KR102176408B1 - BLDC motor control device and method - Google Patents

Abstract

The present invention is to control the BLDC motor stably and sense the current by preventing a failure due to heat generation of the element when controlling the BLDC motor at a high temperature by changing the technique of controlling the BLDC motor based on the temperature of the BLDC motor. When the pulse is smaller than the sampling time, the present invention relates to an apparatus and method for controlling a BLDC motor to adjust a switching timing so that a pulse for sensing a current becomes larger than the sampling time.
A BLDC motor control apparatus and method according to an embodiment of the present invention include a brushless direct current (BLDC) motor using a three-phase power supply, a current measuring unit measuring a current corresponding to the three-phase power supply, and a temperature of the BLDC motor. A temperature sensor to measure, and a control unit for generating a control pulse for supplying the three-phase power to the BLDC motor, the control unit, the control pulse based on the temperature of the BLDC motor measured by the temperature sensor By controlling the switching of the three-phase power supply, when the measured temperature is less than the reference temperature, the control pulse is adjusted according to the first technique, and when the measured temperature is higher than the reference temperature, it is different from the first technique. The control pulse is adjusted according to the second technique.

Description

BLDC motor control device and method {BLDC motor control device and method}

The present invention relates to an apparatus and method for controlling a BLDC motor, and in more detail, by changing the technique of controlling the BLDC motor based on the temperature of the BLDC motor, when controlling the BLDC motor at a high temperature, failure due to heat generation of the element is prevented. The present invention relates to a BLDC motor control apparatus and method for stably controlling a BLDC motor and adjusting a switching timing so that a pulse for sensing current is greater than a sampling time when a pulse for sensing current is less than a sampling time.

BLDC motors (motors) include a stator and a rotor, receive three-phase power supplied through an inverter, and rotate by using an interaction between the stator and the rotor.

Among the techniques for controlling the BLDC motor, the DS (Double Switching) technique can stably control the current characteristics applied to the BLDC motor by increasing the number of switching. However, as the number of switching increases, there is a problem that heat is generated in the device, and thus efficiency decreases. In addition, among other techniques for controlling a BLDC motor, the TS (Time Shift) technique moves pulses, which is advantageous for heat generation because the number of switching does not increase, but there is a problem in that current distortion occurs when the pulse is moved.

The present invention is to solve the above-described problem, by changing the technique of controlling the BLDC motor based on the temperature of the BLDC motor, when controlling the BLDC motor at a high temperature, the BLDC motor is stably prevented from failure due to heat generation. It is an object of the present invention to provide a BLDC motor control apparatus and method for controlling and controlling switching timing so that the pulse for sensing current becomes larger than the sampling time when the pulse for sensing current is smaller than the sampling time.

In addition to the technical problems of the present invention mentioned above, other features and advantages of the present invention will be described below or will be clearly understood by those of ordinary skill in the art from such technology and description.

A BLDC motor control apparatus according to an embodiment of the present invention for achieving the above-described object includes a brushless direct current (BLDC) motor using a three-phase power supply, a current measuring unit measuring a current corresponding to a three-phase power supply, and a BLDC motor. A temperature sensor for measuring the temperature of the BLDC motor and a control unit for generating a control pulse for supplying three-phase power to the BLDC motor, the control unit by adjusting the control pulse based on the temperature of the BLDC motor measured by the temperature sensor The switching of the three-phase power supply is controlled, and when the measured temperature is below the reference temperature, the control pulse is adjusted according to the first technique, and when the measured temperature is above the reference temperature, the control pulse is adjusted according to the second technique different from the first technique. I can.

Here, when the measured temperature is less than the reference temperature, the controller divides one control pulse into at least two sub-control pulses, and a time interval may exist between the divided sub-control pulses.

Further, the lengths of the divided sub-control pulses may be the same, and the sum of the lengths of each of the divided at least two pulses may be the same as the total length of the control pulse before the division.

In addition, when the measured temperature is equal to or higher than the reference temperature, the control unit may adjust the timing of the control pulse.

In addition, the control unit may adjust the control pulse so that the amount of control pulse timing is decreased as the temperature of the BLDC motor increases.

In addition, when the section of the control pulse for sensing the current is smaller than the preset sampling section, the controller may advance or delay the timing of the control pulse by the section of the control pulse for sensing the current.

In addition, since the timing of the control pulse is advanced or delayed, the period of the control pulse for sensing the adjusted current may be larger than the sampling period.

A BLDC motor control method according to an embodiment of the present invention for achieving the above-described object includes measuring a current corresponding to a three-phase power supply of a BLDC motor using a three-phase power supply, and measuring a temperature of the BLDC motor, By controlling the control pulse for supplying the three-phase power based on the temperature of the BLDC motor measured by the control unit, including the step of controlling the switching of the three-phase power, and when the measured temperature of the BLDC motor is less than the reference temperature, the first The control pulse may be adjusted according to the technique, and when the measured temperature of the BLDC motor is higher than the reference temperature, the control pulse may be adjusted according to the second technique different from the first technique.

Here, in the step of controlling the switching of the three-phase power supply, when the temperature measured by the controller is less than the reference temperature, one control pulse is divided into at least two sub-control pulses, and a time interval between the divided sub-control pulses is Can exist.

Also, in the step of controlling the switching of the three-phase power supply, the lengths of the divided sub-control pulses are the same, and the sum of the lengths of each of the divided at least two pulses may be the same as the total length of the pulse before the division. have.

In addition, in the step of controlling the switching of the three-phase power supply, when the temperature measured by the controller is equal to or higher than the reference temperature, the timing of the control pulse may be adjusted.

In addition, in the step of controlling the switching of the three-phase power supply, the controller may adjust the control pulse so that the amount of the control pulse timing decreases as the temperature of the BLDC motor increases.

In addition, in the step of controlling the switching of the three-phase power supply, when the section of the control pulse for sensing the current in the controller is smaller than the sampling section, the timing of the control pulse is advanced or delayed by the section of the control pulse for sensing the current. I can.

In addition, in the step of adjusting the switching of the three-phase power source, the timing of the control pulse is advanced or delayed, so that the period of the control pulse for sensing the adjusted current may be larger than the sampling period.

In the BLDC motor control apparatus and method according to an embodiment of the present invention, when the temperature of the BLDC motor is less than the reference temperature by measuring the temperature of the BLDC motor, the BLDC motor can be stably controlled by controlling the BLDC motor using the DS technique.

In addition, the BLDC motor control apparatus and method can prevent a problem in the BLDC motor from occurring due to heat generation in the element by controlling the BLDC motor using the TS technique when the temperature of the BLDC motor is higher than the reference temperature.

In addition, the BLDC motor control apparatus and method may secure a sampling period for sensing current by moving the pulse when the pulse period for sensing current is smaller than the sampling period.

In addition, other features and advantages of the present invention may be newly recognized through embodiments of the present invention.

1 is a diagram showing the configuration of a BLDC motor control apparatus according to an embodiment of the present invention.
2 is a view showing a BLDC motor according to an embodiment of the present invention.
3 is a diagram illustrating an inverter according to an embodiment of the present invention.
4 is a view showing a BLDC motor control method according to an embodiment of the present invention.

In order to clearly describe the present invention, parts irrelevant to the description have been omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

The terminology used herein is only for referring to specific embodiments and is not intended to limit the present invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. The meaning of “comprising” as used in the specification specifies a specific characteristic, region, integer, step, action, element and/or component, and the presence of another characteristic, region, integer, step, action, element and/or component, or It does not exclude additions.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in a commonly used dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal meaning unless defined.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various forms and is not limited to the embodiments described herein.

1 is a diagram showing the configuration of a BLDC motor control apparatus according to an embodiment of the present invention.

1, the BLDC motor system 10 according to an embodiment of the present invention may include a BLDC motor 110 and a position measuring device 200, the position measuring device 200 is a current measuring unit 120, A temperature sensor 130, a control unit 140, and an inverter 150 may be included.

The BLDC motor 110 may generate rotational energy using electric energy. The BLDC motor 110 may generate a rotational force using the power received from the position measuring device 200. In addition, in the case of the BLDC motor 110, it may operate according to three-phase power.

The position measuring device 200 may measure the position of the rotor of the BLDC motor 110. In order to synchronize the rotating magnetic field formed in the rotor and stator of the BLDC motor 110, it is necessary to measure the position of the rotor.

According to an embodiment of the present invention, the position measuring device 200 may measure the position of the rotor of the BLDC motor 110 by using the magnitude of the current flowing through the inverter 150. The operation of the position finder 200 will be described in more detail below.

The inverter 150 may supply operating power of the BLDC motor 110 to the BLDC motor 110 under the control of the controller 140. According to embodiments, the inverter 150 generates three-phase power (VA, VB, and VC) by using power supplied from the power supply device 300, and BLDC the generated three-phase power supply (VA, VB, and VC). It can be supplied to the motor 110.

The inverter 150 may include a plurality of switches (S1 to S6), and by controlling the plurality of switches (S1 to S6), it is possible to supply operating power (VA, VB and VC) to the BLDC motor 110. have. According to embodiments, the inverter 150 controls the on-off of the plurality of switches (S1 to S6) under the control of the controller 140 to control the operation power (VA, VB and VC) to the BLDC motor 110. Can supply.

Each of the plurality of switches S1 to S6 may be connected to the BLDC motor 110. According to embodiments, the plurality of switches S1 to S6 may be a metal oxide semiconductor field effect transistor (MOSFET).

The current measuring unit 120 may measure the current flowing through each of the switches S1 to S6. For example, when the switches S1 to S6 are MOSFETs, the current measuring unit 120 measures a current for a voltage (hereinafter, drain-source voltage) between the drain and source of each of the switches S1 to S6. can do. In addition, the current measuring unit 120 may measure the current for the voltage at both ends of the switches S4, S4 and S6 disposed on the upper end of the inverter 150.

The temperature sensor 130 may measure the temperature of each of the plurality of switches S1 to S6 to generate temperature information TI, and transmit the temperature information TI to the processor. The temperature sensor 130 is directly connected to the switches S1 to S6 to measure the temperature of the switches S1 to S6 or the switches S1 to S6 without being directly connected to the switches S1 to S6. You can measure the temperature of. Through this, the temperature sensor 130 may measure the temperature of the BLDC motor 110.

The controller 140 may control the operation of the inverter 150. The controller 140 may transmit a control signal for controlling on-off of the plurality of switches S1 to S6 to the inverter 150. As an example, the controller 140 may supply the gate voltage VG of each of the switches S1 to S6 to the inverter 150.

In addition, the controller 140 sets the gate voltage VG of each of the switches S1 to S6 based on the operation mode (eg, rotation speed, rotation angular speed, rotation direction, etc.) of the BLDC motor 110, and The gate voltage VG may be supplied to the inverter 150.

The controller 140 may measure the position of the rotor and control the inverter 150. Here, the control unit 140 may include an element having computing power, for example, a central processing unit or a micro controller unit.

The controller 140 may measure the position of the rotor by using the current for the voltage at both ends of each of the switches S1 to S6 measured by the current measuring unit 120. That is, the controller 140 may measure the position of the rotor by using the current flowing through each of the switches S1 to S6 measured by the current measuring unit 120.

In addition, the controller 140 may control switching of the three-phase power supply by adjusting a control pulse based on the temperature of the BLDC motor 110 measured by the temperature sensor 130. Specifically, when the temperature of the BLDC motor 110 measured by the temperature sensor 130 is less than the reference temperature, the controller 140 adjusts the control pulse according to the first technique and measured by the temperature sensor 130 When the temperature of the BLDC motor 110 is higher than the reference temperature, the control pulse may be adjusted according to the second technique.

According to an embodiment of the present invention, the reference temperature may be preset and stored in a memory. For example, the reference temperature may be a temperature at which an abnormality starts to occur in the BLDC motor 110 or a temperature at which the performance of the BLDC motor 110 starts to deteriorate.

It may be a temperature at which heat is generated according to a control technique. When heat is generated in the device according to the control technique, a problem may occur in the durability of the BLDC motor 110. Here, the control technique that can generate heat in the device may be the first technique. Accordingly, by controlling the control pulse using the first technique only when the temperature of the BLDC motor 110 is less than the reference temperature, it is possible to prevent the occurrence of a problem in the BLDC motor 110 due to heat generation of the element. In addition, when the temperature of the BLDC motor 110 is higher than the reference temperature, a problem occurs in the BLDC motor 110 due to heat generation of the element by adjusting the control pulse using a second technique that does not significantly affect the heat generation of the element. Can be prevented. Accordingly, the degree of heat generation when the BLDC motor 110 is controlled according to the first technique may be greater than the degree of heat generation when the BLDC motor 110 is controlled according to the second technique.

When the measured temperature of the BLDC motor 110 is less than the reference temperature, the controller 140 divides one control pulse into at least two sub control pulses, and a time interval may exist between the divided sub control pulses. Further, the divided lengths of the sub-control pulses may be the same, and the sum of the lengths of each of the divided at least two sub-control pulses may be the same as the total length of the control pulse before the division. Here, the length of the pulse may mean a time period during which the pulse is at a high level. That is, it may mean a time from a rising edge point of a pulse to a falling edge point.

For example, when the temperature of the BLDC motor 110 is less than the reference temperature and the control pulse is at a high level from 2T to 10T, the control unit 140 may divide the control pulse into at least two sub-control pulses. That is, the controller 140 may divide the control pulse into a first sub control pulse having a high level from 2T to 6T and a second sub control pulse having a high level from 6T to 10T. In this case, the controller 140 may have a low level between the first sub-control pulse and the second sub-control pulse so that there is a time interval between the first sub-control pulse and the second sub-control pulse. In this case, as the interval between the first sub-control pulse and the second sub-control pulse becomes a low level, the timing of the first sub-control pulse is advanced by 1T, and the timing of the second sub-control pulse may be delayed by 1T. Here, the timing of the pulse may indicate a time point at which the level of the pulse is changed. That is, the timing of the pulse may indicate a rising edge timing when a pulse changes from a low level to a high level or a falling edge timing when a pulse changes from a high level to a low level. Here, since the first sub-control pulse and the second sub-control pulse are generated by adjusting the timing of the existing control pulse, the sum of the lengths of the first sub-control pulse and the second sub-control pulse is equal to that of the existing control pulse before being divided. May be equal to the total length.

In addition, when the measured temperature of the BLDC motor 110 is equal to or higher than the reference temperature, the controller 140 may adjust the timing of the control pulse. As described above, the timing of the control pulse may indicate a time point at which the level of the pulse is changed. Here, the controller 140 may adjust the timing of the control pulse so that the amount by which the timing of the control pulse is adjusted decreases as the temperature of the BLDC motor 110 increases. For example, when the temperature of the BLDC motor 110 is greater than or equal to the reference temperature, the controller 140 may advance the timing of the control pulse by 2T. At this time, when the temperature of the BLDC motor 110 is higher, the timing of the control pulse may be advanced by 1T. In this way, the controller 140 may adjust the timing of the control pulse so that the amount by which the timing of the control pulse is adjusted decreases as the temperature of the BLDC motor 110 increases under the condition that the temperature of the BLDC motor 110 is higher than the reference temperature. .

In addition, when the period of the control pulse for sensing the current is smaller than the preset sampling period, the controller 140 may advance or delay the timing of the control pulse by the period of the control pulse for sensing the current. Specifically, the current for the three-phase power may be sensed in each section of control pulses for supplying the three-phase power to the BLDC motor 110. However, when the period of the control pulse for sensing the current is smaller than the sampling period, the current cannot be sensed through the corresponding control pulse. Accordingly, the timing of the control pulse can be advanced or delayed in order to secure a section of the control pulse for sensing the current. Here, when the section of the control pulse for sensing current is the start of the high level of the corresponding control pulse, the controller 140 may delay the timing of the control pulse by the section of the control pulse for sensing the current. In addition, when the section of the control pulse for sensing current is the end of the high level of the control pulse, the controller 140 may advance the timing of the control pulse by the section of the control pulse for sensing the current. In this case, when the controller 140 adjusts the timing of the control pulse, the section of the control pulse for sensing the current may be combined with another section of the control pulse for sensing the current and may be larger than the sampling section. Through this, the current measuring unit 120 may measure the current for the three-phase power supply to the BLDC motor 110.

2 is a view showing a BLDC motor according to an embodiment of the present invention.

Referring to FIG. 2, the BLDC motor 110 may include a stator 112 on which a coil is wound and a rotor 114 rotatably installed in the stator 112.

The stator 112 may constitute the outer periphery of the BLDC motor 110, and a tooth wound with a plurality of coils may be disposed on the stator 112 along the stator 112. According to embodiments, the stator 112 may include three coils A, B and C each having a phase difference of 120°. The rotor 114 is provided with a permanent magnet on a surface of the stator 112 facing the coil, and can rotate by a magnetic field generated by the stator 112.

3 is a diagram illustrating an inverter according to an embodiment of the present invention.

Referring to FIG. 3, the inverter 210 may supply operating power of the BLDC motor 110 to the BLDC motor 110 under the control of the inverter control circuit 230. According to embodiments, the inverter 150 generates three-phase power (VA, VB, and VC) using power supplied from the power supply device 300, and generates the three-phase power supply (VA, VB, and VC) to a motor. (110) can be supplied.

The inverter 150 may include a plurality of switches (S1 to S6), and by controlling the plurality of switches (S1 to S6), it is possible to supply operating power (VA, VB and VC) to the BLDC motor 110. have. According to an embodiment of the present invention, the inverter 150 controls the on-off of the plurality of switches S1 to S6 according to the control of the controller 140, thereby operating power VA, VB and VC by the BLDC motor 110. ) Can be supplied.

Each of the plurality of switches S1 to S6 may be connected to the BLDC motor 110. According to embodiments, the plurality of switches S1 to S6 may be a metal oxide semiconductor field effect transistor (MOSFET).

4 is a view showing a BLDC motor control method according to an embodiment of the present invention.

Referring to Figure 4, it is possible to measure the current corresponding to the three-phase power of the BLDC motor 110 using the three-phase power (S10). The current measuring unit 120 may measure a current corresponding to the three-phase power of the BLDC motor 110 to determine the position of the rotor of the BLDC motor 110.

Subsequently, the temperature of the BLDC motor 110 may be measured (S20).

It may be determined whether the measured temperature of the BLDC motor 110 is higher than or equal to the reference temperature (S30). It may be determined whether the temperature of the BLDC motor 110 measured by the temperature sensor 130 is higher than the reference temperature. Here, the reference temperature may be a temperature at which an abnormality starts to occur in the BLDC motor 110 or a temperature at which the performance of the BLDC motor 110 starts to deteriorate.

When the temperature of the BLDC motor 110 is less than the reference temperature, a control pulse for supplying three-phase power may be adjusted according to the first technique (S40). Specifically, as a first technique, the controller 140 may divide one control pulse into at least two sub-control pulses. At this time, a time interval exists between the divided sub-control pulses, and the control pulse may be at a low level during this time interval. In this case, the divided lengths of the sub-control pulses may be the same, and the sum of the lengths of each of the divided at least two sub-control pulses may be the same as the total length of the control pulse before the division. Here, the length of the pulse may mean a time period during which the pulse is at a high level. That is, it may mean a time from a rising edge point of a pulse to a falling edge point.

On the other hand, when the temperature of the BLDC motor 110 is higher than the reference temperature, a control pulse for supplying the three-phase power may be adjusted according to the second technique (S50). Specifically, as a second technique, the controller 140 may adjust the timing of the control pulse. Here, the timing of the control pulse may indicate a time point at which the level of the pulse is changed. In particular, the controller 140 may adjust the timing of the control pulse so that the amount by which the timing of the control pulse is adjusted decreases as the error degree increases.

As described above, by changing the technique of controlling the BLDC motor based on the temperature of the BLDC motor, when controlling the BLDC motor at a high temperature, it prevents failure due to heat generation of the element, thereby stably controlling the BLDC motor and sensing the current. When the pulse for sensing the current is smaller than the sampling time, it is possible to realize a BLDC motor control apparatus and method for adjusting the switching timing so that the pulse for sensing the current becomes larger than the sampling time.

Those skilled in the art to which the present invention pertains, since the present invention may be implemented in other specific forms without changing the technical spirit or essential features thereof, the embodiments described above are illustrative in all respects and should be understood as non-limiting. Only. The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. .

110: BLDC motor
200: position finder
120: current measuring unit
130: temperature sensor
140: control unit
150: inverter

Claims (14)

BLDC (Brushless Direct Current) motor using 3-phase power;
A current measuring unit measuring a current corresponding to the three-phase power supply;
A temperature sensor measuring the temperature of the BLDC motor; And
Including; a control unit for generating a control pulse for supplying the three-phase power to the BLDC motor,
The control unit,
Controlling the switching of the three-phase power supply by adjusting the control pulse based on the temperature of the BLDC motor measured by the temperature sensor,
When the measured temperature is less than the reference temperature, the amount of heat generated is high, and the control pulse is controlled according to the first technique of stably controlling the current, and when the measured temperature is higher than the reference temperature, the amount of heat different from the first technique is low. Adjusting the control pulse according to the second technique,
The BLDC motor control apparatus, wherein the degree of heat generation of the BLDC motor when controlled by the first technique is greater than the degree of heat generation of the BLDC motor when controlled according to the second technique.
The method of claim 1,
The controller divides one control pulse into at least two sub control pulses when the measured temperature is less than a reference temperature, and a time interval exists between the divided sub control pulses.
The method of claim 2,
The lengths of the divided sub-control pulses are the same, and the sum of the lengths of each of the divided at least two pulses is the same as the total length of the control pulse before the division.
The method of claim 1,
The controller controls the timing of the control pulse when the measured temperature is greater than or equal to a reference temperature.
The method of claim 4,
The controller controls the BLDC motor to adjust the control pulse so that an amount of the control pulse timing is decreased as the temperature of the BLDC motor increases.
The method of claim 5,
When the control pulse section for sensing the current is smaller than a preset sampling section, the control unit advances or slows the timing of the control pulse by the section of the control pulse for sensing the current.
The method of claim 6,
The BLDC motor control device in which the timing of the control pulse is advanced or delayed so that the interval of the control pulse for sensing the adjusted current is larger than the sampling interval.
Measuring a current corresponding to the three-phase power of the BLDC motor using three-phase power;
Measuring the temperature of the BLDC motor; And
Including, in a control unit, by adjusting a control pulse for supplying the three-phase power based on the measured temperature of the BLDC motor, controlling the switching of the three-phase power supply; Including,
When the measured temperature of the BLDC motor is less than the reference temperature, the amount of heat generated is high, and the control pulse is controlled according to a first technique of stably controlling the current, and when the measured temperature of the BLDC motor is higher than the reference temperature, the first Adjusting the control pulse according to a second technique with low calorific value different from the technique,
The BLDC motor control method, wherein the degree of heat generation of the BLDC motor when controlled by the first technique is greater than the degree of heat generation of the BLDC motor when controlled according to the second technique.
The method of claim 7, wherein in the step of adjusting the switching of the three-phase power supply,
When the measured temperature is less than the reference temperature by the control unit, one control pulse is divided into at least two sub control pulses, and a time interval exists between the divided sub control pulses.
The method of claim 9, wherein in the step of adjusting the switching of the three-phase power supply,
The lengths of the divided sub-control pulses are the same, and the sum of the lengths of each of the divided at least two pulses is the same as the total length of the pulse before the division.
The method of claim 9, wherein in the step of adjusting the switching of the three-phase power supply,
BLDC motor control method for controlling the timing of the control pulse when the measured temperature by the control unit is higher than the reference temperature.
The method of claim 11, wherein in the step of adjusting the switching of the three-phase power supply,
The BLDC motor control method in which the control pulse adjusts the control pulse so that as the temperature of the BLDC motor increases, the controlled amount of the timing of the control pulse decreases.
The method of claim 11, wherein in the step of adjusting the switching of the three-phase power supply,
When the control pulse section for sensing the current is smaller than the sampling section in the controller, the timing of the control pulse is advanced or delayed by the section of the control pulse for sensing the current.
The method of claim 13, wherein in the step of adjusting the switching of the three-phase power supply,
A BLDC motor control method in which a section of the control pulse for sensing a regulated current by the timing of the control pulse being advanced or delayed is larger than the sampling section.

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