CN110896280A - Slope voltage control device and method thereof - Google Patents
Slope voltage control device and method thereof Download PDFInfo
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- CN110896280A CN110896280A CN201911330393.1A CN201911330393A CN110896280A CN 110896280 A CN110896280 A CN 110896280A CN 201911330393 A CN201911330393 A CN 201911330393A CN 110896280 A CN110896280 A CN 110896280A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
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Abstract
The invention discloses a slope voltage control device and a method thereof, wherein the slope voltage control device comprises a primary side controller, a first adjusting resistor, a second adjusting resistor and a third adjusting resistor; the first end of the first adjusting resistor is connected with the direct current input, and the second end of the first adjusting resistor is respectively connected with the first ends of the second adjusting resistor and the third adjusting resistor and an action voltage pin of the primary side controller; the second end of the second adjusting resistor is grounded; the second end of the third adjusting resistor is connected with a second output pin of the primary side controller; the primary side controller comprises a load current detection circuit, a current selection circuit, a reference voltage generation circuit and a mode control circuit, wherein the load current detection circuit is used for detecting load current and outputting first voltage in a fixed proportion to the load current, the current selection circuit is used for outputting reference voltage when the load is in a constant voltage mode, and the current selection circuit, the reference voltage generation circuit and the mode control circuit are used for outputting the absolute value of the first voltage in other modes. The invention avoids the influence of parameters such as leakage inductance and the like on the load voltage-current curve and improves the accuracy of slope voltage control.
Description
Technical Field
The invention relates to the technical field of ramp voltage control, in particular to a ramp voltage control device and a ramp voltage control method.
Background
Referring to fig. 1, fig. 1 is a schematic diagram of a conventional ramp voltage controller, which is composed of a primary side controller (including a constant current module, a constant voltage module, a logic circuit, a switch driver, etc.), a primary side switching tube Q1, a sampling resistor Rcs, adjusting resistors R1 and R2, a schottky diode D1, a capacitor C1, a transformer, and an auxiliary winding Naux.
The purpose of the ramp voltage controller is to enable the load to operate according to a preset voltage-current curve, where the voltage-current curve of the load comprises three curve segments: the constant voltage section, the slope section and the constant current section respectively correspond to three modes of load operation, wherein the constant voltage section means that the voltage of a load is constant, the constant current section means that the current on the load is constant, and the slope section means that the voltage of the load and the current are changed in an equal ratio relation.
In fig. 1, Vin is a direct current input, when the primary controller turns on Q1, energy is stored in the transformer, and energy required by the load is temporarily provided by a capacitor C1; when the primary controller turns Q1 off, the energy in the transformer is transferred to the output load.
In the way of controlling the load voltage-current curve, the ramp voltage controller in fig. 1 reflects the load output voltage Vout by the voltage of VDD, and CS changes with the change of VDD, and then sets the resistances of the adjusting resistors R1 and R2 in a ramp Segment (SV) by using the voltage relationship between the transformer and the auxiliary winding, so that the voltage of CS changes according to the preset requirement to change the setting of the constant current module, thereby changing the output current Iout; it follows that the change in Iout can be controlled by the change in Vout at this time. That is, Vout affects VDD, VDD affects CS, and CS affects Iout.
However, in practical application, in order to operate at an extremely low output voltage Vout, the auxiliary winding of the transformer has to raise VDD by using the leakage inductance Lleak, so that the voltage of VDD cannot accurately reflect the output voltage Vout, and then CS may also change with the change of VDD, so that a preset voltage-current curve cannot be satisfied between Iout and Vout.
Therefore, how to provide a ramp voltage control device with high control accuracy and a method thereof is a problem that needs to be solved by those skilled in the art at present.
Disclosure of Invention
The invention aims to provide a ramp voltage control device and a ramp voltage control method, which realize ramp control by pin voltage which is not influenced by leakage inductance, avoid the influence of parameters such as leakage inductance on a load voltage-current curve and improve the accuracy of ramp voltage control.
In order to solve the above technical problem, the present invention provides a ramp voltage control device, including: the device comprises a primary side controller, a primary side switching tube, a first adjusting resistor, a second adjusting resistor and a third adjusting resistor;
the first end of the first adjusting resistor is connected with a direct current input, and the second end of the first adjusting resistor is respectively connected with the first end of the second adjusting resistor, the first end of the third adjusting resistor and an action voltage pin of the primary side controller;
the second end of the second adjusting resistor is grounded; the second end of the third adjusting resistor is connected with a second output pin of the primary side controller;
the primary side controller comprises a load current detection circuit, a current selection circuit, a reference voltage generation circuit and a mode control circuit; the output ends of the load current detection circuit and the reference voltage generation circuit are respectively connected with two input ends of the current selection circuit, and the output end of the current selection circuit is connected with the second output pin of the primary side controller; the input end of the mode control circuit is connected with the action voltage pin, and the output end of the mode control circuit is connected with the control end of the primary side switching tube through a first output pin of the primary side controller;
the load current detection circuit is used for detecting load current and outputting a first voltage which is in fixed proportion K to the load current;
the reference voltage generating circuit is used for outputting a reference voltage;
the current selection circuit is used for selecting the reference voltage to output when a load is in a constant voltage mode, and selecting the first voltage in other modes, wherein if K is larger than 1, the first voltage is directly output, and if K is smaller than 1, the first voltage is output after being subjected to axial symmetry conversion;
the mode control circuit is used for controlling the mode change of the load;
the preset slope in ramp mode is the inverse of a particular multiple of the absolute value of the fixed ratio.
Preferably, the preset slope in the ramp mode is the inverse of the absolute value of the fixed ratio.
Preferably, the mode control circuit includes a constant current circuit, a constant voltage circuit, a logic circuit, and a switch driving circuit;
the input end of the constant voltage circuit is connected with an action voltage pin of the primary side controller; the output ends of the constant current circuit and the constant voltage circuit are respectively connected with two input ends of the logic circuit; the output end of the logic circuit is connected with the input end of the switch driving circuit; the output end of the switch driving circuit is connected with the control end of the primary side switch tube through a first output pin of the primary side controller;
the constant voltage circuit is used for outputting constant voltage;
the constant current circuit is used for outputting constant current;
the logic circuit is used for selecting the mode of the load according to the output conditions of the constant voltage circuit and the constant current circuit and outputting a corresponding driving signal to the switch driving circuit;
the switch driving circuit is used for controlling the on-off of the primary side switch tube according to the driving signal.
Preferably, the method further comprises the following steps: the controller is connected with the constant voltage circuit;
the controller is used for outputting corresponding trigger signals to the constant voltage circuit according to a preset voltage-current curve of the load when different mode conditions are met, and the constant voltage circuit outputs corresponding current after receiving the trigger signals; and calculating the resistance values of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor according to the output curve of the current selection circuit.
Preferably, the device further comprises a first resistor and a first diode;
the first resistor is connected with the first diode in series, one end of the series circuit close to the anode of the first diode is connected with the first end of the first adjusting resistor, and one end of the series circuit close to the cathode of the first diode is connected with the direct current input.
Preferably, the method further comprises the following steps: the RC filter circuit, the second diode and the second resistor;
the first end of the RC filter circuit is connected with the direct current input, the second end of the RC filter circuit is connected with the cathode of the second diode, the anode of the second diode is connected with the first end of the second resistor, and the second end of the second resistor is connected with the synonym end of the primary side of the transformer. In order to solve the above technical problem, the present invention further provides a ramp voltage control method, based on the ramp voltage control device as described in any one of the above, the method including:
the mode control circuit controls the mode change of the load according to a preset change condition;
the load current detection circuit detects load current in real time and outputs first voltage with an absolute value in a fixed proportion to the load current to the current selection circuit;
the reference voltage generating circuit outputs reference voltage to the current selecting circuit in real time;
the current selection circuit selects the reference voltage output when the load is in a constant voltage mode, and selects the first voltage output when the load is in the remaining mode.
Preferably, the process of calculating the resistance values of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor specifically includes:
acquiring a turning point voltage VA which is converted from a constant voltage section to a slope section on the voltage-current curve and a voltage VB at any point of the slope section according to a preset voltage-current curve of a load;
calculating voltages Va and VB of two points of VA and VB corresponding to the output voltage-current curve according to the relation between the output of the current selection circuit and the voltage-current curve of the load;
respectively taking VA and VB as the load output voltage, taking Va and VB as the corresponding output of the current selection circuit, and substituting into a relational expression of the output voltage of the current selection circuit and the load voltage;
substituting a preset voltage Vfb at the acting voltage pin of the primary side controller and a preset resistance value of any one of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor into the relational expression;
calculating resistance values of the rest two unset adjusting resistors in the first adjusting resistor, the second adjusting resistor and the third adjusting resistor according to the substituted relational expression;
the relation between the output voltage of the current selection circuit and the load voltage is specifically as follows:
wherein Vout is a load output voltage, Vd is a voltage drop between the transformer and the load, Nas is a turn ratio between an auxiliary winding and a secondary side of the transformer, Vfb is a voltage at an active voltage pin of the primary controller, Vcpc is an output voltage of the current selection circuit, R1 is a resistance value of the first adjusting resistor, R2 is a resistance value of the second adjusting resistor, and R3 is a resistance value of the third adjusting resistor.
Preferably, VB is a voltage at a turning point where the ramp section is changed into the constant current section.
The invention provides a slope voltage control device and a method thereof, wherein the device comprises three adjusting resistors and a primary side controller, wherein the primary side controller comprises a load current detection circuit, a current selection circuit, a reference voltage generation circuit and a mode control circuit, and the load current detection circuit is used for detecting load current and outputting a first voltage which is in fixed proportion to the load current; the current selection circuit is used for selecting the reference voltage output when the load is in a constant voltage mode and selecting the first voltage output when the load is in the rest mode. The three adjusting resistors are disposed between the dc input and the output terminal of the current selection circuit, and are used to adjust the corresponding relationship between the control load voltage Vout and the output voltage of the current selection circuit according to the positions of the three adjusting resistors.
Accordingly, in the constant voltage mode, the current selection circuit outputs a constant voltage; in the slope mode, the output voltage of the current selection circuit is in equal proportion to the load current, and the proportion is in equal proportion to the absolute value of the slope section of the load voltage-current curve; in the constant current mode, the output voltage of the current selection circuit is equal to the load current, and therefore the output voltage of the current selection circuit remains unchanged. Therefore, the curve formed by the output voltage of the current selection circuit and the load current has a corresponding relation with the voltage-current curve of the load. And according to the setting positions of the three adjusting resistors and the kirchhoff current law, the fact that the output voltage of the current selection circuit and Vout meet a specific relational expression can be known.
Therefore, by setting the load voltage-current curve to be satisfied, the corresponding output voltage-load current curve of the current selection circuit can be obtained, and at this time, the corresponding relationship between the two curves can be determined. Then, the resistance values of the three adjusting resistors are set according to the output voltage of the current selection circuit in the two curves and the numerical value of Vout, namely, the corresponding relation determined between the two curves before is always met in the process that the ramp voltage control device works according to the specific relation after the setting is finished, and the later curve in the two curves is obtained according to the former curve, so that the load voltage-current curve set before can be always met when the ramp voltage control device works, and the aim of ramp voltage control is fulfilled. In the process, the relation between the voltage and the current of the load is only influenced by the resistance values of the three adjusting resistors, so that the voltage-current curve of the load cannot be influenced even if the leakage inductance is arranged in the device, and the accuracy of the ramp voltage control is high.
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 conventional ramp voltage controller;
FIG. 2 is a schematic diagram of a voltage-current curve of a load and a curve between an output voltage of a current selection circuit and a load current;
fig. 3 is a schematic structural diagram of a ramp voltage control device according to the present invention.
Detailed Description
The core of the invention is to provide a ramp voltage control device and a method thereof, which realize ramp control by pin voltage which is not influenced by leakage inductance, avoid the influence of parameters such as leakage inductance and the like on a load voltage-current curve and improve the accuracy of ramp voltage control.
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.
The invention provides a ramp voltage control device, as shown in fig. 3, fig. 3 is a schematic structural diagram of the ramp voltage control device provided by the invention. The device includes: the device comprises a primary side controller, a primary side switching tube Q1, a first adjusting resistor R1, a second adjusting resistor R2 and a third adjusting resistor R3;
a first end of the first adjusting resistor R1 is connected with a direct current input, and a second end of the first adjusting resistor R2 is connected with a first end of the second adjusting resistor R3526, a first end of the third adjusting resistor R3 and an action voltage pin FB of the primary side controller;
a second end of the second adjusting resistor R2 is grounded; the second end of the third adjusting resistor R3 is connected with a second output pin CPR of the primary side controller;
the primary side controller comprises a load current detection circuit, a current selection circuit, a reference voltage generation circuit and a mode control circuit; the output ends of the load current detection circuit and the reference voltage generation circuit are respectively connected with two input ends of a current selection circuit, and the output end of the current selection circuit is connected with a second output pin CPR of the primary side controller; the input end of the mode control circuit is connected with an action voltage pin FB, and the output end of the mode control circuit is connected with the control end of a primary side switching tube Q1 through a first output pin of a primary side controller;
the load current detection circuit is used for detecting load current and outputting a first voltage which is in fixed proportion to the load current; the output of the load current detection circuit is load current K, and K is a fixed proportion;
the reference voltage generating circuit is used for outputting a reference voltage;
the current selection circuit is used for selecting reference voltage to output when the load is in a constant voltage mode, and selecting first voltage in other modes, wherein if K is larger than 1, the first voltage is directly output, and if K is smaller than 1, the first voltage is output after axial symmetry conversion;
the mode control circuit is used for controlling the mode change of the load;
the preset slope in ramp mode is the inverse of a particular multiple of the absolute value of the fixed ratio.
Referring to fig. 2, the slope of the load current-first voltage line in fig. 2 is greater than 1, and if K is less than 1, the first voltage decreases with the increase of the load current, at this time, a point corresponding to the first voltage needs to be based on a constant voltage segment on a line with an axisymmetric slope of 1/K (that is, the line takes a as a starting point and has a slope of 1/K), so as to obtain an axisymmetric voltage for output.
It can be understood that, since the current selection circuit is used to select the reference voltage output when the load is in the constant voltage mode, and select the first voltage output when the other modes are performed, and the first voltage is the load current K, where K is a fixed proportional value and K is a positive number, in the constant voltage mode, the current selection circuit outputs a constant voltage; in the ramp mode, the output voltage of the current selection circuit is in equal ratio to the load current; in the constant current mode, the output voltage of the current selection circuit is equal to the load current, and therefore the output voltage of the current selection circuit remains unchanged. Therefore, the output voltage-load current curve (Vcpc-Iout) of the current selection circuit and the voltage-current curve (Vout-Iout) of the load have corresponding relation. And according to the setting positions of the three adjusting resistors and the kirchhoff current law, the fact that the output voltage Vcpc of the current selection circuit and Vout meet a specific relational expression can be known. The specific relation can be deduced according to the following process:
according to the connection relationship of the first adjusting resistor R1, the second adjusting resistor R2, and the third adjusting resistor R3, the first adjusting resistor R1 and the second adjusting resistor R2 of the three adjusting resistors form a voltage division relationship, and according to kirchhoff's current law, the current of the first adjusting resistor R1 is equal to the sum of the current of the second adjusting resistor R2 and the current of the third adjusting resistor R3. And the voltage of the direct current input is (load voltage + voltage drop between the transformer and the load)/the turn ratio of the secondary side and the auxiliary winding is (load voltage + voltage drop between the transformer and the load) × the turn ratio of the auxiliary winding and the secondary side. Accordingly, a specific relationship between the load voltage Vout and the output voltage Vcpc of the current selection circuit is given by:
wherein Vout is a load output voltage, Vd is a voltage drop between the transformer and the load, Nas is a turn ratio between the auxiliary winding and the secondary side of the transformer, Vfb is a voltage at an active voltage pin FB of the primary controller (also equal to a voltage at a midpoint of a connection between a first adjusting resistor R1 and a second adjusting resistor R2, and also equal to a voltage at a second adjusting resistor R2), Vcpc is an output voltage of the current selection circuit, R1 is a resistance value of the first adjusting resistor R1, R2 is a resistance value of the second adjusting resistor R2, and R3 is a resistance value of the third adjusting resistor R3. It will be appreciated that the left side of the equal sign is the current on R1 and the right side of the equal sign is the sum of the currents on R2 and R3.
Therefore, by setting a load voltage-current curve to be satisfied, a corresponding output voltage-load current curve of the current selection circuit can be obtained. And then setting the resistance values of the three adjusting resistors according to the numerical values of Vcpc and Vout in the two curves, so that the corresponding relation determined between the two previous curves is always met in the process that the ramp voltage control device works according to the specific relation after the setting is finished. In the process, the relation between the voltage and the current of the load is only influenced by the resistance values of the three adjusting resistors, so that the voltage-current curve of the load cannot be influenced even if the leakage inductance is arranged in the device, and the accuracy of the ramp voltage control is high.
Wherein, the process of setting three adjusting resistance values is as follows:
referring to fig. 2, fig. 2 is a schematic diagram of a voltage-current curve of a load and a curve between an output voltage of a current selection circuit and a load current. As can be seen from fig. 2, when the ramp voltage control device is initially set, in order to enable the load to output according to a preset curve, a voltage-current curve of the load needs to be set, where the curve is converted from the Constant voltage section to an inflection point a of the ramp section and any point B of the ramp section (preferably, for convenience of setting and data reading, the point B may be an inflection point when the ramp section is converted into the Constant current section), the three curve sections are respectively Constant-V (CV, i.e., Constant voltage section), slope-V (SV, i.e., ramp section) and CC (Constant current section), and then a curve of the output voltage Vcpc-cable-load current of the current selection circuit can be obtained according to the curve. Then, since point A, B is already set, the load current at point A, B can be known, and further, the values of Va-cpc and Vb-cpc can be obtained according to the relationship between the load current and Vcpc, and then Va, Vb, Va-cpc and Vb-cpc are respectively substituted into the specific relational expression, so that two formulas can be obtained:
at this time, the relationship between Vout and Vcpc in the two equations (Vcpc corresponds to the load current, and hence Vcpc can be understood as the relationship between Vout and the load current) is obtained in accordance with the voltage-current curve of the load set up before.
After Vfb, Nas and Vd are set (these values are constant values in normal operation), a value of one adjusting resistor can be set arbitrarily, that is, the resistance values of the other two adjusting resistors can be calculated according to the two relations. After the resistance setting is completed, in the subsequent actual work, the Vout and the Vcpc continuously keep the former relation, so that the load output of the ramp voltage control device meets the voltage-current curve of the load set before, and the whole ramp control is completed.
The specific multiple may be an integer or a fraction, such as k/2, etc., but since the preset slope is a negative value, the specific multiple is a positive value, and the invention is not limited to the specific multiple.
Further, the preset slope in the ramp mode is the inverse of the absolute value of the fixed ratio.
It can be understood that, since there is a corresponding relationship between the voltage-current curve of the load and the output voltage-load current curve of the current selection circuit, for convenience of calculation, it is preferable to make the slope of the two curves in the slope segment be opposite to each other, that is, the absolute values are the same, and the positive and negative are opposite.
In one embodiment, the mode control circuit includes a constant current circuit, a constant voltage circuit, a logic circuit, and a switch driving circuit;
the input end of the constant voltage circuit is connected with an action voltage pin FB of the primary side controller; the output ends of the constant current circuit and the constant voltage circuit are respectively connected with two input ends of the logic circuit; the output end of the logic circuit is connected with the input end of the switch driving circuit; the output end of the switch driving circuit is connected with the control end of a primary side switch tube Q1 through a first output pin of the primary side controller;
the constant voltage circuit is used for outputting constant voltage;
the constant current circuit is used for outputting constant current;
the logic circuit is used for selecting the mode of the load according to the output conditions of the constant voltage circuit and the constant current circuit and outputting a corresponding driving signal to the switch driving circuit;
the switch driving circuit is used for controlling the on-off of the primary side switching tube Q1 according to the driving signal.
The voltage output by the constant voltage circuit is not always equal to the voltage value maintained by the load in the constant voltage section, and the constant voltage output by the constant voltage circuit is mainly used for outputting a corresponding driving signal according to the constant voltage after the constant voltage circuit is selected by the logic circuit so as to finally make the output voltage of the load constant. The ramp section also operates according to a constant voltage circuit. In the present invention, Vfb (i.e., the input voltage of the constant voltage circuit) is changed by modulating the output voltage Vcpc of the current selection circuit, so that the actual value of Vfb is lower than the voltage in the constant voltage mode at the ramp section, and thus, by setting R3 to perform voltage compensation, Vfb can be made as equal to Vcpc as possible. The constant current circuit will limit the maximum output current.
In a specific embodiment, the apparatus further comprises: a controller connected to the constant voltage circuit;
the controller is used for outputting corresponding trigger signals to the constant voltage circuit according to a preset voltage-current curve of the load when different mode conditions are met, and the constant voltage circuit outputs corresponding voltage after receiving the trigger signals; the resistance values of the first adjusting resistor R1, the second adjusting resistor R2 and the third adjusting resistor R3 are calculated according to the output curve of the current selection circuit.
Of course, the above is only a specific embodiment, and the present invention is not limited to the triggering manner of the constant current circuit. Moreover, the above resistance value calculation process may be performed by other devices, which is not limited in the present invention.
In one embodiment, the apparatus further comprises a first resistor R11 and a first diode D11;
the first resistor R11 is connected in series with the first diode D11, one end of the series circuit close to the anode of the first diode D11 is connected with the first end of the first adjusting resistor R1, and one end of the series circuit close to the cathode of the first diode D11 is connected with a direct current input. In addition, a third resistor R13 may be provided in series with the first resistor R11 and the first diode D11. Here, R11, D11 and R13 are used for supplying power to VDD, and these three components may be selectively disposed or not disposed, which is not limited in the present invention.
In addition, in the series circuit, a capacitor may be connected in series between the cathode of the first diode D11 and the ground, the capacitor is a power supply capacitor of VDD, and whether the present invention is provided or not is not limited thereto.
In a preferred embodiment, the apparatus further comprises: the RC filter circuit, a second diode D12 and a second resistor R12;
the first end of the RC filter circuit is connected with the direct current input, the second end of the RC filter circuit is connected with the cathode of a second diode D12, the anode of a second diode D12 is connected with the first end of a second resistor R12, and the second end of a second resistor R12 is connected with the synonym end of the primary side of the transformer.
It can be understood that the circuit is to filter the current flowing into the transformer from the dc input terminal, the RC filter, the primary side of the transformer, the second resistor R12 and the second diode D12 form a small loop to filter the current, so as to prevent noise from affecting the transformation effect, and the second diode D12 is to control the current flowing direction and prevent the current from flowing in the reverse direction, so as to prevent the current from flowing backwards and causing the kickback.
Of course, other filter circuits may be used, and the present invention is not limited thereto.
Preferably, the apparatus further comprises: an auxiliary winding Na; the different name end of the auxiliary winding Na is connected with the first end of the first adjusting resistor R1, and the same name end of the auxiliary winding Na is grounded. The auxiliary winding may reflect the output voltage when the secondary side is turned on, and whether the auxiliary winding is provided or not may be determined according to the requirement, which is not limited in the present invention.
In addition, as shown in fig. 1, a capacitor C1 is connected in parallel to two ends of the load for supplying power to the load when the primary side switching tube Q1 is turned on, and in other embodiments, two capacitors C1 and C2 may be connected in parallel to two ends of the load to prevent the load from being powered off. Of course, the present invention does not limit the number of capacitors connected in parallel across the load.
It should be noted that the present invention is not limited to the specific circuit structure of each circuit in the primary side controller, and the circuit capable of implementing the above functions is within the protection scope of the present invention.
The invention also provides a ramp voltage control method based on the ramp voltage control device as any one of the above, which comprises the following steps:
step s 1: the mode control circuit controls the mode change of the load according to a preset change condition;
step s 2: the load current detection circuit detects load current in real time and outputs first voltage of an absolute value which is in fixed proportion to the load current to the current selection circuit;
step s 3: the reference voltage generating circuit outputs reference voltage to the current selecting circuit in real time;
step s 4: the current selection circuit selects the reference voltage output when the load is in the constant voltage mode, and selects the first voltage output when the load is in the remaining mode.
It should be noted that step s2 and step s3 are not in sequence, and the three steps are performed in parallel. Step s4 is performed after step s2 and step s3, but the flow composed of steps s2 to s4 and step s1 are not in sequence, and step s1 is performed in parallel with steps s2 to s 4.
Preferably, the process of calculating the resistance values of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor is specifically as follows:
acquiring a turning point voltage VA which is converted from a constant voltage section to a slope section on the voltage-current curve and a voltage VB at any point of the slope section according to a preset voltage-current curve of a load;
calculating voltages Va and VB of two points corresponding to VA and VB on an output voltage-current curve according to the relation between the output of the current selection circuit and the voltage-current curve of the load;
respectively taking VA and VB as load output voltages, taking Va and VB as corresponding outputs of the current selection circuit, and substituting the corresponding outputs into a relational expression of output voltage-load voltage of the current selection circuit;
substituting a preset voltage Vfb at a voltage pin of the primary side controller and the resistance value of any one of a preset first adjusting resistor, a preset second adjusting resistor and a preset third adjusting resistor into the relational expression;
calculating the resistance values of the rest two unset adjusting resistors in the first adjusting resistor, the second adjusting resistor and the third adjusting resistor according to the substituted relational expression;
the relationship between the output voltage of the current selection circuit and the load voltage is specifically as follows:
wherein Vout is a load output voltage, Vd is a voltage drop between the transformer and the load, Nas is a turn ratio between an auxiliary winding and a secondary side of the transformer, Vfb is a voltage at an active voltage pin of the primary controller, Vcpc is an output voltage of the current selection circuit, R1 is a resistance value of the first adjusting resistor, R2 is a resistance value of the second adjusting resistor, and R3 is a resistance value of the third adjusting resistor.
Preferably, VB is a voltage at a turning point where the ramp section is changed into the constant current section.
The above embodiments are only preferred embodiments of the present invention, and the above embodiments can be combined arbitrarily, and the combined embodiments are also within the scope of the present invention. It should be noted that other modifications and variations that may suggest themselves to persons skilled in the art without departing from the spirit and scope of the invention are intended to be included within the scope of the invention as defined by the appended claims.
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.
Claims (9)
1. A ramp voltage control device, comprising: the device comprises a primary side controller, a primary side switching tube, a first adjusting resistor, a second adjusting resistor and a third adjusting resistor;
the first end of the first adjusting resistor is connected with a direct current input, and the second end of the first adjusting resistor is respectively connected with the first end of the second adjusting resistor, the first end of the third adjusting resistor and an action voltage pin of the primary side controller;
the second end of the second adjusting resistor is grounded; the second end of the third adjusting resistor is connected with a second output pin of the primary side controller;
the primary side controller comprises a load current detection circuit, a current selection circuit, a reference voltage generation circuit and a mode control circuit; the output ends of the load current detection circuit and the reference voltage generation circuit are respectively connected with two input ends of the current selection circuit, and the output end of the current selection circuit is connected with the second output pin of the primary side controller; the input end of the mode control circuit is connected with the action voltage pin, and the output end of the mode control circuit is connected with the control end of the primary side switching tube through a first output pin of the primary side controller;
the load current detection circuit is used for detecting load current and outputting a first voltage which is in fixed proportion K to the load current;
the reference voltage generating circuit is used for outputting a reference voltage;
the current selection circuit is used for selecting the reference voltage to output when a load is in a constant voltage mode, and selecting the first voltage in other modes, wherein if K is larger than 1, the first voltage is directly output, and if K is smaller than 1, the first voltage is output after being subjected to axial symmetry conversion;
the mode control circuit is used for controlling the mode change of the load; the preset slope in ramp mode is the inverse of a particular multiple of the absolute value of the fixed ratio.
2. The ramp voltage control device according to claim 1, wherein the preset slope in the ramp mode is an inverse of an absolute value of the fixed ratio.
3. The ramp voltage control device according to claim 1 or 2, wherein the mode control circuit includes a constant current circuit, a constant voltage circuit, a logic circuit, and a switch drive circuit;
the input end of the constant voltage circuit is connected with an action voltage pin of the primary side controller; the output ends of the constant current circuit and the constant voltage circuit are respectively connected with two input ends of the logic circuit; the output end of the logic circuit is connected with the input end of the switch driving circuit; the output end of the switch driving circuit is connected with the control end of the primary side switch tube through a first output pin of the primary side controller;
the constant voltage circuit is used for outputting constant voltage;
the constant current circuit outputs a constant current;
the logic circuit is used for selecting the mode of the load according to the output conditions of the constant voltage circuit and the constant current circuit and outputting a corresponding driving signal to the switch driving circuit;
the switch driving circuit is used for controlling the on-off of the primary side switch tube according to the driving signal.
4. The ramp voltage control device according to claim 3, further comprising: the controller is connected with the constant voltage circuit;
the controller is used for outputting corresponding trigger signals to the constant voltage circuit according to a preset voltage-current curve of the load when different mode conditions are met, and the constant voltage circuit outputs corresponding current after receiving the trigger signals; and calculating the resistance values of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor according to the output curve of the current selection circuit.
5. The ramp voltage control device according to claim 1 or 2, further comprising a first resistor and a first diode;
the first resistor is connected with the first diode in series, one end of the series circuit close to the anode of the first diode is connected with the first end of the first adjusting resistor, and one end of the series circuit close to the cathode of the first diode is connected with the direct current input.
6. The ramp voltage control device according to claim 1 or 2, characterized by further comprising: the RC filter circuit, the second diode and the second resistor;
the first end of the RC filter circuit is connected with the direct current input, the second end of the RC filter circuit is connected with the cathode of the second diode, the anode of the second diode is connected with the first end of the second resistor, and the second end of the second resistor is connected with the synonym end of the primary side of the transformer.
7. A ramp voltage control method based on the ramp voltage control device according to any one of claims 1 to 6, the method comprising:
the mode control circuit controls the mode change of the load according to a preset change condition;
the load current detection circuit detects load current in real time and outputs first voltage with an absolute value in a fixed proportion to the load current to the current selection circuit;
the reference voltage generating circuit outputs reference voltage to the current selecting circuit in real time;
the current selection circuit selects the reference voltage output when the load is in a constant voltage mode, and selects the first voltage output when the load is in the remaining mode.
8. The ramp voltage control method according to claim 7, wherein the process of calculating the resistance values of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor is specifically as follows:
acquiring a turning point voltage VA which is converted from a constant voltage section to a slope section on the voltage-current curve and a voltage VB at any point of the slope section according to a preset voltage-current curve of a load;
calculating voltages Va and VB of two points of VA and VB corresponding to the output voltage-current curve according to the relation between the output of the current selection circuit and the voltage-current curve of the load;
respectively taking VA and VB as the load output voltage, taking Va and VB as the corresponding output of the current selection circuit, and substituting into a relational expression of the output voltage of the current selection circuit and the load voltage;
substituting a preset voltage Vfb at the acting voltage pin of the primary side controller and a preset resistance value of any one of the first adjusting resistor, the second adjusting resistor and the third adjusting resistor into the relational expression;
calculating resistance values of the rest two unset adjusting resistors in the first adjusting resistor, the second adjusting resistor and the third adjusting resistor according to the substituted relational expression;
the relation between the output voltage of the current selection circuit and the load voltage is specifically as follows:
wherein Vout is a load output voltage, Vd is a voltage drop between the transformer and the load, Nas is a turn ratio between an auxiliary winding and a secondary side of the transformer, Vfb is a voltage at an active voltage pin of the primary controller, Vcpc is an output voltage of the current selection circuit, R1 is a resistance value of the first adjusting resistor, R2 is a resistance value of the second adjusting resistor, and R3 is a resistance value of the third adjusting resistor.
9. The ramp voltage control method according to claim 8, wherein VB is a voltage at a turning point where a ramp section is turned into a constant current section.
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| CN201911330393.1A CN110896280A (en) | 2019-12-20 | 2019-12-20 | Slope voltage control device and method thereof |
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| CN201911330393.1A CN110896280A (en) | 2019-12-20 | 2019-12-20 | Slope voltage control device and method thereof |
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