Power supply time sequence control circuit

Abstract

The invention belongs to the technical field of power supply time sequence control, and particularly relates to a power supply time sequence control circuit which is characterized in that a current-stage power supply is connected to a window detector, high and low levels of the window detector are set as the maximum value and the minimum value of the normal range of the current-stage power supply, and when the window detector detects that the current-stage power supply is within the high and low levels, namely the normal value, the current-stage power supply is switched to the current-stage power supply. A high level is output, a post-stage power supply chip enables to output a post-stage power supply, meanwhile, a current-stage load power supply switch circuit is closed, and a current-stage power supply supplies power to a load; when the window detector detects that the current-stage power supply is out of high and low levels, namely an abnormal value, the low level is output, the post-stage power supply chip is not enabled, the post-stage power supply is not generated, the current-stage load power supply switch circuit is disconnected, and the load does not supply power.

Description

technical field [0001] The invention belongs to the technical field of power supply sequence control, and in particular relates to a power supply sequence control circuit. Background technique [0002] At present, in the design of electronic products, the function and design of the product are becoming more and more complex, the circuit integration level is getting higher and higher, and the power consumption is increasing. In most cases, the main control controller needs to provide multiple different power sources, and needs Follow a certain sequence. For example, the types of power supplies required by the ZYNQ chip are 1V, 1.8V, 1.5V, and 3.3V. The power-on sequence must also follow 1V-1.8V-1.5V-3.3V, and there are certain requirements for the delay between them. At present, there are mainly three methods for power-on sequence control: [0003] 1) Using the output of the programmable logic device to drive the enable terminal of the power supply chip, this method can rea...

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Problems solved by technology

[0003] 1) Using the output of the programmable logic device to drive the enable terminal of the power supply chip, this method can realize the controllable delay between the power supplies, and the degree of freedom is also high, but the programmable logic device belongs to the main controller, and its own The power supply has not been powered on in sequence, and if it cannot be started, it will not be able to output the enable signal of the power supply.

[0004] 2) Most of the power chips currently in use have a power output indication pin (PG) and an enable pin (EN). The PG of the previous power chip is connected to the EN of the next power chip. PG is generally an open drain. Output, when the output of the power supply chip reaches more than 90% of the nominal output voltage, the PG will output a high-impedance state, and output a low level in other cases

This control method is not applicable when the output voltage is low, because the output voltage of the power supply is relatively low, and a slight fluctuation will trigger the threshold of PG, which requires high power quality.

[0005] 3) Directly use the output of the previous stage to connect to the enable terminal of the power supply chip of the subsequent stage, as attached figure 1 : Preamplifier power supply 1 through the attached figure 1 After the resistor divides the voltage, the triode will be turned on, so as to drive the enable terminal of the next-level power supply chip, but there will be two problems: a. When V1 is small, because the triode will also have a voltage drop, the output of the triode is immediately The voltage at the enable terminal of the power chip is relatively small, and it is likely to be lower than the enable threshold, resulting in no generation of the next-stage power supply V2.

b. Since V1 and V2 are generated by the power chip, the voltage output of the power chip is divided by two resistors and compared with the internal reference to form a feedback loop. If the resistor is damaged, the output voltage of the power chip will directly rise to a higher value. If the value is large, it will damage the power supply chip of the subsequent stage, and at the same time, it will damage the main control chip powered by V1

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