Current detecting circuit AC/DC flyback switching power supply
First Claim
1. A current detecting circuit for a AC/DC flyback switching power supply, the current detecting circuit being connected to a secondary side of a transformer of the AC/DC flyback switching power supply for detecting a current of a direct current (DC) output terminal, the secondary side of the transformer having a first output terminal, a second output terminal and a reference terminal, the current detecting circuit comprising:
- bipolar junction transistors, comprising a first transistor and a second transistor, the first transistor having a base connecting with a base and an emitter of the second transistor to form a common base terminal, the first transistor having an emitter forming a first detecting terminal and having a collector forming a feedback terminal, the second transistor having a collector forming a second detecting terminal; and
a field-effect transistor (FET) having a source, a gate and a drain, the source connecting to the first output terminal of the transformer, the drain connecting to the DC output terminal;
wherein the first detecting terminal is connected with the source of the FET, the second detecting terminal is connected with the drain of the FET, the feedback terminal is connected with the gate of the FET;
via detecting the tiny current of the DC output terminal by using the bipolar junction transistors, the FET being turned on or off to release an energy stored in the transformer.
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Accused Products
Abstract
A current detecting circuit connects to a secondary side of a transformer, including a first, second transistors and a field-effect transistor (FET). The first transistor has a base connecting with the base and emitter of the second transistor to form a common base terminal, an emitter forming a first detecting terminal and a collector forming a feedback terminal. The second transistor has a collector forming a second detecting terminal. The FET is used to replace a prior current rectifying diode. The FET has a source connecting to an output terminal of the transformer and a drain connecting to a direct current (DC) output terminal. The first, second detecting terminals and feedback terminal are connected with the source, drain and gate of the FET, respectively. Via detecting the current of the DC output terminal, the FET is timely turned on and off to release the energy stored in the transformer.
16 Citations
8 Claims
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1. A current detecting circuit for a AC/DC flyback switching power supply, the current detecting circuit being connected to a secondary side of a transformer of the AC/DC flyback switching power supply for detecting a current of a direct current (DC) output terminal, the secondary side of the transformer having a first output terminal, a second output terminal and a reference terminal, the current detecting circuit comprising:
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bipolar junction transistors, comprising a first transistor and a second transistor, the first transistor having a base connecting with a base and an emitter of the second transistor to form a common base terminal, the first transistor having an emitter forming a first detecting terminal and having a collector forming a feedback terminal, the second transistor having a collector forming a second detecting terminal; and
a field-effect transistor (FET) having a source, a gate and a drain, the source connecting to the first output terminal of the transformer, the drain connecting to the DC output terminal;
wherein the first detecting terminal is connected with the source of the FET, the second detecting terminal is connected with the drain of the FET, the feedback terminal is connected with the gate of the FET;
via detecting the tiny current of the DC output terminal by using the bipolar junction transistors, the FET being turned on or off to release an energy stored in the transformer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification