并联电源管理芯片加速电源打开速度 | |
作者: 时间:2008-12-26 来源:52RD硬件研发 | |
In certain applications, design requirements may call upon a system’s switched-mode power supply to more promptly deliver its output than would the garden-variety power supply. Resistor RT and capacitor CH form a trickle-charge circuit that supplies power for bootstrapping IC1 into normal operation. In conventional designs, RT comprises a high resistance that delivers just enough current to overcome the standby current and supply a trickle charge to holdup capacitor CH, which stores enough energy to power the PWM circuit until the power converter begins operation. Under normal circumstances, the circuit’s slow start-up response poses no problems. When faster power-on response becomes important, you can reduce the bootstrap time by reconfiguring the start-up shunt regulator (
At turn-on, the VAUX voltage reaches its peak voltage, VAUX_PEAK, which the ratio of resistors RA and RB determines. Capacitor CT and resistor RC conserve energy by setting the bootstrap circuit’s turn-off time and voltage. Resistor RD supplies bias current to D1, the TL431 shunt-regulator IC, and resistor RE keeps transistor Q1 within its safe operating area by limiting its collector current.
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