TW202030487A - Method of resistance compensation for measuring output current and conversion circuit - Google Patents

Abstract

A method of resistance compensation for measuring output current includes the following steps: (a) providing a secondary side loop of a conversion unit, and the secondary side loop includes a sense resistor and the first line. (b) providing a control unit for controlling the conversion unit, and the control unit is coupled to the first line and the sense resistor. (c) utilizing a first current to flow through the secondary side loop to obtain a first equivalent line resistance of the first line. (d) providing a second current by the control unit flowing through a loop of the sense resistor, the first line and the control unit to obtain a second equivalent line resistance of the second line. (e) compensating the sense resistor by the control unit according to the first equivalent line resistance and the second equivalent line resistance.

Description

Resistance compensation method for measuring output current and its conversion circuit

The present invention relates to a method for measuring output current by resistance compensation and its conversion circuit, in particular to a method for measuring output current by resistance compensation and its conversion circuit which reduces the difficulty of circuit layout.

Nowadays, as the power delivery (PD; Power Delivery) technology is becoming more and more popular, there are more and more adapters with power delivery functions. Generally, when the adapter performs output current detection, a current detection resistor is added to the secondary side of the internal conversion circuit to detect the output current, so as to achieve the purpose of monitoring the output current. In this application, in order to obtain a precise output current detection side, the connection position of the circuit layout becomes very important. Among them, in order to prevent the impedance of the actual circuit from affecting the accuracy of current detection, a special layout must be used in the circuit layout.

Specifically, both ends of the current detection resistor must be directly connected to the two current detection pins of the controller, and cannot be coupled to the current detection pins of the controller from any ground point. The reason is that if it is coupled to the controller from an arbitrary ground point, the circuit from the current detection resistor to the ground point will generate additional line impedance. Since the output current flowing through this line impedance will also cause a voltage drop, it will cause a misjudgment on the current detection side of the controller and incorrectly control the conversion circuit. However, in actual conditions, if the circuit layout is not noticed or familiar, it is easy to mistakenly connect one of the controller ground current detection pins to other grounding points without directly connecting the current detection resistor. This caused a misjudgment on the current detection side.

In addition, as the design of the current controller pins becomes more and more sophisticated, the single pin becomes more and more versatile. Therefore, in addition to the current detection function, one of the current detection pins of the current controller also adds the function of grounding the controller. In this situation, the current detection pin with grounding function must be directly connected to the ground terminal of the output capacitor of the conversion circuit to accurately detect the voltage at the ground point. Therefore, the ground terminal of the output capacitor needs to be directly coupled to one end of the current detection resistor, so that the difficulty of circuit layout is greatly increased when the controller can obtain accurate output current and accurate ground voltage. .

Therefore, how to design a resistance compensation method for measuring output current and its conversion circuit, using a simple resistance compensation calculation method, so as to reduce the circuit layout in order to obtain accurate output current and accurate ground voltage. The degree of difficulty is an important subject for the inventors of this case.

In order to solve the above-mentioned problems, the present invention provides a resistance compensation method for measuring the output current to overcome the problems of the prior art. Therefore, the resistance compensation method of the present invention for measuring output current includes the following steps: providing a secondary side loop of the conversion unit, the secondary side loop including a detection resistor and a first circuit, the first circuit being the first of the detection resistor End to ground point. A control unit for controlling the conversion unit is provided, and the control unit is coupled to the ground point and the second end of the detection resistor. According to the first current flowing through the secondary side loop, the first equivalent line resistance of the first line is obtained. According to the loop of the second current flowing through the detection resistor, the ground point and the control unit provided by the control unit, the second equivalent line resistance of the second line from the ground point to the control unit is obtained. And the control unit compensates the detection resistance according to the first equivalent line resistance and the second equivalent line resistance.

In one embodiment, the first current flows through the detection resistor and the first line to generate a first voltage, and the first line voltage of the first line is obtained by subtracting the detection voltage of the detection resistor from the first voltage.

In one embodiment, the control unit obtains the first equivalent line resistance according to the first current and the first line voltage.

In one embodiment, the second current flows through the detection resistor, the first line and the second line to generate the second voltage, and the second line of the second line is obtained by subtracting the detection voltage and the first line voltage from the second voltage Electricity.

In an embodiment, the control unit obtains the second equivalent line resistance according to the second current and the second line voltage.

In one embodiment, the first current is provided by a load coupled to the secondary side loop.

In one embodiment, the second end is coupled to the control unit with the shortest coupling distance.

In one embodiment, the impedance of the control unit is higher than the detection resistance and the first equivalent line resistance.

In one embodiment, the control unit obtains the first equivalent line resistance and the second equivalent line resistance before the conversion unit is operated, and when the conversion unit is operating, the output current is obtained according to the voltage signal of the detection resistor.

In one embodiment, the control unit completes the measurement of the grounding and output current of the control unit through the first contact coupled to the first end and the second contact coupled to the grounding point.

In order to solve the above-mentioned problems, the present invention provides a conversion circuit for measuring the output current by resistance compensation to overcome the problems of the prior art. Therefore, the conversion circuit for measuring the output current by resistance compensation of the present invention includes: a conversion unit including a secondary side loop, and the secondary side loop includes a detection resistor, which is connected in series with the secondary side loop. And the first line extends from the first end of the detection resistor to the ground point. The control unit is coupled to the ground point and the second end of the detection resistor. Wherein, the control unit obtains the first equivalent line resistance of the first circuit according to the first current flowing through the secondary side loop, and the control unit provides the second current flowing through the detection resistor, the ground point, and the loop of the control unit to obtain the ground point to The second equivalent line resistance of the second circuit of the control unit; the control unit compensates the detection resistance according to the first equivalent line resistance and the second equivalent line resistance.

In one embodiment, the second end is coupled to the control unit with the shortest coupling distance.

In one embodiment, the impedance of the control unit is higher than the detection resistance and the first equivalent line resistance.

In an embodiment, the control unit includes: a first contact, which is coupled to the ground. And the second contact, coupled to the second end. Wherein, the control unit completes the grounding and output current measurement of the control unit through the first contact and the second contact.

In order to further understand the technology, means and effects of the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. I believe that the purpose, features and characteristics of the present invention can be obtained from this in depth and For specific understanding, however, the accompanying drawings are only provided for reference and illustration, and are not intended to limit the present invention.

The technical content and detailed description of the present invention are described as follows with the drawings:

Please refer to FIG. 1 for a circuit block diagram of the conversion circuit for measuring output current by resistance compensation according to the present invention. The conversion circuit 100 includes a conversion unit 1 and a control unit 2, and when the conversion circuit 100 actually operates, the control unit 2 controls the conversion unit 1 to convert the input power Vin to the output power Vo to provide the power required for the operation of the load 200. The conversion unit 1 includes a primary side loop 12 and a secondary side loop 14, and the control unit 2 controls the primary side loop 12 and the secondary side loop 14 to convert the input power Vin into the output power Vo. The secondary side loop 14 includes a filter circuit 142, an isolation switch 144, a feedback compensation circuit 146 and a detection resistor Rs, and the filter circuit 142, the isolation switch 144, the load 200 and the detection resistor Rs are connected in series to form a closed loop. When the conversion circuit 100 is abnormal, the control unit 2 turns off the isolation switch 144 so that the conversion circuit 100 no longer provides output power Vo to the load 200 to provide circuit protection when the conversion circuit 100 is abnormal.

The ground terminal of the output capacitor C is set as the ground point G, and the ground point G is the total ground position of the secondary side loop 14 and the control unit 2. The feedback compensation circuit 146 is coupled to the path from the filter circuit 142 to the load 200, and detects the output power Vo and provides it to the control unit 2 for feedback compensation, so that the control unit 2 can stably control the output power Vo. The line extending from the first end A of the detection resistor Rs to the ground point G is defined as the first line T1, and the line impedance of the first line T1 is the first equivalent line resistance R1. The control unit 2 includes a first contact point P1 and a second contact point P2, the first contact point P1 is coupled to the ground point G, and the second contact point P2 is coupled to the second end B of the detection resistor Rs. The line extending from the first contact point P1 to the ground point G is defined as the second line T2, and the line impedance of the second line T2 is the second equivalent line resistance R2. The line extending from the second end B of the detection resistor Rs to the second contact P2 is defined as the third line T3, and the line impedance of the third line T3 is the third equivalent line resistance R3.

Specifically, since the first line T1, the second line T2, and the third line T3 all have an equivalent line group (R1~R3), the equivalent line group (R1~R3) will make the control unit 2 pass the detection resistor The voltage signal measured by Rs is not accurate enough. The reason is that when the output current Io flows through the equivalent line group (R1~R3), a line voltage drop will also occur. That is, the voltage value of the voltage signal is equivalent to the cross voltage across the equivalent line set (R1~R3) and the detection resistor Rs, not just the cross voltage across the detection resistor Rs. Therefore, the voltage signal measured by the control unit 2 is not actually equal to the output current Io. In addition, in terms of circuit layout, if the first end A and the second end B of the detection resistor Rs are equidistantly coupled to the first contact P1 and the second contact P2 of the control unit 2, the output current can indeed be solved. The problem of inaccurate Io measurement, but the ground terminal of the output capacitor C must be directly coupled to the first terminal A of the detection resistor Rs, and in order to make the level of the ground point accurately zero, the above three points ( The ground terminal of the output capacitor C, the first terminal A of the detection resistor Rs, and the first contact P1) of the control unit must be as close as possible. This makes the circuit layout difficult to consider the above reasons.

Therefore, the main purpose of the present invention is that through the resistance compensation method of the present invention, the ground terminal of the output capacitor C does not need to be as close as possible to the first end A of the detection resistor Rs, and the first end of the detection resistor Rs The terminal A and the second terminal B do not need to be equidistantly coupled to the first contact P1 and the second contact P2 of the control unit 2 respectively. Therefore, due to the above-mentioned characteristics, the conversion circuit 100 of the present invention can achieve the effect of easy circuit layout through the above-mentioned circuit design. In addition, since the control unit 2 performs resistance compensation before the actual operation of the conversion circuit 100, the output current Io can be accurately measured when the conversion circuit 100 is actually operated. Therefore, due to the above characteristics, the conversion circuit 100 of the present invention can achieve the effect of improving the measurement accuracy of the output current Io. It is worth mentioning that, in one embodiment of the present invention, the detailed structure and compensation calculation method of the conversion circuit 100 will be further described later.

Please refer to FIG. 2 for the circuit block diagram of the first step of the resistance compensation calculation method of the present invention. The first step is to use the first current I1 to flow through the secondary side loop 14 to obtain the resistance value of the first equivalent line resistance R1 before the conversion circuit 100 actually operates. The first current I1 can be provided by an external electronic device, and the easiest way to implement is to use an electronic load to couple the conversion circuit 100. This means that the load 200 is an electronic load, which can draw a specific current according to the setting of the operator. When the first current I1 flows through the secondary side loop 14, the first current I1 will flow through the detection resistor Rs and the first line T1. At this time, the control unit 2 obtains the first voltage V1 from the second end B of the detection resistor Rs to the ground point G. Then, the control unit 2 subtracts the detection voltage Vs of the detection resistor Rs from the first voltage V1 to obtain the first line voltage Vt1 of the first line T1. It is worth mentioning that since the impedance of the first contact point P1 and the second contact point P2 of the control unit 2 is high impedance (usually the impedance is kΩ), it must be much higher than the detection resistance Rs and the first equivalent line resistance R1 (Usually, the impedance of the detection resistor Rs and the first equivalent line resistance R1 is less than or equal to the Ω level). Therefore, when the first current I1 flows through the secondary side loop 14, the first current I1 cannot flow to the control unit 2 through the second line T2 and the third line T3 (that is, it is divided to the first contact P1 and the second The current at the contact P2 approaches zero).

Among them, since the resistance value of the detection resistor Rs is known during circuit design, the control unit 2 obtains the resistance value of the detection resistor Rs before performing the first step of the resistance compensation calculation method. Moreover, the first current I1 can draw a specific current according to the setting of the operator, so the control unit 2 has also obtained the current value of the first current I1. When the detection resistance Rs and the first current I1 are known, the control unit 2 can obtain the detection voltage Vs. Then, the control unit 2 subtracts the detection voltage Vs from the first voltage V1 to obtain the first line voltage Vt1 of the first line T1. Finally, the control unit 2 can obtain the resistance value of the first equivalent line resistance R1 through the known first line voltage Vt1 and the first current I1. In summary, the relational expression of the first step of the resistance compensation calculation method can be expressed by: V1=Vs+Vt1=I1*(Rs+R1), and the control unit 2 flows through the secondary side loop 14 through the first current I1. The resistance value of the first equivalent line resistance R1 can be obtained.

Please refer to FIG. 3 for the circuit block diagram of the second step of the resistance compensation calculation method of the present invention, and refer to FIGS. 1 to 2 for complex cooperation. In the second step, first, after obtaining the resistance value of the first equivalent line resistance R1, the control unit 2 provides a second current I2 from the second contact P2 through the detection resistor Rs, the grounding point G to the first contact P1 Or the loop from the first contact P1 through the grounding point G, the detection resistor Rs to the second contact P2, to obtain the second equivalent line resistance R2 of the second line T2. Among them, because this loop also includes the third equivalent line resistance R3 of the third circuit T3 from the second end B of the detection resistor Rs to the second contact P2 of the control unit 2. Therefore, this loop includes two unknown parameters, the second equivalent line resistance R2 and the third equivalent line resistance R3. In the case that this loop includes two unknown parameters, if there is no special calculation method, only the total resistance of the second equivalent line resistance R2 and the third equivalent line resistance R3 can be obtained. Although the control unit 2 can also use the total resistance value to perform resistance compensation, since the resistance value of the second equivalent line resistance R2 and the resistance value of the third equivalent line resistance R3 cannot be accurately known separately, the comparison , The accuracy of the output current Io obtained by the resistance compensation to obtain the total resistance will be slightly lower than the accuracy of the individual resistance values.

In order to obtain high accuracy, the coupling distance between the second end B of the detection resistor Rs and the second contact P2 of the control unit 2 must be as close as possible to shorten the third line T3 as much as possible. When the second end B of the detection resistor Rs is coupled to the second contact P2 of the control unit 2 with the shortest coupling distance, the line length of the third line T3 approaches zero, so that the resistance of the third equivalent line resistance R3 The value will also approach zero. In this way, only one unknown parameter of the second equivalent line resistance R2 can be left in this loop. In terms of circuit layout, since the invented conversion circuit 100 only needs to connect the second end B of the detection resistor Rs to the second contact P2 of the control unit 2 as close as possible, the circuit layout of other grounding circuits is not required. Use a special coupling method. Therefore, the effect of easy circuit layout and easy design can be achieved.

When the second current I2 flows through the loop of the control unit 2, the detection resistor Rs and the ground point G, the second current I2 will flow through the detection resistor Rs, the first line T1, the second line T2, and the third line T3. At this time, the control unit 2 obtains the second voltage V2 from the first contact P1 to the second contact P2 (that is, the voltage across the detection resistor Rs, the first line T1, the second line T2, and the third line T3 ). Then, the control unit 2 subtracts the detection voltage Vs and the first line voltage Vt1 from the first voltage V1 to obtain the second line voltage Vt2 of the second line T2 and the third line voltage Vt3 of the third line T3. Among them, since the resistance value of the third equivalent line resistance R3 approaches zero, the third line voltage Vt3 also approaches zero. Under this condition, the second line voltage Vt2 of the second line T2 can be known.

Among them, since the resistance value of the detection resistor Rs and the resistance value of the first equivalent line resistance R1 are known, the control unit 2 obtains the detection resistance Rs and the first equivalent before performing the second step of the resistance compensation calculation method. The resistance value of the line resistance R1. Moreover, the second current I2 is provided by the control unit 2, so the control unit 2 has also obtained the current value of the second current I2. When the resistance values of the detection resistor Rs and the first equivalent line resistance R1 and the second current I2 are known, the control unit 2 can obtain the detection voltage Vs and the first line voltage Vt1. Then, the control unit 2 subtracts the detection voltage Vs and the first line voltage Vt1 from the second voltage V2 to obtain the second line voltage Vt2 of the second line T2 (the third line voltage Vt3 approaches zero). Finally, the control unit 2 can obtain the resistance value of the second equivalent line resistance R2 through the known second line voltage Vt2 and the second current I2. In summary, the relational expression of the second step of the resistance compensation calculation method can be expressed by: V2=Vs+Vt1+Vt2+Vt3=I2*(R1+R2+R3+Rs), and the control unit 2 passes the second current I2 The resistance value of the second equivalent line resistance R2 can be obtained by flowing through the loop from the first contact point P1 to the second contact point P2.

2 to 3 again, the control unit 2 obtains the resistance values of the first equivalent line resistance R1 and the second equivalent line resistance R2 before the conversion unit 1 actually operates in the resistance compensation method of the present invention. After the control unit 2 obtains the resistance values of the first equivalent line resistance R1 and the second equivalent line resistance R2, the control unit 2 compensates the detection resistance Rs according to the first equivalent line resistance R1 and the second equivalent line resistance R2 , In order to complete the resistance compensation before the conversion unit 1 actually operates. Therefore, during actual operation of the conversion circuit 100, the control unit 2 can accurately know the output current Io of the conversion unit 1 by detecting the voltage signal measured by the resistor Rs. This means that the voltage signal measured by the control unit 2 is actually the voltage drop generated by the detection resistor Rs, the first equivalent line resistance R1, and the second equivalent line resistance R2, and the control unit 2 reuses the voltage drop. The impedance is converted to the corresponding current, which is the accurate output current Io.

It is worth mentioning that, in an embodiment of the present invention, the control unit 2 is applicable to a controller that only uses the first contact P1 and the second contact P2 to complete the grounding of the control unit 2 and the measurement of the output current Io. Specifically, as the design of the controller becomes more and more sophisticated, its single pin becomes more and more versatile. In the conventional controller, the grounding of the controller is usually separated from the pins for measuring the output current Io. Therefore, three pins are required to complete the grounding of the controller and the measurement of the output current Io. The present invention mainly uses the resistance compensation of the present invention to reduce the circuit layout when the control unit 2 integrates the grounding and output current Io measurement pins into two, and its good circuit layout design is more difficult. It is difficult to improve the accuracy of output current Io detection.

To sum up, the main advantage and effect of the embodiment of the present invention is that the conversion circuit of the present invention can make the ground terminal of the output capacitor on the secondary side loop be as close as possible through the resistance compensation method of the present invention. The detection resistor, and the two ends of the detection resistor do not need to be respectively coupled to the control unit at an equal distance, so as to achieve the effect of accurately measuring the output current and reducing the difficulty of circuit layout.

However, the above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the features of the present invention are not limited to these, and are not intended to limit the present invention. The full scope of the present invention should be referred to the following application The scope of the patent shall prevail. All embodiments that conform to the spirit of the scope of the patent application of the present invention and similar variations should be included in the scope of the present invention. Anyone familiar with the art in the field of the present invention can easily think of it. Changes or modifications can be covered in the following patent scope of this case. In addition, the features mentioned in the patent application scope and the specification can be implemented individually or in any combination.

100: Conversion circuit

1: Conversion unit

12: Primary side circuit

14: Secondary side loop

142: filter circuit

144: Isolation switch

146: Feedback compensation circuit

Rs: detection resistance

A: The first end

B: second end

C: output capacitor

G: Ground point

T1: First line

R1: The first equivalent line resistance

T2: second line

R2: Second equivalent line resistance

T3: Third Route

R3: Third equivalent line resistance

2: control unit

P1: The first contact

P2: second contact

200: load

Vin: input power

Vo: output power

V1: first voltage

V2: second voltage

Vt1: first line voltage

Vt2: second line voltage

Vt3: third line voltage

Vs: Detection voltage

Io: output current

I1: first current

I2: second current

Fig. 1 is a circuit block diagram of a conversion circuit for measuring output current by resistance compensation according to the present invention;

2 is a circuit block diagram of the first step of the resistance compensation calculation method of the present invention; and

3 is a circuit block diagram of the second step of the resistance compensation calculation method of the present invention.

100: Conversion circuit

1: Conversion unit

12: Primary side circuit

14: Secondary side loop

142: filter circuit

144: Isolation switch

146: Feedback compensation circuit

Rs: detection resistance

A: The first end

B: second end

C: output capacitor

G: Ground point

T1: First line

R1: The first equivalent line resistance

T2: second line

R2: Second equivalent line resistance

T3: Third Route

R3: Third equivalent line resistance

2: control unit

P1: The first contact

P2: second contact

200: load

Vin: input power

Vo: output power

Io: output current

Claims (14)

A method for measuring output current by resistance compensation includes the following steps: Providing a primary side loop of a conversion unit, the secondary side loop including a detection resistor and a first line, the first line being a first end of the detection resistor to a ground point; A control unit for controlling the conversion unit is provided, and the control unit is coupled to the ground point and a second end of the detection resistor; Obtaining a first equivalent line resistance of the first line according to a first current flowing through the secondary side loop; Obtaining a second equivalent line resistance of a second line from the ground point to the control unit according to the control unit providing a second current flowing through the detection resistor, the ground point and the control unit loop; and The control unit compensates the detection resistance according to the first equivalent line resistance and the second equivalent line resistance. The method for measuring output current by resistance compensation as described in the scope of the patent application, wherein the first current flows through the detection resistor and the first circuit to generate a first voltage, and the first voltage is subtracted from the A detection voltage of the detection resistor obtains a first line voltage of the first line. According to the method for measuring output current by resistance compensation as described in item 2 of the scope of patent application, the control unit obtains the first equivalent line resistance according to the first current and the first line voltage. The method for measuring output current by resistance compensation as described in the scope of patent application, wherein the second current flows through the detection resistor, the first circuit and the second circuit to generate a second voltage, and passes through the first The detection voltage and the first line voltage are subtracted from the second voltage to obtain a second line voltage of the second line. According to the resistance compensation method for measuring output current described in item 4 of the scope of patent application, the control unit obtains the second equivalent line resistance according to the second current and the second line voltage. The resistance compensation method for measuring output current as described in the first item of the scope of patent application, wherein the first current is provided by a load coupled to the secondary side loop. In the method for measuring output current by resistance compensation as described in claim 1, wherein the second terminal is coupled to the control unit with a shortest coupling distance. In the method for measuring output current by resistance compensation as described in item 7 of the scope of patent application, an impedance of the control unit is higher than the detection resistance and the first equivalent line resistance. The method for measuring output current by resistance compensation as described in item 1 of the scope of patent application, wherein the control unit obtains the first equivalent line resistance and the second equivalent line resistance before the conversion unit operates, and the When the conversion unit is operating, the output current is known according to a voltage signal of the detection resistor. According to the method for measuring output current by resistance compensation as described in item 1 of the scope of patent application, the control unit completes the output current through a first contact coupled to the first terminal and a second contact coupled to the ground point The grounding of the control unit and the measurement of the output current. A conversion circuit for resistance compensation and measurement of output current, including: A conversion unit includes a primary side loop, and the secondary side loop includes: A detection resistor connected in series with the secondary side loop; and A first circuit extending from a first end of the detection resistor to a ground point; A control unit coupled to the ground point and a second end of the detection resistor; Wherein, the control unit obtains a first equivalent line resistance of the first circuit according to a first current flowing through the secondary side loop, and the control unit provides a second current flowing through the detection resistor and the ground point And the loop of the control unit obtains a second equivalent line resistance of a second line from the ground point to the control unit; the control unit compensates the detection according to the first equivalent line resistance and the second equivalent line resistance Measure resistance. In the conversion circuit for measuring the output current by resistance compensation as described in item 11 of the scope of patent application, the second terminal is coupled to the control unit with a shortest coupling distance. In the conversion circuit for measuring the output current by resistance compensation as described in item 12 of the scope of patent application, an impedance of the control unit is higher than the detection resistance and the first equivalent line resistance. As described in item 11 of the scope of patent application, the resistance compensation measurement output current conversion circuit, wherein the control unit includes: A first contact, coupled to the ground point; and A second contact, coupled to the second end; Wherein, the control unit completes the grounding of the control unit and the measurement of the output current through the first contact and the second contact.

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