KR102132979B1 - Device for estimating secondary output current - Google Patents

Abstract

The present invention relates to an output current estimation apparatus, and more specifically, a sensing unit for measuring the primary input current of a plant, a processor for estimating the secondary output current of the plant using the input current sensed by the sensing unit, and And a control unit that outputs an output current by controlling an input current according to the output current estimated by the processor, and wherein the processor corrects at least one of a steady state error or a measurement error when estimating the output current. It relates to a current estimation device.

Description

Device for estimating secondary output current

The present invention relates to an output current estimation apparatus, and more specifically, an output current estimation apparatus for use in estimating the secondary side current using the primary input current instead of directly measuring the secondary side current and performing current control. It is about.

The current control is a control method for inputting a constant current to the primary input terminal of the plant including the transformer to regulate the current flowing to the secondary output terminal of the plant, and to flow the current required for the load terminal below.

Conventional current control is achieved by measuring the current flowing through the secondary output terminal and adjusting the amount of primary current based on the measured secondary current.

However, in this conventional method, a current measuring device for measuring the output current of the secondary side must be connected to the secondary side, but the low voltage/high current characteristic (LC/HC, Low Current / High Voltage) of the secondary side prevents the installation of the current measuring device. Not only is it difficult and difficult to accurately measure, but the input current is adjusted using the measured current, it takes a long time to control the current and there is a problem of low precision.

Korean Patent Publication No. 2005-0097975

The present invention is intended to solve the above-described problem, and it is an object of the present invention to accurately estimate the current on the secondary side and to perform rapid and accurate current control.

In particular, it aims to increase the accuracy of current control by reflecting the error of the steady state occurring in the current control device.

On the other hand, it is an object of the present invention to improve the precision of current control in view of current measurement errors caused by a configuration having non-linear characteristics in the current control device.

The output current estimation apparatus of the present invention for solving the above-described problems includes a sensing unit for measuring the primary input current of the plant, a processor for estimating the secondary output current of the plant using the input current sensed by the sensing unit, and And a control unit that outputs an output current by controlling an input current according to the output current estimated by the processor, and the processor may correct at least one of a steady state error or a measurement error when estimating the output current.

At this time, the processor estimates the output current using the sensed input current, and when estimating the output current, the current correction unit calculates an error according to at least one of a steady state error or a measurement error, and is estimated by the current correction unit. It may include a digital control unit for generating a control signal for adjusting the output current to the target output current and transmits it to the control unit.

In one embodiment of the present invention, the current compensator estimates the output current using the average value of the input current, the turns ratio of the transformer included in the plant, and the duty ratio of the plant voltage, and more specifically, I _{out _ bar} = (n * I _The output current can be estimated by _{in _ bar} ) / D (where n is the transformer turns ratio, I _{in _ bar} : the average input current value, and D: the duty ratio of the plant voltage). At this time, the duty ratio may be calculated by D = V _O / V _L (however, D: duty ratio of the plant voltage, V _O : output voltage of the plant, V _L : inductance voltage of the plant output). And, the average value of the input current can be derived by passing the input current through a low-pass filter.

Meanwhile, the current compensator of the present invention can calculate a steady state error or a measurement error due to at least one of the inductance of a switch in a plant or the inductance of a transformer, and more specifically, A = 1/2 * ( L _lk + L _C )/( V _in ) * ( I _{in _ bar} / D) ² (however, A: error component, L _lk : leakage inductance of the transformer included in the plant, L _C : caused by the switching element included in the plant The steady state error or the measurement error can be calculated by the inductance component, V _in : input voltage of the primary side, I _{in_bar} : average of the primary input current, D: duty ratio).

The digital control unit of the output current estimation apparatus according to an embodiment of the present invention may compare the output current and the target output current estimated by the current correction unit, and generate a control signal to attenuate the difference and transmit it to the control unit.

On the other hand, the control unit of the present invention includes a reference voltage signal is input to the + input terminal, an amplifier to which the primary output voltage is input to the-input terminal, and a FET element connected to the + terminal of the amplifier and controlled by the processor. Can. At this time, the FET device receives the control signal input from the digital control unit to adjust the on/off of the gate terminal, and the amplifier adjusts the output current according to the degree to which the gate terminal is turned on/off.

In addition to this, the control unit of the present invention may further include a resistor between the input terminal and the primary output terminal and a series RC circuit between the input terminal and the output terminal of the amplifier.

According to the present invention, even if the output current of the secondary side is not directly measured, it can be estimated, so that a separate current measurement sensor does not need to be connected to the secondary side. As a result, the cost of performing current control can be reduced.

In addition, since current control is performed using the current estimate, it is possible to control the current faster than in the prior art.

Meanwhile, since current is estimated in consideration of various errors that may occur during current measurement and estimation, accurate current control can be performed.

1 is a block diagram conceptually showing an embodiment of an output current estimation apparatus of the present invention.
2 is a circuit diagram showing an embodiment of an output current estimation apparatus of the present invention.
3 is a block diagram schematically showing a detailed configuration in a processor of the present invention and a connection relationship between a control unit.
4 is a block diagram showing an example in which the output current estimation apparatus of the present invention is connected to a plant.
5 is a graph for explaining the process of estimating the output current in the processor of the present invention.
6 is a graph showing a change in voltage input to the amplifier in the controller according to the presence or absence of a steady state error in the output current estimation apparatus of the present invention.
7 is a circuit diagram showing an example of a sensing unit of the present invention.
8 is a graph showing a measurement error generated in the output current estimation apparatus of the present invention and an example for correcting it.

The details of the above-described object and technical configuration of the present invention and the effect of the effect thereof will be more clearly understood by the following detailed description based on the accompanying drawings in the specification of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram conceptually showing an embodiment of an output current estimation apparatus of the present invention.

The output current estimation apparatus according to an embodiment of the present invention uses the sensing unit 100 for measuring the primary input current of the plant, and the secondary output current of the plant using the input current sensed by the sensing unit 100. It includes a processor 200 for estimating and a control unit 300 for controlling the input current according to the output current estimated by the processor 200 to output the output current. At this time, when the output current is estimated, the processor 200 corrects at least one of a steady state error or a measurement error.

Unlike the prior art, the present invention includes a configuration for estimating the secondary-side output current of the plant. Conventionally, the secondary output current of the plant was measured and used for control, but measuring the secondary output current causes great difficulties in precision, time, and cost. To solve this problem, the present invention includes a processor 200 that is a configuration for estimating the secondary-side output current.

The processor 200 of the present invention can estimate the secondary-side output current based on the primary-side input current. At this time, in order to measure the primary input current of the plant, the output current estimation apparatus of the present invention includes a sensing unit 100. On the other hand, according to the output current of the secondary side estimated by the processor 200, the present invention includes a control unit 300 for outputting an output current by controlling the input current in order to send the current required to the actual secondary. The detailed description of the sensing unit 100, the processor 200, and the control unit 300 will be described later.

In one embodiment of the present invention, the processor 200 may correct at least one of a steady state error or a measurement error when estimating an output current. The steady-state error means an error generated by a device having nonlinear characteristics or an error caused by parameter uncertainty. In the case of controlling the current using only passive elements, ideally, the current and voltage of the correct values should be generated, but an error occurs due to various causes of error. In addition, when an active element is included, more various variables act to generate an error, and an error occurs in steady state operation. Therefore, when estimating the output current, the actual output current and the estimated output current are different. On the other hand, in measuring the current input to the plant, errors occur due to various factors.

The present invention makes it possible to more accurately estimate the output current by reflecting such a steady state error or measurement error. Hereinafter, a more detailed embodiment of estimating an output current by reflecting an error will be described.

In one embodiment of the present invention, the processor 200 estimates an output current using the sensed input current, and calculates an error according to at least one of a steady state error or a measurement error when estimating the output current 210 ) And a digital control unit 220 that generates a control signal for adjusting the output current estimated by the current correction unit 210 to a target output current and transmits it to the control unit 300.

The current compensator 210 is a component for calculating an error, and the digital controller 220 is a component for controlling the secondary output current to be controlled as a target output current by reflecting the calculated error.

First, the current correction unit 210 will be described in detail through FIG. 4. 4 is a block diagram showing an example in which the output current estimation apparatus of the present invention is connected to a plant. Referring to FIG. 4, the current compensator 210 in the processor 200 outputs information using the input current I _in , the duty ratio D of the plant voltage, and the turns ratio n of the transformer included in the plant. Estimate the current. In FIG. 4, a detailed process of estimating the output current using the above variables is not illustrated, but is displayed only _in the form of a function (f(I _in , D, V _in )). Let's look at the process of estimating the output current in detail.

5 is a graph for explaining the process of estimating the output current in the processor 200 of the present invention. The graph drawn on the upper side in FIG. 5 is the input current on the primary side, and the graph drawn on the lower side in FIG. 5 is the output current on the secondary side. The input current of the primary side sends the current to the secondary side during the period when the switch is _on (t _on ) in one cycle (T _s ). The average current in one cycle is I _{in _ bar} . The output current of the secondary side is output for one cycle and the average current of I _{out _ bar} flows. On the other hand, the average current during the time during which the primary input current and the secondary output current flow (t _{on in} the case of input current) is A and B, respectively. Based on this, calculating the relationship of each variable,

[Equation 1]

I _{in _ bar} * T _S = A * t _on

It becomes. This is because I _{in _ bar} is an average value of 1 cycle (T _S ).

Based on this, calculating A

[Equation 2]

A = ( I _{in _ bar} * T _S ) / t _on = I _{in _ bar} /D

Becomes. D is the ratio of one cycle of the input current and the time at which the input current was actually input.

Meanwhile, a transformer is present between the primary input current and the secondary output current, and accordingly, A and B are proportional to the turns ratio of the transformer as shown in FIG. 5. That is, it has the relationship of [Equation 3] below.

[Equation 3]

I _{out _ bar} = B = A * n = (n * I _{in _ bar} )/D

In summary, the secondary output current estimate is (n * I _{in _ bar} )/D.

Meanwhile, the duty ratio D is calculated by (t _on / T _S ), but it can also be calculated using the output voltage of the secondary side.

The duty ratio can be calculated using the ratio of the secondary output voltage of the plant shown in FIG. 5 (ratio of V _L and V _O ), as shown in Equation 4 below.

[Equation 4]

D = V _O / V _L

(However, D: Duty ratio of plant voltage, V _O : Output voltage of plant, V _L : Inductance voltage of plant output)

On the other hand, in an embodiment of the present invention, the average value of the input current (I _{in _ bar} ) is used to estimate the output current, and the input current can be passed through a low-pass filter to obtain the average value. The low-pass filter is labeled as LPF in FIG. 2 and FIG. 3 and AVG in FIG. 4, and referring to FIG. 5, a low-pass filter is used to block a current element that changes periodically, and only a current element that does not change passes through one cycle The average input current during can be derived.

Meanwhile, the current compensator 210 of the present invention may calculate a steady state error or a measurement error due to at least one of inductance of a switch in a plant or inductance of a transformer. The process of estimating the secondary-side output current by calculating the steady-state error and the measurement error will be described with reference to FIGS. 2, 6, and 8.

2 is a circuit diagram showing an embodiment of an output current estimation apparatus of the present invention, and FIG. 6 is a diagram of the voltage input to the amplifier 310 in the control unit 300 according to the presence or absence of a steady state error in the output current estimation apparatus of the present invention. 8 is a graph showing a change and a measurement error generated in the output current estimation apparatus of the present invention and an example for correcting the error.

The control unit 300 that outputs the output current by controlling the input current using the estimated output current includes an amplifier 310 in which a reference voltage signal is input to a + input terminal, and a primary output voltage is input to a-input terminal, and It includes a FET device 320 connected to the + terminal of the amplifier 310 and controlled by the processor 200. + The target output current flows to the secondary side according to the open-loop control by adjusting the reference voltage Vref regulated by the input terminal itself, or by controlling the operation of the FET device 320 to control the amplifier 310. By adjusting the voltage level (V+) of the input terminal, the target output current may flow to the secondary side (both may be applied simultaneously). At this time, all elements included in the control unit 300 of FIG. 2 are accurately linear. If it operates as, the relationship between a specific output according to a specific input is made into a look-up table and stored in the processor 200 to generate a target output current or to calculate an output current in the processor 200 It can be input and controlled to generate a target output current according to the input formula.

However, due to the parameter uncertainty of a device or parameter having a nonlinear characteristic, an output current that does not match the input-output current relationship arranged in a table or a formula is generated. An example of such an error is shown in FIG. 6. 6A shows V+ (input voltage of the amplifier 310) over time when an error occurs, and (B) shows V+ when an error is compensated or when no error occurs. Since the output current is generated according to V+, the output current also has the same type of error. The error is caused by a capacitive element connected to the FET. In order to compensate for the above error, the present invention first applies a feedback circuit (this process is indicated in FIG. 1 and 3 as the secondary current flowing to the rear of the plant is input to the processor 200).

The error in the form shown in FIG. 6 can be corrected by the feedback circuit, but in order to accurately control the feedback circuit, the output current of the secondary side must be accurately sensed. However, the present invention is estimated and calculated without directly sensing the output current of the secondary side (the reason for not directly sensing the output current of the secondary side was mentioned in the background art above). In the process of estimating the current, errors in the steady state and errors due to measurement occur. Therefore, it is necessary to compensate for this error.

The error occurring in the current estimation process occurs in the form of FIG. 8. In one embodiment of the present invention, a current measuring circuit of the form shown in FIG. 7 is used to sense the input current of the primary side. In the circuit of FIG. 7, when the current flows positively, the voltage V _CT is induced in R _CT . 8 is a waveform of an input current generated when measuring current by the current measurement circuit of FIG. 7, and area A is a buffer area generated when a switch included in a plant switches from a freewheeling area to an active area, and output current and It is not physically related. This value (A) serves as an error in sensing the primary input current and estimating the secondary output current.

Therefore, the error of the output current can be corrected by subtracting the error. For more detailed process, follow Equation 5 below.

[Equation 5]

A = 1/2 * ( L _lk + L _C )/( V _in ) * ( I _{in _ bar} /D) ²

A is the error component caused by the steady-state error and measurement error, the area of the shaded area in FIG. 8, L _lk is the leakage inductance of the transformer included in the plant, and L _C is the switching included in the plant It is an inductance component generated by a device (ZVS choke). V _in is the input voltage on the primary side, I _{in _ bar} is the average of the input current, and D is the duty ratio.

If the average value of the error obtained by [Equation 5] is taken and reflected in the output current estimated by [Equation 3], the secondary-side output current reflecting the steady state error and the measurement error can be estimated.

Meanwhile, in one embodiment of the present invention, the digital control unit 220 outputs the estimated output current (I _{out _ bar} ) and the target output current (from the current correction unit 210 according to [Equation 3] and [Equation 5]) comparing I ^*), and can be transmitted to the controller 300 generates a control signal _(V D) to attenuate the differences. When a target output current to be generated on the secondary side is compared with an actual current estimated to be output on the secondary side, and a control signal related to the difference between the two is generated and transmitted to the control unit 300, the FET element 320 in the control unit 300 ) Controls on/off of the gate terminal according to the control signal received from the digital control unit 220.

Since V+ is determined according to the on/off operation of the FET device 320 and V _ref and the secondary output current is determined accordingly, the digital control unit based on the secondary output current estimated by the current correction unit 210 ( 220), the secondary-side output current can be adjusted.

Meanwhile, in one embodiment of the present invention, the controller 300 provides a series RC circuit 330 between the input terminal and the output terminal of the amplifier 310 and a resistance 340 between the input terminal and the primary output terminal. It may further include. By the series RC circuit 330 and the resistor 340, it is possible to control the dynamic change due to the sudden change of the load connected to the secondary side, and accordingly, it becomes more accurate to estimate and control the secondary-side output current.

The embodiments of the present invention have been disclosed for purposes of illustration, and those skilled in the art to which the present invention pertains fall within the scope of the claims within the scope of the technical spirit of the present invention. You should see.

100 sensing unit 200 processor
210 current compensation unit 220 digital control unit
300 control unit 310 amplifier
320 FET device 330 series RC circuit
340 resistance

Claims (12)

A sensing unit for measuring a primary input current of the plant;
A processor for estimating the secondary-side output current of the plant using the input current sensed by the sensing unit; And
It includes a control unit for outputting the output current by controlling the input current according to the output current estimated by the processor,
The processor,
The current output unit estimates the output current using the sensed input current and calculates an error according to at least one of a steady state error or a measurement error when estimating the output current, and a target output current calculated by the current correction unit and the output current estimated by the current correction unit It includes a digital control unit to generate a control signal for adjusting to transmit to the control unit,
The current correction unit,
Estimate the output current using the average value of the input current, the turns ratio of the transformer included in the plant, and the duty ratio of the plant voltage,
Output current estimation device that estimates the output current by the formula Iout_bar = (n * Iin_bar)/ D.
(However, n: transformer turns ratio, Iin_bar: average input current value, D: duty ratio of plant voltage)

delete delete delete The method according to claim 1,
The duty ratio is D = V _O / V _L output current estimation device, characterized in that.
(However, D: Duty ratio of plant voltage, V _O : Output voltage of plant, V _L : Inductance voltage of plant output)
The method according to claim 1,
The output current estimation apparatus, characterized in that the average value of the input current is derived by passing the input current through a low-pass filter.
delete A sensing unit for measuring a primary input current of the plant;
A processor for estimating the secondary-side output current of the plant using the input current sensed by the sensing unit; And
It includes a control unit for outputting the output current by controlling the input current according to the output current estimated by the processor,
The processor,
The current output unit estimates the output current using the sensed input current and calculates an error according to at least one of a steady state error or a measurement error when estimating the output current, and a target output current calculated by the current correction unit and the output current estimated by the current correction unit It includes a digital control unit to generate a control signal for adjusting to transmit to the control unit,
The current correction unit,
Calculate the steady state error or measurement error by at least one of the inductance of the switch in the plant or the inductance of the transformer,
Output current estimation device characterized by calculating the steady-state error or measurement error by A = 1/2 * (L _lk + L _C )/(V _in ) * (I _{in_bar} / D) ² .
(However, A: Error component,
L _lk : The leakage inductance of the transformer contained in the plant,
L _C : Inductance component generated by the switching element included in the plant,
V _in : Input voltage on the primary side,
I _{in_bar} : average of primary input current,
D: Duty ratio)
The method according to claim 1,
The digital control unit compares the output current and the target output current estimated by the current correction unit, and generates a control signal to attenuate the difference, and transmits the output current estimation device to the control unit.
A sensing unit for measuring a primary input current of the plant;
A processor for estimating the secondary-side output current of the plant using the input current sensed by the sensing unit; And
It includes a control unit for outputting the output current by controlling the input current according to the output current estimated by the processor,
The processor,
The current output unit estimates the output current using the sensed input current and calculates an error according to at least one of a steady state error or a measurement error when estimating the output current, and a target output current calculated by the current correction unit and the output current estimated by the current correction unit It includes a digital control unit to generate a control signal for adjusting to transmit to the control unit,
The control unit,
An output current estimation apparatus including an amplifier in which a reference voltage signal is input to a + input terminal, a primary output voltage is input to a-input terminal, and a FET element connected to the + input terminal of the amplifier and controlled by the processor. The method according to claim 10,
The FET device receives a control signal input from the digital control unit to adjust the on/off of the gate terminal,
The amplifier is an output current estimation device, characterized in that for adjusting the output current according to the degree of the gate terminal on / off.
The method according to claim 10,
The control unit further comprises a series RC circuit between the input terminal and the output terminal of the amplifier and a resistance between the input terminal and the primary output terminal of the amplifier.

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