Starting circuit

Abstract

The utility model discloses a starting circuit, which is applied to the field of switching power supplies, and is additionally provided with a PFC (Power Factor Correction) module, a signal processing circuit, a judgment circuit, a detection circuit and a second switching tube on the basis of a Boost circuit, the signal processing circuit comprises a time delay module and a time judgment module; when charging of the energy storage capacitor is finished, the judgment circuit conducts a power supply loop of the PFC module based on a first signal representing that charging of the energy storage capacitor is finished, and the signal processing circuit transmits a first control signal to the PFC module based on the first signal representing that charging of the energy storage capacitor is finished, so that after the PFC module receives the first control signal, the power supply loop of the PFC module is switched on. And a second control signal is sent to the second switch tube, so that the starting time and the starting delay of the first switch tube in the Boost circuit are controlled, the purpose of controlling the starting time and the starting delay is achieved, and the problem that the charging current overlaps the starting current of the switch tube and the input current overshoot is caused by the too fast starting of the switch tube is solved.

Description

Technical Field

[0001] This utility model relates to the field of switching power supplies, and in particular to a startup circuit. Background Technology

[0002] During the startup process of a switching power supply, before the switching transistor in the rectified DC circuit starts working, the input voltage charges the energy storage capacitor after the rectifier bridge. If the energy storage capacitor is still in the charging stage when the switching transistor in the DC circuit starts working, the charging current plus the startup current of the switching transistor will cause the input current to overshoot. At the same time, the shorter the startup time of the startup circuit, the larger the startup current will be.

[0003] Taking a Boost circuit as an example, existing technologies typically choose to connect a resistor in series with the branch containing the energy storage capacitor as a solution. Since the impedance of the branch containing the energy storage capacitor increases after series connection, the current passing through it decreases, thus limiting the current to a preset value. However, simply connecting a resistor in series cannot precisely control the specific current value in the Boost circuit, and it cannot solve the problem that the shorter the startup time of the startup circuit, the larger the startup current.

[0004] Therefore, the industry urgently needs a startup circuit that allows control over the startup time and startup moment in a Boost circuit to avoid the problem of input current overshoot. Utility Model Content

[0005] In view of this, the purpose of this utility model is to provide a startup circuit that solves the problem of excessive startup current and current overshoot in Boost circuits due to shorter startup time. The specific solution is as follows:

[0006] In a first aspect, this application provides a startup circuit, including a Boost circuit, and further including: a PFC (Power Factor Correction) module, a signal processing circuit, a judgment circuit, a detection circuit, and a second switching transistor; the signal processing circuit includes: a delay module and a timing judgment module;

[0007] The detection circuit is connected to the branch where the energy storage capacitor is located in the Boost circuit, and is used to detect the charging status of the energy storage capacitor.

[0008] The input terminal of the timing determination module is connected to the output terminal of the detection circuit, and is used to receive a first signal acquired by the detection circuit that represents the charging status of the energy storage capacitor, and to transmit a first control signal to the PFC module after the first signal indicates that the energy storage capacitor has finished charging; wherein, the input terminal of the PFC module is connected to the output terminal of the signal processing circuit.

[0009] The delay module is connected to the time determination module and is used to output the first control signal within a preset time period.

[0010] The input terminal of the judgment circuit is connected to the output terminal of the detection circuit, and is used to receive the charging status of the energy storage capacitor obtained by the detection circuit.

[0011] The output terminal of the judgment circuit is connected to the control terminal of the second switch, and is used to obtain the first signal indicating that the energy storage capacitor has finished charging, and then control the second switch to turn on.

[0012] The power supply terminal of the PFC module is connected to the first terminal of the second switching transistor, and the second terminal of the second switching transistor is connected to the first power supply.

[0013] The output terminal of the PFC module is connected to the control terminal of the first switching transistor in the Boost circuit, and is used to send a second control signal to the control terminal of the first switching transistor based on the first control signal.

[0014] Optionally, the PFC module includes: a voltage loop, a loop parameter control circuit, and a switching transistor control circuit;

[0015] The input terminal of the loop parameter control circuit is connected to the signal processing circuit as the input terminal of the PFC module, and the output terminal of the loop parameter control circuit is connected to the voltage loop, used to receive the first control signal and control the voltage loop to change from the second parameter to the first parameter based on the first control signal;

[0016] The output terminal of the voltage loop is connected to the input terminal of the switching transistor control circuit, and is used to send a switching control signal to the switching transistor control circuit based on the second parameter to the first parameter.

[0017] Optionally, the timing determination module includes: a second operational amplifier;

[0018] The first input terminal of the second operational amplifier is connected to the output terminal of the detection circuit as the input terminal of the signal processing circuit, and the second input terminal of the second operational amplifier is connected to the second reference signal terminal to receive the first signal characterized by the charging status of the energy storage capacitor acquired by the detection circuit.

[0019] The output terminal of the second operational amplifier is connected to the loop parameter control circuit as the output terminal of the signal processing circuit, and is used to transmit the first control signal to the PFC module after the first signal is obtained to indicate that the energy storage capacitor has finished charging.

[0020] The delay module includes: a fourth resistor and a fourth capacitor;

[0021] The first terminal of the fourth capacitor is connected to the first input terminal of the second operational amplifier, and the second terminal of the fourth capacitor is connected to the first terminal of the fourth resistor.

[0022] The second end of the fourth resistor is connected to the output of the second operational amplifier to maintain the output of the first control signal for a set time.

[0023] Optionally, the determination circuit is a comparator;

[0024] The first input terminal of the comparator is connected to the output terminal of the detection circuit as the input terminal of the judgment circuit, and is used to receive the charging status of the energy storage capacitor obtained by the detection circuit.

[0025] The second input terminal of the comparator is connected to the fourth reference signal terminal;

[0026] The output terminal of the comparator is connected to the control terminal of the second switch as the output terminal of the judgment circuit, and is used to obtain the first signal to indicate that the energy storage capacitor has finished charging, and then control the second switch to turn on.

[0027] Optionally, the loop parameter control circuit includes: a fifth resistor, a sixth resistor, a third impedance-adjustable MOSFET, a fourth switching transistor, and a second capacitor;

[0028] The first end of the fifth resistor is connected to the control terminal of the fourth switch; the second end of the fifth resistor is connected to the output terminal of the signal processing circuit as the input terminal of the loop parameter control circuit.

[0029] The first terminal of the fourth switching transistor and the control terminal of the third impedance-adjustable MOS transistor are connected to the second power supply through the sixth resistor, which is used to send a turn-on signal to the third impedance-adjustable MOS transistor when the first control signal is not obtained, and to send a turn-off signal to the third impedance-adjustable MOS transistor when the first control signal is obtained.

[0030] The second terminal of the fourth switch is grounded;

[0031] The first terminal of the second capacitor is connected to the first terminal of the third impedance-adjustable MOS transistor;

[0032] The second terminal of the second capacitor and the second terminal of the third impedance-adjustable MOSFET are connected as the output terminal of the loop parameter control circuit and the first input terminal of the voltage loop. This circuit is used to send the second parameter to the voltage loop when the third impedance-adjustable MOSFET is turned on, and to send the first parameter to the voltage loop when the third impedance-adjustable MOSFET is turned off.

[0033] Optionally, the Boost circuit includes a first voltage divider resistor and a second voltage divider resistor disposed between the positive and negative input terminals;

[0034] The loop parameter control circuit includes: a fifth resistor and a sixth resistor;

[0035] The first end of the fifth resistor is connected between the first voltage divider resistor and the second voltage divider resistor. The second end of the fifth resistor and the second end of the sixth resistor serve as the output terminals of the loop parameter control circuit and are connected to the first input terminal of the voltage loop and the second end of the third capacitor. They are used to send the second parameter to the voltage loop when the signal processing circuit does not receive the first control signal, and to send the first parameter to the voltage loop when the signal processing circuit receives the first control signal.

[0036] Optionally, the loop parameter control circuit includes: a fifth resistor and a sixth resistor;

[0037] The first end of the fifth resistor is connected to the second end of the sixth resistor, and their common end is connected to the second input end of the voltage loop as the output end of the loop parameter control circuit. This is used to send the second parameter to the voltage loop when the signal processing circuit does not receive the first control signal, and to send the first parameter to the voltage loop when the signal processing circuit receives the first control signal.

[0038] The second end of the fifth resistor is connected to the first reference signal end.

[0039] Optionally, the detection circuit includes a detection resistor; the detection resistor is connected in series with the energy storage capacitor and is used to detect the charging status of the energy storage capacitor.

[0040] Optionally, the detection circuit further includes: a current limiting circuit;

[0041] The current limiting circuit includes: a seventh resistor, a fifth capacitor, a fifth impedance-adjustable MOSFET, and a third operational amplifier;

[0042] The first terminal of the fifth impedance-adjustable MOS transistor is connected to the second terminal of the energy storage capacitor; wherein, the first terminal of the fifth impedance-adjustable MOS transistor serves as the output terminal of the detection circuit;

[0043] The second terminal of the fifth impedance-adjustable MOS transistor, the first terminal of the fifth capacitor, and the negative phase input terminal of the third operational amplifier are connected to the detection resistor.

[0044] The second terminal of the fifth capacitor is connected to the first terminal of the seventh resistor;

[0045] The control terminal of the fifth impedance-adjustable MOS transistor is connected to the second terminal of the seventh resistor and the output terminal of the third operational amplifier. It is used to adjust the impedance of the fifth impedance-adjustable MOS transistor based on the electrical signal on the branch where the energy storage capacitor is located, thereby limiting the current on the branch of the energy storage capacitor.

[0046] The non-inverting input terminal of the third operational amplifier is connected to the third reference signal terminal.

[0047] Optionally, it may also include a first auxiliary power supply, a second auxiliary power supply, a first diode, and a second diode;

[0048] The first terminal of the first auxiliary power supply is connected to the voltage input terminal of the rectifier module in the Boost circuit;

[0049] The second terminal of the first auxiliary power supply is connected to the anode of the first diode;

[0050] The first terminal of the second auxiliary power supply is connected to the inductor in the Boost circuit;

[0051] The second terminal of the second auxiliary power supply is connected to the anode of the second diode;

[0052] The cathodes of the first diode and the second diode are connected, and their common terminal is connected to the positive input terminal of the third operational amplifier as the output terminal of the auxiliary power supply.

[0053] This invention adds a PFC module, a signal processing circuit, a judgment circuit, a detection circuit, and a second switching transistor to the Boost circuit. The signal processing circuit includes a delay module and a timing judgment module. The detection circuit detects the charging status of the energy storage capacitor. A first signal is transmitted to the signal processing circuit and the judgment circuit. When the energy storage capacitor finishes charging (i.e., the voltage amplitude across the energy storage capacitor is the average value of the input voltage of the Boost circuit), the first signal output by the detection circuit indicates that the energy storage capacitor has finished charging. The judgment circuit, based on the first signal indicating the end of charging, activates the power supply circuit of the PFC module. The delay module in the signal processing circuit... The timing judgment module transmits a first control signal to the PFC module based on the first signal indicating the end of charging of the energy storage capacitor. After receiving the first control signal, the PFC module sends a second control signal to the second switch, thereby controlling the start-up time and start-up delay of the first switch in the Boost circuit. The first control signal contains instructions on the start-up time and delay of the first switch based on the information indicating the end of charging of the energy storage capacitor. The first control signal causes the PFC module to send the second control signal to the control terminal of the first switch, thereby solving the problem of the charging current superimposed on the start-up current of the switch and the input current overshoot caused by the switch starting too quickly. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0055] Figure 1 A startup circuit provided in an embodiment of this application;

[0056] Figure 2 A specific startup circuit is provided in the embodiments of this application;

[0057] Figure 3 A specific startup circuit is provided in the embodiments of this application;

[0058] Figure 4 A specific startup circuit is provided in the embodiments of this application;

[0059] Figure 5 A specific startup circuit is provided in the embodiments of this application;

[0060] Figure 6 A specific startup circuit is provided in the embodiments of this application;

[0061] Figure 7 A specific startup circuit is provided in the embodiments of this application;

[0062] Figure 8 A specific startup circuit is provided in the embodiments of this application;

[0063] The attached diagram is labeled as follows: 10 is the signal processing circuit, 11 is the voltage loop, 12 is the loop parameter control circuit, and 13 is the current limiting circuit. Detailed Implementation

[0064] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0065] The core of this application is to provide a startup circuit.

[0066] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] During the startup process of a switching power supply, taking the Boost circuit as an example, when the switching transistor in the rectified Boost circuit has not yet started working, the input voltage charges the energy storage capacitor C1 after the rectifier bridge. If the energy storage capacitor C1 is still in the charging stage when the switching transistor in the Boost circuit starts working, the charging current plus the startup current of the switching transistor will cause the input current to overshoot. At the same time, the shorter the startup time of the startup circuit, the larger the startup current will be.

[0068] In existing technologies, a common solution is to connect a resistor in series with the branch containing the energy storage capacitor C1. This increases the impedance of the branch containing C1, reducing the current and thus limiting the current to a preset value. However, simply connecting a resistor in series cannot precisely control the specific current value in the Boost circuit, and it fails to address the issue that a shorter startup time results in a larger startup current.

[0069] Therefore, the industry urgently needs a startup circuit that can control the startup time and startup timing of the switching transistors in the Boost circuit in order to avoid the problem of input current overshoot.

[0070] See Figure 1 As shown, to solve the current overshoot problem of the above-mentioned startup circuit, this application discloses a startup circuit including a Boost circuit.

[0071] It also includes: a PFC module, a signal processing circuit 10, a judgment circuit, a detection circuit, and a second switch Q2; the signal processing circuit 10 includes: a delay module and a timing judgment module;

[0072] The detection circuit is connected to the branch where the energy storage capacitor is located in the Boost circuit, and is used to detect the charging status of the energy storage capacitor.

[0073] The input terminal of the real-time judgment module is connected to the output terminal of the detection circuit. It is used to receive the first signal acquired by the detection circuit, which represents the charging status of the energy storage capacitor, and to transmit the first control signal to the PFC module after the first signal indicates that the energy storage capacitor has finished charging. The input terminal of the PFC module is connected to the output terminal of the signal processing circuit 10.

[0074] The delay module is connected to the time determination module and is used to output the first control signal within a preset time period.

[0075] The input terminal of the judgment circuit is connected to the output terminal of the detection circuit to receive the charging status of the energy storage capacitor obtained by the detection circuit.

[0076] The output of the judgment circuit is connected to the control terminal of the second switch Q2, which is used to obtain the first signal to indicate that the energy storage capacitor has finished charging, and then control the second switch Q2 to turn on.

[0077] The power supply terminal of the PFC module is connected to the first terminal of the second switch Q2, and the second terminal of the second switch Q2 is connected to the first power supply.

[0078] The output of the PFC module is connected to the control terminal of the first switch Q1 in the Boost circuit, and is used to send a second control signal to the control terminal of the first switch Q1 based on the first control signal.

[0079] In this embodiment, when the energy storage capacitor C1 is charging, its branch is essentially short-circuited, and the impedance of the energy storage capacitor C1 is zero. The detection circuit transmits a first signal characterizing the charging status of the energy storage capacitor C1 to the signal processing circuit 10 and the judgment circuit. At this time, the first signal does not indicate that the energy storage capacitor C1 has finished charging. Therefore, the signal processing circuit 10 only accepts the first signal and does not transmit any control signal to the PFC module. At the same time, the second switch Q2 remains open, and the PFC module is not connected to the operating power supply, further preventing the PFC from mistakenly transmitting the second control signal to the control terminal of the first switch Q1, thus improving the reliability of the startup circuit. When the energy storage capacitor C1 finishes charging, the detection circuit transmits a first signal indicating the end of charging of the energy storage capacitor C1 to the signal processing circuit 10 and the judgment circuit. At this time, after receiving the first signal indicating the end of charging of the energy storage capacitor C1, the delay module and the timing judgment module in the signal processing circuit 10 determine that the charging of the energy storage capacitor C1 has ended. Based on the first signal, the delay module outputs a first control signal to the PFC module within a preset time period. At the same time, the judgment circuit turns on the second switch Q2 based on the first signal indicating the end of charging of the energy storage capacitor C1, and the PFC module connects to the power supply and starts working. In a specific implementation, the timing judgment module can be implemented by an operational amplifier. It can be understood that when the timing judgment module is an operational amplifier, the input terminal of the timing judgment module is either the positive or negative input terminal of the operational amplifier, and the other terminal is the reference signal input terminal.

[0080] Therefore, this invention adds a PFC module, a signal processing circuit 10, a judgment circuit, a detection circuit, and a second switch Q2 to the Boost circuit. The signal processing circuit 10 includes a delay module and a timing judgment module. The detection circuit detects the charging status of the energy storage capacitor C1. A first signal is transmitted to the signal processing circuit 10 and the judgment circuit. When the energy storage capacitor C1 finishes charging, i.e., when the voltage amplitude on the energy storage capacitor C1 is the average value of the input voltage of the Boost circuit, the first signal output by the detection circuit indicates that the energy storage capacitor C1 has finished charging. The judgment circuit turns on the power supply circuit of the PFC module based on the first signal indicating that the energy storage capacitor C1 has finished charging. The delay module and the timing judgment module in the signal processing circuit 10 transmit a first control signal to the PFC module based on the first signal indicating that the energy storage capacitor C1 has finished charging. After receiving the first control signal, the PFC module sends a second control signal to the first switch Q1. The output of the judgment circuit is connected to the control terminal of the second switch Q2. It is used to obtain the first signal indicating that the energy storage capacitor has finished charging and control the second switch Q2 to turn on, so that the PFC can be connected to the first power supply as a working power supply. It is understandable that the first control signal contains instructions on the start time and delay of the first switch Q1 based on information indicating the end of charging of the energy storage capacitor C1. Thus, the first control signal enables the PFC module to send a second control signal to the control terminal of the first switch Q1, thereby solving the problem of the charging current superimposed on the start current of the switch and the input current overshoot caused by the switch starting too quickly.

[0081] Based on the above embodiments, this embodiment provides a specific solution, such as... Figure 2 As shown, the PFC module includes: voltage loop 11, loop parameter control circuit 12, and switching transistor control circuit;

[0082] The input terminal of the loop parameter control circuit 12 is connected to the signal processing circuit 10 as the input terminal of the PFC module, and the output terminal of the loop parameter control circuit 12 is connected to the voltage loop 11 to receive the first control signal and control the voltage loop 11 to change from the second parameter to the first parameter based on the first control signal.

[0083] The output of voltage loop 11 is connected to the input of the switching transistor control circuit, and is used to send a switching control signal to the switching transistor control circuit based on the transition from the second parameter to the first parameter.

[0084] In this embodiment, voltage loop 11 is a feedback control loop. Its main function is to compare the output voltage with a reference voltage to generate an error signal, and then adjust the output voltage based on the error signal to achieve a stable output voltage. Loop parameter control circuit 12 is mainly used to adjust some parameters in voltage loop 11, such as the proportional gain and integral time constant, to optimize the performance of voltage loop 11. By adjusting the parameters of voltage loop 11 through loop parameter control circuit 12 and transmitting the parameter adjustment information to the switching transistor control circuit via a switching control signal, voltage loop 11 becomes controllable during the period when the second parameter gradually changes to the first parameter. During this period, the Boost circuit starts up until the output voltage stabilizes. The startup time of the Boost circuit under the control of the second parameter is longer than the startup time of the Boost circuit under the control of the first parameter.

[0085] In a specific implementation, the second parameter state of voltage loop 11 can be the stage when loop parameter control circuit 12 is not connected to voltage loop 11, and the first parameter state of voltage loop 11 can be the stage after loop parameter control circuit 12 is connected to voltage loop 11. Specifically, the FB pin on the switching transistor control circuit is used as a feedback adjustment pin, generally with 1.2V or 0.8V as the reference voltage Vref1. By adjusting the voltage division values ​​of the first voltage divider resistor R1 and the second voltage divider resistor R2, the output voltage is adjusted. That is, if the voltage > 0.8V is detected at the feedback pin FB, the switching transistor control circuit will reduce the modulation frequency or duty cycle to reduce the output voltage, thereby achieving the effect of feedback regulation.

[0086] Therefore, in this embodiment, the loop parameter control circuit 12 changes the parameters of the voltage loop 11, and the sending switch control signal carrying the parameter change information is transmitted to the switching transistor control circuit. As a result, the start-up time of the Boost circuit changes under the control of different parameters of the voltage loop 11: in the initial stage of Boost circuit startup, the voltage loop 11 uses the second parameter, which makes the startup time of the Boost circuit under the control of the switching transistor control circuit longer than the voltage loop 11 using the first parameter. This prevents the problem of large startup current due to the startup time of the startup circuit being too short.

[0087] like Figure 2 As shown, according to the above embodiments, this embodiment provides a specific solution, wherein the timing determination module includes: a second operational amplifier OP2;

[0088] The first input terminal of the second operational amplifier OP2 is connected to the output terminal of the detection circuit as the input terminal of the signal processing circuit 10. The second input terminal of the second operational amplifier OP2 is connected to the second reference signal terminal Vref2 and is used to receive the first signal characterizing the charging status of the energy storage capacitor C1 obtained by the detection circuit.

[0089] The output of the second operational amplifier OP2 is connected to the loop parameter control circuit 12 as the output of the signal processing circuit 10. It is used to transmit the first control signal to the PFC module after the first signal is obtained to represent that the energy storage capacitor C1 has finished charging.

[0090] The delay module includes: a fourth resistor R4 and a fourth capacitor C4;

[0091] The first terminal of the fourth capacitor C4 is connected to the first input terminal of the second operational amplifier OP2, and the second terminal of the fourth capacitor C4 is connected to the first terminal of the fourth resistor R4.

[0092] The second end of the fourth resistor R4 is connected to the output of the second operational amplifier OP2 to maintain the output of the first control signal for a set time.

[0093] In this embodiment, the detection circuit is implemented through a detection resistor Rs. The detection signal of the detection resistor Rs begins to decrease as the charging of the energy storage capacitor C1 approaches its end. When it decreases to the reference signal at the negative inverting input of the second operational amplifier in the signal processing circuit 10, the second operational amplifier outputs a high level. As the voltage of the detection resistor Rs decreases monotonically, the voltage amplitude output by the second operational amplifier OP2 also decreases monotonically.

[0094] It can be seen that the second operational amplifier OP2 is a linear element. As the detection signal of the detection resistor Rs decreases, the first control signal is output within a preset time period through the fourth resistor R4 and the fourth capacitor C4 in the delay module, and the voltage loop 11 parameter gradually changes from the second parameter K2 to the time change of the first parameter K1.

[0095] like Figure 3 As shown, based on the above embodiments, this embodiment provides a specific solution, wherein the judgment circuit is a comparator U1;

[0096] The first input terminal of comparator U1 is connected to the output terminal of the detection circuit as the input terminal of the judgment circuit, and is used to receive the charging status of the energy storage capacitor C1 obtained by the detection circuit.

[0097] The second input terminal of comparator U1 is connected to the fourth reference signal terminal Vref4;

[0098] The output of comparator U1 is connected to the control terminal of the second switch Q2 as the output of the judgment circuit. It is used to obtain the first signal to indicate that the energy storage capacitor C1 has finished charging and then control the second switch Q2 to turn on.

[0099] In this embodiment, the judgment circuit is implemented through comparator U1. When the voltage across the energy storage capacitor C1 approaches the input voltage, the charging phase ends, and the charging current of the energy storage capacitor C1 decreases to zero or near zero. The voltage across the sampling resistor Rs is also zero or near zero. At this time, comparator U1 receives the control output signal, compares it with a preset signal, and obtains the signal indicating that the charging of the energy storage capacitor C1 has ended at that moment. The output terminal is connected to the control terminal of the second switch Q2, controlling the second switch Q2 to turn on. It can be understood that when the current is converted into a voltage signal through the sampling resistor, it is compared with a reference voltage representing an overcurrent threshold. Once the current exceeds the set value, comparator U1 immediately outputs a signal, triggering the protection mechanism to prevent circuit damage due to overcurrent. This rapid response can protect the circuit in a very short time, effectively preventing damage to the equipment.

[0100] Based on the above embodiments, this embodiment provides a specific solution, such as... Figure 2 As shown, the loop parameter control circuit 12 includes: a fifth resistor R5, a sixth resistor R6, a third impedance adjustable MOSFET Q3, a fourth switch Q4, and a second capacitor C2.

[0101] The first end of the fifth resistor R5 is connected to the control terminal of the fourth switch Q4; the second end of the fifth resistor R5 is connected to the output terminal of the signal processing circuit 10 as the input terminal of the loop parameter control circuit 12.

[0102] The first terminal of the fourth switch Q4 and the control terminal of the third impedance-adjustable MOSFET Q3 are connected to the second power supply through the sixth resistor R6. This is used to send a turn-on signal to the third impedance-adjustable MOSFET Q3 when the first control signal is not received, and to send a turn-off signal to the third impedance-adjustable MOSFET Q3 when the first control signal is received.

[0103] The second terminal of the fourth switch Q4 is grounded;

[0104] The first terminal of the second capacitor C2 is connected to the first terminal of the third impedance-adjustable MOSFET Q3.

[0105] The second terminal of the second capacitor C2 and the second terminal of the third impedance-adjustable MOSFET Q3 are connected as the output terminal of the loop parameter control circuit 12 and the first input terminal of the voltage loop 11. This circuit sends the second parameter to the voltage loop 11 when the third impedance-adjustable MOSFET Q3 is turned on, and sends the first parameter to the voltage loop 11 when the third impedance-adjustable MOSFET Q3 is turned off.

[0106] In a specific implementation, the detection circuit is implemented using a detection resistor Rs. For example... Figure 2As shown, voltage loop 11 includes: a third resistor R3, a third capacitor C3, and a first operational amplifier OP1; the first end of the third resistor R3 is connected to the first end of the third capacitor C3; the second end of the third capacitor C3 and the second end of the third impedance-adjustable MOSFET Q3 are connected to the inverting input of the first operational amplifier OP1, and the common end of the three is grounded; the second end of the second capacitor C2 and the second end of the third resistor R3 are connected to the output of the first operational amplifier OP1, and the common end of the three is connected to the feedback terminal of the switching transistor control circuit; the non-inverting input of the first operational amplifier OP1 is connected to the first reference signal terminal.

[0107] In this embodiment, before the loop parameter control circuit 12 is connected, the voltage loop 11 is equivalent to the response of a first-order RC system to a step system. According to the definition of dynamic performance indicators, when hour, Here, t is a time variable used to describe how the system's dynamic process changes over time. In this context, t represents the time elapsed from when the system begins to respond (e.g., when it is excited by an input signal) to a specific moment; it is a continuous variable, usually measured in seconds (s). T is the time constant, an important parameter related to system characteristics. The time constant T determines the speed of the system's response and is an indicator of how quickly the system transitions from its initial state to a steady state. At that point, the system response reaches a specific ratio, which in this case is 0.632 times the final value; The numerical value of the system output as a function of time t reflects the system's output state at different moments. When t equals 2T, 3T, and 4T respectively, The values ​​will be equal to the final values. , and Since the time constant T reflects the inertia of the system, the smaller the inertia of a first-order system, the faster its response; conversely, the larger the inertia, the slower the response.

[0108] In this embodiment, at the moment of power-on, the base voltage of the fourth switching transistor Q4 is 0V, and both BE and CE are cut off. Vcc supplies power to the loop parameter control circuit 12, and the loop parameter control circuit 12 starts up. When the third impedance adjustable MOS transistor Q3 is saturated and turned on, it is equivalent to the second capacitor C2 being connected in parallel to the voltage loop 11. The parameter of the voltage loop 11 is the second parameter K2. The detection signal of the detection resistor Rs begins to decrease as the charging of the energy storage capacitor C1 nears completion. When it decreases to the reference signal at the negative input terminal of the second operational amplifier in the signal processing circuit 10, the second operational amplifier outputs a high level, causing the BE junction of the fourth switch Q4 to be forward biased, and the fourth switch Q4 to conduct linearly. At this time, the third impedance-adjustable MOSFET Q3 in the loop parameter control circuit 12 of the second operational amplifier is controlled. As the voltage of the detection resistor Rs decreases monotonically, the voltage amplitude output by the second operational amplifier OP2 also decreases monotonically, the impedance of the fourth switch Q4 decreases, and the gate voltage of the third impedance-adjustable MOSFET Q3 in the loop parameter control circuit 12 gradually decreases until the impedance of the third impedance-adjustable MOSFET Q3 gradually increases to cut off. This allows the voltage loop 11 to control the parameters of the voltage loop 11 through the loop parameter control circuit 12 during the time from the start of the Boost circuit to the stable output voltage. The parameters of the voltage loop 11 gradually change from the second parameter K2 to the first parameter K1. The first parameter is the original PI adjustment parameter of voltage loop 11, and the second parameter is the control parameter of voltage loop 11 after the saturation on-resistance of the third impedance adjustable MOS transistor Q3 and the second capacitor C2 are combined into voltage loop 11.

[0109] Therefore, when the loop parameter control circuit 12 is incorporated into the voltage loop 11, it is equivalent to increasing the voltage loop damping of the voltage loop 11, i.e., increasing the time constant T, and extending the start-up cycle time of the voltage loop 11 in the Boost circuit, thus preventing current spikes caused by voltage changes. This solves the problem of current overshoot and reduces the damage that current spikes may cause to the devices in the Boost circuit.

[0110] The function of the loop parameter control circuit 12 can be achieved using the same electronic components but with different connection methods. In one specific implementation, such as... Figure 4 As shown, the Boost circuit includes a first voltage divider resistor R1 and a second voltage divider resistor R2 disposed between the positive and negative input terminals;

[0111] The loop parameter control circuit 12 includes: a fifth resistor R5 and a sixth resistor R6;

[0112] The first end of the fifth resistor R5 is connected between the first voltage divider resistor R1 and the second voltage divider resistor R2. The second end of the fifth resistor R5 and the second end of the sixth resistor R6 serve as the output terminals of the loop parameter control circuit 12 and are connected to the first input terminal of the voltage loop 11 and the second end of the third capacitor C3. This is used to send the second parameter to the voltage loop 11 when the signal processing circuit 10 does not receive the first control signal, and to send the first parameter to the voltage loop 11 when the signal processing circuit 10 receives the first control signal.

[0113] In another specific implementation, such as Figure 5 As shown, the loop parameter control circuit 12 includes: a fifth resistor R5 and a sixth resistor R6;

[0114] The first end of the fifth resistor R5 is connected to the second end of the sixth resistor R6. Their common end is connected to the second input end of the voltage loop 11 as the output end of the loop parameter control circuit 12. This is used to send the second parameter to the voltage loop 11 when the signal processing circuit 10 does not obtain the first control signal, and to send the first parameter to the voltage loop 11 when the signal processing circuit 10 obtains the first control signal.

[0115] The second end of the fifth resistor R5 is connected to the first reference signal terminal Vref1.

[0116] In this embodiment, because the loop parameter control circuit 12 intervenes in the sampling signal of the voltage loop 11, the startup time of the voltage loop 11 is extended, that is, the time for the voltage loop 11 to transition from the startup state to the steady-state loop is extended. This prolongs the startup cycle time of the Boost circuit voltage loop 11, preventing current spikes caused by voltage changes. This further solves the problem of current overshoot and reduces the potential damage that current spikes may cause to the devices in the Boost circuit.

[0117] Based on the above embodiments, this embodiment provides a specific solution, such as... Figure 6 As shown, it also includes: a current limiting circuit 13;

[0118] The current limiting circuit 13 includes: a seventh resistor R7, a fifth capacitor C5, a fifth impedance-adjustable MOSFET Q5, and a third operational amplifier OP3;

[0119] The first terminal of the fifth impedance-adjustable MOSFET Q5 is connected to the second terminal of the energy storage capacitor C1; wherein, the first terminal of the fifth impedance-adjustable MOSFET Q5 serves as the output terminal of the detection circuit.

[0120] The second terminal of the fifth impedance-adjustable MOSFET Q5, the first terminal of the fifth capacitor C5, the negative inverting input terminal of the third operational amplifier OP3, and the detection resistor are connected.

[0121] The second terminal of the fifth capacitor C5 is connected to the first terminal of the seventh resistor R7;

[0122] The control terminal of the fifth impedance-adjustable MOSFET Q5 is connected to the second terminal of the seventh resistor R7 and the output terminal of the third operational amplifier OP3. It is used to adjust the impedance of the fifth impedance-adjustable MOSFET Q5 based on the electrical signal on the branch where the energy storage capacitor C1 is located, thereby limiting the current on the branch of the energy storage capacitor C1.

[0123] The non-inverting input of the third operational amplifier OP3 is connected to the third reference signal terminal Vref3.

[0124] In this embodiment, the detection resistor Rs also serves as the sampling unit of the current limiting circuit 13. At the instant the input voltage of the Boost circuit is turned on, the input voltage charges the energy storage capacitor C1 through the inductor and diode of the Boost circuit. The charging current of the energy storage capacitor C1 rises rapidly, and the voltage across the sampling resistor Rs in the current limiting circuit 13 connected to the energy storage capacitor C1 also rises accordingly. The third operational amplifier OP3 receives the voltage signal of the sampling resistor Rs, compares it with the preset current reference signal, and generates a control signal for the fifth impedance adjustable MOS transistor Q5, which increases the impedance of the fifth impedance adjustable MOS transistor Q5, that is, increases the impedance of the current limiting circuit 13, thereby increasing the impedance of the charging circuit of the energy storage capacitor C1 and limiting the charging current to not exceed the preset current value.

[0125] It can be seen that the current limiting circuit 13 directly limits the current in the branch where the energy storage capacitor C1 is located by directly sampling the electrical signal of the branch where the energy storage capacitor C1 is located and by increasing the impedance of the charging circuit of the energy storage capacitor C1, effectively preventing current overshoot.

[0126] In the above embodiment, the energy storage capacitor C1 has already started charging before the Boost circuit starts working. Since the current limiting circuit 13 connected to it contains active devices, an auxiliary power supply is needed to power the current limiting circuit 13. Therefore, this embodiment also provides an auxiliary power supply, including: a first auxiliary power supply, a second auxiliary power supply, a first diode D1, and a second diode D2, as shown below. Figure 7 As shown, in one specific implementation, the first terminal of the first auxiliary power supply is connected to the voltage input terminal of the rectifier module in the Boost circuit.

[0127] The second terminal of the first auxiliary power supply is connected to the anode of the first diode D1;

[0128] The first terminal of the second auxiliary power supply is connected to the inductor in the Boost circuit.

[0129] The second terminal of the second auxiliary power supply is connected to the anode of the second diode D2;

[0130] The cathodes of the first diode D1 and the second diode D2 are connected together, and their common terminal is connected to the positive input terminal of the third operational amplifier OP3 as the output terminal of the auxiliary power supply.

[0131] In the auxiliary power supply circuit of this embodiment, the second auxiliary power supply obtains power from the inductor in the Boost circuit. However, at this time, the Boost circuit is not yet working, the inductor does not store energy, and the second auxiliary power supply has no power input. Therefore, the current limiting circuit 13 cannot be powered by the second auxiliary power supply. The input terminal of the first auxiliary power supply is connected to the stage after the rectifier bridge, and it is powered by the input power supply. Therefore, the operation of the first auxiliary power supply is not limited by whether the Boost circuit is working. As soon as the input voltage is turned on, the first auxiliary power supply starts working, converting the input voltage into an auxiliary voltage to power the current limiting circuit 13 and enable it to work.

[0132] In a specific implementation, the first auxiliary power supply provides an auxiliary voltage Vcc to the current-limiting resistor Rs. When the Boost circuit starts working, the inductor begins to store energy, and the second auxiliary power supply starts working. The stabilized voltage of the second auxiliary power supply is greater than that of the first auxiliary power supply, so the first diode D1 is cut off, and the first auxiliary power supply stops supplying power. The second diode D2 turns on, and the auxiliary voltage Vcc is supplied by the second auxiliary power supply. This embodiment ensures that the current-limiting circuit 13 receives stable power during the startup phase of the Boost circuit by setting the first auxiliary power supply to obtain power from the stage after the rectifier bridge. Because the first auxiliary power supply starts working as soon as the input voltage is connected, this avoids the situation where the current-limiting circuit 13 cannot start due to the Boost circuit not working. This ensures that the current-limiting circuit 13 can always play its role when needed, effectively improving the reliability of the entire circuit. Even if the second auxiliary power supply fails due to the Boost circuit not working or other reasons (such as inductor damage, related conversion circuit failure, etc.), the first auxiliary power supply can still provide power to the current-limiting circuit 13 to maintain the current-limiting function, thereby enhancing the system's fault tolerance and reducing the risk of the entire system failing due to a single power supply failure.

[0133] To enable those skilled in the art to better understand the circuit structure and working principle involved in this application, this embodiment also provides a specific implementation method, such as... Figure 8As shown, at the instant the input voltage of the Boost circuit is turned on, the base voltage of the fourth switching transistor Q4 is 0V, and both BE and CE are cut off. The loop parameter control circuit 12 is powered by Vcc connected to the sixth resistor R6, and the loop parameter control circuit 12 starts. When the third impedance adjustable MOSFET Q3 is saturated and turned on, it is equivalent to the second capacitor C2 being connected in parallel to the voltage loop 11. The parameter of the voltage loop 11 is the second parameter K2. The input voltage charges the energy storage capacitor C1 through the inductor and diode of the Boost circuit. The charging current of the energy storage capacitor C1 rises rapidly, and the voltage across the detection resistor Rs in the detection circuit connected to C1 also rises accordingly. The third operational amplifier OP3 receives the voltage signal from the detection resistor Rs, compares it with the preset reference signal, and generates a control signal for the fifth impedance adjustable MOSFET Q5, which increases the impedance of the fifth impedance adjustable MOSFET Q5, that is, increases the impedance of the current limiting circuit 13, thereby increasing the impedance of the charging circuit of the energy storage capacitor C1 and limiting the charging current to not exceed the preset current value.

[0134] When the voltage across the energy storage capacitor C1 approaches the input voltage, the charging phase ends, and the charging current of the energy storage capacitor C1 decreases to zero or near zero. The voltage across the sensing resistor Rs is also zero or near zero. The third operational amplifier OP3 outputs a control signal to the fifth impedance-adjustable MOSFET Q5, causing Q5 to saturate and conduct. At this time, comparator U1 receives the control output signal and compares it with the fourth reference signal Vref4 to obtain the first signal indicating the end of charging of the energy storage capacitor C1 at that moment. Its output is connected to the control terminal of the second switch Q2, controlling Q2 to conduct.

[0135] After the second switch Q2 is turned on, the auxiliary power supply supplies power to the switch control circuit. The switch control circuit adjusts the output voltage by controlling the opening and closing of the first switch Q1 and its duty cycle in a negative feedback manner.

[0136] Specifically, the FB pin on the switching transistor control circuit serves as the feedback adjustment pin, typically using 1.2V or 0.8V as the reference voltage Vref1. The output voltage is adjusted by changing the voltage division values ​​of the first voltage divider resistor R1 and the second voltage divider resistor R2. That is, if a voltage is detected at the feedback pin FB... At 0.8V, the switching transistor control circuit will reduce the modulation frequency or duty cycle, thereby reducing the output voltage to achieve feedback regulation.

[0137] The detection signal of the detection resistor Rs begins to decrease as the charging of the energy storage capacitor C1 nears completion. When it decreases to the reference signal at the negative input terminal of the second operational amplifier OP2 in the signal processing circuit 10, the second operational amplifier OP2 outputs a high level, causing the BE junction of the fourth switch Q4 to be forward biased, and the fourth switch Q4 to conduct linearly. At this time, the second operational amplifier OP2 controls the third impedance-adjustable MOSFET Q3 in the loop parameter control circuit 12. As the voltage of the detection resistor Rs decreases monotonically, the voltage amplitude of the second operational amplifier OP2 also decreases monotonically, the impedance of the fourth switch Q4 decreases, the gate voltage of the third impedance-adjustable MOSFET Q3 in the loop parameter control circuit 12 gradually decreases, and the impedance of the third impedance-adjustable MOSFET Q3 gradually increases until it is cut off. This allows the voltage loop 11 to control the parameters of the voltage loop 11 through the loop parameter control circuit 12 during the time from the start of the Boost circuit to the stable output voltage. The parameters of the voltage loop 11 gradually change from the second parameter K2 to the first parameter K1.

[0138] Therefore, after the loop parameter control circuit 12 is incorporated into the voltage loop 11, it is equivalent to increasing the damping of the loop system, that is, increasing the time constant T, extending the start-up cycle time of the voltage loop 11, and preventing current spikes caused by voltage changes.

[0139] The above provides a detailed description of a startup circuit provided in this application. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably.

[0140] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A start-up circuit comprising a Boost circuit, characterized in that, Also include: PFC module, signal processing circuit, judgment circuit, detection circuit and second switch tube; The signal processing circuit comprises: delay module and time judgment module; The detection circuit is connected on the branch of the energy storage capacitor in the Boost circuit, and is used for detecting the charging condition of the energy storage capacitor; The input end of the time judgment module is connected with the output end of the detection circuit, and is used for receiving the first signal representing the charging condition of the energy storage capacitor acquired by the detection circuit, and transmitting the first control signal to the PFC module after the first signal represents that the charging of the energy storage capacitor is completed; wherein the input end of the PFC module is connected with the output end of the signal processing circuit; The delay module is connected with the time judgment module, and is used for outputting the first control signal within a preset time period; The input end of the judgment circuit is connected with the output end of the detection circuit, and is used for receiving the charging condition of the energy storage capacitor acquired by the detection circuit; The output end of the judgment circuit is connected with the control end of the second switch tube, and is used for controlling the second switch tube to be turned on after the first signal represents that the charging of the energy storage capacitor is completed; The power end of the PFC module is connected with the first end of the second switch tube, and the second end of the second switch tube is connected with the first power supply; The output end of the PFC module is connected with the control end of the first switch tube in the Boost circuit, and is used for sending the second control signal to the control end of the first switch tube based on the first control signal.

2. The start-up circuit of claim 1, wherein The PFC module comprises: voltage loop, loop parameter control circuit and switch tube control circuit; The input end of the loop parameter control circuit is connected with the signal processing circuit as the input end of the PFC module, and the output end of the loop parameter control circuit is connected with the voltage loop, and is used for receiving the first control signal and controlling the voltage loop to change from the second parameter to the first parameter based on the first control signal; The output end of the voltage loop is connected with the input end of the switch tube control circuit, and is used for sending the switch control signal to the switch tube control circuit based on the change from the second parameter to the first parameter.

3. The start-up circuit of claim 1, wherein The time judgment module comprises: second operational amplifier; The first input end of the second operational amplifier is connected with the output end of the detection circuit as the input end of the signal processing circuit, and the second input end of the second operational amplifier is connected with the second reference signal end, and is used for receiving the first signal representing the charging condition of the energy storage capacitor acquired by the detection circuit; The output end of the second operational amplifier is connected with the loop parameter control circuit as the output end of the signal processing circuit, and is used for transmitting the first control signal to the PFC module after acquiring the first signal representing that the charging of the energy storage capacitor is completed; The delay module comprises: fourth resistance and fourth capacitor; The first end of the fourth capacitor is connected with the first input end of the second operational amplifier, and the second end of the fourth capacitor is connected with the first end of the fourth resistance; The second end of the fourth resistor is connected with the output end of the second operational amplifier, for maintaining the first control signal output for a set time.

4. The start-up circuit of claim 1, wherein The judging circuit is a comparator; The first input end of the comparator is connected with the output end of the detecting circuit as the input end of the judging circuit, for receiving the charging condition of the energy storage capacitor acquired by the detecting circuit; The second input end of the comparator is connected with a fourth reference signal end; The output end of the comparator is connected with the control end of the second switch tube as the output end of the judging circuit, for acquiring the first signal representing the end of charging of the energy storage capacitor, and controlling the second switch tube to be turned on.

5. The start-up circuit of claim 2, wherein, The loop parameter control circuit comprises a fifth resistor, a sixth resistor, a third impedance-adjustable MOS tube, a fourth switch tube and a second capacitor. The first end of the fifth resistor is connected with the control end of the fourth switch tube, and the second end of the fifth resistor is connected with the output end of the signal processing circuit as the input end of the loop parameter control circuit. The first end of the fourth switch tube and the control end of the third impedance-adjustable MOS tube are connected with a second power supply through the sixth resistor, for sending a turn-on signal to the third impedance-adjustable MOS tube when the first control signal is not acquired, and sending a turn-off signal to the third impedance-adjustable MOS tube when the first control signal is acquired. The second end of the fourth switch tube is grounded. The first end of the second capacitor is connected with the first end of the third impedance-adjustable MOS tube. The second end of the second capacitor and the second end of the third impedance-adjustable MOS tube are connected with the first input end of the voltage loop as the output end of the loop parameter control circuit, for sending the second parameter to the voltage loop when the third impedance-adjustable MOS tube is turned on, and sending the first parameter to the voltage loop when the third impedance-adjustable MOS tube is turned off.

6. The start-up circuit of claim 2, wherein The Boost circuit comprises a first voltage dividing resistor and a second voltage dividing resistor arranged between positive and negative input ends. The loop parameter control circuit comprises a fifth resistor and a sixth resistor. The first end of the fifth resistor is connected between the first voltage dividing resistor and the second voltage dividing resistor, and the second end of the fifth resistor and the second end of the sixth resistor are connected with the first input end of the voltage loop and the second end of the third capacitor as the output end of the loop parameter control circuit, for sending the second parameter to the voltage loop when the signal processing circuit does not acquire the first control signal, and sending the first parameter to the voltage loop when the signal processing circuit acquires the first control signal.

7. The start-up circuit of claim 2, wherein The loop parameter control circuit comprises a fifth resistor and a sixth resistor. The first end of the fifth resistor is connected with the second end of the sixth resistor, and the common end of the fifth resistor and the sixth resistor is connected with the second input end of the voltage loop as the output end of the loop parameter control circuit, for sending the second parameter to the voltage loop when the signal processing circuit does not acquire the first control signal, and sending the first parameter to the voltage loop when the signal processing circuit acquires the first control signal. The second end of the fifth resistor is connected with a first reference signal end.

8. The start-up circuit according to any one of claims 1 to 7, characterized in that The detection circuit comprises a detection resistor connected in series with the energy storage capacitor, for detecting the charging condition of the energy storage capacitor.

9. The start-up circuit of claim 8, wherein, The detection circuit further comprises a current limiting circuit. The current limiting circuit comprises a seventh resistor, a fifth capacitor, a fifth impedance adjustable MOS tube and a third operational amplifier. The first end of the fifth impedance adjustable MOS tube is connected with the second end of the energy storage capacitor, wherein the first end of the fifth impedance adjustable MOS tube serves as an output end of the detection circuit. The second end of the fifth impedance adjustable MOS tube, the first end of the fifth capacitor and the negative phase input end of the third operational amplifier are connected with the detection resistor. The second end of the fifth capacitor is connected with the first end of the seventh resistor. The control end of the fifth impedance adjustable MOS tube is connected with the second end of the seventh resistor and the output end of the third operational amplifier, for adjusting the impedance of the fifth impedance adjustable MOS tube based on the electric signal on the branch where the energy storage capacitor is located, so as to limit the current on the branch of the energy storage capacitor. The positive phase input end of the third operational amplifier is connected with a third reference signal end.

10. The start-up circuit of claim 9, wherein, Further comprising a first auxiliary power supply, a second auxiliary power supply, a first diode and a second diode. The first end of the first auxiliary power supply is connected with the voltage input end of the rectification module in the Boost circuit. The second end of the first auxiliary power supply is connected with the anode of the first diode. The first end of the second auxiliary power supply is connected with the inductor in the Boost circuit. The second end of the second auxiliary power supply is connected with the anode of the second diode. The cathode of the first diode and the cathode of the second diode are connected, and the common end thereof is connected with the power supply positive input end of the third operational amplifier as the output end of the auxiliary power supply.

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