Efficient passive clamp
A technology of clamping and clamping circuits, applied in the field of power converters, can solve problems such as limiting operating efficiency, and achieve the effect of reducing heat dissipation
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example 1
[0053] Example 1: Prior Art Flyback Converter with Passive Clamp
[0054] A major disadvantage of the flyback topology is that the leakage inductance between the primary and secondary windings is not recycled as naturally as in other topologies such as two-transistor forward or full-bridge topologies. Figure 3A presents a simplified schematic diagram of the flyback topology 102, and Figure 3B Waveforms for the topology 102 are shown. It is noted here that some reference characters of converter 100 are employed to indicate similar elements. For example, both 100 and 102 have main switches (Ml, 18).
[0055] When the main switch (M1, 18) is turned off, the energy stored in the magnetizing inductance of the transformer (Tr1, 16) is transferred to the secondary via the synchronous rectifier (SR, 28). Leakage inductance (Llk, 37) at Figure 3A is shown as a discrete inductive element to help understand the operation of the flyback when (M1, 18) is turned off. When the main s...
example 2
[0072] Example 2: Prior Art Flyback Converter with Active Clamp
[0073] One attempt to harvest the energy of the leakage inductance is to use an active clamp, eg. Disclosed in US Patent No. 5,434,768. Figure 10 US Patent No. 5,434,768 attempts to illustrate circuitry 300 as applied to a flyback converter. remove figure 1 In addition to the general flyback circuitry 100 presented in FIG. 1 , the circuitry 300 adds a clamp or complementary switch M2, 50 controlled by a control voltage signal VcM2, 54. The circuitry also includes a clamping capacitor Cr, 52 . Switch 50, control voltage signal 54 and clamp capacitor 52 cooperate together to define an active clamp connected between one terminal of primary winding L1 and ground.
[0074] Figure 11 Description has Figure 10Key waveforms of the active clamp flyback circuit 300. These waveforms are presented in order from top to bottom and include: 1) the control signal VcM1 (for the main switch M1); 2) the voltage VdsM1 ac...
example 3
[0079] Example 3: Energy recovery from leakage inductance
[0080] Another approach to harvesting leakage inductance is proposed in U.S. Patent Application No. 16 / 158,202, filed October 11, 2018, entitled "Energy Recovery From The Leakage Inductance Of The Transformer" methods, the disclosure of which is hereby incorporated by reference.
[0081] refer to Figure 12 and Figure 13 Discuss the method of harvesting leakage inductance energy. Here, the problem of wasting electromagnetic energy or "EM" (with the leakage inductance of the flyback of the active clamp) contained in the ringing portion of the clamp waveform and circulating through the clamp is solved by using An active clamp circuit comprising auxiliary electronics or components configured to store EM energy (e.g., in one embodiment, an auxiliary voltage source) supplements the flyback and utilizes this energy through an electronic valve attached to the clamp circuit ( It is otherwise wasted, as in related art sol...
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Abstract
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