Digital control feedback design of a converter using dspic33f

[waqar86]

hello,

I am trying to develop a digital feedback control for a 45-W half-bridge converter, microcontroller used is from microchip dspic33fj16gs502. PWMs provided to the mosfets are around 3Mhz and the power to microcontroller is self-supplied through auxiliary output of transformer. Currently i only have feedback signals of auxiliary voltage and main_current that is passing through the half-bridge.

It has been observed that the relation Vout = A.Vaux + B.Imain holds with a slight error, so probably that can be used to get an idea of the current value of output voltage.

Now i have to develop a feedback mechanism such that the power supply maintains an output voltage of 20v and the PWMs should be set to have maximum efficiency, fo e.g if there is no-load at output , pwm should be in burst-mode.

Anybody having any ideas on how to implement this or anybody having worked on such a thing ??

Thanks in advance

Regards,
Waqar

 

[waqar86]

i have been able to control duty cycle using PID example provided by microchip for their reference designs. but when the required output voltage is achieved and the duty cycle decreases, then ZVS is not met which reduces the efficiency to a great extent. any ideas on how to control both duty cycle and switching frequency simulatneously to meet ZVS at all times.