Transformers gate drive

Designing the gate drive transformer (refer to Seetion 3.5.8)... 

There are control ICs presently in the market. This is one technique to increase the frequency of full-bridge converters and gain three to five percent in efficiency over the normal PWM full-bridge converters. The cost of the supply does increase since more gate drive transformers are required. 

The gate drive transformer is a very simple 1 1 turns ratio forward-mode transformer. There are not extraordinary demands being plaeed on the transformer sinee it is a very low power, ae-eoupled (bipolar flux), 300 kHz transformer. 

The gate drive transformer will be bifilar wound where two identieal wires (about 30AWG) will be wound simultaneously with equal turns. For eonve-nienee, the transformer will be mounted on a four-pin, gull wing, surfaee mount header. 

The purpose of gate or base drive transformers is to provide isolation between the eontroller seetion and a floating power switeh. Their design is relatively easy, but it is important to the reliable operation of the switehing power supply. 

There are several important faetors to eonsider during the design of the gate or base drive transformer ... 

Figure 3-23 Examples of transformer-coupled base and gate drives (a) single MOSFET drive circuit (b) dual MOSEET drive.

This proeedure is identieal to that of designing a forward-mode power transformer. I will use a small E-E eore and will separate the primary and the see-ondary windings with several layers of insulating Mylar tape. The gate drive... 

Circuits where isolated gate drives operate at nearly full duty cycle or nearly zero duty cycle can be difficult to design. The transformer that provides isolation can easily saturate at full duty cycles. The circuit featured here uses a unique idea in order to circumvent this difficulty. 

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