DC power supply device

Abstract

To suppress an increase of a voltage gain at light load to a level which allows voltage control and to output large power even at rated load.SOLUTION: A DC power supply device includes: a first switch and a second switch which are connected in series between a positive side terminal and a negative side terminal of a DC voltage source; a third switch and a fourth switch which are connected in series between the positive side terminal and the negative side terminal of the DC voltage source; a resonance circuit provided between a connection point between the first switch and the second switch and a first intermediate point; a transformer in which a primary coil is provided between the first intermediate point and a connection point between the third switch and the fourth switch; a rectification circuit; a smoothing circuit; a first diode in which an anode is connected to the first intermediate point and a cathode is connected to the positive side terminal of the DC voltage source; and a second diode in which a cathode is connected to the first intermediate point and an anode is connected to the negative side terminal of the DC voltage source.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art DC power supply devices using a series resonant converter are known, and are capable of outputting large amounts of power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-236531 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a DC power supply device using a series resonant converter, ripples occur on the primary side of the transformer under light load conditions. As a result, in a DC power supply device using a series resonant converter, the ripples generated on the primary side are transmitted to the secondary side of the transformer, increasing the voltage gain.

[0005] To solve this problem, a DC power supply device has been proposed that circulates current by connecting a diode between the junction between the inductor and capacitor in the series resonant circuit and a DC voltage source (Patent Document 1). However, although such a DC power supply device that circulates current on the primary side can suppress an increase in voltage gain under light load conditions, it cannot output large power because the voltage is clamped by the diode when a rated load is connected.

[0006] The present invention has been made in view of the above, and provides a DC power supply device that can suppress an increase in voltage gain under light load to a level that allows voltage control, and can output large power under rated load. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a DC power supply device according to the present invention includes a DC voltage source connected in series between a positive terminal and a negative terminal of the DC voltage source, The switching control signal a first switch and a second switch that are alternately turned on and off so as not to be turned on at the same time, and are connected in series between the positive terminal and the negative terminal of the DC voltage source; The switching control signal a third switch and a fourth switch that are alternately turned on and off so as not to be turned on at the same time; and a second switch that is provided between a connection point between the first switch and the second switch and a first intermediate point. , an LC circuit consisting of an inductor and a capacitor connected in series. a resonant circuit, a transformer having a primary coil provided between the first intermediate point and a connection point between the third switch and the fourth switch, a rectifier circuit that outputs a rectified voltage obtained by rectifying an AC voltage output from a secondary coil of the transformer, a smoothing circuit that outputs an output voltage obtained by smoothing the rectified voltage output from the rectifier circuit, a first diode having an anode connected to the first intermediate point and a cathode connected to the positive terminal of the DC voltage source, and a second diode having a cathode connected to the first intermediate point and an anode connected to the negative terminal of the DC voltage source. and a control circuit that outputs the switching control signal so that each of the first switch, the second switch, the third switch, and the fourth switch switches at a predetermined switching frequency, wherein when a ringing voltage having a frequency higher than the switching frequency occurs at the first intermediate point, the first diode and the second diode function to regenerate power due to the ringing voltage to the DC voltage source. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the increase in voltage gain during light load to a level that allows voltage control, and to output large power under a rated load. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a DC power supply device according to an embodiment. [Figure 2] FIG. 2 shows simulated waveforms of the primary side voltage and current at rated load. [Figure 3] FIG. 3 shows a simulated waveform of the time change of the output voltage in the case of the rated load. [Figure 4]FIG. 4 shows simulated waveforms of voltage and current on the primary side under light load. [Figure 5] FIG. 5 is a diagram showing a simulated waveform of the change in output voltage over time in the case of a light load. [Figure 6] FIG. 6 is a diagram showing the configuration of a DC power supply device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 is a diagram showing the configuration of a DC power supply 10 according to an embodiment. The DC power supply 10 outputs a DC output voltage obtained by boosting an input DC voltage from between a first output terminal 12 and a second output terminal 14. For example, the DC power supply 10 is used as a power supply for a pulse generator that generates switching pulses to be supplied to a plasma generator.

[0011] The DC power supply device 10 includes a DC voltage source 22, a first switch 24, a second switch 26, a third switch 28, a fourth switch 30, a resonant circuit 32, a transformer 34, a rectifier circuit 36, a smoothing circuit 38, a first diode 42, a second diode 44, and a control circuit 46.

[0012] The DC voltage source 22 generates a DC voltage. The value of the voltage generated by the DC voltage source 22 may be controlled by the control circuit 46.

[0013] The first switch 24 and the second switch 26 are connected in series. The first switch 24 and the second switch 26 connected in series are provided between the positive terminal and the negative terminal of the DC voltage source 22. The first switch 24 and the second switch 26 are alternately turned on and off under the control of the control circuit 46 so as not to be turned on at the same time.

[0014] Each of the first switch 24 and the second switch 26 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). If the first switch 24 is a MOSFET, its drain is connected to the positive terminal of the DC voltage source 22, its source is connected to the drain of the second switch 26, and a switching control signal output from the control circuit 46 is applied to its gate. If the second switch 26 is a MOSFET, its drain is connected to the source of the first switch 24, its source is connected to the negative terminal of the DC voltage source 22, and a switching control signal output from the control circuit 46 is applied to its gate.

[0015] The third switch 28 and the fourth switch 30 are connected in series. The third switch 28 and the fourth switch 30 connected in series are provided between the positive terminal and the negative terminal of the DC voltage source 22. The third switch 28 and the fourth switch 30 are alternately turned on and off under the control of the control circuit 46 so as not to be turned on at the same time.

[0016] The third switch 28 and the fourth switch 30 are each, for example, a MOSFET. If the third switch 28 is a MOSFET, the drain of the third switch 28 is connected to the positive terminal of the DC voltage source 22, the source of the third switch 28 is connected to the drain of the fourth switch 30, and a switching control signal output from the control circuit 46 is applied to the gate of the third switch 28. If the fourth switch 30 is a MOSFET, the drain of the fourth switch 30 is connected to the source of the third switch 28, the source of the fourth switch 30 is connected to the negative terminal of the DC voltage source 22, and a switching control signal output from the control circuit 46 is applied to the gate of the fourth switch 30.

[0017] The resonant circuit 32 is connected between the connection point of the first switch 24 and the second switch 26 and the first intermediate point 50. The resonant circuit 32 has an impedance at a predetermined resonant frequency. For example, the resonant circuit 32 includes an LC circuit having a resonant frequency that resonates with the switching frequency of the first switch 24 and the second switch 26. For example, the resonant circuit 32 includes an inductor 62 and a capacitor 64 connected in series. The resonant circuit 32 can pass a large current at the resonant frequency.

[0018] The transformer 34 has a primary coil disposed between the first intermediate point 50 and the connection point between the third switch 28 and the fourth switch 30. The transformer 34 generates from the secondary coil an AC voltage that is a predetermined multiple of the amplitude of the AC voltage applied to the primary coil.

[0019] The rectifier circuit 36 ​​outputs a rectified voltage obtained by full-wave rectifying the AC voltage generated in the secondary coil of the transformer 34. The smoothing circuit 38 smoothes the rectified voltage output from the rectifier circuit 36, and outputs a DC output voltage obtained by smoothing the rectified voltage between the first output terminal 12 and the second output terminal 14.

[0020] In this embodiment, the transformer 34 is a center-tapped type, and the midpoint of the secondary coil is connected to the second output terminal 14. In this embodiment, the rectifier circuit 36 ​​includes a third diode 66 and a fourth diode 68. The third diode 66 has an anode connected to one terminal of the secondary coil of the transformer 34 and a cathode connected to the first output terminal 12. The fourth diode 68 has an anode connected to the terminal of the secondary coil of the transformer 34 that is not connected to the third diode 66 and a cathode connected to the first output terminal 12. In this embodiment, the smoothing circuit 38 is a smoothing capacitor connected between the first output terminal 12 and the second output terminal 14.

[0021] The transformer 34 may not have a center tap. The rectifier circuit 36 ​​may be a bridge rectifier circuit or a full-wave rectifier circuit that multiplies the voltage amplitude by a predetermined factor. The smoothing circuit 38 may be a circuit including multiple smoothing capacitors, or a circuit including a smoothing capacitor and a smoothing inductor.

[0022] The first diode 42 has an anode connected to the first intermediate point 50 and a cathode connected to the positive terminal of the DC voltage source 22. The second diode 44 has an anode connected to the negative terminal of the DC voltage source 22 and a cathode connected to the first intermediate point 50.

[0023] The control circuit 46 switches on and off the first switch 24, the second switch 26, the third switch 28, and the fourth switch 30 at a predetermined frequency. The control circuit 46 alternately turns on and off the first switch 24 and the second switch 26 so that they are not turned on at the same time, and alternately turns on and off the third switch 28 and the fourth switch 30 so that they are not turned on at the same time.

[0024] For example, the control circuit 46 turns on / off the first switch 24, the second switch 26, the third switch 28, and the fourth switch 30 in a synchronous control manner. More specifically, the control circuit 46 controls the switching so that the first switch 24 and the fourth switch 30 are turned on / off in synchronization, and the second switch 26 and the third switch 28 are turned on in synchronization. This allows the control circuit 46 to apply an AC voltage of a predetermined frequency to the resonant circuit 32 and the primary coil of the transformer 34.

[0025] The control circuit 46 may also turn on / off the first switch 24, the second switch 26, the third switch 28, and the fourth switch 30 using a phase-shift control method in response to the deviation between the output voltage and a target voltage or the deviation between the output current and a target current. More specifically, the control circuit 46 controls the switching periods of the first switch 24 and the second switch 26 so that they are the same as the switching periods of the third switch 28 and the fourth switch 30. The control circuit 46 also changes the phase of the on-period of the fourth switch 30 relative to the on-period of the first switch 24 and the phase of the on-period of the third switch 28 relative to the on-period of the second switch 26 so that the output voltage matches the target voltage or the output current matches the target current. This allows the control circuit 46 to apply an AC voltage of a predetermined frequency to the resonant circuit 32 and the primary coil of the transformer 34 and to rapidly change the output voltage.

[0026] Control circuit 46 may include a margin period during which first switch 24 and second switch 26 are simultaneously turned off and third switch 28 and fourth switch 30 are simultaneously turned off. This enables control circuit 46 to prevent a situation in which first switch 24 and second switch 26 are simultaneously turned on and DC voltage source 22 is short-circuited, or a situation in which third switch 28 and fourth switch 30 are simultaneously turned on and DC voltage source 22 is short-circuited, due to a shift in switching timing or the like.

[0027] Fig. 2 is a diagram showing simulated waveforms of voltage and current on the primary side in the case of rated load. In Fig. 2, the solid line shows the waveforms of the DC power supply 10 according to the embodiment, and the dotted line shows the waveforms of a device configured by omitting the first diode 42 and the second diode 44 from the DC power supply 10 according to the embodiment. The same applies to Figs. 3, 4, and 5.

[0028] FIG. 2 also shows simulated waveforms when the winding ratio of the transformer 34 is 1:4 and the rectifier circuit 36 ​​is a 4x rectifier circuit. FIG. 2 also shows simulated waveforms when the inductance of the inductor 62 of the resonant circuit 32 is 4.2 μH, the capacitance of the capacitor 64 is 210 nF, the inductance of the parasitic inductor appearing in the series component of the primary coil of the transformer 34 is 1 μH, the capacitance of the parasitic capacitor appearing in the parallel component of the primary coil of the transformer 34 is 1 nF, and the inductance of the parasitic inductor appearing in the parallel component of the primary coil of the transformer 34 is 600 μH. FIG. 2 also shows simulated waveforms when the DC voltage generated by the DC voltage source 22 is 400 V and the switching frequency is 175 kHz. FIGS. 3, 4, and 5 also show simulated waveforms under the same conditions as FIG. 2. Note that the parasitic inductor appearing in the series component of the primary coil of the transformer 34, the parasitic capacitor appearing in the parallel component of the primary coil of the transformer 34, and the parasitic inductor appearing in the parallel component of the primary coil of the transformer 34 are not shown in FIG. 2.

[0029] Furthermore, FIG. 2 shows a simulated waveform when a 10 Ω load is connected between the first output terminal 12 and the second output terminal 14.

[0030] 2A, when a 10 Ω load is connected to the DC power supply device 10, a substantially rectangular voltage synchronized with the switching frequency is applied to the primary coil of the transformer 34. Also, as shown in FIG. 2A, when a 10 Ω load is connected to a device configured without the first diode 42 and the second diode 44, a substantially rectangular voltage synchronized with the switching frequency is applied to the primary coil of the transformer 34.

[0031] 2B, in the DC power supply device 10, when the voltage at the first intermediate point 50 is higher than the positive terminal of the DC voltage source 22 and the first diode 42 is conductive, a current flows through the first diode 42. Furthermore, as shown in FIG. 2C, in the DC power supply device 10, when a 10 Ω load is connected, a current including a frequency component tuned to the resonant circuit 32 flows through the primary coil of the transformer 34. Furthermore, as shown in FIG. 2C, in a device configured without the first diode 42 and the second diode 44, when a 10 Ω load is connected, a current including a frequency component tuned to the resonant circuit 32 flows through the primary coil of the transformer 34.

[0032] FIG. 3 shows a simulated waveform of the change in output voltage over time when a load of 10 Ω, which is an example of a rated load, is connected between the first output terminal 12 and the second output terminal 14.

[0033] 3, the DC power supply device 10 according to the embodiment has an output voltage that is about 2.4% lower than that of a device configured without the first diode 42 and the second diode 44, but the amount of reduction is relatively small. In the case of the circuit shown in Patent Document 1, the output voltage is lower by about 20%. In other words, the DC power supply device 10 according to the embodiment can output more power than the circuit shown in Patent Document 1.

[0034] This phenomenon will be further explained. When a series resonant circuit is configured with an inductor and a capacitor, such as resonant circuit 32 shown in Fig. 1, the resonant characteristics of the series resonant circuit are generally expressed by Q (Quality Factor) shown in equation (1), and it is said that the larger the Q value, the better the resonant characteristics. In equation (1), Rpri is the apparent load resistance value on the primary side, L is the inductance of the inductor, and f is the frequency. Q=2πfL / Rpri (1)

[0035] Under resonant conditions, the voltage at the junction between the inductor and capacitor is approximately "Q" times the voltage applied to the primary coil of the transformer relative to the negative terminal of the DC voltage source, resulting in a high voltage. Therefore, the heavier the load (the higher the output voltage), the higher the voltage applied to the inductor and capacitor that make up the series resonant circuit. Therefore, if a diode is provided at the junction between the inductor and capacitor that make up the resonant circuit, as in the circuit shown in Patent Document 1, the heavier the load, the more likely it is that a voltage exceeding the clamp voltage will be generated, resulting in a corresponding decrease in the output power.

[0036] In contrast, the voltage at the junction between the capacitor and the transformer is lower than the voltage at the junction between the inductor and the capacitor. This is because, under resonance conditions, the absolute value of the voltage applied to the inductor and the absolute value of the voltage applied to the capacitor are the same, but the voltage applied to the inductor and the voltage applied to the capacitor are in phase such that they cancel each other out. Therefore, when a diode is provided at the junction between the capacitor and the transformer, as in the DC power supply device 10 according to the embodiment, a voltage exceeding the clamp voltage is less likely to occur than in the circuit configuration shown in Patent Document 1, and the output power can be increased accordingly.

[0037] FIG. 4 shows simulated waveforms of the voltage and current on the primary side when a load of 1 MΩ, which is an example of a light load, is connected between the first output terminal 12 and the second output terminal 14.

[0038] 4A, when a 1 MΩ load is connected to a device configured without the first diode 42 and the second diode 44, a substantially rectangular voltage synchronized with the switching frequency and a ringing voltage with a frequency higher than the switching frequency are applied to the primary coil of the transformer 34. Therefore, in a device configured without the first diode 42 and the second diode 44, power is transferred from the primary side to the secondary side of the transformer 34 due to the ringing, regardless of switching control.

[0039] In contrast, as shown in A of Fig. 4, when a load of 1 MΩ is connected to the DC power supply 10, no ringing voltage is applied to the primary coil of the transformer 34. Also, as shown in B of Fig. 4, in the DC power supply 10, ringing is included in the current flowing through the first diode 42. Therefore, in the DC power supply 10, power due to ringing is regenerated to the DC voltage source 22 via the first diode 42 and is not transmitted to the secondary side of the transformer 34.

[0040] FIG. 5 shows a simulated waveform of the output voltage when a load of 1 MΩ, which is an example of a light load, is connected between the first output terminal 12 and the second output terminal 14.

[0041] 5, in the device configured without the first diode 42 and the second diode 44, the output voltage increases significantly over time. That is, the voltage gain increases significantly. In contrast, in the DC power supply 10, the rate of increase in the output voltage over time is lower than in the device configured without the first diode 42 and the second diode 44. That is, the increase in the voltage gain is suppressed.

[0042] As described above, in the DC power supply device 10, the first diode 42 and the second diode 44 are provided between the DC voltage source 22 and the first intermediate point 50, which is one terminal of the transformer 34. This prevents a ringing voltage from being applied to the primary coil of the transformer 34 under light load conditions. This makes it possible to suppress the increase in voltage gain under light load conditions to a level that allows voltage control. Furthermore, the DC power supply device 10 experiences only a small drop in output voltage even under rated load conditions. This allows the DC power supply device 10 to output large power under rated load conditions.

[0043] Fig. 6 is a diagram showing the configuration of a DC power supply device 10 according to a modified example. The DC power supply device 10 according to the modified example has substantially the same functions and configuration as the DC power supply device 10 according to the embodiment described with reference to Figs. 1 to 5, and therefore, the same reference numerals are used to designate elements having substantially the same functions and configurations, and descriptions thereof will be omitted except for differences.

[0044] The DC power supply device 10 according to the modified example includes a first capacitor 82 and a second capacitor 84 instead of the third switch 28 and the fourth switch 30 shown in FIG.

[0045] First capacitor 82 and second capacitor 84 are connected in series. First capacitor 82 and second capacitor 84 connected in series are provided between the positive terminal and the negative terminal of DC voltage source 22. Transformer 34 has a primary coil provided between first intermediate point 50 and the connection point between first capacitor 82 and second capacitor 84. Control circuit 46 alternately turns first switch 24 and second switch 26 on and off so that they are not turned on simultaneously.

[0046] In the DC power supply 10 according to this modified example, the first diode 42 and the second diode 44 are provided between the DC voltage source 22 and the first intermediate point 50, which is one terminal of the transformer 34. This prevents a ringing voltage from being applied to the primary coil of the transformer 34 under light load conditions, and reduces the drop in output voltage even under rated load conditions. This allows the DC power supply 10 according to this modified example to output large power under rated load conditions, and to suppress the increase in voltage gain under light load conditions to a level that allows voltage control.

[0047] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Various modifications can be made to the embodiments. [Explanation of symbols]

[0048] 10 DC power supply device, 12 first output terminal, 14 second output terminal, 22 DC voltage source, 24 first switch, 26 second switch, 28 third switch, 30 fourth switch, 32 resonant circuit, 34 transformer, 36 rectifier circuit, 38 smoothing circuit, 42 first diode, 44 second diode, 46 control circuit, 50 first intermediate point, 82 first capacitor, 84 second capacitor

Claims

1. a first switch and a second switch connected in series between a positive terminal and a negative terminal of a DC voltage source, the first switch and the second switch alternately turned on and off in response to a switching control signal so as not to be turned on simultaneously; a third switch and a fourth switch connected in series between the positive terminal and the negative terminal of the DC voltage source, the third switch and the fourth switch alternately turned on and off in response to the switching control signal so as not to be turned on simultaneously; a resonant circuit that is an LC circuit configured by an inductor and a capacitor connected in series and that is provided between a connection point between the first switch and the second switch and a first intermediate point; a transformer having a primary coil disposed between the first intermediate point and a connection point between the third switch and the fourth switch; a rectifier circuit that rectifies the AC voltage output from the secondary coil of the transformer and outputs a rectified voltage; a smoothing circuit that smoothes the rectified voltage output from the rectifier circuit and outputs an output voltage; a first diode having an anode connected to the first intermediate point and a cathode connected to the positive terminal of the DC voltage source; a second diode having a cathode connected to the first intermediate point and an anode connected to the negative terminal of the DC voltage source; a control circuit that outputs the switching control signal so that each of the first switch, the second switch, the third switch, and the fourth switch switches at a predetermined switching frequency; Equipped with the first diode and the second diode function to regenerate power due to a ringing voltage having a frequency higher than the switching frequency at the first intermediate point to the DC voltage source. DC power supply.

2. The control circuit controls switching so that the first switch and the fourth switch are turned on synchronously, and the second switch and the third switch are turned on synchronously.

2. The DC power supply device according to claim 1.

3. The control circuit controls the switching periods of the first switch and the second switch to be the same as the switching periods of the third switch and the fourth switch, and changes the phase of the on period of the fourth switch relative to the on period of the first switch, and the phase of the on period of the third switch relative to the on period of the second switch.

2. The DC power supply device according to claim 1.

4. a first switch and a second switch connected in series between a positive terminal and a negative terminal of a DC voltage source, the first switch and the second switch alternately turned on and off in response to a switching control signal so as not to be turned on simultaneously; a first capacitor and a second capacitor connected in series between the positive terminal and the negative terminal of the DC voltage source; a resonant circuit that is an LC circuit configured by an inductor and a capacitor connected in series and that is provided between a connection point between the first switch and the second switch and a first intermediate point; a transformer having a primary coil disposed between the first intermediate point and a connection point between the first capacitor and the second capacitor; a rectifier circuit that rectifies the AC voltage output from the secondary coil of the transformer and outputs a rectified voltage; a smoothing circuit that smoothes the rectified voltage output from the rectifier circuit and outputs an output voltage; a first diode having an anode connected to the first intermediate point and a cathode connected to the positive terminal of the DC voltage source; a second diode having a cathode connected to the first intermediate point and an anode connected to the negative terminal of the DC voltage source; a control circuit that outputs the switching control signal so that each of the first switch and the second switch switches at a predetermined switching frequency; Equipped with the first diode and the second diode function to regenerate power due to a ringing voltage having a frequency higher than the switching frequency at the first intermediate point to the DC voltage source. DC power supply.

Images