CN117767765B - Resonant circuit, charging control method and charger - Google Patents

Abstract

The embodiment of the present application provides a resonant circuit, a charging control method and a charger, wherein the circuit includes a DC-DC primary module and a DC-DC secondary module; the DC-DC secondary module includes a first side oscillator submodule, a second side oscillator submodule and a second switching switch submodule; when the second switching switch submodule is turned on, the first side oscillator submodule and the second side oscillator submodule are in an enabled state, and the resonant circuit operates in a PFM mode; when the second switching switch submodule is disconnected, the second side oscillator submodule is in an enabled state, and the resonant circuit operates in a PWM mode. The second switching switch submodule is used to control the enabling of the first side oscillator submodule, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode. When the charging gain or output power is small, the PWM mode can be used for charging to reduce the loss of the charging system when the load is light.

Description

Resonant circuit, charging control method and charger

Technical Field

The present application relates to the field of electronic technology, and in particular to a resonant circuit, a charging control method and a charger.

Background technique

With the development of mobile terminal technology, various wearable devices have emerged, making people's production and life more convenient. As one of the key technical competition points in the mobile terminal industry, fast charging technology has attracted more and more attention. The current mainstream fast charging protocols include PD (power delivery), QC (Quick Charge), UFCS (Universal Fast Charging Specification), etc. The above protocols all have specific indicator requirements for fast charging technology: the charger output voltage is continuously adjustable.

Fast charging chargers are required to have the characteristics of high efficiency, high power and small size. The current mainstream technology is still concentrated on flyback and flyback deformation topology, with low conversion efficiency and poor output power scalability, which cannot further support future technological development. The research on the adaptability of new topologies is the future development direction; LLC circuit is a resonant circuit composed of 2 inductors and 1 capacitor, so it is called LLC. LLC circuit has a 50% fixed duty cycle, the transformer works in quadrants 1 and 3, the utilization rate of magnetic materials is increased by 1 times, the device stress is low, and the loss is small. It has gradually become the development direction of fast charging technology.

In related technologies, LLC circuits all use PFM (Pulse Frequency Modulation) for power supply, which changes the power by changing the pulse frequency. The charging gain of PFM is nonlinear. The lighter the load, the smaller the required charging gain and the higher the switching frequency. As a result, when the load is light, the loss of the charging system is greater.

Summary of the invention

The purpose of the embodiments of the present application is to provide a resonant circuit, a charging control method and a charger to reduce the loss of the charging system in the LLC circuit. The specific technical solution is as follows:

According to a first aspect of an embodiment of the present application, a resonant circuit is provided, comprising:

DC-DC primary side module and DC-DC secondary side module;

The DC-DC secondary side module includes a first side oscillator submodule, a second side oscillator submodule and a second switch submodule; the first side oscillator submodule is connected to the second side oscillator submodule and the second switch submodule respectively;

Wherein, when the second switching switch submodule is turned on, the first side oscillation submodule and the second side oscillation submodule are in an enabled state, and the resonant circuit operates in the PFM mode;

When the second switch submodule is disconnected, the second side oscillation submodule is in an enabled state, and the resonant circuit operates in a PWM mode.

In an embodiment of the present application, the second switching switch submodule is used to control the enabling of the first side oscillation submodule, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode. When the charging gain or output power is small, the PWM mode can be used for charging to reduce the loss of the charging system when the load is light.

In a possible implementation, the DC-DC primary module includes a first primary oscillator module, a second primary oscillator module and a first switch submodule; the first primary oscillator module is connected to the second primary oscillator module and the first switch submodule respectively; the second primary oscillator module is connected to the first switch submodule;

Wherein, when the first switching switch submodule is disconnected and the second switching switch submodule is turned on, the first primary oscillator submodule, the first primary oscillator submodule, and the second primary oscillator submodule are in an enabled state, and the resonant circuit operates in the PFM mode;

When the first switching switch submodule is turned on and the second switching switch submodule is turned off, the first primary oscillator submodule, the second primary oscillator submodule and the secondary oscillator submodule are in an enabled state, and the resonant circuit operates in a PWM mode.

In an embodiment of the present application, a first switching switch submodule is used to control the enabling of the second primary side oscillator submodule, and a second switching switch submodule is used to control the enabling of the first primary side oscillator submodule, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode. When the charging gain or output power is small, the PWM mode can be used for charging to reduce the loss of the charging system when the load is light.

In a possible implementation manner, the first primary oscillator module includes a first capacitor, a first transistor, a second transistor, a second capacitor, a third capacitor, a first inductor, a third inductor, and a fifth capacitor;

The first end of the fifth capacitor is respectively connected to the first end of the first transistor and the first end of the first capacitor; the second end of the fifth capacitor is respectively connected to the second end of the second transistor, the second end of the second capacitor, and the second end of the third capacitor;

The second end of the first transistor is respectively connected to the second end of the first capacitor, the first end of the first inductor, the first end of the second transistor, and the first end of the second capacitor;

The second end of the first inductor is connected to the first end of the third inductor, and the second end of the third inductor is connected to the first end of the third capacitor.

In the embodiment of the present application, a specific circuit structure of the first primary oscillator submodule is given, which realizes the switching of the DC-DC primary module between the PFM drive mode and the PWM drive mode, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode.

In a possible implementation manner, the second primary oscillator submodule includes a fourth capacitor and a second inductor, and the first switch submodule includes a first switch and a second switch;

The first end of the second inductor is connected to the first end of the first inductor, the second end of the second inductor is connected to the first end of the first switch, and the second end of the first switch is connected to the first end of the third inductor;

The first end of the fourth capacitor is connected to the first end of the second switch, the second end of the fourth capacitor is connected to the second end of the third capacitor, and the second end of the second switch is connected to the first end of the third capacitor.

In the embodiment of the present application, a specific circuit structure of the second primary oscillator submodule and the first switching switch submodule is given, which realizes the switching of the DC-DC primary module between the PFM drive mode and the PWM drive mode, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode.

In a possible implementation manner, the second side oscillator module includes a fifth inductor, a fourth transistor, and a sixth capacitor.

The first end of the fifth inductor is connected to the first end of the sixth capacitor, the second end of the fifth inductor is connected to the first end of the fourth transistor, and the second end of the fourth transistor is connected to the second end of the sixth capacitor.

In the embodiment of the present application, a specific circuit structure of the second side oscillator module is given, which realizes the switching of the DC-DC secondary side module between the PFM drive mode and the PWM drive mode, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode.

In a possible implementation manner, the first side oscillator submodule includes a fourth inductor and a third transistor, and the second switch submodule includes a fifth transistor;

The first end of the fourth inductor is connected to the first end of the fifth transistor, and the second end of the fourth inductor is connected to the first end of the sixth capacitor;

The second end of the fifth transistor is connected to the first end of the third transistor, and the second end of the third transistor is connected to the second end of the sixth capacitor.

In the embodiment of the present application, a specific circuit structure of the first side oscillator submodule and the second switching switch submodule is given, which realizes the switching of the DC-DC secondary side module between the PFM drive mode and the PWM drive mode, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode.

In a possible implementation manner, the third transistor is replaced by a first diode, the fourth transistor is replaced by a second diode, and/or the fifth transistor is replaced by a third switch.

In the embodiment of the present application, a specific circuit structure of the DC-DC secondary side module is given, which realizes the switching of the DC-DC secondary side module between the PFM driving mode and the PWM driving mode, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode.

In a possible implementation, the circuit further includes: an isolation module;

The DC-DC primary side module also includes a primary side switching control submodule, and the DC-DC secondary side module includes a secondary side switching control submodule;

The isolation module is connected to the primary side switching control submodule and the secondary side switching control submodule respectively;

The primary side switching control submodule is used to control the disconnection and conduction of the first switching switch submodule;

The secondary side switching control submodule is used to control the disconnection and conduction of the second switching switch submodule;

The isolation module is used to implement signal isolation and transmission between the primary-side switching control submodule and the secondary-side switching control submodule.

In the embodiment of the present application, signal isolation transmission between the DC-DC primary module and the DC-DC secondary module is realized, so that the DC-DC primary module and the DC-DC secondary module can communicate through signal isolation transmission, which ensures the electrical safety between the primary and secondary sides and can coordinate the switching between PFM mode and PWM mode.

According to a second aspect of an embodiment of the present application, a charging control method is provided, the method comprising:

Get the current charging gain;

When the current charging mode is the PFM mode, if the current charging gain is less than a preset second gain threshold, and/or the current output power is not greater than a preset power threshold, the charging mode is switched to the PWM mode.

In an embodiment of the present application, when the charging gain or output power is small, the charging mode is switched from PFM mode to PWM mode. Under low load conditions, the charging loss of the PWM mode is lower than the charging loss of the PFM mode, thereby reducing the loss of the charging system when the load is light.

In a possible implementation, the method further includes:

Determine whether the current charging gain is greater than a preset first gain threshold; wherein the preset second gain threshold is less than the preset first gain threshold;

When the current charging mode is the PFM mode and the current charging gain is greater than a preset first gain threshold, the charging mode is switched to the PWM mode.

When the charging system gain is greater than the maximum gain of the LLC circuit, the LLC circuit will enter the capacitive region in PFM mode and cannot work normally. In this case, PFM mode can be used for charging to expand the chargeable gain range.

In a possible implementation, the method further includes:

When the current charging gain is not greater than the preset first gain threshold, determining whether the current charging gain is less than the preset second gain threshold;

When the current charging mode is the PFM mode, if the current charging gain is not less than the preset second gain threshold and the current output power is greater than the preset power threshold, the charging mode is maintained as the PFM mode.

In the embodiment of the present application, when the current charging gain is not less than the preset second gain threshold and the current output power is greater than the preset power threshold, the charging mode is maintained in the PFM mode to maintain a higher charging power.

In a possible implementation, the method further includes:

When the current charging mode is the PWM mode and the current charging gain is not greater than a preset first gain threshold, determining whether the current charging gain is less than a preset second gain threshold, wherein the preset second gain threshold is less than the preset first gain threshold;

When the current charging gain is not less than the preset second gain threshold, obtaining the current output power, and determining whether the current output power is greater than the preset power threshold;

If the current output power is greater than the preset power threshold, the charging mode is switched to PFM mode;

If the current output power is not greater than the preset power threshold, the charging mode is maintained in the PWM mode.

In an embodiment of the present application, a case of switching from PWM mode to PFM mode is given. When the charging gain is not less than a preset second gain threshold and the output power is greater than a preset power threshold, the charging mode is switched from PWM mode to PFM mode, thereby improving charging efficiency and reducing losses.

In a possible implementation manner, after the step of obtaining the current charging gain, the method further includes:

Determine whether the current charging gain is the same as the charging gain obtained last time;

If they are the same, the current charging gain is discarded and the next detection cycle is waited for.

In an embodiment of the present application, when the charging gain of the current detection cycle remains unchanged, it means that there is no need to adjust the charging mode. Therefore, there is no need to perform a subsequent judgment process in this cycle, and the current charging gain is discarded and waits for the next detection cycle to be re-acquired; thereby reducing unnecessary judgment processes and saving computing resources.

According to a third aspect of an embodiment of the present application, a charger is provided, comprising a resonant circuit and a charging control chip as described in any one of the present application; the charging control chip is used to control the resonant circuit to switch the charging mode during operation through any one of the charging control methods described in the present application.

The resonant circuit, charging control method and charger provided by the embodiment of the present application, the resonant circuit includes a DC-DC primary module and a DC-DC secondary module; the DC-DC secondary module includes a first side oscillator submodule, a second side oscillator submodule and a second switching switch submodule; the first side oscillator submodule is connected to the second side oscillator submodule and the second switching switch submodule respectively; wherein, when the second switching switch submodule is turned on, the first side oscillator submodule and the second side oscillator submodule are in an enabled state, and the resonant circuit operates in the PFM mode; when the second switching switch submodule is disconnected, the second side oscillator submodule is in an enabled state, and the resonant circuit operates in the PWM mode. The second switching switch submodule is used to control the enabling of the first side oscillator submodule, so as to realize the switching of the resonant circuit between the PFM mode and the PWM mode, and the PWM mode can be used for charging when the charging gain or output power is small, so as to reduce the loss of the charging system when the load is light.

Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

FIG1 is a schematic diagram of a resonant circuit in the prior art;

FIG2 is a first schematic diagram of a resonant circuit provided in an embodiment of the present application;

FIG3 is a second schematic diagram of a resonant circuit provided in an embodiment of the present application;

FIG4 is a third schematic diagram of a resonant circuit provided in an embodiment of the present application;

FIG5 is a fourth schematic diagram of a resonant circuit provided in an embodiment of the present application;

FIG6 is a fifth schematic diagram of a resonant circuit provided in an embodiment of the present application;

FIG7 is a first schematic diagram of a charging control method provided in an embodiment of the present application;

FIG8 is a second schematic diagram of a charging control method provided in an embodiment of the present application;

FIG9 is a schematic diagram of a resonant circuit in a PFM mode in an embodiment of the present application;

FIG10 is a waveform diagram of key points in the resonant circuit in the PFM mode in an embodiment of the present application;

FIG11 is a schematic diagram of a resonant circuit in PWM mode in an embodiment of the present application;

FIG. 12 is a waveform diagram of key points in the resonant circuit in PWM mode in an embodiment of the present application.

Detailed ways

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field based on the present application belong to the scope of protection of the present application.

The LLC circuit is a resonant circuit composed of two inductors and one capacitor, so it is called LLC. Its topology can be divided into half-bridge or full-bridge types according to the arrangement of transistors (such as MOS tubes). The LLC circuit can realize soft switching of transistors through resonance, reduce switching losses, realize ZVS (Zero Voltage Switch) of the primary switch tube in the full power range, and realize ZCS (Zero Current Switch) of the SR (synchronous rectifier) switch tube. The device stress is low and the loss is small; the leakage inductance of the transformer participates in the resonant circuit, and the leakage inductance energy is transferred to Vbus (power supply pin) and the secondary side through resonance, and the energy loss is small. In addition, the on-state loss of the transistor is also very low, that is, the Joule heat generated is also small, so there is no need to use an additional heat sink for heat dissipation. Because of these advantages, the LLC circuit has gradually become the development direction of fast charging technology.

In the related art, LLC circuits all use PFM (Pulse Frequency Modulation) for power supply. The circuit diagram is shown in Figure 1, where Vin represents the power input end, Vout represents the power output end, MA, MB, MC, and MD are all MOS tubes, LA, LB, LC, and LD are all inductors, and CA and CB are all capacitors. PFM is an analog signal modulation method that changes the power by changing the pulse frequency. The charging gain of PFM is nonlinear. The lighter the load, the smaller the required charging gain and the higher the switching frequency. As a result, when the load is light, the loss of the charging system is greater.

In view of this, an embodiment of the present application provides a resonant circuit, including: a DC-DC primary module and a DC-DC secondary module;

The DC-DC secondary side module includes a first side oscillator submodule, a second side oscillator submodule and a second switch submodule; the first side oscillator submodule is connected to the second side oscillator submodule and the second switch submodule respectively;

Wherein, when the second switching switch submodule is turned on, the first side oscillation submodule and the second side oscillation submodule are in an enabled state, and the resonant circuit operates in the PFM mode;

When the second switch submodule is disconnected, the second side oscillation submodule is in an enabled state, and the resonant circuit operates in a PWM mode.

In an embodiment of the present application, the second switching switch submodule is used to control the enabling of the first side oscillation submodule, thereby realizing the switching of the resonant circuit between the PFM mode and the PWM mode. When the charging gain or output power is small, the PWM mode can be used for charging to reduce the loss of the charging system when the load is light.

In a possible implementation manner, the resonant circuit in the embodiment of the present application may be as shown in FIG. 2 , including:

DC-DC primary module 01 and DC-DC secondary module 02;

The DC-DC primary module 01 includes a first primary oscillator module 011, a second primary oscillator module 012 and a first switch submodule 013; the first primary oscillator module 011 is connected to the second primary oscillator module 012 and the first switch submodule 013 respectively; the second primary oscillator module 012 is connected to the first switch submodule 013;

The DC-DC secondary side module 02 includes a first side oscillator submodule 021, a second side oscillator submodule 022 and a second switch submodule 023; the first side oscillator submodule 021 is connected to the second side oscillator submodule 022 and the second switch submodule 023 respectively;

Among them, when the first switching switch submodule 013 is disconnected and the second switching switch submodule 023 is turned on, the first primary oscillator submodule 011, the first primary oscillator submodule 021, and the second primary oscillator submodule 022 are in an enabled state, and the resonant circuit operates in the PFM mode.

When the first switching switch submodule 013 is turned on and the second switching switch submodule 023 is turned off, the first primary oscillator submodule 011, the second primary oscillator submodule 012 and the secondary oscillator submodule 022 are in an enabled state, and the resonant circuit operates in a PWM (Pulse width modulation) mode.

The PWM mode adjusts power by changing the pulse time width. When the load is light, the switching frequency remains unchanged and the load is reduced by reducing the pulse width. Compared with the PFM mode, it can reduce the loss of the charging system and improve the charging efficiency.

The first switching switch submodule 013 is used to control the enabling of the second primary oscillator submodule 012. When the first switching switch submodule 013 is turned on, the second primary oscillator submodule 012 works; when the first switching switch submodule 013 is turned off, the second primary oscillator submodule 012 does not work. For the DC-DC primary module 01, when the first primary oscillator submodule 011 and the second primary oscillator submodule 012 are both working, the DC-DC primary module 01 is in PWM driving mode; when the first primary oscillator submodule 011 is working and the second primary oscillator submodule 012 is not working, the DC-DC primary module 01 is in PFM driving mode.

The second switching switch submodule 023 is used to control the enabling of the first side oscillator submodule 021. When the second switching switch submodule 023 is turned on, the first side oscillator submodule 021 works; when the second switching switch submodule 023 is turned off, the first side oscillator submodule 021 does not work. For the DC-DC secondary side module 02, when both the first side oscillator submodule 021 and the second side oscillator submodule 022 work, the DC-DC secondary side module 02 is in PFM driving mode; when the second side oscillator submodule 022 works and the first side oscillator submodule 021 does not work, the DC-DC secondary side module 02 is in PWM driving mode.

In an embodiment of the present application, a first switching switch submodule is used to control the enabling of a second primary oscillator submodule, so that the DC-DC primary module can be suitable for the frequency in the PWM mode; and a second switching switch submodule is used to control the enabling of the first primary oscillator submodule, so that the resonant circuit can be switched between the PFM mode and the PWM mode. Therefore, when the charging gain or output power is small, the PWM mode can be used for charging to reduce the loss of the charging system when the load is light.

In a possible implementation, referring to FIG3 , the first primary oscillator module includes a first capacitor C1, a first transistor M1, a second transistor M2, a second capacitor C2, a third capacitor C3, a first inductor L1, a third inductor L3, and a fifth capacitor C5;

The first end of the fifth capacitor C5 is respectively connected to the first end of the first transistor M1 and the first end of the first capacitor C1; the second end of the fifth capacitor C5 is respectively connected to the second end of the second transistor M2, the second end of the second capacitor C2, and the second end of the third capacitor C3;

The second end of the first transistor M1 is respectively connected to the second end of the first capacitor C1, the first end of the first inductor L1, the first end of the second transistor M2, and the first end of the second capacitor C2;

The second end of the first inductor L1 is connected to the first end of the third inductor L3 , and the second end of the third inductor L3 is connected to the first end of the third capacitor C3 .

The second primary oscillator submodule is respectively connected to the first end of the first inductor L1 and the second end of the second capacitor, and the first switch submodule is respectively connected to the first end of the third inductor L3 and the first end of the third capacitor C3.

In a possible implementation manner, the second primary oscillator submodule includes a fourth capacitor C4 and a second inductor L2, and the first switch submodule includes a first switch S1 and a second switch S2;

The first end of the second inductor L2 is connected to the first end of the first inductor L1, the second end of the second inductor L2 is connected to the first end of the first switch S1, and the second end of the first switch S1 is connected to the first end of the third inductor L3;

A first end of the fourth capacitor C4 is connected to a first end of the second switch S2 , a second end of the fourth capacitor C4 is connected to a second end of the third capacitor C3 , and a second end of the second switch S2 is connected to a first end of the third capacitor C3 .

In a possible implementation manner, the second side oscillator module includes a fifth inductor L5, a fourth transistor M4, and a sixth capacitor C6;

The first end of the fifth inductor L5 is connected to the first end of the sixth capacitor C6, the second end of the fifth inductor L5 is connected to the first end of the fourth transistor M4, and the second end of the fourth transistor M4 is connected to the second end of the sixth capacitor C6.

The first side oscillator submodule is connected to the first end and the second end of the sixth capacitor C6 respectively. In a possible implementation, the first side oscillator submodule includes a fourth inductor L4 and a third transistor M3, and the second switch submodule includes a fifth transistor M5;

A first end of the fourth inductor L4 is connected to a first end of the fifth transistor M5, and a second end of the fourth inductor L4 is connected to a first end of the sixth capacitor C6;

The second end of the fifth transistor M5 is connected to the first end of the third transistor M3 , and the second end of the third transistor M3 is connected to the second end of the sixth capacitor C6 .

It is understandable that capacitors do not have polarity distinctions, and the first end of the capacitor and the second end of the capacitor in the embodiment of the present application are only used to distinguish between the two ends of the capacitor. Similarly, the first end of the inductor and the second end of the inductor in the embodiment of the present application are also only used to distinguish between the two ends of the inductor, and the first end of the switch and the second end of the switch are also only used to distinguish between the two ends of the switch. The first end of the transistor can be the source of the transistor, and the corresponding second end of the transistor can be the drain of the transistor; the first end of the transistor can be the drain of the transistor, and the corresponding second end of the transistor can be the source of the transistor; it can be set according to actual conditions, and is not specifically limited in this application.

It can be understood that the fifth transistor acts as a switch, and in some examples, the fifth transistor can be replaced by a third switch S3. The third transistor and the fourth transistor are mainly used to prevent current backflow, so in some examples, the third transistor can be replaced by a first diode D1, and/or the fourth transistor can be replaced by a second diode D2. The cathode of the first diode is directly or indirectly connected to the cathode of the second diode Vout (power output end), for example, as shown in FIG4, the cathode of the first diode is connected to the cathode of the second diode Vout, for example, as shown in FIG5, the cathode of the first diode is indirectly connected to Vout through the fifth transistor.

In the embodiment of the present application, the specific circuit structure of the DC-DC primary module and the DC-DC secondary module are given, and the switching of the resonant circuit between the PFM mode and the PWM mode is realized. Therefore, when the charging gain or output power is small, the PWM mode can be used for charging to reduce the loss of the charging system when the load is light.

In a possible implementation, referring to FIG6 , the circuit further includes: an isolation module 03;

The DC-DC primary module 01 further includes a primary switching control submodule 014, and the DC-DC secondary module 02 includes a secondary switching control submodule 024;

The isolation module 03 is connected to the primary side switching control submodule 014 and the secondary side switching control submodule 024 respectively;

The primary side switching control submodule 014 is used to control the disconnection and conduction of the first switching switch submodule 013;

The secondary side switching control submodule 024 is used to control the disconnection and conduction of the second switching switch submodule 023;

The isolation module 03 is used to implement signal isolation and transmission between the primary-side switching control submodule 014 and the secondary-side switching control submodule 024 .

In an example, the resonant circuit operates in a PWM mode in an initial state, or in other words, the resonant circuit is first charged in a PWM mode after being powered on.

In order to achieve the switching between PFM mode and PWM mode, the DC-DC primary module and the DC-DC secondary module need to communicate through signals to achieve the switching of the driving modes of the DC-DC primary module and the DC-DC secondary module. In order to achieve the electrical isolation of the DC-DC primary module and the DC-DC secondary module, an isolation module can be used to achieve the signal isolation and transmission between the DC-DC primary module and the DC-DC secondary module. The isolation module in the embodiment of the present application can achieve information isolation and transmission by adopting a transformer carrier; or, the primary and secondary sides achieve information isolation and transmission through a capacitive isolation scheme; or, the primary and secondary sides achieve signal isolation and transmission through an optical coupler; or, the primary and secondary sides achieve signal isolation and transmission through a magnetic isolation scheme, etc., all within the protection scope of the present application.

The following is a detailed description of the working process of the resonant circuit in the PFM mode and the PWM mode in the embodiment of the present application. In the PFM mode, the schematic diagram of the resonant circuit is shown in FIG9 , and the key waveform thereof is shown in FIG10 . Among them, Vg1 is the voltage of the control terminal (gate) of the first transistor M1, Vg2 is the voltage of the control terminal (gate) of the second transistor M2, Ip is the primary resonant current (the current of the first inductor L1), VA is the voltage of the second terminal of the first transistor M1, ID1 is the current of the third transistor, and ID2 is the current of the fourth transistor.

In PWM mode, the schematic diagram of the resonant circuit is shown in FIG11, and the key waveforms thereof are shown in FIG12. Among them, Vg1 is the voltage of the control terminal (gate) of the first transistor M1, Vg2 is the voltage of the control terminal (gate) of the second transistor M2, Ip is the primary resonant current (the sum of the currents of the first inductor L1 and the second inductor L2), and Id is the current of the fourth transistor.

It can be seen that the resonant circuit in the embodiment of the present application can realize charging in PFM mode and PWM mode. In addition, in PFM mode and PWM mode, it is necessary to ensure that the transformer ratio N is consistent, so as to ensure the stability of the output voltage when switching between PFM mode and PWM mode.

Among them, in PWM mode:

D = N2 × Vo / (N1 × Vin) × (Lm + Lr) / Lm ≈ N2 × Vo / (N1 × Vin) (1)

Vcr=N×Vo (2)

(Vin-Vcr)×D=N×Vo×（1-D） （3）

Where D is the duty cycle, N1 is the number of turns of the primary transformer, N2 is the number of turns of the secondary transformer, Vo is the secondary output voltage, Vin is the primary input voltage, Lm is the primary transformer inductance, Lr is the primary resonant inductance, N=N1/N2, and Vcr is the voltage of the parallel capacitor of the transistor in the primary side (for example, the voltage of C1 in Figure 11).

Because Lm is much larger than Lr, formula 1 can be transformed into:

D = N2 × Vo / (N1 × Vin) × (Lm + Lr) / Lm ≈ N2 × Vo / (N1 × Vin) (4)

From formulas (2)-(4), we can know that:

Kv= Vo/ Vin=D/N (5)

Among them, Kv is the charging gain.

When Vin is 380V, D=0.5, Vo=20V, the transformer ratio N=380V/20V×0.5=9.5.

In PFM mode, when the LLC circuit operates at the resonant frequency, the charging gain is 1, the LLC circuit is a half-bridge topology, and the transformer transformation ratio is shown in the following formula:

N=Vin/2/Vo (6)

When Vin=380V, Vo=20V, the transformer ratio N=9.5.

It can be seen that when switching between PFM mode and PWM mode, the transformer ratio N is consistent and the output voltage is stable.

The following describes a method for switching between the PFM mode and the PWM mode. Referring to FIG. 7 , an embodiment of the present application provides a charging control method, the method comprising:

S101, obtaining the current charging gain;

The method of obtaining the charging gain can refer to the prior art. For example, the ratio of the primary and secondary inductance coils can be calculated to obtain the charging gain; or the ratio of the input voltage to the output voltage can be calculated to obtain the charging gain, etc.

S102, when the current charging mode is the PFM mode, if the current charging gain is less than a preset second gain threshold, and/or the current output power is not greater than a preset power threshold, the charging mode is switched to the PWM mode.

The second gain threshold can be obtained based on experimental measurements. For example, for a charging system, the charging system losses in PFM mode and PWM mode under different gains are measured in advance to obtain the second gain threshold. The second gain threshold satisfies: when the charging gain of the charging system is less than the second gain threshold, the loss of the charging system in PFM mode is greater than the loss of the charging system in PWM mode, and when the charging gain of the charging system is greater than the second gain threshold, the loss of the charging system in PFM mode is less than the loss of the charging system in PWM mode.

In an example, the second gain threshold can be set to 0.8, that is, when the current charging gain is less than 0.8, the hardware circuit is adjusted to enter the PWM mode. ZVS can also be achieved in the PWM mode to obtain relatively high charging efficiency.

The preset power threshold can be obtained based on experimental measurements. For example, for a charging system, the charging system losses in PFM mode and PWM mode under different powers are measured in advance to obtain the preset power threshold. The preset power threshold satisfies: when the power of the charging system is less than the preset power threshold, the loss of the charging system in PFM mode is greater than the loss of the charging system in PWM mode, and when the power of the charging system is greater than the preset power threshold, the loss of the charging system in PFM mode is less than the loss of the charging system in PWM mode. Alternatively, the preset power threshold can also be an empirical value, which is considered that when the power of the charging system is less than the preset power threshold, the charging efficiency is low and the loss is large, which is unacceptable.

The method for obtaining the output power can refer to the output power calculation method in the prior art. In one example, the output power can be calculated based on the output voltage and output current of the output side (secondary side). The present application does not specifically limit the method for obtaining the output power.

In an example, the power is supplied in PWM mode in the initial state, or the charger first charges in PWM mode after being powered on.

In an embodiment of the present application, when the charging gain or output power is small, the charging mode is switched from PFM mode to PWM mode. Under low load conditions, the charging loss of the PWM mode is lower than the charging loss of the PFM mode, thereby reducing the loss of the charging system when the load is light.

In a possible implementation, the method further includes:

Determine whether the current charging gain is greater than a preset first gain threshold; wherein the preset second gain threshold is less than the preset first gain threshold;

When the current charging mode is the PFM mode and the current charging gain is greater than a preset first gain threshold, the charging mode is switched to the PWM mode.

When the charging system gain is greater than the maximum gain of the LLC circuit, the LLC circuit in PFM mode will enter the capacitive region and cannot work normally. In this case, the PFM mode can be used for charging to expand the chargeable gain range. The preset first gain threshold can be obtained based on experimental measurements and can be determined based on the gain of the LLC circuit entering the capacitive region in PFM mode. For example, for each model of LLC circuit, in PFM mode, when the charging gain is X, the LLC circuit enters the capacitive region, and the preset first gain threshold can be X or slightly less than X.

In a possible implementation, the method further includes:

When the current charging gain is not greater than the preset first gain threshold, determining whether the current charging gain is less than the preset second gain threshold;

When the current charging mode is the PFM mode, if the current charging gain is not less than the preset second gain threshold and the current output power is greater than the preset power threshold, the charging mode is maintained as the PFM mode.

In the embodiment of the present application, when the current charging gain is not less than the preset second gain threshold and the current output power is greater than the preset power threshold, the charging mode is maintained in the PFM mode to maintain a higher charging power.

In a possible implementation, the method further includes:

When the current charging mode is the PWM mode and the current charging gain is not greater than a preset first gain threshold, determining whether the current charging gain is less than a preset second gain threshold, wherein the preset second gain threshold is less than the preset first gain threshold;

When the current charging gain is less than the preset second gain threshold, the charging mode is maintained in the PWM mode; when the current charging gain is not less than the preset second gain threshold, the current output power is obtained, and it is determined whether the current output power is greater than the preset power threshold;

If the current output power is greater than the preset power threshold, the charging mode is switched to PFM mode;

If the current output power is not greater than the preset power threshold, the charging mode is maintained in the PWM mode.

In an embodiment of the present application, a case of switching from PWM mode to PFM mode is given. When the charging gain is not less than a preset second gain threshold and the output power is greater than a preset power threshold, the charging mode is switched from PWM mode to PFM mode, thereby improving charging efficiency and reducing losses.

In a possible implementation manner, after the step of obtaining the current charging gain, the method further includes:

Obtain the input voltage and output voltage of the resonant circuit in the current cycle;

When at least one of the input voltage and the output voltage in the current cycle changes compared to the previous cycle, the step of obtaining the current charging gain is performed; otherwise, waiting for the next detection cycle is performed.

The real-time charging gain can be obtained periodically according to the preset detection cycle. First, the input voltage of the primary side of the resonant circuit and the output voltage of the secondary side in the current cycle are obtained; compared with the previous cycle, if at least one of the input voltage and output voltage of this cycle changes, then execute step S101, otherwise skip the current cycle and wait for the next detection cycle to make another judgment. If both the input voltage and the output voltage have changed, it means that the charging gain has not changed, that is, the charging situation of the current cycle has not changed compared with the charging situation of the previous cycle, or the change is very small. Therefore, there is no need to adjust the charging mode in the current cycle, discard the current charging gain, and wait for the next detection cycle.

In an embodiment of the present application, when the charging gain of the current detection cycle remains unchanged, it means that there is no need to adjust the charging mode. Therefore, there is no need to perform a subsequent judgment process in this cycle, and the current charging gain is discarded and waits for the next detection cycle to be re-acquired; thereby reducing unnecessary judgment processes and saving computing resources.

Referring to FIG. 8 , FIG. 8 is another flow chart of a charging control method according to an embodiment of the present application, including:

S201, obtaining the current charging gain.

Calculate the equivalent charging arrangement of the current system, and the specific process of calculating the charging gain can refer to the prior art. For example, the charging gain can be calculated based on the input voltage of the primary side, the output voltage of the secondary side, the transformer ratio and other parameters. In one example, first obtain the input voltage of the primary side and the output voltage of the secondary side of the current cycle; when at least one of the input voltage and the output voltage of the current cycle changes compared with the previous cycle, execute S201, otherwise skip the current cycle. If both the input voltage and the output voltage have changed, it means that the charging gain has not changed, so the charging mode is adjusted wirelessly in this cycle.

S202, obtaining the current charging mode.

When the current charging mode is the PWM mode, step S203 is executed; when the current charging mode is the PFM mode, step S207 is executed.

S203: Determine whether the current charging gain is greater than a preset first gain threshold.

If the current charging gain is greater than the preset first gain threshold, step S204 is executed; if the current charging gain is not greater than the preset first gain threshold, step S205 is executed.

S204, maintaining the charging mode as the PWM mode.

S205, determining whether the current charging gain is greater than a preset second gain threshold and whether the current output power is greater than a preset power threshold.

If the current charging gain is greater than the preset second gain threshold, and the current output power is greater than the preset power threshold, then step S206 is executed; otherwise, step S204 is executed.

S206, switching the charging mode to the PFM mode.

The hardware circuit exits the PWM mode and enters the PFM mode for charging.

S207: Determine whether the current charging gain is greater than a preset first gain threshold.

If the current charging gain is greater than the preset first gain threshold, step S208 is executed; if the current charging gain is not greater than the preset first gain threshold, step S209 is executed.

S208, switching the charging mode to the PWM mode.

Exit PFM mode and enter PWM mode for charging.

S209, determining whether the current charging gain is greater than a preset second gain threshold and whether the current output power is greater than a preset power threshold.

If the current charging gain is greater than the preset second gain threshold, and the current output power is greater than the preset power threshold, then step S210 is executed; otherwise, step S208 is executed.

S210, maintaining the charging mode as the PFM mode.

In the embodiment of the present application, when the charging gain or output power is small, the charging mode is switched from the PFM mode to the PWM mode, and the charging loss of the PWM mode is lower than the charging loss of the PFM mode under low load conditions, thereby reducing the loss of the charging system when the load is light. In addition, when the charging system gain is greater than the maximum gain of the LLC circuit, the LLC circuit in the PFM mode will enter the capacitive region and cannot work normally. In this case, the PFM mode can be used for charging to expand the chargeable gain range.

In order to ensure the stability of the output voltage before and after the charging mode conversion, whether switching to the PFM mode or switching to the PWM mode, it is necessary to select a suitable switching time. In a possible implementation, the transistor closing time can be selected as the time point for switching to the PFM mode or switching to the PWM mode. The transistor closing time here refers to the closing time of the transistor corresponding to the primary transformer (corresponding to M2 in Figure 3).

An embodiment of the present application also provides a charger, comprising a resonant circuit and a charging control chip as described in any one of the present application; the charging control chip is used to control the resonant circuit to switch the charging mode during operation through any one of the charging control methods described in the present application.

In the charger provided in the embodiment of the present application, the charging control chip executes the charging control method in the embodiment of the present application, and realizes the switching between the PWM mode and the PFM mode through the resonant circuit in the embodiment of the present application.

The resonant circuit, charging control method and charger in the embodiments of the present application can be applicable to scenarios where the output voltage is continuously adjusted from 0V to 1000V, the power range condition can range from 100W to 1000W, and can be applicable to fast charging protocol requirements such as PD, UFCS, QC, and SCP (Super Charge Protocol).

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Each embodiment in this specification is described in a related manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other.

The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims (12)

1. A resonant circuit, comprising: DC-DC primary side module and DC-DC secondary side module; The DC-DC secondary side module includes a first side oscillator submodule, a second side oscillator submodule and a second switch submodule; the first side oscillator submodule is connected to the second side oscillator submodule and the second switch submodule respectively; The DC-DC primary module includes a first primary oscillator module, a second primary oscillator module and a first switch submodule; the first primary oscillator module is connected to the second primary oscillator module and the first switch submodule respectively; the second primary oscillator module is connected to the first switch submodule; Wherein, when the first switching switch submodule is disconnected and the second switching switch submodule is turned on, the first primary oscillator submodule, the first primary oscillator submodule, and the second primary oscillator submodule are in an enabled state, and the resonant circuit operates in the PFM mode; When the first switching switch submodule is turned on and the second switching switch submodule is turned off, the first primary oscillator submodule, the second primary oscillator submodule and the secondary oscillator submodule are in an enabled state, and the resonant circuit operates in a PWM mode. 2. The circuit according to claim 1, characterized in that the first primary oscillator module comprises a first capacitor, a first transistor, a second transistor, a second capacitor, a third capacitor, a first inductor, a third inductor, and a fifth capacitor; The first end of the fifth capacitor is respectively connected to the first end of the first transistor and the first end of the first capacitor; the second end of the fifth capacitor is respectively connected to the second end of the second transistor, the second end of the second capacitor, and the second end of the third capacitor; The second end of the first transistor is respectively connected to the second end of the first capacitor, the first end of the first inductor, the first end of the second transistor, and the first end of the second capacitor; The second end of the first inductor is connected to the first end of the third inductor, and the second end of the third inductor is connected to the first end of the third capacitor. 3. The circuit according to claim 2, characterized in that the second primary oscillator submodule comprises a fourth capacitor and a second inductor, and the first switch submodule comprises a first switch and a second switch; The first end of the second inductor is connected to the first end of the first inductor, the second end of the second inductor is connected to the first end of the first switch, and the second end of the first switch is connected to the first end of the third inductor; The first end of the fourth capacitor is connected to the first end of the second switch, the second end of the fourth capacitor is connected to the second end of the third capacitor, and the second end of the second switch is connected to the first end of the third capacitor. 4. The circuit according to claim 1, characterized in that the second side oscillator module comprises a fifth inductor, a fourth transistor, and a sixth capacitor, The first end of the fifth inductor is connected to the first end of the sixth capacitor, the second end of the fifth inductor is connected to the first end of the fourth transistor, and the second end of the fourth transistor is connected to the second end of the sixth capacitor; The first side oscillator submodule includes a fourth inductor and a third transistor, and the second switch submodule includes a fifth transistor; The first end of the fourth inductor is connected to the first end of the fifth transistor, and the second end of the fourth inductor is connected to the first end of the sixth capacitor; The second end of the fifth transistor is connected to the first end of the third transistor, and the second end of the third transistor is connected to the second end of the sixth capacitor. 5 . The circuit according to claim 4 , wherein the third transistor is replaced by a first diode, the fourth transistor is replaced by a second diode, and/or the fifth transistor is replaced by a third switch. 6. The circuit according to claim 1, characterized in that the circuit further comprises: an isolation module; The DC-DC primary side module also includes a primary side switching control submodule, and the DC-DC secondary side module includes a secondary side switching control submodule; The isolation module is connected to the primary side switching control submodule and the secondary side switching control submodule respectively; The primary side switching control submodule is used to control the disconnection and conduction of the first switching switch submodule; The secondary side switching control submodule is used to control the disconnection and conduction of the second switching switch submodule; The isolation module is used to implement signal isolation and transmission between the primary-side switching control submodule and the secondary-side switching control submodule. 7. A charging control method, characterized in that it is used to control the resonant circuit described in any one of claims 1 to 6 to switch the charging mode, the method comprising: Get the current charging gain; When the current charging mode is the PFM mode, if the current charging gain is less than a preset second gain threshold, and/or the current output power is not greater than a preset power threshold, the charging mode is switched to the PWM mode. 8. The method according to claim 7, characterized in that the method further comprises: Determine whether the current charging gain is greater than a preset first gain threshold; wherein the preset second gain threshold is less than the preset first gain threshold; When the current charging mode is the PFM mode and the current charging gain is greater than a preset first gain threshold, the charging mode is switched to the PWM mode. 9. The method according to claim 8, characterized in that the method further comprises: When the current charging gain is not greater than the preset first gain threshold, determining whether the current charging gain is less than the preset second gain threshold; When the current charging mode is the PFM mode, if the current charging gain is not less than the preset second gain threshold and the current output power is greater than the preset power threshold, the charging mode is maintained as the PFM mode. 10. The method according to claim 7, characterized in that the method further comprises: When the current charging mode is the PWM mode and the current charging gain is not greater than a preset first gain threshold, determining whether the current charging gain is less than a preset second gain threshold, wherein the preset second gain threshold is less than the preset first gain threshold; When the current charging gain is not less than the preset second gain threshold, obtaining the current output power, and determining whether the current output power is greater than the preset power threshold; If the current output power is greater than the preset power threshold, the charging mode is switched to PFM mode; If the current output power is not greater than the preset power threshold, the charging mode is maintained in the PWM mode. 11. The method according to claim 7, characterized in that before the step of obtaining the current charging gain, the method further comprises: Obtain the input voltage and output voltage of the resonant circuit in the current cycle; When at least one of the input voltage and the output voltage in the current cycle changes compared to the previous cycle, the step of obtaining the current charging gain is performed; otherwise, waiting for the next detection cycle is performed. 12. A charger, characterized in that it comprises a charging control chip and a resonant circuit; the charging control chip is used to control the resonant circuit to switch the charging mode during operation through the charging control method described in any one of claims 7 to 11.