JP2013099194A - Insulated type dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated type DC-DC converter which can suitably eliminate bias magnetism occurring in a transformer by only controlling a switching element.SOLUTION: An insulated type DC-DC converter comprises: pulse correction amount calculation means 8 which calculates a pulse correction amount on the basis of a current value detected by primary side current detection means 7 connected in series to a primary side winding of a transformer 2; and control mode switching means 10 which determines, from the direction of a current detected by secondary side current detection means 9 connected in series to a secondary side switching circuit 3, which operation mode, power running or regenerative, is now active and thereby switches over control modes. On the basis of a control mode, pulse correction means 11 selects a switching element to be corrected from among SW1 through SW8 and corrects a pulse command T2 for the selected switching element on the basis of a pulse correction amount. Therefore, not only during the power running mode, but also during the regenerative mode, bias magnetism can be suitably eliminated by only controlling the switching elements.

Description

  The present invention relates to an isolated DC-DC converter having a mechanism for eliminating demagnetization in a transformer.

  Conventionally, as an isolated DC-DC converter that performs power conversion, a DC voltage is converted into an AC voltage in a primary side (input side) switching circuit, the AC voltage is transformed by a transformer, and the obtained AC current is converted. A secondary side (output side) switching circuit that outputs a signal by synchronous rectification is known.

  In such an insulated DC-DC converter, it is necessary to control on / off of the switching element by both the primary side switching circuit and the secondary side switching circuit. When a delay occurs in switching due to the cause, there is a problem that the direction of the current flowing through the winding of the transformer is biased and the magnetism is biased.

  Since the one shown in Patent Document 1 is a unidirectional DC-DC converter corresponding to only one direction, in which a DC voltage is converted into an AC voltage by a primary side switching circuit and a secondary side is simply constituted by a rectifier diode. A method of measuring only the current value with an ammeter connected in series with the primary side winding and correcting the switching timing based on the deviation between the current value and 0 amperes, which only needs to deal with the delay of the secondary side switching. This eliminates the demagnetization.

JP 2010-161842 A

  On the other hand, in a bidirectional DC-DC converter in which a switching element is also provided on the secondary side, the current at the output voltage terminal basically flows in a certain direction (called powering), and the current flows backward at the output voltage terminal (regeneration). Called). In the regenerative state, the demagnetization is caused not only by the primary side but also by the switching delay of the secondary side, so that there is a problem that the demagnetization cannot be completely eliminated by the correction of Patent Document 1.

  As a means for solving such a problem, there is a method of removing a direct current component of a current by inserting a capacitor in series with each winding of the primary side and the secondary side of the transformer. However, although this method can eliminate the bias magnetism during power running and regeneration, there is another problem that the size and cost of the device increase due to the insertion of a capacitor.

  The present invention avoids such an increase in size and cost of the device, and simultaneously eliminates the biasing and regenerative magnetism that is a problem due to bidirectionality only by controlling the switching element by software. It aims to provide a converter.

  In order to achieve this object, the present invention takes the following measures.

  That is, the insulation type DC-DC converter of the present invention includes a primary side switching circuit configured by a switching element, which converts a DC voltage into an AC voltage by controlling on / off of the switching element and outputs the AC voltage. A transformer that transforms the output voltage of the secondary side switching circuit, a secondary side switching circuit that is constituted by a switching element and rectifies the output voltage of the transformer by controlling on / off of the switching element; A pulse control means for generating a pulse command for instructing a voltage pulse to be sent to the gates of switching elements included in the primary side switching circuit and the secondary side switching circuit, and a voltage pulse generated based on the pulse command. Sending the switching element to the gate of the switching element. In an isolated DC-DC converter having a pulse generating means for controlling on / off of the power source and converting power between input and output, the primary side connected in series with the primary side winding of the transformer Pulse correction for calculating a pulse correction amount based on the current value detected by the current detection means, the secondary current detection means connected in series with the output voltage terminal of the secondary side switching circuit, and the primary current detector Control mode switching means for determining whether the operation is in powering or regenerative mode based on the direction of the current detected by the secondary current detector, and switching the control mode based on the mode, and the control Pulse correcting means for selecting a switching element to be corrected based on a mode, and correcting the pulse command for the selected switching element based on the pulse correction amount; An insulation type DC-DC converter, characterized in that it comprises.

  Here, the power running is a state in which a current flows in a direction in which the load is normally driven at the output voltage terminal, and the regeneration is a state in which a current flows in the opposite direction to the power running at the output voltage terminal. Since the isolated DC-DC converter of the present invention selects and corrects a switching element to be corrected for each mode of power running and regeneration, without adding a capacitor to the circuit not only during power running but also during regeneration. Biasing can be preferably eliminated.

  Furthermore, in order to appropriately eliminate the bias magnetism with the minimum control, the pulse correction means switches the switching element of the primary side switching circuit in the control mode at the time of power running, and the above-mentioned 1 in the control mode at the time of regeneration. It is desirable to select the switching element of the secondary side switching circuit and the secondary side switching circuit as a correction target.

  In addition, in order to determine a pulse correction amount suitable for eliminating the demagnetization in the pulse correction amount calculation means, the pulse correction amount calculation means detects the DC component of the current detected by the primary side current detection means. It is preferable that the filter is configured to output a deviation between the DC component and 0 amperes as a pulse correction amount.

  Further, in order to realize the operation of the control mode switching means with a simple configuration, the pulse correction means has one input terminal for each control mode corresponding to power running / regeneration, and the control mode switching means The one or more switches are configured such that one of the input terminals is grounded and the other is connected to the output of the pulse correction amount calculating means, and the current value detected by the secondary side current detecting means is It is desirable that the switch is switched based on a deviation from 0A.

  In addition, in the case where a full bridge circuit in which two pairs of arms in which two pairs of switching elements with freewheeling diodes are arranged in series is used as the primary side switching circuit and the secondary side switching circuit, simple control is used. In order to preferably eliminate the magnetic bias, the pulse correction means corrects the switching element included in one arm constituting the primary side full bridge circuit in the control mode at the time of power running, and the control mode at the time of regeneration. Switching element included in one arm constituting the primary side full bridge circuit and not corrected in the control mode during powering and switching included in both arms constituting the secondary side full bridge circuit It is preferable to correct the element.

  Since the present invention has the above-described configuration, it is possible to suitably eliminate the magnetic bias without adding a capacitor to the circuit not only during power running but also during regeneration.

The block diagram showing the control flow of the insulation type DC-DC converter concerning one embodiment of the present invention. 1 is a circuit diagram showing a basic circuit configuration of an insulated DC-DC converter according to an embodiment of the present invention. The circuit diagram which shows the circuit structure which implement | achieves the pulse correction amount calculating means and the control mode switching means in the insulation type DC-DC converter which concerns on one Embodiment of this invention. The conceptual diagram which represented typically the relationship between the voltage pulse with respect to each switching element and the electric current and voltage which arise in a transformer in the insulation type DC-DC converter which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of the isolated DC-DC converter according to the present embodiment will be described.

  As shown in FIG. 1, the isolated DC-DC converter according to the present embodiment includes a primary side switching circuit 1, a transformer 2 that transforms the output voltage of the primary side switching circuit 1, and a transformer 2 An insulation type converter circuit 4 comprising a secondary side switching circuit 3 for rectifying the output voltage is provided, and the switching elements SW1 to SW4 and the secondary side switching circuit 3 included in the primary side switching circuit 1 based on the output command T1. A pulse control means 5 for generating a pulse command T2 for instructing a voltage pulse to be sent to the gate of the switching element SW5 to SW8 included, and a voltage pulse T3 generated based on the input of the pulse command T2 are supplied to the switching elements SW1 to SW8. Pulse generation means for controlling on / off of the switching elements SW1 to SW8 by sending them to the gate 6 and converts power between input and output.

  An insulating converter circuit 4 including the primary side switching circuit 1, the transformer 2, and the secondary side switching circuit 3 has a configuration as shown in FIG. In the primary side switching circuit 1, switching elements SW1 and SW2 with freewheeling diodes, SW3 and SW4 are respectively configured in series to form an arm A1 and an arm A2, and a full bridge circuit is formed by arranging the two arms in parallel. It is composed. In the secondary side switching circuit 3, switching elements SW5 and SW6 with freewheeling diodes, SW7 and SW8 are respectively configured in series to form an arm A3 and an arm A4, and the two arms are arranged in parallel to form a full bridge circuit. It is composed. Both ends of the primary side winding of the transformer 2 are respectively connected between the switching element SW1 and the switching element SW2 and between the switching element SW3 and the switching element SW4. Are connected between the switching element SW5 and the switching element SW6 and between the switching element SW7 and the switching element SW8, respectively.

  The primary side switching circuit 1 includes a primary side input capacitor 21 disposed in parallel with the input voltage terminal 24, and the secondary side switching circuit 3 includes a smoothing reactor 22 connected in series with the output voltage terminal 25. And a secondary output capacitor 23 installed in parallel with the output voltage terminal 25.

  IGBTs (insulated gate bipolar transistors) are typically used as the switching elements SW1 to SW8, and the on / off state of the IGBT is controlled by a voltage applied to the gate of the IGBT. The pulse correction unit 11, the pulse control unit 5, and the pulse generation unit 6 can be realized by, for example, a single CPU (Central Processing Unit).

  The primary side input capacitor 21 and the secondary side output capacitor 23 are installed to smooth the voltage. Moreover, the smoothing reactor 22 is installed in order to smooth the output current. It is also possible to use as the insulated converter circuit 4 a circuit that does not include these capacitors and smoothing reactors, or a circuit that includes an additional circuit such as a snubber circuit.

  Further, in addition to the above configuration, the insulation type DC-DC converter according to the present embodiment includes a primary side current detecting means connected in series with the primary side winding of the transformer 2, as shown in FIG. 7, a secondary side current detecting means 9 connected in series with the output voltage terminal 25 of the secondary side switching circuit 3, and a pulse for calculating a pulse correction amount based on the current value detected by the primary side current detector A control mode switching means 10 for determining whether the operation is in powering or regenerative mode based on the direction of the current detected by the correction amount calculation means 8 and the secondary current detector and switching the control mode based on the mode; And a pulse correction unit 11 that selects a switching element to be corrected based on the control mode and corrects the pulse command T2 based on the pulse correction amount.

  The pulse correction amount calculation means 8 and the control mode switching means 10 are configured as shown in FIG. As in the present embodiment, it is not always necessary to use a device capable of measuring a specific current value, such as an ammeter, for the primary current detection means 7 and the secondary current detection means 9. It is sufficient if the configuration can reflect the values in the calculation of the pulse correction amount and the switching of the control mode.

  The pulse correction amount calculation means 8 detects the direct current component of the current Iac1 detected by the primary current detection means 7 by the filter 31, and the compensator 32 determines the pulse correction amount based on the deviation between the direct current component and 0 amperes. Is generated. As the filter 31, a general low-pass filter or the like can be used.

  The control mode switching means 10 has two output terminals, compares the magnitude of the current Idc detected by the secondary current detection means 9 by the comparator 33 with the 0 ampere, and based on the result of the comparison, By switching, one of the output terminals is grounded, and the other output terminal is connected to the output of the pulse correction amount calculation means 8. For example, a transistor or a relay can be used as the switch 34. Both output terminals corresponding to the respective control modes of power running and regeneration become inputs to the pulse correction means 11, and the pulse correction means 11 corrects the pulse command T2 based on the inputs.

  Next, the operation of the isolated DC-DC converter according to this embodiment will be described with reference to FIG.

  FIG. 4 is a conceptual diagram schematically showing the relationship between the voltage pulse for the switching elements SW1 to SW8 and the current and voltage generated in the transformer 2 in the insulated DC-DC converter according to the present embodiment.

  As shown in graphs 41 to 44, in the primary side switching circuit 1, the switching element SW1 and the switching element SW2, and the switching element SW3 and the switching element SW4 are inverted so as not to be turned on at the same time. Prevents the occurrence of arm short circuit. The switching element SW1 and the switching element SW3 are driven by pulses whose phases are shifted, and the pulse control means 5 adjusts the phase difference through the pulse command T2, thereby eliminating the difference between the output command T1 and the actual output voltage. .

  As shown in graphs 45 and 46, in the secondary side switching circuit 3, the operations of the switching element SW5 and the switching element SW8, and the switching element SW6 and the switching element SW7 are synchronized, and the switching element SW5 and the switching element The AC voltage obtained as the output of the transformer 2 is converted into a DC voltage by performing an inverting operation with SW6.

  Also, at this time, the voltage across the primary side and secondary side winding of the transformer 2 is shown in graph 47, during power running (when Idc is in the positive direction) and during regeneration (when Idc is in the negative direction). The graph 48 and the graph 49 show the current flowing through the primary side and secondary side windings of the transformer 2 at the time of, respectively.

  Here, consider the case where the rise of the voltage pulse for the switching element SW1 is delayed from the time point a to the time point a ', and the case where the rise of the voltage pulse for the switching elements SW6 and SW7 is delayed from the time point b to the time point b'. .

  As shown in the graph 47, the voltage waveform is affected only by the delay between a and a ′, regardless of power running or regeneration. On the other hand, the current waveform is affected only by the delay of the switching element SW1 between a and a ′ as shown in the graph 48 at the time of power running, but at the time of regeneration, the aa as shown in the graph 49. It is affected by both the delay of the switching element SW1 between 'and the delay of the switching element SW6 and switching element 7 between bb'.

  On the other hand, the control mode switching means 10 uses the primary-side switching elements SW1 and SW2 for power running and the primary-side switching elements SW3 and SW4 and all secondary-side switching elements for correction during regeneration. The pulse correction means 11 corrects the pulse command T2 for the selected switching element based on the pulse correction amount. At this time, it is only necessary to correct each switching element in the same direction, and it is possible to suitably eliminate the magnetic bias by the correction.

  As described above, the insulation type DC-DC converter according to the present embodiment is configured by the switching elements SW1 to SW4, and converts the DC voltage into the AC voltage by controlling on / off of the switching elements SW1 to SW4. The primary side switching circuit 1 that outputs, the transformer 2 that transforms the output voltage of the primary side switching circuit 1, and the switching elements SW5 to SW8 are configured to control on / off of the switching elements SW5 to SW8. The secondary side switching circuit 3 for rectifying the output voltage of the transformer 2 by the above, and the gates of the switching elements SW1 to SW8 included in the primary side switching circuit 1 and the secondary side switching circuit 3 based on the output command T1 Pulse control hand that generates a pulse command T2 that commands a voltage pulse to be sent to 5 and pulse generation means 6 for controlling on / off of the switching elements SW1 to SW8 by sending a voltage pulse T3 generated based on the pulse command T2 to the gates of the switching elements SW1 to SW8, In an isolated DC-DC converter that converts power between input and output, primary-side current detection means 7 connected in series with the primary-side winding of the transformer 2 and the output of the secondary-side switching circuit 3 Secondary side current detection means 9 connected in series with the voltage terminal 25, pulse correction amount calculation means 8 for calculating a pulse correction amount based on the current value detected by the primary side current detector, and secondary side current A control mode switching unit that determines whether it is operating in powering or regenerative mode based on the direction of the current detected by the detector and switches the control mode based on the mode. And a pulse correction unit 11 that selects a switching element to be corrected based on the control mode and corrects the pulse command T2 for the selected switching element based on the pulse correction amount. This is an isolated DC-DC converter.

  As described above, since the isolated DC-DC converter according to the present embodiment selects and corrects the switching element to be corrected for each mode of power running and regeneration, the circuit is used not only during power running but also during regeneration. It is possible to suitably eliminate the bias without adding a capacitor.

  Further, the switching elements SW1 and SW2 of the primary side switching circuit 1 are used in the control mode when the pulse correction means 11 is in power running, and the primary side switching circuit 1 and the secondary side switching are used in the control mode during regeneration. By selecting SW3, SW4, and SW5 to SW8, which are switching elements of the circuit 3, as correction targets, the minimum control for appropriately eliminating the bias is realized.

  The pulse correction amount calculation means 8 includes a filter 31 for detecting a direct current component of the current detected by the primary side current detection means 7, and outputs a deviation between the direct current component and 0 ampere as a pulse correction amount. Thus, the pulse correction amount suitable for eliminating the demagnetization is determined.

  Further, the pulse correction means 11 has one input terminal for each control mode corresponding to power running / regeneration, and as the control mode switching means 10, one or more switches 34 are connected to one of the input terminals. The other end of the ground is connected to the output of the pulse correction amount calculation means 8, and the switch 34 is switched based on the deviation between the current value detected by the secondary current detection means 9 and 0A. The operation of the control mode switching means 10 is realized with a simple configuration.

  Further, as the primary side switching circuit 1 and the secondary side switching circuit 3, in particular, a full bridge circuit in which two pairs of switching diode-equipped switching elements are arranged in series is arranged in parallel, and the pulse correction means 11 is used. Corrects SW1 and SW2, which are switching elements included in one arm constituting the primary side full bridge circuit in the control mode during power running, and controls the primary side full bridge circuit in the control mode during regeneration. SW3 and SW4, which are switching elements included in one of the arms that are not corrected in the control mode at the time of powering, and SW5 that is a switching element included in both arms constituting the secondary side full bridge circuit In order to correct SW8, the configuration is such that the bias is preferably eliminated by simple control. .

  The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Primary side switching circuit 2 ... Transformer 3 ... Secondary side switching circuit 4 ... Insulation type converter circuit 5 ... Pulse control means 6 ... Pulse generation means 7 ... Primary side current detection means 8 ... Pulse correction amount calculation means 9 ... secondary current detection means 10 ... control mode switching means 11 ... pulse correction means 21 ... primary side input capacitor 22 ... smoothing reactor 23 ... secondary side output capacitor 24 ... input voltage terminal 25 ... output voltage terminal 31 ... filter 32 ... Compensator 33 ... Comparator 34 ... Switch 41 ... Graph 42 representing the gate voltage of switching element SW1 ... Graph 43 representing the gate voltage of switching element SW2 ... Graph 44 representing the gate voltage of switching element SW3 ... Gate of switching element SW4 Graph 45 representing voltage ... of switching element SW5 and switching element SW8 Graph representing the gate voltage of the switching element SW6 and the switching element SW7. Graph representing the primary voltage Vac1 and the secondary voltage Vac2 of the transformer 48. Primary of the transformer during power running. Graph 49 representing side current Iac1 and secondary current Iac2 ... Graph SW1 to SW4 representing primary current Iac1 and secondary current Iac2 of the transformer during regeneration SW1 to SW4 ... switching elements SW5 included in the primary side switching circuit SW8... Switching element A1, A2 included in the secondary side switching circuit, arm A3 included in the primary side switching circuit, A4... Arm T1 included in the secondary side switching circuit, output command T2, pulse command T3, voltage pulse
Vac1 ... Primary voltage of the transformer
Vac2 ... Transformer primary voltage
Iac1 ... Transformer primary current
Iac2 ... Transformer primary current
Idc: Current detected by secondary current detection means

Claims (5)

A primary-side switching circuit configured by a switching element that converts a DC voltage into an AC voltage by controlling on / off of the switching element, and a transformer that transforms the output voltage of the primary-side switching circuit; A secondary side switching circuit configured by a switching element to rectify the output voltage of the transformer by controlling on / off of the switching element, and the primary side switching circuit and the secondary side based on an output command Pulse control means for generating a pulse command for instructing a voltage pulse to be sent to the gate of the switching element included in the switching circuit; and sending the voltage pulse generated based on the pulse command to the gate of the switching element. Pulse generating means for controlling on / off, In an isolated DC-DC converter that converts power between outputs, primary current detection means connected in series with a primary winding of the transformer and output voltage terminal of a secondary switching circuit are connected in series. Secondary-side current detection means connected to, pulse correction amount calculation means for calculating a pulse correction amount based on the current value detected by the primary-side current detector, and current detected by the secondary-side current detector Control mode switching means for determining whether the power running or regenerative mode is operating according to the direction of the operation and switching the control mode based on the mode, and selecting the switching element to be corrected based on the control mode, and the pulse correction An insulated DC-DC converter comprising: pulse correction means for correcting the pulse command for the selected switching element based on the quantity . 2. The isolated DC-DC converter according to claim 1, wherein the pulse correction means switches the switching element of the primary side switching circuit in a control mode during power running, and the primary side in a control mode during regeneration. An insulation type DC-DC converter, wherein a switching circuit and a switching element of the secondary side switching circuit are selected as correction targets. 3. The isolated DC-DC converter according to claim 1, wherein the pulse correction amount calculation unit includes a filter that detects a direct current component of the current detected by the primary side current detection unit, An isolated DC-DC converter that outputs a deviation between a direct current component and 0 amperes as a pulse correction amount. 4. The isolated DC-DC converter according to claim 1, wherein the pulse correction unit has one input terminal for each control mode corresponding to power running / regeneration, and the control As the mode switching means, one or more switches are configured such that one of the input terminals is grounded and the other is connected to the output of the pulse correction amount calculating means, which is detected by the secondary current detecting means. An insulated DC-DC converter characterized in that the switch is switched based on a deviation between a current value and 0A. 5. The insulated DC-DC converter according to claim 1, wherein two pairs of switching elements with free-wheeling diodes are arranged in series as the primary side switching circuit and the secondary side switching circuit. A full bridge circuit is configured by arranging two pairs of arms in parallel, and the pulse correction means corrects a switching element included in one arm configuring the primary side full bridge circuit in a control mode during power running, In the control mode at the time of regeneration, both the switching element included in the one arm constituting the primary side full bridge circuit and not corrected in the control mode at the time of power running and the secondary side full bridge circuit are included. An isolated DC-DC converter that corrects a switching element included in an arm.

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