JP6274580B2 - Insulated Cuk converter, power transmission control device - Google Patents

Description

  The present invention relates to a Cuk converter that is a type of DC / DC converter, and more particularly to an insulating Cuk converter in which a primary side and a secondary side are insulated by a transformer.

  The Cuk converter is a DC / DC converter invented by Mr. Slobodan M. Cuk (US Pat. No. 4,184,197). One inductor is added to the circuit of the conventional DC / DC converter, and two inductors are connected to the input side. It suppresses current fluctuation on the output side.

  Some Cuk converters have an input side and an output side insulated by a transformer. This is generally called an insulated Cuk converter. In the insulated Cuk converter, a first inductor, a first capacitor, a switching element, and the like are provided on the primary side of the transformer, and a second inductor, a second capacitor, a rectifying element, and the like are provided on the secondary side of the transformer. Patent Document 1 and Patent Document 2 show circuit examples of such an insulating Cuk converter.

  The Cuk converter of Patent Document 1 is an insulating bidirectional converter capable of bidirectional voltage conversion between a low voltage side and a high voltage side. In this Cuk converter, during the discharge operation of the power storage unit, the DC voltage input to the low voltage side is boosted and output to the high voltage side, and during the charge operation of the power storage unit, the DC voltage input to the high voltage side is stepped down to a low voltage. Output to the side.

  The Cuk converter of Patent Document 2 is also an insulating bidirectional converter. In this Cuk converter, the switching elements on the primary side and the secondary side of the transformer are switched by synchronous rectification, and the charge / discharge current and charge / discharge voltage are controlled linearly at the time of charge / discharge switching. Can be switched continuously.

  In an insulated Cuk converter using a transformer, in the ON / OFF operation of the switching element, due to the high voltage generated by the leakage inductance of the primary winding of the transformer when the element is turned off, A large surge voltage is applied. For this reason, a switching element may be destroyed by a surge. Therefore, a high-breakdown-voltage switching element is used to protect against surge, but this causes a cost increase.

JP 2007-288941 A JP 2013-74779 A

  An object of the present invention is to provide an insulating Cuk converter that can suppress a surge that occurs when a switching element is turned off.

  An insulated Cuk converter according to a first aspect of the present invention includes a transformer having a primary winding and a secondary winding, an input terminal provided on the primary side of the transformer, and an output terminal provided on the secondary side of the transformer. A first inductor having one end connected to the input terminal, a first capacitor connected between the other end of the first inductor and one end of the primary winding, and a connection point between the first inductor and the first capacitor. A first switching element having one electrode connected and the other electrode connected to the other end of the primary winding; a second inductor having one end connected to the output terminal; the other end of the second inductor and the secondary winding A diode having one electrode connected to a connection point between the second capacitor connected to one end of the wire and the second inductor and the second capacitor, and the other electrode connected to the other end of the secondary winding; Insulated Cuk combiner with A motor, between one of the electrodes of one end and the first switching element of the first inductor, is provided with a surge suppression circuit for suppressing a surge generated at turn-off of the first switching element.

  According to such a configuration, when the first switching element is turned off, the high voltage generated due to the energy accumulated in the leakage inductance of the primary winding of the transformer is absorbed by the surge suppression circuit. For this reason, the surge voltage at the time of turn-off of the first switching element is suppressed, and the first switching element can be prevented from being destroyed by the surge. Therefore, it is not necessary to use a high breakdown voltage element as the first switching element, and the cost can be reduced.

  In the insulated Cuk converter according to the first invention, the surge suppression circuit may include a third switching element. In this configuration, when transmitting power from the primary side to the secondary side of the transformer, the first switching element performs a switching operation, and the third switching element is in an off state while the first switching element is on, When the first switching element is turned off, the third switching element is turned on with a time delay, and the third switching element is turned off before the first switching element is turned on.

  The insulated Cuk converter according to the second invention uses a second switching element having a rectifying function instead of the diode in the insulated Cuk converter according to the first invention. One electrode of the second switching element is connected to a connection point between the second inductor and the second capacitor, and the other electrode is connected to the other end of the secondary winding.

  In the insulated Cuk converter according to the second invention, the surge suppression circuit may include a third switching element. In this configuration, when power is transmitted from the primary side to the secondary side of the transformer, the first switching element and the second switching element perform a switching operation in synchronization. Further, while the first switching element is on, the third switching element is in an off state. When the first switching element is turned off, the third switching element is turned on with a time delay, and the first switching element is turned on. Before, the third switching element is turned off.

  In the first and second inventions, the surge suppression circuit further includes a third capacitor connected in series with the third switching element, and a closed loop circuit is formed by the third switching element, the third capacitor, and the first inductor. You may be made to do.

  An insulated Cuk converter according to a third aspect of the invention is provided with a first surge suppression circuit for the first switching element on the primary side and a second surge suppression circuit for the second switching element on the secondary side. Is.

  In the insulated Cuk converter according to the third invention, the first surge suppression circuit may include a third switching element, and the second surge suppression circuit may include a fourth switching element. In this configuration, when power is transmitted from the primary side to the secondary side of the transformer, the second switching element is always in an off state, and the first switching element performs a switching operation. While the first switching element is on, the third switching element is in an off state. When the first switching element is turned off, the third switching element is turned on with a time delay, and before the first switching element is turned on. The third switching element is turned off. Further, when power is transmitted from the secondary side to the primary side of the transformer, the first switching element is always in an off state, and the second switching element performs a switching operation. While the second switching element is on, the fourth switching element is in an off state. When the second switching element is turned off, the fourth switching element is turned on with a time delay, and before the second switching element is turned on. The fourth switching element is turned off.

  In the insulated Cuk converter according to the third invention, the first surge suppression circuit further includes a third capacitor connected in series with the third switching element, and the second surge suppression circuit is in series with the fourth switching element. A fourth capacitor connected may be further included. In this configuration, the third switching element, the third capacitor, and the first inductor form a first closed loop circuit, and the fourth switching element, the fourth capacitor, and the second inductor form a second closed loop circuit. .

  The power transmission control device according to the present invention includes the above-described insulated Cuk converter and a control unit that controls the operation of the insulated Cuk converter.

  ADVANTAGE OF THE INVENTION According to this invention, the insulation type Cuk converter which can suppress the surge which generate | occur | produces at the time of OFF of a switching element can be provided.

It is a circuit diagram of the insulation type Cuk converter concerning a 1st embodiment. It is a circuit diagram of the insulation type Cuk converter concerning a 2nd embodiment. It is a circuit diagram of the insulation type Cuk converter concerning a 3rd embodiment. It is the circuit diagram which showed the electric current path of 1st Embodiment. It is the circuit diagram which showed the electric current path of the comparative example. It is a wave form diagram for demonstrating a surge suppression effect. It is the circuit diagram which showed the electric current path after Q1 ON of 2nd Embodiment. It is the circuit diagram which showed the electric current path at the time of Q1 OFF of 2nd Embodiment. It is the circuit diagram which showed the electric current path at the time of Q3 ON of 2nd Embodiment. It is the circuit diagram which showed the electric current path at the time of Q2 ON of 2nd Embodiment. It is the circuit diagram which showed the electric current path after Q2 ON of 2nd Embodiment. It is the circuit diagram which showed the electric current path at the time of Q3 OFF of 2nd Embodiment. It is the circuit diagram which showed the electric current path at the time of Q2 OFF of 2nd Embodiment. It is the circuit diagram which showed the electric current path at the time of Q1 ON of 2nd Embodiment. It is a time chart which showed operation of a 2nd embodiment. It is the circuit diagram which showed the modification of 1st Embodiment. It is the circuit diagram which showed the modification of 2nd Embodiment. It is the circuit diagram which showed the modification of 3rd Embodiment.

  An embodiment of an insulated Cuk converter (hereinafter simply referred to as “Cuk converter”) according to the present invention will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same or corresponding parts.

  First, the configuration of the Cuk converter according to the first embodiment will be described with reference to FIG. In FIG. 1, a Cuk converter 100 is disposed between a primary side power source 1 and a secondary side power source 2. The primary power source 1 is composed of a direct current battery. The secondary power source 2 is composed of a capacitor or a rechargeable battery (secondary battery). A load may be connected instead of the secondary power source 2. The Cuk converter 100 is provided with input terminals T1 and T2 to which the primary power source 1 is connected and output terminals T3 and T4 to which the secondary power source 2 is connected. The operation of the Cuk converter 100 is controlled by the control unit 3. The control unit 3 includes a CPU, a PWM (pulse width modulation) signal generation circuit, and the like. The Cuk converter 100 and the control unit 3 are mounted on the same circuit board, and the power transmission control device 10 is configured by these components. The power transmission control device 10 is mounted on a vehicle, for example.

  The Cuk converter 100 includes a transformer TR having a primary winding W1 and a secondary winding W2. Each of the windings W1 and W2 is connected at a portion indicated by a broken line K, but this portion may be isolated (the same applies to FIGS. 2 and 3). On the primary side of the transformer TR, input terminals T1 and T2, an inductor L1 (first inductor), a capacitor C1 (first capacitor), a switching element Q1 (first switching element), a surge suppression circuit X, and a capacitor C5 are provided. It has been.

  One end of the inductor L1 is connected to the input terminal T1. A capacitor C1 is connected in series with the inductor L1 between the other end of the inductor L1 and one end of the primary winding W1. The switching element Q1 is made of an FET (field effect transistor) and has a diode D1 connected between the drain d and the source s. The drain d which is one electrode of the switching element Q1 is connected to a connection point between the inductor L1 and the capacitor C1, and the source s which is the other electrode is connected to the other end of the primary winding W1. The gate g of the switching element Q1 is connected to the control unit 3.

  The surge suppression circuit X is connected between one end of the inductor L1 and the drain d of the switching element Q1. The surge suppression circuit X is an active clamp circuit for suppressing a surge generated when the switching element Q1 is turned off, and includes a switching element Q3 (third switching element) and a capacitor C3 (first switch) connected in series with the element. 3 capacitors).

  The switching element Q3 is formed of an FET as in the switching element Q1, and includes a diode D3 connected between the drain d and the source s. The drain d of the switching element Q3 is connected to the capacitor C3, the source s is connected to the drain d of the switching element Q1, and the gate g is connected to the control unit 3. Switching element Q3, capacitor C3, and inductor L1 form a closed loop circuit.

  The capacitor C5 is a capacitor for removing noise of the input voltage, and is provided between the input terminals T1 and T2.

  On the secondary side of the transformer TR, output terminals T3 and T4, an inductor L2 (second inductor), a capacitor C2 (second capacitor), a diode D5, and a capacitor C6 are provided.

  One end of the inductor L2 is connected to the output terminal T3. A capacitor C2 is connected in series with the inductor L2 between the other end of the inductor L2 and one end of the secondary winding W2. The cathode that is one electrode of the diode D5 is connected to the connection point between the inductor L2 and the capacitor C2, and the anode that is the other electrode is connected to the other end of the secondary winding W2. The capacitor C6 is a capacitor for removing noise from the output voltage, and is provided between the output terminals T3 and T4.

  FIG. 2 shows a Cuk converter 200 according to the second embodiment. In the Cuk converter 200, a switching element Q2 (second switching element) is provided instead of the diode D5 of FIG.

  The switching element Q2 is formed of an FET as in the switching element Q1, and includes a diode D2 connected between the drain d and the source s. The drain d, which is one electrode of the switching element Q2, is connected to the connection point between the inductor L2 and the capacitor C2, and the source s, which is the other electrode, is connected to the other end of the secondary winding W2. The gate g of the switching element Q2 is connected to the control unit 3. The Cuk converter 200 and the control unit 3 constitute the power transmission control device 20. Other configurations are the same as those in FIG.

  FIG. 3 shows a Cuk converter 300 according to the third embodiment. In the Cuk converter 300, a surge suppression circuit Y is added to the configuration of FIG. The surge suppression circuit Y is connected between one end of the inductor L2 and the drain d of the switching element Q2. The surge suppression circuit Y is an active clamp circuit for suppressing a surge generated when the switching element Q2 is turned off, and includes a switching element Q4 (fourth switching element) and a capacitor C4 (first element) connected in series with the element. 4 capacitors).

  The switching element Q4 is made of an FET as with the switching element Q2, and has a diode D4 connected between the drain d and the source s. The drain d of the switching element Q4 is connected to the capacitor C4, the source s is connected to the drain d of the switching element Q2, and the gate g is connected to the control unit 3. Switching element Q4, capacitor C4, and inductor L2 form a closed loop circuit. The power transmission control device 30 is configured by the Cuk converter 300 and the control unit 3. Other configurations are the same as those in FIG.

  In the third embodiment, the surge suppression circuit X is a “first surge suppression circuit”, the surge suppression circuit Y is a “second surge suppression circuit”, a closed loop circuit formed by a switching element Q3, a capacitor C3, and an inductor L1. Is a “first closed loop circuit”, and the closed loop circuit formed by the switching element Q4, the capacitor C4, and the inductor L2 is a “second closed loop circuit”.

  In each of the embodiments described above, the diodes D1 to D4 provided in the switching elements Q1 to Q4 may be FET parasitic diodes or may be independent diodes. In any case, the switching elements Q1 to Q4 have a rectifying function by the diodes D1 to D4.

  Next, the operation of the Cuk converter of each embodiment described above will be described. First, the operation of the Cuk converter 100 of the first embodiment will be described with reference to FIGS. 1, 4 to 6, and 8. The thick arrows in FIGS. 4, 5, and 7A to 7H indicate current paths.

  A Cuk converter 100 shown in FIG. 1 is a unidirectional converter that transmits power from the primary side to the secondary side of the transformer TR. When transmitting electric power, the switching elements Q1 and Q3 perform a switching operation by the PWM signal output from the control unit 3. In this case, the Cuk converter 100 may perform either a step-up operation or a step-down operation.

  The on / off timings of the switching elements Q1 and Q3 are as shown in FIGS. 8A and 8B, for example. While the switching element Q1 is on, the switching element Q3 is in an off state. When the switching element Q1 is turned off, the switching element Q3 is turned on with a time delay. Thereafter, the switching element Q3 is turned off before the switching element Q1 is turned on. (FIG. 8 will be described in detail in a second embodiment to be described later.)

  When the switching element Q1 is switched from the on state of FIG. 4A to the off state of FIG. 4B, that is, when the switching element Q1 is turned off, the surge voltage applied between the drain d and the source s of the switching element Q1 is It becomes a problem. This surge voltage is generated due to the energy accumulated in the leakage inductance of the primary winding W1 of the transformer TR.

  However, since the surge suppression circuit X is provided in the present invention, when the switching element Q1 is turned off, the current based on the energy accumulated in the leakage inductance of the primary winding W1 of the transformer TR is the current of the surge suppression circuit X. It flows through the diode D3 and the capacitor C3. The current based on the energy stored in the inductor L1 flows through a closed loop circuit including the diode D3, the capacitor C3, and the inductor L1. As a result, as shown in FIG. 6B, the voltage between the drain d and the source s of the switching element Q1 is suppressed to a low level without becoming an excessive surge voltage. Therefore, it is not necessary to use a high breakdown voltage element as the switching element Q1, and the cost can be reduced.

  In the circuit of FIG. 5 shown as a comparative example, a surge suppression circuit is not provided. For this reason, when the switching element Q1 is switched from the ON state of FIG. 5A to the OFF state of FIG. 5B (at the time of turn-off), the energy accumulated in the leakage inductance of the primary winding W1 of the transformer TR is consumed. Current path is not formed. As a result, when the switching element Q1 is turned off, a large surge voltage is applied between the drain d and the source s of the switching element Q1, as shown in FIG.

  Next, the operation of the Cuk converter 200 of the second embodiment will be described with reference to FIGS. 2, 7A to 7H, and FIG.

  The Cuk converter 200 shown in FIG. 2 is a unidirectional converter that transmits power from the primary side to the secondary side of the transformer TR, similarly to the Cuk converter 100 of FIG. When transmitting electric power, the switching elements Q1 and Q3 perform a switching operation by the PWM signal output from the control unit 3. In this case, the Cuk converter 200 may perform either a step-up operation or a step-down operation.

  The secondary side switching element Q2 performs a switching operation in synchronization with the primary side switching element Q1 by the PWM signal output from the control unit 3. As a result, synchronous rectification is performed by the switching element Q2 and the diode D2 on the secondary side. Synchronous rectification has the advantages of lower power loss and higher conversion efficiency than diode rectification by the diode D5 as shown in FIG.

  The on / off timings of the switching elements Q1 to Q3 are as shown in FIGS. 8A to 8C, for example. While the switching element Q1 is on, the switching elements Q2 and Q3 are in the off state. When the switching element Q1 is off, the switching elements Q2 and Q3 are turned on with a time delay. Thereafter, the switching elements Q2 and Q3 are turned off before the switching element Q1 is turned on.

  FIG. 7A to FIG. 7H show circuit state transitions associated with turning on / off of the switching elements Q1 to Q3. In each figure, a thick arrow represents a current path. FIG. 8 shows the waveforms of the ON / OFF state of each switching element and the current (ds current) and voltage (ds voltage) between the drain and source of each switching element. Sections A to H in FIG. 8 correspond to FIGS. 7A to 7H, respectively.

  In FIG. 7A, the switching element Q1 is on and the switching elements Q2 and Q3 are off. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section A (left end) in FIG. On the primary side of the transformer TR, a current flows to the inductor L1 through the switching element Q1, and a discharge current of the capacitor C1 flows to the switching element Q1 and the primary winding W1. On the secondary side of the transformer TR, the discharge current of the capacitor C2 flows through the inductor L2 and the secondary winding W2.

  When the switching element Q1 is turned off from the state of FIG. 7A, the circuit state transitions to FIG. 7B. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section B in FIG. The switching element Q3 maintains the off state during the dead time τ in FIG. 8 (FIG. 8B). This is to prevent a short circuit between the input terminals T1 and T2 due to the switching elements Q1 and Q3 being simultaneously turned on. Further, the switching element Q2 also maintains the off state.

  7B, on the primary side of the transformer TR, when the switching element Q1 is turned off, the current based on the energy accumulated in the leakage inductance of the primary winding W1 of the transformer TR is the diode D3 and the capacitor C3 of the surge suppression circuit X. Flowing. The current based on the energy stored in the inductor L1 flows through a closed loop circuit including the diode D3, the capacitor C3, and the inductor L1. As a result, the capacitor C3 is charged. As a result, as shown in (d) of FIG. 8 (section B), the ds voltage of the switching element Q1 is suppressed to a low level without becoming an excessive surge voltage. As the energy stored in the leakage inductance of the primary winding W1 is released and charging of the capacitor C3 proceeds, the current flowing through the primary winding W1 of the transformer TR decreases. Along with this, on the secondary side of the transformer TR, a current starts to flow through the diode D2 of the switching element Q2.

  When the switching element Q3 is turned on from the state of FIG. 7B, the circuit state transitions to FIG. 7C. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section C in FIG. The switching element Q2 maintains the off state for a period of δ after the switching element Q3 is turned on.

  In FIG. 7C, on the primary side of the transformer TR, the current flowing through the diode D3 flows through the source s and drain d of the switching element Q3 in the on state. There is no change in the current path on the secondary side of the transformer TR.

  By the way, at the timing when the switching element Q3 is turned on in FIG. 8B, as shown in FIG. 8E, the ds voltage of the switching element Q3 is zero volts. That is, the switching element Q3 performs zero volt switching (ZVS) that turns on when the ds voltage is zero volt. ZVS is also called soft switching, and has an advantage that noise and loss generated in the switching element can be reduced.

  When the switching element Q2 is turned on from the state of FIG. 7C, the circuit state transitions to FIG. 7D. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section D in FIG. As can be seen from FIGS. 8C and 8F, the switching element Q2 is turned on by ZVS. In FIG. 7D, there is no change in the current path on the primary side of the transformer TR. On the secondary side of the transformer TR, the current flowing through the diode D2 flows through the source s and drain d of the switching element Q2 in the on state.

  When the discharge of the energy accumulated in the leakage inductance of the primary winding W1 of the transformer TR is finished from the state of FIG. 7D and the charging current of the capacitor C3 becomes zero, the energy accumulated in the capacitor C3 turns into a discharge, and the circuit The state changes to FIG. 7E. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section E in FIG. In FIG. 7E, on the primary side of the transformer TR, a current flows from the primary power source 1 through the inductor L1, the capacitor C1, and the primary winding W1. Further, a current flows through the capacitor C1 and the primary winding W1 due to the discharge of energy stored in the capacitor C3. On the secondary side of the transformer TR, a current flows through the secondary winding W2 and the switching element Q2. A current flows through the inductor L2 continuously through the switching element Q2.

  When the switching element Q3 is turned off from the state of FIG. 7E, the circuit state transitions to FIG. 7F. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section F of FIG. In FIG. 7F, on the primary side of the transformer TR, current continuously flows from the primary side power source 1 to the inductor L1, the capacitor C1, and the primary winding W1. Although no current flows through the switching element Q3, a current flows through the diode D1 of the switching element Q1 in order to maintain the exciting current flowing through the primary winding W1. As a result, the ds voltage of the switching element Q1 decreases to zero (FIG. 8 (d)). There is no change in the current path on the secondary side of the transformer TR.

  When the switching element Q2 is turned off from the state of FIG. 7F, the circuit state transitions to FIG. 7G. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section G in FIG. As can be seen from FIGS. 8C and 8F, the switching element Q2 is turned off by ZVS. In FIG. 7G, even when the switching element Q2 is turned off, a current flows through the diode D2. There is no change in the current path on the primary side of the transformer TR.

  When the switching element Q1 is turned on from the state of FIG. 7G, the circuit state transitions to FIG. 7H. At this time, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in a section H in FIG. As can be seen from FIGS. 8A and 8D, the switching element Q1 is turned on by ZVS. In FIG. 7H, on the primary side of the transformer TR, when the switching element Q1 is turned on, the current flowing through the diode D1 flows through the source s and drain d of the switching element Q1. There is no change in the current path on the secondary side of the transformer TR.

  When the current flowing through the source s / drain d of the switching element Q1 becomes zero from the state of FIG. 7H, the circuit state returns to FIG. 7A. In this process, the states, currents and voltages of the switching elements Q1 to Q3 are as shown in section A (third from the right) in FIG.

  As described above, in the Cuk converter 200, the transition of the circuit states of FIGS. 7A to 7H is repeated, and the electric power is transferred from the primary side to the secondary side of the transformer TR based on the on / off operation of the switching elements Q1 to Q3. Transmission takes place.

  According to the Cuk converter 200 of the second embodiment described above, the surge voltage at the turn-off of the switching element Q1 can be suppressed by providing the surge suppression circuit X as in the first embodiment. Further, by controlling the on / off timing of each switching element Q1 to Q3 as shown in FIG. 8, zero volt switching at the time of turning on or off of the switching element becomes possible, and noise and loss of the switching element are reduced. Can do.

  In the operation of the first embodiment described above and the operation of the third embodiment described later, the circuit state transition is basically the same as the circuit state transition in FIGS. 7A to 7H described above. Also in the first and third embodiments, zero volt switching is performed, so that the same effect as described above can be obtained.

  Next, the operation of the Cuk converter 300 of the third embodiment will be described with reference to FIG.

  The Cuk converter 300 shown in FIG. 3 is a bidirectional converter that can transmit power not only from the primary side to the secondary side of the transformer TR but also from the secondary side to the primary side of the transformer TR. It is. For this reason, the circuit configuration of the Cuk converter 300 is symmetrical with respect to the transformer TR. In the Cuk converter 300, when power is transmitted from the primary side to the secondary side, either the step-up operation or the step-down operation may be performed, and also when power is transmitted from the secondary side to the primary side, the step-up operation is performed. Either the operation or the step-down operation may be performed.

  When power is transmitted from the primary side to the secondary side, the switching element Q2 is always in an off state, and the switching elements Q1 and Q3 perform a switching operation. In this case, since the switching element Q4 is also in the OFF state, the secondary side circuit is equivalent to the secondary side circuit of the Cuk converter 100 in FIG. 1 (the diode D5 in FIG. 1 corresponds to the diode D2 in FIG. 3). ). Therefore, the operation in this case is basically the same as the operation of the Cuk converter 100, and the ON / OFF timings of the switching elements Q1 and Q3 are as shown in FIGS.

  When power is transmitted from the secondary side to the primary side, the switching element Q1 is always in an off state, and the switching elements Q2 and Q4 perform a switching operation. In this case, since the switching element Q3 is also in the OFF state, the primary side circuit is equivalent to a circuit obtained by horizontally inverting the secondary side circuit when power is transmitted from the primary side to the secondary side. And the control part 3 performs control similar to the control performed with respect to switching element Q1, Q3 in the case of transmitting electric power from the primary side to the secondary side with respect to switching element Q2, Q4.

  Therefore, the ON / OFF timing of the switching elements Q2 and Q4 can be easily understood by replacing Q1 and Q3 in FIGS. 8A and 8B with Q2 and Q4. Specifically, the switching element Q4 is in an off state while the switching element Q2 is on, and when the switching element Q2 is off, the switching element Q4 is turned on with a time delay. Thereafter, the switching element Q4 is turned off before the switching element Q2 is turned on.

  According to the above-described Cuk converter 300 of the third embodiment, the surge suppression circuits X and Y are provided on the primary side and the secondary side, respectively, so that the switching elements Q1 and Q2 can be used regardless of the direction in which power is transmitted. The surge voltage at the turn-off time can be suppressed.

  FIG. 9 shows a modification of the first embodiment (FIG. 1). In the Cuk converter 100 of FIG. 9, the switching element Q3 in the surge suppression circuit X of FIG. 1 is replaced with a diode D6. Other configurations are the same as those in FIG. 1, and the operations are basically the same as those in FIG. However, the control of the diode D6 by the control unit 3 is not performed. Thus, also when the diode D6 is used for the surge suppression circuit X, the same surge suppression effect as that of the first embodiment can be obtained.

  FIG. 10 shows a modification of the second embodiment (FIG. 2). In the Cuk converter 200 of FIG. 10, the switching element Q3 in the surge suppression circuit X of FIG. 2 is replaced with a diode D6. The other configuration is the same as that of FIG. 2, and the operation is basically the same as that of FIG. However, the control of the diode D6 by the control unit 3 is not performed. Thus, also when the diode D6 is used for the surge suppression circuit X, the same surge suppression effect as that of the second embodiment can be obtained.

  FIG. 11 shows a modification of the third embodiment (FIG. 3). In the Cuk converter 300 of FIG. 11, the switching elements Q3 and Q4 in the surge suppression circuits X and Y of FIG. 3 are replaced with diodes D6 and D7. The other configurations are the same as those in FIG. 3, and the operations are basically the same as those in FIG. However, the control of the diodes D6 and D7 by the control unit 3 is not performed. Thus, when the diodes D6 and D7 are used for the surge suppression circuits X and Y, the same surge suppression effect as that of the third embodiment can be obtained.

  In the present invention, the following various embodiments can be employed in addition to the above.

  In FIG. 8, the timing at which the switching element Q2 is turned on / off is delayed by the time δ from the timing at which the switching element Q3 is turned on / off, but this is not essential and δ = 0 may be possible. In FIG. 8, the timing at which the switching element Q2 is turned on / off and the timing at which the switching element Q3 is turned on / off may be reversed. Further, the switching element Q2 may be turned off at the same timing as the switching element Q1 is turned on, and may be turned on at the same timing as the switching element Q1 is turned off.

  In FIG. 3, when power is transmitted from the primary side to the secondary side, the switching element Q2 is always turned off. However, synchronous rectification is performed by switching the switching element Q2 in synchronization with the switching element Q1. May be. Similarly, when power is transmitted from the secondary side to the primary side, synchronous rectification may be performed by switching the switching element Q1 in synchronization with the switching element Q2.

  In each of the above-described embodiments, FETs are used for the switching elements Q1 to Q4. However, transistors or IGBTs may be used instead.

  In each of the embodiments described above, the switching elements Q1 to Q4 are driven by the PWM signal. However, the switching elements Q1 to Q4 may be driven by a signal other than the PWM signal.

  In each of the embodiments described above, the Cuk converter and the power transmission control device mounted on the vehicle are taken as an example. However, the present invention is not limited to the device for the vehicle, and power is supplied between the primary side and the secondary side. The present invention can be applied to all devices that perform transmission.

DESCRIPTION OF SYMBOLS 1 Primary side power supply 2 Secondary side power supply 3 Control part 10, 20, 30 Power transmission control apparatus 100, 200, 300 Insulation type Cuk converter C1 Capacitor (first capacitor)
C2 capacitor (second capacitor)
C3 capacitor (third capacitor)
C4 capacitor (4th capacitor)
D5 Diode L1 Inductor (first inductor)
L2 inductor (second inductor)
Q1 switching element (first switching element)
Q2 switching element (second switching element)
Q3 switching element (third switching element)
Q4 switching element (fourth switching element)
T1, T2 input terminal T3, T4 output terminal X Surge suppression circuit (first surge suppression circuit)
Y Surge suppression circuit (second surge suppression circuit)

Claims (9)

A transformer having a primary winding and a secondary winding;
An input terminal provided on the primary side of the transformer;
An output terminal provided on the secondary side of the transformer;
A first inductor having one end connected to the input terminal;
A first capacitor connected between the other end of the first inductor and one end of the primary winding;
A first switching element having one electrode connected to a connection point between the first inductor and the first capacitor and the other electrode connected to the other end of the primary winding;
A second inductor having one end connected to the output terminal;
A second capacitor connected between the other end of the second inductor and one end of the secondary winding;
In an insulated Cuk converter, comprising: a diode having one electrode connected to a connection point between the second inductor and the second capacitor, and the other electrode connected to the other end of the secondary winding;
An insulated Cuk characterized in that a surge suppression circuit is provided between one end of the first inductor and one electrode of the first switching element to suppress a surge generated when the first switching element is turned off. converter. A transformer having a primary winding and a secondary winding;
A pair of input terminals provided on the primary side of the transformer;
A pair of output terminals provided on the secondary side of the transformer;
A first inductor having one end connected to the input terminal;
A first capacitor connected between the other end of the first inductor and one end of the primary winding;
A first switching element having one electrode connected to a connection point between the first inductor and the first capacitor and the other electrode connected to the other end of the primary winding;
A second inductor having one end connected to the output terminal;
A second capacitor connected between the other end of the second inductor and one end of the secondary winding;
A second switching element having a rectifying function, wherein one electrode is connected to a connection point between the second inductor and the second capacitor, and the other electrode is connected to the other end of the secondary winding. Insulated Cuk converter
An insulated Cuk characterized in that a surge suppression circuit is provided between one end of the first inductor and one electrode of the first switching element to suppress a surge generated when the first switching element is turned off. converter. A transformer having a primary winding and a secondary winding;
An input terminal provided on the primary side of the transformer;
An output terminal provided on the secondary side of the transformer;
A first inductor having one end connected to the input terminal;
A first capacitor connected between the other end of the first inductor and one end of the primary winding;
A first switching element having a rectifying function, in which one electrode is connected to a connection point between the first inductor and the first capacitor, and the other electrode is connected to the other end of the primary winding;
A second inductor having one end connected to the output terminal;
A second capacitor connected between the other end of the second inductor and one end of the secondary winding;
A second switching element having a rectifying function, wherein one electrode is connected to a connection point between the second inductor and the second capacitor, and the other electrode is connected to the other end of the secondary winding. Insulated Cuk converter
A first surge suppression circuit is provided between one end of the first inductor and one electrode of the first switching element to suppress a surge that is generated when the first switching element is turned off.
Insulation characterized in that a second surge suppression circuit is provided between one end of the second inductor and one electrode of the second switching element to suppress a surge generated when the second switching element is turned off. Type Cuk converter. In the insulated Cuk converter according to claim 1,
The surge suppression circuit includes a third switching element,
When transmitting power from the primary side to the secondary side of the transformer, the first switching element performs a switching operation,
While the first switching element is on, the third switching element is in an off state,
When the first switching element is turned off, the third switching element is turned on with a time delay,
The insulated Cuk converter, wherein the third switching element is turned off before the first switching element is turned on. In the insulated Cuk converter according to claim 2,
The surge suppression circuit includes a third switching element,
When transmitting power from the primary side to the secondary side of the transformer, the first switching element and the second switching element perform a switching operation synchronously,
While the first switching element is on, the third switching element is in an off state,
When the first switching element is turned off, the third switching element is turned on with a time delay,
The insulated Cuk converter, wherein the third switching element is turned off before the first switching element is turned on. In the insulated Cuk converter according to claim 3,
The first surge suppression circuit includes a third switching element,
The second surge suppression circuit includes a fourth switching element,
When transmitting power from the primary side to the secondary side of the transformer, the second switching element is always in an off state, and the first switching element performs a switching operation,
While the first switching element is on, the third switching element is in an off state,
When the first switching element is turned off, the third switching element is turned on with a time delay,
Before the first switching element is turned on, the third switching element is turned off,
When transmitting power from the secondary side of the transformer to the primary side, the first switching element is always in an off state, and the second switching element performs a switching operation,
While the second switching element is on, the fourth switching element is in an off state,
When the second switching element is turned off, the fourth switching element is turned on with a time delay,
The insulated Cuk converter, wherein the fourth switching element is turned off before the second switching element is turned on. In the insulated Cuk converter according to claim 4 or 5,
The surge suppression circuit further includes a third capacitor connected in series with the third switching element,
A closed loop circuit is formed by the third switching element, the third capacitor, and the first inductor. In the insulated Cuk converter according to claim 6,
The first surge suppression circuit further includes a third capacitor connected in series with the third switching element,
The second surge suppression circuit further includes a fourth capacitor connected in series with the fourth switching element,
A first closed loop circuit is formed by the third switching element, the third capacitor, and the first inductor,
An insulated Cuk converter, wherein a second closed loop circuit is formed by the fourth switching element, the fourth capacitor, and the second inductor. An insulated Cuk converter according to any one of claims 1 to 8,
And a control unit that controls the operation of the insulated Cuk converter.

Images