| 摘要 |
A circuit for optimizing charging of a bootstrap capacitor connected to a high side floating supply voltage at a first terminal and to a switched node voltage at a second terminal, the circuit for optimizing being included in a gate driver circuit having high- and low-side driver circuits for driving high- and low-side switches connected at the switched node in a half bridge to provide current to a load, the high-side driver circuit receiving a first control voltage referenced to a first level and the low-side driver circuit receiving a second control voltage referenced to a second level, the bootstrap capacitor providing the high-side floating supply voltage for the high-side driver circuit, the optimizing circuit comprising a bootstrap diode emulator circuit comprising a bootstrap diode emulator driver circuit driving a first switch, the first switch connected between the first terminal of the bootstrap capacitor and a supply voltage for the low side driver circuit; and a phase sense comparator circuit responsive to the voltage at the switched node and turning ON the first switch when the voltage at the switched node is LOW, whereby charging of the bootstrap capacitor is optimized when the phase sense comparator circuit is enabled, the phase sense comparator circuit turning OFF or keeping OFF the first switch when the first control voltage goes to a level to turn ON the high-side switch or remains at such level or the bootstrap capacitor supply voltage goes high or remains high such that it is a fixed amount above the low-side driver supply voltage; further wherein the phase sense comparator circuit turns the first switch ON when: the second control voltage is at a level adapted to turn ON the low-side switch and the bootstrap capacitor supply voltage is low such that it is below the fixed amount above the low side driver supply voltage; or the first and second control voltages are both at a level such that the high-side and low-side switches are OFF after the second control voltage transitions from an ON state to an OFF state and the bootstrap capacitor supply voltage goes below the fixed amount above the low-side driver supply voltage; or the first and second control voltages are both at a level such that the high-side and low-side switches are OFF after the first control voltage transitions from an ON state to an OFF state and the bootstrap capacitor supply voltage goes below the fixed amount above the low-side driver supply voltage.
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