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Fly-back switching power supply and loop control circuit thereof

A technology of loop control and switching power supply, which is applied in the direction of battery circuit devices, circuit devices, control/regulation systems, etc., can solve the problems that the flyback switching power supply cannot be applied, and achieve the effect of easy mastery and simple control strategy

Active Publication Date: 2016-03-02
MORNSUN GUANGZHOU SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0019] In view of this, the present invention aims to solve the problem that the existing loop control circuit cannot be applied to the flyback switching power supply for open-loop operation, especially when the flyback switching power supply is used in a balanced charging circuit, the present invention provides a flyback switching power supply The loop control circuit of the exciting switching power supply still maintains an open-loop working state, and can work normally and effectively when used in a balanced charging circuit

Method used

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  • Fly-back switching power supply and loop control circuit thereof
  • Fly-back switching power supply and loop control circuit thereof
  • Fly-back switching power supply and loop control circuit thereof

Examples

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no. 1 example

[0052] see Figure 5 , a loop control circuit of a flyback switching power supply, including an input terminal VI1, an input terminal VI2, an output terminal VO1 (the output terminal of the operational amplifier A1 in the figure is connected to the FB pin of IC2), a booster S1, and a resistor R1, resistor R2, resistor R3, resistor R4, regulator IC1, operational amplifier A1, booster S1 includes three terminals: input terminal 1, ground terminal 2, output terminal 3. The connection relationship is: the input terminal VI1 is connected to the ground terminal 2 of the booster S1, the input terminal VI1 is connected to one end of the resistor R2 at the same time, the input terminal VI1 is connected to the anode of the regulator IC1 at the same time, and the input terminal VI1 is connected to the ground of the operational amplifier A1 at the same time The input terminal VI2 is connected to the input terminal 1 of the booster S1, and the input terminal VI2 is connected to one end of ...

no. 2 example

[0064] The circuit composition and connection relationship of the second embodiment are exactly the same as those of the first embodiment, except that the pulse width modulation controller IC2 is UC3843; and TL431, as mentioned above, the regulator IC1 is a 3.9V regulator, Because the current-limiting resistor R3 is relatively large, which is 51K, the measured terminal voltage of the voltage regulator IC1 is 3.784V, and the temperature drift of the voltage regulator is relatively large. In the second embodiment, it is replaced with a three-terminal reference source TL431; and The maximum duty cycle is limited to 0.65 through the external resistance of its 4th pin. Other circuit parameters are as follows:

[0065] The resistor R1 is 51KΩ, the resistor R2 is 75KΩ, the resistor R3 is 15KΩ, and the resistor R4 is 5.1MΩ. The regulator IC1 is a three-terminal reference source TL431. Connect the reference terminal to the cathode to obtain a 2.50V reference voltage. The operational amp...

no. 3 example

[0079] see Figure 7 ,and Figure 5 In contrast, only a diode D1 is connected in series in the resistor R4, that is, the other end of the resistor R4 is disconnected from the output pin of the operational amplifier A1, and the diode D1 is connected in series. The anode of the diode D1 is connected to the other end of the resistor R4, and the cathode of the diode D1 is connected to the operational amplifier. Output pin of amplifier A1.

[0080] When the diode D1 is connected in series, the working mode of the circuit will change:

[0081] When the input voltage is slightly lower than the first preset value, since the circuit configuration is inverting amplification, the output voltage of the operational amplifier A1 is higher than the voltage at the inverting input terminal, and the output voltage cannot be negatively fed back through the diode D1, thus making the operational amplifier A1 is in the state of open-loop amplification. At this time, the output voltage of the oper...

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Abstract

The invention relates to a loop control circuit of a fly-back switching power supply in open loop work. The loop control circuit comprises input ends VI1 and VI2, a booster S1, resistors R1, R2, R3 and R4, a voltage stabilizer tube IC1 and an operational amplifier A1; an output pin of the operational amplifier A1 is connected with a pin FB of a pulse width modulation controller IC2; when the input voltage is slightly lower than a first preset value, the operational amplifier outputs a high level, and the IC2 outputs a minimal duty ratio; and when the input voltage is greater than the first preset value, the operational amplifier outputs a low level, the IC2 outputs a higher duty ratio, and the trend is the same with that of the input voltage. The loop control circuit is applied to the fly-back switching power supply in open loop work in a balanced charging circuit, the control circuit can work normally, the circuit is simple, and debugging is convenient.

Description

technical field [0001] The invention relates to a flyback switching power supply, in particular to a loop control circuit of the flyback switching power supply. Background technique [0002] At present, for switching power supplies with an input power below 75W, where there is no requirement for power factor (PF, PowerFactor, also known as power factor), the flyback switching power supply has attractive advantages, such as simple circuit topology, Wide input voltage range, etc. Flyback switching power supply is widely used due to its few components and relatively high circuit reliability. For convenience, many documents are referred to as flyback switching power supply. [0003] In order to achieve the stability of the output voltage or for charging purposes, the flyback switching power supply requires the stability of the output current and the stability of the loop. At present, most of them adopt two feedback and loop control methods: [0004] The first one: the classic ...

Claims

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Application Information

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IPC IPC(8): H02M3/156H02J7/00
CPCH02J7/0072H02M3/156H02M1/0003
Inventor 王保均
Owner MORNSUN GUANGZHOU SCI & TECH
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