Rectification circuit, and semiconductor device and power source device using the same

Abstract

To provide a rectification circuit in which the number of semiconductor switching elements to be turned ON among a plurality of synchronization rectification semiconductor switching elements connected in parallel can be determined without use of a current detection unit.SOLUTION: A rectification circuit causes a current to flow in one direction between an anode (A) and a cathode (K) by synchronous rectification, and includes a plurality of semiconductor switching elements (Q1 to Q3) that are connected in parallel with each other between the anode and the cathode, a plurality of drive circuits (GD1 to GD3) that drive the plurality of semiconductor switching elements, and a control unit (COM) that creates control command signals to the respective drive circuits on the basis of the voltage across the main terminals of the plurality of semiconductor switching elements. The control unit determines the number of semiconductor switching elements to be turned ON among the plurality of semiconductor switching elements and creates ON control command signals to the determined number of the drive circuits on the basis of the voltage across the main terminals during the synchronous rectification time period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rectifier circuit, and a semiconductor device and a power supply device that use the rectifier circuit. [Background technology]

[0002] Rectifier circuits used in power supplies to convert AC to DC include diode rectifier circuits and synchronous rectifier circuits using MOSFETs. Synchronous rectifier circuits have low power loss because MOSFETs do not have a built-in potential like diodes and forward current rises from 0V. Therefore, synchronous rectifier circuits are used in power supplies that require low loss, such as front-end power supplies.

[0003] As conventional techniques relating to synchronous rectification circuits, the techniques described in Patent Documents 1 and 2 are known.

[0004] In the technology described in Patent Document 1, a control circuit and a MOSFET are mounted in one package as a low-loss rectifier circuit used in an alternator. This rectifier circuit operates as a two-terminal semiconductor device that has the function of passing current in one direction (rectification function) like a diode.

[0005] The rectifier circuit according to the technology described in Patent Document 1 is composed of a control circuit having a comparator and a gate driver, a capacitor that supplies power to the control circuit, and a MOSFET. The control circuit turns the MOSFET on and off using the gate driver according to the drain-source voltage of the MOSFET detected by the comparator. The capacitor is charged by the drain-source voltage of the MOSFET when the MOSFET is off.

[0006] In the technology described in Patent Document 2, multiple synchronous rectification MOSFETs are connected in parallel. The number of MOSFETs that are turned on among these multiple MOSFETs is set according to the magnitude of the load current, i.e., the rectified current, so as to reduce the total power loss. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-116053 A [Patent Document 2] JP 2010-213366 A Summary of the Invention [Problem to be solved by the invention]

[0008] When the control technology described in Patent Document 2 is applied to the rectifier circuit described in Patent Document 1, it is necessary to newly add a current detection unit for detecting the rectified current, i.e., a current detection shunt resistor and a current detection transformer, etc., which hinders the miniaturization and cost reduction of the rectifier circuit. The present invention provides a rectifier circuit that makes it possible to set the number of semiconductor switching elements that are turned on without adding a current detection section, and a semiconductor device and a power supply device that use the rectifier circuit. [Means for solving the problem]

[0009] In order to solve the above problems, a rectifier circuit according to the present invention causes current to flow in one direction between an anode and a cathode by synchronous rectification, and includes a plurality of semiconductor switching elements connected in parallel between the anode and the cathode, a plurality of drive circuits for driving the plurality of semiconductor switching elements, and a control unit that creates a control command signal to each of the plurality of drive circuits based on the main terminal voltage of the plurality of semiconductor switching elements, and the control unit sets the number of the plurality of semiconductor switching elements to be turned on based on the main terminal voltage during the synchronous rectification period, and generates an on control command signal to the set number of drive circuits.

[0010] In order to achieve the above object, a semiconductor device according to the present invention includes a rectifier circuit and a semiconductor package incorporating the rectifier circuit, the rectifier circuit being the rectifier circuit according to the present invention.

[0011] In order to solve the above problems, a semiconductor device according to the present invention comprises a bridge rectifier circuit composed of a plurality of rectifier circuits, and a semiconductor package incorporating the bridge rectifier circuit, each of the plurality of rectifier circuits being the rectifier circuit according to the present invention.

[0012] In order to achieve the above object, a power supply device according to the present invention has a rectifier circuit section, and the rectifier circuit section is the rectifier circuit according to the present invention. Effect of the Invention

[0013] According to the present invention, the number of semiconductor switching elements to be turned on can be set without adding a current detection section.

[0014] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0015] [Figure 1] 1 is a circuit diagram showing a configuration of a rectifier circuit according to a first embodiment of the present invention. [Diagram 2] 4 is a circuit diagram illustrating a configuration of a comparison unit in the first embodiment. FIG. [Diagram 3] 3 is a schematic circuit diagram showing a configuration example of the holding circuits H1 and H2 (FIG. 2). FIG. [Figure 4] 4 is a current-voltage waveform diagram showing an example of the operation of the rectifier circuit of the first embodiment. FIG. [Diagram 5] FIG. 11 is a circuit diagram showing a configuration of a rectifier circuit according to a second embodiment of the present invention. [Figure 6] 5 is a current-voltage waveform diagram similar to FIG. 4, illustrating an example of the operation of the rectifier circuit of the second embodiment. [Figure 7] FIG. 11 is a circuit diagram showing a configuration of a semiconductor device according to a third embodiment. [Figure 8] FIG. 11 is a circuit diagram showing the configuration of a power supply device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments of the present invention will be described with reference to the following Examples 1 to 3 with reference to the drawings.

[0017] In the various figures, the same reference numbers indicate the same components or components with similar functions. EXAMPLES

[0018] FIG. 1 is a circuit diagram showing the configuration of a rectifier circuit according to a first embodiment of the present invention.

[0019] The symbols for current and voltage in the diagram (the arrows indicate the direction), Is, Vdsi (i=1, 2, 3: the same below), Vgsi, and Vc respectively represent the rectified current, the voltage between the main terminals of MOSFET Qi, i.e., the drain-source voltage, the gate-source voltage of Qi, and the charging voltage of capacitor C0. These symbols will be used appropriately in the following explanation.

[0020] In the rectifier circuit of the first embodiment, a plurality of MOSFETs Q1 to Q3 (three in FIG. 1) are connected in parallel between an anode (A) and a cathode (K) as semiconductor switching elements for synchronous rectification. The drains and sources of Q1 to Q3 are connected to the cathode (K) and the anode (A), respectively. Q1 to Q3 are driven on and off by drive circuits GD1 to GD3, respectively. Q1 to Q3 are driven on during the rectification period (rectification current Is≧0), that is, when the AC voltage applied between the anode (A) and the cathode (K) is in the forward direction.

[0021] In the first embodiment, enhancement type n-channel MOSFETs are used as Q1 to Q3.

[0022] Diodes D1 to D3 are connected in anti-parallel to the MOSFETs Q1 to Q3, respectively. In the first embodiment, D1 to D3 are body diodes built into each MOSFET. Note that D1 to D3 may be individual external diodes.

[0023] The comparison unit COM is a control unit that generates ON / OFF control command signals to GD1 to GD3.

[0024] As described later, the comparator COM sets the number of MOSFETs Q1-Q3 to be turned on based on the anode (A)-cathode (K) voltage, i.e., the drain-source voltage Vds of the MOSFETs connected in parallel, and generates an on / off control command signal to GD1-GD3 according to the set number. GD1-GD3 turn Q1-Q3 on and off, respectively, according to the on / off control command signal from COM.

[0025] Capacitor C0 serves as the power source for GD1 to GD3 and COM. One end of C0 is connected to the anode (A). The other end of C0 is connected to the cathode (K) via a reverse current prevention diode DR1. As a result, during the non-rectification period (rectification current Is=0), that is, when the AC voltage applied between the anode (A) and the cathode (K) is in the reverse direction, C0 is charged by the voltage applied between the anode (A) and the cathode (K). The charged C0 serves as the power source for GD1 to GD3 and COM. In other words, the rectifier circuit of the first embodiment supplies its own power source for its own circuit.

[0026] Here, the operation of the comparison unit COM will be further explained.

[0027] The comparator circuit COM outputs a rectified current I S During the rectification period during which V flows, an on-control command signal is generated based on Vds to turn on n (=1 to 3) MOSFETs so that the total power loss P of Q1, Q2, and Q3 can be reduced.

[0028] If the drain-source voltage of the parallel-connected MOSFETs is Vds, the total power loss P of the n on-MOSFETs is roughly expressed by equation (1). P = n P d +a (n Vds 2 ) / RON … (1) P d is the driving loss per MOSFET, R ON is the on-resistance per MOSFET, and a is a coefficient based on the voltage waveform.

[0029] As shown in equation (1), when Vds is small, P d becomes dominant, so reducing the number of MOSFETs that are turned on reduces P. When Vds becomes large, the second term of equation (1) becomes dominant, so increasing the number of MOSFETs that are turned on reduces P. Therefore, in the first embodiment, the magnitude of Vds is determined during the synchronous rectification period, and a number n (=1 to 3) of MOSFETs that can reduce P are turned on according to the determined Vds. This makes it possible to reduce power loss in the rectifier circuit.

[0030] In the first embodiment, when n=1, the comparison unit COM generates an ON control command to GD1 to turn on Q1. When n=2, the comparison unit COM generates an ON control command to GD1 and GD2 to turn on Q1 and Q2. When n=3, the comparison unit COM generates an ON control command to GD1, GD2, and GD3 to turn on Q1, Q2, and Q3.

[0031] In addition, in order to turn off MOSFETs other than the MOSFET to be turned on, the comparison unit COM generates an off control command signal to the drive circuit of the MOSFET to be turned off.

[0032] The comparison unit COM determines whether to set n to 2 based on Vds during the rectification period when n=1, i.e., when Q1 is on and Q2 and Q3 are off, and generates an ON control command signal to GD2 if it determines that n=2. Also, the comparison unit COM determines whether to set n to 1 based on Vds during the rectification period when n=2, i.e., when Q1 and Q2 are on and Q3 is off, and generates an OFF control command signal to GD2 if it determines that n=1.

[0033] The comparison unit COM determines whether P can be reduced more with n=3 than with n=2 based on Vds during the rectification period when n=2, i.e., when Q1, Q2, and Q3 are on, and generates an ON control command signal to GD3 if it determines that P can be reduced. Also, the comparison unit COM determines whether P can be reduced more with n=2 than with n=3 based on Vds during the rectification period when n=3, i.e., when Q1, Q2, and Q3 are on, and generates an OFF control command signal to GD3 if it determines that P can be reduced.

[0034] In this way, the comparison unit COM switches the number n of MOSFETs to be turned on between 1 and 2, and also between 2 and 3, based on Vds during the rectification period so as to reduce the total power loss P. Note that the comparison unit COM determines whether to switch the number n of MOSFETs to be turned on by comparing Vds during the rectification period with a preset threshold voltage.

[0035] FIG. 2 is a circuit diagram showing a configuration of the comparison unit COM in the first embodiment (FIG. 1).

[0036] Note that the forward direction of the voltages in the MOSFETs Q1 to Q3 is defined as the positive direction. Therefore, Vds≦0 during the rectification period.

[0037] The comparison unit COM includes comparison circuits CO1 to CO5, decision circuits JC1 and JC2, and holding circuits H1 and H2. Each circuit is powered by a charged capacitor C0 (FIG. 1).

[0038] The comparison circuits CO1 to CO5 receive the anode (A)-cathode (K) voltage, i.e., Vds. In the comparison circuits CO1, CO2, CO3, CO4, and CO5, the threshold voltages (<0) to be compared with Vds are set by the reference voltage sources Vtha, Vthb, Vthc, Vthd, and Vthe, respectively. The comparison circuits CO1 to CO5 compare the magnitude relationship between Vds and the threshold voltage, and output either a high-level (H) voltage signal (hereinafter referred to as "voltage signal H") or a low-level (L) voltage signal (hereinafter referred to as "voltage signal L") according to the comparison result. In the first embodiment, the voltage value of the voltage signal H is the power supply voltage value of the capacitor C0 (FIG. 1), and the voltage value of the voltage signal L is zero volts.

[0039] Each reference voltage source is generated by a capacitor CO (FIG. 1) and a voltage dividing resistor or a Zener diode.

[0040] In the following description, unless otherwise specified, Vds indicates the drain-source voltage during the rectification period, and Vds ≦ 0. Therefore, the value of the threshold voltage (Vth1 described later) compared with Vds is also a negative value.

[0041] CO1 to CO3 compare the voltage between AK, i.e., Vds, with a threshold voltage Vth1, and if it is determined that Vds is equal to or less than Vth1 (Vds≦Vth1, |Vds|≧|Vth1|), it outputs a voltage signal H. CO1 to CO3 also compare Vds with a threshold voltage Vth2, and if it is determined that Vds is equal to or more than Vth2 (Vds≧Vth2, |Vds|≦|Vth2|), it outputs a voltage signal L (zero volts). That is, the reference voltage sources Vtha, Vthb, and Vthc correspond to the two threshold voltages Vth1 and Vth2, respectively.

[0042] As a result, CO1 to CO3 output a voltage signal H within the rectification period, and output a voltage signal L outside the rectification period. That is, CO1 to CO3 determine whether or not the current time is within the rectification period.

[0043] In CO1 to CO3, Vth1 is the threshold voltage when MOSFETs Q1 to Q3 are off, and Vth2 is the threshold voltage when MOSFETs Q1 to Q3 are on. That is, in CO1 to CO3, the threshold voltage has hysteresis. For example, CO1 to CO3 are composed of a hysteresis comparator.

[0044] The threshold voltages Vth1 and Vth2 may be the same value, or two different values satisfying Vth1 < Vth2. In the latter case, chattering in which the turn-on and turn-off of Q1 are repeated in a short cycle can be suppressed.

[0045] CO1 outputs the voltage signal H and the voltage signal L to the drive circuit GD1 as an on control command signal and an off control command signal, respectively. Thereby, Q1 is turned on at the start of the rectification period, maintained in the on state during the rectification period, and turned off at the end of the rectification period. That is, Q1 is turned on in each rectification period. Therefore, in the first embodiment, the number n of MOSFETs turned on during the rectification period is at least 1.

[0046] CO4 determines the switching from 1 to 2 and the switching from 2 to 1 of the number n of MOSFETs turned on using the threshold voltages Vthd1 and Vthd2 for switching determination, respectively.

[0047] When only Q1 of Q1 to Q3 is on, CO4 compares the voltage between A and K, that is, Vds, with the threshold voltage Vthd1. When it is determined that Vds is less than or equal to Vthd1 (Vds ≦ Vthd1, |Vds| ≧ |Vthd1|), CO4 outputs the voltage signal H. Thereby, CO4 determines the switching of n from 1 to 2. Based on this voltage signal H, by turning on Q2, n switches from 1 to 2.

[0048] When it is determined that Vds is greater than Vthd1 (Vds > Vthd1, |Vds| < |Vthd1|), CO4 outputs the voltage signal L.

[0049] Furthermore, when Q1 and Q2 of Q1 to Q3 are on and Q3 is off, CO4 compares the voltage between AK, i.e., Vds, with the threshold voltage Vthd2, and if it determines that Vds is equal to or greater than Vthd2 (Vds≧Vthd2, |Vds|≦|Vthd2|), it outputs a voltage signal L. This causes CO4 to determine whether n should be switched from 2 to 1. Based on this voltage signal L, Q2 is turned off, thereby switching n from 2 to 1.

[0050] CO4 has a Vds smaller than Vthd2 (Vds<Vthd2,|Vds|> If it is determined that the voltage Vthd2 is |Vthd2|, it outputs a voltage signal H.

[0051] CO5 judges whether the number n of MOSFETs to be turned on is switched from 2 to 3 and from 3 to 2 using threshold voltages Vthe1 and Vthe2 for judgment of switching, respectively.

[0052] When Q1 and Q2 out of Q1 to Q3 are on and Q3 is off, CO5 compares the voltage between AK, i.e., Vds, with the threshold voltage Vthe1, and if it determines that Vds is equal to or less than Vthe1 (Vds≦Vthe1, |Vds|≧|Vthe1|), it outputs a voltage signal H. This causes CO5 to determine whether n should be switched from 2 to 3. Based on this voltage signal H, Q3 is turned on, thereby switching n from 2 to 3.

[0053] CO5 outputs a voltage signal L when it determines that Vds is greater than Vthe1 (Vds>Vthe1, |Vds|<|Vthe1|).

[0054] Furthermore, when Q1 to Q3 are on, CO5 compares the voltage between AK, i.e., Vds, with the threshold voltage Vthe2, and if it determines that Vds is equal to or greater than Vthe2 (Vds≧Vthe2, |Vds|≦|Vthe2|), it outputs a voltage signal L. This causes CO5 to determine whether n should be switched from 3 to 2. Based on this voltage signal L, Q3 is turned off, thereby switching n from 3 to 2.

[0055] CO5 has a Vds smaller than Vthe2 (Vds<Vthe2,|Vds|> If it is determined that the voltage Vth2 is |Vthe2|, it outputs a voltage signal H.

[0056] Outside the rectification period, Vds≧0, so Vds is greater than each of the threshold voltages (Vthd1, Vthd2, Vthe1, Vthe2<0) described above, and both CO4 and CO5 output a voltage signal L. This causes Q2 and Q3 to be in the OFF state. Therefore, outside the rectification period, all MOSFETs Q1 to Q3 are OFF.

[0057] It should be noted that CO4 and CO5 are, for example, configured from hysteresis comparators, similar to CO1 to CO3.

[0058] In the first embodiment, the above-mentioned judgment results output by CO4 and CO5 are reflected in the rectification period following the rectification period in which CO4 outputs this voltage signal. That is, when CO4 and CO5 judge to switch the number of MOSFETs to be turned on, the number is switched in the rectification period following the judged rectification period. For this reason, the comparator COM includes holding circuits H1 and H2.

[0059] The holding circuit H1 holds the judgment result of CO4 as described above, i.e., the voltage signal H or voltage signal L output by CO4. The holding circuit H1 outputs the held voltage signal to the judgment circuit JC1 in the rectification period following the rectification period in which CO4 output this voltage signal.

[0060] The holding circuit H2 holds the judgment result of CO5 as described above, i.e., the voltage signal H or voltage signal L output by CO5. The holding circuit H2 outputs the held voltage signal to the judgment circuit JC2 in the rectification period following the rectification period in which CO5 output this voltage signal.

[0061] When the judgment circuit JC1 receives the voltage signal H from the holding circuit H1 and also receives the voltage signal H from CO2, which judges that the current time is within the rectification period, it outputs a voltage signal H. The output voltage signal H is input to the drive circuit GD2 as an ON control command signal. GD2 turns on Q2 in response to the input ON control command signal.

[0062] When the determination circuit JC1 receives a voltage signal L from at least one of the holding circuits H1 and CO2, it outputs a voltage signal L. The output voltage signal L is input to the drive circuit GD2 as an OFF control command signal. The drive circuit GD2 turns off Q2 in response to the input ON control command signal.

[0063] When the judgment circuit JC2 receives the voltage signal H from the holding circuit H2 and also receives the voltage signal H from CO3, which judges that the current time is within the rectification period, it outputs a voltage signal H. The output voltage signal H is input to the drive circuit GD3 as an ON control command signal. GD3 turns on Q3 in response to the input ON control command signal.

[0064] When the judgment circuit JC2 receives a voltage signal L from at least one of the holding circuits H2 and CO3, it outputs a voltage signal L. The output voltage signal L is input to the drive circuit GD3 as an OFF control command signal. The drive circuit GD3 turns off Q3 in response to the input ON control command signal.

[0065] The decision circuits JC1 and JC2 are, for example, configured from logical product (AND) gate circuits.

[0066] The decision circuits JC1 and JC2 can reliably generate on / off control command signals in accordance with the decision results of CO4 and CO5 during synchronous rectification in the rectification period, and therefore n can be reliably set based on Vds.

[0067] Incidentally, instead of CO2 and CO3, it may be possible to determine whether or not it is the synchronous rectification period by detecting whether or not an on-gate current flows through the gate of Q1, and input the determination result to JC1 and JC2.

[0068] FIG. 3 is a schematic circuit diagram showing a configuration example of the holding circuits H1 and H2 (FIG. 2).

[0069] The holding circuit in the first embodiment holds the determination result of the comparison circuit by charging and discharging a capacitor.

[0070] The holding circuits (H1, H2) include a capacitor C1 that holds the voltage signal output by the comparison circuits (CO4, CO5), and a switch SW1 that is turned on when the voltage signal held in the capacitor C1 is output to the decision circuits (JC1, JC2).

[0071] One end of the capacitor C1 is connected to the output of the comparison circuit (CO4, CO5) via a reverse current prevention diode DI. The anode and cathode of the reverse current prevention diode DI are connected to the output of the comparison circuit (CO4, CO5) and one end of the capacitor C1, respectively. The other end of the capacitor C1 is connected to the anode (K) of the rectifier circuit (Figure 1). One end of the capacitor C1 is connected to the input of the judgment circuit (JC1, JC2) via a switch SW1.

[0072] In the first embodiment, the switch SW1 is composed of a semiconductor switching element, for example, a MOSFET. The switch SW1 is driven to turn on and off by a drive signal S1 from a drive circuit D. The drive circuit D generates the drive signal S1 in response to a command signal S. The drive circuit D uses a charged capacitor C0 (FIG. 1) as a power source.

[0073] When the drive circuit D receives the voltage signal H output by the comparison circuit (CO4, CO5) as the command signal S, it generates an OFF drive signal as S1 to turn off SW1. At this time, the voltage signal H is held in the capacitor C1. Also, the voltage signal H is not input to the judgment circuits (JC1, JC2).

[0074] When the drive circuit D receives as a command signal S a voltage signal L output by any of CO1-CO3 outputting a voltage signal H, it generates an ON drive signal as S1 to turn on SW1. As a result, the voltage signal H held in the capacitor C1 is input to the determination circuits (JC1, JC2) in the rectification period following the rectification period in which the voltage signal H was held in the capacitor C1.

[0075] FIG. 4 is a current-voltage waveform diagram showing an example of the operation of the rectifier circuit of the first embodiment.

[0076] In the operation example of FIG. 4, the number n of MOSFETs that are turned on is switched from three to two.

[0077] A sinusoidal AC voltage is input to a series-connected circuit consisting of a rectifier circuit (Figure 1) and a resistive load.

[0078] The waveforms in Figure 4, from the top to the bottom, show the rectified current Is, the anode (A)-cathode (K) voltage of the rectifier circuit, i.e., the drain-source voltage Vds of the parallel-connected MOSFETs Q1-Q3 (the forward direction of Q1-Q2 is considered positive), the voltage Vc of the capacitor C0, and the gate-source voltages Vgs1-Vgs3 of Q1-Q3. Vgsth1-Vgsth3 are the gate threshold voltages of Q1-Q3, respectively.

[0079] Vdsp indicates the peak value of the AC voltage. Since C0 is charged by a half-sine wave voltage during the non-rectification period, the maximum value of Vc is Vdsp. Note that Vc gradually decreases as it is discharged, but as shown in FIG. 4, a voltage value greater than Vgsth1 to Vgsth3 is ensured while the rectifier circuit is in operation.

[0080] In the operation example shown in Fig. 4, during the period from the time when the rectified current Is completes commutation from the diodes D1 to D3 to the on-resistance paths of the MOSFETs Q1 to Q3, that is, the time t2a when the diode rectification transitions to synchronous rectification, to the time t3 when Is becomes 0, Vds resulting from the on-resistance (Ron) of Q1 to Q3 and the rectified current Is is compared with the above-mentioned threshold voltage Vthe2. As described above, Vthe2 is a voltage threshold for determining the switching from n=3 to n=2. As shown in Fig. 4, since Vds≧Vthe2 during the synchronous rectification period (t2a to t3), switching to n=2 is performed during the next rectification period (t4 to t5).

[0081] As described above, according to the first embodiment, n is set based on Vds, so that n can be set so as to reduce the total power loss P without providing a current detection unit.

[0082] In the first embodiment, the determination result by the comparison circuit is reflected in the setting of n in the rectification period following the determined rectification period, but this is not limited thereto, and n may be switched in the determined rectification period. In this case, the holding circuits H1 and H2 (FIG. 2) can be omitted. EXAMPLES

[0083] Second embodiment of the present invention will be described below, focusing mainly on the differences from the first embodiment.

[0084] Second Embodiment FIG. 5 is a circuit diagram showing the configuration of a rectifier circuit according to a second embodiment of the present invention.

[0085] In the second embodiment, the anode of the reverse current prevention diode DR1 is connected to the cathode (K) of the rectifier circuit via a semiconductor switch, MOSFET QR1. The source and drain of QR1 are connected to the anode of DR1 and the cathode (K) of the rectifier circuit, respectively.

[0086] FIG. 6 is a current-voltage waveform diagram similar to FIG. 4, showing an example of the operation of the rectifier circuit of the second embodiment.

[0087] The capacitor CO is charged to the target voltage Vcref. At this time, the current flowing from the cathode K of the rectifier circuit to the capacitor C0 is limited by controlling the on and off of QR1 so that the voltage Vc of C0 does not exceed Vcref.

[0088] According to the second embodiment, the rated voltages of the comparison unit COM, the drive circuits GD1 to GD3, and the capacitor C0 can be made lower than the rated voltage of the rectifier circuit. This makes it easier to increase the voltage of the rectifier circuit since the rated voltage of the rectifier circuit is no longer limited by the rated voltages of the comparison unit COM, the drive circuits GD1 to GD3, and the capacitor C0. EXAMPLES

[0089] Third Embodiment FIG. 7 is a circuit diagram showing a configuration of a semiconductor device according to a third embodiment of the present invention.

[0090] 7, in the third embodiment, four rectifier circuits 1 are built into a semiconductor package 2 as a semiconductor circuit. The rectifier circuit of the second embodiment (FIG. 5) is applied as the rectifier circuit 1. The four rectifier circuits 1 configure a single-phase bridge rectifier circuit.

[0091] In the semiconductor package 2, each rectifier circuit 1 is resin-sealed using molded resin or a resin case, and a pair of AC terminals T2, T3 and a pair of DC terminals T1, T4 of the single-phase bridge rectifier circuit are exposed on the outer surface of the resin that seals the four rectifier circuits 1.

[0092] According to the third embodiment, the synchronous rectifier circuit can be easily applied to a single-phase bridge rectifier circuit as a substitute for a rectifier diode, thereby reducing loss in the single-phase bridge rectifier circuit and in an electric / electronic device including the single-phase bridge rectifier circuit.

[0093] The semiconductor device of the third embodiment can be compatible with a packaged diode bridge by matching the arrangement of the AC terminals T2, T3 and the DC terminals T1, T4 in the semiconductor package 2 with that of the packaged diode bridge. In addition, the semiconductor device of the third embodiment operates as a four-terminal rectifier element similar to a single-phase diode bridge, even though it uses synchronous rectification. This makes it possible to reduce the number of steps in designing and mounting an electric / electronic device having a full-wave rectifier circuit.

[0094] The rectifier circuit of Example 1 may be applied as the rectifier circuit 1. A three-phase bridge rectifier circuit can be configured by using six rectifier circuits of any one of Examples 1 and 2. In this case, three AC terminals for three phases and a pair of DC terminals are exposed on the outer surface of the resin that seals the six rectifier circuits. EXAMPLES

[0095] FIG. 8 is a circuit diagram showing the configuration of a power supply device according to a fourth embodiment of the present invention.

[0096] The power supply device in FIG. 8 converts AC power from a commercial AC power source into DC power of a desired voltage and outputs it.

[0097] 8, among the rectifier elements indicated by the circuit symbol of a diode, the rectifier circuit of any one of the first and second embodiments or the semiconductor device of the third embodiment is applied to at least one of the rectifier elements CRD1 to CRD4 constituting a bridge rectifier circuit that rectifies the AC voltage of a commercial AC voltage, the rectifier element FWD for freewheeling in the chopper circuit section, the rectifier elements SSD1 and SSD2 constituting a rectifier circuit section that receives the AC output power of the inverter circuit section via a transformer and converts it into a DC voltage of a desired voltage, and the rectifier element BPD for preventing reverse current. Note that the single-phase bridge rectifier circuit of the third embodiment may be used for the rectifier elements CRD1 to CRD4.

[0098] In addition, in Fig. 8, the rectifying element connected in parallel to the MOSFET is a parasitic diode (body diode) of the MOSFET. In addition, if all the rectifying elements in Fig. 8 are diodes, the circuit configuration of the power supply device in Fig. 8 is a known circuit configuration.

[0099] According to the fourth embodiment, it is possible to reduce the power loss of the power supply device. The power supply device according to the fourth embodiment is suitable for a front-end power supply that requires high efficiency.

[0100] The rectifier circuits of the first and second embodiments and the semiconductor device of the third embodiment can be applied not only to front-end power supplies but also to various power supply devices having a rectifier circuit unit.

[0101] The present invention is not limited to the above-mentioned embodiment, and various modifications are included. For example, the above-mentioned embodiment has been described in detail to aid in understanding the present invention, and is not necessarily limited to those including all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to delete a part of the configuration of each embodiment, add another configuration, or replace it with another configuration.

[0102] For example, the MOSFET is not limited to an n-channel type, but may be a p-channel type. The MOSFET is not limited to an enhancement type, but may be a depletion type. Other unipolar semiconductor switching elements (junction FET, static induction transistor, etc.) may be applied instead of the MOSFET. The semiconductor material constituting the semiconductor switching element is not limited to silicon (Si), but may be a wide band gap semiconductor such as silicon carbide (SiC).

[0103] Moreover, the comparison unit COM may be configured by software using a control device such as a microcomputer. [Explanation of symbols]

[0104] 1: Rectifier circuit 2: Semiconductor packages T1,T4: DC terminal T2,T3: AC terminal

Claims

1. In a rectifier circuit in which current flows in one direction between the anode and cathode by synchronous rectification, a plurality of semiconductor switching elements connected in parallel to each other between the anode and the cathode; a plurality of drive circuits for driving the plurality of semiconductor switching elements; a control unit that generates a control command signal for each of the plurality of drive circuits based on a voltage between main terminals of the plurality of semiconductor switching elements; Equipped with The control unit sets the number of the plurality of semiconductor switching elements to be turned on based on the voltage between the main terminals during a synchronous rectification period, and generates the control command signal to the drive circuit based on the set number.

2. 2. The rectifier circuit according to claim 1, The control unit holds the control command signal and outputs it to the drive circuit during a next synchronous rectification period.

3. 2. The rectifier circuit according to claim 1, The control unit compares the voltage between the main terminals with a predetermined threshold voltage, and sets the number based on a comparison result.

4. 4. The rectifier circuit according to claim 3, The rectifier circuit according to claim 1, wherein the threshold voltage is preset based on a total power loss of the plurality of semiconductor switching elements.

5. 2. The rectifier circuit according to claim 1, The rectifier circuit according to claim 1, wherein the control unit determines whether to increase the number by one or decrease the number by one.

6. 6. The rectifier circuit according to claim 5, The control unit compares the voltage between the main terminals with a predetermined first threshold voltage and a predetermined second threshold voltage, and determines whether to increase or decrease the number by one based on a comparison result.

7. 2. The rectifier circuit according to claim 1, The rectifier circuit according to claim 1, wherein the control unit determines the synchronous rectification period based on the voltage between the main terminals.

8. 2. The rectifier circuit according to claim 1, The control unit determines the synchronous rectification period based on a drive current flowing from the drive circuit to the semiconductor switching element.

9. 2. The rectifier circuit according to claim 1, a capacitor connected between the anode and the cathode; A rectifier circuit, characterized in that the plurality of drive circuits and the control unit use the capacitor as a power source.

10. 10. The rectifier circuit according to claim 9, A rectifier circuit, characterized in that one end of the capacitor is connected to the cathode via a reverse current prevention diode.

11. 10. The rectifier circuit according to claim 9, A rectifier circuit, characterized in that one end of the capacitor is connected to the cathode via a series circuit of a reverse current prevention diode and a semiconductor switch.

12. A rectifier circuit; a semiconductor package incorporating the rectifier circuit; In a semiconductor device comprising:

2. A semiconductor device, wherein the rectifier circuit is the rectifier circuit according to claim 1.

13. a bridge rectifier circuit including a plurality of rectifier circuits; a semiconductor package incorporating the bridge rectifier circuit; In a semiconductor device comprising:

2. A semiconductor device, wherein each of said plurality of rectifier circuits is the rectifier circuit according to claim 1.

14. In a power supply device having a rectifier circuit, A power supply device, wherein the rectifier circuit section comprises the rectifier circuit according to claim 1.

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