Rectification circuit and ac / DC converter

Abstract

To downsize an AC / DC converter.SOLUTION: A first input terminal IN1 and a second input terminal IN2 are connected to an AC voltage 2. A half-wave rectifier 202 charges a smoothing capacitor C1 during a half cycle Tp in which the AC voltage VAC is positive, and generates a half-wave rectified voltage VC1 in the smoothing capacitor C1. The half-wave rectifier 202 is so configured as to be capable of switching the conductive / cut-off state of a path for charging the smoothing capacitor C1 per half cycle Tp. A controller 222 controls the conductive / cut-off state of the charging route on the basis of the voltage VC1 between both ends of the smoothing capacitor C1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a rectifier circuit and an AC / DC converter. [Background technology]

[0002] AC / DC converters are used to supply power from commercial AC power sources to electronic devices. An AC / DC converter includes a rectifier circuit that rectifies the AC voltage, and a DC / DC converter that converts the output voltage of the rectifier circuit to a voltage level suitable for the load.

[0003] AC / DC converters of 75W or less that do not require power factor correction (PFC) typically use an AC rectifier circuit that combines a diode bridge and an electrolytic capacitor. In this configuration, the electrolytic capacitor generates a voltage that is approximately √2 times the AC input voltage. This means that it is necessary to select an electrolytic capacitor with a high voltage resistance of, for example, 400V. This electrolytic capacitor has been an obstacle to miniaturizing and reducing the cost of AC / DC converters. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2024-001433

[0005] [overview] The present disclosure has been made in view of the above circumstances, and one of its exemplary purposes is to reduce the size of an AC / DC converter.

[0006] One aspect of the present disclosure relates to a rectifier circuit including first and second input terminals for receiving an AC voltage, a smoothing capacitor, a half-wave rectifier connected to the first and second input terminals, charging the smoothing capacitor during a half cycle of the AC voltage to generate a half-wave rectified voltage in the smoothing capacitor, and being capable of switching between conduction and interruption of a charging path to the smoothing capacitor during the half cycle, and a controller controlling the conduction and interruption of the charging path in accordance with the voltage across the smoothing capacitor.

[0007] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram of an AC / DC converter according to a first embodiment. [Figure 2] FIG. 2 is a waveform diagram illustrating the operation of the AC / DC converter of FIG. [Figure 3] FIG. 3 is a circuit diagram showing a modification of the AC / DC converter of FIG. [Figure 4] FIG. 4 is a circuit diagram of an AC / DC converter according to the second embodiment. [Figure 5] FIG. 5 is a waveform diagram illustrating the operation of the AC / DC converter of FIG.

[0009] [Detailed explanation] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. This summary is not an exhaustive overview of all possible embodiments, and is not intended to identify key elements of all embodiments or to delineate the scope of some or all aspects. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0010] A rectifier circuit according to one embodiment includes a first input terminal and a second input terminal to be connected to an AC power source, a smoothing capacitor, a half-wave rectifier connected to the first input terminal and the second input terminal, charging the smoothing capacitor during a half cycle of the AC voltage to generate a half-wave rectified voltage in the smoothing capacitor, and configured to be able to switch the conduction / cutoff of a charging path to the smoothing capacitor during the half cycle, and a controller that controls the conduction / cutoff of the charging path depending on the voltage across the smoothing capacitor.

[0011] With this configuration, the voltage across the smoothing capacitor is clamped, thereby lowering the withstand voltage required of the smoothing capacitor. This allows a small electrolytic capacitor to be used as the smoothing capacitor, making it possible to reduce the size and cost of the device.

[0012] In one embodiment, the half-wave rectifier may include a clamp transistor, which is a unidirectional switch, connected between the first input terminal and the first end of the smoothing capacitor, and a rectifier diode, which is connected between the second input terminal and the second end of the smoothing capacitor. The controller may control the clamp transistor. Furthermore, by incorporating the clamp transistor, which is a unidirectional switch, into a current loop including the rectifier diode and the smoothing capacitor, and by setting the current conduction direction of the unidirectional switch in its off state to be opposite to that of the rectifier diode, the charging path to the smoothing capacitor can be switched between conduction and interruption. This configuration allows for a smaller circuit area than when the diode bridge circuit and the voltage clamp circuit are configured separately.

[0013] In one embodiment, the half-wave rectifier may include a clamp transistor that is a bidirectional switch connected between one of the first input terminal and the second input terminal and the first end of the smoothing capacitor, and the controller may control the clamp transistor.

[0014] With this configuration, by configuring the rectifying elements of the half-wave rectifier with transistors, the on-resistance can be reduced compared to when they are configured with diodes, thereby improving efficiency. Furthermore, the rectifying elements also serve as switches for switching the charging path of the smoothing capacitor between conduction and interruption, thereby reducing the circuit area. Furthermore, the circuit area can be reduced compared to when the diode bridge circuit and voltage clamp circuit are configured separately.

[0015] In one embodiment, a first end of the smoothing capacitor may be connected to an input terminal of a downstream DC / DC converter, and a second end of the smoothing capacitor may be connected to a ground line of the DC / DC converter.

[0016] In one embodiment, a first end of the smoothing capacitor may be connected to the ground line of a downstream DC / DC converter, and a second end of the smoothing capacitor may be connected to the input terminal of the DC / DC converter.

[0017] An AC / DC converter according to one embodiment may include any of the rectifier circuits described above and a DC / DC converter connected to the rectifier circuit.

[0018] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. Furthermore, the embodiments are examples and do not limit the disclosure and invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure and invention.

[0019] In this specification, "a state in which component A is connected to component B" includes not only a case in which component A and component B are directly physically connected to each other, but also a case in which component A and component B are indirectly connected to each other via other components that do not substantially affect the electrical connection between them or that do not impair the function or effect achieved by their connection.

[0020] Similarly, "a state in which component C is provided between component A and component B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect the electrical connection state between them or impair the functions or effects achieved by their combination.

[0021] (Embodiment 1) 1 is a circuit diagram of an AC / DC converter 100 according to a first embodiment. The AC / DC converter 100 receives an AC voltage V AC DC voltage V OUT Convert to AC voltage V AC alternates between positive half-periods Tp and negative half-periods Tn.

[0022] The AC / DC converter 100 includes a rectifier circuit 200 and a DC / DC converter 300 .

[0023] The rectifier circuit 200 converts the AC voltage V AC is half-wave rectified and smoothed to produce a DC input voltage V IN The DC / DC converter 300 converts the DC input voltage V IN , the DC output voltage V OUT Convert to.

[0024] The rectifier circuit 200 includes a half-wave rectifier 202 and a controller 222 .

[0025] The first input terminal IN1 and the second input terminal IN2 of the rectifier circuit 200 are connected to an AC power source 2, and an AC voltage V AC receive.

[0026] The half-wave rectifier 202 is connected to the first input terminal IN1 and the second input terminal IN2. The half-wave rectifier 202 outputs an AC voltage V AC During the half-period Tp when is positive, the charging current I C and the half-wave rectified voltage V is supplied to the smoothing capacitor C1. C1 occurs.

[0027] The half-wave rectifier 202 converts the AC voltage V AC is positive, the charging path to the smoothing capacitor C1 can be switched between conductive and cut-off.

[0028] The controller 222 controls the voltage V across the smoothing capacitor C1. C1 The charging path is controlled to be turned on or off depending on the voltage.

[0029] In this embodiment, the half-wave rectifier 202 includes a rectifier diode D1, a clamp transistor Q3, and a gate driver 224.

[0030] The rectifier diode D1 is connected between the second input terminal IN2 and the second end e2 of the smoothing capacitor C1, with its cathode facing the second input terminal IN2. The clamp transistor Q3 is connected between the first input terminal IN1 and the first end e1 of the smoothing capacitor C1. When the clamp transistor Q3 is in the off state, it is a unidirectional switch that blocks the conduction direction of the rectifier diode D1 and the current in one direction. The clamp transistor Q3 can be configured as an N-channel MOSFET with its drain and backgate connected.

[0031] A first terminal e1 of the smoothing capacitor C1 is connected to the input terminal of the DC / DC converter 300, and a second terminal e2 of the smoothing capacitor C1 is connected to a ground line 102 common to the rectifier circuit 200 and the DC / DC converter 300. That is, the voltage V across the smoothing capacitor C1 C1 However, the input voltage V IN Supplied as.

[0032] The rectifier circuit 200 has a voltage clamp function. The controller 222 controls the voltage V across the smoothing capacitor C1. C1 In response to this, the clamp transistor Q3 is controlled to be turned on or off.

[0033] The controller 222 controls the voltage (referred to as the capacitor voltage) V of the smoothing capacitor C1. C1 The controller 222 generates a control signal S1 that instructs the clamp transistor Q3 to be turned on or off based on the voltage V between both ends of the smoothing capacitor C1. C1 However, it is sufficient to generate it so that it does not exceed a certain threshold.

[0034] For example, the controller 222 may be configured to control an AC voltage V AC is the capacitor voltage V C1 When the voltage V V becomes lower, the control signal S1 changes to a level corresponding to turning on the clamp transistor Q3. C1 is the threshold voltage V THWhen this voltage is exceeded, the control signal S1 is changed to a level corresponding to turning off the clamp transistor Q3.

[0035] The gate driver 224 controls the gate voltage V of the clamp transistor Q3 based on the control signal S1. G3 Since the source of the clamp transistor Q3 is a floating node, the gate driver 224 may be configured as an isolated gate drive circuit.

[0036] The above is the configuration of the rectifier circuit 200. Next, the DC / DC converter 300 will be described.

[0037] There are no particular limitations on the topology of the DC / DC converter 300, and an isolated or non-isolated converter can be used. For example, the DC / DC converter 300 may be an asymmetrical half-bridge (AHB) converter.

[0038] The DC / DC converter 300 includes a half-bridge circuit 310, a transformer T1, a resonant capacitor C2, a diode D2, an output capacitor C3, a controller 320, and a gate driver 330. The half-bridge circuit 310 includes a high-side transistor Q1 and a low-side transistor Q2. The controller 320 controls the output voltage V OUT The gate driver 330 generates a control signal S2, which is a pulse signal, so that the gate voltage V of the high-side transistor Q1 and the low-side transistor Q2 approaches a target level. The method for generating the control signal S2 is not particularly limited, and pulse width modulation, pulse frequency modulation, etc. may be used. The gate driver 330 controls the gate voltage V of the high-side transistor Q1 and the low-side transistor Q2 in response to the control signal S2. G1 ,V G2 occurs.

[0039] The controller 222, the gate driver 224, the controller 320, and the gate driver 330 may be integrated on a single semiconductor substrate to form a control IC (Integrated Circuit). The controller 222, the controller 320, and the gate driver 330 are connected to the rectifier circuit 200 and a common ground line 102, and operate based on a common reference voltage (ground voltage).

[0040] The above is the configuration of the AC / DC converter 100. Next, the operation thereof will be described.

[0041] 2 is a waveform diagram illustrating the operation of the AC / DC converter 100 of FIG. 2. In FIG. 2, from the top, the AC voltage V AC , rectified voltage V RECT and the voltage V of the smoothing capacitor C1 C1 (Input voltage V IN ), the charging current I flowing through the smoothing capacitor C1 C , a control signal S1 is shown which instructs the clamp transistor Q3 to be on or off.

[0042] Rectified voltage V RECT is the AC voltage V AC The control signal S1 is high, that is, the clamp transistor Q3 is on during the period T ON , V RECT >V C1 When this occurs, the smoothing capacitor C1 is charged and the voltage V C1 is the rectified voltage V RECT It rises following the

[0043] At time t1, the rectified voltage V RECT (AC voltage V AC ) is the threshold voltage V TH When the voltage V reaches 1 V, the control signal S1 goes low and the clamp transistor Q3 turns off. OFF The smoothing capacitor C1 is discharged by the input current of the DC / DC converter 300 and decreases over time.

[0044] At time t2, the AC voltage V AC is the voltage V of the smoothing capacitor C1 C1 When the voltage Vcc becomes lower, the control signal S1 goes high and the clamp transistor Q3 turns on. The AC / DC converter 100 repeats the above operation.

[0045] The above is the operation of the AC / DC converter 100. In this AC / DC converter 100, the AC voltage V AC In the half period Tp where is positive, V AC >V TH (V RECT >V TH ), the clamp transistor Q3 is turned off, and the voltage V across the smoothing capacitor C1 C1 By clamping the voltage, the withstand voltage required for the smoothing capacitor C1 can be lowered. This allows the use of a small electrolytic capacitor as the smoothing capacitor C1, making it possible to reduce the size and cost of the device.

[0046] Furthermore, by incorporating a clamp transistor Q3, which is a unidirectional switch, into the current loop including the rectifier diode D1 and smoothing capacitor C1 and using it to clamp the voltage of the smoothing capacitor C1, the circuit area can be made smaller than when the diode bridge circuit and voltage clamp circuit are configured separately.

[0047] Fig. 3 is a circuit diagram showing a modification of the AC / DC converter 100A of Fig. 1. The DC / DC converter 300 at the subsequent stage is the same as that in Fig. 1.

[0048] The following describes the differences between the rectifier circuit 200A in Fig. 3 and the rectifier circuit 200 in Fig. 1. In Fig. 3, the positions of the clamp transistor Q3 and the rectifier diode D1 are swapped. A first terminal e1 of the smoothing capacitor C1 is connected to the ground line 102 of the DC / DC converter in the subsequent stage, and a second terminal e2 of the smoothing capacitor C1 is connected to the input terminal of the DC / DC converter 300.

[0049] In this configuration, the source of the clamp transistor Q3 is connected to the ground line 102 and has a fixed potential, so that the gate driver 224A that drives the clamp transistor Q3 can have a simple, non-insulated configuration.

[0050] When the AC / DC converter 100A starts up, the clamp transistor Q3 is off, and the smoothing capacitor C1 cannot be charged by the path including the clamp transistor Q3 and the rectifier diode D1. As a result, the power supply voltage V required for the operation of the rectifier circuit 200A and the DC / DC converter 300 is low. CC Therefore, at startup, the input voltage V AC The power supply voltage V for starting the circuit based on CC1 A voltage circuit 240 is provided to generate a voltage.

[0051] (Embodiment 2) 4 is a circuit diagram of an AC / DC converter 100B according to the second embodiment. A half-wave rectifier 202B includes a smoothing capacitor C1 and a clamp transistor Q4. The clamp transistor Q4 is a bidirectional switch that is configured to block current in both directions when in the off state. This clamp transistor Q4 also functions as the rectifier diode D1 and the clamp transistor Q3 in the first embodiment.

[0052] The controller 222B controls the AC voltage V AC In the half period Tn when the AC voltage V is negative, the controller 222B generates a control signal S1 so that the clamp transistor Q4 is turned off. This allows the clamp transistor Q4 to function as a rectifier diode. AC In the half-period Tp when is positive, the voltage V of the smoothing capacitor C1 C1 is the threshold V TH The clamp transistor Q4 is controlled so that the voltage does not exceed the threshold.

[0053] 5 is a waveform diagram illustrating the operation of the AC / DC converter 100B of FIG. 4. In FIG. 5, from the top, the AC voltage VAC , rectified voltage V RECT and the voltage V of the smoothing capacitor C1 C1 (Input voltage V IN ), the charging current I flowing through the smoothing capacitor C1 C , a control signal S1 is shown which instructs the clamp transistor Q4 to be on or off.

[0054] Rectified voltage V RECT is the AC voltage V AC It is a virtual voltage obtained by half-wave rectifying the AC voltage V AC In the half-period Tn when the voltage is negative, the clamp transistor Q4 is turned off, realizing half-wave rectification. In other words, the clamp transistor Q4 functions as a synchronous rectification switch.

[0055] At time t0, the AC voltage V AC (rectified voltage V AC When the capacitor voltage VC1 is exceeded, the control signal S1 goes high and the clamp transistor Q4 is turned on. ON , the smoothing capacitor C1 is charged, and the voltage V C1 is the rectified voltage V RECT It rises following the

[0056] At time t1, the rectified voltage V RECT (AC voltage V AC ) is the threshold voltage V TH When the voltage V reaches 1 V, the control signal S1 goes low and the clamp transistor Q4 turns off. OFF The smoothing capacitor C1 is discharged by the input current of the DC / DC converter 300 and decreases over time.

[0057] The AC / DC converter 100B repeats the above operations.

[0058] In the rectifier circuit 200B according to the second embodiment, the rectifier elements of the half-wave rectifier 202B are configured with transistors, which reduces the on-resistance and improves efficiency compared to when they are configured with diodes. Furthermore, the rectifier elements also function as switches for switching the charging path of the smoothing capacitor between conduction and interruption, which reduces the circuit area. Furthermore, the circuit area can be reduced compared to when the diode bridge circuit and the voltage clamp circuit are configured separately.

[0059] Although the embodiments of the present disclosure have been described using specific terms, this description is merely an example to facilitate understanding and does not limit the scope of the present disclosure or the claims, and the scope of the present invention is defined by the claims. Furthermore, not only the embodiments but also embodiments, examples, and modifications not described herein are included in the scope of the present invention.

[0060] The circuit topology of the DC / DC converter 300 is not particularly limited, and can be selected to suit the power and application of the AC / DC converter 100. For example, the DC / DC converter 300 may be a flyback converter, a forward converter, or a full-bridge converter. In applications that do not require isolation, the DC / DC converter 300 can be a non-insulated converter such as a buck converter, a boost converter, or a buck-boost converter.

[0061] (Addendum) One aspect of the technology disclosed in this specification can be understood as follows.

[0062] (Item 1) a first input terminal and a second input terminal for receiving an AC voltage; a smoothing capacitor; a half-wave rectifier connected to the first input terminal and the second input terminal, charging the smoothing capacitor in a half cycle of the AC voltage to generate a half-wave rectified voltage in the smoothing capacitor, and configured to be able to switch between conducting and blocking a charging path to the smoothing capacitor in the half cycle; a controller that controls conduction and interruption of the charging path in accordance with a voltage across the smoothing capacitor; A rectifier circuit comprising:

[0063] (Item 2) The half-wave rectifier a clamp transistor which is a unidirectional switch connected between the first input terminal and a first end of the smoothing capacitor; a rectifier diode connected between the second input terminal and the second end of the smoothing capacitor; Item 2. The rectifier circuit of item 1, wherein the controller controls the clamp transistor.

[0064] (Item 3) The half-wave rectifier a clamp transistor which is a bidirectional switch connected between one of the first input terminal and the second input terminal and a first end of the smoothing capacitor; Item 2. The rectifier circuit of item 1, wherein the controller controls the clamp transistor.

[0065] (Item 4) 4. The rectifier circuit according to any one of items 1 to 3, wherein the first end of the smoothing capacitor is connected to an input terminal of a downstream DC / DC converter, and the second end of the smoothing capacitor is connected to a ground line of the DC / DC converter.

[0066] (Item 5) 4. The rectifier circuit according to any one of items 1 to 3, wherein the first end of the smoothing capacitor is connected to a ground line of a downstream DC / DC converter, and the second end of the smoothing capacitor is connected to an input terminal of the DC / DC converter.

[0067] (Item 6) Item 6. A rectifier circuit according to any one of items 1 to 5; a DC / DC converter connected to the rectifier circuit; An AC / DC converter comprising: [Explanation of symbols]

[0068] 2...AC power supply, 100...AC / DC converter, 102...ground line, 200...rectifier circuit, 202...half-wave rectifier, Q3...clamp transistor, Q4...clamp transistor, C1...smoothing capacitor, D1...rectifier diode, 222...controller, 224...gate driver, C2...resonant capacitor, C3...output capacitor, T1...transformer, Q1...high-side transistor, Q2...low-side transistor, 300...DC / DC converter, 310...half-bridge circuit, S1...control signal, 320...controller, 330...gate driver

Claims

1. a first input terminal and a second input terminal for receiving an AC voltage; a smoothing capacitor; a half-wave rectifier connected to the first input terminal and the second input terminal, charging the smoothing capacitor in a half cycle of the AC voltage to generate a half-wave rectified voltage in the smoothing capacitor, and configured to be able to switch between conduction and interruption of a charging path to the smoothing capacitor in the half cycle; a controller that controls conduction and interruption of the charging path in accordance with a voltage across the smoothing capacitor; A rectifier circuit comprising:

2. The half-wave rectifier a clamp transistor, which is a unidirectional switch, connected between the first input terminal and the first end of the smoothing capacitor; a rectifier diode connected between the second input terminal and the second end of the smoothing capacitor; 2. The rectifier circuit of claim 1, wherein the controller controls the clamp transistor.

3. The half-wave rectifier a clamp transistor which is a bidirectional switch connected between one of the first input terminal and the second input terminal and a first end of the smoothing capacitor; The rectifier circuit of claim 1 , wherein the controller controls the clamp transistor.

4. 4. The rectifier circuit according to claim 1, wherein the first end of the smoothing capacitor is connected to an input terminal of a downstream DC / DC converter, and the second end of the smoothing capacitor is connected to a ground line of the DC / DC converter.

5. 4. The rectifier circuit according to claim 1, wherein the first end of the smoothing capacitor is connected to a ground line of a downstream DC / DC converter, and the second end of the smoothing capacitor is connected to an input terminal of the DC / DC converter.

6. A rectifier circuit according to any one of claims 1 to 3; a DC / DC converter connected to the rectifier circuit; An AC / DC converter comprising:

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