A low-cost rectification filter circuit

Abstract

The utility model provides a low -cost rectifier filter circuit, after the alternating current is converted into pulse direct current in MOS pipe rectifier circuit, the current size on sampling resistance is detected through comparator and compares with preset current value, thereby making the output end of comparator corresponding output high level or low level, make the control first N type MOS pipe conduction or cut -off, charge and discharge for filter capacitor, thereby pulse direct current is converted into smooth direct current and is exported, avoid the serious heat of traditional diode rectifier filter circuit, the big energy consumption does not need to adopt the controller chip of special use to control simultaneously, control logic structure is simple, and adopt the N type MOS pipe cooperation control of lower cost, thereby effectively reduced the cost of the whole cosmetic filter. At the same time, when input ac voltage is less than filter capacitor voltage, cut off the first N type MOS pipe thoroughly blocks the back flow of filter capacitor energy to ac input end, prevents the backflow damage device and helps to reduce the cost of rectifier filter.

Description

Technical Field

[0001] This utility model relates to the field of rectifier filtering technology, and in particular to a low-cost rectifier filtering circuit. Background Technology

[0002] While the global power grid primarily uses alternating current (AC), most electronic devices rely on direct current (DC) for operation. This contradiction stems from historical evolution and efficiency trade-offs. Rectifier and filter circuits, as crucial components, bear the core responsibility of efficiently and stably converting AC into the smooth DC required by the equipment.

[0003] Traditional solutions use silicon diodes or Schottky diodes to build rectifier bridges. Although diodes themselves are inexpensive, their inherent forward voltage drop (VF) and reverse recovery loss will be converted into considerable heat loss during operation, directly increasing the system's thermal management costs and energy consumption costs.

[0004] To address the efficiency issues of diodes, using MOSFETs to replace diodes for synchronous rectification has become a popular choice. However, MOSFET rectification and filtering circuits often rely on complex dedicated controller ICs to precisely drive the switching timing of the MOSFETs, ensuring they are turned on and off in the correct phase. This increases the cost of the controller itself and the surrounding drive circuitry. Moreover, the complex circuit design and additional components make the overall solution more expensive, hindering its widespread adoption.

[0005] Therefore, it is necessary to optimize the rectifier and filter circuit using MOSFETs and provide a rectifier and filter circuit that is low in energy consumption, simple to control, and low in cost. Utility Model Content

[0006] To address the problems of low efficiency, complex structure, and high cost in existing rectifier and filter circuits, this invention provides a low-cost rectifier and filter circuit. The rectifier circuit uses a parasitic diode to perform basic rectification. When the input AC voltage exceeds Vgs, the corresponding MOS transistor is turned on to improve efficiency. The filter circuit uses a first N-type MOS transistor with a parasitic diode to perform basic functions. When the current generated on the sampling resistor exceeds a set value, the first N-type MOS transistor is turned on to improve efficiency.

[0007] A low-cost rectifier-filter circuit includes a MOSFET rectifier circuit and a filter circuit. A first N-type MOSFET with a built-in parasitic diode, a first N-type MOSFET control circuit, and a sampling resistor are further provided between the MOSFET rectifier circuit and the filter circuit. The filter circuit includes a filter capacitor, and the first N-type MOSFET control circuit includes a comparator. The output terminal of the MOSFET rectifier circuit is connected to the positive terminal of the comparator and the first terminal of the filter capacitor. The first terminal of the filter capacitor is also connected to the first terminal of the DC output terminal, and the second terminal of the filter capacitor is connected to the first terminal of the sampling resistor and the second terminal of the DC output terminal, respectively. The second terminal of the comparator is grounded and connected to the source of the first N-type MOS transistor; the drain of the first N-type MOS transistor is connected to ground; the non-inverting input of the comparator is connected to the first terminal of the sampling resistor; the inverting input of the comparator is connected to the reference voltage; the output of the comparator is connected to the gate of the first N-type MOS transistor; the MOS transistor rectifier circuit is used to convert the AC input from an AC input terminal into a pulsed DC current and output it; the comparator is used to detect the current on the sampling resistor and compare it with a preset current value, and output a high level or low level to control the conduction or cutoff of the first N-type MOS transistor; the filter capacitor is used to convert the pulsed DC current into a smooth DC current.

[0008] Furthermore, a first P-type MOSFET, a second P-type MOSFET, a second N-type MOSFET, and a third N-type MOSFET, each with a built-in parasitic diode, are provided between the MOSFET rectifier circuit and the filter circuit. The drain of the second N-type MOSFET is connected to the drain of the first P-type MOSFET and to the first terminal of an AC input. The gate of the second N-type MOSFET is connected to the gate of the first P-type MOSFET and to the second terminal of the AC input. The drain of the third N-type MOSFET is connected to the drain of the second P-type MOSFET and to the second terminal of an AC input. The gate of the third N-type MOSFET is connected to the gate of the second P-type MOSFET and to the first terminal of the AC input. The source of the second N-type MOSFET is connected to the source of the third N-type MOSFET and to ground. The source of the first P-type MOSFET is connected to the source of the second P-type MOSFET and to the positive terminal of the comparator and the first terminal of the filter capacitor.

[0009] Furthermore, a resistor R4 is connected in parallel between the source and gate of both the second and third N-type MOS transistors; a resistor R5 is connected in parallel between the source and gate of both the first and second P-type MOS transistors.

[0010] Furthermore, the gates of the second N-type MOS transistor and the first P-type MOS transistor are respectively connected to a resistor R6 and then connected to the first terminal of the AC input terminal; the gates of the third N-type MOS transistor and the second P-type MOS transistor are respectively connected to a resistor R7 and then connected to the second terminal of the AC input terminal.

[0011] Furthermore, the inverting input terminal of the comparator is connected to ground through resistor R1, and to the anode of a diode D through resistor R2. The anode of the diode D is also connected to the positive terminal of the comparator through resistor R3, and the cathode of the diode D is grounded. This causes resistors R2 and R3 to divide the voltage and generate the reference voltage.

[0012] Furthermore, the filter capacitor is a polarized capacitor.

[0013] The beneficial effects of this utility model are as follows: This utility model provides a low-cost rectifier and filter circuit. After the AC power is converted into pulsed DC power by the MOS tube rectifier circuit, the current on the sampling resistor is detected by the comparator and compared with the preset current value, so that the output terminal of the comparator outputs a high level or a low level, thereby controlling the conduction or cutoff of the first N-type MOS tube, charging and discharging the filter capacitor, thus converting the pulsed DC power into smooth DC power and outputting it. While avoiding the serious heat generation and high energy consumption of traditional diode rectifier and filter circuits, it does not require the use of a dedicated controller chip for control. The control logic structure is simple, and the low-cost N-type MOS tube is used for control, thereby effectively reducing the cost of rectifier and filter.

[0014] Meanwhile, when the input AC voltage is less than the filter capacitor voltage, the current on the sampling resistor is less than the preset current value, and the comparator output is low, which turns off the first N-type MOSFET, cuts off the path between the MOSFET rectifier circuit and the filter capacitor, completely blocks the backflow of energy from the filter capacitor to the AC input terminal, prevents backflow from damaging the device, and thus significantly improves the rectification and filtering efficiency, which helps to reduce the cost of rectification and filtering. Attached Figure Description

[0015] Figure 1 A schematic diagram of the structure of a high-efficiency rectifier filter circuit provided by this utility model; Figure 2 This is a schematic diagram illustrating the principle of a high-efficiency rectifier and filter circuit provided by this utility model.

[0016] Attached Figure Labels

[0017] 1. MOSFET rectifier circuit; 2. Filter circuit; 21. Filter capacitor; 3. First N-type MOSFET control circuit; 4. Sampling resistor; 5. AC input terminal; 6. DC output terminal; 7. Comparator; Q1, First P-type MOSFET; Q2, Second P-type MOSFET; Q3, Second N-type MOSFET; Q4, Third N-type MOSFET; Q5, First N-type MOSFET. Detailed Implementation

[0018] To better understand the above-mentioned objectives, features, and advantages of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0019] refer to Figure 2 As shown, a low-cost rectifier and filter circuit includes a MOS transistor rectifier circuit 1 and a filter circuit 2.

[0020] Specifically, a first N-type MOSFET Q5 with a built-in parasitic diode, a first N-type MOSFET control circuit 3, and a sampling resistor 4 are provided between the MOSFET rectifier circuit 1 and the filter circuit 2, and the filter circuit 2 includes a filter capacitor 21. In this embodiment, the filter capacitor is a polarized capacitor.

[0021] The MOS transistor rectifier circuit 1 is used to convert the AC power input at an AC input terminal 5 into pulsed DC power and output it; the first N-type MOS transistor control circuit 3 includes a comparator 7; the filter capacitor 2 is used to convert the pulsed DC power into smooth DC power.

[0022] The MOSFET rectifier circuit includes a first P-type MOSFET Q1, a second P-type MOSFET Q2, a second N-type MOSFET Q3, and a third N-type MOSFET Q4; each of the first P-type MOSFET Q1, the second P-type MOSFET Q2, the second N-type MOSFET Q3, and the third N-type MOSFET Q4 has a built-in parasitic diode.

[0023] The drain of the second N-type MOSFET Q3 is connected to the drain of the first P-type MOSFET Q1 and is connected to the first terminal of an AC input terminal 5; the gate of the second N-type MOSFET Q3 is connected to the gate of the first P-type MOSFET Q1 and is connected to the second terminal of the AC input terminal 5; the drain of the third N-type MOSFET Q4 is connected to the drain of the second P-type MOSFET Q2 and is connected to the second terminal of an AC input terminal 5; the gate of the third N-type MOSFET Q4 is connected to the gate of the second P-type MOSFET Q2 and is connected to the first terminal of the AC input terminal 5; the source of the second N-type MOSFET Q3 is connected to the source of the third N-type MOSFET Q4 and is connected to ground; the source of the first P-type MOSFET Q1 is connected to the source of the second P-type MOSFET Q2 and is connected to the positive terminal of the comparator 7 and the first terminal of the filter capacitor 21.

[0024] When the first terminal of AC input 5 is positive relative to the second terminal, meaning the AC current input to AC input 5 is in the positive half-cycle, the gates of the first P-type MOSFET Q1 and the second N-type MOSFET Q3 are both at low level, so Q1 is turned on and Q3 is turned off. The gates of the second P-type MOSFET Q2 and the third N-type MOSFET Q4 are both at high level, so Q2 is turned off and Q4 is turned on. When the first terminal of AC input 5 is negative relative to the second terminal, meaning the AC current input to AC input 5 is in the negative half-cycle, the gates of the first P-type MOSFET Q1 and the second N-type MOSFET Q3 are both at high level, so Q1 is turned off and Q3 is turned on. The gates of the second P-type MOSFET Q2 and the third N-type MOSFET Q4 are both at low level, so Q2 is turned on and Q4 is turned off. During the positive and negative half-cycles of the AC current input to AC input 5, the corresponding MOSFETs are turned on, converting the AC current input to AC input 5 into pulsating DC current and outputting it.

[0025] The first N-type MOSFET control circuit is used to control the conduction and cutoff of the first N-type MOSFET Q5 connected in reverse according to the current on the sampling resistor 4. When the current on the sampling resistor 4 is less than a preset current threshold, the gate voltage of the first N-type MOSFET control circuit 3 increases and it conducts; otherwise, it is turned off, thereby realizing the rectification and filtering function.

[0026] In this circuit, the output terminal of the MOS transistor rectifier circuit 1 is connected to the positive terminal of the comparator 7 and the first terminal of the filter capacitor 2; the first terminal of the filter capacitor 2 is also connected to the first terminal of the DC output terminal 6, and the second terminal of the filter capacitor 2 is connected to the first terminal of the sampling resistor 4 and the second terminal of the DC output terminal 6, respectively; the second terminal of the sampling resistor 4 is grounded and connected to the source of the first N-type MOS transistor Q5; the drain of the first N-type MOS transistor Q5 is connected to ground; the non-inverting input terminal of the comparator 7 is connected to the first terminal of the sampling resistor 4; the inverting input terminal of the comparator 7 is connected to the reference voltage; and the output terminal of the comparator 7 is connected to the gate of the first N-type MOS transistor.

[0027] A pulsating DC current flows from the negative terminal of the filter capacitor 21 into the first terminal of the sampling resistor 4, and then from the second terminal of the sampling resistor 4 to GND, resulting in a voltage drop across the sampling resistor 4 that is proportional to the current across the sampling resistor 4. The comparator 7 is used to detect the current across the sampling resistor 4 and compare it with a preset current value, correspondingly outputting a high or low level to control the conduction or cutoff of the first N-type MOSFET Q5.

[0028] Specifically, when the pulsating DC voltage output by the MOSFET rectifier circuit 1 is higher than the voltage of the filter capacitor 21, current flows through the MOSFET rectifier circuit 1 to the filter capacitor 2 and the DC output terminal 6, forming an output current flowing through the sampling resistor. The comparator 7 detects that the current on the sampling resistor 4 exceeds the preset current threshold. At this time, the voltage drop across the sampling resistor 4 increases, and the voltage at the non-inverting input terminal is higher than that at the inverting input terminal, causing the output terminal of the comparator 7 to output a high level. This raises the gate voltage of the first N-type MOSFET Q5, causing it to conduct. At this time, the pulsed DC current charges the filter capacitor 21, raising its voltage to near the AC peak value. The pulsed DC current is then filtered to output a smooth DC current.

[0029] When the pulsating DC voltage output by the MOSFET rectifier circuit 1 is less than the voltage of the filter capacitor 21 (for example, at the end of the positive half-cycle), and the energy of the filter capacitor 21 is about to flow back to the AC input terminal 5, the comparator 7 detects that the current on the sampling resistor 4 is less than the preset current threshold, and the voltage drop of the sampling resistor 4 decreases. At this time, the voltage at the non-inverting input terminal is less than that at the inverting input terminal, and the output terminal of the comparator 7 outputs a low level, which reduces the gate voltage of the first N-type MOSFET Q5, and the first N-type MOSFET Q5 is turned off. At this time, the path between the MOSFET rectifier circuit 1 and the filter capacitor 21 is cut off, and the filter capacitor 21 discharges independently to the DC output terminal, maintaining a smooth output voltage through its energy storage characteristics, realizing the filtering function, and outputting smooth DC power to the DC output terminal 6; at the same time, it completely blocks the backflow of energy from the filter capacitor 21 to the AC input terminal, reducing the return energy loss. When the first N-type MOSFET Q5 is turned off, the cathode of its built-in parasitic diode is grounded. When the anode potential rises, the cathode potential rises synchronously, causing its parasitic diode to be reverse biased and unable to conduct, thus preventing reverse current and assisting comparator 7 as an alternative to prevent energy backflow.

[0030] Finally, when the pulsating DC voltage output by the MOSFET rectifier circuit rises again, the first N-type MOSFET control circuit detects that the current on the sampling resistor exceeds the preset current threshold. At this time, the voltage drop across the sampling resistor increases, the output of comparator 7 outputs a high level, the first N-type MOSFET turns on, and a new round of charging and discharging of filter capacitor 21 begins.

[0031] In some embodiments, the inverting input 7 of the comparator is connected to ground through resistor R1 and to the anode of a diode D through resistor R2. The anode of the diode D is also connected to the positive terminal of the comparator 7 through resistor R3, and the cathode of the diode D is grounded. This causes resistors R2 and R3 to divide the voltage to generate the reference voltage. A capacitor C is connected in parallel with resistor R1.

[0032] By adding resistors R1 and C to the non-inverting input of comparator 7, a low-pass filter network is formed. A direct grounding path is established through resistor R1, and the low impedance characteristic of capacitor C to high-frequency noise is utilized to enhance the anti-interference capability of the non-inverting input reference of the operational amplifier. This helps to ensure the gate control signal judgment reference of the first N-type MOS transistor and eliminate the misjudgment of the control of the first N-type MOS transistor caused by grounding noise.

[0033] The DC output voltage of the positive terminal of the filter capacitor C is sampled in real time through a voltage divider network formed by resistors R2 and R3, and the generated reference voltage is supplied to the positive terminal of comparator 7 to realize the dynamic tracking of the output fluctuation of the comparator operating voltage; at the same time, a diode D is connected in parallel between the voltage divider node and the system ground to form a voltage clamp and protect the comparator input terminal from overvoltage or negative voltage damage.

[0034] In some embodiments, a resistor R4 is connected in parallel between the source and gate of the second N-type MOSFET Q3 and the third N-type MOSFET Q4; a resistor R5 is connected in parallel between the source and gate of the first P-type MOSFET Q1 and the second P-type MOSFET Q2. Resistors R4 and R5 provide a low-resistance discharge path to protect the MOSFETs and are also used for electrostatic discharge.

[0035] In some embodiments, the gates of the second N-type MOSFET Q3 and the first P-type MOSFET Q1 are each connected to a resistor R6 and then connected to the first terminal of the AC input terminal 5; the gates of the third N-type MOSFET Q4 and the second P-type MOSFET Q2 are each connected to a resistor R7 and then connected to the second terminal of the AC input terminal 5. Resistors R6 and R7 can limit the surge current to a safe value, thus protecting the MOSFETs.

[0036] This invention provides a low-cost rectifier and filter circuit. It uses a MOS rectifier circuit 1 composed of P-type MOS transistors and N-type MOS transistors to convert AC power into pulsed DC power. MOS transistors have lower internal resistance, higher efficiency, and lower heat generation compared to diodes when conducting, making them particularly suitable for low-voltage, high-current applications.

[0037] Then, the comparator 7 detects the current on the sampling resistor 4 and compares it with the preset current value, so that the output of the comparator 7 outputs a high level or a low level, controlling the conduction or cutoff of the first N-type MOSFET Q5, charging and discharging the filter capacitor 21, thereby converting the pulsed DC current into smooth DC current and outputting it. While avoiding the serious heat generation and high energy consumption of traditional diode rectifier filter circuits, it does not require a dedicated controller chip to control the conduction or cutoff of the first N-type MOSFET Q5. The control logic structure is simple, and the use of low-cost N-type MOSFETs for control effectively reduces the cost of rectifier filtering.

[0038] Meanwhile, when the input AC voltage is less than the filter capacitor voltage, the current on the sampling resistor 4 is less than the preset current value, and the output of the comparator 7 is low, which turns off the first N-type MOSFET Q5, cuts off the path between the MOSFET rectifier circuit 1 and the filter capacitor 21, completely blocks the backflow of energy from the filter capacitor 21 to the AC input terminal, prevents backflow from damaging the device, and thus significantly improves the rectification and filtering efficiency, which helps to reduce the cost of rectification and filtering.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0040] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A low-cost rectifier-filter circuit, comprising a MOSFET rectifier circuit and a filter circuit, characterized in that, Between the MOS rectifier circuit and the filter circuit, there is also a first N-type MOS transistor with a built-in parasitic diode, a first N-type MOS transistor control circuit, and a sampling resistor. The filter circuit includes a filter capacitor, and the first N-type MOS transistor control circuit includes a comparator. The output terminal of the MOS rectifier circuit is connected to the positive terminal of the comparator and the first terminal of the filter capacitor. The first end of the filter capacitor is also connected to the first end of the DC output terminal, and the second end of the filter capacitor is connected to the first end of the sampling resistor and the second end of the DC output terminal, respectively; the second end of the sampling resistor is grounded and connected to the source of the first N-type MOS transistor; the drain of the first N-type MOS transistor is connected to ground. The non-inverting input of the comparator is connected to the first terminal of the sampling resistor; the inverting input of the comparator is connected to the reference voltage; and the output of the comparator is connected to the gate of the first N-type MOS transistor. The MOS transistor rectifier circuit is used to convert the AC input at an AC input terminal into pulsed DC and output it; the comparator is used to detect the current on the sampling resistor and compare it with a preset current value, and output a high level or low level to control the conduction or cutoff of the first N-type MOS transistor; the filter capacitor is used to convert the pulsed DC into smooth DC.

2. A low cost rectifier filter circuit as claimed in claim 1, characterized in that, Between the MOSFET rectifier circuit and the filter circuit, there are also a first P-type MOSFET, a second P-type MOSFET, a second N-type MOSFET, and a third N-type MOSFET, each with a built-in parasitic diode. The first P-type MOSFET, the second P-type MOSFET, the second N-type MOSFET, and the third N-type MOSFET all have built-in parasitic diodes. The drain of the second N-type MOSFET is connected to the drain of the first P-type MOSFET and is also connected to the first terminal of an AC input terminal. The gate of the second N-type MOSFET is connected to the gate of the first P-type MOSFET and is also connected to the second terminal of the AC input terminal. The drain of the third N-type MOS transistor is connected to the drain of the second P-type MOS transistor and is connected to the second terminal of an AC input terminal; the gate of the third N-type MOS transistor is connected to the gate of the second P-type MOS transistor and is connected to the first terminal of the AC input terminal. The source of the second N-type MOS transistor is connected to the source of the third N-type MOS transistor and then connected to ground; the source of the first P-type MOS transistor is connected to the source of the second P-type MOS transistor and then connected to the positive terminal of the comparator and the first terminal of the filter capacitor.

3. A low cost rectifier filter circuit as claimed in claim 2, characterized in that, A resistor R4 is connected in parallel between the source and gate of both the second and third N-type MOS transistors; a resistor R5 is connected in parallel between the source and gate of both the first and second P-type MOS transistors.

4. A low cost rectifier filter circuit as claimed in claim 2, wherein, The gates of the second N-type MOS transistor and the first P-type MOS transistor are respectively connected to a resistor R6 and then connected to the first terminal of the AC input terminal; the gates of the third N-type MOS transistor and the second P-type MOS transistor are respectively connected to a resistor R7 and then connected to the second terminal of the AC input terminal.

5. A low-cost rectifier filter circuit according to claim 1, characterized in that, The inverting input of the comparator is connected to ground through resistor R1 and to the anode of a diode D through resistor R2. The anode of the diode D is also connected to the positive terminal of the comparator through resistor R3, and the cathode of the diode D is grounded. This causes resistors R2 and R3 to divide the voltage and generate the reference voltage.

6. The low-cost rectifier filter circuit according to claim 1, characterized in that, The filter capacitor is a polarized capacitor.

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