CN110045170B - Method, system and device for detecting inductive current of step-up/step-down circuit - Google Patents
Method, system and device for detecting inductive current of step-up/step-down circuit Download PDFInfo
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Abstract
The invention discloses a method, a system and a device for detecting the inductive current of a step-up/step-down circuit, comprising the following steps: acquiring the midpoint current of a switching tube from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube of a target circuit; wherein the target circuit is a boost circuit or a buck circuit; judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit; if so, taking the midpoint current as the average current of the inductor of the target circuit in the current period; if not, multiplying the midpoint current by a coefficient smaller than 1, and taking the result of multiplying the midpoint current by the coefficient as the average current of the inductor. Therefore, the average current of the inductor in the target circuit can be obtained through a series of software programs only by obtaining the midpoint current of the switching tube in the target circuit, namely, only one current transformer needs to be arranged on the line where the switching tube is located, and therefore the detection cost is reduced under the condition that the sampling current is guaranteed not to be invalid.
Description
Technical Field
The invention relates to the field of current detection, in particular to an inductive current detection method, system and device of a step-up/step-down circuit.
Background
At present, a boost circuit is a common switching dc boost circuit, a buck circuit is a common switching dc buck circuit, please refer to fig. 1 and fig. 2, fig. 1 is a schematic structural diagram of a boost circuit in the prior art, and fig. 2 is a schematic structural diagram of a buck circuit in the prior art.
In the application of the boost circuit or buck circuit, it is usually necessary to obtain the current of the inductor, and it is easy to think that a current transformer is arranged at the position 3 in the figure (the boost circuit refers to the mark of fig. 1, and the buck circuit refers to the mark of fig. 2) for sampling the current of the inductor. However, in the case of a large current of the inductor, the current transformer is easily saturated, which may cause the sampling current to fail. In the prior art, in order to prevent the current transformer from being saturated, the inductance current detection method is improved as follows: and current transformers are respectively arranged at the positions marked 1 and 2 in the figure, and the two sampling currents are superposed according to the kirchhoff principle to obtain the current of the inductor. However, the improved inductor current detection method requires two current transformers, thereby increasing the detection cost.
Therefore, how to provide a solution to the above technical problem is a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a method, a system and a device for detecting the inductive current of a step-up/step-down circuit, which only need to arrange a current transformer on a circuit where a switching tube is arranged, thereby reducing the detection cost under the condition of ensuring that the sampling current does not fail.
In order to solve the above technical problem, the present invention provides an inductive current detection method for a buck/boost circuit, including:
acquiring the midpoint current of a switching tube of a target circuit from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube; the target circuit is a boost circuit or a buck circuit;
judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit;
if so, taking the midpoint current as the average current of the target circuit in the current period;
if not, multiplying the midpoint current by a coefficient smaller than 1, and taking the result of the multiplication as the average current of the inductor.
Preferably, the process of obtaining the midpoint current of the switching tube from a current transformer arranged on a line where the switching tube is located at the time of the conduction midpoint of the switching tube of the target circuit includes:
acquiring the duty ratio d of a switching tube in a target circuit and the control period T of the switching tube, and obtaining the duty ratio d and the control period T of the switching tube according to TonCalculating the conduction time T of the switching tubeon；
Starting timing from the moment of the rising edge of the driving signal of the switching tube, and when the timing time reaches tonAnd when the current is in the second conduction period,/2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from a current transformer arranged on a line where the switching tube is located.
Preferably, when the midpoint current is greater than the current continuous critical value, the process of using the midpoint current as the average current of the inductor of the target circuit in the current cycle includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is continuous
Wherein, the current value of the switch tube in the conducting time is equal to the current value of the inductor at the same time, i0 is the current value of the switch tube at the moment of the rising edge of the control period T (k), i2 is the current value of the switch tube at the moment of the falling edge of the control period T (k), toffThe turn-off time of the switching tube;
according to the current integral relation
Is determined in current connectionContinuing to make the average current of the inductor in a control period T (k) equal to i 1; wherein i1 is the midpoint current of the switching tube at the conduction midpoint moment of the control period t (k);
and in the working process of the target circuit, when the midpoint current of the current cycle is greater than the current continuous critical value, determining that the inductor is in a current continuous mode, and taking the midpoint current as the average current of the inductor of the target circuit in the current cycle.
Preferably, when the target circuit is a boost circuit, the inductor current detection method further includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
according to the relation t of input and output voltage of boost circuit and its internal inductance voltageonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage of the boost circuit, VoutIs the output voltage of the boost circuit;
correspondingly, when the midpoint current is not greater than the current continuous critical value, the process of multiplying the midpoint current by a coefficient less than 1 and taking the result of the multiplication as the average current of the inductor comprises the following steps:
during the operation of the boost circuit, when the current at the midpoint of the current period is not more than the current continuous critical value, determining that the inductor is in a current discontinuous mode, and determining that the inductor is in the current discontinuous mode
The result of the multiplication is used as the average current of the inductor of the boost circuit in the current period.
Preferably, when the target circuit is a buck circuit, the inductor current detection method further includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
according to the relation t between the input and output voltage of the buck circuit and the voltage of an inductor thereinonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage, V, of the buck circuitoutThe output voltage of the buck circuit is obtained;
correspondingly, when the midpoint current is not greater than the current continuous critical value, the process of multiplying the midpoint current by a coefficient less than 1 and taking the result of the multiplication as the average current of the inductor comprises the following steps:
when the current at the midpoint of the current cycle is not more than the current continuous critical value in the working process of the buck circuit, the inductor is determined to be in a current discontinuous mode, and the current is measured
The result of the multiplication is used as the average current of the inductor of the buck circuit in the current period.
In order to solve the above technical problem, the present invention further provides an inductor current detection system of a buck/boost circuit, including:
the current acquisition module is used for acquiring the midpoint current of a switching tube of a target circuit from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube; the target circuit is a boost circuit or a buck circuit;
the current comparison module is used for judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit or not, and if so, the first inductive current determination module is executed; if not, executing a second inductive current determining module;
the first inductor current determining module is configured to use the midpoint current as an inductor average current of the target circuit in a current cycle;
and the second inductor current determining module is used for multiplying the midpoint current by a coefficient smaller than 1, and taking the result of multiplying the midpoint current by the coefficient smaller than 1 as the average inductor current.
Preferably, the current obtaining module includes:
the conduction time obtaining submodule is used for obtaining the duty ratio d of a switching tube in a target circuit and the control period T of the switching tube and obtaining the control period T according to TonCalculating the conduction time T of the switching tubeon；
A midpoint current obtaining submodule for starting timing from the moment of the rising edge of the driving signal of the switching tube, when the timing time reaches tonAnd when the current is in the second conduction period,/2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from a current transformer arranged on a line where the switching tube is located.
Preferably, when the target circuit is a boost circuit, the inductor current detection method further includes:
a first current integration module, configured to obtain a current integration relational expression of the inductor in a control period t (k) according to a working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
a first integral correction module for correcting the first integral according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
a first inductor current predetermining module for determining t according to the relation between the input and output voltages of the boost circuit and the inductor voltage thereinonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage of the boost circuit, VoutIs the output voltage of the boost circuit;
correspondingly, the second inductor current determining module is specifically configured to determine that the inductor is in a current interruption mode and will be used for determining that the inductor is in the current interruption mode when the current at the midpoint of the current cycle is not greater than the current continuation critical value during the operation of the boost circuit
The result of the multiplication is used as the average current of the inductor of the boost circuit in the current period.
Preferably, when the target circuit is a buck circuit, the inductor current detection system further includes:
a second current integration module, configured to obtain a current integration relational expression of the inductor in the control period t (k) according to a working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offFor the time required for the current of the inductor to decrease from i2 to 0 within the control period t (k),t'off＜toff，toffthe turn-off time of the switching tube;
a second integral correction module for correcting the second integral according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
a second inductor current predetermining module for determining t according to the relation between the input and output voltages of buck circuit and its inductor voltageonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage, V, of the buck circuitoutThe output voltage of the buck circuit is obtained;
correspondingly, the second inductor current determining module is specifically configured to determine that the inductor is in a current interruption mode and will be used for determining that the inductor is in the current interruption mode when the midpoint current of the current cycle is not greater than the current continuous critical value in the working process of the buck circuit
The result of the multiplication is used as the average current of the inductor of the buck circuit in the current period.
In order to solve the above technical problem, the present invention further provides an inductor current detecting device of a buck/boost circuit, including:
a memory for storing a computer program;
and a processor for executing any one of the above-mentioned inductor current detection methods of the step-up/down circuit when executing the computer program.
The invention provides an inductive current detection method of a step-up/step-down circuit, which comprises the following steps: acquiring the midpoint current of a switching tube from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube of a target circuit; wherein the target circuit is a boost circuit or a buck circuit; judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit; if so, taking the midpoint current as the average current of the inductor of the target circuit in the current period; if not, multiplying the midpoint current by a coefficient smaller than 1, and taking the result of multiplying the midpoint current by the coefficient as the average current of the inductor.
Therefore, the average current of the inductor in the target circuit can be obtained through a series of software programs only by obtaining the midpoint current of the switching tube in the target circuit (which means that only one current transformer needs to be arranged on the line where the switching tube is located), so that the detection cost is reduced under the condition that the sampling current is guaranteed not to fail.
The invention also provides an inductive current detection system and device of the step-up/step-down circuit, and the inductive current detection system and device have the same beneficial effects as the detection method.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed in the prior art and the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of a boost circuit in the prior art;
FIG. 2 is a schematic diagram of a buck circuit in the prior art;
fig. 3 is a flowchart of a method for detecting an inductor current of a buck/boost circuit according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a current cycle of an inductor in a current continuous mode according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a period of an inductor current in a current interruption mode according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of an inductor current detection system of a buck/boost circuit according to an embodiment of the present invention.
Detailed Description
The core of the invention is to provide a method, a system and a device for detecting the inductive current of a step-up/step-down circuit, only a current transformer is needed to be arranged on a circuit where a switching tube is arranged, and thus, the detection cost is reduced under the condition of ensuring that the sampling current does not fail.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 3, fig. 3 is a flowchart of a method for detecting an inductor current of a buck/boost circuit according to an embodiment of the present invention.
The method for detecting the inductive current of the voltage rising/dropping circuit comprises the following steps:
step S1: and acquiring the midpoint current of the switching tube from a current transformer arranged on a line where the switching tube is located at the moment of the conduction midpoint of the switching tube of the target circuit.
Step S2: judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit; if yes, go to step S3; if not, step S4 is executed.
Step S3: and taking the midpoint current as the average current of the inductor of the target circuit in the current period.
Step S4: and multiplying the midpoint current by a coefficient smaller than 1, and taking the result of multiplying the midpoint current by the coefficient smaller than 1 as the average current of the inductor.
It should be noted that the target circuit in this application is a boost circuit or a buck circuit.
Specifically, the operation principle of the boost circuit and the buck circuit is described first:
1) boost circuit: referring to fig. 1, during a stable control period, when the switch Q1 is turned on (the switch Q1 can be regarded as a conducting wire), the input voltage Vin of the boost circuit flows through the inductor L1 and the switch Q1, and the diode D1 prevents the capacitor C1 from discharging to ground. It can be seen that when the switch Q1 is turned on, the current of the inductor L1 is equal to the current of the switch Q1.
Since the boost circuit inputs dc power, the current in the inductor L1 increases linearly at a certain rate (the magnitude of the rate is related to the inductance of the inductor L1). As the current in inductor L1 increases, some energy is stored in inductor L1.
When the switch Q1 is turned off (the switch Q1 can be regarded as an open circuit), the current flowing through the inductor L1 does not immediately drop greatly due to the current holding characteristic of the inductor L1, but drops linearly at a certain rate. In the process, the inductor L1 discharges through the diode D1, that is, the inductor L1 starts to charge the capacitor C1, the voltage across the capacitor C1 rises, and the output voltage Vout of the boost circuit is higher than the input voltage Vin, and the voltage boost is finished.
2) buck circuit: referring to fig. 2, during a stable control period, when the switching transistor Q2 is turned on, the input voltage Vin of the buck circuit charges the capacitor C2 through the inductor L2, i.e., the electric energy is stored in the inductor L2 and also supplies energy to the external load (similarly, when the switching transistor Q2 is turned on, the current of the inductor L2 is equal to the current of the switching transistor Q2). Moreover, the buck circuit inputs direct current, and the same principle can be known as follows: the current on the inductor L2 increases linearly at a certain rate.
When the switching tube Q2 is turned off, due to the current holding characteristic of the inductor L2, the inductor L2 forms a conducting loop through the diode D2, so as to provide energy for the external load, and the capacitor C2 also provides energy for the external load to discharge, at this time, the output voltage Vout of the buck circuit is lower than the input voltage Vin, and the voltage reduction is finished.
In summary, in the boost circuit or buck circuit, when the switch is turned on, the inductor current will increase linearly at a certain rate; when the switch tube is turned off, the inductor current decreases linearly at a certain rate (the variation characteristic of the inductor current).
It is known that when a boost circuit or a buck circuit is actually applied, the average inductor current is usually obtained, so the application can analyze the average inductor current based on the variation characteristic of the inductor current. Meanwhile, the application considers that the inductive current has two modes: current continuous mode and current discontinuous mode, the present application analyzes the average current of the inductor in the current continuous mode and the average current of the inductor in the current discontinuous mode, respectively.
Referring to fig. 4, fig. 4 is a schematic diagram of an inductor current cycle in a current continuous mode according to an embodiment of the present invention. In fig. 4, in the control period t (k), the on-time t of the switch tube isonIn the middle, the inductor current gradually rises from i0 to i 2; in the off period t of the switching tubeoffIn this case, the inductor current gradually decreases from i2 to i 0. The application takes i1 as the midpoint current between i0 and i2, so according to the area equivalent principle, the following can be known: the effective area of the inductor current in the control period T (k) can be equivalent to a rectangular area with a length of the period T and a width of i 1. Therefore, the average inductor current during the control period t (k) is i 1.
Referring to fig. 5, fig. 5 is a schematic diagram of an inductor current cycle in a current interruption mode according to an embodiment of the present invention. In fig. 5, in the control period t (k), the on-time t of the switch tube isonIn the above example, the inductor current gradually increases from i0 to i2(i0 ═ 0A); in the turn-off time period t 'of the switching tube'off(t'off＜toffI.e., the inductor current is reduced to 0A early in the period t (k), the inductor current is gradually reduced from i2 to 0A. The application also takes i1 as the midpoint current between i0 and i2, and it can be understood that the average current of the inductor in the control period t (k) is smaller than i1, so the application approximates the multiplication result of i1 multiplied by a coefficient smaller than 1 as the average current of the inductor in the control period t (k).
Therefore, in the control period t (k), only the inductor current i1 at the conduction midpoint of the switching tube (when the switching tube is conducted, the current of the inductor is equal to the current of the switching tube) needs to be collected, so that in the present application, only the current transformer needs to be arranged on the circuit where the switching tube is located, so that i1 is collected at the conduction midpoint of the switching tube, and the average inductor current in the control period t (k) can be obtained according to the mode of the inductor current in the control period t (k).
In addition, as can be seen from comparing fig. 4 and fig. 5, the inductor current i1 in fig. 4 is greater than the inductor current i1 in fig. 5, so the present application can set a current continuous threshold value for the target circuit, and the setting principle is as follows: when the inductive current i1 is greater than the set current continuous threshold, the inductive current is in a current continuous mode, and when the inductive current i1 is not greater than the set current continuous threshold, the inductive current is in a current discontinuous mode.
Based on the method, at the moment of conducting the midpoint of the switching tube, the midpoint current of the switching tube is obtained from the current transformer arranged on the line where the switching tube is located, then the obtained midpoint current is compared with the current continuous critical value corresponding to the target circuit, and if the obtained midpoint current is larger than the current continuous critical value, the obtained midpoint current is used as the inductance average current of the target circuit in the current period; and if the acquired midpoint current is not more than the current continuous critical value, multiplying the acquired midpoint current by a coefficient less than 1, and taking the multiplication result of the midpoint current and the coefficient as the average current of the inductor of the target circuit in the current period.
The invention provides an inductive current detection method of a step-up/step-down circuit, which comprises the following steps: acquiring the midpoint current of a switching tube from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube of a target circuit; wherein the target circuit is a boost circuit or a buck circuit; judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit; if so, taking the midpoint current as the average current of the inductor of the target circuit in the current period; if not, multiplying the midpoint current by a coefficient smaller than 1, and taking the result of multiplying the midpoint current by the coefficient as the average current of the inductor.
Therefore, the average current of the inductor in the target circuit can be obtained through a series of software programs only by obtaining the midpoint current of the switching tube in the target circuit (which means that only one current transformer needs to be arranged on the line where the switching tube is located), so that the detection cost is reduced under the condition that the sampling current is guaranteed not to fail.
On the basis of the above-described embodiment:
as an optional embodiment, the process of obtaining the midpoint current of the switching tube from the current transformer arranged on the line where the switching tube is located at the time of the conducting midpoint of the switching tube of the target circuit includes:
acquiring the duty ratio d of a switching tube and the control period T of the switching tube in a target circuit, and obtaining the duty ratio d and the control period T of the switching tube according to TonD T is used for obtaining the conduction time T of the switching tubeon；
Starting timing from the time of the rising edge of the driving signal of the switching tube, and when the timing time reaches tonAnd when the current is more than 2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from the current transformer arranged on the line where the switching tube is located.
Specifically, as can be seen from fig. 4 and 5, i0 corresponds to the time at which the rising edge of the driving signal of the switching tube is located, i1 corresponds to the conduction intermediate time of the switching tube, and therefore the time difference between i0 and i1 is obtained as the conduction time t of the switching tubeonOne half of (a). Based on the method, the duty ratio d and the control period T of the switching tube in the target circuit are obtained in advance, and the duty ratio d and the control period T are obtained according to TonD T is used for obtaining the conduction time T of the switching tubeonThen, in the process of the target circuit working, timing is started from the moment of the rising edge of the driving signal of the switching tube, and when the timing time reaches tonAnd when the current is more than 2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from the current transformer arranged on the line where the switching tube is located.
As an alternative embodiment, the process of using the midpoint current as the average current of the inductor of the target circuit in the current cycle when the midpoint current is greater than the current continuous critical value includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is continuous
Wherein, the current value of the switch tube in the conducting time is equal to the current value of the inductor at the same time, i0 is the current value of the switch tube at the moment of the rising edge of the control period T (k), i2 is the current value of the switch tube at the moment of the falling edge of the control period T (k), toffThe turn-off time of the switching tube;
according to the current integral relation
Determining that the average current of the inductor in the control period T (k) is equal to i1 when the current is continuous; wherein i1 is the midpoint current of the switching tube at the conduction midpoint time of the control period t (k);
during the operation of the target circuit, when the midpoint current of the current cycle is greater than the current continuity critical value, the inductor is determined to be in the current continuity mode, and the midpoint current is taken as the average current of the inductor of the target circuit in the current cycle.
Specifically, in addition to the above-mentioned analysis of the average current of the inductor in the current continuation mode according to the area equivalence principle, the present application may also analyze the average current of the inductor in the current continuation mode according to the following manner:
according to the working principle of the inductor in the target circuit when the current is continuous (in combination with fig. 4), obtaining the current integral relation of the inductor in the control period t (k):
it is known that
The current integration relation is simplified to:
it can be seen that the average current of the inductor in the control period t (k) is equal to i1 when the current is continuous.
As an optional embodiment, when the target circuit is a boost circuit, the inductor current detection method further includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in a target circuit when the current is interrupted
Wherein, the current value of the switch tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switch tube at the time of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in the control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
according to the volt-second equilibrium law V of inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonThe voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is shown as i1, and the midpoint current of the switch tube at the turn-on midpoint moment of the control period T (k) is shown as i 1;
according to the relation t of input and output voltage of boost circuit and its internal inductance voltageonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage of the boost circuit, VoutIs the output voltage of the boost circuit;
correspondingly, when the midpoint current is not greater than the current continuous critical value, the process of multiplying the midpoint current by a coefficient less than 1 and using the result of the multiplication as the average current of the inductor comprises the following steps:
during operation of the boost circuitWhen the current at the midpoint of the current period is not greater than the current continuity threshold value, determining that the inductor is in the current interruption mode, and determining that the inductor is in the current interruption mode
The result of the multiplication is the average current of the inductor in the boost circuit during the current cycle.
Further, considering that there is a certain error between the multiplication result of i1 multiplied by a coefficient less than 1 (the coefficient value is set in advance) and the average current of the inductor in the current interruption mode, in order to more accurately obtain the average current of the inductor in the current interruption mode, the present application further analyzes the operation principle of the inductor in the current interruption mode (see fig. 5):
according to the working principle of the inductor in the target circuit when the current is interrupted, obtaining the current integral relation of the inductor in a control period T (k):
given that i2 is 2 × i1, the current integration relation is simplified as follows:
the voltage-second equilibrium law of the inductor in a single cycle is also known (the voltage-second number of the current rise period must be equal in value to the voltage-second number of the current fall period, i.e. the inductor voltage is plotted against time, and the area of the curve corresponding to the current rise period must be equal to the area of the curve corresponding to the current fall period): von*ton＝Voff*t′offAnd further simplifying the current integral relation:
when the target circuit is a boost circuit, the relationship between the input and output voltages of the boost circuit and the voltage of an inductor therein is known: vin＝Von,Vout＝Vin+VoffTherefore, the current integration relation is further simplified as follows:
and is also known as tonD x T, so that the average current of the inductor in the control period T (k) is
Based on the above, in the working process of the target circuit (boost circuit), when the midpoint current i1 of the current cycle is not more than the current continuous critical value, the inductor is determined to be in the current discontinuous mode, and the current discontinuous mode is determined to be used for the target circuit
The result of the multiplication is used as the average current of the inductor of the boost circuit in the current period, so that the average current of the inductor of the boost circuit in the current interruption mode is more accurately obtained.
As an optional embodiment, when the target circuit is a buck circuit, the inductor current detection method further includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in a target circuit when the current is interrupted
Wherein, the current value of the switch tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switch tube at the time of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in the control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
according to the volt-second equilibrium law V of inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonWhen the switch tube is conducted for the inductorVoltage of VoffThe voltage of the inductor when the switch tube is turned off is shown as i1, and the midpoint current of the switch tube at the turn-on midpoint moment of the control period T (k) is shown as i 1;
according to the relation t between the input and output voltage of the buck circuit and the voltage of an inductor thereinonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage, V, of the buck circuitoutThe output voltage of the buck circuit is obtained;
correspondingly, when the midpoint current is not greater than the current continuous critical value, the process of multiplying the midpoint current by a coefficient less than 1 and using the result of the multiplication as the average current of the inductor comprises the following steps:
when the current at the midpoint of the current cycle is not more than the current continuous critical value in the working process of the buck circuit, the inductor is determined to be in the current discontinuous mode, and the current discontinuous mode is used for controlling the current of the inductor to be in the current discontinuous mode
The result of the multiplication is used as the average current of the inductor of the buck circuit in the current period.
Similarly, when the target circuit is a buck circuit, the current integral relation of the inductor in the control period t (k) is obtained according to the working principle of the inductor in the target circuit when the current is discontinuous:
then according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i2 ═ 2 × i1, the current integration relation is reduced to:
the relationship between the input and output voltages of the buck circuit and the voltage of an inductor therein is known as follows:
Vin＝Von+Vout,Vout＝Voffand further simplifying the current integral relation:
Based on this, in the process of the target circuit (buck circuit) working, when the midpoint current i1 of the current cycle is not more than the current continuous critical value, the inductor is determined to be in the current discontinuous mode, and the inductor is determined to be in the current discontinuous mode
The product result is used as the average current of the buck circuit in the current period, so that the average current of the buck circuit in the current interruption mode can be more accurately obtained.
Referring to fig. 6, fig. 6 is a schematic structural diagram of an inductor current detection system of a buck/boost circuit according to an embodiment of the present invention.
The inductance current detection system of the step-up/step-down circuit comprises:
the current acquisition module 1 is used for acquiring the midpoint current of a switching tube from a current transformer arranged on a line where the switching tube is located at the conduction midpoint moment of the switching tube of a target circuit; wherein the target circuit is a boost circuit or a buck circuit;
the current comparison module 2 is used for judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit, and if so, the first inductive current determination module 3 is executed; if not, executing a second inductive current determining module 4;
the first inductance current determining module 3 is used for taking the midpoint current as the inductance average current of the target circuit in the current period;
and the second inductor current determining module 4 is used for multiplying the midpoint current by a coefficient smaller than 1, and taking the result of multiplying the midpoint current by the coefficient smaller than 1 as the average inductor current.
As an alternative embodiment, the current acquisition module 1 comprises:
the conduction time obtaining submodule is used for obtaining the duty ratio d of a switching tube in the target circuit and the control period T of the switching tube and obtaining the control period T according to TonD T is used for obtaining the conduction time T of the switching tubeon；
The midpoint current acquisition submodule is used for starting timing from the moment of the rising edge of the driving signal of the switching tube and starting timing when the timing time reaches tonAnd when the current is more than 2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from the current transformer arranged on the line where the switching tube is located.
As an optional embodiment, when the target circuit is a boost circuit, the inductor current detection method further includes:
a first current integration module, configured to obtain a current integration relation of the inductor in the control period t (k) according to a working principle of the inductor in the target circuit when the current is interrupted
Wherein, the current value of the switch tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switch tube at the time of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in the control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
a first integral correction module for correcting the first integral according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonThe voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is shown as i1, and the midpoint current of the switch tube at the turn-on midpoint moment of the control period T (k) is shown as i 1;
first inductive currentA predetermined module for determining t according to the relation between the input and output voltages of the boost circuit and the voltage of the inductor thereinonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage of the boost circuit, VoutIs the output voltage of the boost circuit;
correspondingly, the second inductor current determining module 4 is specifically configured to determine that the inductor is in the current interruption mode when the current at the midpoint of the current cycle is not greater than the current continuation critical value during operation of the boost circuit, and determine that the inductor is in the current interruption mode
The result of the multiplication is the average current of the inductor in the boost circuit during the current cycle.
As an optional embodiment, when the target circuit is a buck circuit, the inductor current detection system further includes:
a second current integration module, configured to obtain a current integration relation of the inductor in the control period t (k) according to a working principle of the inductor in the target circuit when the current is interrupted
Wherein, the current value of the switch tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switch tube at the time of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in the control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
a second integral correction module for correcting the second integral according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t′offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonThe voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is shown as i1, and the midpoint current of the switch tube at the turn-on midpoint moment of the control period T (k) is shown as i 1;
a second inductor current predetermining module for determining t according to the relation between the input and output voltages of buck circuit and its inductor voltageonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage, V, of the buck circuitoutThe output voltage of the buck circuit is obtained;
correspondingly, the second inductor current determining module 4 is specifically configured to determine that the inductor is in the current interruption mode when the midpoint current of the current cycle is not greater than the current continuous critical value during the buck circuit operation, and determine that the inductor is in the current interruption mode
The result of the multiplication is used as the average current of the inductor of the buck circuit in the current period.
For the introduction of the inductive current detection system provided by the present invention, reference is made to the above-mentioned embodiment of the inductive current detection method, and the present invention is not described herein again.
The invention also provides an inductive current detection device of the step-up/step-down circuit, which comprises:
a memory for storing a computer program;
and a processor for executing any one of the above-mentioned inductor current detection methods of the step-up/down circuit when executing the computer program.
For the introduction of the inductor current detection apparatus provided by the present invention, reference is made to the above embodiments of the inductor current detection method, and the present invention is not described herein again.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A method for detecting an inductor current of a buck/boost circuit, comprising:
acquiring the midpoint current of a switching tube of a target circuit from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube; the target circuit is a boost circuit or a buck circuit;
judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit;
if so, taking the midpoint current as the average current of the target circuit in the current period;
if not, multiplying the midpoint current by a coefficient smaller than 1, and taking the result of the multiplication of the midpoint current and the coefficient as the average current of the inductor;
when the midpoint current is larger than the current continuous critical value, the process of taking the midpoint current as the average current of the inductor of the target circuit in the current period includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is continuous
Wherein, the current value of the switch tube in the conducting time is equal to the current value of the inductor at the same time, i0 is the current value of the switch tube at the moment of the rising edge of the control period T (k), i2 is the current value of the switch tube at the moment of the falling edge of the control period T (k), toffIs the turn-off time, t, of the switching tubeonThe conduction time of the switching tube is;
according to the current integral relation
Determining that the average current of the inductor in a control period T (k) is equal to i1 when the current is continuous; wherein i1 is the midpoint current of the switching tube at the conduction midpoint moment of the control period t (k);
and in the working process of the target circuit, when the midpoint current of the current cycle is greater than the current continuous critical value, determining that the inductor is in a current continuous mode, and taking the midpoint current as the average current of the inductor of the target circuit in the current cycle.
2. The method for detecting the inductor current of the buck/boost circuit according to claim 1, wherein the step of obtaining the midpoint current of the switching tube from the current transformer disposed on the line where the switching tube is located at the conducting midpoint time of the switching tube of the target circuit includes:
acquiring the duty ratio d of a switching tube in a target circuit and the control period T of the switching tube, and obtaining the duty ratio d and the control period T of the switching tube according to TonCalculating the conduction time T of the switching tubeon；
From the aboveStarting timing at the moment of the rising edge of the driving signal of the switching tube, and when the timing time reaches tonAnd when the current is in the second conduction period,/2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from a current transformer arranged on a line where the switching tube is located.
3. The method of claim 2, wherein when the target circuit is a boost circuit, the method further comprises:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t'offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
according to the relation t of input and output voltage of boost circuit and its internal inductance voltageonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage of the boost circuit, VoutIs the output voltage of the boost circuit;
correspondingly, when the midpoint current is not greater than the current continuous critical value, the process of multiplying the midpoint current by a coefficient less than 1 and taking the result of the multiplication as the average current of the inductor comprises the following steps:
during the operation of the boost circuit, when the current at the midpoint of the current period is not more than the current continuous critical value, determining that the inductor is in a current discontinuous mode, and determining that the inductor is in the current discontinuous mode
The result of the multiplication is used as the average current of the inductor of the boost circuit in the current period.
4. The method for detecting an inductor current of a buck/boost circuit according to claim 2, wherein when the target circuit is a buck circuit, the method further comprises:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t'offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
according to the relation t between the input and output voltage of the buck circuit and the voltage of an inductor thereinonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage, V, of the buck circuitoutThe output voltage of the buck circuit is obtained;
correspondingly, when the midpoint current is not greater than the current continuous critical value, the process of multiplying the midpoint current by a coefficient less than 1 and taking the result of the multiplication as the average current of the inductor comprises the following steps:
when the current at the midpoint of the current cycle is not more than the current continuous critical value in the working process of the buck circuit, the inductor is determined to be in a current discontinuous mode, and the current is measured
The result of the multiplication is used as the average current of the inductor of the buck circuit in the current period.
5. An inductor current sensing system for a buck/boost circuit, comprising:
the current acquisition module is used for acquiring the midpoint current of a switching tube of a target circuit from a current transformer arranged on a line where the switching tube is located at the moment of conducting the midpoint of the switching tube; the target circuit is a boost circuit or a buck circuit;
the current comparison module is used for judging whether the midpoint current is larger than a current continuous critical value corresponding to the target circuit or not, and if so, the first inductive current determination module is executed; if not, executing a second inductive current determining module;
the first inductor current determining module is configured to use the midpoint current as an inductor average current of the target circuit in a current cycle;
the second inductor current determining module is used for multiplying the midpoint current by a coefficient smaller than 1, and taking the result of the multiplication of the midpoint current and the coefficient as the average inductor current;
when the midpoint current is larger than the current continuous critical value, the process of taking the midpoint current as the average current of the inductor of the target circuit in the current period includes:
obtaining a current integral relational expression of the inductor in a control period T (k) in advance according to the working principle of the inductor in the target circuit when the current is continuous
Wherein, the current value of the switch tube in the conducting time is equal to the current value of the inductor at the same time, i0 is the current value of the switch tube at the moment of the rising edge of the control period T (k), i2 is the current value of the switch tube at the moment of the falling edge of the control period T (k), toffIs the turn-off time, t, of the switching tubeonThe conduction time of the switching tube is;
according to the current integral relation
Determining that the average current of the inductor in a control period T (k) is equal to i1 when the current is continuous; wherein i1 is the midpoint current of the switching tube at the conduction midpoint moment of the control period t (k);
and in the working process of the target circuit, when the midpoint current of the current cycle is greater than the current continuous critical value, determining that the inductor is in a current continuous mode, and taking the midpoint current as the average current of the inductor of the target circuit in the current cycle.
6. The buck/boost circuit inductor current sense system of claim 5, wherein said current acquisition module comprises:
the conduction time obtaining submodule is used for obtaining the duty ratio d of a switching tube in a target circuit and the control period T of the switching tube and obtaining the control period T according to TonCalculating the conduction time T of the switching tubeon；
A midpoint current obtaining submodule for starting timing from the moment of the rising edge of the driving signal of the switching tube, when the timing time reaches tonAnd when the current is in the second conduction period,/2, acquiring the midpoint current of the switching tube at the moment of conducting the midpoint from a current transformer arranged on a line where the switching tube is located.
7. The system of claim 6, wherein when the target circuit is a boost circuit, the system further comprises:
a first current integration module, configured to obtain a current integration relational expression of the inductor in a control period t (k) according to a working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
a first integral correction module for correcting the first integral according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t'offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
a first inductor current predetermining module for determining t according to the relation between the input and output voltages of the boost circuit and the inductor voltage thereinonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage of the boost circuit, VoutIs the output voltage of the boost circuit;
correspondingly, the second inductor current determining module is specifically configured to determine that the inductor is in a current interruption mode and will be used for determining that the inductor is in the current interruption mode when the current at the midpoint of the current cycle is not greater than the current continuation critical value during the operation of the boost circuit
The result of the multiplication is used as the average current of the inductor of the boost circuit in the current period.
8. The system of claim 6, wherein when the target circuit is a buck circuit, the system further comprises:
a second current integration module, configured to obtain a current integration relational expression of the inductor in the control period t (k) according to a working principle of the inductor in the target circuit when the current is interrupted
The current value of the switching tube in the conduction time is equal to the current value of the inductor at the same time, i2 is the current value of the switching tube at the moment of the rising edge of the control period T (k), t'offIs the time, t 'required for the current of the inductor to decrease from i2 to 0 in a control period T (k)'off＜toff，toffThe turn-off time of the switching tube;
a second integral correction module for correcting the second integral according to the volt-second balance law V of the inductance in a single periodon*ton＝Voff*t'offAnd i 2-2 i1, and correcting the current integration relational expression to obtain a corrected current integration relational expression
Wherein, VonIs the voltage of the inductor when the switch tube is conducted, VoffThe voltage of the inductor when the switch tube is turned off is represented by i1, and the midpoint current of the switch tube at the turn-on midpoint moment of a control period T (k) is represented by i 1;
a second inductor current predetermining module for determining t according to the relation between the input and output voltages of buck circuit and its inductor voltageonDetermining the average current of the inductor in the control period T (k) when the current is interrupted as
Wherein, VinIs the input voltage, V, of the buck circuitoutThe output voltage of the buck circuit is obtained;
correspondingly, the second inductor current determining module is specifically configured to determine that the inductor is in a current interruption mode and will be used for determining that the inductor is in the current interruption mode when the midpoint current of the current cycle is not greater than the current continuous critical value in the working process of the buck circuit
The result of the multiplication is used as the average current of the inductor of the buck circuit in the current period.
9. An inductor current detecting device of a step-up/step-down circuit, comprising:
a memory for storing a computer program;
a processor for performing the inductor current detection method of the buck/boost circuit as claimed in any one of claims 1 to 4 when executing the computer program.
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| CN113156328B (en) * | 2021-03-26 | 2023-09-08 | 国家电网有限公司 | State identification system and method applied to single-stage AC-DC converter |
| CN115389808B (en) * | 2022-10-31 | 2023-02-03 | 深圳市微源半导体股份有限公司 | Current detection circuit and buck converter |
| CN115754484B (en) * | 2022-11-07 | 2023-11-10 | 上能电气股份有限公司 | On-line monitoring method and device for inductance of optical storage system |
| CN117318483B (en) * | 2023-11-30 | 2024-02-09 | 湖南昇辉新能源技术有限公司 | Predictive control method and system for TCM (TCM) mode converter |
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Application publication date: 20190723 Assignee: Zhangzhou Digital Source Technology Testing Co.,Ltd. Assignor: Zhangzhou Kehua Electric Technology Co.,Ltd. Contract record no.: X2024350000006 Denomination of invention: A method, system, and device for detecting inductive current in an up/down circuit Granted publication date: 20210622 License type: Common License Record date: 20240115 |