CN221428773U

CN221428773U - Novel digital power totem pole PFC current sampling and overcurrent protection circuit

Info

Publication number: CN221428773U
Application number: CN202323536241.1U
Authority: CN
Inventors: 李伟; 赵琴琴; 高小朋
Original assignee: Huada Semiconductor Chengdu Co ltd
Current assignee: Huada Semiconductor Chengdu Co ltd
Priority date: 2023-12-22
Filing date: 2023-12-22
Publication date: 2024-07-26
Anticipated expiration: 2033-12-22

Abstract

The utility model relates to a novel digital power supply totem pole PFC current sampling and overcurrent protection circuit. The circuit comprises a transformer, a transformer output demagnetizing circuit, a transformer sampling unidirectional rectifying circuit, a sampling resistor, a first sampling input end, a second sampling input end, a sampling current circuit, a sampling output end and a sampling channel. According to the utility model, two paths of sampling channels are directly pulled to the comparison port of the digital micro control unit or the system-level chip through resistor voltage division, and a 12V comparator is not required to be added for level conversion, so that the effects of reducing delay, simplifying a circuit and saving cost can be achieved.

Description

Novel digital power totem pole PFC current sampling and overcurrent protection circuit

Technical Field

The utility model relates to the technical field of circuit control, in particular to a novel digital power supply totem pole PFC current sampling and overcurrent protection circuit.

Background

In a conventional PFC (Power Factor Correction ) circuit, the loss of the rectifier bridge diode always poses a considerable challenge to overall efficiency and heat dissipation management of the power supply, and if a switch configured by a Totem Pole is used to replace the conventional diode, and meanwhile, the boost PFC function is integrated, the bridge stack loss can be greatly reduced, and the overall energy efficiency is remarkably improved. The totem pole PFC includes two main control modes: CCM (Continuous Current Mode, current continuous mode) and TCM (triangular current mode, delta current mode) control modes. The TCM mode is a further version of CRM (Critical conduction mode ). The CCM control mode is mainly used in high-power occasions, the main pipe switch is not high in general frequency due to hard-on, and the applicability is poor in occasions (such as a server power supply and a communication power supply) with low power and high power density. The TCM mode is mainly used for occasions with medium power and higher requirements on power density, and the frequency can reach more than 1Mhz under the clamping of a third-generation semiconductor at present, so that the power density of a power supply is greatly increased.

Unlike the auxiliary tube current of the CRM mode, which is reduced to 0, the auxiliary tube is turned off, the totem pole PFC power supply can reversely freewheel for a short period of time after the auxiliary tube current is reduced to 0 in the TCM mode, and the auxiliary tube is turned off after the auxiliary tube current reaches a given reverse current value of 1-2A. And discharging the charge on the output capacitor of the main pipe through reverse current freewheeling in the PFC inductor until the Vds of the main pipe is reduced to 0, and then opening the main pipe for driving, thereby realizing ZVS (Zero Voltage Switching ) of the main pipe. And the ZVS of the main pipe is realized, so that the frequency of the main pipe can be designed to be higher, and the volume is made to be smaller.

When the main pipe and the auxiliary pipe are switched in the positive half cycle and the negative half cycle of the mains supply, the upper pipe and the lower pipe of the half bridge are alternately switched to serve as the main pipe and the auxiliary pipe, so that the sampling current can be positive or negative. The current industry mainly has three current sampling schemes based on a ZVS scheme of current sampling control: a shunt, a fluxgate or a hall sensing IC, a transformer.

The shunt is mainly a resistor with low resistance, and can measure the actual current value by detecting the voltage flowing through the resistor. The advantage of the current divider is the full range bandwidth (or bandwidth dependent on the op-amp), and the volume is small. However, the current divider has obvious disadvantages that a certain amount of energy is consumed, and meanwhile, the cost is high because the half-bridge upper tube sampling needs to be conducted by an isolated operational amplifier or one path of isolated power supply. The controlled ground can be set as the common point of the current divider without an operational amplifier, however, the potential change of the point is larger in practice, the influence on the control circuit is larger, and the engineering application is more complex.

The advantage of the fluxgate or the Hall sensing IC is that the fluxgate or the Hall sensing IC is isolated, the circuit design is simple, the disadvantage is mainly that the bandwidth is not wide enough, the current bandwidth is generally about 500K, and the higher bandwidth cost can rise linearly. Moreover, if fluxgate or hall sensing ICs are applied to totem pole of third generation semiconductor strips, the bandwidth is significantly inadequate. Therefore, bandwidth limits the application of such current sampling schemes in third generation semiconductor totem pole PFC hyperfrequency.

The transformer uses the magnetic flux change of the magnetic core caused by the primary side current, the secondary side coil induces corresponding current, and the corresponding current flows through a low resistance to generate a voltage, and the voltage is sent to an ADC interface or a COMP interface of a digital MCU (Microcontroller Unit, a micro-control unit) for sampling or comparison, so that corresponding logic judgment is performed. The mutual inductor has the characteristics of isolation and bandwidth of MHZ level, and low delay can meet the practical application requirements.

In a practical transformer current sampling design, the secondary sampling current of the transformer needs to be used as a current sample of 1A-2A for ZVS freewheel control, while also being used as OCP (Over Current Protection, over-current protection) control for the main tube 15A or larger sampling current. 1A and 15A require a relatively high accuracy, but the sampling range of the ADC of the SOC or the input voltage range of the input IO port of the CMP comparator of the SOC requires 0-3.3V. The actual engineering debugging requires more than 0.4 scale corresponding to 1A to ensure that the TCM_PFC can perform better compensation at the zero crossing point. Therefore, 0.4a×15a=6v, which is far greater than the IO pin required voltage of the SOC. Aiming at the contradiction between the high-scale and high-precision sampling requirement of 1A and the fact that OCP sampling exceeds IO regulated voltage, a new circuit needs to be provided to solve the contradiction point.

In addition, during the soft start process of tcm_pfc, the reverse 1A current detection of the auxiliary pipe may have abnormal detection, and the common method is to sample the current in the power frequency pipe and use the current as negative current detection to make negative auxiliary pipe current OCP. The transformer itself is bulky and costly. Therefore, new control schemes need to be introduced to optimize the current sampling of the power frequency pipe.

Disclosure of utility model

Aiming at part or all of the problems in the prior art, the utility model provides a novel digital power totem pole PFC current sampling and overcurrent protection circuit, which comprises a transformer, a transformer output demagnetizing circuit, a transformer sampling unidirectional rectifying circuit, a sampling resistor, a first sampling input end, a second sampling input end, a sampling current circuit, a sampling output end and a sampling channel;

The transformer comprises a primary winding and a secondary winding, one end of the primary winding is the first sampling input end, the other end of the primary winding is the second sampling input end, the secondary winding is connected with the transformer output demagnetizing circuit in parallel, one end of the secondary winding is electrically connected with an anode terminal of the transformer sampling unidirectional rectifying circuit at the same time, and the other end of the secondary winding is electrically connected with one end of the sampling resistor at the same time;

The cathode terminal of the mutual inductor sampling unidirectional rectification circuit is electrically connected with the other end of the sampling resistor and one end of the sampling current circuit;

The first sampling input end is electrically connected with the power frequency pipe or the PFC inductor, and the second sampling input end is electrically connected with the high-frequency pipe;

The sampling output end is electrically connected with the primary winding of the transformer and the high-frequency tube and comprises an output filter capacitor and an output load which are connected in parallel;

The sampling channel is connected to a comparator input pin of the system on chip.

Further, the transformer is a high-frequency tube current sampling transformer, and current flowing through the high-frequency tube is sampled alternately in a sine period, so that the transformer is used for main tube overcurrent protection, negative current turn-off auxiliary tube and negative current overcurrent protection.

Further, the transformer output demagnetizing circuit ensures that the voltage at two ends of the transformer is within a certain range, and a demagnetizing channel of the transformer is ensured during turn-off.

Further, the resistance value of the sampling resistor is within 100 omega.

Further, the sampling current circuit includes a plurality of resistors.

Further, the sampling channel includes a plurality of resistors.

Further, the maximum resistance value of the plurality of resistors of the sampling channel is preferably 30 times or more the maximum resistance value of the plurality of resistors of the sampling current circuit.

Further, when the transformer is in the main tube current sampling, the sampling channel is mainly used for current overcurrent protection detection of the main tube circuit; when the mutual inductor is used as an auxiliary pipe to detect reverse follow current, the sampling channel is used for detecting negative current sampling and negative current overcurrent protection respectively.

Further, the sampling current circuit is controlled by using an insulated gate field effect transistor, an insulated gate bipolar transistor or a bipolar transistor.

Further, the sampling channel is controlled by using an insulated gate field effect transistor, an insulated gate bipolar transistor or a bipolar transistor.

Compared with the prior art, the utility model has the beneficial effects that:

1. By improving the scale of the sampling current, a good basic condition is provided for the accurate control of the negative current of the sine zero crossing point.

2. The two paths of sampling channels are directly pulled to the comparison port of the digital micro control unit or the system-level chip through resistor voltage division, and a 12V comparator is not needed to be added for level conversion, so that the effects of reducing delay, simplifying a circuit and saving cost can be achieved.

3. Under the soft start working condition, the negative current overcurrent protection of the sampling channel is realized through the overcurrent protection, CT sampling is not needed to be added on a power frequency pipe for overcurrent protection, and the whole PCB space and the system cost can be reduced.

Drawings

To further clarify the above and other advantages and features of embodiments of the present utility model, a more particular description of embodiments of the utility model will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the utility model and are therefore not to be considered limiting of its scope. In the drawings, for clarity, the same or corresponding parts will be designated by the same or similar reference numerals.

Fig. 1 is a schematic diagram of a novel digital power totem pole PFC current sampling and overcurrent protection circuit according to one embodiment of the present utility model;

fig. 2 is a schematic diagram of a range of two-channel sampling currents of a novel digital power totem pole PFC current sampling and overcurrent protection circuit according to an embodiment of the present utility model.

Detailed Description

In the following description, the present utility model is described with reference to various embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other alternative and/or additional methods or components. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the utility model. Similarly, for purposes of explanation, specific numbers and configurations are set forth in order to provide a thorough understanding of embodiments of the present utility model. However, the utility model is not limited to these specific details.

Reference throughout this specification to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present utility model. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

The technical solutions in the embodiments of the present utility model are clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model.

Fig. 1 is a schematic diagram of a novel digital power totem pole PFC current sampling and overcurrent protection circuit according to one embodiment of the present utility model. As shown in fig. 1, the circuit comprises transformers CT1 and CT2, transformer output demagnetizing circuits D2/D3/R1 and D6/D7/R9, transformer sampling unidirectional rectifying circuits D4 and D8, sampling resistors R2 and R10, a first sampling input terminal, a second sampling input terminal, a sampling current circuit, a sampling output terminal, and a sampling channel.

As shown in fig. 1, a first sampling input end of a transformer CT1 is electrically connected with a drain electrode of a power frequency tube Q1, a source electrode of the power frequency tube Q1 is electrically connected with a drain electrode of a power frequency tube Q2 and an input signal ac_n, and a source electrode of the power frequency tube Q2 is electrically connected with a source electrode of a high frequency tube Q4; the second sampling input end of the transformer CT1 is electrically connected with the drain electrode of the high-frequency tube Q3; the first sampling input end of the transformer CT2 is electrically connected with the PFC inductor L1 and the source electrode of the high-frequency tube Q3; the second sampling input end of the transformer CT2 is electrically connected with the drain electrode of the high-frequency tube Q4; the input signal AC_L is electrically connected with the PFC inductor L1; the input signals PWM1, PWM2, PWM3, PWM4 are electrically connected to the gates of the power frequency pipe Q1, the power frequency pipe Q2, the high frequency pipe Q3, and the high frequency pipe Q4, respectively.

The mutual inductor CT1/CT2 is a high-frequency tube current sampling mutual inductor, and is used for executing alternating sampling of current flowing through the high-frequency tube Q3/Q4 in a sine period and is used for main tube overcurrent protection, negative current turn-off auxiliary tube and negative current overcurrent protection. The transformer comprises a primary winding and a secondary winding, wherein one end of the primary winding is the first sampling input end, and the other end of the primary winding is the second sampling input end.

As shown in fig. 1, a secondary winding of a transformer CT1 is connected in parallel with a transformer output demagnetizing circuit D2/D3/R1, a cathode terminal of D2 is electrically connected with one end of the secondary winding of the transformer CT1, one end of a resistor R1 and an anode terminal of a transformer sampling unidirectional rectifying circuit D4, a cathode terminal of D3 is electrically connected with the other end of the secondary winding of the transformer CT1, the other end of the resistor R1, one end of a sampling resistor R2 and the ground, and an anode terminal of D2 is electrically connected with an anode terminal of D3; the secondary winding of the transformer CT2 is connected with the transformer output demagnetizing circuit D6/D7/R9 in parallel, the cathode terminal of the D6 is electrically connected with one end of the secondary winding of the transformer CT2, one end of the resistor R9 and the anode terminal of the transformer sampling unidirectional rectifying circuit D8, the cathode terminal of the D7 is electrically connected with the other end of the secondary winding of the transformer CT2, the other end of the resistor R9, one end of the sampling resistor R10 and the ground, and the anode terminal of the D6 is electrically connected with the anode terminal of the D7.

The output demagnetizing circuit of the transformer ensures that the voltage at two ends of the transformer is within a certain range, and a demagnetizing channel of the transformer is ensured during turn-off.

The positive half period and the negative half period of the whole sine wave are currents in one direction, so that D4 and D8 are mutual inductor sampling unidirectional rectification circuits. The cathode terminal of the mutual inductor sampling unidirectional rectification circuit D4 is electrically connected with the other end of the sampling resistor R2 and one end of the R3 in the sampling current circuit. The cathode terminal of the mutual inductor sampling unidirectional rectification circuit D8 is electrically connected with the other end of the sampling resistor R10 and one end of the R11 in the sampling current circuit.

The resistance values of the sampling resistors R2 and R10 are within 100 omega.

As shown in FIG. 1, the sampling current circuit comprises a plurality of resistors, R2/R3/R6 forms the sampling current circuit of the transformer CT1, one end of R6 is connected to the clamping voltage of 2.5V, R10/R11/R12 forms the sampling current circuit of the transformer CT2, and one end of R12 is connected to the clamping voltage of 2.5V. In one embodiment of the utility model, the sampling current circuit is controlled using an insulated gate field effect transistor, or an insulated gate bipolar transistor, or a bipolar transistor.

As shown in fig. 1, the sampling output terminal includes an output filter capacitor C1 and an output load R18 connected in parallel. One ends of the sampling output ends C1 and R18 are electrically connected with one end of a primary winding of the transformer CT1, and the connection point voltage is Vout. The other ends of the sampling output ends C1 and R18 are electrically connected with the source electrode of the high-frequency tube Q4 and grounded.

As shown in FIG. 1, sample1/Sample2/Sample3/Sample4 is taken as 4 sampling channels, which include comparator input pins connected to the system on chip SOC.

The sampling channel includes a plurality of resistors. As shown in FIG. 1, R5/D5 forms an OCP sampling channel when the CT1 down tube is used as a main tube and a negative current OCP sampling channel when the CT1 down tube is used as an auxiliary tube, namely a Sample1 sampling channel; R4/R7 forms an OCP sampling channel when the CT1 upper tube is used as a main tube and a negative current OCP sampling channel when the CT1 upper tube is used as an auxiliary tube, namely a Sample2 sampling channel; R13/D9 forms an OCP sampling channel when the CT2 lower pipe is used as a main pipe and a negative current OCP sampling channel when the CT2 lower pipe is used as an auxiliary pipe, namely a Sample3 sampling channel; R14/R15 forms an OCP sampling channel when the CT2 upper tube is used as a main tube and a negative current OCP sampling channel when the CT2 upper tube is used as an auxiliary tube, namely a Sample4 sampling channel. The cathode terminals of D4, D9 are connected to a clamping voltage of 2.5V. In one embodiment of the utility model, the sampling channel is controlled using an insulated gate field effect transistor, or an insulated gate bipolar transistor, or a bipolar transistor.

The control principle of the circuit of the present utility model is described below with reference to fig. 1.

Because of the alternating positive and negative half cycles, transformer CT2 is selected for analysis. Assuming that the primary side current is triangular wave current with the peak value of Ip, the turn ratio of the primary side winding to the secondary side winding of the transformer CT2 is 1: n, the output sampling voltage Vs formula is:

Vs＝2.5*(R10+R11)/(R10+R11+R12)+Ip/n*(R12*R10)/(R10+R11+R12)

Where, represents multiplication,/represents division. Assuming that r12=20k, r11=10k, r10=60, n=100, and input current ip=15a, the range of two-channel sampling currents as shown in fig. 2 can be simulated. The sampling scale of the output current of the transformer is 1A corresponding to 0.4V.

In order to facilitate detection of an IO port of the SOC, the SOC is divided into two sampling channels, a first channel and a second channel. The first channel is the Sample3 sampling channel in fig. 1, and the second channel is the Sample4 sampling channel in fig. 1.

A first channel: r13 and D9, the maximum output voltage of the auxiliary tube negative current detection circuit formed by clamping voltage 2.5V is clamped at 3.3V, and the interval of detection current is smaller.

A second channel: r14 and R15, the voltage of the current sample of the transformer is reduced to be below 3.3V through voltage division, the actual detection precision is reduced relative to the first channel, but the precision for protection can be slightly lower than that of control.

Meanwhile, when the transformer CT2 is in the auxiliary tube freewheel state, the first channel is used as a detection reverse 1A freewheel channel, and the second channel can be used as an overcurrent protection circuit for detecting failure of the reverse freewheel 1A, which is approximately designed to be about 5A, and such a working condition mainly occurs in a special working condition, such as soft start. Therefore, sampling by using a transformer on the power frequency pipe can be avoided for protection.

The transformer sampling circuit comprises two channels, wherein when the transformer is in main pipe current sampling, the sampling channels are mainly used for current overcurrent protection detection of the main pipe circuit; when the mutual inductor is used as an auxiliary pipe to detect reverse follow current, the sampling channel is used for detecting negative current sampling and negative current overcurrent protection respectively.

In order to avoid influencing the sampling circuit, the maximum resistance value in R13/R14/R15 of the sampling channel is preferably more than 30 times of the maximum resistance value in R10/R11/R12 of the sampling current circuit.

The novel digital power totem pole PFC current sampling and overcurrent protection circuit provided by the utility model can be extended to a two-phase or multi-phase staggered digital power totem pole PFC circuit. In one embodiment of the present utility model, the auxiliary tube reverse current comparator may use an external comparator.

According to the novel digital power totem pole PFC current sampling and overcurrent protection circuit, two paths of sampling channels are directly pulled to the comparison port of the digital micro control unit or the system-level chip through resistor voltage division, a 12V comparator is not required to be added for level conversion, and the effects of reducing delay, simplifying the circuit and saving cost can be achieved.

While various embodiments of the present utility model have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to those skilled in the relevant art that various combinations, modifications, and variations can be made therein without departing from the spirit and scope of the utility model. Thus, the breadth and scope of the present utility model as disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. The novel digital power totem pole PFC current sampling and overcurrent protection circuit is characterized by comprising a transformer, a transformer output demagnetizing circuit, a transformer sampling unidirectional rectifying circuit, a sampling resistor, a first sampling input end, a second sampling input end, a sampling current circuit, a sampling output end and a sampling channel;

2. The totem pole PFC current sampling and overcurrent protection circuit of claim 1, wherein the transformer is a high frequency tube current sampling transformer that performs alternating sampling of current flowing through the high frequency tube in a sinusoidal cycle for main tube overcurrent protection, negative current turn-off auxiliary tube, and negative current overcurrent protection.

3. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the transformer output demagnetization circuit ensures that a voltage across the transformer is within a range and that a demagnetization channel of the transformer is ensured during turn-off.

4. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the sampling resistor has a resistance within 100 Ω.

5. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the sampling current circuit comprises a plurality of resistors.

6. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the sampling channel comprises a plurality of resistors.

7. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein a maximum resistance value of the plurality of resistors of the sampling channel is preferably greater than 30 times a maximum resistance value of the plurality of resistors of the sampling current circuit.

8. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the sampling channel is primarily used as current over-current protection detection for a main circuit when the transformer is in main current sampling; when the mutual inductor is used as an auxiliary pipe to detect reverse follow current, the sampling channel is used for detecting negative current sampling and negative current overcurrent protection respectively.

9. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the sampling current circuit is controlled using insulated gate field effect transistors, or insulated gate bipolar transistors, or bipolar transistors.

10. The totem pole PFC current sampling and over-current protection circuit of claim 1, wherein the sampling channel is controlled using an insulated gate field effect transistor, or an insulated gate bipolar transistor, or a bipolar transistor.