Closed loop diode emulator for DC-DC converter
First Claim
Patent Images
1. For use with a DC—
- DC voltage converter, having a controller which generates a pulse width modulation (PWM) switching signal, that switchably controls operation of a switching circuit, containing first and second electronic power switching devices coupled between respective power supply terminals, and having a common node thereof coupled through an inductor element to an output voltage terminal and a capacitor element, a method of emulating diode operation of said switching circuit during off time of said PWM switching signal, said method comprising the steps of;
(a) during an interval other than a switch-on state of said PWM switching signal, sensing a state of a voltage at said common node;
(b) generating a switch off signal for turning off one of said first or second electronic power switching devices; and
(c) over successive cycles of said PWM switching signal, adjusting the turn off time of said switch off signal in accordance with successively sensed states of said voltage at said common node.
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Abstract
A diode emulator for a DC—DC buck converter employs a variable current ramp-based circuit that monitors the state of the phase voltage at the common node between two power switching devices. Incrementally with each pulse width modulation cycle, the diode emulator adjusts the time of turn-off of the lower power switching device, until the monitored phase voltage indicates that the emulator is effectively tracking the negative going, zero-crossing of the ripple current through an output inductor.
61 Citations
16 Claims
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1. For use with a DC—
- DC voltage converter, having a controller which generates a pulse width modulation (PWM) switching signal, that switchably controls operation of a switching circuit, containing first and second electronic power switching devices coupled between respective power supply terminals, and having a common node thereof coupled through an inductor element to an output voltage terminal and a capacitor element, a method of emulating diode operation of said switching circuit during off time of said PWM switching signal, said method comprising the steps of;
(a) during an interval other than a switch-on state of said PWM switching signal, sensing a state of a voltage at said common node;
(b) generating a switch off signal for turning off one of said first or second electronic power switching devices; and
(c) over successive cycles of said PWM switching signal, adjusting the turn off time of said switch off signal in accordance with successively sensed states of said voltage at said common node. - View Dependent Claims (2, 3, 4, 5, 6)
step (a) comprises sensing said state of said voltage at said common node during an off state of said first and second electronic power switching devices, and step (c) comprises incrementally adjusting the on-time of one of said first and second electronic power switching devices over said successive cycles of said PWM switching signal.
- DC voltage converter, having a controller which generates a pulse width modulation (PWM) switching signal, that switchably controls operation of a switching circuit, containing first and second electronic power switching devices coupled between respective power supply terminals, and having a common node thereof coupled through an inductor element to an output voltage terminal and a capacitor element, a method of emulating diode operation of said switching circuit during off time of said PWM switching signal, said method comprising the steps of;
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7. A diode emulator for a DC—
- DC voltage buck converter having a controller, which generates a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing first and second electronic power switching devices coupled between respective power supply terminals, a common node thereof being coupled through an inductor element to an output voltage terminal and a capacitor, said diode emulator comprising;
a phase voltage sample and hold circuit that is operative to sense a state of a voltage at said common node during an interval other than a switch on state of said PWM switching signal; and
a switch off signal control circuit, which is operative to generate a turn off signal for turning off said first electronic power switching device, and to adjust the turn off time of said switch off signal in accordance with successively sensed states of said voltage at said common node, as sensed by said phase voltage sample and hold circuit over successive cycles of said PWM switching signal. - View Dependent Claims (8, 9, 10, 11)
- DC voltage buck converter having a controller, which generates a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing first and second electronic power switching devices coupled between respective power supply terminals, a common node thereof being coupled through an inductor element to an output voltage terminal and a capacitor, said diode emulator comprising;
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12. A diode emulator for a DC—
- DC voltage buck converter having a controller, which generates a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing first and second electronic power switching devices coupled between respective power supply terminals, a common node thereof being coupled through an inductor element to an output voltage terminal and a capacitor, said diode emulator comprising;
a phase voltage sample and hold circuit that is operative to generate a representation of phase voltage at said common node during an off interval of said PWM switching signal; and
a switch off signal control circuit, which is operative to incrementally adjust the time of turn-off of one of said first and second electronic power switching devices, with each PWM switching signal cycle, until said representation of said phase voltage indicates that the emulator is effectively tracking a zero-crossing of the ripple current through the inductor. - View Dependent Claims (13, 14, 15, 16)
- DC voltage buck converter having a controller, which generates a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing first and second electronic power switching devices coupled between respective power supply terminals, a common node thereof being coupled through an inductor element to an output voltage terminal and a capacitor, said diode emulator comprising;
Specification