Directly amplified ripple tracking control scheme for multiphase DC-DC converter
A controller for a multiphase power converter has a plurality of DC to DC converters coupled in parallel between a voltage source and a single output terminal is provided. The controller includes a voltage sensing circuit coupled to the output terminal. An internal pulse generating circuit is couplable to the voltage sensing circuit for generating an internal pseudo-pulse width modulated signal. An ON time signal distribution circuit is couplable to an output of the internal pulse generating circuit and couplable to driver circuit for driving each of the plurality of DC to DC converters. A multiphase power converter and method also disclosed.
1. A multiphase power converter comprising:
DC to DC converters having separate inputs and having outputs connected together in an output terminal;
a voltage sensing circuit having an input coupled to the output terminal and having a voltage sense output;
an internal pulse generating circuit having an input coupled to the voltage sensing output and generating an internal pseudo-pulse width modulated signal;
logic circuitry having an input coupled to the modulated signal and including clock generator circuitry producing clock pulses from the modulated signal, the clock generator circuitry producing a rising edge of a clock pulse from a first modulated signal and generating a falling edge of the clock pulse from a next modulated signal, distribution of the clock pulses being synchronized by having a clock pulse for a phase at a higher amplitude than the other clock pulses;
an ON time trigger signal distribution circuit having an input coupled to the clock pulses and outputs each carrying an On time signal;
a circuit board carrying the On time signals; and
driver circuits, each driver circuit having an input coupled to one On time signal and having an output connected to a separate input of a DC to DC converter.
2. The multiphase power converter of claim 1 in which the plurality of DC to DC converters are buck converters.
3. The multiphase power converter of claim 1 in which the internal ON time signal width is approximately Kint*1/(f sw *phase number), where Kint=0.1 to 1.0 f sw =switching frequency of each DC to DC converter phase number=number of phases in the multiphase power converter.
4. The multiphase power converter of claim 1 including a ripple generator according to the duty cycle of the internal pseudo-pulse width modulated signal and the input voltage.
5. The multiphase power converter of claim 4 in which the ripple generator includes a resistor/capacitor network.
6. The multiphase power converter of claim 5 in which the resistor/capacitor network is coupled between an output of an ON time signal generator and the input to a comparator which triggers the ON time signal generator.
7. The multiphase power converter of claim 6 in which the ON time signal generator is a one-shot.
8. A method of driving a plurality of parallel connected DC to DC converters comprising:
sensing a voltage across an output of the converters;
generating a pseudo-pulse width modulated signal;
distributing a constant ON time signal to each of the plurality of DC to DC converters;
driving each of the plurality of DC to DC converters with the constant ON time signal;
in which the distribution of the constant ON time signal utilizes a clock signal in which a first pulse width modulated signal generates a rising edge of the clock signal and a second internal pulse width modulated signal generates a falling edge of the clock, the clock being synchronized to one of the phases by having a clock signal for that phase at a higher amplitude than a clock signal utilized for other phases.