CN116937958A

CN116937958A - Start control circuit, power adapter and start control method

Info

Publication number: CN116937958A
Application number: CN202210321725.5A
Authority: CN
Inventors: 郭红光; 张晨松; 李建国; 张锦; 纪策; 田晨; 张加亮
Original assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Current assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2023-10-24

Abstract

The application relates to a start control circuit, a power adapter and a start control method. The starting control circuit comprises a voltage drop circuit and a DCDC circuit which are connected with the output end of the rectifying circuit; the voltage drop circuit is used for conducting under the condition that the input voltage of the rectifying circuit meets the preset voltage drop condition so as to reduce the starting voltage input to the DCDC circuit by the rectifying circuit; and the DCDC circuit is used for being conducted when the starting voltage is reduced to a preset voltage threshold value. The technical scheme provided by the embodiment of the application can promote the flexibility of the starting control of the DCDC circuit.

Description

Start control circuit, power adapter and start control method

Technical Field

The present application relates to the field of circuit technologies, and in particular, to a startup control circuit, a power adapter, and a startup control method.

Background

High-voltage DCDC (Direct Current-Direct Current) is a conversion circuit for converting a high voltage into a low voltage. Common high voltage DCDC circuits are DCDC circuits such as LLC circuits, LLC-DCX circuits, etc.

Taking an LLC circuit as an example, the LLC circuit comprises a resonant cavity formed by connecting elements such as a resonant inductor, a resonant capacitor and the like in series, and when the LLC circuit is started, a large impact current is easily formed, so that a switching tube of the LLC circuit is damaged. In the related art, in order to achieve safe start-up of an LLC circuit, a separate inductor having a large inductance is generally used as a resonant inductor to avoid excessive rush current.

However, the mode for implementing the DCDC circuit start control has certain application limitations, and the flexibility of the start control is poor.

Disclosure of Invention

The embodiment of the application provides a starting control circuit, a power adapter and a starting control method, which can promote the flexibility of starting control of a DCDC circuit.

In a first aspect, a start-up control circuit is provided, the start-up control circuit comprising a voltage drop circuit and a DCDC circuit connected to an output of a rectifying circuit;

the voltage drop circuit is used for being conducted under the condition that the input voltage of the rectifying circuit meets the preset voltage drop condition so as to reduce the starting voltage input to the DCDC circuit by the rectifying circuit;

the DCDC circuit is used for being conducted when the starting voltage is reduced to a preset voltage threshold value.

In a second aspect, there is provided a power adapter comprising a start-up control circuit as described in the first aspect above.

In a third aspect, there is provided a start-up control method for use in a control circuit in a start-up control circuit as described in the first aspect, the method comprising:

detecting the input voltage of a rectifying circuit, and controlling the voltage drop circuit to be conducted under the condition that the input voltage meets the preset voltage drop condition so as to reduce the starting voltage input to a DCDC circuit by the rectifying circuit;

and detecting the starting voltage, and controlling the DCDC circuit to be conducted when the starting voltage is reduced to a preset voltage threshold value.

The technical scheme provided by the embodiment of the application has the beneficial effects that at least:

the starting control circuit comprises a voltage drop circuit and a DCDC circuit, wherein the voltage drop circuit is connected with the output end of the rectifying circuit, the voltage drop circuit is used for being conducted under the condition that the input voltage of the rectifying circuit meets the preset voltage drop condition so as to reduce the starting voltage input to the DCDC circuit by the rectifying circuit, the DCDC circuit is used for being conducted when the starting voltage is reduced to a preset voltage threshold value, namely the starting voltage of the DCDC circuit is reduced through the voltage drop circuit, and the DCDC circuit is conducted after the starting voltage is reduced, so that the DCDC circuit can be safely started based on lower voltage, and the large current impact on the DCDC circuit caused by overlarge voltage during starting is avoided.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of a half-bridge LLC circuit;

FIG. 2 is a schematic diagram of a start-up control circuit according to an embodiment of the application;

FIG. 3 is a schematic diagram of another start-up control circuit according to an embodiment of the application;

FIG. 4 is a schematic diagram of another start-up control circuit according to an embodiment of the application;

FIG. 5 is a schematic diagram of another start-up control circuit according to an embodiment of the application;

FIG. 6 is a schematic diagram of a waveform of a starting current during a high voltage start of a DCDC circuit according to a conventional technique;

FIG. 7 is a schematic diagram of a waveform of a start-up current during a high voltage start-up of a DCDC circuit according to an embodiment of the present application;

FIG. 8 is an enlarged view of a portion of FIG. 7;

fig. 9 is a flowchart of a startup control method according to an embodiment of the present application.

Reference numerals illustrate:

a rectifying circuit: 100; a voltage drop circuit: 200; voltage conversion element: 201; capacitance: 202; a switching element; 203, a base station; DCDC circuit: 300; and the voltage stabilizing circuit comprises: 400.

Detailed Description

In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Embodiments of the application are illustrated in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the application. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

It is to be understood that in the following embodiments, "connected" is understood to mean "electrically connected", "communicatively connected", etc., if the connected circuits, modules, units, etc., have electrical or data transfer between them.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.

A high-voltage DCDC (Direct Current-Direct Current) circuit is a conversion circuit for converting a high voltage into a low voltage, and is a common DCDC circuit such as an LLC circuit, an LLC-DCX (Direct Current Transformer ) circuit, and the like. The LLC circuit can adjust its output voltage through the frequency conversion, and LLC-DCX circuit mainly differs from LLC circuit in that LLC-DCX circuit is fixed in the frequency of switch tube when the during operation.

Taking an LLC circuit as an example, referring to fig. 1, fig. 1 is a schematic diagram of a half-bridge LLC circuit. As shown in fig. 1, the resonant inductance Ls, the resonant capacitance Cs and Lm form a resonant circuit, and the series circuit of these three components is between the middle point of the two switching tubes (M1 and M2) and GND, this series circuit is also called "resonant cavity", and this topology has the greatest advantage that ZVS (Zero Voltage Switch, zero-voltage switching) of the two switching tubes can be realized, thereby improving the efficiency of voltage conversion.

When the LLC circuit is started, a large impact current is easy to form due to high input voltage, and because gallium nitride of a switching tube cannot bear too high current, in order to prevent the switching tube from being damaged due to gallium nitride failure, the traditional LLC circuit generally uses an independent inductor with large inductance as a resonant inductor to avoid the impact current from being too large.

However, as technology advances, many DCDC circuits (e.g., LLC circuits, LLC-DCX circuits) begin to use the leakage inductance of the transformer itself as the resonant inductance. The advantage of using the leakage inductance of the transformer itself as the resonant inductance is that the cost of the independent inductance can be saved and the volumes of the LLC circuit and the LLC-DCX circuit are reduced. However, the leakage inductance of the transformer is generally limited in inductance, and cannot have good current abrupt change inhibiting capability like an independent inductance, so that damage to a switching tube caused by excessive impact current cannot be effectively avoided.

In view of this, an embodiment of the present application provides a start-up control circuit, which includes a voltage drop circuit and a DCDC circuit connected to an output terminal of a rectifying circuit, where the voltage drop circuit is configured to be turned on when an input voltage of the rectifying circuit meets a preset voltage drop condition, so as to reduce a start-up voltage input to the DCDC circuit by the rectifying circuit, where the DCDC circuit is configured to be turned on when the start-up voltage is reduced to a preset voltage threshold, that is, the start-up voltage of the DCDC circuit is reduced by the voltage drop circuit, and then the DCDC circuit is turned on after the start-up voltage is reduced, so that the DCDC circuit can be safely started up based on a lower voltage, and a large current impact caused by an excessive voltage on the DCDC circuit during start-up is avoided.

In the following, some exemplary embodiments are described to describe technical solutions of embodiments of the present application.

Referring to fig. 2, a schematic diagram of a start control circuit according to an embodiment of the application is shown. As shown in fig. 2, the start-up control circuit includes a voltage drop circuit 200 and a DCDC circuit 300 connected to an output terminal of the rectifying circuit 100, and an input terminal of the rectifying circuit 100 may be an ac high voltage input, for example, the input terminal of the rectifying circuit 100 may be connected to a power grid.

In the embodiment of the present application, the voltage drop circuit 200 is configured to be turned on when the input voltage of the rectifying circuit 100 meets the preset voltage drop condition, so as to reduce the starting voltage input to the DCDC circuit 300 by the rectifying circuit 100.

The voltage drop circuit 200 is turned on when the input voltage of the rectifying circuit 100 meets the preset voltage drop condition, so that the starting voltage (Vbus shown in fig. 2) input to the DCDC circuit 300 by the rectifying circuit 100 is the input voltage of the voltage drop circuit 200, and the voltage drop circuit 200 drops the input voltage.

With respect to an exemplary implementation of the voltage drop circuit 200, description will be made in the examples related below. Hereinafter, preset depressurization conditions will be exemplarily described.

In the embodiment of the present application, the waveform of the input voltage of the rectifying circuit 100 is a sine wave, and the rectifying circuit 100 is turned on when the input voltage is greater than the starting voltage. Therefore, if the input voltage of the rectifying circuit 100 is larger, for example 220V, even if the voltage-dropping circuit 200 is turned on at this time, the voltage-dropping circuit 200 drops the starting voltage of the rectifying circuit 100 input to the DCDC circuit 300 to a smaller value, for example, less than 50V, and illustratively, the smaller value is 0V, but since the rectifying circuit 100 is turned on at this time, the starting voltage is quickly restored to 220V, and thus the voltage-dropping circuit 200 cannot achieve the reduction of the starting voltage.

Based on this, in one possible implementation, the preset step-down condition is that the input voltage of the rectifying circuit 100 is equal to zero, i.e. the voltage drop circuit 200 is turned on when the input voltage of the rectifying circuit 100 is equal to zero.

In this way, when the input voltage of the rectifying circuit 100 is equal to zero, the voltage drop circuit 200 is turned on, and the voltage drop circuit 200 reduces the starting voltage of the rectifying circuit 100 input to the DCDC circuit 300 to a smaller value, at this time, since the input voltage of the rectifying circuit 100 is less than or equal to the starting voltage, the rectifying circuit 100 is not turned on, and thus the voltage drop circuit 200 can smoothly reduce the starting voltage.

In another possible embodiment, the preset step-down condition may be that the absolute value of the input voltage of the rectifying circuit 100 is greater than zero and less than a preset threshold, for example, 1V, that is, the input voltage of the rectifying circuit 100 may fluctuate in a small range around zero, when the voltage-dropping circuit 200 is turned on.

Thus, after the voltage drop circuit 200 is turned on, the voltage drop circuit 200 reduces the starting voltage of the rectifying circuit 100 input to the DCDC circuit 300 to a smaller value, for example, less than 50V, and the rectifying circuit 100 may be turned on or not. In the case that the rectifying circuit 100 is not turned on, the voltage drop circuit 200 can smoothly reduce the starting voltage; in the case where the rectifier circuit 100 is turned on, the start-up voltage is restored to the input voltage of the rectifier circuit 100, but since the input voltage of the rectifier circuit 100 is small and fluctuates in a small range around zero, the start-up voltage also fluctuates in a small range around zero, and the voltage drop circuit 200 can smoothly reduce the start-up voltage as well.

With the above embodiment, the voltage drop circuit 200 reliably reduces the start-up voltage input to the DCDC circuit 300 by the rectifying circuit 100.

In the embodiment of the present application, the DCDC circuit 300 is configured to be turned on when the starting voltage is reduced to a preset voltage threshold.

When the starting voltage decreases to a preset voltage threshold, the preset voltage threshold is, for example, less than 50V, that is, the starting voltage is a small value, and the DCDC circuit 300 is turned on again, so that the starting voltage of the DCDC circuit 300 is the small value. Thus, the embodiment of the application reduces the starting voltage of the DCDC circuit 300, reduces the impact current of the switching tube in the DCDC circuit 300 to a reasonable range, and realizes the safe starting of the DCDC circuit 300.

In the embodiment of the present application, the DCDC circuit 300 is an LLC circuit or an LLC-DCX circuit, and a schematic diagram of the LLC circuit or the LLC-DCX circuit may be shown in fig. 1, where the LLC circuit may adjust its output voltage by frequency conversion, and the main difference between the LLC-DCX circuit and the LLC circuit is that the frequency of the switching tube is fixed when the LLC-DCX circuit works.

In an embodiment of the present application, the DCDC circuit 300 includes a transformer, such as T1 shown in fig. 1, and leakage inductance of the transformer is used as a resonant inductance of a resonant cavity in the DCDC circuit 300. In the LLC circuit or LLC-DCX circuit using the leakage inductance of the transformer as the resonant inductance, the embodiment of the application can realize the effect of small current opening of the resonant cavity without additionally adding an independent inductance, and realize better current inhibition capability.

The embodiment of the application better solves the problem of current impact when the LLC circuit or the LLC-DCX circuit is started, and avoids the risk of failure of gallium nitride used for a switching tube in the LLC circuit or the LLC-DCX circuit in the starting process.

In addition, when the starting control circuit is arranged on the adapter, the safe starting of the DCDC circuit 300 can be realized without adding an independent inductor, so that the starting control circuit has an important effect on the volume reduction of the adapter and is beneficial to the realization of the requirement of an ultrathin adapter.

In summary, the start-up control circuit includes a voltage drop circuit 200 and a DCDC circuit 300 connected to the output terminal of the rectifying circuit 100, where the voltage drop circuit 200 is used to be turned on when the input voltage of the rectifying circuit 100 meets a preset voltage drop condition, so as to reduce the start-up voltage input to the DCDC circuit 300 by the rectifying circuit 100, and the DCDC circuit 300 is used to be turned on when the start-up voltage is reduced to a preset voltage threshold, that is, the start-up voltage of the DCDC circuit 300 is reduced by the voltage drop circuit 200, and then the DCDC circuit 300 is turned on after the start-up voltage is reduced, so that the DCDC circuit 300 can be safely started up based on a lower voltage, and a large current impact caused by an excessive voltage on the DCDC circuit 300 during start-up is avoided.

In addition, it should be noted that, for the DCDC circuit 300 that still uses the independent inductor as the resonant inductor and has a smaller inductance value, the embodiment of the present application can also implement safe starting of the DCDC circuit 300 by reducing the voltage when the DCDC circuit 300 is started, so as to further improve the flexibility of starting control of the DCDC circuit 300.

In an embodiment, based on the embodiment shown in fig. 2, the start-up control circuit of this embodiment further includes a control circuit (not shown) connected to the voltage drop circuit 200 and the DCDC circuit 300, respectively, and connected to the input terminal and the output terminal of the rectifying circuit 100, respectively.

The control circuit is configured to detect an input voltage of the rectifying circuit 100, and control the voltage drop circuit 200 to be turned on when the input voltage meets a preset voltage drop condition.

In the embodiment of the present application, after the control circuit is started and powered on, the control circuit performs a process of detecting the input voltage of the rectifying circuit 100. As described above, the waveform of the input voltage of the rectifying circuit 100 is a sine wave, the control circuit first detects the magnitude of the input voltage of the rectifying circuit 100 in the first waveform period of the input voltage of the rectifying circuit 100, and detects whether the magnitude of the input voltage meets the preset voltage reduction condition, if the magnitude of the input voltage meets the preset voltage reduction condition, the control circuit stops detecting the input voltage and controls the voltage reduction circuit 200 to be turned on.

If the control circuit does not detect that the input voltage of the rectifying circuit 100 meets the preset voltage reduction condition in the first waveform period, the control circuit continues to detect the magnitude of the input voltage of the rectifying circuit 100 in the second waveform period and detects whether the magnitude of the input voltage meets the preset voltage reduction condition, if the magnitude of the input voltage meets the preset voltage reduction condition, the control circuit stops detecting the input voltage and controls the voltage reduction circuit 200 to be turned on, and so on.

The control circuit is further configured to detect a starting voltage input to the DCDC circuit 300 by the rectifying circuit 100, and control the DCDC circuit 300 to be turned on when the starting voltage is reduced to a preset voltage threshold.

After the control circuit controls the voltage drop circuit 200 to be turned on, the control circuit starts to detect the starting voltage input to the DCDC circuit 300 by the rectifying circuit 100, and compares the starting voltage with a preset voltage threshold, which may be set by itself, for example, to be less than 50V, or directly set to be 0V, or the like. If the control circuit detects that the starting voltage is equal to the preset voltage threshold, the DCDC circuit 300 is controlled to be turned on to start the DCDC circuit 300.

Thus, the starting voltage of the DCDC circuit 300 is the preset voltage threshold, which is a smaller dc voltage, so as to realize safe starting of the DCDC circuit 300.

Optionally, after the control circuit controls the DCDC circuit 300 to be turned on, the control circuit is further configured to control the switching frequency of the DCDC circuit 300 to be reduced from the preset starting frequency to the operating frequency in a preset starting period, where the starting frequency is greater than the operating frequency.

The switching frequency of the DCDC circuit 300 is the switching frequency of the switching tube in the DCDC circuit 300, and the starting frequency is a high frequency, for example, the operating frequency of the DCDC circuit 300 in normal operation is 100KHz, and the starting frequency can be set to be 1MHz. In the starting stage of the DCDC circuit 300, the control circuit controls the switching tube of the DCDC circuit 300 to operate at the high-frequency starting frequency, and then controls the switching tube of the DCDC circuit 300 to gradually decrease to the normal operating frequency.

Because the switching frequency of the DCDC circuit 300 is inversely related to the input voltage of the DCDC circuit 300, that is, the switching frequency of the DCDC circuit 300 increases, the input voltage of the DCDC circuit 300 decreases, and therefore, taking the DCDC circuit 300 as the LLC circuit shown in fig. 1 as an example, in the embodiment of the application, the frequency of the switching tube of the DCDC circuit 300 is controlled to be the high-frequency starting frequency in the starting time period, so that the voltage at two ends of the input capacitor of the input end of the DCDC circuit 300 is smaller, and excessive impact current to the switching tube and the resonant cavity can be avoided, thereby further ensuring safe starting of the DCDC.

In addition, in the embodiment of the present application, the DCDC circuit 300 includes an output capacitor. Continuing with the DCDC circuit 300 as an example of the LLC circuit shown in fig. 1, the output capacitance is "COUTPUT" shown in fig. 1. The capacitance value of the output capacitor is smaller than the preset capacitance threshold, that is, the output capacitor is smaller, so that larger impact current brought by the load to the resonant cavity when the DCDC circuit 300 is started can be avoided by setting the output capacitor of the DCDC circuit 300 smaller; and because the output capacitance of the DCDC circuit 300 is smaller, the mode of controlling the DCDC circuit 300 to start at high frequency by the control circuit can be used as an alternative mode, and a mode of starting at high frequency is not needed as in the conventional LLC topology because of large capacitive load, so that the flexibility of starting control is further improved.

Based on the above-described embodiment shown in fig. 2, the present embodiment will exemplarily describe an implementation of the voltage drop circuit 200.

In one possible implementation of the voltage drop circuit 200, referring to fig. 3, the voltage drop circuit 200 includes a voltage conversion element 201. The voltage conversion element 201 may be turned on when the input voltage of the rectifying circuit 100 meets a preset voltage reduction condition, which is described above and will not be described herein. The voltage conversion element 201 can reduce the start-up voltage input to the DCDC circuit 300 by the rectifying circuit 100 after being turned on.

The voltage drop circuit 200 further comprises an energy storage element connected to the output of the voltage converting element 201. With continued reference to fig. 3, the energy storage element may be, for example, the capacitor 202 shown in fig. 3, and in other embodiments, the energy storage element may be in the form of a parallel resistor of the capacitor 202, which is not limited herein.

Taking the energy storage element as a capacitor as an example, after the voltage conversion element 201 is turned on, energy is extracted from Vbus shown in fig. 3 to Vcap, that is, the capacitor 202 is quickly charged by using the starting voltage, so as to achieve the purpose of reducing the starting voltage.

In the embodiment of the present application, the voltage conversion element 201 may be a step-down element or a step-up element.

Taking the voltage conversion element 201 as a voltage-reducing element, which may be, for example, a Buck circuit, the voltage-reducing element first reduces the starting voltage Vbus to reduce the current applied to the capacitor 202, and then charges the capacitor 202 with the voltage Vcap output by the voltage-reducing element, so as to reduce the starting voltage.

Taking the voltage conversion element 201 as a Boost element, for example, the Boost element may be a Boost circuit, where the Boost element first boosts the starting voltage Vbus, and then charges the capacitor 202 with the voltage Vcap output by the Boost element, so as to reduce the starting voltage.

Note that, in the case where the voltage conversion element 201 is a step-down element, since the input voltage is higher than the output voltage, the step-down element needs to have a relatively large number of capacitors 202 connected in parallel in order to achieve a relatively low output voltage; in the case where the voltage conversion element 201 is a voltage boosting element, the number of capacitors 202 is not necessarily large, but the capacitors 202 are required to withstand high voltage, that is, the performance requirement of the capacitors 202 is high, so in the practical application process, the voltage boosting element or the voltage reducing element may be selected to be used based on the practical design requirement, for example, the requirement of the volume of the start control circuit.

In the embodiment of the present application, the DCDC circuit 300 can convert the dc high voltage output by the rectifying circuit 100 into the dc low voltage after the safe start, and then output the dc low voltage to the back-end circuit or the load.

Illustratively, referring to fig. 4, the start-up control circuit may further include a voltage stabilizing circuit 400, an input of the voltage stabilizing circuit 400 being connected to an output of the DCDC circuit 300, and an output of the voltage stabilizing circuit 400 being operable to connect to a load.

Because the input voltage and the output voltage of the DCDC circuit 300 are in a proportional relationship, if the input voltage of the DCDC circuit 300 is not constant, the output voltage of the DCDC circuit 300 is also not constant, and in order to improve this phenomenon, the voltage stabilizing circuit 400 is arranged at the output end of the DCDC circuit 300 to process the unstable voltage output by the DCDC circuit 300 and output the unstable voltage at a constant voltage, thereby meeting the power supply requirement of a load.

In another possible embodiment of the voltage drop circuit 200, the voltage drop circuit 200 comprises a switching element 203 and an energy storage element, see fig. 5, which may be, for example, a capacitor 202 as shown in fig. 5, the switching element 203 being connected between the output of the rectifying circuit 100 and the energy storage element.

The switching element 203 may be turned on when the input voltage of the rectifying circuit 100 meets a preset voltage-reducing condition, and after the switching element 203 is turned on, the capacitor 202 is quickly charged by the starting voltage Vbus, so as to achieve the purpose of reducing the starting voltage.

Thus, the voltage drop circuit 200 can achieve the purpose of reducing the starting voltage through any one of the embodiments, the embodiments are simple and easy to operate, the starting current of the DCDC circuit 300 is reduced through the voltage drop circuit 200, and the problems of high circuit cost and large volume caused by adding an external inductor are avoided.

The effect of the start control circuit for the start control of the impact current according to the embodiment of the application is described below by a set of experimental comparison diagrams.

Referring to fig. 6-8, fig. 6 is a waveform diagram of a starting current during a high voltage start of a DCDC circuit in the prior art.

As shown in fig. 6, in the case where the starting voltage input to the DCDC circuit by the rectifying circuit is 50V, the DCDC rush current has reached 2.152a, and if the starting voltage is raised again, for example, to 200V or 300V, a large rush current will be generated to damage the switching tube of the DCDC circuit.

Fig. 7 is a waveform schematic diagram of a starting current at the time of high voltage starting of the DCDC circuit according to an embodiment of the present application, and fig. 8 is a partial enlarged view of fig. 7.

Referring to fig. 7 and 8, after the voltage-dropping circuit is turned on, the output voltage Vcap of the voltage-dropping circuit is increased, so that the starting voltage Vbus input to the DCDC circuit by the rectifying circuit is reduced by the voltage-dropping circuit, and under the condition that the output voltage of the rectifying circuit is 200V high voltage, the impulse current of the DCDC circuit is 3.5A, so that no great impulse current is generated, and safe starting of the DCDC circuit is ensured.

In one embodiment, a power adapter is provided, which includes the start control circuit according to any of the above embodiments, and the power adapter may be used with an electronic device such as a mobile phone, a mobile power supply, a notebook computer, a tablet computer, a smart watch, a smart bracelet, a smart glasses, a floor sweeping machine, a wireless earphone, a bluetooth sound, an electric toothbrush, a rechargeable wireless mouse, or a desktop computer.

The specific limitation and advantageous effects of the power adapter can be found in the above-mentioned embodiments of the start control circuit, and are not described herein.

In one embodiment, referring to fig. 9, there is provided a start-up control method for use in a control circuit in a start-up control circuit according to any one of the embodiments, the method comprising the steps of:

step 901, detecting an input voltage of the rectifying circuit, and controlling the voltage drop circuit to be turned on to reduce a starting voltage input to the DCDC circuit by the rectifying circuit when the input voltage meets a preset voltage drop condition.

In step 902, the start-up voltage is detected, and the DCDC circuit is controlled to be turned on when the start-up voltage is reduced to a preset voltage threshold.

Optionally, after step 902, the startup control method according to the embodiment of the present application further includes the following step A1:

and step A1, controlling the switching frequency of the DCDC circuit to be reduced from a preset starting frequency to a working frequency in a preset starting time period, wherein the starting frequency is larger than the working frequency.

The specific limitation and beneficial effects of the start control method can be referred to the embodiments of the start control circuit described above, and will not be described herein.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. The starting control circuit is characterized by comprising a voltage drop circuit and a DCDC circuit which are connected with the output end of the rectifying circuit;

2. The start-up control circuit of claim 1, further comprising a control circuit connected to the voltage drop circuit and the DCDC circuit, respectively;

the control circuit is used for detecting the input voltage of the rectifying circuit and controlling the voltage drop circuit to be conducted under the condition that the input voltage meets the preset voltage drop condition;

the control circuit is also used for detecting the starting voltage and controlling the DCDC circuit to be conducted when the starting voltage is reduced to the preset voltage threshold value.

3. The start-up control circuit as set forth in claim 2, wherein,

the control circuit is further configured to control the switching frequency of the DCDC circuit to be reduced from a preset starting frequency to a working frequency in a preset starting time period, where the starting frequency is greater than the working frequency.

4. The start-up control circuit of claim 1, wherein the preset buck condition is the input voltage being equal to zero.

5. The start-up control circuit of any one of claims 1-4, wherein the voltage drop circuit comprises a voltage conversion element.

6. The start-up control circuit of claim 5, wherein the voltage conversion element is a buck element or a boost element.

7. The start-up control circuit of claim 5, wherein the voltage drop circuit further comprises an energy storage element coupled to the output of the voltage conversion element.

8. The start-up control circuit of any one of claims 1-4, wherein the voltage drop circuit comprises a switching element and an energy storage element, the switching element being connected between the output of the rectifying circuit and the energy storage element.

9. The start-up control circuit of claim 1, wherein the DCDC circuit is an LLC circuit or an LLC-DCX circuit.

10. The start-up control circuit of claim 1, wherein the DCDC circuit includes a transformer having leakage inductance as a resonant inductance of a resonant cavity in the DCDC circuit.

11. A power adapter comprising a start-up control circuit as claimed in any one of claims 1 to 10.

12. A start-up control method for use in a control circuit in a start-up control circuit according to any one of claims 1-10, the method comprising:

13. The method of claim 12, wherein after said controlling the DCDC circuit to conduct, the method further comprises:

and in a preset starting time period, controlling the switching frequency of the DCDC circuit to be reduced from a preset starting frequency to a working frequency, wherein the starting frequency is larger than the working frequency.