Self-adaptive adjustment method for dead time of low-power bidirectional DCDC half-bridge circuit

Abstract

The invention provides a dead zone time self-adaptive adjusting method of a low-power bidirectional DCDC half-bridge circuit. The method comprises the following steps: S1, adjusting the dead zone time of the low-power bidirectional DCDC half-bridge circuit; the method comprises the steps that a battery voltage value Vbat and a battery current value Ibat are collected, a given voltage value Vref is set, the battery voltage value Vbat and the given voltage value Vref are input into a first PI controller, and the battery voltage value Vbat and the given voltage value Vref are calculated through the first PI controller to obtain a target current value Iref; by dynamically adjusting the dead time of the rising edge and the falling edge of the switching tube, the dead time of the rising edge and the falling edge is adjusted when the duty ratio is too low (Dlt; and the problem that the output current is unstable or the system cannot work normally due to unreasonable dead time is avoided, so that the low-voltage working range of the system is expanded. When the dead zone time is adjusted, the mode that the rising edge dead zone time is increased and the falling edge dead zone time is synchronously reduced is adopted, it is guaranteed that the first switching tube Q1 and the second switching tube Q2 cannot be conducted at the same time, and the system safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment, and more particularly to a method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit. Background Art

[0002] Among existing low-power bidirectional DC-DC converters, the half-bridge topology is widely adopted due to its simple structure, low component count, and low cost. This is particularly true in applications such as battery charge and discharge management, energy storage systems, and electric vehicle onboard power supplies. The bidirectional DC-DC half-bridge circuit enables flexible energy flow between the high- and low-voltage sides.

[0003] In actual control systems, to prevent the simultaneous on-state of the upper and lower MOSFETs (metal oxide semiconductor field-effect transistors), which could cause a shoot-through short circuit, a "dead time" is often introduced into the control signal. Dead time refers to the delay between the top switch turning off and the bottom switch turning on, or vice versa. During this time, both switches are off, thus avoiding the risk of a short circuit caused by current flowing directly from the high-voltage side through the two switches to the low-voltage side.

[0004] However, the presence of this dead time limits the system's minimum controllable duty cycle. Because dead time must be included in the PWM waveform, the effective on-time cannot approach zero infinitely within a switching cycle. This leads to a physical lower limit for the minimum duty cycle. For a bidirectional DC-DC half-bridge circuit operating in buck mode, this minimum duty cycle directly affects the output voltage's minimum regulation range, thereby limiting the device's lowest controllable output voltage in discharge mode. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a dead time adaptive adjustment method for a low-power bidirectional DCDC half-bridge circuit, which ensures a smooth transition of current and enhances the reliability and flexibility of the system, in response to the shortcomings of the above technical solutions.

[0006] In one aspect, the present invention provides a method for adaptively adjusting the dead time of a low-power bidirectional DC-DC half-bridge circuit, which is applied to battery formation and detection. The method comprises the following steps:

[0007] S1; collecting the battery voltage value Vbat and the battery current value Ibat, and setting the given voltage value Vref, inputting the battery voltage value Vbat and the given voltage value Vref into the first PI controller, and calculating the battery voltage value Vbat and the given voltage value Vref by the first PI controller to obtain the target current value Iref;

[0008] S2: Input the target current value Iref and the battery current value Ibat into the second PI controller, and calculate the target current value Iref and the battery current value Ibat by the second PI controller to obtain an initial duty cycle D; set the first duty cycle judgment value to D1, set the second duty cycle judgment value to D2, set the initial rising edge dead zone time of the first switch tube Q1 and the second switch tube Q2 to prevent direct conduction to TDBREDInit, and set the initial falling edge dead zone time of the first switch tube Q1 and the second switch tube Q2 to prevent direct conduction to TDBFEDInit;

[0009] S3; when it is detected that the initial duty cycle D is less than the first duty cycle judgment value D1 and the current rising edge dead time TDBRED is equal to the initial rising edge dead time TDBREDInit, enter the low-voltage discharge mode and perform the dead time adjustment operation; at the same time, according to the adjusted dead time, the output duty cycle is synchronously adjusted to D=Dlast+t / T to ensure a smooth transition of the current; where t is the adjustment value of the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period;

[0010] S4; when it is detected that the duty cycle D is greater than the second duty cycle judgment value D2 and TDBRED is equal to TDBREDInit+t, the normal working mode is entered and the dead time recovery operation is performed, and the output duty cycle is synchronously adjusted to D=Dlast-t / T to ensure a smooth transition of the current; where t is the adjustment value to the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period.

[0011] In the dead time adaptive adjustment method of the low-power bidirectional DCDC half-bridge circuit described in the present invention; in the step S1, the calculation formula of the target current value Iref is: Iref = Kp(Vref-Vbat)+Ki*∫(Vref-Vbat), where Kp is the proportional coefficient and Ki is the integral coefficient.

[0012] In the dead time adaptive adjustment method of the low-power bidirectional DCDC half-bridge circuit described in the present invention; in the step S2, the calculation formula of the duty cycle D is: D=Kp(Iref-Ibat)+Ki*∫(Iref-Ibat), where Kp is the proportional coefficient and Ki is the integral coefficient.

[0013] In the dead time adaptive adjustment method of the low-power bidirectional DCDC half-bridge circuit described in the present invention, in the step S3, the dead time adjustment operation is performed to adjust TDBRE to TDBREDInit+t, and at the same time, the falling edge dead time TDBFE is adjusted to TDBFEDInit-t; the duty cycle is adjusted to Dlast+t / T, where t is the adjustment value of the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period.

[0014] In the dead time adaptive adjustment method of the low-power bidirectional DCDC half-bridge circuit described in the present invention; in the step S4, the dead time recovery operation is performed to restore TDBRE to TDBREDInit, and at the same time, TDBFED is restored to TDBFEDInit, and the duty cycle is adjusted to Dlast-t / T, where Dlast is the duty cycle value before adjustment, and T is the switching period.

[0015] On the other hand, the present invention also provides a dead time adaptive adjustment system for a low-power bidirectional DCDC half-bridge circuit, the system comprising:

[0016] A voltage sampling module, which is used to collect the battery voltage Vbat;

[0017] A current sampling module, which is used to collect the battery current Ibat;

[0018] a first PI controller, configured to calculate a target current value Iref according to a given voltage Vref and a sampled battery voltage Vbat;

[0019] a second PI controller, configured to calculate a duty cycle D according to the target current Iref and the sampled battery current Ibat;

[0020] The dead time adjustment module is used to perform dead time adjustment and recovery operations according to the relationship between the duty cycle D and the first duty cycle judgment value D1 and the second duty cycle judgment value D2.

[0021] The dead-time adaptive adjustment method of the low-power bidirectional DCDC half-bridge circuit of the present invention dynamically adjusts the dead time of the rising edge and falling edge of the switching tube, avoiding problems such as unstable output current or abnormal system operation caused by unreasonable dead time when the duty cycle is too low (D < D1), thereby expanding the low-voltage operating range of the system. When adjusting the dead time, the rising-edge dead time is increased and the falling-edge dead time is synchronously reduced, ensuring that the first switching tube Q1 and the second switching tube Q2 will not conduct simultaneously, improving the system safety. While adjusting the dead time, the output duty cycle is compensated, so that the current will not change suddenly during the dead-time change process, improving the stability and dynamic response quality of the system control. When the system voltage rises and the duty cycle returns to D > D2, the dead time is automatically restored to the initial value, and the duty cycle is synchronously adjusted, enabling the system to smoothly switch from the low-voltage discharge mode back to the normal charge-discharge mode, improving the intelligence level and applicability of the system. By accurately calculating the target current and duty cycle through a double-loop PI controller (voltage loop + current loop) and combining the dynamic dead-time adjustment strategy, the adaptability of the system under complex working conditions is enhanced, and it is applicable to high-precision battery charge-discharge control scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flowchart of the dead-time adaptive adjustment method of the low-power bidirectional DCDC half-bridge circuit of the present invention;

[0023] Figure 2 is a circuit topology diagram of the dead-time adaptive adjustment system of the low-power bidirectional DCDC half-bridge circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] like Figure 1 As shown, Figure 1 This is a flow chart of an embodiment of a method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit according to the present invention. A method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit is provided, which is applied in battery formation and testing. The method comprises the following steps:

[0027] In step S1, a battery voltage value Vbat and a battery current value Ibat are collected, and a given voltage value is set as Vref. The battery voltage value Vbat and the given voltage value Vref are input into a first PI controller, and the battery voltage value Vbat and the given voltage value Vref are calculated by the first PI controller to obtain a target current value Iref.

[0028] In step S2, the target current value Iref and the battery current value Ibat are input into the second PI controller, and the target current value Iref and the battery current value Ibat are calculated by the second PI controller to obtain an initial duty cycle D; the first duty cycle judgment value is set to D1, the second duty cycle judgment value is set to D2, the initial rising edge dead zone time of the first switch tube Q1 and the second switch tube Q2 to prevent direct conduction is set to TDBREDInit, and the initial falling edge dead zone time of the first switch tube Q1 and the second switch tube Q2 to prevent direct conduction is set to TDBFEDInit;

[0029] In step S3, when it is detected that the initial duty cycle D is less than the first duty cycle judgment value D1 and the current rising edge dead time TDBRED is equal to the initial rising edge dead time TDBREDInit, the low-voltage discharge mode is entered and the dead time adjustment operation is performed; at the same time, the output duty cycle is synchronously adjusted to D=Dlast+t / T according to the adjusted dead time to ensure a smooth transition of the current; where t is the adjusted value of the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period;

[0030] In step S4; when it is detected that the duty cycle D is greater than the second duty cycle judgment value D2 and TDBRED is equal to TDBREDInit+t, the normal working mode is entered and the dead time recovery operation is performed, and the output duty cycle is synchronously adjusted to D=Dlast-t / T to ensure a smooth transition of the current; where t is the adjustment value adjusted to the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period.

[0031] In one embodiment, the target current value Iref in step S1 is calculated as follows: Iref=Kp(Vref-Vbat)+Ki*∫(Vref-Vbat), where Kp is a proportional coefficient and Ki is an integral coefficient.

[0032] In one embodiment, the calculation formula of the duty cycle D in step S2 is: D=Kp(Iref-Ibat)+Ki*∫(Iref-Ibat), where Kp is the proportional coefficient and Ki is the integral coefficient.

[0033] In one embodiment, the dead time adjustment operation performed in step S3 is to adjust TDBRE to TDBREDInit+t, and at the same time adjust the falling edge dead time TDBFE to TDBFEDInit-t; and adjust the duty cycle to Dlast+t / T, where t is the adjustment value of the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period.

[0034] In one embodiment, the dead time recovery operation performed in step S4 is to restore TDBRE to TDBREDInit, and restore TDBFED to TDBFEDInit, and adjust the duty cycle to Dlast-t / T, where Dlast is the duty cycle value before adjustment and T is the switching period.

[0035] like Figure 2 As shown, the present invention also provides a dead time adaptive adjustment system for a low-power bidirectional DCDC half-bridge circuit, the system comprising:

[0036] A voltage sampling module, which is used to collect the battery voltage Vbat;

[0037] A current sampling module, which is used to collect the battery current Ibat;

[0038] a first PI controller, configured to calculate a target current value Iref according to a given voltage Vref and a sampled battery voltage Vbat;

[0039] a second PI controller, configured to calculate a duty cycle D according to the target current Iref and the sampled battery current Ibat;

[0040] The dead time adjustment module is used to perform dead time adjustment and recovery operations according to the relationship between the duty cycle D and the first duty cycle judgment value D1 and the second duty cycle judgment value D2.

[0041] This application introduces a dynamic dead time adjustment mechanism and a duty cycle compensation algorithm, combined with a dual closed-loop PI control structure, to solve the problems of unstable control and low efficiency of the traditional bidirectional DCDC half-bridge topology under low-voltage discharge conditions. It significantly improves the system's operating stability, safety and control accuracy over a wide voltage range, and is particularly suitable for application scenarios with high precision and high reliability requirements, such as battery formation and testing.

[0042] This application can automatically determine whether to enter the low-voltage discharge mode or the normal working mode according to the software, and achieve a lower voltage discharge voltage by adjusting the dead time and ensuring that the first switch tube Q1 and the second switch tube Q2 of the bridge arm are not directly connected;

[0043] This application solves the current fluctuation caused by adjusting the dead zone time by recalculating the output duty cycle, so that the current transition after adjusting the dead zone is smooth.

[0044] This application achieves a lower discharge voltage by implementing software control in a low-power bidirectional DCDC half-bridge topology circuit. The software automatically determines whether to enter low-voltage discharge mode or normal operating mode. By adjusting the dead time and ensuring that the bridge arm switches do not bypass, a lower discharge voltage is achieved. Current fluctuations caused by adjusting the dead time are resolved by recalculating the duty cycle, achieving smooth current transitions.

[0045] It should be noted that for the aforementioned method embodiments, for simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, because according to the present invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0046] Through the description of the above embodiments, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus the necessary general hardware platform, and of course it can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0047] Therefore, the above is only a preferred specific embodiment of the present invention, and the scope of protection of the present invention is not limited to this. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered within the scope of protection of the present invention. The scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit, used in battery formation and detection, characterized in that: The method comprises the following steps: S1; collecting the battery voltage value Vbat and the battery current value Ibat, and setting the given voltage value Vref, inputting the battery voltage value Vbat and the given voltage value Vref into the first PI controller, and calculating the battery voltage value Vbat and the given voltage value Vref by the first PI controller to obtain the target current value Iref; S2: Input the target current value Iref and the battery current value Ibat into the second PI controller, and calculate the target current value Iref and the battery current value Ibat by the second PI controller to obtain an initial duty cycle D; set the first duty cycle judgment value to D1, set the second duty cycle judgment value to D2, set the initial rising edge dead zone time of the first switch tube Q1 and the second switch tube Q2 to prevent direct conduction to TDBREDInit, and set the initial falling edge dead zone time of the first switch tube Q1 and the second switch tube Q2 to prevent direct conduction to TDBFEDInit; S3; when it is detected that the initial duty cycle D is less than the first duty cycle judgment value D1 and the current rising edge dead time TDBRED is equal to the initial rising edge dead time TDBREDInit, enter the low-voltage discharge mode and perform the dead time adjustment operation; at the same time, according to the adjusted dead time, the output duty cycle is synchronously adjusted to D=Dlast+t / T to ensure a smooth transition of the current; where t is the adjustment value of the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period; S4; when it is detected that the duty cycle D is greater than the second duty cycle judgment value D2 and TDBRED is equal to TDBREDInit+t, the normal working mode is entered and the dead time recovery operation is performed, and the output duty cycle is synchronously adjusted to D=Dlast-t / T to ensure a smooth transition of the current; where t is the adjustment value to the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period.

2. The method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit according to claim 1, characterized in that: In step S1 , the target current value Iref is calculated as follows: Iref=Kp(Vref-Vbat)+Ki*∫(Vref-Vbat), where Kp is a proportional coefficient and Ki is an integral coefficient.

3. The method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit according to claim 2, wherein: In step S2, the calculation formula of the duty cycle D is: D=Kp(Iref-Ibat)+Ki*∫(Iref-Ibat), where Kp is the proportional coefficient and Ki is the integral coefficient.

4. The method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit according to claim 3, characterized in that: In step S3, the dead time adjustment operation is performed to adjust TDBRE to TDBREDInit+t, and at the same time, the falling edge dead time TDBFE is adjusted to TDBFEDInit-t; the duty cycle is adjusted to Dlast+t / T, where t is the adjustment value of the new dead time, Dlast is the duty cycle value before adjustment, and T is the switching period.

5. The method for adaptively adjusting the dead time of a low-power bidirectional DCDC half-bridge circuit according to claim 4, characterized in that: In step S4, the dead time recovery operation is performed to restore TDBRE to TDBREDInit, and at the same time restore TDBFED to TDBFEDInit, and the duty cycle is adjusted to Dlast-t / T, where Dlast is the duty cycle value before adjustment and T is the switching period.

6. A dead time adaptive adjustment system for a low-power bidirectional DCDC half-bridge circuit, characterized in that: The system comprises: A voltage sampling module, which is used to collect the battery voltage Vbat; A current sampling module, which is used to collect the battery current Ibat; a first PI controller, configured to calculate a target current Iref according to a given voltage Vref and a sampled battery voltage Vbat; a second PI controller, configured to calculate a duty cycle D according to the target current Iref and the sampled battery current Ibat; The dead time adjustment module is used to perform dead time adjustment and recovery operations according to the relationship between the duty cycle D and the first duty cycle judgment value D1 and the second duty cycle judgment value D2.

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