High-order energy supplementing bootstrap circuit and control method thereof

Abstract

The invention discloses a high-order energy supplementing bootstrap circuit and a control method thereof. An isolation power supply taking a bus positive P as the ground is added on the basis of a traditional bootstrap circuit; when the voltage of an upper tube bootstrap capacitor is reduced, the power supply charges the upper tube bootstrap capacitor through a resistor and a switch tube, so the prominent problem of a traditional bootstrap circuit is solved, the stability of the driving voltage of the upper tube can be ensured even if the upper tube is continuously switched on or continuouslyswitched on at a high duty ratio, and the adaptive working conditions and application occasions of the bootstrap circuit are greatly expanded. Compared with an isolation power supply scheme, the scheme of the invention can reduce N-1 isolation power supplies, wherein N is the phase number of the bridge circuit; the power supply design is greatly simplified, the power supply size is reduced, and the power supply cost is reduced.

Description

technical field [0001] The invention relates to a high-level energy supplement type bootstrap circuit and a control method thereof. Background technique [0002] Since the midpoint level of the bridge circuit is floating, the upper tube drive in the bridge circuit needs to use an isolated power supply. The usual solution is that the upper tube drive of each phase needs to be powered by an isolated power supply, and the lower tube drive can be shared. Isolated power supply, the system needs N+1 isolated power supplies in total, where N is the phase number of the bridge circuit, such as figure 1 As shown, this undoubtedly increases the complexity, size and cost of the auxiliary power supply in the system. [0003] Aiming at the shortage of the isolated power supply scheme, the bootstrap circuit came into being. figure 2 It is a traditional bootstrap circuit structure in the prior art. When the down switch is turned on, the midpoint level of the bridge arm is pulled down, an...

AI Technical Summary

Problems solved by technology

The advantage of this circuit is that it can greatly simplify the design of the power supply, reduce the size of the power supply, and reduce the cost of the power supply. The more phases, the more obvious the advantage; the disadvantage is that only the lower tube is turned on, and the upper tube drives the power supply capacitor C H In order to be charged, if the upper tube of a certain phase is continuously turned on, or the duty cycle of the turn-on exceeds a certain value for a period of time, it will cause C H The supplemented energy is less than the consumed energy, resulting in a decrease in the driving supply voltage, increasing the conduction loss of the tube, and even generating an undervoltage alarm of the gate drive power supply and shutting down

This problem is particularly prominent in some applications. For example, when high-power MOSFETs work above 20kHz, the power consumption of the driving power supply is large, and the bootstrap capacitor is prone to undervoltage, which limits the application of the bootstrap circuit.

Images