JP2019180128A - Converter and bidirectional converter - Google Patents

Abstract

To provide a converter capable of obtaining stable output by preventing a peak value of a transformer secondary-side current from being drifted, and a bidirectional converter.SOLUTION: With regard to a converter and a bidirectional converter, the timing to turn off a switching element (S3 or S4) in a step-up operation is set before a current to flow to a secondary coil 11b of a transformer 11 becomes zero. In the case of digital control, a control circuit 3 turns on a switching element (S2 or S1) which is turned off after the switching element (S3 or S4) and then turns it off after the lapse of a time which is calculated from the timing to perform ON/OFF control on switching elements (S1-S6). In the case of analog control, the control circuit 3 monitors the current to flow to the secondary coil 11b, turns off the switching element (S5 or S6) which is conducted forwards, and then turns off the switching element (S3 or S4) when the current is decreased and achieves a threshold value.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to converters and bidirectional converters.

  Patent Documents 1 and 2 disclose converter and bidirectional converter circuits that are effective over a wide range of input / output conditions. In these converters, the operation of each switch is controlled so that zero volt switching (ZVS) is performed when the switch is turned on in order to reduce switching loss in a wide input / output voltage current range. For example, the operation of each switch can be controlled using a triangular wave signal and an error amplification signal described in Patent Document 3.

JP 2014-075943 A JP, 2014-075944, A JP, 2006-005323, A

  1 and 2 are diagrams for explaining circuits of a converter and a bidirectional converter, respectively. The converters and bidirectional converters described in Patent Documents 1 and 2 also have the circuits shown in FIGS. FIG. 3 is a diagram illustrating the problem of the present invention. In addition, in the converter of FIG.1 and FIG.2, the connection of a capacitor | condenser (Ca-Cd) is arbitrary.

  The converter of FIG. 1 and the bidirectional converter of FIG. 2 control the on / off operation timing of the secondary side switching elements (Q5, Q6) during the boosting operation. This will be specifically described with reference to FIG. After the secondary side switching elements (Q5, Q6) are turned off at time ta, the transformer secondary side current (secondary side diode current) decreases. Then, during the reverse recovery time in which the reverse current flows through the diodes (D7, D8) after the transformer secondary side current becomes zero, or during the subsequent charging / discharging of the parasitic capacitances (C7, C8) (in FIG. When the primary side switching elements (Q3, Q4) are turned off at time tb after the secondary side current becomes zero or less), the slope of the reverse recovery current and the charge / discharge current of the parasitic capacitance changes (FIG. 3A). Reference numeral 51 of (B)). In FIG. 3C, since the charging and discharging of the parasitic capacitance is completed before the primary side switching elements (Q3, Q4) are turned off, there is no inclination changing portion.

  Here, as described in Patent Document 3, the ON / OFF operation timing of the secondary side switching elements (Q5, Q6) is determined by the intersection of the error amplification signal and the triangular wave signal (see FIG. 4). The error amplification signal fluctuates due to a disturbance such as a load (after time ti in FIG. 4). Since the triangular wave signal does not change, the ON / OFF operation timing of the secondary side switching elements (Q5, Q6) changes when the error amplification signal changes. FIG. 3A shows a state in which the error amplification signal has dropped from the state of FIG. 3B and the off timing ta of the secondary side switch elements (Q5, Q6) has been advanced. FIG. 3C shows a state in which the error amplification signal has risen from the state of FIG. 3B and the off timing ta of the secondary side switching elements (Q5, Q6) has been delayed.

  In the step-up operation, the off timing tb of the primary side switching elements (Q3, Q4) does not change, and therefore the reverse recovery time and the current value 52 after completion of parasitic capacitance charging / discharging (time tb) vary depending on the state of the error amplification signal. It will be. This current value 52 is an initial value of the transformer secondary current in the next half cycle of the switch control. For this reason, the peak value of the transformer secondary current increases (FIG. 3 (A)) or decreases (FIG. 3 (C)) according to this initial value. That is, the reverse recovery current of the diodes (D7, D8) and the parasitic capacitance when the primary side switch elements (Q3, Q4) are turned off due to the change in the pulse width of the switch element drive signal due to the minute fluctuation of the error amplification signal. As the discharge state changes and the initial value of the transformer secondary current increases or decreases, the peak value of the transformer secondary current increases in one direction (from FIG. 3C to (A) or FIG. A drifting phenomenon from A) to (C) occurs.

  As described above, the converters of Patent Documents 1 and 2 have a problem that even in a steady state, the peak value of the transformer secondary current drifts in the direction of increasing or decreasing, and the output tends to become unstable. there were.

  Therefore, in order to solve the above-described problems, an object of the present invention is to provide a converter and a bidirectional converter that prevent the peak value of the transformer secondary side current from drifting and obtain a stable output.

  In order to achieve the above object, the converter according to the present invention forcibly turns off the primary side switches (Q3, Q4) before the reverse recovery time.

Specifically, the converter according to the present invention is:
A transformer having a primary winding and a secondary winding;
A switching element having a switching element in which an antiparallel diode and a parallel capacitor are connected in parallel is used as an upper and lower arm, and a first leg and a second leg are connected in parallel between the first terminal and the second terminal, respectively. A first circuit connected to the primary winding side;
At least two of the unidirectional elements to be bridge-connected have a bridge connection circuit in which switching elements including switching elements each having a parallel capacitor connected in parallel are connected in parallel, and the bridge A second circuit in which the rectified output side of the connection circuit is connected to the third terminal and the fourth terminal, and the AC input side is connected to the secondary winding side;
The unidirectional elements have the same polarity via the primary winding or in the bridge connection circuit between the connection point side of the upper and lower arms of the first leg and the connection point side of the upper and lower arms of the second leg Inductance means connected via the secondary winding between the connection point side connected in series and the other connection point side connected in series with the same polarity between the unidirectional elements,
Direct current input from the first and second terminal sides by alternately switching on and off the switching element of the upper arm of the first or second leg and the switching element of the lower arm of the second or first leg. Is converted into alternating current and output from the first circuit, and the switching elements in the set are alternately turned on and off, and the switching elements of the upper arm of the first or second leg in the set in the on state A control circuit that turns off one of the switching elements of the lower arm of the second or first leg before the other switching element,
The control circuit includes:
The detected value of the voltage, current or power output from the side between the third and fourth terminals or the detected value of the voltage, current or power input from the side between the first and second terminals approaches the target value. One of the switching elements of the second circuit is forwarded so that the energy input from the first and second terminal sides is accumulated in the inductance means during a period in which the switching elements of the first circuit in the set are in the ON state. When performing a step-up operation for turning off the switching element of the second circuit that has been conducted in the forward direction before turning off the switching element of the first circuit that is conducted in the direction and turned off first,
The switching element of the first circuit that is turned off first in the boosting operation is turned off before the current flowing through the secondary winding of the transformer becomes zero.

  By forcibly turning off the primary side switches (Q3, Q4) before the reverse recovery time, the initial value of the transformer secondary side current becomes constant, and the peak of the transformer secondary side current increases or decreases. Fluctuating drift can be prevented. Therefore, the present invention can provide a converter and a bidirectional converter that can prevent the peak value of the transformer secondary current from drifting and can provide a stable output.

  The present invention can provide a converter and a bidirectional converter that prevent the peak value of the transformer secondary current from drifting and that can provide a stable output.

It is a figure explaining the circuit of a converter. It is a figure explaining the circuit of a bidirectional | two-way converter. It is a figure explaining the subject of this invention. It is a figure explaining the principle which carries out on-off control of each switch of a converter. It is a figure explaining the effect of the converter concerning the present invention. It is a figure explaining the timing which turns off the primary side switch of the converter which concerns on this invention. It is a figure explaining the timing which turns off the primary side switch of the converter which concerns on this invention. It is a figure explaining the reactor value of the transformer of a converter, and an inductance means.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 1 is a circuit for explaining the converter of this embodiment. The connection of the capacitors (Ca to Cd) is arbitrary.
This converter
A transformer (11) having a primary winding and a secondary winding;
A switching element (S1-S4) having a switching element (Q1-Q4) in which an antiparallel diode (D1-D4) and a parallel capacitor (C1-C4) are respectively connected in parallel is used as a first arm (T1). And a first circuit (1) connected to the primary winding side, each having a first leg (12) and a second leg (13) connected in parallel between the first terminal and the second terminal (T2). ,
At least two of the unidirectional elements (D5-D8) to be bridge-connected include switching elements (Q5, Q6) each having a parallel capacitor (C5, C6) connected in parallel. S5, S6) each have a bridge connection circuit connected in parallel, the rectified output side of the bridge connection circuit is connected to the third terminal and the fourth terminal (T3, T4), and the AC input side is the secondary winding A second circuit (2) connected to the side;
The one-way through the primary winding or in the bridge connection circuit between the connection point side of the upper and lower arms of the first leg (12) and the connection point side of the upper and lower arms of the second leg (13). Are connected via the secondary winding between the connection point side where the directional elements are connected in series with the same polarity and the other connection point side where the unidirectional elements are connected in series with the same polarity. Inductance means (L),
A switching element (S1 or S3) of the upper arm of the first or second leg (12 or 13) and a switching element (S4 or S2) of the lower arm of the second or first leg (13 or 12) are combined. Then, the switching elements (S1) are turned on and off alternately to convert the direct current input from the first and second terminals (T1 and T2) into alternating current and output the alternating current from the first circuit (1). And S4 or S3 and S2) are alternately turned on and off, the upper arm switching element (S1 or S3) and the second arm of the first or second leg (12 or 13) in the on-state set. Alternatively, one of the switching elements (S3 or S4) of the lower arm switching elements (S4 or S2) of the first leg (13 or 12) is replaced with the other switching element (S2 or S1). A control circuit (3) for turning off the Ri destination, a converter, comprising the,
The control circuit includes:
Detected value of voltage, current or power output from the side between the third and fourth terminals (T3 and T4) or voltage, current or power input from the side between the first and second terminals (T1 and T2) The first and second terminals (T1 and T2) side during the period in which the switching elements (S1 and S4 or S3 and S2) of the first circuit in the set are in an ON state so that the detected value of the The switching element (S3) of the first circuit that makes one switching element (S5 or S6) of the second circuit conduct in the forward direction so as to accumulate the energy input from the inductance means (L) and turns off first. Or when performing a boosting operation to turn off the switching element (S5 or S6) of the second circuit that has been conducted in the forward direction before turning off S4),
The timing of turning off the switching element (S3 or S4) of the first circuit that is turned off first in the boosting operation is set before the current flowing through the secondary winding of the transformer becomes zero.

  In the present embodiment, the case where the detection value is detected by the output voltage detection means 18 will be described. The output voltage detection means 18 detects the output voltage of the second circuit 2 output between the third terminal T3 and the fourth terminal T4. This output voltage detection value is input to the control circuit 3. In the case of detecting other detection values, a detection means capable of detecting the detection value of the target is arranged where appropriate.

  The basic operation of this converter is as described in Patent Document 1 when there is a capacitor (Ca to Cd), and as described in Patent Document 2 when there is no capacitor (Ca to Cd). Further, the control circuit 3 uses the three triangular wave signals and the error amplification signal (AVR) created from the detected value to switch the switching elements (S1-S4) and the second circuit (2) as in Patent Document 3. A pulse signal for controlling on / off of the elements (S5-S8) is generated, and the detection value is controlled so as to approach the target value.

  For example, during the boosting operation in which the voltage output from the third terminal T3 and the fourth terminal T4 is higher than the voltage input from the first terminal T1 and the second terminal T2, the error amplification signal AVR and the switching element are switched as shown in FIG. The triangular waves for (Q5, Q6) intersect. For this reason, the control circuit 3 has the first and second terminals (S1 and S4 or S3 and S2) in the ON state with the pulse width of the pulse signal resulting from the intersection during the period in which the switching elements are on. The switching element (S3 or S4) of the first circuit that is turned off first is turned off by conducting the switching element (S5 or S6) in the forward direction so that the energy input from the T1 and T2) side is stored in the inductance means L. The switching element (S5 or S6) of the second circuit that has been conducted in the forward direction before turning off is turned off.

  On the other hand, during the step-down operation in which the voltage output from the third terminal T3 and the fourth terminal T4 is lower than the voltage input from the first terminal T1 and the second terminal T2, the error amplification signal AVR and the switch element are switched as shown in FIG. The triangular waves for (Q3, Q4) intersect. For this reason, the control circuit 3 has the first and second terminals (S1 and S4 or S3 and S2) in the ON state with the pulse width of the pulse signal resulting from the intersection during the period in which the switching elements are on. The switching element (S5 or S6) of the second circuit is conducted in the forward direction so that the energy input from the T1 and T2) side is supplied to the third and fourth terminals (T3 and T4) side through the inductance means L. Control not to let it.

  As described above, the converter according to the present embodiment uses the inductance means connected to the primary winding or the secondary winding side of the transformer to turn on / off the switching element of the first circuit on the input side and the first side on the output side. By realizing the operation of causing the two circuits to function as a rectifier circuit, a wide range of input / output voltage currents can be handled. In addition, the switching loss that occurs when the switching element is turned off while the current is flowing can be reduced, and occurs when one of the switching elements of the first circuit to be paired is turned off later. Switching loss can be reduced. Furthermore, switching loss can be reduced by realizing zero voltage switching.

Hereinafter, operations different from those of Patent Documents 1-3 will be described.
The control circuit 3 of the converter of the present embodiment forces the switching element (S3 or S4) of the first circuit to be turned off first in the step-up operation before the current flowing through the secondary winding 11b of the transformer 11 becomes zero. Forced off control to turn off automatically. The forced off control includes a digital method and an analog method.

  First, forced off control performed digitally will be described. In the forced-off control performed digitally, the control circuit 3 uses a time calculated from the timing at which each switch element is turned on / off. The control circuit turns on the switching element (S2 or S1) of the first circuit to be turned off after the switching element (S3 or S4) of the first circuit to be turned off first, and then turns on the switching element (S1- S4) and the switching elements (S5, S6) of the second circuit are turned off after time t1 calculated from the timing of on / off control.

また、ｔｘの値は、次式より求める。

The digital forced-off control will be described in the case where power is input from the first terminal T1 and second terminal T2 sides and output from the third terminal T3 and fourth terminal T4 sides.
FIG. 5 is a diagram for explaining an example of forced-off control performed digitally. FIG. 5 shows the timing for switching each switch and the transformer secondary current 50. t0 is the time (fixed value) when the switching element (S1 or S2) of the first circuit is turned on. The timing for turning on the switching element (S3 or S4) is while the antiparallel diode (D3 or D4) is conducting, and before the switching element (S1 or S2) is turned on. Time t1 (time from t0) at which the switching element (S3 or S4) of the first circuit is turned off is calculated by the following equation.
(Equation 1)
t1 = t2 + t3 + tx−tz (1)
Here, t2 is the time from t0 to the time when the switching element (S5 or S6) of the second circuit is turned off. The value of t2 is obtained from the value of AVR that determines the phase shift amount of the switching element (S5 or S6) of the second circuit (see FIG. 4). The value of t3 is obtained from the following equation.

The value of tx is obtained from the following equation.

  Here, Ein is an input voltage inputted to the first terminal T1 and the second terminal T2, Eo is an output voltage outputted from the third terminal T3 and the fourth terminal T4 side, and n1 and n2 are primary side windings of the transformer 11. And the number of secondary windings, La is the reactor value of the inductance means arranged on the first circuit 1 side, Lb is the reactor value of the inductance means arranged on the second circuit 2 side, and L1 is the primary side excitation of the transformer 11 It is a reactor (refer FIG. 8). When the inductance means L (reactor value L) is arranged only on the primary side of the transformer 11 as shown in FIGS. 1 and 2, La = L and Lb = 0.

  The current value ix is the current value 52 described with reference to FIG. 3. However, since it is difficult to calculate, the current value ix is an arbitrary constant. Further, tz is a margin for reliably turning off the primary side switching element (S3 or S4) before the transformer secondary side current becomes zero.

  When the time t1 is calculated, the control circuit sets the lower limit value as the time t1 when the time becomes smaller than a preset lower limit value. This is to prevent t1 from becoming negative as a result of the calculation. Further, an upper limit value (for example, a time determined by the triangular waves for Q3 and Q4 in FIG. 3) is determined for t1, and when the denominators of Equations 2 and 3 become zero or negative (switching elements (S3, S4 ) Is on, the secondary side current does not become zero), or even if it is positive, if the value is very small (t1 exceeds the upper limit value), the primary side switching element (S3 or It is desirable to turn off S4).

  The control circuit 3 calculates t1 as described above, and turns off the switching element (S3 or S4) of the first circuit when t1 has elapsed from time t0.

  Next, forced off control performed in an analog manner will be described. In the forced-off control performed in an analog manner, the control circuit 3 compares the transformer secondary current with a threshold value to turn off the switching element (S3 or S4) of the first circuit. The control circuit has a threshold value that is greater than or equal to zero and less than or equal to a maximum value of the current flowing through the secondary winding with respect to the current flowing through the secondary winding, and monitors the current flowing through the secondary winding. Then, after the switching element (S5 or S6) of the second circuit that has been conducted in the forward direction is turned off, when the current flowing through the secondary winding decreases and reaches the threshold value, it is turned off first. The switching element (S3 or S4) of the first circuit to be turned off is turned off.

The analog forced off control will be described in the case where power is input from the first terminal T1 and second terminal T2 side and output from the third terminal T3 and fourth terminal T4 side.
FIG. 6 is a diagram illustrating an example of forced-off control performed in an analog manner. FIG. 6 shows the switching timing, the transformer secondary current 50, and the threshold value 54. The transformer secondary side current 50 starts to increase at the same time when the primary side switching element (S1 or S2) is turned on, and starts to decrease as the switching element (S5 or S6) of the second circuit is turned off. The timing for turning on the switching element (S3 or S4) is while the antiparallel diode (D3 or D4) is conducting, and before the switching element (S1 or S2) is turned on. The transformer secondary current 50 that continues to decrease falls below the threshold value 54 at some point. At this point, the control circuit 3 forcibly turns off the switching element (S3 or S4) of the first circuit. Note that there is a time lag td until the switching element (S3 or S4) of the first circuit is actually turned off even if the control circuit 3 gives an instruction to turn it off. For this reason, the value of the threshold value 54 is set so that the switching element (S3 or S4) of the first circuit can actually be turned off before the transformer secondary current 50 becomes zero in consideration of the time lag td.

  In addition, since the slope of decrease of the transformer secondary current 50 changes depending on the input / output voltage of the converter, the switching element (S3 or S4) of the first circuit cannot be turned off before the transformer secondary current 50 becomes zero. is there. In order to cope with such a situation, it is desirable that the control circuit has a switching function for changing the threshold value.

  FIG. 7 is a diagram for explaining the effect when the forced-off control is performed. 7A illustrates a case where the peak of the transformer secondary side current 50 is large, and FIG. 7B illustrates a case where the peak of the transformer secondary side current 50 is small. Although the time for turning on the switching element (S3 or S4) of the first circuit is the same, the timing for turning off the switching element (S3 or S4) of the first circuit varies depending on the situation of the transformer secondary current 50. The transformer secondary current value 52 is constant. For this reason, the peak drift of the transformer secondary side current 50 can be prevented, and the output is stabilized.

(Embodiment 2)
FIG. 2 is a circuit for explaining the bidirectional converter of the present embodiment. The connection of the capacitors (Ca to Cd) is arbitrary. In the present embodiment, a configuration and operation different from those of the converter according to the first embodiment will be mainly described.

In the bidirectional converter, the bridge connection circuit of the second circuit is a switching element (Q5-Q8) in which parallel capacitors (C5-C8) are connected in parallel for all the unidirectional elements (D5-D8). ) Including switching elements (S5-S8) connected in parallel, and the switching elements (S5-S8) of the second circuit as upper and lower arms between the third terminal (T3) and the fourth terminal (T4). Each of the third leg 24 and the fourth leg 25 is connected in parallel.
The control circuit includes switching elements (S5, S7) of the second circuit of the upper arm of the third or fourth leg and switching elements (S8, S6) of the second circuit of the lower arm of the fourth or third leg. Are alternately turned on and off to convert direct current input from the third and fourth terminal sides into alternating current and output from the second circuit, and the switching elements (S5 & S8, In the on / off control of S7 & S6) alternately, the switching element (S5 or S7) of the second circuit of the upper arm of the third or fourth leg that is in the ON state and the lower part of the fourth or third leg Of the switching element (S8 or S6) of the second circuit of the arm, the switching element (S5 or S6) of one of the second circuits is used as the switching element (S8 or S7) of the other second circuit. Above, wherein the turning off to.

  In the bidirectional converter according to the second embodiment, the second circuit is configured in the same manner as the first circuit in order to operate in both directions. For this reason, in FIG. 2, the second circuit 22 has a circuit structure in which the switching elements are upper and lower arms of two legs. In addition, since the drive signal is also given to the switching elements S7 and S8 of the second circuit 22, the control circuit 23 is used here. The first leg 12, the second leg 13 and the third leg 24 of the second circuit 22 of the first circuit 1 are the same as the configuration shown in FIG. 1 described in the first embodiment. Similarly to FIG. 1, in FIG. 2, the inductance means L is connected to the primary winding 11a side, but may be connected to the secondary winding 11b side.

  When power is supplied from the first circuit 1 to the second circuit 22 side, the control circuit 23 operates each switch element similarly to the operation described in the first embodiment. However, the switch elements (Q7, Q8) are always turned off. On the other hand, when power is supplied from the second circuit 22 to the first circuit 1 side, the control circuit 23 operates each switch element in a mirror manner with respect to the operation described in the first embodiment. Specifically, when power is supplied from the second circuit 22 to the first circuit 1, the control circuit 23 uses the switching elements (S7, S8) as the switching elements (S1, S2) described in the first embodiment. The switching elements (S5, S6) are operated as the switching elements (S3, S4) described in the first embodiment, and the switching elements (S3, S4) are operated as the switching elements (S5, S6) described in the first embodiment. In this case, the switch elements (Q1, Q2) are always turned off.

  In the case of supplying power from the first circuit 1 to the second circuit 22 side, the control circuit 23 of the bidirectional converter according to the present embodiment is configured so that the current flowing through the secondary winding 11b of the transformer 11 becomes zero before the current flows. If the switching element (S3 or S4) of one circuit 1 is forcibly turned off and power is supplied from the second circuit 22 to the first circuit 1, the current flowing through the primary winding 11a of the transformer 11 becomes zero. Before that, the switching element (S5 or S6) of the second circuit 22 is forcibly turned off.

  In the case of digital control, the control circuit 23 is the first circuit if power is supplied from the first circuit 1 to the second circuit 22 side from the timing of switching the switching elements (S3, S4, S5, S6). When the switching element (S3 or S4) is turned off by the equation (1) and power is supplied from the second circuit 22 to the first circuit 1 side, the switching element (S5 or S6) of the second circuit 22 The time to turn off is calculated by Equation 1.

  In the case of analog control, the control circuit 23 compares the current flowing through the secondary winding 11b of the transformer 11 with a threshold value when supplying power from the first circuit 1 to the second circuit 22 side. If a command to turn off the switching element (S3 or S4) of one circuit is issued and power is supplied from the second circuit 22 to the first circuit 1, the current flowing through the primary winding 11a of the transformer 11 and the threshold value are set. In comparison, a command to turn off the switching element (S5 or S6) of the second circuit 22 is issued.

  The bidirectional converter of the present embodiment can also always make the reverse recovery time and the current value 52 after the end of parasitic capacitance charging / discharging constant by performing the switch forced-off control described in the first embodiment. For this reason, the drift of the peak of the current flowing through the winding on the output side of the transformer 11 can be prevented, and the output is stabilized.

(Other embodiments)
In the first and second embodiments described above, the control circuits 3 and 23 allow the voltage values detected by the output voltage detection means 18 of the second circuit and the output voltage detection means 19 of the first circuit to approach the target values. However, the detection value to be used may be a combination of these in addition to the output current value and the output power. Similarly, the detected value of voltage, current, or power on the input side may approach the target value. In general, a calculated value obtained by multiplying the detected voltage and current is used as the detected power value. The above output voltage, current or power detection value or input voltage, current or power detection value is calculated by multiplying or dividing a certain coefficient by these values or adding or subtracting a certain value. The value obtained in this way is also included.

T1 ... 1st terminal, T2 ... 2nd terminal, T3 ... 3rd terminal, T4 ... 4th terminal,
DESCRIPTION OF SYMBOLS 1 ... 1st circuit, 2, 22 ... 2nd circuit, 3, 23 ... Control circuit, 11 ... Transformer, 12 ... 1st leg, 13 ... 2nd leg, 24 ... 3rd leg, 25 ... 4th
Legs 16, 17 ... capacitors, 18 ... second circuit output voltage detection means, 19 ...
-Output voltage detection means of the first circuit, S1 to S4 ... switching elements of the first circuit, Q1
Q4... Switch element, D1 to D4 .. antiparallel diode, C1 to C4... Parallel capacitor, D5 to D8 .. unidirectional element (antiparallel diode), S5 to S8.
Circuit switching elements, Q5 to Q8 ... switch elements, C5 to C8 ... parallel capacitors, Ca to Cd ... first to fourth capacitors, L ... inductance means

(Embodiment 1)
FIG. 1 is a circuit for explaining the converter of this embodiment. The connection of the capacitors (Ca to Cd) is arbitrary.
This converter
A transformer (11) having a primary winding and a secondary winding;
A switching element (S1-S4) having a switching element (Q1-Q4) in which an antiparallel diode (D1-D4) and a parallel capacitor (C1-C4) are respectively connected in parallel is used as a first arm (T1). And a first circuit (1) connected to the primary winding side, each having a first leg (12) and a second leg (13) connected in parallel between the first terminal and the second terminal (T2). ,
It has a bridge connection circuit composed of bridge connections of unidirectional elements (D5-D8), the rectification output side of the bridge connection circuit is connected to the third terminal and the fourth terminal (T3, T4), and the AC input side is A second circuit (2) connected to the secondary winding side;
The one-way through the primary winding or in the bridge connection circuit between the connection point side of the upper and lower arms of the first leg (12) and the connection point side of the upper and lower arms of the second leg (13). Are connected via the secondary winding between the connection point side where the directional elements are connected in series with the same polarity and the other connection point side where the unidirectional elements are connected in series with the same polarity. Inductance means (L),
A switching element (S1 or S3) of the upper arm of the first or second leg (12 or 13) and a switching element (S4 or S2) of the lower arm of the second or first leg (13 or 12) are combined. Then, the switching elements (S1) are turned on and off alternately to convert the direct current input from the first and second terminals (T1 and T2) into alternating current and output the alternating current from the first circuit (1). And S4 or S3 and S2) are alternately turned on and off, the upper arm switching element (S1 or S3) and the second arm of the first or second leg (12 or 13) in the on-state set. Alternatively, one of the switching elements (S3 or S4) of the lower arm switching elements (S4 or S2) of the first leg (13 or 12) is replaced with the other switching element (S2 or S1). A control circuit (3) for turning off the Ri destination, a converter, comprising the,
Two unidirectional elements (D5, D6) of the bridge connection circuit include switching elements (S5, S6) configured by connecting switching elements (Q5, Q6) and parallel capacitors (C5, C6) in parallel. Each connected in parallel,
The control circuit includes:
Detected value of voltage, current or power output from the side between the third and fourth terminals (T3 and T4) or voltage, current or power input from the side between the first and second terminals (T1 and T2) The first and second terminals (T1 and T2) side during the period in which the switching elements (S1 and S4 or S3 and S2) of the first circuit in the set are in an ON state so that the detected value of the The switching element (S3) of the first circuit that makes one switching element (S5 or S6) of the second circuit conduct in the forward direction so as to accumulate the energy input from the inductance means (L) and turns off first. Or when performing a boosting operation to turn off the switching element (S5 or S6) of the second circuit that has been conducted in the forward direction before turning off S4),
The timing of turning off the switching element (S3 or S4) of the first circuit that is turned off first in the boosting operation is set before the current flowing through the secondary winding of the transformer becomes zero.

First, forced off control performed digitally will be described. In the forced-off control performed digitally, the control circuit 3 uses a time calculated from the timing at which each switch element is turned on / off. The control circuit turns on the switching element (S2 or S1) of the first circuit to be turned off after the switching element (S3 or S4) of the first circuit to be turned off first, and then turns on the switching element (S1- The switching element (S3 or S4) of the first circuit is turned off after time t1 calculated from S4) and the timing at which the switching elements (S5, S6) of the second circuit are on / off controlled.

Incidentally, the control circuit, when it becomes less than the lower limit value is the time t1 when calculating the time t1 is set in advance, characterized in that the time t1 and the lower limit value. This is to prevent t1 from becoming negative as a result of the calculation. Further, an upper limit value (for example, a time determined by the triangular waves for Q3 and Q4 in FIG. 3) is determined for t1, and when the denominators of Equations 2 and 3 become zero or negative (switching elements (S3, S4 ) Is on, the secondary side current does not become zero), or even if it is positive, if the value is very small (t1 exceeds the upper limit value), the primary side switching element (S3 or It is desirable to turn off S4).

Claims (6)

A transformer having a primary winding and a secondary winding;
A switching element having a switching element in which an antiparallel diode and a parallel capacitor are connected in parallel is used as an upper and lower arm, and a first leg and a second leg are connected in parallel between the first terminal and the second terminal, respectively. A first circuit connected to the primary winding side;
At least two of the unidirectional elements to be bridge-connected have a bridge connection circuit in which switching elements including switching elements each having a parallel capacitor connected in parallel are connected in parallel, and the bridge A second circuit in which the rectified output side of the connection circuit is connected to the third terminal and the fourth terminal, and the AC input side is connected to the secondary winding side;
The unidirectional elements have the same polarity via the primary winding or in the bridge connection circuit between the connection point side of the upper and lower arms of the first leg and the connection point side of the upper and lower arms of the second leg Inductance means connected via the secondary winding between the connection point side connected in series and the other connection point side connected in series with the same polarity between the unidirectional elements,
Direct current input from the first and second terminal sides by alternately switching on and off the switching element of the upper arm of the first or second leg and the switching element of the lower arm of the second or first leg. Is converted into alternating current and output from the first circuit, and the switching elements in the set are alternately turned on and off, and the switching elements of the upper arm of the first or second leg in the set in the on state A control circuit that turns off one of the switching elements of the lower arm of the second or first leg before the other switching element,
The control circuit includes:
The detected value of the voltage, current or power output from the side between the third and fourth terminals or the detected value of the voltage, current or power input from the side between the first and second terminals approaches the target value. One of the switching elements of the second circuit is forwarded so that the energy input from the first and second terminal sides is accumulated in the inductance means during a period in which the switching elements of the first circuit in the set are in the ON state. When performing a step-up operation for turning off the switching element of the second circuit that has been conducted in the forward direction before turning off the switching element of the first circuit that is conducted in the direction and turned off first,
The converter according to claim 1, wherein the first circuit switching element to be turned off first in the step-up operation is turned off before the current flowing through the secondary winding of the transformer becomes zero.   The control circuit turns on and off the switching element of the first circuit and the switching element of the second circuit after turning on the switching element of the first circuit to be turned off after the switching element of the first circuit to be turned off first. 2. The converter according to claim 1, wherein the converter is turned off after a time t1 calculated from.   The converter according to claim 2, wherein the control circuit sets the lower limit value as the time t <b> 1 when the time t <b> 1 is smaller than a preset lower limit value when the time t <b> 1 is calculated.   The control circuit has a threshold value that is greater than or equal to zero and less than or equal to a maximum value of the current flowing through the secondary winding with respect to the current flowing through the secondary winding, and monitors the current flowing through the secondary winding. Then, after turning off the switching element of the second circuit that has been conducted in the forward direction, when the current flowing through the secondary winding decreases and reaches the threshold value, the first circuit that is turned off first The converter according to claim 1, wherein the switching element is turned off.   The converter according to claim 4, wherein the control circuit has a switching function for changing the value of the threshold value. In the bridge connection circuit of the second circuit, switching elements including switching elements each having a parallel capacitor connected in parallel are connected in parallel for all of the unidirectional elements, and the switching elements of the second circuit are moved up and down. The arm is composed of a third leg and a fourth leg connected in parallel between the third terminal and the fourth terminal, respectively.
The control circuit alternately turns on and off a pair of switching elements of the second circuit of the upper arm of the third or fourth leg and switching elements of the second circuit of the lower arm of the fourth or third leg. The direct current input from the third and fourth terminal sides is converted into alternating current and output from the second circuit, and the on-off control is alternately performed on the switching elements of the second circuit in the set. The switching element of the second circuit of one of the switching element of the second circuit of the upper arm of the third or fourth leg and the switching element of the second circuit of the lower arm of the fourth or third leg that form a set The bidirectional converter having the converter according to any one of claims 1 to 5, wherein the second switching circuit is turned off before the other switching element of the second circuit.

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