阅读说明：本技术 一种高位补能型自举电路及其控制方法 (High-order energy-complementing type bootstrap circuit and control method thereof ) 是由 姚瑱 余国军 徐小军 钱巍 于 2019-10-25 设计创作，主要内容包括：本发明公开了一种高位补能型自举电路及其控制方法,在传统自举电路的基础上增加一路以母线正P为地的隔离电源,当上管自举电容电压降低时,该电源通过电阻、开关管给上管自举电容充电,解决了传统自举电路的突出问题,即使上管持续开通,或者持续高占空比开通,都能保证上管驱动电压稳定,大大拓展了自举电路的适应工况和应用场合。且与隔离电源方案相比,本发明的方案能够减少N-1路隔离电源,其中N为桥式电路的相数,大大简化电源设计,缩小电源体积,降低电源成本。(The invention discloses a high-order energy-supplementing type bootstrap circuit and a control method thereof.A path of isolation power supply taking a positive P of a bus as the ground is added on the basis of the traditional bootstrap circuit, when the voltage of a tube loading bootstrap capacitor is reduced, the power supply charges the tube loading bootstrap capacitor through a resistor and a switching tube, thereby solving the outstanding problem of the traditional bootstrap circuit, ensuring the driving voltage of the tube loading to be stable even if the tube loading is continuously switched on or is continuously switched on with high duty ratio, and greatly expanding the adaptive working condition and application occasions of the bootstrap circuit. Compared with the scheme of the isolated power supply, the scheme of the invention can reduce N-1 paths of isolated power supplies, wherein N is the phase number of the bridge circuit, thereby greatly simplifying the power supply design, reducing the power supply volume and lowering the power supply cost.)

1. A high-order energy-complementing type bootstrap circuit comprises a bootstrap circuit and is characterized in that: an isolation power supply V taking the positive P of the bus as the ground is added in the bootstrap circuit_PIsolated power supply V_POne path is connected with a positive P of the bus through a capacitor Cp to isolate a power supply V_PThe other path is connected to each switch S after passing through a resistor R_iI =1, 2, … …, N, switch S_iThe other end of the connecting rod is respectively connected with each upper tube bootstrapAnd (4) a capacitor.

2. The high-order energy-complementing type bootstrap circuit as claimed in claim 1, wherein: the switch S_iLogically sharing PWM with corresponding upper tube_iuAnd (5) driving.

3. The high-order energy-complementing type bootstrap circuit as claimed in claim 1, wherein: each phase of upper tube is correspondingly provided with an upper tube driving voltage comparison circuit, when the driving voltage of a certain phase of upper tube is lower than a threshold value, an enable signal is output, the enable signal and the upper tube PWM signal do AND logic to generate a switch signal of the phase, and a corresponding switch S is controlled_i。

4. A method for controlling the high complementary bootstrap circuit as recited in claim 1, 2 or 3, characterized by: an isolation power supply V taking the positive P of the bus as the ground is added in the bootstrap circuit_PIsolated power supply V_POne path is connected with a positive P of the bus through a capacitor Cp to isolate a power supply V_PThe other path is connected to each switch S after passing through a resistor R_iOne end of (1), switch S_iThe other end of the capacitor is respectively connected with the bootstrap capacitor of each upper tube; when the upper tube bootstrap capacitor voltage is reduced, the isolation power supply V_PThrough a resistor R, a switch S_iAnd charging the upper tube bootstrap capacitor.

5. The method for controlling a bootstrap circuit of the high-side energy-complementing type as recited in claim 4, further comprising: the switch S_iLogically sharing PWM with corresponding upper tube_iuDriving; each phase of upper tube is correspondingly provided with an upper tube driving voltage comparison circuit, when the driving voltage of a certain phase of upper tube is lower than a threshold value, an enable signal is output, the enable signal and the upper tube PWM signal do AND logic to generate a switch signal of the phase, and a corresponding switch S is controlled_i。

6. The method for controlling a bootstrap circuit of the high-side energy-complementing type as recited in claim 4, further comprising: the MCU/CPU controlled by the multiplexing system is judged according to the duty ratio of the PWM signal of each phase of the tube, if so, the MCU/CPU is controlled by the multiplexing systemA certain phase tube is continuously opened₁Time, or upper tube conduction duty ratio exceeding D₁For a period of time t₂Then, the enable signal is output, and the enable signal and the phase tube PWM signal are processed by AND logic to generate the PWM signal of the switch.

Technical Field

The invention relates to a high-order energy-complementing type bootstrap circuit and a control method thereof.

Background

Since the midpoint level of the bridge circuit is floating, the upper tube driver in the bridge circuit needs to use an isolated power supply, and a common solution is that each phase of the upper tube driver needs to be powered by the isolated power supply, the lower tube driver can share one isolated power supply, and the system needs N +1 isolated power supplies in total, where N is the number of phases of the bridge circuit, as shown in fig. 1, which undoubtedly increases the complexity, volume and cost of the auxiliary power supply in the system.

The bootstrap circuit arises from the inadequacies of the isolated power supply scheme. FIG. 2 is a conventional bootstrap circuit structure of the prior art, when the lower transistor is turned on, the bridge arm midpoint level is pulled low, and the capacitor C_LThe capacitor C is supplied by a bootstrap diode and a current-limiting resistor_HCharging, capacitance C_HThe upper tube is provided for driving power supply, and the three paths of isolation power supplies are not needed. The circuit has the advantages that the design of a power supply can be greatly simplified, the size of the power supply is reduced, the cost of the power supply is reduced, and the advantages are more obvious when the number of phases is more; the disadvantage is that only the lower tube is switched on, and the upper tube drives the power supply capacitor C_HCan be charged, if a certain phase tube is continuously turned on or the on duty ratio exceeds a certain value for a period of time, C will be caused_HThe supplemented energy is less than the consumed energy, so that the driving power supply voltage is reduced, the conduction loss of the tube is increased, and even the gate driving power supply is under-voltage to alarm and stop the machine. The problem is particularly prominent in some application occasions, for example, when a high-power MOSFET works above 20kHz, the power consumption of a driving power supply is large, and a bootstrap capacitor is easy to generate undervoltage, so that the application of a bootstrap circuit is limited.

Disclosure of Invention

Aiming at the scheme of an isolation power supply and the defects of the traditional bootstrap circuit, the invention provides a high-order energy-supplementing type bootstrap circuit, wherein an isolation power supply taking a positive P of a bus as the ground is added on the basis of the traditional bootstrap circuit, when the voltage of a tube loading bootstrap capacitor is reduced, the power supply charges the tube loading bootstrap capacitor through a resistor and a switch tube, the outstanding problem of the traditional bootstrap circuit is solved, the driving voltage of the tube loading can be ensured to be stable even if the tube loading is continuously switched on or is continuously switched on with a high duty ratio, and the adaptive working condition and the application occasion of the bootstrap circuit are greatly expanded. Compared with the scheme of the isolated power supply, the scheme of the invention can reduce (N-1) paths of isolated power supplies (wherein N is the phase number of the bridge circuit), greatly simplify the power supply design, reduce the power supply volume and reduce the power supply cost.

The invention relates to a high-order energy-complementing type bootstrap circuit,the method is characterized in that: on the basis of a bootstrap circuit, an isolation power supply V taking a positive P of a bus as the ground is added_PIsolated power supply V_POne path is connected with a positive P of the bus through a capacitor Cp to isolate a power supply V_PThe other path is connected to each switch S after passing through a resistor R_iOne end of (i =1, 2, … …, N), switch S_iThe other end of the capacitor is respectively connected with the bootstrap capacitor of each upper tube; the control method comprises the following steps: when the upper tube bootstrap capacitor voltage is reduced, the isolation power supply V_PThrough a resistor R, a switch S_i(i =1, 2, … …, N) charges the upper tube bootstrap capacitor.

The invention relates to a high-order energy-supplementing bootstrap circuit, a switch S_i(i =1, 2, … …, N), logically sharing PWM with the corresponding upper tube_iuAnd (5) driving.

The invention further improves the scheme of the high-order energy-compensating bootstrap circuit: each phase of upper tube is correspondingly provided with an upper tube driving voltage comparison circuit, when the driving voltage of a certain phase of upper tube is lower than a threshold value, an enable signal is output, the enable signal and the upper tube PWM signal do AND logic to generate a switch signal of the phase, and a corresponding switch S is controlled_i （i=1，2，……，N）。

The invention further improves the scheme of the high-order energy-compensating bootstrap circuit: the MCU/CPU controlled by the multiplexing system judges according to the duty ratio of each phase tube if a certain phase tube is continuously opened t₁Time, or upper tube conduction duty ratio exceeding D₁For a period of time t₂Then, the enable signal is output, and the enable signal and the phase tube PWM signal are processed by AND logic to generate the PWM signal of the switch.

According to the invention, on the basis of the bootstrap circuit in the prior art, an isolation power supply taking the positive P of the bus as the ground is added, and when the voltage of the upper tube bootstrap capacitor is reduced, the power supply charges the upper tube bootstrap capacitor through the resistor and the switch tube, so that the outstanding problem of the traditional bootstrap circuit is solved, the driving voltage of the upper tube can be ensured to be stable even if the upper tube is continuously switched on or is continuously switched on with a high duty ratio, and the adaptive working condition and application occasion of the bootstrap circuit are greatly expanded. Compared with the scheme of the isolated power supply, the scheme of the invention can reduce N-1 paths of isolated power supplies (wherein N is the phase number of the bridge circuit), greatly simplify the power supply design, reduce the power supply volume and reduce the power supply cost.

Drawings

FIG. 1 shows an N-phase bridge circuit and the isolated power supply for driving.

Fig. 2 is a prior art bootstrap circuit.

FIG. 3 is a schematic diagram of a high complementary bootstrap circuit according to the present invention.

FIG. 4 is a circuit diagram of a control method 1 of the high-side energy-complementing bootstrap circuit of the present invention.

FIG. 5 is a schematic circuit diagram of a control method 2 of the high-side energy-complementing bootstrap circuit of the present invention.

FIG. 6 is a schematic circuit diagram of a control method 3 of the high-side energy-complementing bootstrap circuit of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.