Improved hybrid trapezoidal converter with efficient output capacitance charge recovery function
Through the improved hybrid trapezoid converter, the on-conductance method and charge recovery solution are optimized, and the problems of low light load efficiency and serious output capacitor dissipation in traditional trapezoid converters are solved, and high-efficiency energy conversion and extended battery life are achieved. It is suitable for wearable devices and Internet of Things devices.
Patent Information
- Application Number
- CN202510456910.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-12
- Publication Date
- 2025-07-01
AI Technical Summary
Traditional trapezoidal hybrid converters have low efficiency under light load conditions, large RMS current of switch tubes, inaccurate zero crossing detection, defective phase control, insufficient input pressure resistance, severe dissipation of output capacitor charge, high circuit complexity, and difficult to meet the power management needs of wearable devices and IoT devices.
An improved hybrid trapezoid converter is designed, using power transistor group, inductor, fly capacitance and DC capacitor, optimized conduction method, realize accurate zero crossing detection and phase-separation control, and the output capacitor charge is recovered into the fly capacitance through a unique charge recovery scheme, reducing the RMS current of the switch tube, reducing the IR voltage drop, and avoiding additional auxiliary LDO and off-chip filter capacitors.
It improves light load efficiency, extends battery life, reduces circuit complexity and cost, improves energy usage efficiency, and extends battery life, which is suitable for the long-term and stable operation of wearable devices and IoT devices.
Smart Images
Figure CN120237927A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an improved hybrid ladder converter, particularly to an improved hybrid ladder converter with an efficient output capacitor charge recovery function, belonging to the technical field of improved hybrid ladder converters. Background Art
[0002] In the current trend of continuous miniaturization and portability of electronic devices, wearable devices, Internet of Things devices, etc. have put extremely stringent requirements on power management technology.
[0003] Among them, as the core component of the device, the system-on-chip (SoC) is crucial for meeting its power supply requirements.
[0004] Taking wearable devices as an example, the internal SoC usually requires an efficient buck converter to convert the 2.8 - 4.2V voltage (VBAT) provided by the lithium-ion battery into a SoC supply voltage VO below 1V.
[0005] To further reduce system power consumption and extend battery life, dynamic voltage scaling (DVS) or power gating technology is widely used to reduce unnecessary energy consumption by periodically waking up and sleeping the device.
[0006] In the field of power management technology, the hybrid DC / DC converter is a key component for achieving this voltage conversion task.
[0007] Traditional ladder hybrid converters have exposed many problems in practical applications.
[0008] In the case of light load, its working efficiency is low, and the root mean square (RMS) current on the switching tube is large, which not only causes energy waste but also may shorten the service life of the switching tube. Moreover, its zero-crossing detection is not precise enough, and there are defects in phase control, affecting the overall conversion performance.
[0009] From the perspective of transistor characteristics, as the semiconductor process continues to advance to lower process nodes, it is increasingly difficult to obtain high-voltage transistors.
[0010] This makes it difficult for traditional DCDC converters to meet the input voltage resistance requirements, limiting their application in complex power environments.
[0011] In Internet of Things devices, although the periodic wake-up mechanism helps to save energy, it also brings the problem of charge dissipation of the output capacitor.
[0012] Each time it wakes up, the output capacitor needs to be recharged, and the consumption of this part of energy greatly reduces the energy use efficiency, resulting in a significant shortening of the battery life.
[0013] In previous technical attempts to solve these problems, some solutions adopted an additional auxiliary low-dropout linear regulator (LDO) and off-chip filtering capacitors. However, this undoubtedly increased the complexity and cost of the PCB, reduced the energy conversion efficiency, and was not conducive to the miniaturization development of the device.
[0014] In summary, when the existing power management technologies meet the power requirements of wearable devices and Internet of Things devices, they face multiple challenges such as low light-load efficiency, insufficient input voltage resistance, serious output capacitor charge dissipation, and complex circuit with high cost. There is an urgent need for a new technical solution to solve these problems. Therefore, an improved hybrid ladder converter with an efficient output capacitor charge recovery function is designed to solve the above problems. Summary of the Invention
[0015] The main purpose of the present invention is to provide an improved hybrid ladder converter with an efficient output capacitor charge recovery function.
[0016] The object of the present invention can be achieved by adopting the following technical solutions: An improved hybrid ladder converter with an efficient output capacitor charge recovery function includes a power transistor group, an inductor L, a flying capacitor CF, a DC capacitor CDC, and an output capacitor CO; The power transistor group serves as the control switch of the circuit, controlling the current flow direction and energy conversion through different on and off combinations. The inductor L is used to store and release magnetic energy to achieve voltage conversion and current smoothing. The flying capacitor CF, the DC capacitor CDC, and the output capacitor CO are used to store and transfer charges to stabilize the voltage.
[0017] Preferably, the power transistor group includes power transistors M1 - M6; The drain of the power transistor M1 is connected to the power supply voltage V BAT , serving as the energy input end of the entire circuit; The source of the power transistor M1 is connected to one end of the flying capacitor CF and the drain of the power transistor M2. When the power transistor M1 is turned on, the power supply voltage charges the flying capacitor CF and provides current for the subsequent circuit.
[0018] Preferably, the drain of the power transistor M2 is connected to the source of the power transistor M1 and CF, and the source is connected to the drain of the power transistor M3; The power transistor M2 plays a role in conducting or cutting off the current path at different working stages of the circuit.
[0019] Preferably, the drain of the power transistor M3 is connected to the source of the power transistor M2, and the source is connected to the drain of the power transistor M4; The power transistor M3 works in coordination with the power transistors M2 and M4 to control the flow of charge between different capacitors and inductors.
[0020] Preferably, the drain of the power transistor M4 is connected to the source of the power transistor M3, and the source of the power transistor M4 is grounded; The power transistor M4 cooperates with the zero-current detection circuit to detect whether the inductor current has returned to zero and control the switching of the working stage of the circuit.
[0021] Preferably, the drain of the power transistor M5 is connected to one end of the DC capacitor CDC, and the source of the power transistor M5 is connected to one end of the inductor L; The on and off of the power transistor M5 control the energy transfer between the DC capacitor CDC and the inductor L.
[0022] Preferably, the drain of the power transistor M6 is connected to the other end of the flying capacitor CF, and the source is connected to V MD ; The power transistor M6 cooperates with the power transistors M1 and M5 to achieve the charge transfer between the flying capacitor CF and the DC capacitor CDC.
[0023] Preferably, one end of the inductor L is connected to the source of the node power transistor M5, and the other end of the inductor L is connected to one end of the output capacitor CO and the load; The inductor L plays the role of energy storage and filtering in the circuit, smoothing the output current.
[0024] Preferably, one end of the flying capacitor CF is connected to the source of the power transistor M1 and the drain of the power transistor M2, and the other end of the flying capacitor CF is connected to the drain of the power transistor M6.
[0025] Preferably, one end of the DC capacitor CDC is connected to the drain of the power transistor M5 and the source of the power transistor M6; One end of the output capacitor CO is connected to the output end of the inductor L and the load, and the other end of the output capacitor CO is grounded; The output capacitor CO is used to smooth the output voltage.
[0026] Advantageous technical effects of the present invention: The improved hybrid ladder converter provided by the present invention with an efficient output capacitor charge recovery function successfully overcomes the defects of traditional ladder converters under light load. By subdividing the ON stage and optimizing the conduction mode of power transistors, the RMS current on the switching transistors is reduced. This improvement reduces the power loss under light load, improves the light load efficiency, enables the device to efficiently utilize energy in a low-power operation state, and extends the battery life in light load scenarios.
[0027] The improved design achieves precise zero-crossing detection and phase-splitting control. The optimized circuit structure, especially that M4 no longer conducts the IC current, significantly reduces the IR voltage drop, ensuring the accuracy of zero-current detection (ZCD), providing guarantee for the stable operation of the circuit and efficient energy conversion, making the switching of each stage more precise, and improving the overall conversion efficiency.
[0028] Innovatively solve the problem of charge dissipation of the output capacitor during periodic wake-up in the use of the Internet of Things. With the unique charge recovery scheme, the charge of the output capacitor is recovered into the flying capacitors (CF, CMID) of the converter, greatly improving the energy usage efficiency.
[0029] This function reduces the unnecessary energy consumption of the battery, extends the battery life of the power supply port, and is of great significance for the long-term stable operation of Internet of Things devices.
[0030] Use VMID to power the gate drive and control circuit, avoiding the use of additional auxiliary LDOs and off-chip filter capacitors.
[0031] This not only simplifies the circuit design, but also reduces the circuit complexity and cost, reduces the chip area occupation, and is conducive to the miniaturization and integration development of the device. Description of the Drawings
[0032] Figure 1 The circuit diagram of a preferred embodiment of an improved hybrid trapezoidal converter with an efficient output capacitor charge recovery function according to the present invention; Figure 2 The circuit decomposition diagram of a preferred embodiment of an improved hybrid trapezoidal converter with an efficient output capacitor charge recovery function according to the present invention. Detailed Embodiments
[0033] To make the technical solutions of the present invention clearer and more definite to those skilled in the art, the present invention will be further described in detail below with reference to the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.
[0034] In this embodiment, a specific circuit system is constructed. MOSFETs with a rated voltage of 2.5V are selected as M1-M6. This is considered because in low process nodes, such transistors can better adapt to the circuit requirements and meet certain voltage withstand requirements at the same time.
[0035] The inductor is selected as an inductor with a suitable inductance value, such as an inductor with an inductance value of 10 μH, and its inductance value is determined comprehensively according to factors such as the power demand of the circuit, the operating frequency, and the desired current ripple.
[0036] The flying capacitor CF and the DC capacitor CDC are respectively selected as 4.7 μF and 10 μF capacitors. The determination of these capacitance values is to achieve efficient charge storage and transfer on the premise of ensuring the stable operation of the circuit.
[0037] The input voltage VBAT is set within the typical voltage range of 2.8 - 4.2 V of a lithium-ion battery, and the output voltage VO is set to a voltage lower than 1 V, such as 0.8 V, to meet the power supply requirements of a system-on-chip (SoC) according to the actual application needs.
[0038] The control circuit is the core part of the entire converter. It is responsible for coordinating the conduction and turn-off of each power transistor to achieve different operating modes.
[0039] A dedicated control chip is used to implement the COT control strategy, and the time of the ON stage, OFF stage, and IDLE stage is precisely set.
[0040] In the light-load optimization mode, by programming the control chip, the ON stage is split into ON1 and ON2, and their alternating conduction times are precisely controlled.
[0041] In the charge recovery mode and recharge mode, the control chip accurately controls the conduction and turn-off of transistors such as M3 and M5 according to the system requirements to ensure the effective recovery and redistribution of charges.
[0042] After building the circuit system, a series of experimental tests are carried out. In the normal operating mode, an oscilloscope is used to monitor key parameters such as the inductor current IL, capacitor voltages VCF and VMID.
[0043] The experimental results show that in the ON stage, the inductor can effectively store energy through the CF charging current IC1 and the CDC discharging current IC2; in the OFF stage, the inductor releases energy, CF discharges and CDC charges, and the time control of each stage is precise, which is in line with the theoretical design.
[0044] In the light-load optimization mode, by measuring the RMS current on the switching transistor, it is found that compared with the traditional trapezoidal converter, the RMS current is significantly reduced. For example, under specific light-load conditions, the RMS current is reduced from the original 50 mA to 30 mA, effectively reducing power loss and improving light-load efficiency.
[0045] For the charge recovery mode and recharge mode, by monitoring the charge changes of the output capacitor CO and the flying capacitors CF and CDC, it is verified that when the Internet of Things device is periodically awakened, the charge of the output capacitor can be successfully recovered to CF and CDC, and can be smoothly transferred back to CO when needed.
[0046] For example, in an experiment simulating the periodic wake-up of an IoT device, after multiple wake-up and sleep cycles, it was found that after adopting this improved converter, the battery usage time was extended by 30% compared to the case without the charge recovery function, greatly increasing the energy usage efficiency and extending the battery life.
[0047] Working process: Normal working mode: Adopting COT (Constant On-Time) control, it is divided into three stages: ON (conducting), OFF (turning off), and IDLE (idle). In the ON stage, M1 and M6 are turned on simultaneously. At this time, the inductor stores energy with the charging current IC1 of CF and the discharging current IC2 of CDC.
[0048] During this process, the flow of current accumulates energy for the inductor, which is a key step in electrical energy storage, and its energy storage efficiency affects the performance of the entire converter.
[0049] In the OFF stage, M2, M4, and M5 are turned on, and the inductor releases the previously stored energy while CF discharges and CDC charges.
[0050] When the zero-current detection (ZCD) circuit of M4 detects that the inductor current (IL) returns to zero, it means that the energy release of the inductor is complete and the OFF stage ends.
[0051] In the IDLE stage, M2 and M5 remain conducting, and the DC voltages VCF and VMID on CF and CDC both reach VBAT / 2. At this time, the circuit is in a relatively stable state, preparing for the subsequent stage.
[0052] In this working mode, the time control of each stage is precise, and the orderly conduction and turning off of the power transistors in different stages ensure the orderly conversion and transmission of circuit energy.
[0053] Light load optimization mode: Traditional trapezoidal converters have poor efficiency under light load.
[0054] To improve the light load efficiency, this improved converter divides the ON stage into ON1 and ON2. In the ON1 stage, the IC1 current is conducted, and in the ON2 stage, the IC2 current is conducted. The two alternate, changing the working sequence to ON1 - OFF - IDLE - ON2 - OFF - IDLE.
[0055] In this way, the current can be controlled more flexibly, reducing the RMS (Root Mean Square) current on the switching tube, reducing power loss, and improving the energy conversion efficiency under light load conditions.
[0056] For example, when the wearable device is in a low-power operation state (light load), this mode can significantly extend the battery life.
[0057] Charge recovery mode: To address the issue of charge dissipation in the output capacitor caused by the periodic wake-up of IoT devices, this converter is equipped with a unique charge recovery mode.
[0058] In the recovery mode, M3 and M5 are turned on, and the charge in the output capacitor CO is transferred to CDC and CF during the ON phase.
[0059] This process enables effective charge recovery. The charge that would otherwise be lost during device wake-up is preserved and reused, greatly improving the energy usage efficiency.
[0060] For example, when the IoT node device wakes up periodically, this mode can recover the charge into the flying capacitor, reducing unnecessary energy consumption of the battery.
[0061] Recharge mode: Contrary to the charge recovery mode, in the recharge mode, the charge stored in CDC and CF is transferred back to CO.
[0062] When the device needs to use this recovered charge, this mode is activated to ensure that the recovered charge can power the device again, further extending the battery life and enhancing the energy utilization rate of the entire power supply system.
[0063] The above are only further embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the scope disclosed by the present invention, making equivalent substitutions or changes based on the technical solution and its concept of the present invention, shall fall within the protection scope of the present invention.
Claims
1. An improved hybrid ladder converter with high efficiency output capacitor charge recovery function, characterized in that: It includes a power transistor group, an inductor L, a flying capacitor CF, a DC capacitor CDC and an output capacitor CO; The power transistor group acts as the control switch of the circuit, controlling the flow of current and the conversion of energy through different on and off combinations; The inductor L is used to store and release magnetic energy to achieve voltage conversion and current smoothing; The flying capacitor CF, DC capacitor CDC and output capacitor CO are used to store and transfer charges and stabilize the voltage; The flying capacitor CF and the DC CDC capacitor are used to recover the charge of the output capacitor CO.
2. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 1, characterized in that: The power transistor group includes a power transistor M1 to a power transistor M6; The drain of power transistor M1 is connected to the power supply voltage V BAT , as the energy input terminal of the whole circuit; The source of the power transistor M1 is connected to one end of the flying capacitor CF and the drain of the power transistor M2. When the power transistor M1 is turned on, the power supply voltage charges the flying capacitor CF and provides current for subsequent circuits.
3. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 2, characterized in that: The drain of the power transistor M2 is connected to the source of the power transistor M1 and CF, and the source is connected to the drain of the power transistor M3; The power transistor M2 plays a role of turning on or off the current path in different working stages of the circuit.
4. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 2, characterized in that: The drain of the power transistor M3 is connected to the source of the power transistor M2, and the source is connected to the drain of the power transistor M4; The power transistor M3 works together with the power transistor M2 and the power transistor M4 to control the flow of charges between different capacitors and inductors.
5. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 2, characterized in that: The drain of the power transistor M4 is connected to the source of the power transistor M3, and the source of the power transistor M4 is grounded; The power transistor M4 cooperates with the zero current detection circuit to detect whether the inductor current returns to zero and to control the working phase conversion of the circuit.
6. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 2, characterized in that: The drain of the power transistor M5 is connected to one end of the DC capacitor CDC, and the source of the power transistor M5 is connected to one end of the inductor L; The on and off of the power transistor M5 controls the energy transfer between the DC capacitor CDC and the inductor L.
7. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 6, characterized in that: The drain of power transistor M6 is connected to the other end of flying capacitor CF, and the source is connected to V MD ; The power transistor M6 cooperates with the power transistor M1 and the power transistor M5 to realize the charge transfer between the flying capacitor CF and the DC capacitor CDC.
8. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 7, characterized in that: One end of the inductor L is connected to the source of the node power transistor M5, and the other end of the inductor L is connected to one end of the output capacitor CO and the load; Inductor L plays the role of energy storage and filtering in the circuit, smoothing the output current.
9. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 8, characterized in that: One end of the flying capacitor CF is connected to the source of the power transistor M1 and the drain of the power transistor M2 , and the other end of the flying capacitor CF is connected to the drain of the power transistor M6 .
10. The improved hybrid ladder converter with high-efficiency output capacitor charge recovery function according to claim 9, characterized in that: One end of the DC capacitor CDC is connected to the drain of the power transistor M5 and the source of the power transistor M6; One end of the output capacitor CO is connected to the output end of the inductor L and the load, and the other end of the output capacitor CO is grounded; The output capacitor CO is used to smooth the output voltage.