Novel zero-voltage switching control circuit and method and voltage converter

Abstract

The invention discloses a novel zero-voltage switching control circuit and a control method. A controller chip controls a first switch unit to switch on and off of an input winding and controls a second switch unit to switch on and off of an auxiliary winding and a negative voltage level; before the input winding is connected, the auxiliary winding of the voltage converter is connected with a negative voltage level in advance, the input winding generates negative current based on the coupling effect between the input winding and the auxiliary winding, stray capacitance cross-voltage energy in the first switch unit is released, and the polarity of the input winding is further reversed. The first switch unit is pulled down across the voltage to a switching potential. According to the invention, zero-voltage switching can be realized in a continuous mode CCM or a discontinuous mode QR / DCM, the switching loss of the first electronic switch is reduced, primary current and secondary current which are crossed originally in the continuous mode CCM operation can be mutually staggered, the occurrence of a transconductance phenomenon of approximate short circuit is avoided, and the secondary side synchronous rectification control difficulty is reduced.

Description

technical field [0001] The invention belongs to the technical field of power supplies, and in particular relates to a novel zero-voltage switching control circuit, method and voltage converter. Background technique [0002] In recent years, the market demand for the miniaturization of power chargers for consumer electronic products such as mobile phones and laptops is rapidly increasing. However, the biggest obstacle to this goal is that the operating frequency of power converters cannot be greatly increased. The most The core reason is that the power crystal will cause huge switching loss with the increase of operating frequency, which will lead to a significant decrease in conversion efficiency, and the lost power (heat energy) cannot be effectively dissipated by the radiator because the charger itself is in a sealed state. . [0003] The switching loss of this semiconductor power crystal mainly comes from its output parasitic capacitance Coss (Coss=Cds+Cgd), which can be...

AI Technical Summary

Problems solved by technology

Although the QR technology can greatly reduce the switching loss and at the same time allow the system to operate in Boundary Mode to reduce the conduction loss, however, the real lowest efficiency point of the converter is actually the Low-Line 90Vac, and under the condition of 90Vac, the conduction loss is still Is the key factor leading efficiency, the conduction loss of CCM is smaller than that of DCM

[0009] It is a pity that QR technology must rely on DCM to achieve it. Moreover, QR technology has not fully achieved ZVS, and there may still be a hard switching of up to 250 volts at high voltage 264Vac input, such as Figure 4 As shown, and currently there is no effective solution to CCM-ZVS in the market

[0010] Also, see Image 6 , because the control signal on the primary side of the existing converter dominates the operation of the entire converter, the primary current in the next cycle is turned on first, and then the secondary current on the secondary side is turned off, so there will be a crossover instant The phenomenon of simultaneous conduction (Cross Conduction), the so-called short-circuit (Short Through) phenomenon, for this, in the operating conditions that support CCM, what the prior art needs most is a fast turn-off speed, so as to reduce such a short-circuit as much as possible phenomenon, but this is very difficult to control

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