51 and an output terminal 53. An output smoothing capacitor 6 is connected between the output terminals 52 and 53 for smoothing the voltage output to the load.

  The IGBT elements 1a and 1b are ON / OFF controlled by a gate signal output from the suppress circuit 200 which is a novel configuration of this embodiment. Here, the IGBT elements 1a and 1b operate as an on signal when the gate signal output from the suppress circuit 200 is true, and as an off signal when false.

  The control unit 100 calculates a gate signal for controlling on / off of the IGBT elements 1 a and 1 b and outputs the gate signal to the suppress circuit 200. Specifically, the control unit 100 inputs to the PWM controllers 1002 and 1003 the modulated wave output from the modulated wave calculator 1000 and the triangular waves Carrier1 and Carrier2 output from the carrier wave generator 1001 that are 180 degrees out of phase with each other. The PWM controller 1002 outputs a true signal to the suppressor circuit 200 as the gate signal of the IGBT element 1b when the modulated wave is equal to or greater than the triangular wave Carrier1 and false when the modulated wave is smaller than the triangular wave Carrier1. Similarly, the PWM controller 1003 outputs true to the suppressor circuit 200 as the gate signal of the IGBT element 1a when the modulated wave is equal to or greater than the triangular wave Carrier2, and false when the modulated wave is smaller than the triangular wave Carrier2.

  The suppress circuit 200 includes a reference power supply 2001, a comparator 2002, 2003, an OR circuit 2004, a hold circuit 2005, an inverter 2006, and AND circuits 2007 and 2008. The outputs of the current sensors 10 and 11 are less than the output voltage of the reference power supply 2001. If so, the gate signal output by the control unit 100 is output as the gate signal of the IGBT elements 1a and 1b.

  The output voltage of reference power supply 2001 is set lower than the output voltage of current sensors 10 and 11 when a current equal to the maximum cutoff current value of IGBT elements 1a and 1b flows through reactors 2a and 2b. Here, the maximum cutoff current value is a maximum current value at which the current flowing through the IGBT element can be cut off without damaging the IGBT element itself.

  If the outputs of the current sensors 10 and 11 are less than the output voltage of the reference power supply 2001, the suppress circuit 200 outputs a closing command to the circuit breaker 4. Here, the signal output from the suppress circuit 200 is true or false. When true, the signal is an input command, and when false, the signal is an open command.

  The circuit operation when the outputs of the current sensors 10 and 11 are smaller than the output voltage of the reference power supply 2001 will be described with reference to FIG.

  FIG. 3 shows an operation waveform of the DC-DC converter 1. From the top, the IGBT element 1 a gate signal, the gate signal of the IGBT element 1 b, the inter-terminal voltage VC of the connection point 56 viewed from the terminal 51, and the connection from the connection point 56 Reactor 2a terminal voltage looking at point 54, reactor 2b terminal voltage looking at connection point 55 from connection point 56, current Ia flowing through reactor 2a, current Ib flowing through reactor 2b, IGBT element flowing from connection point 54 to IGBT element 1a 1a current, IGBT element 1b current flowing from the connection point 55 to the IGBT element 1b, and high-voltage side current Ic flowing from the connection point 57 to the output terminal 52 side are shown. Here, VH0 is a voltage between terminals of the output smoothing capacitor 6 in a steady state.

  When the currents Ia and Ib are positive and the IGBT element 1a is turned off and 1b is turned on, the connection point 54 has the same potential as the output terminal 52. Further, since the connection point 55 has the same potential as the output terminal 53, the terminal voltage of the output smoothing capacitor 6 is applied to the reactors 2a and 2b.

  Since the reactors 2a and 2b have a turns ratio of 1: 1 and are wound so as to be magnetically coupled in the opposite direction, the inter-terminal voltage VC between the connection point 56 and the terminal 51 is the terminal of the output smoothing capacitor 6. VH0 / 2, which is half of the voltage.

  Since the inter-terminal voltage VC is VH0 / 2, the reactor 2a terminal voltage is VH0 / 2, the reactor 2b terminal voltage is -VH0 / 2, a current that excites the common iron core of the reactor 2a and the reactor 2b flows, and the current Ia Decreases gradually while being limited by the excitation inductance of the iron cores of reactors 2a and 2b, and current Ib gradually increases.

  The current Ib flows through the IGBT element 1b because the IGBT element 1b is on, and the current Ia flows to the output side via the diode 1p because the IGBT element 1a is off.

  When the IGBT element 1a is turned on and the IGBT element 1b is turned off, the inter-terminal voltage VC similarly becomes VH0 / 2 which is half of the terminal voltage of the output smoothing capacitor 6.

  At this time, the reactor 2a terminal voltage becomes −VH0 / 2, the reactor 2b terminal voltage becomes VH0 / 2, the current Ia gradually increases, and the current Ib gradually decreases.

  In a steady state, the voltage across the terminals of the current change rate suppression reactor 3 is zero if the resistance component of the current change rate suppression reactor 3 can be ignored. Therefore, the average value VC0 of the input voltage VL and the inter-terminal voltage VC is equal. Therefore, Formula 1 is established.

VL = VC0 = VH0 / 2 (1)
From Equation 1, the output voltage VH0 in the steady state of the DC-DC converter 1 described in the present embodiment is twice the input voltage VL. Therefore, the DC-DC converter 1 of the present embodiment can supply a voltage twice as much as the input DC voltage to the load.

  Next, operations of the suppressor circuit 200 and the circuit breaker 4 which are new components of the present embodiment will be described with reference to FIG.

  The waveform shown in FIG. 4 is an operation waveform when the horizontal axis when time is short-circuited at the output terminals 52 and 53 is time, and the gate signals, the inter-terminal voltage VC, and the reactor of the IGBT elements 1a and 1b in order from the top. 2a terminal voltage, reactor 2b terminal voltage, currents Ia, Ib, IGBT element 1a current, IGBT element 1b current, comparator 2002 output, comparator 2003 output, logical sum 2004 output, hold circuit 2005 output, and circuit breaker 4 state Show. In FIG. 4, VH0 is a voltage in a steady state of the inter-terminal voltage VH before the output terminals 52 and 53 are short-circuited.

  At time t1, the output terminals 52 and 53 are short-circuited. Since the output voltage smoothing capacitor 6 is short-circuited, the inter-terminal voltage VH becomes zero.

  Since the IGBT element 1 a is on, the connection point 54 has the same potential as the terminal 53. Further, since the current Ib is positive, the diode 1q is turned on, and the connection point 55 has substantially the same potential as the output terminal 52. Since the output terminals 52 and 53 are short-circuited, the connection point 55 has the same potential as the output terminal 53. Since the reactors 2a and 2b are magnetically coupled in the reverse direction with a turns ratio of 1: 1, the potential at the connection point 56 is equal to the average value of the potentials at the connection point 54 and the connection point 55. Therefore, the potential of the connection point 56 becomes equal to that of the output terminal 53, and the inter-terminal voltage VC becomes zero.

  Since the DC power supply 80 is connected to the input terminals 50 and 51, a larger current flows from the DC power supply 80 than during normal operation. However, in the DC-DC converter 1 of this embodiment, a newly installed current change rate is obtained. The current change rate of the DC power supply 80 can be limited by the suppression reactor 3.

  The current flowing from DC power supply 80 is divided into currents Ia and Ib flowing through reactors 2a and 2b. The current Ia is divided into a current flowing through the diode 1p and a current flowing through the IGBT element 1a, and a larger current flows through the IGBT element 1a than during normal operation.

  At time t2, the outputs of the current sensors 10 and 11 become higher than the terminal voltage of the reference power supply 2001, and the output of the comparator 2003 becomes true. Since the output of the comparator 2003 becomes true, the output of the OR circuit 2004 becomes true.

  When the output of the OR circuit 2004 becomes true, the hold circuit 2005 holds the output at a true value.

  Since the output of the hold circuit 2005 becomes true, the output of the inverter 2006 becomes false.

  Since the output of the inverter 2006 becomes false, the outputs of the AND circuits 2007 and 2008 become false and the IGBT elements 1a and 1b are turned off. At the same time, a false signal, that is, an opening command is output to the circuit breaker 4.

  In this embodiment, the circuit breaker 4 is used as means for electrically disconnecting the DC power supply 80 and the DC-DC converter 1, but a semiconductor switching element having a large current interruption capacity may be used instead of the circuit breaker 4. A fuse may be used instead of the circuit breaker 4.

  The IGBT elements 1a and 1b are turned off at the time t3 slightly delayed from the time t2 due to the operation delay of the OR circuit 2004, the hold circuit 2005, the inverter 2006, and the AND circuits 2007 and 2008. However, since the rate of change of the current flowing through the IGBT element 1a in the meantime is suppressed by the current change rate suppressing reactor 3, the IGBT element 1a is turned off in a state where the current flowing through the IGBT element 1a is smaller than the maximum cutoff current of the IGBT element 1a. can do. Therefore, the current can be cut off without damaging the IGBT element 1a, and the IGBT element 1a can be protected.

  At time t2, the circuit breaker 4 starts opening the circuit breaker 4 because the output of the inverter 2006 becomes false.

  Even if the IGBT elements 1a and 1b are turned off, since the output terminals 52 and 53 are short-circuited, the current output from the DC power supply 80 continues to increase. However, the circuit breaker 4 is opened at time t4, and the DC power supply 80 Thus, it is possible to avoid continuously supplying the short-circuit current.

  The electric charge remaining in the input smoothing capacitor 5 is discharged through the reactors 2a and 2b, the diodes 1p and 1q, and the shorted terminals 52 and 53, and the current flowing through the diodes 1p and 1q becomes zero when the discharge is completed.

  As described above, in the DC-DC converter 1 of the present embodiment, the IGBT element can be turned off before the maximum cutoff current of the IGBT element flows in the IGBT elements 1a and 1b. Even if a short circuit occurs, the IGBT elements 1a and 1b can be protected.

  Further, by opening the circuit breaker 4 when the output terminal is short-circuited, it is possible to avoid that the DC power supply 80 continues to supply a short-circuit current.

  In this embodiment, since it takes time to open the circuit breaker 4, a circuit for suppressing the IGBT elements 1a and 1b is provided. However, when the circuit breaker 4 is opened quickly enough, the IGBT elements 1a and 1b The gate signal may be a gate signal output from the control unit 100, and the AND circuits 2007 and 2008 may be omitted.

  In the present embodiment, the suppress circuit 200 is constituted by an electric circuit, but the same operation may be realized by software.

  Further, in this embodiment, the overcurrents of the reactors 2a and 2b are detected by the current sensors 10 and 11. However, as shown in FIG. 13, FIG. 14 or FIG. And the output of the current sensor and the output voltage of the reference power supply 2050 may be compared. Here, it is desirable that the output voltage of the reference power supply 2050 be a voltage twice that of the reference power supply 2001.

  In the above description, the current change rate suppressing reactor is described as a single reactor. However, as shown in FIG. 7, the current change rate suppressing reactor of the DC-DC converter 1 is magnetically coupled to the reactors 2a and 2b. Reactors 3a and 3b to be connected may be provided.

  Moreover, although the connection position of the current change rate suppressing reactor shown in FIG. 7 is between the reactors 2a and 2b and the input terminal 50, as shown in FIG. 8, it is between the reactors 2a and 2b and the IGBT elements 1a and 1b. You may connect.

  Furthermore, in the present embodiment, the number of parallel IGBT elements has been described as 2. However, as shown in FIG. 12, the number of parallel IGBT elements is n, and the carrier wave Carrier 1, 2, 3,. , 1n may be configured to be PWM controlled as triangular waves having equal phase and 360 / n degrees different phases.

  By the way, since the DC-DC converter 1 of the present embodiment includes the current change rate suppressing reactor 3, even if a period in which the IGBT elements 1a and 1b are simultaneously turned on is provided, an excessive current flows through the IGBT elements 1a and 1b. Can be avoided.

  FIG. 9 shows operation waveforms when the DC-DC converter 1 is operated with a period in which the IGBT elements 1a and 1b are simultaneously turned on.

  When the IGBT elements 1a and 1b are turned on at the same time, the potential at the connection points 54 and 55 becomes equal to the output terminal 53, so that the terminal voltage VC becomes zero. At this time, the terminal voltages of the reactors 2a and 2b are also zero.

  Therefore, since the input voltage VL is applied to the current change rate suppression reactor 3, the current flowing through the current change rate suppression reactor 3 increases. Since the current flowing through the current change rate suppressing reactor 3 is divided into the currents Ia and Ib flowing through the reactors 2a and 2b, the currents Ia and Ib also increase.

  When IGBT element 1a is turned off and IGBT element 1b is turned on, a voltage of VH0 / 2 is applied to reactor 2a, and -VH0 / 2 is applied to reactor 2b. At this time, the inter-terminal voltage VC is VH0 / 2.

  As described above, the inter-terminal voltage VC is either zero or VH0 / 2, so that the average value of the inter-terminal voltage VC is lower than VH0 / 2 only during a period in which the IGBT elements 1a and 1b are simultaneously turned on.

  In the steady state, the average value of the voltage generated between the terminals of the current change rate suppression reactor 3 is zero, and therefore the DC power supply 80 terminal voltage VL and the average value VC0 of the terminal voltage VC are equal. Therefore, the following equation is established among the voltage VL between the terminals of the DC power supply 80, the average value VC0 of the voltage VC between the terminals, and the voltage VH0 in the steady state of the output smoothing capacitor terminal voltage VH.

VL = VC0 <VH0 / 2
∴2VL = 2VC0 <VH0 (2)
Therefore, by providing a period in which the IGBT elements 1a and 1b are simultaneously turned on, a voltage higher than the voltage obtained by doubling the voltage between the terminals of the DC power supply 80 can be supplied to the load.

  As a specific application example of the DC-DC converter 1 of this embodiment, a feeder voltage drop suppression device for electric railways is conceivable. FIG. 6 shows a schematic circuit diagram.

  The output terminal 52 of the DC-DC converter 1 is connected to the feeder 20 and the output terminal 53 is connected to the rail 21. Further, a substation 23 and a vehicle 22 are connected to the feeder 20 and the rail 21. The substation 23 outputs a DC voltage between the feeder 20 and the rail 21 and supplies DC power to the vehicle 22 via the feeder 20 and the rail 21.

  The vehicle 22 includes an inverter 220 and a motor 221. The inverter 220 converts the DC power received from the feeder 20 and the rail 21 into AC power and supplies the AC power to the motor 221. The motor 221 generates torque on the wheels of the vehicle and accelerates the vehicle 22.

  When the distance between the vehicle 22 and the substation 23 is long, the DC voltage supplied to the vehicle 22 is reduced due to the voltage drop at the feeder 20 or the rail 21, which may hinder the vehicle operation such as a decrease in the acceleration performance of the vehicle 22. is there. The DC-DC converter 1 of the present embodiment uses a DC power supply 80 having a terminal voltage lower than the voltage between the feeder line 20 and the rail 21 (the feeder voltage), and boosts the output terminal voltage of the DC power supply 80. Thus, power can be supplied to the vehicle 22 via the feeder line 20 and the rail 21, and a decrease in the feeder voltage can be suppressed to realize stable operation of the vehicle 22. Here, the DC power supply 80 may be a secondary battery such as a lithium battery or an electric double layer capacitor.

  When the feeder 20 and the rail 21 are short-circuited due to an accident, the DC-DC converter 1 of this embodiment is turned off before an excessive current flows through the IGBT elements 1a and 1b as described with reference to FIG. It is possible to avoid breakage and to avoid continuously supplying a short-circuit current from the DC power supply 80 to the feeder 20 side, thereby avoiding damage to the DC power supply 80.

  As described above, even when the output terminal is short-circuited, the DC-DC converter 1 according to the present embodiment includes the current change rate suppressing reactor 3 and the suppress circuit 200, so that an excessive current flows through the IGBT element before the IGBT element flows. The element can be turned off and the IGBT element can be protected. In addition, a circuit breaker for disconnecting the DC power source 80 connected to the DC-DC converter 1 is provided, and when the output terminal is short-circuited, the suppress circuit 200 outputs a signal for opening the circuit breaker. Since it is possible to avoid the continuous supply, it is possible to avoid the damage of the DC power supply 80 due to the continuous flow of an excessive current.

  Further, by providing the current change rate suppressing reactor, the IGBT elements can be simultaneously turned on, and a voltage more than twice the voltage of the DC power supply 80 terminal can be supplied to the load.

  A second embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in that IGBT elements 1c and 1d are provided instead of the diodes 1p and 1q, and regenerative operation is possible. In FIG. 10, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The suppressor circuit 200 of the DC-DC converter 1 of this embodiment includes AND circuits 2009 and 2010 and inverters 2011 and 2012 in addition to the arithmetic unit of the first embodiment shown in FIG.

  The inverter 2011 receives the gate signal of the IGBT element 1 a output from the control unit 100, and the inverter 2011 outputs a signal obtained by inverting the gate signal to the AND circuit 2009. The AND circuit 2009 receives the output of the inverter 2011 and the output of the inverter 2006 as inputs, and outputs the logical product to the IGBT element 1c as a gate signal of the IGBT element 1c.

  Therefore, when the output of inverter 2006 is true, when one of IGBT elements 1a and 1c is on, the other is off.

  The inverter 2012 receives the gate signal of the IGBT element 1 b output from the control unit 100, and the inverter 2012 outputs a signal obtained by inverting the gate signal to the AND circuit 2010. The AND circuit 2010 receives the output of the inverter 2012 and the output of the inverter 2006 as inputs, and outputs the logical product to the IGBT element 1d as a gate signal of the IGBT element 1d.

  Therefore, when the output of inverter 2006 is true, when one of IGBT elements 1b and 1d is on, the other is off.

  DC-DC when a load 90 having a back electromotive force of VH is connected between the output terminals 52 and 53, and a DC power source having an output voltage VL slightly lower than half of VH is connected between the input terminals 50 and 51. The operation waveform of the converter 1 will be described with reference to FIG.

  When the IGBT element 1a is off and the IGBT element 1b is on, the IGBT element 1c is on and the IGBT element 1d is off.

  At this time, when the voltage in the steady state between the output terminals 52 and 53 is VH, the inter-terminal voltage VC is VH0 / 2.

  Since the DC voltage VL applied to the input terminal is slightly lower than half of VH, the currents Ia and Ib flow in the negative direction via the reactors 2a and 2b and the current change rate suppressing reactor 3.

  The sum of the currents Ia and Ib is the output current of the input DC power supply 80, and since the currents Ia and Ib are negative, it can be seen that the regenerative current flows into the DC power supply 80 connected to the input terminals 50 and 51.

  When the IGBT element 1a is off and the IGBT element 1b is on, the terminal voltage of the reactor 2a is VH0 / 2 and the terminal voltage of the reactor 2b is -VH0 / 2, so that the current Ia changes in the negative direction and the current The current of Ib changes in the positive direction.

  When the current flowing from the terminal 54 toward the IGBT element 1c is the IGBT element 1c current and the current flowing from the terminal 55 toward the IGBT element 1d is the IGBT element 1d current, the IGBT element 1c current is obtained when the IGBT element 1c is on. The IGBT element 1d current flows only when the IGBT element 1d is on. The high-voltage side current Ic is the sum of the IGBT element 1c current and the IGBT element 1d.

  As can be seen from FIG. 11, since the high-voltage side current Ic is negative, regenerative power is supplied from the load 90 connected to the output terminals 52 and 53.

  When the output terminals 52 and 53 are short-circuited, a large positive current flows through the reactors 2a and 2b as in the first embodiment, the output voltage of the current sensors 10 and 11 exceeds the output voltage of the reference power supply 2001, and the OR circuit 2004. The output of becomes true.

  Therefore, the hold circuit 2005 continues to output true, and the output of the inverter 2006 continues to output false that is an inversion of the output of the hold circuit 2005.

  The AND circuits 2007, 2008, 2009, and 2010 output a false signal corresponding to the OFF signal to the IGBT elements 1a, 1b, 1c, and 1d regardless of the output of the control unit 100 because the output of the inverter 2006 is false.

  With the circuit operation described above, the IGBT elements 1a and 1b can be turned off before a current larger than the maximum cutoff current flows through the IGBT elements 1a and 1b, and the IGBT elements 1a and 1b can be protected.

  The IGBT elements 1c and 1d continue to flow through the built-in diode even if an OFF signal is input. However, when the circuit breaker 4 is opened and the input smoothing capacitor 5 is discharged, the current flowing through the IGBT elements 1c and 1d is zero. Thus, it is possible to protect the IGBT elements 1c and 1d by avoiding excessive current from continuing to flow through the IGBT elements 1c and 1d.

  As described above, even when the output terminal is short-circuited, the DC-DC converter 1 according to the present embodiment includes the current change rate suppressing reactor 3 and the suppress circuit 200, so that an excessive current flows through the IGBT element before the IGBT element flows. The element can be turned off and the IGBT element can be protected. In addition, a circuit breaker for disconnecting the DC power source 80 connected to the DC-DC converter 1 is provided, and when the output terminal is short-circuited, the suppress circuit 200 outputs a signal for opening the circuit breaker. Since it is possible to avoid the continuous supply, it is possible to avoid the damage of the DC power supply 80 due to the continuous flow of an excessive current.

  Furthermore, by providing the IGBT elements 1c and 1d instead of the diodes 1p and 1q, it is possible to regenerate electric power.

  The present invention can be applied to a power converter that boosts the voltage of a DC power supply by a booster circuit and supplies power to a load.

Explanatory drawing of the DC-DC converter of 1st Example of this invention. Explanatory drawing of the DC-DC converter of 1st Example of this invention. Operation | movement explanatory drawing of the DC-DC converter of 1st Example of this invention. Operation | movement explanatory drawing of the DC-DC converter of 1st Example of this invention. Explanatory drawing of the DC-DC converter of a prior art. A specific application example of the DC-DC converter of the first embodiment of the present invention. 4 is another configuration example of the DC-DC converter according to the first embodiment of the present invention. 4 is another configuration example of the DC-DC converter according to the first embodiment of the present invention. Operation | movement explanatory drawing of the DC-DC converter of 1st Example of this invention. Explanatory drawing of the DC-DC converter of 2nd Example of this invention. Operation | movement explanatory drawing of the DC-DC converter of 2nd Example of this invention. 4 is another configuration example of the DC-DC converter according to the first embodiment of the present invention. 4 is another configuration example of the DC-DC converter according to the first embodiment of the present invention. 4 is another configuration example of the DC-DC converter according to the first embodiment of the present invention. 4 is another configuration example of the DC-DC converter according to the first embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC-DC converter 1a, 1b, 1c, 1d, ..., 1n IGBT element 1p, 1q Diode 3 Current change rate suppression reactor 4 Circuit breaker 80 DC power supply 90 Load 100 Control unit 200 Suppress circuit 300 DC-DC converter 1 main circuit unit 1000 modulation wave calculator 1001, 1004 carrier wave generator 1002, 1003, 3001, 3002,..., 300n PWM controller 2001, 2050 reference power supply 2002, 2003, 5001, 5002,. Comparator 2006, 2011, 2012 Inverter 2007, 2008, 2009, 2010, 4001, 4002, ..., 400n AND circuit

Claims (8)

Two semiconductor switching elements connected to the negative electrode of the output terminal;
Two diodes each connected between the semiconductor switching element and the positive terminal of the output terminal;
A reactor connected between the input terminal and the semiconductor switching element, having a common iron core and a turns ratio of about 1: 1, and magnetically coupled in the opposite direction;
In the DC-DC converter that boosts the DC voltage connected to the input terminal and outputs it to the output terminal by PWM control of the semiconductor switching element with carrier waves having different phases,
A DC-DC converter comprising a current change rate suppressing reactor between an input terminal and the semiconductor switching element. Two semiconductor switching elements connected to the negative electrode of the output terminal;
Two diodes each connected between the semiconductor switching element and the positive terminal of the output terminal;
A reactor connected between the input terminal and the semiconductor switching element, having a common iron core and a turns ratio of about 1: 1, and magnetically coupled in the opposite direction;
In the DC-DC converter that boosts the DC voltage connected to the input terminal and outputs it to the output terminal by PWM control of the semiconductor switching element with carrier waves having different phases,
A DC-, comprising a circuit breaker and a current change rate suppressing reactor between an input terminal and the semiconductor switching element, and having a suppressor circuit that opens the circuit breaker when an overcurrent is generated in the magnetically coupled reactor. DC converter. Two semiconductor switching elements connected to the negative electrode of the output terminal;
Two diodes each connected between the semiconductor switching element and the positive terminal of the output terminal;
A reactor connected between the input terminal and the semiconductor switching element, having a common iron core and a turns ratio of about 1: 1, and magnetically coupled in the opposite direction;
In the DC-DC converter that boosts the DC voltage connected to the input terminal and outputs it to the output terminal by PWM control of the semiconductor switching element with carrier waves having different phases,
A reactor for suppressing the rate of change of current is provided between the input terminal and the semiconductor switching element,
A DC-DC converter comprising a suppress circuit that suppresses the semiconductor switching element when an overcurrent is generated in the magnetically coupled reactor. Two semiconductor switching elements connected to the negative electrode of the output terminal;
Two diodes connected between the semiconductor switching element and the positive terminal of the output terminal;
A reactor connected between the input terminal and the semiconductor switching element, having a common iron core and a turns ratio of about 1: 1, and magnetically coupled in the opposite direction;
In the DC-DC converter that boosts the DC voltage connected to the input terminal and outputs it to the output terminal by PWM control of the semiconductor switching element with carrier waves having different phases,
A circuit breaker and a current change rate suppressing reactor between the input terminal and the semiconductor switching element;
A current sensor for detecting a current flowing through the winding of the magnetically coupled reactor;
A DC-DC converter comprising a suppress circuit that suppresses the semiconductor switching element and opens the circuit breaker when the output of the current sensor exceeds a predetermined value. A DC-DC converter according to any one of claims 1 to 3,
A DC-DC converter characterized by having a period during which both of the two semiconductor switching elements are turned on. A DC-DC converter according to any one of claims 1 to 4,
A semiconductor switching element connected in reverse parallel to a diode provided between the semiconductor switching element and the positive electrode of the output terminal,
A DC-DC converter comprising a controller for performing complementary PWM control on the semiconductor switching element and a semiconductor switching element connected to the negative electrode of the output terminal, and enabling regenerative operation. A DC-DC converter according to any one of claims 1 to 5,
A DC-DC converter characterized in that a storage battery is connected to an input terminal and the voltage of the storage battery is boosted to suppress a drop in feeder voltage in a DC feeding section.   6. The DC-DC converter according to claim 1, wherein an electric double layer capacitor is connected to an input terminal, and the voltage of the storage battery is boosted to suppress a drop in feeder voltage in a DC feeding section. DC-DC converter characterized by performing.

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