TWM244644U - Current detection circuit of fly-back switching power supply - Google Patents

Description

M244644 V. Creation Instructions (1) [Technical Field to which the New Type belongs] This creation is a current detection circuit for a flyback switching power supply, especially about a type used in a flyback switching power supply (AC / DC On the secondary circuit of Flyback Switching Power Supply), the bipolar transistor is used to detect when the output of the transformer is positive and negative, and the field effect transistor is driven to release the stored energy on the transformer in a timely manner. [Previous technology] According to the current known DC power supply devices, such as AC To DC Switching Power Supply, in order to reduce the size of the transformer, most of them use high-frequency pulse width modulation (PWM) control The DC output voltage, as shown in the first figure, is a schematic circuit diagram of a conventional flyback switching power supply device, and the primary circuit and the secondary circuit of the transformer T 1 are divided into a primary side 1 0 1 and a secondary side 1 0 2, the primary side 1 0 1 and the secondary side 10 2 are separated by a photoelectric crystal 1 1 1 and a light-emitting diode 1 1 2 between the primary side 1 1 and the secondary side 10 2 Signal, but the optical signal can be used to feedback the voltage or current output change signal of the secondary side 1 0 2 to the primary side 1 0 1 to adjust the voltage of the primary side 10 1 and the secondary side 10 2 simultaneously. The amount of current change, or as a feedback signal for overcurrent and short circuit protection.

This conventional flyback switching power supply is mainly a circuit that converts AC voltage to DC voltage output. As shown in the second figure, it is a pulse width modulation output waveform diagram. Its principle is: on the primary side 1 0 1 When the field effect transistor Q 1 is turned on, the energy of the transformer is inconsistent due to the reverse polarity of the primary and secondary sides of the transformer.

M244644 V. Creative Instructions (2) The rectifier diode D 1 is stored on the transformer T 1. After the field effect transistor Q 1 is turned on, the polarity of the transformer T 1 is reversed and the secondary rectifier diode is used instead. The body D 1 is then turned on to release the stored energy stored on the transformer T 1. However, when the rectified diode D 1 is turned on, a voltage drop of 0.4 V to 1.5 V is generated with the output load. This voltage drop multiplied by the load current is the power loss of the rectified diode D 1. When the load current is large, the output power efficiency of the DC power supply device will be greatly reduced. [A new type of low-return horse-powered technology is provided in the new post. It is used to measure the amount of closed and late routes. The detection content of the (C) form is that it has a flyback operation. The detection current of the hand-made creator The main current and electricity from the lack of switching circuit in this case are suitable for the input including a first connection to the first transistor. The power supply is changed to achieve the required technical detection voltage. When the output is turned off, the end of the inverting crystal secondary electric body is turned off, and the effective electrician is the source secondary circuit detection circuit. The output circuit closes the secondary current variant and the crystal emitter, and the crystal is the power and current system of the anti-cavitating device. , Tied to the first

Transistor-Source The above-mentioned research on the existing DC power supply equipment and the use of theory, the current detection circuit can greatly reduce the rate loss, and the purpose of this creation is to provide a flyback switching electrical connection The field-effect transistor Q 2 is detected when the positive and negative polarities of the voltage transformer on the secondary side of a transformer alternate, preventing the current-detecting transistor from being closed due to T 1. Its base (B) is connected to the base (E ) Terminal to form a common base terminal to form a first detection terminal and collector terminal

(C) forming a first gate (G) and terminal; giving back a field

M244644

V. Creative Instructions (3)-Drain (D), the source (S) is connected to the first Wm outlet of the transformer σ port, and the drain (D) is connected to the voltage outlet where the The first detection terminal is connected to the source (; 3) of the field effect transistor, the second detection terminal is connected to the drain (D) of the field effect transistor, and the feedback terminal is connected to the field effect transistor. The gate of the crystal (G) The field effect transistor Q 2 uses the auxiliary coil of the transformer T 1 to provide an auxiliary voltage via the buffer circuit to drive 5 and detects the field effect transistor with the bipolar transistor. When the current change of Q 2 is close to zero, the field-effect transistor is turned off to replace the rectifier diode D 1 in the traditional flyback circuit to improve the efficiency of the output power supply. The next technical feature of this creation is to provide the flyback type described above. Switching Power Supply The current detection circuit 1 further includes a buffer circuit including a diode whose positive terminal is connected to the second output terminal j of the transformer and the negative terminal is connected to the auxiliary power terminal; a third transistor whose collector (C) Is connected to the auxiliary power terminal 9 a fourth transistor 1 whose emitter (E) is connected to the emitter (E) of the third transistor and connected to the field effect. ¾ the gate (G) of the crystal, the The base (B) is connected to the base (B) of the third transistor and connected to the __ — feedback terminal, the collector (C) is connected to the first detection terminal 3 and a second resistor, The buffer circuit is connected between the feedback terminal and the auxiliary power terminal. The buffer circuit is used to achieve the effect of assisting the bipolar transistor to turn on the field effect transistor. [Embodiment] In order to enable your review committee to Learn more about this As the technical means and effects adopted to achieve the predetermined §5, please refer to the following page M244644 of the original creation. V. Creation Instructions (4) Detailed descriptions and drawings. I believe that the purpose, characteristics and features of this creation can be determined by This requires a deep and specific understanding, however, the drawings are provided for reference and explanation only, and are not intended to limit the creation. Please refer to the third picture, which is the circuit diagram of this creation. This creation is mainly connected to the output circuit of the DC power supply device, used to detect the voltage output terminal 1 0 of the secondary side of the transformer T 1 when the current is reduced from large to nearly zero, and the field effect transistor is turned off in time. In order to prevent the transformer T 1 from turning on due to the field-effect transistor Q 1 being turned on again, the output polarity of the transformer is reversed to drive the field-effect transistor Q 2 to release the stored energy on the transformer D 1. The secondary side of the transformer T 1 includes a first output terminal 103, a second output terminal 104, and a reference potential terminal 105. The reference potential terminal 105 of the transformer D 1 may be an electrical connection terminal. The current detection circuit 10 is mainly composed of a bipolar transistor and a first resistor R 8, and the bipolar transistor system includes a base of a first transistor Q4 and a second transistor Q 3 (B) is connected and combined, and is connected to the emitter (E) of the second transistor q3 to form a common base terminal 200, and the emitter (E) of the first transistor Q4 forms a The first detection terminal 21 1, the collector (C) forms a feedback terminal 2 1 2, and the collector (C) of the second transistor Q 3 forms a second detection terminal 2 2 1. The first transistor Q 4 and the second transistor Q 3 may be two identical N P N transistors. The first resistor R 8 has a first pin and a second pin, the first pin is connected to the common base terminal 2 0 0, and the second pin is connected to an auxiliary power terminal 3 0 1 . The field effect transistor Q 2 has a source (S), a gate (G), and a drain (D). The source (S) is connected to the transformer.

Page 9 M244644 V. Creative Instructions (5) The first output terminal 103 of T 1 is connected with the drain electrode (D) connected to the DC output terminal 4 0 0. This field-effect transistor Q 2 has a low on-resistance characteristic. The resistance value of this conduction can be selected from a field-effect transistor with a minimum of 10 milliohms.

The second output terminal 104 of the transformer T1 is further connected to a buffer circuit 20 to assist the bipolar transistor to drive the field effect transistor Q2 to conduct. The buffer circuit 20 includes a diode D2. A third transistor Q5, a fourth transistor Q6, and a second resistor R7, wherein the diode D 2 has a positive terminal (P) and a negative terminal (N); the positive terminal (P) Connected to the second output terminal 104 of the transformer D1, and the negative terminal (N) is connected to the auxiliary power terminal 3 0 1. The third transistor Q 5 ® is an NPN transistor, which has a collector (C), a base (B), and an emitter (E). The collector (C) is connected to the auxiliary power terminal. 3 0 1. The fourth transistor Q 6 is a P NP transistor having an emitter (E), a base (B), and a collector (C). The emitter (E) is connected to the third transistor. The emitter (E) of the transistor Q5 is connected to the gate (G) of the field effect transistor Q2, and the base (B) is connected to the base (B) of the third transistor Q5, And is connected to the feedback terminal 2 1 2, and the collector (C) is connected to the first detection terminal 2 1 1. The second resistor R 7 is connected between the feedback terminal 2 1 2 and the auxiliary power terminal 3 0 1. The first detection terminal 2 1 1 is connected to the source (S) of the field effect transistor Q 2 ·, and the second detection terminal 2 2 1 is connected to the drain of the field effect transistor Q 2 ( D), that is, the DC output terminal 4 0 0, and the feedback terminal 2 1 2 is connected to the gate (G) of the field effect transistor Q 2, by the _

Page 10 M244644 V. Creation instructions (6) Bipolar transistor detects the micro-summer current of the voltage output terminal 1 0 3 of the transformer T 1 after the field effect transistor Q 2 is turned on to drive the field effect transistor The crystal Q 2 is turned off, releasing the stored energy on the transformer T 1. The circuit principle of this creation is: when the polarity of the voltage output terminal 103 of the transformer T 1 changes from negative to positive, an auxiliary power source is provided from the second output terminal 104 of the transformer T 1 to the diode D. 2. The second resistor R7 is biased by the auxiliary power source to turn off the fourth transistor Q6, and the third transistor Q5 is turned on, so that the field-effect transistor Q2 is turned on, and the field-effect transistor is turned on. When the crystal Q 2 is turned on, the current passing through it decreases in a negative slope manner, and the field effect transistor Q 2 generates some slight voltage drop due to the current passing. This voltage drop also decreases in a negative slope manner, as shown in the second figure, which makes the The first transistor Q 4 of the bipolar transistor is turned off and the second transistor Q 3 is turned on. When the current of the field effect transistor Q 2 is reduced to a certain value, the voltage drop is not enough to make the second transistor Q 3 is turned on and turned off, so that the first transistor Q 4 is turned on by itself, so that the third transistor Q 5 is turned off and the fourth transistor Q 6 is turned on, and the field effect transistor Q 2 is turned off to wait The next turn on and turn off alternately. The job is that this creation can indeed use the technology disclosed above to provide a design that is quite different from the learner, which can increase the overall use value. It has not been seen in publications or public use before application, and it has already met the requirements of new patents. , Yi filed a new patent application according to law. However, the drawings and descriptions disclosed above are only examples of this creation. Those skilled in this art can make other improvements based on the above description, and these changes still belong to the creative spirit and Bounded by

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Claims (1)

M244644 6. Scope of patent application 1. A current detection circuit of a flyback switching power supply, which is connected to the secondary side of a transformer of a DC power supply device to detect-a voltage output terminal is rectified The minute current in the output, the secondary side of the transformer includes a first output terminal, a second output terminal and a reference potential terminal. The current detection circuit includes: a bipolar transistor, which is composed of a first transistor And the base (B) of a second transistor is connected and combined, and is connected to the emitter (E) end of the second transistor to form a common base terminal, and the emitter (E) of the first transistor A first debt measuring terminal is formed, a collector (C) forms a feedback terminal, and a collector (C) of the second transistor forms a second detection terminal; and a field-effect transistor having a source ( S) '-the gate electrode (G) and a drain electrode (D), the source electrode (S) is connected to the first output terminal of the transformer, and the drain electrode (D) is connected to the voltage output terminal; The first detection terminal is connected to the source (S) of the field effect transistor, and the second detection terminal is Connected to the drain (D) of the field effect transistor, the first feedback terminal is connected to the gate (G) of the field effect transistor, and the voltage output terminal is rectified by the bipolar transistor. A small amount of current during output to drive the field effect transistor to turn on and off, and release the stored energy on the transformer. 2. The current detection circuit of the flyback switching power supply as described in item 1 of the scope of patent application, wherein the reference potential terminal of the transformer is a 0-terminal. 3. The 'current detection circuit' of the flyback switching power supply described in item 1 of the scope of patent application, wherein the first transistor and the second transistor system are Page 15 M244644 VI. Patent application scope Two identical NP N transistors. 4. The current measurement circuit 5 of the flyback switching power supply as described in item 1 of the scope of the patent application, wherein the field effect transistor system has a low on-resistance characteristic, and the on-resistance value can be as low as 10 milliohms. . 5. The current detection circuit of the flyback switching power supply according to item 1 of the scope of patent application, further comprising: a first resistor having a first pin and a second pin, the first A pin is connected to the common base terminal, and the second pin forms an auxiliary power terminal. 6. The current detection circuit of the flyback switching power supply according to item 3 of the patent application scope, wherein the auxiliary power terminal is connected to the feedback terminal through a second resistor. 7. The current detection circuit of the flyback switching power supply as described in item 1 of the scope of patent application, further comprising a buffer circuit to assist the bipolar transistor to drive the field effect transistor to conduct, and the buffer The circuit includes: a diode having a positive terminal (P) and a negative terminal (N) ', the positive terminal is connected to the second output terminal of the transformer, and the negative terminal is connected to the auxiliary power terminal; A third transistor, which is an NPN transistor, having a collector (C), a base (B), and an emitter (E), and the collector (C) is connected to the auxiliary power terminal; A fourth transistor is a PNP transistor and has an emitter (E), a base (B), and a collector (C). The emitter (E) is connected to the third transistor. Emitter (E) and connected to the gate of the field effect transistor Page 16 M244644 6. The scope of patent application (G), the base (B) is connected to the base (B) of the third transistor, and is connected to the feedback terminal, and the collector (C) is connected to The first detection terminal and a second resistor are connected between the feedback terminal and the auxiliary power terminal. 8. The current of the flyback switching power supply as described in item 7 of the patent application scope. Detection circuit, wherein the circuit principle of the buffer circuit is: When the polarity of the voltage output terminal changes from negative to positive, an auxiliary power is provided to the diode by the second output terminal of the transformer, and the second resistor is biased by the auxiliary power to make the fourth transistor turn off. The third transistor is turned on, which causes the field effect transistor to be turned on. When the field effect transistor is turned on, the current decreases in a negative slope manner, and the field effect transistor generates a slight voltage drop when the current passes, making the bipolar The first transistor of the transistor is turned off and the second transistor is turned on. When the current of the field effect transistor is reduced to a certain value, the voltage drop is not enough to make the second transistor turn on and turn off. The crystal is turned on by itself, so that the third transistor is turned off and the fourth transistor is turned on, and the field effect transistor is turned off, waiting for the next turn-on and turn-off of the transistor. Page 17