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An input undervoltage protection circuit and method

A technology for input undervoltage and circuit protection, applied to electrical components, output power conversion devices, etc., can solve problems such as restarting and unstable product output, and achieve the effect of preventing malfunctions

Active Publication Date: 2018-08-03
MORNSUN GUANGZHOU SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] In view of this, the technical problem to be solved by the present invention is to provide an input undervoltage protection circuit and method to solve the problem of unstable output or restart of the product caused by the existing input undervoltage technology

Method used

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  • An input undervoltage protection circuit and method

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Embodiment 1

[0052] Figure 4 It is the schematic circuit diagram of the first embodiment of the present invention. The sampling circuit 100 includes: a resistor R1 and a resistor R2; The output of the connection point of the above-mentioned resistor R2 is the above-mentioned sampling signal. The control circuit 200 includes: capacitor C1, error amplifier TL431 ( Figure 4 U1) and resistor R5; switching power supply control IC ( Figure 5 The Vcc pin of U2) is grounded sequentially through the resistor R5, the cathode of the error amplifier TL431, and the anode of the error amplifier TL431; the capacitor C1 is connected in parallel to the error amplifier TL431 Between the anode and the reference pin; the reference pin of the error amplifier TL431 receives the sampling signal; the cathode of the error amplifier TL431 outputs the control signal; the reference pin of the error amplifier TL431 is the The input terminal of the control circuit described above. The hysteresis circuit 300 incl...

Embodiment 2

[0062] Figure 7 It is the schematic circuit diagram of the second embodiment of the present invention, Figure 8 It is the schematic diagram of the circuit applied in the DC-C switching power supply of the second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that it also includes a diode D1 and a diode D2, and the anode of the diode D1 is connected to the The resistor R6, the cathode of the diode D1 is connected to the collector of the transistor Q1. The anode of the diode D2 is connected to the control terminal of the Vcc pin regulator circuit of the switching power supply control IC, and the cathode of the diode D2 is connected to the cathode of the diode D1.

[0063] The voltage stabilizing circuit above is a voltage stabilizing circuit between the Vcc pin of the switching power supply control IC and the auxiliary winding, and is generally composed of a triode and a voltage stabilizing diode, such as Figure...

Embodiment 3

[0066] Figure 9 It is the schematic circuit diagram of the third embodiment of the present invention, Figure 10It is the schematic diagram of the circuit applied in the DC-C switching power supply of the third embodiment of the present invention. The difference between the third embodiment and the second embodiment is that it also includes a Zener diode D3, and the anode of the Zener diode D3 The collector and cathode of the transistor Q1 are connected to the cathode of the diode D1. When the transistor Q1 is turned on, the regulator tube D3 maintains the level of the Vcc pin of the control IC at an appropriate value to ensure that the hysteresis circuit 300 is in a working state and avoid small-scale fluctuations in the input voltage after the product input undervoltage occurs the product restarts.

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Abstract

The invention discloses an input undervoltage protection circuit and method. A sampling circuit samples an input voltage and outputs a sampling signal; a control circuit receives the sampling signal and outputs a control signal to a switching circuit and a hysteresis circuit; when an undervoltage occurs, the switching circuit lowers a Vcc pin electrical level of a control IC of the switch power supply; a feedback circuit detects the Vcc pin electrical level and provides a feedback signal to the control circuit to enable the Vcc pin electrical level to be rapidly lowered, and a product is subjected to undervoltage protection; meanwhile, the hysteresis circuit lowers the sampling signal to generate a hysteresis voltage for performing undervoltage protection so as to enable the undervoltage protection for the product to be more reliable; when undervoltage recovers, the switching circuit stops the lowering of the Vcc pin electrical level; the feedback circuit detects the Vcc pin electrical level and provides a feedback signal to the control circuit to enable the switch circuit to rapidly release the Vcc pin electrical level; the Vcc pin electrical level is charged to an IC operating voltage range by an external start circuit, and the product smoothly recovers to operate; and a hiccup phenomenon in the recovery process of the product is eliminated.

Description

technical field [0001] The invention discloses an input undervoltage protection circuit and method, in particular to the input undervoltage protection of a switching power supply. Background technique [0002] In the existing modular switching power supply, it is generally required to have the input undervoltage protection function, especially in the occasions such as grid voltage fluctuations or photovoltaic power generation, the undervoltage protection function is to prevent the power supply from being damaged when the input voltage is too low. If the product itself or the power supply equipment is damaged, a protection circuit is designed to control the power off, and it also prevents the product from restarting continuously when the input voltage fluctuates at a low level, resulting in malfunction of the subsequent equipment. [0003] figure 1 For the existing undervoltage protection circuit diagram, figure 1 The undervoltage protection circuit includes a sampling circ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M1/32
CPCH02M1/32
Inventor 李国强王小亮冯刚
Owner MORNSUN GUANGZHOU SCI & TECH
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