JP7389642B2 - switching power supply - Google Patents

Description

The present invention comprises a three-phase power factor correction circuit (hereinafter referred to as "three-phase PFC") and two DC/DC converters connected to the output side of the circuit to convert direct current (DC) power to a predetermined level of direct current (DC) power. The present invention relates to a two-stage switching power supply device having a DC converter.

Patent Document 1 discloses a Vienna type three-phase PFC, which is one of high-efficiency converters for reactor current discontinuous mode control. Furthermore, there is also a two-stage switching power supply system in which two DC/DC converters are connected to the rear stage of the Vienna type three-phase PFC, and the three-phase PFC in the front stage and the DC/DC converter in the latter stage are controlled independently. It is being In such a two-stage switching power supply device, high accuracy can be expected even over a wide input voltage range and load conditions without interference between the circuit operations of the preceding and succeeding stages.

FIG. 4 is a circuit diagram showing a configuration example of a conventional two-stage switching power supply device.

This two-stage switching power supply device includes a three-phase PFC 10 at the front stage connected to a three-phase AC power supply 1, and two first converters 18-1 and a second converter 18 at the rear stage connected in parallel to the output side of the three-phase PFC 10. -2. The three-phase PFC 10 at the front stage has three-phase input terminals 11a, 11b, and 11c connected to the three-phase AC power supply 1, and a line capacitor for removing high frequency components is connected between the three-phase input terminals 11a, 11b, and 11c. 12a, 12b, and 12c are connected. Furthermore, a three-phase boosting inductor 13 consisting of three inductors 13a, 13b, 13c, three connection points N1, N2, N3, and a switching circuit 14 are connected in series to the three-phase input terminals 11a, 11b, and 11c. It is connected.

The switching circuit 14 includes three bidirectional switching elements 14a, 14b, and 14c. A full-wave rectifier circuit 15 in which six diodes 15a, 15b, 15c, 15d, 15e, and 15f are bridge-connected is connected to the connection points N1, N2, and N3. Two series-connected smoothing capacitors 16a and 16b are connected in parallel to the full-wave rectifier circuit 15. A first terminal 17a and a second terminal 17b for output are connected to both electrodes of the two smoothing capacitors 16a and 16b.

The input sides of two first converters 18-1 and two second converters 18-2 are connected in parallel to the first terminal 17a and the second terminal 17b. The first converter 18-1 and the second converter 18-2 are configured by DC/DC converters (for example, LLC converters) having the same characteristics. The output sides of the first converter 18-1 and the second converter 18-2 are connected in parallel to the first output terminal 20a and the second output terminal 20b. A smoothing output capacitor 19 is connected between the first output terminal 20a and the second output terminal 20b.

In such a two-stage switching power supply, three-phase AC power output from a three-phase AC power supply 1 is input to three-phase input terminals 11a, 11b, and 11c, and is converted into high-frequency power by line capacitors 12a, 12b, and 12c. components are removed. The three-phase AC power from which high-frequency components have been removed is input to the on-state bidirectional switching elements 14a, 14b, and 14c in the switching circuit 14 via the three-phase boosting inductor 13, and is then input to the three-phase inductor 13. , the input power is accumulated. Next, the bidirectional switching elements 14a, 14b, and 14c in the switching circuit 14 are turned off, and the total power of the input power and the power accumulated in the three-phase inductor 13 is converted into a full-wave rectifier circuit 15. rectified. The full-wave rectified total power is smoothed by smoothing capacitors 16a and 16b, and a DC voltage Vm is output from the first terminal 17a and the second terminal 17b.

The DC voltage Vm output from the first terminal 17a and the second terminal 17b is converted into a DC voltage at a predetermined level by the first converter 18-1 whose switching is controlled at the first switching frequency, and at the same time at the second switching frequency. It is converted into a DC voltage at a predetermined level by a second converter 18-2 whose switching is controlled, and smoothed by an output capacitor 19. The smoothed output voltage Vo is output from the first output terminal 20a and the second output terminal 20b, and is supplied to a load (not shown).

China Patent Publication No. CN104811061A

The conventional switching power supply shown in FIG. 4 uses a first converter 18-1 and a second converter 18-2 having the same characteristics. However, there are variations between the main components of the first converter 18-1 and the second converter 18-2, and when the first converter 18-1 and the second converter 18-2 are synchronously controlled, the first converter 18-1 Since the output power characteristics of the first converter 18-1 and the second converter 18-2 change, and the output power becomes unbalanced, separate power balance control is required between the first converter 18-1 and the second converter 18-2. become. Normally, the output currents, etc. of the first converter 18-1 and the second converter 18-2 are monitored respectively so that the output power of the first converter 18-1 and the second converter 18-2 is balanced. The balance is maintained using power balance control.

However, if the first converter 18-1 whose switching is controlled at the first switching frequency and the second converter 18-2 whose switching is controlled at the second switching frequency are individually controlled, the first switching frequency and the second Due to the difference with the switching frequency, a beat voltage (that is, a low-frequency beat voltage caused by interference between voltage waveforms of two similar frequencies) is generated at the input and output of the first converter 18-1 and the second converter 18-2. do. As a method of suppressing the beat voltage, for example, it is possible to operate the first converter 18-1 and the second converter 18-2 synchronously and remove unnecessary frequency components with a filter. However, in a circuit configuration that requires two first and second switching frequencies, the number of control signals increases, the number of drive circuits increases, and furthermore, it becomes necessary to control the switching of the first and second converters 18-1 and 18-2. For example, problems arise such as an increase in the processing load on the digital signal processor (DSP).

Therefore, it has been difficult to realize a two-stage switching power supply device that does not require power balance control and has a simple circuit configuration.

The switching power supply device of the present invention performs rectification and smoothing after switching the input three-phase AC power by a switching circuit , outputs a first DC voltage with improved power factor from the first terminal and the intermediate terminal, and A three-phase PFC that outputs a second DC voltage with improved power factor from the intermediate terminal and the second terminal, and a full bridge circuit and transformer for the first DC voltage output from the first terminal and the intermediate terminal. A first converter converts the voltage by a converter and outputs it from a first output terminal and a second output terminal, and converts the second DC voltage outputted from the intermediate terminal and the second terminal into a voltage by a full bridge circuit and a transformer. a second converter that converts and outputs from the first output terminal and the second output terminal; a control unit that controls the three-phase PFC, the first converter, and the second converter; The converter has the same characteristics as the first converter, the output side of the second converter is connected in parallel or series to the first output terminal and the second output terminal , and the control section The switching circuit of the phase PFC is controlled by duty control of pulse width modulation so that the output voltage consisting of the sum of the first DC voltage and the second DC voltage becomes a constant voltage, and the switching circuit of the first converter is controlled by duty control of pulse width modulation. Switching of the circuit and the full bridge circuit of the second converter is controlled by synchronized pulse frequency modulation control .

Here, for example, the three-phase PFC includes a three-phase input terminal that inputs the three-phase AC power , a three-phase inductor connected to the three-phase input terminal, and one end connected in series to the three-phase inductor. a switching circuit, a connection point between the three-phase inductor and the switching circuit, the intermediate terminal connected to the other end of the switching circuit, the first terminal that outputs the first DC voltage, and the intermediate terminal. a terminal, the intermediate terminal and the second terminal that output the second DC voltage , a rectifier circuit connected between the connection point and the first terminal and the second terminal, and the first terminal and the second terminal. It has a first smoothing circuit connected between the intermediate terminals, and a second smoothing circuit connected between the intermediate terminal and the second terminal.

Further, the first converter has a first input side connected to the first terminal and the intermediate terminal, a first output side connected to the first output terminal and the second output terminal, and an input side from the first input side. The second converter has a second input side connected to the intermediate terminal and the second terminal, and a second output side connected to the second converter. 1 output terminal and the second output terminal, and converts the second DC voltage input from the second input side and outputs the converted voltage to the second output side. It has become.

According to the present invention, the first converter is connected to the first terminal and the intermediate terminal among the first terminal, intermediate terminal, and second terminal provided on the output side of the three-phase PFC, and the first converter is connected to the intermediate terminal and the second terminal. A second converter having the same characteristics as the first converter is connected to the second converter, and an intermediate terminal of a three-phase PFC is used. Therefore, if the power between the first converter and the second converter becomes unbalanced due to variations between the main parts of the first converter and the second converter, the input voltage of the converter with a large amount of power will decrease, and the amount of power will decrease. The input voltage of the small converter increases. Since the voltage between the first terminal and the second terminal is controlled at a constant voltage, the first DC voltage and the second DC voltage change while maintaining the constant voltage, and the power between the first converter and the second converter is Balance is achieved. Thereby, there is no need to perform power balance control on the first converter side and the second converter side, so it is possible to realize a switching power supply device with a simple circuit configuration.

A circuit diagram showing the configuration of a switching power supply device in Embodiment 1 of the present invention A circuit diagram showing the configuration of a switching power supply device in Embodiment 2 of the present invention A circuit diagram showing the configuration of a switching power supply device in Embodiment 3 of the present invention Circuit diagram showing a configuration example of a conventional switching power supply

Modes for carrying out the invention will become apparent from the following description of preferred embodiments when read in conjunction with the accompanying drawings. However, the drawings are solely for illustrative purposes and do not limit the scope of the present invention.

(Configuration of Example 1)
FIG. 1 is a circuit diagram showing the configuration of a two-stage switching power supply device according to a first embodiment of the present invention.

The two-stage switching power supply device includes a first-stage Vienna-type three-phase PFC 30 connected to a three-phase AC power supply 21, and two subsequent stages, a first converter 40 and a second converter 50, connected to the output side of the two-stage switching power supply. It is equipped with

The three-phase PFC 30 at the front stage has three-phase input terminals 31a, 31b, and 31c connected to the three-phase AC power supply 21, and a line capacitor for removing high frequency components is connected between the three-phase input terminals 31a, 31b, and 31c. 32a, 32b, and 32c are connected. Further, the three-phase input terminals 31a, 31b, 31c are connected to a three-phase inductor 33 for boosting the voltage consisting of three inductors 33a, 33b, 33c, three connection points N11, N12, N13, a switching circuit 34, and an output. The first terminal 37a on the side and the intermediate terminal 37c at the middle point between the second terminal 37b are connected in series.

The switching circuit 34 includes three bidirectional switching elements 34a, 34b, and 34c connected between three connection points N11, N12, and N13 and an intermediate terminal 37c, respectively. Each of the bidirectional switching elements 34a, 34b, and 34c includes, for example, two MOS field effect transistors (hereinafter referred to as "MOSFETs") connected in series and having different polarities. A parasitic diode is connected in antiparallel to each MOSFET. Note that each of the bidirectional switching elements 34a, 34b, and 34c may be constructed of other power semiconductor elements such as an insulated gate bipolar transistor (hereinafter referred to as "IGBT").

A rectifier circuit (for example, a full-wave rectifier circuit) 35 is connected to the connection points N11, N12, and N13. The full-wave rectifier circuit 35 includes six diodes 35a, 35b, 35c, 35d, 35e, and 35f connected in a bridge manner. To the full-wave rectifier circuit 35, two series-connected first smoothing circuits (for example, smoothing capacitors) 36a and second smoothing circuits (for example, smoothing capacitors) 36b are connected in parallel. A first terminal 37a and a second terminal 37b are connected to both electrodes of the two smoothing capacitors 36a and 36b.

The input side of the first converter 40 is connected to the first terminal 37a and the intermediate terminal 37c, and the input side of the second converter 50 is also connected to the intermediate terminal 37c and the second terminal 37b. The output sides of the first converter 40 and the second converter 50 are connected in parallel, and are connected to a first output terminal 60a and a second output terminal 60b via a smoothing output capacitor 59.

The first converter 40 and the second converter 50 are configured by DC/DC converters (for example, LLC converters) having the same characteristics (that is, the same configuration).

The first converter 40 has a smoothing input capacitor 41 connected in parallel to the first terminal 37a and the intermediate terminal 37c, and a bridge circuit (for example, a full bridge circuit) 42 connected in parallel to the input capacitor 41. is connected. The full bridge circuit 42 is a circuit that switches the first DC voltage V1 generated between the first terminal 37a and the intermediate terminal 37c, and is configured by four switching elements 42a, 42b, 42c, and 42d connected in a bridge manner. Each of the switching elements 42a to 42d is composed of a MOSFET, and a parasitic diode is connected in antiparallel to each of the MOSFETs. Note that each of the switching elements 42a to 42d may be constructed of other power semiconductor elements such as IGBTs.

A resonant circuit is connected to the connection point between the switching elements 42a and 42b and the connection point between the switching elements 42c and 42d. The resonant circuit is a circuit that resonates due to the output voltage of the full bridge circuit 42, and is constituted by a series circuit of a resonant capacitor 43, a resonant choke coil 44, and an excitation choke coil 45a1. The excitation choke coil 45a1 is configured by the excitation impedance of the transformer 45, for example. The transformer 45 converts the voltage level of the output voltage of the resonant circuit, and has a primary winding 45a and a secondary winding 45b.

A rectifying and smoothing circuit is connected to the secondary winding 45b. The rectifying and smoothing circuit rectifies and smoothes the output voltage of the secondary winding 45b, and includes a full-wave rectifier circuit 46, a smoothing choke coil 47, and a smoothing capacitor 48. Both electrodes of the smoothing capacitor 48 are connected to a first output terminal 60a and a second output terminal 60b that output a DC output voltage Vo.

The second converter 50 has a smoothing input capacitor 51 connected in parallel to the intermediate terminal 37c and the second terminal 37b where the second DC voltage V2 is generated. Like the first converter 40, the input capacitor 51 includes a bridge circuit (for example, a full bridge circuit) 52 having four switching elements 52a, 52b, 52c, and 52d, a resonant capacitor 53, a resonant choke coil 54, and an excitation choke. A resonant circuit having a coil 55a1 and a transformer 55 having a primary winding 55a and a secondary winding 55b are connected. Furthermore, a full-wave rectifier circuit 56 including four diodes 56a, 56b, 56c, and 56d, and a smoothing circuit including a smoothing choke coil 57 and a smoothing capacitor 58 are connected to the output side of the secondary winding 55b. has been done. Both electrodes of the smoothing capacitor 58 are connected in parallel to the smoothing capacitor 48 of the first converter 40 to a first output terminal 60a and a second output terminal 60b.

The switching circuit 34 in the three-phase PFC 30, the full bridge circuit 42 in the first converter 40, and the full bridge circuit 52 in the second converter 50 are controlled in switching by a control section (not shown). For example, the switching circuit 34 is controlled by pulse width modulation (hereinafter referred to as "PWM") duty control, and the full bridge circuits 42 and 52 are controlled by synchronized pulse frequency modulation (hereinafter referred to as "PFM") control. , has a switching controlled configuration.

(Operation of Example 1)
In the switching power supply device of FIG. 1, three-phase AC power output from the three-phase AC power supply 21 is input to three-phase input terminals 31a, 31b, and 31c in the three-phase PFC 30. When the bidirectional switching elements 34a, 34b, 34c in the switching circuit 34 are turned on by a control unit (not shown), the input three-phase AC power is transferred to the three-phase inductor 33 and the two-way switching elements 34a, 34b in the on-state. , 34c to the intermediate terminal 37c, and the input three-phase AC power is accumulated in the three-phase inductor 33. When the bidirectional switching elements 34a, 34b, and 34c are turned off by a control unit (not shown), the input three-phase AC power and the three-phase AC power accumulated in the three-phase inductor 33 are summed. The total power is full-wave rectified by a full-wave rectifier circuit 35 and smoothed by smoothing capacitors 36a and 36b. Then, the first DC voltage V1 is output from the first terminal 37a and the intermediate terminal 37c, and the second DC voltage V2 is output from the intermediate terminal 37c and the second terminal 37b. The output first DC voltage V1 is supplied to the first converter 40, and the output second DC voltage V2 is supplied to the second converter 50.

Here, the output voltage between the first terminal 37a and the second terminal 37b (=first DC voltage V1 + second DC voltage V2) is measured by a voltage sensor (not shown), and this voltage measurement value is sent to a control unit (not shown). is compared with a target voltage value, and feedback control (for example, proportional integral (hereinafter referred to as "PI") control, proportional integral derivative (hereinafter referred to as "PID") control, etc.) is performed so that the comparison result decreases, and the PWM A drive pulse is generated by controlling the duty of . The generated drive pulse turns on/off the bidirectional switching elements 34a, 34b, and 34c, and if the output voltage (V1+V2) decreases, the on-duty of the drive pulse increases and the output voltage (V1+V2) increases. However, if the output voltage (V1+V2) increases, the on-duty of the drive pulse becomes smaller and the output voltage (V1+V2) decreases. By such constant voltage control of the control unit, the output voltage (V1+V2) of the three-phase PFC 30 is maintained at the target voltage.

In the first converter 40 to which the first DC voltage V1 is supplied, the first DC voltage V1 is smoothed by the input capacitor 41 and turned on/off by the full bridge circuit 42. For example, when the switching elements 42a and 42d in the full bridge circuit 42 are in the on state and the switching elements 42b and 42c are in the off state, the positive electrode side of the input capacitor 41→switching element 42a→resonant capacitor 43→resonant choke coil 44→excitation choke Current flows from the coil 45a1 and the primary winding 45a of the transformer 45 to the switching element 42d to the negative electrode side of the input capacitor 41.

Next, when the switching elements 42a and 42d are turned off and the switching elements 42b and 42c are turned on, the charges accumulated in the resonance capacitor 43 are discharged, and the positive electrode side of the resonance capacitor 43 → the switching element 42b → the switching element A current flows from the parasitic diode 42d to the excitation choke coil 45a1 and the primary winding 45a of the transformer 45, to the resonant choke coil 44, and to the negative electrode side of the resonant capacitor 43. As a result, the resonant circuit resonates, and an alternating current voltage is induced in the secondary winding 45b of the transformer 45. The induced AC voltage is rectified by a full-wave rectifier circuit 46 and smoothed by a choke coil 47 and a smoothing capacitor 48. The smoothed DC voltage is outputted to the first and second output terminals 60a and 60b via the output capacitor 59.

Further, the second converter 50 to which the second DC voltage V2 is supplied also performs the same operation as the first converter 40. That is, the second DC voltage V2 is smoothed by the input capacitor 51 and turned on/off by the full bridge circuit 52. Then, the resonant circuit made up of the resonant capacitor 53, the resonant choke coil 54, and the excitation choke coil 55a1 resonates, and an alternating current voltage is induced in the secondary winding 55b of the transformer 55. The induced AC voltage is rectified by a full-wave rectifier circuit 56 and smoothed by a choke coil 57 and a smoothing capacitor 58. The smoothed DC voltage is outputted to the first and second output terminals 60a and 60b via the output capacitor 59. As a result, the DC output voltage Vo between the first output terminal 60a and the second output terminal 60b is supplied to a load (not shown).

Here, the output voltage Vo is measured by a voltage sensor (not shown), this voltage measurement value is compared with a target voltage value in a control section (not shown), and feedback control (for example, PI control) is performed so that the comparison result decreases. , PID control, etc.), and drive pulses having a switching frequency are generated by PFM control. The generated drive pulse turns on/off the switching elements 42a to 42d, 52a to 52d, and if the output voltage Vo decreases, the switching frequency of the drive pulse decreases, the output voltage Vo increases, and the output voltage If Vo increases, the switching frequency of the drive pulse increases, and the output voltage Vo decreases. By such constant voltage control of the control section, the output voltage Vo is maintained at the target voltage.

(Comparison of operation between conventional and Example 1)
In the conventional switching power supply device shown in FIG. 4, the main components (the capacitance value of the resonant capacitor, the inductance value of the resonant choke coil, and the inductance value of the excitation choke coil) between the first converter 18-1 and the second converter 18-2 are If there is variation in the output power characteristics of the first converter 18-1 and the second converter 18-2, the output power characteristics will change and the output power will become unbalanced. Individual power balance control is required between the two. Therefore, there was a problem that the circuit configuration became complicated.

In order to solve such problems, in the first embodiment, the first terminal 37a, the intermediate terminal 37c, and the second terminal 37b provided on the output side of the three-phase PFC 30 at the front stage shown in FIG. A first converter 40 is connected to the terminal 37a and the intermediate terminal 37c, a second converter 50 having the same characteristics as the first converter 40 is connected to the intermediate terminal 37c and the second terminal 37b, and the intermediate terminal 37c of the three-phase PFC 30 is connected to the intermediate terminal 37c. I am using it.

When the output power between the first converter 40 and the second converter 50 becomes unbalanced due to variations between the main components of the first converter 40 and the second converter 50, the output voltage (V1+V2) of the three-phase PFC 30 becomes Change while maintaining the target voltage.

For example, assume that (output power of first converter 40>output power of second converter 50). At this time, the relationship is (output voltage of first converter 40>output voltage of second converter 50). From this state, the first DC voltage V1 decreases and the second DC voltage V2 increases, so that (output voltage of the first converter 40 ≒ output voltage of the second converter 50), and the first converter 40 and the second converter The output power can be balanced between 50 and 50 (that is, self-balancing). Similarly, self-balancing can be performed during transient operations such as sudden changes in load, and the conventional power balance control on the first converter 18-1 and second converter 18-2 sides shown in FIG. 4 is no longer necessary.

(Effects of Example 1)
According to the first embodiment, the configuration uses the intermediate terminal 37c of the three-phase PFC 30 shown in FIG. 1. Therefore, if the output power between the first converter 40 and the second converter 50 becomes unbalanced due to variations between the main components of the first converter 40 and the second converter 50 having the same characteristics, the converter with a large amount of power The input voltage of the converter decreases, and the input voltage of the converter with low power consumption increases. Since the output voltage (V1+V2) of the three-phase PFC 30 is controlled at a constant voltage, the output voltage (V1+V2) changes while maintaining the constant voltage, and the output power between the first converter 40 and the second converter 50 becomes self-controlled. balance. As a result, it is not necessary to perform power balance control on the first converter 40 and second converter 50 sides as in the conventional case, so it is possible to realize a switching power supply device with a simple circuit configuration.

(Configuration of Example 2)
FIG. 2 is a circuit diagram showing the configuration of a two-stage switching power supply device according to a second embodiment of the present invention. In FIG. 2, elements common to those in FIG. 1 are given the same reference numerals.

The two-stage switching power supply device of the second embodiment has a front-stage Vienna-type three-phase PFC 30 similar to the first embodiment, and two stages connected to the output side of the latter stage, which have a different configuration from the first embodiment. It includes a first converter 40A and a second converter 50A.

In the second embodiment, unlike the first embodiment, the output side of the first converter 40A and the output side of the second converter 50A are connected in series to the first output terminal 60a and the second output terminal 60b. There is.

The first converter 40A and the second converter 50A are configured by DC/DC converters (for example, LLC converters) having the same characteristics (that is, the same configuration) as in the first embodiment.

Like the first embodiment, the first converter 40A has a smoothing input capacitor 41 connected in parallel to the first terminal 37a and the intermediate terminal 37c, and in parallel with the input capacitor 41, a bridge circuit ( For example, a full bridge circuit) 42 is connected. The full bridge circuit 42 is configured by connecting four switching elements 42a, 42b, 42c, and 42d in a bridge manner, as in the first embodiment. Similar to the first embodiment, a resonant circuit consisting of a series circuit of a resonant capacitor 43, a resonant choke coil 44, and an excitation choke coil 45a1 is connected to the connection point between the switching elements 42a and 42b and the connection point between the switching elements 42c and 42d. is connected. The transformer 45 has a primary winding 45a and a secondary winding 45b, as in the first embodiment.

As in the first embodiment, the second converter 50A includes a smoothing input capacitor 51 connected in parallel to the intermediate terminal 37c and the second terminal 37b. As in the first embodiment, the input capacitor 51 includes a bridge circuit (for example, a full bridge circuit) 52 having four switching elements 52a, 52b, 52c, and 52d, a resonant capacitor 53, a resonant choke coil 54, and an excitation choke coil. A resonant circuit having 55a1 and a transformer 55 having a primary winding 55a and a secondary winding 55b are connected.

Unlike the first embodiment, the secondary winding 45b of the first converter 40A and the secondary winding 55b of the second converter 50A are connected in series. A full-wave rectifier circuit 46A consisting of four diodes 46a, 56b, 46c, and 56d, a smoothing choke coil 47, and a smoothing output capacitor 59 are connected to the output side of the secondary windings 45b and 55b connected in series. A rectifying and smoothing circuit having a rectifying and smoothing circuit is connected. Both electrodes of the output capacitor 59 are connected to a first output terminal 60a and a second output terminal 60b.

The switching circuit 34 in the three-phase PFC 30, the full bridge circuit 42 in the first converter 40A, and the full bridge circuit 52 in the second converter 50A are controlled in switching by a control section (not shown), as in the first embodiment. . For example, the switching circuit 34 is configured to have its switching controlled by PWM duty control, and the full bridge circuits 42 and 52 are configured to be switched controlled by synchronized PFM control.

(Operation of Example 2)
In the switching power supply device of FIG. 2, when the three-phase AC power output from the three-phase AC power supply 21 is input to the three-phase input terminals 31a, 31b, and 31c in the three-phase PFC 30, as in the first embodiment, The three-phase PFC 30 operates, and the first DC voltage V1 is output from the first terminal 37a and the intermediate terminal 37c, and the second DC voltage V2 is output from the intermediate terminal 37c and the second terminal 37b. The output first DC voltage V1 is supplied to the first converter 40A, and the output second DC voltage V2 is supplied to the second converter 50A.

In the first converter 40A to which the first DC voltage V1 is supplied, the first DC voltage V1 is smoothed by the input capacitor 41 and turned on/off by the full bridge circuit 42 to form a resonant circuit, as in the first embodiment. resonates. Furthermore, in the second converter 50A to which the second DC voltage V2 is supplied, the second DC voltage V2 is smoothed by the input capacitor 51 and turned on/off by the full bridge circuit 52, as in the first embodiment. The resonant circuit resonates.

When the resonant circuit of the first converter 40A resonates, an alternating current voltage is induced in the secondary winding 45b of the transformer 45. Furthermore, when the resonant circuit of the second converter 50A resonates, an alternating current voltage is induced in the secondary winding 55b of the transformer 55. The AC voltage induced in the secondary windings 45b and 55b is rectified by a full-wave rectifier circuit 46A, and smoothed by a choke coil 47 and an output capacitor 59. A smoothed DC output voltage 2Vo (=a voltage twice the output voltage Vo of Example 1) is output from the first and second output terminals 60a and 60b, and is supplied to a load (not shown).

Here, as in the first embodiment, the output voltage 2Vo is measured by a voltage sensor (not shown), and this voltage measurement value is compared with a target voltage value in a control section (not shown) so that the comparison result is decreased. A drive pulse having a switching frequency is generated by feedback control and PFM control. The switching elements 42a to 42d and 52a to 52d are turned on and off by the generated drive pulses, and the output voltage 2Vo output from the first output terminal 60a and the second output terminal 60b is controlled by the constant voltage control of the control section. , maintained at the target voltage.

(Effects of Example 2)
According to the second embodiment, as in the first embodiment, the configuration uses the intermediate terminal 37c of the three-phase PFC 30 shown in FIG. There is no need to perform power balance control on the side. Therefore, a switching power supply device with a simple circuit configuration can be realized.

(Configuration of Example 3)
FIG. 3 is a circuit diagram showing the configuration of a two-stage switching power supply device according to a third embodiment of the present invention. In FIG. 3, elements common to those in FIG. 1 are given the same reference numerals.

The two-stage switching power supply device of the third embodiment has a front-stage Vienna-type three-phase PFC 30 similar to the first embodiment, and two stages connected to the output side of the latter stage, which have a configuration different from that of the first embodiment. It includes a first converter 40B and a second converter 50B.

The first converter 40B and the second converter 50B of the third embodiment have the same configurations as the first converter 40 and the second converter 50 of the first embodiment, respectively, but the smoothing capacitor 48 on the output side of the first converter 40B This embodiment differs from the first embodiment in that the smoothing capacitor 58 on the output side of the second converter 50B is connected in series. The other configurations are the same as in the first embodiment.

(Operation of Example 3)
The entire operation of the switching power supply device of the third embodiment is substantially the same as that of the first embodiment. The difference from Embodiment 1 is that the charges accumulated in the smoothing capacitor 48 on the output side of the first converter 40B and the charges accumulated in the smoothing capacitor 58 on the output side of the second converter 50B are added to form the output capacitor. It is accumulated in 59. Therefore, similarly to the second embodiment, an output voltage 2Vo that is twice the output voltage Vo of the first embodiment is output from the output terminals 60a and 60b.

(Effects of Example 3)
According to the third embodiment, as in the first embodiment, the intermediate terminal 37c of the three-phase PFC 30 shown in FIG. 3 is used. Therefore, as in the first embodiment, the output power between the first converter 40B and the second converter 50B becomes unbalanced due to variations between the main components of the first converter 40B and the second converter 50B, which have the same characteristics. Then, the input voltage of the converter with a large amount of power decreases, and the input voltage of the converter with a small amount of power increases. Since the output voltage (V1+V2) of the three-phase PFC 30 is controlled at a constant voltage, the output voltage (V1+V2) changes while maintaining the constant voltage, and the output power between the first converter 40B and the second converter 50B becomes self-controlled. balance. Thereby, it is not necessary to perform power balance control on the first converter 40B and second converter 50B sides as in the conventional case, so it is possible to realize a switching power supply device with a simple circuit configuration.

(Modifications of Examples 1 to 3)
The present invention is not limited to the first to third embodiments described above, and can be used in various ways and modified. Examples of usage patterns and modifications include the following (a) and (b).

(a) The three-phase PFC 30 at the front stage may have a configuration other than that shown. For example, a capacitor is connected between each of the three-phase input terminals 31a, 31b, 31c and the intermediate terminal 37c, together with the line capacitors 32a to 32c, or in place of the line capacitors 32a to 32c, to remove high frequency components. It may be configured to do so.

(b) The first converters 40, 40A, 40B and the second converters 50, 50A, 50B in the latter stages may have configurations other than those shown in the drawings. For example, the full bridge circuits 42 and 52 may be replaced with a herb bridge circuit or the like. The choke coils 47, 57 may be omitted. Further, instead of the PFM-controlled LLC converter, a DC/DC converter whose duty is controlled by PWM (for example, a buck converter, a boost converter, a buck-boost converter, etc.) may be used. Even if this configuration is changed, substantially the same effects as in Examples 1 to 3 can be expected.

30 3 phase PFC
21 3-phase AC power 31a, 31b, 31c 3-phase input terminal 32a, 32b, 32c Line capacitor 33 3-phase inductor 34 Switching circuit 35 Full-wave rectifier circuit 36a, 36b, 48, 58 Smoothing capacitor 37a, 37b 1st, 1st 2 terminals 37c Intermediate terminals 40, 40A, 40B 1st converter 41, 51 Input capacitor 42, 52 Full bridge circuit 43, 53 Resonant capacitor 44, 54 Resonant choke coil 45a1, 55a1 Excitation choke coil 45, 55 Transformer 46, 46A, 56 Full wave rectifier circuit 48, 58 Smoothing capacitor 50, 50A, 50B 2nd converter 59 Output capacitor 60a, 60b 1st, 2nd output terminal

Claims (8)

The input three-phase AC power is switched by a switching circuit , then rectified and smoothed, and a first DC voltage with improved power factor is output from the first terminal and the intermediate terminal, and a first DC voltage with improved power factor is output from the intermediate terminal and the second terminal. , a three-phase power factor correction circuit that outputs a second DC voltage with improved power factor;
a first converter that converts the first DC voltage output from the first terminal and the intermediate terminal using a full bridge circuit and a transformer , and outputs the converted voltage from the first output terminal and the second output terminal;
a second converter that converts the second DC voltage output from the intermediate terminal and the second terminal using a full bridge circuit and a transformer, and outputs the converted voltage from the first output terminal and the second output terminal;
a control unit that controls the three-phase power factor improvement circuit, the first converter, and the second converter;
Equipped with
The second converter has the same characteristics as the first converter, and the output side of the second converter is connected in parallel or series to the first output terminal and the second output terminal ,
The control unit includes:
Switching the switching circuit of the three-phase power factor improvement circuit is controlled by pulse width modulation duty control so that the output voltage, which is the sum of the first DC voltage and the second DC voltage, becomes a constant voltage;
A switching power supply device characterized in that switching control of the full bridge circuit of the first converter and the full bridge circuit of the second converter is performed by synchronized pulse frequency modulation control. In the control unit of the switching power supply device,
The switching power supply according to claim 1, wherein the measured value of the output voltage is compared with a target voltage value, and the switching circuit of the three-phase power factor correction circuit is feedback-controlled so that the comparison result decreases. Device. The three-phase power factor improvement circuit is
a three-phase input terminal for inputting the three-phase AC power;
a three-phase inductor connected to the three-phase input terminal;
a switching circuit with one end connected in series to the three-phase inductor;
a connection point between the three-phase inductor and the switching circuit;
the intermediate terminal connected to the other end of the switching circuit;
the first terminal and the intermediate terminal that output the first DC voltage;
the intermediate terminal and the second terminal that output the second DC voltage ;
a rectifier circuit connected between the connection point and the first terminal and the second terminal;
a first smoothing circuit connected between the first terminal and the intermediate terminal;
a second smoothing circuit connected between the intermediate terminal and the second terminal;
The switching power supply device according to claim 1, characterized in that it has: The first converter is
A first input side is connected to the first terminal and the intermediate terminal, a first output side is connected to the first output terminal and the second output terminal, and the first DC voltage input from the first input side is converting the voltage and outputting it to the first output side;
The second converter is
A second input side is connected to the intermediate terminal and the second terminal, a second output side is connected in parallel or series to the first output terminal and the second output terminal, and the input is input from the second input side. voltage converting the second DC voltage and outputting it to the second output side;
The switching power supply device according to claim 1, characterized in that: Between the three-phase inductors,
A line capacitor is connected to remove high frequency components.
The switching power supply device according to claim 3 , characterized in that: The three-phase inductor is a three-phase inductor for boosting voltage,
The switching circuit is composed of a plurality of switching elements,
The rectifier circuit is composed of a full-wave rectifier circuit,
The first smoothing circuit and the second smoothing circuit each include a capacitor,
The switching power supply device according to claim 3 , characterized in that: The first converter and the second converter each include:
Consists of a DC/DC converter including a resonant converter,
The switching power supply device according to claim 4 , characterized in that: The resonant converter is
A bridge circuit that switches DC voltage using multiple switching elements,
a resonant circuit that resonates due to the output voltage of the bridge circuit;
a transformer that converts the voltage level of the output voltage of the resonant circuit;
a rectifying and smoothing circuit that rectifies and smoothes the output voltage of the transformer;
The switching power supply device according to claim 7 , characterized in that it has:

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