Switched mode assisted linear regulator with dynamic buck turn-off using ZCD-controlled tub switching

摘要

A switched mode assisted linear regulator includes a linear amplifier (LA) and a buck converter configured as a current source. In example embodiments, the buck converter circuit includes a power switch M1 with an M1 body diode (tub), and includes buck turn-off circuitry configured to avoid negative inductor current by controlled switching of the tub to the higher of VIN and a second voltage. For DC-coupled configurations, boost functionality is provided by an LA boost supply, and the tub is switched to the boost supply. For AC-coupled configurations, boost functionality can be provided without boosting the LA supply rail by constraining signal peak-to-peak amplitude to be less than the LA supply voltage (maintaining a DC-average voltage on the AC-coupling capacitor), and the tub is switched to the higher of VIN and VOUT. The buck turn-off circuitry can include zero crossing detection to control M1 tub switches.

主权项

1. A power supply circuit with a switched mode assisted linear amplifier architecture with an amplifier, and a buck switched mode converter configured for operation as a current source with a buck inductor, the power supply circuit operable to receive an input voltage VIN, and supply a regulated output voltage VOUT, and associated output current to a dynamic load, comprising:
an amplifier circuit and a buck switched mode converter (buck converter) circuit coupled in parallel at a supply node coupled to the load, the buck converter configured to couple to the supply node through the buck inductor; the amplifier circuit configured to set load voltage VOUT; the buck converter configured for operation as a current source supplying a buck inductor current that is a controlled portion of the output current; the buck converter including a PMOS power switching transistor M1, with an M1 body diode, coupled between VIN and the buck inductor, with switching controlled by M1 gate driver circuitry including turning M1 off during buck turn-off conditions; buck turn-off circuitry operable during buck turn-off conditions to switch off the M1 channel, and switch the M1 body diode to the higher of VIN and a second voltage, including
buck on/off circuitry configured to provide a BUCK_off signal that is asserted when zero buck inductor current is detected, including:zero crossing detector (ZCD) circuitry configured to detect when buck inductor current is zero; andVOUT detect circuitry configured to detect when VOUT is greater that VIN;such that BUCK_off is asserted when buck inductor current is zero and VOUT is greater than VIN; tub switching circuitry responsive to BUCK_off asserted by the ZCD circuitry to switch the M1 body diode to the higher of VIN and the second voltage.