CN218301226U - Voltage reduction circuit and power supply system - Google Patents

Abstract

The embodiment of the application provides a voltage reduction circuit and a power supply system, and relates to the technical field of power supply circuits. The voltage reduction circuit comprises a switch tube and a capacitor, the first end of the switch tube is electrically connected with the first end of the capacitor, the second end of the switch tube and the second end of the capacitor are used for connecting two ends of an input power supply, the first end and the second end of the capacitor are also used for connecting two ends of a load, and the control end of the switch tube is used for connecting a controller. The fast recovery diode and the inductor are not needed, the voltage reduction is realized by the switching tube and the capacitor, the number of devices is saved, and the cost is reduced.

Description

Voltage reduction circuit and power supply system

Technical Field

The application relates to the technical field of power supply circuits, in particular to a voltage reduction circuit.

Background

In recent years, household appliances using an inverter control method have rapidly spread to achieve energy saving, and among them, an air conditioner inverter Circuit is divided into a Main Circuit (Main Circuit) and a control Circuit (Controller Circuit) for controlling the Main Circuit as shown in fig. 1.

As shown in fig. 1, the meanings of the symbols in the figure are as follows: v _AC A Power supply, a Main Circuit, a Controller Circuit-control Circuit, a D1, a D2, a D3, a D4-rectifier bridge, a C1-electrolytic capacitor, and an IPM-Intelligent Power Module. The control circuit comprises a control power supply (1), a communication circuit (2) and an MCU (single chip microcomputer) circuit (3), wherein the control power supply provides power for the driving communication circuit and the MCU circuit and needs to output various voltages, for example, the air conditioner control power supply outputs 15V, 12V, 5V and 3.3V voltage.

As shown in fig. 2, the meanings of the symbols in the figure are as follows: v _AC -AC power supply, D5, D6, D7, D8-rectifier bridge, C2-electrolytic capacitor, circuit 1-snubber Circuit, IC 1-switching power supply IC, T1-isolation transformer. In the conventional technique of fig. 2, in order to output a plurality of voltages at a time, it is necessary to use an insulating transformer T1 having a plurality of channels, and to output various voltages by switching the main pole side by a control IC (IC 1).

However, in recent years, in view of miniaturization and cost reduction of the controller, as shown in fig. 3, the respective symbols in the figure have the following meanings: v _DC Main circuit of frequency converter V _DC The Circuit comprises a Circuit2, a voltage reduction Circuit, C3, C4 and C5 electrolytic capacitors, D10, D11, D12 and D13 diodes, and an IC2 and IC3 linear voltage stabilizer. FIG. 3 uses a main circuit V using a frequency converter _DC Voltage is applied directly to a non-insulated control power supply system using a self-excited power supply IC. (self-excited is the way in which the IC generates its own supply voltage without taking power from elsewhere.)

However, in general, the self-excited power supply IC outputs only 1 channel, and if other various voltages are to be output, a circuit of only about 3 watts is capable of outputting a plurality of voltages only by using a high-cost linear regulator as shown in fig. 3 and using a voltage drop of a plurality of diodes, which results in an increase in the number of devices and an increase in the cost. Further, in the linear regulator and the diode series connection type output various voltages, since repetitive currents (fig. (1) and (2)) are generated, the current capacity of the device needs to be increased, and the cost is also increased. Generally, the voltage reduction circuit in the prior art has more devices and higher cost.

Therefore, how to reduce the cost of the voltage reduction circuit is a technical problem to be solved.

SUMMERY OF THE UTILITY MODEL

An object of the application is to provide a step-down circuit and a power supply system to solve the technical problem of how to reduce the cost of the step-down circuit in the prior art.

In order to achieve the above purpose, the embodiments of the present application adopt the following technical solutions.

In a first aspect, an embodiment of the present application provides a voltage dropping circuit, including: the power supply comprises a switch tube and a capacitor, wherein the first end of the switch tube is electrically connected with the first end of the capacitor, the second end of the switch tube and the second end of the capacitor are used for connecting the two ends of an input power supply, the first end and the second end of the capacitor are also used for connecting the two ends of a load, and the control end of the switch tube is used for connecting a controller.

Optionally, the voltage reduction circuit further comprises a controller, and the control end of the switching tube is electrically connected with the PWM output end of the controller. Different voltage outputs are achieved by utilizing different duty ratios of signals at the PWM output end.

Optionally, the voltage reduction circuit further includes a voltage detection module, the voltage detection module is connected in parallel with the capacitor, and the voltage detection module is electrically connected with the controller.

Optionally, the voltage detection module includes a first resistor and a second resistor, a first end of the first resistor is electrically connected to a first end of the second resistor, a second end of the first resistor is electrically connected to a first end of the capacitor, a second end of the second resistor is electrically connected to a second end of the capacitor, and the first end of the first resistor is electrically connected to the AD end of the controller. The voltage is divided by the first resistor and the second resistor, and the output voltage is taken as feedback according to the proportion.

Optionally, the voltage reduction circuit further includes a comparator, the first end of the first resistor is electrically connected to the inverting input end of the comparator, the non-inverting input end of the comparator is used for being electrically connected to the reference voltage source, and the output end of the comparator is connected to the control end of the switching tube.

Optionally, the voltage-reducing circuit further includes a bias circuit, the bias circuit includes a third resistor and a fourth resistor, the third resistor is connected between the second end and the control end of the switching tube, and the control end of the switching tube is electrically connected to the PWM output end of the controller through the fourth resistor.

Optionally, the voltage reducing circuit further includes a driving circuit, and the control end of the switching tube is electrically connected to the PWM output end of the controller through the driving circuit.

Optionally, the voltage dropping circuit further includes a current limiting resistor connected between the first end of the capacitor and the first end of the switching tube.

In a second aspect, an embodiment of the present application provides a power supply system, including a first voltage-dropping circuit and a second voltage-dropping circuit, where the first voltage-dropping circuit and the second voltage-dropping circuit both belong to the voltage-dropping circuit of the first aspect, input ends of the first voltage-dropping circuit and the second voltage-dropping circuit are both connected to an input power supply, and output voltages of the first voltage-dropping circuit and the second voltage-dropping circuit are different.

In a third aspect, an embodiment of the present application provides a power supply system, including a first voltage-reducing circuit and a second voltage-reducing circuit, where the first voltage-reducing circuit and the second voltage-reducing circuit both belong to the voltage-reducing circuit of the first aspect, an input end of the first voltage-reducing circuit is connected to an input power supply, an output end of the first voltage-reducing circuit is electrically connected to an input end of the second voltage-reducing circuit, and an output voltage of the first voltage-reducing circuit is greater than an output voltage of the second voltage-reducing circuit.

Compared with the prior art, the method has the following beneficial effects:

the voltage reduction circuit and the power supply system provided by the embodiment of the application do not need a fast recovery diode and an inductor, voltage reduction is realized by using the switching tube and the capacitor, the number of devices is saved, and the cost is reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a schematic diagram of an inverter circuit of an air conditioner in the prior art;

FIG. 2 is a schematic diagram of a prior art step-down circuit for a multi-channel isolation transformer;

FIG. 3 is a schematic diagram of a voltage step-down circuit of a self-excited power supply IC in the prior art;

fig. 4 is a schematic diagram of a voltage step-down circuit according to an embodiment of the present disclosure;

FIG. 5 is a prior art buck circuit including a fast recovery diode and an inductor;

FIG. 6 is a schematic current diagram of the circuit of FIG. 5 at SW1 ON;

FIG. 7 is a schematic diagram of the circuit of FIG. 5 with the current at SW1 OFF;

FIG. 8 is a timing diagram of the current flow of the circuit of FIG. 5;

FIG. 9 is a voltage control system diagram of the circuit of FIG. 5;

FIG. 10 is a current schematic of the circuit of FIG. 4 at SW2 ON;

FIG. 11 is a timing diagram of the current and voltage at SW2 ON for the circuit of FIG. 4;

FIG. 12 is a schematic diagram of the circuit of FIG. 4 with the current at SW2 OFF;

FIG. 13 is a timing diagram of the current and voltage at SW2 OFF for the circuit of FIG. 4;

FIG. 14 is a circuit diagram of embodiment 1;

FIG. 15 is a control block diagram of embodiment 1;

FIG. 16 is a circuit diagram of embodiment 2;

FIG. 17 is a control block diagram of embodiment 2;

FIG. 18 is a circuit diagram of embodiment 3;

FIG. 19 is a circuit diagram of embodiment 4;

FIG. 20 is a schematic circuit diagram of embodiment 5.1;

FIG. 21 is a circuit diagram of embodiment 5.2;

FIG. 22 is a simulation diagram of the model of embodiment 1;

FIG. 23 is a graph showing simulation results of example 1;

FIG. 24 is a simulation diagram of the model of embodiment 2;

FIG. 25 is a graph showing simulation results of example 2;

FIG. 26 is a simulation diagram of the model of embodiment 3;

FIG. 27 is a graph showing simulation results of example 3;

FIG. 28 is a simulation diagram of the model of embodiment 4;

fig. 29 is a graph of simulation results of embodiment 4.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and the described embodiments are some embodiments, but not all embodiments, of the present application. The components of the embodiments of the present application, as generally described in the figures herein, may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

In the description of the present application, it is noted that relational terms such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The term "connected" is to be understood broadly, for example, as being fixedly connected, detachably connected, or integrally connected; may be directly connected or indirectly connected through an intermediate.

The existing voltage reduction circuit has more devices, and particularly, when various voltages need to be output, the number of the devices is large and the cost is high.

In order to overcome the above problem, referring to fig. 4, an embodiment of the present application provides a voltage reduction circuit, including: switch tube SW2 and capacitorC ₇ First end of switch tube SW2 and capacitor C ₇ Is electrically connected with the first end of the switch tube SW2, the second end of the switch tube SW2 and the capacitor C ₇ The second terminal of (2) is used for connecting the two ends of an input power supply, and a capacitor C ₇ Is also used for connecting a Load (Load R) _L ) And the control end of the switch tube SW2 is used for connecting the controller MCU.

A Circuit7 driving Circuit (e.g., a triode Circuit) may be connected to the PWM output terminal of the controller MCU, and may be disposed between the PWM output terminal of the controller MCU and the switching tube SW 2.

A Circuit5 voltage detection module and a capacitor C can be arranged ₇ And in parallel connection, the Circuit5 voltage detection module is connected to the AD end of the MCU, so that voltage feedback can be provided for the MCU. To obtain a large capacitance value, the capacitor C ₇ May be an electrolytic capacitor.

According to the embodiment of the application, a fast recovery diode and an inductor are not needed, voltage reduction is achieved through a switch tube and a capacitor, the number of devices is saved, and the cost is reduced. In contrast to fig. 5, fig. 5 shows a step-down circuit that requires a fast recovery diode D14 and an inductor L1, and more fast recovery diodes and inductors, which means higher cost, especially when a plurality of different voltages are to be output.

Specifically, each symbol in fig. 5 has the following meaning: DC-DC power supply, IC 4-switching power supply IC, SW 1-switching device, D14-fast recovery diode, L1-inductor, C ₆ Electrolytic capacitor, R _L Load (virtual resistance), circuit 3-controller, circuit 4-gate drive Circuit.

In FIG. 5, the input voltage V _IN The switching device SW1 is controlled to be switched to an arbitrary target voltage V by a control power supply IC4 with built-in switching devices SW1, circuit3, and Circuit4 _OUT . At this time, V _IN And V _OUT Is expressed by the following formula (1), and generates a load current I _RL And charging and discharging current I _C6 . Further, the output voltage V can be also found by the formula (1) _OUT With a fixed duty cycle and a fixed frequency f _sw Input voltage V _IN And (4) determining.

V _OUT ＝DutyV _IN (1)

Wherein the content of the first and second substances,

duty: duty cycle (% in units), i.e. the product of ON pulse width rate, ON time and switching frequency, i.e.

f _sw (unit Hz): switching frequency

T _ON (unit sec): ON time

T _OFF (unit sec): the OFF time.

The above will be explained in detail. When the switching device SW1 is ON, as shown in FIGS. 6 and 8, the current I is inputted ₅ Electrolytic capacitor C ₆ And load R _L Respectively pass through I ₆ 、I ₇ (ii) a In the OFF state, as shown in FIG. 7, the fast recovery diode D14 accumulates the electric energy in the inductor L1

Supply load current I ₈ (I _L1 ＝I ₅ The inductor L1 passes a current), and a timing chart of the respective currents at this time is shown in fig. 8. From V _IN Generated energizing current I ₇ And L1 generated electric energy current I ₈ Constantly applying load R _L Supply load current I _RL 。

In comparison with fig. 4 of the embodiment of the present application, the MCU is used to control (1) the fast recovery diode D14 and the inductor L1, and (2) the control IC4 and (3) the switching device SW2 are controlled to change from the fixed duty mode to the PWM mode. FIG. 9 shows a voltage control system, where PI is PI Controller, SW2 is a switch device, and V1 is V _OUT General PI control, voltage-only control, in which the drive period (1/f) is used _sw ) And C ₇ R _L The product relationship is as the following formula (2), and the specifications of each circuit device are as shown in the following table 1.

Table 1 electronics suitable for use in the present application

Unlike fig. 5, the present invention is not a system in which a constant current is passed through a load by a fixed frequency/fixed duty ratio switch and an inductor L1 using a controller, but a system in which a constant current is automatically passed through a MCU originally provided by the present invention by a fixed frequency/PWM method switch, that is, an electrolytic capacitor C can be used as the basis of the MCU ₇ Duty ratio of discharge capacity, automatically controlling output voltage V _OUT Thus, the fast recovery diode D14 and the inductor L1 in fig. 5 are deleted, and a low-cost switching step-down circuit is provided.

First, see the SW2 ON time scenario of FIG. 4. Fig. 10 shows an equivalent circuit in SW2 ON. R ₁ The ON resistance at SW2 ON. Output voltage V _OUT And an electrolytic capacitor C ₇ The correlation can be expressed by the following formula (3). Δ V charge only in steady state, so I ₁₁ Can be expressed by the following formula (4), load current I ₁₂ Can be expressed by the following formula (5). The respective currents and voltages are shown in fig. 11.

Then, see the SW2 OFF time scenario of FIG. 4. FIG. 12 shows an equivalent circuit at SW2 OFF, which can be regarded as C ₇ R _L A discharge circuit of the product. Thus, the output voltage V _OUT Can be expressed as formula (6), load current I ₁₃ Can be represented by formula (7).

Here, if T in formula (7) _OFF Relative time constant (C) of output unit ₇ R _L Product) is sufficiently small (T) _OFF <<C ₇ R _L ) Is what is needed

Then the load current I ₁₃ And an output voltage V _OUT Control may be achieved without attenuation, and the semiconductor switches may be driven by PWM control voltage control, preferably with the MCU controlling the drive period at less than 0.5 times the output CR product. Therefore, according to the formula (2), the operation can be realized only by discharging the electrolytic capacitor without using an inductor. The respective currents and voltages are shown in fig. 13.

V _OUT ＝R _L I ₁₃ (6)

Other embodiments are described below.

Example1 is shown in FIG. 14 as V _IN ：15V、V _OUT :12V, load: 12 Ω, consumed power: the 12W step-down circuit, whose circuit parameters are shown in table 2, can achieve a cost reduction of 80% or more compared with the conventional method of fig. 5. In addition, by the drive frequency f _sw :10kHz driving, and output voltage V _OUT Load current: 1A. Fig. 15 is a control block diagram of embodiment 1. Table 2 below shows the circuit parameters of example 1.

Table 2 implementation case 1 circuit parameters

Example2 is shown in FIG. 16 as V _IN ：15V、V _OUT :12V, load: 12 Ω, consumed power: 12W step-down circuit, circuit parameters of which are shown in Table 3, and a limiting resistor R was added to the step-down circuit as compared with embodiment 1 in FIG. 14 ₇ . When the SW3 ON resistance is small, the electrolytic capacitor C ₈ Possibly by surge current, so that it can be used for electric currentCan exceed the electrolytic capacitor C ₈ Rated ripple current scenario of (1).

In this case, the resistor R was added to embodiment 1 ₇ Therefore, the cost can be reduced by 75% or more compared with the conventional method shown in fig. 5. In addition, by the drive frequency f _sw :10kHz driving, and output voltage V _OUT Load current: 1A. The control block diagram of fig. 17 is the same as that of embodiment 1 of fig. 15. Table 3 below shows the circuit parameters of example 2.

Table 3 implementation case 2 circuit parameters

Example 3 is shown in FIG. 18 as V _IN ：15V、V _OUT :12V, load: 12 Ω, consumed power: the 12W step-down circuit, whose circuit parameters are shown in table 4, is used in the PWM and AD functional scenarios where MCU cannot be used or cannot be used, compared to the implementation case 1 in fig. 14.

Using a comparator (IC 5) instead of MCU, a target output voltage V is set by dividing R8 and R9 _OUT And detects the actual output voltage V through FB _ Vol _OUT If the detected value is lower than the target output voltage, SW3 is ON, and if the detected value is higher than the target output voltage, SW3 is OFF.

Compared with embodiment 1, R8, R9 and IC5 are added, so that the cost can be reduced by more than 35% compared with the conventional method shown in fig. 4. In addition, the output voltage V can be known _OUT Load current: 1A. Table 4 below shows the circuit parameters of example 3.

Table 4 embodiment example 3 circuit parameters

Example 4 is shown in FIG. 19 as V _IN ：15V、V _OUT :12V, load: 12 Ω, consumed power: 12W step-down circuit, circuit parameters are shown in Table 5, and a limiting resistor R is added to the step-down circuit in comparison with embodiment 3 in FIG. 18 ₁₀ . Same embodiment 2Similarly, when the SW3 ON resistance is smaller in embodiment 3, the electrolytic capacitor C ₈ May pass through a rush current, and thus its use for current may exceed that of the electrolytic capacitor C ₈ Rated ripple current scenario of (1).

In this case, R8, R9, R10, and IC5 are added as compared with embodiment 1, and therefore, the cost can be reduced by 30% or more as compared with the conventional method shown in fig. 4. In addition, the output voltage V can be known _OUT Load current: 1A. Table 5 below shows the circuit parameters of example 4.

Table 5 implementation case 4 circuit parameters

Embodiment 5.1 as shown in fig. 20, the present application is applied to the structure in parallel connection with respect to fig. 3, in which the Circuit2 uses the conventional control power IC, and 3.3V is the MCU power, so the prior art linear regulator is used. In addition, 12V and 5V can be used for replacing the embodiment 1 or the embodiment 2 (the sample 1 or the sample 2 is marked in the figure). Therefore, compared with the prior circuit shown in FIG. 3, the cost can be reduced. Since the cost increases, embodiment 3 and embodiment 4 are not adopted here.

Embodiment 5.2 is shown in fig. 21, and the structure of the present application when connected in series is the same as that of fig. 3 except that only embodiment 5.1 is connected in series.

Overall, the present application can achieve the following advantageous effects:

1. a low-cost step-down circuit is realized.

2. The MCU is used for control, and intermittent poor operation can not occur. The voltage protection can be freely set.

3. The MCU is used for control, the output voltage can be realized only by modifying a program, and fine circuit parameter design is not needed.

4. The high-frequency driving of tens of kHz is not needed, and the influence of noise terminal voltage can not occur.

5. Although a limiting resistor is added, the circuit belongs to a switch type circuit and has smaller loss compared with a linear type circuit.

The following are supplementary descriptions and effects of the respective embodiments.

Example1 is simulated as fig. 22, and it can be seen from fig. 23 that the output current 1A and the output voltage 12V are obtained. The cost reduction effect is shown in the following table 6.

TABLE 6 price comparison table (approximate value) RMB 20 yen/yen conversion

Fig. 24 shows the simulation results of the model of embodiment 2. As can be seen from fig. 25, the output current 1A and the output voltage 12V are obtained. The cost reduction effect is shown in the following table 7.

TABLE 7 price comparison table (approximate value) RMB 20 yen/yen conversion

Fig. 26 shows the simulation results of the model of embodiment 3. As can be seen from fig. 27, the output current 1A and the output voltage 12V are obtained. The cost reduction effect is shown in the following table 8.

TABLE 8 price comparison table (approximate value) RMB 20 yen/yen conversion

Fig. 28 shows the simulation results of the embodiment 4 model. As can be seen from fig. 29, the output current 1A and the output voltage 12V are obtained. The cost reduction effect is shown in the following table 9.

TABLE 9 price comparison table (approximate value) RMB 20 yen/yen conversion

Example 5 the cost-reducing effect is shown in table 10 below.

TABLE 10 price comparison Table (approximate value) RMB 20 yen/yen conversion

The above embodiments are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application are also included in the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. A voltage reduction circuit, comprising: switch tube and electric capacity, the first end of switch tube with the first end electricity of electric capacity is connected, the second end of switch tube with the second end of electric capacity is used for connecting the both ends of input power, the first end and the second end of electric capacity still are used for connecting the both ends of load, the control end of switch tube is used for connection director.

2. The voltage-reducing circuit of claim 1, further comprising a controller, wherein the control terminal of the switching tube is electrically connected to the PWM output terminal of the controller.

3. The voltage-reduction circuit of claim 2, further comprising a voltage detection module connected in parallel with the capacitor, the voltage detection module being electrically connected to the controller.

4. The voltage reduction circuit according to claim 3, wherein the voltage detection module comprises a first resistor and a second resistor, a first terminal of the first resistor is electrically connected to a first terminal of the second resistor, a second terminal of the first resistor is electrically connected to a first terminal of the capacitor, a second terminal of the second resistor is electrically connected to a second terminal of the capacitor, and the first terminal of the first resistor is electrically connected to the AD terminal of the controller.

5. The voltage-reducing circuit according to claim 4, further comprising a comparator, wherein the first terminal of the first resistor is electrically connected to the inverting input terminal of the comparator, the non-inverting input terminal of the comparator is electrically connected to a reference voltage source, and the output terminal of the comparator is connected to the control terminal of the switching tube.

6. The voltage-reducing circuit according to claim 2, further comprising a bias circuit, wherein the bias circuit comprises a third resistor and a fourth resistor, the third resistor is connected between the second terminal and the control terminal of the switching tube, and the control terminal of the switching tube is electrically connected to the PWM output terminal of the controller through the fourth resistor.

7. The voltage-reducing circuit of claim 2, further comprising a driving circuit, wherein the control terminal of the switching tube is electrically connected to the PWM output terminal of the controller through the driving circuit.

8. The voltage-reducing circuit according to claim 1, further comprising a current-limiting resistor connected between the first terminal of the capacitor and the first terminal of the switching tube.

9. A power supply system comprising a first step-down circuit and a second step-down circuit, wherein the first step-down circuit and the second step-down circuit both belong to the step-down circuit of any one of claims 1 to 8, wherein input terminals of the first step-down circuit and the second step-down circuit are both connected to an input power supply, and wherein output voltages of the first step-down circuit and the second step-down circuit are different.

10. A power supply system is characterized by comprising a first voltage reduction circuit and a second voltage reduction circuit, wherein the first voltage reduction circuit and the second voltage reduction circuit belong to the voltage reduction circuits of any one of claims 1 to 8, the input end of the first voltage reduction circuit is connected to an input power supply, the output end of the first voltage reduction circuit is electrically connected with the input end of the second voltage reduction circuit, and the output voltage of the first voltage reduction circuit is greater than the output voltage of the second voltage reduction circuit.

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