Starting circuit of switch power supply chip and starting method of starting circuit

Abstract

The invention provides a starting circuit of a switch power supply chip, comprising a power supply voltage Vcc electrifying module, a chip voltage bias / current bias generating and chip low voltage part power supply generating module and a UVLO (under voltage lock out) module of the chip, wherein the power supply voltage Vcc electrifying module is used for generating analog signals E8 when an external power supply voltage Vcc voltage is higher than the predetermined starting voltage; the chip voltage bias / current bias generating and chip low voltage part power supply generating module is used for receiving the analog signals E8, establishing voltage bias signals and current bias signals needed by the chip, establishing a low voltage working voltage Vdd needed by the chip, and finishing starting the chip when the output POW_R signal is H; and the UVLO module of the chip is used for enabling the whole power supply chip to stop working when the power supply voltage Vcc is lower than a Vcc UVLO voltage value. The invention provides the starting circuit of the switch power supply chip and a starting method of the starting circuit; the starting current is low, the starting power consumption is reduced, and the Vcc voltage lower limit for enabling the switch power supply chip to stop working is flexibly and exactly set.

Description

Technical field [0001] The present invention relates to the technical field of switching power supplies, in particular to a low power consumption startup circuit of a switching power supply chip and a startup method thereof. Background technique [0002] Switching power supplies have the advantages of small size, high efficiency and large current, so they are widely used in mobile phone chargers, laptop adapters and LED drivers. [0003] See figure 1 , The figure is a circuit diagram of a switching power supply in the prior art. The voltage source 103 charges the Vcc terminal of the chip 110 through the resistor 114. When the Vcc terminal reaches the starting voltage of the chip 110, the internal circuit of the chip 110 starts to work, making the output terminal output high level, the switch tube 101 is turned on, and the transformer 102 is the primary side Inductive energy storage. When the voltage on the resistor 104 reaches the internal reference level of the chip, the switch 1...

AI Technical Summary

Problems solved by technology

The start-up and uvlo (undervoltage lock out) module 203 uses the breakdown potential of zener (zener breakdown) to determine the start-up and uvlo voltage. Due to the limitation of the zener clamping voltage, the Vcc uvlo voltage cannot be precisely designed

At the same time, it needs to consume a relatively large starting current

In addition, the structure also requires the use of high voltage thick gate MOS devices

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