Critically continuous boost converter

A critically continuous boost converter having an input connectable through a rectifier to a sinusoidal line voltage, said converter comprising:

• an inductor;
• a power switch in series with said inductor, the series combination coupled to the line voltage for receiving power therefrom;
• a rectifier means connected between a load and the junction of said inductor and said power switch, said rectifier means poled to conduct power to said load when said power switch is not conducting;
• control loop means, responsive to a signal proportional to the output voltage of the load, for controlling the on time of said power switch, said control means including means for generating an error signal proportional to the difference of said signal proportional to the output voltage and a first reference voltage, first and second consecutive timing means, said first timing means for extending the turn on time of said power device, said first timing means including means for generating a first signal proportional to the input voltage, means for integrating said first signal, means for comparing said integrated signal to a second reference signal for starting operation of said second timing means for determining when said power switch on time ceases.

A boost converter having an input connectable to a voltage source, comprising:

• an inductor;
• a power switch in series with said inductor, the series combination connectable to the voltage source for receiving power therefrom;
• a rectifier means connected between a load and the junction of said inductor and said power switch, said rectifier means poled to conduct power to said load when said power switch is not conducting;
• control loop means, responsive to a signal proportional to the output voltage of the load, for controlling the on time of said power switch, said control means including means for generating a compensating voltage signal from a comparison of said signal proportional to the output voltage and a first reference voltage, means for generating an error signal proportional to the square root of said compensation signal and inversely proportional to the input voltage, timing means for generating a signal inversely proportional to said error signal, means for integrating said signal, means for comparing said integrated signal to a second reference signal for turning off said power switch when said second reference signal is exceeded, whereby the open loop gain of the control loop is independent of the boost converter DC output current and the boost converter input voltage.