Power supply device

Abstract

To provide a current resonance converter power supply capable of facilitating suppressing a noise generated in an output voltage without increasing the number of components.SOLUTION: A power supply 1 comprises a current resonance converter 11, a saturable reactor 12 whose AC winding 32 is connected in series to a resonance path 51 of the current resonance converter, and a control unit 13. The control unit controls current output to control winding or the AC winding of the saturable reactor, based on an output voltage, an output current, an input voltage or an input current of the current resonance converter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply device. [Background technology]

[0002] The current resonant converter (LLC converter) performs PFM (Pulse Frequency Modulation) control, which controls the output voltage by varying the switching frequency of the bridge circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-195511 [Patent Document 2] Japanese Patent Publication No. 2020-22309 [Patent Document 3] Japanese Patent Application Publication No. 2017-192281 Summary of the Invention [Problem to be solved by the invention]

[0004] With PFM control, the switching frequency varies over a wide band, so the noise generated in the output voltage also varies over a wide band, making noise suppression difficult.

[0005] In Patent Document 1, a power factor correction circuit is provided in the front stage of the LLC converter, and the output voltage is controlled by varying the output voltage of the power factor correction circuit. However, this also changes the input voltage of other circuits that receive power from the power factor correction circuit. In addition, the need for a power factor correction circuit increases the circuit size.

[0006] In Patent Document 2, a step-up / step-down converter is provided in the preceding stage of the LLC converter, and the same problems as those in Patent Document 1 arise.

[0007] In Patent Document 3, the output voltage is adjusted by varying the capacitance of the LLC resonant circuit by turning on and off switches connected to multiple capacitors. However, this only allows the capacitance to be varied discretely. In addition, this increases the circuit size and the number of components.

[0008] An object of the present invention is to provide a power supply device that can easily take measures against noise that occurs in the output voltage. [Means for solving the problem]

[0009] A power supply device according to one aspect of the present invention comprises: a current resonant converter; a saturable reactor having an AC winding connected in series to a resonant path of the current resonant converter; a control unit that outputs a current to a control winding or the AC winding of the saturable reactor based on an output voltage, an output current, an input voltage, or an input current of the current resonant converter; Including, It is characterized by:

[0010] In the power supply device, The saturable reactor is The inductance of the coil varies depending on the current input to the control winding or the AC winding. It is characterized by:

[0011] In the power supply device, The control unit a first circuit that outputs a current to the control winding of the saturable reactor based on an output voltage or an output current of the current resonant converter; Including, It is characterized by:

[0012] In the power supply device, The control unit a first circuit that outputs a current to the AC winding of the saturable reactor based on an output voltage or an output current of the current resonant converter; Including, It is characterized by:

[0013] In the power supply device, The control unit a second circuit that outputs a current to the control winding of the saturable reactor based on an input voltage or an input current of the current resonant converter; Including, It is characterized by:

[0014] In the power supply device, The control unit a second circuit that outputs a current to the AC winding of the saturable reactor based on an input voltage or an input current of the current resonant converter; Including, It is characterized by:

[0015] In the power supply device, The control unit a third circuit for switching the bridge circuit of the current resonant converter at a constant switching frequency; Further comprising: It is characterized by:

[0016] In the power supply device, The control unit a fourth circuit for switching the bridge circuit of the current resonant converter at a switching frequency based on the output voltage or the output current of the current resonant converter; Further comprising: It is characterized by: [Effects of the Invention]

[0017] Advantageous Effects of Invention A power supply device according to one aspect of the present invention has an effect of making it easy to take measures against noise occurring in an output voltage. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a power supply device according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of an output monitoring circuit of the power supply device according to the first embodiment and a circuit that outputs a current to a saturable reactor. [Figure 3] FIG. 3 is a diagram illustrating an example of output voltage-switching frequency characteristics of the power supply device according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of output voltage-output current characteristics of the power supply device according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of a waveform of an output voltage relative to a control voltage of the power supply device according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of an FFT waveform related to the output voltage of the power supply device according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating a configuration of a power supply device according to the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of the configuration of an output monitoring circuit of a power supply device according to the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating the configuration of a power supply device according to the third embodiment. [Figure 10] FIG. 10 is a diagram illustrating the configuration of a power supply device according to the fourth embodiment. [Figure 11] FIG. 11 is a diagram illustrating the configuration of a power supply device according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power supply device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0020] First Embodiment FIG. 1 is a diagram illustrating a configuration of a power supply device according to a first embodiment.

[0021] The power supply device 1 receives an input voltage Vin and an input current Iin from a DC power supply 2, and outputs a DC output voltage Vout and an output current Iout to a load 3.

[0022] The power supply device 1 includes an LLC converter 11, a saturable reactor 12, and a control unit 13.

[0023] The LLC converter 11 is a current resonance converter including a bridge circuit 21, capacitors 22 and 25, a transformer 23, and a rectifier circuit 24.

[0024] The bridge circuit 21 includes transistors Tr1 and Tr2. In the first embodiment, the bridge circuit 21 is a half-bridge circuit, but the present disclosure is not limited to this. The bridge circuit 21 may be, for example, a full-bridge circuit.

[0025] In the present disclosure, each transistor is a MOSFET, but is not limited to this, and each transistor may be a silicon power device, a GaN power device, a SiC power device, or the like.

[0026] Each transistor has a parasitic diode (body diode) that can actively conduct current, or has a diode connected in anti-parallel: the pn junction between the back gate and the source and drain of the MOSFET.

[0027] The drain of the transistor Tr1 is electrically connected to the high potential side terminal of the DC power supply 2. The source of the transistor Tr1 is electrically connected to the node N1. The drain of the transistor Tr2 is electrically connected to the node N1. The source of the transistor Tr2 is electrically connected to the low potential side terminal of the DC power supply 2.

[0028] One end of the capacitor 22 is electrically connected to the node N1, and the other end of the capacitor 22 is electrically connected to one end of the AC winding 31 of the saturable reactor 12.

[0029] The transformer 23 includes a primary winding 23a, a secondary winding 23b, and a core 23c. The primary winding 23a and the secondary winding 23b are wound around the core 23c. The primary winding 23a includes an exciting inductance 23d.

[0030] The LLC converter 11 includes a leakage inductance 23e between the bridge circuit 21 and the transformer 23. The leakage inductance 23e may be included in the transformer 23.

[0031] One end of the leakage inductance 23e is electrically connected to the other end of the AC winding 31. The other end of the leakage inductance 23e is electrically connected to one end of the primary winding 23a. The other end of the primary winding 23a is electrically connected to the source of the transistor Tr2.

[0032] The capacitor 22 , the AC winding 31 , the leakage inductance 23 e and the magnetizing inductance 23 d form a resonant path 51 of the LLC converter 11 .

[0033] The AC winding 31 is inserted in series with the resonant path 51. In the first embodiment, the AC winding 31 is inserted in series between the capacitor 22 and the leakage inductance 23e, but the present disclosure is not limited to this. The AC winding 31 may be inserted in series between the leakage inductance 23e and the excitation inductance 23d, for example.

[0034] The bridge circuit 21 outputs a forward DC voltage to the primary winding 23a of the transformer 23 when the transistor Tr1 is on and the transistor Tr2 is off.

[0035] The bridge circuit 21 short-circuits the primary winding 23a of the transformer 23 when the transistor Tr1 is in an off state and the transistor Tr2 is in an on state.

[0036] When the transistor Tr1 is in the off state and the transistor Tr2 is in the off state, the bridge circuit 21 opens the primary winding 23a of the transformer 23. Alternatively, the transformer 23 is short-circuited through the parasitic diode of the transistor Tr2. Alternatively, the current of the transformer 23 is circulated to the DC power supply 2 through the parasitic diode of the transistor Tr1.

[0037] The rectifier circuit 24 includes diodes D1 and D2. The anode of the diode D1 is electrically connected to one end of the secondary winding 23b of the transformer 23. The anode of the diode D2 is electrically connected to the other end of the secondary winding 23b of the transformer 23.

[0038] The cathode of the diode D1 and the cathode of the diode D2 are electrically connected to one end (high potential end) of the capacitor 25. The other end (low potential end) of the capacitor 25 is electrically connected to the midpoint of the secondary winding 23b of the transformer 23.

[0039] Rectifier circuit 24 rectifies the voltage excited in secondary winding 23b of transformer 23 and outputs the rectified voltage to capacitor 25. Capacitor 25 smoothes the voltage rectified by rectifier circuit 24. The voltage of capacitor 25 is output voltage Vout.

[0040] The saturable reactor 12 includes an AC winding 31, a control winding 32, and a core 33. The AC winding 31 and the control winding 32 are wound around the core 33.

[0041] The saturable reactor 12 is a circuit element having a characteristic that its inductance varies depending on the current input to the AC winding 31 or the control winding 32 .

[0042] The control unit 13 includes an output monitoring circuit 41 and an oscillation circuit 42 .

[0043] The output monitoring circuit 41 corresponds to an example of a "first circuit" in the present disclosure. The oscillation circuit 42 corresponds to an example of a "third circuit" in the present disclosure.

[0044] The oscillator circuit 42 outputs a switching control signal of a constant frequency to the gates of the transistors Tr1 and Tr2, controlling each of the transistors Tr1 and Tr2 to an on or off state at the constant switching frequency.

[0045] The output voltage Vout is input to the output monitoring circuit 41. The output monitoring circuit 41 outputs a current I1 to the control winding 32 of the saturable reactor 12 based on the output voltage Vout.

[0046] When the target voltage is higher than the output voltage Vout, the output monitoring circuit 41 outputs a current I1 to the control winding 32 of the saturable reactor 12. This causes the saturable reactor 12 to change toward saturation, reducing the inductance of the AC winding 31 of the saturable reactor 12, reducing the inductance of the resonant path 51, and increasing the output voltage Vout.

[0047] This allows the power supply device 1 to control the output voltage Vout to the target voltage.

[0048] When the target voltage is lower than the output voltage Vout, the output monitoring circuit 41 does not output the current I1 to the control winding 32 of the saturable reactor 12. This causes the saturable reactor 12 to change in a direction that prevents it from saturating, increasing the inductance of the AC winding 31 of the saturable reactor 12, increasing the inductance of the resonant path 51, and causing the output voltage Vout to decrease.

[0049] This allows the power supply device 1 to control the output voltage Vout to the target voltage.

[0050] FIG. 2 is a diagram illustrating an example of the configuration of an output monitoring circuit of the power supply device according to the first embodiment and a circuit that outputs a current to a saturable reactor.

[0051] The output monitoring circuit 41 includes resistors 61, 62, 65, and 67, a constant voltage source 63, an error amplifier 64 (differential amplifier), and a transistor 66.

[0052] The output voltage Vout is input to one end of the resistor 61. The other end of the resistor 61 is electrically connected to the node N2. One end of the resistor 62 is electrically connected to the node N2. The other end of the resistor 62 is electrically connected to a reference potential. The reference potential is exemplified by the ground potential, but the present disclosure is not limited thereto.

[0053] An inverting input terminal (negative terminal) of the error amplifier 64 is electrically connected to the node N2. A voltage Vsense obtained by dividing the output voltage Vout by resistors 61 and 62 is input to the inverting input terminal (negative terminal) of the error amplifier 64.

[0054] The non-inverting input terminal (+ terminal) of the error amplifier 64 is electrically connected to the constant voltage source 63. The constant voltage source 63 outputs a reference voltage Vref corresponding to the target voltage to the non-inverting input terminal (+ terminal) of the error amplifier 64.

[0055] The error amplifier 64 operates by receiving a power supply voltage Vcc. The output terminal of the error amplifier 64 is electrically connected to one end of a resistor 65. The error amplifier 64 outputs a voltage Verr corresponding to the difference between a reference voltage Vref and a voltage Vsense to one end of the resistor 65.

[0056] The voltage Verr changes continuously according to the voltage Vsense.

[0057] The other end of the resistor 65 is electrically connected to the base of a transistor 66. A power supply voltage Vcc is supplied to the collector of the transistor 66. The emitter of the transistor 66 is electrically connected to one end of a resistor 67. The transistor 66 outputs a current I1 corresponding to the voltage Verr to one end of the resistor 67.

[0058] The current I1 changes continuously in response to the voltage Verr, that is, the current I1 changes continuously in response to the voltage Vsense.

[0059] The control winding 32 of the saturable reactor 12 includes a winding 32a and a winding 32b connected in series. One end of the winding 32a is electrically connected to the other end of the resistor 67. The other end of the winding 32a is electrically connected to one end of the winding 32b. The other end of the winding 32b is electrically connected to a reference potential.

[0060] When the reference voltage Vref is higher than the voltage Vsense, the error amplifier 64 outputs a high-level voltage Verr, which turns on the transistor 66 and outputs a current I1 corresponding to the voltage Verr to the control winding 32 via the resistor 67.

[0061] When current I1 is input to control winding 32 of saturable reactor 12, core 33 is biased to DC. The inductance of AC winding 31 decreases depending on the degree of bias. When core 33 is saturated, the inductance of AC winding 31 becomes minimum. When the inductance of AC winding 31 decreases, the inductance of resonant path 51 decreases, and output voltage Vout increases.

[0062] This allows the power supply device 1 to control the output voltage Vout to the target voltage.

[0063] When the reference voltage Vref is lower than the voltage Vsense, the error amplifier 64 outputs a low-level voltage Verr, which turns the transistor 66 off and does not output the current I1 to the control winding 32.

[0064] Since an AC current is supplied to the AC winding 31, the core 33 is magnetized in both positive and negative directions. Therefore, the core 33 does not saturate, and the inductance of the AC winding 31 reaches a maximum. Furthermore, since the control winding 32 has windings 32a and 32b connected in series, the voltage across the control winding 32 is zero regardless of the voltage of the AC winding 31. When the inductance of the AC winding 31 increases, the inductance of the resonant path 51 also increases, and the output voltage Vout decreases.

[0065] This allows the power supply device 1 to control the output voltage Vout to the target voltage.

[0066] FIG. 3 is a diagram illustrating an example of output voltage-switching frequency characteristics of the power supply device according to the first embodiment.

[0067] 3, waveform 71 shows an example of output voltage Vout when the inductance of AC winding 31 is at its lower limit. Waveform 72 shows an example of output voltage Vout when the inductance of AC winding 31 is at its intermediate value. Waveform 73 shows an example of output voltage Vout when the inductance of AC winding 31 is at its upper limit.

[0068] Line 74 indicates an example of the lower limit of the switching frequency of bridge circuit 21. Line 75 indicates an example of the upper limit of the switching frequency of bridge circuit 21. Arrow 76 indicates an example of the range of the switching frequency of bridge circuit 21.

[0069] Within the range of switching frequencies indicated by the arrow 76, the output voltage Vout decreases as the inductance of the AC winding 31 increases.

[0070] The oscillator circuit 42 keeps the switching frequency of the bridge circuit 21 constant at any one of the switching frequencies within the range indicated by the arrow 76. The output monitor circuit 41 continuously varies the inductance of the AC winding 31 within the range from waveform 71 to waveform 73.

[0071] This allows the power supply device 1 to continuously and variably control the output voltage Vout.

[0072] FIG. 4 is a diagram illustrating an example of output voltage-output current characteristics of the power supply device according to the first embodiment.

[0073] 4, waveform 81 shows an example of output voltage Vout when the inductance of AC winding 31 is at its lower limit. Waveform 82 shows an example of output voltage Vout when the inductance of AC winding 31 is at its intermediate value. Waveform 83 shows an example of output voltage Vout when the inductance of AC winding 31 is at its upper limit.

[0074] An area 84 shows an example of a range in which the power supply device 1 can perform constant voltage output control.

[0075] Within the range indicated by region 84 where constant voltage output control is possible, the output current Iout decreases as the inductance of AC winding 31 increases.

[0076] The oscillator circuit 42 controls the switching frequency of the bridge circuit 21 to be constant. The output monitor circuit 41 continuously varies the inductance of the AC winding 31 within the range from waveform 81 to waveform 83.

[0077] This allows the power supply device 1 to perform constant voltage control of the output voltage Vout.

[0078] 5 and 6 are diagrams showing examples of waveforms of the power supply device according to the first embodiment.

[0079] FIG. 5 shows the results of a circuit simulation when the voltage Verr is manipulated (set).

[0080] 5, a waveform 91 shows an example of the reference voltage Vref, a waveform 92 shows an example of the voltage Verr of the error amplifier 64, and a waveform 93 shows an example of the output voltage Vout of the power supply device 1.

[0081] During the period from timing t0 to timing t1, the voltage Verr of the error amplifier 64 is set to a high level, and the output voltage Vout then rises in accordance with the voltage Verr during the period from timing t0 to timing t1.

[0082] In this way, the output voltage Vout shown by the waveform 93 changes in accordance with the voltage Verr shown by the waveform 92.

[0083] FIG. 6 shows an example of a spectrum waveform obtained by FFT (Fast Fourier Transform) of the output voltage Vout shown as waveform 93 in FIG.

[0084] Noise peaks occur at integer multiples of the switching frequency fsw (for example, 2fsw).

[0085] Therefore, the power supply device 1 can easily suppress noise because it is only necessary to take measures against noise at the switching frequency fsw and its harmonic frequency components.

[0086] In the first embodiment, the output monitoring circuit 41 outputs the current I1 to the control winding 32 of the saturable reactor 12 based on the output voltage Vout, but the present disclosure is not limited to this. The output monitoring circuit 41 may also output a current to the control winding 32 of the saturable reactor 12 based on the output current Iout. For example, the output monitoring circuit 41 may compare a target current with the output current Iout, and when the target current is greater than the output current Iout, output a current I1 corresponding to the difference between the target current and the output current Iout to the control winding 32.

[0087] <Second embodiment> Of the components of the second embodiment, the same components as those of the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0088] FIG. 7 is a diagram illustrating a configuration of a power supply device according to the second embodiment.

[0089] Compared to power supply device 1 (see FIG. 1) of the first embodiment, power supply device 1A of the second embodiment includes a control unit 13A instead of control unit 13. Also, compared to power supply device 1, power supply device 1A includes a saturable reactor 12A instead of saturable reactor 12. Compared to saturable reactor 12, saturable reactor 12A does not include a control winding 32.

[0090] Compared to the control unit 13, the control unit 13A includes an output monitoring circuit 41A instead of the output monitoring circuit 41.

[0091] The output monitoring circuit 41A corresponds to an example of a "first circuit" in the present disclosure.

[0092] The output monitoring circuit 41A outputs a current I2 to the other end of the AC winding 31 of the saturable reactor 12A based on the output voltage Vout.

[0093] FIG. 8 is a diagram illustrating an example of the configuration of an output monitoring circuit of a power supply device according to the second embodiment.

[0094] The output monitoring circuit 41A further includes a diode 68 in comparison with the output monitoring circuit 41 (see FIG. 2).

[0095] The anode of the diode 68 is electrically connected to the other end of the resistor 67. The cathode of the diode 68 is electrically connected to the other end of the AC winding 31.

[0096] When the reference voltage Vref is higher than the voltage Vsense, the error amplifier 64 outputs a high-level voltage Verr, which turns on the transistor 66 and outputs a current I2 corresponding to the voltage Verr to the other end of the AC winding 31 via the resistor 67.

[0097] When current I2 is input to AC winding 31, saturable reactor 12A changes toward saturation, the inductance of AC winding 31 decreases, the inductance of resonant path 51 decreases, and output voltage Vout increases.

[0098] This allows the power supply device 1A to control the output voltage Vout to the target voltage.

[0099] When the reference voltage Vref is lower than the voltage Vsense, the error amplifier 64 outputs a low-level voltage Verr, which turns the transistor 66 off and does not output the current I2 to the AC winding 31.

[0100] When the current I2 is not input to the AC winding 31, the saturable reactor 12A changes in a direction that prevents it from saturating, the inductance of the AC winding 31 of the saturable reactor 12 increases, the inductance of the resonant path 51 increases, and the output voltage Vout decreases.

[0101] This allows the power supply device 1A to control the output voltage Vout to the target voltage.

[0102] In the second embodiment, the output monitoring circuit 41A outputs the current I2 to the AC winding 31 of the saturable reactor 12A based on the output voltage Vout, but the present disclosure is not limited to this. The output monitoring circuit 41A may also output the current I2 to the AC winding 31 of the saturable reactor 12A based on the output current Iout. For example, the output monitoring circuit 41A may compare a target current with the output current Iout, and when the target current is greater than the output current Iout, output the current I2 corresponding to the difference between the target current and the output current Iout to the AC winding 31.

[0103] <Third embodiment> Of the components of the third embodiment, the same components as those of the other embodiments are denoted by the same reference numerals and the description thereof will be omitted.

[0104] FIG. 9 is a diagram illustrating the configuration of a power supply device according to the third embodiment.

[0105] Compared to power supply device 1 (see FIG. 1) of the first embodiment, power supply device 1B of the third embodiment includes control unit 13B instead of control unit 13.

[0106] Compared to the control unit 13, the control unit 13B includes a frequency modulation circuit 43 instead of the oscillation circuit .

[0107] The frequency modulation circuit 43 corresponds to an example of the "fourth circuit" of the present disclosure.

[0108] The frequency modulation circuit 43 receives the voltage Vsense (see FIG. 2) from the output monitoring circuit 41. The voltage Vsense is a voltage obtained by dividing the output voltage Vout by resistors.

[0109] The frequency modulation circuit 43 switches the bridge circuit 21 at a switching frequency based on the voltage Vsense, that is, the output voltage Vout.

[0110] The power supply device 1B controls the output voltage by controlling the switching frequency of the bridge circuit 21 in addition to controlling the output voltage by the saturable reactor 12, thereby enabling the output voltage control range to be expanded while maintaining the resonance of the resonant path 51.

[0111] In the power supply device 1B, output voltage control by the saturable reactor 12 is the main control, and output voltage control by control of the switching frequency of the bridge circuit 21 is the secondary control.

[0112] Therefore, the power supply device 1B has a narrow switching frequency band and is easier to suppress noise compared to conventional PFM control.

[0113] In the third embodiment, the output monitoring circuit 41 outputs the current I1 to the control winding 32 of the saturable reactor 12 based on the output voltage Vout, but the present disclosure is not limited to this. The output monitoring circuit 41 may also output the current I1 to the control winding 32 of the saturable reactor 12 based on the output current Iout.

[0114] It is also possible to combine the circuit of the third embodiment with the circuit of the second embodiment. That is, the control unit 13B may include an output monitoring circuit 41A instead of the output monitoring circuit 41.

[0115] <Fourth embodiment> Of the components of the fourth embodiment, the same components as those of the other embodiments are denoted by the same reference numerals and the description thereof will be omitted.

[0116] FIG. 10 is a diagram illustrating the configuration of a power supply device according to the fourth embodiment.

[0117] Compared to power supply device 1 (see FIG. 1) of the first embodiment, power supply device 1C of the fourth embodiment includes control unit 13C instead of control unit 13.

[0118] Compared to the control unit 13, the control unit 13C includes an input monitoring circuit 44 instead of the output monitoring circuit 41.

[0119] The input monitoring circuit 44 corresponds to an example of the "second circuit" of the present disclosure.

[0120] The input voltage Vin is input to the input monitoring circuit 44 .

[0121] When the input voltage Vin increases, the output voltage Vout tends to increase. When the input voltage Vin decreases, the output voltage Vout tends to decrease. In other words, there is a positive correlation between the input voltage Vin and the output voltage Vout.

[0122] Therefore, the input monitoring circuit 44 outputs a current I1 to the control winding 32 of the saturable reactor 12 based on the input voltage Vin.

[0123] When the input reference voltage is higher than the input voltage Vin, the input monitoring circuit 44 outputs a current I1 to the control winding 32 according to the input voltage Vin.

[0124] The input monitoring circuit 44 does not output the current I1 to the control winding 32 when the input reference voltage is lower than the input voltage Vin.

[0125] As a result, the power supply device 1C achieves the same effects as the power supply device 1.

[0126] In the fourth embodiment, the input monitoring circuit 44 outputs the current I1 to the control winding 32 of the saturable reactor 12 based on the input voltage Vin, but the present disclosure is not limited to this. The input monitoring circuit 44 may also output the current I1 to the control winding 32 of the saturable reactor 12 based on the input current Iin. For example, the input monitoring circuit 44 may compare the input reference current with the input current Iin, and when the input reference current is greater than the input current Iin, output the current I1 corresponding to the difference between the input reference current and the input current Iin to the control winding 32.

[0127] It is also possible to combine the circuit of the fourth embodiment with the circuit of the second embodiment. That is, the input monitoring circuit 44 may output the current I2 to the AC winding 31 of the saturable reactor 12 based on the input voltage Vin or the input current Iin.

[0128] <Fifth embodiment> Of the components of the fifth embodiment, the same components as those of the other embodiments are denoted by the same reference numerals and the description thereof will be omitted.

[0129] FIG. 11 is a diagram illustrating the configuration of a power supply device according to the fifth embodiment.

[0130] Compared to power supply device 1C (see FIG. 10) of the fourth embodiment, power supply device 1D of the fifth embodiment includes control unit 13D instead of control unit 13C.

[0131] Compared to the control unit 13C, the control unit 13D includes an output monitoring circuit 41 and a frequency modulation circuit 43 instead of the oscillation circuit .

[0132] The power supply device 1D controls the output voltage by controlling the switching frequency of the bridge circuit 21 in addition to controlling the output voltage by the saturable reactor 12, thereby enabling the output voltage control range to be expanded while maintaining the resonance of the resonant path 51.

[0133] In the power supply device 1D, output voltage control by the saturable reactor 12 is the main control, and output voltage control by control of the switching frequency of the bridge circuit 21 is the secondary control.

[0134] Therefore, the power supply device 1D has a narrow switching frequency band and is easier to suppress noise compared to conventional PFM control.

[0135] In the fifth embodiment, the input monitoring circuit 44 outputs the current I1 to the control winding 32 of the saturable reactor 12 based on the input voltage Vin, but the present disclosure is not limited to this. The input monitoring circuit 44 may also output the current I1 to the control winding 32 of the saturable reactor 12 based on the input current Iin.

[0136] It is also possible to combine the circuit of the fifth embodiment with the circuit of the second embodiment. That is, the input monitoring circuit 44 may output the current I2 to the AC winding 31 of the saturable reactor 12 based on the input voltage Vin or the input current Iin.

[0137] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0138] Although the present disclosure uses an LLC converter as an example of a current resonant converter, the present disclosure is not limited to this and can be applied to current resonant converters other than LLC converters. [Explanation of symbols]

[0139] 1, 1A, 1B, 1C, 1D power supply 2 DC power supply 3. Load 11 LLC Converter 12, 12A saturable reactor 13, 13A, 13B, 13C, 13D Control section 21 Bridge Circuit 22, 25 Capacitor 23 Transformer 24 Rectifier circuit 31 AC winding 32 Control Winding 33 cores 41, 41A Output monitoring circuit 42 Oscillator Circuit 43 Frequency Modulation Circuit 44 Input monitoring circuit 61, 62, 65, 67 Resistance 63 Constant voltage source 64 Error amplifier 66, Tr1, Tr2 transistors 68, D1, D2 diodes

Claims

[Claim 1] a current resonant converter; a saturable reactor having an AC winding connected in series to a resonant path of the current resonant converter; a control unit that outputs a current to a control winding or the AC winding of the saturable reactor based on an input voltage or an input current of the current resonant converter; Including, The saturable reactor is The inductance of the coil varies depending on the current input to the control winding or the AC winding. The control unit an input monitoring circuit that outputs a current to the control winding or the AC winding of the saturable reactor based on an input voltage or an input current of the current resonant converter; an output monitoring circuit that outputs a signal based on the output voltage or the output current of the current resonant converter; a frequency modulation circuit that switches a bridge circuit of the current resonant converter at a switching frequency based on the signal; Including, A power supply device comprising:

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