JP2019062664A - Electric power supply - Google Patents

Abstract

To stably control an output voltage of a power factor improvement circuit.SOLUTION: An electric power supply 1 includes: a rectification circuit 20 that outputs a rectification voltage obtained by full wave rectifying an AC voltage; and a PFC circuit 30 connected between a DC power supply wiring PL to which a smoothing capacitor C is connected and the rectification circuit 20. The PFC circuit 30 includes: an inductor L; and a semiconductor switching element SW for performing a switching control of an inductor current. A power supply microcomputer 50 controls ON/OFF of the semiconductor switching element SW by using an average value in each period of the rectification voltage in an output voltage Vdc of the PFC circuit 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply device, and more particularly to a power supply device provided with a power factor correction (PFC) circuit.

  A power supply apparatus is known that includes a rectifier circuit that full-wave rectifies an AC voltage from a system power source or the like, and a power factor improvement circuit provided on the output side of the rectifier circuit. The control device performs control to synchronize the phase of the input current of the power factor correction circuit with the phase of the input voltage of the power factor correction circuit (the pulsating current voltage after full-wave rectification of the AC voltage). Improve the power factor of the output power of the

  With respect to such a power supply device, for example, Japanese Patent No. 593 9 848 (PTL 1) discloses a PWM (Pulse Width Modulation) signal for controlling on / off of a semiconductor switching element of a PFC circuit, a magnitude of an output voltage of the PFC circuit. According to the above, a configuration for feedback control is disclosed.

Patent No. 593 9 848

  At the output voltage of the PFC circuit, a ripple voltage is generated in accordance with the frequency of the rectified voltage of the AC voltage (generally, the frequency twice the AC voltage). Also, in general, the output voltage of the PFC circuit is smoothed by a capacitor. Therefore, the phase of the ripple voltage does not coincide with the phase of the rectified voltage.

  Therefore, in the feedback control of the output voltage as described in Patent Document 1, if the control gain is increased in order to suppress the ripple voltage, there is a concern that voltage fluctuation may be expanded due to hunting or the like of control. As a result, if the capacitance of the capacitor is increased to reduce the ripple voltage, there is a concern that the size and cost of the device may be increased.

  The present invention has been made to solve such problems, and an object of the present invention is to stably control the output voltage of a PFC circuit.

  According to an aspect of the present invention, a power supply device includes a rectifier circuit, a power factor correction circuit, and a control unit that controls the power factor correction circuit. The rectifier circuit is configured to output a rectified voltage obtained by full-wave rectifying an AC voltage. The power factor correction circuit is connected between the DC power supply wiring to which the smoothing capacitor is connected and the rectifier circuit. The power factor correction circuit includes an inductor electrically connected between the rectifier circuit and the DC power supply wiring, and a semiconductor switching element for switching control of the current of the inductor. The control device controls the output voltage of the power factor correction circuit by controlling the on / off of the semiconductor switching element using an average value calculated according to the period of the rectified voltage.

  According to the above power supply device, it is possible to prevent the control in the power factor correction circuit from being destabilized by the influence of the ripple voltage generated depending on the frequency of the AC voltage input to the rectification circuit. In particular, since the fluctuation of the output voltage due to the influence of control can be suppressed, the enlargement of the capacity of the smoothing capacitor can be suppressed, and the miniaturization and cost reduction of the power conversion device can be achieved.

  Preferably, the control device turns on and off the semiconductor switching element to control the current of the inductor in accordance with the current target waveform generated as the similar waveform of the rectified voltage. The similarity between the current target waveform and the rectified voltage waveform is adjusted according to the deviation of the average value of the output voltage from the target voltage value.

  With this configuration, by controlling the inductor current according to the current target waveform by turning on and off the semiconductor switching element, it is possible to control the output voltage to the target voltage value together with the power factor improvement control.

  More preferably, if the absolute value of the deviation is smaller than a predetermined threshold value, the current value of the similarity ratio is maintained on the assumption that the deviation is zero.

  With this configuration, it is possible to prevent fluctuation of the output voltage due to excessive control in the power factor correction circuit when the current consumption of the load is small by simple control calculation.

  Further preferably, the control device controls the on / off of the semiconductor switching element based on the deviation between the target voltage value and the average value of the output voltage. The target voltage value is increased or decreased according to the load parameter value which increases in response to the increase of the supply current to the load connected to the DC power supply wiring. For example, the controller lowers the target voltage value below the current value if the load parameter value is lower than the first reference value. Alternatively, the control device raises the target voltage value higher than the current value when the load parameter value is higher than the second reference value set above the first reference value.

  With such a configuration, the power loss of the power factor correction circuit can be reduced without destabilizing the load operation by reducing the target voltage value of the output voltage of the power factor correction circuit according to the current supplied to the load. Can be reduced.

  More preferably, the load has a plurality of load devices electrically connected to the DC power supply wiring, and the target voltage value is adjusted within a range of a first predetermined voltage or more and a second predetermined voltage or less Be done. The control device sets the target voltage value to the second predetermined voltage when the operating conditions of the plurality of load devices change in the direction to increase the current consumption.

  With this configuration, when the operating condition of the load device changes in the direction of increasing power consumption, the target voltage value is once increased to prioritize the stable operation of the load device, which affects the operation of the load. Instead, control can be performed to reduce the target voltage value of the power factor correction circuit according to the load parameter value.

  More preferably, the target voltage value is set to a second predetermined voltage when the power supply apparatus is started.

  Thus, it is possible to execute control to lower the target voltage value of the power factor correction circuit according to the load parameter value, prioritizing the stable operation of the load at startup.

  According to the present invention, the output voltage of the PFC circuit can be stably controlled.

FIG. 1 is a schematic diagram showing an example of an entire configuration of a power supply device according to a first embodiment. It is a notional wave form diagram for explaining power factor improvement control by a PFC circuit. It is a flowchart which shows an example of the process sequence of the power factor improvement control and constant voltage control by a power supply microcomputer. It is a notional wave form diagram of the output voltage of a PFC circuit. FIG. 6 is a flowchart for illustrating control processing of constant voltage control in the power supply device according to Embodiment 1. FIG. 7 is a flowchart illustrating control processing added according to a modification of the first embodiment. FIG. 17 is a flowchart illustrating target voltage variable control according to the second embodiment. It is a block diagram of a load for explaining an example of setting of a load parameter value. FIG. 9 is a circuit diagram showing a configuration example of a step-down chopper in FIG. 8. It is a wave form diagram explaining control of the step-down chopper shown by FIG. It is a conceptual diagram explaining the example of control of the target voltage of constant voltage control based on load parameter value. FIG. 6 is a conceptual waveform diagram for explaining an operation example of target voltage variable control. FIG. 16 is a flowchart illustrating target voltage variable control according to a modification of the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding portions in the drawings are denoted by the same reference characters and description thereof will not be repeated.

FIG. 1 is a schematic diagram showing an example of the entire configuration of power supply device 1 according to the first embodiment.
Referring to FIG. 1, power supply device 1 is connected to an alternating current power supply (commercial power system grid or the like) 10 via alternating current lines A1 and A2, and is connected to a load 60 via positive electrode line PL3. Power supply device 1 converts AC power input from AC power supply 10 into DC power, and outputs the DC power to positive electrode line PL3 to which load 60 is connected. Positive electrode line PL3 corresponds to "DC power supply wiring".

  Hereinafter, the AC voltage input from AC power supply 10 to power supply device 1 is also referred to as “input voltage Vac”, and the DC voltage output from power supply device 1 to load 60 (positive electrode line PL3) is also referred to as “output voltage Vdc”. write.

  The power supply device 1 includes a rectifier circuit 20, a PFC circuit 30, a voltage conversion circuit 40, and a power supply microcomputer (control device) 50. The input side of the rectifier circuit 20 is connected to the AC power supply 10 via the AC lines A1 and A2, and the output side of the rectifier circuit 20 is connected to the PFC circuit 30 via the positive electrode line PL1 and the negative electrode line NL.

  The rectifier circuit 20 includes a plurality of diodes forming a diode bridge. The rectifier circuit 20 outputs a rectified voltage obtained by full-wave rectification of the AC voltage from the AC power supply 10. The rectified voltage is a unipolar pulsating voltage waveform that is generated by folding a sinusoidal alternating waveform at the zero crossing point. The rectified voltage output from the rectifier circuit 20 is input to the PFC circuit 30.

  The PFC circuit 30 is a circuit for improving the power factor of the power after passing through the rectifier circuit 20. The PFC circuit 30 includes an inductor L, a switching element SW, a diode D, a smoothing capacitor C, a drive circuit 32, a current sensor 34, and a voltage sensor 36.

  The inductor L is a boosting coil connected between the positive electrode lines PL1 and PL2. The switching element SW is a field effect transistor (FET) or the like connected between the positive electrode line PL2 and the negative electrode line NL. The inductor L and the switching element SW function as a step-up chopper circuit.

  Diode D is arranged between positive electrode line PL2 and positive electrode line PL3 with the direction from positive electrode line PL2 toward positive electrode line PL3 as the forward direction. Thus, the inductor L is electrically connected between the rectifier circuit 20 and the positive electrode line PL3 via the positive electrode line PL2 and the diode D. Smoothing capacitor C is arranged between positive electrode line PL3 and negative electrode line NL, and smoothes the output voltage of PFC circuit 30.

  Current sensor 34 is connected in series with switching element SW between positive electrode line PL2 and negative electrode line NL. For example, the current sensor 34 can be arranged to detect the current flowing through the connection line N1 connecting the switching element SW and the negative electrode line NL.

  When the switching element SW is in the on state, a current flowing through the inductor L (input current input from the rectifier circuit 20 to the PFC circuit 30) passes through the switching element SW and flows to the negative electrode line NL. Therefore, the detection value of the current sensor 34 is a value indicating the current flowing through the inductor L. Hereinafter, the detection value of the current sensor 34 is also referred to as “inductor current IL”. Voltage sensor 36 detects an output voltage Vdc between positive electrode line PL3 and negative electrode line NL.

  The voltage conversion circuit 40 is connected to the AC lines A1 and A2 and to the power supply microcomputer 50. The voltage conversion circuit 40 includes a plurality of diodes D1 and D2 and a plurality of resistors R1 to R4. The voltage conversion circuit 40 full-wave rectifies the input voltage Vac applied from the AC power supply 10 to the AC lines A1 and A2, and outputs the rectified voltage to the power supply microcomputer 50.

  The waveform of the voltage output from the voltage conversion circuit 40 to the power supply microcomputer 50 is a unipolar pulsating voltage waveform generated by folding back the waveform of the sinusoidal input voltage Vac at the zero crossing point. Hereinafter, the voltage output from the voltage conversion circuit 40 to the power supply microcomputer 50 (the voltage after the full-wave rectification of the input voltage Vac by the voltage conversion circuit 40) is also referred to as “pulsating voltage Vpu”. The pulsating current voltage Vpu has the same frequency and phase as the rectified voltage input from the rectifier circuit 20 to the PFC circuit 30.

  The power supply microcomputer 50 includes a central processing unit (CPU), a memory, an input / output buffer, and the like. Although the example in which the power supply microcomputer 50 is provided inside the PFC circuit 30 is shown in FIG. 1, the power supply microcomputer 50 may be provided outside the PFC circuit 30.

  The power supply microcomputer 50 is connected to the voltage conversion circuit 40, the current sensor 34 and the voltage sensor 36. The pulsating current voltage Vpu from the voltage conversion circuit 40, the inductor current IL from the current sensor 34, and the output voltage Vdc from the voltage sensor 36 are input to the power supply microcomputer 50. The power supply microcomputer 50 generates a control signal for driving (turning on and off) the switching element SW using these voltages, and outputs the generated control signal to the drive circuit 32. The drive circuit 32 drives (turns on and off) the switching element SW in accordance with a control signal from the power supply microcomputer 50.

  The load 60 operates by receiving power supply from the power supply device 1 (PFC circuit 30). For example, load 60 includes a DC pump used to circulate bath water in a water heater (not shown), a DC motor that rotationally drives a fan for supplying combustion air, and the like.

  The water heater microcomputer 65 includes a CPU, a memory, an input / output buffer and the like, and controls the operation of the water heater. The water heater microcomputer 65 can output, to the power supply microcomputer 50, a signal indicating whether the load 60 receiving power supply from the power supply device 1 (PFC circuit 30) is in operation.

Next, control by the PFC circuit 30 will be described.
The PFC circuit 30 performs constant voltage control to control the output voltage Vdc to the target voltage Vdc *, and power factor improvement control to synchronize the phase of the current flowing through the inductor L (input current of the PFC circuit 30) to the phase of the pulsating voltage Vpu. And perform DC / DC conversion. The DC / DC conversion is realized by the power supply microcomputer 50 controlling on / off of the switching element SW.

  A conceptual waveform diagram for illustrating power factor correction control and constant voltage control by the PFC circuit 30 is shown in FIG. In FIG. 2, the horizontal axis indicates time, the upper end of the vertical axis indicates a voltage value (pulse voltage Vpu), and the lower end of the vertical axis indicates a current value (target inductor current ILtag and inductor current IL).

  Referring to FIG. 2, the pulsating current voltage Vpu has a waveform obtained by full-wave rectification of a sinusoidal alternating voltage. That is, the pulsating current voltage Vpu shows a pulsating current waveform having a frequency twice as high as that of the AC voltage Vac, which is turned back at times t0, t1 and t2 corresponding to the zero crossing point. The power supply microcomputer 50 acquires a full-wave rectified waveform by sampling the pulsating current voltage Vpu after filter processing for removing high frequency noise by A / D conversion. In the following, it is assumed that the pulsating current voltage Vpu indicates a voltage after filtering.

  Furthermore, the power supply microcomputer 50 generates a target inductor current ILtag by multiplying the voltage value of the pulsating current voltage Vpu by the parameter KA. Therefore, the phase of the target inductor current ILtag is synchronized with the pulsating current voltage Vpu, that is, the rectified voltage output from the rectifier circuit 20.

  While the inductor current IL (the detection value of the current sensor 34) rises in the on period of the switching element SW, the inductor current IL decreases in the off period of the switching element SW. Therefore, by controlling the switching of the inductor current IL by turning on and off the switching element SW, the waveform of the inductor current IL can be made close to the waveform of the target inductor current ILtag. Thus, power factor improvement control can be performed in which the power factor is set to 1.0 by matching the phases of the voltage and current supplied from the AC power supply 10.

  In the configuration example of FIG. 1, the inductor current IL can be detected by the current sensor 34 only during the on period of the switching element SW. Therefore, on timing of switching element SW is periodically provided at high frequency (for example, about 50 KHz), and control is performed to turn off switching element SW according to inductor current IL reaching target inductor current ILtag at each on timing. The waveform of the inductor current IL can be controlled according to the waveform of the target inductor current ILtag by repeating.

  Also, the average value of the inductor current IL is proportional to the power supplied from the AC power supply 10. The target inductor current ILtag has a phase synchronized with the pulsating current voltage for power factor correction control, and its average value can be adjusted by the parameter KA. Therefore, the power supply microcomputer 50 can execute constant voltage control of the output voltage Vdc by adjusting the parameter KA by feedback control of the output voltage Vdc.

  FIG. 3 is a flowchart showing an example of processing procedures of power factor improvement control and constant voltage control by the power supply microcomputer 50. The control process shown in FIG. 3 is repeatedly executed by the power supply microcomputer 50 at predetermined control cycles.

  Referring to FIG. 3, first, power supply microcomputer 50 acquires a voltage value in the current cycle of pulsating current voltage Vpu from voltage conversion circuit 40 by A / D conversion and filter processing (step S100).

  Next, the power supply microcomputer 50 calculates a parameter KA for constant voltage control (step S200). The calculation of the parameter KA will be described in detail later. Furthermore, the power supply microcomputer 50 calculates the target inductor current ILtag according to the following equation (1) (step S300).

ILtag = Vpu × KA (1)
In Equation (1), the value acquired in step S100 is used as Vpu, and the value calculated in step S200 is used as KA. In addition, since the target inductor current ILtag is basically set to a value of 0 or more, when the target inductor current ILtag calculated by the equation (1) is a negative value, the target inductor current ILtag = 0 Set to

  Thereby, as shown in FIG. 2, the phase of the target inductor current ILtag is synchronized with the phase of the pulsating current voltage Vpu. Furthermore, the magnitude (amplitude) of the target inductor current ILtag is adjusted to bring the output voltage Vdc closer to the target voltage Vdc *. As described above, since the pulsating current voltage Vpu has the same frequency and phase as the rectified voltage output from the rectifying circuit 20, the waveform of the target inductor current ILtag becomes a similar waveform of the rectified voltage. It is also understood that the similarity ratio of the rectified voltage waveform and the target inductor current waveform is adjusted by the parameter KA.

  Next, in steps S400 to S480, the power supply microcomputer 50 performs on / off control of the switching element SW such that the current flowing through the inductor L approaches the target inductor current ILtag.

  Specifically, the power supply microcomputer 50 determines whether the switching element SW is in the off state (step S400). If switching element SW is in the off state (YES in step S400), power supply microcomputer 50 determines whether or not it is the on timing of switching element SW (step S420).

  In the present embodiment, the on-timing of the switching element SW is set every fixed period. (For example, about every 20 microseconds) It turns on. Therefore, the power supply microcomputer 50 determines that it is the on-timing of the switching element SW when a predetermined time has elapsed from the timing when the switching element SW was switched from off to on last time.

  If it is the on timing of the switching element SW (YES in step S420), the power supply microcomputer 50 switches the switching element SW from the off state to the on state (step S440). On the other hand, when it is not the on timing of the switching element SW (at the time of NO determination of step S420), the power supply microcomputer 50 skips the process of step S440 and shifts the process to return.

  If switching element SW is not in the off state (NO in step S400), that is, if switching element SW is in the on state, power supply microcomputer 50 causes inductor current IL (the detection value of current sensor 34) to be reduced in step S300. It is determined whether it is equal to or more than the calculated target inductor current ILtag (step S460).

  If the inductor current IL is equal to or higher than the target inductor current ILtag (YES in step S460), the power supply microcomputer 50 switches the switching element SW from the on state to the off state (step S480).

  Preferably, the on / off control process of the switching element SW in steps S400 to S480 is performed separately from the setting process (S100 to S300) of the target inductor current ILtag. That is, as described above, the processing of steps S400 to S480 can be realized by turning on the switching element SW in a constant cycle and utilizing the so-called "trip function" of the power supply microcomputer 50.

  According to the trip function, the power supply microcomputer 50 turns off the switching element SW when the current detected by the current sensor 34 (inductor current IL) reaches the upper limit current. At this time, the processes of steps S460 and S480 can be realized by sequentially setting the target inductor current ILtag calculated in step S300 as the upper limit current of the trip function.

  As described above, by providing the on-timing of the switching element SW at a high frequency and utilizing the trip function, the inductor current IL can be controlled according to the waveform of the target inductor current ILtag as shown in FIG. In particular, by utilizing the trip function, the control of FIG. 2 can be realized without excessively shortening the control cycle of steps S100 to S300.

Next, setting of the parameter KA by constant voltage control will be described in detail.
FIG. 4 is a conceptual waveform diagram of the output voltage of the PFC circuit 30. As shown in FIG.

  Referring to FIG. 4, a ripple voltage is generated in output voltage Vdc according to the frequency of pulsating current voltage Vpu, that is, the frequency twice the power supply frequency of AC power supply 10. The phase of the voltage fluctuation due to the ripple voltage does not match the phase of the pulsating current voltage Vpu due to the influence of the inductor L and the smoothing capacitor C. That is, time t0, t1 corresponding to the zero crossing point of the pulsating current voltage Vpu in FIG. 2 does not coincide with the timing at which the output voltage Vdc becomes minimum.

  Therefore, if the control gain is increased to suppress the ripple voltage by feedback control of the output voltage as described in Patent Document 1, there is a concern that voltage fluctuation may be expanded due to occurrence of hunting due to overcompensation, etc. . As a result, if the capacity of the smoothing capacitor C is increased to reduce the ripple voltage, there is a concern that the size and cost of the apparatus may be increased. On the other hand, there is a concern that raising the control accuracy by increasing the frequency of feedback control, that is, shortening the control cycle may lead to an increase in cost due to the high specification of the power supply microcomputer 50.

  Therefore, in the power supply device according to the first embodiment, the control operation is stabilized by executing constant voltage control using an average voltage of one cycle of the pulsating current voltage Vpu.

  FIG. 5 shows a flowchart for describing control processing of constant voltage control in the power supply device according to the first embodiment. The control process shown in FIG. 5 explains the details of step S200 of FIG.

  Referring to FIG. 5, step S200 shown in FIG. 3 has steps S210 to S250. When the value of the current control period of the pulsating current voltage Vpu is acquired in step S100, the power supply microcomputer 50 samples the output voltage Vdc using the voltage sensor 36 in step S210.

  Further, in step S220, the power supply microcomputer 50 determines whether or not it is the zero crossing point of the pulsating current voltage Vpu. For example, in step S220, the value of the flag FLGZ is set according to the comparison result of the reference voltage Vr for detecting the zero cross point (Vr ≒ 0) set in advance and the pulsating current voltage Vpu obtained in step S100. When Vpu> Vr, the flag FLGZ = 1 is set, while when Vpu ≦ Vr, FLGZ = 0, FLGZ = 1 in the previous control cycle, and the present control When FLGZ = 0 in the cycle, step S220 may be determined as YES, and otherwise, it may be determined as NO.

  When the zero crossing point of Vpu is not detected (NO at S220), power supply microcomputer 50 stores the sampling value of output voltage Vdc at step S225 and maintains parameter KA at the current value, and then performs processing. The process proceeds to step S300. Thereby, the PFC circuit 30 is controlled according to the target inductor current ILtag based on the maintained parameter KA.

  When the zero crossing point of Vpu is detected (YES in S220), the power supply microcomputer 50 calculates an average voltage Vdcm of the output voltage Vdc stored in step S225 in step S230. Furthermore, the stored output voltage Vdc is cleared. Thus, the average voltage Vdcm is calculated as an average value of the output voltage Vdc in a period corresponding to one cycle of the pulsating current voltage Vpu.

  In step S240, the power supply microcomputer 50 further calculates the voltage deviation ΔV using the average voltage Vdcm calculated in step S230 (ΔV = Vdc * −Vdcm). In step S250, the power supply microcomputer 50 calculates the parameter KA by control calculation for compensating the voltage deviation ΔV. For example, the parameter KA can be calculated by the following equation (2) by PI control. In equation (2), Kp represents a proportional control gain, and Ki represents an integral control gain.

KA = (ΔV × Kp) + [Σ (ΔV × Ki)] (2)
As a result, the parameter KA is updated for each zero-crossing point detection of the pulsating current voltage Vpu. The power supply microcomputer 50 advances the process to step S300 (FIG. 2) to calculate the target current ILtag in accordance with the updated parameter KA.

  Referring again to FIG. 4, at time t0 and t1 corresponding to the zero cross timing of the pulsating current voltage Vpu, step S220 is determined as YES, and the average voltage Vdcm is calculated from the output voltage Vdc accumulated for one cycle. . For example, the average voltage Vdcm calculated at time t1 corresponds to the average value of the output voltage Vdc sampled in the period from time t0 to t1. Then, the parameter KA based on the average voltage Vdcm calculated at time t1 is maintained until the next zero cross timing (time t2 in FIG. 2).

  As a result, it is possible to prevent the magnitude (amplitude) of the target inductor current ILtag in the PFC circuit 30 from fluctuating due to the influence of the ripple voltage. As a result, it is possible to suppress the fluctuation of the output voltage Vdc due to the instability of feedback control for constant voltage control, thereby suppressing the size increase due to the increase of the capacity of the smoothing capacitor C, and downsizing and cost reduction of the power converter. Can be

[Modification of Embodiment 1]
Referring back to FIG. 1, in constant voltage control of power supply device 1, when output voltage Vdc decreases according to power consumption at load 60, parameter KA is increased to reduce inductor current IL, that is, from PFC circuit 30. The output current to the load 60 increases. Therefore, when the power consumption by the load 60 is small, so-called light load, if the parameter KA is excessively increased according to the occurrence of the voltage deviation ΔV (ΔV> 0), there is a concern that the output voltage Vdc may excessively increase. .

  On the other hand, if the control gains Kp and Ki are set to different values in accordance with the difference in the power consumption of the load 60 as described above, an increase in the adjustment load of the control gain is concerned.

  Therefore, in the modification of the first embodiment, the control process shown in FIG. 6 is added. Specifically, step S245 shown in FIG. 6 is performed between steps S240 and S250 of FIG.

  Referring to FIG. 6, step S245 has steps S246 to S248. When the voltage deviation ΔV is calculated in step S240, the power supply microcomputer 50 determines whether the absolute value | ΔV | of the voltage deviation is smaller than a predetermined reference value Vp in step S246.

  If | ΔV | <Vp (YES at S246), the power supply microcomputer 50 clears the voltage deviation ΔV = 0 at step S247, and advances the process to step S250. On the other hand, if | ΔV | ≧ Vp (at the time of NO determination at S246), the power supply microcomputer 50 decreases the absolute value of | ΔV | by Vp at step S248. Specifically, when ΔV> 0, Vp is subtracted from ΔV, and when ΔV <0, Vp is added to ΔV.

  Therefore, when voltage deviation ΔV is small (in the range of −Vp <ΔV <Vp), parameter KA does not change from the current value in step S250. Also, constant voltage control will adjust the parameter KA to maintain the output voltage Vdc within the range of Vdc * ± Vp.

  Thus, when the power consumption of the load 60 is small by making the target voltage Vdc * have an equivalent width (± Vp), excessive correction of the magnitude (amplitude) of the inductor current IL results in an output voltage The fluctuation of Vdc can be prevented by a simple control operation.

Second Embodiment
In the second embodiment, variable control of the target voltage Vdc * of constant voltage control will be described.

  The PFC circuit 30 shown in FIG. 1 generates a boosted output voltage Vdc. Generally, in the PFC circuit 30, the power loss increases as the boost ratio increases. On the other hand, when the power consumption of the load 60 is constant, the current of the load 60 increases as the output voltage Vdc decreases. If the current increases too much, a semiconductor element of the step-down chopper 70 described later may fail, for example, due to overheating of a component (for example, a semiconductor switching element) due to an increase in power loss (proportional to the square of the current) at the load 60 There is concern that the operation of the load 60 will be affected.

  Therefore, in the second embodiment, control for changing target voltage Vdc * of output voltage Vdc in accordance with the current consumption state of load 60 (hereinafter, also referred to as “target voltage variable control”) will be described. The target voltage variable control according to mode 2 can be applied to setting of the target voltage Vdc * used for constant voltage control in the power supply 1 described in the first embodiment.

  FIG. 7 is a flowchart illustrating target voltage variable control according to the second embodiment. The control process shown in FIG. 7 is performed separately from the control process of FIG. The target voltage Vdc * set in the control process of FIG. 7 is used in step S240 of FIG.

  Referring to FIG. 7, power supply microcomputer 50 obtains load parameter value Pld indicating the current consumption state of load 60 in step S510. The load parameter value Pld is defined as a quantitative value set to a high value when the current consumption is large.

FIG. 8 shows a block diagram of a load for explaining an example of setting of load parameter values.
Referring to FIG. 8, load 60 includes load devices 61 and 62. The load devices 61 and 62 are configured by power consumption devices such as a pump or a fan. The operation and stop of the load devices 61 and 62 are controlled by the water heater microcomputer 65 shown in FIG. In addition, the power consumption at the time of operation of the load devices 61 and 62 changes in accordance with the operation state (for example, the number of revolutions etc.) in accordance with the operation command value from the water heater microcomputer 65.

  Load device 61 is electrically connected to positive electrode line PL3 through current sensor 76. The supply current Il1 to the load device 61 that operates by receiving the output voltage Vdc of the PFC circuit 30 can be detected by arranging the current sensor 76. The detected value of the current sensor 76 is input to the power supply microcomputer 50. For the load device 61, the current value detected by the current sensor 76 can be used as the load parameter value Pld.

  On the other hand, load device 62 is electrically connected to positive electrode line PL3 via step-down chopper 70. The step-down chopper 70 steps down the DC voltage Vdc on the positive electrode line PL3 and outputs the DC voltage Vs to the positive electrode line PLs. The load device 62 operates by receiving the output voltage Vs of the step-down chopper 70.

FIG. 9 is a circuit diagram showing a configuration example of the step-down chopper 70. As shown in FIG.
Referring to FIG. 9, the step-down chopper 70 includes an inductor 71, a switching element 72, and a diode 73. Switching element 72 is connected between positive electrode line PL3 and node Nc. It is turned on and off according to the control pulse signal SP from the power supply microcomputer 50. The inductor 71 is connected between the positive electrode line PLs to which the load device 62 is connected and the node Nc.

  The diode 73 is connected between the node Nc and the negative electrode line NL, with the direction from the negative electrode line NL to the node Nc as a forward direction. An output voltage Vs of the step-down chopper 70 is detected by a voltage sensor 75. The detected value of the voltage sensor 75 is input to the power supply microcomputer 50.

  In the step-down chopper 70, the on period and the off period of the switching element 72 are alternately provided. During the on period of the switching element 72, a current is supplied from the positive electrode line PL3 to the positive electrode line PLs via the inductor 71, so the output voltage Vs rises. On the other hand, during the off period of the switching element 72, the energy stored in the inductor 71 supplies a current to the positive electrode line PLs, so the output voltage Vs decreases.

FIG. 10 shows an example of a control waveform of the step-down chopper.
Referring to FIG. 10, power supply microcomputer 50 turns on switching element 72 at a constant switching cycle Tsw. The on period length Ton of the switching element 72 in each switching cycle is set in accordance with the duty ratio DT (DT = Ton / Tsw). That is, by changing the duty ratio DT by feedback control of the output voltage Vs based on the voltage detection value by the voltage sensor 75, the output voltage Vs of the step-down chopper 70 can be controlled to be constant.

  Referring again to FIG. 9, when the power consumption of the load device 62 is large and the supply current Il2 to the load device 62 is large, the duty ratio DT for controlling the output voltage Vs constant becomes high. On the other hand, when the supply current I12 to the load device 62 is small, the duty ratio DT for controlling the output voltage Vs constant becomes low.

  Therefore, the supply current Il2 can be detected indirectly from the duty ratio DT of the step-down chopper 70 without arranging a current sensor for detecting the supply current Il2. That is, for the load device 62, the duty ratio DT in the step-down chopper 70 for supplying a constant voltage to the load device 62 can be used as the load parameter value Pld.

  Thus, setting the load parameter value Pld having a quantitative value according to the current supplied to the load 60 using the current detection value by the current sensor or the control parameter value such as the duty ratio in the step-down chopper it can.

  Referring again to FIG. 7, in step S520, the power supply microcomputer 50 compares the load parameter value Pld acquired in step S510 with the reference value P1. If Pld <P1 and the supply current to the load 60 is small (YES in S520), the power supply microcomputer 50 lowers the target voltage Vdc * for constant voltage control from the current value in step S530. On the other hand, when Pld ≧ P1 (when NO in S520), the power supply microcomputer 50 maintains or raises the target voltage Vdc * in step S540.

  FIG. 11 is a conceptual diagram illustrating an example of control of the target voltage Vdc * based on the load parameter value.

  Referring to FIG. 11, when load parameter value Pld <P1, target voltage Vdc * is lowered by Vu1 from the current value by the above-described step S530. Furthermore, when Pld ≧ P1 (step S540), it is possible to select whether to maintain or increase the target voltage Vdc * by comparing the load parameter value Pld with the reference value P2 higher than the reference value P1. . The reference value P1 corresponds to the "first reference value", and the reference value P2 corresponds to the "second reference value".

  That is, at step S540, the power supply microcomputer 50 raises the target voltage Vdc * by Vu2 when Pld> P2 while keeping the target voltage Vdc * at the current value when PL1 ≦ Pld ≦ PL2. be able to. The decrease width Vu1 and the increase width Vu2 of the target voltage Vdc * may be the same value or different values.

FIG. 12 shows an operation example of the target voltage variable control according to the second embodiment.
Referring to FIG. 12, at time ta when power supply device 1 is activated, target voltage Vdc * is set to a predetermined initial voltage Vini. The initial voltage Vini corresponds to a rated voltage at which the operation of the load 60 is sufficiently guaranteed. The target voltage variable control according to the second embodiment aims to reduce the power loss in the PFC circuit 30 by reducing the target voltage Vdc * within a range where the current of the load 60 does not become excessive.

  From time tb, target voltage Vdc * is gradually decreased based on load parameter value Pld. On the other hand, at time tc, as a result of output voltage Vdc decreasing according to target voltage Vdc *, load parameter value Pld becomes higher than reference value P2, and target voltage Vdc * is increased.

  Thereafter, load parameter value Pld changes according to the increase or decrease of target voltage Vdc *, so that target voltage Vdc * can be as small as possible within the range where load parameter value Pld does not become excessive (the range of Pld ≦ P2). It can be set low.

  Upper limit value Vmax and lower limit value Vmin are set as the setting range of target voltage Vdc *, and increase and decrease of target voltage Vdc * are performed within the range of Vmin ≦ Vdc * ≦ Vmax. In the example of FIG. 12, Vmax = Vini. The lower limit value Vmin corresponds to the “first predetermined voltage”, and the upper limit value Vmax (initial voltage Vini) corresponds to the “second predetermined voltage”.

  By executing the control process shown in FIG. 7 in a longer cycle than the control process of FIG. 3, interference between the two controls can be prevented. Further, it is preferable that the load parameter value Pld acquired in step S510 is not a sampling value for each execution cycle of FIG. 7 (that is, for each cycle of the target voltage variable control), but an average value within the cycle.

  As described above, by reducing the target voltage Vdc * in the constant voltage control of the PFC circuit 30 according to the current supplied to the load 60, the power from the PFC circuit 30 can be reduced without destabilizing the operation of the load 60. Loss can be reduced.

[Modification of Embodiment 2]
When the above-described target voltage variable control is performed under constant power consumption at the load 60, the behavior of the target voltage Vdc * converges to an appropriate value as shown in FIG.

  On the other hand, when the load 60 is configured by a plurality of load devices as in the example of FIG. 8, the power consumption of the entire load 60 changes due to the operation or stop of the load devices. In the water heater, the power consumption of the load 60 is changed by changing the operation and stop of the fan and the pump or the rotation speed command value at the time of operation according to the command from the water heater microcomputer 65 (FIG. 1).

  Therefore, it is preferable to further combine control for returning the target voltage Vdc * to the initial voltage Vini every time the operation pattern of the load 60, for example, the number or type of load devices in operation, changes.

  FIG. 13 is a flowchart for describing target voltage variable control according to a modification of the second embodiment.

  Referring to FIG. 13, when power supply device 1 is activated, power supply microcomputer 50 sets target voltage Vdc * to initial voltage Vini in step S610. Then, in step S620, the target voltage variable control according to steps S510 to S540 in FIG. 7 is executed. When the power supply 1 is turned off during the execution of step S620, the control process of FIG. 13 is ended as indicated by a dotted line in the drawing.

  During the target voltage variable control, the power supply microcomputer 50 determines in step S630 whether or not the operating condition of the load 60 has changed. For example, in the case where the load 60 is configured by a plurality of load devices, when the operation / stop of any load device is switched, step S630 can be determined as YES.

  The power supply microcomputer 50 repeatedly executes the target voltage variable control in step S620 while the operating state of the load does not change (NO in S630). On the other hand, when the operating condition of the load changes (YES in S630), the power supply microcomputer 50 determines in step S640 whether the change in the operating condition is in the direction of increasing the power consumption. For example, when the number of operating load devices increases, step S640 is determined as YES.

  If there is a change in the operating condition such that the power consumption increases (YES at S640), the power supply microcomputer 50 returns the process to step S610 and returns to Vdc * = Vini to change the target voltage The control (S620) is resumed. On the other hand, if the power supply microcomputer 50 does not change the operating condition such that the power consumption increases (NO at S640), the target voltage Vdc * is maintained at the current value at step S650 and the target voltage The variable control (S620) is continued.

  In this way, when the operating condition of load 60 changes in the direction of increasing power consumption, target voltage Vdc * of PFC circuit 30 is temporarily restored to initial voltage Vini to give priority to stable operation of the load device. The power loss of the PFC circuit 30 can be reduced without affecting the operation of the load 60.

  As described above, the target voltage variable control of the PFC circuit according to the second embodiment and the modification thereof is the target voltage Vdc in constant voltage control in which the average value Vdcm of the output voltage in each cycle of the pulsating current is fed back. Not only for setting *, it is also possible to combine with normal output voltage (Vdc) feedback control.

  Specifically, in the constant voltage control in the PFC circuit 30, even if the voltage deviation ΔV and the parameter KA are modified so as to feed back the output voltage Vdc for each control cycle of FIG. 3, the voltage deviation ΔV is calculated. The target voltage Vdc * to be set can be set using the target voltage control according to the second embodiment and the modification.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all the modifications within the meaning and scope equivalent to the claims.

  DESCRIPTION OF SYMBOLS 1 power supply device, 10 alternating current power supply, 20 rectification circuit, 30 PFC circuit, 32 drive circuit, 34, 76 current sensor, 36, 75 voltage sensor, 40 voltage conversion circuit, 50 power supply microcomputer, 60 load, 61, 62 load apparatus, 65 water heater microcomputer, 70 step-down chopper, 71, L inductor, 72, SW switching element, 73, D, D1, D2 diode, A1, A2 AC wire, C smoothing capacitor, IL inductor current, KA parameter, NL negative electrode wire, N1 connection line, Nc node, P1, P2, Vp reference value, PL1 to PL3, PLs positive electrode line, Pld load parameter value, Vdc output voltage (PFC circuit), Vdc * target voltage (Vdc), Vs output voltage (step-down chopper) ), Vini initial voltage (Vdc *), Vpu pulsating current voltage.

Claims (8)

A rectifier circuit that outputs a rectified voltage obtained by full-wave rectifying an AC voltage;
A power factor correction circuit connected between a DC power supply wire to which a smoothing capacitor is connected and the rectification circuit;
A controller for controlling the power factor correction circuit;
The power factor correction circuit
An inductor electrically connected between the rectifier circuit and the DC power supply wire;
A semiconductor switching element for switching control of the current of the inductor;
The controller is
A power supply device controlling an output voltage of the power factor correction circuit by controlling on / off of the semiconductor switching element using an average value calculated according to a cycle of the rectified voltage. The controller is
Turning the semiconductor switching element on and off to control the current of the inductor according to a current target waveform generated as a similar waveform of the rectified voltage;
The power supply device according to claim 1, wherein a similarity ratio of the current target waveform and the waveform of the rectified voltage is adjusted in accordance with a deviation of the average value from a target voltage value of the output voltage.   The power supply device according to claim 2, wherein the control device maintains the current value of the similarity ratio as the deviation being zero when the absolute value of the deviation is smaller than a predetermined threshold value. The control device controls on / off of the semiconductor switching element based on a deviation between a target voltage value of the output voltage and the average value.
The power supply device according to claim 2, wherein the target voltage value is increased or decreased according to a load parameter value which increases in response to an increase in supply current to a load connected to the DC power supply wiring.   The power supply device according to claim 4, wherein the control device lowers the target voltage value below a current value when the load parameter value is lower than a first reference value.   The controller is configured to raise the target voltage value above a current value when the load parameter value is higher than a second reference value set to the first reference value or more. The power supply device according to 5. The load includes a plurality of load devices electrically connected to the DC power supply wiring,
The target voltage value is adjusted within a range equal to or higher than a first predetermined voltage and equal to or lower than a second predetermined voltage,
The control device sets the target voltage value to the second predetermined voltage when the operating conditions of the plurality of load devices change in a direction to increase current consumption. Power supply as described.   The power supply device according to claim 7, wherein the control device sets the target voltage value to the second predetermined voltage when the power supply device is activated.

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