# Current Sense Transformer Reset Circuitry Help

#### Enforcer83

Joined Oct 29, 2010
25
I am working on a theoretical design for a boost converter. I utilize two 1:100 current sense transformers in my design and I am having an issue with designing the reset circuitry on the transformers. An application note for the PWM IC I am planning on using shows the current sense transformers in the configuration as shown in the attached document Current Sense2.pdf. Inductors L5 and L6 are the secondary side of the current transformers while the inductors L2 and L3 (not shown) are the primary side of the current transformers and are in line before the transistor and after the output diode (Current Sense1.pdf). L2:L5 are coupled and L3:L6 are coupled in my simulation. Inductors L2 and L3 have the theoretical values listed below.

What I am trying to do is find the value of resistors R2 and R3 when: $$V_{\tiny{RS}}=1V$$, $$I_{\tiny{RS}}=0.2175A$$, $$V_{\tiny{CC}}=20V$$, $$f_{\tiny{SW}}=100kHz$$, and $$L2=L3=1{\mu}H$$. The duty cyle of the PWM signal has a minimum of 7% and a maximum of 69%.

With this in mind, the circuity has to completely reset the transformers within 2.5 to 3 microseconds. I am trying to find the equation(s) that can provide me this design information. Does anyone know where I can look to find this information?

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