CONSTANT ON TIME (COT) CONTROL IN ISOLATED CONVERTER

摘要

The present invention discloses a constant on-time isolated converter comprising a transformer with a primary side and a secondary side. The primary side is connected to an electronic switch and secondary-side is connected to a load and a processor. The processor is connected to a driver on primary side through at least one coupling element and to the electronic switch. The processor receives an output voltage or an output current across the load generating a control signal accordingly. The driver receives the control signal through the coupling element and accordingly changes the ON/OFF state of the electronic switch, regulating the output voltage and the output current via the transformer, where the duration of the ON/OFF state of the electronic switch is determined between the moment control signal changes from negative to positive and the moment it changes from positive to negative to achieve a high-speed load transient response.

主权项

1. A constant on-time (COT) isolated converter connected to an input terminal for receiving an input voltage, the constant on-time isolated converter comprises:
a transformer including a primary side and a secondary side, wherein the primary side is connected to the input terminal and the secondary side is connected to a load with an output signal applied onto the load; a processor connected to the secondary side of the transformer and the load being provided with a first preset reference voltage, a low threshold frequency and a high threshold frequency; wherein the processor receives the output signal and captures a first detection voltage and a second detection voltage sequentially from the output signal, when the first detection voltage is less than the first reference voltage, the processor generates a first pulse signal and a first clock signal synchronous to and of same frequency as the first pulse signal, thereafter the processor generates a second pulse signal and a second clock signal synchronous to and of same frequency as the second pulse signal, based on at least one frequency of the first clock signal, the low threshold frequency and the high threshold frequency when the second detection voltage is less than the first reference voltage; at least one coupling element connected to the processor and to the primary side and the secondary side of the transformer respectively, wherein the coupling element transmits the first pulse signal and the second pulse signal sequentially to the primary side of the transformer; a driver connected to the primary side of the transformer and the coupling element, wherein the driver receives and amplifies the first pulse signal and the second pulse signal sequentially, respectively generating a first digital signal and a second digital signal sequentially; and a first electronic switch connected to the primary side of the transformer and the driver, wherein the first electronic switch receives the first digital signal and the second digital signal sequentially and accordingly changes its ON/OFF states to control the transformer receiving the input voltage from the input terminal, thus regulating the output signal.