Rectifier circuit and control method of rectifier circuit

Abstract

To perform control so as to reduce total power loss.SOLUTION: A rectifier circuit with an anode A and a cathode K has a first switching element Q1 in which a first terminal is connected to a cathode and a second terminal is connected to an anode, a first diode D1 in which a cathode is connected to the cathode and an anode is connected to the anode, a first capacitor C1 in which a third terminal is connected to the anode, a backflow preventing diode Dr in which a cathode is connected to a fourth terminal of the first capacitor, a second switching element Q2 in which a fifth terminal is connected to the cathode of the rectifier circuit and a sixth terminal is connected to an anode of the backflow preventing diode, a first comparison circuit Co1 controlling the first switching element based on voltage between the anode and the cathode of the rectifier circuit, and a second comparison circuit Co2 controlling the second switching element so as to control voltage between terminals of the first capacitor to be target voltage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a configuration of a rectifier circuit and a control method thereof, and particularly relates to a technique effective when applied to a semiconductor device mounted on a power supply device, an electric vehicle charger, etc. that require low loss.

Background Art

[0002] As a rectifier circuit used in a power supply device for converting alternating current to direct current, a diode rectifier circuit or a synchronous rectifier circuit using MOSFETs is used. In a synchronous rectifier circuit, since the MOSFET does not have a built-in potential like a diode and the forward current rises from 0V, the power loss is low. Therefore, in a power supply device that requires low loss such as a front-end power supply, a synchronous rectifier circuit is used.

[0003] As prior arts related to synchronous rectifier circuits, for example, techniques such as Patent Document 1 and Patent Document 2 are known. Patent Document 1 and Patent Document 2 show rectifier circuits that realize synchronous rectification.

[0004] In the technique described in Patent Document 1, as a low-loss rectifier circuit used in an alternator, a control circuit and a MOSFET are mounted in one package. This rectifier circuit operates as a two-terminal semiconductor device having a function (rectification function) of flowing current in one direction, like a diode. Also, the power for operating the circuit that drives the MOSFET is generated inside the package, and it may be called a self-powered synchronous rectifier circuit.

[0005] The rectifier circuit of 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 by 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, a plurality of MOSFETs for synchronous rectification are connected in parallel. Among these plurality of MOSFETs, the number of MOSFETs that are turned on is set according to the load current, that is, the magnitude of the rectified current, so that the total power loss is reduced.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] As described above, in a power supply device that requires low loss, such as a front-end power supply, a synchronous rectification circuit is used to reduce the loss generated in the diode.

[0009] In addition, in a front-end power supply that is redundant for reliability improvement, in order to share the output power among a plurality of front-end power supplies, the ratio of the light-load operation time of each front-end power supply tends to increase. Therefore, when improving the efficiency of the entire system, reducing the loss of the synchronous rectification circuit during light-load operation is effective.

[0010] Therefore, for example, it is conceivable to configure a more low-loss rectification circuit by combining the synchronous rectification control as in Patent Document 2 with the synchronous rectification circuit of Patent Document 1.

[0011] However, the control technology described in Patent Document 2 is premised on the fact that two or more MOSFETs for synchronous rectification are connected in parallel. Therefore, it is difficult to apply it to a rectification circuit in which only one MOSFET for synchronous rectification is described in Patent Document 1.

[0012] Therefore, an object of the present invention is to provide a rectifier circuit and a control method thereof capable of controlling to reduce the total power loss when the load current (rectified current) is relatively small.

Means for Solving the Problems

[0013] In order to solve the above problems, the present invention is a rectifier circuit having an anode and a cathode, a first switching element having a first terminal connected to the cathode of the rectifier circuit and a second terminal connected to the anode of the rectifier circuit, a first diode having a cathode connected to the cathode of the rectifier circuit and an anode connected to the anode of the rectifier circuit, a first capacitor having a third terminal connected to the anode of the rectifier circuit, a reverse current prevention diode having a cathode connected to a fourth terminal of the first capacitor, a second switching element having a fifth terminal connected to the cathode of the rectifier circuit and a sixth terminal connected to the anode of the reverse current prevention diode, a first comparison circuit for controlling the first switching element based on the voltage between the anode and the cathode of the rectifier circuit, and a second comparison circuit for controlling the second switching element so as to control the voltage between the third terminal and the fourth terminal of the first capacitor to a target voltage.

[0014] Further, the present invention is a control method for a self-powered rectifier circuit using one synchronous rectification MOSFET, characterized in that the voltage of a capacitor for supplying power to the gate drive circuit of the synchronous rectification MOSFET is controlled based on the magnitude of the current flowing from the anode to the cathode of the rectifier circuit.

Effects of the Invention

[0015] According to the present invention, it is possible to realize a rectifier circuit and a control method thereof capable of controlling to reduce the total power loss when the load current (rectified current) is relatively small.

[0016] As a result, for example, during light load operation of the power supply device, the gate charge loss of the rectifier circuit can be reduced, and high efficiency of the power supply device can be achieved.

[0017] Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or similar components are denoted by the same reference numerals, and detailed descriptions of overlapping parts are omitted.

[0020] Also, symbols indicating current and voltage in the figure (the attached arrows indicate the direction), Is, Vds1, Vgs1, and Vc1 represent the rectified current, the voltage between the main terminals of MOSFET Q1, i.e., the drain-source voltage, the gate-source voltage of MOSFET Q1, and the voltage of capacitor C1, respectively. These symbols are appropriately used in the following description.

Embodiment

[0021] With reference to FIGS. 1 to 3, and FIGS. 9 and 10, the circuit configuration and control method of the rectifier circuit according to Embodiment 1 of the present invention will be described.

[0022] FIG. 1 is a circuit diagram showing the configuration of the rectifier circuit of this embodiment. FIG. 2 is a current-voltage waveform diagram showing an example of the operation of the rectifier circuit of FIG. 1. FIG. 3 is a diagram showing the relationship between the total loss of the rectifier circuit and the rectified current Is and the gate-source voltage Vgs1. Note that FIGS. 9 and 10 are a circuit diagram of a conventional rectifier circuit and a current-voltage waveform diagram showing an example of its operation, which are shown as comparative examples for easy understanding of the present invention.

[0023] As shown in FIG. 1, in the rectifier circuit of this embodiment, as a semiconductor switching element for synchronous rectification, MOSFET Q1 is connected between the anode (A) and the cathode (K). The drain of MOSFET Q1 is connected to the cathode (K), and the source is connected to the anode (A).

[0024] MOSFET Q1 is turned on and off based on the drain-source voltage of MOSFET Q1 detected by the comparison circuit Co1. MOSFET Q1 is turned on during the rectification period (rectified current Is ≧ 0), that is, when the AC voltage applied between the anode (A) and the cathode (K) is in the forward direction.

[0025] In this embodiment, an enhancement-type n-channel MOSFET is applied as MOSFET Q1.

[0026] A diode D1 is connected in reverse parallel to the MOSFET Q1. In this embodiment, the diode D1 is a body diode built into the MOSFET. Note that an externally attached individual diode may be used as the diode D1.

[0027] The rectifier circuit of this embodiment detects the voltage drop when the rectified current (load current) Is flowing from the anode (A) to the cathode (K) of the rectifier circuit passes through the MOSFET Q1 or the diode D1, and realizes synchronous rectification by controlling the MOSFET Q1 to be turned on during the rectification period.

[0028] The comparison circuit Co1 compares the drain-source voltage of the MOSFET Q1 (i.e., the voltage between the anode (A) and cathode (K) of the rectifier circuit) Vds1 with the threshold voltage generated by the threshold voltage generation circuit Rv1, and controls the on / off of the MOSFET Q1.

[0029] For example, when the threshold voltage generation circuit Rv1 generates a negative threshold voltage Vth1, if Vds1 ≤ Vth1, the comparison circuit Co1 controls the MOSFET Q1 to be turned on, and if Vds1 > Vth1, the comparison circuit Co1 controls the MOSFET Q1 to be turned off.

[0030] Note that in order to suppress the chattering in which the MOSFET Q1 repeatedly turns on and off in a short cycle, the threshold voltage generation circuit Rv1 generates a negative threshold voltage Vth2 greater than the threshold voltage Vth1, and when Vds1 > Vth2 (i.e., when Vds1 > Vth2 > Vth1), the comparison circuit Co1 may control the MOSFET Q1 to be turned off.

[0031] The rectifier circuit of this embodiment reduces the loss of the rectifier circuit by controlling the maximum value of the voltage Vc1 of the capacitor C1 during the period when the capacitor C1 is charged based on the magnitude of the detected rectified current Is.

[0032] The capacitor C1 is charged by the drain-source voltage Vds1 of the MOSFET Q1 that occurs when the MOSFET Q1 is off. Also, the maximum value of the voltage Vc1 of the capacitor C1 is controlled by controlling the on / off of the switching element Q2.

[0033] The on / off of the MOSFET Q2 is controlled by the comparison circuit Co2. The comparison circuit Co2 compares the drain-source voltage Vds1 of the MOSFET Q1 with the threshold voltage generated by the threshold voltage generation circuit Rv2, and controls the switching element Q2 to be on when Vds1 is less than or equal to the threshold voltage generated by the threshold voltage generation circuit Rv2, and controls the switching element Q2 to be off when Vds1 is greater than the threshold voltage generated by the threshold voltage generation circuit Rv2. Therefore, when the maximum value of the drain-source voltage Vds1 applied to the MOSFET Q1 during the period when the MOSFET Q1 is off is greater than the threshold voltage generated by the threshold voltage generation circuit Rv2, the voltage Vc1 of the charged capacitor C1 increases to the threshold voltage generated by the threshold voltage generation circuit Rv2.

[0034] The threshold voltage generation circuit Rv2 generates at least two different threshold voltages.

[0035] As an example, it is shown that the threshold voltage generation circuit Rv2 generates two different threshold voltages Vcref1 or Vcref2, and the maximum value of the voltage Vc1 of the charged capacitor C1 is controlled to Vcref1 or Vcref2, thereby reducing the loss of the rectifier circuit. However, Vcref1 and Vcref2 are positive values, and Vcref1 > Vcref2. Also, Vcref1 and Vcref2 are sufficiently larger than the gate threshold voltage Vgsth1 of the MOSFET Q1 and smaller than the rated voltages of the comparison circuits Co1, Co2, and Co3.

[0036] Vcref1 and Vcref2 generated by the threshold voltage generation circuit Rv2 are determined, for example, as follows.

[0037] The losses generated in the rectifier circuit include the conduction loss of MOSFET Q1 caused by the load current (rectified current) Is, the gate charge loss when driving MOSFET Q1, and the loss of the control circuit (gate driver).

[0038] The conduction loss is the product of the square of the effective value of the load current (rectified current) Is and the on-resistance of MOSFET Q1. The gate charge loss is the product of the square of the gate-source voltage Vgs1 of MOSFET Q1, the input capacitance of MOSFET Q1, and the switching frequency of MOSFET Q1. The loss of the control circuit (gate driver) is estimated by the product of the voltage Vc1 of capacitor C1 and the current consumption of the control circuit (gate driver).

[0039] Assuming that the gate-source voltage of MOSFET Q1 and the voltage of capacitor C1 are approximately equal when MOSFET Q1 is on, the sum of these losses can be expressed with the effective value of the load current (rectified current) Is as a variable for each of the maximum voltages when capacitor C1 is charged, that is, Vcref1 or Vcref2. Therefore, as shown in Figure 3, when the sum of the losses is plotted on the vertical axis and the effective value of the load current (rectified current) Is is plotted on the horizontal axis, the graphs when the threshold voltage generated by the threshold voltage generation circuit Rv is Vcref1 and when it is Vcref2 intersect at a certain effective value of the load current (rectified current) Is. Therefore, when the effective value of the actually flowing load current (rectified current) Is is smaller than that effective value of the load current (rectified current) Is, the threshold voltage generated by the threshold voltage generation circuit Rv2 is switched to Vcref2, and when it is larger, the threshold voltage generated by the threshold voltage generation circuit Rv2 is switched to Vcref1, thereby reducing the loss of the rectifier circuit.

[0040] The switching between the threshold voltages Vcref1 and Vcref2 generated by the threshold voltage generation circuit Rv2 is detected based on the rectified current Is and determined according to its magnitude.

[0041] In the rectifier circuit of this embodiment, in order to detect the rectified current (load current) Is, the rectified current (load current) Is and the voltage drop generated by the on-resistance of the MOSFET Q1, that is, the drain-source voltage Vds1 of the MOSFET Q1 during the on-period of the MOSFET Q1 are detected.

[0042] The comparison circuit Co3 compares the detected Vds1 with the threshold voltage generated by the threshold voltage generation circuit Rv3, and inputs a signal for switching the threshold voltage generated by the threshold voltage generation circuit Rv2 to the threshold voltage generation circuit Rv2.

[0043] The threshold voltage generated by the threshold voltage generation circuit Rv3 is determined as follows, for example. Assuming that the waveform of the rectified current Is is a sine wave, the maximum value of the rectified current Is is uniquely determined with respect to the effective value of the load current (rectified current) Is at the intersection of the graph in FIG. 3. Also, assuming that the voltage of the capacitor C1 and the gate-source voltage of the MOSFET Q1 are approximately equal and the MOSFET Q1 is driven under the condition of being sufficiently cooled, the on-resistance of the MOSFET Q1 is uniquely determined in each case where the threshold voltage generated by the threshold voltage generation circuit Rv2 is Vcref1 or Vcref2. Therefore, the minimum value Vds1onmin of the drain-source voltage of the MOSFET Q1 during the on-period of the MOSFET Q1 is uniquely determined in each case where the threshold voltage generated by the threshold voltage generation circuit Rv2 is Vcref1 or Vcref2 with respect to the effective value of the load current (rectified current) Is at the intersection of the graph in FIG. 3.

[0044] Assume that the threshold voltage generation circuit Rv3 generates two threshold voltages Vthl1 and Vthl2, and sets Vds1onm corresponding to the case where the threshold voltage generated by the threshold voltage generation circuit Rv2 is Vcref1 to Vthl1 and Vds1onm corresponding to the case where the threshold voltage generated by the threshold voltage generation circuit Rv2 is Vcref2 to Vthl2. Also, when the threshold voltage generated by the threshold voltage generation circuit Rv2 is Vcref1, the threshold voltage generation circuit Rv3 generates the threshold voltage Vthl1, and when the threshold voltage generated by the threshold voltage generation circuit Rv2 is Vcref2, the threshold voltage generation circuit Rv3 generates the threshold voltage Vthl2.

[0045] FIG. 2 is an operation waveform of the rectifier circuit of this embodiment when the threshold voltage generated by the threshold voltage generation circuit Rv2 switches from Vcref1 to Vcref2. The comparison circuit Co3 detects the drain-source voltage Vds1 during the on-period of the MOSFET Q1, compares its minimum value Vdsonm with the threshold voltage Vthl1 generated by the threshold voltage generation circuit Rv3, determines that Vdsonm > Vthl1, inputs a signal to the threshold voltage generation circuit Rv2, and as a result, the threshold voltage generated by the threshold voltage generation circuit Rv2 switches to Vcref2. Similarly, when the threshold voltage generated by the threshold voltage generation circuit Rv2 switches from Vcref2 to Vcref1, it is when the comparison circuit Co3 determines that Vdsonm < Vthl2, and is realized by the comparison circuit Co3 inputting a signal for switching the threshold voltage generated by the threshold voltage generation circuit Rv2 from Vcref2 to Vcref1.

[0046] In the above description, assumptions are used such as the voltage of the capacitor C1 is approximately equal to the gate-source voltage of the MOSFET Q1, the waveform of the rectified current Is is a sine wave, and the MOSFET Q1 is driven under the condition of being sufficiently cooled. However, these assumptions are only used to simply determine the threshold voltage generated by the threshold voltage generation circuit Rv3, and the threshold voltage generated by the threshold voltage generation circuit Rv3 may be determined in consideration of the waveform of the rectified current Is under actual driving conditions and the temperature characteristics of the on-resistance of the MOSFET Q1.

[0047] Also, when the switching loss generated in the MOSFET Q1 is large, the switching loss may be added to the loss generated in the rectifier circuit, and Vcref1 and Vcref2 may be determined by the same means.

[0048] As shown in FIG. 9, in the conventional rectifier circuit, the voltage Vc1 of the capacitor C1 increases to the voltage between the cathode (K) and anode (A) of the rectifier circuit. However, the voltage drop of the reverse current prevention diode Dr is ignored. Therefore, as shown in FIG. 10, the voltage Vc1 of the capacitor C1 and the gate-source voltage Vgs1 of the MOSFET Q1 are constant regardless of the magnitude of the load current Is.

[0049] As shown in FIGS. 2 and 10, the present invention is different from the conventional rectifier circuit in that it controls the magnitudes of Vc1 and Vgs1 according to the magnitude of the rectified current (load current) Is.

[0050] In addition to the configuration shown in FIG. 9, the conventional rectifier circuit also has a configuration in which a switching element is inserted between the reverse current prevention diode Dr and the cathode (K) of the rectifier circuit, and the charging current of the capacitor C1 is controlled by controlling the switching element, and the magnitude of Vc1 is controlled to a desired value below the voltage between the cathode (K) and anode (A) of the rectifier circuit. However, this conventional rectifier circuit does not control Vc1 according to the magnitude of the rectified current (load current) Is.

[0051] As described above, the rectifier circuit of the present embodiment is a rectifier circuit having an anode (A) and a cathode (K), a first switching element (MOSFET Q1) whose first terminal is connected to the cathode (K) of the rectifier circuit and whose second terminal is connected to the anode (A) of the rectifier circuit, a first diode (diode D1) whose cathode is connected to the cathode (K) of the rectifier circuit and whose anode is connected to the anode (A) of the rectifier circuit, a first capacitor (capacitor C1) whose third terminal is connected to the anode (A) of the rectifier circuit, a reverse current prevention diode Dr whose cathode is connected to the fourth terminal of the first capacitor (capacitor C1), a second switching element (switching element Q2) whose fifth terminal is connected to the cathode (K) of the rectifier circuit and whose sixth terminal is connected to the anode of the reverse current prevention diode Dr, a first comparison circuit (comparison circuit Co1) that controls the first switching element (MOSFET Q1) based on the voltage between the anode (A) and cathode (K) of the rectifier circuit, and a second comparison circuit (comparison circuit Co2) that controls the second switching element (switching element Q2) so as to control the voltage between the third terminal and the fourth terminal of the first capacitor (capacitor C1) to a target voltage.

[0052] The target voltage is at least two different values, and the target voltage is controlled based on the magnitude of the current flowing from the anode (A) to the cathode (K) of the rectifier circuit.

[0053] Also, according to this embodiment, in a self-powered synchronous rectifier circuit using one MOSFET for synchronous rectification, when the load current, i.e., the rectified current, is small, the voltage of the power supply that supplies power to the drive circuit for driving the MOSFET is controlled to be reduced so that the total power loss of the rectifier circuit is reduced.

Embodiment

[0054] Referring to FIG. 4, the circuit configuration of the rectifier circuit according to Embodiment 2 of the present invention will be described.

[0055] FIG. 4 is a circuit diagram showing the configuration of the rectifier circuit of this embodiment, which corresponds to a modified example of Embodiment 1 (FIG. 1). In the rectifier circuit of Embodiment 1 (FIG. 1), the switching element Q2 for controlling the charging current of the capacitor C1 according to the magnitude of the rectified current (load current) Is is arranged between the reverse current prevention diode Dr and the cathode (K) of the rectifier circuit, whereas in the rectifier circuit of this embodiment (FIG. 4), the switching element Q2 is arranged between the capacitor C1 and the anode (A) of the rectifier circuit, which is different.

[0056] Even if the switching element Q2 for controlling the charging current of the capacitor C1 according to the magnitude of the rectified current (load current) Is is arranged between the capacitor C1 and the anode (A) of the rectifier circuit as in this embodiment (FIG. 4), the same effects as those of Embodiment 1 (FIG. 1) can be obtained.

Embodiment

[0057] Referring to FIG. 5, the circuit configuration of the rectifier circuit according to Embodiment 3 of the present invention will be described.

[0058] FIG. 5 is a circuit diagram showing the configuration of the rectifier circuit of this embodiment, which corresponds to a modified example of Embodiment 1 (FIG. 1). In the rectifier circuit of Embodiment 1 (FIG. 1), one of the input terminals of the comparison circuit Co2 is connected between the switching element Q2 and the cathode (K) of the rectifier circuit, whereas in the rectifier circuit of this embodiment (FIG. 5), it is different in that it is connected between the reverse current prevention diode Dr and the capacitor C1, that is, to the terminal to which the positive voltage of the capacitor C1 is applied.

[0059] By adopting the configuration as in this embodiment (FIG. 5), the voltage Vc1 of the capacitor C1 can be controlled to the target voltage without including the voltage drop variation of the reverse current prevention diode Dr.

Embodiment

[0060] Referring to FIG. 6, the circuit configuration of the rectifier circuit according to Embodiment 4 of the present invention will be described.

[0061] FIG. 6 is a circuit diagram showing the configuration of the rectifier circuit of this embodiment, which corresponds to a modified example of Embodiment 1 (FIG. 1). In the rectifier circuit of Embodiment 1 (FIG. 1), one of the input terminals of the comparison circuit Co1 and one of the input terminals of the comparison circuit Co2 are connected between the switching element Q2 and the cathode (K) of the rectifier circuit, whereas in the rectifier circuit of this embodiment (FIG. 6), it is different in that it is connected between the switching element Q2 and the reverse current prevention diode Dr.

[0062] In the rectifier circuit of this embodiment, the on / off of the switching element Q2 is controlled by the threshold voltage generated by the threshold voltage generation circuit Rv4. The threshold voltage generated by the threshold voltage generation circuit Rv4 is controlled based on the output signal of the comparison circuit Co2 so as to realize the desired on / off control of the switching element Q2.

[0063] By adopting the configuration as in this embodiment (FIG. 6), the rectifier circuit of the present invention can be applied even when a voltage higher than the rated voltages of the comparison circuits Co1 and Co2 is applied between the cathode (K) and the anode (A) of the rectifier circuit.

Embodiment

[0064] Referring to FIG. 7, a semiconductor device according to Embodiment 5 of the present invention will be described.

[0065] FIG. 7 is a circuit diagram showing the configuration of the semiconductor device of this embodiment, and is a configuration example of a semiconductor device equipped with the rectifier circuit of the present invention described in Embodiments 1 to 4. FIG. 7 shows an example in which the rectifier circuit of Embodiment 1 (FIG. 1) is mounted.

[0066] As shown in FIG. 7, for example, a bridge circuit can be configured using four rectifier circuits 1 and built into one semiconductor package 2 to configure a four-terminal semiconductor device. The semiconductor package 2 has terminals T1 to T4 as external terminals.

[0067] Not limited to the configuration of FIG. 7, the rectifier circuit 1 may be built into a semiconductor package having the cathode (K) and the anode (A) as external terminals.

[0068] According to the semiconductor device of this embodiment, when designing and manufacturing a product using a rectifier circuit, it is only necessary to purchase and incorporate a rectifier circuit with a drive circuit and a capacitor as in this embodiment, eliminating the man-hours for designing and mounting the drive circuit and the capacitor, so that the overall man-hours for design and mounting can be reduced.

Embodiment

[0069] Referring to FIG. 8, a power supply device according to Embodiment 6 of the present invention will be described.

[0070] FIG. 8 is a circuit diagram showing the configuration of the power supply device of this embodiment, and is a configuration example of a power supply device equipped with the rectifier circuit and semiconductor device of the present invention described in Embodiments 1 to 5.

[0071] The applicable ranges of the rectifier circuits and semiconductor devices of Examples 1 to 5 are all rectifier circuits used for power supplies. For example, in a front-end power supply as shown in FIG. 8, the rectifier circuits and semiconductor devices of Examples 1 to 5 can be applied as commercial rectifier diodes CRD1 to CRD4, freewheeling diodes FWD, secondary-side rectifier diodes SSD1 to SSD2, and reverse-current prevention diodes BPD.

[0072] By applying the rectifier circuits and semiconductor devices of Examples 1 to 5 to a power supply device such as a front-end power supply, it is possible to contribute to the high efficiency and miniaturization of the power supply device.

[0073] Note that the present invention is not limited to the above-described examples, and various modifications are included. For example, the above-described examples have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one example can be replaced with the configuration of another example, and the configuration of another example can also be added to the configuration of one example. Further, it is possible to add, delete, or replace a part of the configuration of each example with another configuration.

Explanation of Reference Numerals

[0074] 1: Rectifier circuit 2: Semiconductor package T1 to T4: Terminals K: Cathode A: Anode Q1: MOSFET Q2: Switching element D1, D2: Diodes Dr: Reverse-current prevention diode C1: Capacitor Co1 to Co3: Comparison circuits Rv1 to Rv4: Threshold voltage generation circuits Vth1, Vth2, Vthl1, Vthl2: Threshold voltages Is: Rectified current (load current) Vds1: Drain-source voltage of MOSFET Q1 (voltage between the cathode and anode of the rectifier circuit) Vds1onmin: Minimum value of the drain-source voltage of MOSFET Q1 during the on-period Vc1: Voltage of capacitor C1 Vgs1: Gate-source voltage of MOSFET Q1 Vgsth1: Gate threshold voltage of MOSFET Q1 Vcref1, Vcref2: Target voltages of capacitor C1 t, T1, T2, T1a, T1b, T2a: Time CRD1~CRD4: Commercial rectifier diodes FWD: Freewheeling diode SSD1~SSD2: Secondary-side rectifier diodes BPD: Backflow prevention diode.

Claims

1. A rectifier circuit having an anode and a cathode, a first switching element in which a first terminal is connected to the cathode of the rectifier circuit and a second terminal is connected to the anode of the rectifier circuit; a first diode in which the cathode is connected to the cathode of the rectifier circuit and the anode is connected to the anode of the rectifier circuit; a first capacitor in which a third terminal is connected to the anode of the rectifier circuit; a reverse current prevention diode in which the cathode is connected to a fourth terminal of the first capacitor; a second switching element in which a fifth terminal is connected to the cathode of the rectifier circuit and a sixth terminal is connected to the anode of the reverse current prevention diode; a first comparison circuit that controls the first switching element based on the voltage between the anode and the cathode of the rectifier circuit; a second comparison circuit that controls the second switching element so as to control the voltage between the third terminal and the fourth terminal of the first capacitor to a target voltage; A rectifier circuit characterized by comprising:

2. The rectifier circuit according to claim 1, wherein the target voltage is at least two different values, and the rectifier circuit is characterized in that the target voltage is controlled based on the magnitude of the current flowing from the anode to the cathode of the rectifier circuit.

3. The rectifier circuit according to claim 1, wherein a first input terminal of the first comparison circuit is connected to the cathode of the rectifier circuit, and a second input terminal is connected to a first threshold voltage generation circuit.

4. The rectifier circuit according to claim 3, wherein the first threshold voltage generation circuit generates at least two different threshold voltages.

5. The rectifier circuit according to claim 1, wherein a first input terminal of the second comparison circuit is connected to the cathode of the rectifier circuit.

6. The rectifier circuit according to claim 5, wherein a second input terminal of the second comparison circuit is connected to a second threshold voltage generation circuit.

7. The rectifier circuit according to claim 6, wherein the second threshold voltage generation circuit generates at least two different threshold voltages, and the rectifier circuit is characterized in that the generated threshold voltage is changed based on the magnitude of the current flowing from the anode to the cathode of the rectifier circuit.

8. The rectifier circuit according to any one of claims 1 to 7, A rectifier circuit characterized by being incorporated in a semiconductor package.

9. The rectifier circuit according to any one of claims 1 to 7, characterized by being mounted on a power supply device.

10. A control method for a self-powered rectifier circuit using one synchronous rectification MOSFET, characterized by controlling the voltage of a capacitor that supplies power to the gate drive circuit of the synchronous rectification MOSFET based on the magnitude of the current flowing from the anode to the cathode of the rectifier circuit.

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