Adaptive control of resonant power converters
A power converter including a transformer, a resonant circuit including the transformer and a resonant capacitor having a characteristic resonant frequency and period, and output circuitry connected to the transformer for delivering a rectified output voltage to a load. Primary switches drive the resonant circuit, a switch controller operates the primary switches in a series of converter operating cycles which include power transfer intervals of adjustable duration during which a resonant current at the characteristic resonant frequency flows through a winding of the transformer. The operating cycles may also include energy recycling intervals of variable duration for charging and discharging capacitances within the converter. A gate driver includes a transformer, a plurality of switches, a current monitor, and a controller that operates the switches in a series of driver operating cycles having adjustable ON periods and adjustable transition periods during which capacitances are resonantly charged and discharged.
1. A method of controlling power train switches in a power converter, the method comprising:
providing a gate drive circuit including a gate drive source having a positive terminal and a negative terminal, an inductor having a first end connected to a first node and a second end connected to a second node, a plurality of gate drive switches, including a first gate drive switch and a second gate drive switch connected to the first node, a third gate drive switch and a fourth gate drive switch connected to the second node, and a switch controller connected to operate the plurality of gate drive switches in a series of driver operating cycles;
coupling one or more input capacitances associated with the power train switches to the inductor;
wherein each driver operating cycle includes:
a first interval during which (i) the first and fourth gate drive switches are ON and (ii) the first and fourth gate drive switches connect the first node to the positive terminal and the second node to the negative terminal, wherein at the end of the first interval a positive current flows through the inductor;
a first transition following the first interval during which the first and second gate drive switches are OFF and a current flowing in the inductor charges and discharges capacitances coupled to the first node;
a second transition following the first interval during which the third and fourth gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the second node;
a second interval during which (i) the second and third gate drive switches are ON and (ii) the second and third gate drive switches connect the second node to the positive terminal and the first node to the negative terminal, wherein at the end of the second interval a negative current flows through the inductor;
a third transition following the second interval during which the first and second gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the first node; and
a fourth transition following the second interval during which the third and fourth gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the second node; and
configuring the switch controller to directly or indirectly adjust, during operation of the power converter, one or more of: (a) a duration of the driver operating cycle, (b) a duration for the first and second intervals, (c) a duration for the first, second, third, and fourth transitions, or (d) a relative timing for the first and second transitions and the third and fourth transitions.
2. The method of claim 1 wherein selected driver operating cycles further comprise:
a clamp interval during which the second and fourth gate drive switches are ON and the second and fourth gate drive switches connect the first end of the inductor to the second end of the inductor during which an average non-zero current flows through the inductor.
3. The method of claim 2 wherein each driver operating cycle further comprises:
a fifth transition following the first interval during which the first and fourth gate drive switches are turned OFF and the current flowing in the inductor charges and discharges capacitances coupled to the inductor; and
a sixth transition following the second interval during which the second and third gate drive switches are turned OFF and the current flowing in the inductor charges and discharges capacitances coupled to the inductor.
4. The method of claim 1 , further comprising:
providing the power converter for converting DC power received from a converter input for delivery to a converter output at an essentially fixed voltage transformation ratio, K=Vout/Vin and an output resistance;
providing circuitry having a first input connected to the converter input for sensing an input voltage, a second input connected to the converter output for sensing an output voltage, and circuitry adapted to provide a signal proportional to a difference between the output voltage and a scaled replica of the input voltage; and
wherein the switch controller adaptively operates the power converter as a function of the signal.
5. A method of controlling power train switches in a power converter, the method comprising:
providing a gate drive circuit including a gate drive source having a positive terminal and a negative terminal, an inductor having a first end connected to a first node and a second end connected to a second node, a plurality of gate drive switches, including a first gate drive switch and a second gate drive switch connected to the first node, a third gate drive switch and a fourth gate drive switch connected to the second node;
coupling control terminals, including respective input capacitances of the power train switches, to the inductor; and
providing a switch controller connected to operate the plurality of gate drive switches in a series of driver operating cycles during which each of the plurality of gate drive switches is turned-on with zero voltage switching (ZVS);
wherein the switch controller selectively varies a duration of a time interval that each of the plurality of gate drive switches stays ON as a function of operating conditions of the power converter to adaptively control the power converter;
wherein each driver operating cycle comprises:
a first interval during which (i) the first and fourth gate drive switches are ON and (ii) the first and fourth gate drive switches connect the first end of the inductor to the positive terminal and the second end of the inductor to the negative terminal, wherein at the end of the first interval a positive current flows through the inductor;
a second interval during which (i) the second and third gate drive switches are ON and (ii) the second and third gate drive switches connect the second end of the inductor to the positive terminal and the first end of the inductor to the negative terminal, wherein at the end of the second interval a negative current flows through the inductor;
a first transition following the first interval during which the first and second gate drive switches are OFF and a current flowing in the inductor charges and discharges capacitances coupled to the first node;
a second transition following the first interval during which the third and fourth gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the second node;
a third transition following the second interval during which the first and second gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the first node; and
a fourth transition following the second interval during which the third and fourth gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the second node.
6. The method of claim 5 wherein selected driver operating cycles further comprise:
a clamp interval during which the second and fourth gate drive switches are ON and the second and fourth gate drive switches connect the first end of the inductor to the second end of the inductor during which an average non-zero current flows through the inductor.
7. The method of claim 6 wherein each driver operating cycle further comprises:
a fifth transition following the first interval during which the first and fourth gate drive switches are turned OFF and the current flowing in the inductor charges and discharges capacitances coupled to the inductor; and
a sixth transition following the second interval during which the second and third gate drive switches are turned OFF and the current flowing in the inductor charges and discharges capacitances coupled to the inductor.
8. The method of claim 5 , further comprising:
providing the power converter for converting DC power received from a converter input for delivery to a converter output at an essentially fixed voltage transformation ratio, K=Vout/Vin and an output resistance;
providing circuitry having a first input connected to the converter input for sensing an input voltage, a second input connected to the converter output for sensing an output voltage, and circuitry adapted to provide a signal proportional to a difference between the output voltage and a scaled replica of the input voltage; and
wherein the switch controller adaptively operates the power converter as a function of the signal.
9. The method of claim 8 wherein the switch controller is adapted to operate the plurality of gate drive switches to clamp the inductor of the gate drive circuit.
10. The method of claim 8 wherein selected driver operating cycles further comprise:
a clamp interval during which the second and fourth gate drive switches are ON and the second and fourth gate drive switches connect the first end of the inductor to the second end of the inductor during which an average non-zero current flows through the inductor.
11. A method of controlling power train switches in a power converter, the method comprising:
providing a gate drive circuit including a gate drive source having a positive terminal and a negative terminal, an inductor having a first end connected to a first node and a second end connected to a second node, a plurality of gate drive switches, including a first gate drive switch and a second gate drive switch connected to the first node, a third gate drive switch and a fourth gate drive switch connected to the second node;
coupling control terminals, including respective input capacitances of the power train switches, to the inductor; and
providing a switch controller connected to operate the plurality of gate drive switches in a series of driver operating cycles during which each of the plurality of gate drive switches is turned-on with zero voltage switching (ZVS);
wherein the switch controller selectively varies a duration of a time interval that each of the plurality of gate drive switches stays ON as a function of operating conditions of the power converter to adaptively control the power converter;
wherein each driver operating cycle comprises:
a first interval during which (i) the first and fourth gate drive switches are ON and (ii) the first and fourth gate drive switches connect the first end of the inductor to the positive terminal and the second end of the inductor to the negative terminal, wherein at the end of the first interval a positive current flows through the inductor;
a second interval during which (i) the second and third gate drive switches are ON and (ii) the second and third gate drive switches connect the second end of the inductor to the positive terminal and the first end of the inductor to the negative terminal, wherein at the end of the second interval a negative current flows through the inductor;
a first transition following the first interval during which the first and fourth gate drive switches are turned OFF and a current flowing in the inductor charges and discharges capacitances coupled to the inductor; and
a second transition following the second interval during which the second and third gate drive switches are turned OFF and the current flowing in the inductor charges and discharges capacitances coupled to the inductor; and
wherein selected driver operating cycles further comprise:
a clamp interval during which the second and fourth gate drive switches are ON and the second and fourth gate drive switches connect the first end of the inductor to the second end of the inductor during which an average non-zero current flows through the inductor.
12. The method of claim 11 wherein each driver operating cycle further comprises:
a third transition following the first interval during which the first and second gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the first node;
a fourth transition following the first interval during which the third and fourth gate drive switches are OFF and the current flowing in the inductor charges and discharges capacitances coupled to the second node.
13. The method of claim 11 , further comprising:
providing the power converter for converting DC power received from a converter input for delivery to a converter output at an essentially fixed voltage transformation ratio, K=Vout/Vin and an output resistance;
providing circuitry having a first input connected to the converter input for sensing an input voltage, a second input connected to the converter output for sensing an output voltage, and circuitry adapted to provide a signal proportional to a difference between the output voltage and a scaled replica of the input voltage; and
wherein the switch controller adaptively operates the power converter as a function of the signal.