Patent ID: 9035635
Filing Date: 2015-05-19
Classification: H02J,H02M,H03K,Y02B

Abstract:
1. A switch-mode power supply (SMPS) having selectable asynchronous and synchronous converter modes, said SMPS comprising: a high-side power transistor; a low-side power transistor coupled in series with the high-side power transistor; a power diode coupled in parallel with the low-side power transistor; a filter capacitor coupled in parallel with the series connected high-side and low-side power transistors; a power inductor having a first end coupled to a junction between the high-side and the low-side power transistors and a second end coupled to a power source; a current sensor; and a dual power transistor driver having a high-drive output coupled to a control input of the high-side power transistor, a low-drive output coupled to a control input of the low-side power transistor, and a pulse width modulation (PWM) input adapted for receiving three voltage levels, wherein when the PWM input is at a low logic level the low-drive output is asserted and the low-side power transistor is on, when the PWM input is at a high logic level the high-drive output is asserted and the high-side power transistor is on, and when the PWM input is at a half logic level the high-drive and low-drive outputs are both deasserted and the high-side and low-side power transistors are both off; first and second resistors having first ends coupled to the PWM input of the dual power transistor driver, wherein the first and second resistors are substantially the same resistances; and a microcontroller having a PWM output coupled to a second end of the first resistor, a digital output coupled to a second end of the second resistor, a voltage sense input coupled to the filter capacitor, and a current sense input coupled to the current sensor; wherein the microcontroller supplies a PWM signal from the PWM output thereof and has a duty cycle determined by a voltage on the filter capacitor compared to a voltage reference; wherein when a current measured by the current sensor is less than a certain current value a logic level from the digital output is opposite to a logic level from the PWM output and the PWM input is at the half logic level, and when the current measured by the current sensor is equal to or greater than the certain current value the logic level from the digital output is at the same logic level as the logic Level from the PWM output, and the PWM input is at the same logic level as the PWM output from the microcontroller.