CN109842301B - Current control circuit and control method thereof - Google Patents
Current control circuit and control method thereof Download PDFInfo
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- CN109842301B CN109842301B CN201910088957.9A CN201910088957A CN109842301B CN 109842301 B CN109842301 B CN 109842301B CN 201910088957 A CN201910088957 A CN 201910088957A CN 109842301 B CN109842301 B CN 109842301B
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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
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Abstract
The invention discloses a current control circuit, which obtains current information of an output side of a bidirectional converter through a current sampling circuit, utilizes the outputs of a first voltage regulating circuit and a second voltage regulating circuit as the inputs of an error amplifier, the output of the error amplifier is used as the input of an optical coupler feedback circuit, current signals of the output side are converted and processed by various stages of circuits and fed back to a PWM circuit, and a control circuit controls the duty ratio of a switching tube at the input side in a main power circuit to realize the constant current of the current at the output side; the invention can ensure that the bidirectional converter has no current oscillation and current peak when the working direction is switched, can realize constant current of the output side of the bidirectional converter under the condition of only using one positive band-gap voltage reference source, and has simple circuit.
Description
Technical Field
The invention belongs to the technical field of electronics, and relates to a current control circuit for a bidirectional DC-DC converter.
Background
Since the bidirectional DC-DC converter can operate in the forward direction or the reverse direction, bidirectional transmission of energy can be realized, that is, electric energy is allowed to be transmitted from a defined input side to an output side and electric energy is also allowed to be transmitted from a defined output side to an input side.
The bidirectional converter can define two working directions, and when the bidirectional converter works in the positive direction, energy is transmitted from the input side to the output side; in reverse operation, energy is transferred from the output side to the input side. The bidirectional converter has different requirements for voltage or current or power at an output side according to different application occasions, for example, in the application occasion of battery equalization, the input side and the output side of the bidirectional converter are connected with a battery or a battery pack, the current at the output side of the bidirectional converter needs to be controlled by constant current, and the output current is required to be unchanged in magnitude after the bidirectional converter switches the working direction, and only the direction is changed.
For realizing the current control of the output side, the prior art provides a control circuit for realizing the constant current of the output side current, and as shown in fig. 1, the current of the output side of the converter can be stabilized at different current values by arranging different voltage dividing resistors or different bandgap voltage reference sources on the output side. However, the following problems exist when such a control circuit is applied to a bidirectional converter: 1. when the converter works in the forward direction and the reverse direction, the current directions on the current sampling resistors are opposite: the voltage obtained by the current sampling resistor is positive when the converter works in the reverse direction, and the voltage obtained by the current sampling resistor is negative when the converter works in the forward direction, so that a positive band-gap voltage reference source and a negative band-gap voltage reference source are needed to enable the control circuit to work normally when the converter works in the forward direction or the reverse direction, but the realization of the negative band-gap voltage reference source is difficult under the condition that external power supply only has positive voltage. 2. When the working direction of the converter is switched, the switching of the working direction of the bandgap voltage reference source is performed, so that the control circuit is changed, and the electric signal oscillation or the electric signal spike generated when the control circuit is changed affects the input of an error amplifier in the converter, so that the current at the output side of the converter is jittered or spiked.
In summary, the existing method is difficult to meet the requirement of constant current control of the bidirectional converter, so that the application range of the bidirectional converter is limited.
Disclosure of Invention
In view of this, the technical problem solved by the present invention is to overcome the deficiencies of the existing methods, and to provide a current control circuit for a bidirectional converter in a battery 6 balancing application, which can ensure that the bidirectional converter has no current oscillation and current peak when switching the working direction, and can realize constant current at the output side of the bidirectional converter under the condition of using only one forward bandgap voltage reference source, and the circuit is simple.
The technical scheme for solving the technical problems is as follows:
a current control circuit for realizing constant current control of an output side of a bidirectional converter, the bidirectional converter including a main power circuit, a drive circuit and a PWM circuit, the current control circuit comprising:
the current sampling circuit is connected between the output side of the bidirectional converter and the ground and is used for sampling current information of the output side, converting the current information into a voltage signal and outputting the voltage signal to the second voltage regulating circuit;
the first voltage regulating circuit is used for regulating the static working point of the current control circuit;
the second voltage regulating circuit is connected with the output end of the current sampling circuit and used for receiving and processing the voltage signal output by the current sampling circuit;
the current direction control circuit is connected with one end of the second voltage regulating circuit and is used for regulating the voltage bias generated by the second voltage regulating circuit to the sampling voltage signal;
the error amplifier is connected with the output end of the second voltage regulating circuit at one end and the output end of the first voltage regulating circuit at the other end, and is used for receiving output voltage signals of the second voltage regulating circuit and the first voltage regulating circuit, comparing and amplifying the output voltage signals and outputting the output voltage signals to the optical coupler feedback circuit;
the loop compensation circuit is connected between the inverting input end and the output end of the error amplifier and is used for improving the loop stability;
the optical coupling feedback circuit is connected with the output end of the error amplifier and is used for carrying out isolation feedback on the voltage signal output by the error amplifier to the PWM circuit of the bidirectional converter;
the band-gap voltage reference source is simultaneously connected with the first voltage regulating circuit and the second voltage regulating circuit, and the second voltage regulating circuit generates positive voltage bias to the voltage obtained by the current sampling circuit and is used as the voltage input of the inverting input end of the error amplifier through the first voltage regulating circuit.
Preferably, the current sampling circuit includes an eleventh resistor; one end of the eleventh resistor is connected to the output side of the bidirectional converter and serves as the output end of the current sampling circuit, and the other end of the eleventh resistor is connected with the ground of the output side of the bidirectional converter.
Preferably, the second voltage regulating circuit comprises a first resistor, a second resistor, a fifth resistor, a sixth resistor, a seventh resistor and a fourth capacitor; the connection relationship is as follows:
one end of the first resistor is connected with the non-inverting input end of the error amplifier and one end of the second resistor, and the other end of the first resistor is connected with one end of the fifth resistor, one end of the sixth resistor and one end of the fourth capacitor; the other end of the second resistor is connected with the output end of the current sampling circuit; the other end of the fifth resistor is connected with a band gap voltage reference source, and the other end of the sixth resistor is connected with one end of the seventh resistor and one end of the current direction control circuit; the other end of the fourth capacitor is connected with the other end of the seventh resistor and is simultaneously connected with the ground of the output side of the bidirectional converter;
or the following steps: one end of the first resistor is connected with the inverting input end of the error amplifier and one end of the second resistor, and the other end of the first resistor is connected with one end of the fifth resistor, one end of the sixth resistor and one end of the fourth capacitor; the other end of the second resistor is connected with the output end of the current sampling circuit; the other end of the fifth resistor is connected with a band gap voltage reference source, the other end of the sixth resistor is connected with one end of the seventh resistor and one end of the current direction control circuit, and the other end of the fourth capacitor is connected with the other end of the seventh resistor and is also connected with the ground at the output side of the bidirectional converter.
Preferably, the first voltage regulating circuit includes a third resistor and a fourth resistor; the connection relationship is as follows:
one end of the third resistor is connected with the inverting input end of the error amplifier and one end of the fourth resistor, and the other end of the third resistor is connected with the ground at the output side of the bidirectional converter; the other end of the fourth resistor is connected with a band gap voltage reference source;
or the following steps: one end of the third resistor is connected with the non-inverting input end of the error amplifier and one end of the fourth resistor, the other end of the third resistor is connected with the ground at the output side of the bidirectional converter, and the other end of the fourth resistor is connected with the band-gap voltage reference source.
Preferably, the current direction control circuit comprises a switch; one end of the switch is connected with the ground of the output side of the bidirectional converter, and the other end of the switch is connected with one end of the second voltage regulating circuit.
Preferably, the optocoupler feedback circuit comprises an optocoupler, a ninth resistor, a tenth resistor, a third capacitor, a first auxiliary power supply and a second auxiliary power supply; the connection relation of the optical coupling feedback circuit is as follows:
the first auxiliary power supply is connected with the anode of the light emitting diode of the optical coupler; the cathode of the light-emitting diode of the optical coupler is connected with one end of a tenth resistor, the other end of the tenth resistor is connected with the output end of the error amplifier, one end of a ninth resistor is used as the output end of the optical coupler feedback circuit and is connected with the collector electrode of the triode of the optical coupler, and the other end of the ninth resistor is connected with a second auxiliary power supply; one end of the third capacitor is connected with the collector electrode of the triode of the optical coupler, and the other end of the third capacitor is connected with the emitter electrode of the triode of the optical coupler and the ground at the input side of the bidirectional converter;
or the following steps: one end of the tenth resistor is connected with the output end of the error amplifier, the other end of the tenth resistor is connected with the cathode of the light-emitting diode of the optical coupler, the anode of the light-emitting diode of the optical coupler is connected with the first auxiliary power supply, the collector of the triode of the optical coupler is connected with the second auxiliary power supply, the emitter of the triode of the optical coupler is connected with one end of the ninth resistor and one end of the third capacitor and serves as the output end of the optical coupler feedback circuit, and the other end of the ninth resistor is connected with the other end of the third.
Preferably, the invention also provides a control method applying the current control circuit, the current sampling circuit samples the current on the output side and outputs the current as a voltage signal to the second voltage regulating circuit, the second voltage regulating circuit responds to the voltage signal output by the current sampling circuit and the constant voltage output by the band-gap voltage reference source, the input end of the error amplifier is embodied as a first voltage, the first voltage regulating circuit receives a constant voltage response output by the band gap voltage reference source and outputs the constant voltage response to the other input end of the error amplifier to be embodied as a second voltage, the error amplifier compares the two voltages to output a comparison signal, the optical coupling feedback circuit responds to the comparison signal and feeds the comparison signal back to the PWM circuit, the PWM circuit converts a voltage signal transmitted by the optical coupling feedback circuit into a PWM signal and sends the PWM signal to the driving circuit, and the PWM signal received by the driving circuit executes duty ratio control on a switching tube in the power circuit.
The working principle of the scheme provided by the invention is explained in detail in the specific embodiment, and the invention overcomes the defects of the constant current control technology of the bidirectional converter in the prior art by combining the working principle of the invention, and has the beneficial effects that:
(1) when the bidirectional converter switches the working direction, the current change is smooth, and no current spike and oscillation exist;
(2) only one forward bandgap voltage reference source and one error amplifier are needed;
(3) the constant current control of the current of the output side can be realized when the converter works in the forward direction and works in the reverse direction.
Drawings
Fig. 1 is a schematic circuit diagram of a control circuit for realizing constant current of an output side in a practical application circuit in the prior art;
FIG. 2 is a block diagram of a bidirectional converter to which a first embodiment of the current control circuit of the present invention is applied;
FIG. 3 is a schematic circuit diagram of a bidirectional converter with a first embodiment of the current control circuit according to the present invention;
FIG. 4 is a timing diagram illustrating the control of the switching transistors Q1-Q4 of the main power circuit of the bidirectional converter of the present invention;
FIG. 5 is a diagram illustrating the current test result of the current control circuit according to the first embodiment of the present invention when the bidirectional converter operates in the forward direction;
FIG. 6 is a diagram showing the current test result of the current control circuit according to the first embodiment of the present invention when the bidirectional converter operates in reverse;
FIG. 7 is a diagram of the current waveform of the current control circuit during the switching of the operation direction of the bidirectional converter according to the first embodiment of the present invention;
fig. 8 is a block diagram showing a configuration in which a second embodiment of the current control circuit of the present invention is applied to a bidirectional converter;
fig. 9 is a schematic circuit diagram of a bidirectional converter to which a second embodiment of the current control circuit of the present invention is applied.
Detailed Description
The overall thought of the invention is as follows: the current sampling circuit acquires current information of the output side of the bidirectional converter, the current information is used as an object of current loop feedback control, the voltage output by the current sampling circuit passes through the second voltage regulating circuit to acquire forward voltage bias, the forward voltage bias is used as the voltage input of one input end of the error amplifier, the band gap voltage reference source enables the second voltage regulating circuit to generate the forward voltage bias on the voltage acquired by the current sampling circuit, and also enables the second voltage regulating circuit to serve as the voltage input of the other input end of the error amplifier, and when the system reaches a stable state, the output voltage of the first voltage regulating circuit is equal to the output voltage of the second voltage regulating circuit; when the current at the output side is not constant, the error amplifier outputs a comparison signal as the input of the optical coupler feedback circuit, the comparison signal is processed and converted by each stage of circuits, the current information at the output side is fed back to the PWM circuit and the control circuit by the optical coupler feedback circuit, and the duty ratio of the switching tube at the input side in the main power circuit is adjusted by the control circuit, so that the current at the output side is correspondingly adjusted, and the constant current at the output side is realized.
The present invention will be described below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
First embodiment
Fig. 2 is a block diagram showing a first embodiment of a current control circuit according to the present invention applied to a bidirectional converter, and fig. 3 is a schematic diagram showing a circuit in which the circuit of this embodiment is applied to a bidirectional converter, where as shown in the figure, the bidirectional converter includes a main power circuit, a driving circuit, and a PWM circuit, and the current control circuit includes a current sampling circuit for sampling an output-side current and outputting the sampled output-side current to a second voltage regulating circuit; the first voltage regulating circuit is used for regulating the static working point of the current control circuit; the second voltage regulating circuit is used for receiving and processing the voltage signal output by the current sampling circuit; the current direction control circuit is used for adjusting the voltage bias generated by the second voltage regulating circuit to the sampling voltage signal; the error amplifier is used for respectively receiving output voltage signals of the first voltage regulating circuit and the second voltage regulating circuit, carrying out differential amplification and then outputting the output voltage signals to the optical coupler feedback circuit; the loop compensation circuit is used for improving the loop stability; the optical coupling feedback circuit is used for receiving voltage signals at the output side transmitted by each stage of circuit, isolating the voltage signals and transmitting the isolated voltage signals to the input side of the bidirectional converter; the band-gap voltage reference source not only enables the second voltage regulating circuit to generate positive voltage bias on the voltage obtained by the current sampling circuit, but also enables the voltage to be used as the voltage input of the inverting input end of the error amplifier through the first voltage regulating circuit; the PWM circuit is used for converting the voltage signal output by the optical coupler feedback circuit into a PWM signal; the driving circuit is used for driving the switching tubes Q1-Q4 in the main power circuit according to the received PWM signal.
The main power circuit comprises a transformer T1, capacitors C5-C8 and switching tubes Q1-Q4, the transformer T1 comprises a primary winding N1 and a secondary winding N2, and the current sampling circuit comprises: a resistor R11; the second voltage regulating circuit includes: the resistor R1, the resistor R2, the resistor R5, the resistor R6, the resistor R7 and the capacitor C4; the first voltage regulating circuit includes: a resistor R3 and a resistor R4; the current direction control circuit includes: a switch; the loop compensation circuit comprises a resistor R8, a capacitor C1 and a capacitor C2; the opto-coupler feedback circuit includes: the power supply comprises an optocoupler, a resistor R9, a resistor R10, a capacitor C3, an auxiliary power supply VCC1 and an auxiliary power supply VCC 2; preferably, the PWM circuit and the driving circuit are composed of a single chip microcomputer and a driving chip (e.g., Si8235), wherein the error amplifier is implemented by an operational amplifier.
The connection relationship is as follows: one end of a capacitor C7 is connected with the positive end VIN + of the input side, the other end of the capacitor C7 is connected with the drain of a switch tube Q1, the source of the switch tube Q1 is connected with the dotted end of a primary winding N1 and the drain of a switch tube Q2, the dotted end of the primary winding N1 is connected with the positive end Vin + of the input side, the gate of the switch tube Q1 is connected with the first driving end of the driving circuit, the gate of the switch tube Q2 is connected with the second driving end of the driving circuit, the source of the switch tube Q2 is connected with the ground of the input side, the dotted end of a secondary winding N2 is connected with the positive end Vo + of the output side, the dotted end of a secondary winding N2 is connected with the drain of a switch tube Q3 and the source of a switch tube Q4, the source of the switch tube Q3 is connected with one end of a resistor R11, the gate of the switch tube Q3 is connected with the third driving; one end of the resistor R11 is connected with the source of the switch tube Q3 and one end of the capacitor C5, and the other end of the capacitor C5 is connected with the positive output end Vo +; the other end of the resistor R11 is connected with the output side ground, the two ends of the capacitor C6 are connected between the output positive terminal Vo + and the output side ground, one end of the resistor R2 is connected with the source of the switching tube Q3, the other end of the resistor R2 is connected with one end of the resistor R1 and the non-inverting input end of the operational amplifier, the other end of the resistor R1 is connected with one ends of the resistor R5, the resistor R6 and the capacitor C4, the other end of the resistor R5 is connected with the band gap voltage reference source, the other end of the resistor R6 is connected with one end of the resistor R7 and one end of the switch, the other end of the capacitor C4 is connected with the other end of the resistor R7 and the other end of the switch and is simultaneously connected with the output side ground, one end of the resistor R3 is connected with the output side ground, the other end of the resistor R3 is connected with one end of the resistor R4 and the inverting input end of the operational amplifier, the other end of the band gap, the two ends of a capacitor C1 are bridged at the inverting input end and the output end of the operational amplifier, one end of a resistor R10 is connected with the output end of the operational amplifier, the other end of a resistor R10 is connected with the cathode of a light-emitting diode of an optical coupler, the anode of the light-emitting diode of the optical coupler is connected with an auxiliary power supply VCC1, the emitter of a triode of the optical coupler is connected with the ground of the input side and one end of a capacitor C3, the other end of a capacitor C3 is connected with one end of a resistor R9 and the collector of the triode of the optical coupler and is used as the output of an optical coupler feedback circuit to be connected.
The working principle of the embodiment is as follows: when the bidirectional converter operates in a forward direction, a current flows through the current sampling resistor R11, and the output side is located on the right side of the resistor R11, so that the voltage of the node on the left side of the resistor R11 is a negative value, voltages in the directions of left negative and right positive are generated at two ends of the resistor R11, and the absolute value of the voltage of the node on the left side of the resistor R11 is larger as the current flowing through the resistor R11 is larger, namely the absolute value of the voltage obtained by the current sampling resistor R11 is larger. Similarly, when the bidirectional converter operates in the reverse direction, the current also flows through the current sampling resistor R11, the voltage at the node on the left side of the resistor R11 is a positive value, voltages in the left positive and right negative directions are generated across the current sampling resistor R11, and the larger the current flowing through the resistor R11 is, the larger the absolute value of the voltage at the node on the left side of the resistor R11 is, that is, the larger the absolute value of the voltage obtained by the current sampling resistor R11 is.
The voltage signal obtained by the current sampling resistor is transmitted to the second voltage regulating circuit, the band-gap voltage reference source provides a constant voltage for the first voltage regulating circuit and the second voltage regulating circuit, and the constant voltage can generate a forward voltage bias for the voltage obtained by the current sampling resistor R11 after passing through the second voltage regulating circuit, so that when the converter works in the forward direction, the voltage of the non-inverting input end of the operational amplifier is reduced along with the increase of the current (the absolute value of the voltage of the node on the left side of the resistor R11) on the output side of the converter, but can be kept at a positive voltage all the time; when the bidirectional converter works in reverse, the voltage of the non-inverting input end of the operational amplifier increases along with the increase of the current (the voltage of the node on the left side of the resistor R11) on the output side of the converter; meanwhile, the constant voltage is input into the first voltage regulating circuit, and after voltage division is carried out through the resistor R3 and the resistor R4, a positive voltage is formed at the inverting input end of the operational amplifier. The voltage signal output by the operational amplifier is transmitted to a PWM circuit in the bidirectional converter after passing through the optocoupler feedback circuit, and the PWM circuit converts the voltage signal output by the optocoupler feedback circuit into a PWM signal and then transmits the PWM signal to a control circuit to execute the control of a switch tube in the main power circuit; when the voltage of the inverting input end of the operational amplifier is equal to the voltage of the non-inverting input end, the input end of the operational amplifier is short virtually, so that the operational amplifier works in a linear amplification area.
The driving signals Vg1, Vg2, Vg3 and Vg4 outputted by the driving circuit are sequentially driving signals applied between the gates and the sources of the switching tubes Q1, Q2, Q3 and Q4 (the reference ground of the driving signals is sequentially the source of the corresponding switching tubes, and the reference ground of the driving signals is omitted in fig. 1, 2, 3, 8 and 9). The drive signals Vg1, Vg2, Vg3 and Vg4 of the four-way drive switch tube are all drive signals with the same frequency and fixed frequency, and when the drive signals are all high level, the corresponding switch tube is switched on, and when the drive signals are low level, the corresponding switch tube is switched off. Fig. 4 is a control timing chart of the drive signals Vg1, Vg2, Vg3, Vg4, as shown in the figure:
the driving signal Vg2 and the driving signal Vg3 are complementary pulse signals with fixed time range, dead time and adjustable duty ratio, that is, in a working cycle, when the driving signal Vg2 is inverted from a high level to a low level, the driving signal Vg3 is inverted from the low level to the high level after a dead time; after the two signals are maintained for a period of time, when the driving signal Vgs3 is inverted from a high level to a low level, the driving signal Vg2 is inverted from the low level to the high level after a dead time; the next working period is entered by the circulation.
In a working cycle, after a plurality of time when the drive signal Vg3 changes to high level, the drive signal Vg1 is in high level, has a period of time which is same as the high level of the drive signal Vg3, and changes to low level with the drive signal Vg3 to turn off the switch tubes Q1 and Q3; in a working cycle, after a plurality of times when the drive signal Vg2 changes to the high level, the drive signal Vg4 is at the high level, and has a period of time which is at the high level with the drive signal Vg2, and then changes to the low level with the drive signal Vg2 to turn off the switching tubes Q4 and Q2.
The switch Q2 is a bidirectional converter input side switch and the switch Q3 is a bidirectional converter output side switch, and preferably, the duty cycle of the drive of the switch Q2 increases as the output voltage of the optocoupler (i.e., the collector of the optocoupler transistor) increases, whereas the duty cycle of the drive of the switch Q2 decreases as the output voltage of the optocoupler decreases. In the application of battery equalization, the input side and the output side of the bidirectional converter are connected with a battery or a battery pack, which is equivalent to that the input side and the output side have large capacitance, the voltage of the input side and the voltage of the output side are unchanged in a short time, namely before the duty ratio of the switching tube Q2 is not regulated to be stable, the input side and the output side of the bidirectional converter can be regarded as constant voltages, and thus, a reasonable regulation range is set for the duty ratio of the switching tube Q2, so that: an increase in the duty cycle of the switching tube Q2 will increase the output current of the output side of the bidirectional converter in the forward direction, that is: when the bidirectional converter operates in the forward direction, the output current on the output side increases with the increase of the duty ratio of the switching tube Q2, and the decrease of the duty ratio of the switching tube Q2 causes the output current to decrease in the forward direction (i.e., increase in the reverse direction).
In summary, when the bidirectional converter works in the forward direction, the system outputs a constant current, the operational amplifier is short, and if the sampling resistor R11 detects that the current on the output side increases, the following will occur: the current on the output side is increased → the voltage of the non-inverting input end of the operational amplifier is reduced along with the increase of the current on the output side → the voltage of the output of the operational amplifier is reduced → the current of the light emitting diode of the optical coupler is increased → the collector voltage of the optical coupler is reduced → the duty ratio of the switching tube Q2 on the input side is reduced → the current on the output side is reduced by regulation, and on the contrary, when the sampling resistor R11 detects that the current on the output side is reduced, the current on the output side is increased by the feedback regulation of the control circuit, and the feedback control process ensures that the output current of the.
When the bidirectional converter works reversely, the system outputs a constant current, the operational amplifier is short, and if the sampling resistor R11 detects that the current of the output side is increased, the current will appear: the current on the output side is increased → the voltage of the non-inverting input end of the operational amplifier is increased along with the increase of the current on the output side → the voltage output by the operational amplifier is increased → the current of the light emitting diode of the optical coupler is reduced → the voltage of the collector of the optical coupler is increased → the duty ratio of the switching tube Q2 on the input side is increased → the current on the output side is reduced by regulation, otherwise, the current on the output side is increased by the feedback regulation of the control circuit when the sampling resistor detects the reduction of the current on the output side, and the current on the output side of the converter is also constant current during the reverse.
In addition, the circuit utilizes the current direction control circuit to adjust the voltage offset generated by the second voltage regulating circuit, and meanwhile, the current direction control circuit can be used for realizing the switching of the working direction of the bidirectional converter by controlling the voltage offset of the second voltage regulating circuit. When the converter works in the forward direction, the voltage output by the current sampling circuit (the node on the left side of the sampling resistor R11) is negative, and is converted into positive voltage under the action of the second voltage regulating circuit and the band-gap reference voltage source and output to the non-inverting input end of the operational amplifier; when the converter works in the reverse direction, the voltage of the output (the node on the left side of the sampling resistor R11) of the current sampling circuit is positive, and compared with the forward direction work of the converter, the forward direction voltage bias can be equivalently obtained by the output voltage of the current sampling circuit. After the current direction control circuit works, the voltage offset generated by the second voltage regulating circuit is reduced, so that the equivalent forward voltage offset obtained by the current sampling circuit after the bidirectional converter is switched from the forward working state to the reverse working state is offset. Therefore, the current direction control circuit can enable the bidirectional converter to work in a forward direction or a reverse direction, and the voltage at the non-inverting input end of the operational amplifier is the same, so that the bidirectional current constant-current control of the converter is realized under the condition that only one band-gap voltage reference source is used.
Preferably, the current direction control circuit is implemented by a switch in this embodiment, and the switch is connected in parallel with the resistor R7. The resistance voltage division relationship shows that: the voltage across the capacitor C4 is different between the on and off states of the switch. The voltage of the capacitor C4 increases after the switch is turned off, and conversely, the voltage of the capacitor C4 decreases after the switch is turned on. When the current at the output side is constant, namely the current at the output side is the same in magnitude and opposite in direction when the bidirectional converter works in the forward direction and works in the reverse direction. The condition that the voltage of the capacitor C4 is changed in the same size and opposite direction with the voltage obtained by the current sampling circuit before and after the switch is turned off is that the voltage is changed in the same size and opposite direction. After the switch is turned off, the voltage of the capacitor C4 is greater than the voltage of the capacitor C4 when the switch is turned on, and there will be: the voltage of the capacitor C4 is increased → the voltage of the non-inverting input end of the operational amplifier is increased → the voltage of the output of the operational amplifier is increased → the current of the light-emitting diode of the optical coupler is reduced → the voltage of the collector of the optical coupler is increased → the duty ratio of the input side switching tube Q2 is increased → the output current is adjusted to be increased in the forward direction, the voltage of the non-inverting input end of the operational amplifier is reduced under the action of the second voltage adjusting circuit and the band gap reference voltage source → the voltages of the non-inverting input end and the inverting input end of the operational amplifier are equal, and the output current reaches the forward constant current value (the condition that the voltage change amount of the capacitor C4 is equal to the voltage change amount obtained by the current sampling circuit before and. Therefore, the working direction of the bidirectional converter is changed into a forward working state by switching off the switch, and similarly, the working direction of the bidirectional converter is changed into a reverse working state by switching on the switch, so that the current direction of the bidirectional converter is switched.
Meanwhile, the capacitor can prevent voltage mutation, the voltage output by the current sampling circuit and the voltage of the capacitor C4 are coupled through the resistors R1 and R2 and then output to the in-phase input end of the operational amplifier, after the switching state is changed, the voltage of the capacitor C4 is slowly changed, the voltage of the in-phase input end of the operational amplifier is also slowly changed, so that when the working direction of the bidirectional converter is switched, the operational amplifier works in a linear amplification area, and the current change of the bidirectional converter is smooth and has no peak.
Fig. 4 and 5 are graphs showing the test results of the output current of the bidirectional converter of the present embodiment in the forward operation and the reverse operation, respectively, where Vin is the input-side voltage, Vo is the output-side voltage, and Io is the output-side current. As can be seen from the data in FIG. 4 and FIG. 5, the full range of the output current of the bidirectional converter is about 9.1A-9.6A when the bidirectional converter works in the forward direction or the reverse direction, and the control precision of the constant current is less than or equal to +/-4%. Fig. 6 is the current waveform of the embodiment during the switching of the working direction, and it can be seen that the current change is smooth and has no peak during the switching of the working direction.
Second embodiment
Fig. 7 is a block diagram showing a structure in which a circuit according to a second embodiment of the current control circuit of the present invention is applied to a bidirectional converter, fig. 8 is a schematic diagram showing a circuit according to this embodiment applied to a bidirectional converter, and compared with the first embodiment, a connection point of a resistor R3 and a resistor R4 is modified to be connected to an op-amp non-inverting input terminal, and a connection point of a resistor R1 and a resistor R2 is modified to be connected to an op-amp inverting input terminal, so that an output of a second voltage regulating circuit is inverted with respect to an output of an error amplifier; the connection relation of the optical coupling feedback circuit is modified as follows: the emitter of the optical coupler triode is connected with one end of a resistor R9 and one end of a capacitor C3 and is connected with a PWM circuit as the output of an optical coupler feedback circuit, the other end of the capacitor C3 is connected with the ground of the input side, the resistor R9 is connected with the capacitor C3 in parallel, and the collector of the optical coupler triode is connected with an auxiliary power supply VCC2, so that the output of the error amplifier and the output of the optical coupler feedback circuit are reversed in phase.
In the first embodiment, the output of the second voltage regulating circuit is in phase with the output of the error amplifier, the output of the error amplifier is in phase with the output of the optical coupling feedback circuit, so the output of the second voltage regulating circuit is in phase with the output of the optical coupling feedback circuit; in this embodiment, the output of the second voltage regulating circuit is in phase opposition to the output of the error amplifier, and the output of the error amplifier is in phase opposition to the output of the optical coupler feedback circuit, so that the output of the second voltage regulating circuit is in phase with the output of the optical coupler feedback circuit, and similarly to the first embodiment, when the bidirectional converter operates in the forward direction and the operational amplifier is in an output constant current state, if the sampling resistor R11 detects that the output-side current increases, the following occurs: the output side current increases → the voltage at the inverting input terminal of the op-amp decreases with the increase of the output side current → the voltage at the output of the op-amp increases → the photo-coupler reflector voltage decreases → the duty cycle of the input side switch Q2 decreases → the output side current decreases and returns to the output constant current state, whereas the output side current increases through the feedback regulation of the control circuit when the sampling resistor R11 detects the decrease of the output side current, which is the same as the feedback control principle of the first embodiment. Similarly, when the bidirectional converter operates in reverse, the feedback control principle is the same as that of the first embodiment, and therefore the second embodiment can make the output-side current of the bidirectional converter constant.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-described preferred embodiment should not be construed as limiting the present invention. For those skilled in the art, it is obvious that several modifications and embellishments can be made without departing from the spirit and scope of the present invention, such as current sampling by using a current transformer instead of a resistor, and switching by using a MOS transistor or a triode instead of a resistor, and these modifications and embellishments should be regarded as the protection scope of the present invention, and are not described in detail herein, and the protection scope of the present invention should be subject to the scope defined by the claims. In addition, all the connection/connection relations referred to in the patent do not mean that the components are directly connected, but mean that a better connection structure can be formed by adding or reducing connection auxiliary components according to specific implementation conditions. All technical characteristics in the invention can be interactively combined on the premise of not conflicting with each other.
Claims (7)
1. A current control circuit is used for realizing constant current control of an output side of a bidirectional converter, the bidirectional converter comprises a main power circuit, a drive circuit and a PWM circuit, and the bidirectional converter is characterized in that: the current control circuit includes:
the current sampling circuit is connected between the output side of the bidirectional converter and the ground and is used for sampling current information of the output side, converting the current information into a voltage signal and outputting the voltage signal to the second voltage regulating circuit;
the first voltage regulating circuit is used for regulating the static working point of the current control circuit;
the second voltage regulating circuit is connected with the output end of the current sampling circuit and used for receiving and processing the voltage signal output by the current sampling circuit;
the current direction control circuit is connected with one end of the second voltage regulating circuit and is used for regulating the voltage bias generated by the second voltage regulating circuit to the sampling voltage signal;
the error amplifier is connected with the output end of the second voltage regulating circuit at one end and the output end of the first voltage regulating circuit at the other end, and is used for receiving output voltage signals of the second voltage regulating circuit and the first voltage regulating circuit, comparing and amplifying the output voltage signals and outputting the output voltage signals to the optical coupler feedback circuit;
the loop compensation circuit is connected between the inverting input end and the output end of the error amplifier and is used for improving the loop stability;
the optical coupling feedback circuit is connected with the output end of the error amplifier and is used for carrying out isolation feedback on the voltage signal output by the error amplifier to the PWM circuit of the bidirectional converter;
the band-gap voltage reference source is simultaneously connected with the first voltage regulating circuit and the second voltage regulating circuit, and the second voltage regulating circuit generates positive voltage bias to the voltage obtained by the current sampling circuit and is used as the voltage input of the inverting input end of the error amplifier through the first voltage regulating circuit.
2. The current control circuit of claim 1, wherein: the current sampling circuit comprises an eleventh resistor; one end of the eleventh resistor is connected to the output side of the bidirectional converter and serves as the output end of the current sampling circuit, and the other end of the eleventh resistor is connected with the ground of the output side of the bidirectional converter.
3. The current control circuit of claim 1, wherein: the second voltage regulating circuit comprises a first resistor, a second resistor, a fifth resistor, a sixth resistor, a seventh resistor and a fourth capacitor; the connection relationship is as follows:
one end of the first resistor is connected with the non-inverting input end of the error amplifier and one end of the second resistor, and the other end of the first resistor is connected with one end of the fifth resistor, one end of the sixth resistor and one end of the fourth capacitor; the other end of the second resistor is connected with the output end of the current sampling circuit; the other end of the fifth resistor is connected with a band gap voltage reference source, and the other end of the sixth resistor is connected with one end of the seventh resistor and one end of the current direction control circuit; the other end of the fourth capacitor is connected with the other end of the seventh resistor and is simultaneously connected with the ground of the output side of the bidirectional converter;
or the following steps: one end of the first resistor is connected with the inverting input end of the error amplifier and one end of the second resistor, and the other end of the first resistor is connected with one end of the fifth resistor, one end of the sixth resistor and one end of the fourth capacitor; the other end of the second resistor is connected with the output end of the current sampling circuit; the other end of the fifth resistor is connected with a band gap voltage reference source, the other end of the sixth resistor is connected with one end of the seventh resistor and one end of the current direction control circuit, and the other end of the fourth capacitor is connected with the other end of the seventh resistor and is also connected with the ground at the output side of the bidirectional converter.
4. The current control circuit of claim 1, wherein: the first voltage regulating circuit comprises a third resistor and a fourth resistor; the connection relationship is as follows:
one end of the third resistor is connected with the inverting input end of the error amplifier and one end of the fourth resistor, and the other end of the third resistor is connected with the ground at the output side of the bidirectional converter; the other end of the fourth resistor is connected with a band gap voltage reference source;
or the following steps: one end of the third resistor is connected with the non-inverting input end of the error amplifier and one end of the fourth resistor, the other end of the third resistor is connected with the ground at the output side of the bidirectional converter, and the other end of the fourth resistor is connected with the band-gap voltage reference source.
5. The current control circuit of claim 1, wherein: the current direction control circuit comprises a switch; one end of the switch is connected with the ground of the output side of the bidirectional converter, and the other end of the switch is connected with one end of the second voltage regulating circuit.
6. The current control circuit of claim 1, wherein: the optical coupler feedback circuit comprises an optical coupler, a ninth resistor, a tenth resistor, a third capacitor, a first auxiliary power supply and a second auxiliary power supply; the connection relation of the optical coupling feedback circuit is as follows:
the first auxiliary power supply is connected with the anode of the light emitting diode of the optical coupler; the cathode of the light-emitting diode of the optical coupler is connected with one end of a tenth resistor, the other end of the tenth resistor is connected with the output end of the error amplifier, one end of a ninth resistor is used as the output end of the optical coupler feedback circuit and is connected with the collector electrode of the triode of the optical coupler, and the other end of the ninth resistor is connected with a second auxiliary power supply; one end of the third capacitor is connected with the collector electrode of the triode of the optical coupler, and the other end of the third capacitor is connected with the emitter electrode of the triode of the optical coupler and the ground at the input side of the bidirectional converter;
or the following steps: one end of the tenth resistor is connected with the output end of the error amplifier, the other end of the tenth resistor is connected with the cathode of the light-emitting diode of the optical coupler, the anode of the light-emitting diode of the optical coupler is connected with the first auxiliary power supply, the collector of the triode of the optical coupler is connected with the second auxiliary power supply, the emitter of the triode of the optical coupler is connected with one end of the ninth resistor and one end of the third capacitor and serves as the output end of the optical coupler feedback circuit, and the other end of the ninth resistor is connected with the other end of the third.
7. The control method of the current control circuit according to any one of claims 1 to 6, characterized in that: the current sampling circuit samples current on an output side and reacts the current to form a voltage signal which is output to the second voltage regulating circuit, the second voltage regulating circuit responds to the voltage signal output by the current sampling circuit and constant voltage output by the band gap voltage reference source to obtain forward voltage bias, the forward voltage bias is represented as first voltage at one input end of the error amplifier, the first voltage regulating circuit receives the constant voltage output by the band gap voltage reference source and responds to the other input end of the error amplifier to represent second voltage, the error amplifier compares the two voltages to output a comparison signal, the optical coupling feedback circuit responds to the comparison signal and feeds the comparison signal back to the PWM circuit, the PWM circuit converts the voltage signal transmitted by the optical coupling feedback circuit into the PWM signal to be transmitted to the driving circuit, and the PWM signal received by the driving circuit executes duty ratio control on a switching tube in the power circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910088957.9A CN109842301B (en) | 2019-01-30 | 2019-01-30 | Current control circuit and control method thereof |
| PCT/CN2019/119641 WO2020155799A1 (en) | 2019-01-30 | 2019-11-20 | Current control circuit and control method therefor |
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| CN201910088957.9A CN109842301B (en) | 2019-01-30 | 2019-01-30 | Current control circuit and control method thereof |
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| CN109842301B (en) * | 2019-01-30 | 2020-09-15 | 广州金升阳科技有限公司 | Current control circuit and control method thereof |
| CN110311571B (en) * | 2019-07-26 | 2021-04-16 | 广州金升阳科技有限公司 | Bidirectional constant-current control circuit for bidirectional converter |
| CN116365886B (en) * | 2023-03-10 | 2024-04-12 | 深圳麦格米特电气股份有限公司 | Bidirectional DC/DC converter and energy storage device |
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| FR2729516B1 (en) * | 1995-01-13 | 1997-04-18 | Sextant Avionique | BIDIRECTIONAL CONTINUOUS-CONTINUOUS VOLTAGE CONVERTERS AND CURRENT SENSOR |
| CN101471602B (en) * | 2007-12-29 | 2012-11-07 | 比亚迪股份有限公司 | Bidirectional DC power supply circuit |
| TW201110821A (en) * | 2009-09-04 | 2011-03-16 | Fitipower Integrated Tech Inc | Drive apparatus and lighting apparatus |
| WO2012109680A2 (en) * | 2011-02-11 | 2012-08-16 | De Vries Ian Douglas | Hysteretic current mode controller for a bidirectional converter with lossless inductor current sensing |
| CN103023320B (en) * | 2012-11-23 | 2014-09-03 | 矽力杰半导体技术(杭州)有限公司 | High-efficiency bidirectional direct current converter and control method thereof |
| CN102931849A (en) * | 2012-11-26 | 2013-02-13 | 宁德时代新能源科技有限公司 | Bidirectional DC (direct current)/DC conversion device |
| TWI585421B (en) * | 2015-05-22 | 2017-06-01 | 登騰電子股份有限公司 | Current sensing module and power conversion apparatus and electronic apparatus using the same |
| US10164535B2 (en) * | 2016-11-23 | 2018-12-25 | Texas Instruments Incorporated | Cycle-by-cycle peak current limiting in current mode buck/boost converters |
| CN109842301B (en) * | 2019-01-30 | 2020-09-15 | 广州金升阳科技有限公司 | Current control circuit and control method thereof |
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