A circuit capable of reducing LLC starting inrush current and enhancing LLC reliability

Abstract

The utility model discloses a can reduce LLC starting impact current and strengthen LLC reliability's circuit, 1 foot of C_in links to 2 foot of LLC upper bridge arm MOS pipe Q1 with 2 foot of resistance R1, 3 foot of MOS pipe Q1, 1 foot of resistance R1, 2 foot of LLC lower bridge arm MOS pipe Q2, 2 foot of resistance R2 links to 1 foot of resonant inductance, 2 foot of resonant inductance links to 2 foot of transformer T1, 1 foot of transformer T1 links to 1 foot of resonant capacitor C1, 5 foot of transformer links to 2 foot of diode D1, 6 foot of transformer links to 2 foot of diode D2, 3 foot of transformer, 4 foot of transformer links to GND, the utility model discloses utilize resistance voltage division mode and give LLC resonant capacitor before LLC starting precharge, make LLC's resonant capacitor to exist certain voltage before starting, reduce LLC starting impact current, improve LLC circuit's reliability.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology, and in particular to a circuit that can reduce the starting inrush current of LLC and enhance the reliability of LLC. Background Technology

[0002] Currently, LLC topology circuits are frequently used in the power supply industry. When starting up an LLC, it is usually done when the voltage across the LLC resonant capacitor is 0V.

[0003] During startup, the lower the voltage across the LLC resonant capacitor, the greater the current that the LLC's MOSFET will draw to charge the resonant capacitor. Current LLC systems start up directly when there is no voltage across the resonant capacitor, causing a large inrush current to flow through the LLC's MOSFET during startup. The larger this inrush current, the greater the probability of the LLC's MOSFET failing. Utility Model Content

[0004] To address the aforementioned issues, the present invention aims to provide a method that reduces the inrush current during LLC startup, lowers the risk of MOSFET failure during startup, and improves LLC reliability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A circuit that can reduce the startup inrush current of an LLC circuit and enhance its reliability is described. The C_in capacitor is the input capacitor of the LLC circuit. Pin 1 of C_in is connected to pin 2 of the upper bridge arm MOSFET Q1 and pin 2 of the resistor R1. Pin 3 of MOSFET Q1, pin 1 of resistor R1, pin 2 of the lower bridge arm MOSFET Q2, pin 2 of resistor R2, and pin 1 of the resonant inductor are connected to pin 2 of the resonant inductor. Pin 2 of the resonant inductor is connected to pin 2 of transformer T1. Pin 1 of transformer T1 is connected to pin 1 of resonant capacitor C1. Pin 5 of the transformer is connected to pin 2 of diode D1. Pin 6 of the transformer is connected to pin 2 of diode D2. Pins 3 and 4 of the transformer are connected to GND. Pins 1 of diode D1, pin 1 of diode D2, and pin 1 of C_out are connected to the LLC output. Pin 2 of C_out is connected to GND_LLC. Pin 2 of C_in, pin 3 of MOSFET Q2, pin 1 of resistor R2, and pin 2 of resonant capacitor C1 are connected to AGND. After the power supply is turned on, the front bus charges the LLC resonant capacitor through the voltage divider resistor, so that the LLC resonant capacitor has a certain voltage before the LLC starts up.

[0006] Compared with the prior art, the present invention has the following advantages: The present invention uses a resistor voltage divider to precharge the LLC resonant capacitor before the LLC starts, so that the LLC resonant capacitor has a certain voltage before starting, reducing the inrush current when the LLC starts and improving the reliability of the LLC circuit. Attached Figure Description

[0007] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation

[0008] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0009] like Figure 1 As shown, a circuit that can reduce the startup inrush current of an LLC circuit and enhance its reliability is described. The C_in capacitor is the input capacitor of the LLC circuit. Pin 1 of C_in is connected to pin 2 of the upper bridge arm MOSFET Q1 and pin 2 of the resistor R1. Pin 3 of MOSFET Q1, pin 1 of resistor R1, pin 2 of the lower bridge arm MOSFET Q2, pin 2 of resistor R2, and pin 1 of the resonant inductor are connected to pin 2 of the resonant inductor. Pin 2 of the resonant inductor is connected to pin 2 of the transformer T1. Pin 1 of the transformer T1 is connected to pin 1 of the resonant capacitor C1. Pin 5 of the transformer is connected to pin 2 of diode D1. Pin 6 of the transformer is connected to pin 2 of diode D2. Pins 3 and 4 of the transformer are connected to GND. Pins 1 of diode D1, pin 1 of diode D2, and pin 1 of C_out are connected to the LLC output. Pin 2 of C_out is connected to GND_LLC. Pin 2 of C_in, pin 3 of MOSFET Q2, pin 1 of resistor R2, and pin 2 of resonant capacitor C1 are connected to AGND. After the power supply is turned on, the front bus charges the LLC resonant capacitor through the voltage divider resistor, so that the LLC resonant capacitor has a certain voltage before the LLC starts up.

[0010] The implementation method is as follows: VBUS+ precharges the resonant capacitor C1 in the LLC resonant cavity by dividing the voltage through resistors R1 and R2, which increases the voltage of the resonant capacitor C1 in the LLC. When the LLC circuit is turned on, the inrush current on the MOS transistor of the LLC can be reduced, thereby improving the reliability of the LLC.

[0011] By observing the LLC startup waveforms when the voltage across the resonant capacitor is 0V and 200V, it can be seen that the LLC starts up with a peak inrush current of 58.7A when the resonant capacitor voltage is 0V, while the inrush current is only 29.1A when the resonant capacitor voltage is 200V. This data comparison shows that when the LLC starts up, a certain voltage across the resonant capacitor results in a smaller inrush current flowing through the MOSFET, significantly improving the reliability of the LLC circuit.

[0012] The above description is a preferred embodiment of the present utility model. For those skilled in the art, any changes, modifications, substitutions and variations made to the implementation methods without departing from the principles and spirit of the present utility model, based on the teachings of the present utility model, still fall within the protection scope of the present utility model.

Claims

1. A circuit that can reduce the starting inrush current of an LLC and enhance its reliability, characterized in that, The C_in capacitor is the input capacitor of the LLC circuit. Pin 1 of C_in is connected to pin 2 of MOSFET Q1 in the upper arm of the LLC circuit and pin 2 of resistor R1. Pin 3 of MOSFET Q1, pin 1 of resistor R1, pin 2 of MOSFET Q2 in the lower arm of the LLC circuit, pin 2 of resistor R2, and pin 1 of resonant inductor are connected to pin 2 of resonant inductor. Pin 2 of resonant inductor is connected to pin 2 of transformer T1. Pin 1 of transformer T1 is connected to pin 1 of resonant capacitor C1. Pin 5 of transformer is connected to pin 2 of diode D1. Pin 6 of transformer is connected to pin 2 of diode D2. Pins 3 and 4 of transformer are connected to GND. Pins 1 of diode D1, pin 1 of diode D2, and pin 1 of C_out are connected to the LLC output. Pin 2 of C_out is connected to GND_LLC. Pin 2 of C_in, pin 3 of MOSFET Q2, pin 1 of resistor R2, and pin 2 of resonant capacitor C1 are connected to AGND.

Images