Open source license: Public Domain
A current mode boost converter is a type of boost converter in which the peak switch current limit during the on-time is controlled in each cycle. This is done by sensing the switch current, adding a ramp to it and comparing it to the error signal generated by an error amplifier. This comparison leads to the generation of reset pulses which help generate the required PWM signal.
This curcuit takesin 10V and outputs 35V at over 1A.
A close up of the output voltage looks like this:
The switch current looks like this:
and the inductor current looks like this:
The switch current is sensed using a current sensing resistor. The voltage drop across this resistor is sensed.
In order to prevent subharmonic oscillations, a ramp is added to the voltage generated from the switch current (the parameters of the ramp waveform are not calculated and are selected arbitrarily, but the circuit works fine none-the-less):
This ramp waveform is compared with an error signal in order to generate reset pulses, which are fed to an op-amp based SR latch. The clock pulses set the SR latch while the reset pulses from the comparator reset the SR latch, thus creating a PWM signal.
Vn009 : PWM signal
Vn012: Set pulses from clock(green)
vn008: Reset pulses from comparator(blue)
This is how the required PWM signal is generated.
The efficiency of the circuit is 92.46%
SchematicOpen in editor