JP2011147202A - Switching power unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power unit improving a power factor and efficiency by maintaining stability of an output voltage. <P>SOLUTION: A bidirectional current flows in a choke coil 10 from an AC power supply E in accordance with switching operations by switching elements 16, 18. In this case, a current detection signal, which has a voltage proportional to a unidirectional current flowing in a resistor 24, is selectively supplied to an IC 40 for control from a FET 54 when the unidirectional current flows in the choke coil 10, and a current detection signal, which has a voltage proportional to the unidirectional current flowing in a resistor 22, is selectively supplied to the IC 40 for control from a FET 52 when current in the other direction flows in the choke coil 10. Thus, the current flowing in the choke coil 10 has linearity and is faithfully reproduced as a voltage of the current detection signal at a light load. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to current detection of a power factor correction circuit that operates in a continuous current mode, and more particularly to a switching power supply device including a bridgeless power factor correction circuit without a diode bridge.

  The power factor correction circuit in the continuous current mode is controlled by a feedback circuit using a voltage loop and a current loop. The voltage control detects the output voltage of the power factor correction circuit and controls the switching operation of the switching elements constituting the power factor correction circuit so that the output voltage becomes substantially constant. The current control detects the current flowing through the choke coil that constitutes the power factor correction circuit, and controls the input current waveform to approach the input voltage waveform. By such current control, the power factor can be improved.

  In a circuit configuration in which an AC input voltage is rectified by a conventional diode bridge and the rectified voltage is input to a power factor correction circuit, the current flowing through the choke coil is unidirectional, whereas a power factor not using a diode bridge is used. In the improvement circuit (bridgeless PFC), the current flowing through the choke coil is not unidirectional. Regarding the control of the bridgeless PFC, for example, it is necessary to perform the method shown in Patent Document 1. In this method, currents flowing through two switching elements constituting a bridgeless PFC are detected, and the detected signals are added by an adder and then supplied to a current detection amplifier for current control. The current loop is formed.

Special table 2007-527687

  In the switching power supply device having the bridgeless PFC described above, the currents flowing through the two switching elements are detected by the first current detector and the second current detector, respectively, and according to the direction of the current flowing through the choke coil. The first selection element and the second selection element that selectively supply either the current detection signal from the first current detector or the current detection signal from the second current detector are required. However, when the current detection signal is supplied through these selection elements, if the current flowing through the choke coil 10 cannot be faithfully reproduced due to the characteristics of the selection elements, the stability of the output voltage is lost. The problem was that power factor and efficiency were reduced.

  The present invention has been made paying attention to the above problems, and an object thereof is to provide a switching power supply device capable of improving the power factor and efficiency while maintaining the stability of the output voltage.

  In order to achieve the above object, a switching power supply device of the present invention includes a choke coil connected in series to an AC power supply, a first switching element and a second switching element that perform switching operation, a first rectifier, and a second A rectifier, a first current detector and a second current detector for detecting a current flowing through the choke coil, and a controller for supplying a pulse drive signal to the first switching element and the second switching element; When either the first switching element or the second switching element is on, a current is passed from the AC power source to the choke coil, energy is stored in the choke coil, and the first switching element is Stored in the choke coil when either the element or the second switching element is off. And the first and second current detectors have a function of converting currents flowing through the first rectifier and the second rectifier into voltages, respectively, and the first current detection A first selection element that selectively supplies a current detection signal of the detector to the control unit, and a second selection element that selectively supplies a current detection signal of the second current detector to the control unit. And the control unit generates the pulse drive signal based on a current detection signal from the first selection element or the second selection element, wherein the first selection element is the first selection element A current flowing through the first current detector, and a first active switch element in which the current detection signal has linearity, and the second selection element includes a current flowing through the second current detector; The current detection signal is linear Characterized in that it is constituted by a second active switch devices, such as with.

  In this case, a drive unit that switches on and off of the first active switch element and the second active switch element according to the polarity of the AC input voltage from the AC power supply may be further provided.

  According to the switching power supply device of the present invention, a bidirectional current can flow from the AC power supply to the choke coil in accordance with the switching operation by the first switching element and the second switching element. When the current flows, a current detection signal having a voltage proportional to the current in one direction flowing in the first current detector is selectively supplied from the first active switch element to the control unit, and the choke coil is supplied in the other direction. When a current flows, a current detection signal having a voltage proportional to a one-way current flowing through the second current detector is selectively supplied from the second active switch element to the control unit. Therefore, at light loads with low output current, the current flowing through the choke coil is faithfully reproduced as the voltage of the current detection signal with linearity, maintaining the output voltage stability and improving the power factor and efficiency. Is possible.

  Further, in the present invention, the first active switch element and the second active switch are not dependent on the switching frequency of the first switching element or the second switching element, depending on the polarity of the AC input voltage from the AC power supply. It becomes possible to appropriately switch on and off the elements.

It is a circuit diagram which shows the basic composition of the switching power supply device relevant to this invention. It is a wave form diagram of each part same as the above. It is a figure which shows the current-voltage characteristic of each part same as the above. It is a circuit diagram of the switching power supply device proposed by the present invention. It is a figure which shows the current-voltage characteristic of each part same as the above. It is a wave form diagram of each part which shows another example same as the above.

  Embodiments of a switching power supply apparatus according to the present invention will be described below with reference to the accompanying drawings.

  First, a basic configuration as a switching power supply device will be described with reference to FIG. This is a circuit example in which a diode is used as means for selecting any one of detection signals of currents flowing through the respective switching elements in Patent Document 1. Such a circuit example and the waveform of each part are shown in FIGS. 1 and 2, respectively.

  In FIG. 1, reference numeral 100 denotes a switching power supply device having input terminals Vin1, Vin2 and an output terminal + Vout, GND. The switching power supply device 100 includes a choke coil 10, a first diode 12, a second diode 14, and a first diode. And a step-up chopper type power factor correction circuit 20 comprising a switching element 16 and a second switching element 18. The switching elements 16 and 18 are both N-channel MOSFETs (field effect transistors), and built-in diodes 16A and 18A are equivalently connected between the source and drain. As the switching elements 16 and 18, other semiconductor elements with control terminals may be used, and the diodes 16A and 18A may be externally attached.

  The power factor correction circuit 20 connects one end of the choke coil 10 to one input terminal Vin1, connects the other end of the choke coil 10 to a connection point between the anode of the diode 12 and the drain of the switching element 16, and the other input terminal Vin1. The input terminal Vin2 is connected to a connection point between the anode of the diode 14 and the drain of the switching element 18, and the cathodes of the diodes 12 and 14 are connected to the output terminal + Vout. Here, the AC input voltage from the AC power source E is directly applied to the power factor correction circuit 20 from the input terminals Vin1 and Vin2 without passing through a rectifier such as a diode bridge.

  Further, in order to detect the current flowing through the switching element 16 and the diode 16A, a resistor 22 as a second current detector is connected in series with the switching element 16. Similarly, a resistor 24 serving as a first current detector is connected in series with the switching element 18 in order to detect a current flowing through the switching element 18 and the diode 18A. Further, 26 is an output capacitor connected between the output terminal + Vout and GND on the output side of the power factor correction circuit 20.

  A signal selection unit 30 selects one of the two current detection signals obtained by the resistors 22 and 24 and supplies only the current detection signal corresponding to the current flowing through the choke coil 10 to the control IC 40 described later. Circuit. The signal selection circuit 30 includes a diode 32 having a cathode connected to one end of the resistor 22 and a diode 34 having a cathode connected to one end of the resistor 24. The anodes of these diodes 32 and 34 are currents of the control IC 40. Commonly connected to the detection signal input terminal. The control IC 40 detects the output voltage between the output terminals + Vout and GND, stabilizes the output voltage, and based on one of the current detection signals selected by the signal selection circuit 30, A pulse drive signal having a conduction width that approximates the input current waveform to the input voltage waveform is supplied to the gates that are the control terminals of the switching elements 16 and 18.

  FIG. 2 shows the waveform of each part. In the same figure, the upper stage is the input voltage of the AC power supply E, and hereinafter, the drive signal to the switching element 16 and the drive signal to the switching element 18 are respectively shown.

  As shown in FIG. 2, regardless of the polarity of the AC power supply E, each switching element 16 and 18 is given a pulse drive signal having a conduction width depending on the current detection signal from the signal selection circuit 30 at the same timing. The switching elements 16 and 18 are both switched on or off.

  Here, during a period in which the input voltage from the AC power source E is positive, that is, a period in which a positive voltage is generated at the input terminal Vin1, when the switching elements 16 and 18 are turned on, the AC power source E, the choke coil 10, and the first A current flows through the path of the switching element 16, the resistor 22, the resistor 24, the second switching element 18, and the AC power supply E, energy is accumulated in the choke coil 10, and the output terminal 26 is charged with the charge accumulated in the output capacitor 26. Power is supplied to a load (not shown) connected between + Vout and GND.

  In addition, since a current from the switching element 16 to GND flows through the resistor 22 and a current from GND to the switching element 18 flows through the resistor 24, the diode 32 connected to the resistor 22 is turned off while the resistor 24 is turned off. The diode 34 to be connected is turned on, and only the current detection signal detected by the resistor 24 through the diode 34 is selectively supplied to the control IC 40.

  Thereafter, when the switching elements 16 and 18 are turned off, a current flows through the path of the AC power source E, the choke coil 10, the first diode 12, the output capacitor 26 (and load), the resistor 24, the diode 18A, and the AC power source E. Power is supplied from the power source E to the output capacitor 26 and the load through the choke coil 10. The output voltage of the power factor correction circuit 20 generated between the output terminals + Vout and GND is higher than the input voltage of the AC power supply E because the voltage of the choke coil 10 is superimposed on the voltage of the AC power supply E.

  In addition, since no current flows through the resistor 22 and a current flows from the GND toward the switching element 18 through the resistor 24, the diode 32 is continuously turned off while the diode 34 is turned on and is detected by the resistor 24 through the diode 34. Only the detected current signal is selectively supplied to the control IC 40.

  On the other hand, when the switching elements 16 and 18 are turned on during a period when the input voltage from the AC power source E is negative, that is, when a negative voltage is generated at the input terminal Vin1, the AC power source E and the second switching element are turned on. 18, a resistor 24, a resistor 22, a first switching element 16, a choke coil 10, and an AC power source E, a current in a direction opposite to a period in which a positive voltage is generated in the AC power source E flows, and the choke Energy is stored in the coil 10, and power is supplied to the load by the electric charge stored in the output capacitor 26.

  Further, since a current from GND to the switching element 16 flows through the resistor 22 and a current from the switching element 18 to GND flows through the resistor 24, the diode 32 connected to the resistor 22 is turned on, while the resistor 24 The diode 34 to be connected is turned off, and only the current detection signal detected by the resistor 22 through the diode 32 is selectively supplied to the control IC 40.

  Thereafter, when the switching elements 16 and 18 are turned off, a current flows through the path of the AC power source E, the second diode 14, the output capacitor 26 (and load), the resistor 22, the diode 16A, the choke coil 10, and the AC power source E, thereby choking. Electric power is supplied from the coil 10 to the output capacitor 26 and the load through the AC power source E. Also in this case, the output voltage of the power factor correction circuit 20 generated between the output terminals + Vout and GND is higher than the input voltage of the AC power supply E because the voltage of the choke coil 10 is superimposed on the voltage of the AC power supply E. It will be a thing.

  Further, since no current flows through the resistor 24 and a current flows from the GND toward the switching element 16 through the resistor 22, the diode 32 is continuously turned on, while the diode 34 is turned off and is detected by the resistor 22 through the diode 32. Only the detected current signal is selectively supplied to the control IC 40.

  FIG. 3 shows a characteristic X1 of the voltage generated across the resistors 22 and 24 with respect to the output current in the above series of operations, a characteristic X2 of the voltage of the current detection signal through the diode 32 or the diode 34 with respect to the output current, The characteristic X3 of the output voltage with respect to the output current is shown.

  In this case, since the diodes 32 and 34 have a voltage Vf (forward voltage drop) necessary for flowing a current in the forward direction, even if a current flows through the choke coil 10 and the switching elements 16 and 18, the resistance 22 , 24 until the voltage generated between both ends of the diodes 32, 34 reaches the forward voltage drop Vf of the diodes 32, 34, no current is generated as a current detection signal, and the current undetected state shown in FIG. Therefore, especially at the time of a light load with a small output current, the control IC 40 tries to widen the conduction width of the pulse drive signal supplied to the switching elements 16 and 18, and the output voltage to the load becomes higher than the original. .

  As described above, the signal selection circuit 30 using the diodes 32 and 34 selects the necessary current detection signal from either one of the resistors 22 and 24 to the control IC 40 without directly monitoring the direction of the current flowing through the choke coil 10. However, the current detection signal at the time of light load cannot faithfully reproduce the current flowing through the choke coil 10, the stability of the output voltage is lost, and the power factor and efficiency are reduced. There is a fear.

  A switching power supply device 1 shown in FIG. 4 has been proposed to eliminate such concerns. Here, the same components as those in FIG. 1 are denoted by the same reference numerals. The structural differences from FIG. 1 are as follows.

  Instead of the diodes 32 and 34, an active switch element having linearity in the flowing current and voltage is provided here. The signal selection circuit 50 of FIG. 4 includes, for example, N-channel MOSFETs 52 and 54 as active switch elements. The active switch element may be any element as long as the element has linearity in flowing current and voltage. In the signal selection circuit 50, the drain of the FET 52 is connected to one end of the resistor 22, the drain of the FET 54 is connected to one end of the resistor 24, and the sources of the FETs 52 and 54 are input to the current detection signal of the control IC 40. Commonly connected to terminals.

  Further, in FIG. 4, a drive circuit 60 for turning on or off the FETs 52 and 54 is added. The drive circuit 60 monitors the AC input voltage from the AC power source E, generates a drive signal for determining the on-timing of the switch element 52 by comparing the negative voltage generated at the input terminal Vin1 with the reference voltage, A drive signal that determines the ON timing of the switch element 54 is generated by supplying the gate to the switch element 52 and comparing the positive voltage generated at the input terminal Vin1 with the reference voltage, and the drive signal is supplied to the gate of the switch element 54. Is.

  In addition, the configuration of the switching power supply 1 including the power factor correction circuit 20 and the control IC 40 is the same as that of the switching power supply 100 of FIG.

  Next, the operation of the switching power supply device 1 in this embodiment will be described.

  The operation as the power factor correction circuit 20 is as described in the example of FIG. 1, and the waveforms of the respective parts are the same as those shown in FIG. That is, regardless of the polarity of the AC power supply E, each switching element 16, 18 is given a pulse drive signal having a conduction width depending on the current detection signal from the signal selection circuit 50 from the control IC 40 at the same timing. The switching elements 16 and 18 are both switched on or off.

  Here, during a period in which the input voltage from the AC power source E is positive, that is, a period in which a positive voltage is generated at the input terminal Vin1, when the switching elements 16, 18 are turned on, the AC power source E, choke coil 10, first Current flows through the path of the switching element 16, the resistor 22, the resistor 24, the second switching element 18, and the AC power source E, energy is accumulated in the choke coil 10, and the output is accumulated by the charge accumulated in the output capacitor 26. Power is supplied to a load connected between the terminals + Vout and GND.

  Thereafter, when the switching elements 16 and 18 are turned off, a current flows through the path of the AC power source E, the choke coil 10, the first diode 12, the output capacitor 26 (and load), the resistor 24, the diode 18A, and the AC power source E. Power is supplied from the power source E to the output capacitor 26 and the load through the choke coil 10. The output voltage of the power factor correction circuit 20 generated between the output terminals + Vout and GND is higher than the input voltage of the AC power supply E because the voltage of the choke coil 10 is superimposed on the voltage of the AC power supply E.

  On the other hand, when the switching elements 16 and 18 are turned on during a period when the input voltage from the AC power source E is negative, that is, when a negative voltage is generated at the input terminal Vin1, the AC power source E and the second switching element are turned on. 18, a resistor 24, a resistor 22, a first switching element 16, a choke coil 10, and an AC power source E, a current in a direction opposite to a period in which a positive voltage is generated in the AC power source E flows, and the choke Energy is stored in the coil 10, and power is supplied to the load by the electric charge stored in the output capacitor 26.

  Thereafter, when the switching elements 16 and 18 are turned off, a current flows through the path of the AC power source E, the second diode 14, the output capacitor 26 (and load), the resistor 22, the diode 16A, the choke coil 10, and the AC power source E, thereby choking. Electric power is supplied from the coil 10 to the output capacitor 26 and the load through the AC power source E. Also in this case, the output voltage of the power factor correction circuit 20 generated between the output terminals + Vout and GND is higher than the input voltage of the AC power supply E because the voltage of the choke coil 10 is superimposed on the voltage of the AC power supply E. It will be a thing.

  As an operation of the power factor correction circuit 20, if at least only the switching element 16 is in a switching operation during a period when the input voltage from the AC power source E is positive, another switching element 18 is in an on state or an off state. It may be left as it is. This is because the switching element 18 includes a diode 18A. Similarly, during a period in which the input voltage from the AC power supply E is negative, if at least only the switching element 18 performs a switching operation, the switching element 16 including the diode 16A may remain on or off. Good.

  Next, the operation of the signal selection circuit 50 and the drive circuit 60 will be described. The drive circuit 60 determines the ON / OFF timing of the FETs 52 and 54 using the AC input voltage from the AC power supply E. In the present embodiment, the drive signal for determining the ON timing of the FET 52 is generated based on a comparison between the voltage when the input voltage from the AC power source E becomes negative and the built-in reference voltage, and the ON timing of the FET 54. Is generated based on a comparison between a voltage when the input voltage from the AC power supply E becomes positive and a built-in reference voltage. Thereby, at least while the input voltage from the AC power supply E is negative, the FET 52 is turned on while the FET 54 is turned off. At least while the input voltage from the AC power supply E is positive, the FET 52 is turned off. The FET 54 is turned on.

  When the switching elements 16 and 18 are turned on during a period in which the input voltage from the AC power source E is positive, a current flowing from the switching element 16 to GND flows through the resistor 22, and a current from the GND to the switching element 18 flows through the resistor 24. When the switching elements 16 and 18 are turned off, no current flows through the resistor 22, and a current flows from the GND to the switching element 18 through the resistor 24, and eventually flows in one direction of the choke coil 10. A current is detected as a current flowing in one direction of the resistor 24. Since the FET 54 is on during this period, the signal selection circuit 50 can supply a current detection signal having a voltage proportional to the current flowing in one direction of the resistor 24 to the control IC 40.

  On the other hand, when the switching elements 16 and 18 are turned on while the input voltage from the AC power source E is negative, a current from the GND to the switching element 16 flows through the resistor 22 and the resistor 24 passes through the GND from the switching element 18. When the switching elements 16 and 18 are turned off, no current flows through the resistor 24, and a current flows from the GND toward the switching element 16 through the resistor 22 and eventually flows in the other direction of the choke coil 10. A current is detected as a current flowing in one direction of the resistor 22. During this period, since the FET 52 is on, the signal selection circuit 50 can supply a current detection signal having a voltage proportional to the current flowing in one direction of the resistor 22 to the control IC 40.

  In this way, the current detection signal is selected from one of the FETs 52 and 54 to the control IC 40 with a voltage proportional to the current flowing bidirectionally through the choke coil 10 from a light load with a small output current to a heavy load with a large output current. Therefore, as the power factor improving circuit 20, the stability of the output voltage to the load is maintained, and the power factor and efficiency are improved.

  FIG. 5 shows a voltage characteristic X1 generated across the resistors 22 and 24 with respect to the output current, an output voltage characteristic X3 ′ with respect to the output current, and a current through the FET 52 or FET 54 with respect to the output current in the series of operations described above. A voltage characteristic X4 of the detection signal is shown.

  In the case of this embodiment, the current-voltage characteristics when the FETs 52 and 54 are in the on state depend on the on-resistance of the FETs 52 and 54, so that the current and voltage are independent of the magnitude of the current flowing into the FETs 52 and 54. Linearity is maintained. Therefore, even at a light load with a small output current, a current detection signal having a voltage proportional to the current flowing through the choke coil 10 is supplied to the control IC 40, and pulses supplied to the switching elements 16 and 18 based on the current detection signal. Since the conduction width of the drive signal is determined, the output voltage to the load becomes a proper proper value, the stability of the output voltage to the load is maintained, and the power factor and efficiency can be improved. As is clear from this result, the present invention does not replace the diodes 32 and 34 with the FETs 52 and 54 for the purpose of reducing the loss, but linearity in the current flowing through the current detector (resistors 22 and 24) and the current detection signal. It is an object of the present invention to provide a power factor correction circuit 20 that provides

  As described above, in this embodiment, the choke coil 10 connected in series to the AC power source E, the first switching element 16 and the second switching element 18 that perform the switching operation, the diode 12 that is the first rectifier, and the second switching element. A pulse drive signal to the switching elements 16 and 18, the diode 14 as the rectifier, the resistor 24 as the first current detector for detecting the current flowing through the choke coil 10 and the resistor 22 as the second current detector. A control IC 40 is provided as a controller to supply, and when either of the switching elements 16 and 18 is on, a current is supplied from the AC power source E to the choke coil 10 to store energy in the choke coil 10. , 18 is turned off, the energy stored in the choke coil 10 is transferred to the first diode. The resistors 22 and 24 serving as the first and second current detectors have a function of converting the currents flowing through the resistors 22 and 24 into voltages, respectively. A first selection element that selectively supplies the current detection signal of the resistor 24 to the control IC 40, and a second selection element that selectively supplies the current detection signal of the resistor 22 to the control IC 40. In the switching power supply apparatus in which the control IC 40 generates the pulse drive signal based on the current detection signal from the first selection element or the second selection element, the first selection element is a current flowing through the resistor 24. And the FET 54 as a first active switching element in which the current detection signal has linearity, and the second selection element includes a current flowing through the resistor 22 and the current detection No. is composed of FET52 as the second active switch devices, such as having a linearity.

  In this case, a bidirectional current can flow from the AC power source E to the choke coil 10 in accordance with the switching operation by the switching elements 16 and 18. However, when a one-way current flows through the choke coil 10, the current flows through the resistor 24. When a current detection signal having a voltage proportional to the current in one direction is selectively supplied from the FET 54 to the control IC 40 and a current in the other direction flows through the choke coil 10, the current detection signal is proportional to the current in one direction flowing through the resistor 22. A voltage current detection signal is selectively supplied from the FET 52 to the control IC 40. Therefore, at a light load with a small output current, the current flowing through the choke coil 10 is faithfully reproduced as the voltage of the current detection signal with linearity, and the power factor and efficiency are improved while maintaining the stability of the output voltage. It becomes possible.

  In the present embodiment, a drive circuit 60 is further provided as a drive unit that switches the FETs 52 and 54 on and off according to the polarity of the AC input voltage from the AC power supply E.

  In this way, the FETs 52 and 54 can be appropriately switched on and off according to the polarity of the AC input voltage from the AC power supply E without depending on the switching frequency of the switching elements 16 and 18. .

  In the above circuit example, the switching elements 16 and 18 are turned on and off at the same timing regardless of the polarity of the AC input voltage from the AC power supply E, but the loss due to the current flowing through the diodes 16A and 18A. In order to avoid this increase as much as possible, a driving method of the switching elements 16 and 18 as shown in FIG. 6 may be employed.

  In the figure, a pulse drive signal having a conduction width depending on the current detection signal is given to the switching element 16 during a period in which the input voltage from the AC power source E is positive, whereas the switching element 18 A continuous on drive signal is provided. Therefore, during the OFF period of the switching element 16, a current flows through the switching element 18 instead of the diode 18A, and the loss as the power factor correction circuit 20 is reduced.

  Further, during a period when the input voltage from the AC power supply E is negative, a pulse drive signal having a conduction width depending on the current detection signal is supplied to the switching element 18, whereas the switching element 16 is continuously turned on. A signal is given. Also in this case, during the OFF period of the switching element 18, a current flows through the switching element 16 instead of the diode 16A, and the loss as the power factor correction circuit 20 is also reduced.

  The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, in the present embodiment, the choke coil 10 is connected only to one end of the AC power source E, but the present invention is also applicable to a bridgeless power factor correction circuit in which the choke coil 10 is connected to one end and / or the other end of the AC power source E. Is possible. Further, the diode 12 as the first rectifier and the diode 14 as the second rectifier may be replaced with an FET or the like with less loss.

10 choke coil 12 diode (first rectifier)
14 Diode (second rectifier)
16 First switching element 18 Second switching element 22 Resistance (second current detector)
24 Resistance (first current detector)
40 Control IC (control unit)
52 FET (second selection element, second active switching element)
54 FET (first selection element, first active switch element)
60 Drive circuit (drive unit)

Claims (2)

A choke coil connected in series to an AC power source, a first switching element and a second switching element that perform switching operation, a first rectifier and a second rectifier, and a first current that detects a current flowing through the choke coil A detector and a second current detector; and a controller that supplies a pulse drive signal to the first switching element and the second switching element,
When either the first switching element or the second switching element is on, a current is passed from the AC power source to the choke coil, and energy is stored in the choke coil,
When either the first switching element or the second switching element is off, the energy stored in the choke coil is released through the first rectifier or the second rectifier, and
The first and second current detectors have a function of converting a current flowing therethrough into a voltage,
A first selection element that selectively supplies a current detection signal of the first current detector to the control unit; and a first selection element that selectively supplies a current detection signal of the second current detector to the control unit. 2 selection elements,
In the switching power supply in which the control unit generates the pulse drive signal based on a current detection signal from the first selection element or the second selection element.
The first selection element is composed of a first active switch element in which the current flowing through the first current detector and the current detection signal have linearity,
The switching power supply device, wherein the second selection element includes a current flowing through the second current detector and a second active switch element in which the current detection signal has linearity.   The drive unit for switching on and off of the first active switch element and the second active switch element according to the polarity of an AC input voltage from the AC power supply is further provided. Switching power supply.

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