Bidirectional soft start circuit

Abstract

The utility model discloses a bidirectional soft start circuit, which comprises a first signal conversion module, a second signal conversion module, a first soft start module, a second soft start module and a pull-down module, a first input end of the first signal conversion module and a first input end of the second signal conversion module are electrically connected with a power supply end; the second input end of the first signal conversion module is grounded after passing through the first soft start module; a second input end of the second signal conversion module is grounded after passing through a second soft start module; and the first signal conversion module and the second signal conversion module are grounded after passing through the pull-down module. By adopting the bidirectional soft start circuit provided by the invention, a buffer effect can be provided for the charging and discharging switching circuit, and the problem of energy waste caused by starting an MOS tube which does not need to be started at a complementary PWM signal is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of energy storage equipment, in particular to a bidirectional soft starting circuit. Background Art

[0002] In existing active balancing circuits, bidirectional DCDC is often used as an energy converter. When the battery needs to be charged, the DCDC current is transmitted in the forward direction, and when the battery needs to be discharged, the DCDC current is transmitted in the reverse direction, realizing the transfer of battery power to achieve the purpose of balancing.

[0003] like Figure 1 As shown, the existing bidirectional DCDC converter is equivalent to using two independent flyback switching power supplies. During the charging process, the control chip U3 controls the MOS tube Q7 to turn on; the control chip U4 controls the MOS tube Q8 to be in the off state; the output current is rectified by the diode D4 to charge the battery, R14 is the current detection resistor, when the current reaches the set value, U6 is turned on, and the current state is fed back to U3 through the FB1 pin of U6, realizing the current closed-loop control. During the discharging process, the control chip U3 controls the MOS tube Q7 to turn off; the control chip U4 controls the MOS tube Q8 to turn on; the output current is rectified by D3 to make the output end reverse charge the power supply, R14 is the sampling resistor, the current at both ends of R14 flows from left to right, and when the set value is reached, U5 is turned on, and the current state is fed back to U4 through FB2 of U5, realizing the current open-loop control. However, with this charging and discharging method, because the current must be rectified by the diode D3 or D4, the voltage drop of the rectifier tube is large, the current loss is high, and the equipment temperature is high. In addition, this topology generally sets a fixed current value, and the current cannot be edited, so it is not suitable for use in precision calculation applications. Figure 2 As shown, the applicant proposes an adaptive active balanced charge and discharge switching circuit. By using the MCU to output a complementary first PWM signal and a second PWM signal, the MOS tube Q3 or the MOS tube Q4 can be controlled to turn on by controlling the duty cycle of the two complementary PWM signals, so as to realize the function switching of battery charging or discharging.

[0004] However, in the actual charging process, when the signal starts to output, the duty cycle of the PWM1 signal is 1%, and the duty cycle of the PWM2 signal is 99%. The duty cycle of PWM1 is smaller than that of PWM2. Q3 is cut off and Q4 is turned on at the same time. At this time, VB+ will cause current to flow to the secondary coil of the transformer due to the opening of MOS tube Q4, resulting in discharge. It will not switch to charging until PWM1 is greater than PWM2. Similarly, in the usage scenario where discharge is required, it will be charged first when discharging starts, which will cause energy waste. Utility Model Content

[0005] The utility model aims to disclose a bidirectional soft start circuit, which solves the defect of the existing charge and discharge circuit that energy is wasted due to the start of the MOS tube.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A bidirectional soft start circuit comprises: a first signal conversion module for responding to a first PWM signal generated by a first signal output terminal of an MCU and outputting a first conduction control signal to a control terminal of a first switch module when the first PWM signal is higher than a threshold, a second signal conversion module for responding to a second PWM signal generated by a second signal output terminal of the MCU and outputting a second conduction control signal to a control terminal of a second switch module when the second PWM signal is higher than a threshold, a first soft start module for reducing a voltage rise speed at a second input terminal of the first signal conversion module, a second soft start module for reducing a voltage rise speed at a second input terminal of the second signal conversion module, and a pull-down module; the first input terminal of the first signal conversion module and the first input terminal of the second signal conversion module are both electrically connected to a power supply terminal; the second input terminal of the first signal conversion module is grounded through the first soft start module; the second input terminal of the second signal conversion module is grounded through the second soft start module; the first signal conversion module and the second signal conversion module are both grounded through the pull-down module.

[0008] Optionally, the first soft start module includes: a first capacitor; and the second input end of the first signal conversion module is grounded after passing through the first capacitor.

[0009] Optionally, the first signal conversion module includes: a first triode, a third triode, a first voltage-stabilizing diode, a first resistor, a third resistor and a fifth resistor; the anode of the first voltage-stabilizing diode is electrically connected to the first signal output terminal of the MCU; the cathode of the first voltage-stabilizing diode is electrically connected to the base of the third triode through the fifth resistor; the base of the third triode is also grounded after passing through the first capacitor; the emitter of the third triode is grounded; the collector of the third triode is also electrically connected to the base of the first triode; the base of the first triode is electrically connected to the collector of the first triode after passing through the first resistor; the collector of the first triode is electrically connected to the power supply terminal; the emitter of the first triode is grounded after passing through the third resistor; the emitter of the first triode is also electrically connected to the control end of the first switch module.

[0010] Optionally, the pull-down module includes: a seventh resistor; and the emitter of the third transistor is grounded after passing through the seventh resistor.

[0011] Optionally, the second soft start module includes: a second capacitor; and a second input terminal of the second signal conversion module is grounded after passing through the second capacitor.

[0012] Optionally, the second signal conversion module includes: a second triode, a fourth triode, a second voltage-stabilizing diode, a second resistor, a fourth resistor and a sixth resistor; the anode of the second voltage-stabilizing diode is electrically connected to the second signal output terminal of the MCU; the cathode of the second voltage-stabilizing diode is electrically connected to the base of the fourth triode after passing through the sixth resistor; the base of the fourth triode is also grounded after passing through the second capacitor; the emitter of the fourth triode is grounded; the collector of the fourth triode is also electrically connected to the base of the second triode; the base of the second triode is electrically connected to the emitter of the second triode after passing through the second resistor; the emitter of the second triode is electrically connected to the power supply terminal; the collector of the second triode is grounded after passing through the fourth resistor; the collector of the second triode is also electrically connected to the control end of the second switch module.

[0013] Optionally, the pull-down module includes: a seventh resistor; and the emitter of the fourth transistor is grounded after passing through the seventh resistor.

[0014] Compared with the prior art, the utility model has the following beneficial effects:

[0015] The utility model provides a bidirectional soft start circuit, comprising: a first signal conversion module for responding to a first PWM signal generated by a first signal output terminal of an MCU, and outputting a first conduction control signal to a control terminal of a first switch module when the first PWM signal is higher than a threshold, a second signal conversion module for responding to a second PWM signal generated by a second signal output terminal of an MCU, and outputting a second conduction control signal to a control terminal of a second switch module when the second PWM signal is higher than a threshold, a first soft start module for reducing a voltage rise speed at a second input terminal of the first signal conversion module, a second soft start module for reducing a voltage rise speed at a second input terminal of the second signal conversion module, and a pull-down module; the first input terminal of the first signal conversion module and the first input terminal of the second signal conversion module are both electrically connected to a power supply terminal; the second input terminal of the first signal conversion module is grounded after passing through the first soft start module; the second input terminal of the second signal conversion module is grounded after passing through the second soft start module; the first signal conversion module and the second signal conversion module are both grounded after passing through the pull-down module. The bidirectional soft start circuit provided by the present application can provide a buffering effect for a charge and discharge switching circuit, and avoid the problem of energy waste caused by turning on a MOS tube that does not need to be turned on when a complementary PWM signal turns on. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a schematic diagram of a charge and discharge switching circuit in the prior art;

[0018] Figure 2 It is a circuit schematic diagram of a bidirectional soft start circuit in the prior art;

[0019] Figure 3 The utility model is a circuit schematic diagram of a soft start circuit.

[0020] In the figure, 1, a first signal conversion module; 2, a second signal conversion module; 3, a first soft start module; 4, a second soft start module; 5, a pull-down module. DETAILED DESCRIPTION

[0021] In the present utility model, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to the specific circumstances. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0022] In the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features being in contact not directly but through another feature between them. Moreover, the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. The terms "vertical", "horizontal", "left", "right", "above", "below" and similar expressions are for illustrative purposes only, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0024] Embodiment 1

[0025] A bidirectional soft start circuit comprises: a first signal output terminal (corresponding to a first signal output terminal of an MCU) for responding to a first signal output terminal of an MCU Figure 3 The first PWM signal generated by the PWM1 signal terminal in the first switch module is sent to the control terminal ( Figure 3 The A endpoint in corresponds to Figure 2 The gate of the MOS tube Q3 in the MCU) corresponds to the first signal conversion module 1 that outputs the first conduction control signal, and the second signal output terminal (corresponding to Figure 3 The second PWM signal generated by the PWM2 signal terminal in the control terminal ( PWM2 signal terminal in the control terminal) of the second switch module is sent to the control terminal ( Figure 3 The B endpoint in corresponds to Figure 2a second signal conversion module 2 for outputting a second conduction control signal corresponding to the gate of the MOS tube Q4 in the first signal conversion module, a first soft start module 3 for reducing the voltage rising speed of the second input terminal of the first signal conversion module, a second soft start module 4 for reducing the voltage rising speed of the second input terminal of the second signal conversion module, and a pull-down module 5; the first input terminal of the first signal conversion module 1 and the first input terminal of the second signal conversion module 2 are both electrically connected to the power supply terminal VCC; the second input terminal of the first signal conversion module 1 is grounded through the first soft start module 3; the second input terminal of the second signal conversion module 2 is grounded through the second soft start module 4; the first signal conversion module 1 and the second signal conversion module 2 are both grounded through the pull-down module 5.

[0026] Specifically, in order to avoid the problem of energy waste caused by direct conduction of the MOS tube Q3 or the MOS tube Q4 after receiving a PWM signal higher than the turn-on threshold, the present application provides a bidirectional soft start circuit, wherein the first signal conversion module 1 is used to control the first signal output port (that is, Figure 3 The second signal conversion module 2 is used to control the second signal output port (that is, Figure 3 The B port in the PWM signal outputs a high level or a low level. In order to avoid energy waste caused by the MOS tube that does not need to be turned on during the change of the duty cycle of the PWM signal, the present application sets a capacitor at the input end of the first signal conversion module 1 and the input end of the second signal conversion module 2 respectively. When the PWM signal is input, the capacitor can be charged according to the duty cycle of the PWM signal, and the start-up speed of the start-up module is reduced, so that the duty cycle of the two complementary PWM signals will not additionally turn on the MOS tube that does not need to be turned on in the process of reaching the corresponding ratio, thereby avoiding energy waste. It is known to those skilled in the art that the threshold value can be set according to actual needs. In the present application. Since PWM is complementary, it is more reasonable to set the threshold value at the voltage corresponding to the duty cycle of 50%. It is also possible to set a higher threshold value to delay the conduction of the MOS tube, or set a lower threshold value to turn on the MOS tube in advance.

[0027] Furthermore, the first soft start module 3 includes: a first capacitor C3; and the second input end of the first signal conversion module 1 is grounded after passing through the first capacitor C3.

[0028] Further, the first signal conversion module 1 includes: a first transistor Q1, a third transistor Q6, a first voltage stabilizing diode D1, a first resistor R1, a third resistor R3 and a fifth resistor R5; the anode of the first voltage stabilizing diode D1 is electrically connected to the first signal output terminal of the MCU; the cathode of the first voltage stabilizing diode D1 is electrically connected to the base of the third transistor Q6 through the fifth resistor R5; the base of the third transistor Q6 is also grounded after passing through the first capacitor C3; the emitter of the third transistor Q6 is grounded; the collector of the third transistor Q6 is also electrically connected to the base of the first transistor Q1; the base of the first transistor Q1 is electrically connected to the collector of the first transistor Q1 after passing through the first resistor R1; the collector of the first transistor Q1 is electrically connected to the power supply terminal; the emitter of the first transistor Q1 is grounded after passing through the third resistor R3; the emitter of the first transistor Q1 is also connected to the control terminal ( Figure 3 The A endpoint in corresponds to Figure 2 The gate of the MOS tube Q3 in the circuit is electrically connected.

[0029] Furthermore, the pull-down module 5 includes: a seventh resistor R7; and an emitter of the third transistor Q6 is grounded after passing through the seventh resistor R7.

[0030] Furthermore, the second soft-start module 4 includes: a second capacitor C4; and the second input terminal of the second signal conversion module 2 is grounded after passing through the second capacitor C4.

[0031] Further, the second signal conversion module 2 includes: a second triode Q2, a fourth triode Q5, a second voltage stabilizing diode D2, a second resistor R2, a fourth resistor R4 and a sixth resistor R6; the anode of the second voltage stabilizing diode D2 is electrically connected to the second signal output terminal of the MCU; the cathode of the second voltage stabilizing diode D2 is electrically connected to the base of the fourth triode Q5 after passing through the sixth resistor R6; the base of the fourth triode Q5 is also grounded after passing through the second capacitor C2; the emitter of the fourth triode Q5 is grounded; the collector of the fourth triode Q5 is also electrically connected to the base of the second triode Q2; the base of the second triode Q2 is electrically connected to the emitter of the second triode Q2 after passing through the second resistor R2; the emitter of the second triode Q2 is electrically connected to the power supply terminal VCC; the collector of the second triode Q2 is grounded after passing through the fourth resistor R4; the collector of the second triode Q2 is also electrically connected to the control end of the second switch module.

[0032] Furthermore, the pull-down module 5 includes: a seventh resistor R7; and an emitter of the fourth transistor Q5 is grounded after passing through the seventh resistor R7.

[0033] In actual use, Figure 2As shown; during the charging process, the MCU outputs complementary PWM1 and PWM2, which drive Q3 and Q4 respectively through U3 current amplification. When PWM1 is high, Q3 is turned on, and VDD current flows to the primary winding of the transformer to store energy. Then PWM1 turns to a low level to cut off Q3, and PWM2 outputs a high level to drive Q4 to turn on. At this time, the transformer reverses the secondary to release energy, and the current flows through VB+ to the positive electrode of the battery through the negative electrode of the battery, and flows back to the secondary winding of the transformer through Q4, completing a working cycle. R11 is the current sampling resistor, and the sampling chip feeds back the current state to the MCU through the ADC to achieve current closed-loop control. During the discharge process, the MCU outputs PWM1 and PWM2, which drive Q3 and Q4 respectively through the U3 current amplifier. When PWM2 drives Q4 to turn on at a high level, the VB+VDD current flows to the secondary winding of the transformer to store energy. Then PWM2 turns to a low level to cut off Q4, and at the same time, PWM1 outputs a high level to drive Q3 to turn on. At this time, the transformer reverses the primary to release energy. The current at pin 1 of the transformer flows through the positive pole of the power supply through VDD to the negative pole of the power supply (GNG), flows to pin 2 through pin 3 of Q3, and flows back to the primary winding of pin 2 of the transformer, completing a working cycle. R11 is the current sampling resistor, and the sampling chip feeds back the current state to the MCU through the ADC to achieve current open-loop control.

[0034] like Figure 3 As shown in the figure, the drive control signal output by the MCU is two complementary PWM signals. Complementary signals mean that when the PWM1 signal is high, the PWM2 signal is low. Conversely, when the PWM1 signal is low, the PWM2 signal is high. Therefore, the sum of the duty cycles of the two PWM signals remains 100%. During the charging process, the PWM1 signal starts with a duty cycle of 1% and the PWM2 signal starts with a duty cycle of 99%. Figure 3The first capacitor C3 is charged slowly, and the second capacitor C4 is charged quickly. By utilizing the characteristic that the capacitor charging voltage rises slowly, even if the second capacitor C4 is charged quickly, the base of the fourth transistor Q5 will not obtain the turn-on voltage, so the corresponding output point B still maintains a low level. As the capacitor is charged and the duty cycle of the PWM signal changes, the duty cycle of the PWM1 signal increases and the duty cycle of the PWM2 signal decreases, and the voltage of C3 also increases. When the voltage of C3 rises to the same level as the voltage of C4, the third transistor Q6 is turned on, and point A is high. The duty cycle of the PWM2 signal is not enough to turn on the fourth transistor Q5, so point B remains low. The enable channel A of the soft start module 1 is turned on, so that the first MOS tube Q3 is turned on, so that the primary winding of the transformer is charged. As the signal duty cycle changes further, the duty cycle of the PWM1 signal rises to the peak and then begins to decrease, and the duty cycle of the PWM2 signal drops to the lowest point and then begins to rise. The levels of the output ends controlled by the PWM1 and PWM2 signals alternate, and the first MOS tube Q3 is turned off and the second MOS tube Q4 is turned on. After the primary winding of the transformer is disconnected and the secondary winding is connected, the secondary winding discharges to the battery to realize the battery charging process. Subsequently, the duty cycle of PWM1 and the duty cycle of the PWM2 signal change alternately, controlling the alternating connection of the two ends of the transformer to realize the battery charging. Similarly, those skilled in the art can realize the discharge of the battery to the power supply terminal based on the same principle.

[0035] In summary, the present application provides a soft start module that can solve the problem of reverse current charging during traditional charging and discharging due to the unstable battery power and the need for a fixed PWM signal duty cycle at the start; and by using the soft start module of the present application, charging and discharging can be soft started in both directions and can automatically switch according to the direction of the current.

[0036] The present invention is not limited to the above-mentioned embodiments. If various changes or modifications to the present invention do not depart from the spirit and scope of the present invention, and if these changes and modifications fall within the claims of the present invention and the scope of equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A bidirectional soft start circuit, characterized in that: include: A first signal conversion module for responding to a first PWM signal generated by a first signal output terminal of the MCU and outputting a first conduction control signal to a control terminal of the first switch module when the first PWM signal is higher than a threshold value, a second signal conversion module for responding to a second PWM signal generated by a second signal output terminal of the MCU and outputting a second conduction control signal to a control terminal of the second switch module when the second PWM signal is higher than a threshold value, a first soft start module for reducing a voltage rise speed at a second input terminal of the first signal conversion module, a second soft start module for reducing a voltage rise speed at a second input terminal of the second signal conversion module, and a pull-down module; The first input end of the first signal conversion module and the first input end of the second signal conversion module are both electrically connected to the power supply end; The second input terminal of the first signal conversion module is grounded after passing through the first soft start module; The second input end of the second signal conversion module is grounded after passing through the second soft start module; The first signal conversion module and the second signal conversion module are both grounded through the pull-down module.

2. A bidirectional soft start circuit according to claim 1, characterized in that: The first soft start module includes: a first capacitor; and a second input terminal of the first signal conversion module is grounded after passing through the first capacitor.

3. A bidirectional soft start circuit according to claim 2, characterized in that: The first signal conversion module includes: a first triode, a third triode, a first voltage stabilizing diode, a first resistor, a third resistor and a fifth resistor; The anode of the first voltage stabilizing diode is electrically connected to the first signal output terminal of the MCU; The cathode of the first voltage stabilizing diode is electrically connected to the base of the third transistor through a fifth resistor; The base of the third transistor is also grounded after passing through the first capacitor; The emitter of the third triode is grounded; The collector of the third triode is also electrically connected to the base of the first triode; The base of the first transistor is electrically connected to the collector of the first transistor through a first resistor; The collector of the first transistor is electrically connected to the power supply terminal; The emitter of the first transistor is grounded after passing through a third resistor; The emitter of the first transistor is also electrically connected to the control end of the first switch module.

4. A bidirectional soft start circuit according to claim 3, characterized in that: The pull-down module comprises: a seventh resistor; and the emitter of the third transistor is grounded after passing through the seventh resistor.

5. A bidirectional soft start circuit according to claim 1, characterized in that: The second soft start module includes: a second capacitor; and a second input end of the second signal conversion module is grounded after passing through the second capacitor.

6. A bidirectional soft start circuit according to claim 5, characterized in that: The second signal conversion module includes: a second triode, a fourth triode, a second voltage stabilizing diode, a second resistor, a fourth resistor and a sixth resistor; The anode of the second voltage stabilizing diode is electrically connected to the second signal output terminal of the MCU; The cathode of the second voltage stabilizing diode is electrically connected to the base of the fourth transistor through a sixth resistor; The base of the fourth transistor is also grounded after passing through the second capacitor; The emitter of the fourth triode is grounded; The collector of the fourth triode is also electrically connected to the base of the second triode; The base of the second triode is electrically connected to the emitter of the second triode through the second resistor; The emitter of the second transistor is electrically connected to the power supply terminal; The collector of the second triode is grounded after passing through a fourth resistor; The collector of the second transistor is also electrically connected to the control end of the second switch module.

7. A bidirectional soft start circuit according to claim 6, characterized in that: The pull-down module includes: a seventh resistor; the emitter of the fourth transistor is grounded after passing through the seventh resistor.

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