A driving device for a bridgeless PFC power supply, its control method, and a motor system

Abstract

The present invention discloses a driving device for a bridgeless PFC power supply, its control method, and a motor system. The device includes: any one of a first inductor module, a second inductor module, and a third inductor module, which charges itself with a first alternating current input from an AC power supply when its own charging circuit is turned on; a control unit that controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current; a bus capacitor unit that stores the electric energy obtained by charging at least one inductor module when the charging circuit of at least one inductor module is turned on and charged, to obtain direct current. With this solution, by providing a bridgeless PFC circuit with three-way interleaved parallel driving, the conduction loss of the PFC circuit can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of power supplies, and particularly relates to a driving device for a bridgeless PFC power supply, a motor system, and a control method for the driving device of the bridgeless PFC power supply. In particular, it relates to a three-way interleaved parallel driving circuit for a bridgeless PFC circuit, a motor system having the three-way interleaved parallel driving circuit for the bridgeless PFC circuit, and a control method for the three-way interleaved parallel driving circuit of the bridgeless PFC circuit. Background Art

[0002] In related solutions, for driving a motor (such as a motor in a compressor), an inverter uses the AC-DC-AC frequency conversion technology (i.e., the AC-DC-AC frequency conversion technology). In the AC-DC-AC frequency conversion technology, a single-phase input voltage of 220V is converted from AC to DC voltage of 310V through a rectifier. After passing through a PFC (Power Factor Correction) circuit, the DC bus voltage is close to 380V. The DC bus voltage is supplied to the fan IPM (Intelligent Power Module) module and the compressor IPM module to achieve coordinated control of the fan, compressor, valve body, etc. However, in the AC-DC-AC frequency conversion technology, the PFC circuit has the disadvantage of large on-state loss.

[0003] The above content is only used to assist in understanding the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The object of the present invention is to provide a driving device for a bridgeless PFC power supply, its control method, and a motor system, so as to solve the problem of large on-state loss in the PFC circuit in the AC-DC-AC frequency conversion technology, and achieve the effect of reducing the on-state loss of the PFC circuit by setting a three-way interleaved parallel driving bridgeless PFC circuit.

[0005] The present invention provides a driving device for a bridgeless PFC power supply, comprising: a charging unit, a control unit, and a bus capacitor unit; the charging unit includes: a first inductor module, a second inductor module, and a third inductor module; wherein, any one of the first inductor module, the second inductor module, and the third inductor module is configured to receive a first alternating current input from an AC power supply, and when its own charging circuit is turned on, charge itself with the first alternating current input from the AC power supply; the control unit is configured to control the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply; the bus capacitor unit is configured to store the electric energy obtained by charging at least one of the first inductor module, the second inductor module, and the third inductor module when the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module is turned on and charged, so as to obtain direct current electricity.

[0006] In some embodiments, it further includes: an inversion unit; the inversion unit is configured to invert the direct current electricity stored in the bus capacitor unit to obtain a second alternating current required for the operation of the device to be powered.

[0007] In some embodiments, the control unit includes: a control module; the control module includes: a first switching tube module, a second switching tube module, a third switching tube module, a fourth switching tube module, a fifth switching tube module, and a sixth switching tube module, as well as a first direction module and a second direction module; wherein, each switching tube module can form a charging circuit with an inductor module and the positive half-cycle or negative half-cycle of the AC power supply; the first direction module is arranged between the input port of the AC power supply and the second switching tube module, the fourth switching tube module, and the fifth switching tube module, and can be conducted from any one of the second switching tube module, the fourth switching tube module, and the fifth switching tube module to the input port of the AC power supply; the second direction module is arranged between the input port of the AC power supply and the first switching tube module, the third switching tube module, and the sixth switching tube module, and can be conducted from the input port of the AC power supply to any one of the first switching tube module, the third switching tube module, and the sixth switching tube module.

[0008] In some embodiments, the control unit controls the connection of the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is less than the first set current threshold, controlling the connection of the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module; wherein: controlling the second switch tube module to conduct, and controlling the first switch tube module, the third switch tube module to the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply is supplied to the first inductor module through the first direction module and supplies power to the bus capacitor unit; controlling the second switch tube module to disconnect, and controlling the first switch tube module, the third switch tube module to the sixth switch tube module to also disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply, combined with the charging energy on the first inductor module, charges the bus capacitor unit through the body diode of the switch tube in the first switch tube module; controlling the first switch tube module to conduct, and controlling the second switch tube module to the sixth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply is supplied to the first inductor module through the second direction module and supplies power to the bus capacitor unit; controlling the first switch tube module to disconnect, and controlling the second switch tube module to the sixth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply, combined with the charging energy on the first inductor module, charges the bus capacitor unit through the body diode of the switch tube in the second switch tube module.

[0009] In some embodiments, the control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is greater than a first set current threshold and less than a second set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on; wherein: controlling the second switch tube module and the fourth switch tube module to conduct, and controlling the first switch tube module, the third switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply is used to charge the first inductor module and the second inductor module after passing through the first direction module, and supply power to the bus capacitor unit; controlling the second switch tube module and the fourth switch tube module to be turned off, and controlling the first switch tube module, the third switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module and the second inductor module, passes through the body diode of the switch tube in the first switch tube module and the body diode of the switch tube in the third switch tube module, and after passing through the first direction module, charges the bus capacitor unit; controlling the first switch tube module and the third switch tube module to conduct, and controlling the second switch tube module, the fourth switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply is used to charge the first inductor module and the second inductor module after passing through the second direction module, and supply power to the bus capacitor unit; controlling the first switch tube module and the third switch tube module to conduct, and controlling the second switch tube module, the fourth switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module and the second inductor module, is used to charge the first inductor module and the second inductor module after passing through the second direction module, passes through the body diode of the switch tube in the second switch tube module and the body diode of the switch tube in the fourth switch tube module, and after passing through the second direction module, charges the bus capacitor unit.

[0010] In some embodiments, the control unit further includes a switching module. The switching module includes a first switching transistor module and a second switching transistor module. The first switching transistor module is disposed on the output side of the second inductor module. The second switching transistor module is disposed on the output side of the third inductor module. The control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is greater than a second set current threshold and less than a third set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on; wherein: controlling the second switch transistor module, the fourth switch transistor module, and the fifth switch transistor module to be turned on, and controlling the first switch transistor module, the third switch transistor module, and the sixth switch transistor module to be turned off, so that in the positive half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply is supplied to the first inductor module, the second inductor module, and the third inductor module for charging through the first direction module, and power is supplied to the bus capacitor unit; controlling the second switch transistor module, the fourth switch transistor module, and the fifth switch transistor module to be turned off, and controlling the first switch transistor module, the third switch transistor module, and the sixth switch transistor module to be turned off, so that in the positive half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply, combined with the charging energy on the first inductor module, the second inductor module, and the third inductor module, passes through the first direction module and is used to charge the bus capacitor unit; controlling the first switch transistor module, the third switch transistor module, and the sixth switch transistor module to be turned on, and controlling the second switch transistor module, the fourth switch transistor module, and the fifth switch transistor module to be turned off, so that in the negative half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply is supplied to the first inductor module, the second inductor module, and the third inductor module for charging through the second direction module, and power is supplied to the bus capacitor unit; controlling the first switch transistor module, the third switch transistor module, and the sixth switch transistor module to be turned off, and controlling the second switch transistor module, the fourth switch transistor module, and the fifth switch transistor module to be turned off, so that in the negative half cycle of the AC power supply, the first alternating current input from the input port of the AC power supply, combined with the charging energy on the first inductor module, the second inductor module, and the third inductor module, passes through the second direction module and is used to charge the bus capacitor unit.

[0011] In some embodiments, the bus capacitor unit includes: a first capacitor module, a second capacitor module, and a third capacitor module; the first capacitor module, the second capacitor module, and the third capacitor module are arranged in parallel.

[0012] Matched with the above device, on the other hand, the present invention provides a motor system, including: the driving device of the bridgeless PFC power supply described above.

[0013] Matched with the above device, on the other hand, the present invention provides a control method for a driving device of a bridgeless PFC power supply, including: through a control unit, according to the magnitude of the current of the first alternating current input from an AC power supply, controlling the connection of the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module; any one of the first inductor module, the second inductor module, and the third inductor module receives the first alternating current input from the AC power supply, and when its own charging circuit is connected, uses the first alternating current input from the AC power supply to charge itself; through the bus capacitor unit, when the charging circuits of at least one of the first inductor module, the second inductor module, and the third inductor module are connected and charged, storing the electric energy obtained by charging at least one of the first inductor module, the second inductor module, and the third inductor module to obtain direct current.

[0014] In some embodiments, it further includes: through an inverter unit, inverting the direct current stored in the bus capacitor unit to obtain a second alternating current required for the operation of the device to be powered.

[0015] Thus, the solution of the present invention combines a bridgeless PFC circuit and interleaved parallel technology, sets three-way interleaved parallel drive circuits for the bridgeless PFC circuit, and controls the on / off of the three-way interleaved parallel drive circuits according to the magnitude of the current of the input AC power supply. Therefore, by setting a bridgeless PFC circuit with three-way interleaved parallel drive, the conduction loss of the PFC circuit can be reduced.

[0016] Other features and advantages of the present invention will be described in the following specification, and part of them will become obvious from the specification or be understood by implementing the present invention.

[0017] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of an embodiment of the driving device of the bridgeless PFC power supply of the present invention;

[0019] Figure 2Schematic structural diagram of an embodiment of a three-phase interleaved parallel drive circuit for a bridgeless PFC circuit of the present invention;

[0020] Figure 3 Schematic flowchart of an embodiment of a control method for a drive device of a bridgeless PFC power supply of the present invention. Detailed implementation manners

[0021] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0022] Considering that in related solutions, the converter of the PFC circuit has the advantages of high reliability, low cost, simple structure and small common-mode interference, but has the disadvantage of large conduction loss. Conduction loss is the loss when the IGBT conducts and turns off.

[0023] According to an embodiment of the present invention, a drive device for a bridgeless PFC power supply is provided. Refer to Figure 1 Schematic structural diagram of an embodiment of the device of the present invention shown. The drive device for the bridgeless PFC power supply may include: a charging unit, a control unit, and a bus capacitor unit. The charging unit, the control unit, and the bus capacitor unit are connected in sequence. The charging unit includes: a first inductor module, a second inductor module, and a third inductor module. Each inductor module among the first inductor module, the second inductor module, and the third inductor module may include only one inductor. For example, the first inductor module may include inductor L1, the second inductor module may include inductor L2, and the third inductor module may include inductor L3. Each inductor module among the first inductor module, the second inductor module, and the third inductor module may also include an inductor group, such as an inductor group formed by several inductors connected in series and parallel.

[0024] Wherein, any one of the first inductor module, the second inductor module, and the third inductor module is configured to receive a first alternating current input from an AC power supply, and when its own charging circuit is turned on, charge itself with the first alternating current input from the AC power supply.

[0025] The control unit is configured to control the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply, so that at least one of the first inductor module, the second inductor module, and the third inductor module whose charging circuit is turned on can receive the first alternating current input from the AC power supply and charge itself with the first alternating current input from the AC power supply.

[0026] The bus capacitor unit is configured to store the electric energy obtained by charging at least one of the first inductor module, the second inductor module, and the third inductor module when the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module is turned on and charged, so as to obtain direct current.

[0027] In this way, the solution of the present invention provides a driving device for a bridgeless PFC power supply, specifically a three-way interleaved parallel driving circuit for a bridgeless PFC circuit, which makes the voltage and current in the same phase, can improve the power factor of the PFC circuit, thereby improving the efficiency of the PFC circuit and reducing the current harmonic distortion. Specifically, through the first inductor module, the second inductor module, and the third inductor module, the AC power supply can be divided into 3 segments, each segment being 120°, with better current sharing effect and higher electric energy conversion efficiency.

[0028] In some embodiments, it further includes: an inversion unit. The inversion unit, such as an inverter, is arranged on the output side of the bus capacitor unit and is used to supply power to a device to be powered, such as a motor.

[0029] The inversion unit is configured to invert the direct current stored in the bus capacitor unit to obtain a second alternating current required for the operation of the device to be powered.

[0030] In order to improve the efficiency of the driver of the bridgeless PFC power supply (i.e., the PFC circuit), many topologies of the driver of the bridgeless PFC power supply have been proposed. Compared with the driver of the bridgeless PFC power supply in the related solution, there is one less diode on the power loop of the driver of the bridgeless PFC power supply, thereby improving the efficiency of the driver of the bridgeless PFC power supply. The three-way interleaved parallel driving circuit of the bridgeless PFC circuit provided by the solution of the present invention uses four fewer diodes compared with the three-way interleaved PFC circuit, the cost is relatively reduced, the device cost is saved, and the volume of the device is also reduced.

[0031] In some embodiments, the control unit includes a control module. The control module includes a first switch tube module, a second switch tube module, a third switch tube module, a fourth switch tube module, a fifth switch tube module, and a sixth switch tube module, as well as a first direction module and a second direction module. The first switch tube module is, for example, a power MOS tube module UND1, the second switch tube module is, for example, a power MOS tube module UND2, the third switch tube module is, for example, a power MOS tube module UND3, the fourth switch tube module is, for example, a power MOS tube module UND4, the fifth switch tube module is, for example, a power MOS tube module UND5, and the sixth switch tube module is, for example, a power MOS tube module UND6. The first direction module is, for example, a diode D1, and the second direction module is, for example, a diode D2.

[0032] Figure 2 FIG. is a schematic structural diagram of an embodiment of a three-phase interleaved parallel drive circuit of a bridgeless PFC circuit of the present invention. As Figure 2 shown, the three-phase interleaved parallel drive circuit of the bridgeless PFC circuit includes an input port J3 of an input power supply, input inductors of an AC power supply such as inductors L1, L2, and L3, a control module such as power MOS tube modules UND1 to UND6, low-speed diodes such as diodes D1 and D2, an inverter such as an inverter formed by power MOS tube modules UND7 to UND12, and three-phase output terminals of the inverter such as terminals X1, X2, and X3. A voltage of 220V can be input from the input port J3 of the input power supply. In the power MOS tube module, a power MOS tube (metal-oxide-semiconductor field effect transistor, MOSFET) and a body diode of the power MOS tube are provided.

[0033] Among them, each switch tube module can form a charging circuit with an inductor module and the positive or negative half cycle of the AC power supply.

[0034] The first direction module is arranged between the input port of the AC power supply, the second switch tube module, the fourth switch tube module, and the fifth switch tube module, and can be conducted from any one of the second switch tube module, the fourth switch tube module, and the fifth switch tube module to the input port of the AC power supply.

[0035] The second direction module is arranged between the input port of the AC power supply, the first switch tube module, the third switch tube module, and the sixth switch tube module, and can be conducted from the input port of the AC power supply to any one of the first switch tube module, the third switch tube module, and the sixth switch tube module.

[0036] For example, the first switch tube module can form a charging circuit with the first inductor module and the positive half cycle of the AC power supply. The second switch tube module can form a charging circuit with the first inductor module and the negative half cycle of the AC power supply. The third switch tube module can form a charging circuit with the second inductor module and the positive half cycle of the AC power supply. The fourth switch tube module can form a charging circuit with the second inductor module and the negative half cycle of the AC power supply. The sixth switch tube module can form a charging circuit with the third inductor module and the positive half cycle of the AC power supply. The fifth switch tube module can form a charging circuit with the third inductor module and the negative half cycle of the AC power supply.

[0037] In some embodiments, the control unit controls the connection of the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is less than the first set current threshold, controlling the connection of the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module.

[0038] Among them, when the current of the first alternating current is less than the first set current threshold, the control unit controls the connection of the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module, including:

[0039] The control unit is specifically further configured to control the second switch tube module to conduct, and control the first switch tube module, the third switch tube module to the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply is used to charge the first inductor module after passing through the first direction module and supply power to the bus capacitor unit.

[0040] The control unit is specifically further configured to control the second switch tube module to disconnect, and control the first switch tube module, the third switch tube module to the sixth switch tube module to also disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module, charges the bus capacitor unit through the body diode of the switch tube in the first switch tube module.

[0041] The control unit is further configured to control the first switch tube module to be turned on, and control the second to sixth switch tube modules to be turned off, so that in the negative half cycle of the AC power supply, the first AC power input into the input port of the AC power supply charges the first inductor module via the second direction module and supplies power to the bus capacitor unit.

[0042] The control unit is further configured to control the first switch tube module to be disconnected, and to control the second to sixth switch tube modules to be disconnected, so that in the negative half cycle of the AC power supply, the first AC power input into the input port of the AC power supply, combined with the charging energy on the first inductor module, charges the bus capacitor unit via the body diode of the switch tube in the second switch tube module.

[0043] For example: Figure 2 In the example shown, the three-way interleaved parallel drive circuit of the bridgeless PFC circuit operates as follows: In the first operating condition, an AC voltage of 220V is input from the input port J3 of the input power supply. When the input current corresponding to the input AC voltage is less than 10A, the system operates in a critical state. The control module controls the following conditions:

[0044] Step 11: Power MOS transistor module UND2 is closed, and the other power MOS transistor modules UNDX are disconnected. During the positive half-cycle of the 220V voltage input to input port J3 of the input power supply, pin 3 of input port J3 is positive and pin 1 of input port J3 is negative, charging inductor L1 through diode D1. Capacitors C1, C2, and C3 provide DC power (positive at the top and negative at the bottom) to the inverter, driving the motor (such as the motor in a compressor). Here, the other power MOS transistor modules UNDX are other power MOS transistor modules other than the power MOS transistor module UND2 involved in the control, such as the other power MOS transistor modules among power MOS transistor modules UND1-UND6 other than power MOS transistor module UND2. The following steps are similar to this one.

[0045] Step 12: Power MOS transistor module UND2 is disconnected, and the other power MOS transistor modules UNDX are disconnected. The positive half cycle of the 220V voltage input to input port J3 of the input power supply, plus the charging energy of inductor L1, passes through the body diode of power MOS transistor module UND1, and is charged through capacitors C1, C2, and C3 (electrolytic capacitors). Capacitors C1, C2, and C3 can be electrolytic capacitors.

[0046] Step 13: The power MOS transistor module UND1 is closed, and other power MOS transistor modules UNDX are open. During the negative half-cycle of the 220V voltage input at the input port J3 of the input power supply, the 3-pin of the input port J3 is negative and the 1-pin of the input port J3 is positive. The inductor L1 is charged through the diode D2. The capacitors C1, C2, and C3 provide direct current with positive voltage at the top and negative voltage at the bottom for the inverter to drive the motor (such as the motor in a compressor) to operate.

[0047] Step 14: The power MOS transistor module UND1 is open, and other power MOS transistor modules UNDX are open. During the negative half-cycle of the 220V voltage input at the input port J3 of the input power supply, with the charging energy of the inductor L1 added, it is charged through the body diode of the power MOS transistor module UND2 and the capacitors C1, C2, and C3.

[0048] In some embodiments, the control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is greater than a first set current threshold and less than a second set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on.

[0049] Wherein, when the current of the first alternating current is greater than a first set current threshold and less than a second set current threshold, the control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on, including:

[0050] The control unit is specifically further configured to control the second switch transistor module and the fourth switch transistor module to conduct, and control the first switch transistor module, the third switch transistor module, the fifth switch transistor module, and the sixth switch transistor module to be open, so that during the positive half-cycle of the AC power supply, the first alternating current input at the input port of the AC power supply is used to charge the first inductor module and the second inductor module after passing through the first direction module, and supply power to the bus capacitor unit.

[0051] The control unit is further specifically configured to control the second switch tube module and the fourth switch tube module to be turned off, and control the first switch tube module, the third switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module and the second inductor module, passes through the body diode of the switch tube in the first switch tube module and the body diode of the switch tube in the third switch tube module, and after passing through the first direction module, charges the bus capacitor unit.

[0052] The control unit is further specifically configured to control the first switch tube module and the third switch tube module to be turned on, and control the second switch tube module, the fourth switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply charges the first inductor module and the second inductor module after passing through the second direction module, and supplies power to the bus capacitor unit.

[0053] The control unit is further specifically configured to control the first switch tube module and the third switch tube module to be turned on, and control the second switch tube module, the fourth switch tube module, the fifth switch tube module, and the sixth switch tube module to be turned off, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module and the second inductor module, charges the first inductor module and the second inductor module after passing through the second direction module, passes through the body diode of the switch tube in the second switch tube module and the body diode of the switch tube in the fourth switch tube module, and after passing through the second direction module, charges the bus capacitor unit.

[0054] For example: In Figure 2 In the example shown, the working conditions of the three-way interleaved parallel drive circuit of the bridgeless PFC circuit include: The second working condition: An AC voltage of 220V is input from the input port J3 of the input power supply. When the input current corresponding to the input AC voltage is greater than 10A and less than 20A, the system works in a critical state, and the power MOS tube module UND13 is closed. The control situation of the control module is as follows:

[0055] Step 21: The power MOSFET modules of UND2 and UND4 are closed, and the other power MOSFET modules of UNDX are open. During the positive half-cycle of the 220V voltage input at the input port J3 of the input power supply, the 3-pin of the input port J3 is positive, and the 1-pin of the input port J3 is negative. The voltage passes through the diode D1 to charge the inductors L1 and L2. The capacitors C1, C2, and C3 provide DC power with positive voltage at the top and negative voltage at the bottom to drive the motor (such as the motor in a compressor) to operate.

[0056] Step 22: The power MOSFET modules of UND2 and UND4 are open, and the other power MOSFET modules of UNDX are open. During the positive half-cycle of the 220V voltage input at the input port J3 of the input power supply, with the charging energy of the inductors L1 and L2 added, the voltage passes through the body diodes of the power MOSFET modules of UND1 and UND3, through the diode D1, and charges through the capacitors C1, C2, and C3 to drive the motor (such as the motor in a compressor) to operate.

[0057] Step 23: The power MOSFET modules of UND1 and UND3 are closed, and the other power MOSFET modules of UNDX are open. During the negative half-cycle of the 220V voltage input at the input port J3 of the input power supply, the 3-pin of the input port J3 is negative, and the 1-pin of the input port J3 is positive. The voltage passes through the diode D2 to charge the inductors L1 and L2. The capacitors C1, C2, and C3 provide DC power with positive voltage at the top and negative voltage at the bottom to drive the motor (such as the motor in a compressor) to operate.

[0058] Step 24: The power MOSFET modules of UND1 and UND3 are open, and the other power MOSFET modules of UNDX are open. During the negative half-cycle of the 220V voltage input at the input port J3 of the input power supply, with the charging energy of the inductors L1 and L2 added, the voltage passes through the body diodes of the power MOSFET modules of UND2 and UND4, and charges through the capacitors C1, C2, and C3 to drive the motor (such as the motor in a compressor) to operate.

[0059] In this way, the three-way interleaved parallel drive circuit of the bridgeless PFC circuit provided by the solution of the present invention can achieve valley switching (VS) or zero-voltage switching (ZVS) of the power MOSFET, as well as zero-current turn-off of the diode, thereby reducing the switching loss of the power MOSFET and the reverse recovery loss of the diode. Thus, in the control strategy of the three-way interleaved parallel drive circuit of the bridgeless PFC circuit, zero-voltage switching (ZVS) and zero-current turn-off of the diode are achieved, thereby reducing the switching loss of the power MOSFET and the reverse recovery loss of the diode, reducing the self-loss of circuit switching, and reducing the conduction loss of the PFC circuit. The conduction loss is the product of the forward voltage drop of the diode and the forward current when the diode is in the forward conduction state.

[0060] In some embodiments, the control unit further includes: a switching module. The switching module includes: a first switching transistor module and a second switching transistor module. The first switching transistor module is disposed on the output side of the second inductor module. The second switching transistor module is disposed on the output side of the third inductor module. For example: the first switching transistor module is the power switch transistor module UND13, and the second switching transistor module is the power switch transistor module UND14. As Figure 2 shown, the three-way interleaved parallel drive circuit of the bridgeless PFC circuit further includes: a commutation module such as the power MOS transistor modules UND13 to UND14.

[0061] The control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is greater than a second set current threshold and less than a third set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on.

[0062] Among them, when the current of the first alternating current is greater than a second set current threshold and less than a third set current threshold, the control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on, including:

[0063] The control unit is further specifically configured to control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to conduct, and control the first switch tube module, the third switch tube module, and the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply passes through the first direction module and then charges the first inductor module, the second inductor module, and the third inductor module, and supplies power to the bus capacitor unit.

[0064] The control unit is further specifically configured to control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to disconnect, and control the first switch tube module, the third switch tube module, and the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply combines the charging energy on the first inductor module, the second inductor module, and the third inductor module, and after passing through the first direction module, charges the bus capacitor unit.

[0065] The control unit is further specifically configured to control the first switch tube module, the third switch tube module, and the sixth switch tube module to conduct, and control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply passes through the second direction module and then charges the first inductor module, the second inductor module, and the third inductor module, and supplies power to the bus capacitor unit.

[0066] The control unit is further specifically configured to control the first switch tube module, the third switch tube module, and the sixth switch tube module to disconnect, and control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply combines the charging energy on the first inductor module, the second inductor module, and the third inductor module, and after passing through the second direction module, charges the bus capacitor unit.

[0067] For example: in Figure 2 In the example shown, the working conditions of the three-way interleaved parallel drive circuit of the bridgeless PFC circuit include: the third working condition: an AC voltage of 220V is input from the input port J3 of the input power supply. When the input current corresponding to the input AC voltage is greater than 20A and less than 30A, the system works in a critical state, and the power MOS tube modules UND13 and UND14 are switched on. The control situation of the control module is as follows:

[0068] Step 31: The power MOS transistor modules UND2, UND4, and UND5 are turned on, and other power MOS transistor modules UNDX are turned off. During the positive half-cycle of the 220V voltage input at the input port J3 of the input power supply, the 3-pin of the input port J3 is positive, and the 1-pin of the input port J3 is negative. The voltage charges the inductors L1, L2, and L3 through the diode D1. The capacitors C1, C2, and C3 provide direct current with positive voltage at the top and negative voltage at the bottom for the inverter to drive the motor (such as the motor in a compressor) to operate.

[0069] Step 32: The power MOS transistor modules UND2, UND4, and UND5 are turned off, and other power MOS transistor modules UNDX are turned off. During the positive half-cycle of the 220V voltage input at the input port J3 of the input power supply, with the charging energy of the inductors L1, L2, and L3 added, the voltage charges the capacitors C1, C2, and C3 through the body diodes of the power MOS transistor modules UND1, UND3, and UND6, and then through the diode D1 to drive the motor (such as the motor in a compressor) to operate. The capacitors C1, C2, and C3 are set to achieve current sharing, considering cost.

[0070] Step 33: The power MOS transistor modules UND1, UND3, and UND6 are turned on, and other power MOS transistor modules UNDX are turned off. During the negative half-cycle of the 220V voltage input at the input port J3 of the input power supply, the 3-pin of the input port J3 is negative, and the 1-pin of the input port J3 is positive. The voltage charges the inductors L1, L2, and L3 through the diode D2. The capacitors C1, C2, and C3 provide direct current with positive voltage at the top and negative voltage at the bottom for the inverter to drive the motor (such as the motor in a compressor) to operate.

[0071] Step 34: The power MOS transistor modules UND1, UND3, and UND6 are turned off, and other power MOS transistor modules UNDX are turned off. During the negative half-cycle of the 220V voltage input at the input port J3 of the input power supply, with the charging energy of the inductors L1, L2, and L3 added, the voltage charges the capacitors C1, C2, and C3 through the body diodes of the power MOS transistor modules UND2, UND4, and UND5 to drive the motor (such as the motor in a compressor) to operate.

[0072] Among them, the power MOS transistors in the above power MOS transistor modules can also be replaced by other switching devices such as IGBTs (Insulated Gate Bipolar Transistors) and bridgeless PFC modules.

[0073] In the solution of the present invention, three input inductors such as inductor L1, inductor L2, and inductor L3 are adopted. Compared with the solution that adopts one input inductor in the related art, the power density ratio is improved. Moreover, the bridgeless PFC circuit is combined with three-way parallel interleaved control, and the current evenly distributed on the three inductors is smaller, so the lifespan of the entire driving solution is relatively longer. In addition, for the control logic judgment of the system input current, the circuit is reasonably switched according to the current level of the system, making the control of the system more balanced.

[0074] In some embodiments, the bus capacitor unit includes: a first capacitor module, a second capacitor module, and a third capacitor module. The first capacitor module, the second capacitor module, and the third capacitor module are arranged in parallel.

[0075] For example: the first capacitor module is capacitor C1, the second capacitor module is capacitor C1, and the third capacitor module is capacitor C3. As Figure 2 shown, in the three-way interleaved parallel driving circuit of the bridgeless PFC circuit, the DC bus capacitors are capacitor C1, capacitor C2, and capacitor C3.

[0076] The three-way interleaved parallel driving circuit of the bridgeless PFC circuit provided by the solution of the present invention combines the bridgeless and interleaved parallel technologies, improving the efficiency and power density of the driver of the bridgeless PFC power supply. Compared with the interleaved parallel Boost type PFC circuit (i.e., boost type PFC circuit) in the related solution, the current sharing performance and conversion efficiency are significantly improved.

[0077] Verified by a large number of experiments, adopting the technical solution of the present invention, by combining the bridgeless PFC circuit and the interleaved parallel technology, setting the three-way interleaved parallel driving circuit of the bridgeless PFC circuit, and controlling the on / off of the three-way interleaved parallel driving circuit according to the magnitude of the current of the input AC power supply, thereby, by setting the bridgeless PFC circuit with three-way interleaved parallel driving, the conduction loss of the PFC circuit can be reduced.

[0078] According to an embodiment of the present invention, there is also provided a motor system corresponding to the driving device of the bridgeless PFC power supply. The motor system may include: the driving device of the bridgeless PFC power supply described above.

[0079] Since the processing and functions implemented by the motor system in this embodiment are basically corresponding to the embodiments, principles, and examples of the foregoing device, for the parts not described in detail in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments, and details will not be repeated here.

[0080] After a large number of experimental verifications, by adopting the technical solution of the present invention, through the combination of a bridgeless PFC circuit and interleaved parallel technology, a three-way interleaved parallel drive circuit of the bridgeless PFC circuit is set up. By controlling the on-off of the three-way interleaved parallel drive circuit according to the magnitude of the current of the input AC power supply, zero-voltage switching (ZVS) and zero-current turn-off of the diode are achieved, thereby reducing the switching loss of the power MOSFET and the reverse recovery loss of the diode, and reducing the self-loss of circuit switching.

[0081] According to an embodiment of the present invention, there is also provided a control method for a drive device of a bridgeless PFC power supply corresponding to a motor system, as Figure 3 shown in the schematic flowchart of an embodiment of the method of the present invention. The control method of the drive device of the bridgeless PFC power supply may include: step S110 and step S120.

[0082] At step S110, through a control unit, according to the magnitude of the current of the first alternating current input from an AC power supply, at least one charging circuit of the first inductor module, the second inductor module, and the third inductor module is controlled to be turned on, so that at least one charging module among the first inductor module, the second inductor module, and the third inductor module whose charging circuit is turned on can receive the first alternating current input from the AC power supply and charge itself with the first alternating current input from the AC power supply. Any one of the first inductor module, the second inductor module, and the third inductor module receives the first alternating current input from the AC power supply and, when its own charging circuit is turned on, charges itself with the first alternating current input from the AC power supply.

[0083] At step S120, through a bus capacitor unit, when at least one charging circuit of the first inductor module, the second inductor module, and the third inductor module is turned on and charged, the electrical energy charged by at least one of the first inductor module, the second inductor module, and the third inductor module is stored to obtain direct current.

[0084] In this way, the solution of the present invention provides a drive device for a bridgeless PFC power supply, specifically a three-way interleaved parallel drive circuit of a bridgeless PFC circuit, which makes the voltage and current in the same phase, can improve the power factor of the PFC circuit, thereby improving the efficiency of the PFC circuit and reducing the current harmonic distortion. Specifically, through the first inductor module, the second inductor module, and the third inductor module, the AC power supply can be divided into 3 segments, each segment being 120°, with better current sharing effect and higher electrical energy conversion efficiency.

[0085] In some embodiments, it further includes: inverting the direct current stored in the bus capacitor unit through an inverting unit to obtain a second alternating current required for the operation of the device to be powered. The inverting unit, such as an inverter, is disposed on the output side of the bus capacitor unit and is used to supply power to a device to be powered such as a motor.

[0086] In order to improve the efficiency of the driver (i.e., the PFC circuit) of the bridgeless PFC power supply, many topologies of the driver of the bridgeless PFC power supply have been proposed. Compared with the driver of the bridgeless PFC power supply in the related solutions, there is one less diode on the power loop of the driver of the bridgeless PFC power supply, thereby improving the efficiency of the driver of the bridgeless PFC power supply. The three-way interleaved parallel drive circuit of the bridgeless PFC circuit provided by the solution of the present invention uses four fewer diodes compared with the three-way interleaved PFC circuit, the cost is relatively reduced, the device cost is saved, and the volume of the device is also reduced.

[0087] Since the processing and functions implemented by the method of this embodiment are basically corresponding to the embodiments, principles and examples of the aforementioned driving device of the bridgeless PFC power supply, for the details not described in the description of this embodiment, reference can be made to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0088] Through a large number of experimental verifications, by adopting the technical solution of this embodiment, by combining the bridgeless PFC circuit and the interleaved parallel technology, a three-way interleaved parallel drive circuit of the bridgeless PFC circuit is set up, and by controlling the on-off of the three-way interleaved parallel drive circuit according to the magnitude of the current of the input AC power supply, the on-state loss is small; and, compared with the three-way interleaved PFC circuit, four fewer diodes are used, the cost is relatively reduced, the device cost is saved, and the volume of the device is also reduced.

[0089] In summary, it is easy for those skilled in the art to understand that, on the premise of no conflict, the above advantageous ways can be freely combined and superimposed.

[0090] The above are only the embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A driving device for a bridgeless PFC power supply, characterized in that, Including: A charging unit, a control unit, and a bus capacitor unit; The charging unit includes: a first inductor module, a second inductor module, and a third inductor module; wherein, Any one of the first inductor module, the second inductor module, and the third inductor module is configured to receive a first alternating current input from an AC power source and, when its own charging circuit is turned on, charge itself using the first alternating current input from the AC power source; The control unit is configured to control the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power source; The bus capacitor unit is configured to store the electric energy obtained by charging at least one of the first inductor module, the second inductor module, and the third inductor module when the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module is turned on and charged, to obtain direct current; by combining a bridgeless PFC circuit and interleaved parallel technology, a three-way interleaved parallel drive circuit of the bridgeless PFC circuit is set, and the on / off of the three-way interleaved parallel drive circuit is controlled according to the magnitude of the current of the input AC power source.

2. The driving device of the bridgeless PFC power supply according to claim 1, wherein, It further includes: An inverter unit; The inverter unit is configured to invert the direct current stored in the bus capacitor unit to obtain a second alternating current required for the operation of the device to be powered.

3. The driving device of the bridgeless PFC power supply according to claim 1 or 2, characterized in that, The control unit includes: a control module; the control module includes: a first switch tube module, a second switch tube module, a third switch tube module, a fourth switch tube module, a fifth switch tube module, and a sixth switch tube module, as well as a first direction module and a second direction module; Wherein, each switch tube module can form a charging circuit with an inductor module and the positive or negative half cycle of the AC power source; The first direction module is arranged between the input port of the AC power source and the second switch tube module, the fourth switch tube module, and the fifth switch tube module, and can be conducted from any one of the second switch tube module, the fourth switch tube module, and the fifth switch tube module to the input port of the AC power source; The second direction module is arranged between the input port of the AC power source, the first switch tube module, the third switch tube module, and the sixth switch tube module, and can be conducted from the input port of the AC power source to any one of the first switch tube module, the third switch tube module, and the sixth switch tube module.

4. The driving device of the bridgeless PFC power supply according to claim 3, characterized in that, The control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power source, including: when the current of the first alternating current is less than a first set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on; Wherein: Control the second switch tube module to conduct, and control the first switch tube module, the third switch tube module to the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply passes through the first direction module and then charges the first inductor module, and supplies power to the bus capacitor unit; Control the second switch tube module to disconnect, and control the first switch tube module, the third switch tube module to the sixth switch tube module to also disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module, charges the bus capacitor unit through the body diode of the switch tube in the first switch tube module; Control the first switch tube module to conduct, and control the second switch tube module to the sixth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply passes through the second direction module and then charges the first inductor module, and supplies power to the bus capacitor unit; Control the first switch tube module to disconnect, and control the second switch tube module to the sixth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module, charges the bus capacitor unit through the body diode of the switch tube in the second switch tube module; 5. The driving device of the bridgeless PFC power supply according to claim 3, characterized in that, The control unit controls the charging circuit of at least one of the first inductor module, the second inductor module and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is greater than the first set current threshold and less than the second set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module and the third inductor module to be turned on; Wherein: Control the second switch tube module and the fourth switch tube module to conduct, and control the first switch tube module, the third switch tube module, the fifth switch tube module and the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply passes through the first direction module and then charges the first inductor module and the second inductor module, and supplies power to the bus capacitor unit; Control the second switch tube module and the fourth switch tube module to disconnect, and control the first switch tube module, the third switch tube module, the fifth switch tube module and the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module and the second inductor module, passes through the body diode of the switch tube in the first switch tube module, and the body diode of the switch tube in the third switch tube module, and then passes through the first direction module and charges the bus capacitor unit; Control the first switch tube module and the third switch tube module to conduct, and control the second switch tube module, the fourth switch tube module, the fifth switch tube module, and the sixth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply is charged to the first inductor module and the second inductor module after passing through the second direction module, and supply power to the bus capacitor unit; Control the first switch tube module and the third switch tube module to conduct, and control the second switch tube module, the fourth switch tube module, the fifth switch tube module, and the sixth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module and the second inductor module, is charged to the first inductor module and the second inductor module after passing through the second direction module, and passes through the body diode of the switch tube in the second switch tube module and the body diode of the switch tube in the fourth switch tube module, and after passing through the second direction module, charges the bus capacitor unit.

6. The driving device of the bridgeless PFC power supply according to claim 3, characterized in that, The control unit further includes: a switching module; the switching module includes: a first switching switch tube module and a second switching switch tube module; the first switching switch tube module is arranged on the output side of the second inductor module; the second switching switch tube module is arranged on the output side of the third inductor module; The control unit controls the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on according to the magnitude of the current of the first alternating current input from the AC power supply, including: when the current of the first alternating current is greater than the second set current threshold and less than the third set current threshold, controlling the charging circuit of at least one of the first inductor module, the second inductor module, and the third inductor module to be turned on; Wherein: Control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to conduct, and control the first switch tube module, the third switch tube module, and the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply is charged to the first inductor module, the second inductor module, and the third inductor module after passing through the first direction module, and supply power to the bus capacitor unit; Control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to disconnect, and control the first switch tube module, the third switch tube module, and the sixth switch tube module to disconnect, so that in the positive half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply, combined with the charging energy on the first inductor module, the second inductor module, and the third inductor module, passes through the first direction module and then charges the bus capacitor unit; Control the first switch tube module, the third switch tube module, and the sixth switch tube module to conduct, and control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply passes through the second direction module and then charges the first inductor module, the second inductor module, and the third inductor module, and supplies power to the bus capacitor unit; Control the first switch tube module, the third switch tube module, and the sixth switch tube module to disconnect, and control the second switch tube module, the fourth switch tube module, and the fifth switch tube module to disconnect, so that in the negative half cycle of the AC power supply, the first alternating current input at the input port of the AC power supply combines with the charging energy on the first inductor module, the second inductor module, and the third inductor module, and after passing through the second direction module, charges the bus capacitor unit.

7. The driving device of the bridgeless PFC power supply according to claim 1 or 2, characterized in that, The bus capacitor unit includes: a first capacitor module, a second capacitor module, and a third capacitor module; the first capacitor module, the second capacitor module, and the third capacitor module are arranged in parallel.

8. A motor system, characterized in that, Includes: The driving device of the bridgeless PFC power supply according to any one of claims 1 to 7.

9. A control method for a driving device of a bridgeless PFC power supply according to any one of claims 1 to 7, characterized in that, Includes: Through a control unit, according to the magnitude of the current of the first alternating current input from the AC power supply, control at least one of the charging circuits of the first inductor module, the second inductor module, and the third inductor module to be turned on; any one of the first inductor module, the second inductor module, and the third inductor module receives the first alternating current input from the AC power supply, and when its own charging circuit is turned on, uses the first alternating current input from the AC power supply to charge itself; Through the bus capacitor unit, when at least one of the charging circuits of the first inductor module, the second inductor module, and the third inductor module is turned on and charged, store the electrical energy obtained by charging at least one of the first inductor module, the second inductor module, and the third inductor module to obtain direct current.

10. The control method of the driving device of the bridgeless PFC power supply according to claim 9, characterized in that, Further includes: Through an inverter unit, invert the direct current stored in the bus capacitor unit to obtain the second alternating current required for the operation of the device to be powered.

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