Power supply

Abstract

To provide a power supply unit capable of reducing output current.SOLUTION: A power supply unit has a DC-DC converter, and a control device controlling the DC-DC converter by a first mode of changing a switching frequency of a switching control signal of the DC-DC converter at a side where power is higher than first output current of the DC-DC converter-an output voltage characteristic, and controlling the DC-DC converter by a second mode of changing a pulse width by fixing the switching frequency of the switching control signal or of changing the switching frequency by fixing the pulse width at a side where power is lower than the first output current-the output voltage characteristic.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 describes a DC-DC converter that operates a switching transistor intermittently. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-68684 A [Non-patent literature]

[0004] [Non-Patent Document 1] Andrea Merello, "Application Note: AN-1123", [online], International Rectifier Japan, [Retrieved December 10, 2020], Internet (URL: https: / / www.infineon.com / dgdl / AN-1123J.pdf?fileId=5546d46256fb43b301574c5f2b487be7) Summary of the Invention [Problem to be solved by the invention]

[0005] A current resonant converter (LLC converter) can change the output current by changing the switching frequency (hereinafter referred to as "frequency modulation"). That is, in an LLC converter, if the switching frequency is increased, the output current can be reduced, and if the switching frequency is decreased, the output current can be increased.

[0006] However, LLC converters controlled only by frequency modulation have a lower limit on the output current, especially in the low output voltage range. However, it would be desirable to reduce the output current even further.

[0007] An object of the present invention is to provide a power supply device capable of reducing the output current. [Means for solving the problem]

[0008] A power supply device according to one aspect of the present invention comprises: A DC-DC converter that converts the input voltage and outputs it; a control device that controls the DC-DC converter in a first mode in which a switching frequency of a switching control signal of the DC-DC converter is changed on the higher power side of a first output current-output voltage characteristic of the DC-DC converter, and controls the DC-DC converter in a second mode in which the switching frequency of the switching control signal is fixed and the pulse width is changed, or the pulse width is fixed and the switching frequency is changed, on the lower power side of the first output current-output voltage characteristic; Equipped with It is characterized by:

[0009] In the power supply device, The control device includes: When an operation amount is less than a predetermined first threshold and is equal to or greater than a predetermined second threshold smaller than the first threshold, on a lower power side than the first output current-output voltage characteristic, a control is performed to fix a switching frequency of the switching control signal and change a pulse width, and when an operation amount is less than the second threshold, a control is performed to fix the pulse width and change the switching frequency. It is characterized by:

[0010] In the power supply device, The control device includes: When switching between the first mode and the second mode, the DC-DC converter is controlled in the second mode up to a second output current-output voltage characteristic that is on a higher power side than the first output current-output voltage characteristic. It is characterized by:

[0011] In the power supply device, The control device includes: When switching from the first mode to the second mode, the DC-DC converter is controlled in the first mode until the first output current-output voltage characteristic is reached, and when a switching frequency of the switching control signal continues to be an upper frequency limit in the frequency modulation of the first mode for a certain period of time, the DC-DC converter is controlled by a manipulation amount that is predetermined for each output voltage of the second mode. It is characterized by:

[0012] In the power supply device, an operation amount upper limit value, which is an upper limit value of an operation amount, is determined in advance for each output voltage of the second mode so as to obtain the second output current-output voltage characteristic; and an output current upper limit value, which is an upper limit value of an output current, is determined in advance for each output voltage of the second mode so as to obtain the second output current-output voltage characteristic; The control device includes: When switching from the second mode to the first mode, if the manipulated variable continues to be the manipulated variable upper limit value for a certain period of time, or if the output current value continues to be the output current upper limit value for a certain period of time, the DC-DC converter is controlled at or near the upper limit of the frequency of the frequency modulation in the first mode. It is characterized by:

[0013] In the power supply device, the control device includes a drive circuit that outputs the switching control signal to a high-side switching element and a low-side switching element in the DC-DC converter; a power supply circuit of a circuit that outputs the switching control signal to the high-side switching element in the drive circuit is a power supply circuit that does not depend on a switching operation of the low-side switching element. It is characterized by: Effect of the Invention

[0014] The power supply device according to one embodiment of the present invention has an advantage that the output current can be reduced. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a power supply device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of the output current-output voltage characteristics of a DC-DC converter. [Diagram 3] FIG. 3 is a diagram illustrating operation modes of the power supply device according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating a configuration of a power supply device according to the second embodiment. [Diagram 5] FIG. 5 is a diagram illustrating a configuration of a power supply device according to the third embodiment. [Figure 6] FIG. 6 is a diagram illustrating a configuration of a power supply device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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 drawings. However, the present invention is not limited to the embodiment.

[0017] <First embodiment> (Overall composition) 1 is a diagram showing the configuration of a power supply device according to a first embodiment. The power supply device 1 receives an input voltage Vin from a DC power supply 2, and outputs a DC output voltage Vout to a load 3.

[0018] The power supply device 1 includes a DC-DC converter 4, a current sensor 5, a voltage sensor 6, and a control device 7.

[0019] The DC-DC converter 4 includes a transformer driving circuit 11, a transformer 12, a rectifier circuit 13, and a capacitor .

[0020] The DC-DC converter 4 is a half-bridge current resonant converter (LLC converter), but the present disclosure is not limited to this.

[0021] The transformer driving circuit 11 includes transistors 11a and 11b and capacitors 11c and 11d. In the first embodiment, the transformer driving circuit 11 is a half-bridge circuit.

[0022] In the present disclosure, each transistor is a MOSFET, but is not limited to this. Each transistor may be a silicon power device, a GaN power device, a SiC power device, an IGBT (Insulated Gate Bipolar Transistor), or the like.

[0023] Each transistor has a parasitic diode (body diode). A parasitic diode is a pn junction between the back gate of a MOSFET and the source and drain. The parasitic diode can be used as a freewheeling diode to release the transient back electromotive force when the transistor is turned off. In addition to the parasitic diode, a diode element may be added between the drain and source of each transistor.

[0024] Each of the transistors 11a and 11b is controlled by the control device 7 to be in an on or off state.

[0025] The source of the transistor 11a is electrically connected to the drain of the transistor 11b. The drain of the transistor 11a is electrically connected to one end (high potential end) of the capacitor 11c. The other end (low potential end) of the capacitor 11c is electrically connected to one end (high potential end) of the capacitor 11d. The source of the transistor 11b is electrically connected to the other end (low potential end) of the capacitor 11d.

[0026] A connection point between the drain of the transistor 11a and one end of the capacitor 11c is one input terminal of the transformer driving circuit 11. A connection point between the source of the transistor 11b and the other end of the capacitor 11d is the other input terminal of the transformer driving circuit 11.

[0027] One input terminal of the transformer driving circuit 11 is electrically connected to one end (high potential end) of the DC power supply 2. The other input terminal of the transformer driving circuit 11 is electrically connected to the other end (low potential end) of the DC power supply 2.

[0028] An input voltage Vin is input from a DC power supply 2 to two input terminals of the transformer driving circuit 11.

[0029] A connection point between the other end of the capacitor 11c and one end of the capacitor 11d is one output terminal of the transformer driving circuit 11. A connection point between the source of the transistor 11a and the drain of the transistor 11b is the other output terminal of the transformer driving circuit 11.

[0030] The transformer 12 includes a primary winding 12a, a secondary winding 12b, and a core 12c. The primary winding 12a and the secondary winding 12b are wound around the core 12c.

[0031] The DC-DC converter 4 includes an inductance 12e between the transformer driving circuit 11 and the transformer 12. The inductance 12e may be included in the transformer 12.

[0032] The primary winding 12a includes an excitation inductance 12d. One end of the primary winding 12a is electrically connected to one output terminal of the transformer driving circuit 11. The other end of the primary winding 12a is electrically connected to the other output terminal of the transformer driving circuit 11. If the excitation inductance 12d is insufficient, an element having an inductance may be further added.

[0033] The transformer driving circuit 11 outputs a positive DC voltage, a negative DC voltage, or a resonant voltage to the primary winding 12a of the transformer 12. The resonant voltage is a voltage generated by LC resonance between the capacitance components of the transistors 11a and 11b and the inductance components (the inductance 12e and the excitation inductance 12d).

[0034] For example, the transformer driving circuit 11 outputs a forward DC voltage to the primary winding 12a of the transformer 12 when the transistor 11a is in an off state and the transistor 11b is in an on state.

[0035] Furthermore, for example, the transformer driving circuit 11 outputs a negative DC voltage to the primary winding 12a of the transformer 12 when the transistor 11a is in an on state and the transistor 11b is in an off state.

[0036] Furthermore, for example, the transformer driving circuit 11 outputs the resonant voltage to the primary winding 12a of the transformer 12 when the transistor 11a is in the off state and the transistor 11b is in the off state.

[0037] The rectifier circuit 13 includes diodes 13a and 13b. The anode of the diode 13a is electrically connected to one end of the secondary winding 12b of the transformer 12. The anode of the diode 13b is electrically connected to the other end of the secondary winding 12b of the transformer 12.

[0038] The cathode of the diode 13a and the cathode of the diode 13b are electrically connected to one end (high potential end) of the capacitor 14. The other end (low potential end) of the capacitor 14 is electrically connected to the midpoint of the secondary winding 12b of the transformer 12.

[0039] The rectifier circuit 13 rectifies the voltage excited in the secondary winding 12b of the transformer 12 and outputs the rectified voltage to the capacitor 14. The capacitor 14 smoothes the voltage rectified by the rectifier circuit 13. The rectifier circuit 13 may be formed of a synchronous rectifier switching element.

[0040] One end of the capacitor 14 is electrically connected to one end of the load 3 (for example, the positive electrode of a lithium ion battery). The other end of the capacitor 14 is electrically connected to the other end of the load 3 (for example, the negative electrode of a lithium ion battery). A DC voltage smoothed by the capacitor 14 is input to the load 3.

[0041] The current sensor 5 is electrically connected between the other end of the capacitor 14 and the other end of the load 3. The current sensor 5 outputs a current sensor signal S1 representing the output current Iout flowing from the DC-DC converter 4 to the load 3 to the control device 7.

[0042] The voltage sensor 6 is electrically connected across the capacitor 14. The voltage sensor 6 outputs a voltage sensor signal S2 representing the output voltage Vout applied from the DC-DC converter 4 to the load 3 to the control device 7.

[0043] The control device 7 controls the DC-DC converter 4 so that the output current value represented by the current sensor signal S1 becomes the current, power, and voltage indication value represented by the current, power, and voltage indication value signal S3 input from the current, power, and voltage indication unit 8.

[0044] The control device 7 includes a subtractor 7a, a current controller 7b, a switching control unit 7c, a drive circuit 7d, and a target current value output unit 7e. The drive circuit 7d includes a first drive circuit 7d1 and a second drive circuit 7d2.

[0045] The target current value output unit 7e decreases the target current if the voltage represented by the voltage sensor signal S2 is higher than the target voltage represented by the current, power, and voltage instruction value signal S3. The target current value output unit 7e increases the target current if the voltage represented by the voltage sensor signal S2 is lower than the voltage represented by the current, power, and voltage instruction value signal S3. The target current value output unit 7e outputs a target current signal S9 representing the target current to the subtractor 7a.

[0046] The subtractor 7a subtracts the current sensor signal S1 from the target current signal S9 input from the target current value output unit 7e, and outputs a current deviation signal S4 to the current controller 7b.

[0047] The current controller 7b executes a control calculation on the current deviation signal S4 to output a manipulated variable S5 to the switching control unit 7c. The control calculation executed by the current controller 7b is exemplified by a PID (proportional integral differential) control calculation, a PI control calculation, a PD control calculation, etc., but the present disclosure is not limited thereto.

[0048] The operation amount S5 takes a larger value as the load becomes heavier, and takes a smaller value as the load becomes lighter.

[0049] The switching control unit 7c determines a switching frequency and a pulse width based on the current sensor signal S1, the voltage sensor signal S2, and the manipulated variable S5. The switching control unit 7c outputs a control signal S6 representing the switching frequency and the pulse width to the drive circuit 7d.

[0050] The first drive circuit 7d1 outputs a switching control signal S7 to the gate of the transistor 11a based on the control signal S6. The second drive circuit 7d2 outputs a switching control signal S8 to the gate of the transistor 11b based on the control signal S6.

[0051] (Control Action) Fig. 2 is a diagram showing an example of the output current-output voltage characteristics of a DC-DC converter. In Fig. 2, the horizontal axis represents the output current of the DC-DC converter 4, and the vertical axis represents the output voltage. Line 100 represents the maximum value of the maximum output (rated output) in the specifications of the DC-DC converter 4. Line 101 represents the minimum value of the maximum output in the specifications of the DC-DC converter 4. Line 102 represents the actual measured value of the maximum output of the DC-DC converter 4.

[0052] Line 103 indicates the lower limit of the output current that the DC-DC converter 4 can output with the same frequency modulation as the general control of an LLC converter. Line 103 is determined by the element values ​​of the elements that make up the DC-DC converter 4 and the upper limit of the switching frequency.

[0053] As shown by line 103, the DC-DC converter 4 can make the output current very small when the output voltage is high. However, the DC-DC converter 4 cannot make the output current small when the output voltage is low.

[0054] The characteristic of the power supply device 1 represented by the line 103 corresponds to an example of the "first output current-output voltage characteristic" of the present disclosure.

[0055] FIG. 3 is a diagram illustrating operation modes of the power supply device according to the first embodiment.

[0056] As shown in table 110, the power supply device 1 has a first mode (heavy load mode) and a second mode (light load mode).

[0057] The first mode is a frequency modulation mode which is the same as general control of an LLC converter, while the second mode is a mode specific to the power supply device 1 and includes a fixed frequency pulse width modulation control and a fixed pulse width frequency modulation control.

[0058] When the operation amount S5 is equal to or greater than a predetermined first threshold Th1, the switching control unit 7c operates the DC-DC converter 4 in the first mode. In the first mode, the switching control unit 7c fixes the dead time. Then, the switching control unit 7c varies the switching frequency in a range from a predetermined f3 [kHz (kilohertz)] to a predetermined f4 [kHz] according to the operation amount S5. Here, f3 > f4.

[0059] When the operation amount S5 is less than the first threshold Th1, the switching control unit 7c operates the DC-DC converter 4 in the second mode.

[0060] Furthermore, when the operation amount S5 is less than the first threshold Th1 and equal to or greater than a predetermined second threshold Th2, the switching control unit 7c controls the DC-DC converter 4 by frequency-fixed pulse width modulation. Here, Th2 < Th1.

[0061] In the frequency-fixed pulse width modulation control of the second mode, the switching control unit 7c fixes the switching frequency to a predetermined f2 [kHz]. Then, the switching control unit 7c varies the pulse width in a range from a predetermined fixed value of A [μs (microsecond)] to a variable B [μs] according to the operation amount S5. Here, f2 < f3 and A < B. Note that B [μs] may vary according to the output voltage Vout.

[0062] On the other hand, when the operation amount S5 is less than the second threshold Th2, the switching control unit 7c controls the DC-DC converter 4 by pulse width-fixed frequency modulation.

[0063] In the pulse width-fixed frequency modulation control of the second mode, the switching control unit 7c fixes the pulse width to A [μs]. Then, the switching control unit 7c varies the switching frequency in a range from f1 [kHz] to f2 [kHz] according to the operation amount S5. Here, f1 < f2.

[0064] Referring again to FIG. 2, line 104 is a line indicating the lower limit of the output current that the DC-DC converter 4 can output in pulse width fixed frequency modulation control in the second mode.

[0065] Basically (for example, during steady-state operation), the switching control unit 7c operates the DC-DC converter 4 in the first mode on the higher output side of line 103 (the right side in Figure 2), and operates the DC-DC converter 4 in the second mode on the lower output side of line 103 (the left side in Figure 2).

[0066] However, when switching between the first mode and the second mode, the switching control unit 7c operates the DC-DC converter 4 in the second mode up to the line 105, which is on the higher output side than the line 103. The reason for this is to prevent the first mode and the second mode from switching frequently.

[0067] The characteristic of the power supply device 1 represented by the line 105 corresponds to an example of the "second output current-output voltage characteristic" of the present disclosure.

[0068] When switching from the first mode to the second mode, the switching control unit 7c operates the DC-DC converter 4 in the first mode up to the line 103. Then, when operation within a certain range from the line 103 continues for a certain period of time, the switching control unit 7c operates the DC-DC converter 4 in the second mode with a control amount predetermined for each output voltage Vout so that the DC-DC converter 4 is on the line 103.

[0069] For example, when the switching frequency remains at the upper frequency limit in the frequency modulation in the first mode for a certain period of time, the switching control unit 7c controls the DC-DC converter 4 with a manipulated variable predetermined for each output voltage Vout in the second mode.

[0070] As a result, the output current of the DC-DC converter 4 is disturbed for a period of about 1 ms (milliseconds) to 3 ms, but this disturbance in the output current quickly settles down.

[0071] Furthermore, when switching from the second mode to the first mode, the switching control unit 7c operates the DC-DC converter 4 in the second mode up to line 105. Then, when operation within a certain range from the line 105 continues for a certain period of time, the switching control unit 7c operates the DC-DC converter 4 in the first mode on line 103.

[0072] For example, a manipulated variable upper limit value, which is an upper limit value of the manipulated variable S5, is determined in advance for each output voltage Vout in the second mode so as to obtain the output current-output voltage characteristic of the line 105. Also, an output current upper limit value, which is an upper limit value of the output current Iout, is determined in advance for each output voltage Vout in the second mode so as to obtain the output current-output voltage characteristic of the line 105. Then, when the manipulated variable S5 continues to be the manipulated variable upper limit value for a certain period of time, or when the output current Iout continues to be the output current upper limit value for a certain period of time, the switching control unit 7c operates the DC-DC converter 4 at or near the upper frequency limit in the frequency modulation in the first mode. The vicinity of the upper frequency limit is, for example, a range of about 1 kHz to 10 kHz from the upper frequency limit, but the present disclosure is not limited thereto.

[0073] As a result, the output current of the DC-DC converter 4 is disturbed for a period of about 1 ms to 3 ms, but this disturbance in the output current quickly settles down.

[0074] Summarizing the above, the range from line 103 to the high output side (right side in FIG. 2) is an operating range 106 in which DC-DC converter 4 operates in the first mode. Moreover, the range from line 104 to line 105 is an operating range 107 in which DC-DC converter 4 operates in the second mode.

[0075] (effect) In general frequency modulation control of an LLC converter, the output current can only be reduced to line 103. On the other hand, the power supply device 1 can reduce the output current to line 104 by operating in the second mode.

[0076] (Modification) Incidentally, a bootstrap circuit (for example, see Non-Patent Document 1) is generally used as the power supply circuit of the first drive circuit 7d1 that outputs the switching control signal S7 to the gate of the high-side transistor 11a.

[0077] An N-channel transistor is on / off controlled by the potential difference (voltage) between the gate and source. The low-side transistor 11b has a source at the reference potential, so it can be on / off controlled even if the potential of the switching control signal S8 applied to the gate is not high. However, the high-side transistor 11a has a source at a high potential, so it cannot be on / off controlled unless the potential of the switching control signal S7 applied to the gate is high. Therefore, the first drive circuit 7d1 requires a high power supply voltage to apply a high-potential switching control signal S7 to the gate of the high-side transistor 11a.

[0078] In order to realize the above-mentioned high power supply voltage simply and at low cost, a bootstrap circuit is generally used.

[0079] However, in the bootstrap circuit, unless the low-side transistor 11b operates at a certain switching frequency and pulse width, the capacitor is not sufficiently charged and a sufficient voltage cannot be generated. For this reason, there is a lower limit to the switching frequency and pulse width of the transistor 11b. The line 104, which is the lower limit of the second mode, is due to this lower limit.

[0080] In the conventional frequency modulation control (corresponding to the first mode of this embodiment), since the line 103 was the lower limit, whether or not the power supply circuit of the first drive circuit 7d1 was a bootstrap circuit did not matter to the lower limit. On the other hand, since this embodiment is provided with the second mode and the line 104 is the lower limit, whether or not the power supply circuit of the first drive circuit 7d1 is a bootstrap circuit matters to the lower limit.

[0081] Therefore, it is preferable that the power supply circuit of the first drive circuit 7d1 is an independent power supply circuit that does not depend on the switching operation of the low-side transistor 11b, rather than a bootstrap circuit. This makes it possible for the power supply device 1 to reduce the output current even further than that of the line 104, since there is essentially no lower limit to the switching frequency and pulse width of the transistor 11b.

[0082] <Second embodiment> Among the components of the second embodiment, the same components as those of the first embodiment are given the same reference numerals and the description thereof will be omitted.

[0083] In the first embodiment, the DC-DC converter 4 is a half-bridge type LLC converter, but it may be a full-bridge type LLC converter.

[0084] Figure 4 is a diagram showing the configuration of a power supply device according to the second embodiment. Compared to power supply device 1 (see Figure 1), power supply device 1A includes a DC-DC converter 4A instead of DC-DC converter 4. DC-DC converter 4A is a full-bridge type LLC converter.

[0085] Compared to the DC-DC converter 4 (see FIG. 1), the DC-DC converter 4A includes a transformer drive circuit 11A instead of the transformer drive circuit 11. Moreover, the DC-DC converter 4A includes a rectifier circuit 13A instead of the rectifier circuit 13.

[0086] Compared to the transformer driving circuit 11 (see FIG. 1), the transformer driving circuit 11A includes transistors 11e and 11f instead of the capacitors 11c and 11d.

[0087] Each of the transistors 11a, 11b, 11e and 11f is controlled by the control device 7 to be in an on or off state.

[0088] The source of the transistor 11a is electrically connected to the drain of the transistor 11b. The drain of the transistor 11a is electrically connected to the drain of the transistor 11e. The source of the transistor 11e is electrically connected to the drain of the transistor 11f. The source of the transistor 11b is electrically connected to the source of the transistor 11f.

[0089] The connection point between the drain of the transistor 11a and the drain of the transistor 11e is one input terminal of the transformer driving circuit 11A, and the connection point between the source of the transistor 11b and the source of the transistor 11f is the other input terminal of the transformer driving circuit 11A.

[0090] One input terminal of the transformer driving circuit 11A is electrically connected to one output terminal of the DC power supply 2. The other input terminal of the transformer driving circuit 11A is electrically connected to the other output terminal of the DC power supply 2.

[0091] An input voltage Vin of a DC power supply 2 is input to two input terminals of the transformer driving circuit 11A.

[0092] The connection point between the source of the transistor 11e and the drain of the transistor 11f is one output terminal of the transformer driving circuit 11A, and the connection point between the source of the transistor 11a and the drain of the transistor 11b is the other output terminal of the transformer driving circuit 11A.

[0093] One end of the primary winding 12a of the transformer 12 is electrically connected to one output terminal of the transformer driving circuit 11A via a capacitor 12f, and the other end of the primary winding 12a is electrically connected to the other output terminal of the transformer driving circuit 11A.

[0094] The transformer driving circuit 11A outputs a positive DC voltage, a negative DC voltage, or a resonant voltage to a primary winding 12a of the transformer 12.

[0095] For example, the transformer driving circuit 11A outputs a forward DC voltage to the primary winding 12a of the transformer 12 when the transistors 11b and 11e are on and the transistors 11a and 11f are off.

[0096] Furthermore, for example, the transformer driving circuit 11A outputs a negative DC voltage to the primary winding 12a of the transformer 12 when the transistors 11b and 11e are in an off state and the transistors 11a and 11f are in an on state.

[0097] Furthermore, for example, the transformer driving circuit 11A outputs the resonant voltage to the primary winding 12a of the transformer 12 when the transistors 11a, 11b, 11e, and 11f are in the off state.

[0098] The rectifier circuit 13A is a bridge diode, but the present disclosure is not limited to this.

[0099] The rectifier circuit 13A includes diodes 13c to 13f. The anode of the diode 13c is electrically connected to the cathode of the diode 13d. The anode of the diode 13e is electrically connected to the cathode of the diode 13f.

[0100] The cathode of the diode 13c and the cathode of the diode 13e are electrically connected to one end of the capacitor 14. The anode of the diode 13d and the anode of the diode 13f are electrically connected to the other end of the capacitor 14.

[0101] The connection point between the anode of the diode 13c and the cathode of the diode 13d is one input terminal of the rectifier circuit 13A, and the connection point between the anode of the diode 13e and the cathode of the diode 13f is the other input terminal of the rectifier circuit 13A.

[0102] One input terminal of the rectifier circuit 13A is electrically connected to one end of the secondary winding 12b of the transformer 12. The other input terminal of the rectifier circuit 13A is electrically connected to the other end of the secondary winding 12b of the transformer 12.

[0103] The connection point between the cathode of the diode 13c and the cathode of the diode 13e is one output terminal of the rectifier circuit 13A, and the connection point between the anode of the diode 13d and the anode of the diode 13f is the other output terminal of the rectifier circuit 13A.

[0104] Rectifier circuit 13A full-wave rectifies the voltage excited in secondary winding 12b of transformer 12, and outputs the full-wave rectified voltage to capacitor 14. Capacitor 14 smoothes the voltage that has been full-wave rectified by rectifier circuit 13A.

[0105] The power supply device 1A has the same effects as the power supply device 1.

[0106] <Third embodiment> Among the components of the third embodiment, the same components as those of the first or second embodiment are given the same reference numerals, and the description thereof will be omitted.

[0107] Fig. 5 is a diagram showing the configuration of a power supply device according to a third embodiment. Compared with power supply device 1A (see Fig. 4), power supply device 1B includes a choke coil 22, a first power factor correction circuit 23B-1, and a second power factor correction circuit 23B-2. Moreover, power supply device 1B includes a DC-DC converter 4B instead of DC-DC converter 4A.

[0108] Compared to the DC-DC converter 4A (see FIG. 4), the DC-DC converter 4B includes a first transformer driving circuit 11A-1 and a second transformer driving circuit 11A-2 instead of the transformer driving circuit 11A. Moreover, the DC-DC converter 4B includes a first transformer 12-1 and a second transformer 12-2 instead of the transformer 12.

[0109] The first power factor correction circuit 23B-1 includes diodes 23a and 23c, transistors 23b and 23d, and a capacitor 23e.

[0110] The anode of the diode 23a is electrically connected to the drain of the transistor 23b. The anode of the diode 23c is electrically connected to the drain of the transistor 23d. The cathode of the diode 23a is electrically connected to the cathode of the diode 23c. The source of the transistor 23b is electrically connected to the source of the transistor 23d.

[0111] The transistors 23b and 23d are controlled by the control device 7 to be in an on or off state.

[0112] The cathode of the diode 23a and the cathode of the diode 23c are electrically connected to one end (high potential end) of the capacitor 23e. The sources of the transistors 23b and 23d are electrically connected to the other end (low potential end) of the capacitor 23e.

[0113] A connection point between the anode of the diode 23a and the drain of the transistor 23b is one input terminal of the first power factor correction circuit 23B-1. A connection point between the anode of the diode 23c and the drain of the transistor 23d is the other input terminal of the first power factor correction circuit 23B-1. Both ends of the capacitor 23e are output terminals of the first power factor correction circuit 23B-1.

[0114] The circuit configuration of the second power factor correction circuit 23B-2 is the same as the circuit configuration of the first power factor correction circuit 23B-1, and therefore a description thereof will be omitted.

[0115] One input terminal of the first power factor correction circuit 23B-1 is electrically connected to one output terminal of the AC power supply 21 via the choke coil 22. The other input terminal of the first power factor correction circuit 23B-1 is electrically connected to one input terminal of the second power factor correction circuit 23B-2. The other input terminal of the second power factor correction circuit 23B-2 is electrically connected to the other output terminal of the AC power supply 21.

[0116] That is, the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 are connected in series (cascade).

[0117] When the voltage of the AC power supply 21 is positive, first, the transistors 23b and 23d of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 are controlled to be in the ON state. As a result, a current flows through the AC power supply 21 → the choke coil 22 → the transistor 23b of the first power factor correction circuit 23B-1 → the transistor 23d → the transistor 23b of the second power factor correction circuit 23B-2 → the transistor 23d → the AC power supply 21. As a result, energy is stored in the choke coil 22.

[0118] Next, the transistors 23b of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 are controlled to be in an OFF state, and the transistor 23d is controlled to be in an ON state. As a result, a current flows through the AC power source 21 → the choke coil 22 → the diode 23a of the first power factor correction circuit 23B-1 → the capacitor 23e → the transistor 23d → the diode 23a of the second power factor correction circuit 23B-2 → the capacitor 23e → the transistor 23d → the AC power source 21. As a result, the capacitors 23e of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 are charged.

[0119] When the voltage of the AC power supply 21 is negative, first, the transistors 23b and 23d of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 are controlled to be in the ON state. As a result, a current flows through the path of the AC power supply 21 → the transistor 23d of the second power factor correction circuit 23B-2 → the transistor 23b → the transistor 23d of the first power factor correction circuit 23B-1 → the transistor 23b → the choke coil 22 → the AC power supply 21. As a result, energy is stored in the choke coil 22.

[0120] Next, the transistor 23d of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 is controlled to be in an OFF state, and the transistor 23b is controlled to be in an ON state. As a result, a current flows through the AC power source 21 → the diode 23c of the second power factor correction circuit 23B-2 → the capacitor 23e → the transistor 23b → the diode 23c of the first power factor correction circuit 23B-1 → the capacitor 23e → the transistor 23b → the choke coil 22 → the AC power source 21. As a result, the capacitor 23e of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2 is charged.

[0121] The circuit configurations of the first transformer driving circuit 11A-1 and the second transformer driving circuit 11A-2 are the same as the circuit configuration of the transformer driving circuit 11A (see FIG. 4), and therefore will not be described.

[0122] The voltage of the capacitor 23e in the first power factor correction circuit 23B-1 is input to two input terminals of the first transformer driving circuit 11A-1. The voltage of the capacitor 23e in the second power factor correction circuit 23B-2 is input to two input terminals of the second transformer driving circuit 11A-2.

[0123] One end of the primary winding 12a of the first transformer 12-1 is electrically connected to one output terminal of the first transformer driving circuit 11A-1 via a capacitor 12f, and the other end of the primary winding 12a of the first transformer 12-1 is electrically connected to the other output terminal of the first transformer driving circuit 11A-1.

[0124] One end of the primary winding 12a of the second transformer 12-2 is electrically connected to one output terminal of the second transformer driving circuit 11A-2 via a capacitor 12f, and the other end of the primary winding 12a of the second transformer 12-2 is electrically connected to the other output terminal of the second transformer driving circuit 11A-2.

[0125] The other end of the secondary winding 12b of the first transformer 12-1 and one end of the secondary winding 12b of the second transformer 12-2 are electrically connected together, that is, the secondary winding 12b of the first transformer 12-1 and the secondary winding 12b of the second transformer 12-2 are connected together in series.

[0126] One input terminal of the rectifier circuit 13A is electrically connected to one end of the secondary winding 12b of the first transformer 12-1, and the other input terminal of the rectifier circuit 13A is electrically connected to the other end of the secondary winding 12b of the second transformer 12-2.

[0127] The rectifier circuit 13A full-wave rectifies the voltage excited in the secondary winding 12b of the first transformer 12-1 and the secondary winding 12b of the second transformer 12-2, and outputs the rectified voltage to the capacitor .

[0128] The power supply device 1B provides the same effects as the power supply devices 1 and 1A.

[0129] <Fourth embodiment> Among the components of the fourth embodiment, the same components as those of the first, second or third embodiment are given the same reference numerals and the description thereof will be omitted.

[0130] Fig. 6 is a diagram showing the configuration of a power supply device according to a fourth embodiment. Compared with power supply device 1B (see Fig. 5), power supply device 1C includes a full-wave rectifier circuit 24. Moreover, power supply device 1C includes a first power factor correction circuit 23C-1 and a second power factor correction circuit 23C-2 instead of the first power factor correction circuit 23B-1 and the second power factor correction circuit 23B-2. Moreover, power supply device 1C includes a DC-DC converter 4C instead of the DC-DC converter 4B.

[0131] The full-wave rectifier circuit 24 is a bridge diode, but the present disclosure is not limited thereto.

[0132] The full-wave rectifier circuit 24 includes diodes 24a to 24d. The anode of the diode 24a is electrically connected to the cathode of the diode 24b. The cathode of the diode 24a is electrically connected to the cathode of the diode 24c. The anode of the diode 24b is electrically connected to the anode of the diode 24d. The anode of the diode 24c is electrically connected to the cathode of the diode 24d.

[0133] A connection point between the anode of the diode 24a and the cathode of the diode 24b is one input terminal of the full-wave rectifier circuit 24. A connection point between the anode of the diode 24c and the cathode of the diode 24d is the other input terminal of the full-wave rectifier circuit 24. The two input terminals of the full-wave rectifier circuit 24 are electrically connected to the AC power supply 21.

[0134] The connection point between the cathode of the diode 24a and the cathode of the diode 24c is one (high potential side) output terminal of the full-wave rectifier circuit 24. The connection point between the anode of the diode 24b and the anode of the diode 24d is the other (low potential side) output terminal of the full-wave rectifier circuit 24.

[0135] The full-wave rectifier circuit 24 full-wave rectifies the AC input voltage input from the AC power supply 21 and outputs the result.

[0136] The first power factor correction circuit 23C-1 includes a diode 23f, a transistor 23g, and a capacitor 23h.

[0137] The anode of the diode 23f is electrically connected to the drain of the transistor 23g.

[0138] The transistor 23g is controlled by the control device 7 to be in an on or off state.

[0139] The cathode of the diode 23f is electrically connected to one end (high potential end) of the capacitor 23h. The source of the transistor 23g is electrically connected to the other end (low potential end) of the capacitor 23h.

[0140] A connection point between the anode of the diode 23f and the drain of the transistor 23g is one input terminal of the first power factor correction circuit 23C-1. A connection point between the source of the transistor 23g and the other end of the capacitor 23h is the other input terminal of the first power factor correction circuit 23C-1. Both ends of the capacitor 23h are output terminals of the first power factor correction circuit 23C-1.

[0141] The circuit configuration of the second power factor correction circuit 23C-2 is the same as the circuit configuration of the first power factor correction circuit 23C-1, so a description thereof will be omitted.

[0142] One input terminal of the first power factor correction circuit 23C-1 is electrically connected to one output terminal of the AC power source 21 via the choke coil 22-1. The other input terminal of the first power factor correction circuit 23C-1 is electrically connected to one input terminal of the second power factor correction circuit 23C-2. The other input terminal of the second power factor correction circuit 23C-2 is electrically connected to the other output terminal of the AC power source 21 via the choke coil 22-2.

[0143] That is, the first power factor correction circuit 23C-1 and the second power factor correction circuit 23C-2 are connected in series (cascade).

[0144] Although the power supply device 1C includes two choke coils 22-1 and 22-2, the present disclosure is not limited to this.

[0145] The voltage of the capacitor 23h in the first power factor correction circuit 23C-1 is input to two input terminals of the first transformer driving circuit 11A-1. The voltage of the capacitor 23h in the second power factor correction circuit 23C-2 is input to two input terminals of the second transformer driving circuit 11A-2.

[0146] One input terminal of the rectifier circuit 13A is electrically connected to one end of the secondary winding 12b of the first transformer 12-1 via a choke coil 25-1, and the other input terminal of the rectifier circuit 13A is electrically connected to the other end of the secondary winding 12b of the second transformer 12-2 via a choke coil 25-2.

[0147] The rectifier circuit 13A full-wave rectifies the voltage excited in the secondary winding 12b of the first transformer 12-1 and the secondary winding 12b of the second transformer 12-2, and outputs the rectified voltage to the capacitor .

[0148] One end of the capacitor 14 is electrically connected to one end of the load 3 via the choke coil 26. The other end of the capacitor 14 is electrically connected to the other end of the load 3.

[0149] The power supply device 1C provides the same effects as the power supply devices 1, 1A, and 1B.

[0150] 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 implemented 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 in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0151] 1, 1A, 1B, 1C power supplies 2 DC power supply 3. Load 4, 4A, 4B, 4C DC-DC Converter 5 Current Sensor 6 Voltage Sensor 7 Control Device 7a Subtractor 7b Current Controller 7c Switching control section 7d Drive circuit 7d1 First drive circuit 7d2 Second driver circuit 8 Current, power, and voltage indicator 11, 11A transformer drive circuit 11A-1 First transformer drive circuit 11A-2 Second transformer drive circuit 12. Transformer 12-1 1st transformer 12-2 2nd transformer 13, 13A rectifier circuit 14 Capacitor 21 AC power supply 22, 22-1, 22-2, 25-1, 25-2, 26 Choke coil 23B-1 First power factor correction circuit 23B-2 Second power factor correction circuit 23C-1 First power factor correction circuit 23C-2 Second power factor correction circuit 24 Full wave rectifier circuit

Claims

1. A power supply device having a heavy load mode, a first light load mode in which a load is lighter than that in the heavy load mode, and a second light load mode in which a load is lighter than that in the first light load mode, A DC-DC converter that converts an input voltage and outputs the converted voltage; a control device that controls the DC-DC converter by changing a switching frequency of a switching control signal of the DC-DC converter when an operation amount of the DC-DC converter is larger than a first threshold value that separates the heavy load mode and the first light load mode, by fixing the switching frequency and changing a pulse width of the switching control signal when the operation amount of the DC-DC converter is smaller than the first threshold value and larger than a second threshold value that separates the first light load mode and the second light load mode, and by fixing the pulse width and changing the switching frequency when the operation amount of the DC-DC converter is smaller than the second threshold value; Equipped with A power supply device comprising:

2. The control device includes: When switching between the heavy load mode and the first light load mode, the DC-DC converter is controlled in the first light load mode up to a second output current-output voltage characteristic on a higher power side than the first output current-output voltage characteristic separated by the first threshold value.

2. The power supply device according to claim 1 .

3. The control device includes: When switching from the heavy load mode to the first light load mode, the DC-DC converter is controlled in the heavy load mode up to the first output current-output voltage characteristic, and when a switching frequency of the switching control signal continues to be an upper frequency limit in the frequency modulation of the heavy load mode for a certain period of time, the DC-DC converter is controlled by an operation amount that is predetermined for an output voltage of the first light load mode.

3. The power supply device according to claim 2 .

4. an operation amount upper limit value, which is an upper limit value of an operation amount, is determined in advance for each output voltage in the first light load mode so as to obtain the second output current-output voltage characteristic; and an output current upper limit value, which is an upper limit value of an output current, is determined in advance for each output voltage in the first light load mode so as to obtain the second output current-output voltage characteristic; The control device includes: When switching from the first light load mode to the heavy load mode, if the manipulated variable continues to be the manipulated variable upper limit value for a certain period of time, or if the output current continues to be the output current upper limit value for a certain period of time, the DC-DC converter is controlled at or near the upper limit of the frequency of the frequency modulation in the heavy load mode.

4. The power supply device according to claim 2 or 3.

5. the control device includes a drive circuit that outputs the switching control signal to a high-side switching element and a low-side switching element in the DC-DC converter; a power supply circuit of a circuit that outputs the switching control signal to the high-side switching element in the drive circuit is a power supply circuit that does not depend on a switching operation of the low-side switching element.

5. A power supply device according to claim 1, wherein the power supply device is a power supply unit.

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