Output stabilizing circuit and DCDC converter circuit

Abstract

An output stabilizing circuit (1) includes a primary side circuit (2) including a self-oscillating circuit (10) connected to a DC power supply, and a secondary side circuit (3) obtaining an output voltage by oscillation of the self-oscillating circuit, wherein the self-oscillating circuit has a drive transformer whose secondary side coil is connected to a gate electrode of each of a plurality of switching elements connected in half-bridge or full-bridge, a feedback transformer whose primary side coil is connected to a power transmission coil, and a phase shift filter connected between a secondary side coil of the feedback transformer and a primary side coil of the drive transformer, the phase shift filter including a primary side control coil having a characteristic in which an inductance changes according to a current flowing in a secondary side control coil of the secondary side circuit.

Description

Technical Field

[0001] This invention relates to a self-oscillating circuit and a DC-to-DC converter circuit. Background Technology

[0002] Current resonant DC-DC converters use an externally excited method where control circuits, such as control ICs, provide on / off signals to the switching elements.

[0003] Patent Document 1 discloses a DC-DC converter formed by connecting a series circuit of switching elements 1 and 2 to a DC power supply, and connecting a series circuit of capacitor 3 and the primary winding 5 of transformer 4 in parallel with switching element 2. In this DC-DC converter, a tertiary winding 6 and a quaternary winding 7 are further added to transformer 4. The tertiary winding 6 provides an on / off signal to switching element 2, and the quaternary winding 7 is used as the power supply winding for control circuit 18. The control circuit 18 detects the switching timing of the positive and negative values ​​of the quaternary winding voltage and provides an on / off signal to switching element 1 at that timing. By shortening the on-time of switching element 1 in this way, ineffective current is reduced.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2002-209381 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, the aforementioned self-excited oscillation circuit requires a control circuit, which complicates the circuit.

[0009] This invention provides a series resonant self-excited oscillation circuit technology that stabilizes the output voltage with a simple circuit structure.

[0010] Solution for solving the problem

[0011] According to the present invention, an output stabilization circuit is provided, comprising a primary side circuit and a secondary side circuit. The primary side circuit includes a self-excited oscillation circuit connected to a DC power supply. The secondary side circuit obtains an output voltage through the oscillation of the self-excited oscillation circuit. The self-excited oscillation circuit includes: a power supply coil; a resonant capacitor connected in series with the power supply coil, forming a series resonant circuit together with the power supply coil; a switching circuit including a plurality of switching elements connected in a half-bridge or full-bridge configuration, configured to switch the direction of current flowing in the power supply coil according to the on / off state of the plurality of switching elements; and a drive transformer, the secondary side coil of which is connected to the plurality of switching elements. The gate electrodes of each of the switching elements are respectively connected; a feedback transformer, the primary winding of which is connected to the power supply coil; and a phase-shifting filter connected between the secondary winding of the feedback transformer and the primary winding of the drive transformer, the secondary winding circuit having: a receiving coil magnetically coupled to the power supply coil; and a secondary control coil, the magnitude of the current flowing in the secondary control coil being controlled according to the magnitude of the output voltage, the phase-shifting filter including a primary control coil magnetically coupled to the secondary control coil, the primary control coil having an inductance that changes according to the current flowing in the secondary control coil.

[0012] The effects of the invention

[0013] Based on the above method, a series resonant self-excited oscillation circuit technology that stabilizes the output voltage with a simple circuit structure can be provided. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of the power supply circuit in the first embodiment.

[0015] Figure 2 This is a circuit diagram of the power supply circuit in the second embodiment.

[0016] Figure 3 This is a circuit diagram of the secondary side circuit of the power supply circuit in Example 1.

[0017] Figure 4 This is a graph showing the results of simulating voltage changes at various points in the power supply circuit of Example 1.

[0018] Figure 5 This is a graph showing the results of simulating voltage changes at various points in the power supply circuit of Example 1. Detailed Implementation

[0019] Hereinafter, examples of preferred embodiments of the present invention (hereinafter referred to as this embodiment) will be described. Furthermore, the embodiments listed below are merely illustrative, and the present invention is not limited to the structure of the following embodiments.

[0020] [First Implementation Method]

[0021] Figure 1 This is a circuit diagram of the power supply circuit 1 in the first embodiment.

[0022] The power supply circuit 1 is a circuit that includes a primary-side circuit 2 having a battery device BT and a secondary-side circuit 3 that obtains power from the primary-side circuit 2, and stably provides an output to a load connected to the secondary-side circuit 3. In the first embodiment, an example is shown where the battery device BT is configured as a battery device supplying DC power, the secondary-side circuit 3 includes a DC-DC conversion circuit, and the power supply circuit 1 as a whole functions as a DC-DC converter circuit.

[0023] [Primary side circuit]

[0024] The primary side circuit 2 includes a battery device BT, a fuse FU, a capacitor C1, and a self-excited oscillation circuit 10.

[0025] In the event of an excessive current generated due to an abnormality in the self-excited oscillation circuit 10 of the primary side circuit 2, the fuse FU disconnects the battery device BT from the primary side circuit 2. This prevents abnormal heating of the battery device BT caused by the excessive current.

[0026] Capacitor C1 absorbs the voltage changes caused by the charging and discharging of the battery device BT.

[0027] The self-excited oscillation circuit 10 has resistors R11, R12, R13, and R14 connected in series. Resistors R11, R12, R13, and R14 are connected in parallel with the battery device BT, applying bias voltages to the gates of transistors Q11 and Q12. Resistors R11, R12, R13, and R14 can be referred to as a bias circuit.

[0028] Capacitor C11 is connected in parallel with resistor R12, and capacitor C12 is connected in parallel with resistor R14. Capacitors C11 and C12 act as bypass capacitors, decoupling the AC component of the power (drive signal) induced in the drive coils Ld1 and Ld2, which serve as the secondary windings of the drive transformer DT (described later), thereby applying a stable voltage to the gates of transistors Q11 and Q12.

[0029] The self-excited oscillation circuit 10 also has two transistors Q11 and Q12 connected in a half-bridge configuration. Transistors Q11 and Q12 are FETs (Field Effect Transistors), which are switching elements.

[0030] The source of transistor Q11 is connected to the drain of transistor Q12. The drain of transistor Q11 is connected to the positive terminal of battery device BT, and the source of transistor Q12 is connected to the negative terminal of battery device BT.

[0031] The gates of transistors Q11 and Q12 are connected to the bias circuit described above via the secondary winding of the drive transformer DT, which will be described later. Specifically, the output of resistor R11 is connected to resistor R12 and drive winding Ld1, which serves as the secondary winding of the drive transformer DT, and the output of resistor R13 is connected to resistor R14 and drive winding Ld2, which serves as the secondary winding of the drive transformer DT.

[0032] Additionally, resistors R15 or R16 are connected between the gate and source of transistors Q11 and Q12. Resistors R15 and R16 discharge the charge of the electrostatic capacitance (Ciss) between the gate and source of transistors Q11 and Q12, thereby increasing the turn-off time of transistors Q11 and Q12.

[0033] Thus, the self-excited oscillation circuit 10 is configured to switch the direction of the current flowing in the power supply coil L11 (described later) according to the on / off states of transistors Q11 and Q12, and can be described as a switching circuit including transistors Q11 and Q12.

[0034] The self-excited oscillation circuit 10 also includes a power supply coil L11 and a resonant capacitor C15 connected in series. The power supply coil L11 and the resonant capacitor C15 together form a series resonant circuit.

[0035] This series resonant circuit is connected to the source of transistor Q11 and positioned between the drain and source of transistor Q12. Thus, when transistor Q11 is on and transistor Q12 is off, current flows from the resonant capacitor C15 towards the power supply coil L11. Conversely, when transistor Q11 is off and transistor Q12 is on, the current flows from the power supply coil L11 towards the resonant capacitor C15 due to the power stored in the resonant capacitor C15.

[0036] The transmitting coil L11 is magnetically coupled to the receiving coil L31 of the secondary circuit 3 to form the main transformer MT. As a result, the oscillating power generated by the self-excited oscillation circuit 10 is transmitted from the transmitting coil L11, which is the primary coil of the main transformer MT, to the receiving coil L31, which is the secondary coil of the main transformer MT.

[0037] The self-excited oscillation circuit 10 also has a feedback transformer CT and a drive transformer DT.

[0038] The feedback transformer CT consists of a feedback coil Lf1, which serves as the primary winding, and a feedback coil Lf2, which serves as the secondary winding. That is, the feedback coils Lf1 and Lf2 are magnetically coupled.

[0039] Feedback coil Lf1 is connected in series with power transmission coil L11 and resonant capacitor C15. Feedback transformer CT is a current transformer that detects the alternating current generated on the primary side of main transformer MT through feedback coil Lf1 and transmits it to feedback coil Lf2. In feedback transformer CT, the number of turns in feedback coil Lf1 (the primary winding) is smaller than the number of turns in feedback coil Lf2 (the secondary winding). The current flowing in feedback coil Lf1 is converted into a smaller current and induced in feedback coil Lf2.

[0040] The feedback coil Lf2 is connected to the phase-shifting filter F10.

[0041] The drive transformer DT consists of a drive coil Ld3 as the primary winding and drive coils Ld1 and Ld2 as the secondary windings. That is, drive coil Ld3 is magnetically coupled to drive coils Ld1 and Ld2.

[0042] The drive coil Ld3 is connected to the phase-shifting filter F10. One side of the drive coil Ld1 is connected to the gate of transistor Q11, and the other side is connected to the output of resistor R11 and the input of resistor R12. One side of the drive coil Ld2 is connected to the gate of transistor Q12, and the other side is connected to the output of resistor R13 and the input of resistor R14.

[0043] In addition, such as Figure 1 As shown, the drive coils Ld1 and Ld2 are connected in such a way that the polarities of the drive coils are opposite to those of the gates of transistors Q11 or Q12.

[0044] Thus, in this embodiment, the output of the drive transformer DT is applied to the gates of transistors Q11 and Q12, and the switching timing of transistors Q11 and Q12 is obtained by the drive transformer DT.

[0045] The phase-shifting filter F10 is connected between the feedback coil Lf2, which is the secondary winding of the feedback transformer CT, and the drive coil Ld3, which is the primary winding of the drive transformer DT.

[0046] The phase-shifting filter F10 consists of a resistive element Rf, a control coil Lc1, and a capacitor Cf, and can also be described as an RLC filter. Figure 1In the example, the resistive element Rf and the control coil Lc1 are connected in parallel with the feedback coil Lf2 and the drive coil Ld3, and the capacitor Cf is connected in series with the feedback coil Lf2 and the drive coil Ld3.

[0047] With this structure, the phase-shifting filter F10 applies the AC voltage applied to the resistive element Rf according to the AC current generated in the feedback coil Lf2 to the drive coil Ld3, which is the primary winding of the drive transformer DT, in a phase-shifted manner.

[0048] Here, the phase of the AC voltage applied to the drive coil Ld3 is offset from the phase of the output of the secondary coil of the feedback transformer CT by a phase shift amount corresponding to the polarity of the feedback coil Lf2 and the drive coil Ld3, the filter constant of the phase shift filter F10, etc.

[0049] The phase shift amount of the phase shift filter F10 can be changed according to the filter constant of the phase shift filter F10, such as the resistance value of the resistor element Rf, the inductance of the control coil Lc1, and the capacitance of the capacitor Cf. In this embodiment, the inductance of the control coil Lc1 can be changed according to the output voltage of the secondary side circuit 3, so the phase shift amount of the phase shift filter F10 is also set to be variable.

[0050] Specifically, the control coil Lc1 of the phase-shifting filter F10 and the control coil Lc31 of the secondary circuit 3 (described later) constitute a control transformer FT, which has the characteristic that its inductance changes according to the current flowing in the control coil Lc31. Hereafter, the control coil Lc1 of the phase-shifting filter F10 included in the primary circuit 2 is sometimes referred to as the primary-side control coil Lc1, and the control coil Lc31 included in the secondary circuit 3 is sometimes referred to as the secondary-side control coil Lc31.

[0051] [Secondary side circuit]

[0052] The secondary side circuit 3 includes a receiving coil L31, a rectifier circuit SR30, and a reference voltage circuit RV30.

[0053] As described above, the receiving coil L31 serves as the secondary coil of the primary coil L11 to form the main transformer MT, and generates an induced electromotive force through the current in the primary coil L11.

[0054] The rectifier circuit SR30 is connected to the receiving coil L31. SR30 consists of a bridge rectifier circuit composed of diodes D31, D32, D33, and D34, and a smoothing filter composed of coil L32 and capacitor C31. SR30 functions as a full-wave rectifier circuit. That is, SR30 performs full-wave rectification and smoothing of the AC voltage generated in the receiving coil L31 to convert the AC voltage into DC voltage.

[0055] The reference voltage circuit RV30 is a circuit that includes resistors R31 and R32 and a voltage regulator Ic31, used to stabilize the output voltage from the secondary side circuit 3 to a level above the reference voltage.

[0056] The voltage regulator element Ic31 receives the input voltage after the output voltage is divided by resistors R31 and R32 at the reference terminal, and controls the voltage between the reference terminal and the anode to be the reference voltage.

[0057] In addition, the reference voltage circuit RV30 also has a secondary-side control coil Lc31.

[0058] A current flows in the secondary-side control coil Lc31, corresponding to the voltage control of the regulator element Ic31. That is, when the output voltage is higher than the reference voltage, the current flowing in the secondary-side control coil Lc31 increases, and when the output voltage is lower than the reference voltage, the current flowing in the secondary-side control coil Lc31 decreases.

[0059] The secondary control coil Lc31 is magnetically coupled to the primary control coil Lc1 via the control transformer FT, as described above, and is designed to change the inductance of the primary control coil Lc1 according to the amount of current flowing in the secondary control coil Lc31.

[0060] The primary-side control coil Lc1 and the secondary-side control coil Lc31 are wound as primary and secondary windings on a common core to form a transformer with a single magnetic circuit. Furthermore, this transformer is configured, for example, with the following inductance-DC superposition characteristic: the larger the DC current flowing in the secondary-side control coil Lc31, the greater the rate of inductance reduction of the primary-side control coil Lc1. Therefore, according to the characteristics of an RLC filter, the larger the inductance value of the primary-side control coil Lc1 of the phase-shifting filter F10, the greater the phase shift.

[0061] With this structure, the phase shift of the phase-shifting filter F10 can be increased or decreased according to the output voltage from the secondary side circuit 3. By changing the driving timing of the accompanying transistors Q11 and Q12, the oscillation frequency of the primary side of the main transformer MT can be made closer to or further away from the resonant frequency, thereby stabilizing the output voltage from the secondary side circuit 3.

[0062] 〔action〕

[0063] The operation of the power supply circuit 1 having the structure described above in the first embodiment will now be explained.

[0064] In the primary side circuit 2, when DC power is supplied from the battery device BT to the resistors R11, R12, R13, and R14, which serve as the bias circuit, the voltage after voltage division by the resistors in the bias circuit is applied as the bias voltage to the gates of transistors Q11 and Q12 respectively. As a result, one of transistors Q11 and Q12 first becomes the conducting state.

[0065] At this time, with transistor Q11 in the on state and transistor Q12 in the off state, current flows through the drain-source of transistor Q11, capacitor C15, power supply coil L11, and feedback coil Lf1, powered by the power supplied from the battery device BT. This current becomes the primary-side leakage inductance of the main transformer MT and the resonant current of capacitor C15, at which point capacitor C15 is charged.

[0066] A magnetic field is generated in the main transformer MT by the current flowing in the primary coil L11, and an induced electromotive force is generated in the secondary coil L31. The output impedance can be set according to the winding ratio of the primary coil L11 to the secondary coil L31 regarding the induced electromotive force generated in the secondary coil L31.

[0067] In addition, the current flowing in the feedback coil Lf1, which is the primary coil of the feedback transformer CT, also induces a current in the feedback coil Lf2, which is the secondary coil of the feedback transformer CT. A voltage is applied to the resistive element Rf based on the current induced in the feedback coil Lf2, and this voltage is applied to the drive coil Ld3 with its phase out of phase by the phase-shifting filter F10.

[0068] When power is supplied to drive coil Ld3, which serves as the primary coil of drive transformer DT, a magnetic field is generated in drive transformer DT, inducing an electromotive force in drive coils Ld1 and Ld2, which serve as secondary coils. As described above, drive coils Ld1 and Ld2 are configured with opposite polarities relative to the gate of transistor Q11 or Q12; therefore, the voltages induced in drive coils Ld1 and Ld2 are out of phase.

[0069] Therefore, when a negative voltage is applied to transistor Q11 and the bias voltage applied to transistor Q11 is below the threshold voltage, transistor Q11 becomes off. On the other hand, when a positive voltage is applied to transistor Q12 and the bias voltage applied to transistor Q12 exceeds the threshold voltage, transistor Q12 becomes on. That is, the on / off states of transistors Q11 and Q12 are switched.

[0070] When transistor Q11 is off and transistor Q12 is on, the power charged to capacitor C15 causes current to flow in the opposite direction to the above situation in the path between the drain and source of transistor Q12, the feedback coil Lf1, the power supply coil L11, and capacitor C15. This current also becomes the primary-side leakage inductance of the main transformer MT and the resonant current of capacitor C15.

[0071] Thus, in the primary side circuit 2, by alternating between the on and off states of transistors Q11 and Q12, currents with different directions flow alternately in the power supply coil L11 and the feedback coil Lf1.

[0072] Through the operation of the primary circuit 2, a magnetic field is generated in the main transformer MT, and an AC voltage is induced in the receiving coil L31, which serves as the secondary coil in the secondary circuit 3.

[0073] In the secondary side circuit 3, the AC voltage generated in the receiving coil L31 is input to the rectifier circuit SR30, and is converted into a DC voltage by full-wave rectification and smoothing. This DC voltage is input to the reference voltage circuit RV30, thereby controlling the output voltage to the reference voltage and outputting it through the voltage regulator element Ic31.

[0074] At this time, a current corresponding to the output voltage flows in the secondary-side control coil Lc31. The inductance of the primary-side control coil Lc1, which is magnetically coupled to the secondary-side control coil Lc31, changes according to this current. As the inductance of the primary-side control coil Lc1 changes, the phase shift of the phase-shifting filter F10 changes.

[0075] In this embodiment, when the output voltage is higher than the reference voltage, the current flowing in the secondary-side control coil Lc31 increases, the inductance of the primary-side control coil Lc1 decreases, and the phase shift of the phase-shifting filter F10 increases. On the other hand, when the output voltage is lower than the reference voltage, the current flowing in the secondary-side control coil Lc31 decreases, the inductance of the primary-side control coil Lc1 increases, and the phase shift of the phase-shifting filter F10 decreases.

[0076] When the phase shift of the phase-shift filter F10 increases, the driving timing of the output driving transistors Q11 and Q12 based on the drive transformer DT is advanced (the self-oscillation frequency increases), and the oscillation frequency on the primary side of the main transformer MT deviates from the resonant frequency. As a result, the output voltage from the secondary side circuit 3 decreases. On the other hand, when the phase shift of the phase-shift filter F10 decreases, the driving timing of the output driving transistors Q11 and Q12 based on the drive transformer DT is delayed (the self-oscillation frequency decreases), and the oscillation frequency on the primary side of the main transformer MT approaches the resonant frequency. As a result, the output voltage from the secondary side circuit 3 increases.

[0077] Therefore, according to this embodiment, unlike externally excited oscillating circuits, a series resonant self-excited oscillating circuit capable of stabilizing the output voltage can be implemented with a simple circuit structure. Thus, the power supply circuit 1 in this embodiment can be described as an output stabilization circuit.

[0078] [Second Implementation]

[0079] Figure 2 This is a circuit diagram of the power supply circuit 1 in the second embodiment.

[0080] The power supply circuit 1 in the second embodiment differs from the power supply circuit 1 in the first embodiment in that the switching circuit in the primary side circuit 2 includes transistors Q11, Q12, Q21, and Q22 that are connected in a full-bridge configuration.

[0081] The power supply circuit 1 in the second embodiment will now be described with a focus on the differences from the first embodiment, while omitting some of the same features as in the first embodiment.

[0082] In the second embodiment, the self-excited oscillation circuit 10 further includes resistors R21, R22, R23, and R24 connected in series. Resistors R21, R22, R23, and R24 are connected in parallel with the battery device BT, applying bias voltages to the gates of transistors Q21 and Q22. Similar to resistors R11, R12, R13, and R14, resistors R21, R22, R23, and R24 can also be referred to as a bias circuit.

[0083] Capacitor C21 is connected in parallel with resistor R22, and capacitor C22 is connected in parallel with resistor R24. Capacitors C21 and C22 act as bypass capacitors, decoupling the AC component of the power (drive signal) induced in the drive coils Ld4 and Ld5, which are the secondary windings of the drive transformer DT, to apply a stable voltage to the gates of transistors Q21 and Q22.

[0084] In the second embodiment, the self-excited oscillation circuit 10 also has four transistors Q11, Q12, Q21, and Q22 connected in a full-bridge configuration. Transistors Q11, Q12, Q21, and Q22 are FETs (Field Effect Transistors), which are switching elements.

[0085] The connection method of transistors Q11 and Q12 with other circuit structures is the same as that in the first embodiment.

[0086] The source of transistor Q21 is connected to the drain of transistor Q22. The drain of transistor Q21 is connected to the positive terminal of battery device BT, and the source of transistor Q22 is connected to the negative terminal of battery device BT.

[0087] The gates of transistors Q21 and Q22 are connected to the aforementioned bias circuit via the secondary winding of the drive transformer DT. Specifically, the output of resistor R21 is connected to resistor R22 and drive winding Ld4, which serves as the secondary winding of the drive transformer DT, and the output of resistor R23 is connected to resistor R24 ​​and drive winding Ld5, which serves as the secondary winding of the drive transformer DT.

[0088] Additionally, resistors R25 and R26 are connected between the gate and source of transistors Q21 and Q22. Resistors R25 and R26 discharge the charge of the electrostatic capacitance (Ciss) between the gate and source of transistors Q21 and Q22, thereby increasing the turn-off time of transistors Q21 and Q22.

[0089] In the second embodiment, the direction of the current flowing in the power supply coil L11 (described later) is switched according to the on / off states of transistors Q11, Q12, Q21, and Q22. The self-excited oscillation circuit 10 can be described as having a switching circuit including transistors Q11, Q12, Q21, and Q22 that are connected in a full bridge configuration.

[0090] In the second embodiment, the drive transformer DT consists of a drive coil Ld3 as the primary winding and drive coils Ld1, Ld2, Ld4, and Ld5 as secondary windings. That is, drive coil Ld3 is magnetically coupled to drive coils Ld1, Ld2, Ld4, and Ld5.

[0091] One side of the drive coil Ld4 is connected to the gate of transistor Q21, and the other side is connected to the output terminal of resistor R21 and the input terminal of resistor R22. One side of the drive coil Ld5 is connected to the gate of transistor Q22, and the other side is connected to the output terminal of resistor R23 and the input terminal of resistor R24.

[0092] In addition, such as Figure 2As shown, the drive coils Ld4 and Ld5 are connected in such a way that the polarities of the drive coils are opposite to those of the gates of transistors Q21 or Q22. Further, the drive coils Ld1 and Ld5 are connected in such a way that the pairs of drive coils have the same polarity relative to the gates of transistors Q11 or Q22; the drive coils Ld2 and Ld4 are connected in such a way that the pairs of drive coils Ld1 and Ld5 and Ld2 and Ld4 have opposite polarities relative to their respective gates, so that the pairs of transistors Q11 and Q22, and the pairs of transistors Q12 and Q21, are in the same on or off state.

[0093] Thus, in the second embodiment, the output of the drive transformer DT is applied to the gates of transistors Q11, Q12, Q21 and Q22, and the switching timing of transistors Q11, Q12, Q21 and Q22 is obtained by the drive transformer DT.

[0094] 〔action〕

[0095] The operation of the power supply circuit 1 having the structure described above in the second embodiment will now be explained.

[0096] In the primary side circuit 2, when DC power is supplied from the battery device BT to the resistive elements R11, R12, R13, R14, R21, R22, R23, and R24, which serve as the bias circuit, the voltage obtained by voltage division by each resistive element in the bias circuit is applied as the bias voltage to the gates of transistors Q11, Q12, Q21, and Q22 respectively. As a result, one of the pairs of transistors Q11 and Q22, or one of the pairs of transistors Q12 and Q21, becomes the conducting state first.

[0097] At this time, with transistors Q11 and Q22 in the on state and transistors Q12 and Q21 in the off state, current flows through the path of transistor Q11 (drain-source), capacitor C15, power supply coil L11, feedback coil Lf1, and transistor Q22 (drain-source) supplied by the battery device BT. This current becomes the primary-side leakage inductance of the main transformer MT and the resonant current of capacitor C15.

[0098] Similar to the first embodiment, when power is supplied to drive coil Ld3, which serves as the primary coil of drive transformer DT, a magnetic field is generated in drive transformer DT, inducing an electromotive force in drive coils Ld1, Ld2, Ld4, and Ld5, which serve as secondary coils. As described above, the pairs of drive coils Ld1 and Ld5 are connected to the pairs of drive coils Ld2 and Ld4 in such a way that the polarities between the pairs are opposite with respect to each gate. Therefore, the power induced in the pairs of drive coils Ld1 and Ld5 is out of phase with respect to the pairs of drive coils Ld2 and Ld4.

[0099] Therefore, when a negative voltage is applied to transistors Q11 and Q22, and the bias voltage applied to transistors Q11 and Q22 is below the threshold voltage, transistors Q11 and Q22 become off. On the other hand, when a positive voltage is applied to transistors Q12 and Q21, and the bias voltage applied to transistors Q12 and Q21 exceeds the threshold voltage, transistors Q12 and Q21 become on.

[0100] When transistors Q11 and Q22 are in the off state and transistors Q12 and Q21 are in the on state, current flows in the opposite direction to the above situation in the paths of the drain-source of transistor Q12, the drain-source of transistor Q21, the feedback coil Lf1, the power supply coil L11, and capacitor C15. This current also becomes the primary-side leakage inductance of the main transformer MT and the resonant current of capacitor C15.

[0101] Thus, in the primary side circuit 2, by alternating between the on and off states of the pairs of transistors Q11 and Q22 and the pairs of transistors Q12 and Q21, currents with different directions flow alternately in the power supply coil L11 and the feedback coil Lf1.

[0102] Furthermore, other operations are the same as in the first embodiment, so the description is omitted.

[0103] Therefore, in the second embodiment, similar to the first embodiment, unlike the externally excited oscillating circuit, a control circuit is not required, and a series resonant self-excited oscillating circuit that can stabilize the output voltage can be realized with a simple circuit structure.

[0104] The following examples illustrate the above content in further detail. However, the description of the following examples does not impose any limitation on the above content.

[0105] Example

[0106] The embodiments show the results obtained by verifying the effects of the first embodiment described above through simulation.

[0107] Figure 3This is a circuit diagram of the secondary side circuit 3 of the power supply circuit 1 in Embodiment 1.

[0108] In the simulation of Example 1, the inductance control of the primary control coil Lc1 based on the magnetic coupling between the primary control coil Lc1 and the secondary control coil Lc31 is not performed. Instead, the inductance value of the primary control coil Lc1 is set virtually by manual means.

[0109] Therefore, the reference voltage circuit RV30 is not provided in the secondary side circuit 3, but a load resistor RO is connected instead. Furthermore, the primary side circuit 2 is connected to... Figure 1 The first embodiment shown has the same structure.

[0110] Figure 4 and Figure 5 This is a graph showing the results of simulating voltage changes at various points in the power supply circuit 1 of Embodiment 1. Figure 4 and Figure 5 In the figure, (a) shows the simulation results when the inductance value of the primary side control coil Lc1 is set to a first value, and (b) shows the simulation results when the inductance value of the primary side control coil Lc1 is set to a second value that is smaller than the first value.

[0111] exist Figure 4 (a) and Figure 4 (b) shows the voltage waveform induced in the feedback coil Lf2 (thick line) and the voltage waveform applied to the drive coil Ld3 after the phase-shift filter F10 is applied to the output of the feedback coil Nf2 (after the output of the feedback coil Nf2 passes through the phase-shift filter F10) (thin line).

[0112] according to Figure 4 In (a), when the inductance of the primary control coil Lc1 is set to the first value (large), the phase shift of the phase shift filter F10 becomes smaller. Therefore, it can be known that the phase of the voltage induced in the feedback coil Lf2 will not be applied to the gates of transistors Q11 and Q12 in such an offset manner.

[0113] On the other hand, Figure 4 In (b), with the inductance of the primary-side control coil Lc1 set to the second value (small), the phase shift of the phase-shifting filter F10 is related to... Figure 4 Compared to case (a), the phase of the voltage generated in the feedback coil Lf2 is staggered and applied to the gates of transistors Q11 and Q12 due to the phase-shifting filter F10. As a result, as... Figure 4 As shown in (b), it can be seen that: whether it is the voltage waveform generated in the feedback coil Lf2 (thick line) or the voltage waveform applied to the drive coil Ld3 (thin line), relative to Figure 4The frequencies of the waveforms shown in (a) all change.

[0114] exist Figure 5 (a) and Figure 5 (b) shows the voltage waveform at the gate of transistor Q12 (thick line), the voltage waveform between the drain and source of transistor Q12 (thin line), and the DC voltage level applied to the load resistor (approximately straight line).

[0115] By Figure 5 (a) and Figure 5 Comparing with (b), it can be seen that: when the inductance value of the primary control coil Lc1 is set to the first value (large), the oscillation period is longer and the DC voltage level applied to the load resistor, i.e., the output voltage, is larger.

[0116] This can be described as follows: when the inductance value of the primary side control coil Lc1 is set to the first value (large), the oscillation frequency of the primary side circuit 2 is the same as or close to the resonant frequency, so the output voltage increases. When the inductance value of the secondary side control coil Lc1 is set to the second value (small), the oscillation frequency of the primary side circuit 2 is far from the resonant frequency, so the output voltage decreases.

[0117] Thus, according to this embodiment, the following was verified: In the power supply circuit 1 of the first embodiment, by changing the phase shift of the phase shift filter F10 according to the inductance value of the primary side control coil Lc1, the output voltage can be controlled, thereby achieving output voltage stabilization.

[0118] It is also possible to determine some or all of the above-described embodiments and variations as follows. However, the above-described embodiments and variations are not limited to the following description. (1)

[0120] An output stabilization circuit includes a primary-side circuit and a secondary-side circuit. The primary-side circuit includes a self-excited oscillation circuit connected to a DC power supply. The secondary-side circuit obtains its output voltage through the oscillation of this self-excited oscillation circuit.

[0121] The self-excited oscillation circuit has the following characteristics:

[0122] Power supply coil;

[0123] A resonant capacitor is connected in series with the power supply coil, and together with the power supply coil, they form a series resonant circuit.

[0124] A switching circuit comprising a plurality of switching elements connected in a half-bridge or full-bridge configuration, and configured to switch the direction of current flowing in the power supply coil according to the on / off state of the plurality of switching elements.

[0125] A drive transformer, wherein the secondary winding of the drive transformer is connected to the gate electrode of each of the plurality of switching elements respectively;

[0126] A feedback transformer, wherein the primary winding of the feedback transformer is connected to the power transmission coil; and

[0127] A phase-shifting filter is connected between the secondary winding of the feedback transformer and the primary winding of the drive transformer.

[0128] The secondary side circuit has:

[0129] A receiving coil, which is magnetically coupled to the transmitting coil; and

[0130] The secondary-side control coil, wherein the magnitude of the current flowing in the secondary-side control coil is controlled according to the magnitude of the output voltage.

[0131] The phase-shifting filter includes a primary-side control coil, which is magnetically coupled to the secondary-side control coil and has the characteristic that its inductance changes according to the current flowing in the secondary-side control coil. (2)

[0133] A DC-DC converter circuit includes an output stabilization circuit according to (1), wherein in the DC-DC converter circuit,

[0134] The secondary circuit also includes a DC-DC conversion circuit that converts the AC voltage generated in the energized coil into a DC voltage.

Claims

1. An output stabilization circuit, comprising a primary-side circuit and a secondary-side circuit, wherein, The primary-side circuit includes a self-excited oscillation circuit connected to a DC power supply, and the secondary-side circuit obtains its output voltage through the oscillation of this self-excited oscillation circuit. The self-excited oscillation circuit has the following characteristics: Power supply coil; A resonant capacitor is connected in series with the power supply coil, and together with the power supply coil, they form a series resonant circuit. A switching circuit comprising a plurality of switching elements connected in a half-bridge or full-bridge configuration, and configured to switch the direction of current flowing in the power supply coil according to the on / off state of the plurality of switching elements. A drive transformer, wherein the secondary winding of the drive transformer is connected to the gate electrode of each of the plurality of switching elements respectively; A feedback transformer, wherein the primary winding of the feedback transformer is connected to the power transmission coil; as well as A phase-shifting filter is connected between the secondary winding of the feedback transformer and the primary winding of the drive transformer. The secondary side circuit has: A receiving coil, which is magnetically coupled to the transmitting coil; as well as The secondary-side control coil, wherein the magnitude of the current flowing in the secondary-side control coil is controlled according to the magnitude of the output voltage. The phase-shifting filter includes a primary-side control coil that is magnetically coupled to a secondary-side control coil. The primary-side control coil has an inductance that changes according to the current flowing in the secondary-side control coil.

2. The output stabilization circuit according to claim 1, wherein, The drive transformer, based on the AC voltage applied to the primary winding of the drive transformer, applies the AC voltage induced in the secondary winding of the drive transformer to the gate electrodes of each of the plurality of switching elements. The phase-shifting filter is an RLC filter that includes the primary-side control coil, a capacitor, and a resistive element, so that the phase of the AC voltage applied to the primary-side coil of the drive transformer is shifted by an amount of phase shift that varies according to the inductance of the primary-side control coil.

3. A DC-DC converter circuit, comprising the output stabilization circuit according to claim 1, The secondary circuit also includes a DC-DC conversion circuit that converts the AC voltage generated in the energized coil into a DC voltage.

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