WO2024057591A1

WO2024057591A1 - Rectifier circuit and power supply using same

Info

Publication number: WO2024057591A1
Application number: PCT/JP2023/013972
Authority: WO
Inventors: 明寛三輪; 浩幸庄司; 順一坂野; 智之内海; 孝裕樋口
Original assignee: 株式会社日立パワーデバイス
Priority date: 2022-09-15
Filing date: 2023-04-04
Publication date: 2024-03-21
Also published as: JP2024042220A

Abstract

The present invention provides a rectifier circuit which uses a rectifying switching element and which can reduce the required capacitance of a capacitor that supplies power to a drive circuit for driving the rectifying switching element. A rectifier circuit 2 having an anode A and a cathode K comprises: a rectifying switching element (MOSFETQ1); a diode (body diode DQ1); a drive circuit 1 that drives the rectifying switching element (MOSFETQ1); and a capacitor C1 that supplies power to the drive circuit 1, wherein during the period from when the rectifying switching element (MOSFETQ1) turns off until the rectifying switching element (MOSFETQ1) subsequently turns on, the capacitor C1 has a first charging period and a second charging period in which the capacitor C1 is charged, and a charging stop period which is provided between the first charging period and the second charging period and in which charging of the capacitor C1 is stopped.

Description

Rectifier circuit and power supply using it

The present invention relates to a rectifier circuit and a power supply using the same.

As rectifier circuits that rectify alternating current into direct current, there are known ones that use diodes and ones that perform synchronous rectification using switching elements such as MOSFETs instead of diodes.

In the case of rectification using diodes, there is a voltage drop due to the built-in potential of the diodes, so there is a problem of large losses. On the other hand, synchronous rectification using a MOSFET, for example, has the advantage of low loss because there is no built-in potential of the MOSFET and the forward current rises from 0V. Therefore, especially in switching power supplies such as front-end power supplies that have strict efficiency regulations, synchronous rectification using MOSFETs is mainly used to achieve lower loss.

Examples of rectifier circuits that realize synchronous rectification include Patent Document 1 and Patent Document 2.

A rectifier circuit that performs synchronous rectification generally includes a MOSFET that is a first switching element for synchronous rectification, a drive circuit for the MOSFET, a capacitor that supplies power to the drive circuit, and a MOSFET that controls the voltage of the capacitor. It has two switching elements and a control circuit for the second switching element. The drive circuit controls on/off of the MOSFET based on a predetermined threshold voltage and the detected drain-source voltage of the MOSFET.

FIG. 9 is a diagram showing operating waveforms of a conventional rectifier circuit. In FIG. 9, the vertical axis represents voltage or current, and the horizontal axis represents time t.

The capacitor that supplies power to the drive circuit connects the drain terminal of the MOSFET to the second switching terminal between time t1 and time t2 after the gate-source voltage Vgs1 of the MOSFET becomes 0 at time t0 and the MOSFET is turned off. It is charged by the current flowing through the source terminal of the element, capacitor, and MOSFET. When charging of the capacitor starts, the voltage Vc1 of the capacitor increases to follow the drain-source voltage Vds1 of the MOSFET.

In this rectifier circuit, after the voltage Vc1 of the capacitor reaches the target voltage Vcref1 at time t2, the second switching element inserted between the drain terminal of the MOSFET and the positive terminal of the capacitor is turned off. Cut off the charging current Ic. Thereby, the capacitor voltage Vc1 is controlled to be equal to or lower than the target voltage Vcref1.

Japanese Patent Application Publication No. 2001-251861 US Patent No. 10756645

Here, in the conventional rectifier circuit, as shown in FIG. 9, from time t2 to time t5, the power accumulated in the capacitor is consumed by the standby power of the drive circuit, so the voltage Vc1 of the capacitor decreases. do. After that, after the MOSFET is turned on starting from time t5, the MOSFET is turned off again at the next time t0 and the capacitor starts charging at time t1.The power accumulated in the capacitor is then consumed by the drive circuit. The voltage on the capacitor continues to decrease as it is used to generate power or the gate-to-source voltage of the MOSFET.

Therefore, during the period from when charging of the capacitor is completed at time t2 until charging of the capacitor starts again at the next time t1, the voltage Vc1 of the capacitor is, for example, the guaranteed operation voltage of the drive circuit or the voltage of the MOSFET. It is necessary to set the voltage lower limit value Vcref2 of the capacitor so that it is equal to or higher than the gate threshold voltage, and to select the capacitance of the capacitor so as to satisfy this value.

However, in conventional rectifier circuits, as mentioned above, it is necessary to ensure the capacity of the capacitor that supplies power to the MOSFET drive circuit for synchronous rectification, so there is a limit to reducing the volume of the capacitor, and the rectifier circuit This has been an obstacle to miniaturization and cost reduction.

The problem to be solved by the present invention is that in a rectifier circuit using a switching element for rectification, it is possible to reduce the required capacity of a capacitor that supplies power to a drive circuit for driving the switching element for rectification. The object of the present invention is to provide a rectifier circuit that can be made smaller and lower in cost by reducing the volume of a capacitor, and a power supply using the rectifier circuit.

In order to solve the above problems, a rectifier circuit of the present invention includes, for example, a rectifier circuit having an anode and a cathode, in which a first terminal is connected to the cathode of the rectifier circuit, and a second terminal is connected to the rectifier circuit. a first switching element connected to the anode of the first switching element; a first diode having a cathode connected to the first terminal and an anode connected to the second terminal; and driving the first switching element. a drive circuit that supplies power to the drive circuit; and a first capacitor that supplies power to the drive circuit; A first charging period and a second charging period in which the first capacitor is charged, and a charging period provided between the first charging period and the second charging period, in which charging of the first capacitor is stopped. The battery is characterized by having a charging stop period.

Furthermore, the power supply of the present invention is characterized in that it includes, for example, the above-mentioned rectifier circuit.

According to the rectifier circuit and power supply of the present invention, the capacitor is charged in two times, the first charging period and the second charging period, and the amount of the capacitor discharged during the charging stop period after the first charging period is Since at least a portion of the charge can be compensated for in the second charging period, the required capacitance of the capacitor can be reduced, and as a result, the volume of the capacitor can be reduced, making it possible to realize miniaturization and cost reduction of the rectifier circuit and power supply.

FIG. 3 is a circuit diagram of a rectifier circuit of Example 1. 3 is a diagram showing operating waveforms of the rectifier circuit of Example 1. FIG. FIG. 2 is a circuit diagram of a rectifier circuit according to a second embodiment. FIG. 3 is a circuit diagram of a rectifier circuit according to a third embodiment. FIG. 4 is a circuit diagram of a rectifier circuit according to a fourth embodiment. FIG. 7 is a diagram showing an example of a configuration of a rectifier circuit according to a fifth embodiment. 7 is a diagram showing another example of the configuration of the rectifier circuit of Example 5. FIG. FIG. 7 is a circuit diagram of a power supply according to a sixth embodiment. The figure which shows the operating waveform of the conventional rectifier circuit.

Embodiments of the present invention will be described below with reference to the drawings. In each figure and each embodiment, the same or similar components are denoted by the same reference numerals, and overlapping explanations will be omitted.

First, the basic principle of Example 1 will be explained.

FIG. 1 is a circuit diagram of the rectifier circuit of Example 1.

As shown in FIG. 1, the rectifier circuit 2 of the first embodiment includes an anode A, a cathode K, a MOSFET Q1 which is a first switching element for rectification, a body diode DQ1 of the MOSFET Q1, and a drive circuit that drives the MOSFET Q1. 1 and a capacitor C1 that supplies power to the drive circuit 1. Furthermore, the rectifier circuit 2 of the first embodiment includes a second switching element MOSFETQ2 for controlling the voltage Vc1 of the capacitor C1, a body diode DQ2 of the MOSFETQ2, a control circuit CTR for controlling the MOSFETQ2, and a diode D. has. The drive circuit 1 includes a comparator Co1 and a gate driver GD1.

In FIG. 1, an n-channel enhancement type MOSFET is used as the MOSFET Q1, and an n-channel depletion type MOSFET is used as the MOSFET Q2, but the present invention is not limited to this, and other switching elements may be used. Further, the body diode DQ1 and the body diode DQ2 are not limited to body diodes built into the MOSFET, and other diodes such as external diodes may be used.

MOSFET Q1 has a gate terminal that is a control terminal, a drain terminal that is one main terminal, and a source terminal that is the other main terminal. MOSFET Q1 is a switching element for rectification, and has a drain terminal connected to the cathode K of the rectifier circuit 2, a source terminal connected to the anode A of the rectifier circuit 2, and a gate terminal connected to the drive circuit 1.

The body diode DQ1 has a cathode connected to the drain terminal of MOSFETQ1, and an anode connected to the source terminal of MOSFETQ1.

FIG. 2 is a diagram showing operating waveforms of the rectifier circuit of Example 1.

FIG. 2 is a diagram corresponding to FIG. 9, and shows operating waveforms when a resistive load is connected to a bridge circuit configured using four rectifier circuits 2 shown in FIG. 1 and a sine wave voltage is input. . In FIG. 2, the vertical axis indicates the drain-source voltage Vds1 of MOSFET Q1, the gate-source voltage Vgs1 of MOSFET Q1, the charging current Ic of capacitor C1, and the voltage Vc1 of capacitor C1, and the horizontal axis indicates time t. ing. Further, Vgth1 is the gate threshold voltage of MOSFETQ1. Note that illustration and detailed description of the drain-source voltage Vds2 of MOSFETQ2, the gate-source voltage Vgs2 of MOSFETQ2, and the gate threshold voltage Vgth2 of MOSFETQ2 are omitted.

As shown in FIG. 2, in the rectifier circuit 2 of the first embodiment, the capacitor C1 that supplies power to the drive circuit 1 is connected to the Between the first charging period (from time t1 to time t2) and the second charging period (from time t3 to time t4) during which capacitor C1 of No. 1 is charged, and between the first charging period and the second charging period. This differs from the conventional operating waveform shown in FIG. 9 in that it has a charging stop period (from time t2 to time t3) in which charging of the capacitor C1 is stopped.

In the conventional case shown in FIG. 9, the capacitor is charged only once from time t1 to time t2, and thereafter, the capacitor is charged so that the capacitor voltage Vc1 can be maintained at a voltage lower limit value Vcref2 or higher until the next charging period, time t1. It is necessary to select the capacity of On the other hand, according to the rectifier circuit 2 of the first embodiment, the capacitor C1 is charged in two times, the first charging period and the second charging period, and the charging stop period is performed after the first charging period. Since at least a part of the discharged amount can be compensated for in the second charging period, the required capacity of the capacitor C1 can be reduced, and as a result, the volume of the capacitor C1 can be reduced and the rectifier circuit 2 and the rectifier circuit using it can be reduced. It is possible to realize smaller power supplies and lower costs. Further, it becomes possible to use a drive circuit and a control IC that consume a large amount of power during the off period of the MOSFET.

In FIG. 2, as an example, the first charging period and the second charging period are periods in which the drain-source voltage Vds1 of MOSFET Q1 is equal to or lower than a predetermined threshold voltage Vref1, and the charging stop period is a period between the drain-source of MOSFET Q1. The period is defined as a period in which the voltage Vds1 is higher than the predetermined threshold voltage Vref1. As a result, the first charging period is a period during which the drain-source voltage Vds1 of MOSFET Q1 is increasing, and the second charging period is a period during which the drain-source voltage Vds1 of MOSFET Q1 is decreasing. In FIG. 2, the threshold voltage Vref1 is set to the total voltage of the target voltage Vcref1 of the capacitor C1 and the forward voltage Vf of the diode D.

When capacitor C1 is charged during a period when the drain-source voltage Vds1 of MOSFETQ1 is large, the drain-source voltage Vds2 of MOSFETQ2 on the path also becomes large, and the loss (Vds2×Ic) generated in MOSFETQ2 also becomes large. Put it away. Therefore, in the rectifier circuit 2 of the first embodiment, the period in which the drain-source voltage Vds1 of the MOSFET Q1 is higher than the predetermined threshold voltage Vref1 is set as a charging stop period, thereby suppressing the occurrence of loss and increasing the charging efficiency. Furthermore, since the second charging period is a period in which the drain-source voltage Vds1 of MOSFET Q1 is decreasing, the period until the next first charging period can be shortened, reducing the required capacity of the capacitor C1. It is highly effective.

Next, the detailed configuration and operation of the first embodiment will be described using FIGS. 1 and 2.

MOSFETQ2 has a gate terminal that is a control terminal, a drain terminal that is one main terminal, and a source terminal that is the other main terminal. MOSFETQ2 is a switching element for controlling voltage Vc1 of capacitor C1, and its drain terminal is connected to the drain terminal of MOSFETQ1, its source terminal is connected to capacitor C1 via diode D, and its gate terminal is connected to control circuit CTR. It is connected.

The cathode of the body diode DQ2 is connected to the drain terminal of MOSFET Q2, and the anode is connected to the source terminal of MOSFET Q2.

The diode D has an anode connected to the source terminal of the MOSFET Q2, and a cathode connected to the positive terminal of the capacitor C1.

The positive terminal of the capacitor C1 is connected to the cathode of the diode D, and the negative terminal is connected to the source terminal of the MOSFET Q1.

The drive circuit 1 includes a comparator Co1 to which power is supplied from a capacitor C1 and detects the voltage between the source terminal of MOSFETQ2 and the source terminal of MOSFETQ1, an input terminal connected to the output terminal of the comparator Co1, and an output terminal connected to the MOSFETQ1. The MOSFET Q1 is connected to the gate terminal of the MOSFET Q1, is supplied with power from the capacitor C1, and has a gate driver GD1 that controls the MOSFET Q1 based on the output signal of the comparator Co1.

The control circuit CTR inputs a signal for controlling MOSFETQ2 to the control terminal of MOSFETQ2. Then, the control circuit CTR controls the MOSFET Q2 to be in the ON state during a period in which the drain-source voltage Vds1 of the MOSFET Q1 is less than or equal to the total voltage (threshold voltage Vref1) of the target voltage Vcref1 of the capacitor C1 and the forward voltage Vf of the diode D. , during a period in which the drain-source voltage Vds1 of MOSFET Q1 is greater than the total voltage (threshold voltage Vref1) of the target voltage Vcref1 of capacitor C1 and the forward voltage Vf of diode D, MOSFET Q2 is controlled to be in the off state, so that the voltage Vds1 between the drain and source of MOSFET Q1 is Controls the flowing charging current Ic.

Here, the target voltage Vcref1 of the capacitor C1 is set to be sufficiently larger than the gate threshold voltage Vgth1 of the MOSFET Q1 so that the drive circuit 1 can drive the MOSFET Q1. Further, the target voltage Vcref1 of the capacitor C1 is set to be less than or equal to the minimum of the maximum rated voltage of the comparator Co1, the maximum rated voltage of the gate driver GD1, and the maximum rated voltage of the gate-source voltage Vgs1 of the MOSFET Q1. ing. This can prevent the drive circuit 1 and MOSFET Q1 from being destroyed.

Note that the control circuit CTR may have a configuration including a differentiation circuit for determining the timing to control MOSFETQ2. For example, the charging timing can be determined based on the slope of the drain-source voltage Vds1 of MOSFETQ1.

As an example, in FIG. 2, by detecting a period in which the slope of the drain-source voltage Vds1 of MOSFET Q1 is larger than the slope at time t3 and smaller than the slope at time t2, the slope of the drain-source voltage Vds1 of MOSFET Q1 is detected. It is possible to detect the period (from time t2 to time t3) in which the source-to-source voltage Vds1 is higher than the threshold voltage Vref1, and based on this, it is possible to control the MOSFET Q2. Note that the slope of the drain-source voltage Vds1 of the MOSFET Q1 is not limited to a predetermined range, for example, a predetermined range corresponding to the slope from time t0 to time t2 or from time t1 to time t2, and from time t3 to time t5. Alternatively, by detecting that the slope falls within a predetermined range corresponding to the slope from time t3 to time t4, it is detected that it is the first charging period or the second charging period, and based on this, the first charging period or the second charging period is detected. MOSFETQ2 may also be controlled by

In addition, as another example, the magnitude of the drain-source voltage Vds1 of MOSFETQ1 is detected, and its slope is also detected by a differential circuit, and the drain-source voltage Vds1 of MOSFETQ1 is equal to or lower than the threshold voltage Vref1, and The capacitor C1 may be controlled to be charged when the slope is within a predetermined slope range that is not too steep. For example, if the drain-source voltage Vds1 of the MOSFET Q1 is not a clean sine wave but contains noise, it may drop below the threshold voltage Vref1 for a moment, but return to the original level immediately. In such a case, if the slope is not taken into account, MOSFET Q2 will turn off immediately after being turned on, resulting in a loss. In this case, since the slope is steeper than usual, malfunctions due to noise can be prevented by detecting the slope with a differential circuit and using it for control.

Next, the operation of the rectifier circuit 2 of the first embodiment will be explained based on FIG. 2.

At time t0, the rectification period ends and the non-rectification period begins.

The period from time t0 to time t1 is a non-rectification period, and MOSFET Q1 is off. Furthermore, as the sinusoidal voltage input to the bridge circuit increases, the drain-source voltage Vds1 of MOSFET Q1 increases. Furthermore, during this period, since the drain-source voltage Vds1 of the MOSFET Q1 is smaller than the threshold voltage Vref1, the control circuit CTR turns on the MOSFET Q2. At this time, the drain-source voltage Vds1 of the MOSFET Q1 is smaller than the voltage Vc1 of the capacitor C1, but the diode D prevents current from flowing backward from the positive terminal of the capacitor C1 to the drain terminal of the MOSFET Q1.

During the period from time t1 to time t2, the drain-source voltage Vds1 of MOSFET Q1 is smaller than the threshold voltage Vref1, so the control circuit CTR continues to control MOSFET Q2 to turn on. Further, the drain-source voltage Vds1 of the MOSFET Q1 is larger than the sum of the voltage Vc1 of the capacitor C1 and the forward voltage Vf of the diode D. As a result, charging of the capacitor C1 is started, and the voltage Vc1 of the capacitor C1 increases. The charging current Ic of the capacitor C1 flows through a path including the drain terminal of the MOSFET Q1, the MOSFET Q2, the diode D, the capacitor C1, and the source terminal of the MOSFET Q1.

At time t2, the drain-source voltage Vds1 of MOSFET Q1 is equal to the threshold voltage Vref1.

During the period from time t2 to time t3, the drain-source voltage Vds1 of MOSFET Q1 is higher than the threshold voltage Vref1, so the control circuit CTR controls MOSFET Q2 to turn off, making it a charging stop period. As a result, the charging current Ic of the capacitor C1 is cut off. During this period, the power accumulated in the capacitor C1 is consumed as standby power for the drive circuit 1, but since the capacitor C1 is not charged, the voltage Vc1 of the capacitor decreases. Furthermore, during this period, the sine wave voltage input to the bridge circuit increases in the first half and decreases in the second half. Along with this, the drain-source voltage Vds1 of MOSFET Q1 also increases in the first half, and begins to decrease in the second half.

At time t3, the drain-source voltage Vds1 of MOSFET Q1 is equal to the threshold voltage Vref1.

During the period from time t3 to time t4, the drain-source voltage Vds1 of MOSFET Q1 is smaller than the threshold voltage Vref1, so the control circuit CTR turns on MOSFET Q2. In addition, during the period from time t2 to time t3, the voltage Vc1 of the capacitor C1 decreases, so the drain-source voltage Vds1 of the MOSFET Q1 is greater than the sum of the voltage Vc1 of the capacitor C1 and the forward voltage Vf of the diode D. . As a result, the charging current Ic of the capacitor C1 flows through the path of the drain terminal of the MOSFET Q1, the MOSFET Q2, the diode D, the capacitor C1, and the source terminal of the MOSFET Q1, and the voltage Vc1 of the capacitor C1 increases. The difference from the conventional example shown in FIG. 9 is that the capacitor C1 is charged even during this period.

Time t4 is when the voltage of MOSFET Q1 becomes equal to the sum of voltage Vc1 of capacitor C1 and forward voltage Vf of diode D.

During the period from time t4 to time t5, the drain-source voltage Vds1 of MOSFET Q1 is smaller than the threshold voltage Vref1, so the control circuit CTR continues to control MOSFET Q2 to turn on. At this time, diode D prevents electric charge from flowing out from the positive terminal of capacitor C1 to the drain terminal of MOSFET Q1.

Finally, in the period from time t5 to time t0, there is a rectification period again, and the drive circuit 1 turns on the MOSFET Q1, and a rectified current flows from the anode A to the cathode K.

Here, the operation of the drive circuit 1 and the control method of MOSFET Q1 will be explained.

The comparator Co1 of the drive circuit 1 detects the drain-source voltage Vds1 of the MOSFETQ1 from the source terminal of the MOSFETQ2 and the source terminal of the MOSFETQ1. Based on the detected voltage, the drive circuit 1 turns on and turns off the MOSFET Q1.

The rectified current flowing from the anode A to the cathode K first flows through the body diode DQ1 of the MOSFET Q1. Due to the voltage drop across the body diode DQ1, the drain-source voltage Vds1 of the MOSFET Q1 takes a negative value.

When the voltage detected by comparator Co1 becomes smaller than the first threshold voltage of comparator Co1, comparator Co1 outputs an on signal, and gate driver GD1 pulls up the gate-source voltage Vgs1 of MOSFET Q1 to the voltage Vc1 of capacitor C1. By doing so, MOSFET Q1 is turned on.

After that, the drain-source voltage Vds1 of MOSFETQ1 becomes a voltage determined by the rectified current and the on-resistance of MOSFETQ1.

As time passes, the rectified current decreases. As the rectified current decreases, the drain-source voltage Vds1 of MOSFET Q1 increases. When the voltage detected by the comparator Co1 becomes larger than the second threshold voltage of the comparator Co1, the comparator Co1 outputs an off signal, and the gate driver GD1 pulls down the gate-source voltage Vgs1 of MOSFET Q1 to 0V. Then, MOSFETQ1 is turned off.

The first threshold voltage and the second threshold voltage of the comparator Co1 may be the same value, or the first threshold voltage may be smaller than the second threshold voltage. When the first threshold voltage is lower than the second threshold voltage, it is possible to suppress chattering in which the MOSFET repeatedly turns on and off in short cycles.

Returning to the explanation of FIG. 2 again.

During the period from time t5 to time t0, the drain-source voltage Vds1 of MOSFET Q1 is smaller than the threshold voltage Vref1, so the control circuit CTR continues to control MOSFET Q2 to turn on. On the other hand, since the drain-source voltage Vds1 of the MOSFET Q1 is smaller than the sum of the voltage Vc1 of the capacitor C1 and the forward voltage Vf of the diode D, the capacitor C1 is not charged. At this time, although the drain-source voltage Vds1 of the MOSFET Q1 is smaller than the voltage Vc1 of the capacitor C1, the diode D prevents current from flowing backward from the positive terminal of the capacitor C1 to the drain terminal of the MOSFET Q1.

As a result, in this period, the voltage Vc1 of the capacitor C1 decreases because the power stored in the capacitor C1 is used for the power consumption of the drive circuit 1 and for generating the gate-source voltage Vgs1 of the MOSFET Q1.

By repeating the above control, the rectifier circuit 2 of the first embodiment realizes synchronous rectification.

In the above control, since the capacitor C1 is not charged during the period from time t2 to time t3 and from time t4 to the next time t1, the voltage Vc1 of the capacitor C1 decreases. It is necessary to select the capacitance of the capacitor C1 so that the minimum value of the voltage Vc1 of the capacitor C1 in any period is equal to or higher than the voltage lower limit value Vcref2 of the capacitor C1. The voltage lower limit value Vcref2 of the capacitor C1 is, for example, a value larger than the lowest operating voltage of the drive circuit 1 and larger than the gate threshold voltage Vgth1 of the MOSFET Q1 such that the on-resistance of the MOSFET Q1 becomes sufficiently small.

As explained above, according to the rectifier circuit 2 of Example 1, the required capacity of the capacitor C1 can be reduced, and as a result, the volume of the capacitor C1 can be reduced, realizing miniaturization and cost reduction of the rectifier circuit 2 and the power supply. can.

FIG. 3 is a circuit diagram of the rectifier circuit of Example 2.

Example 2 is a modification of Example 1. The second embodiment differs from the first embodiment in that it shows an example of a specific configuration of the control circuit CTR, and the other configurations and effects are basically the same as the first embodiment. Therefore, in the second embodiment, differences from the first embodiment will be mainly explained, and explanations that overlap with the first embodiment will be omitted.

The control circuit CTR of the rectifier circuit 2 of the second embodiment includes a resistor R1 and a resistor R2 that divide the drain-source voltage Vds1 of the MOSFET Q1, and a comparator Co2 that is supplied with power from the capacitor C1 and detects the voltage of the resistor R2. It has a gate driver GD2 whose input terminal is connected to the output terminal of the comparator Co2, whose output terminal is connected to the gate terminal of the MOSFET Q2, to which power is supplied from the capacitor C1, and which controls the MOSFET Q2 based on the output signal of the comparator Co2.

Here, the resistor R1 and the resistor R2 are set so that the voltage of the resistor R2 is equal to or lower than the rated voltage of the comparator Co2. Comparator Co2 compares the detected voltage of resistor R2 with threshold voltage Vref2 and outputs a signal to gate driver GD2. At this time, the threshold voltage Vref2 is selected so that when the drain-source voltage Vds1 of the MOSFET Q1 becomes equal to the threshold voltage Vref1, the voltage of the resistor R2 becomes equal to the threshold voltage Vref2.

According to the rectifier circuit 2 of the second embodiment, the operation described in FIG. 2 of the first embodiment can be realized.

FIG. 4 is a circuit diagram of the rectifier circuit of Example 3.

Example 3 is a modification of Example 1. The third embodiment differs from the first embodiment in that it includes a resistor R3, and the other configurations and effects are basically the same as the first embodiment. Therefore, in the third embodiment, differences from the first embodiment will be mainly explained, and explanations that overlap with the first embodiment will be omitted. Note that the third embodiment may be applied to the second embodiment.

The rectifier circuit 2 of Example 3 has a resistor R3 with one terminal connected to the drain terminal of MOSFET Q1 and the other terminal connected to the drain terminal of MOSFET Q2. In other words, the resistor R3 is inserted between the drain terminal of MOSFETQ1 and the drain terminal of MOSFETQ2.

In the rectifier circuits 2 of Examples 1 and 2, when the capacitor C1 is charged, the charging current Ic of the capacitor C1 flows through the path of the drain terminal of the MOSFET Q1, the MOSFET Q2, the diode D, the capacitor C1, and the source terminal of the MOSFET Q1. In particular, immediately after charging of the capacitor C1 is started, the charging current Ic increases sharply. As a result, the efficiency of the rectifier circuit 2 may decrease due to an increase in loss in the path of the charging current Ic, and the temperature of the MOSFET Q2 and the diode D may rise beyond their ratings.

According to the rectifier circuit 2 of the third embodiment, a steep increase in the charging current Ic of the capacitor C1 can be suppressed by inserting the resistor R3 in series on the path of the charging current Ic. That is, the resistor R3 functions as an inrush current prevention resistor. Thereby, it is possible to suppress a decrease in efficiency of the rectifier circuit 2 due to an increase in loss in the path of the charging current Ic and a rise in temperature of the MOSFET Q2 and the diode D.

FIG. 5 is a circuit diagram of the rectifier circuit of Example 4.

Example 4 is a modified example of Example 3. Example 4 differs from Example 3 in that it has a capacitor C2, but other configurations and effects are basically the same as Example 3. Therefore, in Example 4, the differences from Example 3 will be mainly described, and descriptions that overlap with Example 3 will be omitted. Note that Example 4 may be applied to Examples 1 and 2.

The rectifier circuit 2 of Example 4 has a capacitor C2 whose positive terminal is connected to the source terminal of MOSFETQ2 and whose negative terminal is connected to the source terminal of MOSFETQ1.

In the rectifier circuits of Examples 1 to 3, the comparator Co1 may malfunction due to high frequency noise contained in the voltage detected by the comparator Co1. As a result, for example, MOSFET Q1 may turn off during the rectification period, and the loss reduction effect of synchronous rectification may be impaired.

According to the rectifier circuit 2 of the fourth embodiment, high-frequency noise contained in the voltage detected by the comparator Co1 can be suppressed by configuring a low-pass filter with the on-resistance of the MOSFET Q2, the resistor R3, and the capacitor C2. Note that even if the resistor R3 is not inserted, the on-resistance of the MOSFET Q2 and the capacitor C2 constitute a low-pass filter, so it is possible to similarly suppress high-frequency noise contained in the voltage detected by the comparator Co1. Thereby, malfunction of the comparator Co1 and unintended turn-on and turn-off of the MOSFET Q1 can be suppressed, and the loss reduction effect of synchronous rectification is not impaired.

FIG. 6 is a diagram showing an example of the configuration of the rectifier circuit of Example 5. FIG. 7 is a diagram showing another example of the configuration of the rectifier circuit according to the fifth embodiment.

Example 5 is a modification of Example 1. The fifth embodiment differs from the first embodiment in that the rectifier circuit 2 is built into the semiconductor package, and the other configurations and effects are basically the same as the first embodiment. Therefore, in the fifth embodiment, differences from the first embodiment will be mainly explained, and explanations that overlap with the first embodiment will be omitted. Note that although FIGS. 6 and 7 of Example 5 are explained using an example applied to FIG. May be applied.

FIG. 6 shows a configuration in which the rectifier circuit 2 is built into the semiconductor package 3. The semiconductor package 3 has a cathode K and an anode A as external terminals.

FIG. 7 shows a configuration in which a plurality of rectifier circuits 2, such as a bridge circuit configured using four rectifier circuits 2, are built into one semiconductor package 4. The semiconductor package 4 has terminals T1 to T4 as external terminals.

According to Example 5, when designing and manufacturing a product that uses a rectifier circuit, it is sufficient to purchase and incorporate a rectifier circuit with a built-in drive circuit and capacitor as in this example, and the design of the drive circuit and capacitor is simple. This has the effect of reducing the overall design and implementation man-hours.

FIG. 8 is a circuit diagram of the power supply of Example 6.

Example 6 is an example of a power supply to which the rectifier circuit 2 described in Examples 1 to 5 is applied.

The scope of application of the rectifier circuits 2 of Examples 1 to 5 is all rectifier circuits used in power supplies. For example, in a front-end power supply as shown in FIG. 8, the rectifier circuits of Embodiments 1 to 5 are used as commercial rectifier diodes CRD1 to CRD4, free-wheeling diodes FWD, secondary rectifier diodes SSD1 to SSD2, and backflow prevention diodes BPD. 2 is applicable.

By applying the rectifier circuit 2 of Examples 1 to 5 to a power source such as a front-end power source, it is possible to contribute to downsizing and cost reduction of the power source.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the embodiments, and various changes can be made within the scope of the technical idea of the present invention. Further, some or all of the configurations described in each embodiment may be combined and applied.

1: Drive circuit, 2: Rectifier circuit, 3, 4: Semiconductor package, T1 to T4: Terminal, K: Cathode, A: Anode, C1, C2: Capacitor, R1, R2, R3: Resistor, Q1, Q2: MOSFET , DQ1, DQ2: body diode, D: diode, Co1, Co2: comparator, GD1, GD2: gate driver, CTR: control circuit, t, t0 to t5: time, Ic: charging current, Vc1: capacitor voltage, Vref1 , Vref2: threshold voltage, Vcref1: target voltage of capacitor C1, Vcref2: lower limit voltage of capacitor C1, Vf: forward voltage of diode D, Vds1 to Vds2: drain-source voltage of MOSFETs Q1 to Q2, Vgs1 to Vgs2: Gate-source voltage of MOSFETQ1~Q2, Vgth1~Vgth2: Gate threshold voltage of MOSFETQ1~Q2, CRD1~CRD4: Commercial rectifier diode, FWD: Freewheeling diode, SSD1~SSD2: Secondary side rectifier diode, BPD: Backflow prevention diode

Claims

In 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 first terminal and an anode connected to the second terminal;
a drive circuit that drives the first switching element;
a first capacitor that supplies power to the drive circuit;
The first capacitor has a first charging period and a second charging period in which the first capacitor is charged during a period from when the first switching element is turned off to when it is next turned on, and a second charging period when the first switching element is charged. A rectifier circuit comprising a charging stop period provided between the first charging period and the second charging period in which charging of the first capacitor is stopped.
In claim 1,
The first charging period and the second charging period are periods in which the voltage between the first terminal and the second terminal of the first switching element is equal to or lower than a predetermined voltage,
The rectifier circuit, wherein the charging stop period is a period in which a voltage between the first terminal and the second terminal of the first switching element is higher than the predetermined voltage.
In claim 2,
The first charging period is a period during which the voltage between the first terminal and the second terminal of the first switching element is increasing,
The rectifier circuit is characterized in that the second charging period is a period during which a voltage between the first terminal and the second terminal of the first switching element is decreasing.
In claim 2,
a second switching element whose third terminal is connected to the first terminal of the first switching element;
a second diode having an anode connected to the fourth terminal of the second switching element and a cathode connected to the third terminal of the second switching element;
a third diode whose anode is connected to the fourth terminal of the second switching element;
the first capacitor having a positive terminal connected to the cathode of the third diode and a negative terminal connected to the second terminal of the first switching element;
a control circuit that inputs a signal for controlling the second switching element to a control terminal of the second switching element,
The drive circuit receives power from the first capacitor and detects a voltage between the fourth terminal of the second switching element and the second terminal of the first switching element. 1 comparator, an input terminal is connected to an output terminal of the first comparator, an output terminal is connected to a control terminal of the first switching element, power is supplied from the first capacitor, and the first a first gate driver that controls the first switching element based on the output signal of the comparator;
The control circuit is configured such that a voltage between the first terminal and the second terminal of the first switching element is a sum of a target voltage of the first capacitor and a forward voltage of the third diode. In a period below the voltage, the second switching element is controlled to be on, and the voltage between the first terminal and the second terminal of the first switching element is equal to the target voltage of the first capacitor. A rectifier circuit, characterized in that the charging current flowing to the first capacitor is controlled by controlling the second switching element to be in an off state during a period when the total voltage is greater than the sum of the forward voltage of the diode and the forward voltage of the diode.
In claim 4,
The first switching element is a first MOSFET in which the first terminal is a drain terminal, the second terminal is a source terminal, and the control terminal is a gate terminal,
The rectifier circuit, wherein the first diode is a body diode of the first MOSFET.
In claim 4,
The rectifier circuit, wherein the second switching element is a second MOSFET in which the third terminal is a drain terminal, the fourth terminal is a source terminal, and the control terminal is a gate terminal.
In claim 6,
A rectifier circuit characterized in that the second MOSFET is an n-channel depression type MOSFET.
In claim 4,
The target voltage of the first capacitor is the maximum rated voltage of the first comparator, the maximum rated voltage of the first gate driver, and the voltage between the control terminal and the second terminal of the first switching element. A rectifier circuit characterized in that the voltage is less than or equal to the minimum of the maximum rated voltages between.
In claim 4,
A rectifier circuit characterized in that the control circuit includes a differentiating circuit for determining timing for controlling the second switching element.
In claim 4,
The first comparator has a first threshold voltage and a second threshold voltage, and detects the fourth terminal of the second switching element and the second terminal of the first switching element. an on signal is generated when the voltage between the two voltages is smaller than the first threshold voltage, and an off signal is generated when the voltage is larger than the second threshold voltage, and the first threshold voltage is the second threshold voltage. A rectifier circuit characterized in that the voltage is below.
In claim 4,
The control circuit includes a first resistor and a second resistor that divide the voltage between the first terminal and the second terminal of the first switching element; a second comparator that is supplied and detects the voltage of the second resistor, an input terminal connected to the output terminal of the second comparator, and an output terminal connected to the control terminal of the second switching element; and a second gate driver to which power is supplied from the first capacitor and which controls the second switching element based on the output signal of the second comparator.
In claim 4,
a third resistor having a fifth terminal connected to the first terminal of the first switching element and a sixth terminal connected to the third terminal of the second switching element; Features a rectifier circuit.
In claim 4,
A rectifier comprising a second capacitor having a positive terminal connected to the fourth terminal of the second switching element and a negative terminal connected to the second terminal of the first switching element. circuit.
In any one of claims 1 to 13,
A rectifier circuit, wherein the rectifier circuit is built into a semiconductor package, and the anode and cathode of the rectifier circuit are external terminals of the semiconductor package.
In any one of claims 1 to 13,
A rectifier circuit characterized in that a plurality of the rectifier circuits are built into one semiconductor package.
A power source comprising the rectifier circuit according to any one of claims 1 to 13.